PHYSIOLOGY 
 
 BRIEFER COURSE 
 
 GOLTON 
 
BIOLOGY 
 
 LIBRARY 
 
 G 
 
.wt 
 
X-RAY PHOTOGRAPH OF HAND 
 
 SHOWING SHOT CARRIED FOR TWENTY YEARS 
 
 (From Recreation, by permission of G. O. Shields.) 
 
BRIEFER COURSE 
 
 PHYSIOLOGY 
 
 ILLUSTRATED BY EXPERIMENT 
 
 BY 
 
 BUEL P. COLTON, A.M. 
 
 AUTHOR OF " PHYSIOLOGY, EXPERIMENTAL AND DESCRIPTIVE 
 
 "PRACTICAL ZOOLOGY"; AND PROFESSOR OF NATURAL 
 
 SCIENCE IN THE ILLINOIS STATE NORMAL 
 
 UNIVERSITY 
 
 BOSTON, U.S.A. 
 
 D. C. HEATH & CO., PUBLISHERS 
 1900 
 
BIOLOGY 
 
 LIBRARY 
 
 G 
 
 COPYRIGHT, 1899, 
 BY BUEL P. COLTON. 
 
 Nortooob 
 
 J. S. Gushing & Co. - Berwick & Smith 
 Norwood Mass. U.S.A. 
 
PREFACE. 
 
 THE author's " Experimental and Descriptive Physiol- 
 ogy" has been adopted by a large number of schools and 
 colleges. But there are many schools in which, owing to 
 the youth of the pupils, the shortness of the time allotted to 
 the subject, or the meagerness of laboratory facilities, such 
 a rigorous course cannot be taken. For such schools this 
 simpler book is written. While it contains considerably 
 less experiment and dissection than the larger book, it is 
 still based upon experimental work. No teaching of physi- 
 . ology is worthy of the name unless it rests upon experi- 
 ment, observation, and dissection. The ridiculous answers 
 of the pupil who has learned mere "book physiology" 
 furnish the standard jest of the educational journal. Try- 
 ing to teach physiology without experiment is not only in 
 opposition to modern views of pedagogy and psychology, 
 but it is equally at variance with the common sense of the 
 business man's view. Such teaching is a mere mummery 
 of words it teaches neither how to know nor to do. 
 
 In fitting this work for the less mature mind, special 
 attention has been paid to conciseness and brevity of state- 
 ment and to clearness of exposition. Sentences and para- 
 
 iii 
 
 735021 
 
iv PR El- ACE. 
 
 graphs have been made short; chapters are short, with 
 definite summaries appended. 
 
 Function, rather than structure, has been made promi- 
 nent. Only so much of anatomy as is really needed to 
 understand the working of the organs has been introduced. 
 The experimental work and directions for dissection, as 
 well as some of the more difficult points, have been put in 
 smaller type, so they may more readily be omitted where 
 it is not possible to complete all the work in the given 
 time. 
 
 Although hygiene has been given a prominent place, 
 yet it may be claimed that when the pupil is well grounded 
 in the functions of the different organs, from observational 
 and experimental work, many of the rules of hygiene will 
 readily occur to him as natural inferences. When other 
 rules for the preservation of health, which might not occur 
 to him, are suggested, he will see their significance because 
 he understands the underlying principle ; and he not only 
 can, but will, obey the rule better because he sees reason 
 in it, and does not follow it blindly as an arbitrary law 
 thrust upon him. Questions are given, at the end of each 
 chapter, to test the pupil's knowledge of principles by 
 application to new cases. 
 
 Some of the more desirable reforms in nomenclature have 
 been adopted ; among these are the use of the terms ante- 
 rior, meaning toward the head ; posterior, in the opposite 
 direction ; dorsal, toward the back ; ventral, toward the 
 region of the belly. These terms, used instead of " up " 
 
PREFACE. V 
 
 and "down," "front" and "back," will do away with 
 much confusion, especially since we are obliged to use the 
 structure of horizontal-bodied animals to illustrate human 
 anatomy. Many Latin terms, such as "vena cava" should 
 be replaced by English, as caval vein. Postcaval vein and 
 precaval vein are easier and better than " vena cava infe- 
 rior " and "vena cava superior." In many cases the 
 English plural may well replace the Greek or Latin form, 
 as ganglion, plural ganglions. Blood tube is better than 
 "bloodvessel." The best authorities say spinal bulb in- 
 stead of the long "medulla oblongata." Food tube is 
 simpler than " alimentary canal," especially as the tube is 
 not canal-like. The rib-bearing vertebras are thoracic, and 
 are no more "dorsal" than the other parts of the spinal 
 column. 
 
 Effort has been made to lay stress on the more impor- 
 tant topics, and the skeleton is relegated to a subsidiary 
 place, as a knowledge of it has so little to do with practical 
 hygiene. The heart and the stomach receive full treat- 
 ment, while matters of such slight importance as the hair 
 and nails are briefly dismissed. 
 
 The order of topics is the result of long experience. 
 For many years the author has sought to find the most 
 natural sequence of subjects, so that, as the work pro- 
 gressed, the pupil would find the way best prepared for 
 him. Without claiming that this is the best sequence, the 
 writer is sure that it is the " path of least resistance." 
 
 The subject of Alcohol has been treated in full com- 
 
vi PREFACE. 
 
 pliance with the law. Copious quotations have been taken 
 from the best authorities on this subject. The same 
 high-grade illustrations have been used that brought such 
 favorable comment on the earlier work. 
 
 This briefer edition has, too, the full benefit of the 
 criticism of the eminent authorities whose names are listed 
 in the larger work. 
 
 TO THE TEACHER. 
 
 For any practical work in physiology it is very desirable 
 to have a room furnished with tables and supplied with 
 water. 
 
 Each pupil should make full notes and drawings of the 
 work done and the organs studied and dissected. Only by 
 so doing will he firmly fix and retain what he gathers from 
 day to day. 
 
 In the larger work by the author are many experiments 
 and dissections given in full which are here omitted in 
 order to present a briefer course. In the larger work there 
 is also given a list of books which are most helpful in 
 teaching physiology. 
 
CONTENTS. 
 
 CHAPTER I. 
 
 PAGE 
 
 INTRODUCTION l 
 
 Health. Care of the Body. Hygiene. Physiology. Organ. Func- 
 tion. Anatomy. Tissues. Cells. Physiological Division of Labor. 
 
 CHAPTER II. 
 
 MOTION 7 
 
 Motion Necessary to Life. Experiments with our Muscles. Action 
 of Muscle. Structure of Muscle. Connective Tissue. Laws of 
 Muscle Action. Flexors and Extensors. Symmetry. Muscles and 
 Bones. Levers. Locomotion. Uses of Bones. 
 
 CHAPTER III. 
 
 THE GENERAL FUNCTIONS OF THE NERVOUS SYSTEM SENSATION 
 
 AND. MOTION 2 4 
 
 Muscles controlled by Nerves. Voluntary and Involuntary Motion. 
 The Spinal Cord. The Spinal Nerves. Structure of Nerves. 
 Function of Nerves. Structure of the Spinal Cord. Ganglions. 
 Reflex Action of the Spinal Cord. Reflex Action of the Spinal 
 Cord in the Frog. Function of the Nerve Roots. Importance of 
 Reflex Action. Inhibition. Nature of a Nervous Impulse. Har- 
 mony in Muscle Action. Nerves depend on Blood Supply. 
 
 CHAPTER IV. 
 
 CIRCULATION OF THE BLOOD 39 
 
 The Blood and its Work. The Rate of the Heart Beat. Position 
 and Size of the Heart. The Valves of the Heart. The Blood 
 Tubes Connected with the Heart. The Action of the Heart. Work 
 and Rest of the Heart. Action of the Large Arteries. Variation 
 in Blood Supply. Plain Muscle Fibers in the Walls of the Arteries. 
 
 vii 
 
viii CONTENTS. 
 
 I'AGK 
 
 Circulation of Blood in the \Yel> of the Frog's Foot. Blood Mow in 
 the Capillaries. The Veins. The Valves in the Veins. F.t'fect of 
 Pressure on the Veins. Rate of Blood Flow. Nourishment of the 
 Walls of the Heart. Effect of Gravity on Circulation. 
 
 CHAPTER V. 
 
 CONTROL OF CIRCULATION. THE BLOOD AND THE LYMPH .... 64 
 The Effect of Emotions on Circulation. Rhythmic Action of the 
 Heart. Nerve Control of the Heart. Sympathetic Nervous System. 
 The Vagus Nerve. Inhibition. Vaso-motor Nerves. Blushing. 
 Regulation of the Size of the Arteries. Effect of Exercise on the 
 Size of the Arteries. Effects of Alcohol on Circulation. The 
 Bloocl. The Corpuscles of the Blood. The Plasma. Hemoglobin. 
 Coagulation of Blood. Fibrin. Amount of Blood. Distribution of 
 Blood. The Lymph Spaces. Lymph Tubes. Lymphatic Glands. 
 Flow of Lymph. Massage. Transfusion of Blood. 
 
 CHAPTER VI. 
 
 RESPIRATION 84 
 
 The Close Relation between Circulation and Respiration. Organs 
 of Respiration. Structure of the Lungs. The Windpipe. Cilia. 
 The Pleura. The Diaphragm. Action of the Diaphragm. Move- 
 ments of Respiration. Forces of Inspiration. Resistances to Inspi- 
 ration. Elastic Reactions of Expiration. Forced Respiration. Rate 
 of Respiration. Modifications of Respiration. Lung Capacity. 
 Hygiene of Respiration. Breathing through the Mouth. Control 
 of Respiration. Chemistry of Respiration. Composition of the 
 Air. Exchanges between the Air and the Blood in the Lungs. 
 Oxyhemoglobin. The Gases in the Blood. Production of Heat 
 and Motion in the Body. Oxidation of Live Tissues. Body and 
 Locomotive Compared. Storage of Oxygen in the Tissues. Re- 
 breathing Air. 
 
 CHAPTER VII. 
 
 VENTILATION AND HEATING. DIST AND BACTERIA 114 
 
 Need of Ventilation. Grates. Principles of Ventilation. Stoves. 
 Furnaces. Foul-air Shafts and Fans. Steam and Hot-water 
 Heating. Direct and Indirect Heating. Dead Dust. Sources of 
 Dust. Live Dust. Consumption. Disease Germs. Bacteria. How 
 to avoid Dust. Sweeping. Contagious Diseases. Putrefaction. 
 Preservation of Foods. Need of Removal of Waste. 
 
CONTENTS. ix 
 
 CHAPTER VIII. 
 
 PAGE 
 
 EXCRETION 130 
 
 The Skin throws off Perspiration. The Structure of the Skin. The 
 Epidermis. Color of the Skin. The Dermis. Sweat Glands. Es- 
 sentials of a Gland. Blood Supply of Glands. Oil Glands. 
 Composition of Sweat. Amount of Perspiration. Functions of the 
 Skin. Regulation of Bodily Temperature by the Skin. Distribu- 
 tion of Heat in the Body. Regulation of Bodily Temperature by 
 Food and Clothing. The Kidneys. Work of the Kidneys. Rela- 
 tion of the Skin and Kidneys. 
 
 CHAPTER IX. 
 
 Foons AND COOKING 144 
 
 Necessity of Food. Food Defined. Foodstuffs. Proteids. Impor- 
 tance of Proteids. Meat. Fish. Eggs. Milk. Cheese. Vege- 
 table Proteids. Carbohydrates. Grains. Wheat. Corn. Rice. 
 Oats. Potatoes. Vegetables. Fruits. Water. Impurities in 
 Water. Typhoid Fever. Ice-water. Boiling Water. Salts. 
 Necessity of a Mixed Diet. Effects of Cold on Appetite for Fats. 
 Vegetarians. Tea. Coffee. Beef Tea. Cooking. Soups. 
 
 CHAPTER X. 
 THE DIGESTIVE SYSTEM 159 
 
 The Object of Food. The Digestive Tube. Organs of Digestion. 
 The Mouth. The Teeth Kinds, Structure, Arrangement. Care 
 of the Teeth. Salivary Glands. Action of Salivary Glands. Saliva 
 and its Uses. Mucus and Mucous Glands. The Pharynx. Swal- 
 lowing. The Gullet. The Structure of the Stomach. Gastric 
 Glands. Blood Supply of the Stomach. Stomach Digestion. 
 Churning Action of the Stomach. Time of Stomach Digestion. 
 Chyme. Absorption from the Stomach. The Intestine. The 
 Liver. The Pancreas. Bile. Pancreatic Juice. The Portal Circu- 
 lation. Functions of the Bile. Work of the Pancreatic Juice. 
 Intestinal Juice. 
 
 CHAPTER XL 
 
 ABSORPTION DIGESTION COMPLETED 181 
 
 Absorption. Villi. Routes of Different Foods after Absorption. Dif- 
 fusion and Osmosis. Absorption a Vital Process. The Lacteals 
 and the Lymphatics. Outline of Digestion. The Colon. Work 
 of the Large Intestine. Constipation. Laxative and Constipating 
 
X CONTENTS. 
 
 PAGE 
 
 Foods. Hygiene of Digestion. Deliberation in Eating. Thorough 
 Mastication. Fleets of Repose on Digestion. Conversation at 
 Meals. Value of Soups and Desserts. Hot Drink at Meals. Time 
 of Meals. Eating between Meals. Amount of Food Needed. 
 Errors in Diet. 
 
 CHAPTER XII. 
 
 NUTRITION 195 
 
 Ledger Account of the Body and its Organs. Blood a Mixture of 
 Good and Bad. Action of Diseased Kidneys. Blood Stream like 
 Water Pipes and Sewer Combined. A Living Eddy. Importance 
 of Renewal of Blood and Lymph. Fat as a Tissue. Hibernation. 
 Respiration and Oxidation of Candle. Glycogen. Muscular Exer- 
 tion and Excretion of Urea. Metabolism. Indestructibility of 
 Matter. Indestructibility of Force. Utilization of Energy in the 
 Body and in Machines. Correlation and Conservation of Energy. 
 
 CHAPTER XIII. 
 
 ALCOHOL 208 
 
 Alcohol and Crime. Alcohol and Energy. Alcohol and Heat. Alco- 
 hol and Muscular Energy. Arctic Explorers. Alcohol and Train- 
 ing. Stimulants. Narcotics. Temperance Drinks. Testimony of 
 Physiologists. Testimony of Army Officers. Testimony of a Natu- 
 ralist. Physiological Effects of Alcohol. 
 
 CHAPTER XIV. 
 
 EXERCISE AND BATHING 226 
 
 How Exercise is Beneficial. Exercise for General Health. Nature's 
 Rewards and Punishments. Exercise prolongs Life. Choice of 
 Exercise. Games of School Children. Tennis. Baseball and 
 Football. Boxing. Bicycling. Exercise for Middle-aged Men. 
 Taking Cold. Diarrhea. Bathing. Cold Baths. Bath Mits. Time 
 for Bathing. Warm Baths vs. Cold Baths. Exercise Arterial Mus- 
 cles. Habit of Cold Bathing acquired gradually. 
 
 CHAPTER XV. 
 
 THE BRAIN 235 
 
 The Coverings of the Brain. Parts of the Brain. The Cerebrum. 
 The Cerebellum. ' The Spinal Bulb. Brain of a Cat or Rabbit. 
 Cranial Nerves and their Functions. Hemispheres of the Cerebrum. 
 Brain Convolutions and Intelligence. Gray and White Matter of 
 the Brain. Neuroglia. Functions of the Cerebrum. Pigeon 
 with Cerebrum Removed. Functions of Cerebral Cortex. Center 
 
CONTENTS. xi 
 
 PAGE 
 
 of Sensations itself Insensible. Crossed Control of the Body. Lo- 
 cation of Brain Functions. Left Hemisphere better Developed. 
 Location of Sensation Centers. Brain Work and Brain Rest. 
 Sleeplessness. Fatigue. Control of Mind. Habit of Resting the 
 Brain. Nervous Tissues least Affected by Starvation. Blood Supply 
 of the Brain. Fainting. Apoplexy. Meningitis. The Water 
 Cushion of the Brain. Relative Activity of Gray and White Matter. 
 
 CHAPTER XVI. 
 
 EFFECTS OF ALCOHOL ON THE NERVOUS SYSTEM 250 
 
 The Chief Effect of Alcohol is on the Nervous System. Inebriety re-" 
 garded as a Disease. Moral Deterioration produced by Alcohol. 
 Narcotics. Opium. Cocaine. Chloral Hydrate. Chloroform. 
 Tobacco. Cigarette Smoking. 
 
 CHAPTER XVII. 
 
 GENERAL CONSIDERATIONS CONCERNING THE NERVOUS SYSTEM . . . 261 
 Nerve Stimuli. Kinds of Nerve Stimuli. Essential Similarity of All 
 Nerve Fibers. Relation of Stimulus and Sensation. Reaction 
 Time. Reflex Action. Connection of Brain 'Centers. Nature of 
 Sensation. Subjective Sensations. The Relative Nature of Sensa- 
 tion. Induction Currents used in Physiological Experiments. 
 Dreams. Lingering Effect of Sensations. Habits are Acquired 
 Reflex Actions. Usefulness of Resting. Nervous System vs. Tele- 
 graph System. Efferent Currents. Afferent Currents. 
 
 CHAPTER XVIII. 
 
 THE GENERAL SENSES 271 
 
 The Body a Collection of Organs. Influence from the External World. 
 Classification of the Senses. General Sensations and Special Senses. 
 The Muscular Sense. Importance of Muscular Sense. Dependence 
 of Sight on Muscular Sense and Touch. Pain. Pain a General 
 Sense. Extent of Pain. Use of Pain. Hunger and Thirst. 
 
 CHAPTER XIX. 
 
 THE SPECIAL SENSES TOUCH AND TEMPERATURE SENSE .... 278 
 What we learn by Touching Objects. Cutaneous Sensations. Nerve 
 Endings in the Skin. Touch Corpuscles. Touch the most General 
 of the Senses. Pressure Sense. Local Sign. Test by Compass 
 Points. Reference of Sensation to the Region of the Nerve End- 
 ings. Temperature Sense. 
 
xil CONTEWS. 
 
 CHAPTKR XX. 
 
 PAGE 
 
 THE SENSE OF SIGHT 285 
 
 Protection of the Eye. The Lacrymal Secretion. External Parts of 
 the Eye. The Conjunctiva. Muscles of the Eyeball. Movements 
 of the Eye. Coats of the Eye. The Sclerotic Coat. The Choroid 
 Coat. The Retina. The Cornea. The Iris. The Pupil. Regula- 
 tion of the Amount of Light admitted into the Eye. The Refract- 
 ing Media of the Eye. The Aqueous Humor. The Vitreous Humor. 
 The Crystalline Lens. The Lens Capsule. The Hyaloid Mem- 
 brane. The Ciliary Muscle. Inversion of the Image. Adjustment 
 for Distance. Action of the Ciliary Muscle. Defects of Eyesight. 
 Structure of the Retina. Importance of the Retina. The Blind 
 Spot. The Optic Nerve not Sensitive to Light. Sympathy between 
 the Eyes. Pain in the Eyes. Color Sensations. Color Blindness. 
 Stereoscopic Vision. After-images. Care of the Eyes. 
 
 CHAPTER XXI. 
 
 TASTE, SMELL, AND HEARING ^01 
 
 Uses of the Sense of Taste. The Papilla;. Nerve Supply of the 
 Tongue. Solution Necessary for Tasting. Flavors. Effect of 
 Temperature on Taste. The Sense of Smell. Why we Sniff. The 
 Sense of Bearing. The External Ear. The Tympanum. The 
 Middle Ear. The Eustachian Tube. The Internal Ear. The Pro- 
 duction of Sound. The Equilibrium Sense. The Care of the Far. 
 The Use of the Ears. 
 
 CHAPTER XXII. 
 THE VOICE 309 
 
 The Ear and the Voice. What we can learn from our own Throats. 
 The Vocal Cords. Reinforcement of Sound. Pitch and Voice. 
 Voice and Speech. Vowels and Consonants. Difference between 
 Voices. Hoarseness. Whispering. Culture of the Voice. 
 
 CHAPTER XXIII. 
 
 ACCIDENTS. WHAT TO DO TILL THE DOCTOR COMES 314 
 
 How to stop Flow of Blood from Arteries. Bleeding from the Upper 
 Arm. Bleeding from the Neck. Wounds in the Thigh. Bleeding 
 from Veins. Hemorrhage of the Lungs or Stomach. Bleeding from 
 the Nose. Treatment of Burns. Danger from Burning Clothing. 
 
CONTENTS. xiii 
 
 Treatment of Fainting. Broken Bones. Sunstroke. Treatment of 
 the Drowned. Swimming. Suffoeation in Wells. Bites of Cats, 
 Dogs, etc. Wounds from Thorns, Rusty Nails, etc. Snake Bites. 
 Poisons and their Antidotes. Poison Ivy. The Sick-room. Qual- 
 ities of the Nurse. Care of the Sick. 
 
 CHAPTER XXIV. 
 
 THE SKELETON 330 
 
 Axial Skeleton. Appendicular Skeleton. Uses of the Bones. Study 
 of a Vertebra. Table of the Bones. The Spinal Column. Articu- 
 lations of a Vertebra. The Cervical Vertebras. Atlas and Axis. 
 The Thoracic Vertebras. The Lumbar Vertebras. The Sacrum and 
 the Coccyx. Flexibility of the Spinal Column. Curves of the Spinal 
 Column. Cavities of the Skeleton. Pronation and Supination. 
 Weight of the Bones. Microscopic Structure of Bone. Classifica- 
 tion of Joints. Sprains and Dislocations. 
 
 CHAPTER XXV. 
 
 THE MUSCLES 341 
 
 The Number of Muscles. The Arrangement of Muscles. Forms of 
 Muscles. Names of Muscles. Peculiar Muscles. Heart Muscle. 
 Three kinds of Muscular Fiber Compared. Each Fiber a Cell. 
 Muscles of Expression. Muscles and Fat. Convulsions. Rigor 
 Mortis. Some Prominent Muscles. Sculpture and Anatomy. 
 
 APPENDIX . . 347 
 
 Antidotes. Disinfectants. Vital Statistics. 
 
 GLOSSARY 360 
 
 INDEX .... 371 
 
PHYSIOLOGY. 
 
 CMA.P,TER I. ,'.:: 
 
 Health. Is it not a splendid thing to be well and 
 strong ? To be full of bounding health ? To " feel one's 
 life in every limb " ? 
 
 Who does not desire to prolong, so far as possible, this 
 condition characteristic of youth ? 
 
 Natural and Artificial Modes of Life. An animal 
 living in a state of nature may keep well and live its 
 natural period of life without knowing anything about the 
 laws of health. But as students or indoor workers, many 
 of us lead a sedentary life ; we are not natural, but often 
 highly artificial, in our mode of living. We move about 
 but little, whereas the animal abounds in motion. We 
 concentrate energy upon mental effort, thus diverting a 
 large share of our sum total of energy away from the pro- 
 cess of nutrition. We often shut ourselves in rooms nearly 
 air-tight. We eat poorly chosen and ill-prepared food. 
 We devour it hastily, often when we are not in fit con- 
 dition to take food. In short, we frequently disobey the 
 laws of Nature. Now, Nature punishes every violation of 
 her laws. She never forgives, never forgets. 
 
 1 
 
Value of Knowledge. The out-of-door worker may 
 not suffer so much from ignorance in these matters. 
 From the character of his occupation, he is, to a certain 
 extent, obliged to obey Nature. He gets enough fresh 
 air. His bodily exertion generally brings a hearty appe- 
 tite, vigorous digestion, active circulation of the blood. 
 Still, he would greatly profit by knowing something of the 
 nature of his food, its wholesomeness or unwholesomeness. 
 The fact that he has fair health is no proof that he always 
 does the best thing. His natural mode of life may keep 
 him in tolerably good condition in spite of his violation of 
 certain laws V b#t ^(f J-coldd :uXidpubtedly learn how to 
 economize in the purchase, preparation, and proper com- 
 bination of foods. 
 
