ELEMENTARY PHYSIOLOGY AND HYGIENE CONN SILVER.BURDETT &COMPANXJ UNIVERSITY OF CALIFORNIA SAN FRANCISCO LIBRARY AN ELEMENTARY PHYSIOLOGY AND HYGIENE FOR USE IN UPPER GRAMMAR GRADES: BY H. W. CONN, PH.D. PROFESSOR OF BIOLOGY IN WESLEYAN UNIVERSITY REVISED AND ENLARGED EDITION QP 37 C7Z SILVER, BURDETT AND COMPANY NEW YORK BOSTON CHICAGO COPYRIGHT, 1903, 1906, 1909 BY SILVER, BURDETT AND COMPANY. PREFACE THE aim of the author in writing the present work has been to furnish an elementary text-book in physi- ology and hygiene which should recognize some of the more important discoveries of recent years concerning matters pertaining to health, and which should also attempt to exemplify in the clearest way the inter- relation between physiology and hygiene. The primary object of the study of physiology in our schools is to inculcate an intelligent care of the body. With this in view, matters of hygiene must in one sense take first place, although our understanding of hygiene must be based upon a knowledge of physi- ology. In the present work the study of the body, of its various parts and their functions, is given full and comprehensive treatment; at the same time lessons on hygiene are given as natural results of the principles of physiology and as closely related thereto. A knowledge of foods and their values and of the causes and distribution of contagious and other germ diseases is of vital importance to every boy and girl. The effect of alcohol upon the various functions of the body is treated throughout the book in direct rela- tion with the particular organs or functions concerned. The dangers connected with the use of alcohol will be found plainly indicated in accord with the results of the latest investigations in that department of science. 3 4 PREFACE The author desires to express his hearty acknowledg- ments to Superintendent W. P. Ferguson of Middle- town and Dr. George W. Fitz of Boston for their kindness in looking over the proofs of the work and giving him the benefit of their criticisms. He wishes also to express his obligations to Professor W. O. At- water, Professor William N. Kice, and Dr. F. G. Bene- dict of Wesleyan University, to Professor C. F. Hodge of Clark University, to the Kev. J. H. James, President of the Connecticut Temperance Union, and to Superin- tendent J. G. Edgerly of Fitchburg, Massachusetts, for their valuable suggestions. While acknowledging ob- ligations to these gentlemen, it is not implied that any of them can be held responsible for the method of treat- ment in the work or as necessarily indorsing it. In connection with this new edition, the author de- sires to call particular attention to the four additional chapters on the important subjects of public hygiene, tuberculosis, exercise, and the voice. The advantage of intelligent interest in public hygiene on the part of our boys and girls is evident; and the remarkable re- duction in the death rate from tuberculosis in localities where the facts with regard to it have been made clear to the general public, justifies the presentation here of its causes, prevention, and cure. The two supplementary chapters on the development of 'the body and on the training of the voice contain many practical suggestions, and are intended for fre- quent reference and use throughout the course. MIDDLE-TOWN, March, 1906. CONTENTS CHAPTER I. II. FOODS AND DRINKS Purposes of Food Kinds of Food Sources of Food Other Food Material PAGE 11-36 Alcohol Amount of Food Needed Comparative Food Values DIGESTION . The Mouth Food in the Mouth and Throat Food in the Stomach Food in the Intestines 37-64 Digestibility of Foods How the Food gets into the Blood Undigested Portions of the Food III. FOOD HABITS AND COOKING 65-79 Proper Habits of Eating The Habit of using Alco- hol IV. CIRCULATION The Blood What makes the Blood Flow Blood Vessels How the Blood Flows V. RESPIRATION The Air Passages and the Lungs How Air is drawn into the Lungs Purposes of Cooking Principles of Cooking Methods of Cooking 80-103 How the Flow of Blood is Controlled Summary of the Circula- tion Process 104-123 What Breathing does for the Blood Ventilation How to restore Respiration 6 CONTENTS CHAPTER PAGE VI. THE FRAMEWORK AND MOTION OF THE BODY 124-152 The Skeleton Joints The Bones The Muscles Cartilage VII. THE KIDNEYS AND THE SKIN AND THEIR DUTIES 153-171 Waste Products The Skin The Kidneys Functions of the Skin VIII. THE CARE OF THE SKIN 172-179 Bathing Burns Clothing Frostbites IX. ALCOHOL AND OTHER NARCOTICS . . . 180-188 Opium Alcohol Tobacco X. THE NERVOUS SYSTEM 189-197 The Brain The Nerves The Spinal Cord XL THE NERVOUS SYSTEM IN ACTION . . . 198-212 Duties of the Nerves The Cerebellum and Cerebrum Duties of the Spinal Cord The Importance of Habits and Medulla The Care of the Mind XII. THE SENSES 213-236 The Sense of Sight The Sense of Smell The Sense of Sound Skin Sensations The Sense of Taste XIII. HEALTH AND DISEASE 237-251 Parasitic Diseases The Duty of preserving The Use of Alcohol Health XIV. WHAT TO DO IN EMERGENCIES . . . 252-255 XV. PUBLIC HYGIENE 256-267 Boards of Health Foods Water Garbage and Sewage Fresh Air Protection from Contagious Diseases CONTENTS CHAPTER XVI. A WAR FOR THE NATION PAGE 268-282 Consumption not He- reditary Consumption can be Prevented Consumption can be Cured SUPPLEMENTARY CHAPTERS XVII. How TO DEVELOP OUR BODIES Alcohol and Consumption Precautions for Consump- tives Animal Tuberculosis How to Combat the Bac- teria . 283 283-301 Breathing Walking Exercises for Supple- ness Ease of Motion XVIII. THE VOICE Position in Speaking and Heading Breathing Exercises Articulation The Vowels The Consonants GLOSSARY .... INDEX Exercises to Develop Vari- ous Parts of the Body Games and Sports Physical Expression 302-315 Phonetic Reading Enunciation Accent, Emphasis, and In- flection Character in Speech 317-324- 325-334 ILLUSTRATIONS '!&. PAGE 1. Starch Grains 16 2. Fat Cells .... 17 3. A Small Bit of a Grain of Wheat ..... 21 4. The Oat Plant ,22 5. A Small Bit of Potato 23 6. Yeast Plant 27 7. Sugar Solution undergoing Fermentation by Yeast . 28 8. Showing the Proportion of Alcohol and Water in Beer, Wine, and Whisky . . . . . . .29 9. The Upper Teeth 39 10. The Mouth 40 11. A Diagram of the Side of the Face 41 12. A Section through the Head 44 13. The Digestive Organs of the Abdomen .... 47 14. A Section of the Wall of the Stomach .... 48 15. Showing the Location of the Digestive Organs . . 50 16. A Bit of the Intestine 58 17. A Bit of the Intestine 59 18. A Single Villus 60 19. A Simple Device for showing how Foods may pass through Membranes . . . . . . .61 '20. A Little Blood as it appears under a Microscope . . 81 21. The Heart 83 22. A. The Chief Arteries and Veins. B. Showing the Entrance of the Chief Veins into the Heart facing 84 23. The Right Side of the Heart 84 24. The Left Side of the Heart 84 25. Capillaries "26. Diagram showing General Circulation . 89 27. Showing Main Artery of the Arm . 8 ILLUSTRATIONS 9 FIG. PAQB 28. Showing Main Artery in the Leg 91 29. Showing how to compress the Arm to stop Bleeding . 92 30. Showing the Method of applying a Ligature ... 93 31. Showing the Clotting of Blood 94 32. Section of an Artery and a Vein 98 33. The Lungs 107 34. Air Sacs 108 35. The Air Sac of the Lungs .... facing 108 36. Muscle Fibers . . . . . . . facing 108 37. Showing Chest with Lungs and Heart behind the Ribs . 109 38. Showing Movement of the Diaphragm in Breathing . 110 39. Showing Movement of the Ribs in Breathing . . . Ill 40. Ventilation 119 41. The Method of Moving the Arms to produce Artificial Breathing 121 42. The Human Skeleton ... ... 125 43. Two Vertebrae in Position 126 44. The Human Skull 127 45. A Section of the Femur 128 46. The Cramped Foot 130 47. The Uncramped Foot . . . . ' . . .130 48. An Improperly Shaped Shoe 131 49. The Properly Shaped Shoe 131 50. Two Vertebrae 133 51. The Bones forming the Knee Joint 135 52. The Knee Joint 136 53. The Bones of the Shoulder Joint 138 54. The Shoulder Joint 139 55. Showing Method of Attachment of Biceps Muscle to move the Forearm 141 56. Showing Muscles and Tendons of the Arm . . . 142 57. A Bit of Muscle 143 58. A Bit of Muscle 143 59. The Surface Muscles of the Body 147 60. The Kidneys ,155 61. A Section of a Bit of Skin . . . . . ,157 62. A Hair 159 63. A Section through the Tip of the Finger . . .161 10 ILLUSTRATIONS PAGE 64. A Bit of Skin as it appears under a Microscope . . 164 65. The Human Brain 190 66. The Nervous System 192 67. Two Pieces of the Spinal Cord 193 68. A Nerve 195 69. A Nerve Cell 196 70. Showing Connection of Hand with Brain by a Nerve . 199 71. The Brain in Position 206 72. The Eye, viewed from in Front 214 73. The Eye, viewed from the Side 216 74. A Comparison of the Structure of a Camera and the Eye 217 75. A Diagram representing a Section through the Human Eye 218 76. The Ear 222 77. The Tongue 227 78. A Vertical Section of the Nose 230 79. Bacteria that Produce Certain Diseases . . . . 240 80. A Well properly located 258 81. An Unhealthful Location for a Well 259 82. Diagram of House and Street Connections with the City Sewers 263 83. Diagram illustrating the Deaths Due to Four Years of Civil War and Deaths caused by Tuberculosis for 1900-1904 Relatively Compared . . . .269 84. A Sleeping Veranda enclosed by Awning Cloth at a Consumptive's Home 274 85. The Sun Parlor of a Large Hospital .... 275 86. 87. Illustrating Exercises 1 and 2 290 88. Illustrating Exercise 4 292 89, 90, 91. Illustrating Exercises 5, 7 and 8 . . .293 92, 93. Illustrating Exercises 18 and 19 . . . .296 94, 95. Illustrating Exercises 20 and 21 .... 297 96. Hammer Throwing 299 97. The Larynx or Voice-Rox ...... 304 PHYSIOLOGY AND HYGIENE CHAPTER I FOODS AND DRINKS OUR bodies are in some respects like an engine that is constantly at work. As an engine is cold and powerless without fuel, so our bodies without food would starve and die. As the engine usually works smoothly and strongly, so the body, when we are in good health, is strong and active. But sometimes the body, like the engine, breaks down in part, and cannot do all its work. Then we say that we are ill. Smooth action of the engine means good health. When any- thing interferes with its working properly, sickness results. If the machine stops entirely, we say there is death. Physiology teaches us about the body, what the work of each part is; and Hygiene teaches us how we may treat the body wisely, just as the skillful engineer cares for his engine in the best possible way. PURPOSES OF FOOD When we speak of food, we ordinarily mean materials suitable for us to eat. In this chapter we shall include in the word "food," only the portion of the food 11 12 PHYSIOLOGY AND HYGIENE material that can be taken into the blood, and so can give nourishment to the body without injuring any of its parts, and not including that which passes out as waste. In order that an engine may be kept running, it is necessary, of course, that coal or other fuel be regularly supplied, so that the engine may continue to have heat under its boilers, and power to run. But the coal could not keep the wheels revolving if an important part of the engine should break down. The care of the engine, then, includes also the repairing or re- placing of parts that break or wear out. In much the same way our bodies need not only heat and energy, but also the constant building and repair of parts which are used up from day to day. Our food supplies us with material for building and repair, as well as for heat and energy. Foods for Building and Repair. When you say, " I have grown two inches since last year," you mean that your bones and muscles have increased in size a certain amount during the last twelve months. Even after we have reached our full height, certain parts of the body still continue to grow. The hair and finger nails need frequent cutting, and the skin is all the time wearing away. Although we cannot see so readily that the bones and muscles wear out and require constant repair, it is equally true. It is neces- sary, then, that our bodies receive in food some building material which can be used to increase the size of growing muscles and bones, and to replace those parts that are worn out. FOODS AND FOOD MATERIALS 13 Foods for Fuel. In addition to the material used for building and repair, our bodies need food that will serve as fuel, like the coal on the steamship, to supply heat, and power to use the muscles. Although we may feel so cold that our bodies fairly ache, as we say, still, as long as our hearts beat, that is, as long as we live, our bodies are always warm. If you look at a thermom- eter, you will see that a certain point on the scale is marked "blood heat." This means that the point marked 98 is about the normal temperature of the blood. If the blood is cooler than this, we are ill; even a de- gree or two of additional heat in the body is fever. As we shall learn in a later chapter, our bodies are kept at the proper temperature by using up certain food materials, much as a stove or heater is warmed by the burning of coal. The flame which we see when wood or coal is burned is caused by the uniting of the fuel with a gas in the air which is called oxygen. In a similar way, but without flame, the heat-giving foods which we eat combine in our bodies with the oxygen which has been taken in with the air we breathe. KINDS OF FOOD The kinds of food which people eat appear to be numerous. As we study them carefully, however, we find that although our dinner table may hold a number of delicious things, the different articles of food are made up of a very few substances. Some of these substances, of which we shall learn more very soon, furnish our bodies with both building material and fuel, others chiefly with fuel. 14 PHYSIOLOGY AND HYGIENE Let us now consider these special food substances which are contained in the things we eat. Foods used for both Fuel and Repair. Albumen. If we break an egg carefully, we can separate the white from the yolk. This white, transparent, jellylike sub- stance is known as albumen, and is a valuable food substance. The white of the egg is one of the purest forms of albumen, but though we cannot see it so readily, albumen is found in meat, milk, and other articles of food. If you heat the white of the egg, it becomes solid, undergoing a change called coagulation. Myosin. The lean part of meat after the gristle has been removed is another important food substance, and is called myosin. Uncooked myosin is soft and elas- tic ; but cooking coagulates it, just as boiling hardens the white of the egg. Gluten. If we wrap a little flour in a piece of fine muslin and allow water to run through it, most of the flour will be washed away. A sticky, gummy, white mass will be left. This is gluten. Casein. Milk contains a food substance called casein. If we pour a little weak acid, like vinegar, into the milk, the latter curdles. The curd, or thick whitish substance, is casein. When pressed into cakes and dried in a certain way, it becomes cheese. These foods, albumen, myosin, gluten, and casein, build up the body, help to keep it in repair, and serve also as fuel. They are called proteids, or nitrogenous foods, and without them the body would starve. It must not be supposed, however, that eggs, meat, flour, and FOODS AND FOOD MATERIALS 15 milk are the only proteid foods, since there is some proteid in almost all classes of foods. Peas, beans, lentils, and similar vegetables are very rich in pro- teids, and are for millions of people the cheapest and most convenient of proteid foods. Foods used chiefly for Fuel. A man might have the muscles of a Samson, but if he were unable to lift anything with his sinewy arm, or to run upon his well- built legs, he would be of no more use to the world than a statue. To enable us to use our muscles we need more than the building and repairing foods; we must give our bodies something that will supply warmth and muscular power. The proteids or building foods may be used partly for this purpose, but we have in addition three important food substances that act mainly as fuels, starch, sugar, and fats. They furnish us with heat and the power necessary for motion. Although our diet cannot be confined to either class, we really need a larger amount of the fuel foods than of the proteids. Starch. Starch is found in certain of our vegetable foods, such as flour, oats, and potatoes. For use in the laundry and as stiffening for puddingb, the starch is separated from the other substances found in pota- toes and corn ; we then call it either laundry starch or corn starch. We must remember, however, that starch is really present in every potato, every kernel of corn, and every grain of wheat. We can easily see whether starch is contained in a fruit or a vegetable by touching it with a drop of water containing a little 16 PHYSIOLOGY AND HYGIENE iodine. 1 If there is starch in the vegetable, the spot touched will turn blue. The starch always appears in the form of very minute grains. Figure 1 shows starch grains as they look when seen through a power- ful microscope. We can cook our starch by putting a little into water and boiling it. The heat swells the grains of starch and the mass becomes a thick paste. Sugar. Sugar, like starch, is a fuel food, although in appear- ance and taste the two differ widely. There are several kinds, the so-called cane sugar, made from sugar cane, being one of the sweetest. Beet sugar, manufactured from the sugar beet, is also of excellent quality. Grlucose or grape sugar, which is found in fruits and in corn, is less sweet than cane or beet sugar, but as it is more cheaply prepared for market, it is often used for adulterating other sugars. Milk contains a kind of sugar known as milk sugar. All sugars are of about equal value as foods, despite their different degrees of sweetness. We can readily observe a difference between sugar and starch by placing a little sugar in water and heat- ing gently, and then repeating the experiment with starch. The sugar quickly dissolves, while the starch FIG. 1. STARCH GRAINS. As seen through a microscope. 1 A few drops of tincture of iodine in a teaspoonful of water is sufficient for a number of tests. FOODS AND FOOD MATERIALS 17 does not, but, as we have already seen, swells if the heat is sufficient. Starch and sugar, though so different in some re- spects, are closely related and have much in zommon. Starch is changed to sugar in fruits as they ripen, in seeds and bulbs as they grow, and the same process takes place in our starchy foods as they are digested. Fats. Fats are among the very best fuel foods. It is because of its excellent heat-giving qualities that the Eskimos eat so much of the blubber or fat of seals and other animals ; the fat enables them to endure the severity of their cold climate. Butter, tallow, lard, olive oil, and cottonseed oil are fats. Some of the fats used as foods, such as butter and lard, come from ani-mals ; and others, such as olive and cottonseed oils, from the vege- table world. Several of the fats, like lard, are solid when they come from the market, becoming liquid only when subjected to heat ; others, like olive oil, are always liquid. Animal fat is made up of little drops, each in- closed in a sac. The sacs can be seen only with the aid of a microscope. Figure 2 shows a group FlG - 2. -FAT CELLS. As they appear in a piece of meat of fat cells as they vbn ^ a micr( f scope . appear ; the figure shows five fat drops in their sacs, in the form in which they are found in animal foods, such as a piece of beef- steak. We must remember, however, that when we 18 PHYSIOLOGY AND HYGIENE look at animal fat it is solid and white because it is cold. In the living animal it is liquid, because of the heat of the body, and it is transparent. Melted fats or oils, when mixed with certain liquids, break up into very small drops, making the liquids look white. The millions of minute fat drops in milk aid in giving the liquid its white color. To test this, place a few drops of olive oil or castor oil and some water in a small bottle and shake rapidly. Then let it stand for an hour or so and note the change. Material for Bone Making. As we shall see later, bones are made up of two widely different materials. Part of the bone, what is called the organic matter, is made up from the proteids which are so useful in build- ing up other parts of the body. The harder mineral matter of the bone is lime, which is contained in small quantities in such common foods as meat, bread, milk, and eggs. Thus our ordinary food furnishes us with all material needed for bone building. SOURCES OF FOODS Although the substances about which we have just been studying are the foods necessary to sustain life, we seldom eat any one of them singly or in a pure form. Take bread, for example. As usually made, it contains flour, milk, sugar, lard, and salt. The flour gives us starch and gluten, the milk casein and sugar, the lard fat. And so it is with almost everything we eat. Usually several food substances are to be found in each single article of diet. See tables, pages 33-35. FOODS AND FOOD MATERIALS 19 Foods come both from animals and from plants. The principal animal foods are milk, meats, and eggs. Milk. Milk is one of the cheapest and best of foods. We may be sure, as it is the natural food for babies, that it is easily digested and contains all the materials necessary for life, growth, and activity. The curd is the body -building food, and the cream, or fat, and the milk sugar are the force-producing foods. We should always remember that milk should be used as a food, and not to take the place of water as a drink to quench thirst. Milk should usually be the chief food for a child until his first teeth appear. When he becomes active and begins to walk, milk does not furnish enough force-producing material, and this must be obtained from starchy foods, such as bread, crackers, and other cereal foods. The fat or cream may be allowed to rise to the sur- face of the milk and can then be taken off and churned into butter. The skimmed milk remaining still holds most of the sugar and just as much of the building food as could be found before the cream was re- moved ; therefore it remains a valuable food. Skimmed milk contains a little less fuel substance than does new milk, but it is equally serviceable for body build- ing. It is so cheap that it is a valuable food for those who have but little money to spend. The curd, when separated from the rest of the milk, is pressed and dried to make cheese. Both cheese and Gutter are very useful foods. 20 PHYSIOLOGY AND HYGIENE Danger in Milk. Since milk is capable of holding and transmitting the germs of certain diseases, it is sometimes a source of danger. Typhoid fever, diph- theria, scarlet fever, and tuberculosis (consumption) are occasionally caused by impure milk. Much of the illness suffered by babies and little children in warm weather may be traced to milk which has been made impure by a lack of cleanliness about milkmen, cows, barns, milk-houses, or milk-cans. It is necessary that milk, and all utensils holding it, should be kept per- fectly clean. Some dealers send men to inspect the farms from which they obtain milk, to see that every- thing about the dairy is kept neat. To avoid these dangers, milk should be bought from a reliable dealer. It should be kept cold until used, and all dishes in which it is to stand should be washed with boiling water before the milk is put into them. It is wise also, especially in warm weather, to " scald " the milk which is to be used by young children or invalids. This removes much of the possibility of danger, and is very little trouble, as the milk needs only to be brought to the boiling point (but not boiled) and then cooled. Milk that has been boiled is not so wholesome as milk that has merely been "scalded." Meats. Common meats consist of lean substance, or flesh, with some fat and considerable water. The flesh (myosin) is one of our most valuable body- building foods. So far as the amount of useful food is concerned, cheap meats are as nourishing as the more expensive cuts. A pound of round steak will FOODS AND FOOD MATERIALS 21 give us just as much good food as an equal quantity of porternouse steak. The extra money for high-priced meat is paid largely because these cuts are more tender than the cheaper parts and because the taste is in some respects better. Eggs. Albumen and fats are the principal foods in eggs. When cooked but a little, whether boiled in the shell or dropped into hot water, eggs are health- ful and nourishing. Hard-boiled eggs are less easily digested, because the juices of the stomach do not act readily upon the tough, coagulated mass. When very thoroughly chewed, however, they are more readily digested. Plant Foods. A large part of our food comes from plants. The most impor- tant of the plant foods are grains or cereals. The chief cereals eaten in this country are wheat, oats, rye, and corn (which are ground into flour, graham meal, oatmeal, rye meal, and Indian meal), and rice. In the countries of eastern Asia rice is the chief cereal used for food. Starch Cdls Gluten Cells FIG. 3. A SMALL BIT OF A GRAIN OF WHEAT. Highly magnified. 22 PHYSIOLOGY AND HYGIENE All cereals contain a large proportion of starch, or fuel food, and a small amount of the building materials, such as gluten. Wheat is one of the best cereals, since it has more gluten (that is, more building food) than most of the others. Figure 3 shows a small piece of a grain of wheat as it appears under the micro- scope. Some of the cells, as indicated, are loaded with starch, and others, fewer in number, contain gluten. About one eighth of our wheat flour is glu- ten. Oats (Fig. 4) are even better food than wheat, containing, as they do, a still larger propor- tion of gluten. Hice fur- nishes less building food than wheat, but more fuel food (starch). Corn con- tains also considerable fat. All of these cereals are thus excellent foods. They give us more fuel than meat and eggs, but less of the proteids or building foods. Wheat bread supplies a good proportion of the necessary materials for fuel and repair. A person could keep from starvation on a diet of bread and butter alone, but a variety of foods is always desirable. Meat and cheese go well with cereals, since they furnish the proteid and fat elements lacking in the grains. FIG. 4. THE OAT PLANT. FOODS AND FOOD MATERIALS 23 Beans and Peas. As beans, peas, lentils, and peanuts contain large quantities of starch and proteids, they are especially nourishing foods. More than one fifth of the substance of the bean is proteid, a larger proportion than is contained even in meat. Although they are not so easily digested as meat, they serve as an excel- lent substitute, and they are cheaper. Fruits and Vegetables. Although most fruits and vegetables contain little of the real food substances, they stimulate the appetite and thus give relish to the more substantial foods. They are composed largely of water, with a small amount of starch or sugar, flavoring matter which makes them pleasant to the taste, and also certain salts which aid digestion. Some of them, however, such as potatoes, beets, bananas, cocoanuts, and nuts, contain sufficient starch, proteid, sugar, or fat to be valuable as foods. Indeed, vege- tables and acid fruits seem to be needed by the body, as sailors or explorers, when deprived of them, suffer from scurvy and other diseases. Figure 5 represents a bit of potato magnified, showing the grains of starch. As the potato consists so largely of starch, it is a fuel food, and we should eat with it meat, milk, cheese, or Starch FIG. 5. A SMALL BIT OF POTATO. Highly magnified. Showing cells filled with grains of stareh. 24 PHYSIOLOGY AND HYGIENE some other food which will supply proteids for the building material which the potato lacks. We may eat freely of fruits if they are ripe and per- fectly sound, but unripe and overripe fruits are un- wholesome and injurious to health. OTHER MATERIALS NOT TRUE FOODS There are certain other substances which we eat or drink that are not true foods. Some of them are neces- sary to life, some of them are of use, others may be harmful. Let us see what some of these are. Water. The shipwrecked sailor who is cast ashore on a rocky island or drifts about in an open boat can live for many days without food, but without water he soon becomes almost crazed with thirst, and in a very few days he dies. Our blood, muscles, and vital organs all contain water. Without this necessary fluid, the foods eaten could not be dissolved and thus made ready for transformation into blood and muscle. The various other drinks, such as milk, soda water, tea, and coffee, allay thirst only because of the water they contain, and none of them is equal to water itself for this purpose. If we quench our thirst with water only, we are not so likely to drink too much as we are when we attempt to satisfy ourselves with liquids containing other material. When we drink something that has an especially pleasing taste, the pleasure of taste may iead us to drink more than is wise. Cool water is one of the most refreshing of drinks OD a hot day, but extremely cold water, if taken in large FOODS AND FOOD MATERIALS 25 quantities when the body is overheated, may produce a shock which is harmful. Ice water or other cold water should be drunk very slowly. After violent exercise in the hot sun, it is wise to wait for a few minutes before drinking cold water. Impurities in Water. It is not easy to find abso- lutely pure water. Some of the impurities in drinking water are harmless ; others are very injurious. Water sometimes contains certain minerals which it gets from the earth. These make the water "hard"; but though hard water sometimes produces slight bowel troubles, it is not especially harmful. The most dangerous impurities in water are minute living plants called bacteria. Some of these, as we shall notice in a later chapter, may produce disease, if they are taken into the body. One kind of bacteria, occa- sionally found in drinking water, gives rise to typhoid fever. It is impossible to judge either by the appear- ance or by the taste, whether water does or does not con- tain injurious bacteria. It may be perfectly clear and of the finest taste, and yet be unsafe to drink. Spring water is almost always pure, if the spring is deep and a good distance from any foul place, such as an open drain or a barnyard. The lakes and reservoirs from which cities obtain water are usually kept in good condition by the authorities ; if at any time the water becomes unfit to drink, people are advised to boil it. Wells, particularly if they are on a lower level than the houses or barns for which they supply water, are likely to contain injurious bacteria. These may either pass 26 PHYSIOLOGY AND HYGIENE down through the soil or drain into the wells from the surface. River water is usually unfit to drink, especially if there are towns or cities on the banks that allow sewage to pour into the stream. Such water can be made healthful only by boiling. The dangerous bac- teria are destroyed by heat. When typhoid fever pre- vails, it is always a wise precaution to boil the drinking water. Mineral Substances. Several mineral substances, called salts, are needed by the body in small amounts. Lime is required to make bone. We eat common salt with most of our food. Although salt neither builds up the body nor supplies fuel, it is absolutely necessary for health. Cattle will eat the grass grown on salt marshes, in spite of its coarseness, because they like the salty taste. Our ordinary food contains sufficient lime for bone material, as well as whatever other salts, aside from common salt, the body requires. Flavors. While we do not partake of food simply because we enjoy eating, still the different articles of diet give us a certain pleasure because of their various flavors, and indeed some flavor to our foods is neces- sary to enable us properly to digest them. The taste of puddings, cakes, pies, and similar dishes is due largely to certain substances added to give a desired flavor. The most common of these flavorings are lemon, vanilla, and spices. Tea and coffee are liked partly because of their pleasant taste, partly because of their slight stimulating effect. Young people are better off without them, and taken in excess they are FOODS AND FOOD MA1ERIALS 27 injurious to the nerves and the digestion of every one. Chocolate, in addition to having a fine flavor, contains real food. ALCOHOL Alcohol is a clear, transparent liquid, in appearance resembling water, but very different from water in its nature and effects. Although alcohol is found in smaller or larger quantities in various materials used for drinking purposes, it will neither quench thirst nor take the place of water in the body. Pure alcohol has a strong odor and an unpleasant taste. Although alcohol and water appear so much alike, we can test the difference : 1. By smelling them water is odorless, while alcohol has a pungent odor. 2. By pouring a few drops of alcohol and water into saucers and applying a lighted match the alco- hol burns. 3. By putting salt into water and also into alcohol- upon being FlG ' 6 -- Y ^ 8T - Highly magnified, shaken gently, the salt dissolves in the water, while in the alcohol it remains undissolved. Similar results are obtained if we sub- stitute sugar for salt. How Alcohol is made. Alcohol is made from sugar by a process called fermentation. The fermentation is brought about by a minute plant called yeast, to be seen only with the aid of a microscope. The common yeast which may be purchased at the grocery store con- PHYSIOLOGY AND HYGIENE Sugar Solution sists of many hundreds of thousands of these tiny plants (Fig. 6). If a bit of yeast is placed in a sirup made of water and sugar or molasses, the yeast grows, feeding on the sugar and very decidedly chang- ing in its nature. Bubbles of gas rise through the liquid in which the yeast is growing (Fig. 7). Besides this gas there is produced at the same time a certain amount of alcohol which re- mains in the liquid. When the sirup has become entirely fermented, the sugar has disappeared and alcohol has taken its place. It is not always necessary to add yeast in order to start fermentation. Grape juice is changed into wine and .Carbonic Dioxide, apple juice into cider without any yeast being put into them. But in these cases a ferment gets into the juice from the air. These air ferments Solution are - n rea }ity almost the same thing as the yeast from the store. Like yeast they are tiny plants, so small and FIG. 7. Sugar J J \ solution undergo- light that they are blown about in the air, and are soon ready to act upon sugary liquids if they fall into them. Fermented and Distilled Liquors. Many kinds of drinks are made by fermenting sweet liquids obtained from the juices of fruits, such as grapes and apples. Other drinks are made from corn, barley, and various Gas Alcohol 'left in ing fermentation by yeast. FOODS AND FOOD MATERIALS 29 grains by sprouting the grain, and thereby changing its starch to sugar, which is then soaked out with water. These sweet liquids are caused to ferment by the action of yeast, either added in a form similar to baker's yeast or carried into the liquids from the sur- face of the crushed fruits or from the air. The com- mon drinks made by fermenting sweet liquids are beer, ale, wine, and cider. All of these contain alcohol as soon as they begin to ferment. It is the alcohol in Whisky YIG. 8. Showing the proportion of alcohol and water in beer, wine, and whisky. these drinks that makes them harmful. The drinks that contain alcohol are usually called liquors. Those obtained by fermentation are called fermented liquors. One danger of their use is that they cultivate an appe- tite for stronger beverages. The amount of alcohol which they contain ranges from one fiftieth to one fifth of the total volume of the liquor. The rest of the material is principally water (Fig. 8). Certain drinks called distilled liquors are made from fermented mixtures. By the process known as distill- 30 PHYSIOLOGY AND HYGIENE ing, a part of the water is taken away, thus leaving a larger proportion of alcohol in the mixture. The strength of the liquor depends, of course, upon the amount of alcohol which remains. The proportion of alcohol in the distilled liquors used as drinks varies from one quarter to one half. The rest of the material, which is chiefly water with a little flavoring matter, contains nothing useful except the water itself. The distilled liquors include rum, whisky, gin, and brandy. Because of their large proportion of alcohol, such drinks are very harmful. A small amount of whisky will intoxicate much more quickly than a large amount of beer or ale. There is nothing in either fermented or distilled liquors that makes them necessary to any person in sound health. The boy or girl who wishes to be as vigorous, as useful, and as successful as possible should let them alone. Why People drink Alcohol. Although when taken in very small quantities alcohol acts as a fuel, its value in this respect is practically nothing. 1 A few cents' worth of bread will furnish more heat and muscular energy than a much larger sum of money spent for any form of alcoholic drink. Why, then, do people use alcoholic drinks ? Some use them under the mistaken idea that they give muscular power and make us stronger. They cer- 1 Although alcohol does thus act as a fuel, we should not for this reason class it with the fuel foods, like starches and sugars, since its general effect is to harm rather than to benefit the body. FOODS AND FOOD MATERIALS 31 tainly do not make us stronger ; their tendency is rather to make us weaker, and they do this very decidedly if any considerable amount is used. Sometimes they are used to quench thirst. But it is only the water they contain that quenches thirst, and water alone will do much better. Indeed, the alcoholic drinks tend to excite the thirst instead of quenching it, so that people wish soon to drink again. Some people enjoy the taste, although pure alcohol is unpleasant to the taste, and most beers and wines are disagreeable at first to the majority of people. Then there are those who enjoy the excitement which the alcohol produces, a dangerous enjoyment, since it may lead them to do foolish or wrong things. Some who have become accustomed to using alcoholic drinks find it difficult to overcome the habit. Here is one of the great dangers in using alcoholic liquors. All such drinks are apt to create an appetite for more and more alcohol. Many people who seem to be strong and capable of resisting the appetite, are finally mas- tered by it. No one is so safe from this danger as he who never begins to use alcoholic drinks. Intelligent people do not usually drink alcohol be- cause they consider it valuable as a food, and if they do, it is a mistaken idea. They drink it because they like the taste or the exhilaration it produces, or be- cause they cannot overcome the appetite for it. 32 PHYSIOLOGY AND HYGIENE AMOUNT OF FOOD NEEDED How much food we should eat is a question not easy to answer. The amount depends somewhat upon a person's occupation. If a locomotive is running fast, it needs more fuel than if it moves more slowly, and when it stops, it requires only sufficient coal to keep the fire burning. So long as we live, our bodies never entirely cease action, for the heart always continues to beat ; but at certain times we are more active than at others, and when we are hard at work, more food is required than when we rest. A poorly fed person can- not do hard work. If a man, from a false idea of econ- omy, subsists largely upon starchy foods, like potatoes and rice, he will be unable to do as much hard work as his neighbor whose diet contains more of the muscle- building materials. The man of small income should spend more of his money on beans or cheese, or per- haps on skimmed milk, as these will aid in supplying strength for muscular work. The using of the body substance for muscular strength can be tested with the aid of scales. If a boy be weighed carefully before taking active exercise for an hour or two, and again after the exercise, the scales will show a difference in his weight. If the weighing is accurate and the boy has taken neither food nor water between the two weighings, the scales show just how much of the body substance has been used up during the muscular action, and consequently how much food and water are required to replace the loss. FOODS AND FOOD MATERIALS COMPARATIVE FOOD VALUES The following table shows the food values which can be obtained for ten cents : COMPARATIVE COST OF DIFFERENT FOOD MATERIALS AT AVERAGE PRICES. Amounts for ten cents T>-5 rt rt Cost of Total Kind of Food Material .rrice per 1 pound pro- weight of food Proteid Fat Starch pound teidai material Cents Dollars Pounds Pounds Pounds Pounds, 25 1.60 0.40 0.06 0.06 _ Be6f round . ... 16 .87 .63 .11 .08 Mutton . . 16 1.10 .63 .09 .09 Pork . . . 18 1.30 .56 .08 .18 Pork-fat, salt .... 12 6.67 .83 .02 .68 _ Butter 25 25.00 .40 _ .32 _ Eggs, 24^ a doz. . . 16 1.39 .63 .07 .06 - Cheese 16 .64 .63 .16 .20 .02 Milk, 6^ a qt 3 .94 3.33 .11 .13 .17 Wheat flour 3 .31 3.33 .32 .03 2.45 Corn meal, granular . . 2| .32 4.00 .31 .07 2.96- Wheat breakfast food . . H .73 1.33 .13 .02 .93 Oatmeal . . 4 .29 2.50 .34 .16 1.66 Rice 8 1.18 1.25 .08 .97 Wheat bread 5 .64 2.00 .16 .02 1.04 iieans, white dried . . 5 .29 2.00 .35 .03 1.16 Corn, canned .... 10 4.21 1.00 .02 .01 .18 Potatoes, 60 ^ a bush. . . 1 .67 10.00 .15 .01 1.40 1 The cost of one pound of proteids means the cost of enough of the given material to furnish one pound of proteids, without regard to the amounts of other food substances present. .34 PHYSIOLOGY AND HYGIENE Proteids Fats Garbo- \ hydratesl This table shows the comparative amount of the dif- ferent food materials which can be purchased for ten -cents. It shows that beans give the most proteid for .the money and oysters the least. FOODS A^D FOOD MATERIALS 35 Potatoes | cm **f* fat, Water This table shows the amount of the different food materials contained in the different foods. From this it will be seen that cheese is the most nutritious food. Beef is also very nutritious, but its high price makes it an expensive food, as is shown by the table on page 34. 36 PHYSIOLOGY AND HYGIENE QUESTIONS 1. For what purposes do we need food? 2. What are the two classes of foods? 3. In what respect is meat a valuable food ? 4. Why are beans especially useful as foods? 5. If we drink skimmed milk, what food will go well with it ? 6. Of what use to the body are starch, sugars, and fats ? 7. With what does albumen furnish the body? 8. Why is milk made more healthful by boiling? 9. Why do people buy porterhouse instead of round steak? 10. What food substances do we get from cereals? 11. Why are potatoes so widely used as foods? 12. Which would be the best meal : one made up of potatoes and rice, or one of potatoes and beans ? 13. Why are not potatoes alone a good diet? What kind of food should we eat with them ? 14. W T hat is the chief use of fruits and vegetables ? 15. Why do we need to drink water? 16. How can impure water be made fit for drinking? 17. What does alcohol look like ? How is it made ? 18. Why should people abstain from the use of alcoholic drinks? 19. Why do people use alcoholic drinks? 20. What food do we get from cheese ? What does this food do for the body ? 21. If you had one dollar to spend for a meal for four persons, what would you buy to make the most useful meal? (Consult tables on pp. 33-35.) CHAPTER II DIGESTION BEFORE the bread and butter which we eat for breakfast becomes the blood and later the muscle of our body it meets with a number of changes. The process by which the food taken into the body is changed so that it can be absorbed into the blood, and thus be used for growth, repair, and warmth, is called digestion. Certain organs of our body have charge of this work and are called the digestive organs. THE MOUTH The food is received into the mouth, where the first step is taken in preparing it to enter the blood. The mouth is a large cavity with the cheeks for its sides, the tongue for a floor, and the palate for a roof. The front part of the palate is a hard, flat bone. The back part is a soft membrane, with a little finger-like piece called the uvula hanging from the middle and reaching almost to the tongue. (See Fig. 10.) The Teeth. Around the sides and front of the mouth are two rows of teeth fastened securely in sockets in the jawbones. The front teeth have sharp edges for cutting or biting food, while those farther back 38 PHYSIOLOGY AND HYGIENE in the mouth have broader surfaces and are used for grinding or chewing the food into a fine mass. Each tooth consists of a crown, the part we see as we look into the mouth; a neck, which is surrounded by the gums; and a root, which fits into the socket in the jaw- bone. Each tooth has a tiny blood vessel entering through its root, and is also supplied with a nerve. When the nerve is exposed to the air as a result of decay, the tooth may ache. The crown of the tooth is covered with enamel, the hardest substance in the body. Growth of the Teeth. In the course of life we have two sets of teeth. The first, or temporary teeth, begin to grow when the child is five or six months old, and they con- tinue to appear, one after another, for about three years. The temporary teeth are twenty in number. When the child is about six years of age, the second, or perma- nent teeth, begin to push their way through the gums ; the milk teeth are gradually loosened as the others push their way out. The first of the permanent teeth, called the " six-year molars," come so early that they are often mistaken for the last of the milk teeth. The permanent teeth are thirty-two in number. Figure 9 shows the permanent teeth. Their arrange- ment, as can be readily seen from the figure, is as follows, beginning at the middle of the upper set: two incisors, one canine, two bicuspids, and three molars. The other side of the upper row is similarly arranged, and the lower jaw holds sixteen teeth to match these, with names corresponding. Notice the sharp edges of the front teeth and the broad grinding surfaces of the DIGESTION FIG. 9. THE UPPER TEETH. double teeth farther back; also the six-year molars. If you shut your teeth tightly together, you will appre- ciate how well the upper and lower teeth match. The edges of the upper front teeth slip over those of the corresponding lower teeth, so that the food may be bitten off as if cut by scissors. >v( *s-~3T\, ^\ HFsH./ The projections of- the upper back teeth are opposite the hollows of the corresponding lower ones, so that the food may be ground fine without difficulty. Care of the Teeth. The teeth, when once they are fully grown, will never repair themselves. If -A bone of the arm is broken, the two edges can be set in the proper position, and the bone will knit, or grew to- gether again. If, on the other hand, a tooth is broken off or worn out, it will never repair itself. Teeth are liable to decay. The outside of the tooth, che enamel, is hard, but the inside is comparatively soft. As long as the enamel is in perfect condition, the tooth will remain sound, but if there is a crack in the enamel, decay is likely to start at the crack and enter the soft part inside. The tooth then decays rapidly until it is ruined. Even a very small hole in the enamel may result in a large cavity in the softer sub- 40 PHYSIOLOGY AND HYGIENE stance within. We should never pick the teeth with anything hard, such as needles or pins, because these are liable to scratch, and so crack, the enamel. For the same reason we should not crack nuts or other hard substances with the teeth. It is also harmful to the teeth to take extremely hot and cold foods or drinks in close succession. Particles of food lodged between the teeth become decayed and help to decay the teeth in turn. It is well, therefore, to brush the teeth after each meal, and also at night, so as to remove any bits of food that might do injury if allowed to remain. To keep the teeth healthy and sound, it is necessary, in addition to brushing them, to re- move, with a soft toothpick or thread, all bits of food which cling to them. When a tooth begins to decay, it should be at- tended to at once by a den- tist ; for if the small cavities are promptly filled, the tooth may perhaps be preserved for years, and much pain and expense be saved. Uvula Pillars of Fauces Ton*//* - FIG. 10, THE MOUTH. Showing the opening into the throat. DIGESTION 41 Figure 10 shows the open mouth as it appears when we look within. Notice the palate and the uvula. By placing the tip of the tongue on the roof of the mouth just inside the upper teeth arid drawing the tongue slowly backward over the roof of the mouth, we can discover the difference between the hard and soft portions of the palate. Salivary Glands. If some one says the word "lemon," our mouths are apt to water, as we think how sour the juice of the lemon is. The fluid which moistens the mouth, and whose flow is thus increased by the aid of the imagination, comes from the organs known as the salivary glands. The liquid produced is called saliva. There are three pairs of salivary glands. Those who have had the mumps can locate one of these pairs of glands without difficulty. These are the parotid glands, which are inflamed and swollen in that painful disease. They are situated just below and a little in front of the ears. There are two sali- Safivory Gland* FIG. 11. A DIAGRAM OF THE SIDE OP THE FACE. Showing the position of the salivary glands and their ducts. 42 PHYSIOLOGY AND HYGIENE vary glands under the lower jaw and two more beneath the tongue. All these glands are connected with the mouth by little tubes, called ducts, which carry the saliva from the glands into the mouth. The saliva is poured out of the tubes whenever it is needed. Although the salivary glands are constantly sending out enough saliva to keep the mouth moist, the act of chewing stimulates the action of the glands so that the amount is largely increased. Figure 11 shows the salivary glands on one side of the face, also the ducts that connect them with the mouth. FOOD IN THE MOUTH AND THROAT Need of Mastication. After we have taken a bite of bread and butter, the first step towards its digestion is chewing or mastication. We chew our food to break it into small pieces so that the saliva may become thoroughly mixed with the food, and also that the di- gestive juices may afterwards do their work easily. The digestive juices in the stomach can act only on the outside of each piece of meat, and therefore the smaller the pieces, the shorter the time required to digest them. Many a person suffers from dyspepsia as a result of the foolish habit of swallowing his food partly chewed. Rapid eating is injurious, since it forces the stomach to do work that belongs to the teeth. Very solid foods, like nuts or hard-boiled eggs, can be digested properly only after they are thoroughly chewed. Some foods, such as oatmeal and mushes of different kinds, do not DIGESTION 43 need much mastication, but solid food should not be swallowed until it is ground into a fine pulp. Use of Saliva. While the food is being chewed it is moistened by the saliva that is poured into the mouth. The saliva serves two different purposes. 1. Saliva moistens the food and the mouth. If the mouth becomes dry, for any reason, we are very uncom- fortable, and even talking is difficult. Sometimes, if we are frightened, the glands stop producing saliva entirely, and as a result we find it difficult to swallow. How impossible it is to swallow food that is not thoroughly moist may be comprehended by eating a cracker. 2. Saliva begins the process of digestion. The water in the saliva dissolves some of the foods, like sugar, but this is not digestion proper. If, however, we chew a bit of bread for a few minutes, we find that it becomes a trifle sweet. The saliva changes the starch into sugar. The change begins as soon as the food is mixed with the saliva. It is the beginning of real digestion, although ordinarily the starch does not remain in the mouth long enough for much of it to be thus acted upon. If the food is acid (sour), as when it is mixed with vinegar, no change takes place in the mouth. The amount of saliva in the mouth may be increased by chewing gum. In the case of an athlete who wishes to keep his mouth moist during exercise, gum chewing may be useful. Under ordinary circumstances, how- ever, not only is the habit vulgar and impolite to the people about us, but the constantly stimulated action of the salivary glands is probably injurious. 