 Importance of the Care of the Body. Any machine 
 of man's invention must be kept in good running order if 
 we would have it do good work, or last long. We must 
 keep a machine clean, well oiled, and not overtax it. Are 
 not our bodies worth equal care ? If some part of a ma- 
 chine is broken, we may replace it at moderate expense ; 
 but none of the vital organs can be replaced. We may 
 get a new mainspring for a watch, but we cannot obtain a 
 new stomach or lungs. 
 
 Its Admirable Mechanism. Aside from the above 
 considerations the human body is worthy of study for its 
 own sake. Viewed simply as a mechanism, it is wonder- 
 ful. Each organ is so well adapted to its work, and all 
 the organs work so harmoniously through their connection 
 and control by the nervous system, that we never cease to 
 admire it. We admire a doll, or other toy, so ingeniously 
 constructed that it can move its eyes or walk a short time 
 after being wound up. But this live mechanism, which is 
 
INTRODUCTION. 3 
 
 self-winding, self-regulating, self-repairing, self-directing, 
 amazes us. 
 
 Hygiene. We take up the study of the human body 
 mainly that we may learn how to preserve health ; the 
 science of health is hygiene. 
 
 Physiology. In order to keep the various organs in 
 good order we must know what their natural work is, and 
 how they do it ; the science of the action of the body and 
 its parts is physiology. 
 
 Organ. Any part, or member, of the body, which has 
 a special work to do, is called an organ, as the hand, the 
 eye, or the stomach. 
 
 Function. -- The work, or action, of each organ is 
 its function. 
 
 Anatomy. In order to understand the working of 
 each organ it is usually necessary to know something 
 of its construction ; the science of structure is anatomy. 
 We do not need to go far into anatomy to obtain a fail- 
 knowledge of the manner in which our organs do their 
 work. The surgeon, of course, must be able to locate 
 accurately the various blood tubes, nerves, muscles, etc. 
 We need to know only the general structure of the body 
 and, more in detail, some of the more important organs, 
 such as the heart, the lungs, the larynx, the eye, etc. 
 It is fortunate for us that these organs in the sheep, pig, 
 and cow are so nearly like our own that they serve 
 admirably to enable us to understand ourselves. 
 
 Tissues. Every organ is composed of several different 
 kinds of material. For instance, in a slice across a ham 
 we see the skin on the outside, then fat, lean, and bone. 
 
4 I'HYSIOLOGY. 
 
 These "primary building materials" of the body we call 
 tissues. A tissue may be defined as an aggregation of 
 similar cells devoted to a common work. 
 
 Cells. The whole body is made up of small parts 
 called cells, comparable to the bricks in a house. These 
 cells are of various shapes in the different tissues. 
 
 In the more active tissues the cells are alive, and each 
 cell may be compared to the ameba, a little mass of living 
 jelly-like substance called protoplasm. The ameba is a 
 protozoan often found in the slime at bottom of stagnant 
 water. Within this is a small, rounded part called the 
 nucleus. Most of the cells of the body differ from 
 the ameba in having a distinct 
 outer covering or cell wall. A grape 
 serves very well to show what a cell 
 is like. The whole body is built up 
 Nucleus. f cells, few of them large enough 
 
 Fig. i. Epithelial Ceils from to be seen by the naked eye. 
 Although the cells are closely 
 
 packed together, each cell leads, in one sense, an inde- 
 pendent life. But all work together to maintain the life 
 of the body. The cell is like the individual in a com- 
 munity. Each lives primarily for itself, yet all work 
 together for the good of the whole. 
 
 Epithelial Cells from the Inside of the Cheek. With the blade of 
 a very dull knife, or the handle of a scalpel, gently scrape the inside of 
 the cheek. Place a little of the white scraping on a slide in a drop 
 of water, cover with a cover slip, and examine under a quarter-inch 
 objective. Many cells will be seen, some of them showing nuclei. 
 Compare these cells with the accompanying figure. 
 
 The Physiological Division of Labor. We are aware 
 of the advantages of division of labor in a community. If 
 
INTRODUCTION. 5 
 
 each person learns to do one thing well, all together work 
 economically for the common good, time is saved, and 
 better goods are produced. In the body there is a division 
 of labor similar to that of a community. Each organ has 
 its own work to do, and all work together for the common 
 welfare. The cells of each tissue have certain properties 
 and peculiarities of form differing from the form and 
 properties of the cells of any other tissue. While the 
 general structure of all cells is essentially the same, and 
 while they all have certain properties in common, each has 
 some one kind of work that it can do well, and to which 
 work it devotes itself. The nerve cells receive impressions 
 from the outer world, carry nervous impulses, and control 
 the various activities of the body. The muscle cells have 
 as their work the production of motion. All the cells 
 must take food for themselves and grow. Each has a 
 birth, life, and death, as each individual in a community 
 of men ; and as the community endures, while the indi- 
 vidual members are continually changing, so, in the body, 
 while the form remains about the same from year to year, 
 the cells are continually changing, some dying, and others 
 taking their places. . 
 
 In an animal of a single cell, like the ameba, the one 
 cell must do everything for itself. The higher animals all 
 begin their individual life as an egg, which is, in fact, a 
 single minute cell. This grows and divides, forming two 
 cells. By repeated division there accumulates a mass 
 of cells. These take on the arrangement peculiar to the 
 kind of animal from which the egg came. But as the cells 
 increase in number one group of cells takes up one part 
 of the work of .the body, other cells another part of the 
 work, and so on. 
 
 In studying history (sociology) we have to deal with the 
 
6 J'HYSIOLOGY. 
 
 individual, the community, the state, and the nation. The 
 cell is an individual, the community is a tissue, the state is 
 an organ, and the nation is one body. 
 
 Let us proceed to study the nature of the individual cell, 
 and the combined actions of these individuals in that com- 
 munity called the human body. 
 
 Summary. i. Health is essential to comfort and efficiency in 
 work. 
 
 2. Our artificial mode of life is at variance with nature's laws. 
 
 3. Only by obeying the laws of nature can we preserve health. 
 
 4. We should learn these laws of nature from the advice and ex- 
 perience of others, and not by the expensive process of suffering from 
 disobedience. 
 
 5. Anatomy is the science of structure. Human anatomy is the 
 science of the structure of the human body. 
 
 6. Physiology is the science of function. 
 
 7. Hygiene is the art of preserving health. 
 
 8. Cells are the units of structure in the body. 
 
 9. A tissue is a group of similar cells having a single function. 
 
 10. An organ is a part having a special work or function. The 
 organs work together for the common good of the whole organism. 
 This working together results in 
 
 1 1 . The physiological division of labor, in which each organ works 
 for all the others, and is dependent on all the other organs. 
 
 Questions. i. What are some of the ways in which we most fre- 
 quently violate the laws of health ? 
 
 2. Name the more important organs of the body and their functions. 
 
 3. Name the different tissues of one of these organs. 
 
CHAPTER II. 
 MOTION. 
 
 Motion and Life. Motion is the most manifest sign of 
 life. While we are sitting still, as we say, there are fre- 
 quent slight motions of the head, body, and limbs. Even 
 during sleep the movements of breathing may be seen ; 
 the hand laid upon the chest may feel .the beating of the 
 heart, and the finger detect the pulse in a number of 
 places. 
 
 We must move to get our food, or at least to eat and 
 digest it. Motion is necessary for breathing, for circu- 
 lating the blood, for getting rid of wastes. We often move 
 to avoid injury. 
 
 Motion is necessary for seeing : we must turn the face 
 toward the object; we move the eyeballs; within the eye 
 are motions to regulate the amount of light admitted, and 
 to adapt the eye for seeing at different distances. 
 
 In feeling, we put forth the hand to touch the object. 
 In tasting, we touch the tongue to the object. In smelling, 
 we sniff ; and sniffing is a respiratory motion. In hearing 
 and in speech there is also motion. 
 
 How are all these motions produced ? 
 
 Experiments with the Muscles in our own Bodies. i. Clasp 
 the front of the right upper arm ; draw up the forearm strongly 
 and as far as possible. Note what changes are felt in the biceps 
 muscle. 
 
 2. Repeat the experiment, and with the thumb and finger feel the 
 cord, or tendon, at the lower end of the muscle, just within the angle of 
 the elbow. 
 
 7 
 
8 PHYSIOLOGY. 
 
 3. Place a weight in the hand, and repeat the act, noting the con- 
 dition of the muscle during the experiment ; also note the condition 
 of the tendon. 
 
 4. Span the muscle, placing the tips of the fingers in the angle of 
 the elbow, and the tip of the thumb as far as you can up the arm ; again 
 bend the arm. What change in the muscle does this show ? Any 
 muscle that bends a limb, as does the biceps, is called a flexor muscle. 
 
 5. Clasp the back of the right upper arm ; forcibly straighten the 
 arm. The muscle lying along the back of the arm is the triceps muscle. 
 It is called an extensor muscle because it extends, or straightens, the 
 arm. 
 
 6. Clasp the upper side of the right forearm near the elbow ; 
 clench the right hand quickly and forcibly ; repeat rapidly. 
 
 7. Notice the thick mass of muscle at the base of the thumb ; 
 pinch the forefinger and thumb strongly together. What changes can 
 be seen and felt ? 
 
 8. Place the hand on the outside of the shoulder ; raise the arm to 
 a horizontal position; repeat with a weight in the hand. 
 
 Fig. 2. The Shortening and Thickening of the Biceps Muscle in raising the 
 Forearm. 
 
 9. Stand erect with the heels close to each other, but not quite 
 touching; let the arms hang freely by the sides; rise on tiptoes, 
 without moving otherwise ; repeat ten times. 
 
 10. Place the tips of the fingers on the angles of the lower jaw; 
 shut the teeth firmly on a piece of rubber, and note the bulging of the 
 masseter muscles. 
 
MOTION. , 9 
 
 11. Press the fingers on the temples ; again shut the jaw firmly, and 
 feel the action of the temporal muscles. 
 
 12. Make a narrow band of paper that will snugly fit the forearm 
 when the hand is open ; now clench the fist strongly. 
 
 13. With a tape measure take the circumference of the upper arm 
 when the arm hangs free ; again when the forearm is strongly flexed. 
 
 14. In the same way measure the forearm when the hand is open, 
 and when the hand is clenched. 
 
 By these experiments we learn that when a muscle works it becomes 
 shorter, thicker, and harder. 
 
 Nerves and Muscles of a Rabbit's Leg. In the hind leg of a 
 rabbit the sciatic nerve may be found by separating two large 
 muscles on the sides of the thigh, beginning behind the knee joint. 
 The shape and connections of the muscles may be learned, and also 
 the distribution of the nerve. 
 
 The Action of Muscle. The action of muscle is always 
 a "pull." The muscle shortens, at the same time thick- 
 ening and hardening. These changes in muscle are 
 roughly shown in the preceding experiments of feeling 
 the arm during its action. But the isolated calf muscle of 
 the frog may be made to prove the characteristic changes 
 with great clearness. 
 
 Action of Frog's Muscle. A frog may be killed painlessly by put- 
 ting a teaspoonful of ether into a fruit jar of water, immersing the frog 
 and capping the jar. When the frog becomes motionless, its head 
 should be cut off and a wire run down the spinal column to destroy the 
 spinal cord. After cutting the skin around the base of one thigh the 
 skin may easily be stripped from the whole hind limb. If the muscles 
 on the back of the thigh be gently separated there will be found a white 
 thread running lengthwise, the sciatic nerve. It should be severed 
 near the hip and carefully turned down upon the calf muscle. It should 
 not be pinched or dragged. The muscles of the thigh should now all 
 be cut away, being careful not to sever the nerve near the knee. The 
 hip joint should be unjointed. With the handle of the scalpel the calf 
 muscle should be separated from the shin bone, and just below the 
 knee the shin bone and all the muscles except the calf muscle severed 
 
10 
 
 PHYSIOLOGY. 
 
 It now the heel cord be cut off below the heel there will remain such a 
 preparation as is represented in the accompanying figure, consisting of 
 the thigh bone with the calf muscle hanging from it, and the sciatic 
 
 Femur 
 
 Origin ~ 
 
 Belly of Muscle - 
 
 Insertion 
 
 Weight 
 
 SHORTENED 
 
 ELONGATED 
 
 Fig. 3. Action of the Calf Muscle of the Frog, showing the Relations of the 
 Sciatic Nerve. 
 
 Origin 
 
 Bundle of Muscle Fibers 
 
 nerve still connected with the calf muscle. This may be supported by 
 holding the end of the thigh bone in a clamp on a retort stand. A 
 
 light weight should be attached to 
 the heel cord. The muscle and 
 nerve should be moistened with 
 water containing a little salt. On 
 pinching the free end of the nerve, 
 or cutting off the least bit with 
 scissors, the muscle will be made 
 to act. The shortening and thick- 
 ening will be plainly seen, and 
 by taking it between the thumb 
 and finger the hardening may be 
 felt. 
 
 Muscle Sheath 
 
 CROSS SECTION 
 
 Tendon 
 
 Insertion 
 LONGITUDINAL SECTION 
 
 Fig. 4. The Structure of Muscle. 
 
 Structure of Muscle. 
 
 Chipped beef shows well 
 the structure of muscle. The 
 
MOTION. 
 
 II 
 
 white network is the connective tissue. In the meshes 
 is the red muscular tissue. The partitions which run all 
 through the muscle are continuous with the muscle sheath, 
 and both are continuous with the tendons at the ends of 
 the muscle. In fresh muscle the sheath and the parti- 
 tions are nearly transparent, and are not easily seen. 
 When the meat is cooked or salted the connective tissue 
 becomes white and opaque. 
 
 Microscopic Structure of Muscle. In frog's or rabbit's muscle 
 observe the thin, transparent membrane covering the muscle, the muscle 
 sheath. With forceps tear away part of the 
 muscle sheath. Tear the muscle to pieces, 
 and note its fibrous structure. A shred of 
 muscle may be mounted in a drop of nor- 
 mal saline solution on a slide, and exam- 
 ined with low power of the microscope. If 
 examined with a higher power the cross- 
 markings, or striations, will be seen. Such 
 muscle is called striated or striped muscle. 
 All of the muscles used in ordinary motions 
 are of this kind. 
 
 Fig. 5. Two Muscular Fibers 
 showing the Terminations of 
 the Nerves. 
 
 Effects of Cooking Muscle. In 
 well-cooked corned beef the connec- 
 tive tissue is thoroughly softened, 
 
 and the muscle fibers are easily separated. Thorough 
 cooking, especially slow boiling, will soften the connective 
 tissue, and may render palatable meat that, cooked other- 
 wise, would be exceedingly tough on account of the large 
 amount of connective tissue. 
 
 Imitation of Structure of Muscle. A good way to 
 represent the structure of muscle is to take a number of 
 pieces of red cord to represent the muscle fibers. Wrap 
 each in white tissue paper ; this represents the individual 
 
12 
 
 fiber sheath. Lay a number of these side by side ; wrap 
 all in a common sheath ; let the tissue paper project be- 
 yond the threads, and here compress it into a compact 
 cylinder ; this last corresponds to the tendon. 
 
 Connective Tissue the Skeleton of Muscle. If all 
 the muscular tissue were removed from a muscle, the 
 sheaths and partitions would remain, just as they do in a 
 squeezed lemon or orange. The connective tissue forms 
 a framework for all the soft tissues of the body, and if 
 their working cells were removed, the connective tissue 
 would remain, and show more or less completely the form 
 of the part. Connective tissue, therefore, may be called 
 the skeleton of the soft tissues. Muscle consists, then, 
 essentially of a collection of soft, transparent tubes, filled 
 with the semi-fluid muscle substance. By scraping the 
 surface of a steak with a dull knife the muscle substance 
 may be obtained, leaving the connective tissue. This is a 
 good way to get the nutritious part of beef for an invalid. 
 
 Importance of Muscles. The different materials of 
 which the body is built up are called tissues. Thus we 
 find muscular tissue, bony tissue, nervous tissue, etc. The 
 muscles make up nearly half of the weight of the body. 
 This fact of itself should lead us to consider the muscles 
 of high importance. Add to this the facts above noted, 
 that the muscles are so largely concerned in the nutrition 
 of the body, the chief agents for its protection, essential 
 for the reception of ideas, and absolutely indispensable for 
 the expression of ideas, and we can see the reason for 
 beginning the study of physiology with the examination 
 of the muscles and their action. 
 
 Laws of Muscle Action. The chief characteristic of 
 muscle is its ability to shorten ; incidentally, it at the 
 
MOTION'. 1 3 
 
 same time thickens and hardens. But it does its work by 
 shortening, pulling on the bones by means of the strong, 
 inelastic tendons, thus producing motion. The action of 
 the muscle as a whole is the result of the characteristics 
 of the cells of which it is composed. The individual cells 
 and fibers shorten, and their combined action is seen in 
 the muscular movement. 
 
 Extent of Muscle Shortening. A muscle may be 
 made to shorten one third of its length, but probably 
 never shortens that much in the living body. 
 
 Duration of Muscle Shortening. A muscle cannot be 
 kept shortened for any great length of time. If one holds 
 his arm out horizontally as long as possible he soon feels ' 
 fatigue, later pain, and he may feel soreness in the muscle 
 for several days. The law of muscle action is to alternate 
 periods of rest with periods of action. In many exercises, 
 as in walking, the limbs act alternately, one resting or 
 recovering position while the other works. 
 
 Alternate Action of Flexors and Extensors. If we 
 
 consider the biceps and triceps of the arm, we see that 
 they are compelled to act alternately if they would do 
 effective work. They might both shorten at the same 
 time, and are made to do so in such an attempt as that 
 of holding the arm rigidly bent at a right angle ; as, for 
 instance, in wrestling " square hold," in which case one 
 wishes to prevent his opponent from either pushing or 
 pulling him. But while the two muscles act, no motion is 
 produced. When the flexor shortens, the extensor length- 
 ens, and vice versa. 
 
 Normal Condition of Muscle. The muscles are always 
 slightly stretched, as shown by the fact that when a cut 
 is made into a muscle the wound gapes open ; the tension 
 
14 PHYSIOLOGY. 
 
 of the muscle is further shown by the fact that when a 
 bone is broken, as in the upper arm or thigh, the ends 
 of the bones slip by each other, and the limb has to be 
 strongly stretched to bring the ends back together. Mus- 
 cles act better when slightly stretched, and probably need 
 a slight resistant action of the opponent muscle. 
 
 Symmetrical Development of the Muscles; The mus- 
 cles of the two sides of the body are the same in number 
 and arrangement. At birth they are probably about equal 
 in size, weight, and strength. Most persons early become 
 right-handed, and the greater use of the right hand and 
 shoulder makes the muscles of this side larger and heavier. 
 The muscles pulling on the bones slightly modify them 
 in shape. The whole body may become noticeably un- 
 symmetrical. Most persons step harder on one foot than 
 the other, as shown by the sound of the footstep, and as 
 shown by the constant wearing of one shoe sole or heel 
 faster than the other. In many persons one shoulder is 
 habitually carried higher than the other. Symmetrical 
 development should be carefully sought, and any tendency 
 to a one-sided development should, so far as possible, be 
 avoided. We should use the left hand more. There are 
 many advantages in being able to use either hand. In 
 carving, in shaving, in bandaging, in administering medicine, 
 it may be necessary to use the left hand skillfully. The 
 pianist and the harpist use the two hands about equally, 
 while the violinist puts much more skill into his left hand. 
 Trainers of athletes often begin by developing the left 
 side of the body till it equals the right in size and strength. 
 
 Muscles the Source of Strength. Our strength de- 
 pends on our muscles. It is a fine thing to have strong, 
 well-developed muscles, not only because they give beauty 
 
MOTION, 1 5 
 
 of form, but because extra strength and endurance may 
 be needed in case of accident, to save one's own life or that 
 of others. In a case of fire the ability to climb, to go up 
 or down a rope "hand over hand," may be all important. 
 Any one's life may depend on his ability to run far and 
 swiftly, to swim, to jump, or to lift a heavy weight. 
 
 Skeletal Muscles. When we look at the skinned car- 
 cass of an animal in the market, we observe that the mus- 
 cles almost completely cover the bones. Those which are 
 attached to the bones are called skeletal muscles. They act 
 upon them as levers, giving to motion strength, quickness, 
 and precision. Without bones our motions would be like 
 those of an earthworm or slug, slow and uncertain. The 
 muscles, acting through the bones, can lift a weight that 
 would crush the muscles if laid directly upon them, while 
 a bone, able to support a heavy weight without being 
 crushed, has no power in itself. The muscles have active 
 strength, the bones have passive strength. 
 
 Relation of the Muscles and the Bones. Suspend the skeleton 
 from the ceiling in the most open space in the room. Let the pupils 
 study it ; not to learn the names of all the bones, but to get a general 
 idea of the forms and relations of the parts. It is well to have the 
 skeleton constantly at hand, to show the location of the various organs 
 as they are taken up. If possible, supply the class with separate bones 
 from another skeleton, and let the pupils place each separate bone 
 alongside the corresponding one in the complete skeleton. 
 
 Pass to the skeleton, and locate the biceps muscle. After examining 
 Fig. 2, show the points of its origin and insertion. Feel the biceps 
 of your arm. Note that its thickest part is opposite the most slender 
 part of the bone. But at the enlarged end of the bone the muscle has 
 narrowed to a slender tendon, which passes over the joint to be attached 
 to the next bone, thus giving more slenderness, flexibility, and freedom 
 of motion to the joint. The muscle which closes the mouth, as in 
 pursing up the lips, is not attached to any bone, but in shortening 
 reduces the aperture. 
 
1 6 /'//}'S/OUhi}'. 
 
 Flexion of the Forearm. Take the bones of the arm that are 
 articulated (if there is not an artificial hinge at the elbow, one can 
 readily be made of wire) ; put a strong rubber band in place of the 
 biceps muscle ; fasten this to the head of the humerus by cords, and 
 by the lower end to the radius, where the rough place, an inch or so 
 from the elbow joint, shows the insertion of the tendon. Have the 
 rubber stretched so that when not held it will flex the forearm. This 
 will serve to show the action of the biceps, though we must be careful 
 to bear in mind that the muscle does not pull the arm up because it has 
 been stretched, as is the case with the rubber. In the case of the 
 muscle, we know that the live muscle has the power of shortening when 
 stimulated, and in this respect is totally unlike the rubber. The live 
 cells, or units, act in concert. 
 
 Levers. The essentials of a lever are the point about 
 which the lever turns, called the fulcrum, the place where 
 the power is applied, called the power, and the part to be 
 moved, called the weight. In the body, the fulcrum is 
 some joint, the power is the place where the muscle is 
 attached, and the weight is the part to be moved. 
 
 Kinds of Levers. In flexing the forearm, the weight 
 is the hand or the hand and what is in it ; the fulcrum is 
 the elbow joint ; and the power is the point where the 
 tendon of the biceps is attached to the radius. This kind 
 of a lever is what the books call a lever of the third class. 
 The triceps, on the back of the arm, pulls on the projection 
 of the ulna (the inner bone of the forearm when the palm 
 is up), back of the elbow. The elbow is here, also, the 
 fulcrum, and the hand (or the object to be pushed by the 
 hand) is the weight. This kind of lever, where the fulcrum 
 is between the power and the weight, is called a lever of the 
 first class. In raising the weight of the body, by stand- 
 ing on tiptoe, we use a lever of the second class. Here 
 the ball of the foot is the fulcrum. The weight is the 
 weight of the whole body, resting on the ankle joint, while 
 
MOTION. I/ 
 
 the power is the calf muscle. We may find many exam- 
 ples of levers in the body if we look for them. 
 
 (1) Tapping on Floor. (2) Rising on Toe. (3) Lifting Weight. 
 
 Fig. 6. Three Kinds of Levers as shown by the Foot. 
 
 P Power. W Weight. F Fulcrum. 
 
 Kinds of Levers shown by the Foot. The different 
 classes of levers may be further illustrated by different 
 motions of the foot. In tapping the toes on the floor 
 while the heel is lifted, or in pressing down the ball of the 
 foot while running the treadle of a sewing machine, we 
 have an example of a first-class lever. In raising the 
 weight of the body on tiptoes, or as the foot is used in 
 taking each step, the foot is used as a lever of the second 
 class. When one lifts a weight with the toes, the foot is 
 used as a lever of the third class. These three classes of 
 levers are illustrated in the accompanying figures. 
 