44 PHYSIOLOGY AND HYGIENE Tonsils. At the back of the mouth, as may be seen in Figure 10, there is a large opening leading to the throat. As soon as the food is chewed and moistened it is pushed back by the tongue through this opening. At each side of the opening may be seen a small rounded body called a tonsil. Sometimes when a per- son has taken cold, the ton- sils become swollen, and a kind of sore throat called tonsilitis re- sults. It is not known whether the tonsils have a special use or not. The Throat. A cavity, called the throat, is situ- ated just back of the mouth. Into this the food passes after being chewed. The upper part of the throat opens into the nasal cavity, and from there, by way of the nostrils, to the exterior. Thus both the mouth FIG. 12. A SECTION THROUGH THE HEAD. Showing the relation of mouth, throat, etc. DIGESTION 45 and the nostrils are connected directly with the throat. Figure 12 shows this relation. Two large tubes open downward from the throat. One, the gullet or oesophagus, extends to the stomach ; the other, the windpipe or trachea, connects with the lungs. The windpipe is placed in front of the oesopha- gus, and it opens at the top, so that the air we breathe may pass into it readily. The opening is the glottis. If a particle of food drops into the windpipe, it causes violent coughing and sometimes choking. To keep food from entering the windpipe as it passes over the entrance on the way to the gullet, the wind- pipe is provided with an elastic lid, somewhat like soft India rubber, which rests upon the opening. When we are breathing, this lid, which is called the epiglottis, is lifted as in the illustration (Fig. 12); but as food passes from the mouth, the lid closes for the moment so as completely to cover the opening into the windpipe and allow the food to slip safely over. As soon as the food has passed, the lid flies up again, and the windpipe is open once more, ready for its regular work of carrying air to the lungs. If we talk or laugh while our mouths are full of food, or while we are drinking, a bit of the food or water is liable to "go down the wrong way" ; that is, we may have the epiglottis open for a breath just at the moment the food or water ought to pass over to the oesophagus. Some of it then drops into the windpipe instead of slip- ping over the top, and violent coughing results, until the foreign matter is coughed out. 46 PHYSIOLOGY AND HYGIENE Figure 12 shows a section of the head, indicating the shape of the throat and the openings into the mouth and nose, with the location of the windpipe and oesophagus. Notice the epiglottis at the top of the windpipe. Sore Throat. Any soreness of the tonsils, the palate, or the throat makes swallowing painful, and we say we have a sore throat. Sore throat, especially in the case of children, should receive immediate attention. If a child feels any soreness when swallowing, his throat should be examined, and if there are whitish spots on the palate or the tonsils, a physician should be called at once, as the trouble may be serious. Swallowing. After the food reaches the throat it is rapidly swallowed. While food remains in the mouth we can control it, but the moment it enters the oesopha- gus it has passed beyond our control. If we should then discover that it was poison, we should be obliged to keep on swallowing just the same. The food is pushed through the oesophagus into the stomach by the muscles of the throat and oesophagus. It does not simply fall, but it is actually forced down. A person can swallow water even when he is standing on his head, and a horsey when he drinks, of course swallows the water upward. FOOD IN THE STOMACH The Stomach. A few seconds after the food has entered the oesophagus it passes into a large cavity called the stomach (see Figs. 13 and 15). This is a chamber similar to a gourd in shape, lying just below the ribs and a little to the left side of the body. It is closed at DIGESTION 47 both ends by small folds or valves. The valve between the oesophagus and the stomach ordinarily prevents the food from going back into the oesophagus. Sometimes, however, when ill- ness causes us to vomit or " throw up, the valve be- tween the stomach and the oesophagus opens and allows the food to return to the mouth. The valve at the lower end, which con- nects with the tube called the intestine, prevents the food from leaving the stomach too soon. Figure 13 shows the stomach with its valves. The stomach itself is elastic, and will stretch so as to hold a large amount of food, but it shrinks again as soon as the food passes out. The stomach of an ordinary grown-up person can hold three pints of food very comfortably. FIG. 13. THE DIGESTIVE ORGANS OP THE ABDOMEN. 48 PHYSIOLOGY AND HYGIENE The outer walls of the stomach consist principally of muscular fibers which run around it in various directions, some crosswise, some lengthwise, and some obliquely. As these fibers contract and relax, they cause the stomach to undergo a variety of motions, which mix together the different foods inside and keep them moving around and around. As long as the food remains in the stomach it is thus kept in constant motion. The inner lining of the stomach contains hundreds Inner Surface of Stomach Gastric Glands Muscles Muscles Fia. 14. A SECTION OF THE WALL OF THE STOMACH. Highly magnified. of thousands of tiny glands. Each of these glands is shaped somewhat like a little bottle, with its mouth opening into the stomach, as shown in Figure 14. The DIGESTION 49 glands produce a liquid called gastric juice, which is poured out of their mouths into the stomach. Action of the Gastric Juice. As soon as the food enters the stomach, the glands begin to pour gastric juice upon it. At the same time the stomach, by con- tracting, begins to churn the food, and mix it with the gastric juice. In a short time the two are com- pletely mixed, so that the gastric juice can begin to act upon the food and produce in it the changes that we call digestion. Action on Starch. When we chewed our mouthful of bread until it turned sweet, we found that the saliva had changed some of the starch in the bread to sugar. This digestive action of the saliva upon the starch is stopped as soon as the gastric juice begins to- work upon the food. This is because the gastric juice is an acid, and we have already learned that the presence, of anything sour prevents the action of the saliva upon starch. The starch, then, is not digested in the stomach, but it will be taken care of farther on. Action on Meats. A portion of the work of the gas- tric juice is to break the food into small parts. Meat is made up of a great number of tiny threads, called muscle fibers, which are glued together by a material that holds them in little bundles. The gastric juice dissolves this gluey material, and the fibers fall apart. Just as soon as the juice gets them separated it pro- ceeds to act upon each one separately, changing it to a liquid form ready for the blood to take up, or r as we say, digesting it. We have noticed (see Fig. 2)> 50 PHYSIOLOGY AND HYGIENE -Oesophagus \ .Stomach Westine that the fat is in little sacs held together by a connect- ing mass of threads. Both the sacs and the threads are dissolved by the gastric juice, so that the fat floats about freely in the stomach. Action on Proteids. It is also a portion of the work of the gastric juice to get the proteids ready for the blood to use as the building material of the body. We found, when we cooked the albumen of the egg and when we caught the glu- ten of flour in muslin cloth, that these proteids could not be dissolved in water. But, until these substances are in liquid form, they cannot be taken up by the blood. What the gastric juice does for the proteids is to change them in such a way as to make it possible for them to dissolve in the water that is in the stomach. After the gastric juice has done its work, a part of these glutens, albumens, and caseins become dissolved and are ready to enter the blood. Usually a part of the proteid food leaves the stomach undissolved and is changed to a liquid form later. FIG. 15. SHOWING THE LOCATION OF THE DIGESTIVE ORGANS. DIGESTION 51 Action on Milk. After a hearty meal a baby often throws up a part of his milk in a curdled condition. This does not mean that the stomach is "sour," but simply that the child has overfilled his stomach. The milk ought to be curdled in the stomach, and if it did not curdle, it would mean that the stomach was out of order. The curdling has been caused by the gastric juice. The gastric juice in a baby's stomach curdles the milk more readily than that in the stomach of a grown person, but under all circumstances curdling is the first step in the healthful digestion of the milk. The curdled milk looks exactly as if it had soured. We can see just how the curdling takes place by put- ting a teaspoonful of rennet or a rennet tablet (to be had at the druggist's) into a cup of milk warmed to about the temperature of the body (98). In the course of half an hour the milk will be curdled. Notice that the curd, which is casein, is a solid mass. In the stomach this curd is later dissolved again. Chyme. We swallow our food in the form of solid meat, solid bread, and liquid milk, and in a short time, from an hour and a half to three hours, it becomes quite changed. It is now a thick liquid. The fats, freed from their sacs, as we have seen, have been melted by the heat of the body; the meat has been divided into threads and partly dissolved; the sugars have been dissolved in the water; some of the starches have been turned to sugar and also dissolved; while the milk has been curdled and partly turned to liquid form again. These materials have been churned by the motions of 52 PHYSIOLOGY AND HYGIENE the stomach until they are thoroughly mixed together. They now form a gray, slimy mass called chyme. Although we pay no attention to the matter and think little about it, our hearts continue their accus- tomed beating, hour after hour and day after day. And so it is with the stomach's work. We do nothing to supply the materials required by the body except to eat when we are hungry, and yet the wonderful work of digestion goes on, usually without inconvenience to us. A Few Good Rules. Though we cannot do much to help the stomach in the churning and digesting process, we may assist it by our manner of eating our food. If we are too thoughtless of the rights of the stomach, we are certain to receive our just punishment sooner or later in the form of indigestion and dyspepsia. We can aid the stomach and preserve our own health by following a few simple rules. We should eat slowly and be sure that the food is well chewed before it is swallowed. The habit of eat- ing often between meals is very trying to the stomach, since it keeps the gastric glands in constant action. We should never eat a hearty meal when we are either very tired or very warm; it is wise to rest first. No hard work, either mental or physical, should be entered upon for at least half an hour after a hearty meal. This is the stomach's busiest time ; we should help it as much as possible by keeping the rest of the body quiet. We should be careful as to the quantity of water that we drink with our meals. Some water is required, but DIGESTION 53 the food should never be "washed down" with water. Nor is it well to drink much water immediately before a meal. Ice-water, if drunk at all, should be sipped slowly, so that as it passes down through the throat, it may be warmed more nearly to the temperature of the stomach. FOOD IN THE INTESTINES After the food has spent from one to two hours turn- ing around and around in the stomach, the fold forming the valve or lid to the intestine opens and allows a small amount to pass out. The contents of the stomach thus from time to time pass into the intestines, until, at the end of three or four hours, the outlet relaxes and allows the remaining food to leave the stomach, even though some of the particles may still be quite solid. The stomach is now empty, and, after a rest, is ready for the next meal. The Intestines. The food which has passed through the opening at the lower and smaller end of the stomach enters the intestines, more commonly called the bowels. The intestines consist of a long tube, very much coiled, filling the larger part of the abdomen below the stom- ach, as is shown by Figures 13 and 15. The part which is connected with the stomach, or the small intestine, is from one to two inches in diameter, and about twenty feet long. The large intestine is about two and one half inches in diameter and five feet long. The Liver. We all have seen the liver of the ox or calf either exposed for sale at the market or on the breakfast table cooked with bacon. The human liver 54 PHYSIOLOGY AND HYGIENE resembles the ox liver very closely. It is of a dark red color, and lies a little above and at the right of the stomach. It is one of the largest organs in the body, weighing several pounds, and it is one of the most important. It produces a liquid called bile. The bile passes through a tube and empties into the intes- tines near the stomach. When digestion is not going on, the bile collects in a little sac at the lower side of the liver, known as the gall bladder. Figure 13 shows the liver, the gall bladder, and its tube or duct. The Pancreas. The pancreas is a long, somewhat thin gland, placed just below the stomach. This also produces a liquid secretion which passes through a tube and empties into the intestines. This liquid, which is called the pancreatic fluid, empties into the intestines with the bile. Thus the food from the stomach is mixed with the bile from the liver and the fluid from the pancreas almost as soon as it enters the intes- tines. Notice the pancreas, with its duct, as shown in Figure 13. Use of the Liver. Probably most of us know from experience how a person looks and feels when he is "bilious." The skin becomes a dull yellow, the eyes lose their sparkle, and the person seems to lose all his ambition without being sufficiently ill to be con- fined to his bed. The trouble is that the bile has ceased to pass freely from the liver. The bile aids the pancreatic fluid in its work of digestion, especially on fats, tends to prevent decomposition in the contents of the intestines, and aids in the regularity of the action DIGESTION 55 of the bowels. But the bile is, however, chiefly a waste product, and it pours into the intestines partly as a way of disposing of itself. The liver has several functions to perform ; one of the most important is to help to remove this waste material. When, for any reason, the bile cannot thus escape into the intestines, it passes back into the blood in the liver, and is then carried to all parts of the body, producing illness and turning the skin to a peculiar yellow. We then say we are bilious. Changes in the Intestines. As soon as the food enters the intestines it is mixed with the secretions from the liver and pancreas. Further changes are at once pro- duced in the food, principally by the pancreatic fluid. The pancreatic juice acts upon all kinds of food in such a way as to make liquid those not already dissolved. Starch. We have learned that most of the starch escapes from the mouth without being turned into* sugar by the saliva and passes into the stomach and out again to the intestines, still in the form of starch. But the pancreatic juice has just the same effect on starch as has saliva it turns the starch to sugar. The pancreatic juice takes up and completes this work of changing starch into sugar. The sugar is then dis- solved like all of the other food. Proteids. The pancreatic juice has the same effect upon the proteids as the gastric juice. It changes into a soluble form any proteids that may have passed into the intestines in solid state, whether they be the lean part of meat, the gluten of the wheat, or the casein of milk. The food in the intestines becomes more and more liquid. 56 PHYSIOLOGY AND HYGIENE Fats. The last we knew of the fats they formed an oily mixture in the stomach, where the gastric juices could not act upon them. When they pass into the intestines the pancreatic juice begins to digest them. We have already seen that when we shake olive oil with water, the water separates the oil into minute drops that float, making the liquid look milky. In a somewhat similar way the pancreatic juice acts upon the fats as they pass along the intestines. It breaks the fat into millions of tiny drops which are mixed with the contents of the intestines, giving the whole mass a milky white appearance. The breaking up of the fat into drops is the digestion of fat. The fat is not actu- ally dissolved like the sugar, but when it is broken up in this way the particles of fat are small enough to pass into the blood. Chyle. The food was swallowed as solid bread, meat, and potatoes, but now, after from two to four hours or more, it has become in the intestines a milk- white liquid, somewhat thicker than milk, but not so thick as molasses. It is called chyle, and it contains most of the foods, dissolved into liquid form. The food is now ready to be absorbed into the blood vessels. THE DIGESTIBILITY OF FOODS If our food were not digested, it would be of no more use to us than stones, for it could not be taken into the blood. People who have weak digestive organs suffer from lack of food, no matter how much they eat. For this reason the value of the food we eat depends as DIGESTION 57 much upon whether it is easily digested as upon the food substances that it contains. Cheese, for example, contains a very large amount of valuable food, but it is so hard to digest that it is less useful than meat, which, although it contains less food than cheese, digests more easily. Beans are in some respects a more nourishing food than meat, but as they do not digest so easily, much of their value may be lost, passing away in the waste. In choosing what we shall eat we should be careful not to load the stomach with food hard to digest. Although it is perfectly safe, if we are strong and well, to eat some foods that do not digest easily, we should not do so frequently. The following table will give us a little idea of some of the more easily digested foods and some of those less easily digested : FOODS EASY TO DIGEST FOODS DIFFICULT TO DIGEST Milk Bread Rice Raw oysters Soft-boiled eggs Boiled beef Mutton Boiled chicken Broiled meats Fried foods Beans and peas Hard-boiled eggs Pork Veal Cheese Boiled or broiled foods are, in general, more quickly digested than those that are roasted, because boiling 58 PHYSIOLOGY AND HYGIENE softens the solid foods so that the digestive fluids can act upon them. Fried foods are more difficult to digest than the same foods cooked in any other way, since the frying is apt to soak the food with fat, which makes it difficult for the digestive juices to act. HOW THE FOOD GETS INTO THE BLOOD All this process has not yet put the food where it can be used to build up, repair, warm, and provide muscular power for the body. We are now ready for the final chapter of our story how the digested food gets into the blood. We have learned that by the time the food has been in the intestines from two to four hours it has all become digested and turned into chyle. The long in- testinal tube which holds the chyle, is not loose in the body, bat is held in position by a thin sheet. Suchasheet is called a mem- brane, and this par- ticular one is the mesentery. It is folded many times and is wrapped around the intestines as shown in Figure 16. There are many blood vessels in the mesentery, blood Vessels Lacttals or Intes FIG. 16. A BIT OF THE INTESTINE. Showing how it is held in position by the mesentery. DIGESTION 59 some of them carrying blood to the intestines, and others carrying the same blood away again. These blood vessels take away a large part of the digested food. A bit of the intestinal wall is shown in Figure 17. The wall is rather thick and has two layers of muscleSo Villi Glands FIG. 17. A BIT OF THE INTESTINE. Showing the muscles, glands, and the numerous villi on its under surface. Moderately magnified. The inside surface is covered with tiny projections, like little fingers, extending inward. They are called villi. Figure 17 shows some of the villi enlarged, so that we may see what they are like. Villi are really so very tiny that they can only just be seen with the naked eye. There are millions of them, so many that they line the whole inside of the intestines, giving it a soft, velvety surface. Duties of the Villi. The villi are very interesting to study, for they take the digested food out of the intes- tines and give it to the blood. Unlike the glands of 60 PHYSIOLOGY AND HYGIENE vthelium Wood Vessel the stomach, of which we have learned, these villi have no opening into the intestines. Their walls, however, are so thin and so delicate that the dissolved food can pass through them readily. A single one of these little bodies, much magnified, is shown in Figure 18. It is covered on the outside with tiny cells, which form the epithelium. Inside there are a great many minute blood vessels. One blood vessel, the artery, brings blood into the villus, and another, the vein, takes it away. The artery brings the blood from the heart; the vein carries it away to the liver. Just how the villi take the food and send it where it belongs is a particularly interesting chapter in our story of digestion. The white chyle moving along the intestines bathes the villi as it passes. Each little villus is constantly at work taking the digested food from the chyle as it comes along, leaving the undigested and waste matters. The dissolved sugars and albumens pass through the thin A Cell -Artery Vessel ;tecl FIG, 18. A SINGLE VILLUS. Highly magnified. DIGESTION 61 membrane into the inside of the villus. Even the par- ticles of fat are seized and passed into the inside. Thus as the food passes on through the intestines, more and more of it is taken up by villi, until most of the useful part has been removed- The way in which this food is taken into the intestines is illustrated in Figure 19. A bladder is tied tightly upon a tube and filled with water, and the whole is then lowered into a dish containing some sugar dissolved in water. It will be found after a little time that the water inside of the bladder has become sweet. The sugar has passed from the dish into the bladder. In much the same way the sugars and other foods pass from the intestines into the villi. After the food gets into the villi it does not all go in the same direction. The sugars, proteids, water, and salt are taken out of the villi by their tiny blood vessels and are carried away in the blood to the liver. Of course the starch has already been turned to sugar by the digestive processes, so that all the foods go to the liver, except the fat. FIG. 19. A simple device for show- ing how foods may pass through membranes, as they do when they enter the villus. 62 PHYSIOLOGY AND HYGIENE The fat takes a different direction. It does not enter the blood vessels of the villi at all. The middle of the villus, as shown in Figure 18, is a clear space called a lymph vessel or lacteal. This opening or tube is made to receive the fat, and the little drops of fat pass directly into it. The vessels are called lacteals, which means milk holders, because the liquid fat with which they are filled is white like milk. After taking the fat from the intestines the lymph vessels empty it into larger, similar vessels and these empty into still larger ones which pass through the sheet of membrane sur- rounding the intestines. The large lacteals pass up through the chest, back of the heart, and empty the fat into one of the large blood vessels in the neck, so that all of the absorbed food material finally reaches the blood. There are thus in the membrane shown in Figure 16 three sets of tubes : 1. Blood vessels bringing blood to the intestines. 2. Other blood vessels carrying the blood which has taken up food, from the intestines to the liver. 3. Lacteals carrying fat to the blood vessels in the neck. UNDIGESTED PORTIONS OF THE FOOD We have learned that the food passes from the stomach through the intestines. The material is kept moving by a contraction of the wall of the intestines. This contraction causes a gentle writhing motion of the intestines, which forces the food slowly along. The movement is somewhat similar to the wriggling of an earthworm as it tries to make its way along the surface of the ground. As the food mass passes on, DIGESTION 68 the villi take up more and more of what can serve the body as real food, together with much of the water. Finally, very little is left in the intestines except undi- gested refuse, together with excretions, like bile, which are of no further use. These are waste materials. As more and more of the water and dissolved food are absorbed, the waste materials become quite solid, until they pass out of the body. The bowels should get rid of the waste material every day. Regular habits in this respect are necessary for avoidance of discomfort and of sickness. Now the story of food digestion is nearly completed. Let us recall briefly the history of our piece of bread and butter. It was carried to the mouth, and was bitten off and chewed by the teeth. With the aid of the saliva it was moistened and then swallowed. After a safe passage over the windpipe, the oesophagus carried it to the stomach. There it was thoroughly churned and mixed with gastric juice. Little by little it passed from the stomach into the intestines, was mingled with the bile and pancreatic juice, and then the digested part was taken up by the villi, leaving the waste materials to be discarded. As we shall see later, the food material finally reaches through the blood all the parts of the body which need it for growth or work. 64 PHYSIOLOGY AND HYGIENE QUESTIONS 1. What is meant by digestion ? 2. Why is it necessary to digest food ? 3. What are the parts of the mouth? 4. Of what parts does a tooth consist ? 5. How many permanent teeth are there? What are their names? 6. What causes a tooth to decay? 7. What and where are the salivary glands? 8. What are the uses of saliva ? 9. What prevents food from passing into the windpipe instead of the oesophagus? 10. How does the stomach digest the food? 11. What is the action of the gastric juices on meats? On proteids? On milk? 12. What is chyme? 13. What are the liver and the pancreas? 14. Of what use is the liver ? 15. What changes are made in starch, proteids, and fats in the intestines? 16. What is chyle? 17. How does the food get into the blood? 18. If you chew finely a piece of meat, does saliva start its digestion ? How would it be with bread ? 19. Notice your method of swallowing, and see if you use your tongue. 20. What part of a lunch of bread and butter is digested in the mouth ? What in the stomach ? What in the intestines ? 21. Since cheese is made of milk, why is it not a good food for babies ? CHAPTER III FOOD HABITS AND COOKING Unwise habits with regard to eating and drinking- are probably the cause of more sickness than anything* else. Indigestion, which is very common, may fre- quently be remedied more easily by changing the habits of eating and drinking than by taking medicine. PROPER HABITS OF EATING Suppose a company of boys from different parts of the world should come together for a picnic. Their- lunch baskets would contain a good variety of what the owners would consider delicacies. The American boy would probably have sandwiches and cake; the German,, rye bread and sausages; the Chinese, some form of rice; the young Eskimo, a fish or a piece of seal. Each boy would be well nourished and satisfied, if only he had_ enough of his own kind of food. In other words, just what we eat is largely a matter of custom and climate. We are mistaken if we think we must have certain kinds of food, for we can adapt ourselves to almost anything, provided it is nutritious and digestible. We have a very large variety of foods from which to choose, but it is wise to adapt the appetite to< C5 66 PHYSIOLOGY AND HYGIENE what is conveniently obtained. We should particularly guard against allowing ourselves to be controlled wholly by taste, and we should not refuse to eat what is whole- some just because we fancy it is not quite to our liking. Substances with very strong taste, like mustard, for in- stance, we may properly refuse whenever they are dis- tasteful, but there is no sensible reason for objecting to a dish of oatmeal; we can eat it, and learn to like it, if we will. C 0s t. People with small incomes are likely to live principally upon starchy foods, such as bread, rice, or potatoes, because these are comparatively cheap. But we cannot live upon starch and sugar alone. We must all of us have some proteids. If we will remember that we can get our proteids cheapest in beans and cheese, we shall be able to make better use of our money than by spending it all for starchy foods. A simple meal of bread, butter, milk, cheese or meat, and some vege- tables, with perhaps a dessert of fruit or a simple pud- ding, is far better than a heavy dinner, with numerous courses. Some people make the mistake of having too many kinds of food at one meal, many of them highly seasoned. The pleasurable taste encourages us to eat more than the body requires, and the result is frequently a loss of healthy appetite. The man who spends a great deal of money for his food usually gets less pleasure from it than the one who lives upon plain foods varied by an occasional luxury. Times for Eating. Most people in this country eat three meals a day. In some countries four or five FOOD HABITS AND COOKING 67 meals are the rule, in others only two or even one. Whatever our habit in this regard, we should eat at certain specified times, so that the stomach may be called upon to work regularly, and may also have a chance to rest. We frequently hear that candy is injurious, although we have learned that sugar is a useful food. The trouble is not with the candy, but with our abuse of it. If we have sweets in our possession, we are apt to be munch- ing them all day long, keeping the stomach constantly at work. Moreover, the pleasant taste of the candy is likely to make us eat too much, so that we suffer from overeating. Some people, especially children, like to be eating all the time. This is very unjust to the stomach. Continuous good health is impossible unless the stomach and other digestive organs are given regular times to rest as well as to work. Although breakfast is an important meal, it need not be a heavy one. Nor, on the other hand, ought we to make too light a meal of it. This error often leads to headache, faintness, and weakness before the noon meal. Fruit, oatmeal or some other cereal, and eggs, with bread, form an excellent breakfast. There is no better drink to go with it than water. Milk, chocolate or cocoa may also be taken, but we should remember that they are foods as well as drinks. The heartiest meal should be in the middle or at the close of the day, and should be followed by rest of at least an hour. A little food before going to sleep at night helps some to rest easily. A glass of hot milk taken just before a person 68 PHYSIOLOGY AND HYGIENE retires is frequently an excellent remedy for habitual wakefulness. The Appetite as a Guide. When we are in need of food we feel hungry, and when we need water we are thirsty. Hunger and thirst are, then, the guides given us by nature to indicate the want of food and water. If we treat them wisely, they guide us well, so long as we are in good health. But these appetites may be abused so that we cannot follow them safely. Some people, especially children, continue to eat anything that they happen to like particularly, even after their desire for food is gone, and they keep on drinking pleasant tasting liquids after the thirst is quenched. This is almost sure to do injury. We should eat to satisfy the desire for food. One who continues eating after the body has taken suffi- cient nourishment is both foolish and intemperate. Overindulgence in eating is probably one of the most common causes of ill health. It is always wise to stop eating as soon as the food ceases to be relished as much as it was when the meal began, instead of continuing to eat until there is a feeling of fullness in the stom- ach. If we make this a habit, we are not likely to suffer either from eating too little or from eating too much. Pleasure in Eating. The old proverb, " Laugh and grow fat," is a saying with sound sense behind it. Good temper and merriment certainly aid digestion. Mealtimes should be among the pleasantest occasions of the day. There is no reason why we should not FOOD HABITS AND COOKING 69 enjoy partaking of the food, as well as take pleasure in the companionship of those who share our table. This enjoyment is lost in many homes, not only through making mealtimes the occasion for disputes, but by the unfortunate habit of " bolting " the food, which renders conversation an impossibility, and takes away all pleas- ure in the food itself. Overeating, eating rich foods in great variety, and eating too frequently and rapidly, are the causes of most of the indigestion so generally suffered. Few maladies occasion more discomfort than indigestion. When one must always ask whether this or that article of food will agree with him or give him pain, a great part of his pleasure in life is gone, and it is no wonder that he becomes soured in disposition, as so many dys- peptics do. Children usually, however, have strong digestive organs, and the boy or girl who will eat whole- some food regularly and slowly will probably have good digestion throughout life. The use of too much food or of food that is too rich is likely to lead to lasting discomfort. THE HABIT OF USING ALCOHOL Alcohol and Digestion. Some people try to stimulate digestion in various ways, most commonly by the use of alcoholic drinks, especially wine. But it is a mistake for a boy or girl or any healthy person to use alcohol for this purpose. It does not aid digestion in any nor- mal individual. In this connection it should be re- garded as a drug, and be used, if at all, only under medical direction. 70 PHYSIOLOGY AND HYGIENE Many persons use alcoholic drinks for this or some other purpose until they get into such condition that they think they cannot properly digest food without using wine or alcohol in some form, to stimulate the weakened digestive powers. They have become like a horse that will not travel without a whip. The con- tinued use of the alcohol is very likely to injure the stomach so that finally proper digestion is impossible. The person who wishes to grow up strong and vigorous, with healthy digestive organs, will let alcoholic drinks entirely alone. The Appetite for Alcohol. There is one character- istic of all alcoholic drinks that makes them very dangerous. If a person eats ordinary foods, such as sugars and starches, he may sometimes eat too much ; but this does not develop a desire for larger amounts of the food. We may eat enough candy to make us ill, but this does not produce a craving for candy. On the contrary, it sometimes even causes us to lose all fondness for sweets, at least for a time. But alcohol frequently acts in a different way, its use creating a desire for more. The first glass a person takes is generally not pleas- ing ; but if he continues to use alcoholic drinks, after a little he comes to enjoy the taste and the effect, and in time he finds that he has a craving for it, and feels a certain lack if this craving is not satisfied. Whereas at first a small amount of the alcoholic drink was all he wanted, he soon becomes accustomed to this, and al- most. without knowing it he takes a little more. This FOOD HABITS AND COOKING 71 later fails to satisfy him, and, not realizing how serious a matter it is, he increases the amount of alcohol he uses, sometimes by drinking larger amounts of weaker liquors, and sometimes by taking stronger ones. And so the appetite grows until he finds it almost impossible to conquer it. In other words, instead of being a free man he has become a slave, and frequently a willing slave, for the use of alcohol regularly and in large amounts ordinarily destroys all desire to live a healthful, clean life. In most cases the person who drinks does not know that the appetite is growing until it has become so strongly fixed as to do him great injury. In just this fact lies the greatest danger, for if he could realize how he is coming under the influence of the unfortunate habit, he would break it before it mastered him, and before it destroyed his will power. When that is gone the best of the person is lost. Now, it is true that people who use small amounts of alcohol are not immediately mastered by the habit. But it is equally true that the use of small amounts of alcohol may lead to the development of an appetite which in time will completely master the user. Habit- ual drunkards are made out of boys and girls who did not intend to use alcohol enough to injure them. Unfortunately, even science has no way of telling which people can drink alcohol without falling under the sway of its appetite. Strong people, as well as weak, give way to it. The moment a person begins to use alcoholic drinks, even in a mild way, he places himself in the class of people from whom drunkards 72 PHYSIOLOGY AND HYGIENE may be made. The only safe way is to keep as far from the danger as possible, by letting drink abso- lutely alone. Intemperance in Eating and Drinking. Although alcohol is likely to do us more harm than any other kind of drink or any food, still we should be careful to avoid all forms of overindulgence. We may injure our- selves by eating too much candy or any other enjoyable food. We should make up our minds to be moderate in all our eating and to avoid alcoholic drinks alto- gether, for in this way only can we insure the strong, healthful growth of the body, and only thus shall we be able to do oar share of the world's work. PURPOSES OF COOKING No one who, on entering the house tired and hungry after a half day at school, has been greeted with the appetizing odors coming from the kitchen, need be told that cooking has its advantages. We eat very few foods without cooking, except milk, a few vege- tables, and fruits. Most foods are not considered fit to eat until they are cooked. There are three purposes in cooking food. 1. Cooking develops a flavor. We have only to notice the difference in taste between raw beefsteak and the same steak broiled and ready for the table to comprehend how cooking improves the flavor. It is true that cooking injures the flavor of certain fruits, such as strawberries, but it improves the taste of all meats and most vegetables. FOOD HABITS AND COOKING 73 2. Cooking makes food easier to digest. The cooking of vegetable foods is usually necessary to enable us to digest them. Potatoes, for example, contain large amounts of starch; but it is shut up in little sacs of a kind of woody substance, as shown in Figure 5, and so long as the starch is in these sacs the digestive juices cannot get at it. The juices have little or no power to dissolve the sacs, and consequently raw potato cannot be digested. Cooking softens the woody sacs and sets the starch free. Moreover, it causes the starch grains themselves to burst and when burst they are more easily digested. We should remember that all starchy foods should be well cooked before they are eaten. The cook- ing of meats is not of great importance so far as mere ease of digestion is concerned. In fact, most meats are more easily digested if they are not cooked too much. 3. Cooking removes danger from parasites. Some of our foods contain minute living animals, called para- sites. Some of these, harmless in themselves, throw off products which are poisonous ; others are themselves dangerous, and might do us considerable injury if swal- lowed alive. Pork, especially, sometimes contains large numbers of very small living worms, which, if taken into our bodies alive, are likely to cause serious dis- ease, perhaps death. Pork has occasionally another parasite which may develop in the human stomach into a tapeworm several feet long. Heat kills the parasites, and pork, including ham, should therefore always be thoroughly cooked. Beef and mutton are less likely to contain these parasites, but neither should 74 PHYSIOLOGY AND HYGIENE be eaten uncooked. We have already learned that mill? is frequently cooked, or sterilized as we say, to destroy any disease bacteria it may contain. PRINCIPLES OF COOKING The ambitious girl who takes pride in her ability to make an appetizing cake or to prepare a dinner does not need to be taught the effect of cooking on the various articles of food. Neither does the boy who goes camping in the summer and gets his own meals. Nevertheless, there are certain principles underlying cooking that we cannot learn over stove or camp-fire, but which we can easily understand. We have already found by testing the white of an egg that cooking coagulates albumen. We know, too, from boiling starch, that cooking changes starch foods into pulpy masses. Experience in the kitchen has shown us that vegetables are softened by cooking, and that fatty sub- stances are melted or made liquid by the same process. In general, cooking softens foods so that they are made easier to chew and to digest. Another general prin- ciple which should be borne in mind in all cooking, is that proteids are coagulated by heat. This is especially important as related to beef tea and soups. Beef Tea. If raw beef is cut fine and soaked in water, a part of the nutritious material is dissolved, and the liquid is good food as it stands. But if, after the beef has been soaked, the liquid is boiled, all of the dissolved material is coagulated and appears as a brownish scum. This can be separated from the FOOD HABITS AND COOKING 75 rest by straining the liquid through a cloth. Beef tea is usually strained, the liquid being used and the scum thrown away. Such tea is pleasant to the taste, but after the scum has been taken off it contains almost no food. Nothing is left except the salts and flavors. These are, however, frequently of use to invalids. The salts and flavors have a stimulating action on the diges- tive glands, and thus assist in giving the sick person an appetite, so that he can take, and more easily digest, real food. Beef tea is therefore of use in sickness or for persons with weak digestion ; but it should always, if possible, be taken together with something more sub- stantial. If the tea were made of finely minced beef put into cold water and very slowly heated, until quite hot, but without boiling, it would be very nutritious, for it would then contain the food material, which is not all coagulated except when actually boiled. Soups and Stews. The straining out of the food applies also to the making of soups from meats and vegetables. The heat of boiling produces coagula- tion, and the clear liquid, which is strained off and served as the soup, contains little more than the salts and flavors. Soups are not, however, usually regarded as foods. They are served at the beginning of a meal as a slight stimulant to digestion. Stews, on the other hand, the whole cooked mass of which is eaten, are nourishing and useful foods. Though the proteid has been coagulated, this does not injure the stew as a food, since the coagulated material as well as the liquid is eaten. 76 PHYSIOLOGY AND HYGIENE METHODS OF COOKING If some one should ask us how our mothers cook, the most natural answer would be, u ln all sorts of ways." The answer would be correct in a certain sense, and yet all kinds of cooking may be included under the four heads of boiling, baking, broiling, and frying. We put a cover on top of the kettle of boiling meat to hinder the escape of the steam and the odor. Simi- larly, whenever we can, we put a cover or crust around the object which is being cooked, to keep all the food material and flavors inside. This may be done by heat- ing the object very hot when the cooking begins. Thus a crust is formed on the outside of the loaf of baking bread. The high heat forms a similar protective coat around the meat by hardening the proteid and so keeping the juices and flavors within. Boiling. Boiling is one of the commonest and best methods of cooking, although it does not produce the finest flavor*. The article is cooked or boiled in water. One of the standing rules of housekeeping is, " If you want to have the richness in the liquid, you must put the article into cold water and heat slowly ; if you want the richness in the article itself, it must be put into boiling water." So vegetables must be dropped into boiling water, while meat for stews should be put upon the stove in cold water. If the meat is placed in boiling water, a coat is formed on the outside at once, and then the whole may be allowed FOOD HABITS AND COOKING 77 to simmer over the fire for a long time without much further loss. Meat cooked thus will retain its juices and have an excellent flavor, while the water in which it is cooked will contain practically nothing of value. The liquid of the stew, on the other hand, is to be eaten with the solid matter, so the meat should be placed in cold water and then allowed to simmer slowly, in order that the liquid may contain part of the food. Stewing is an economical method of cook- ing, since in this way nothing of the original food is lost. Baking or Roasting. Baking and roasting are two good methods of cooking which differ slightly from each other, but are similar in principle. The food is cooked in hot air, either in an oven or over a hot fire. When the food is cooked over the open fire we call it roasting ; when cooked in an oven, we commonly speak of it as baking, or, in the case of meats, we call it roasting. As the heat causes the liquid juices, especially of meat, to ooze to the surface, it is best to prevent the loss of these juices as far as possible. This is done, as in boiling, by heating the meat very hot at the beginning, so that a crust may be formed. The flavor and richness of the meat are much improved by pouring over it, say once in every fifteen minutes, the liquids which ooze out, a process called lasting. If there is not sufficient liquid for this purpose, melted butter or suet, or even salt water is used. In baking bread and cake it is also desirable to use high heat at the start. 78 PHYSIOLOGY AND HYGIENE Broiling. One of the quickest and most desirable ways of cooking is broiling. Especial care should be taken to begin the cooking over a very hot fire in order that the surface of the meat may be quickly seared over, and the juices thus kept in it. Frying. Frying is a method of cooking very com- mon, but not wholesome. As the food is cooked in hot fat, butter, suet, or olive oil, it is apt to become satu- rated with the fat. While fat of itself is nutritious, food soaked in it is very difficult to digest. To fry with the least injury to the food, there should be an abundance of fat, and it should be very hot. The high heat, as in other methods of cooking, forms a crust on the outside, which prevents, in considerable measure, the fat from getting into the food. Yeast and Baking Powder. To make bread we mix flour with water, or milk, add yeast, and set the mix- ture in a warm place to "rise." The yeast grows in the bread, producing a very small amount of alcohol and a gas called carbon dioxide. The bubbles of gas appear in the dough, causing it to rise up like a sponge. In baking, both the alcohol and the gas are driven off by the heat, but the bread is filled with the little holes which were previously occupied by the carbon dioxide. This makes the bread "light," and easy to masticate and digest. Similar bubbles are made in cake and biscuit by putting baking powder into the dough. As baking powder produces the gas very quickly, it is adapted to rapid baking. To develop the necessary gas with yeast requires that the dough rise for several hours. FOOD HABITS AND COOKING 79 QUESTIONS 1. Why does an Eskimo eat fish and seal, while a Chinaman eats rice ? 2. What facts should be considered in choosing our diet ? 3. What kinds of food should be used together? 4. When should we eat? 5. Is food with a pleasant taste more useful to the body than food without flavor ? Why ? 6. How can we best enjoy our food? 7. Why is rapid eating unwise? 8. What effect has alcohol on digestion ? 9. How is an appetite for alcohol developed? 10. What are the purposes of cooking? 11. How does cooking make a potato easier to digest? 12. What does cooking generally do to food? 13. Why is a stew nutritious while beef tea is only a stimulant? 14. What are the three methods of cooking? 15. How is cooking done by boiling ? 16. How is food cooked by baking? 17. Why is fried food apt to be indigestible ? 18. What foods may properly be eaten without cooking? 19. What do yeast and baking powder do to food ? 