 Advantages and Disadvantages of Levers in the Body. The 
 
 action of the bones of the forearm as a lever may perhaps be better 
 understood by the following considerations : If the arm consisted 
 merely of the biceps, suspended from the shoulder, it is evident that 
 its only action would be a straight pull. Suppose the biceps, thus 
 hanging alone from the shoulder, had a hook at its lower end, it could, 
 when it shortened, lift a weight just as far as it shortened, and no 
 
i8 
 
 PHYSIOLOGY. 
 
 farther. It could not swing the wi:ight outward, or push it upward. 
 But from the way in which the biceps is attached to the forearm, when 
 the muscle shortens an inch it may move the hand a foot. Of course 
 the hand moves much faster, and we have a great gain in speed by 
 reason of this lever arrangement. But we cannot lift so heavy a weight 
 
 at this faster rate, as we could at the 
 elbow. For instance, suppose one were 
 to carry a heavy basket with a bail 
 handle by slipping the arm through 
 the bail up to the elbow. Now. it is 
 evident that the biceps is supporting 
 the weight. If it is as heavy as can be 
 held here, we know that we could not 
 hold the same weight in the hand with 
 the elbow bent at a right angle. 
 
 Ball 
 
 Articular Extremity 
 
 Medullary Cavity 
 
 Hard Bone 
 
 Study of One of the Long Bones. 
 For this, take, preferably, a femur 
 or a humerus. Let us suppose we ha\ 
 a femur. 
 
 1. Observe its shape, cylindrical, 
 somewhat curved, enlarged at the ends. 
 
 2. The ends have smooth places, 
 where they fitted other bones. 
 
 3. Along the sides, especially near 
 the ends, are ridges and projections, 
 where the muscles were attached. 
 
 4. There are small holes in the 
 bone, where blood tubes passed in and 
 out. 
 
 5. Saw a femur in two, lengthwise, 
 and make a drawing showing : 
 
 (#) The central marrow cavity. 
 
 () The spongy extremities, noting especially the directions of the 
 bony plates and fibers. 
 
 6. Observe the width of the lower end of the femur, where it rests 
 on the tibia. Suppose these two bones were as narrow at their ends, 
 where they meet to form the knee joint, as they are at their centers, 
 what kind of a joint would they make ? Illustrate by piling up a num- 
 
 Spongy Bone 
 
 Articular Extremity 
 
 r. 7. Longitudinal Section of 
 Femur. 
 
MOTION. 
 
 her of spools on end ; the column is more lightened than it is weak- 
 ened by the hollowing out of the sides of each spool. And the central 
 hollow of the spool does not greatly weaken it. A given weight of 
 material has more strength when in the form of a hollow cylinder. The 
 bones combine well two very desirable quali- 
 ties, lightness and strength. If in our col- 
 umn of spools we place a wide rubber band 
 around the junction of two spools, we have 
 something very similar to the capsular liga- 
 ment, which surrounds the joints. 
 
 Joints. The ends of the bones, where 
 they fit together in the joints, are covered 
 with a layer of smooth, elastic, whitish or 
 transparent cartilage. The motion in the 
 joints is made still more easy by the synovia, 
 resembling white of egg. The ends of the 
 bones are held together by tough bands and 
 cords of ligament, a form of connective 
 tissue very much like tendon. Bones are 
 closely covered by a tough coat of connective 
 tissue called the periosteum. 
 
 All these structures can easily be found 
 by dissecting a sheep shank gotten from the 
 butcher, or in the hind leg of a rabbit. 
 
 Locomotion. Locomotion is mov- 
 ing from place to place and should 
 be distinguished from mere motion. 
 By continuing such observations as 
 we made when we began to study 
 our motions, we can analyze and 
 understand many of the common 
 movements which we habitually 
 make. 
 
 Standing. Although we are not ordinarily conscious of 
 the fact, when we are standing still we are using many 
 muscles. The accompanying figure illustrates how some 
 
 Action of the Muscles 
 in Standing. 
 
20 PHYSIOLOGY. 
 
 of the muscles act in keeping the body upright. Our 
 weight, or, we would better say, the force of gravity, is 
 continually trying to pull us down to the ground. The 
 joints are all freely movable, and hence as soon as the 
 muscles cease to act properly, in balancing against each 
 other, we lose our equilibrium, and fall if we do not 
 quickly regain it. 
 
 Walking. In walking, we lean forward, and if we take 
 no further action we fall. But we keep one foot on the 
 ground, pushing the body forward, while the other leg is 
 flexed and carried forward to save us from the fall. We 
 catch the body on this foot, and repeat the action. To 
 show how we are really repeatedly falling and catching 
 ourselves, recall how likely one is to fall if some obstacle 
 is placed in the way of the foot as it moves forward to 
 catch the weight of the body. 
 
 Running. In running, the action is more vigorous. 
 The propulsion by the rear leg is now greater. It gives 
 such a push as to make the body clear the ground, whereas 
 in walking, the rear foot is not lifted till the front foot 
 touches the ground. But in running there is a time when 
 both feet are off the ground. 
 
 Locomotion by Reaction. Take two broomsticks and place them 
 crosswise under the ends of a board. Run along the board. This 
 shows that the direct effort in running is to push one's support from 
 under him. When a horse plunges forward in the mud, he only thrusts 
 his feet farther into the mud. Our effort in progression is primarily to 
 push the earth out from under us, and it is by reaction that we go 
 forward. It is the same problem with the fish swimming forward by 
 striking backward and sideways against the water, and with the bird 
 beating downward and backward upon the air. 
 
 Bones combine Lightness and Strength. The mus- 
 cles, then, make use of the bones as levers. We carry 
 
MOTION. 21 
 
 these levers with us all the time. Hence the desirability 
 of having them as light as is consistent with the requisite 
 degree of strength. The body follows the same law of 
 mechanics that we use outside of the body. A hollow 
 pillar or hollow tube has a greater strength than the same 
 amount of material in the form of a solid cylinder. The 
 long bones of the limbs are hollow, and near their ends, 
 where we have found that they need to be enlarged, we 
 find a spongy structure, where lightness and strength are 
 secured by the interlacing fibers and plates of bony 
 material. 
 
 Uses of Bones. The part that the bones play is of a 
 passive nature ; they support the tissues, protect some 
 parts, and serve as levers on which the muscles act. We 
 may not call the bones dead tissues, for they receive blood 
 and grow. But the active muscles use them as a man uses 
 a crowbar, as a mere tool. It will therefore be more 
 interesting to return to the muscles, and learn the causes 
 and conditions of their activity. 
 
 What makes Complex Muscular Action Harmoni- 
 ous. Have you ever seen two persons, each using the 
 right hand, try to sew, one holding the cloth, the other 
 using the needle ? Would they get along well ? Suppose 
 one were to hold the needle, and the other were to try to 
 thread it, each using one hand ? Why is it that the right 
 hands of two persons cannot work so well together as the 
 right and left hands of one person ? What connection is 
 there between the two, that one knows just what the other 
 is doing and when it does it ? Why can two individuals 
 never, with any amount of practice, work so in unity as the 
 parts of the individual ? 
 
22 PHYSIOLOGY. 
 
 Let us seek the answers to these questions in the follow- 
 ing lessons. 
 
 READING. How to Get Strong and How to Stay So^ 
 Blaikie ; Sound Bodies for Onr Boys and Girls, Blaikie ; 
 Physiology of Bodily Exercise, Lagrange. 
 
 Summary. i . Motion is involved in nearly every activity of the 
 body. 
 
 2. The action of muscle is a shortening, accompanied by a thick- 
 ening and hardening. 
 
 3. Muscle consists of fibers with a connective tissue sheath for 
 each fiber, bundle of fibers, and for the muscle as a whole. 
 
 4. The skeletal muscle fibers are striated. 
 
 5. The muscles make about half the body's weight. 
 
 6. Muscles may shorten one third their length. 
 
 7. They cannot remain shortened long at a time. 
 
 8. The muscles should be developed symmetrically. 
 
 9. In the limbs the muscles are fusiform and have their greatest 
 diameter opposite the central, or narrower, portions of the bones, con- 
 cealing the fact that the bones are largest at the ends, as is so manifest 
 in the skeleton. 
 
 10. The bones serve as levers by which the muscles exert their 
 force. 
 
 1 1 . The bones of the limbs are hollow cylinders combining lightness 
 -and strength. 
 
 12. The joints have a smooth motion due to the cartilage and 
 synovia. 
 
 13. Locomotion is brought about by reaction. 
 
 Questions. i . What effect is produced by carrying a heavy satchel 
 for a long distance without resting? 
 
 2. Which is more tiresome, standing still or walking? Why? 
 
 3. When the boy, who thinks he can strike a hard blow, says, 
 Feel my muscle,' 1 does he usually call attention to the muscle used in 
 striking? 
 
 4. Find other examples of levers in the body. 
 
 5. Find examples of the three kinds of levers, not in the body, 
 which we use often. 
 
MOTION. 23 
 
 6. Why is it easier to sit with one leg crossed over the other? 
 
 7. What is the effect on muscles of light clothing? 
 
 8. How may the arms be used to illustrate the three kinds of 
 levers ? 
 
 9. Analyze and explain jumping, hopping, etc. 
 
 10. What is "curvature of the spine"? How caused and how 
 avoided ? 
 
 1 1 . What makes people bow-legged ? 
 
 12. Why are the sides of the body often sore after walking on icy 
 pavements ? 
 
CHAPTER III. 
 
 THE GENERAL FUNCTIONS OF THE NERVOUS SYSTEM. 
 SENSATION AND MOTION. 
 
 What makes Muscles Shorten ? We have seen that 
 the muscles have the power of shortening ; that in shorten- 
 ing they act on the bones as levers to produce our varied 
 motions. What makes the muscles shorten ? 
 
 Voluntary and Involuntary Motions. Some motions 
 we will to make. We will to sit, to stand, to walk, to run, 
 or to stretch out the hand. Such motions, originating in 
 a brain activity, are called Voluntary. Other motions are 
 Involuntary. The will does not control the heart beat. 
 Most persons cannot keep from winking when a quick 
 motion is made toward the face, even if they know they 
 will not be hit. But all of these motions, whether volun- 
 tary or involuntary, are dependent upon the nervous 
 system. 
 
 The Cerebro-spinal Nervous System. This consists 
 of the brain, the spinal cord, and the spinal nerves. The 
 brain will be described later. 
 
 The Spinal Cord. The spinal cord is a cylindrical 
 body extending from the brain along the cavity of the 
 spinal column. Its diameter is not uniform throughout. 
 Between the shoulders is an enlargement called the cer- 
 vical enlargement, where the large nerves are given off to 
 
 24 
 
NERVOUS SYSTEM. 
 
 Fig. 9. Diagram showing Arrangement of Nervous System. 
 
26 PHYSIOLOGY. 
 
 the arms. In the region of the loins is the lumbar enlarge- 
 ment, where the nerves are given off to supply the poste- 
 rior limbs. The cord is not so long as the cavity of the 
 spinal column, and the space posterior to the cord is occu- 
 pied by the nerves extending to the posterior limbs, and 
 these nerves are given off at a very sharp angle, and con- 
 tinue backward for some distance before they emerge 
 from the cavity of the spinal column. But in the region 
 of the shoulders the nerves spring off at about a right 
 angle with the cord. The outside of the cord is white, but 
 the central portion consists of what is called gray matter. 
 The white portion is made up of fibers, but the gray matter 
 consists of nerve cells as well. 
 
 The Spinal Nerves. These are given off in pairs from 
 the sides of the spinal cord, passing out between the suc- 
 cessive vertebrae. In the regions of the shoulders and 
 loins the spinal nerves are large, as they supply the large 
 muscles of the limbs ; but in the middle of the back, where 
 only the muscles of the body wall are supplied, the nerves 
 are small. We have thirty-one pairs of spinal nerves. 
 
 The Roots of the Spinal Nerves. Each spinal nerve 
 arises by two roots, one nearer the back, called the dorsal 
 root, the other nearer the ventral surface, the ventral root. 
 These two roots soon unite to form one spinal nerve. 
 
 The Ganglion of the Dorsal Root. On the dorsal 
 root, just before it unites with the ventral root, is a swell- 
 ing, the ganglion of the dorsal root. Like all ganglions, it 
 is largely made up of nerve cells, being a center of con- 
 trol rather than a means of communication. 
 
 The Cerebro-spinal Nervous System of the Rabbit or Cat. It 
 will prove helpful at this point to examine the nervous system of a 
 
NERVOUS SYSTEM. 2*] 
 
 rabbit. The animal may be killed painlessly by shutting it in a tight 
 box with a sponge holding a teaspoonful of chloroform or ether. The 
 smaller the box, the less anesthetic necessary. A large glass jar inverted 
 over the animal is convenient. 
 
 For a support, nail a foot of two-by-four scantling edgewise to a base 
 board. Lay the animal on this and tack out the feet. Slit and pull 
 aside the skin from the nose along the back to the base of the tail. 
 Remove the muscle along the sides of the back and neck. Between 
 the skull and the first vertebra is a space covered by a thin membrane. 
 This may be cut through with scissors. Then bone forceps may be 
 employed by inserting the point of a blade on each side of the cord and 
 cutting through the bone. In this way the whole of the dorsal portion 
 of the spinal column may be removed, exposing the spinal cord through- 
 out its entire length. With care the nerves and their roots may be 
 found. The nerves extending to the anterior limbs are easily traced, 
 but for the nerves to the posterior limbs more work is needed. 
 
 Structure of Nerves. When we trace the sciatic nerve 
 outward, we find that it is continually subdividing. This 
 division continues until the branches are too small to be 
 seen by the naked eye. Microscopic examination shows 
 that a nerve is made up of a great number of fibers bound 
 together in a common sheath of connective tissue, as is 
 the case with muscle. When the nerve divides there is 
 ordinarily no true branching or forking, but certain of 
 the fibers simply separate from the rest, as in the separa- 
 tion of the fibers in floss silk. 
 
 Structure of a Nerve Fiber. A single nerve fiber is 
 too small to be seen by the naked eye, being only about 
 one two-thousandth of an inch in diameter. It consists of 
 the following parts : 
 
 1. The Axis Cylinder, a central strand, or core, of semi- 
 transparent, gray material. 
 
 2. The Medullary Sheath is a layer of white, oily 
 material around the axis cylinder. 
 
28 rnvsjoLOGY. 
 
 3. The Nerve Fiber Sheath is a thin, transparent outer 
 sheath of cdnnective tissue. 
 
 Function of Nerve Fibers. -The sole function of the 
 nerve fiber is to convey nerve impulses. The nerve im- 
 pulse passes along the axis cylinder as an electric current 
 passes along an insulated wire. 
 
 Nerve Fiber Sheath 
 
 Axis Cylinder 
 
 Medullary Sheath 
 Fig. 1 0. Structure of a Nerve Fiber. 
 
 Gray Nerve Fibers. In the sympathetic nerves there 
 are many fibers which have no medullary sheath, but con- 
 sist simply of the axis cylinder and the nerve-fiber sheath. 
 These are called gray nerve fibers. 
 
 Cross-section of the Spinal Cord. If a thin slice of 
 the spinal cord be made as shown in Fig. 11, it will be 
 seen that the central part is darker in color than the outer 
 part. The central part is known as the gray matter, in 
 distinction from the rest, which is called the white matter. 
 The white matter of the nervous system is made up of 
 nerve fibers whose structure and use we have just con- 
 sidered. But the gray matter has a different structure and 
 a different function. Instead of being made up mainly of 
 fibers it is composed of cells, one of the forms of which is 
 represented in Fig. 12. Some of the branches of these 
 cells are continued, and become the axis cylinders of nerves, 
 and it is believed that every nerve fiber begins as a branch 
 of some nerve cell. One of the best places to see these 
 nerve cells is in the gray matter of the spinal cord, near 
 
NERVOUS SYSTEM. 29 
 
 the place where the ventral root of the spinal nerve arises. 
 This part of the gray matter is called the ventral horn of 
 the gray matter. If this portion be examined under a 
 moderately high power of the microscope, there may be 
 seen a number of cells with radiating branches. 
 
 Dorsal or Sensor 
 Root 
 
 Ganglion 
 
 i 
 
 Ventral or Motor Root 
 
 Fig. 1 1 . Cross-section of Spinal Cord. 
 
 Functions of the Spinal Cord. The spinal cord has 
 two main functions : 
 
 1. Its conducting power, by means of the white fibers 
 which make up the outer part of the cord. These fibers 
 may be regarded as connecting the gray matter of the 
 brain with all parts of the body. 
 
 2. The gray matter is the center of the reflex actions of 
 the cord. 
 
 Ganglia. Masses of nerve cells make up nerve centers, 
 or ganglia, such as are on the dorsal roots of the spinal 
 nerves. These also would show under the microscope 
 that their chief constituent is a collection of nerve cells 
 which give off one or more branches. 
 
30 /V/KVA >/.(;<;r. 
 
 The gray matter of the spinal cord is considered LI col- 
 lection of ganglions. We see that the outer layer of the 
 brain is grayish in color. Within is white matter, consist- 
 ing of nerve fibers that connect the cells of the gray layer 
 
 Fig. 12. A Large Nerve Cell from the Gray Matter of the Spinal Cord. 
 
 with the various parts of the body through the base of the 
 brain, the spinal cord, and spinal nerves. 
 
 No Sensation without the Brain. After a fowl's head is cut off it 
 " flops " around for some time, and it may even jump clear from the 
 ground. If one takes hold of its feet to pick it up, it may begin to 
 struggle as if it were trying to escape. 
 
 Now, we know that the bird cannot feel anything after its head is 
 cut off, because the body is completely separated from the brain, which 
 is the center of sensation. So with the frog. After its head is cut 
 off, it cannot feel anything. 
 
 Reflex Action of the Spinal Cord of the Frog. A frog may be 
 killed as directed on p. 9. Cut off its head and suspend the body 
 from any convenient support, such as the ring of a retort stand. 
 
 1. On pinching the toes the foot will be drawn up. 
 
 2. The sciatic nerve should now be severed as before directed 
 (p. 9). At the instant of cutting the nerve the muscles below will 
 twitch, because the nerve fibers running to them are stimulated. 
 
NERVOUS SYSTEM. 31 
 
 3. If the toes are again pinched, it is found that the uninjured leg 
 will draw up, but not the one whose sciatic nerve has been severed. 
 
 4. If a wire be run down the spinal cavity, the spinal cord will- be 
 destroyed, and during the operation the uninjured leg will act spas- 
 modically, because the nerve fibers going to its muscles from the cord 
 are stimulated. 
 
 5. Pinching the toes no longer gives response, because the cord, 
 which acted as the center of this reflex action, is destroyed. 
 
 The Gray Matter of the Cord the Center of Reflex 
 Action. In simple sensation of touch, pressure on the 
 
 Afferent Dorsal Root 
 
 Sensor Fiber 
 
 Skin 
 
 Motor Fiber v v 
 
 Efferent Ventrg| Root 
 
 Fig. 1 3. Diagram of Reflex Action of the Spinal Cord. 
 (After Landois and Stirling.) 
 
 toes starts a nerve current or nerve impulse which runs up 
 to the brain. The sensation is in the brain, but is referred 
 to the foot. Hence we should be careful not to speak of 
 a sensation being carried. In voluntary muscular action 
 the impulse starts from the brain, goes to the muscles, and 
 makes them shorten or relax. 
 
 But in reflex action the current runs up the nerve to the 
 spinal cord. The gray matter of the central part of the 
 cord receives the message, and sends back a nerve impulse 
 to the muscles to make them shorten and pull the foot 
 away from the source of injury. 
 
32 PHYSIOLOGY. 
 
 The Parts Essential to Reflex Action of the Spinal 
 Cord : - 
 
 1. A sensitive surface (the skin, for instance). 
 
 2. Afferent nerve fibers. 
 
 3. A nerve cell, or cells, in the center of the spinal cord. 
 
 4. Efferent nerve fibers. 
 
 5. Working organ, as muscle or gland. 
 
 Phases of Reflex Action. In the above experiment 
 on the frog the steps in order were : 
 
 1. Stimulation of the nerve endings in the skin of the 
 toe. 
 
 2. Passage of a nerve impulse up the afferent fibers to 
 the spinal cord. 
 
 Nerve-Cell 
 
 Afferent Fiber ^ \ ,_ _., 
 
 x Efferent Fiber 
 
 Skin !, 
 
 &-- Muscle 
 
 Fig. 14. Scheme of Reflex Arc. 
 
 3. Reception of the impulse by a cell, or cells, of the 
 gray matter in the cord. 
 
 4. Sending back a nerve impulse 
 
 5. Along an efferent fiber, or fibers, to 
 
 6. Muscles which shorten and move the foot. 
 
 Importance of Reflex Action. It is important that 
 we understand the nature of reflex action, for very many 
 of the processes of the body are regulated by it. Not 
 only the more manifest motions, such as winking when 
 
NERl/OUS SYSTEM. 33 
 
 anything comes quickly toward the eye, dodging, jumping 
 when suddenly touched by anything hot or when pricked 
 by a pin, but also the adjustments of the essential processes 
 of life, circulation, respiration, and digestion, are brought 
 about through reflex action. 
 
 Destination of Nerve Fibers. The sciatic nerve is 
 composed of many fibers. If this nerve is traced outward, 
 it is found to be continually subdividing, and sending small 
 branches to the muscles, and finally in the muscles one 
 fine nerve fiber goes to each muscle fiber. (See Fig. 13.) 
 Many fibers go on past the muscles to the skin. We can 
 feel in any part of the skin, and we can tell just where we 
 are touched. These fibers from the skin, then, carry 
 nerve impulses inward, as those going to the muscles 
 carry impulses outward. 
 
 Nerve Roots and their Functions. Experiments on 
 the lower animals, and accidents in the case of man, show 
 that all the fibers of the nerves that carry currents to the 
 muscles pass out from the spinal cord into the ventral 
 root, and that all the fibers that carry currents inward 
 enter the spinal cord through the dorsal root. Hence, the 
 dorsal root is often called the afferent root, and the ventral 
 the efferent root. Since ingoing impulses produce sensa- 
 tion, the dorsal root is called the sensory root, while the 
 ventral root, carrying currents outward to produce motion, 
 is called the motor root. 
 
 Effect of Stimulating a Spinal Nerve. Experiments 
 have shown that if, in an uninjured animal, a nerve, or 
 more properly a nerve trunk, as the sciatic nerve, be 
 stimulated, for instance, by a suitable electric shock, two 
 effects are produced : first, motion in the parts whose 
 
34 PHYSIOLOGY. 
 
 muscles are supplied by the nerve ; second, sensation, 
 which is referred to the parts of the skin supplied by the 
 branches of the nerve. 
 
 Effect of Severing a Spinal Nerve. If. instead of simply stimu- 
 lating the nerve, the nerve is severed, the same two effects will he pro- 
 duced. After severing the nerve, if we stimulate the end of the nerve 
 still connected with the limb, we get action of the muscles in that limb. 
 If we stimulate the end of the nerve connected with the body, a sensa- 
 tion will be produced, and this sensation will be referred to the parts 
 from which the nerve fibers arise, probably in the skin of the limb. 
 
 Effect of Stimulating the Ends of Severed Nerve Roots. If we 
 now turn to the roots of the nerve, and make similar experiments, we 
 obtain the following results : Stimulating the dorsal root causes sensa- 
 tion referred to some outer surface, and no other effect is noticed. 
 Cutting the dorsal root also causes sensation. Stimulating the end of 
 this root still connected with the spinal cord causes sensation: but 
 stimulating the end of the root connected with the nerve gives no 
 appreciable result. 
 
 Stimulating or cutting the ventral root causes motion in the parts 
 whose muscles are supplied by fibers from this root. After severing 
 this root, if the end connected with trie spinal cord be stimulated, no 
 effect is noticed ; but stimulating the end still connected with the nerve 
 is followed by shortening of the muscles supplied. 
 