20. Why is plain food more healthful than rich food? CHAPTER IV CIRCULATION EVERY house in a large city is supplied with water from faucets. The water is carried to the house by pipes laid in the ground, and the pipes come from a reservoir which supplies the whole city. In many places a large pump near the reservoir forces the water into the pipes. If the pump stops working, the water throughout the city ceases to run. We have seen how the food which we have eaten gets into the blood. This food is needed in ail parts of the body. It is carried to the arms, the head, and the various organs by the blood vessels, very much as the city is supplied with water by the water pipes. The blood vessels are tubes running through the body, dividing into branches, and these again into smaller branches, so that every organ of the body, no matter how small it may be, has at least one. The heart acts as the pumping station, and by it the blood is kept in constant motion. THE BLOOD Let us see what this liquid is which flows so con- stantly through the blood vessels. We already know that it contains the part of the food we have eaten 80 CIRCULATION 81 which has been dissolved and absorbed from the intes- tines. But it has in it other materials besideso The blood that oozes from the finger when we have a cut looks bright red. If, however, we look at it through a microscope, we find that the liquid itself is almost as clear as water. In fact, the liquid part of the blood, called blood plasma, is largely water, although several substances are dissolved in it. The red color is pro- duced by millions of little red bodies floating about in the liquid. These minute bodies are called corpuscles. Red Corpuscles. The most prominent of the solid bodies in the blood are the red corpuscles. These are Corpuscle mm^Corpuscle ztct^^Red *%%,(. Corpusc/e l&t&JUo*/ Plasma FIG. 20. A LITTLE BLOOD, AS IT APPEARS UNDER A MICROSCOPE. shown in Figure 20. They are small, thin disks, cir- cular in shape. As may be seen from (7, they are slightly thinner in the center than at the edge. They are very small, only about ^W ^ an ^ ncn ^ n diameter, and 82 PHYSIOLOGY AND HYGIENE consequently they are invisible except through a micro- scope. They are present in the blood in immense num- bers, there being some 5,000,000 of them in a very small drop. Each red corpuscle contains a red substance called hemoglobin. The important work performed by the red corpuscles we shall study in a later chapter White Corpuscles. The white corpuscles act as the street-cleaners in the body. They are fewer in num- ber than the red corpuscles. They are transparent, and of a slightly bluish appearance. They have no definite shape, and in fact they are changing shape constantly, although they are most commonly some- what spherical, as shown in Figure 20. All the cor- puscles, both white and red, flow through the blood vessels with the blood. The red corpuscles can go only where the blood carries them; but the white corpuscles sometimes crawl out of the blood vessels entirely, push- ing their way through the walls. They then travel around independently among the muscles and various parts of the body. There they catch and carry off any minute irritating substances which might produce trouble and perhaps disease, if allowed to remain. Thus the white corpuscles of the blood are believed to have a very important part in warding off certain diseases. WHAT MAKES THE BLOOD FLOW The Heart. The heart is situated in the chest a little below the neck and slightly on the left side, where, as we know, its beating may be felt. In an adult, the heart is about the size of a man's fist, and is somewhat CIRCULATION 83 pear-shaped, as shown in Figure 21. When in the nat- ural position, the apex, or small end, is turned down- ward and a little to the left. As long as a person lives, his heart continues to pump the blood through his blood vessels, so that the To Head motion of the and of the never ceases. a pump, the blood heart Like heart To Arm ^ To Arm Left . , Aur/cfo Artery has tubes entering it / JHOSMitfVk (Aorta) on one side bringing the blood in, and others on the oppo- site side carrying the blood away from it. The blood vessels bringing blood to the heart are called veins ; those carry- ing it away are called arteries. In Figure 22 (facing p. 84) the arteries are colored red, the veins, blue. If we cut open the heart of some large animal, such as a sheep or an ox, we shall find that, like the human heart, it contains four cavities, as shown in Figures 23 and 24. The two cavities on the right side, called the right auricle and right ventricle, "Aorta FIG. 21. THE HEART. Showing the veins and arteries con- nected with it. 84 PHYSIOLOGY AND HYGIENE FIG. 23. THE RIGHT SIDE OP THE HEART. are connected with each other. The two on the other side, the left auricle and the left ventricle, are also con- nected with each other There is no connection be tween the two sides of the heart ; the blood can- not flow directly from one side to the other. As the heart beats, blood which has just com- pleted the round of the body, and is full of im- purities which it hag gathered, flows into the right auricle through the large veins from the head and body, indicated in Figure 23, and fills both the right auricle and the right ventricle. Then the heart contracts, that is, the muscles of the walls press the blood out, as we squeeze the juice out of a lemon by closing the hand tightly about it. When the heart contracts, the blood forces its way into the pulmo- nary artery, shown in Figure 23. The pulmonary artery carries it to the lungs to be purified. From the lungs the purified blood comes back to the heart again, this time by veins which send it into the upper of the two chambers at From Aortd FIG. 24. THE LEFT SIDE OF THE HEART. W CIRCULATION 85 the left side of the heart, that is, into the left auricle ; thence it goes to the left ventricle, as shown in Figure 24, and by this it is sent through the large artery (the aorta, Figs. 22 and 24) in all directions through the body. Thus every time the heart beats, one side of it takes blood in from the head and body, sending it to the lungs, and at the same time the other side of the heart takes blood in from the lungs and sends it out through the body, In order to keep the blood flowing in the right direc- tion and to prevent its flowing backward, the heart con- tains several valves. - These are folds inside the heart. When open, as in Figure 23, they allow blood to pass freely in the direction indicated by the arrow; when lifted, as in Figure 24, they completely close the opening between the auricle and the ventricle and prevent blood from being forced back into the auricle when the ven- tricle contracts. As soon as the heart relaxes, they open again and allow the ventricle to fill up once more. There are also some valves called semilunar valves (shown in Fig. 23), which in a similar way prevent blood from flowing back from the artery into the heart. The Beating of the Heart. The heart never seems to get tired. All day and all night our whole lives through it keeps at its work of pumping the blood. The heart of a grown person beats about seventy times a minute, that of a child somewhat faster. It spends about three tenths of a second in beating, and then rests for four tenths of a second. In this way it really works less time than it rests, only instead of working in the daytime and resting at night, like the body ia 86 PHYSIOLOGY AND HYGIENE general, it does a bit of its work and then rests. In this way it is able to keep beating without becoming worn out. When we are in good health the heart beat is strong ; it weakens when we are ill. One reason why the use of tobacco and alcohol is injurious is that they are likely to weaken the proper action of the heart. Both alcohol and tobacco are very likely to cause heart difficulties, particularly if used by young people. Nearly every boy knows, from his own observation, that neither the habitual smoker nor the youth who uses alcohol wins in the athletic contest. The Pulse. When a stone is thrown into a pond, the water is disturbed in the form of a circular wave which grows larger and larger, but all the time lessens in height, until it disappears. A somewhat similar effect is produced by the heart as it forces the blood into the arteries. The wave of pressure produced by the heart is felt all through the arteries, though it is less strong the farther it is from the heart. The wave causes a slight swelling of the arteries as the blood passes. The artery at the wrist is so near the surface that we can feel the wave, known as the pulse. The pulse can be found in any of the arteries where they are near the surface; but as most of them are deep in the muscles, there are few places where we can feel the throbbing. The usual place for testing the pulse beat is at the wrist, but it can be felt at the neck, just under the lower jaw, and also at the temples. By feeling of the pulse the physician can obtain consider- able information regarding the general condition of the patient's health. CIRCULATION 87 BLOOD VESSELS Arteries. When the blood is forced out of the heart from the left ventricle it passes into the large artery shown as red in Figure 22. This serves as the main artery to supply the body. The artery bends over to the left and runs down the body, giving off several branches on its way. The first branches extend to the head and the arms, while others lead to the stomach and the intestines, and still others run down into the legs. This main artery thus supplies blood to all parts of the body, just as the water main furnishes water for every house. The farther the branching arteries are from the heart the smaller they become, until finally each is divided into thousands of minute tubes which enter every organ of the body. Capillaries. If we should follow up a single one of the minute branches of an artery, we should find that it ends in a set of even smaller tubes, like those shown in Figure 25. These are called capillaries. The capillaries are too small to be seen except with the aid of a micro- scope. They divide into many branches which come together in a somewhat irregular manner, differing in different localities, as shown in the figure. The blood flows from the small arteries into these capillaries, and Ji is here that the food materials held in solution are given up to the living parts of the body. Every part of the body is filled with capillaries, and through them each part gets its share of food from the blood. We must remember that the blood, whether in the 38 PHYSIOLOGY AND HYGIENE arteries, or in the veins, or in the tiny capillaries, is always flowing in closed tubes. It never empties into the tissues, but passes to them through the delicate walls of the capillaries. Only the liquid part passes through, the corpuscles remaining in the blood vessels. Veins. A four- track railroad usually has two tracks for the trains, say from Chicago, and two for y . s\ the trains going to Artery \\V Chicago. Let us say that the two tracks from the railroad center represent the arteries which take the blood away from the heart. After its journey through smaller arteries or branch roads, and through the capil- Showing their method of branching. The larieg Qr gwitches figure on the right shows capillaries in the skin ; on the left, capillaries in the where it leaves the muscles ' food, the blood is ready to go back to the heart on the return tracks. The little capillary branches combine into larger tubes or blood vessels called veins, which carry the blood back to the heart. The veins in turn combine, and the nearer they get to the heart the larger and the fewer in number they become. Finally they unite into two large veins, which pour all the blood back into the heart. Figure 22 B shows the connection of the heart FIG. 25. CAPILLARIES. CIRCULATION 89 Head with these veins. With the next beat after the blood has been poured into the heart from the veins, it is pumped out again, and sent once more on its circuit to the lungs and around the body. The general arrange- ment of the heart, arteries, capillaries, and veins may be understood from Figure 26. The whole process of cir- culation, as it is called, is like what would happen if all the water that flows from our water faucets, and, after being used, is thrown into our sinks, were carried back to the reservoirs, there to be thoroughly purified, and sent out once more to the various houses. All of the arteries, except those going to the lungs, carry pure blood, while the FIG. 26. A DIAGRAM SHOWING veins, except those coming from the lungs, carry im- pure blood. The pure blood becomes impure as it takes up waste material in the capillaries, as explained in a later chapter. The arteries are embedded deeply in the flesh ; the veins are nearer the surface. A cut in the flesh is almost sure to sever one or more small veins, but Capillaries THE GENERAL CIRCULATION. The blood flows in the direction of the arrows. 90 PHYSIOLOGY AND HYGIENE unless it is very deep the arteries will not be injured. The blue lines appearing on the back of the hand, when the hand is allowed to hang downward, show the positions of the veins. HOW THE BLOOD FLOWS Most of us are familiar with some form of pump. We have noticed that the water flows out of the spout in spurts; but if it is allowed to pass for some distance through a trough or along the ground, it flows as steadily as if it had come from the pump in a contin- uous stream. The movement of the blood in our bodies is similar. The heart sends the blood into the main artery in spurts, pumping it with force, just as the pump forces water into the trough. As the blood goes farther and farther from the heart, it flows along more quietly, until, by the time it has passed through the capillaries and is on tho home trip through the veins, the spurting has ceased entirely. When the heart beats, it forces more blood into the arteries than can easily flow through them. Instead of being stiff, however, like iron water pipes, the arteries are elastic like India rubber. The blood flowing into them in spurts causes the arteries to stretch, so that it flows more smoothly than it would if flowing in similar spurts through iron pipes. Bleeding. The blood is pumped into the arteries with so much force that it flows out very rapidly in strong jets if an artery is cut or broken. The bleed- ing must be stopped quickly, or the person may bleed CIRCULATION 91 Artey to death. The veins, on the other hand, do not become stretched, since the blood flows in them with less force. If a vein is cut, the bleeding is not so rapid as from a severed artery, and it is not so dangerous. But in any case the bleeding must be stopped, for even a small wound in a vein would cause death if the flow of blood were not checked. Many of the most common accidents to which we are liable produce bleeding. If the wound is only a slight break or a cut in the skin, the bleed- ing will not be serious. We 27. SHOWING need only to THE MAIN ARTERY . ,-1 i OF THE ARM bring the edges together and bind the cut or other wound some- what tightly with a cloth or a bit of adhesive plaster, and the bleed- ing soon stops. Even wounds which are comparatively deep will usually stop bleeding, if they are tightly bound and held quiet for a time. Bleeding from Arteries. An artery wound is more FIG. FIG. 28. SHOWING In front of the leg above the knee, but behind it below the knee. 92 PHYSIOLOGY AND HYGIENE serious, and must be treated promptly in order to save the person's life. If a cut or wound of any sort is followed by a forcible spurting of blood, it is certain that an artery has been cut. The only way to stop the bleeding is to compress the artery above the cut, that is, between the cut and the heart. Severed arteries are most common in the arms and the legs, and the treat- ment in such cases is simple. Figures 27 and 28 show the course of the chief arteries in the arm and the leg. Figure 29 shows a simple method of grasping the arm so as to compress the artery and stop the bleeding, temporarily, anywhere in the arm below the elbow. The easiest and most effectual method of stopping the flow is, however, to put a bandage or liga- ture around the arm above the cut, FIG. 29. - SHOWING and tO P laCS a Stick lnside ^ aS HOW TO COMPRESS indicated in Figure 30. The stick THE ARM TO STOP k then to be turned, twisting the BLEEDING. bandage, Mid binding the arm more and more tightly, until the bleeding stops. If a stone or a tightly rolled handkerchief is placed under the ligature and over the artery, less pressure is required. A physician must then be summoned as soon as possible. The ligature must be kept in position until the physician can tie the artery and prevent further bleeding. With a wound in the leg the CIRCULATION 93 method of stopping the flow of blood is similar. Prompt action is of supreme importance in all such cases. Why the Bleeding stops. If there is a break in the water pipe laid along a city street, the water continues to flow out until the workmen have repaired the pipe. The leaking would never stop of itself. How is it then that bleeding from a vein stops itself, or can be stopped, so readily ? If, whenever there was a break in the pipes, the water should freeze a short distance above the break, the ice would close up the open- ing and stop the leak. Some- thing of this sort really occurs in the case of a wound. The blood does not freeze, of course, but it becomes some- what solid; a change takes FIG place in it which we call clotting. Blood Clotting. Blood, as we know, is a liquid. If blood be drawn into a small dish, it will at first be liquid, like water. But if it is allowed to stand for a few minutes, it stiffens, becoming somewhat jelly like. The hardening continues until the blood is changed into such a firm jelly that it will not flow out, even if the dish is turned upside down. In other words, the blood has clotted, as is shown in Figure 31. A great 30. SHOWING THE METHOD OF APPLYING A LIGATURE. 94 PHYSIOLOGY AND HYGIENE change has been produced in the nature of the blood, and after clotting it would naturally be of no further use, as it could no longer flow through the blood vessels. If blood is taken out of the blood vessels, it always clots in a very few minutes, no matter whether it is heated or cooled, or whether it is brought in con- tact with the air or not. So long as it remains inside -Clot Blood 1 Clotted Blood FIG. 31. SHOWING THE CLOTTING OF BLOOD. At A it is liquid ; at B it is solid. At C it is partly liquid again. the blood vessels it continues in liquid form. If, how- ever, the blood vessels themselves are injured by a cut or bruise, the blood begins to clot rapidly near the wound. From this fact we learn how bleeding is stopped. Whenever a bruise or a cut breaks a blood vessel, the wound at once begins to bleed. But the injury to the blood vessel causes a clotting in the blood near the bruise, and the clot soon closes the wound. As a result, CIRCULATION 95 any ordinary wound soon ceases to bleed; but if there is a large cut through a vein or an artery, the blood may flow out so rapidly that it does not have time to clot. In such cases the bleeding must be stopped by a ligature or some other artificial means. Effect of Gravity. If we hold the hand downward for a few minutes, it becomes red, because it is filled with blood. If, on the contrary, the hand is held above the head, it turns whiter. This shows us that the blood flows down more easily than it flows up. Of course, the blood in flowing through the blood ves- sels, is pushed on by the force of the heart. Even when the blood flows downwards into the legs, it must be pushed by the beating heart. But the weight of the blood itself has some influence upon its flow, helping the heart to send the blood down, and holding back, more or less, the upward flow. The aiding and checking of the flow by the weight of the blood, or gravity, is, however, of no practical importance except under cer- tain conditions, such as fainting. Fainting. Fainting is commonly due to lack of suffi- cient blood in the brain. This causes unconsciousness. Recovery from the fainting fit occurs as soon as the necessary amount of blood is restored to the brain. When a person faints it usually means that the heart is not beating vigorously enough to force the blood upward to the brain. We should, accordingly, assist the heart by placing the head of the patient a little lower than the body. This will help the blood to run into the head from its own weight. The return of blood 96 PHYSIOLOGY AND HYGIENE to the brain may also be hastened by stimulating the action of the heart. Dashing a little cold water upon the face hastens the beating of the heart, helps to re- store the blood to the brain, and so insures recovery from the fainting fit. Our natural impulse, when a person faints, is to lift his head, but as a rule this will hinder recovery. HOW THE FLOW OF BLOOD IS CONTROLLED Regulation of the Heart Beat. The circulation of the blood is produced by the beating of the heart, and at the same time the heart is partly controlled by the brain. The heart can be entirely removed from the body of a cat or a dog and yet it will continue to beat, sometimes for hours. This shows that the heart is able to beat independently of the brain. Nevertheless the brain has the power of hastening and checking the heart's action. The brain is, in fact, the central organ of the body, and as such it controls the action of every part. Passing from the brain to the heart are two nerves which serve, like telegraph wires, to connect the two. Over these nerves the brain is constantly sending mes- sages to the heart. Sometimes the heart beats more rapidly than is necessary, and the brain sends a message which checks its action a little and makes it beat more slowly. At other times the heart does not beat fast enough, and needs to be hastened. If a boy starts to run, he needs to have an extra amount of blood sent to the muscles. Immediately a message is sent from the brain that sets the heart to beating faster, CIRCULATION 97 which, of course, causes the blood to flow more rapidly. After the boy stops running, another message causes the heart beat to become gradually slower until it reaches the ordinary rate. There are many other occasions when a quickened heart beat is desirable. In every case of need responses come from the brain, and the heart is accordingly controlled. All this is done without our being conscious of it. We cannot by will power change the rate of the heart's beating, and usually we do not even know when a change occurs. We can readily test the difference in the rate of the beating by counting the number of beats a minute, (1) after we have been sitting quietly for some time, (2) after we have walked up a flight of stairs or have run for some distance, and again (3) after fifteen min- utes of quiet. Regulation of the Blood Vessels. The flow of water from the city water pipes is regulated in two ways. The pump may work more or less rapidly as occasion demands ; the faster its movement, the greater the amount of water flowing into the pipes. This action corresponds to the changes in the rate of the heart beat. The flow of water in the various houses depends upon how wide we open the faucet, whether to its full extent, halfway, or not at all. So in our bodies there is a means of changing the size of each little blood vessel, to allow either more or less of the blood to pass through. All of the small arteries have muscle fibers running around them, as indicated in Figure 32. When these muscle fibers contract, they narrow the blood vessel, 98 PHYSIOLOGY AND HYGIENE lessening the amount of blood allowed to pass. When they relax again, the blood vessel opens and the blood flows in a larger stream. These mus- cle fibers are all con- nected with the brain, or the spinal cord, by nerves through which they can be made to relax or contract. In FIG. 32. SECTION OF AN ARTERY AND , . A y EIN this way the flow of blood in any organ of Showing the thick elastic wail of the J artery and the thinner wall of the /ein. the body can be in- creased or decreased. If for any reason a particular part of the body needs more blood, than usual, it is not always necessary to increase the rate of the heart beat. The little muscles around the arteries simply relax, so that these blood vessels become larger, and at once- more blood flows through them. On the other hand, if less blood is needed in a certain organ, the brain causes the muscle fibers to contract, so as to close, or partly close, the blood vessels. When any part of the body is actively at work, it needs plenty of blood, since the blood brings it nourish- ment. The more vigorous the work, the greater is the amount of blood needed. The brain needs an extra sup- ply when we think hard, the leg muscles when we run. After a hearty dinner the stomach and the intestines need a large amount of blood for the work of digestion. CIRCULATION 99 By means of the nerves from the brain (vaso-motor nerves, they are called), the small arteries in the intes- tines are made to relax and allow the blood to flow through more quickly than usual. ' The walls of the intestines and the stomach become filled with blood, and digestion goes on rapidly. This large flow through the intestines necessarily draws some blood from the brain and other parts of the body. Accordingly, after a heavy meal most people are a little stupid and rather inclined to sleep. On the other hand, when a person is studying very hard, so that the brain is especially active, the blood vessels in the brain itself are relaxed to allow of a large flow of blood. It is therefore difficult to do profitable studying and to digest a heavy meal at the same time. Either the brain will take too much blood to allow of good digestion, or else the stomach and the intestines will have so large a share of the blood that the brain is sluggish and the lessons suffer. Blushing results from a similar action of the blood vessels in the skin of the face ; these vessels are relaxed, and allow an extra amount of blood to flow through them. The cheeks become thereby red and warm. On the other hand, an unusual contraction of the vessels in the face causes the skin to become pale. A flushed skin thus means expanded blood vessels, while a pale or white skin means contracted ones. The Feeling of Warmth and Cold. The expansion and contraction of the small arteries in the skin cause our feelings of heat and cold. The blood is warmer in 100 PHYSIOLOGY AND HYGIENE the interior of the body than at the surface, but since only the skin feels warm or cold, we do not notice the warmth of the blood as long as it is below the skin. When we exercise vigorously, as in running, we feel very warm. The reason is that the exercise causes the blood vessels in the skin to expand so that an extra large amount of blood flows through them. The skin becomes red and the blood so warms it that we feel the heat. Although we feel especially warm when the blood flows rapidly through the skin, the body is in fact no warmer than usual. Indeed, the sending of the warm blood through the skin is the means by which the body cools its blood, to keep us from really becoming warmer. If the body seems likely to become too warm, it sends blood to the skin at once, to be cooled by the air. But if the body has too little heat, the blood vessels con- tract, and the warm blood is kept away from the sur- face, causing pallor of the skin. The skin blood vessels thus serve much the same purpose as little windows, which are opened or closed to regulate the temperature. Sometimes we are deceived by the feeling of warmth. Whenever the blood vessels in the skin are opened wider than usual, so that warm blood flows through them, we may be sure we are cooling off, no matter how warm we feel. Now there are certain substances which, if taken into the stomach, cause the blood vessels to enlarge. For example, a certain amount of alcohol causes the skin to become flushed and the body to feel warm. Many people believe, therefore, that the alcohol has CIRCULATION 101 actually warmed them, and so they take it on a cold day to keep them warm. Exactly the opposite is the case. The alcohol has caused the blood vessels to expand, or, in other words, it has opened the windows in the skin, and the body has begun to cool. The person feels warm simply because the skin is heated, but he is really losing heat more rapidly than before. Arctic explorers find that they cannot endure the extreme cold so well if they use alcoholic drinks. In very cold weather the use of alcohol would only make us colder if we were going out of doors immedi- ately afterwards. Sometimes when a person has been overcome with cold and is half frozen, and perhaps un- conscious from the exposure, alcohol is given to quicken the heart action temporarily and to hasten recovery. Under such circumstances it is not used to warm the person, but as a drug to meet an emergency. SUMMARY OF THE CIRCULATION PROCESS Let us trace briefly once more the journey made by the blood, beginning when it enters the heart after a journey around the body. It enters the right auricle and ventricle of the heart through large veins coming from the head and body. Then it is forced into the pulmonary artery, which carries it to the lungs to be purified. From the lungs it returns to the heart, this time entering the left auricle and ventricle, from which it passes into the main artery of the body. The main artery divides into branches which take blood to the head, the limbs, and the various organs; and the 102 PHYSIOLOGY AND HYGIENE branches subdivide into smaller and smaller branches which finally end in the little tubes called capillaries. There the pure blood gives up its food, and at the same time takes up the waste products. From the capillaries the impure blood enters small veins which connect with larger veins, and these with still larger ones, until finally all unite in the two large veins which carry the blood to the heart once more. The beating of the heart is continuous, but the rate can be increased or diminished through the action of cer- tain centers of the brain ; blood supply of any organ can be increased or diminished by the expansion or contrac- tion of the small blood vessels. The whole circulation is controlled without our being conscious of the fact or being able voluntarily to change it in any way. QUESTIONS 1. What is the purpose of circulation? 2. Describe the red blood corpuscles. 3. What is the use of the white blood corpuscles? 4. What is the duty of the heart ? 5. What are arteries ? Veins ? 6. Do any of the arteries carry impure blood ? 7. How can we tell when an artery is cut? What should be done in such case ? Why is such a cut more serious than a cut vein ? 8. How does nature stop bleeding from wounds ? 9. If the blood would not clot, what would happen when a per- son is cut ? 10. What is the pulse ? Why does a physician count a patient's pulse ? CIRCULATION 103 11. What are the capillaries ? 12. What is fainting ? What is the remedy for ib? 13. How is the flow of blood regulated ? 14. How is the amount of blood that each organ receives regu- lated? 15. Why should we not study immediately after a hearty dinner ? 16. If a person should run rapidly immediately after dinner, would it help or hinder digestion? Why? 17. Why do we feel warm after running ? 18. Why is it that alcohol makes a cold man feel warmer? Is he actually warmer ? CHAPTER V RESPIRATION ONLY as the fuel in a locomotive is burned does it drive the engine. The burning of the fuel is really a union of the coal with a certain part of the air called oxygen. The process is oxidation, and it produces heat. As a result of the burning, a large amount of another gas, carbon dioxide, is produced, which passes out of the smoke-stack with the smoke, and there is left in the grate a quantity of ashes. In order that the fires in the engine may be kept burning brightly, it is necessary that there be a supply of air. This is fur- nished by means of the draft. It is necessary also that the gases have some means of passing off, as they do through the smoke-stack. The ashes must also be frequently removed from the grate to keep the fires free, and allow the air to reach the burning coal. The processes which take place in our bodies are somewhat similar to those in the engine. The food is oxidized, although the process differs much from the burning of coal, and a certain amount of heat is pro- duced which warms the body. Oxygen gas from the air is as necessary for the body oxidation as for burning the coal. What is more, there is produced in the body the same kind of gas as in the engine, carbon 104 RESPIRATION 105 dioxide, and a certain material is left that corresponds in a way to the ashes, and of this the body must dis- pose. How the body gets its oxygen, and gets rid of its carbon dioxide, is a story in itself. This exchange of gases between the air and the blood is brought about by breathing, or respiration. THE AIR PASSAGES AND THE LUNGS When we breathe properly, air is taken in at the nos- trils, and after passing through the large nasal cavities above the mouth enters the throat. The nostrils, as we saw in Figure 12, lead directly to the throat, so that the air has a free passage. We have seen, too, that the mouth also leads directly to the throat. If the mouth is open, air may be taken through it even more easily than through the nostrils. In either case the air passes directly into the throat, and then down to the lungs. Mouth-breathing is not, however, the natural method of taking in air, and is always injurious if continued for any length of time. The air passes much more rapidly through the mouth than through the nostrils, and consequently it is not so thoroughly warmed when it reaches the lungs. What is more, the dust in the air is not so completely removed as when it passes through the nostrils. The narrow, irregular passages of the nose, with their moist surfaces and hairs, hold the dust and prevent it from passing into the lungs. We should carefully avoid getting into the habit of breathing through the mouth, even when walking fast or when running, lest we cause throat and lung troubles that 106 PHYSIOLOGY AND HYGIENE may be a serious menace to health. If a person should find that he really is unable to breathe excepting with the mouth open, it indicates that something is wrong in his throat or nose, and he should be examined by a physician. The Windpipe or Trachea. The air passes from the throat into the windpipe (see Fig. 12). This is a large tube at the front of the neck. As we have seen, it is always open, except that at the instant when food is being swallowed the epiglottis closes down over it like a lid. The epiglottis springs up again, how- ever, as soon as the food has slipped by, to allow the free passage of air to and from the tube. The wind- pipe itself is held open by a series of hard, cartilage rings in its walls, which prevent it from collapsing. Just within the upper end of the windpipe is situated a very important organ, the larynx. If we place our fingers upon the outside of the throat just below the jaw, we can feel a hard bunch move up and down as we swallow. This bunch, sometimes called the Adam's apple, is the larynx. Figure 33 shows its location at the beginning of the windpipe. Inside of the larynx are the so-called vocal cords, by means of which we are able to make sound when talking. Below the larynx the windpipe passes down through the neck in a straight line and enters the chest, where, as shown in Figure 33, it divides into two branches. The Lungs. When the windpipe divides, one branch enters one of the lungs, and the other branch enters the other lung. The lungs look like two elastic bags, as RESPIRATION 107 indicated in Figure 33, and are capable of being dis- tended when air is drawn in, and of collapsing when the air is expelled. Each of the bags seems to be filled with a mass of spongy material, which is made up prin- ..Larynx FIG. 33. THE LUNGS. Upon the left is shown the lung from the outside ; upon the right the lung is opened to show the branches of the air tubes. cipally of air tubes, air cells, and blood vessels. Each branch of the windpipe, on entering the lung, divides into numerous smaller branches. Each of these divides 108 PHYSIOLOGY AND HYGIENE again, and so the division continues, until finally the smallest of the branches form a system of very minute tubes similar in its irregular divisions to the twigs of a tree. The whole lung, in fact, appears somewhat like a tree with the branches upside down. Each twig ends in a small rounded sac or air chamber. The air taken in through the nostrils finally enters and expands these little chambers, which are shown in Figures 33 and 34. The lungs contain many thousands of the sacs, and every time we breathe they expand with the air which they take in. Thus the whole lung, being filled with air, is light and FIG. 34. AIR SACS, spongy. It is an excellent plan Found at the ends of the ^ o draw several long breaths every air tubes in the lungs. ... little while, to distend the air sacs as much as possible, thus "clearing the lungs" as we say. Blood Vessels of the Lungs. We have already learned that the right side of the heart receives the impure blood and sends it through the pulmonary artery to the lungs. When this artery enters the lungs it divides and subdivides into small blood vessels, which in turn divide into very small capillaries. The capillaries are wrapped around the air sacs, appearing like a sort of net about them (Fig. 35). While the blood from the heart is flowing through the capillaries it is very close to the air which fills the sacs. It is so close, in fact, that it takes some of the oxygen out of the sacs, RESPIRATION 109 giving up to them in exchange the impure gases which it holds. After leaving these gases and taking the oxygen, the blood is purified and ready to go back to the heart. HOW AIR IS DRAWN INTO THE LUNGS When the handles of a pair of bellows are extended the cavity inside is enlarged, and air is sucked in to fill the increased space. If a rubber ball with a hole in it is com- pressed until it col- lapses, and is then held in a dish of water and allowed to take its normal shape, the hollow fills with water. Breathing is based upon a similar prin- ciple. The air is FIG. 37. SHOWING THE CHEST WITH THB r 1-4 J.-L LDNGS AND HEART IN POSITION BEHIND forced into the THB Rms . lungs in much the same way that bellows are filled with air and the ball is filled with water. The Chest or Thorax. The lungs are inclosed in a box called the chest. This is closed in front, at the sides, and at the top by the ribs, muscles, and skin. Figure 37 shows the chest and the position of the lungs. At the rear the chest is closed by the backbone and 110 PHYSIOLOGY AND HYGIENE the ribs. A thin muscular partition, the diaphragm, stretches across the bottom, shutting the box up com- pletely. The windpipe is the only opening in the chest for the entrance of air. The position which the diaphragm would take if left to itself is that of a slight upward curve, as shown in Figure 38. Each time we draw in a breath, the muscles of the diaphragm shorten and draw it down to the posi- tion shown by the dotted line in Figure 38. This enlarges the space in the chest, and the outside air, rushing in through the nostrils and the windpipe, enters the lungs, and fills the enlarged space. The diaphragm is helped by the ribs in making the space within the chest larger. The ribs, in their usual posi- tion, tend to bend downward. As we breathe, the numerous muscles surrounding the ribs FIG. 38. SHOWING THE MOVE- raise them upward and for- MENT OF THE DIAPHRAGM IN war d, increasing considerably BREATHING. The dotted line represents the the space within. The dotted position at the end of an lines in Figure 39 show the inhalation. position of the ribs when the lungs are full. Air is drawn in when we breathe ; RESPIRATION 111 when the cavity of the chest is enlarged, the pressure of the air forces it in to fill the enlarged cavity, much as air is forced into a pair of bellows. After the lungs are thus filled with air, the muscles relax, and the ribs fall of their own weight into the position shown in the solid lines of Figure 39. At the same time the diaphragm re- laxes, and is pushed up to its former position. This is chiefly accomplished loy the pressure of the organs below, which it had compressed. Both motions decrease the size of the chest cavity, and the air is squeezed out exactly as the air is forced from the bel- lows by the pressure on the handles. Drawing the air into the lungs is called inspiration or inhalation. Forcing the air out by contraction is called expiration or exhalation. The whole process is controlled through nerves by the brain. Capacity of the Lungs. A certain amount of air is drawn into the lungs with each breath, and about the same amount forced out. But the lungs are never completely filled by an ordinary FIG. 39. SHOWING THE MOVEMENT OF THE RIBS IN BREATHING. 112 PHYSIOLOGY AND HYGIENE breath, nor are they ever completely emptied after the exhalation. After taking an ordinary breath we can still breathe in more air by an additional deep breath, and after an ordinary exhalation we can expel more air by an effort. Thus in ordinary breathing we change only a part of the air in the lungs. In fact, the lungs of a grown person commonly hold about 350 cubic inches of air, of which only about 30 inches are changed with each ordinary quiet breath. We might renew most of the air by very rapid and very deep breathing, but to do so continuously would be too great an effort. Lung Exercise. The lungs should by all means be completely filled with pure air occasionally. If the air in the little air sacs is seldom changed, but remains more or less stagnant, the sacs furnish excellent lodg- ing places for dangerous bacteria, and they may even be the starting point for consumption, pneumonia, or some other lung disease. If people exercised the air sacs more vigorously, filling them constantly with fresh air, the danger of lung trouble would be decreased. How shall we give our lungs the needed exercise ? By drawing long, deep breaths, filling the lungs as full as possible, and then blowing out the air slowly and forci- bly. If we acquire a habit of frequently filling the lungs deeply with fresh out-of-door air, we shall strengthen them, increase their capacity, and improve our general health. Persons whose work is such as to produce vig- orous activity of the lungs do not need such special exercise. If one is obliged to walk up a steep hill daily, so that he becomes somewhat breathless, the lungs RESPIRATION 113 receive all the exercise needed to keep them properly active. The active boy or girl ordinarily gets plenty of lung exercise in play. It is important to remember, however, that with the quiet life which many persons live, especially in our cities, the lungs need special exercise to make them strong and to give them the amount of fresh air necessary for health. WHAT BREATHING DOES FOR THE BLOOD How Blood is changed in the Lungs. The blood which enters the lungs to be purified is very different from the blood which returns from the lungs to the heart. Four important changes occur in the lungs. 1. The Hood takes up oxygen from the air. The red corpuscles have the power of taking up oxygen from the air. Each one of the millions of these corpuscles takes from the air in the lungs as much of the oxygen as it can hold. As soon as the oxygen has been absorbed, the corpuscle becomes a brighter red than before, and consequently the blood itself is of a more brilliant color. The blood that flows into the lungs is bluish red ; the blood that comes out is bright scarlet. 2. The Hood gives up carbon dioxide gas. The car- bon dioxide gas leaves the blood, enters the air in the lungs, and is then expelled in the exhalation. 3. The blood is cooled. The blood is somewhat cooled while it is flowing through the lungs. The air which we breathe into our lungs is usually cooler than the body. In an ordinary schoolroom it is about 70. But the same air when expelled from the lungs is nearly 114 PHYSIOLOGY AND HYGIENE as warm as the body (about 98). It has been warmed in the lungs by the blood, the blood itself being cooled at the same time. 4. The blood loses some of its water in the lungs. If we breathe upon a cold windowpane, little drops of water collect, making the glass cloudy. These drops condense from the moisture we exhale. The air P breathed from the lungs is usually nearly saturated with vapor. When we walk out of doors on a cold winter's morning, we can "see our breath"; that is, the water in the breath condenses into a slight fog as it comes from the mouth or nostrils. This water all comes from the blood. Thus the blood on leaving the lungs contains less water than when it enters. How the Oxygen is Used. After the blood has taken the oxygen from the air in the lungs, it goes directly to the left side of the heart. From there, as we have already learned, it is sent to all parts of the body through the arteries, finally reaching the capillaries. The blood flows through the capillaries very slowly, and here each red corpuscle lets go of the oxygen it took while in the lungs. The oxygen passes at once from the blood to the tissues of the body around the capillaries. The red corpuscles are thus the oxygen carriers. They go to the lungs, seize the oxygen, and then carry it to every part of the body needing it. After they have given up the oxygen they become bluish red, so that the blood which leaves the capil- laries to go back through the veins to the heart is a dark bluish red. RESPIRATION 115 We have already seen that the oxygen is brought into the body to unite with the food, just as it unites with the fuel in a locomotive, and that as a result there is produced the waste gas, carbon dioxide. While the blood is passing through the capillaries, it not only gives up oxygen to the tissues but it takes from them the carbon dioxide which has been pro- duced. Thus when it comes back from the tissues to the heart, the blood is carrying carbon dioxide in the place of the oxygen. Such blood is called venous blood, and is said to be impure because it contains waste prod- ucts. When this blood reaches the lungs again it gives off the waste carbon dioxide it is carrying and gets another load of oxygen. Respiration is then an exchange of gases between the body and the air. The blood is all the time passing through the lungs where it gives up carbon dioxide, water, and other gaseous waste products and takes oxygen. Going thence to the various parts of the body, it supplies them with the oxygen and takes away the carbon dioxide. If anything hinders breathing, there is trouble, for the same reason that a fire will not burn unless there is a draft to furnish air to the burning coal. If breathing stops for more than a few minutes death follows, since the body is then unable to obtain oxygen or get rid of waste gas. Breathing and Exercise. We can readily under- stand why, if we exercise vigorously, the rate and the depth of breathing will be increased. If an engine is to work rapidly, it must have a good draft, and it must 116 PHYSIOLOGY AND HYGIENE burn large quantities of coal ; a large amount of ashes will be left, and a great deal of smoke will issue from its chimney. So with our bodies. If we are to work our muscles vigorously, we must have a large supply of oxygen to oxidize the necessary food, and an in- creased amount of waste will be produced. The blood must consequently flow faster than usual, both to furnish the oxygen and to carry off the waste. To accomplish this the heart begins to beat faster so as to increase the speed of the blood, and at the same time our breathing becomes more rapid, so that the rapidly flowing blood may be supplied with oxygen, and all the waste may be carried away. VENTILATION Need of Ventilation. It is evident that we need a great deal of pure air. The rooms in which we live should be well ventilated. There are two purposes in ventilation : 1. To furnish us with a sufficient supply of oxygen; 2. To provide air that can carry off dust, noxious gases, and moisture. Anything which uses up the oxygen in a room, or which allows too large an amount of breathed air to accumulate, renders the air unwholesome. If a great many people are breathing the air in a room, or if gas or oil stoves or lamps are using up the oxygen and giving out carbon dioxide, the air, unless changed, becomes oppressive and poisonous. In such cases it is especially necessary to attend well to the matter of ventilation. RESPIRATION 117 Evils of Indoor Life. People who live in warm climates spend much of their time out of doors. We in the colder climates have formed the habit of living in close rooms, where we remain for hours at a time. In the close rooms we are often forced to breathe over and over the air which has already been breathed by ourselves or other people, and this is most unwhole- some. The habitual breathing of impure air is partly the cause of some of the lung diseases, as pneumonia and consumption. This does not mean that people living out of doors never have lung troubles ; but such diseases are most common among those who live in close rooms. City workmen, though better fed than country workmen, are usually less healthy. If we could be in the open air most of the time, we should avoid many of these difficulties; but since in cold climates this is not pleasant in winter, we must at least keep our rooms supplied with plenty of fresh air. The Need of Fresh Air. Many people arrange their living rooms with a wholly mistaken idea of what is healthful. They seem actually afraid of fresh air. So careful are they to prevent drafts that they exclude fresh air. They think that they take cold because the rooms are not warm enough, or because of changes in temperature, so they keep the air as uniformly warm as possible. Probably more colds are due to over- heated or impure air than to drafts or cold air. We take cold from drafts frequently because we accustom ourselves to living in warm rooms. A temperature of from 65 to 70, depending upon how actively we are 118 PHYSIOLOGY AND HYGIENE ^mployed at the time, is the proper temperature for living rooms in cold weather. A very large class of people consider night air especially dangerous, and for this reason they sleep in rooms closed up tightly, to prevent fresh air from entering. Night air is no more injurious than day air, except that it is likely to bring mosquitoes, which should be kept out of the sleeping room ; and there is no time when a person should be more partic- ular that the air is pure than when he sleeps. The attempt to shut out night air from sleeping rooms is a grave mistake, and this is true both in winter and in summer. Fresh air is one of nature's best remedies for many diseases. If we determine to make it a point through life to breathe plenty of wholesome, fresh air, we have laid a firm foundation for vigorous health. How Rooms are Ventilated. More or less fresh air gets into the rooms of an ordinary dwelling house, no matter how tightly they may be closed. If a stove is used in a room, the fire causes a continuous draft up the chimney ; this draft always removes air from the room, and fresh air is drawn in from outside to take its place. The air comes in through the cracks about the doors and windows, through the keyholes, and more or less through cracks in the floors. The direction of the currents of air may be seen from Figure 40. When there are only one or two persons in a room, and the doors are opened frequently, sufficient fresh air is usually supplied from these sources. At night such ventilation is not enough. Unless the wind blows very hard, some RESPIRATION 119 arrangements should be made for constant change of air, such as opening a window at the top in such a way that those sleeping in the room will not feel a direct draft. An open fireplace, even if there be no fire in it, is an excellent means of ventilation, as shown in Figure 40. In houses heated by means of hot-air furnaces special devices are usually adopted for supplying fresh air. FIG. 40. VENTILATION. Showing the means by which air enters and leaves an ordinary room. The furnace is connected with what is called the cold box, which is open to the outdoor air. The air enters this box, passes into the furnace, is there heated, and then rises through the flues into the different rooms. All the while air is passing out of the rooms through cracks in the doors and windows, or rising through halls or ventilating flues in chimneys, which are usually left open in such houses. When houses are heated by steam radiators it is not so easy to keep the air pure ; for although currents of 120 PHYSIOLOGY AND HYGIENE air move up and down in the room they do not readily pass out, and we must depend for fresh air upon flues and open fireplaces. The difficulty in keeping a free circulation of air is partly the reason why a room heated by steam is apt to be "stuffy." In such a room there should always be some special arrangement for the outlet and inlet of air. Sufficient movement of the air may be obtained by means of open fireplaces, flues in the chimneys, ventilators around the windows, or windows slightly open at top and bottom. When a house with many doors and windows has many of its rooms opening into each other, ventilating flues are not especially necessary. When a room such as a schoolroom or a public hall holds a number of persons, special means should be adopted for replacing impure air. Such rooms are usually provided with special ventilating apparatus. It is worth while to remember, in any case, that cold, fresh air, from whatever source it may come, is less injurious than breathing repeatedly the air of a close, ill-ventilated room. There is one simple test of the ventilation of a room: Does the air seem fresh and sweet as you come from the pure outside air ? HOW TO RESTORE RESPIRATION Occasionally some accident stops a person's breath- ing and tends to produce suffocation. For example, when a person is submerged in water he can no longer take air into his lungs. If, however, the drowning person can be removed from the water RESPIRATION 121 while the heart still beats, and breathing can be started again, his life can usually be saved. After being taken from the water, the patient should be placed so that the head is lower than the shoulders, and turned face downward, to allow the water to run out of the mouth and throat. The process of arti- ficial breathing should then be started. The patient should be placed on his back, with the head on a level with the body. The arms should be first pressed against the sides of the body, and then raised outward and upward until they meet above the patient's head. Lifting the arms in this way raises the shoulders and ribs ; the FIG. 41. THE METHOD OF MOVING THE ARMS TO PRODUCE ARTIFICIAL BREATHING. size of the chest is thus increased, and air is drawn into the lungs. It is important to know that the air actually passes into the lungs. To be sure of this, the tongue must be drawn forward so as to open the throat and permit the air to pass. After the arms have been lifted, they should be lowered again, while a second person, if pos- sible, presses the abdomen and sides of the body. The 122 PHYSIOLOGY AND HYGIENE lowering of the arms and the pressure on the abdomen tend to force the air out by compressing the chest. The raising and lowering of the arms in this manner should be continued regularly from ten to twelve times a minute, and should be kept up until natural breathing starts. Although this work is hard, it should be kept up for at least two hours if normal breathing is not resumed earlier. A feather or other light object placed in front of the mouth will show when natural breathing begins. If there is any motion of the feather to indicate natural breathing, the movements of the arms may be stopped. The person should then be wrapped in warm clothing or in blankets, and nature will complete the restoration, although it will be an aid to have the extremities of the patient rubbed during the whole process. This method of restoration should be employed if a person becomes nearly suffocated from any cause. Persons have sometimes been in the water a quarter of an hour or even longer, and have still been brought back to consciousness. QUESTIONS 1. What gas is necessary for oxidation? What products re- sult from oxidation ? 2. Why should we keep our mouths shut except when talking or eating ? 3. Where is the windpipe ? 4. Of what use is the larynx ? 5. Where are the lungs situated ? 6. How does the blood get oxygen from the lungs? 7. How is air drawn into the lungs ? . RESPIRATION 123 8. Could a person breathe if there were a hole through the chest ? Why ? 9. What form the walls of the chest V 10. How is the chest cavity made larger or smaller? 11. If air is taken into the chest only, why does the abdomen swell out with each inspiration ? 12. How much of the air in the lungs is changed at a single breath ? 13. How can we exercise the lungs ? 14. What four things happen to the blood in the lungs? 15. What does the blood do with the oxygen it takes from the lungs? 16. If one should have too few red corpuscles in his blood, what would be the result ? 17. What is respiration ? 18. When you are running, can you breathe more easily through your mouth ? If you do, can you run farther? 19. Why does a schoolroom need better ventilation than a com- mon dwelling room? 20. What are the purposes in ventilation ? 21. What are the evils of indoor life? 22. How should rooms heated by stoves and furnaces be venti- lated? 23. What may be done to ventilate houses heated by steam? 24. How may natural breathing be restored when a person has been almost drowned ? CHAPTER VI THE FRAMEWORK AND MOTION OF THE BODY THE stomach digests food, the heart and the blood vessels are in constant action, the lungs never cease to expand and contract as long as we live. Those organs, then, all have a part in aiding us to accomplish the work that is given us to do. But with stomach, heart, and lungs alone we could neither step, nor speak, nor move in any way. We must have in addition muscles and bones. Of these our bodies are largely made, and it is to repair and renew these, as well as to render them of practical use, that we possess the organs about which we have already studied. THE SKELETON Most of the parts of our bodies are soft, and if there were not a hard framework to support them, we should be nearly as flexible as jellyfish. But inside the pli- able flesh we have solid bones, which serve, like the beams of a house, as a support for the softer parts. This framework of bones is called the skeleton. A grown person has in his body two hundred different bones. A child has even more, but several of the bones grow together later, making just two hundred. 124 FRAMEWORK AND MOTION OF THE BODY 125 FIG. 42. THE HUMAN SKELETON. 126 PHYSIOLOGY AND HYGIENE The bones are of different shapes and sizes. Figure 42 shows the framework of the body, indicating the position and shape of the various bones. As will be seen from the figure, there is in the middle of the back a strong support, called the backbone. It is not one single piece, however, but a series of small bones fitting snugly to- Spinol Cord gether and capable of being moved. If the back contained only one bone, it would be stiff and easily broken, but this series of small bones enables us to bend the back with- out danger of break- j n g it. Each of the smaller bones of the back is called a verte- bra. Figure 43 shows two vertebrae. Many other animals have backbones made up of vertebrae. These include fishes, reptiles, birds, and the four-footed animals with which we are familiar. All such animals are called vertebrates. Figure 42 shows a large, rounded box just above the backbone. This is the skull, which forms the head. A side view is given in Figure 44. The skull is one of the most important parts of the body, because of the organs it contains. In it are the brain, the eyes, the ears, and the organs of taste and smell. Cord FIG. 43. Two VERTEBRA IN POSITION. Showing the spinal cord passing through them. FRAMEWORK AND MOTION OF THE BODY 127 The chest, as we already know, contains the heart and the lungs. It is nearly surrounded by curved bones called the ribs. These extend from the back- bone around to the front. The heart and the lungs Craniuin Facials fonts \ Occipital Mandible FIG. 44. THE HUMAN SKULL. are surrounded and thoroughly protected by these ribs and the breastbone, or sternum. Each of the arras and legs is made up of several bones. In Figure 42 these bones are named. The bones of the arms and legs are the longest in the body. Since they are the ones that must bear the heaviest strains, they are also the strongest bones of the body. 128 PHYSIOLOGY AND HYGIENE ftorro* THE BONES Structure of Bone. The different bones are of various shapes, but they are all so made as to have the greatest strength and at the same time to be comparatively light. For example, the long bones of the leg and the arm, which must bear the greatest strains, are hollow. Figure 45 represents the longest bone of the leg, cut open lengthwise. At the ends the bones are spongy, but throughout the length of the shaft they are hollow. This shape gives the greatest possible amount of strength to the bone for a given weight of bony substance. Although not all the bones are hollow like those of the leg, still all are so built as to make the skeleton strong and light. This allows greater ease of motion than would be possible if the bones were heavier, and yet renders them sufficiently strong for the work they must ^0. Bone Materials. Bones are made of two different materials, one of which is called mineral matter, the other animal mat- ter. The mineral matter is hard and brittle, and gives stiffness to the bone. If we put a bone upon a hot coal fire, and allow it to stay there for half OF THE FEMUR. Showing the spongy ends and hollow center FRAMEWORK AND MOTION OF THE BODY 129 an hour, it will be very much changed. Though the shape will be the same, the heat has made the bone light and very brittle, so that it can be crumbled to a powder in the fingers. The hot fire has burned the animal matter out of the bone, leaving only the mineral matter, which is something like stone, and cannot be burned. On the other hand, if we put a small bone, such as a chicken bone, into a dish of dilute nitric acid and allow it to remain there for a day or two, the acid will take out all the mineral matter. Upon removing the bone from the acid, we shall find it unchanged in shape and size, but soft and flexible, so that we can bend it, and perhaps even tie it into a knot. What is left is animal matter only. The mineral and the animal matter are united in bone so as to form one substance. The animal matter gives strength, while the mineral matter gives hardness. Bones of Children. Occasionally a child may fall down a flight of stairs with no ill effects save a few black-and-blue spots, while the same fall would be likely to injure a grown person seriously. The reason is that there is proportionately more animal matter in the bones of children than in those of adults, and the bones of children are therefore more easily bent and are not so brittle. In very early childhood the bones are made entirely of animal matter, and are conse- quently soft and flexible like the bone which has been soaked in acid. As the child grows, more and more of mineral matter is deposited in the bones, until finally they become hard and stiff. 130 PHYSIOLOGY AND HYGIENE During the first few years of a child's life the bones are so flexible that they can be bent out of shape more easily than in later life. For this reason special pains should be taken to teach children to hold the body erect. A good carriage in walking can be learned by every one, but most easily by children. The chest should be held up properly, and the chin kept in, not thrust forward. If the chest is kept up and the shoulders are thrown back, the body will take the best position for walking and standing. When sitting we should take care to sit with head erect, and with the back against the back of the chair or bench. Misshapen Bones. If the bones of a child are con- stantly bent in one direction, they will be deformed. Although it is easy for a child to stand and sit erect, it is equally easy to become "round-shouldered." After the bones have hardened it is as difficult to change the habits as it was easy to form them, and later in life it may be impossible. Any kind of dress that causes strong and long- continued pressure on the bones is likely to cause a misshapen body. Wearing tight shoes will deform the bones of the feet. Figure 46 indicates the shape of the toes of a FIG. 46. THE CRAMPED FOOT. FIG. 47. THE UNCRAMPED FOOT. person who wears tight shoes. Figure 47 indicates the shape the foot takes when it is not cramped. Wrongly FRAMEWORK AND MOTION OF THE BODY 131 shaped and tight shoes cause much discomfort and render walking difficult, besides putting the feet in such a condition that the person is likely to suffer from the effects all through life. Deformed feet may be FIG. 48. AN IMPROPERLY FIG. 49. A PROPERLY SHAPED SHAPED SHOE. SHOE. produced by shoes with narrow toes or with heels so placed as to throw the weight of the body upon the toes, as shown in Figure 48. A properly shaped shoe is shown in Figure 49. A habit even worse than pinching the feet is that of wearing tight bands round the waist, or tight cor- sets. This gives rise to serious deformities, affecting not only the bones but also the important vital organs of the abdomen which are pressed out of proper posi- tion. The leather belts sometimes worn by boys and young men with outing costumes, if drawn tight around the waist, instead of being placed over the hips, are almost equally bad. Good health requires that the body be allowed to grow as nature intended, unconfined by tight clothing. 132 PHYSIOLOGY AND HYGIENE Habits of stooping over one's work, of leaning against a support instead of standing erect, of standing con- stantly upon one foot without bearing sufficient weight upon the other, of walking or sitting with stooped shoulders and with the head thrown forward, or of wearing clothing which binds the body any of these habits will destroy the beauty of the form and impair bodily strength. Among the prime necessities for attractiveness in appearance is an erect manner of walking and sitting, without slouching. The cadets in the military schools owe much of their fine appearance to constant drills, which exercise all the muscles, and which keep the body erect. Repair of Broken Bones. As many a boy knows from personal experience, bones will occasionally get broken in spite of the fact that they are tough and strong. Very fortunately, unlike broken teeth, bones when broken can be mended. Each bone is supplied with one or more tiny blood vessels, which furnish blood for its nourishment. The animal matter in the bone is alive, and so is able to grow. If, after a bone is broken, the two ends are brought nicely together, this living part of the bone begins to make new bony material, which grows between the ands, finally uniting them again as strongly as ever. The bone must be kept still until it is firmly knit, for any motion would pull the ends apart. For this rea- son the physician binds the broken bone tightly in splints. The setting of a broken lone consists simply in bringing the broken ends together and binding them in the proper position. FRAMEWORK AND MOTION OF THE BODY 133 Since there is more animal matter in the bones of a child than in those of a grown person, broken bones are more easily mended in childhood. In old age the amount of animal matter is less, so that the bones are more brittle and more easily broken. They are also less easily repaired. CARTILAGE The framework of the body is not wholly bone. A part of it is made of a substance called cartilage. This is so soft that it can be cut with a knife. It is so flexible that it can be bent easily, but at the same time it is very tough. It is found in several places in the body where there is need of greater flexibility than bone would give. For example, the ribs are united with the breastbone at the front of the chest (see Fig. 42) by little pieces of cartilage. This makes them slightly movable and not Cartilage easily broken. Little cushions of cartilage are also found between the vertebrae of the backbone, as indicated in Figure 50. Here they relieve the jar which would result from a jump, if the bones actu- FIG. 50. Two VERTEBRA. ally touched each other. Showin S the cartila s e cushion that separates them. There are pieces of carti- lage around the larynx, and the outer ear is made entirely of cartilage covered with skin. Cartilage 134 PHYSIOLOGY AND HYGIENE is not easily broken, but if once severed, it does not mend so easily as bone. JOINTS When we consider that the framework of our bodies is made of two hundred separate pieces, we wonder how they can ever be united in a firm struc- ture. They are fastened as firmly as the parts of a house are nailed together. In some places, as in the skull, they are so united that they cannot be moved. In other places, as at the elbow and in the fingers, they can be turned about freely. Whenever two bones come together they form a joint. If it were not for our joints we could not move ; and when an accident injures a joint, we become stiff and lame. There are two principal kinds of joints in the body, the hinge joint and the ball-and-socket joint. Let us see what each is like. A Hinge Joint. The bones forming a hinge joint can be moved back and forth in one direction only, like a door on its hinges. The joints at the knee and the elbow are of this character, as is also each joint of the finger. If we try to move the finger or the elbow, we find that it will move in one direction only. The hinge joints are all so much alike that we need to study only one in detail. Let us take the knee joint as an illustration. Two bones come together at the knee to form the joint, the thigh bone, or femur, and the shin bone, or tibia, as shown in Figure 51. The ends of these bones FRAMEWORK AND MOTION OF THE BODY 135 are large and rounded, and the two fit together so as to be very easily moved. As can be seen from Figure 51, these bones are so shaped that they can be moved back and forth, but not sidewise. The ends Cartil( Fibul^ FIG. 51. THE BONES FORMING THE KNEE JOINT. of the bones, which are rounded and smooth in them- selves, are made still smoother by being covered with a layer of soft cartilage. To keep the parts of a bicycle in smooth running order we oil them. The various joints of the body are provided with a liquid that takes the place of oil in the wheel. This is the way it is arranged : the bones of the joint are partly surrounded by a thin membrane or tissue, which supplies a liquid to the joint between the two bones. The liquid moistens the ends of the bones, thus preventing friction. If it were not for this liquid the bones would rub against each other, and it would be impossible to use the joint. The 136 PHYSIOLOGY AND HYGIENE of the bones themselves and their smooth ends, together with the liquid, allow very free motion. How the Bones are held together. No matter how nicely two bones might be fitted together, if they were not well fastened in some way the slightest twist would put them "out of joint." As it is, a bone occasionally ..Anterior Copsular Ugdme Posterior Ligament FIG. 62. THE KNEE JOINT. Showing the ligaments connecting the bones. slips out of place, but only when there is a severe strain of the joint. To avoid such danger the ends of the bones are fastened together by two kinds of con- necting bands which extend from one bone to the other. These are ligaments and muscles. The ligaments are made of a white, tough, flexible sub- stance. Several ligaments may be seen in Figures 51 and 52. They pass from one bone to the other across the joint. Some of them are placed in front, some at the sides, and some at the back. The ligaments are, however, rather loose, so that while the bones cannot slip out of place, they might, if they were held in no other way, move too freely. FRAMEWORK AND MOTION OF THE BODY 137 In addition to the ligaments, therefore, the bones are held in position by means of certain muscles. The motion of the bones at the knee joint is produced by the muscles, all of which lie above the knee. From the ends of the muscles, long, slender cords or tendons pass down over the knee joint and are attached to the bones below the knee. These muscles are elastic and, being slightly stretched, they help to hold the bones in close contact. Outside of the muscles is the skin, which covers the bones, tendons, ligaments, and muscles, form- ing a protection for them all. We move our joints so unconsciously, as we take a step forward or sit down in a chair, that we hardly realize how complicated they really are. But when we consider that so complicated and well-fitted an arrange- ment is provided simply to enable us to move a knee, we cannot fail to hold these bodies of ours in great respect. A single hinge joint means that we have two smooth bones rounded just so as to fit into each other, strong ligaments to bind them together, muscles and tendons to assist in movement, and a protecting skin surrounding all. Other Hinge Joints. The other hinge joints of the body are like the knee joint. In all cases the bones are rounded and are moistened with the liquid to pre- vent friction. All are held together by muscles and ligaments, and all are so arranged that they can be moved in only one direction. The joints at the elbows, at the wrist and ankle, and in the fingers and leg are all hinge joints. 138 PHYSIOLOGY AND HYGIENE A Ball-and-Socket Joint. To show the arrangement of a ball-and-socket joint we will study the shoulder joint. In general such a joint allows the bones to move in every direction. We can lift the arm above the head, to the front, to the side, turn it around, and bend it backward as far as the hinge joint at the elbow will allow. The two bones which form the shoulder joint are the shoulder blade, or scapula, and the upper arm bone, or humerus. The shapes of these bones may be seen from Figure 53. As is evident from the illustration, the shoulder blade has a somewhat rounded hollow. The up- per end of the arm bone is rounded like a ball and fits into this socket or hollow. Since the end of the arm bone is a ball, and the socket in the shoulder blade is a hollow cavity, the arm can be moved in all directions. It is this shape of the bones that gives us our great freedom in lifting the arms. The ends of the bones are not only rounded, but they are made particu- larly smooth by being covered with cartilage, and they are also moistened with liquid like that in the hinge joint. The bones are bound together at the shoulder by just such strong bands as we saw at the knee. There is, FIG. 53. THE BONES OF THE SHOULDER JOINT. FRAMEWORK AND MOTION OF THE BODY 139 however, as Figure 54 shows, only one important liga- ment. It is a loose, leathery sac fastened to the shoulder blade. From the shoulder blade it passes over the joint on all sides, and is attached to the upper end of the arm bone, so as to cover the joint com- pletely, and hold the end of the arm bone in the socket. If this ligament Should be cut, the bones p IG . 54. THE SHOULDER JOINT. could be taken apart very Showing ligaments, easily. The strength of the shoulder joint is due very largely to the fact that it is surrounded by strong muscles. These muscles cover the joint on all sides, giving it great strength and firmness. The muscles in the shoulder have tendons which pass down over the joint and are fastened to the arm bone, thus holding it firmly in position. Other Ball-and-Socket Joints. The only large ball- and-socket joints in the body, besides those at the shoulders, are at the hips. The hip joint allows the leg to be moved in various directions, but the movement is not quite so free as that at the shoulder. Injuries to Joints. There are two kinds of injuries to joints which are common. They are dislocations and sprains. A bone pulled out of its place in the socket pro- 140 PHYSIOLOGY AND HYGIENE duces a dislocation. If, for example, a fall or a wrench should pull the end of the arm bone from the hollow in the shoulder blade into which it fits, we say the shoulder is dislocated. When a bone is thus wrenched from its proper position it cannot be moved in the ordinary way. The bone must be put back in its normal place in the joint. This should be done by a physician, unless it chances to be one of the small bones in the finger, which almost any one can pull back into place by slightly pulling the bones apart and then slipping the dislocated bone into position. When a bone is dislocated, it is very likely that some of the connect- ing bands or ligaments may be strained or slightly torn. A sprain is a tear or strain in one or more of the ligaments of a joint, A sprain is common in con- nection with dislocated joints, but it occurs frequently, also, when there is no dislocation. A violent strain at any joint may cause such a pulling on the ligaments as to injure them and produce a sprain. The injury is sometimes very slight and sometimes very great. A sprain may be even more serious than a dislocation or a broken bone, requiring a longer time to heal. In case of a sprain, the joint should be placed in a comfortable position. Water, as hot as can be endured, should then be applied, and this should be followed by cold water. The joint should be bound tightly with band- ages. It is wise, of course, to rest the joint, but it is not wise to keep it perfectly still during the healing process, lest it be stiff for a long time. The sprain will be more quickly healed if, beginning say a day or FRAMEWORK AND MOTION OF THE BODY 141 two after the accident, the joint is used a little each day. THE MUSCLES A large part of the food we eat is used to enable us to move. The motions of the body are brought about by the muscles. The lean part of meat consists of muscles, and the muscles in our bodies are very similar in appearance to lean beef, as it comes from the market. The joints, ligaments, and tendons of themselves would be unable to move the body. It is through the muscles that the power is applied. Structure of a Muscle. To understand the structure of a muscle, let us look at the one in the front part of the upper arm, known as the biceps, which we see represented in Fig- mre 55. The biceps muscle, as the figure shows, is a rather long mass of flesh, large in the middle but taper- ing at the two ends. The middle part is made up of reddish flesh, and is the mus- cle itself. At the ends firm, white bands or cords, which neither contract nor expand, connect the muscle with the bones. These are tendons or cords. Ufno FIG. 55. Showing the method of attachment of the biceps muscle to move the fore- arm. 142 PHYSIOLOGY AND HYGIENE Most of the muscles in the body are connected with bones by tendons. The tendons differ in length, some of them being very short. A series of such cords at the wrist extends from the arm to the fingers, and at the ankle from the leg to the toes. If we grasp the left arm just below the elbow with the right hand, and then open and close the fingers of the left hand, we can feel the motion of the arm muscles. These muscles move the fingers, and are connected with them by the long tendons which pass to the finger bones. If we clinch the fingers of the left hand and grasp the wrist with the right hand, we can feel how tightly the tendons are stretched as they pass along the front of the wrist. Figure 56 shows their arrangement. A muscle seems to be a solid mass FIG. 56. f flesh. If we examine it under a Showing the muscles microscope, however, we find that it is and tendons of the rea }iy ma d e up of an immense number Erm. of threads or muscle fibers, as they are called. We can see how the fibers are arranged, from Figures 57 and 58. These muscle fibers are too small to be seen without a microscope. They run lengthwise in the muscle, and they are very numerous. They are bound together by a thin, delicate substance which fastens them firmly to one another. FRAMEWOIIK AND MOTION OF THE BODY 143 Great numbers of minute blood vessels run in and out among the fibers, furnishing the muscle with its nourishment, as shown in Figure 36, facing page 108. These blood vessels are the capillaries which, as we learned, receive the blood when it leaves the arteries, before its return to the heart by way of the veins. The walls of the capillaries are so thin that the food which is FIG. 57. A BIT OF MUSCLE. Slightly magnified. Musclf? fibers FIG. 58. A BIT OF MUSCLE. Highly magnified, showing muscle fibers. in the blood passes through them to the muscle fibers, giving them power to move and building them up. Involuntary Muscles. There is another kind of muscle which we hear less about. These muscles are called involuntary muscles, because we do not consciously control them. The most important are those which form the walls of the stomach and intestines and propel the food, and those which contract and expand the arteries 144 PHYSIOLOGY AND HYGIENE and thus regulate the flow of blood. These muscles are very different in appearance from the ones we have just described, but they also are made of microscopic fibers, bound together in flat masses. They are much more sluggish in their action than the other muscles, and we not only have no control over them, but we are not even conscious of their action. But since they drive the food along the intestines and control the flow of blood, they are of great importance. The Contraction of a Muscle. If we stretch a rubber band, it becomes longer and thinner ; when we let go of the ends, it shortens and becomes as thick as before. In somewhat the same way the muscles of the body are shortened, the muscle growing thicker as it con- tracts. If we clinch the left fist, grasp the left arm above the elbow with the right hand, and then lift the forearm forcibly, we find that the biceps mus- cle becomes larger and harder as the hand is raised. After the arm has been lifted, the muscle may hold it up for a time, but to do so constant effort is required. The moment we relax the effort the arm falls of its own weight. To lift the arm the muscle must be con- tracted, but no muscular effort is required to lower it. There is, however, on the back of the arm, as shown in Figure 55, a muscle which acts in the opposite way from the biceps. If this muscle shortens or contracts, it pulls the arm down, stretching the biceps, as may be understood from Figure 55. The two muscles thus form a pair opposed to each other ; when one of them contracts, the other is lengthened. One lifts the arm FRAMEWORK AND MOTION OF THE BODY 145 up, and the other straightens it. It is the contraction of a muscle that produces motion or action. What makes the Muscles contract. In addition to the blood vessels in each muscle, there is connected with it a white cord a nerve. This nerve is larger in the large muscles than in the small ones. The nerve is made up of nerve fibers, and each muscle fiber re- ceives its nerve fiber. All of these fibers are connected with the spinal cord, and through the spinal cord, with the brain. Why are the muscles connected with the brain? Just this : The nerves serve much the same purpose as electric wires. The muscles never contract of their own accord any more than an electric bell will ring itself. To ring the bell we must press a button. This sends an electric current through the wire and causes the bell to ring. In about the same way the muscles of the body act, when the proper kind of message comes to them. If the current, or stimulus, as it is called, never comes, the muscle will remain quiet for- ever. The stimulus is given to the muscle through the nerves. The brain, which is the central station for all kinds of action, is able to send stimuli down to the muscles through these thousands of little threads, and when the muscles get the message they contract. The involuntary muscles are excited into action in the same way, for, although we do not will to move them, the brain sends stimuli to them as it does to the other (voluntary) muscles. This power which the brain has over the muscles 146 PHYSIOLOGY AND HYGIENE is very wonderful. Not only can the brain cause a single muscle to contract at any time, but it can cause many muscles to act together, either in connec- tion with one another or separately. For example, when a boy throws a stone, he lifts his arm, closes his fingers about the stone, presses one foot hard against the ground, and sets his body firmly to assist in the throw- ing ; then he must quickly contract the muscles of the arm and shoulder, and loosen the stone from his fingers. In all, from fifty to a hundred muscles must be con- tracted at nearly the same time. The boy does not realize that he is using such a wonderful machine, or even that he is contracting muscles. He simply thinks, " I will throw the stone," and the brain gives the proper order to the numerous muscles. The message must be sent to each of these muscles at the same time, and must cause each to contract just the right amount. If the brain should make a mistake, and cause some muscles to contract too much or not enough, the stone would go wide of the mark. This really happens many times when the boy is learning to throw straight. We say that " prac- tice makes perfect"; that is, the boy must learn how to throw the stone just where he wants it to go. In other words, the brain must learn how to make the muscles work in the proper way. Number and Positions of the Muscles. The fleshy part of our bodies is made up of a little more than five hundred muscles. They differ in size and shape. Most of them are fastened to at least two bones, so FRAMEWORK AND MOTION OF THE BODY 147 that as the muscles are contracted the bones are moved. Figures 56 and 59 show how the muscles are arranged in the body, though compara- tively few are represented here. The various muscles are so attached to the bones that they can be moved in all the directions that the joints permit. We can bend the arm or straighten it ; we can move it to either side or turn it around, each motion being produced by a different set of muscles. Muscle Growth. It is a peculiarity of muscles that the more they are used, the stronger they grow. The blacksmith, because he con- stantly swings his heavy hammer, develops very strong muscles in his arms. When a person learns to ride a bicycle, he finds that certain muscles of his legs are weak, but, as he continues the exer- cise, the muscles become stronger, until he can climb even high hills without any great strain. One set of muscles, however, should not be developed and others FIG. 59. THE SURFACE MUS- CLES OF THE BODY. 148 PHYSIOLOGY AND HYGIENE neglected. The man who has all his muscles moderately well developed is stronger and more healthy than the one who has highly developed his arm muscles with- out exercising equally the other muscles of the body. If muscles are not used, they become small and weak. If a muscle were left idle for a few months, it would lose much of its power, so that we could not use it at all. Children in their active play ordinarily use all their muscles, so that they develop evenly. But as people grow older, certain muscles are used less and less. We take the trolley-car and the elevator to save the trouble of walking: as a result, we find that we cannot walk so far as we could a few years ago. We use the right hand in our work rather than the left, and the left hand is weaker and less skillful. We sit in a comfortable easy-chair until the muscles of the back are weakened, and as a result we cannot sit upright for any length of time without fatigue. Although we really want our bodies to be well developed and vigorous, we get into these habits of neglecting the muscles from carelessness. Exercise. It is worth our while to make special efforts to use all the muscles of the body. If we find that certain muscles are weak, those are the ones that we should take pains to exercise. Too frequently we do the reverse. If we find something that is particularly hard for us to do, perhaps sweeping or sawing wood, that is just what we should do every day, until the muscles are so developed that we find it easy work. In large cities the chances that young people have FRAMEWORK AND MOTION OF THE BODY 149 for muscular exercises are limited. For this reason gymnasiums have been erected in cities, and especially in schools and colleges. The person who commonly needs the most urgent advice to take exercise is the boy or girl who is ambitious to become a scholar. He prefers to spend all his time at his books, and is not willing to give even a little time each day to ac- tive exercise. He should remember that the person who studies all the time is likely to be outstripped by the one who studies and plays as well. Many students break down because they do not take sufficient exercise. Out-of-door games afford the best possible exercise, since these not only develop the muscles but give the player fresh air and recreation at the same time. Such games as baseball, golf, and tennis are excellent. Bicy- cling is good exercise, though " century runs " and very fast riding are dangerous, and the habit of bending over the handle bars makes one liable to what is known as bicyclers' stoop. Brisk walking and running are very good exercise ; strolling can hardly be called exer- cise at all, although in other ways a quiet walk in the open country is beneficial. The royal maxim for perfect body development is : A perfect body requires the development of all muscles ; all powers unused are weakened. So-called "Stimulants." Some people have the mis- taken idea that they can increase their muscular power by using what are wrongly called stimulants, generally meaning some form of liquor. For a short time after a 150 PHYSIOLOGY AND HYGIENE person has taken the alcohol there may be a slight increase of muscular power, but a decrease of such power follows very soon, so that there is in the end an actual loss of power. If alcohol is used in any consid- erable amounts, there is a great weakening of muscular power. The use of alcohol will unfit any boy for good work in an athletic contest. Under no conditions does alco- hol enable an athlete to do his best. It has a tendency both to weaken the muscles and to dull the senses. Boys and young men sometimes make the mistake of trying to " brace themselves up " for a contest by the use of alcohol. Professional athletes know enough to let alcohol alone under these circumstances. QUESTIONS 1. Of what is the framework of the body made ? What is this framework called? 2. What organs are inclosed in the skull ? 3. How are the long bones of the arm and leg constructed ? 4. Of what are bones made ? 5. If we did not have enough lime in our food, what effect would it have on the bones? 6. How do children's bones differ from those of a grown person ? 7. What happens to the bones if there is unnatural pressure upon them ? 8. What are the results of wearing tight clothing ? 9. How are broken bones repaired ? 10. What is cartilage? Where is it found? 11. What two kinds of joints are there in the body? 12. How is a hinge joint made ? FRAMEWORK AND MOTION OF THE BODY 151 13. Mention all of the kinds of supporting and connecting tis- sues found in the body. }4. What is a ligament ? 15. What is a tendon? 16. How does the ball-and-socket joint differ from the hinge joint ? 17. How are the bones in a ball-and-socket joint fitted and fastened together ? 18. Whj do we have a hinge joint at the knee instead of a ball- and-socket joint? 19. Why do we need a ball-and-socket joint at the shoulder? 20. What is meant by dislocation ? 21. What is a sprain ? 22. What are the parts of a muscle? 23. How is a muscle contracted? 24. How is the muscle contraction controlled by the brain ? 25. W T hy is it that a person falls over if he suddenly faints or dies, when in a sitting or standing position ? 26. W r hat effect have exercise and lack of exercise upon the muscles ? 27. What are the best kinds of exercise? 28. Give some examples from your own observation of loss of power from disuse. 29. W T hat is the effect of alcohol upon the muscles ? 152 PHYSIOLOGY AND HYGIENE A LIST OF THE CHIEF BONES IN THE BODY All forming the skull. The nasal bones. The frontal bones. The parietal bones. The occipital bone. The mandible or lower jaw j The sternum or breastbone. 1 Forming the The ribs from the backbone to the sternum, j thorax. The vertebrae forming the spine. The sacrum at the lower end of the vertebrae between the hips* The coccyx, a small piece of bone below the sacrum. The scapula or shoulder blade. The clavicle or collar bone. The humerus, from the shoulder to the elbow. ] The radius and the ulna, from the elbow to the wrist. The carpals or wrist bones, eight in number. The metacarpals, from the wrist to the fingers. The phalanges or finger bones. The ilium, i Fused together to form the hip bone, or pelvic girdle. The arm. The pubis. The ischium. The femur, from hip to knee. The tibia and fibula, from knee to ankle. The tarsals or ankle bones. The metatarsals, from ankle to the toes. The phalanges, or bones of the toes. The leg. CHAPTER VII THE KIDNEYS AND THE SKIN AND THEIR DUTIES WASTE PRODUCTS Use of Food by Muscles. A muscle is like a little steam engine which cannot work except when burning fuel. We have seen how the different foods are carried throughout the body by the blood. When these foods reach the capillaries, the muscle fibers take what they need for their use. The proteids serve especially to make new muscle tissue, which is constantly needed to take the place of that used up by the work of the muscle. The proteid or building foods are also needed to repair any injury that may have come to the muscle, and to supply the new material needed when the muscle is developing and growing. The sugars and fat, with some of the proteids, simply furnish heat and force ; in other words, they are fuel foods. The food is oxidized in the muscles by means of the oxygen brought by the blood. As a result, force is developed to enable the muscles to contract, and heat is produced to warm the body. Waste Products of Muscle Action. When coal or other fuel is burned, or oxidized, smoke and gas pass off into the air and ashes are left in the grate. These 153 154 PHYSIOLOGY AND HYGIENE are waste products, because they are not used and can- not be used for heating. When the fuel food of the body is oxidized in the muscles and tissues, waste products are left, which are of no further use. These are carbon dioxide, water, and other substances. These waste products must be gotten rid of. We have already seen how the carbon dioxide is taken away by the blood, and breathed out of the body from the lungs. We know also that some water goes out in the breath. A larger quantity of water passes off through the skin and from the kidneys, as we shall see presently. The third waste product, known as urea, is taken from the blood by the kidneys, and finally leaves the body in the urine. A large proportion of the food we eat is taken by the muscles to supply muscular force. Some of it is used in the brain, a small amount in the glands, and certain quantities in every active part of the body. But, al- though the uses made of the food may differ in the various places, the same oxidation takes place, and the same waste products always result. Secretions and Excretions. The materials produced by the body are generally classified under two heads. Those like carbon dioxide and urea are simply waste products and of no use at all. They are generally called excretions. But some of the materials are pro- duced for special purposes. For example, the gastric glands in the stomach produce gastric juice to aid digestion, and the salivary glands produce saliva for the same purpose. Materials which are thus of use to the KIDNEYS AND SKIN AND THEIR DUTIES 155 body are called secretions, and they are generally pro- duced by special organs called glands. We have already learned of several of these, the salivary glands, the gastric glands, and the pancreas. The excretions are not only of no use, but if allowed to collect in the body they act as poisons. Hence they must be gotten rid of promptly. Some of them can pass off through the lungs in the breath, and some from the skin in perspiration, but some are disposed of in other ways. The urea in particular is eliminated by special organs. THE KIDNEYS Urea is thrown off from the body by means of a pair of organs called the kidneys. Each kidney is, in a grown FIG. 60. THE KIDNEYS. The one on the right is cut open to show the tubes which secrete the urea. 156 PHYSIOLOGY AND HYGIENE person, some four inches long and one and a half inches wide. The kidneys are located in the back part of the abdomen, just below and behind the stomach, and close to the backbone. Their shape is indicated in Figure 60. A large artery brings the blood to each kidney, as the same figure shows, and a large vein takes the blood away. There is also a tube, called the ureter, that passes from the kidney to the bladder, and takes away the material removed from the blood by the kidney. The kidney is made up of a large number of blood vessels, together with a series of small tubes, called kidney tubules, as shown in Figure 60. As the blood passes through the kidney, the tubules take the urea and some other solid matters which are dissolved 4 in the blood. This material, together with considerable water, which is also taken from the blood, is poured into the ureters, and passes to the bladder and then out of the body. THE SKIN Although mainly of use as a covering for the body, the skin has special functions of its own. It serves as a means for the passing out of waste and for regulating the heat of the body. A healthy skin is absolutely necessary if the body is to be in good condition. Slug- gishness or improper action of the skin in its work is likely to cause sickness. Structure of the Skin. The skin is a thick sheet like a close-fitting garment, covering the entire body. A grown person has about sixteen square feet of skin. KIDNEYS AND SKIN AND THEIR DUTIES 157 The average thickness is about one sixteenth of an inch, though it is thinner in some places than others. It is thickest on the soles of the feet and the palms of the hands. If we take a thin slice of skin and look at it through a microscope, we find that it has two layers, one outside of the other, as shown in Figure 61. The outer layer is called the epidermis, and the inner layer is the dermis. We can stick a pin through the epider- mis without feeling it, but the instant the point enters the dermis we feel pain. All the epidermis, except a thin layer on the inner side, is practically lifeless, and contains neither nerves nor blood vessels. The dermis is full of blood vessels and nerves, and is very sensitive. The Epidermis. The epidermis, though lifeless at the outer surface, is continually growing on the inside, where it is in contact with the dermis. Very often FIG. 61. A SECTION OF A BIT OF SKIN. Highly magnified. 158 PHYSIOLOGY AND HYGIENE when we look at our hands we can see one or more bits of loose skin which may be pulled off without harm. The outside skin is all the time being thus worn or rubbed off, bit by bit, arid it keeps growing from the inside. The epidermis is so firmly attached to the dermis that the two are not easily separated. Occasion- ally we burn a spot on the finger, or are severely sun- burned, so that blisters appear, that is, a little watery material has gathered between the epidermis and the dermis. If the blister is broken and the outer skin removed, the dermis is exposed. This is always sen- sitive and tender. Thick Parts of the Epidermis. A boy who is an en- thusiastic ball-player is very proud of certain bunches on the palms of his hands, called callosities. The constant rubbing and striking of the ball causes the epidermis to grow more rapidly at these spots than elsewhere, and so it becomes thicker. Any part of the skin that has an extra amount of use grows thicker than the rest, this being nature's means of protection against injury. If we wear tight or poorly fitting shoes that con- stantly rub the toes, round bunches called corns are formed by the thickening of the skin. We can pre- vent the growth of corns by wearing shoes large enough not to pinch the toes, and yet snug enough not to chafe the feet. It is difficult to get rid of corns after they have once formed, so it is wise to avoid the great discomfort which they cause by taking proper care of the feet. Children who go barefooted in the summer rarely have either corns or deformed toes. KIDNEYS AND SKIN AND THEIR DUTIES 159 -Hair Occasionally certain parts of the skin grow too thick, causing what are known as warts. Children are apt to be superstitious about these growths, because they come and go so suddenly. Some children believe that warts result from handling toads, and that they can be cured by the use of certain charms, both of which are absurd ideas. If a wart grows large enough to be really troublesome, it can be burned off with acid, but under ordi- nary conditions warts had better be let alone. They will disappear without assistance in time. Hair. Nearly all parts of the skin are covered with hair, which is an outgrowth from the epidermis. Oil Gland Hair Follicle r "* Cells FIG. 62. A HAIR. Showing its root and follicle. Figure 62 shows that each hair extends down through the skin into a little pocket. This is called the hair follicle. papilla, which is the place where the hair grows, is located at the bottom of the pocket. The hair is thus constantly growing at its root, and being thus pushed out of the pocket. In other words, the hair grows from A very small mound, or 160 PHYSIOLOGY AND HYGIENE the roots, not from the ends. If a hair is pulled out, the little mound at the root usually keeps on sending out more substance, so that a new hair grows to take the place of the old one. If the whole follicle, includ- ing the mound at the bottom, is destroyed, no new hair will grow. Each hair is supplied with oil from tiny oil glands. These open into the follicle from the sides, as shown in Figure 62. They produce an oily substance that mois- tens the outside of the hair, keeping it soft and flexible. If the hair is brushed frequently, the oil will be distrib- uted over it, so that no hair oil need be used to keep it in good condition. We should never brush the hair with anything but a soft hairbrush. Wire brushes are likely to scrape the scalp so that the follicles may be injured, and they may pull out the hair. Hair is lifeless and has no sensations. If we place a hand upon the head, we may feel the touch, but the feeling is not in the hair itself ; we feel the pushing of the hair against the nerves in the skin. We say that a cat's whiskers are very sensitive. The feeling is not in the hairs themselves, but in the very delicate nerves about the roots. Hair grows on all parts of the body excepting the palms of the hands and the soles of the feet. In some places it hardly more than reaches the surface and is therefore so short that we do not notice it. Certain animals, like the cat and the dog, have very thick hair, which serves as a protection and covering for the skin. The hair of human beings is of no particular KIDNEYS AND SKIN AND THEIR DUTIES 161 use except for ornament and for its protection to the head. The hair of the head has a tendency to fall out and produce baldness. This is especially true of the hair of men. Just why this is the case physicians do not know. Some think that it is due largely to the habit of wearing heavy hats with stiff rims which bind the scalp ; they advise the use of loose, cool hats. Others are of the opinion that "shampooing" the hair with the aid of diluted ammonia and soap, or other sub- stances, causes baldness. It is necessary, however, to keep the hair clean, and it may safely be washed with water containing a little soap. The soap sh6uld be carefully rinsed off and the hair thoroughly dried. Hair oil and hair restorers of all kinds should be avoided. Toe Nails and Finger Nails. The toe nails and finger nails are parts of the epidermis developed in a special way. Figure 63 represents a cross section of a finger, ^^ Afpi/ showing the nail. The purpose of the nails is to protect the fingers and toes. They also help to beautify the hand, and they aid us in picking up small objects by enabling us to grasp them firmly. The nail grows outward from the root at the base, and unless the root is injured, the growth continues as FIG. 63. A SECTION THROUGH THE TlP OF THE FlNGER. Showing the nail. 162 PHYSIOLOGY AND HYGIENE long as we live. The white " half moon " at the lower edge is where the nail is new and quite thin. If a nail is injured, it sometimes comes off. A new one will grow in its place, unless the root has been destroyed. We all dislike finger nails that are grimy or dirty at the ends. They should be kept clean and neatly trimmed with a knife or scissors. They should be cut only at the ends ; neither the surface of the nail nor the skin covering the root should be scraped or cut. Some young people form the habit of biting the nails. This is likely to injure the shape of the fingers, besides rendering the person disagreeable to all with whom he comes in contact. While various reminders may be employed to aid in overcoming the habit, such as some bitter substance placed upon the nails, the difficulty should be conquered by the exercise of will power. The Dennis. The dermis, show^n in Figure 61, is thicker than the epidermis, and is very different in structure. It consists principally of a mass of fibers, running in every direction. The fibers are packed close together on the side next to the epidermis, but they are less dense near the muscles, which lie below the skin. Tiny fat cells are found between the fibers, as shown in Figure 61. The dermis is full of blood vessels, so that, when cut, it always bleeds. It is also very sensitive, because of the many nerves it contains. Some of these nerves are particularly sensitive to heat and cold. KIDNEYS AND SKIN AND THEIR DUTIES 163 FUNCTIONS OF THE SKIN As a Protection. The epidermis is made of flat, scalelike cells, packed together so closely that they are a very great protection to the flesh beneath. Some of the cells may be seen in Figure 61. We can plunge the hand into poisons without injury, because the sub- stances cannot quickly make their way through these cells. Some diseases, as we shall see later, are caused by microscopic living germs getting into the body and growing there. The epidermis helps to protect us from such diseases by keeping out the germs. If they get through the skin, they may produce sores, boils, abscesses, or even more serious troubles. They cannot pass through the healthy epidermis, but often a slight scratch or bruise breaks the skin enough to let the germs in. As a result of the growth of these germs, the scratch becomes inflamed and painful, or perhaps develops a sore or boil. If the germs can be kept out, these sores will not appear. Special care should be taken to wash all cuts and bruises, and to cover them with a plaster or bandage so as to prevent bacteria from entering where the epidermis has been broken. As an Excreting Organ. When we have been taking vigorous exercise, or on a very warm day, small drops of moisture, or sweat, appear on the forehead, the nose, and other parts of the body. This moisture is secreted by the sweat glands, of which we have about two and a half millions in our skin. 164 PHYSIOLOGY AND HYGIENE A sweat gland is too small to be seen with the naked eye, but it consists of a tube passing through the epi- dermis, and coiled up in a knot on the inside, as shown in Figure 61. This tube secretes the sweat, which passes out through a minute hole in the epidermis, called a pore, and is discharged upon the surface of the skin, The skin of the whole body is covered with these tiny FIG. 64. A BIT OF SKIN AS IT APPEARS UNDER A MICROSCOPE. Showing furrows and pores. pores, each leading into a gland. Though they are found all over the body, there are more of them upon the forehead, the palms of the hands, and the soles of the feet than elsewhere. If we look at the skin of the fingers, we see that it is covered with irregular furrows. If we compare two fingers, we find that the furrows are unlike. The pores in the skin of the fingers are along the ridges between these furrows, as shown in Figure 64 ; they may be seen with a magnifying glass. KIDNEYS AND SKIN AND THEIR DUTIES 165 We notice the sweat only when it appears in drops upon the surface of the skin, or when it moistens the clothing. It is then being poured out of the glands in especially large quantities, but the glands are bringing