 Effect of Severing All the Spinal Nerves. Severing 
 all the spinal nerves destroys all power of sensation and 
 voluntary motion in all parts of the body except the head. 
 After severing all the dorsal roots, no sensation would be 
 produced by stimulating any part of the body, and after 
 severing all the ventral roots no act of the will can cause 
 any of the muscles of the body to act. Severing all the 
 nerves, or severing all the roots, cuts off all communication 
 of the brain with the body, and so far as motion and sensa- 
 tion in the body generally are concerned, has the same 
 effect as severing the spinal cord below the head. 
 
NERVOUS SYSTEM. 35 
 
 Cramp. Cramp is a spasmodic shortening of the 
 muscles, attended with pain. 
 
 Tetanus. Tetanus (or locked jaw) is a spasmodic and 
 continuous shortening of the muscles, causing rigidity of 
 the parts they supply. It is due to the disordered and 
 excessive stimulation of the muscles through the nerves. 
 
 Crossing of the Fibers from the Brain to the Spinal 
 Cord. Both the brain and the spinal cord consist of two 
 lateral halves connected by cross fibers. Each half of the 
 brain is connected with the opposite half of the body. 
 This is accomplished by the crossing of the fibers. The 
 fibers that carry nerve impulses outward are now known 
 to cross as they leave the brain, at the very beginning of 
 the spinal cord, in the part known as the spinal bulb. 
 The sensations arising from touching anything with the 
 right hand, therefore, are in the left half of the brain, and 
 the right half of the brain controls the left hand. 
 
 Voluntary Interference with Reflex Actions. We 
 
 have seen that the jerking of the hand away from a hot 
 object is due to reflex action of the spinal cord. One 
 might, by a powerful effort of the will, keep the hand on 
 an object that is hot enough to burn the skin. One may 
 command the foot to remain quiet when it is tickled ; but 
 as soon as the person is asleep, the same stimulations 
 would be followed by the reflex actions such as we have 
 considered. 
 
 In these cases of interference it is understood that the 
 brain sends a nerve impulse down to the centers of the 
 reflex action, and stops or diminishes their operation. 
 This retarding influence of a group of cells is called inhi- 
 bition. It is not always due to voluntary interference, 
 but may be due to reflex interference, as we may see later. 
 
36 rHYSIOLOGY. 
 
 The Nature of a Nervous Impulse. Of the nature 
 of a nerve impulse we know but little. It is convenient 
 to compare the nervous system, with its conducting fibers 
 and central ganglia, to a telegraph system. And electric- 
 ity is the most convenient stimulus for exciting nerve im- 
 pulses. Yet a nerve impulse is very different from an 
 electric current. A nerve fiber is a poor conductor of 
 electricity. An electric current may travel along a copper 
 wire at the rate of between 100,000 and 200,000 miles a 
 second, while a nerve impulse in a motor nerve travels 
 only 1 70 feet in a second. 
 
 Transmission of Motor Impulses. When a motor fiber is stimu- 
 lated in the middle of its course we observe only one effect, the 
 shortening of the muscle at its lower end. But there is every reason 
 to believe that the nerve current, or impulse, runs along the nerve in 
 both directions from its starting point. But while the action of the 
 muscle at the peripheral extremity manifests the existence of the cur- 
 rent, there is nothing at the central extremity to give such evidence. 
 
 Transmission of Sensory Impulses. Similarly, when a sensor 
 nerve fiber is stimulated at some intermediate point, we have a sensa- 
 tion in the brain due to the current brought by the afferent fiber, and 
 which we refer to the outer end of the nerve fiber. Probably a nerve 
 impulse passed from the point of stimulation to the outer end of the 
 fiber ; but as there is nothing at the outer end of the nerve fiber to 
 interpret it, we get no evidence of such impulse except, by refined 
 physiological tests. 
 
 Harmony in Muscle Action. In throwing a stone a 
 number of muscles are used. Each one of these must 
 shorten in the right way and at the right time or the throw 
 will not be accurate. Each muscle shortens under the 
 influence of a nerve impulse started by the brain and 
 brought by a motor nerve. If any muscle shortens an 
 instant too soon, or a little too strongly, the stone goes to 
 
NERVOUS SYSTEM. 37 
 
 one side. In a tune on a piano we know that the right 
 keys must be struck ; that each must be struck at the right 
 time, with the proper degree of force, and held for the 
 right length of time, or we have discord instead of har- 
 mony. What the player is to the instrument, the brain 
 is to the body. 
 
 Temporary Loss of Muscular Power. It may have 
 happened to you that after sitting long in one position you 
 attempted to stand, but found that you could not do so. 
 One leg failed to act at the bidding of your will. When 
 the foot is " asleep " we get little sensation from it ; we 
 hardly know whether it is touching the floor or not. Press- 
 ing on it with the other foot causes no pain. 
 
 We try to stand when the foot is asleep, but we are 
 unable to do so. The brain starts the nerve currents, and 
 they run along the nerve as far as the compressed part ; 
 here they stop. They cannot reach the muscles of the 
 leg below. Hence the muscles do not shorten, and we 
 do not rise, no matter how strongly we will to do so. 
 
 Why is it that the nerves and muscles thus sometimes 
 lose their ability to perform their natural activities ? 
 
 Dependence of Nerves and Muscles. This has been 
 explained by saying that owing to external pressure, the 
 nerve has temporarily lost its power of conducting nerve 
 currents. But what beside the nerve has been com- 
 pressed ? What process in the limb has been interfered 
 with by the pressure due to the position in which one has 
 been sitting or lying ? What is the temperature of the 
 benumbed limb ? 
 
 On what are the nerves and muscles so dependent for 
 the maintenance of their activity ? 
 
38 niYSioi.OGY. 
 
 READING. Power through Repose, Call ; The Technique 
 of Rest, Brackett; Muscles ami Xerres^ Rosenthal. 
 
 Summary. I . Motions are voluntary or involuntary, but all are 
 under control of the nervous system. 
 
 2. The cerebro-spinal nervous system consists of the brain, the 
 spinal cord, and the spinal nerves. 
 
 3. Each spinal nerve has two roots : the dorsal, which is afferent 
 and sensory ; the ventral, which is efferent and motor. 
 
 4. A ganglion is a nerve center largely composed of nerve cells. 
 
 5. Nerves are made up of nerve fibers. 
 
 6. A nerve fiber consists, of the central core (or axis cylinder), 
 which conducts the nerve impulse, the medullary sheath, and, outside, 
 the nerve-fiber sheath. 
 
 7. The spinal cord has in its outer part white nerve fibers, in its 
 center gray nerve cells. 
 
 8. These cells are branched, and at least one branch becomes the 
 axis cylinder of a nerve fiber. 
 
 9. The gray matter of the cord is the center of the reflex action. 
 
 10. The nerve fibers from each half of the brain connect with the 
 opposite half of the body. 
 
 11. The nervous system is comparable to a telegraph system. 
 
 Questions. i. Name as many involuntary motions as you know. 
 
 2. What other cases of reflex action do you know ? 
 
 3. The story is told of a young Roman (Mucius Scaevola) that to 
 show his fortitude he thrust his hand into the fire and held it there 
 until it was destroyed. What physiological action does this illustrate ? 
 
 4. Why is a man partially paralyzed when he has broken his neck 
 or back ? 
 
 5. How does the nervous system differ from a telegraph system? 
 
CHAPTER IV. 
 CIRCULATION OF THE BLOOD. 
 
 The Blood and its Work. We know that if any animal 
 is bled freely, it soon becomes weak, then unconscious, and 
 soon dies, if the escape of blood be not stopped. 
 
 We observe the natural difference in color of different 
 parts of our bodies ; for instance, the lips and cheeks. 
 We often note varying color, as in blushing and pallor. 
 
 We wish to understand these differences and changes ; 
 also to know what to do in case of fainting or bleeding 
 from wounds. We may prolong and make more useful 
 our own lives and those of others by knowing, in a practical 
 way, something about the causes, prevention, and remedies 
 of the colds, congestions, and inflammations to which we 
 are subject. 
 
 Nearly every part of the body bleeds when cut. There 
 is no bleeding when we trim the nails or cut the hair, and 
 the outer skin has no blood in it. But the inner skin, and 
 almost every tissue within it, if pierced even by the finest 
 needle, yields blood. We see a little blood oozing from 
 the surface of a fresh steak or roast. 
 
 What kind of a substance is the blood ? Is it uniformly 
 distributed through the tissues, like water soaked up into a 
 cloth, or is it in distinct cavities ? Why is it so essential to 
 life ? How does it do its work ? 
 
 The Rate of the Heart Beat. The heart beats about 
 seventy-two times a minute in men ; in women, about 
 
 39 
 
4O PHYSIOLOGY. 
 
 eighty. At birth the rate is from one hundred and thirty 
 to one hundred and forty, and gradually decreases till 
 about the age of twenty, when the average of seventy-two 
 is reached. This rate holds till old age, when it increases. 
 The rate is increased by muscular activity, food, external 
 heat, internal heat (fever), pain, and mental excitement. 
 Music accelerates the pulse rate. The pulse rate varies 
 during the twenty-four hours, being lowest during the 
 night, and highest about 1 1 A.M. Certain diseases increase 
 the frequency of the pulse. Some drugs quicken the 
 pulse rate, and others dimmish it. 
 
 The Heart Beat and the Pulse. i . The heart beat, felt at the left 
 of the breast bone. 
 
 2. The pulse, felt at the wrist and at various parts of the body. 
 Perhaps the most convenient place to study it is at the temple. Lay 
 the forefinger lightly along the cheek just in front of the ear. Count 
 the pulsations for a minute. 
 
 Let one or two pupils who are quick at figures step to the blackboard 
 and put down the number of pulsations of each pupil, and divide by the 
 number thus reporting, to get the average. 
 
 1 . Let all in the class count the pulse while sitting. Probably it 
 will be best to discard the first trial, as there are likely to be several 
 failures from one cause or another. Then, too, there is usually a slight 
 excitement at the beginning of a wholly new experiment. Get the aver- 
 age of the class. 
 
 2. Find the pulse while sitting; rise quickly, and immediately begin 
 to count the pulse. Compare with the pulse as taken while sitting. 
 
 3. Compare the pulse before and after meals. 
 
 4. With the thumb and finger lightly clasp the windpipe, well back. 
 The pulse in the carotid arteries will be felt. 
 
 The Position of the Heart. The base of the heart is 
 in the center of the chest, just back of the breast bone, but 
 the apex points downward and to the left. 
 
 The Covering of the Heart. The heart is inclosed in 
 a loosely fitting membranous bag, the pericardium. Within 
 
CIRCULATION OF THE BLOOD. 41 
 
 the pericardium and around the heart ivS a small quantity 
 of liquid, called the pericardial fluid. 
 
 The Size of the Heart. A person's heart is about the 
 size of his clenched hand. 
 
 The External Features of the Heart. The heart is 
 cone-shaped and the bulk of it is made up of the ventricles, 
 the auricles being two ear-like flaps at the base, one on 
 each side. There is a deep notch between the auricles 
 and the ventricles. The line of division between the two 
 ventricles is marked by a groove, which runs obliquely 
 along the ventral surface. In this groove are blood tubes 
 and usually considerable fat. 
 
 The Internal Structure of the Heart. The two halves 
 of the heart are completely separated from one another 
 by a partition. Each half, in turn, has valves which, 
 part of the time, separate the cavity of each auricle (at 
 the base) from the cavity of the corresponding ventricle 
 (at the apex). 
 
 The Valves of the Heart. Between the auricles and 
 the ventricles are curtain-like valves, whose upper edges 
 are attached to the inner surface of the walls at the upper 
 margin of the ventricle. These flaps are somewhat tri- 
 angular, and have strong white, tendinous cords extending 
 from their edges and under surfaces to the walls of the 
 ventricle below. In the right half of the heart there are 
 three flaps, and this valve is called the tricuspid valve. In 
 the left side there are two flaps, which, together, constitute 
 the mitral valve. In the resting heart these flaps hang 
 down along the walls of the ventricles so that on opening 
 the heart one would see only a single cavity in each half 
 of the heart. 
 
42 
 
 The Semilunar Valves. From the base of the right 
 ventricle arises the pulmonary artery. Within its base, 
 just as it leaves the ventricle, are three pocket-like valves, 
 like " patch-pockets." They are in a circle, with their edges 
 touching, and thus surround the opening, with their 
 mouths opening away from the heart. A similar set of 
 valves are within the base of the aorta, which arises from 
 the left ventricle. Both these sets of valves are called 
 semilunar valves. 
 
 Dissection of the Heart. No description (nor even figures) can 
 give a clear idea of the heart. A good model will be of some assist- 
 ance. But the heart itself should be examined carefully and then dis- 
 sected. The heart and lungs of a sheep should be obtained (ask the 
 butcher to save the "pluck," i.e. the heart and lungs taken out together). 
 The relations of the heart to the lungs and other organs should first 
 be studied, and then the pericardium opened. Observe the outside of 
 the heart, and then cut the heart open to see the points given in the 
 above description. After the heart is severed from the lungs the auri- 
 cles may be cut off; then, by pouring water into the ventricle, the 
 action of the valves between the auricles and the ventricles will be 
 seen. Pressing on the outer surface of the right ventricle will make 
 the water escape through the pulmonary artery. If this be split open, 
 the semilunar valves at its base may be found. 
 
 The Blood Tubes connecting the Heart with Other 
 Organs. The aorta (the largest artery in the body) 
 arises from the base of the left ventricle, and supplies 
 with blood every organ of the body except the lungs. 
 The pulmonary artery springs from the base of the right 
 ventricle and sends blood to the right and left lungs. 
 Two large veins enter the right auricle, the precaval vein 
 from the anterior regions of the body and the postcaval 
 vein brings blood from all the organs of the posterior por- 
 tions of the body. The pulmonary veins return the blood 
 from the lungs to the left auricle, two from each lung. 
 
CIRCULATION OF THE BLOOD. 
 
 43 
 
44 
 
 PHYSIOLOGY. 
 
 fL External Jugular Vein 
 
 Internal Jugular Vein 
 
 2 Subclavian Artery 
 b Subclavian Vein 
 1 Carotid Artery 
 
 i Aorta 
 in Precaval Vein 
 
 IV Postcaval Vein 
 
 Gastric Artery 
 Splenic Artery 
 Hepatic Artery 
 Pancreatic Artery 
 
 ff Renal Veins 
 5 Renal Arteries 
 
 T Iliac Arteries 
 i Iliac Veins 
 
 Fig. 16. Distribution of Arteries and Veins. 
 
CIRCULATION OF THE BLOOD. 
 
 45 
 
 The Distribution of the Arteries and Veins. The 
 
 organs of the body receive a supply of blood in propor- 
 tion to their size and activity. The artery supplying the 
 blood and the vein which returns it usually lie side by side 
 (see Fig. 16). The larger arteries are usually deep-seated 
 and in protected places. 
 
 Demonstration of the Action of the Heart. The heart may be 
 mounted as shown in Fig. 17, and its action illustrated by compressing 
 the ventricles with both hands. Instead of the apparatus here shown 
 two retort stands may be used, though not so convenient. 
 
 Capillaries 
 of the Lungs 
 
 Capillaries 
 of the Body 
 
 Fig. 17. Demonstration of the Action of the Heart (Heart Diagrammatic). 
 
 The Action of the Heart. - - The -heart consists of 
 muscle fibers so arranged that they form a thick-walled 
 bag, which stands expanded when the muscles relax. But 
 when the fibers shorten the whole heart contracts, and the 
 
46 PHYSIOLOGY. 
 
 cavity is much reduced in size, if not entirely obliterated, 
 and the blood is forced out. 
 
 The complete action of the heart consists of three parts, 
 the contraction of the auricles, the contraction of the 
 ventricles, and the pause. 
 
 The Pause. During the pause the blood is steadily 
 pouring into the auricles ; into the right auricle from the 
 caval veins, into the left auricle from the pulmonary veins. 
 At this time the curtain-like valves between the auricles 
 and the ventricles are open, and their flaps hang loosely 
 beside the walls of the ventricles. The blood, therefore, 
 as it passes into the auricles, passes on into the ventricles. 
 As the ventricle fills, the valves float up, as seen in the 
 experiment of pouring water into the ventricle. 
 
 The Contraction of the Auricle. When the ventricle 
 is full, but not stretched, and the auricle partly full, the 
 auricle suddenly contracts, thus forcing more blood into 
 the ventricle, and distending it. At the same time the 
 valves, which were already nearly closed, are tightly closed 
 by the pressure of the blood which is forced up behind 
 them. The flaps of the valves are kept from going up too 
 far by the tendinous cords and by the papillary muscles to 
 which the cords are attached. 
 
 The Contraction of the Ventricle. Next comes the 
 contraction of the ventricle, slower, but more powerful 
 than that of the auricle. As the walls of the ventricle are 
 drawn together, the blood is subjected to pressure. It 
 cannot go back into the auricles, for the more it presses 
 against the valves, the more tightly they are closed. The 
 semilunar valves are closed by back pressure in the aorta 
 and pulmonary artery. But the pressure of the blood in 
 the ventricles is so much greater that the semilunar valves 
 
CIRCULATION OF THE BLOOD, 
 
 47 
 
 are forced open, and nearly all the blood is driven out of 
 the ventricles ; from the right ventricle into the pulmonary 
 artery, and from the left ventricle into the aorta. 
 
 While the ventricles are contracting and forcing their 
 blood out, the auricles are slowly filling by the steady 
 inflow through the veins. 
 
 Systole and Diastole. The contraction of the heart is 
 called the systole, and its dilation the diastole. 
 
 Dilation of the Ventricle. As soon as the ventricle 
 has completed its contraction it dilates, and most of the 
 blood that has accumulated in the auricle simply falls into 
 the ventricle. The dilating ventricle exerts a slight suc- 
 tion, so the blood is in part drawn into the ventricle. Dur- 
 ing the remainder of the pause the blood accumulates in 
 
 Auricle 
 
 Fig. 1 8. Diagram of the Heart, showing the Action of the Valves. 
 
 the auricle and ventricle till the auricle again contracts and 
 the cycle is repeated. This is true of both halves of the 
 heart, which work simultaneously, the right heart pumping 
 dark blood while the left heart pumps bright blood. The 
 left ventricle is thicker walled and stronger than the right. 
 
48 PHYSIOLOGY. 
 
 Work and Rest of the Heart. The time taken by the 
 different parts of the heart beat are about as follows : The 
 auricle contracts about one eighth of the time and rests 
 the other seven eighths. The ventricle contracts about 
 three eighths of the time and dilates during about five 
 eighths. If we suppose the whole period of the heart beat 
 to be twenty-four hours (instead of eight tenths of a sec- 
 ond), we can more easily see how much of the time the 
 heart is actually at work, and how much of the time the 
 heart is resting. 
 
 Auricle contracting (working) \ of the time 3 h., resting 21 h. 
 Ventricle contracting (working) f of the time 9 h., resting 15 h. 
 
 No part of the heart, therefore, is working longer than a 
 man would who only works nine hours a day. Some ob- 
 servers state that the resting period is even greater than 
 these figures would show. 
 
 Since the contraction of the ventricles immediately fol- 
 lows that of the auricles, one half of the time is occupied 
 by the whole contraction of the heart, and during half the 
 time the whole heart is resting. This is different from our 
 usual statements regarding the work of the heart. We 
 hear it said that the heart never rests. Its work and rest 
 follow each other at such short intervals that we do not 
 appreciate the interval of rest that comes between the suc- 
 cessive impulses that we feel. Suppose a policeman had 
 the power of sleeping at will, and that he slept thirty min- 
 utes of each hour, and that in the remaining thirty minutes 
 he made the rounds of a block. If we saw him passing 
 regularly once an hour, every hour of the twenty-four, we 
 might suppose that he did not sleep at all during the entire 
 time. This ratio of work and rest is fairly constant in 
 the varying rates of heart beat. 
 
CIRCULATION OF THE BLOOD. 
 
 49 
 
 The Beat of the Heart. The apex of the heart is 
 always in contact with the chest wall. Consequently, it 
 never strikes it. At each beat it pushes hard against the 
 chest wall. This push may be felt and seen, and is called 
 the heart beat. 
 
 The Sounds of the Heart. There are two sounds of 
 the heart : 
 
 1. A short, sharp sound made by the closing of the semi- 
 lunar valves. 
 
 2. Just preceding this sound a longer, duller sound may 
 be heard during the contraction of the ventricles. This is 
 supposed to be due to the vibrations of the walls of the 
 ventricles and of the large valves. 
 
 As soon as 
 
 Nucleus 
 
 Isolated Fibers 
 
 Fibers Joined 
 
 Action of the Large Arteries. The large arteries 
 have in their walls a yellow elastic tissue. When the 
 blood is forced into them, they are stretched, 
 the ventricle ceases to contract, 
 and sends no more blood into 
 the arteries, they "stretch back." 
 We should not say contract, for 
 it is simply an elastic reaction. 
 As the artery reacts it presses on 
 the blood, and hence the blood 
 tries to escape in every possible 
 way. It cannot go back, for it 
 fills the pockets of the semilunar 
 valves, and closes them with a 
 click. A rapid wave is sent for- 
 ward that gives the pulse, and a slower but still rapid 
 stream flows along the arteries, through the pulmonary 
 artery to the lungs, and through the aorta and its branches 
 to all the other parts of the body. 
 
 Fig. 1 9. Plain (Unstriated) Muscu- 
 lar Fibers from the Bladder. 
 
50 PHYSIOLOGY. 
 
 The elastic reaction of the arteries thus helps to make 
 steady the flow of blood, which is intermittent as it leaves 
 the heart. The medium-sized arteries also have elastic 
 tissue in their walls, and regulate the blood flow in the 
 same way. 
 
 Variation of the Amount of Blood Needed. Each 
 organ requires a supply of blood in proportion to its 
 activity. An actively working organ, like the brain, de- 
 mands much more blood than bone, practically inactive. 
 Further, working tissues, such as the brain and muscles, 
 need a great deal more blood while they are at work than 
 when they are resting. An organ needing a constant large 
 supply of blood might secure this by having a large artery. 
 But how can the supply be regulated so that an organ 
 may receive, now more, now less, according to its needs ? 
 
 Plain Muscle Fibers in the Walls of the Arteries. 
 This is regulated by the medium-sized and small arteries 
 
 Connective Tissue 
 
 Endothelium 
 
 Muscle Fiber 
 
 Fig. 20. Plain Muscle Fiber. Isolated and in Wall of Artery. 
 
 leading to the parts. In the walls of these arteries are 
 muscle fibers of a different kind from those of the skele- 
 
CIRCULATION OF THE BLOOD. 51 
 
 ton. These fibers are spindle-shaped cells, as shown in 
 Fig. 19, with a nucleus near the center, and do not have 
 the cross-markings of the fibers of the skeletal muscles ; 
 they are in consequence called nonstriated, smooth, or 
 plain muscle fibers. They are arranged circularly in the 
 walls of the arteries. These fibers have, in common with 
 all muscle fibers, the power of shortening. When they 
 shorten they reduce the size of the artery, and, there- 
 fore, for the time, less blood can flow through the 
 artery. When the muscle fibers cease to shorten, the 
 artery widens, and allows more blood to pass through it. 
 
 Illustration of the Action of Muscles in Arterial Walls. To 
 
 illustrate the action of the muscles in the walls of an artery, let the 
 water run through a hose or large 
 rubber tube. Now, if a row of per- 
 sons take hold of this tube, the grip Endotheiium 
 
 of their hands is like that of the 
 
 muscles. When the hands tighten internal Elastic 
 
 their grip, the caliber of the hose La y er 
 
 or tube is diminished, and less water 
 
 is allowed to flow through it. When Circular Mus- 
 cle Fibers 
 the hands relax, the tube, being 
 
 elastic, allows more liquid to flow 
 through it. 
 
 Illustration of a Small Artery. 
 
 To represent a small artery, take 
 a small, thin-walled rubber tube and 
 wind a red thread around it. Now, 
 
 if the thread could be made to Fl * 21 - Coats of a Small Artery. 
 shorten, it would diminish the cali- 
 ber of the tube. The representation would be more exact if the thread 
 were cut into many short pieces, and if each piece were thicker in 
 the middle, and were then glued to the tube. If the whole were 
 covered by a layer of tissue paper, the structure of the artery would be 
 roughly represented. 
 