it out all the time. The sweat is usually evaporated as fast as it comes to the surface, not becoming visible, but simply moistening the skin. If we hold the fingers close to a cold window pane, vapor collects on the glass. This shows that water is evaporating from the fingers, even though sweating is not apparent. The sweat itself is principally water, though small amounts of salt and other substances are dissolved in it. In fever, sweating is reduced very much or stops entirely. As a Regulator of Body Temperature. The air, both in doors and out, is usually cooler than our skin. The air is constantly taking heat from the skin, cooling it and the blood which flows near the surface. The faster the blood flows through the skin, the faster it is thus cooled by the air. We have already seen that the skin is full of small blood vessels. These, like all the rest of the blood vessels, can be expanded and contracted as is needed. If the body is producing more heat than usual, brain centers cause the blood vessels in the skin to expand; the blood then flows faster, and more blood is cooled. If the body is not producing as much heat as usual, these blood vessels are made to contract. The blood is thus kept away from the surface and does not lose its heat by giving it out to the air. By opening and 166 PHYSIOLOGY AND HYGIENE closing these blood vessels, the brain is able, without our knowledge, to increase or decrease the amount of heat lost through the skin. In this way our tempera- ture is controlled very closely and accurately. If the body is too warm, the blood vessels expand and let the heat out ; if too cold, they contract and keep it in. The nerves that are sensitive to heat and cold are located in the skin. When the warm blood pours through the skin, it warms these nerves and we feel the heat. When the blood vessels contract, so that the warm blood is kept away from the skin, these nerves are cooled by the air outside, and we feel cold. On a warm day we feel hot, not because the body is warmer than usual, but because the warm blood is flowing over the heat nerves in the skin. The body has practi- cally no sensations of heat and cold except those in the skin and in the lining of the mouth and the digestive canal. Cold-blooded Animals. Frogs, snakes, and certain other small creatures are called cold-blooded animals. The amount of heat produced in their bodies is not very great, and it passes off as fast as it is formed. The cold-blooded animals are never much warmer than the air about them. On a warm day they may be very warm, on a cold day they will be cold. Such animals are usually rather sluggish, especially in cold weather. Warm-blooded Animals. The amount of heat pro- duced in our own bodies, and in those of such animals as dogs, cats, and horses, is comparatively large. This heat warms the blood to a certain temperature, which KIDNEYS AND SKIN AND THEIR DUTIES 167 does not change with the temperature of the air, but remains about the same all through life. We call ani- mals whose bodies keep the same temperature warm- blooded. Their blood is usually warmer than the air, although on a hot summer's day the air may be the warmer. To keep the blood at this temperature requires con- siderable activity and a large amount of food, just as a considerable quantity of coal is required to keep our rooms very warm in winter. A cold-blooded turtle may live for six months without eating a mouthful; its activity is so slight that the small amount of food stored in the body is enough to sustain life, and no heat is needed to warm the body. A warm-blooded animal, on the other hand, must not only have a large supply of food, but it must have this food more or less regularly, and it can live but a short time if deprived of the regular supply. When we are in perfect physical condition, the tem- perature of our bodies is almost exactly 98-|- F. If the temperature rises above this point or falls below, it is commonly an indication of ill health. We feel so much warmer on a hot summer afternoon than we do on a winter morning that it seems to us the temperature of our bodies cannot be the same, but a test with a ther- mometer would show, in both cases, just the 98J, if we are well. Some warm-blooded animals bears, for example sleep throughout the winter. When thus asleep they burn less fuel (food) and do not keep warm ; their body 168 PHYSIOLOGY AND HYGIENE temperature falls very much, but this does them no injury. When they wake in the spring, they begin to burn food more rapidly and are soon warmed again. Such animals are called hibernating animals. Regulation of Heat by the Lungs. The skin is aided in regulating heat by the lungs. As our bodies are always producing much more heat than is needed to warm them, a large proportion of this heat must be given out, in order to keep the proper temperature. Much of the extra heat passes off in breathing. If we take in a breath of cool air and then breathe it out close to the back of the hand, we find that it is much warmer. The warm blood passing through the lungs has heated the air, and the blood is correspondingly cooled. The amount of heat which the body loses in breathing differs very greatly on different days. In winter the cold air may take much heat from the blood in the lungs. Sweating as a Means of regulating Heat. In summer the air may be about as warm as the body, and in this case no heat at all would be lost through either the lungs or the skin by simply warming the air. In hot weather, therefore, another means of getting rid of the extra heat is provided. If we wet a finger and blow upon it gently, or hold it in the wind, the finger feels cool. The water is evaporated by the wind, and it takes a large amount of heat to evaporate water. The heat required to evaporate the water on the finger is taken from the finger itself, leaving this somewhat cooled. In the same way the sweat that is poured out upon the skin is evaporated, taking heat from the body KIDNEYS AND SKIN AND THEIR DUTIES 169 and leaving this correspondingly cooler. The more we perspire the more the evaporation of the sweat cools our bodies. The sweat glands are connected with the brain through nerves, and when the body has too much heat a message from the brain makes the glands begin to secrete sweat profusely. The sweat is rapidly evapo- rated, and in this way we get rid of the extra heat that would make the blood too hot, if there were no way of escape. The evaporation of the sweat takes so much heat that the body is kept at its ordinary temperature, no matter how warm the day may be. Dogs do not sweat very much, and are apt to suffer greatly from the heat of summer. By their rapid breathing, or panting, they take in large quantities of air, which, passing through the lungs and taking heat from the blood, helps to keep down the temperature of the body. " Taking Cold." There are people who seem to take a certain pride in their sensitiveness to drafts, and who are always ready, and expecting, to "take cold." Such persons usually do take cold oftener than other people, because they wrap their necks closely when out of doors, and in the house they sit near a register or with shawls about the shoulders if the air of the room is a bit chilly. Now " taking cold " is a habit which may be almost wholly avoided, if we will learn to treat the skin properly. In the first place, colds are not due to exposure to cold. Explorers do not take cold when in the Arctic regions, 170 PHYSIOLOGY AND HYGIENE although they may do so after their return home. Soldiers can sleep on the damp ground or may be out in the rain for days at a time without catching cold. People who live out of doors seldom suffer from colds. We may feel cold from such exposure, but we do not take cold. We know from experience that we can have the face and the hands exposed when the tem- perature is very low, without catching cold. Yet it is true that we do sometimes suffer this disagreeable malady if cold air strikes some part of the skin which is usually protected. A slightly cool draft striking the bare shoulders may be sufficient cause. This fact has given rise to the idea that the best way to prevent taking cold is to protect the neck and shoulders by means of extra wraps. This is a wrong method. If we should cover our faces with wraps in the same way, they would soon become so ten- der that drafts striking them would produce colds. If, on the other hand, we should expose the neck as we do the face, it would soon become so accustomed to changes in temperature that it would be as impervious to cold as is the face. It is, then, very unwise to get into the habit of wearing furs or mufflers around the neck, or of turning up the coat collar about the ears. The extra protection may be necessary for comfort on an occa- sional extremely cold day, but the more we wrap the neck the more sensitive it becomes, and consequently the more liable we are to take cold. KIDNEYS AND SKIN AND THEIR DUTIES 171 QUESTIONS 1. What are the three waste products of muscle action ? 2. What becomes of each of these waste products? 3. What are excretions and secretions? Is sweat a secretion or an excretion? 4. What organs produce secretions? 5. Mention as many kinds of secretions as you can. 6. What is the duty of the kidneys? V. How are the kidneys constructed ? 8. What are the two parts of the skin ? 9. Where is the epidermis, and what are its characteristics? 10. What are callosities and corns? Can callosities and blisters both be produced by rubbing ? How ? 11. What are the parts of a hair? 12. How should we take care of the hair ? 13. What are warts? 14. How do the toe and finger nails grow? Have the nails any sensations ? 15. What is the structure of the dermis? 16. How does the skin act as a protection ? 17. What are the sweat glands? 18. How is the heat lost through the skin ? 19. What are cold-blooded animals? 20. If a cold-blooded and a warm-blooded animal were placed in an ice box, what effect would be produced on each ? 21. How is the heat of the body regulated by the lungs? 22. Why do we need sweating to aid in regulating body heat? 23. How may we avoid taking cold? CHAPTER VIII THE CARE OF THE SKIN THE skin, as we have learned, is an organ of great importance to the body. It is important as a protect- ing organ, as an organ of excretion removing waste products from the body, and it is at the same time the chief organ concerned in regulating the temperature. BATHING Cleanliness. In order that the skin may keep in healthy condition, it is necessary that the sweat glands be kept free and open. The fat glands connected with the hairs constantly pour oil upon the skin, and the sweat glands secrete considerable solid material with the sweat. These substances remain upon the skin, and unless they are frequently removed they will in time clog the pores, and will also give to a person an unpleasant odor which renders him disagreeable to those about him. Frequent bathing and washing of the body is therefore desirable. No positive rule can be given as to the frequency with which we should bathe. A daily bath is advisable, although it is not essential to health. Cold Baths. Cleanliness is not the only reason for bathing. The bath stimulates the skin, and this would 172 THE CARE OF THE SKIN 173 render it of value even if it were not required for pur- poses of cleanliness. We have seen how the delicate blood vessels expand and contract with changes in tem- perature. The muscle fibers of these blood vessels and the nerves controlling them need exercise as much as do the other muscles of the body. Our habits of life give them little chance for this needed exercise; we keep our rooms uniformly warmed, and when we go out of doors on a cold day we cover all parts of the body except the face. Under these conditions the blood vessels in the skin are likely to become sluggish, and they need stimulation. The simplest way of giv- ing this is by means of the cold bath. Effects of a Cold Bath on the Skin. A cold bath, whether a plunge in cold water, a shower bath, or merely a sponge bath, has always with a vigorous person the same effect. At first there is a sensation of cold, which causes the blood vessels to contract. For a short time the skin may be white and cold, but this is presently followed by what is called the reaction. The blood vessels open once more, allowing the warm blood from the interior to flow rapidly through the skin. The skin becomes flushed and warm, and there is a feeling of exhilaration, due to this after glow. A person should leave the water while still under the influence of the reaction. If he stays longer, he becomes chilly again, and will remain cold and uncom- fortable for hours. The length of time the after glow- lasts depends upon the person, the temperature, and the water. It remains longer with salt water than 174 PHYSIOLOGY AND HYGIENE with fresh. The greater the after glow, the more bene- ficial is the bath. If the body is rubbed vigorously with a rough towel after the bath, the glow is much increased, and the benefit correspondingly greater. Indeed, vigorous friction with a towel is of fully as much benefit as the bath itself. The expansion and contraction of the blood vessels thus brought about furnishes the skin with the needed exercise. If a person lives out of doors, exposed to all sorts of weather, such exercise is not necessary ; but to people spending most of the time in the house, such a bath is to the skin what the gymnasium is to the muscles. A warm bath does not accomplish the same purpose. It frequently makes one tired instead of exhilarated, and should therefore be taken only after the work of the day is done, instead of in the morning. Sometimes women and young girls who have not a great amount of vitality find that the cold plunge, or even the cold sponge bath, fails to give the desired reaction. In such a case tho body should be accus- tomed to the cold water gradually. Little by little the space covered by the cold water may be extended until the skin has become sufficiently toughened so that the bath may be made general. This may usually be accomplished in the course of half a dozen mornings. To become accustomed to the cold plunge it is best to begin with slightly warm water, using it a little cooler each day, until we find we can endure water which is really cold. All young persons will find in the cold bath, either plunge or sponge, a source of pleasure THE CARE OF THE SKIN 175 which, after they have become accustomed to it, the warm bath cannot give. Cold Baths a Protection against Colds. This skin exercise renders the cold bath a protection against colds. If we will accustom ourselves to a cold sponge bath every morning, and will avoid covering the neck with thick wraps, we are much more likely to escape the habit of taking cold. The person who, by means of heavy wraps, protects his skin from exposure, and who takes only warm baths, is pretty sure to get into a con- dition that favors taking cold. He then regrets that he " takes cold so easily." The remedy may be in his own hands. It consists in adopting a mode of life that will give his skin the needed exercise. Hot Baths. We can easily test the difference in effect of the cold and the hot bath. If we bare the arm and pour cold water upon it, then rub it briskly, the skin becomes red and warm with the after glow. If we plunge the arm into water as hot as can comfort- ably be borne it first grows red, then turns white, and there is no after glow. There are times, however, when a hot bath is beneficial. It may enable one who is rest- less and wakeful to go to sleep, since it draws the blood from the brain. When we feel a cold coming on, a hot bath or even soaking the feet in hot water may draw the blood from the throat and nose suffi- ciently to prevent the cold from developing. An occa- sional hot bath is also desirable for the cleansing of the body, even though cold baths are frequently taken. 176 PHYSIOLOGY AND HYGIENE CLOTHING We should remember that we wear clothing for the purpose of comfort or adornment rather than to protect us from taking cold. For comfort it is necessary, in cold weather, to cover the body very completely with clothing. We should remember, however, that the clothing does not warm the body, but simply holds in our body heat, keeping it from passing off by way of the skin. Any clothing that conducts or sends off heat rapidly will cool the body quickly. Clothing that con- ducts heat slowly will keep the body warm. Linen and cotton carry the heat away rapidly, while woolen cloth- ing holds it back. We should therefore wear linen or cotton garments in the summer time, and woolen cloth- ing in the winter. Coarsely woven cloth, which is filled with air spaces, carries the heat away very slowly. Clothing made of such material is, then, the very best for keeping the body warm in cold weather. Similarly, two light garments, worn one over the other, are warmer than one heavy one of equal weight. The air space between the two acts as a "non-conductor" of heat. When we sleep, our bodies should be more warmly covered than when we are awake. A good rule to keep in mind is that for sleeping the feet should be warm and the head cool. As the body, during sleep, needs rest as much as possible, it ought not to be compelled to keep up any extra amount of heat. Paper is a material which readily holds back heat, and if a couple of news- papers be placed between two pieces of bed clothing THE CARE OF THE SKIN 177 they do as good service in keeping the body warm as a blanket. BURNS Burns are very common injuries to the skin and are often very serious. In case of a slight burn we can usually relieve the pain for a time with cold water. One of the best applications for a burn is a paste which can be quickly made by rubbing soda or baking powder into some vaseline or sweet oil. Place this paste, which should be thin enough to spread easily, on a clean cloth and apply it so that it shall completely cover the burn. Another method is to apply a cloth wet in a solution of baking powder or saleratus and water. This solution is, however, less soothing than the paste, and the cloth must be soaked in it frequently. The burn should always be protected from the air. This may be done in an emergency by applying linseed oil, lime water, or even flour, to the place, but no cotton wadding should be put on the wound or anything else that might leave little particles on the surface. If the burn is neither very deep nor very extensive, it will heal readily; but if it is severe, it should be cared for by a physician. Life might sometimes be saved if people would re- member what to do in case the clothing catches fire. If the clothing gets afire, one should catch up any woolen article that may be at hand, wrap it closely around the burning clothing, and immediately lie down flat upon the floor or the ground, and roll over and over. Without air the fire cannot burn, and the rapid rolling, 178 PHYSIOLOGY AND HYGIENE even if one cannot reach any woolen stuff to serve as an extinguisher, will usually put out the fire. People have lost their lives by standing up while attempting to remove burning clothes. The flames rise, and if the person is standing, he is very liable to breathe the fire into his lungs. This causes almost instant death. If a person whose clothing is on fire loses his wits and starts to run, he should be thrown down as a means of saving his life, for running is very dangerous. He should then be wrapped in a rug, a blanket, a coat, or any similar heavy article that may be at hand, to smother the flames. After the fire is out, if the flesh of the person is burned, the clothing must be removed. Care must be taken, however, that the skin is not torn off. The clothing is likely to stick to the skin, and if it does so, it should be allowed to remain, at least where it adheres, the cloth being cut off around the place if necessary. If there are blisters, they should be opened and the liquid pressed out. Any further treatment should be given by a physician. FROSTBITES The freezing of fingers, toes, nose, or ears is not an uncommon occurrence on an extremely cold day. In such a case, the water in the blood and the muscles is actually turned to ice. If the frozen parts are thawed out slowly, no permanent injury may result ; but if they are thawed rapidly, serious trouble may follow, which may render amputation of the toes or fingers necessary. For this reason frostbites should be thawed THE CARE OF THE SKIN 179 slowly. Rubbing the frozen parts with snow or cold water is recommended. This will thaw them out with the least possible danger of injury. In general, to preserve a part of the body that has been frozen, it must be promptly but very gradually thawed. After this the person may be warmed and given some warm drink, such as hot water, milk, or coffee. Many people wrongly suppose that the uncomfort- able affection of the feet known as " chilblains " is the result of frostbite. They are really due to getting the feet very cold and then warming them too quickly, and do not appear in children with a vigorous circu- lation. Warming cold feet over a register or in a stove oven is very likely to cause the difficulty. The best way to protect the feet against chilblains is to wear warm stockings and thick shoes in cold weather, and give the feet plenty of exercise. QUESTIONS 1. Why should the sweat glands be kept free and open? 2. What is the use of sweat? 3. What is the effect of the cold bath ? 4. What are the advantages of the cold bath ? 5. How do cold baths act as a protection against colds ? 6. What is the difference in effect between the cold and the hot bath ? 7. What clothing is most suitable for summer? For winter? 8. Are silk underclothing and stockings as useful as woolen? Why? 9. Why should the body be warmly covered during sleep ? 10. What should be done when a person's clothing catches fire ? 11. What should be done for frostbite ? CHAPTER IX ALCOHOL AND OTHER NARCOTICS MANY people have the habit of using certain sub- stances which interfere with the health of various parts of the body. These substances are chiefly alcohol and narcotics. Alcohol is sometimes incorrectly called a stimulant. A true stimulant is some agent that increases the activity of some organ. For example, hot water stimu- lates heart action ; chewing rubber stimulates the secre- tion of saliva. Sometimes the term is wrongly used to apply to the action of some poison like strychnine that makes the body very excitable but really decreases instead of increasing its efficiency. Narcotics have just the opposite effect. They soothe and dull the action of the body and have a tendency to put people to sleep. Although narcotics and stimu- lants are thus very different, they are sometimes con- fused, since the same drug may seem to possess both effects. Alcohol, for example, is a narcotic. But its first action is to dull the powers of self : restraint in the brain, and this causes the person to do and say things that give the false impression of extra strength. For this reason it has been wrongly called a stimulant. As its action increases, however, its dulling effect becomes more evident and is more lasting. Its true action is, therefore, that of a narcotic and not that of a stimulant. When a larger quantity is taken, the narcotic effect is unmistakable. 180 ALCOHOL AND OTHER NARCOTICS 181 OPIUM Opium is one of the most dangerous of narcotics. Morphine and laudanum are two common forms of the drug. Paregoric and soothing sirup, both of which contain opium, are especially dangerous, and should not be given to children. Opium dulls the senses and finally puts a person to sleep. The reason why it is so dangerous is that it has a tendency to produce a terrible craving for opium. A person begins by taking a small amount, possibly prescribed for him by a physician as a remedy for toothache, headache, or neuralgia. The drug not only soothes the pain, but produces a pleasant, restful feel- ing. Whenever the person has a pain which he wishes to relieve, he uses the same remedy, or he even imagines the pain for the sake of taking the drug. Soon the small doses with which he began cease to produce the desired effect, and he takes larger amounts. Before he suspects the fact, he has become an " opium eater,'* and no longer even pretends to make the excuse that he takes the drug as a medicine. Opium destroys the ability to think clearly and ruins the moral nature. The opium eater frequently becomes a liar and a thief. His health is undermined. He no longer finds pleasure in work or in recreation, and after a while even the drug itself ceases to give him relief or satisfaction. The use of the drug so affects his will power that when he finds himself a slave to the habit he has not the strength of will to restrain the appetite. 182 PHYSIOLOGY AND HYGIENE When once the terrible habit has obtained a hold upon a man, it is almost impossible for him to control it. The use of opium in any form, except under the direct advice of a physician, is consequently exceedingly dangerous. Many physicians are unwilling to pre- scribe it, knowing as they do how easily the habit is formed. The use of Moral and cocaine is equally dangerous, the effects being similar to those of opium. TOBACCO Tobacco is a milder narcotic than opium, and one much more widely used. Tobacco contains a poison which is deadly when taken in considerable quantity. Whether or not the amount of this poison taken into the body by a grown person who smokes but little is enough to produce injury, there is no question about the ill effects of tobacco on young people, however moderately it may be used. Used freely, it is un- doubtedly injurious to adults. Moreover, mild narcotics like tobacco share with the stronger narcotics, though in less degree, that power of making the user want more and more of them. There are many other .excellent reasons for refraining from the habit of using tobacco. 1. Tobacco is of absolutely no value to the healthy body. It neither acts as a food nor does it serve any other useful purpose. 2. The use of tobacco by young people may check the ALCOHOL AND OTHER NARCOTICS 183 proper growth and development of the body. Careful study of college students has shown that those who are addicted to the use of tobacco are, on the average, con- siderably less developed than those who let it alone. The tobacco habit handicaps a boy in his physical development at the very start of life. 3. The use of tobacco temporarily reduces one's muscular power, and may do so permanently. 4. Its use often causes heart trouble. The " cigarette heart " is well known to physicians. Brain difficulty, insanity, and even death are sometimes traceable to tobacco. 5. It is an expensive habit. The money spent for tobacco could certainly be put to better use, and could be employed in ways that, to a young person at least, would give more pleasure and profit. 6. It is a habit that renders one disagreeable to others and tends to selfishness. Most people who do not use tobacco, women especially, find the use of it by their acquaintances very disagreeable. Its use sometimes tends to selfishness and to a disregard of the feelings of others. 7. The use of tobacco is likely to lead boys into inju- rious company, inviting them to idleness and to other bad habits. Of all forms of tobacco, cigarettes probably do the greatest amount of injury. A person who uses cig- arettes is likely to " inhale " the smoke. This means breathing the smoke into the lungs, which is far more injurious than simply taking it into the mouth. Boys 184 PHYSIOLOGY AND HYGIENE in particular should know this, for cigarettes are gener- ally used by them on account of their cheapness. For these reasons the wise course is to leave tobacco alone. ALCOHOL One of the greatest dangers that a young person has to meet is that of acquiring the alcohol habit. Fortunately, it is not so common as the tobacco habit. Nevertheless, it has destroyed the lives of hundreds of thousands of young people, and has been a stumbling block in the way of hundreds of thousands of others. It has led to countless crimes, and has caused an ines- timable amount of poverty and suffering. The use of alcohol is particularly dangerous, because it frequently obtains a mastery over young people without their real- izing the fact. Use of Alcohol in Large Quantities. The effect of alcohol upon the body depends largely upon the amount used. When speaking of the use of alcohol in large quantities, people mean its use in quantities sufficient to produce intoxication, or with a frequency that keeps the person more or less under its influence. The use of alcohol in such quantities is disastrous to health. It in- jures the action of the heart, interferes with circulation, and impairs the digestive powers. Moreover, it has a very important influence upon the moral nature. The drunkard loses his sense of responsibility and ceases to be a normal man. His whole body becomes dis- eased and unable to carry on its proper functions. His ALCOHOL AND OTHER NARCOTICS 185 mind becomes dull and his ambitions disappear. The use of alcohol in large quantities destroys a man's chance of the highest success. Alcohol causes the death of thousands of men and women every year. Use of Alcohol in Smaller Quantities. When alco- holic drinks are used in quantities insufficient to pro- duce intoxication, their effect upon the body may also be serious, although unfortunately not always apparent. The injury is so gradual that there may be little to call attention to it. Some people use wines or beers in small amounts for years without realizing that they are injured by them; nevertheless, alcoholic drinks, when habitually used, even in small quantities, frequently produce .decidedly injurious effects. There is always the danger of forming the craving for more. The effect of using alcohol in small quantities does not appear at once. Its action when so used was shown recently by a series of experiments upon dogs, made by Dr. Hodge, of Clark University. Four dogs were selected from the same litter, all as nearly alike as possible. Two of them were given only ordi- nary food. The other two were treated in exactly the same way, except that they were given a small amount of alcohol with each meal. They were never given alcohol enough to make them intoxicated, and, taking into consideration the relative size of the dogs and a man, the amount given was relatively about as much as would be taken by many moderate drinkers. At first the four dogs were practically alike, but little by little differences began to appear between those that 186 PHYSIOLOGY AND HYGIENE were given the alcohol and those that had nothing but the regular food. In the- course of a few months the "alcohol" dogs were quite inferior in appearance to the other two. By the end of a year and a half the difference was very marked. The "alcohol" dogs were sleepy, and had a general ap- pearance of worthlessness. They were less active than the other dogs, and were much more quickly tired out. They would not bring back a ball when it was thrown for them so often as the others, and they frequently lay down to rest. In other words, the use of alcohol had lowered the intelligence, the brightness, and the muscular power of the dogs. If a moderate use of alcohol affects dogs so much in eighteen months, we may be sure that it has some injurious effect on the people who continue its use in this way for years. Whatever success in life has been made by a man who is a moderate drinker, he would certainly have amounted to as much without the alco- hol, and perhaps a great deal more. Competition is so great in these days, in business, in the professions, and, in fact, along every possible line of work, that the boy or young man of the present day needs to have every possible power of mind and body at his command. The man with clear and unimpaired brain, with a healthy, well-cared-for body, with body and brain controlled by a determined, resolute will he is the man who will make a success in the coming years of the twentieth century. The Alcohol Appetite. We have already learned that ALCOHOL AND OTHER NARCOTICS 187 one of the most dangerous things about alcohol is its tendency to create a desire for more. This desire may be very slight at first, but it is likely to grow. More- over, although at first a small amount of alcohol is all that a person wants, or can drink, when his body be- comes accustomed to this amount, he almost without knowing it takes a little more. Quite unconscious of how serious a thing it is, he slowly increases the amount used, sometimes by taking a larger amount of weak liquors and sometimes by taking stronger ones. He begins with beer and finally uses distilled liquors. The appetite grows with indulgence, and sooner or later it may become so firmly fixed that he is quite unable to break it. Danger of the Appetite. The fact that the appetite grows slowly and imperceptibly is what makes alcohol so dangerous. If a boy or young man could appreciate how the appetite is increasing, if he could realize to what it is likely to lead him, and if he could under- stand at the beginning how he is slowly becoming bound by a habit, he would in most cases curb the habit before it developed much strength. But the habit grows im- perceptibly, and at the same time undermines his will, until it finally produces disastrous results. The continued use of alcohol, moreover, is likely to crush out all desire to reform. The alcohol appetite might be overcome in most cases if the person had a sufficiently strong desire to do so ; but his will power and his desire for a better life are taken away as the appetite grows upon him. 188 PHYSIOLOGY AND HYGIENE It is undoubtedly true that thousands of people who begin to use alcohol in small quantities, develop the alcohol appetite and are finally mastered by it. Every boy who begins to drink runs the danger of developing such an appetite. He may not become mastered by it, but experience has shown that in many cases the boy finds himself in time mastered by the habit. It is never possible to predict what will be the result. Drunkards are commonly made out of boys and girls who do not intend to use enough alcohol to injure them. If a boy never begins to use alcoholic liquors, he will never be- come a drunkard ; but if he does begin, even in a mild way, he places himself among those from whom drunk- ards are made. The only sure way to avoid this danger is to avoid its beginning, and, in avoiding that, the boy also insures for himself a healthier body, a clearer brain, and a better chance for success in life. QUESTIONS 1. What is the difference between a stimulant and a narcotic ? 2. What is the effect of opium, and why is it a dangerous drug? 3. Why should tobacco not be used? 4. What is the effect upon the body of using alcohol in large quantities ? 5. What are the effects of a moderate use of alcohol ? 6. What do you regard as the strongest reason for avoiding alcoholic drinks? CHAPTER X THE NERVOUS SYSTEM EVERY large factory must have a superintendent. Otherwise the persons employed to do various tasks would work independently of one another, and as a result little would be accomplished. The superin- tendent is indeed the most important man in the entire factory. Within our bodies various actions are going on. About five hundred muscles, numerous glands, and many other organs are constantly at work. If they should act independently there would be great confusion. In our bodies, however, as in the factory, there is a super- intendent, whose duty it is to control all the different parts and keep them working in harmony with each other. A few of the body actions, like the beating of the heart, can take place without direct command from the superintendent, but with the others the order of the superintendent is required before the organs will work at all. The muscles will never act unless they are com- manded to do so by the central controlling organ. As we have already learned, the organ that corresponds in the body to the superintendent of a factory, and that controls the numerous activities, is the brain. 189 190 PHYSIOLOGY AND HYGIENE The brain is connected with every part of the body by a series of nerves. This is the organ with which we think, and by means of which we will to do any- thing. The brain also causes a great many actions to take place in our bodies without any knowledge on our part. We do not realize, for instance, that mes- sages are being sent from the brain to the blood vessels of the skin, causing them to open or shut. THE BRAIN The brain fills the bony box called the skull. Figure 65 shows its shape and structure. It is a very large (Brtathing \VasoMotor \HeartControl Swallowing FIG. 65. THE HUMAN BRAIN. organ, that of an adult weighing some three pounds. There is considerable difference in the weight of vari- ous brains. The more intelligent races commonly have large brains, while those of less intelligence usually THE NERVOUS SYSTEM 191 have smaller ones. There are, however, among individ- uals, some remarkable exceptions to this general rule. The brain is a very complicated organ. As shown in Figure 65, it is divided into three main parts, each of which has special duties to perform. The Medulla Oblongata. Forming the very lowest part of the brain is the medulla, or medulla oblongata, which lies between the spinal cord and the main part of the brain. It is not more than one and a quarter inches in length, yet it contains the centers that control some most important body actions. As Figure 65 indi- cates, the breathing, the vasomotor system (i.e. expan- sion and contraction of blood vessels), the heart control, and swallowing, together with other functions, are the special care of this part of the brain. The Cerebellum. A little higher than the medulla is situated a larger rounded part of the brain, about half as large as a baseball, called the cerebellum. It is somewhat flattened and, as Figure 65 indicates, is marked with numerous furrows. It lies over the medulla. The cerebellum is thought to influence mus- cular action. We have seen how wonderfully the muscles are adjusted so as to act together, as, for instance, when a boy throws a stone. This is sup- posed to be accomplished in part through the action of the cerebellum. The Cerebrum. The cerebrum is the largest part of the brain. Figure 65 shows that it is covered with deep furrows which divide it into folds called convo- lutions. These folds are not exactly alike in all brains. 192 PHYSIOLOGY AND HYGIENE though the larger ones are almost always present. The cerebrum is divided by a very deep furrow into two parts, called the right and the left hemispheres. The division is indicated in Figure 66. The two parts are connected with the body in such a way that the right hemisphere controls the left side of the body, and the left hemisphere the right side of the body. The cerebrum is the part of the brain that is active in thought and in the exercise of will power. What we call the " mind " is centered in the cerebrum. It is the center which starts and con- trols the activity of the body. THE SPINAL CORD FIG. 66. THE NERVOUS SYSTEM. Showing the brain and the A long, soft, white cord, spinal cord with its nerves. called ^ spinal ^ starts from the lower end of the medulla (shown in Fig. 66), and passes down through the backbone or spine. The vertebrae of the backbone protect the cord on all sides. In other words, the spinal cord runs inside the back- bone (see Fig. 43, p. 126). As may be seen from Fig- ure 66, the cord is not of the same thickness throughout its length, but it becomes gradually smaller as it passes down the back. At the lower end it divides into fine THE NERVOUS SYSTEM 193 threads. When in its proper position inside the back- bone, the cord is covered not simply with bones, but with certain softer membranes, which act as a further protection, so that it is very thoroughly guarded from injury. If we cut the cord directly across, it will appear as we see it in Figure 67. Like the. brain, it is divided by deep furrows into two parts, the right half and the left half. The fur- rows, as the figure Shows, do not ex- AnteriorRoot tend all the way FlG . 67. Two PIECES OF THE SPINAL across the cord, CORD. but the two halves Showing the gray matter and the two roots of the spinal nerves. The arrows show the are united at their direction of the stimulh center. At the very center of the cord, Figure 67 shows a rather irreg- ular mass, shaped somewhat like the letter H, with four arms running off to the sides. This material is of a dull gray color, and is called the gray matter. It con- tains nerve cells, which start and receive nervous im- pulses, or "messages." Outside the gray matter is a substance, whiter and more glistening, called the white matter of the cord. This consists of nerve fibers, whose duty it is to carry up and down the cord the nervous impulses which are started and received by the gray matter. 194 PHYSIOLOGY AND HYGIENE THE NERVES The brain may be regarded as the superintendent of the body. If this superintendent is to have any control over the different organs in the body, it must in some way be connected with them. The superintendent of a factory often has telephone connection with every room in the building by means of electric wires which run in various directions. In a similar way the super- intendent of our body, the brain, is connected with every part of the body by a series of connecting fibers which we call nerves. Figure 66 shows these nerves coming from the spinal cord as it passes down through the back. The nerves start in the gray matter of the cord, and then pass from the cord between the vertebrae, extending outward into the body to connect with all the organs controlled by the brain. As may be seen from Figure 67, each of these nerves rises from the cord in two branches, known as roots. The front branch, called the anterior root, carries nervous impulses from the brain to the muscles; while the other, the posterior root, carries nervous impulses from the skin and other organs to the spinal cord and thence to the brain. After the two branches unite, as shown in the figure, they form what we call a nerve trunk. Such a trunk is made up of thousands of nerve fibers, or wires, bound together in a bundle. Each fiber runs to a distinct part of the body. Figure 68 shows a bundle of fibers that make up a nerve. A nerve trunk usually con- THE NERVOUS SYSTEM 195 tains some fibers that carry impulses toward the brain and some that carry them away from it. A few nerves, however, contain only one kind of fiber. By means of these hundreds of thousands of nerve fibers every muscle, every gland, every part of the skin, receives and sends nervous impulses to and from the brain. The wire that rings an electric bell is always connected with two different pieces of apparatus, with- out which it would be useless. At one end of the wire is placed the bell to be rung ; at the other end there is a battery, which starts the electric current that rings the bell. The wire serves simply to connect Cylinder^ the battery with the bell. The nerves in our body serve, in a similar way, to connect two pieces Meduh Axis Single, N&rve Fiber FIG. 68. A NERVE. of apparatus placed at their ends, Showing on the right a corresponding to the battery and nerve composed of the bell. If we could examine carefully the nerve fibers, we should find that many of them end in a minute, somewhat rounded body, with numerous branches extending from it on all sides (Fig. 69). This body is called a nerve cell and it corresponds in its work to the battery that starts the electric impulse to ring the bell. Since the many nerve fibers and on the left a single nerve fiber. 196 PHYSIOLOGY AND HYGIENE the nerve cells are the organs that start and receive nervous impulses, we should expect to find them most numerous where stimuli are sent out to the various organs ; and this is the case. There are a great many nerve cells in the spinal cord, and in the brain they are so numerous that we cannot even conceive of their num- ber. It is estimated that the brain contains 9,000,000,- 000 such cells. We may think of one of these cells as a tiny battery which can start nervous im- pulses over the nerve fibers leading from it, or as a bit of apparatus which receives im- pulses coming over other nerves. Each nerve cell is connected by a long nerve fiber with some part of the body. There is no part of the body, no matter how small, that is not connected with the nerve cells of the brain and spinal cord. The nerve cells in the brain are, most of them, near the surface. The rest of the brain consists of a com- plex tangle of fibers running in all directions, somewhat like the series of wires that run into a central telephone station ; only instead of a few hundred such wires the brain has hundreds of thousands. FIG. 69. A NERVE CELL. Showing branches and a single nerve fiber arising from it. THE NERVOUS SYSTEM 197 QUESTIONS 1. What is the relation of the nervous system to the rest of the body? 2. What is the brain? 3. What are the parts of the brain ? 4. Where is the medulla? What is its work? 5. If the cord is cut across below the medulla, why would breathing stop at once? 6. What is the cerebellum ? What actions does it control? 7. How is the cerebrum arranged? What powers does it control ? 8. What is the spinal cord ? Where is it situated? 9. What does a cross section of the spinal cord show of its structure ? 10. What is the purpose of the nerves? 11. If the posterior root of a nerve (see Fig. 67) were cut, could the person receive sensations through that nerve ? Why ? 12. How do the brain and spinal cord resemble an electric battery ? 13. Why are there more nerve cells in the brain than elsewhere? CHAPTER XI THE NERVOUS SYSTEM IN ACTION DUTIES OF THE NERVES IF we touch the hand with a hot match, instantly we have a feeling of pain and the hand is drawn away. The hand is connected with the brain by the nerve shown in Figure 70. If this nerve of the arm should be cut at the point indicated in the figure, and then the match should be touched to the hand, no pain would be felt. What is more, if we should wish to move the hand, we should be quite unable to do so. Cutting the nerve, therefore, destroys all sensation and all power of motion in the hand. The cutting does not injure the muscles. They would still be able to contract, if they were stimulated by an electric shock. Moreover, cutting does not destroy sensation; for if the end of the nerve which is still attached to the brain (called the central end in Fig. 70) were pinched, we should feel pain. And what seems most strange of all, we should think that we felt the pain in the hand and fingers, although the nerve had really been touched at a point above the elbow. These facts teach us several things in regard to the action of the nerves. 1. The nerves form a line of communication be- tween the brain and spinal cord and the muscles. Muscles are caused to act by means of nerves. 198 THE NERVOUS SYSTEM IN ACTION 199 2. Muscles commonly act only when they receive a nervous impulse from the brain or spinal cord. 3. Nerves form a means of communication between the different parts of the body and the brain, by which messages (sensations of pain, for example) are sent to the brain. 4. Sensations are really felt in the brain, although we seem to feel them in other parts of the body. The burning match touched to the skin of the hand causes a message to travel up the nerve, but no feeling of pain results unless the message reaches the brain. When, therefore, the nerve is cut or compressed so that the message cannot get to the brain, no sensa- tion of pain is felt. If the message does reach the brain, however, it produces pain, and we locate this pain in the hand where the match touched it. The brain always locates the pain at the end of the nerve which brings the message, and for this reason it sometimes makes a mistake. For example, the nerve from the hand has all our We/re FIG. 70. Showing the connection of the hand with the brain by a nerve. It is supposed to be cut above the elbow. 200 PHYSIOLOGY AND HYGIENE lives brought messages to the brain from the hand. Now if this nerve is cut above the elbow, as in Figure 70, it can no longer bring messages from the hand. But if the central end, also shown in the figure, is pinched, the nerve carries the impulse to the brain. Since the brain has always received over this nerve impulses coming from the hand, it is now not able to recognize that this impulse does not come from the same place. So the sensation seems to come from the hand, when in reality it started from above the elbow. These facts make it clear that the nerves are merely conducting wires carrying impulses that start at their ends. Some impulses start at the outer ends and go to the brain, producing sensation there. Other impulses start in the brain and pass down the spinal cord and out to the muscle fibers, where they cause motion of the muscles. Messages travel thus through the nerves in both directions, and by means of them the brain is placed in communication with every part of the body. The nerve fibers by means of which sensation is communicated to the brain are called sensory nerve fibers. Those which convey the impulses from the brain to the muscles are called motor nerve fibers. DUTIES OF THE SPINAL CORD AND MEDULLA The spinal cord has more complicated duties to per- form than have the nerves. Carrying messages to and from the brain is simply one of these manifold duties. As can be seen from Figure 66, large numbers of nerves THE NERVOUS SYSTEM IN ACTION 201 enter the spinal cord, and in the cord itself they pass up to the brain. These nerves are all so arranged that messages passing through them from the right side of the brain reach the left side of the body, and messages starting from the right side of the body reach the left side of the brain. Independent Action of the Cord. We have learned that the spinal cord contains nerve cells as well as nerve fibers. If these nerve cells serve the same purpose as batteries, we should naturally expect that the spinal cord could do something besides simply carry messages. The cord does indeed have another kind of duty, called reflex action. If, for example, a finger is pinched, an impulse is started which passes to the spinal cord on its way to the brain. In the spinal cord it excites certain cells. These in turn excite other cells, from which instantly motor impulses are sent out from the spinal cord to the muscles controlling the arm and hand, causing contraction and the withdrawal of the finger. This is called reflex action, and it takes place very quickly in less than one tenth of a second. The original sensory impulse, of course, may pass on to the brain, where it will cause pain, but the instan- taneous withdrawal of the finger from danger was a re- flex action, and might take place without brain action. Reflex action does not require any will power and can take place just as well when a person or an animal is asleep as when he is awake. In the case of some ani- mals it will take place when the brain has been entirely removed from the body. 202 PHYSIOLOGY AND HYGIENE A reflex action never starts itself. It must always be started by some outside stimulus. To produce such a reflex action something must stimulate the body in such a way as to cause a message to go to the spinal cord. The action never begins in the spinal cord itself, but always at the outer ends of the nerves, usually because something touches the skin or some other part of the body. Although the brain is not necessary to reflex action, still it is possible for the brain partly to control such action, especially if the action is a repeated one, or one of which we are aware in advance. For example, if the bottom of the foot is tickled, the foot is pulled away. This is a reflex action and will take place when we are asleep just as readily as when we are awake. If, however, we are awake and know what is to be done, we can often use sufficient will power to prevent the foot from being pulled away even when it is tickled. The will power is exerted through the brain alone and, therefore, in this case the brain stops the reflex action. But under some circumstances, even when we are awake, our will power is not strong enough to prevent the reflex action. If a bit of food becomes caught in the windpipe, for instance, it will cause us to cough, and no matter how hard we try, we shall be unable to keep from coughing until the food is dislodged. The coughing is a reflex action and, in this case, is too strong to be controlled by will power. Reflex Action in the Medulla. A study of the me- dulla, indicated in Figure 65 as at the top of the spinal THE NERVOUS SYSTEM IN ACTION 203 cord, shows that this part of the brain controls a number of the most important vital functions. Here are centered the powers that control breathing, the rapidity of the heart beat, swallowing, the size of the blood vessels (thus regulating circulation), and some others of less importance. These actions are all reflex. It will be recognized that these actions are the primary functions of life. If they continue, the person will live, even though all others cease for a time. The activity of the cerebellum and cerebrum may stop for a while and yet the person may continue to live if the medulla is not injured ; but if the medulla is injured, it may stop the heart beat and breathing at once, and thus produce instantaneous death, even though the rest of the brain is uninjured. The medulla may thus be said to be the center of the vital functions. The cen- ters controlling these vital functions may act quite independently of will power or consciousness, as they do when we are asleep. THE CEREBELLUM AND CEREBRUM The Work of the Cerebellum. The cerebellum also controls reflex actions more complex than those connected with the spinal cord. Such actions as walking are at first controlled by our will power and are not reflex at all. After a time, however, they become reflex in a measure, and take care of themselves. When we first begin learning to play the piano we must think care- fully of the action of each finger, but after playing for a number of years, we no longer need to attend par- 204 PHYSIOLOGY AND HYGIENE ticularly to the fingers. We simply place our hands on the piano and the fingers fall naturally upon the proper keys and make the proper motions for pro- ducing music. A skilled pianist can talk to a friend and at the same time continue playing, paying no atten- tion to his fingers and yet never striking wrong notes. Through long practice certain parts of his brain, prob- ably in the cerebellum, have learned to take care of the motions of the fingers, so that the mind is free to attend to something else. Some of these complex actions are controlled by the cerebellum, but physiolo- gists as yet know little about them or where they are located. The Work of the Cerebrum. The upper and larger part of the brain, the cerebrum, is the real center from which all the impulses of our conscious activity come. It is the center that regulates the conscious action of the whole body. The relation of the cerebrum to the other parts of the body may be best understood by the comparison already used, of the superintendent and the factory. The cerebrum itself is like the general superintendent who directs the work of the whole factory. The vari- ous centers in the cerebellum and the spinal cord are like the foremen of different rooms or of different parts of the work. When the superintendent wishes some- thing to be done, he sends a message to the foreman of a special room, and the foreman gives the order to the individual workmen. In this way the superintendent is not obliged to pay attention to the detailed work of THE NERVOUS SYSTEM IN ACTION 205 every employee, but can give his time to planning the operations of the factory as a whole. So the mind, when it wishes some special action to be performed, such as moving the hand, sends a message to some of the centers in the lower parts of the brain, and these forward the necessary commands by way of the nerves to the muscles in the arm and hand, so that the hand is moved. After the various centers have learned their duty, the mind itself does not need to attend to the little details. Our minds are then free for thought. We can talk as we play on the piano because the mind has trained some of its servants in the cerebellum to look after the contractions which cause the fingers to touch the keys correctly. If these servants in the cerebellum are not carefully trained, the plans made by the mind will not be properly carried out. Our education, from the time of our earliest childhood, is largely given to training the servants of the mind. We sometimes call the training of these servants acquiring habits. THE IMPORTANCE OF HABITS We can readily see how necessary it is that we should have well-trained servants to do our work, and, there- fore, that we should form good habits. After we have once formed a habit it is very difficult to get rid of it. The training of children at home and at school is for the purpose of developing right habits of thinking and acting, in order that, after they become men and 206 PHYSIOLOGY AND HYGIENE women, they may be properly guided by these good habits. By doing the same thing again and again the body becomes so accustomed to a certain kind of action that FIG. 71. THE BRAIN IN POSITION. Showing the location of the different powers in the brain. it will be "second nature" to perform that action. Every time that we do something in a certain way it becomes easier to do the same thing in that way again. If the habit is an injurious one, like the alcohol habit, THE NERVOUS SYSTEM IN ACTION 207 we come more and more under its influence by yielding to it. If, on the other hand, the habit is a useful one, we fit ourselves better for life every time we perform the action. This is as true of moral actions as it is of muscular movements. If we exaggerate the facts when we tell a story, we are forming a habit that will grow until we become liars, unless the fault is overcome. If we dawdle over our books instead of giving our best thought to study, we are forming habits of inattention that are likely to hinder successful work through life. We are constantly forming habits whether we wish to do so or not. Inasmuch as these habits are to be our servants through life, it is wise to see to it that we form those that will be useful rather than those that may do us harm. We know very little in regard to the location of the different powers of the cerebrum. Figure 71 indicates about all that is really understood. The power of think- ing is probably connected with the front of the brain, certain powers of motion with the middle, while some of the senses are located in the back part of the brain. THE CARE OF THE MIND Our entire lives are directed by the mind. We should, then, take the best possible care of these minds of ours. A few facts of importance are worth remem- bering. Sleep. We cannot continue one form of activity very long without some kind of rest, for both the body and the mind need to rest. The most complete kind 208 PHYSIOLOGY AND HYGIENE of rest for mind and body is sleep. When we sleep, the mind is largely free from its usual forms of activ- ity, although our dreams show us that the mind is not entirely inactive. The deeper the sleep the less distinct will be the dreams. The amount of sleep needed by various people differs greatly. A young child needs twelve hours out of the twenty -four for sleep, a growing boy or girl about ten, while most grown people require only about seven or eight. Some persons seem to get on very comfortably with even less. It is best to remember, however, that we are much more likely to have too little sleep than too much. Sometimes a boy or girl takes a kind of pride in sitting up late and studying far into the night. This is likely to be done just before examination time, under the impression that better preparation can thus be made for the tests. This is a great mistake. Sit- ting up late to study, the night before, usually renders one less fitted to pass an examination. The many facts we try to cram into our heads during such midnight study are not all found there the next morning. We are weary, and the brain does not work as it should. To get a good night's rest is a much better method of preparing for an examination than to study until the mind gets tired. Concentration. The person who accomplishes the most is the one who is able to turn his whole attention to his work. When we are thinking of several things at once, we can give none of them careful considera- tion. If, when we are supposed to be studying, we let THE NERVOUS SYSTEM IN ACTION 209 our thoughts wander to the athletic field, then to the woods and the trout brook, then to something going on in the schoolroom, bringing them back finally with an effort to the lesson, it will take us much longer to master the lesson than it will if we give our attention to that and nothing else. The pupil who applies his mind wholly to the lesson he is preparing will do his work much more quickly and much better than his neighbor across the aisle who studies one minute and dreams the next. The ability to think of one thing at a time is largely a habit, and one of the most useful of habits. It is one that can and should be acquired by every boy and girl. If we allow our thoughts to wander from one thing to another, we shall let this habit master us, and in later life we may, as a result, find it very diffi- cult to think continuously and vigorously. Recreation. The mind needs recreation as well as work and rest. It ought to be employed at times in such a way as to obtain relief from its required tasks. We ought just as much to give our minds recreation as to give them sleep. Without it we become dull, and our bodily health is likely to suffer. Recreation is even more necessary for the boy or girl who wishes to be a scholar than it is for the person who works prin- cipally with his muscles. Each of us should choose his own recreation. It should be something that gives pleasure and enjoyment, and it must be something that we do from choice, riot because we must. It is also necessary that the kind of recreation a person takes should occasionally be 210 PHYSIOLOGY AND HYGIENE changed. Much of a person's success as well as happi- ness in life depends upon his having enjoyment. We can work harder and do better, if we may look forward to pleasant recreation as the reward for faithful labor. Dependence of the Mind upon the Body. Our minds and our bodies are related so closely that their welfare cannot be separated. If we allow our bodies to become weak from lack of exercise or want of the proper kinds of food, our minds will not be vigorous. The most active mind, and the one that thinks best, will be found in a healthy body. The boy or girl who enjoys books and study is the one who must be especially careful to give proper attention to health. The student must have recreation, exercise, good, wholesome food, fresh air and sunshine, if he wishes to preserve at its best that valuable treasure, his mind. The boy or girl who neglects mind for body cannot compete in after life with the person who studies hard. On the other hand, the boy or girl who neglects bodily health for the sake of knowledge is sure to fall behind the one who develops a healthy mind in a healthy body. The Mind and Narcotics. One matter of importance in connection with the proper care of the mind is keep- ing it free from the control of all narcotics. The use of alcohol has its first and most important effect upon the action of the brain. The first result of taking alcohol seems to be to excite the brain, and thus alcohol has been wrongly called a stimulant. This excitation is really one of the results of its narcotic action. Its action upon the brain is really the opposite of a stimulant, for almost THE NERVOUS SYSTEM IN ACTION 211 at once it begins to dull the mental powers. This dulling action becomes very noticeable when large amounts of alcohol are used. Careful testing has shown that one who has taken even small quantities of alcohol cannot add a column of figures so quickly as usual, or that if he can add the column as quickly he may fail to do it accurately. He may be able to talk more rapidly, but he will com- monly not think so clearly. He acts more slowly than usual. If he is hunting, he loses his straight aim ; if setting type, he works less rapidly and makes more mistakes. He is perhaps not conscious of all this, and feeling somewhat excited and exhilarated, he may actually think that he is doing more work than usual, while he is really doing less. He may believe himself to be bright and witty, when he is uttering only foolish jests. The man with whom he has business dealings, and who keeps sober, gets the better of him in a bargain. The more alcohol he uses, the greater its dulling action on the brain. Finally he may notice it himself, but even though he does not appreciate it, others find that he is not able to talk intelligently ; he becomes confused and stupid, and finally is unable even to walk straight. When he is completely under the influence of alcohol, nearly all the actions of his body cease, except breathing and the beating of the heart. There are various degrees in this dulling effect of alcohol. It is slight when small amounts are used, and complete when large quantities are taken. How large an amount a person can take without having his judg- 212 PHYSIOLOGY AND HYGIENE ment seriously affected it is impossible to say. But even the very small amounts appear to have some dulling action upon the mind. Some of the keenest thinkers have found that their power of concentrated thought is dulled by taking even very small amounts of alcohol. The primary effect of alcohol is to disorganize the nervous system. Its effect may be slight if only small amounts are used, but the effect is nevertheless there, the same in kind though less in degree even when small amounts are taken. QUESTIONS 1. How do we know that sensations are felt only in the brain ? 2. If the spinal cord were cut across at the shoulders, what effect would it have on the lower parts of the body ? 3. What have the nerves to do with sensation ? 4. What is reflex action ? 5. Where is reflex action controlled? 6. If a person's foot is tickled, what action and reflex action occur? Do you suppose the foot would be pulled away if the person were asleep ? 7. What reflex actions are controlled by the medulla ? 8. What kind of reflex actions are controlled by the cerebellum ? 9. Why should you think coughing to be a reflex action? 10. What are the duties of the cerebrum? 11. Why is it important that good habits be formed ? 12. In what ways can the mind be cared for? 13. Why is sleep necessary ? 14. If a person goes to sleep while sitting up, he is likely to fall over. Why is this? Would he be as liable to fall over as he would be if he fainted ? 15. Why should we learn the habit of concentration? How may it be learned? 16. What is recreation? Why is it necessary? 17. Wh'at is the effect of alcohol upon the mind? CHAPTER XII THE SENSES THE brain is shut up tight in its bony box, the skull. It has no direct contact with the external world, and yet it succeeds in finding out very well what is going on outside of our bodies, just as a telegraph operator, shut up in his little office, can learn what is going on in the world. As we have learned, the brain is con- nected with the outer parts of the body by the sensory nerves, which bring messages, or impulses, from the exterior. They extend from every part of the body to the spinal cord and the brain, and bring messages from every part. The messages, when they reach the brain, produce what are called sensations, and it is through the sensations that we get our knowledge of the outer world. There are several outside forces that may excite the sensory nerves to send impulses to the brain. One of the most common of these is a touch upon the skin, which sends an impulse that gives rise in the brain to a sensation which we call touch. Similar sensations can come from every part of the skin. There are also several forces capable of starting impulses through spe- cial nerves. Light, for example, starts impulses from the eye through its nerve., sound from the ear. Through 213 214 PHYSIOLOGY AND HYGIENE these special nerves we get our sense of sight and of hearing. Some substances excite impulses from the tongue, giving a sense of taste, and others from the nose, giving the sense of smell. These act by means of special organs, situated at the ends of particular nerves, which we call sense organs. These represent four of the so-called special senses. THE SENSE OF SIGHT The Eyeball. The eye itself is shaped like a ball, as shown in Figure 73, although as we look at it in a person's face it appears quite unlike a sphere. This is because we see only a small portion of the front of the eye, the rest being hidden be- hind the eyelids. The only part of the eye- ball that we can see is just what appears be- FIG. 72. THE EYE, VIEWED FROM IN FRONT. Showing the tear gland and tear duct. Duct tween the eyelids, and the eye will look large or small accord- ing to whether the eyelids are wide open or partly closed. Different people appear to have eyes of vari- ous sizes, but the dimensions are really always about the same ; that is, the diameter is close to one inch. The eyeballs are set in deep sockets in the front of the skull, as may be seen from Figure 73, only the THE SENSES 215 front surfaces being exposed. The sockets protect the balls from injuries which might come from blows. The Eyelids. Two folds of skin hang over the eye t one above and the other below, as may be seen in Figure 73. These are eyelids, which open and close over the eye. When closed, they serve to protect the eye and also to keep its surface clean and moist. Even when we are awake the eyelids close every few seconds. We are quite unconscious of this movement of the eyelids, but we can easily observe it by watching the eyes of some one near us. The front of the eye is extremely delicate, and if the lids did not constantly cleanse its surface,, and if the tear secretions did not wash the dust away, the eye would become inflamed, and the sight be affected. The eyelids, by means of their long lashes and their exceedingly quick motion, serve also to guard the eye against accident. The hairs on the edges of the lids,, called the eyelashes, assist in keeping out the dust. The Tear Gland. The lids are aided in keeping the eyes clear by the tears. A small lachrymal gland, or tear gland, is lodged just above each eye, on the side away from the nose. This gland produces a watery liquid, which flows down over the eye and keeps its- surface moist. The liquid flows over the eyeball to the inner edge of the eye near the nose, where there is a tube, the tear duct, leading to the cavity inside the nose, as shown in Figure 72. The tears, after washing the surface of the eye, pass through the duct into the nose and the throat, and are then swallowed. Usu- ally the gland produces just liquid enough to wash the 216 PHYSIOLOGY AND HYGIENE eyeballs and to pass easily down the lachrymal duct. But when a person cries, the tears are produced so Nerve FIG. 73. THE EYE, VIEWED FROM THE SIDE. Showing its shape, the socket, and the attachment of muscles. rapidly that they cannot all pass through the duct into the nose. They then overflow and run down the cheeks. The Eye Muscles. Six small muscles are attached to each eyeball to move it. One is on the top, one on the bottom, one on each side, and two others have an oblique position. Figure 73 shows the form and position of these muscles. By the contraction of the muscles the eyeball can be turned in any desired direction. Structure of the Eyeball. If we examine a photog- rapher's camera, we find that it has three chief parts. There is (1) a dark chamber, the box of the camera, closed so as to admit light only from the front. In the opening in front which admits the light there is (2) a lens, which makes an image of the object to be photo- THE SENSES 217 graphed ; at the back of the camera is (3) the sensitive plate, upon which the picture is taken. The human eye is made upon much the same plan as the camera, although differing in details. Like the camera, it has a dark chamber and a lens, and also a sensitive surface at the back. If we ex- rr-'-~- ~ "."-.i-j^iY Image amine Figure 74, we can see how closely the eye and the camera may be compared. The eyeball is a dark chamber, which, like the camera, admits light only from the front. At the point where the light is ad- mitted there is a lens, shown in Figure 74, and at the back of the eyeball is a sensitive surface called the retina, shown in Figure 75. Between the front of the eye and the retina the eyeball is filled with trans- parent liquids, through which the light can easily pass, Light enters the eye from the front, passing through the small opening known as the pupil (Fig. 75). Just inside of this pupil is a transparent lens. The lens is so shaped that the rays of light are changed in their direction and come together at the back part of the eye. When they come together they produce a little picture or image of the objects from which the FIG. 74. A COMPARISON OF THE STRUCTURE OF THE CAMERA AND THE EYE. 218 PHYSIOLOGY AND HYGIENE light comes. This image is similar to what we see on the ground-glass screen at the back of a photographer's Aqueous, Humor/ , x ,. " V/trtous Humor FIG. 75. A DIAGRAM REPRESENTING A SECTION THROUGH THE HUMAN EYE. camera, which shows a picture of the objects toward which the camera is pointed. In the same way a little picture is formed upon the back part of the eye. The part of the eye upon which the image is formed is the retina, and is the sensitive part. The retina is full of nerves, and in some wonderful way, not fully understood, these nerves send impulses to the brain, by which the brain receives and recognizes the picture. If the nerves that connect the eye with the brain were cut, the message could never reach the brain, even though the image should be formed on the retina. If the eye were injured so that the image could not be formed on the retina, we could not see, even though the nerve were in good condition. THE SENSES 219 The lens that forms the picture on the retina is not able to form a picture of both a near and a distant object at the same time ; hence we cannot see clearly near objects and distant objects at the same moment. If we are observing a hill some distance off, and wish to look at a pencil in our hands, the shape of the lens changes a little so that the pencil becomes sharply pictured on the retina, but, at the same time, the hill necessarily becomes blurred to our sight. Nearsightedness. If the eyeball is of exactly the right shape, ordinary objects will be sharply pictured upon the retina. If, however, the ball is a little too long, distant objects will not be clear, not sharply focused as we say, but they will look blurred. A per- son with such eyes cannot see distant objects clearly, though he can readily see objects quite close to the eyes. We say he is nearsighted, and, in order to see clearly, he is obliged to wear glasses especially prepared to overcome his difficulty. Nearsightedness is very common. It is often due to improper habits of study. We are likely to lean over a desk or a table when we read, thus bringing the book very close to the eyes. This habit, if continued, is certain to cause such changes that the eyes, which at first could see clearly, become little by little so affected that only near objects can be clearly seen. Such near- sightedness is quite common among people who spend their early years in study. The difficulty is less com- mon among those who live out of doors and who do little or no reading. If we will take pains to sit erect 220 PHYSIOLOGY AND HYGIENE when reading or studying, and to hold our books no nearer than a foot or eighteen inches from the eyes, we shall greatly reduce the tendency to nearsightedness. If we lean over our work, holding a book within six inches of the eyes, we shall be quite sure to develop nearsightedness. Color Blindness. Some people have the sense of color poorly developed, and we call them color blind. This does not mean that they cannot see any color at all, but that they confuse the various colors. The most common form of color blindness is the inability to distinguish clearly reds from greens. Since red and green are the colors used as signals on railroads and steamboats, a pilot or a railroad engineer who cannot distinguish them readily may commit such blunders that accidents will result. Persons who are to hold responsible positions on railroads or steamboats are accordingly required to have their eyes specially tested for color, and no one who is color blind should ever think of taking such a position. The difficulty is more common among men than among women, and no remedy for it is known. Care of the Eyes. 1. The eyes were made to be used, and it does them no harm to exercise them con- stantly. If, however, they are used on work that requires close attention, such as reading or sewing, they become tired and should frequently be allowed a moment for rest, such as is gained by closing the eye- lids or by looking at distant objects. 2. We should not abuse the eyes by reading in a THE SENSES 221 dim or flickering light. Nor should a bright light, like the sun's rays, be allowed to fall upon the page we are reading. We should never look directly at a bright light. 3. The only proper position for holding the head when we read is erect. Reading, when lying on the back or in a hammock, is very injurious to the eyes. We must not forget, moreover, that using the eyes means also working the brain. When the brain is tired, one is often inclined to lie down and read a book setting the tired brain to work again, and under conditions bad for the eyes themselves. 4. If a child has difficulty in seeing objects clearly, his eyes should be examined by an oculist. Headaches are frequently due to trouble with the eyes, and if a child has a tendency to headache, his eyes should be examined. It frequently happens that the trouble with the head may be cured by the use of glasses pre- scribed by a competent oculist. 5. Particles of dust that get into the eyes are usually carried off with the tears by way of the tear duct, and a few winks remove them. If this is not sufficient, the trouble may frequently be remedied by lifting the upper eyelid with the fingers and drawing it down over the lower eyelid. If this does not remove the particle of dust, it may be taken out by some com- petent person who can pass gently over the eyeball the end of a soft handkerchief rolled up to a point. If this attempt fails, a physician should be called. The eyes, in such cases, should never be rubbed. The eyes are 222 PHYSIOLOGY AND HYGIENE organs too delicate and too important to be treated by incompetent persons. If one has trouble of any kind with his eyes, he should consult a physician or an oculist. THE SENSE OF HEARING The Ears. The two projections on the sides of the head, which we commonly call the ears, have very lit- \ Ntrvz Eustazhian Tube,, tot he throat FIG. 76. THE EAR. A section through the " stony bone," showing the parts of the ear. tie to do with hearing. They are only bits of carti- lage covered with skin, which serve, perhaps, to col- lect waves of air, and probably make sounds a little louder. The real hearing organ is the inner, or true ear, which is wholly inside the head and embedded in the bones. The ear itself is in the middle of the hardest bone in the body, called the stony bone. The THE SENSES 223 ear is thus more thoroughly protected from external injury than any other organ. The ear is a very complicated organ. Its general structure may be seen from Figure 76, which shows a sec- tion through the side of the head, giving the chief parts of the ear. The passage from the outside to the true ear, as the figure shows, is slightly bent. In it there is secreted a little wax, which helps keep it moist and flexi- ble. The passage is closed at the inner edge by a mem- brane which is stretched across. This is the tympanic membrane. Is is tough and elastic. Earache in chil- dren is usually caused by sores in the ear ; these occa- sionally make little holes through the membrane, which interfere somewhat with hearing. Sometimes very loud noises, like explosions, break the membrane and make the person deaf. Figure 76 shows that beyond the membrane there is a cavity. It is known as the ear drum, or tympanic cavity, and is also sometimes called the middle ear. The ear drum is filled with air, which enters it through a tube in the lower side. This tube leads to the throat, as indicated in Figure 76, and is opened every time we swallow. In this way the drum is filled with air, and the pressure of the air in the drum is kept the same as the pressure of the air outside. If this tube becomes closed, as sometimes happens with inflamma- tion of throat or nose, the air within the ear is partly absorbed, so that the pressure inside becomes less and the membrane is pushed in by the pressure of the out- side air. This affects the hearing injuriously. This 224 PHYSIOLOGY AND HYGIENE is the reason why throat troubles are very apt to extend to the ears and interfere with hearing. Indeed, the most common cause of deafness is to be found in diffi- culties of the throat. Catarrh in the throat is one of the first things that a physician attends to in most cases of difficulty in hearing. In Figure 76 it will be seen that three small bones (malleus, incus, and stapes) are stretched across the cavity of the middle ear. The outer of these ear bones is attached to the membrane and the inner one con- nects with the inner ear, which contains the real hearing organ. In this inner ear are many nerves. Sound is produced by waves of air which enter the ear and shake the tympanic membrane. This shakes the bones at- tached to it, and by their motion the effect of the air wave is transferred to the inner ear, where it reaches the nerves. This shaking or vibration upon the nerves starts nervous impulses which travel rapidly to the brain. When the messages reach the brain they pro- duce a sensation which we call hearing. Hearing. Our ears tell us very little in regard to sounds except their loudness or softness, and their pitch (high or low). Our power of determining dis- tance is limited. If we know what causes a certain sound, we can determine something of its distance by the loudness. We judge the distance simply by the loudness of the sound as compared with what we should hear if the sound were nearer or farther away. If, for example, we hear the whistle of a locomotive, and it sounds faint, we are sure that the engine must be a long 1 THE SENSES 225 distance away, because we know that the sound itself is really very loud. If, on the other hand, we hear the buzz of a mosquito, and it sounds loud, we know that the Insect is close to the ear. We can determine the distance of sound in no other way than by the compara- tive loudness. Our power of determining the direction from which sound comes is not much greater. Noises coming to the ear from the side of the head may sound louder in one ear than they do in the other, and in that case we judge that the sound is on the side of the head where it seems loudest. Sometimes we unconsciously turn the head around a little, until we find that the sound appears to be loudest when the head is in a certain position. We then conclude that the noise comes from the direc- tion toward which the ear is turned. But this test is by no means accurate. Care of the Ears. The ears require very little care. The use of solid objects, like pins or needles, to remove the ear wax is very unsafe. The ears may be kept suffi- ciently clear of wax by means of the little finger, which should be pushed downward as it is placed in the open- ing. Very loud sounds close to the head are likely to do harm. Boxing children's ears is liable to injure the membranes within. Pain in the ear may sometimes be relieved by placing hot cloths upon the ear ; but if it persists, a physician should be called. It is well to re- member that deafness is most commonly produced by throat troubles, and if one has any difficulty in hearing, he should first of all look to the condition of his throat. 226 PHYSIOLOGY AND HYGIENE Slight deafness is not unusual with children ; it renders a pupil apparently inattentive and dull. The child does not realize that he has any difficulty in hearing, and very likely neither his teacher nor his parents suspect it. Therefore a child who is inattentive should have his hearing tested. If deafness is the cause of the difficulty, a physician should be consulted at once to remedy the defect, if possible. THE SENSE OF TASTE By the sense of taste we learn something of the nature of liquids. Solid substances do riot produce taste. It is true that many solid bodies have a certain taste, when taken into the mouth, but not until they are more or less dissolved in the saliva. If we rub the tongue dry, and then place upon it a lump of sugar, we notice no taste at first, but, as soon as the liquids of the mouth begin to dissolve the sugar, we perceive the sweet taste. Location. The sense of taste is located in the mouth, but not, as is commonly supposed, wholly in the tongue. The upper side of the tongue has a sense of taste, but the under side has not. Besides this, the roof of the mouth, especially at the back, has a sense of taste. When a substance is rolled around by the tongue at the back of the mouth, we find there the strongest sense of taste. The Tongue. The tongue of a healthy person is of a pinkish red color. If it is otherwise, the stomach is probably out of order. One of the simplest methods employed by physicians for detecting signs of certain diseases is an examination of the tongue. When this is THE SENSES 227 Papillae with taste, buds -,- [ covered with a whitish or yellowish coating, or when it is bright red, the physician knows that something is wrong. If we examine the tongue carefully, we find that it appears much as in Figure 77. It is covered with numerous little bunches or papillae, which differ in appearance and vary in use. Some of them, particularly those at the back of the mouth, are associated with the sense of taste and are called taste buds (see Fig. 77). The tongue itself is made up principally of muscles, which run in many directions and enable us to move the tongue very easily. In addition to the muscles there are glands which secrete a watery material that keeps the tongue moist. There are also many blood vessels and nerves, among them some which are particularly connected with taste, and which carry to the brain the messages that enable us to determine the presence of sweet, sour, or bitter substances in the mouth. Tastes. We think of the substances that we eat as having many different tastes. All kinds of tastes FIG. 77. THE TONGUE. Showing the papillae on its surface. 228 PHYSIOLOGY AND HYGIENE may, however, be classified under four heads, bitter, sweet, acid (sour), and salt. These different tastes are not perceived equally well in all parts of the mouth. We taste sweet things most delicately at the tip of the tongue, and bitter things at the back part of the mouth. We are very apt to confuse tastes and smells, and many sensations that we call tastes are really tastes and smells combined. When we drink a glass of soda water, for example, we have the sweet taste of the sirup, but the gases from the soda water pass into the nose and produce a very strong sense of smell. The two together are what we call the pleasant taste of the soda water. Many other so-called tastes are largely smells, as can be tested by blindfolding a person, hold- ing his nose so that he cannot catch the odor, and then giving him successively small pieces of apple, onion, and potato. Duration of the Sense of Taste. Our sense of light is gone at almost the instant the light ceases to shine into the eye, and the sense of sound stops as soon as the vibration that produces it ceases or becomes too distant to affect the ear. The sense of taste, however, does not cease so quickly, but it may last many seconds, or even several minutes, after the substance tasted has been swallowed, partly because some of the substance remains in the mouth. An unusually bitter taste, like that of quinine, may last as long as half an hour. The sense of taste easily becomes tired, and in this respect it is quite different from the sense of sight. We may use our eyes all day long, and yet see as clearly at THE SENSES 229 night as in the morning. But, if we continue to use our sense of taste for even a few minutes, it loses its acute- ness. We can test this characteristic by eating a lemon. Food does not have so pleasant a taste at the close of a meal as at its beginning, so we often finish our dinner with a highly flavored dessert to please our taste, which has by this time become dull. Our sense of taste is one of our greatest enjoyments, but to obtain the most pleasure from it we must not gratify it too much. If we live upon plain food, with an occasional luxury, we shall find more enjoyment in it than do people who are constantly eating highly flavored foods. The luxury gives special pleasure only when it is unusual. If we should eat the most delicious food constantly, it would soon come to give us less enjoyment. The bulk of our food should be such as satisfies the appetite rather than the taste. Finely flavored substances, like candies, sauces, and sweets in general, should be used in comparatively small quanti- ties, if we wish to enjoy them as much as possible. THE SENSE OF SMELL The sense of smell enables us to determine the pres- ence of certain gases. Only substances that are in the form of a gas or vapor can be smelled. Rose water is a liquid, but the only part that we smell is the vapor that rises from it. The amount of vapor required to excite the sense of smell is exceedingly minute. If a bottle of peppermint oil be opened for a few moments, it will give off a vapor that will fill the room and will be smelled 230 PHYSIOLOGY AND HYGIENE Olfactory Nerves by every one present. Yet if the bottle of liquid be weighed in the most delicate scales, there will be no perceptible difference in the weight before and after the bottle was opened. No other sense is as delicate as that of smell. Location. The sense of smell is located in the cavities of the nose. The two nostrils lead into two large cavi- ties above the mouth, separated from each other by a bony parti- tion. The cavities extend backward to the throat. They are partly filled with large, thin, folded bones, which bend around so as to form curved sur- faces. They give a large amount of ex- posure to the air, as it passes over them. Upon these bones are the nerves of smell (olfactory nerves), as shown in Figure 78. Vapors entering the nose, as we breathe, act upon these nerves in such a way that they send messages to the brain, and produce in the brain the sensation that we call odor or smell. Its Use. The sense of smell in human beings is not so well developed as in some animals, or so useful. We may occasionally notice by its aid the presence of inju- rious gases, such as illuminating gas which is escaping FIG. 78. A VERTICAL SECTION OF THE NOSE. Showing the nerves of smell. THE SENSES 231 from a burner. Sometimes, also, we perceive through the sense of smell the presence of some body or substance which gives off a special odor, but which is concealed from our eyes. With some animals the sense of smell is much more keen than it is with human beings. A dog can follow his master's footsteps by means of his very keen sense of smell. The acuteness of the sense of smell is blunted by con- tinued use even more than is that of taste, as we can readily prove with cologne or other strong odor. The first whiff of cologne on a handkerchief gives a strong sensation. If, however, we bury our face in the hand- kerchief and continue to breathe the odor, we cease to smell the cologne. In order to perceive it again, we must remove the handkerchief from the nose and let the smelling organs rest for a time. OTHER SENSATIONS We frequently say we have five senses, seeing, hear- ing, tasting, smelling, and feeling. The first four of these are quite distinct. The fifth, which we call feeling, is made up of several different kinds of sensations. There are really two different senses in the skin, touch and temperature. In addition to these the term feeling usually covers the pain sense, hunger, thirst, and some other sensations. The Touch or Pressure Sense. The skin is sensitive to the touch or pressure of objects. Whenever a sub- stance presses even very lightly upon the skin it excites the nerves in such a way that nervous impulses are 232 PHYSIOLOGY AND HYGIENE sent to the brain, which builds out of these impulses an impression, more or less distinct, of the object that touched us. We can easily test this by shutting our eyes and letting some one touch us with different kinds of unknown objects. The whole skin is thus an organ of touch, although it is more sensitive in some places than in others. Through the messages that come to the brain from the skin we not only get a sensation that the skin is touched, and that the object touching it causes a cer- tain amount of pressure, but we know quite accurately what part of the body is in contact with the object. We can tell whether the ring is on the finger or is lying on the palm of the hand, and whether it is on the little finger or the thumb. The delicacy with which we can determine where the skin is touched differs very much on different parts of the body, as can be easily discov- ered by experiment. It is most delicate at the tips of the fingers and the tip of the tongue. We can tell within a twenty -fifth of an inch where an object, like a needle point, touches the skin of the finger tips or the tongue. The sense of location is much less delicate on the back of the fingers, and still less so on various parts of the arms and shoulders. Upon the back of the shoul- ders it is least delicate of all ; in fact, we cannot deter- mine within two and a half inches where an object touches the back part of the shoulder. We can see from this that the parts of the body most used are the ones in which the sense of touch is the most delicate. It is the sense of touch, or of location of touch THE SENSES 23B sensations, that gives us our most intimate knowledge of the nature of objects outside our bodies. By the sense of touch alone we can tell whether such objects are rough or smooth, whether they are blunt or sharp, whether they are solid or liquid. The Temperature Sense. When a warm body touches the skin, nervous impulses go to the brain, and we have a feeling of warmth. The skin, in general, is sensitive to both cold and heat, though some points on the skin are sensitive to heat and not to cold, while others are sensitive to cold and not to heat. The warm and cold spots are very close together, so that a body no larger than the head of a pin will in some places touch both. Every part of the body has a certain tem- perature, and if some object warmed to that exact temperature touches the skin, the pressure of the object will be felt, but it will seem to be neither warm nor cold. If, however, the object is a little warmer than is the skin at the point where it touches, it will seem warm ; if it is a little cooler than the skin at that point, it will seem cold. The temperature of the skin is not just the same on all parts of the body. The temperature of the hand is usually a little lower than that of the forehead, so that an object which feels warm to the hand may feel cool to the forehead. The forehead itself feels warm to the hand. If we step in cold weather from a carpet to a bare floor, the floor feels colder to the feet than the carpet, although the two are actually of the same temperature. The bare floor draws the heat away from the feet more 234 PHYSIOLOGY AND HYGIENE rapidly than the carpet does. Any object feels cool when it takes heat away from the body rapidly. If it withdraws no heat from the body, we feel that the object touches the skin, but we feel no sensation of cold resulting from the contact. Some substances draw heat more rapidly than others, and this is why, in cold weather, for example, metal objects seem colder than cloth to the touch. Sense of Pain. Almost any nerve which carries mes- sages to the brain will carry a sense of pain, if it is strongly excited. If the pain is slight, we can deter- mine very closely where it comes from ; but if it is severe, we cannot locate it so accurately. A slight toothache, for example, can be located in the proper tooth, but when it is severe, it seems to come from the entire jaw, or the whole side of the head. Occasionally the whole upper part of the body appears to be in pain, although the trouble is confined to a single tooth. We find it hard to realize that pain is of any use, but it really is of great value. If it did not hurt to burn the fingers, children would get their fingers so badly burned as to render them useless. In fact, they would probably destroy the fingers entirely before they were old enough to know how to take care of themselves. Pain thus warns us to guard our bodies from accidents and disease, and to keep them in as good a condition as possible. Pain is a warning to our bodies, and we should heed it as carefully as does the engineer the danger signal beside the railroad track. THE SENSES 235 The Muscle Sense. We seldom hear any one speak of the muscle sense, but it is really of considerable im- portance. It is the sense by which we know when and how much we contract our muscles. Even when we shut our eyes we can move our fingers very accurately, knowing almost exactly how much the muscles contract. Let us say, for example, that we will allow one hand to rest upon the table while we close our eyes. If, while our eyes are still closed, another person lifts the hand, we can tell very accurately by means of the muscle sense how far it has been lifted. This sense is of great importance, for it enables us to control our actions and to move our muscles together. If we could not feel how much we move the muscles, we could not possibly make the body motions that require the contraction of a number of muscles at the same time, as when we throw a stone. The muscle sense is not situated in any particular place, but is present in all parts of the body, especially in the joints. QUESTIONS 1. How does the brain get a knowledge of the world? 2. What are the chief sense organs ? 3. What is the shape of the eyeball, and where is it located? 4. What are the eyelids ? What is their purpose? 5. Where are the tear glands located ? What is their use? 6. How are the eyeballs moved ? 7. What are the principal parts of the eye ? 8. Why is it desirable to sit erect when reading? 9. If the lens of the eye should become opaque, what would be the result? 236 PHYSIOLOGY AND HYGIENE 10. Some persons cannot distinguish between green and ripe cherries. Can you explain the reason? 11. In what five ways should we care for the eyes? 12. Where are the real hearing organs? 13. What are the important parts of the ear? 14. How do the ears enable us to hear ? 15. How should we care for the ears ? 16. If two colors are mixed, do we get a new color? If two sounds are mixed, do we get a new sound or do we hear both sounds ? 17. If you close the nose and swallow, what effect is produced in the ears? Can you explain why ? 18. Where is the sense of taste located? 19. What is the structure of the tongue ? 20. Mention several duties of the tongue? 21. What may be said of the duration of the sense of taste ? 22. Where is the sense of smell located? How may this sense be dulled? 23. How could you tell whether soda water, without sirup, has a taste or only a smell ? 24. What three sensations compose the sense of feeling? 25. What is the use of the touch or pressure sense ? 26. What do we learn from the sense of heat and cold ? 27. Lay the palm of the hand upon the cheek. Does the hand appear warm or cool? Do the same upon the forehead. What do you observe? 28. Of what use is pain ? 29. Of what importance is the muscle sense ? CHAPTER XIII HEALTH AND DISEASE THE body is a very delicate piece of machinery, as we can readily appreciate. It needs to be treated carefully, but most of us have bodies that will keep in good condition if we care for them properly. The Body cures Most of its Own Ills. The human body is such a beautifully constructed machine that it will of itself take care of the ordinary slight illnesses. If we have a cold, the body soon cures it ; wounds are rapidly healed ; broken bones are mended ; digestive troubles usually disappear. All of these little maladies the body itself can care for. We need simply to do our part toward keeping in good condition by eating plain, wholesome food, taking plenty of exercise, and living as much as possible out of doors in the fresh air and sunshine. Many people have the idea that the proper way to treat ailments of all sorts is to take medicines. This is a great mistake. Medicines cannot cure disease. The most they can do is to aid the body to right itself. Most people would be better off by letting nature cure their little ailments, giving her the aid that comes from such simple remedies as baths, soaking the feet in hot water, and rubbing, rather than by dosing themselves 237 238 PHYSIOLOGY AND HYGIENE with drugs. Medicines should be used only under a physician's guidance. The constant use of drugs rather weakens than strengthens the general physical powers. If people used fewer drugs and more common sense, took less medicine and more exercise, wore fewer wraps in winter and spent more time out of doors, we should hear less about sickness, and the whole race would be more robust. Disease. When the machinery of the body is out of order we speak of the condition as sickness or disease. The causes of diseases are numerous. Sometimes they are the result of improper food habits, or intemperance, of breathing impure air, or of other improper conditions of life. One class of very important diseases is pro- duced by parasitic animals or plants growing in the body. Some diseases we say are " catching," by which we mean that one person very readily gets the disease from another. This class includes such diseases as measles, scarlet fever, mumps, whooping cough, etc. Such dis- eases are called contagious. Another class of troubles, like rheumatism, malaria, etc., are non-contagious, since healthy persons do not " catch " them from sick people. PARASITIC DISEASES Contagious diseases are probably all caused by very small animals or plants that get into the human body and multiply there. Most of them are so small that they can be seen only with the aid of a very powerful microscope. HEALTH AND DISEASE 239 Parasitic Animals. There are a few animal parasites that occasionally get into our bodies and cause trouble. One of these is the tapeworm, which enters the body from raw or insufficiently cooked beef or pork. It lives in the intestines and makes considerable trouble, al- though it is not usually very dangerous. Another such parasitic animal is the trichina, which also comes from eating pork, not properly cooked, such as rare or slightly cooked ham or sausage. The disease resulting is violent and painful, and often causes death. The simple method of avoiding both tapeworm and trichina is to eat no meat that is riot thoroughly cooked. Another form of animal parasite produces malaria, or chills and fever. This parasite is a minute animal, to be seen only through a microscope, which gets into the body, usually from the bite of the mosquito. Certain kinds of mosquitoes are liable, when they bite, to leave in the skin some of these little parasites. The best way to protect ourselves against malaria or chills and fever is to keep from being bitten by mosquitoes. This may be done generally by covering the doors and windows of our houses with mosquito netting, particu- lar care being taken to remain behind such netting at night. Parasite Bacteria. The most important of the para- sites that make their way into the body are a type of plant called bacteria. These minute plants are so small that a powerful microscope is required to see them, and so light that they can easily float around in the air in the form of dust. They are very abundant everywhere. 