52 PHYSIOLOGY. 
 
 Plain and Striated Muscle Fibers Compared. These plain mus- 
 cle fibers are further like those of the skeletal*muscles in that they are 
 under the control of the nerves, but they are involuntary in their action. 
 
 PIGMENT 
 CELLS 
 
 ARTERY 
 Fig. 22. Part of Frog's Web (low magnifying power). 
 
 We cannot interfere with the action of these muscles, no matter how 
 strongly we may will to do so. Without our thinking about it, more 
 
CIRCULATION OF THE BLOOD. 
 
 53 
 
 blood goes to the muscles of the legs when we walk, more to the brain 
 when we are studying, to the digestive organs after eating, etc. The 
 
 Walls of Capillari 
 
 Tissues of Web 
 
 \ 
 
 Fig. 23. Part of Frog's Web (highly magnified). 
 
 plain muscle fibers shorten at a much slower rate than the striated 
 fibers. They are also slower in relaxing. Since the plain muscles are 
 usually found in the walls of hollow organs such as the heart, blood 
 
54 
 
 PHYSIOLOGY. 
 
 tubes, digestive tube, etc., they are sometimes called visceral muscles in 
 distinction from the skeletal muscles. 
 
 The Circulation of Blood in the Web of a Frog's Foot. For this 
 get a frog with a pale web. Take a piece of shingle six inches long 
 and three inches wide. Cut a round hole, half an inch in diameter, 
 near one end of it. Wrap the frog in a wet cloth, with one leg project- 
 ing, and tie it, thus wrapped, to the shingle. Tie threads around two 
 of the toes, and stretch the web, but not too tightly, over the hole. 
 Keep the web moist. Place the shingle firmly on the stage of a micro- 
 scope. Examine first with a low power. The large tubes which grow 
 smaller by subdivision are arteries. The large tubes which are 
 formed by the union of smaller ones are 
 the veins. The finer tubes, forming a net- 
 work in every direction, are the capillaries. 
 They receive the blood from the arteries 
 and pass it on to the veins. 
 
 Put on a higher power, a one-fifth or 
 one-sixth objective. It may now be seen 
 that the colored corpuscles float more in 
 the center of the stream, and with a steady 
 motion, while the colorless corpuscles keep 
 close to the walls of the capillary, and seem 
 to adhere to them, advancing with a hesi- 
 tant motion, seeming to roll along against 
 the wall of the capillary. 
 
 Close your eyes for a moment, and re- 
 flect that in all the active tissues of your 
 body for example, the muscles, brain, and 
 digestive organs there is a similar net- 
 work of fine tubes with a current of blood 
 
 running through them. The current is not so rapid as it seems, for the 
 microscope magnifies the rate of flow as well as the size of the cor- 
 puscles. The blood really is moving slowly in the capillaries, and it is 
 very important that it should be so, for in the capillaries the work of 
 the blood is done. Part of the liquid of the blood soaks through the 
 thin walls of the capillaries, and nourishes the surrounding tissues. All 
 the other parts of the circulatory system exist for the purpose of send- 
 ing a continuous, slow, and steady stream of blood through the 
 capillaries. (See pages 72 and 73.) 
 
 Fig. 24- Capillary Blood 
 Tubes of Muscle. 
 
CIRCULATION OF THE BLOOD. 
 
 55 
 
 Connective 
 
 Tissuf 
 
 Artery 
 
 Fig. 25. 
 
 Cross-section of Small Artery 
 and Vein. 
 
 The Blood Flow in the Capillaries. The arteries 
 
 divide and subdivide, and become capillaries, which have 
 
 connecting branches, form- 
 ing a close network of tiny 
 thin-walled tubes. These 
 penetrate nearly every tis- 
 sue of the body. The blood 
 cannot do its full work till it 
 is in the tissues/and to reach 
 the tissues it must soak 
 through the walls of the 
 capillaries. The work of 
 the heart and arteries is to 
 keep a steady flow of blood 
 
 through the capillaries, that the tissues may be constantly 
 
 supplied. 
 
 How is it that the jerky action of the heart, at each 
 
 contraction sending a jet of 
 
 blood into the arteries, 
 
 shown by a spurt when an 
 
 artery is severed, and also 
 
 indicated by the intermit- 
 tent pulse, how is this 
 
 intermittent flow converted 
 
 into the steady, uniform 
 
 current that we have seen 
 
 in the capillaries ? 
 
 Experiments illustrating the 
 Blood Flow in the Capillaries. 
 
 A few experiments may make this Fig. 26. 
 
 Surface View 
 
 Longitudinal Section 
 
 matter more clear. 
 
 Capillaries, composed of a single 
 layer of cells. 
 
 Material : i . A common rubber syringe. 
 
 2. A glass tube three feet long and seven sixteenths of an inch 
 outside diameter. 
 
56 PHYSIOLOGY. 
 
 3. Four inches of the same size glass tubing, for making connec- 
 tions. 
 
 4. Several nozzles, made of the same size glass tubing, all fine, but 
 of varying degrees of fineness. 
 
 5. India-rubber tubing, twelve feet, three eighths of an inch inside 
 diameter. This should be black, pure gum, rubber which is more 
 highly elastic than the other kinds. 
 
 6. Three feet of rubber tubing, same size as above. 
 
 7. Four inches of white rubber tubing, same size as above, for 
 making connections. 
 
 In all the experiments, have one of the students assist by holding 
 the outlet tube, so that (i) all the members of the class may see the 
 stream, and (2) that the stream may be suitably directed, as into a pail 
 or sink. 
 
 Count aloud, to mark the exact time of each compression of the 
 bulb, so the students can compare this with. the time and duration of 
 the jets of water. 
 
 Be very careful to use perfectly clean water, as any fine particles of 
 sediment drawn into the tube are likely to clog the fine outlet of the 
 nozzle. And it is well to take the further precaution not to let the 
 supply tube touch the bottom of the water-supply dish, as some fine 
 sediment may get in in spite of previous care. 
 
 EXPERIMENT i. Remove the nozzle of the syringe, and put in its 
 place the long glass tube. Work the syringe, and note that the jet is 
 jerky, following each contraction of the bulb. 
 
 EXPERIMENT 2. Substitute the rubber tube, three feet long, for 
 the glass tube. On working the bulb the stream will be found inter- 
 mittent. 
 
 EXPERIMENT 3. Take off the rubber tube and replace the glass 
 tube, adding the nozzle. Here the pressure will be so great that it is 
 likely to push off the nozzle unless the assistant holds it firmly. It 
 could be tied on, but this takes more time. On working the bulb, 
 greater effort must be made on account of the resistance caused by the 
 narrower outlet. 
 
 EXPERIMENT 4. Once more substitute the rubber tube, this time 
 with a glass nozzle in its end. Now, on working the bulb, resistance 
 will be felt, and the stream will be constant, or nearly so, and will con- 
 tinue for some time when the bulb is no longer worked. This is be- 
 cause the rubber has been stretched, chiefly laterally, and is now 
 
CIRCULATION OF THE BLOOD. 
 
 57 
 
 " stretching back." That is, by the elastic reaction of the rubber tube 
 the jerky action of the bulb is converted into the steady flow that we 
 see. In the first experiment we had a rigid tube and practically no 
 resistance. In the second, although the tube was elastic, there was no 
 resistance, so the elasticity was not brought into play. In the third, 
 there was resistance, but the tube was inelastic. In the fourth, the 
 resistance brought into play the elasticity of the rubber tube, and the 
 elastic reaction of the tube continues (so to speak) the action of the bulb 
 between two successive strokes. In this experiment the pulse can be 
 felt in the tube. 
 
 The Veins. The capillaries, after penetrating the tis- 
 sues, reunite to form small veins, which in turn reunite 
 to form larger ones, till finally two great veins, the caval 
 veins, precaval and postcaval, return the blood to the 
 heart. The veins, like the arteries, are smooth inside and 
 elastic (though less elastic than the arteries). They are 
 thinner than the arteries, and, in consequence, collapse 
 when the blood flows out of them, whereas the larger 
 arteries stand open, after they are emptied of blood. 
 
 The Valves in the Veins. The only valves in the arte- 
 ries are those which we have seen at the beginning of the 
 aorta and pulmonary artery. 
 Many of the veins have 
 similar pocket-like valves, 
 though less strong than 
 those of the arteries. They 
 are usually in pairs, but some- 
 times single or in threes. It 
 is important to note that they 
 all have the mouths of the 
 pockets toward the heart, so 
 that the blood flows freely 
 toward the heart, but is prevented from flowing the other 
 way on account of the filling of the valves by the reflow 
 
 Open Shut 
 
 Fig. 27. Venous Valves. 
 
58 PHYSIOLOGY. 
 
 of the blood stream. When the blood is flowing through 
 the veins toward the heart the valves lie against the walls 
 of the veins. 
 
 The valves are most numerous in the medium-sized veins, 
 and especially in the veins of the extremities ; more abun- 
 dant in the leg than in the arm. Valves are absent from the 
 caval and some other veins, and from the very small veins. 
 
 Illustration of Venous Valves. Make a cloth tube (or take the 
 lining of a boy's coat sleeve) and sew three patch-pockets on the in- 
 side, in a circle, i.e. with edges touching each other. Make the pockets 
 a little " full." Pour sand, shot, or grain through the sleeve first in 
 one direction and then in the other. 
 
 Evidences of Valves in our Veins. With the forefinger stroke 
 one of the veins on the hand or wrist toward the tips of the fingers. 
 The veins swell out. The blood meets resistance in the valves of the 
 vein. Their location may be determined by their bulging out during 
 the experiment. 
 
 Stroke a vein toward the body, and the blood is pushed along with- 
 out resistance. 
 
 Let the left hand hang by the side. Note the large vein along the 
 thumb side of the wrist. Place the tip of the second finger on this 
 vein just above the base of the thumb. Now, while pressing firmly 
 with the tip of the second finger, let the forefinger, with moderate 
 pressure, stroke the vein up the wrist. It may be seen that the blood 
 is pushed on freely, but comes back only part way. It stops where it 
 reaches the valves, filling the vein full to this point, but leaving it col- 
 lapsed beyond, as shown by the groove. Remove the second finger, 
 and the vein immediately fills from the side nearer the tip of the fingers. 
 
 These experiments show that the blood in the veins moves freely 
 toward the body, but cannot flow outward to the extremities. 
 
 Dissection of the Valves in a Vein. The valves may be seen by 
 dissecting out the jugular vein (or any other large superficial vein) of a 
 cat, dog, or rabbit. Split the vein and pin it out on a board. 
 
 Effect of Pressure on the Veins. Since the valves in 
 the veins open toward the heart, any intermittent pressure 
 on the veins helps to push the blood on toward the heart. 
 
CIRCULATION OF THE BLOOD. 59 
 
 The valves are most numerous in the superficial veins and 
 those of the muscles. The pressure of the muscles during 
 their action (thickening while shortening) produces pres- 
 sure on the veins ; and as the muscles act for a short time 
 only, and then relax, this alternate compression and release 
 aids very considerably in moving the blood on toward the 
 heart. It is worthy of remark that this effect is more 
 pronounced at the time the muscles need the most active 
 circulation ; namely when they are in action, and are using 
 the most blood. The heart has power enough to pump 
 the blood clear around from each ventricle to the auricle 
 of the other side of the heart ; but this outside aid comes 
 in good play to relieve the heart at a time when it has an 
 unusual amount of work to do, as when one is using a 
 large number of muscles vigorously. 
 
 " Every active muscle is a throbbing heart, squeezing 
 its blood tubes empty while in motion, and relaxing so 
 as to allow them to fill up anew." 
 
 Rate of Blood Flow in the Arteries, Capillaries, and 
 Veins. The blood flows most rapidly in the arteries, 
 slowest in the capillaries. Why is this ? 
 
 When an artery divides, the two branches taken together 
 are larger than the one artery that divided to form them. 
 Stated more exactly, the sum of the areas of the cross- 
 sections of the branches is greater than the area of the 
 cross-section before branching. Hence as the blood flows 
 on it is continually entering wider and wider channels ; 
 and we are told that the united cross-section of all the 
 capillaries fed by the aorta is several hundred times that 
 of the aorta itself. 
 
 The Flow of the Blood compared with the Current of 
 a Stream. If we walk along a stream, we see that the 
 
6o 
 
 PHYSIOLOGY. 
 
 channel varies considerably in width and depth. Where 
 the channel is large, whether from increased width or depth, 
 there the current is slower, but wherever the channel is 
 reduced, the current is more rapid. So the stream in 
 the relatively narrow artery is swift. In the capillaries, 
 
 Pulmonary Vein - 
 
 Left Auricle .. 
 
 Left Ventricle 
 
 Aorta 
 
 Digestive Tube 
 
 Pulmonary Artery 
 Lymph Vein 
 
 Right Auricle 
 
 - Right Ventricle 
 Caval Vein 
 
 - Liver 
 
 Fig. 28. Plan of Circulation. (Dorsal View.) 
 
 although any individual channel is small, these channels 
 all together are wide ; the result is the same whether a 
 river widens out into a single lake, or divides into a great 
 number of channels running past innumerable islands. 
 
CIRCULATION OF THE BLOOD. 6l 
 
 All the tissues of the body may be regarded as so many 
 islands lying between the capillary streams. 
 
 The Blood Flow in the Veins. When the blood re- 
 collects in the veins it is entering narrower channels, and 
 its rate is quickened ; but as the veins are wider than the 
 arteries, the stream does not enter the heart with the veloc- 
 ity with which it left that organ. The veins hold more 
 blood than the arteries, and in dissecting the cat or rabbit 
 it will be noticed that the arteries are emptied of blood; 
 that the tissues of most of the organs are fairly free from 
 blood ; but -that the great veins, such as the caval veins, 
 are full. 
 
 Blood Tubes compared to Two Funnels. If the blood 
 tubes leaving the heart could all be united, they would be 
 best represented by a funnel with its tube connected with 
 the heart. If another funnel were placed with its mouth 
 to the mouth of the first, their point of union, the widest 
 point, would represent the capillaries; and if the second 
 funnel had a wider tube than the first, it would fairly rep- 
 resent the veins which return the blood to the heart. 
 
 Nourishment of the Walls of the Heart and Blood 
 Tubes. The cardiac (coronary) arteries spring from the 
 aorta just above the semilunar valves, and send blood into 
 the muscular walls of the heart ; and these arteries, like 
 others, divide, forming capillaries, through which the heart 
 muscle is nourished, The cardiac veins return the blood 
 to the right auricle. 
 
 Influence of Gravity on Circulation. Although the 
 heart pumps the blood around through the body inde- 
 pendent of the force of gravity, yet the circulation is influ- 
 enced by this force. For instance, a person who has 
 
62 PHYSIOLOGY. 
 
 fainted should be laid flat on his back, that the heart may 
 more easily drive blood to the brain. Many persons go to 
 sleep more readily while sitting than while lying down. 
 A sore hand feels less pain if held up, as in a sling, than 
 when hanging by the side, and a sprained ankle does 
 better rested on a chair, as less blood flows to it. Nearly 
 every one has noted the pain following the pressure of 
 blood when a sore hand, or foot, is suddenly lowered. 
 
 Experiments illustrating the Effect of Gravity on Circulation. 
 Let all the pupils in the class stand. Let one arm hang freely by the 
 side. Hold the other arm straight up as far as the clothing will readily 
 permit. Observe : 
 
 1. The difference in the color of the two hands. 
 
 2. The difference in fullness, both in the feeling of fullness and in 
 the prominence of the veins. 
 
 3. The difference in temperature ; place the backs of the hands 
 against the cheeks. 
 
 The position largely determines the amount of blood in the hand, 
 and the amount of blood determines the temperature, the size, and the 
 color. 
 
 Summary. i. The heart beats about seventy-two times a minute. 
 
 2. The pulse is a wave running along an artery. 
 
 3. The pulse varies with age, health, food, etc. 
 
 4. The heart has two main cavities, one in each half of the heart, 
 and two independent streams are flowing through it. 
 
 5. Valves allow the blood to flow through the heart in one direc- 
 tion, but prevent a reversal of the current. 
 
 6. The heart is a hollow muscle, and. by contraction forces the 
 blood out into the arteries. 
 
 7. The heart works rather less than half the time. 
 
 8. The large arteries, by elastic reaction, push the blood on while 
 the heart is resting. 
 
 9. Circular muscle fibers in the walls of the medium-sized arteries 
 regulate the blood supply to the organs. 
 
 10. In the arteries the blood flow is rapid and intermittent, in the 
 capillaries slow and constant. 
 
CIRCULATION" OF THE BLOOD. 63 
 
 11. The thin walls of the capillaries allow the liquid part of the 
 blood to soak out and nourish the tissues, and to soak back into the 
 capillaries bearing waste matter. 
 
 12. The veins are thin walled, and collapse when empty, while the 
 arteries are thick walled, and stand open when empty of blood. 
 
 13. Arteries carry blood from the heart, while veins carry it toward 
 the heart. 
 
 14. The veins have valves which allow the blood to pass toward 
 the heart, but not away from it. 
 
 15. Any intermittent pressure on the veins aids the blood flow. 
 
 1 6. The blood flow is most rapid in the arteries, slower in the veins, 
 slowest in the capillaries. 
 
 17. Gravity influences circulation. 
 
 Questions. i. Why do the large arteries lie deep? 
 
 2. In which direction should the limbs be stroked to promote circu- 
 lation? 
 
 3. How does slapping the hands around the body warm the ringers? 
 
 4. How can a horse or a cow be comfortable with the head down 
 for a long time? 
 
 5. Why are the walls of the left ventricle thicker than those of the 
 right ? 
 
CHAPTER V. 
 
 CONTROL OF CIRCULATION. THE BLOOD AND 
 THE LYMPH. 
 
 The Effect of the Emotions on Circulation. In our 
 every-day experience we have evidence of the control of 
 the heart and blood tubes by the nervous system. We know 
 that certain emotions affect the circulation of the blood ; 
 for instance, blushing and pallor. Certain emotions may 
 also quicken or retard the action of the heart. Excessive 
 grief or joy has produced sudden death by stopping the 
 beat of the heart. 
 
 Let us look a little more closely at that part of the 
 nervous system that has such intimate relation to the 
 blood system. 
 
 The Rhythmic Action of the Heart. In the first 
 place, the action of the heart is automatic. The heart of 
 the frog continues to beat a long time after it is removed 
 from the body. This is regarded by many as due to the 
 action of certain ganglia imbedded in the walls of the 
 heart, especially in the auricles ; while others say that 
 since the ventricle, in which no ganglia have been found, 
 may beat independently of the auricles, rhythmic contrac- 
 tion is characteristic of heart muscle, and that we are, at 
 present, unable to explain it. 
 
 But while the impulses that originate the action of the 
 heart arise within the heart itself, still the beat of the heart 
 is constantly modified by nerve impulses reaching it from 
 without. 
 
 6 4 
 
Carotid Plexus 
 
 Superior Cervical Ganglion 
 
 Middle Cervical Ganglion 
 
 Pharyngeal Branches 
 
 Cardiac Branches 
 
 Deep Cardiac Plexus 
 
 Superficial Cardiac Plexus 
 
 Solar Plexus 
 
 Aortic Plexus 
 
 Lumbar Ganglia 
 
 Fig. 29. Vertical Section of Body, showing Sympathetic Nerves and Ganglia of Right 
 Sid,e and their Connection with the Cerebro-spinal Nerves. 
 
66 
 
 PHYSIOLOGY. 
 
 Sympathetic Nerve Chains 
 GRAY 
 
 Sources of the Heart's Nerve Supply. The heart re- 
 ceives its nerves from two sources, the sympathetic system 
 and the vagus (or pneumogastric) nerves. 
 
 The Sympathetic Nervous System. The sympathetic 
 nervous system consists of two rows of ganglia in the body 
 cavity, one along each side 
 of the spinal column, re- 
 ceiving branches from the 
 spinal nerves, and sending 
 branches to all the 
 internal organs of 
 the body, the 
 heart and lungs in . 
 the thorax, and the 
 stomach, intestines, and the 
 other organs of the abdomi- 
 
 Ganglion of 
 Dorsal Root 
 
 Sympathetic 
 Ganglion 
 
 Fig. 30. Relation of Spinal Cord and 
 Sympathetic Nervous System (Diagram). 
 
 nal cavity. In many places 
 these nerves form a thick 
 network called a plexus. 
 
 One very large plexus is on the dorsal surface of the 
 
 stomach, and is called 
 spinal cord the solar plexus. 
 
 Sympathetic 
 Ganglion 
 
 The Vagus Nerves. 
 The vagus nerves 
 are a pair of the cranial 
 nerves arising from the 
 sides of the spinal bulb ; 
 and passing downward, 
 they give branches to 
 the pharynx, the gullet, 
 
 the stomach, the larynx, the windpipe, the lungs, and the 
 heart. Now, whatever other function the vagus nerves 
 
 Fig- 31. Ideal Cross-section of the Nervous 
 System. (After Landois and Stirling.) 
 
CONTROL OF THE CIRCULATION. 
 
 6 7 
 
 may have, they seem to have the power of retarding, or 
 stopping altogether, the beat of the heart ; and stimulation 
 of the vagus nerves may make the heart pause in a relaxed 
 condition. Other nerves may quicken the heart beat, but 
 the vagi are regarded as a break on the heart's action. 
 
 Inhibition. This is a case of inhibition. It is well 
 known that a severe blow over the stomach may cause one 
 to faint by stopping the heart. This 
 is due to reflex inhibition of the heart. 
 The blow sends a nerve impulse by 
 fibers of the sympathetic system to 
 the center in the spinal bulb, and 
 thence an impulse is taken by the 
 vagus nerves to stop the heart. 
 
 Vaso-constrictor Nerves. In an 
 
 experiment with the rabbit's 
 ear it has been shown that 
 stimulating the sympathetic 
 nerve in the neck causes the 
 ear to become pale. This is 
 due to the constriction of the 
 arteries of the ear, because 
 the nerves have made the 
 muscle fibers of these arteries 
 shorten. Such nerve fibers 
 are called constrictors, or vaso-con- 
 strictors. They run in the sympa- 
 thetic nerve, but have their origin 
 and center in the spinal bulb. 
 
 Vaso-dilator Nerves. Other fibers 
 
 may cause the opposite effect, namely, dilation, and are 
 therefore called vaso-dilators. Examples of these may be 
 
 Lungs - 
 
 Heart 
 
 Stomach 
 
 Fig. 32. 
 
 Diagram of vagus 
 
 Nerve. 
 
68 PHYSIOLOGY. 
 
 found running to the arteries of the limbs. When the 
 muscles of any organ, say the legs, act, they need a greater 
 supply of blood. Now, at the same time that nerve im- 
 pulses are sent to the muscles of the legs to make the 
 muscles shorten, impulses are sent along other fibers of 
 the same nerves to make the arteries dilate, and allow 
 more blood to flow to these muscles. 
 
 Vaso-motor Nerves. The vaso-constrictor and the 
 vaso-dilator nerves taken together are called vaso-motor 
 nerves. 
 
 Centers of Control of Circulation. The centers of 
 control of the blood tubes are in the cerebro-spinal nervous 
 system. There is no evidence that the sympathetic gan- 
 glia are centers of reflex action. 
 
 Blushing. How is it that the face sometimes flushes 
 so suddenly ? Because of some emotion, you say. But 
 how does the emotion bring this about ? We have already 
 learned about the muscles in the wall of the arteries. We 
 are now prepared to understand that in the normal condi- 
 tion nervous impulses are acting on these muscles, keeping 
 them partly shortened, and so keeping the arteries of a 
 moderate size. Under the influence of certain emotions, 
 the caliber of the arteries is suddenly enlarged, and hence 
 the change in color. 
 
 The Regulation of the Size of the Arteries. Through 
 the sympathetic system the blood supply of all the organs 
 of the body is regulated. Any organ needing more blood 
 sends a message (nerve impulse) to some nerve center, and 
 in response nerve impulses are sent to the muscle fibers of 
 the supplying artery, and the amount of blood sent to that 
 organ is regulated. For instance, a piece of ice is laid 
 
CONTROL OF THE C/RCULATfOJV. 
 
 6 9 
 
 upon the skin of the hand. The part becomes pale, as 
 the arteries have become narrowed. If this action be con- 
 tinued, there may set in a decided reaction, and the part 
 become more red than usual, when the reaction has 
 widened the artery more than it was 
 before the constriction. 
 