240 PHYSIOLOGY AND HYGIENE Some of them, instead of being harmful, are directly useful to us. Bacteria cause the souring of milk and the decay of meat ; they produce vinegar and the flavor of butter and cheese; and they prepare the soil for the growth of plants. These tiny parasites are, on the whole, very useful friends of ours. But while some bacteria are healthful, others, which may live as parasites in our bodies, produce certain diseases. Some of these are shown in Figure 79. Typhoid fever, con- sumption (tuberculosis), diphtheria, and boils and abscesges of the gkin are produced by them. Other contagious dis- eases, like measles, scar- let fever, mumps, and whooping cough, are FIG. 79. -BACTERIA THAT PRODUCE pro b a bly caused either CERTAIN DISEASES. by bacteria or by some other microscopic parasites. Each of the different dis- eases is produced by its own kind of bacteria. Protection against Harmful Bacteria. Bacteria can- not ordinarily injure us unless they get inside the body. We have already seen how the skin forms a covering which protects the body from the entrance of external objects, and this commonly keeps out dangerous bac- teria. So well are we protected that the majority of them do no harm whatever, because they do not obtain HEALTH AND DISEASE 241 entrance to the body. We need not be frightened, then, because bacteria are present in milk and water, for this is the natural condition. The bacteria in milk, and also those in water, are usually, though not always, harmless. Even if the bacteria of diseases do find their way into the body, it does not necessarily follow that they will effect injury. The human body is able to fight these bacteria, and in many cases to destroy them before they do harm. When we are in the best condition of health, our power of resisting them is greatest, and conse- quently we are then less liable to take some contagious diseases than when we are in a more or less weakened state. In general, the best method of avoiding all bac- terial diseases is to keep in robust health, although even perfect health apparently cannot protect one against taking some contagious diseases. Robust health, as we have seen, depends upon plain, whole- some food, plenty of fresh air and outdoor exercise, and living a regular life. Immunity from Contagious Diseases. Many conta- gious diseases, such as smallpox, scarlet fever, mumps, chicken pox and yellow fever, are rarely taken by the same person more than once. In some way, which we do not fully understand, the first attack acts upon the body so that it is able to resist the action of the para- sites ever afterward. A person who has had one attack of such a disease is said to be immune to future attacks. Advantage is taken of this fact by vaccination, by which we are protected against smallpox. When vaccination 242 PHYSIOLOGY AND HYGIENE " takes," it causes what is really much like a mild form of smallpox, which makes us for a certain time immune to that disease. Prevention of Contagious Disease. The best way to check the spread of contagious diseases is to prevent the distribution of the bacteria that cause them. If we can keep these minute growths from passing from one person to another, we can frequently stay the spread of the disease. The rules adopted by the boards of health in our cities, especially in connection with schools, are made for the sake of preventing the spread of bacteria. That is why persons having contagious diseases, such as diphtheria, are placed in rooms by themselves. That is why children are not allowed to attend school when, for example, a member of the family has the measles. In general, the regulation of these matters may be left to boards of health, but there are a few facts which it is well for us all to understand. How Bacteria get out of the Body. When a conta- gious disease is "taken" from a person by another, the bacteria which produce the disease must have passed from the body of the patient to that of the other individual. Usually, the bacteria pass from the body of the sick person in some of the secretions or excre- tions. If the disease is accompanied by sores, such as boils, the bacteria leave the body in the discharges from the sores. If there is an eruption from the skin, as in scarlet fever and measles, the bacteria prob- ably leave the body from the skin, as well as from the discharges of the mouth and nose. If there is a dis- HEALTH AND DISEASE 243 charge from the digestive canal, as in typhoid fever, bacteria find exit with what passes from the bowels. If the disease is in the mouth or throat, as in diphtheria, bacteria will usually be found in the saliva. If it is in the lungs, as in consumption, we may look for the bacteria in the saliva and phlegm coughed up by the patient. If the disease is accompanied by a cough, as in whooping cough, we may regard the breath during the coughing as carrying the bacteria. How Bacteria are Carried. 1. Many of the dis- charges from patients get into sewage through drains and closets. Hence the sewage of a city is almost sure to contain hosts of dangerous bacteria, and it should be disposed of in the safest and most careful manner possible. If it enters a river, and the water of the same river is used for drinking, many cases of typhoid fever are almost sure to arise. Most of the sewage of a city enters into common sewers, and each house is connected with these sewers. It is necessary, there- fore, to have means for preventing the bacteria in the sewers from entering the house. This is accomplished by properly devised plumbing. We can thus compre- hend the importance of having and keeping the plumbing of a house in good condition. 2. Bacteria may be transferred by contact, either actual contact with a patient or with something that he has touched. A nurse may get bacteria upon her hands from handling the patient or his clothing. If she washes her hands frequently and refrains from put- ting her fingers to her mouth, the danger from conta- 244 PHYSIOLOGY AND HYGIENE gion will be largely reduced. Other persons in the house may take a contagious disease by using spoons, knives, forks, cups, or saucers which have been em- ployed in the sick room. Bacteria cling to such arti- cles, and may thus be transferred to any person using the dishes. The danger may be avoided by allowing no one to use the same eating utensils as the sick per- son, or by washing them thoroughly in boiling water before they are used by others. Bacteria are also fre- quently left by sick persons upon door knobs, stair rails, etc., and these should, therefore, be carefully washed. In general, it is an excellent rule always to wash the hands before eating, and to avoid eating food which has been handled by others. 3. Bacteria may be carried by the air. When the skin peels, as in scarlet fever, or when there is a skin eruption, as in smallpox, the germs probably pass into the air, and may thus be carried to other persons. The same is true of diseases with which there is a cough, such as whooping cough and consumption. It is not very easy to guard against this danger if we must stay in the same room with the 1 patient ; but the danger may be reduced, as much as this is possible, by insisting upon a constant supply of fresh air in the sick room. The germs, after floating in the air for a while, settle with the dust. Every time the room is swept or dusted they are stirred up again. Sweeping and dusting schoolrooms increases the chance of the spread of con- cagious diseases. So far as possible, wiping with damp cloths should replace sweeping and dusting. After the HEALTH AND DISEASE 245 bacteria have reached the out-of-door air, most of them are killed by the sunshine, although this is not true of the bacteria of all diseases. 4. Uncooked food sometimes distributes disease bac- teria. This applies chiefly to water and milk. Water from a river receiving city sewage is the most common source of typhoid fever. Milk is occasionally the source of diphtheria, scarlet fever, typhoid fever, or diarrhoea. In case of epidemics from water, we may protect our- selves by having the water boiled before we drink it. The only protection against disease carried by milk is either to buy the milk from reliable sources or to boil it before it is usedo Other foods which we eat un- cooked, such as lettuce, celery, raw oysters, and fruit, are occasionally sources of disease. Cooking is an efficient safeguard against the danger. 5. Occasionally flies or other insects may carry disease germs, particularly those of cholera, typhoid fever, and some eye diseases. The chief precaution to be taken is, as far as possible, to prevent flies from alighting on our food or eating utensils. We have already learned that mosquitoes distribute malaria, and it is also true that they carry yellow fever. Every one should bear in mind a few simple rules which, if followed, will help to prevent the spread of contagious diseases. They are particularly important in schools where children from many families are brought together. Do not spit on the floor or sidewalk. Do not put pencils or penholders into the mouth. 246 PHYSIOLOGY AND HYGIENE Do not put the fingers in the mouth. Do not put money in the mouth. Never put into the mouth anything that another per- son has had in his mouth (gum, bean blowers, whistles, drinking cups, etc.). When coughing turn the face away from others, and avoid allowing others to cough in your face. Wash the face and hands often. By these means we may largely avoid the germs which might get into our bodies. THE USE OF ALCOHOL We have learned in previous pages that alcoholic bev- erages are quite unnecessary to health, and are in many cases extremely harmful. They interfere to a large extent with the perfect health and happiness of man- kind. The question might naturally be asked, Why is it that people learn to use alcoholic beverages when these are not only of no use, but liable to do so much injury ? There are three main reasons : (1) The boy does not realize the risk he is running. He does not expect that he will become addicted to the use of alcohol in such a way as to injure him. Com- monly he does not know the danger that lies before him. (2) The, boy sometimes knows well enough that alcohol is dangerous and likely to do him harm, but he thinks it manly to drink, and is afraid of being called odd or priggish if he does not. But it is not manliness that causes a boy to follow his companions into a saloon. On the contrary, it is usually cowardice. He HEALTH AND DISEASE 247 is afraid that he may be laughed at. It is really the manly aiid courageous boy who dares to stay outside and to refuse to follow others into useless danger, and in the end his associates never fail to recognize and to admire his real courage and manliness. (3) The third reason is the desire to be social. The boy finds that his companions drink beer, and he feels it more social to follow their lead, even at the cost of some danger to himself, than to oppose them, especially if they are a little older than he. He should remember that the kind of sociability that leads to a saloon, or into any other useless danger, had better be shunned. There is companionship far pleasanter than that which comes through a glass of beer, and there are friends more use- ful than those who invite one to a saloon or urge one to join in a social glass. Reasons why Alcohol should be entirely avoided as a Beverage. The only wise course is to let alcohol en- tirely alone. There are three important reasons for so doing : (1) It will do us physical harm. It is impossible for any one to tell where the injurious effects begin, or to say how much he may use without harm to himself. Small quantities are liable to lead to larger ones, and the habit of using alcohol is apt to cause an appetite which will result in untold evil. The only safety lies in avoiding alcoholic beverages altogether. Many a person who seemed strong-willed has to his sorrow found his will power insufficient to resist the craving which alcohol has developed. 248 PHYSIOLOGY AND HYGIENE (2) The constant use of alcohol, even in moderate amounts, frequently lowers one's moral tone and intelli- gence and thus interferes with ones chance of success. The parts of the city which show the greatest poverty are the parts which abound in saloons. Prisons are "filled with men and women who have used alcohol. The use of alcohol not only means the waste of large amounts of money, but if continued, it has a tendency to reduce a person's chance in life. It frequently ruins ambition ; it tends to destroy the power of attending strictly to work; it makes a man careless about fulfilling his responsibilities, and is likely to lead to loss of employ- ment. Some corporations, especially railroads, refuse to put into responsible positions, such as those of engineers and switchmen, persons who use alcohol even " in mod- eration," or occasionally. It is not simply those who use alcohol in large amounts who risk their chances of filling responsible positions. The use of alcohol is likely to bring a boy into a circle of acquaintances who will injure rather than benefit him. It is likely also, when he has become a man, to destroy his interest in his family and all that is good, and to lead him to live a life upon a low plane. (3) Our example will influence others. We all have some responsibility for those about us, and to lead another, by our example, into a course of life that in- jures him, is a very serious thing, the results of which we cannot measure. When people see their friends using alcohol, they are very likely to think that they can do the same. They may be led to use alcohol in HEALTH AND DISEASE 249 excess from seeing others use it in moderation. The mod- erate drinker is the one whom others try to follow. He is thus in a measure responsible for the downfall of the friend who, weaker than himself, tries to follow his lead. The healthy person does not need alcoholic drinks and is better off without them. They always produce an abnormal mental condition. What is needed for the best success in life is a mind acting in its normal con- dition and uninfluenced by drugs, either by narcotics or stimulants. Alcohol always makes the mind's action unnatural and hence inferior to its natural action. This effect, in impairing the keenness of the mental action, is just as sure whether small or large amounts are used, though differing in degree. THE DUTY OF PRESERVING HEALTH It is our duty to make the most of our opportunities in life. Whether we decide upon a business career or a profession, we are sure to find that, in the sharp com- petition of to-day, a good body and abundant physi- cal health are wonderful aids in reaching the greatest success in life. Physical strength will give one power to become a leader among men. Failure to develop our powers to their highest extent will result in a life unsatisfactory to ourselves. It is our duty to set our ambitions high. There is no one who may not hope for success, and no one who should not endeavor to live a broad and useful life. The higher we aim, the higher the position we shall reach. It is perfectly right and honorable to determine to reach a responsible position 250 PHYSIOLOGY AND HYGIENE in business, to acquire wealth and power, and to become a person of influence. These things are possible to every American youth who will make proper use of his opportunities. Without perfect health, however, suc- cess is likely to slip from the grasp. One of the best assurances for a successful life is a well-developed, active, healthful body. We should remember that the body is a marvelous machine. Its value depends upon its being in a condi- tion of the greatest efficiency. A locomotive with a leak- ing valve may still pull a few cars, but it is much less useful than a perfect engine. So our bodies, even when more or less out of order from abuse of one sort or another, may still keep alive and carry on some of the duties of life; but they will do less work than when they are in perfect condition. The value of the human body as a machine is lowered by every form of overindulgence. Excess in eating, in talking, in playing, or in working reduces our chances of future success. Immoderate eating and drinking injure digestion ; excessive talking destroys confidence in our statements ; too much play makes a boy unready for the more serious duties in life ; and too much work makes him tired and dull. The study of our body teaches that any kind of indulgence results in a general lowering of the powers of the body and mind, and makes us less capable of achieving the highest end in life. The study of these pages has resulted in showing that two great fundamental laws for developing a perfect body and living a useful life are : HEALTH AND DISEASE 251 (1) Use every power you possess. (2) Avoid the overindulgence of all appetites and all desires. QUESTIONS 1. What is the purpose of medicine ? 2. Why should medicine be avoided as much as possible ? 3. What causes most contagious diseases? 4. What is meant by parasitic animals? 5. How are tapeworms and trichinae taken into the human sys- tem? What is the result with each? 6. How are malarial organisms taken into the body ? 7. How can the body best be protected against injurious bacteria? 8. How may the spread of contagious diseases be prevented? 9. How do the injurious bacteria pass from a person who has sores or boils? Scarlet fever or measles? Typhoid fever? 10. In what important ways may bacteria be carried ? 11. Why should plumbing be kept in good condition? 12. How may bacteria be transferred through contact? 13. How may bacteria be carried in the air? 14. Why is wiping with a damp cloth better than dusting in a schoolroom ? 15. How may bacteria in food be destroyed ? 16. How can we reduce the danger of taking a disease dis- tributed by coughing? 17. How may we prevent diseases being spread by insects? 18. Why should we have light and air in our sleeping rooms ? 19. What three conditions most commonly lead a person to use alcohol as a beverage ? 20. Why should alcohol be entirely avoided as a beverage ? 21. What are the two fundamental laws of health and use- fulness ? CHAPTER XIV WHAT TO DO IN EHERGENCIES THERE are many times when a knowledge of simple methods of procedure in case of accident is of great advantage, and occasionally such knowledge may be the means of saving life. Some possible emergencies, with the proper treatment, have been mentioned on various pages of this book. Drowning. See page 120. Dislocations. See page 140, Burns. See page 177. Foreign Bodies in the Eye, Broken Bones. See page See page 221. 132. Freezing. See page 178. Treatment for Poisoning. The treatment to be fol- lowed when one swallows poison varies with each kind of poison. The ordinary course should consist of three steps, although with certain poisons one of these may be omitted. In every case of poisoning a phy- sician should be sent for at once. Until he arrives there are in most cases two things to do: (1) cause vomiting, and (2) administer an antidote to the poison. 1. Induce immediate vomiting so as to remove as much as possible of the poison from the stomach. This may be done by giving a teaspoonful of powdered mus- tard in a glass of warm water. After the mustard has been swallowed, tickle the back part of the throat with 252 WHAT TO DO IN EMERGENCIES 253 the finger or a feather. If vomiting does not occur at once, repeat the dose in about ten minutes. Common salt will sometimes serve in the place of mustard if the latter is not at hand. 2. Administer some antidote to counteract the effect of the poison which remains in the body. The anti- dote to be used depends upon the poison. The most common poisons and their antidotes are given below. In their treatment vomiting should be induced, unless otherwise stated. Acid poisons, like sulphuric acid (oil of vitriol), nitric acid (aqua fortis), muriatic acid, oxalic acid, carbolic acid, etc. In these cases the vomiting should be omitted, and three or four spoonfuls of soda or of baking powder should be given to neutralize the acid. Limewater or even soapsuds may also be used. Oxalic acid and carbolic acid, even when neutralized, remain poisonous. The services of a physician are needed to wash out the stomach. Arsenic is an ingredient of paris green, many fly powders, and green paints. Mix some tincture of iron with baking powder and give the patient a spoonful of the brownish powder which appears. Admin- ister every minute or two. Lead. Found in sugar of lead, white lead used by painters, tinfoil of tobacco coverings, etc. Ad- minister a strong solution of Epsom salts or Glauber's salts. Mercury. Found in corrosive sublimate, used for various purposes, chiefly as a disinfectant. Omit try- 254 PHYSIOLOGY AND HYGIENE ing to induce vomiting and administer the white of an egg, or flour beaten up with milk or water. Opium. In laudanum, paregoric, soothing sirups, cholera mixtures, etc. Give strong coffee or aromatic spirits of ammonia (fifteen drops of the ammonia every few minutes). Use all means to keep the patient moving and to prevent his sleeping. Strychnine. Use chloroform or ether to relieve the violent spasms. Aromatic spirits of ammonia or bromide of sodium may be used, five grains of the latter every half-hour. Artificial respiration may be necessary. The after-treatment for poisoning must be such as to combat dangerous symptoms which have arisen. This, however, must be left to a physician, and cannot be done without special knowledge of medicine. Snake Bites. The bites of poisonous snakes are not very common in this country. In biting, the snake forces a very violent poison into the flesh, which is soon carried over the body through the circulation. The first thing to do is to tie a handkerchief around the limb that is bitten, above the bite, and then insert a stick inside the handkerchief, twisting the stick so as to compress the blood vessels and stop the flow of blood. This will prevent the poison from flowing with the blood over the body. The wound should then be sucked to remove as much of the poison as possible. The poison does no injury in the mouth and no harm to the person who sucks it, if care is taken to empty the mouth at once. If the wound does not bleed, it should WHAT TO DO IN EMERGENCIES 255 be cut open to induce bleeding. Strong coffee should then be given. Bites of Animals. The bites of animals are liable to be poisonous. All such wounds should be thoroughly washed, and as a precaution against poisoning they should be rubbed with nitrate of silver or cauterized with a hot iron. It should be always remembered that a bite from the teeth of any animal is more likely to be serious than almost any other kind of wound. Stings of bees and other insects may be relieved by placing a piece of cold mud on the spot. A weak solu- tion of carbolic acid, one part to twenty of water, sopped on with a cloth, is useful. Common ammonia is also sometimes efficient in relieving the pain. If the sting is left in the wound, as is likely if it comes from a honeybee, it should be removed with the sharp point of a knife blade. Mosquito bites may be commonly relieved by the use of ammonia water or carbolic acid solution, one part to twenty of water. Cuts and wounds should first be carefully cleansed by washing them thoroughly with water that has been boiled, and if necessary should be cleansed further with a brush that has also been boiled. The wound may then be washed with diluted carbolic acid (one part of acid to twenty parts of water). A compress of clean cloth, which has been baked to destroy germs, should then be placed over the wound, covering it com- pletely from the air and the germs in the air. CHARTER XY PUBLIC HYGIENE Private and Public Hygiene. We study physiology that we may learn how to live healthy lives; and the rules by which we should guide our own lives constitute personal hygiene. But there are problems connected with the maintenance of health which it is impossible for each to regulate for himself. This is because so many people live together in towns and cities where each one is more or less dependent on others. Our scientific men have learned the causes of many diseases and have devised methods of preventing them. To make these methods effective, the condition of the whole community must be considered in any preventive meas- ures that are used. For the purpose of safeguard- ing the public health various regulations are adopted for the whole community. These constitute public hygiene. BOARDS OF HEALTH AS PUBLIC PROTECTORS Hidden Dangers. If wild beasts were to run in our streets, we should feel that we had a right to demand that the officers take care of them; but there are in our streets sources of disease more dangerous than wild animals. We have already learned that some diseases are caused by microscopic germs. These germs we can- not see. Most people know nothing about them, not 256 PUBLIC HYGIENE 257 even where they are found. If we are to be protected against these great dangers, it must be by obeying the directions of some who understand how to combat them. We have a right to demand protection against these unseen dangers as well as against those that are seen. Boards of Health. To protect the public from these hidden dangers, Boards of Health have been very gen- erally established by law. These boards are usually of two kinds. One, a State Board of Health, consists of a number of men appointed from different parts of the State. The duty of this board is to make regulations for the whole State and to give advice to the different towns and cities on matters relating to public health. The other, a city or town Board of Health, consists of a number of men, including one or more physicians, whose duty it is to see that the proper rules for the protection of the public are carried out in the different towns and cities. Besides these, there are Water Boards whose duty it is to guard the water supply; milk inspectors to watch the milk; and food commis- sioners and inspectors to see that only proper food is offered for sale in the markets. Sometimes there are other officers whose duty it is to look after other mat- ters of public interest. The good health of the com- munity depends primarily upon the proper regulation of its food, water, and air, and upon the control of contagious diseases. We should always remember that the various officers who have these matters in charge are working for our good. 258 PHYSIOLOGY AND HYGIENE INSPECTION OF WATER, VENTILATION, AND FOOD Water. Disease germs are sometimes distributed by water. It is necessary for us all to drink water, but if our drinking water contains the germs of typhoid fever, it is very dangerous. In the country we can guard our own well or spring or cistern, but in a town or city we FIG. 80. A WELL PROPERLY LOCATED WITH REFERENCE TO THE WATERSHED. drink the water that is supplied, and perhaps do not even know its source. We cannot discover either by looking at water or by tasting it whether it is whole- some or dangerous. Hence, in well-governed cities and towns, it is the duty of the Water Commissioners to guard the public water supply for all citizens. Such Commissioners try to secure for us a sufficient supply of pure water and to guard the supply from pollution. The most dangerous material that can get into water is sewage, and no water that has sewers emptying into PUBLIC HYGIENE 259 it is fit to drink. Hence a community should if possible take its drinking water from some other source than rivers, for these are almost sure to receive sewage from other cities and towns on their banks. For a similar FIG. 81. AN UNHEALTHFUL LOCATION FOB A WELL. reason, too, the Water Commissioners frequently fence in the reservoirs in order to keep people away from them and thus protect them from the dirt and filth that would be dangerous to all drinking the water. "When a community is compelled to get its water sup- ply from a river or any other source that is contaminated 260 PHYSIOLOGY AND HYGIENE with sewage, the Commissioners try to devise some method of filtering the water that shall remove the disease germs, or some method of rendering them harm- less. This filtering must be done on a large scale and according to scientific methods. We know that the small filters that are used in houses are seldom more than good strainers. They may separate from the water particles of dirt and vegetable matter, but they do not exclude the dangerous disease germs. What we have learned about the minute size of such germs will serve to explain this. If the water supply is not properly filtered, the Commissioners often advise boiling it in order to de- stroy the disease germs. The most important means of protecting the water is to prevent all forms of excrement and decaying matter from getting into the water supply. Money spent in improving the water supply yields great returns in increasing the healthful- ness of the community. Fresh Air. We have already learned how necessary it is to our health that we should have an abundance of clean, fresh air; but many people do not appreciate this, and they and their friends suffer in consequence. In rooms made almost air-tight by keeping the windows and doors closed, the air becomes foul and is sure to be loaded with germs, some of which are likely to be dangerous to breathe. In such rooms we breathe over and over again the poisonous gases and bacteria, and much evil necessarily results. Many people do not understand this, and in order to keep warm and to save PUBLIC HYGIENE 261 money, they live and sleep crowded together, several in a room, without ventilation. Under these condi- tions they " catch" diseases from one another by contact and breathing the germs in the impure air. Such homes are dangerous not only to the occupants, but to all who live in the neighborhood, for the disease germs from them are sure to be scattered widely. We have a right to demand protection from such dangers, and our public officials sometimes find it necessary to enter such homes and insist on better conditions. In some cases this arouses much opposition to the health officers, for the occupants of such homes may feel that their rights are being interfered with. But they have no more right to breed disease in this way than they would have to breed ferocious wild animals and turn them loose on the community. In the same way, public hygiene demands good ven- tilation in school rooms, factories, work-rooms, stores, public halls, and in all places where many people live together. Plenty of fresh, pure air wherever people congregate is an important public safeguard. Foods. Pure foods are no less needed than pure air. In trying to get rich quickly, some dealers mix with the food they sell cheap materials of little or no food value. Water is put into milk, ground beans into coffee. Many other foods, such as flours, spices, teas, etc., are fre- quently adulterated. It is well to remember that pre- pared foods are most likely to be thus adulterated, and there is more danger in the cheaper grades than in those costing a little more. Cheap canned goods are 282 PHYSIOLOGY AND HYGIENE not really cheap, for we are likely to buy in them a considerable proportion of worthless material. Sometimes the manufacturers put into food substances that are actually harmful. There are kinds of food that will not keep well for any length of time, and to preserve them certain chemicals are sometimes used. These are called preservatives. Those most generally used are borax, salicylic acid, and formalin. These are all mild poisons, and their constant use in foods is harmful. Meats, fish, milk and canned goods are most frequently treated with these preservatives. Here again it is the cheaper grades that are most likely to be thus "pre- served " ; the better grades are safer and cheaper in the long run. It is usually impossible for us to know by examina- tion or taste whether our foods are pure or whether they are adulterated and " preserved." This matter, therefore, is left to public officials. Pure food laws make it a crime to treat food in these ways, and trained inspectors can thus protect us from fraud and dangers that we should not otherwise know. PREVENTION OF CONTAGIOUS DISEASES Garbage and Sewage. Every household produces a quantity of refuse material that is both unpleasant and dangerous. There is the garbage, or waste from our kitchens and our tables. There is also the sewage consisting of excrement and other secretions from our bodies. The latter is dangerous, especially if there is a sick person in the family. In earlier centuries such PUBLIC HYGIENE 263 waste was thrown into the streets or gutters, or else allowed to soak into the soil until that became saturated with filth. When we remember that all this material is likely to contain disease germs, we can easily under- stand that such disposition of it was not only unsightly FIG. 82. DIAGRAM OF HOUSE AND STREET CONNECTIONS WITH THE CITY SEWERS. and unpleasant, but dangerous as well. Epidemics used to sweep through such cities and people were constantly dying from preventable germ diseases. Indeed, in many cities people then died faster than children were born, and but for the flocking of the country people to them, these cities would have disappeared from the map. 264 PHYSIOLOGY AND HYGIENE Our modern cities have learned to take care of those forms of waste that breed disease. Garbage is required to be placed in cans furnished by the householder, and the waste from them is regularly removed by garbage wagons. Our streets are filled with large underground tunnels called sewers, and into these all of the more offensive materials from our homes are conducted and are washed along in them by water from our sinks and closets, and by rain from the gutters. This mass of water washes the material out of the city, where it is disposed of in some way, and thus the city is kept sweet and clean. To make these sewerage systems of real use, each house should be properly connected with them. Hence the need of careful plumbing. If there are leaks in pipes connecting our sinks and closets with the sewers, the danger from disease germs is great. A careful inspection of plumbing is thus necessary for health. In many cities people are now prohibited from throw- ing papers or any other refuse matter into the streets; they are required to put it into receptacles provided at certain places on the streets for the purpose. Most cities forbid spitting in the street cars, and some forbid it on the sidewalks, for this habit is not only filthy and unsightly, but is likely to distribute disease germs. The result of these improvements is very noticeable. "Not, only are our cities becoming sweeter, cleaner, and more attractive places to live in, but they are also be- coming more healthful. PUBLIC HYGIENE 265 PROTECTION FROM CONTAGIOUS DISEASES The Spread of Contagious Diseases. There are some diseases, as has been fully explained in Chapter XIII, that pass from person to person. When one has such a disease the germs that produce them are constantly leaving his body. If another person remains near the patient the germs may be taken into his body, and then he may have the disease. Diseases that may be contracted in this way we call contagious. The diseases most commonly distributed in this way are smallpox, diphtheria, scarlet fever, measles, mumps, and whoop- ing-cough. If people mingle freely with each other a single case of such a disease is likely to spread and to cause an epidemic. Schools may distribute contagious diseases not only when the sick children go to school, but also when the brothers and sisters of a sick child are allowed to attend school, for they may carry the disease germs in their clothes. To prevent the distribution of contagious diseases is one of the most important duties of the health officers. Various rules for isolation have been devised. Isola- tion means simply keeping the patient away from those who are liable to take the disease from him. A child who has a contagious disease should never be allowed to attend school, and should always be kept in a room by himself , away from all members of the family except the one who nurses him. In the more severe contagious diseases, such as smallpox, scarlet fever and diphtheria, where the chances of contagion are great, the patient is frequently taken to a special hospital 266 PHYSIOLOGY AND HYGIENE where he can be more carefully attended and where there is no chance of his spreading the disease. He is thus kept away from others until he has so completely recovered that he can no longer give the disease, the length of time being determined by physicians. Care of the Sick Room. The health officers also perform a very important service in caring for the room in which a patient has been ill with some contagious disease. After the recovery of the patient, the bacteria that cause the disease are generally still present in the room ; indeed, some of these germs live for many months in dark corners or in clothing if no attempt is made to destroy them. Hence it is very important that a room and its furnishings, which may probably con- tain large numbers of such dangerous germs, should be thoroughly cleansed and all the bacteria there destroyed before it is used again. This the health officers under- take to do; the process is called fumigation or disin- fection. A common method is first to make the room as near air-tight as possible by stuffing all the cracks with cotton, or better, pasting strips of paper over all places where air may enter; then a large quantity of sulphur, or some other germ-destroyer, is burned in the room, which is left closed for twenty -four hours. Hospitals. As an aid in the treatment of disease, our modern cities have built hospitals. Here the best of care and medical attendance is given to the sick. So carefully are the hospitals managed that the patient has usually much greater chance of speedy recovery PUBLIC HYGIENE 267 there than if he remains at home. Patients are cared for at small expense, and frequently no charge is made to those who cannot afford to pay for the care. Value of Public Hygiene. The value of this thorough and general control of matters affecting the public health is very great. In former times people were shorter lived than they are to-day. Violent epidemics of preventable diseases used to sweep through cities. To-day, as we have seen, our cities are cleaner and more wholesome; epidemics of germ diseases are un- usual, and when they do occur they are soon checked. Public hygiene, by its health boards, water commis- sioners, food inspectors, etc. , has made the city nearly as healthful a place to live in as the country, and has very considerably increased the chances of a long, healthful life for each city resident. QUESTIONS 1. What do we mean by personal hygiene ? 2. What do we mean by public hygiene ? 3. What are germs ? 4. Why do cities have Boards of Health ? 5. Name some officials who care for the health of the public. 6. Why must water always be kept clean and pure ? 7. How may the drinking water become impure ? 8. What are the dangers from drinking impure water ? 9. Explain the importance of fresh air. 10. Why do we have food inspectors ? 11. How should garbage and sewage be disposed of? 12. How can we avoid taking or spreading contagious diseases ? 13. What can you say about the value of public hygiene ? CHAPTER XVI A WAR FOR THE NATION EVEKY boy and girl who has studied American history knows how important it is, when a battle is to be fought, for each army to find out as nearly as possible how many men the other side has, how many cannon, and all that can be learned about the strength or weakness of the enemy. The side that does not take these precautions risks defeat in the struggle. So in the great war for the health of the nation, which is now being waged, we must first of all study the nature and resources of our enemy. TUBERCULOSIS It is not, as a rule, a good thing to think very much about diseases. We should think rather of how to make our bodies strong and keep them so ; and then, in case the germs of disease attack us, we shall have the very best means of defense. What We Have to Face. There is, however, one disease, the most widespread and deadly of any known to man, which, if we all knew its causes and how to guard against it, might perhaps be entirely stamped out. We surely should be eager to learn everything that we can about it, so as to save ourselves and others from its attacks. 268 A WAR FOR THE NATION 269 This terrible disease is tuber- culosis, which we generally hear spoken of as consumption. When we study about our Civil War we are shocked at the terrible loss of life in battle, yet the number killed in battle during that entire war was not as great as the number of those who die from tuberculosis in the United States every year. Is it not true, then, that our nation is in great danger and that we should study how best to defend it ? The Hopeful Side. This would be a terrifying picture in- deed if there were not a hopeful side, which depends, how- FIG. 83. DIAGRAM ILLUSTRATING THE ever, upon every man DEATHS DuE T0 FouR YEARS OF CIVIL WAR AND DEATHS CAUSED BY TUBERCU- and woman and boy LOSIS FOR i 90 0-04 RELATIVELY COMPARED. and girl throughout the country knowing the danger and doing his share to overcome it. CONSUMPTION NOT HEREDITARY The Tubercle Bacillus. Until very recently tuber- culosis, or consumption, was considered a hereditary 270 PHYSIOLOGY AND HYGIENE disease, which could neither be prevented nor cured, and against which it was therefore useless to fight. The causes were unknown, and no medicine could be relied upon to effect a cure. But not many years ago it was discovered that tuberculosis is caused by a small plant called tubercle bacillus, so small indeed that it can be seen only with a microscope. Since this plant may be breathed in with the dust in the air, it is most often found in the lungs, though it may attack other parts of the body. The discovery of this tiny bacillus proved first of all that the disease cannot be inherited, because it would be impossible for a plant organism of this kind to be passed on from parents to children. A child might appear to inherit the disease when, as a matter of fact, the disease was " caught" while the child was very young from its mother or some one else in the family who was ill with it. CONSUMPTION CAN BE PREVENTED Disease Spread by Contact. Then, the discovery and study of this bacillus also showed that the disease can be prevented. No one can have consumption unless he in some way, directly or indirectly, comes in con- tact with a person who is a consumptive; and even then, if proper care be taken to prevent contagion, or if his body is in good condition, he is in no danger. But people do not, as a rule, know how to take the proper care, and that is the reason why the disease is so widespread and so dangerous. A WAR FOR THE NATION 271 How the Bacillus Travels. The common means by which the bacillus leaves the body of the sick per- son, if the disease is in the lungs, is by means of the ' ' spit, ' ' or sputum, as it is more properly called, which is the matter coughed up from the diseased lungs. If this is allowed to soil the hands or clothes of the patient, or articles used by him, or if allowed to dry upon the floor so as to become powdered and mingle with the dust, anyone who comes into the room may get the bacteria on his hands and so into his mouth, or may breathe them into his lungs. Then, if the condi- tions are favorable, the disease develops. For those who come in contact with a consumptive in this manner, we shall explain in the section on " Precautions for Consumptives " how all danger from direct contact with a patient may be avoided. The Crime of Spitting. But it is by indirect contact that the disease has been spread so widely, and this is brought about by the filthy and unnecessary habit of spitting upon the floors or walls of a room, upon sidewalks, or in cars and other public places. Each bit of phlegm, or sputum, deposited in this way, may contain thousands of bacteria, and when the sputum becomes dry it flies about in the air as dust, and is breathed in by everyone in the vicinity. It would not be strange if among a number of people present anywhere there should be some whose bodies were in a more or less weakened condition from one cause or another; and so the disease is continually finding new victims. 272 PHYSIOLOGY AND HYGIENE It is safe to say that if all spitting about rooms or in public places, or anywhere but in vessels provided for the purpose, could be done away with, we should have gone a long way toward stamping out the disease of tuberculosis. And when we consider that this simple precaution, with proper care of the people who actually have the disease, would result in the saving of thousands of lives in our own country every year, it is clearly worth our while to do all that we can to help bring this about. SOME WONDERFUL RESULTS OF THE STRUGGLE The actual results of the war against this disease in places where the people have been taught the facts about it that are given in this chapter, and have worked together to stamp it out, have been marvelous. In Maine, where pamphlets giving such facts and simple rules and precautions were distributed through- out the State, the number of deaths from consumption decreased from 1,352 in 1892 to 901 in 1903 a decrease of from 20.24 per cent, of deaths per 10,000 inhabitants to 12.97 per cent, for the same number. In the two largest boroughs of New York City, where the most vigorous fight is being carried on, the death rate from pulmonary tuberculosis has decreased from 4.27 per cent, in 1881 to 2.29 per cent, in 1903, though during the same time the population has greatly in- creased. 1 1 These figures are given for 1903 because some special circum- stances affected the comparative death rate of the later years, which would require too much adjustment and explanation. A WAR FOR THE NATION CONSUMPTION CAN BE CURED The third important result of the discovery of the tubercle bacillus and its nature is the knowledge that consumption is not at all a hopelessly fatal disease, but can be cured if taken in time and treated in the proper way. Everyone ought to know about this, so that even if he does not need the information for himself ,. he may be able to tell others who do need it. Dangers from the Bacteria. For the protection of others, as well as of the patient himself, the sputum should be destroyed immediately by being coughed into paper napkins which can be burned, or into cups containing a weak solution of carbolic acid or some other sterilizing material; these cups should be washed frequently with hot water and strong soap or lye. It is better not to use handkerchiefs or cloths; put into- the pocket, they will soil the clothes. The hands and mouth should be washed very frequently in warm water and soap. As the saliva or the small drops of moisture coughed or sneezed out may contain the bacteria, equal care should be taken to cover the mouth and nose with a paper napkin, and thus prevent the distribution of the bacteria in this way. The patient may, by taking these precautions, effect- ually guard against spreading the disease among those with whom he daily comes in contact. In fighting the tubercle bacillus, the patient should take every precaution to prevent the possibility of new growths developing in his own system, as well as to use such preventive measures as he can, to avoid distributing the disease among others. 274 PHYSIOLOGY AND HYGIENE Special directions with regard to articles that are convenient for use will be given under "Precautions for Consumptives." Importance of Fresh Air. First, the patient must have all the fresh air possible, night and day, summer and winter. The air should be in circulation, and with warm clothing and something wrapped about the head, no one need be afraid of " draughts ". There must be draughts, that is, currents of air, in order to keep the air absolutely pure and to ensure the large supply of oxygen needed. If possible, the patient should live and sleep, summer and winter, in a well ventilated tent or on a ver- anda. It is now claimed by many physicians that climate has little to do either with causing or curing consumption. Still, if the patient does not need to consider expense, there is an advan- tage in his going to some health resort. A change of climate is usually beneficial, and he is likely also to 84. A SLEEPING VERANDA ENCLOSED BY AWNING AT A CONSUMPTIVE'S HOME. A WAR FOR THE NATION 275 receive better care than he could have at home. How- ever, when cases of tuberculosis are taken in time, the patient can generally be cured in his own home, pro- vided that he will live out of doors and will follow some other special directions. Nourishing Food. After the fresh air comes food. The science of curing consumption consists simply in FIG. 85. THE SUN PARLOR OF A LARGE HOSPITAL. taking in all the oxygen that can be secured, in order to purify the blood, thus enabling the tissues of the body to get all the nourishment possible out of the food. At the same time it is important to take all the nourishing food possible. If enough nourishment can be taken so that the tissues will be built up faster than the disease can break them down, the cure of the pa- tient is assured. Last of all, but very important to the cure, come carefully regulated exercise and rest. 276 PHYSIOLOGY AND HYGIENE HOW TO COMBAT BACTERIA Healthy Tissues Resist Disease. The measures we must employ for keeping the bacteria out of our own systems, or throwing them off if they do enter, are very simple. The whole body, let us repeat, should be kept in as good condition as possible. Bacteria cannot prey upon vigorous and healthy tissue, and if the organs of the body they may attack are made up of healthy cells and tissue the bacteria soon die and are cast out of the body. Thus, with a perfectly healthy body, we shall win in the fight without even knowing that we have been attacked. Importance of Increasing Lung Capacity. An unde- veloped chest lessens the capacity of the lungs. Those parts of the lungs that are not used are more liable to become the lodging place of the bacillus. So here, again, deep breathing and exercises to develop the chest and lungs are important. Those who have catarrh of the nose or throat should wash these parts out with warm salt and water at least twice a day. This will keep the membranes clean and healthy and prevent the bacteria from finding an open- ing for attack there. How to Destroy the Bacteria. The fact that the bacteria, when given off by the consumptive, are easily destroyed by exposure to sunlight, or heat, makes the problem of fighting the disease much simpler than if the bacillus usually lived and multiplied outside the bodj 7 . A WAR FOR THE NATION 277 But the bacillus may live for years in dark, damp places, or in undisturbed corners. It is in this way that houses in which consumptives have lived become infected and are breeding places for the disease, lead- ing to the belief that the disease i ' runs in the family. ' > In rooms which have been occupied by a consumptive the walls and woodwork should be scraped and scoured, repainted and repapered and the floors and every nook and cranny that may contain dust or dirt, scrubbed with a chloride of lime mixture, made of one part lime and twelve parts water. The halls, banisters, and other parts of the house should also be cleaned just as thoroughly as possible. Then if all the members of the consumptive's family will devote themselves to building up healthy bodies there will no longer be cause to fear the i ' inherited ' ' disease. As the bacteria are carried in the dust, a feather duster or a dry broom should never be- used in cleaning a room occupied by a patient, as they only stir up the dust which floats about in the air and settles down again. It is better to put damp paper or sawdust on the carpet when sweeping, and to use for dusters soft or damp cloths, which can be shaken out of doors. Children in school should never use a common drink- ing cup. The other children may be quite well them- selves, but some one in their homes may have this disease or some other that is communicable, and in that case they could carry the bacteria to others. 278 PHYSIOLOGY AND HYGIENE ALCOHOL AND CONSUMPTION The best physicians agree that one of the strongest allies the tubercle bacillus has is alcohol. In the cure of consumption our great need is, as we have seen, to take as much nourishment as possible in order to build up the tissues and counteract the power of the bacteria. For this we need to have the diges- tion in the best possible condition ; and it is important also that the lungs, so actively engaged in the purify- ing of the blood, should not be hindered in their work. Both stomach and lungs are unfavorably affected by the use of alcohol; the extent of the injury depending in part upon the amount of liquor taken, and in part upon the condition of these organs. Any appearance of a good effect from taking alcohol is deceptive, and if we need further proof of its bad effects we find from statistics that there is a larger proportion of tuberculosis cases among those who drink than among non-drinkers. Tobacco, also, is very bad for consumptives, and for those predisposed to the disease, as it may weaken the heart and thus obstruct the circulation, making it more difficult for the lungs to resist attack. PRECAUTIONS FOR CONSUMPTIVES The following simple directions, taken from a cir- cular issued by the Charity Organization Society of New York City, should be familiar to everyone, as each of us will probably at some time in his life come in A WAR FOR THE NATION 279 contact with someone who has the disease, and may, by knowing these precautions and teaching others how to take them, save many lives in this great national struggle. If we know any one among oar relatives or friends who has consumption or is threatened with it, we could bear our share in the fight by copying these directions for them, or better still, by writing to the Charity Or- ganization Society, 'New York City, for copies of their circular for distribution where they will do the most good. In this way we may help the patients them- selves to get well and protect those about them. DIRECTIONS " Consumption can often be cured if its nature be recognized early and if proper means be taken for its treatment. In a majority of cases it is not a fatal disease. "Consumptives are warned against the many widely advertised cures, specifics and special methods of treatment of consumption. No> cure can be expected from any kind of medicine or method, except the regularly accepted treatment, which depends upon pure air, an out-of- door life and nourishing food. " Consumption is a disease of the lungs, which is taken from oth- ers, and is not simply caused by colds, although a cold may make it easier to take the disease. It is caused by very minute germs, which usually enter the body with the air breathed. The matter which consumptives cough or spit up contains these germs in great num- bers frequently millions are discharged in a single day. This mat- ter, spit upon the floor, wall or elsewhere, dries and is apt to become powdered and float in the air as dust. The dust contains the germs, and thus they enter the body with the air breathed. This dust is especially likely to be dangerous within doors. The breath of a con- sumptive does not contain the germs and will not produce the dis- 280 PHYSIOLOGY AND HYGIENE ease. A well person catches the disease from a consumptive only by in some way taking in the matter coughed up by the consumptive. "It is not dangerous to live with a consumptive, if the matter coughed up by him be promptly destroyed. This matter should not he spit upon the floor, carpet, stove, wall or sidewalk, but always, if possible, in a cup kept for that purpose. The cup should contain water so that the matter will not dry, or better, carbolic acid in a five per cent, water solution (six teaspoonfuls in a pint of water). This solution kills the germs. The cup should be emptied into the water closet at least twice a day, and carefully washed with boiling water. " Great care should be taken by consumptives to prevent their hands, face and clothing from becoming soiled with the matter coughed up. If they do become thus soiled, they should be at once washed with soap and hot water. Men with consumption should wear no beards at all, or only closely cut -mustaches. When con- sumptives are away from home, the matter coughed up should be received in a pocket flask made for this purpose. If cloths must be used, they should be immediately burned on returning home. If handkerchiefs be used (worthless cloths, which can be at once burned, are far better), they should be boiled at least half an hour in water by themselves before being washed. When coughing or sneez- ing, small particles of spittle containing germs are expelled, so that consumptives should always hold a handkerchief or cloth before the mouth during these acts ; otherwise, the use of cloths and handker- chiefs to receive the matter coughed up should be avoided as much as possible, because it readily dries on these, and becomes separated and scattered into the air. Hence, when possible, the matter should be received into cups or flasks. Paper cups are better than ordinary cups, as the former with their contents may be burned after being used. A pocket flask of glass, metal, or pasteboard is also a most convenient receptacle to spit in when away from home. Cheap and convenient forms of flasks and cups may be purchased at many drug stores. Patients too weak to use a cup should use moist rags, which should at once be burned. If cloths are used they should not be carried loose in the pocket, but in a water-proof receptacle (tobacco A WAR FOR THE NATION 281 pouch), which should be frequently boiled. A consumptive should never swallow his expectoration. "A consumptive should have his own bed, and if possible, his own room. The room should always have an abundance of fresh air the window should be open day and night. The patient's soiled wash-clothes and bed linen should be handled as little as possible when dry, but should be placed in water until ready for washing. " If the matter coughed up be rendered harmless, a consumptive may frequently not only do his usual work without giving the dis- ease to others, but may also thus improve his own condition and increase his chances of getting well." FOOD AND EXERCISE The first articles of diet for a consumptive person should be milk and eggs as much of each of these as he can be prevailed upon to consume. The eggs may be beaten up in milk if they are easily digested in this way. But the milk and egg diet should not take the place of the three regular meals. A good deal of meat should be eaten, also vegetables and fruit. Care should be taken in exercising not to use up the strength, but to increase the amount of exercise gradu- ally as the strength increases. Kest is of greater im- portance. ANIMAL TUBERCULOSIS When it was discovered that cattle, particularly dairy cows, were subject to tuberculosis, great fear was felt that human beings acquired the disease from the milk and meat of diseased cattle. There seems to be no doubt 282 PHYSIOLOGY AND HYGIENE that this disease is sometimes distributed by milk, espe- cially in the case of children, but the question as to how frequently this occurs is not yet definitely settled. QUESTIONS 1. What disease have we been studying about in this chapter? 2. Why can the struggle be truthfully called a "war for the nation " ? 3. What causes tuberculosis ? 4. How do we know that tuberculosis cannot be inherited ? 5. How may tuberculosis be prevented ? 6. How may this disease be cured ? 7. How can we protect our own bodies from the bacteria ? 8. How does alcohol affect the consumptive ? 9. Is animal tuberculosis dangerous to human beings ? 10. Explain the method by which tuberculosis could be stamped out. SUPPLEMENTARY CHAPTERS CHAPTEK XYII HOW TO DEVELOP OUR BODIES Introductory. While we are learning about the different parts of the body we should not forget that the object of all this study is to learn how to care for the body as a whole, and we should consider what we may do to keep it at its best, working easily and to advantage. In the chapters on ' ' Respiration, " " The Muscles, ' ' and ' ' The Blood ' ' there are references to exercise, to breathing, and to the uniform develop- ment of all the muscles; let us in this chapter look especially into the practical side of the matter. It is easy to learn what we should do, but unless we take the time and trouble to practice what we learn, regularly and thoroughly, we cannot expect to get much benefit. We must remember, too, that the most wonderful of those bodily changes and actions that take place day after day do not happen on the surface of the body, where we might see and feel them. Because this is true we are inclined to think that breaking the laws of health is harmless if we feel no ill effects from such mistakes. That, however, is as foolish as it would be for us to think that the sun stopped shining on a cloudy day just be- cause we were unable to see it. We cannot make our 283 284 PHYSIOLOGY AND HYGIENE feelings a test of the physical effects of our actions; nor can we expect to see or to feel any extraordinary ben- efit when we begin to follow carefully the rules of health which we have been taught, or to take systematic exer- cise, as will be suggested in this chapter. Still we may be sure that in these ways we shall certainly be adding to our strength and to the power of our bodies; and in time the effects will be evident. Importance of Developing the Body. The muscular system is developed by work and by exercise; both are necessary to our health and therefore to our usefulness and happiness. Our bodies are the means by which we accomplish all that we have to do in this world, and unless they are strong and each organ does its part well, we cannot expect to accomplish what we wish. Good work is impossible without good bodies. Necessity of Work and Exercise. Why is it that peo- ple after they are grown frequently lose the good health that they had when they were children? Usually they give some parts of their bodies plenty of work to do, but they do not give the whole body systematic exer- cise and healthful recreation. Perhaps as boys and girls they were not taught a few simple facts which everyone should know with regard to the care of the body and how to exercise it in order to strengthen and develop all its parts. It is true that most boys and girls get a great deal of out-of-door ex- ercise in their sports and games, and thus keep some of the muscles strong and well; but something more than this is needed. HOW TO DEVELOP OUR BODIES 285 Dangers of Unequal Development. Perfect health re- quires that all the muscles be developed uniformly, but our games and sports, as a rule, influence only certain sets of muscles, often at the expense of others. Even athletes may have consumption or heart trouble, be- cause in training particularly the muscles they wish to use, they neglect the training that is necessary to de- velop equally the strength of the lungs not the chest muscles only and the heart; two most important organs of the body, upon which the proper working of all the others depends. In addition to our games, we need, therefore, to practice exercises by which each part of the body shall receive a reasonable share of attention and be developed in proportion to its usefulness and needs. Relation of Oxygen to Muscular Effort. When we exercise a muscle vigorously it requires more nourish- ment, and for this oxygen is the first essential (page 116). As we must secure the oxygen by drawing the air into the lungs, exercises which will help us to breathe more deeply and thus take more oxygen into the sys- tem should receive most careful consideration. BREATHING Deep Breathing. To breathe deeply, then, is the first rule to be observed in healthful exercise, "We must first understand the importance of breathing through the nose (page 105). Even in violent exercise there are seldom conditions that properly admit of mouth breath- ing. The fact that certain forms of vigorous exercise 286 PHYSIOLOGY AND HYGIENE compel us to fill and empty the lungs frequently, shows us one of the reasons why they are beneficial. Significance of Yawning and Stretching. Nature tries to meet this necessity for oxygen in many ways; one of them is by giving us the desire to yawn and stretch when we are tired or have been sitting still for a long time. People frequently discourage this habit in chil- dren because it " looks lazy", but when we consider that it relieves the muscles and organs of the body from a cramped or strained position, and at the same time fills the lungs with a fresh supply of oxygen, we can see that this is really a valuable exercise, though one that cannot be taken at all times and in all places. When we feel like stretching, it is well to take some light form of exercise to relieve the strain and fatigue against which the body is protesting. Since, however, it is necessary in performing these exercises that our bodies be in a correct position, it is very important that we should first learn to know when the body is in proper poise. Sitting. Yery few of us know how to sit or stand properly, and yet the correct position of the body is the basis for all our physical development. We think it is more comfortable and restful to lounge down in our seats or lean upon our desks at school, or to sit in rocking chairs at home, but as a matter of fact such positions are in the end weakening and tiresome. Why? Because in these positions the chest is con- tracted so that it is impossible to get the proper amount of air into the lungs, and the organs of the abdomen are HOW TO DEVELOP OUR BODIES 287 pressed together or out of position, so that they cannot work freely. All these things cause a strain on the body which does not exist if we sit erect, with the body comfortably poised, and give each organ plenty of space and nourishment. So, if you would keep your strength and secure the proper development of your bodies, learn first of all to sit erect. Standing. If we do not stand erect the organs of the trunk the lungs, heart, stomach, etc. have not suffi- cient room, and so cannot perform their functions prop- erly, causing unnecessary fatigue and sometimes actual discomfort. Then, too, we must consider the force of gravitation, which is continually drawing objects toward the earth. If we stand erect, our bodies are well balanced; that is, the force is distributed evenly; while if we stoop forward there is a strain that we constantly resist, which causes us to grow tired sooner than otherwise. Poise. For a graceful, well-balanced poise, we should stand with the legs straight, head erect, chin drawn slightly in, and chest high, and with the weight chiefly on the balls of the feet. Too frequently we stand with the weight on the heels, the hips coming forward and the abdomen thrust forward. Watch some day the people you meet, and see what proportion of them stand in this way. Compare the ease and grace of those who stand with the body properly poised. Faulty poise is not to be corrected by drawing the abdomen in and holding it back tensely. This is not necessary if 288 PHYSIOLOGY AND HYGIENE the proper balance of the body is secured as indicated above. Further, it is an unwise way of correcting the fault, as the muscles of the abdomen should be left free to expand and contract naturally; and this may be accomplished without allowing the abdomen to be thrust forward. The chest should not be thrown too far forward ; this, however, is not a common fault in position. A good rule to follow is to stand in such a way that the lips, chin, outer line of the chest, and the tips of the toes are in a straight line. A long pole or fishing rod held vertically against the front of the body may be used to test the position. The balance of the body may be tested by a simple little exercise. Stand squarely on both feet in the posi- tion that is most natural to you. Then carry the weight forward to the toes; carry it back to the heels, and finally to the balls of the feet ; resting there. Compare this position with the natural one you first assumed. You will probably discover that you are accustomed to stand with the weight too near the heels. BREATHING EXERCISES The Process of Breathing. Before we think of special breathing exercises for the development of the body, let us see what is said in Chapter Y about the proc- ess of breathing or respiration. We read how air is drawn into the lungs largely through the action of the muscular wall called the diaphragm, which by moving downward increases the size of the chest cavity, HOW TO DEVELOP OUR BODIES 289 thus causing the air to enter the lungs to fill the en- larged space. Its upward motion by decreasing the same cavity, causes the air to leave the lungs, as there is not then room for so much air. While all this happens easily and regularly, we are probably hardly conscious, even of the fact that we are breathing ; we usually have no sensation from the motion of the diaphragm, and the upward and outward movement of the ribs during respiration is likewise unnoticed. Necessity of Deep Breathing. The important point is that the lungs should be well filled with fresh air, and this frequently. In ordinary breathing we expand the top of the lungs, while the lower part of them may be inactive, not doing its proper duty toward purifying the blood and enriching it with oxygen. So our prob- lem is to set all portions of our lungs to work. If you find that your abdomen does not move in and out noticeably as you breathe, call a halt and see whether you are not letting the upper part of your lungs do- work that ought to be done by the lower lungs, aided by the ribs and the diaphragm. In the beginning we may have to think about it every time we take a long breath, and perhaps shall forget the deep breathing unless we are reminded; bat if we per- sist, we can finally form the habit, and when this is done, it will be sure proof that we have greatly in- creased our strength and our power of endurance. The following exercises are recommended by several well-known experts in physical training, prominent among whom is Dr. Claes J. Enebuske, from whose 290 PHYSIOLOGY AND HYGIENE " Progressive Gymnastic Day's Orders" ' many valu- able suggestions have been drawn. They are so sim- ple that they may be taken at home without any super- vision; the pupil who practices them regu- larly, night and morning, will certainly find a gain in his strength and in muscle control. Exercise i. Stand erect, heels together, toes out, hands down at side. DraAv a deep breath slowly, and at the same time raise the arms slowly from the sides until the palms nearly meet over the head, as shown in Fig- ure 86. Lower the arms gradually, exhaling slowly. Eepeat each of these exercises about eight times. Exercise 2. Stretch the arms straight out in front of the body, palms facing. Keeping the arms in a hor- izontal position (see Fig. 87), move them slowly backward, and see how near you can come to bringing the hands together at the back, without bending or lowering the arms. Inhale and exhale as before. Exercise 3. Arms straight out in front, palms down. Raise the arms slowly over the head, then as far back as possible, 1 The illustrations used in this chapter are taken from the same "book. Published by Silver, Burdett & Company. FIG. 86. FIG. 87. HOW TO DEVELOP OUR BODIES 291 down, and to original position, making in this way a sort of crooked circle in the air with the hands. In- hale slowly as the arms are raised, and exhale as they are lowered. To vary these exercises from time to time, instead of exhaling as the arms descend, hold the breath until the arms are in their original position. Then exhale very slowly. WALKING Having learned to - stand correctly, and to breathe deeply, we must next learn how to walk in such a way as to make the best possible use of our muscles, and gain strength and endurance. Probably a majority of people rest their weight as they step more on the heel than on the forward part of the foot. This is not right. As each foot touches the ground the weight should be thrown upon the ball of the foot, and as it leaves the ground pressure should be exerted upon the same part and upon the toes. This will carry the body forward easily, and the movement when once acquired will enable one to walk much more rapidly and with less fatigue. It also develops the muscles of the foot and ankle, and of the lower part of the leg. The Indians, and athletes who are trained for walk- ing long distances, use this method. At first it should be practiced for only a few minutes at a time, as one is using muscles that are not accustomed to the work, and so tire quickly. But when one comes to realize the 292 PHYSIOLOGY AND HYGIENE delightful ease of motion which is secured in this way, he will think the lesson was well worth while. Deep breathing as we walk adds very much to our feeling of buoyancy and ease in motion. When we have learned to sit, stand, and walk cor- rectly, we shall have formed the valuable and necessary foundation for the correct performance of all other phy- sical exercises. EXERCISES FOR SUPPLENESS EASE OF MOTION Power of endurance and skill in the use of the body depend very largely upon ease of motion. "We usually think of farmers and other out-of-door laborers as types of strong men. But frequently we notice that they are awkward and stiff in their movements, and clumsy in the use of their hands; any exercise to which they are not accustomed soon tires them. This is because their work compels them to use only certain sets of muscles. The muscles which are not used get stiff and do not respond readily when the brain orders them to move. So, to acquire ease of motion, we must practice exercises to keep all the muscles flexible. Exercise 4. Stand erect, hands on hips (see Fig. 88). Keeping the legs straight, bend forward from the waist until the upper part of the body is parallel HOW TO DEVELOP OUR BODIES 293 FIG. 89. with the floor, then back as far as possible. Eeturn slowly to an erect position. Exercise 5. Same position. Bend the body from the waist, first to one side then to the other, as shown in Figure 89. Exercise 6. Stand as before, rise on tiptoe, then bend the knees, letting the body sink quickly, then up, still on tiptoe, and back to position again. The body and head must be kept erect in this exercise. These exercises are also valuable in strengthening the muscles of the abdomen and waist. Dancing is excellent for giving flexibility and grace. DEVELOPMENT EXERCISES FOR THE ARMS Exercise 7. Stand with hands on shoulders, as in Figure 90. Thrust arms quickly out sideways and back to position, then straight up and back. Re- peat four times. Exercise 8. Arms out at sides, palms up. Bend elbows, as shown in Figure 91. Thrust one FIG. 90. FIG. 91. 294 PHYSIOLOGY AND HYGIENE arm out to full length, at the same time bending the other so that the hand strikes the shoulder. Repeat, the arms bending and straightening alternately. These arm movements may be varied by using light dumb-bells or other objects of about the same weight. As the strength increases the weight may be increased. Exercises on the bars and rings are especially good for the development of the arms, and any boy who can- not go to a gymnasium can rig up a single bar or pair of rings at his own home. Bar or Ring Exercise. Grasp the bar or rings firmly, letting the body hang perfectly straight, feet together. Draw the body up by the hands until the chin is on a level with the hands. As the muscles grow stronger it will be possible to bring the breast on a level with the hands. FOR THE SHOULDERS, BACK AND CHEST Exercise g. Arms hanging loosely at the sides. Eaise the right shoulder, throw it forward, down, back, up, thus describing a circle. Repeat with the other shoulder. Then circle in the opposite direction. Exercise 10- Arms straight out at sides, palms front. Swing the whole arm from the shoulder, each hand thus describing a circle in the air. Exercise n. Arms over right shoulder as if holding a bat. Left foot forward. Fling arms and body for- ward and down as if striking very hard at something on the ground. Repeat with arms over left shoulder, right foot forward. HOW TO DEVELOP OUR BODIES 295 FOR THE NECK Exe else 12. Body erect. Bend head forward and back several times, then to the right and left. Exercise 13. Roll the head around, circling first to the right, then to the left. FOR THE HANDS AND WRISTS Exercise 14. Arms straight out at sides, palms down. Bend the wrists, throwing hands as far back as possible, then down. Repeat several times. Exercise 15. Keeping wrist and back of hand level, fingers straight, bend fingers down from the knuckles, then back as far as they will go. Exercise 16. Relax the muscles of hands and fingers, and letting the hands droop from the wrists, shake them until they are thoroughly relaxed; as the hands are con- tinually employed in grasping things, the muscles are generally contracted, and they should be frequently relaxed. FOR WAIST AND ABDOMINAL MUSCLES All exercises that involve bending from the waist are good. We have found several of these in the section on suppleness. Exercise 17. Stand with feet slightly apart. Roll the body from the waist, describing a circle in the air with the head. Circle in the opposite direction. Exercise 18. Stand with feet apart, arms straight 296 PHYSIOLOGY AND HYGIENE FIG. 92. above the head. Bend forward from the waist until the body takes almost the position of an inverted Y, as in Figure 92. Exercise 19. Stand with hands on hips. Take a long step forward, bearing the weight on the forward foot (see Fig. 93). Back to posi- tion. Repeat with the other foot forward. jr i\ I &/ and it shows itself at once in his manner and voice. The words will be mumbled, the tones un- certain, and the whole manner anything but attractive or convincing. THE VOICE 315 Children may have these faults of speech and man- ner, somewhat through diffidence or uncertainty in the use of the language, and if so, they are all the more in need of training in the use of the voice and in proper carriage of the body, lest the bad habits of speech and manners grow upon them until they give an impression of weakness of character which does not exist. Let a person speak in clear, full tones, with head erect, body under good control, and eye steady and clear, and we instinctively feel confidence in him and in his ultimate success. QUESTIONS 1. Why should we try to acquire a good speaking voice ? 2. Describe the vocal organs. 3. How does the breathing affect the voice ? 4. Show the proper position in speaking and reading. 5. How may we acquire distinct articulation ? 6. How are the vowel sounds produced ? The consonants ? 7. Define enunciation. 8. How may we learn to enunciate well ? 9. How is character shown by our manner of speaking ? GLOSSARY OF TECHNICAL TERMS Abdomen. The lower cavity of the body, containing the stomach, intestines, and other organs. Albumen. One of the proteids, such as the white of egg. Anterior root. The branch of each nerve of the spinal cord which carries messages from the brain to the muscles. See Fig. 67. Aorta. The artery carrying blood from the heart. See Fig. 21. Aqueous humor. One of the transparent liquids of the eye. See Fig. 75. Arterial blood. Blood that has been purified by passing through the lungs. Artery. A blood vessel carrying blood away from the heart. Artificial breathing. Breathing produced by moving a patient's arms and chest without action on his part. Auricles. The chambers of the heart that receive blood from the veins. See Fig. 24. Axis cylinder. The central thread in a nerve fiber. See Fig. 68. Bacteria. Very minute plants. Bacillus. One of these plants. Ball-and-socket joint. A joint that allows of free motion in all direc- tions. See Fig. 53. Biceps. The front muscle of the upper arm. See Fig. 65. Bicuspids. Eight of the teeth, of which four are in each jaw, between the canines and the molars. See Fig. 9. Bile. The liquid secreted by the liver. Bladder. The sac which temporarily holds the kidney secretion. Blood corpuscles. Small solid bodies found in the blood. See Fig 20. Blood heat. The ordinary temperature of the body -98. 6 F. Brain. The central organ of the nervous system, located in the skull. Breastbone. The bone in front of the chest. See Fig. 42. Bronchii. The branches of the windpipe, one entering each lung. See Fig. 33. 317 318 GLOSSARY OF TECHNICAL TERMS Callosities. Parts of the epidermis thickened as the result of friction. Canines. Four teeth just back of the incisors. See Fig. 9. Capillaries. The small blood vessels that connect the arteries with the veins. See Fig. 25. Carbon dioxide. The gas which results from the burning of carbon in oxygen. Carpals. The wrist bones. See Fig. 42. Cartilage. The tough, flexible material that forms the softer part of the skeleton. See Figs. 33, 42, and 50. Casein. A proteid contained in milk, the basis of cheese. Cells. The microscopic bits of living matter of which the whole body is composed. Cereals. Food materials obtained from grains, such as wheat, oats, rice, etc. Cerebellum. The back part of the brain. See Fig. 65. Cerebrum. The highest and largest part of the brain. See Fig. 65. Chest, or thorax. The cavity within the ribs which holds the lungs and the heart. See Fig. 38. Choroid. The middle coat of the eyeball. See Fig. 75. Chyle. The name given to food in the intestines after it is thoroughly digested. Chyme. The name given to the food mass when it leaves the stomach. Clavicle. The collar bone. See Fig. 42. Coagulation. A change from a liquid to a solid condition that occurs in some liquids, such as the change that takes place in the white of an egg when it is heated. Coccyx. A small bit of bone at the lower end of the spinal column. Contagious diseases. Diseases which one person may "catch " from another. Cords. See Tendons. Corn. A thickened portion of the epidermis, usually on the toes, caused by friction or pressure. Cornea. The transparent covering of the eye, in front. See Fig. 75. Cranium. The rounded part of the skull containing the brain. See Fig. 44. Dermis. The inner layer of the skin. See Fig. 61. Diaphragm. A tough muscular membrane separating the thorax and abdomen. See Fig. 38. Dislocation. The wrenching of bones out of position at a joint. GLOSSARY OF TECHNICAL TERMS 319 Distilled liquors. Liquors made by separating alcohol from a fer- mented substance. Duct. A slender tulje by which secretions are carried from a gland. See Fig. 11. Dyspepsia. The name of certain diseases of the digestive organs. Ear- Drum. The middle cavity of the ear. See Fig. 76. Enamel. The outer, hard covering of the teeth. Epidemic. A disease spread among great numbers of people. Epidermis. The outer layer of the skin. See Fig. 61. Epiglottis. The lid covering the opening of the windpipe in the throat. See Fig. 12. Epithelium. A layer of cells covering various internal and external surfaces of the body. Eustachian tube. A tube leading from the middle ear to the mouth. See Figs. 12 and 76. Excretions. Waste materials that pass out from the body. Exhalation. Breathing air out of the lungs. Facial bones. The bones forming the face. See Fig. 44. Fat cells. Minute drops of fat, such as exist in meat. See Fig. 2. Femur. The bone extending from the hip to the knee. See Fig. 42. Fermentation. A change occurring in sugar solutions by which alcohol is produced. Fermented liquors. Drinks made from simple fermented material. Fibula. The small bone in the leg below the knee. See Fig. 42. Foramen ovale. The opening from the middle ear into the inner ear. See Fig. 76. Frontal bone. The bone forming the forehead. See Fig. 44. Fuel foods. Foods used for developing heat and energy. Gall-bladder. A sac which collects bile secreted by the liver. See Fig. 13. Ganglion. A knot of nervous matter containing nerve cells. See Fig. 67. Gastric juice. The digestive fluid secreted by the glands of the stomach. Glottis. The opening from the throat into the windpipe. See Fig. 12. Glucose, or grape sugar. Sugar found, or similar to that found, in fruits. Gluten. A proteid derived from wheat and some other substances. 320 GLOSSARY OF TECHNICAL TERMS Gray matter. A substance containing nerve cells, found in the brain and the spinal cord. Gullet. See (Esophagus. Hair follicles. The little pockets from which hairs grow. See Fig. 62. Hard water. Water containing some mineral substance, usually lime. Hemispheres. The two halves of the cerebrum. See Fig. 66. Hinge joint. A joint in which the bones move in one direction only. Humerus. The bone extending from the shoulder to the elbow. See Fig. 42. Ilium. One of the bones of the pelvic girdle. See Fig. 42. Incisors. The eight middle front teeth. See Fig. 9. Incus. One of the bones of the ear. See Fig. 76. Inhalation. Breathing air into the lungs. Intestine. The long tube through which the food passes after leaving the stomach. See Fig. 13. Iris. The membrane surrounding the pupil of the eye. See Fig. 75. Ischium. One of the bones of the pelvis. See Fig. 42. Kidneys. The organs for taking from the body the waste products found in the urine. See Fig. 60. Lachrymal duct. The duct which carries tears from the eyes to the nasal cavity. See Fig. 72. Lachrymal gland. The gland which secretes the tears. See Fig. 72. Lacteals. Small tubes which carry fat from the intestine to the blood vessels. See Fig. 16. Larynx, or "Adam's apple." An enlarged part of the windpipe con- taining the vocal cords. See Fig. 12. Ligaments. Bands of a white connective substance, which join bones together. See Figs. 51 and 52. Ligature. A band drawn tightly around some part of the body, as, to stop bleeding. See Fig. 30. Lime. A mineral substance required for making bone. Liver. A large red gland lying near the stomach. See Fig. 13. Lungs. Two organs in the chest cavity which absorb oxygen and get rid of carbon dioxide. See Figs. 33 and 37. Malleus. One of the bones of the ear. See Fig. 76. Mandible. The jawbone. See Fig. 44. GLOSSARY OF TECHNICAL TERMS 321 Marrow. A fatty material in the middle of the long bones. See Fig. 45. Medulla. The lowest part of the brain. See Fig. 65. Medullary sheath. Covering of the axis cylinder in a nerve fiber. See Fig. 68. Mesentery. A sheet of tissue wrapped around the intestines and rilled with blood vessels. See Fig. 16. Metacarpals. The bones between the wrist and the fingers. See Fig. 42. Metatarsals. The bones between the ankle and the toes. See Fig. 42. Milk-teeth. The first teeth of children, which are later replaced by the permanent teeth. Molars. The large back teeth, twelve in number. See Fig. 9. Muscle fibers. The microscopic threads of which muscles are made. See Fig. 58. Myosin. A proteid contained in lean meat. Narcotic. A drug which dulls body action. Nerve cells. Minute bodies at the ends of nerve fibers, which cause and receive stimuli. See Fig. 69. Nerve fibers. The microscopic threads of which nerves are composed. See Fig. 68. Nerves. Long bundles of fibers which carry messages in the body. Occipital The bone forming the back of the skull. See Fig. 44. (Esophagus, or gullet. A tube extending from the throat to the stomach. See Fig. 13. Oxidation. A union of some substance with oxygen. Oxygen. A gas forming about one fifth of the air. Palate. The roof of the mouth. Pancreas. A large gland which secretes a fluid to digest proteids, starches, and fats. See Fig. 13. Pancreatic fluid. The fluid secreted by the pancreas. Parasites. Animals or plants which live on or in the bodies of other animals or plants. ' Parietals. The bones forming the sides of the cranium. See Fig. 44, Parotid glands. The salivary glands in front of the ears. See Fig. 11, Patella. A round bone in front of the knee. See Fig. 42. Pelvis, or pelvic girdle. The hip bone. See Figs. 38 and 42. 322 GLOSSARY OF TECHNICAL TERMS Petrous bone. The very hard bone which contains the ear. Phalanges. A name given to the bones of the fingers and toes. Pillars of Fauces. Two curtain-like sheets between the mouth and the throat. See Fig. 10. Pores. The small openings in the skin through which sweat passes. Posterior root. The branch of each nerve of the spinal cord, which carries messages from the muscles and skin to the brain. See Fig. 67. Proteids. Foods which are useful for building body tissue, such as albumen, gluten, etc. Pubis. One of the bones of the pelvic girdle. See Fig. 42. Pulmonary artery. The artery which carries blood from the heart to the lungs. See Fig. 23. Pulmonary circulation. The circulation of blood from the heart to the lungs and back. Pulse. A wave of pressure which passes along the artery with each heart beat. Radius. One of the bones of the forearm. See Fig. 42. Reflex actions. Actions which take place without the exercise of will. Rennet. A ferment secreted by the stomach, which curdles milk. Retina. The sensitive surface at the back of the eyeball. See Fig. 75. Sacrum. The part of the spinal column between the hips. Saliva. The secretion, produced by the salivary glands, that moistens the mouth. Salivary glands. The glands which secrete saliva. See Fig. 11. Scapula. The bone of the shoulder blade. See Fig. 42. Sclerotic. The outer coat of the eyeball. See Fig. 75. Secretions. Materials produced by glands for the use of the body. Sensory nerves. Nerves which carry the messages to the brain, re- sulting in sensations. Sewage. Waste materials disposed of through closets, sinks, etc. Skull. The bony box which holds the brain. Spinal cord. The part of the nerve system which extends down within the backbone. See Figs. 43 and 66. Spinal nerves. Nerves rising from the spinal cord. Spine. The name given to the backbone. Spleen. A small gland in the abdomen. See Fig. 13. GLOSSARY OF TECHNICAL TERMS 323 Sprain. The tearing or straining of ligaments at a joint. Sputum. Matter spit up from throat or lungs. Stapes. One of the bones of the ear. See Fig. 76. Sterilizing. Heating some substance until all living organisms (bac- teria) are destroyed. Sternum. The breastbone. See Fig. 42. Stimulant. A substance which excites some part of the body into unusual activity. Stimulus. A shock which causes a muscle or other organ to act. Suspensory ligament. A thin band that holds the lens of the eye in position. See Fig. 75. Systemic circulation. The circulation in all of the body except the lungs. Tarsals. The ankle bones. See Fig. 42. Taste buds. The organs of taste in the tongue. Tendons. Bands of white substance uniting muscles with bone. See Fig. 56. Thorax. The chest. Throat. A cavity back of the mouth into which mouth and nose open. See Fig. 12. Tibia. The large bone extending from the knee to the ankle. See Fig. 42. Tonsils. Two rounded bodies at the back of the mouth. See Fig. 10. Trachea. See Windpipe. Tubules. The tubes in the kidney that secrete urine. See Fig. 60. Tympanic cavity. See Ear- Drum. Tympanic membrane. A membrane stretched across the passage leading into the ear. See Fig. 76. Ulna. One of the bones of the forearm. See Fig. 42. Urea. The chief waste product of muscle action, secreted by the kid- neys. Ureter. The duct leading from the kidney to the bladder. See Fig. 60. Uvula. A small piece of the soft palate hanging downward from the back of the mouth. See Fig. 10. Vaso-motor nerves. A series of nerves controlling the size of the small blood vessels. Vein. A blood vessel carrying blood toward the heart. 324 GLOSSARY OF TECHNICAL TERMS Venous blood. Blood made impure by gathering up the waste of the body. Ventricles. The chambers of the heart that send blood into the arteries. See Fig. 23. Vermiform appendix. A small projection from the end of the large intestine. See Fig. 13. Vertebrae. The bones forming the backbone. See Fig. 43. Vertebrates. Animals possessing backbone and vertebrae. Villi. Little projections on the inside of the intestine for absorbing food. See Fig. 17. Vitreous humor. One of the transparent liquids of the eye. See Fig. 75. Vocal cords. Two membranes in the larynx whose vibrations pro- duce the voice. White nerve matter. That part of the nervous system composed mostly of nerve fibers. Windpipe, or trachea. The tube leading from the throat to the lungs. See Fig. 12. INDEX Abdominal muscles, Exercises for, 295. Abscesses, 240 Accent, 313. Acid poisons, 253. Adulterated foods, 261. Air, as a distributor of bac- teria, 244, 260. Need of fresh, 117,260,274. passages, 105. sacs, 108. Albumen, 14. Alcohol, 27, 100, 184. and consumption, 278. Appetite for, 70, 186. Use of, 30, 69, 86, 101, 184, 246-249. Ale, 29. Animal tuberculosis, 281. Antidotes to poisons, 253. Appetite as a guide, 68. Arms, Exercises for, 293. Arsenic poisoning, 253. Arteries, 83, 87, 91. Location of, 89. Artery, Pulmonary, 84. Articulation, 308. Artificial breathing, 121. Auditory nerve, 224. Auricles, 83. Back, Exercises for, 294. Backbone, 126, 133. Bacteria, 25, 163, 239, 256, 270. Bacteria continued. how carried, 243, 258, 260. how they get out of the body, 242, 270. Protection against, 240, 257, 271. Baking, 77. powder, 78. Balance of the body, 288. Ball-and-socket joints, 138, 139. Bananas, 23. Bar and Ring exercise, 294. Baseball, as exercise, 297. Baths, 172, 237. Cold, 172. Hot, 175. Beans, 23. Beef tea, 74. Beer, 29. Beets, 23. Biceps muscle, 141. Bicuspid teeth, 38. Bile, 54. Bites of animals, 255. Bladder, 156. Bleeding, 90. how stopped, 91. Blisters, 158. Blood, 80. Circulation of, 80. Clotting of, 93. Impure, 89. Pure, 89. Respiratory changes in, 113. 325 326 INDEX Blood vessels, 87. of lungs, 108. of skin, 100, 162. Regulation of, 97, 191, 203. Blushing, 99. Boards of Health, 256. Body, Development of the, 283. Dangers of unequal, 285. Importance of, 284. Results of, 300. Boiling, 57, 76, 260. Boils, 240. Bones, 124, 128. Broken, 132, 237. Carpal, 125. how held together, 136. List of, 152. Material for, 18, 128. Misshapen, 130. of children, 129. Structure of, 128. Bowels, 53. Brain, 96, 99, 145, 166, 189, 190. Brandy, 30. Bread raising, 78. Breastbone (see Sternum). Breathing, 110. and exercise, 115. and the voice, 304. Artificial, 121. Center of, 191, 202, 203. Exercises for, 112, 288, 290, 305, 307. Process of, 288. Purpose of, 113, 285, 289. through mouth, 105, 285. Broiling, 57, 78. Bronchus, 107. Burns, Treatment of, 177. Butter, 17, 19. Callosities, 158. Candy, 67, 229. Canine teeth, 38. Capillaries, 87, 88. of lungs, 108. of muscles, 153. Carbolic acid, 253. Carbon dioxide, 104, 113, 115, Carpal bones, 125, 152. Cartilage, 133. Casein, 14. Cereals, 21, 67. Cerebellum, 191. Duties of the, 203. Cerebrum, 191. Duties of the, 204. Hemispheres of the, 192. Character, and physical train- ing, 300. and speech, 315. Cheeks, 37. Cheese, 19. Chest, 109, 294. Chicken pox, 241. Chilblains, 179. Chills and fever, 239. Chloral, 182. Chocolate, 27, 67. Cholera mixture, 254. Chyle, 56. Chyme, 51. Cider, 29. Cigarettes, 183. Circulation of blood, 80, 89. Clavicle, 125, 152. Cleanliness, 172. Clothing, 176. Clotting of blood, 93. Cocaine, 182. Cocoanuts, 23. INDEX 32T Coffee, 26. Cold-blooded animals, 166. Colds, 117, 169, 237. Cold, Sensation of, 99, 233. Taking, 117, 169. Color blindness, 220. Concentration of thought, 208. Consonants, Formation of, 310. Consumption, or Tuberculosis, 20, 117, 240, 268. Consumptives, Precautions for, 278. Contagious diseases, 238, 242. Immunity from, 241. Prevention of, 242. Cooking, Purpose of, 72. Methods of, 76. Principles of, 74. Cords, 137, 141. Corn, 21, 22, 29. Corns, 158. Corpuscles of blood, red, 81, 114; white, 82. Corrosive sublimate, 253. Cottonseed oil, 17. Coughing, 45, 202, 244, 246. Cuts, Treatment of, 163, 255. Deafness, 224, 226. Development of the body, 283. Dermis, 157, 162. Diaphragm, 110. Digestibility of foods, 56. Digestion, 37, 49. in the intestines, 55. in the mouth, 43. in the stomach, 49. Diphtheria, 20, 240, 265. Direction of sound, how Judged, 225. Diseases, 238. Contagious, 238, 262. Distribution of, 20, 258, 260, 262, 265. Immunity from, 241. Parasitic, 238. Disinfectants, 266. Dislocation of joints, 140. Distance of sound, how judged,. 225. Distilled liquors, 29. Drowning, Treatment in case of, 120. Dumb-bells, 294. Ear bones, 224, drum (see Tympanic cav* ity). Middle, 222. Ears, 222. Care of, 225. Ease of motion, 292. Eating, Pleasure in, 68. Time of, 66. Eggs, 21, 67. Emergencies, 252. Emphasis, 313. Enunciation, 311. Epidemics, 267. Epidermis, 157. Thickened parts of, 158. Epiglottis, 44, 45, 106. Epithelium, 60. Eustachian tube, 44, 222. Excretions, 154. Exercise, Need of, 148, 284, 285, Exercises, for breathing, 112, 290, 305, 307. for development of various muscles, 293. 328 INDEX Exercises continued. for suppleness, 292. in articulation, 309. Expiration, 111. Expression, physical 300. Eye, 217. Eyeball, 214, 216. Size of, 214. Eyelashes, 215. Eyelids, 215. Eyes, Care of, 220. Fainting, 95. Fat, 17, 153. Absorption of, 61. cells, 17, 157. Digestion of, 56. Feeling, 231. Femur, 125, 134, 152. Fermentation, 27. Fermented liquors, 29. Fever, Scarlet, 20, 240, 241. Typhoid, 20, 240. Yellow, 241. Filtering, 260. Finger nails, 161. Flavor, Use of, 26. produced by bacteria, 240. produced by cooking, 72. Flour, 21. Fly powders, 253. Food, Absorption of, 58-62. Amount of, needed, 31. habits, 65. Kind of, 13. Mastication of, 42. Purposes of, 11. Uncooked, as a distributor of disease, 245. values, 32. Food continued. value tables, 33, 34, 35. Foods, Adulteration of, 261. Cost of, 32, 66. Digestibility of, 56. for building purposes, 12, 19, 32. for fuel, 13, 15, 19, 153. Inspection of, 257, 261. Preservatives used in, 262. Source of, 18. Undigested portions of, 62. Frostbites, Treatment of, 178. Fruits, 23, 67. Frying, 58, 78. Fumigation, 266. Gall bladder, 47, 54. Games and sports, 284, 297. Ganglion, 193. Garbage, 262. Gastric juice, 49. Germs (see Bacteria). Gin, 30. Glands, 155. Ducts of, 42. Gastric, 48, 155. Lachrymal, 214. of tongue, 227. Pancreatic, 54. Salivary, 41, 155. Sweat, 157, 163, 169. Tear, 215. Glottis, 44, 45, 303. Gluten, 14. Graham meal, 21. Grape juice, 29. Gravity, Effect of, on circula- tion, 95. Gullet, 45. INDEX 329 Habits, Acquiring of, 205. Hair, 159. Follicle of, 159. Hammer throwing, 298. Hands, Exercises for, 295. Health, Disease and, 237. Duty of preserving, 249. Boards of, 256. Hearing, Sense of, 222, 224. Heart, 82. Beating of, 85. Center of control of, 191, 203. Regulation of, 96. Valves of the, 85. Hemoglobin, 82. Hibernating animals, 167. Hinge joints, 134, 137. Hospitals, 266. Humerus, 125, 138. Hunger, 68, 231. Hygiene, Personal and Public, 256. Incisors, 38. Incus, 222. Indian meal, 21. Indoor life, Evils of, 117. Inflection, 313. Insects as distributors of dis- ease, 245. Inspection, 257. of food, 257, 261. of ventilation, 260. of water, 258. Inspiration, 111. Intemperance, 72, 250. Intestines, 47, 53. Involuntary muscles, 143, 145. Isolation, 265. Joints, 134. Ball-and-socket, 138. Dislocation of, 140. Hinge, 134, 137. Injuries at, 139. Knee, 134. Shoulder, 138. Jumping, 297. Kidneys, 155. Tubules of the, 156. Lachrymal duct, 214. gland, 214. Lacteals, 62. Lard, 17. Larynx, 44, 106, 107, 133, 303. Laudanum, 181, 254. Lead poisoning, 253. Legs, Exercises for, 296. Lens of eye, 217. Lentils, 23. Ligaments, 135, 136, 139. Lime, 18, 26. Liquors, Distilled, 29. Fermented, 29. Liver, 53. Duties of the, 54. Lung diseases associated with impure air, 117. Lungs, 106. Capacity of, 111. Exercise of, 112. Lymph vessels, 62. Malaria, 239. Malleus, 222. Malt, 28. Meals, Frequency of, 66. Measles, 240, 265. 330 INDEX Meats, 20. Cooking of, 73. Digestion of, 49. Medicines, 237. Medulla oblongata, 191. Duties of the, 202. Mercury poisoning, 253. Mesentery, 58. Metacarpals, 125, 152. Metatarsals, 125, 152. Middle ear, 222. Milk, 19. Curdling of, 51. Digestion of, 51. Diseases distributed by, 20, 257. Inspection of, 257. Mind, Dependence of, on body, 210. Care of the, 207. Mineral substances, 26. Modulation, 314. Molar teeth, 38. Molasses, 28. Morphine, 181. Mosquito bites, the cause of malaria, 239. Treatment of, 255. Motor centers, Location of, 206, 207. nerve fibers, 200. Mouth, 37. -breathing, 105. Mumps, 240, 241, 265. Muriatic acid poisoning, 253. Muscle, Biceps, 141. fibers, 142. sense, 235. Muscles, 141. at joints, 137, 139. Muscles continued. Contraction of, 144, 145. Developing of, 284. Exercises for, 292. Growth of the, 147. Involuntary, 143, 145. Number of, 146. of blood vessels, 97. of breathing, 109. of eye, 216. Structure of, 141. Myosin, 14. Nails of fingers and toes, 161. Narcotics, 180. Effect of, upon mind, 210. Nasal cavities, 41, 44, 230. Nearsightedness, 219. Neck, Exercises for, 295. Nerve cells, 195. fibers, 145, 194. trunks, 194. Nerves, 96, 190, 194. Anterior root of the, 194. Duties of the, 198. Motor, 200. of hearing, 224. of muscles, 145. of nose, 230. of retina, 218. of skin, 157, 162. of tongue, 227. Posterior root of, 194. Sensory, 200. Vaso-motor, 99. Nervous system, 189. Night air, 118. Nitric acid poisoning, 253. Nitrogenous foods, 14. Nuts, 23. INDEX 331 Oatmeal, 21, 67. Oats, 21, 22. (Esophagus, 44, 45. Oil glands, 160. Olfactory nerve, 230. Olive oil, 17. Opium, 181, 254. Optic nerve, 216, 218. Organic matter, 18. Overindulgence, 72, 250. Oxalic acid poisoning, 253. Oxidation, 104, 153. Oxygen, 13, 104, 113, 115, 116, 285. Use of, 114. Pain sense, 234. Palate, 37, 44. Pancreas, 47, 54, 155. Papillae of hair, 159. of tongue, 227. Paragoric, 181, 254. Parasites, 73. Parasitic animals, 239. bacteria, 239. diseases, 238. Paris green, 253. Peanuts, 23. Peas, 23. Pelvic girdle, 125. Phonetic reading, 314. Physical expression, 300. Physical training (see Body, Development of). Piano, Learning to play the, 203. Plumbing, Importance of, 243. Pneumonia, 117. Poise, 287. Poisoning, Treatment for, 252. Pores of skin, 164. Position, in reading and speak- ing, 306. in sitting, 286. in standing, 287. in walking, 291. Potatoes, 23, 32. Cooking of, 73. Preservatives in foods, 262. Pressure, Sense of, 231. Proteids, 14, 153. Absorption of, 61. coagulated by heat, 74. Digestion of, 50, 55. Need of, 50, 55. Source of, 33, 34, 35. Pulmonary artery, 84. Pulse, 86. Pupil of the eye, 217. Quarantine (see Isolation). Radius, 125, 152. Reading, Position in, 306. Recreation, 209. Reflex action in spinal cord, 201. in medulla, 202. Rennet, 51. Repair of body, 12. Reservoirs, Care of, 259. Respiration, 105, 115. Restoration of, 120. Retina, 217. Ribs, 125, 127, 133, 152. Rice, 21, 22. Roasting, 57, 77. Rubbing, 174, 237. Rum, 30. Running, 297. Rye, 21. Saliva, Use of, 41, 43. 332 INDEX Salivary glands, 41, 155. Salt, 26. Sauces, 220. Scapula, 125, 138, 152. Scarlet fever, 20, 240, 241, 265. Secretions, 154. Sensations, 213. Location of, in brain, 199, 207. Sense organs, 214. Senses, 213, 231. Sensory nerve fibers, 200. Sewage, 243, 259, 262. Sewerage systems, 264. Shoes, 131. Shot putting, 299. Shoulder joint, 138. Shoulders, Exercises for, 294. Sick Room, Care of, 266. Sight, Sense of, 214. Sitting, Importance of correct, 286. Skeleton, 124, 125. Skin, 156. Care of, 172. Functions of, 163. Sensations of, 231. Structure of, 156. Skull, 127. Sleep, 207. Smallpox, 241, 265. Smell, Sense of, 214, 229. Duration of, 231. Location of, 230. Use of, 230. Snake bites, Treatment of, 254. Soothing sirup, 181, 254. Sore throat, 46. Sound, Direction of, how judged, 225. Sound continued. Distance of, how judged, 225. (See Hearing.) Soups, 75. Speaking, Position in, 306. Special senses, 214. Speech, 302. Spinal cord, 126, 192, 201. Duties of, 200. Gray matter of, 193. White matter of, 193. Spine (see Backbone). Spitting, Dangers of, 271. Sports and games, 284, 297. Sprain, 140. Sputum, 271. Standing, Correct position in, 287. Stapes, 222. Starch, 15. Absorption of, 61. Digestion of, 43, 55. State Board of Health, 257. Sternum, 125, 127. Stews, 75. Stimulants, 149, 180. Stimulus, 145. Stings, Treatment of, 255. Stomach, Structure of, 46. Digestion in, 49. Strychnine poisoning, 254. Sugar, 16, 28, 153. Absorption of, 61. Sulphuric acid poisoning, 253. Suppleness, Exercises for, 292. Swallowing, 46. Center of, 191, 203. Sweat, 163. glands, 157, 163, 169. INDEX 333 Sweating as a heat regulator, 168. Swimming, 297. Taking cold, 117, 169. Tallow, 17. Tapeworm, 239. Tarsal bones, 125, 152. Taste, 214, 226. buds, 227. Confusion of, with smell, 228. Duration of, 228. Tastes, Different kinds of, 227. Tea, 26. Tear glands, 215. Teeth, 37, 38. Care of the, 39. Growth of, 38. Milk, 38. Permanent, 38. Temperature of body, 13, 167. Regulation of, 165, 168. Sense of, 233. Tendon, 137, 141. Tennis, 298. Thinking, Location of, in brain, 207. Thirst, 68, 231. Thorax, 109. Throat, 44. Sore, 46. Tibia, 125, 134, 152. Tinfoil poisoning, 253. Tissues, 88. Tobacco, 86, 182. Use of, 182. Toe nails, 161. Tone, 302, 312. Tongue, 37, 44, 226. Tonsilitis, 44. Tonsils, 40, 44. Touch, Sense of, 213, 231. Trachea, 45, 106, 107. Trichina, 239. Tuberculosis, or Consumption, 20, 117, 240, 268. Tubules of kidney, 156. Tympanic cavity, 223. membrane, 223. Typhoid fever, 20, 240, 258. Ulna, 125, 152. Urea, 154. Ureter, 156. Uvula, 37. Vaccination, 241. Vaso-motor nerves, 99. Center of, 191. Vegetables, 23. Veins, 83, 88. Venous blood, 115. Ventilation, 116, 118, 260. Ventricles, 83. Vermiform appendix, 47. Villi, 59. Duties of, 61. Structure of, 60. Vertebrae, 126. Vertebrates, 126. Vocal cords, 106, 303. Voice, Training of the, 302. Production of the, 303. Vomiting, 47, 252. Vowels, Formation of, 309. Waist Muscles, Exercises for, 295. Walking, Correct method of, 291. 334 INDEX Warm-blooded animals, 166. Warmth, Feeling of, 99, 233. Warts, 159. Waste products, 54, 63, 153. Water Commissioners, 257. Water, 24, 25. Absorption of, 61. Filtering of, 260. Impurities in, 25, 258, 260. Inspection of, 258. Loss of, through lungs, 114. of lakes, 25. of reservoirs, 25. of rivers, 26, 243. Water continued. of springs, 25. of wells, 25. Wheat, 21, 22. Whisky, 30. Whooping cough, 240, 265. Windpipe, 44, 45, 106. Wounds, Treatment of, 255. Wrists, Exercises for, 295. Yawning, Significance of, 286. Yeast, 27, 78. Yellow fever, 241. Date Du-