 Effect of Exercise on the Size of the 
 Arteries. As there is only a certain 
 amount of blood in the body, it is evi- 
 dent that if one organ receives 
 an extra supply, some other sympathetic 
 organ or organs must, for the Ganglions 
 time, receive less. For in- 
 stance, one begins to walk vigorously. 
 The large muscles of the lower limbs 
 and trunk become active, and they need 
 more blood. They therefore send mes- 
 sages to some nerve center (probably in 
 the spinal cord), and by reflex action the 
 arteries supplying the lower limbs are 
 widened, and these muscles receive more 
 blood. But these muscles make up a 
 very considerable part of the weight and 
 bulk of the body. While in action they 
 take the lion's share of the blood. The 
 brain, at such a time, would receive less, Fig . 33 . Ventral Vie 
 and it would be folly to expect the brain 
 to work at its full capacity while the 
 blood was called away to other organs. 
 
 of Spinal Cord with 
 Sympathetic Gang- 
 lions of One Side. 
 
 Regulation of the Effects of Exercise. When we ex- 
 ercise vigorously, the heart beats faster, and this of itself 
 would tend to increase the blood supply to all organs. 
 
70 PHYSIOLOGY. 
 
 But this mechanism for widening the channel leading to 
 the working organs, while the arteries to the other organs 
 are made smaller, or at least are not enlarged, solves the 
 problem of supplying each part according to a greatly 
 varying need, while not sending too much to a part not 
 needing it. 
 
 EFFECTS OF ALCOHOL ON THE CIRCULATION. 
 
 " Alcohol stimulates the heart, producing increased force 
 and rapidity of the cardiac beat. It thus tends to increase 
 the blood pressure by acting on the heart, and to increase 
 the flow of blood from the arteries into the veins. The 
 effect on the blood pressure is, however, partly counter- 
 acted by a coincident dilatation of the blood vessels of the 
 skin, which thus become flushed, and tends to produce 
 more sensible perspiration." Treatise on Hygiene, STE- 
 VENSON and MURPHY. 
 
 "The warm and flushed condition of the skin which 
 follows the drinking of alcoholic fluids is probably, in a 
 similar manner, the result of an inhibition of that part 
 of the vaso-motor center which governs the cutaneous 
 arteries." FOSTER. 
 
 The control of the muscles in the walls of the arteries 
 being thus interfered with, the circular muscles are no 
 longer made to shorten, and the artery dilates, thus allow- 
 ing more blood to flow into it. 
 
 We may thus account for the flushing of the skin of the 
 face, which in many individuals quickly betrays indulgence 
 in alcoholic drink. If this flushing is too often repeated, 
 the arteries gradually "lose tone," and the condition be- 
 comes permanent. The circulation in the whites of the 
 eyes may be affected, making them "bloodshot." 
 
CONTROL OF THE CIRCULATION. ?1 
 
 Similar congestion occurs in the mucous membrane of 
 the stomach from the presence of alcohol, which may 
 become a permanent inflammation followed in time by 
 very extensive changes in appearance and function. It 
 is said that most of the alcohol swallowed is absorbed 
 directly from the stomach, and hence the intestines are 
 not so directly affected. 
 
 Good authorities state that alcohol arrests the develop- 
 ment of the corpuscles. It diminishes the size, alters the 
 form, and reduces the number of the corpuscles. Since 
 the work of the blood corpuscles is so important this 
 reduction in their number and efficiency must very 
 appreciably affect the nutrition of the body as a whole. 
 When the blood is " out of order" the body is out of order. 
 
 The Blood, The blood is composed of a clear liquid, 
 the plasma, and the blood cells, or corpuscles. In a drop 
 of blood under the microscope the plasma occupies the 
 clear spaces between the corpuscles. The corpuscles 
 make up one third of the bulk of the blood, and the 
 plasma two thirds. 
 
 Microscopic Examination of the Blood. To get a drop of blood 
 from the finger, wind a cord around the finger, beginning at the base, 
 drawing the cord moderately tight, until the last joint is reached. By 
 this time the end of the finger is usually well distended with blood. 
 With a clean needle make a quick, sharp, light puncture near the base 
 of the nail ; this ordinarily brings a small amount of blood. Put a 
 small drop on each of several slides and quickly cover with coverslips. 
 Examine with a high power. 
 
 The Colored Corpuscles. These are often called the 
 red corpuscles. But while in the mass they give the 
 blood a red appearance, individually they are faint yellow- 
 ish red. In shape they are seen to be circular disks, hol- 
 lowed on each side like a sunken biscuit. As they are 
 
72 PHYSIOLOGY. 
 
 hollowed on both sides they are more accurately described 
 as biconcave. These corpuscles tend to gather side by 
 side, in rolls, like coins. They are cells without nuclei. 
 
 The Colorless Corpuscles. In the open spaces be- 
 tween the rolls of colored corpuscles may occasionally 
 be found some spherical corpuscles. They are usually 
 
 White Corpuscles 
 
 HIGHLY MAGNIFIED 
 
 White Corpuscle 
 
 Red Corpuscles 
 in Rolls 
 
 MODERATELY MAGNIFIED 
 Fig. 34. Red and White Corpuscles of the Blood. 
 
 called the white corpuscles, but are better designated as 
 the colorless corpuscles, since the others have only a slight 
 color, and these have none. They usually have a dotted 
 appearance. It is not so easy to distinguish the two kinds 
 of corpuscles as it is in the case of the frog's blood, for the 
 two kinds are more nearly of the same size in the human 
 
CONTROL OF THE CIRCULATION. 73 
 
 blood ; and, further, when the colored corpuscles of human 
 blood are seen flatwise they present a circular outline, while 
 the frog's colored corpuscles are elliptical. But with a 
 little study the two may be distinguished. As in the frog's 
 blood, the colorless corpuscles have ameboid movements, 
 though they are not very marked unless the blood be 
 warmed to about the temperature of the human body. 
 
 Flexibility and Elasticity of the Corpuscles. It will 
 be well here to examine again the frog's web. (See p. 54.) 
 It will occasionally be seen that when one of the colored 
 corpuscles is pressed against an angle at the forking of 
 the blood stream, it is sometimes bent, and that as soon as 
 the pressure is discontinued the corpuscle springs back to 
 its former shape, showing that it is elastic. 
 
 Frog's Blood. A drop of frog's blood, mounted as the human blood 
 was, will be helpful, as there is a very decided difference in the size and 
 shape of the colored and colorless corpuscles. Further, the colorless 
 corpuscles of the frog will show ameboid movements, i.e. slow changes 
 of form, if watched a while. 
 
 The Plasma. The plasma consists chiefly of water, 
 having in solution various salts, including common salt; 
 it also contains the nourishing materials for the tissues. 
 These nourishing materials, obtained from the food by 
 digestion, consist chiefly of proteids, fats, and sugar. The 
 plasma also contains waste matters, from the working 
 tissues, on their way out of the body. How the food is pre- 
 pared for the building of tissue, and how the waste matter 
 is removed from the body, we shall study a little later. 
 
 The Color of Blood. The difference in color of an in- 
 dividual corpuscle and the blood in the mass may be better 
 understood by comparing it with something that we see 
 more frequently. A tumbler of currant jelly has a rich, 
 
74 PHYSIOLOGY. 
 
 red color, but a thin layer of the same jelly, as when one 
 takes a spoonful on a plate, has a pale color, more yellow- 
 ish. The colorless plasma with the colored bodies in it 
 may be compared to a glass dish filled with cranberries 
 and water. 
 
 Hemoglobin. The coloring matter in the blood, then, 
 is wholly in the colored corpuscles. Examination of these 
 corpuscles shows that their color is due to a substance 
 called hemoglobin. There is a small amount of iron in 
 the hemoglobin, and the presence of this small quantity 
 of iron appears to be essential to give the blood its color. 
 When we come to the study of respiration we shall see 
 that the hemoglobin in the corpuscles is the chief agent in 
 picking up the oxygen from the air in the lungs and carry- 
 ing it to the tissues in the body. 
 
 The Coagulation of Blood. When the blood escapes 
 from its natural channels it usually changes from a liquid 
 to a jelly-like condition. This is known as coagulation. 
 It is due to the formation of threads of fibrin from the 
 plasma. These threads of fibrin entangle and inclose the 
 corpuscles, and the two constitute the clot, or coagulum, as 
 it is more technically termed. The liquid that afterward 
 separates from the clot is the serum, and differs from the 
 plasma only in the removal of the fibrin, which is exceed- 
 ingly small in quantity, though of great importance in its 
 action. Many experiments have been made, and much 
 has been written about the coagulation of the blood, and 
 perhaps its real cause is not yet clear. But we know that 
 the coagulation often serves to stop the flow of blood from 
 wounds, and this is its main use. 
 
 Fibrin. If freshly drawn blood be stirred rapidly with 
 a bundle of wires (perhaps the most convenient stirrer is 
 
CONTROL OF THE CIRCULATION. ?$ 
 
 a little roll of wire screen), there will soon collect on the 
 wires a stringy substance. Thorough washing will soon 
 leave this colorless. It is fibrin. If the stirring has been 
 done thoroughly, the blood will no longer clot, no matter 
 how long it may stand. 
 
 Liquid Blood and Coagulated Blood. The following 
 scheme shows the difference between the liquid blood and 
 the coagulated blood : 
 
 ( Serum 
 
 Liquid Blood 
 
 Plasma. 
 
 ( Fibrin 
 
 Clot 
 
 Coagulated Blood. 
 
 Corpuscles 
 
 Amount of Blood. The blood constitutes about one 
 thirteenth of the weight of the body. In a body weighing 
 one hundred and fifty pounds this would be about six 
 quarts. 
 
 Chemical Reaction of Blood. Blood is alkaline. 
 
 Specific Gravity of Blood. Blood is somewhat heavier 
 than water, owing to the salts and other matters dissolved 
 in it. 
 
 Quantity of Blood in Different Organs (approximately). 
 i. One fourth is in the heart and the larger arteries 
 and veins (including those of the lungs). 
 
 2. One fourth in the liver. 
 
 3. One fourth in the skeletal muscles. 
 
 4. One fourth in the other organs. 
 
 The Lymph Spaces. We have seen that the capillaries 
 have very thin walls. Through their walls part of the 
 plasma of the blood soaks out, and is then called lymph. 
 It passes into irregular cavities in the tissue called lymph 
 spaces. Most of these lymph spaces are minute chinks or 
 
76 PHYSIOLOGY. 
 
 crevices in the connective tissues of the different parts of 
 the body. 
 
 The Lymph Tubes. Opening out of the lymph spaces 
 are irregular passage ways called lymph capillaries, and 
 these lymph capillaries are continuous with thin-walled 
 tubes, the lymph tubes. These lymph tubes might be 
 called the lymph veins, since they join still larger tubes, 
 closely set with valves, similar to those of the veins. But, 
 unlike the blood veins, the lymph veins do not gradually 
 increase in size by confluence. They suddenly form a 
 large tube, the receptacle of the chyle, beginning in the 
 upper part of the abdomen. This tube soon narrows and 
 passes through the diaphragm, close to the spinal column, 
 and up along the column near the aorta, and empties into 
 the veins of the neck at the junction of the left jugular 
 and left subclavian veins. This tube is the thoracic duct, 
 or the main lymph duct. It has numerous valves, and, 
 like some of the smaller lymph veins, it presents a beaded 
 appearance, due to the filling and bulging out of the valves. 
 In the right side of the neck is a short right lymph duct 
 which receives lymph from the right side of the head, 
 neck, and thorax, and from the right arm. The lymph 
 tubes, as a whole, are usually called the "lymphatics." 
 
 Lymph Spaces in the Frog. In dissecting the frog, the looseness 
 of the skin is very noticeable. The large spaces under the skin are 
 lymph spaces. Sometimes considerable lymph is found here, so that 
 in holding up a frog the sagging of the skin from the weight of the 
 lymph may be easily seen. 
 
 Valves at the Mouth of the Lymph Tubes. There 
 are valves where these lymph ducts empty into the veins 
 which prevent any reflow of liquid into the ducts, but allow 
 the lymph to pass freely into the veins. 
 
CONTROL OF THE CIRCULATION. 77 
 
 Muscle Fibers in the Walls of the Lymph Tubes. - 
 
 There are plain muscle fibers in the walls of the lymph 
 ducts. 
 
 Lymphatic Glands. In its course the lymph passes 
 through many kernel-like masses, the lymphatic glands. 
 Lymph contains corpuscles which are considered identical 
 with the colorless blood corpuscles. It is tho'ught that 
 these corpuscles are formed in the lymphatic glands. 
 
 The Flow of Lymph. The flow of lymph is partly 
 due to the blood pressure in the capillaries ; this pressure 
 is caused by the heart. (In the frog there are two small 
 hearts, not, however, near the blood-pumping heart, 
 and these pump the lymph along.) In our bodies the flow 
 of lymph is largely aided by any pressure that may be 
 brought to bear on the lymph veins ; for, on account of 
 the valves, as in the blood veins, any pressure must push 
 the liquid toward the heart. Thus the action of the mus- 
 cles in the limbs, in the chest, in the abdomen, in the 
 movements of breathing, and in the bending of the body, 
 etc., all help in this flow, which is always, probably, very 
 much slower than that in the blood veins. 
 
 Relations of Blood Flow and Lymph Flow. It will 
 now be seen that while the blood leaves the left ventricle 
 by one tube, the aorta, it returns to the right auricle, not 
 merely by the two caval veins, but that a part of the blood 
 (i.e. of the liquid part of it) does not return by blood veins, 
 but having left the blood system proper through the thin 
 walls of the capillaries, it is brought back to the heart by 
 the lymph veins, which, however, join the blood veins just 
 before they empty into the heart. There is, in other 
 words, only one set of distributing tubes, but there are two 
 sets of collecting or returning tubes. 
 
PHYSIOLOGY. 
 
 Left Jugular Vein 
 
 Mouth of Lymph ... 
 Vein 
 
 Right Lymph Vein 
 
 Right Subclavian 
 Vein 
 
 Precaval Vein 
 
 Postcaval Vein 
 
 Main Lymph Vein 
 (Thoracic Duct) 
 
 Lymph Capillaries 
 
 Blood Capillaries 
 
 Fig. 35. Diagram of the Circulation of Blood and Lymph (Dorsal View). 
 
CONTROL OF THE CIRCULATION. 
 
 79 
 
 Lymph 
 
 Capillary 
 
 The Lymph. Lymph is a clear liquid. (Chyle and 
 the lacteals will be considered when we study digestion.) 
 It is more watery than the blood plasma, but contains a 
 share of all its nutritious substances. Lymph may be 
 defined as "diluted blood minus red corpuscles." The 
 blood proper never reaches the tissues. 
 
 The Cells of the Body live in Lymph. The cells 
 of the tissues are bathed in the lymph which fills the 
 spaces in the connective 
 tissue (and we have seen 
 that the connective tissue 
 pervades nearly all the tis- 
 sues of the body), as water 
 may fill the spaces left 
 between stones built into 
 a wall. The cells get all 
 their nourishment from the 
 lymph, and into the lymph 
 they throw all their waste 
 matter. Each cell may be 
 compared to an individual 
 ameba, which lives in 
 water, and takes all its 
 nourishment from that 
 water, and throws all its 
 waste product into the 
 same water. As water is 
 the medium in which the 
 
 ameba lives, so we may say lymph is the medium in 
 which the cells of the body live. 
 
 Cells of the Body Aquatic. The cells of the body, 
 i.e. all the active, working cells, may, therefore, be said 
 
 Oxygen 
 
 Food 
 
 Water 
 
 Other 
 Wastes 
 
 Fig. 36. Relation of Blood and Muscle. 
 (Lymph being Middleman.) 
 
80 PHYSIOLOGY, 
 
 to live an aquatic life, and only dead cells, as of hair, 
 epidermis, etc., live in air. We might also say that not 
 only the human body, but all animal life is aquatic. 
 
 Importance of Lymph. We can see that the move- 
 ment and renewal of lymph are as necessary as the circu- 
 lation of the blood itself ; is, in fact, the most important 
 part of it. 
 
 Lymph Cavities or Serous Cavities. We have noticed 
 the pericardial liquid. There is also a small quantity of 
 similar liquid around the lungs in the pleural cavities, and 
 in the abdominal or peritoneal cavity, around the digestive 
 organs ; also in the cavities of the brain. The liquid in 
 each case is lymph, and these cavities, often called serous 
 cavities, are lymph cavities. They communicate with the 
 lymph tubes. 
 
 Dropsy. In health the amount of the liquid in these 
 cavities is small, but in certain disorders it may accumu- 
 late. In general, such affections are called "dropsy." 
 The lymph may also accumulate in the tissues of the 
 extremities, causing swelling of the limbs. 
 
 Variation in the Composition of Lymph. It is evi- 
 dent that the materials needed by the cells of the different 
 tissues are not the same. So, as one tissue takes certain 
 materials and another tissue others, it is clear that the 
 lymph will not be of quite the same composition in the 
 different parts of the body. This difference is further 
 due to the difference in the waste products thrown out 
 by the different cells. Hence the composition of the 
 blood varies considerably in different regions. But the 
 lymph from all the tissues unites with the blood from all 
 the tissues in the right heart, and on their way to it in the 
 
CONTROL OF THE CIRCULATION. 8 1 
 
 larger veins. So the constant slight differences in com- 
 position of the blood and lymph in the various tissues are 
 counterbalanced by the mingling of the currents from 
 these various parts in the large arteries and veins. 
 
 The Spleen. The function, or functions, of the spleen are not well 
 understood. It is believed to have something to do with the renova- 
 tion of the blood, perhaps forming colorless corpuscles and destroying 
 colored corpuscles. At any rate, the physiologists generally call it a 
 blood gland. It is unlike true glands in that it has no duct, and forms 
 no secretion to be poured into any cavity, like the glands of excretion 
 and secretion. It has been found, in the case of accidents to man, and 
 by experiment on the lower animals, that life may continue after this 
 organ has been removed. 
 
 Massage. A system of pressing, rubbing, and knead- 
 ing the muscles is known as massage. It helps the flow 
 of the blood and lymph, thus aiding in washing out the 
 waste products from the muscles and other parts of the 
 body that are to be reached by pressure. We have seen 
 that one of the benefits of exercise is to promote the cir- 
 culation of the blood and of the lymph, and so to help 
 get rid of the waste matters that are produced by the 
 activity of the various organs. Many invalids cannot take 
 active exercise. So this passive exercise may very fairly 
 take its place, and assist in the nutrition of the tissue by 
 accelerating the flow of blood and lymph, bringing new 
 nourishment and carrying away wastes. For students 
 who do not take sufficient exercise it is a good thing to 
 rub the body thoroughly and briskly, not only after a 
 bath, but often with the hands or with a dry towel. 
 
 Transfusion of Blood. Transfusion of blood is the transfer of 
 blood from the blood vessels of one animal to those of another. Trans- 
 fusion may be direct or immediate, as when the blood vessels of the 
 two animals are connected by tubing so that the blood passes from one 
 to the other without exposure to the air ; in indirect or mediate trans- 
 
82 PHYSIOLOGY. 
 
 fusion the blood is first drawn into a receptacle. In indirect transfusion 
 the blood is often defibrinated before transference. The blood may be 
 introduced either into an artery or a vein; if -into a vein it is sent in 
 the direction of the natural flow, i.e. toward the heart ; if into an artery, 
 in either direction. Soon after the discovery of the circulation of the 
 blood the operation of transfusion began to be practiced, and high 
 hopes were indulged in as to its value. But it was soon found to be 
 attended by so much danger that it is now seldom used. It is resorted 
 to (i) after great loss of blood, (2) after some forms of poisoning part 
 of the blood is withdrawn and replaced by fresh blood, and (3) in 
 certain disordered conditions of the blood. The chief dangers are (i) 
 the introduction of air which forms minute bubbles and stops the blood- 
 flow in the capillaries, (2) the introduction sometimes causes coagula- 
 tion within the blood vessels, and (3) the serum of the introduced 
 blood sometimes destroys the corpuscles of the blood to which it is 
 added. In the earlier practice lamb's blood was employed, but now 
 when transfusion is practiced on man only human blood is used. It 
 has been found safer and better after great loss of blood from hemor- 
 rhage, to introduce a salt solution of about the natural degree of salt- 
 ness of the blood ; this restores the normal volume of circulating liquid, 
 and avoids most of the dangers except that of introducing air. The 
 numerous fatal results of this operation have shown that it should not 
 be resorted to except in cases of extreme necessity. 
 
 For directions about stopping the flow of blood from 
 wounds see Chapter XXIII. and the books named below. 
 
 READING. Prompt Aid to the Injured, Doty ; Emer- 
 gencies, Dulles; Emergencies, Howe; First Aid to the 
 Injured, Lawless; First Aid to the Injured, Morton; First 
 Aid in Illness and Injury, Pilcher ; Sickness and Accidents, 
 Curran. 
 
 What other process keeps pace with the coursing of the 
 blood through the body, being its running mate, so to 
 speak ? 
 
 Summary. i . Blushing, and other variations in blood supply, are 
 under the control of the sympathetic nervous system. 
 
 2. The sympathetic nervous system consists of two rows of ganglia 
 
CONTROL OF THE CIRCULATION". 83 
 
 in the body cavity near the spinal column, with fibers running to the 
 internal organs. It is also connected with the cerebro-spinal nervous 
 system. 
 
 3. The heart beat is automatic and rhythmic. 
 
 4. The heart beat is regulated by the sympathetic nervous system 
 and by the vagus nerves. 
 
 5. The blood consists of a liquid, the plasma, in which float the 
 colored and colorless corpuscles. 
 
 6. When blood is shed it coagulates, tending to check its own 
 escape. 
 
 7. Lymph is like the blood diluted and lacking the colored cor- 
 puscles. 
 
 8. A set of lymph tubes conveys the lymph into the veins to join 
 the flow toward the heart. 
 
 9. In its course the lymph passes through the lymphatic glands. 
 
 Questions. i. What makes the hands grow red and puff up on 
 sitting in a warm room after snow balling? 
 
 2. How is a mustard plaster effective? 
 
 3. Why does light exercise before retiring promote sleep? 
 
 4. Why are the feet often cold after studying? 
 
 5. How does the application of ice, or cold water, relieve head- 
 ache? 
 
 6. Why should the clothing be changed after getting wet? 
 
 7. What is the meaning of humor, in the expressions "good- 
 humored," " bad-humored " ? Have these expressions a real physio- 
 logical significance? 
 
CHAPTER VI. 
 
 RESPIRATION. 
 
 The Close Relation between Circulation and Respira- 
 tion. Is it not a very striking fact that we take one 
 breath for every four heart beats ? That whatever quick- 
 ens the breathing also quickens the heart, so that the two 
 
 always keep in al- 
 most the same ratio ? 
 Let us learn what 
 are the many inti- 
 mate relations of 
 the blood pump and 
 the air pump, the 
 blood system and 
 the air system, of 
 Circulation and Res- 
 piration. 
 
 The Organs of 
 Respiration. 
 
 1 . The lungs and 
 air tubes. 
 
 2. The structures 
 which increase and diminish the size of the chest, princi- 
 pally the diaphragm, and the muscles acting on the ribs. 
 
 The Parts of the Lungs. i. The Air Vesicles, an 
 
 immense number of small sacs, which communicate with 
 
 8 4 
 
 Fig. 37. The Trachea and Bronchial Tubes, showing 
 Two Clusters (Alveoli)) of Air Vesicles. 
 
RESPIRATION. 
 
 1. Pulmonary Orifice 
 
 2. Aortic Orifice 
 
 3. Left Auriculo-Ventricular Orifice 
 
 4. Right Auriculo-Ventricular Orifice 
 
 The heavy black line between the heart and the liver represents the diaphragm. 
 
 Fig. 38. Front View of the Thorax. The Ribs and Sternum are represented in 
 
 Relation to the Lungs, Heart, and other Internal Organs. 
 
86 
 
 PHYSIOLOGY. 
 
 the outer air by the bronchial twigs, the bronchi, and the 
 trachea. 
 
 2. The Pulmonary Capillaries, forming a thick network 
 around and between the air sacs. These capillaries receive 
 their blood from the pulmonary artery, and return it to the 
 heart by the pulmonary veins. 
 
 Elastic Tissue in the Lungs. The air vesicles, with 
 their supplying air tubes and their surrounding blood tubes, 
 are bound together by elastic tissue, which fills up most of 
 the intervening space. 
 
 The Windpipe or Trachea. The windpipe has in its 
 walls C-shaped cartilages, with the open part of the C 
 on the dorsal surface. These cartilages continue in the 
 bronchi, and so on until in the smaller twigs they finally 
 disappear. The cartilages are held together, and the 
 dorsal gap of the cartilages (the gap would be like that of 
 a series of horseshoes piled one on top of another) bridged, 
 by tough fibrous tissue, with much elastic tissue, and 
 with plain muscle fibers ; the plain muscle fibers are very 
 abundant in the smaller air tubes. 
 
 The Mucous Membrane. The lining of the trachea 
 
 is a mucous mem- 
 brane. It pours 
 out on its surface 
 a substance some- 
 what like white of 
 egg, called mucus. 
 This keeps the air 
 
 Fig. 39. Ciliated Cells lining the Air Tubes (x 300). 
 
 particles of dust that are in the inspired air. There is a 
 constant slow current of mucus toward the throat, whence 
 it is, from time to time, hawked up. 
 
RESI'IRATION. 
 
 Cilia. This current of mucus is caused by the cilia 
 projecting from the lining cells of the trachea. They are 
 little hairlike projections, in countless numbers, like a field 
 of grass, each stalk having the power of bending back and 
 forth, making a quick stroke toward the throat, then a 
 slower recover stroke. Thus the united wavelike action 
 of the myriads of lashing cilia paddles the mucus head- 
 ward. It is a very common error to suppose that the cilia 
 produce air currents. This is not their function, and it 
 can readily be seen that they cannot create currents of air, 
 as they are wholly submerged, like grass growing on the 
 bottom of a shallow pond of slimy water. 
 
 Location of Mucous Membrane. All the cavities and 
 passages in the body to which the air has access, such as 
 the digestive and respiratory passages, etc., are lined by 
 mucous membrane (not all 
 
 Ciliated). Trachea 
 
 The Pleura. The out- 
 side of each 
 lung is cov- 
 ered by a thin 
 adherent mem- 
 brane, the pleu- 
 ra, which com- 
 pletely invests 
 it, except at the root of 
 the lung, where the bron- 
 chus and blood tubes 
 enter. Here the pleura 
 turns toward and adheres to the inner wall of the chest, 
 forming its lining (still called the pleura), and below passes 
 over the anterior surface of the diaphragm. The lung is 
 
 Pleural Space 
 (Exaggerated) 
 
 Chest Wall- - 
 
 ~~~ Pleura 
 
 Fig. 40. Diagram of the Lungs and Pleurae. 
 
88 PHYSIOLOGY. 
 
 thus free, except at its root, where the air and blood tubes 
 enter. A very small quantity of liquid moistens the con- 
 tiguous surfaces of the pleurae on the outside of the lung 
 and the inside of the chest wall, so they move easily one 
 upon the other during respiration. As the lungs are 
 always distended enough to fill the chest cavity, these two 
 surfaces are always in contact. In pleurisy (inflammation 
 of the pleurae) pain is felt in breathing from friction or 
 adhesion of these surfaces. 
 
 Important Facts concerning Respiration. In study- 
 ing respiration, let us constantly keep in mind these 
 facts : 
 
 1. The lungs are highly elastic, and 
 
 2. Highly porous, each air vesicle being in direct com- 
 munication with the outer air by means of 
 
 3. Air tubes that always stand open 
 
 4. And are always moist internally. 
 
 5. The pulmonary capillaries closely invest each air 
 vesicle. 
 
 6. The lungs are always expanded enough to fill all 
 the space in the chest not occupied by other organs, and 
 
 7. Freely movable, except at the place of entrance of 
 the bronchi and blood tubes. 
 
 8. The smooth, moist pleurae. 
 
 The Diaphragm. The diaphragm is a thin muscle 
 making a complete partition between the abdominal cavity 
 and the chest cavity. It is convex anteriorly, concave pos- 
 teriorly ; its ventral border is attached to the inside of the 
 chest wall about opposite the lower end of the breast bone, 
 thence obliquely along the border of the ribs (as felt in 
 front), and the dorsal attachment is posterior to the ventral 
 
RESPIRATION'. 
 
 8 9 
 
 attachment. Its general position is shown in Figs. 38, 40, 
 and 43. 
 
 To show the Action of the Diaphragm and Lungs. MATERIAL. 
 Bell jar with stopper, sheet of rubber large enough to cover the mouth 
 of the jar, toy rubber balloon, cork (rubber preferred), glass tube, strong 
 rubber band (such as boys use for slung shots), marble. 
 
 Triangularis Sterni 
 Internal Mammary Vessels v. 
 
 Left Phrenic 
 Nerve 
 
 Pleura 
 Puimonalis 
 
 Pleura Costalis 
 
 Mediastinum \ Sympathetic Nerve 
 
 ( Thoracic Duct 
 
 Vena Azygos Major I p osterior 
 , Pneumogastric Nerves ) 
 
 Fig. 41. A Transverse Section of the Thorax, showing the Relative Position of the 
 Viscera and Reflections of the Pleurae. 
 
 PREPARATION. Lay the marble on the center of the sheet of rub- 
 ber, double the rubber over it, stretching the rubber strongly over the 
 marble, and tie the marble firmly in its place. Stretch the sheet of 
 rubber over the mouth of the jar with the projection made by the marble 
 on the outside, and fasten with rubber band. Bore a hole in the cork, 
 
90 PHYSIOLOGY. 
 
 and fix the glass tube snugly in it, so that the lower end of the tube will 
 extend about half-way down the jar. Tie the balloon on the lower end 
 of the glass tube. 
 
 EXPERIMENT i. Inflate the balloon. Consider that it requires 
 some expenditure of energy to do this. When the mouth is taken away 
 from the tube the balloon immediately collapses. 
 
 EXPERIMENT 2. Insert the balloon and tube into the jar, but do 
 not cork, and repeat Experiment i. The same results as before are 
 noticed, and it will further be seen, or rather heard and felt, that when 
 the balloon is inflated some air comes out of the jar around the tube, 
 and when the balloon collapses air again enters the jar. 
 
 EXPERIMENT 3. Again inflate the balloon, and while it is inflated 
 tightly cork the jar. If all the parts fit well, the balloon should now 
 remain inflated. This may at first seem strange, as the mouth is taken 
 away from the tube, and the tube left entirely open to the air. But it 
 will be seen that to just the extent that the balloon contracts, so much 
 more space is left in the jar outside the balloon. This means diminished 
 pressure, and the pressure of the outer air presses the diaphragm up, 
 and keeps the balloon partly distended, maintaining equilibrium. 
 
 EXPERIMENT 4. Pull the diaphragm down, using the marble as a 
 handle. This shows the expansion of the lung by the pressure of the 
 external air when more space is given by the depression of the dia- 
 phragm. On releasing the diaphragm, it springs upward, and the 
 balloon becomes reduced in size, driving out part of the air that was in 
 it. This shows how expiration is accomplished, so far as the diaphragm 
 is concerned. 
 
 If a bell jar be not at hand, a lamp chimney or a quart bottle may be 
 used, after cutting off the bottom, as follows : File a deep notch across 
 near the bottom ; heat an iron rod, and apply the end of it to one end 
 of the notch, and slowly draw the rod around to the other end of the 
 notch (the rod may need to be reheated) . After cracking off the bot- 
 tom of the jar, file the edges so they will not cut the rubber. 
 
 Let each pupil make a drawing, showing the position of the parts in 
 inspiration and in expiration. 
 
 Illustration of the Minute Anatomy of the Lung. To illustrate 
 the minute anatomy of the lung, take a rubber balloon, a glass tube, 
 two rubber tubes, one dyed red, the other blue, a bag of netting, with 
 one side dyed red and the other side blue. Tie the balloon on the end 
 of the glass tube, slip the bag of netting over the balloon and tie it, 
 
RESPrRATION. 91 
 
 with the ends of the rubber tubes on the corresponding sides of the 
 bag. Slip a short piece of the rubber tube on the end of the glass 
 tube, and when the balloon is inflated shut the air in by means of a 
 
 CILIA I i.BRONCHIAL TUBE. 
 
 Fig. 42. Minute Structure of the Lungs, showing Air Vesicles 
 and Capillaries. 
 
 pinchcock. The balloon represents an air vesicle, the glass tube a 
 bronchial twig, the blue tube a subdivision of the pulmonary artery, 
 the netting the capillaries around the vesicle, and the red tube one of 
 the branches of the pulmonary veins. 
 
 The Movements of Respiration. The process of res- 
 piration consists of two acts, inspiration and expiration. 
 
 Two Active Forces in Inspiration. In inspiration 
 the principal active forces in the body are, first, the dia- 
 phragm ; and, second, the muscles which elevate the ribs. 
 
 Work of the Diaphragm in Inspiration. The dia- 
 phragm is a muscle, and when its fibers shorten, the dia- 
 phragm is pulled down. In moving down it presses on 
 the abdominal organs, and makes the abdomen protrude 
 laterally and ventrally. This lowering of the diaphragm 
 increases the space in the chest ; the air already in the 
 
PHYSIOLOGY. 
 
 chest expands to fill this greater space. When expanded 
 it exerts less pressure than before, and the air outside, 
 having greater pressure, enters till equilibrium is produced. 
 The air enters through the trachea, presses on the inside 
 of the elastic lungs, and makes their bases extend, follow- 
 ing the diaphragm in its descent. The bases of the lungs 
 remain in contact with the upper surface of the diaphragm 
 all the time. 
 
 . . . . Increased Air 
 Space 
 
 Inspiration Expiration 
 
 Fig. 43. Diagrammatic Sections of the Body in Inspiration and Expiration. 
 
 Work of the Chest Walls in Inspiration. Certain 
 muscles of the chest wall elevate the, ribs and breast bone. 
 This act widens the chest, and the air, as before, presses 
 in through the open trachea, and keeps the sides of the 
 lungs in contact with the inner surfaces of the chest walls. 
 
 Effort required in Depressing the Diaphragm. - 
 Inspiration requires considerable effort, because the dia- 
 
RESPIRATION. 93 
 
 phragm in its descent presses upon the elastic organs of 
 the abdomen (stomach, liver, etc.), and these organs, in 
 turn, are pressed against the elastic walls of the abdomen. 
 It is somewhat like pressing a pillow down into a rubber 
 bag; the pillow springs up as soon as the pressure is 
 stopped, because of its own elasticity as well as that of the 
 bag. Therefore, as soon as the diaphragm relaxes, the 
 elastic walls of the abdomen retreat, and the abdominal 
 organs rise to their former place. 
 
 Effort Required in raising the Ribs. When the ribs 
 are elevated, the cartilages which connect the ventral ends 
 of the. bony parts of the ribs with the breast bone are 
 slightly bent. When the muscles relax, the elasticity of 
 the rib cartilages helps to bring the ribs back to their 
 former position, thus reducing the chest to its former 
 width. 
 
 Expiration Easy. Thus we see why expiration is easy ; 
 in fact, " does itself " (in ordinary respiration) by elastic 
 reactions. But inspiration is harder than it would be if it 
 were not for the fact that the descent of the diaphragm 
 meets resistance, and the ribs, in rising, have to overcome 
 resistance in bending the costal cartilages, and in raising 
 the weight of the chest walls and shoulders. 
 
 Potential Energy stored in a Door Spring. When 
 one opens a door that has a spring to shut it, he has to 
 expend more energy to open the door than he would if he 
 did not have to bend (twist or compress) the spring at the 
 same time. But no effort is needed to shut the door. The 
 door was opened and shut at the same time ; i.e. when 
 the door was opened force was stored in the spring (in the 
 form of what is called potential energy), and this stored 
 energy shuts the door while we pass on. We can better 
 
94 PHYSIOLOGY. 
 
 afford to employ more energy while opening the door than 
 to take the extra time to shut it. If, then, a door with such 
 spring were fastened open, it might remain open for a long 
 time. When released it flies shut. If one, in this case, 
 asks, "Who shut the door?" the answer is, "The person 
 who opened it." 
 
 The Storing of Energy during Inspiration. So in 
 
 the act of inspiration we perform a double work in storing 
 energy by which the expiration is performed without active 
 muscular effort. 
 
 Review of Forces of Respiration : 
 
 FORCES OF INSPIRATION. 
 
 1. Depression of the diaphragm. 
 
 2. Muscles elevating the ribs. 
 
 3. Pressure of the external air. 
 
 RESISTANCES TO INSPIRATION. 
 
 1. Compression of the abdominal organs and stretching 
 abdominal walls. 
 
 2. Bending the rib cartilages and lifting the chest. 
 
 3. Stretching the lungs. 
 
 ELASTIC REACTIONS OF EXPIRATION. 
 
 1. Elastic reaction of the abdominal walls and contents. 
 
 2. Elastic reaction of the rib cartilages. 
 
 3. Elastic reaction of the lungs. 
 
 Forced Respiration. Thus far we have been speaking 
 of ordinary respiration. In forced respiration, as in shout- 
 ing, many muscles are brought into play to expel the air 
 rapidly and forcibly. In such an act as coughing there is 
 vigorous action of the abdominal muscles. 
 
RESPIRATION. 95 
 
 Abdominal and Thoracic Respiration. The main part 
 of respiration is performed by the diaphragm, and the more 
 common mode of respiration is therefore called abdominal 
 or diaphragmatic respiration. In women of the civilized 
 races respiration is more largely accomplished by the action 
 of the thoracic muscles, and is called thoracic or costal res- 
 piration. In children the respiration is of the abdominal 
 type. 
 
 The Rate of Respiration. The rate of respiration in 
 the adult varies from sixteen to twenty-four per minute, 
 the average being about seventeen times a minute ; about 
 one respiration for every four heart beats. Light is favor- 
 able to respiratory activity. The rate is affected by the 
 position of the body, state of activity, temperature, diges- 
 tion, emotions, age, disease, etc. Ordinary inspiration 
 takes slightly less time than expiration. 
 
 Modifications of Respiration. Coughing is a forcible expiration, 
 usually directed through the mouth, and for the purpose of getting rid 
 of some foreign substance, or caused by irritation. In sneezing there is 
 first a deep inspiration, and then the current of air is forced out, chiefly 
 through the nose. Sneezing may be prevented by pressing firmly on 
 the upper lip. Crying, laughing, sobbing, are modifications of respira- 
 tion connected with certain emotions. Yawning and sighing are deeper 
 breathings, caused by etijiui, depressing emotions, or a deficient ventila- 
 tion. Hiccuping is sudden inspiration, produced by spasmodic action 
 of the diaphragm, accompanied by sudden closure of the glottis, and is 
 often caused by some disorder of stomach digestion. Snoring is caused 
 by breathing through the mouth and setting the soft palate into vibra- 
 tion. Sniffing is sudden inspiration : the diaphragm is suddenly pulled 
 down, the air in the nasal cavity is thus drawn downward, and the air 
 we wish to test, or the odor we wish to inhale, is thus drawn into the 
 upper nasal cavities ; whereas in ordinary inspiration most of the air 
 passes along the lower part of the nasal passage. In hawking, the air 
 is forced out through the narrowed passage between the root of the 
 tongue and the soft palate to remove mucus. Gargling is forcing air up 
 
96 PHYSIOLOGY. 
 
 through liquid held between the tongue and the soft palate. Panting, 
 whistling, blowing, spitting, sucking, and drinking are also modifica- 
 tions of respiration. In case of choking it is well to hold the head for- 
 
 Jl 
 
 II 
 
 COMPLEMENTAL AIR. 
 
 120 CUBIC INCHES. 
 AIR THAT CAN BE BUT SELDOM IS TAKEN IN. 
 
 TIDAL AIR. 20 to 30 Cubic Inches Air Taken in 
 and Sent out at Each Breath. 
 
 RESERVE AIR. 
 
 100 CUBIC INCHES. 
 
 m 
 
 ^ AIR THAT CAN BE BUT IS SELDOM DRIVEN OUT. 
 
 RESIDUAL AIR. 
 
 100 CUBIC INCHES. 
 
 AIR THAT CANNOT BE DRIVEN OUT. 
 
 II 
 
 t> 
 
 -S -S 
 
 - 
 
 QU 
 
 Figr. 44. Diagram of Lung Capacity. 
 
 ward, and perhaps downward. A smart slap between the shoulders 
 sometimes helps dislodge anything stuck in the throat, and it may be 
 necessary, in addition, to hold a child with its head downward. 
 
RESPIRATION. 97 
 
 Capacity of the Lungs. Have the class stand, and each pupil raise 
 his right hand. 
 
 1 . Tidal Air. Let all breathe together, at the ordinary rate and 
 depth, and let the hand rise about three inches during inspiration, and 
 fall again during expiration. The amount of air taken in at an ordinary 
 breath is from 20 to 30 cubic inches, or about a pint. This is called 
 tidal air. 
 
 2. Complemental Air. As before, let the hand go up and down 
 with the breathing, but at the end of the third inspiration, instead of 
 stopping with the usual amount, keep on breathing in as much as pos- 
 sible, letting the hand rise accordingly. This air that can be taken in 
 above the ordinary breath is called the complemental air, and it is 
 estimated to be, on the average, about 120 cubic inches. 
 
 3. Reserve Air. Begin as before, and at what would be the end 
 of the third expiration continue to drive out as much air as possible, 
 indicating the degree by correspondingly lowering the hand. This air 
 that can be breathed out beyond the ordinary expiration is called the 
 reserve air, and is reckoned at about 100 cubic inches. 
 
 4. Residual Air. The air cannot all be breathed out. The re- 
 mainder is called the residual air, and is computed to be about 100 
 cubic inches. 
 
 The Vital Capacity. All the air that can be breathed out after a 
 full inspiration, i.e. the sum of the complemental, tidal, and reserve 
 air, would be about 240 to 250 cubic inches, and is called the vital 
 capacity. Of course these figures represent only the average of cer- 
 tain experiments and observations. By practice any one can con- 
 siderably increase his vital capacity. 
 
 A Test of the Capacity of the Lungs. A simple method of 
 measuring these stages of respiration is to take a gallon bottle and 
 first carefully graduate it to pints by pouring in water and marking on 
 the outside with a file. Then invert the bottle in a trough of water, 
 and inhale from it by means of a rubber tube. Or fill the bottle, in- 
 vert in water, and exhale into it. 
 
 Hygiene of Breathing. Those persons who take con- 
 stant exercise in the open air are likely not to suffer much 
 from deficient respiration. But persons following seden- 
 
98 PHYSIOLOGY. 
 
 tary occupations, such as that of the student, not calling 
 for deep breathing (and often the air taken in is of poor 
 quality), need to pay especial attention to the matter. 
 
 Breathing through the Mouth. We should breathe 
 through the nose, and not through the mouth. The nasal 
 passages are fitted for the introduction of the air (i) by 
 being narrow, but of large area; (2) by having their lining 
 membranes richly supplied with blood ; (3) by the abun- 
 dant secretion of mucus by this membrane. The air, 
 coming through this narrow channel, is warmed, and a 
 large part of any dust it may contain is caught by the 
 sticky mucus that covers all the walls of this passageway. 
 If we breathe through the mouth (especially out of doors 
 in cold weather), the air may not be sufficiently warmed 
 before entering the lungs, and much more dust would be 
 carried into the lungs. Then, too, the air has a drying 
 effect on the throat, whereas the mucus of the nasal pas- 
 sages will moisten the air as it enters. The cilia, which 
 extend from most of the cells lining the respiratory pas- 
 sages, are constantly causing the mucus to slowly flow 
 toward the external opening, so a good share of the dust 
 is gotten rid of. A further advantage of breathing through 
 the nose is that we detect odors, and can thus judge of the 
 quality of the air. 
 
 Breathing and Circulation. The fact has been noted 
 that breathing directly aids the circulation of the blood. 
 This is due to the way air pressure is made to affect the 
 large veins. Breathing also may very considerably aid 
 the flow of lymph. Every deep inspiration brings pres- 
 sure to bear on the main lymph duct as the diaphragm 
 descends. Every forced expiration has the same effect. 
 We must keep in mind that the tissues are fed directly by 
 
RESPIRATION. 99 
 
 the lymph that surrounds them ; that while the lymph is 
 continually fed by the blood, there is not a great pressure 
 given in this way. The lymph stream is largely depend- 
 ent on the pressure of the surrounding organs. When 
 one takes a good deal of muscular exercise the lymph is 
 renewed with rapidity enough to supply the tissues with 
 food, and to carry away their wastes. But in those who 
 sit quiet a large share of the day, taking no more exercise 
 than is necessary to take them to and from their places 
 of business, the lymph becomes too nearly stagnant, the 
 tissues are not well nourished, and the whole body suffers. 
 
 Deep Breathing. It is a grateful relief to the whole 
 system to stand, stretch, inhale deeply and slowly several 
 times, and to repeat this every hour or so. Every one en- 
 gaged in office work or studying should form this habit, 
 especially if he does not give an hour daily to exercise in 
 a gymnasium, or otherwise. 
 
 Respiratory Sounds. During respiration sounds are 
 produced by which the skilled physician can tell much as 
 to the condition of the respiratory organs. 
 
 The Control of Respiration. Breathing is an involun- 
 tary act. Still we can modify it. We can hold the breath 
 for a time ; but it is stated that one cannot hold the breath 
 long enough to produce death by suffocation. 
 
 The muscles of respiration are under the control of 
 nerves. The center of respiratory control is believed to 
 be in the lower portion of the spinal bulb. This respira- 
 tory center is one of the most vital points in the body, for 
 if it is destroyed, breathing is completely stopped, and 
 death ensues. This center is affected by the condition of 
 the blood. For instance, if the blood going to this center 
 has not enough oxygen, the center hastens the process 
 
100 PHYSIOLOGY. 
 
 of breathing by nerve impulses sent to the muscles of 
 respiration. 
 
 The Control of the Diaphragm. The diaphragm is 
 under the control of the phrenic nerves, which arise from 
 the third, fourth, and fifth cervical nerves. If the neck is 
 broken above the point where these nerves are given off, 
 death almost always immediately follows, because the con- 
 nection of the respiratory center and the diaphragm is 
 broken. 
 
 Composition of Dry Air (by volume) : 
 
 Oxygen . . . . . . .... . 2 1 .00 
 
 Nitrogen . . . . . v . . . . . 79.00 . 
 
 Carbon Dioxid .04 
 
 100.04 
 
 Experiments illustrating the Chemistry of Respiration. EX- 
 PERIMENT i . If a piece of phosphorus be burned under a fruit jar 
 inverted and with the mouth under water (for directions consult any 
 chemistry), the oxygen will be consumed and water will enter part way 
 to take its place. The remainder is nitrogen. 
 
 EXPERIMENT 2. If a burning taper be lowered into this nitrogen, 
 the flame will be extinguished. 
 
 EXPERIMENT 3. If a chemical laboratory is at hand, some carbon 
 dioxid should be generated and tested to -show that it extinguishes 
 flame. 
 
 EXPERIMENT 4. Lime water is the test of carbon dioxid, and may 
 easily be prepared by putting a piece of quicklime the size of a hen's 
 egg into a quart of water. 
 
 EXPERIMENT 5. Pour a little clear lime water into a jar contain- 
 ing carbon dioxid, and on shaking the contents the lime water will be 
 rendered milky. 
 
 EXPERIMENT 6. By means of a tube (a straw will serve) breathe 
 through a small quantity of lime water to show that there is carbon 
 dioxid in the expired breath. 
 
 EXPERIMENT 7. If a jar be inverted over a lighted taper, the flame 
 will soon be extinguished. Test the gas with lime water to see that 
 carbon dioxid is produced by a burning candle. 
 
RESPIRATION. IOI 
 
 EXPERIMENT 8. By holding a clean, cold tumbler over a burning 
 taper it will be seen that water vapor is produced by the burning. 
 
 EXPERIMENT 9. Breathing into a clean, cold tumbler shows that 
 water is produced also in the process of respiration. 
 
 EXPERIMENT 10. A very brilliant experiment and one that is very 
 instructive at this point is to burn a watch spring in oxygen. In this 
 process the oxygen unites with the iron, forming iron oxid. 
 
 EXPERIMENT n. If a piece of watch spring be placed in water, it 
 will soon rust. Rust is also an iron oxid, only the process is slow, 
 instead of rapid as in the case of combustion, and just as much heat is 
 given off, but not much at any given instant. 
 
 EXPERIMENT 12. If a short piece of magnesium ribbon can be 
 obtained, it may be burned in the presence of the class, though it is not 
 well to look long at the excessively strong while light. 
 
 EXPERIMENT 13. ManMslimi;wild also 'ru^'in water, forming a 
 white rust, or magnesium oxid, as in burning. , , , , 
 
 EXPERIMENT 14. If a <fer be ftlz& whVthfi jsScwiy expired breath, 
 capped tightly, and set in a warm place it will acquire a bad odor. 
 
 EXPERIMENT 15. Hold a thermometer at arm's length. It indi- 
 cates the temperature of the air of the air that you are breathing in. 
 Breathe for a few minutes upon the bulb of the thermometer, and the 
 fact is clearly shown that the air we breathe out is much warmer than 
 the air that we breathe in. 
 
 EXPERIMENT 16. With a pair of bellows force the air of the room 
 through a small quantity of lime water. By continuing this process a 
 long time it may be shown that there is carbon dioxid in the air, but not 
 nearly so much as in the expired breath. 
 
 Result of Experiments. These experiments show that 
 breathed air has gained : 
 
 1. Heat. 
 
 2. Water vapor. 
 
 3. Carbon dioxid. 
 
 4. Waste products, or impurities, having no definite 
 name, because not well known, highly putrescible, often 
 called by the general name of ''organic waste matter." 
 
102 
 
 PHYSIOLOGY. 
 
 IN 10,000 VOLUMES. 
 
 i Represented by Largo Square.) 
 
 PER CENT. 
 
 AMOUNT OF CARBON 
 
 DIOXID. 
 
 IN 
 
 INSPIRED AIR. EXPIRED AIR. 
 
 4 400 
 
 (Small Square.) (Medium Square). 
 
 .04 4 
 
 COMMON FRACTION ^~ 
 
 r 
 
 25 
 
 20 100 
 
 Fig. 45. Amount of Carbon Dioxid in Inspired and Expired Air. 
 
 The Composition of Inspired and Expired Air. - 
 
 Oxygen. Nitrogen. Carbon Dioxid. 
 Inspired air ... 21 79 .04 
 
 Expired air ... 16 79 4.00 
 
 While the amount of nitrogen remains about the same, 
 some oxygen has disappeared, and its place is taken by 
 carbon dioxid, while the amount of carbon dioxid has in- 
 creased a hundred-fold. 
 
RESPIRATION. 
 
 103 
 
 Exchanges between the Air and the Blood in the 
 Lungs. Whatever the air coming from the lungs cen- 
 tains that was not in the air entering them, it has taken 
 from the blood, and what the air has lost it has given to 
 the blood. The air in the air vesicle is separated from the 
 
 BRONCHIAL TUBE 
 
 FROM PULMONARY ARTERY 
 
 TO PULMONARY VEIN 
 
 Fig. 46. Exchanges between the Air and the Blood in the Lungs. 
 
 blood in the pulmonary capillaries only by the thin wall of 
 the air vesicle and the thin capillary wall. Carbon dioxid, 
 water, and other waste matters pass from the blood through 
 this thin partition into the air vesicle, to be sent out by 
 later expiration. Oxygen from the air in the vesicle passes 
 
104 PHYSIOLOGY. 
 
 through these layers into the plasma, and most of it is 
 quickly picked up by the colored corpuscles. The colored 
 corpuscles are the carriers of oxygen. 
 
 Hemoglobin and Oxy hemoglobin. As has already 
 been stated, the hemoglobin in the colored corpuscles has 
 an affinity for oxygen. Hemoglobin is of a dark color, 
 and gives the dark color to the blood which enters the 
 lungs. When oxygen unites with the hemoglobin it forms 
 oxyhemoglobin, which is of a bright red color. Hence 
 the change in the color of the blood in the lungs from a 
 dark bluish red to a bright scarlet. This bright blood is 
 usually called "arterial," and the dark "venous"; but it 
 must be remembered that the blood in the pulmonary 
 artery is dark, and in the pulmonary veins bright. 
 
 Amount of Oxygen Used. We take into the blood 
 only about one fourth of the oxygen of the air that passes 
 through the lungs. In like manner the blood, passing 
 through the tissues, gives up to those tissues (in ordinary 
 circumstances) only about half the oxygen it contains (per- 
 haps holding the remainder as a reserve). 
 
 The Gases in the Blood. If a quart of blood be placed 
 under the receiver, and the air exhausted, it will be found 
 that the blood contained about three fifths of a quart of 
 gas. This gas is a mixture of oxygen, carbon dioxid, and 
 nitrogen, and the proportions vary according to the kind 
 of blood taken. If from the left heart, or pulmonary veins, 
 there will be more oxygen and less carbon dioxid ; if from 
 the right heart, pulmonary artery, or caval veins, there 
 will be less oxygen and more carbon dioxid. Oxyhemo- 
 globin blood ("arterial blood ") contains about one fifth its 
 volume of oxygen. Hemoglobin blood ("venous blood") 
 contains about one tenth its volume of oxygen. Oxy- 
 
RESPIRATION. 
 
 105 
 
 hemoglobin blood holds about two fifths its bulk of carbon 
 dioxid, while hemoglobin blood has nearly one half its 
 bulk of carbon dioxid. 
 
 , THE GASES IN THE BLOOD. 
 
 From 100 volumes of May be obtained 
 
 Oxygen. Carbon dioxid. Nitrogen. 
 
 Oxyhemoglobin (arterial) blood . 2ovols. /pvols. ito2vols. 
 
 Hemoglobin (venous) blood . . lovols. 46vols. ito2vols. 
 
 Illustration of the Changes in the Color of the Blood. The 
 
 changes that take place in the color of the blood, both in the lungs 
 and in the tissues of the other parts of the body, may be illustrated as 
 
 Fig. 47. 
 
 follows : Prepare a heart as directed on page 45. Use for the liquid a 
 strong solutiofl of litmus, neutralized or slightly alkaline ; place in the 
 throat of each funnel a small sponge. Saturate with ammonia the 
 sponge in the funnel representing the capillaries of the body, and 
 
106 PHYSIOLOGY. 
 
 saturate with hydrochloric acid the one in the funnel representing the 
 capillaries of the lungs. 
 
 Now, on working the heart the liquid will change from red to blue 
 in the funnel representing the body, and from blue to red in the funnel 
 representing the lungs. 
 
 " Anatomically there are two lungs, and the heart lies between them ; 
 physiologically, the lungs form a single organ, which is interposed be- 
 tween the two hearts." WILDER. 
 
 The Changes in the Blood. What does the blood do 
 with the oxygen that it gets in the lungs, and where did it 
 get the carbon dioxid and other impurities that it brings 
 to the lungs ? Let us follow the blood and see. From 
 the pulmonary veins the blood goes to the left heart, and 
 is pumped to all the tissues except the lungs. Let us- 
 follow a branch of the aorta that leads to a muscle. 
 
 The Production of Heat and Motion in the Body. - 
 
 When a muscle works it becomes warmer. This has been 
 repeatedly proved by experiment. We know that we feel 
 warmer when we exercise. We know that the blood is 
 flowing more rapidly through the muscle when it is at 
 work. This more rapid stream brings the muscle more 
 oxygen. This it needs, for the heat of the muscle is pro- 
 duced by the oxidation of substance in the muscle. We 
 have seen that the oxidation of iron produces heat, and it 
 is the oxidation of the materials in the candle that enable 
 it to give out heat. But our bodies do not give out the 
 intense heat of a burning candle, nor do they produce 
 light, as is the case with the oxidation of iron and magne- 
 sium when those metals are burned. The slow oxidation 
 of the metals, in the presence of moisture, is more like 
 the oxidations in our bodies. It is by the oxidations of 
 the muscle (or substance in it) that the muscles produce 
 heat and that form of energy which gives motion. In the 
 
RESPIRATION. 
 
 Case of the rusting of the metals there is as much heat pro- 
 duced as when they are burned, but the heat is so slowly 
 generated that it is given off about as fast as it is pro- 
 duced, and we do not notice it. The oxidation produces 
 the waste matters, just as the burning of the various 
 substances produces waste. 
 
 Oxidation of Live Tissues and Dead Matter. In our 
 
 experiments with oxygen we see that substances which 
 burn in air will burn still more actively in oxygen. But 
 we must not infer from this that in our bodies the oxida- 
 tion of the tissues would be faster in pure oxygen. This 
 is not the case. The tissues take as much oxygen as they 
 need (if they can get it), and they will not take any more 
 than they need, no matter how much is offered them. It 
 does not injure the body, nor any part of it, to breathe 
 pure oxygen. It does not make one feverish, it does not 
 produce any more heat, nor make one "live faster." This 
 point should be specially noticed,- as it was formerly sup- 
 posed that the oxidation of the tissues of the body was 
 just like any combustion of dead material. But the tissues 
 are alive. They know their own needs. Each cell takes 
 what it requires and no more, just as it does of food 
 brought to it by the blood. The amount of oxygen pres- 
 ent does not determine the degree of muscular activity, 
 but the degree of muscular activity determines the amount 
 of oxygen consumed. 
 
 Increased Blood Flow is the Result of Exercise. - 
 When we exercise, the muscles need more oxygen. They 
 also need to have removed the waste matters that they are 
 so rapidly producing at this time. How is the oxygen 
 brought and the waste removed ? By the blood, you 
 answer. True ; but what makes the blood come and 
 
I08 PHYSIOLOGY. 
 
 go faster at this time ? By reflex action, you reply. The 
 muscles send a message to a nerve center, and this nerve 
 center sends back a message to the blood tubes, making 
 them widen, and the heart also may be made to beat 
 faster. But would it do any good to have the blood flow 
 through the muscles faster, if it could not bring more oxy- 
 gen, and take away and get rid of more wastes ? You 
 will say no. To give the extra oxygen, and take out the 
 carbon dioxid, the lungs cannot, of themselves, take in and 
 send out air. The work of pumping air depends on the 
 muscles of respiration, the diaphragm, and the muscles 
 that elevate the ribs. These will not work faster unless 
 they are ordered to do so. A message must be sent to 
 these telling of the need in the muscles that we are con- 
 sidering, say one of the large muscles of the lower limbs. 
 Thus, by a series of reflex actions, all these processes are 
 kept in harmonious relation to each other. It must be 
 borne in mind that increased blood flow is the conse- 
 quence, and not the cause, of the increased activity of the 
 tissues. 
 
 Temperature of the Body. Insert the bulb of a thermometer into 
 the mouth, and keep it there three or four minutes to find the tempera- 
 ture of the inside of the body. For this it is better to use a clinical 
 thermometer, if one can be obtained. The average temperature of the 
 tissues within the body is about 98.5 F. 
 
 How the Body is like a Stove. The body may be 
 compared to a stove. Into one we put fuel and produce 
 heat. In the other we get heat from food. 
 
 How the Body differs from a Stove. But the body is 
 not like the stove in burning the fuel (food) directly. The 
 food is first made into tissues, or " storage compounds " in 
 the tissues. It is as though we were to build a stove 
 
RESPIRA T1ON. 1 09 
 
 entirely of coal, and then start a fire in it. In that case it 
 would produce heat not merely by burning in one place 
 within, but would be burning throughout the whole of its 
 substance. This is the case with the body. 
 
 Oxidation in Tissue the Source of Heat in the Body. - 
 
 We have seen that the muscles constitute nearly half of 
 the weight of the body. We know, too, that they are more 
 active than most of the tissues. We would now naturally 
 infer, as indeed is the fact, that they are the chief source 
 of the heat produced in our bodies. 
 
 The tissues of the body are oxidizing all the time. But 
 when they are in vigorous action they oxidize very much 
 more rapidly. 
 
 Next to the muscles, in importance as a heat producer, 
 is the liver, which is the largest gland in the body, and, as 
 we shall soon see, one of the most active. The blood, as 
 it leaves the liver by the hepatic vein, is hotter than 
 anywhere else in the body. 
 
 How the Body is like a Locomotive. But it will be 
 better to compare the body to a locomotive, as we produce 
 not only heat, but motion as well. 
 
 If a visitor from another planet, unfamiliar with such 
 creatures as we are, were to observe closely a man and a 
 locomotive, he would see several points in common : 
 
 1. Both are warm. 
 
 2. Both move. 
 
 3. Both use fuel (food or coal). 
 
 4. Both take in air, and (if it were a winter day) 
 
 5. Both give off smoke (which is essentially the same 
 in the two, carbon dioxid and water vapor being the chief 
 constituents). 
 
no PHYSIOLOGY. 
 
 How the Body differs from a Locomotive. By a 
 
 closer examination he would find out some of the differ- 
 ences that we have noticed : 
 
 1. That the body does not get hot enough to burn ; i.e. 
 the oxidation is relatively slow, and is not combustion. 
 
 2. That the oxidation of the body never produces light. 
 
 3. That the oxidation here is always in the presence of 
 moisture. 
 
 The Amount of Carbon Dioxid given off. When the 
 breath is held for some time, the carbon dioxid in the ex- 
 pired air may reach 7 or 8 per cent. During violent 
 exercise the amount of carbon dioxid given off may be 
 from two to two and a half times as much as when we are 
 at rest. The amount of carbon dioxid given off is in- 
 creased in cold weather, and by taking food, and decreased 
 from one fifth to one fourth during sleep. Oxygen is 
 carried chiefly in the corpuscles, but the carbon dioxid is 
 carried in both plasma and corpuscles. 
 
 Storage of Oxygen in the Tissues. The activity of the tissues 
 from their oxidation does not necessarily mean that the oxidation is 
 direct ; that is, that the oxygen is used as soon as it is brought to the 
 tissue. For instance, in the muscles it is believed that the oxygen is 
 stored in some form, probably in combination, so that it can be used 
 when needed, perhaps much more rapidly than could be supplied by the 
 respiration at the time. If we study the chemistry of explosion, we 
 learn that it is a very rapid combustion. In the explosives are ma- 
 terials that unite instantaneously, instead of slowly burning, as in the 
 case of ordinary combustibles. 
 
 The Action of Muscles like an Explosion. Now, many physiolo- 
 gists hold that a sort of explosive compound is formed in the muscles, 
 and that when the muscle acts it does so as the result of the explosion, 
 so to speak, of this material. And, to carry out the figure, the nerve is 
 compared to the match that ignites the explosive. A little heat is 
 enough to cause the most violent explosion. So the force that passes 
 
RESTIRA 77 ON. 1 1 1 
 
 along a nerve fiber is slight. But it rouses a great amount of energy 
 that lay dormant in the muscle. It would seem to have "touched off 11 
 a lot of explosive material that was already there, rather than merely 
 started an action that depends on the comparatively slow process of 
 respiration at the time. We cannot follow this theory farther, as it 
 takes us too deep into the study of chemistry in its most difficult 
 branch, physiological chemistry. 
 
 Summary of Respiration. The tissues need oxygen ; 
 air is pumped into the lungs ; this air gives oxygen to the 
 blood ; the blood carries it to the tissues. 
 
 In oxidizing, the tissues produce energy (heat and mo- 
 tion) and give off waste matter (water, carbon dioxid, etc.); 
 these the blood carries to the lungs, the lungs give them 
 to the air, and the air carries them out of the body. 
 
 The pumping of the air in and out may be called " me- 
 chanical respiration." The changes between the air and 
 the blood in the lungs we will call the " ventilation of the 
 blood," and the interaction of the blood and the tissues 
 the "real, or internal respiration." 
 
 The Two Breaths. " Every time you breathe you 
 breathe two different breaths ; you take in one, you give 
 out another. The composition of these two breaths is 
 different. Their effects are different. The breath which 
 has been breathed out must not be breathed in again. "- 
 KINGSLEY. 
 
 Breathing Expired Air. The air in the vesicles re- 
 ceives from the blood carbon dioxid, water vapor, and 
 other impurities above mentioned. It has been believed 
 for a number of years that the organic impurities consti- 
 tute the most dangerous element in expired air. Carbon 
 dioxid, though to some extent a poison, is not very injuri- 
 ous in such quantities as ordinarily exist in the air, even in 
 poorly ventilated rooms ; while the headache and drowsi- 
 
112 rilYSlOLOGY. 
 
 ness that one experiences in a close room where there are 
 a number of people is due to the reabsorption of these or- 
 ganic matters. It is not due to lack of oxygen, for the 
 oxygen may be reduced to 13 per cent without causing 
 discomfort. A person may breathe air containing i per 
 cent of carbon dioxid, with a corresponding reduction of 
 oxygen, when the carbon dioxid is generated by ordinary 
 chemical processes (as in a small room with a large kero- 
 sene lamp, or a gasoline stove); but air having I per 
 cent of carbon dioxid produced by breathing is highly in- 
 jurious, because it contains the organic impurities above 
 noted, and the term "crowd poison" has been employed 
 for this material. Later investigators, however, maintain 
 that there is nothing injurious in the freshly expired breath. 
 
 Summary. i. In the lungs the air and blood are brought very 
 close together, only the wall of the capillary and that of the air vesicle 
 intervening. 
 
 2. Through these two layers oxygen passes from the air vesicle 
 into the blood. Carbon dioxid, water vapor, ancj other wastes pass 
 from the blood into the air vesicle. 
 
 3. The mucous membrane of the air passages secretes mucus 
 which is driven toward the nostrils by the cilia. 
 
 4. The chest is lengthened by the depression of the diaphragm, 
 and widened by the elevation of the ribs, giving greater space, which is 
 filled by external air expanding the lungs. 
 
 5. Inspiration acts in opposition to resistances, whose elastic re- 
 action performs ordinary expiration without active effort. 
 
 6. There are four heart beats for each respiration. 
 
 7. The lungs are never emptied. 
 
 8. Respiratory capacity may be increased by exercise and practice. 
 
 9. Respiration is controlled by the nervous system ; the respiratory 
 center is in the spinal bulb. 
 
 10. Internal respiration is an oxidation in the tissues, illustrated by 
 the rusting of moist iron. 
 
RES PI R A TION. 1 1 3 
 
 11. In passing through the lungs air loses oxygen, and gains water, 
 carbon dioxid, and other wastes. 
 
 12. Oxygen is carried chiefly by the colored corpuscles of the blood ; 
 it unites with hemoglobin in the corpuscles, forming oxyhemoglobin, 
 and gives the blood its bright scarlet color. 
 
 13. The energy of heat and motion in the body results from the 
 oxidations in the tissues. 
 
 14. Air once breathed is unwholesome. The air of living and sleep- 
 ing rooms needs constant renewal. 
 
 Questions. i . Is it a good thing to see how long one can hold his 
 breath ? 
 
 2. Should the head be covered by bedclothes ? 
 
 3. What are the " lights "" in an animal ? 
 
 4. How is respiration affected by a stooping posture ? 
 
 5. In what part of the lungs is the best air ? Where the worst ? 
 
 6. Can you explain how respiration affects circulation ? 
 
 7. Is it easy to determine by the color of blood flowing from a 
 wound whether it is arterial or venous ? Why ? 
 
 8. Of what advantage is it that the cartilages of the windpipe are 
 C-shaped and not complete rings ? 
 
 9. How is it that in respiration 5 per cent of the oxygen disappears 
 while only 4 per cent of carbon dioxid appears in its place in the ex- 
 pired breath ? (See p. 102.) 
 
CHAPTER VII. 
 VENTILATION AND HEATING DUST AND BACTERIA. 
 
 Need of Proper Ventilation. When one is actively 
 exercising his muscles he may keep warm outdoors through 
 our winter days. For the heat of the body depends on its 
 internal fires, the oxidation of its tissues. But if we are 
 inactive, these fires burn feebly, and we need outside heat. 
 While air is free, it really costs a good deal of money to 
 have it properly warmed. 
 
 A Lack of Effective Systems of Ventilation. Lung 
 diseases are rare in the regions where the windows and 
 doors may be kept open most of the days of the year. It 
 is from shutting ourselves in so closely that we suffer. 
 This is especially true where many people are housed in a 
 comparatively small space, as in many public buildings. 
 But in our private dwellings, even when the owners are 
 amply able to secure the most sanatory appliances, defec- 
 tive apparatus is often put in. Any system that does not 
 provide for a constant renewal of the air is defective. 
 
 Grates as Heaters and Ventilators. Grates will aid 
 largely in renewing the air. Although in themselves they 
 merely have provision for sending radiant heat out into the 
 room and much air up the chimney, yet, without any 
 special provision for inlet of air to the room, they draw air 
 in through every crack and crevice. It would probably be 
 very much better to have special ducts for the admission 
 
 114 
 
VENTILATION AND HEATING. 11$ 
 
 of air, which is suitably warmed while on its way into the 
 room, and to make the doors shut snugly, and to have 
 double windows, as then both the admission of fresh air 
 and the regulation of heat will be better secured. But 
 it is a serious question whether, with all our modern ap- 
 pliances, conveniences, and luxuries, we have better air 
 in our houses, and take cold less frequently, than our 
 ancestors who depended more on the fireplace, even if 
 they did " roast on one side while they froze on the other." 
 Fireplaces are expensive as mere heaters, but they are 
 excellent ventilators. 
 
 Ventilating Flues around a Smoke Flue. If small 
 ventilating flues could be built around the flue of the main 
 heating apparatus, and connected with the various rooms 
 of the house, air could be drawn from these rooms by 
 ascending currents created by the heat of the central smoke 
 flue. Such flues surrounding smoke flues, would have the 
 added advantage of protecting the house from fire through 
 the too common " defective flue." 
 
 The General Principles of Ventilation. Of the forces 
 that operate to renew the air two are natural, diffusion 
 and the wind ; and two are artificial, warm air shafts and 
 fan systems. 
 
 Diffusion. Gases tend to mix. We know that if a 
 bottle containing an odorous substance be opened in 
 a room where there are no air currents the odor tends to 
 spread equally through the room. So if a person is in 
 one corner of a large room, where there are no inlets 
 or outlets, and no currents, as he uses the oxygen immedi- 
 ately around him, the oxygen farther away will diffuse 
 toward him so that he will continue to get oxygen till the 
 amount of oxygen in the room is nearly exhausted. So, 
 
u6 
 
 too, the gases that he breathes out will not remain confined 
 to the space directly about him, but will spread nearly 
 evenly throughout the room. The same takes place in the 
 open air, without wind. So, then, if the windows and 
 doors are open, the air of the room will, by diffusion, be 
 renewed. 
 
 Wind. Motion of the air renews faster than mere dif- 
 fusion. Strong wind forces its way through the cracks 
 around windows, and when windows are open on opposite 
 sides of a room there is usually enough breeze to renew the 
 air. But during the greater part of the year this cannot be 
 done. 
 
 Artificial Renewal of the Air. The renewal of the 
 air in most cases depends on the fact that heated air rises. 
 Heat expands air. It is then lighter, bulk for bulk, than 
 cooler air. The heavier surrounding air presses the lighter 
 air upward. If there are outlets above and below, the 
 heavier, colder air will press in at any opening left below, 
 and push the lighter, warmer air out above. 
 
 The Common Stove. In the case of the common stove 
 we very well know that there are currents of heated air 
 rising above the stove. Children make whirligigs and 
 various toys to place in these up-currents above stoves. 
 Air is, at the same time, flowing toward the stove along 
 the floor and lower part of the room. Cold air can usually 
 be detected entering around the windows and doors, which 
 presses downward and toward the source of heat. The 
 stove does not do much to renew 'the air in the room 
 except in this general way ; some heated air escapes at 
 openings in the upper part of the room, and some is passed 
 out through the stove, taken in as a draft. But in the 
 
VENTILATION AND HEATING. 1 1/ 
 
 main, the action of the heat of the stove is to make a 
 current of warm air up from the stove, which current 
 passes along the ceiling to the more distant corners of the 
 room, then descends, joining the cold air, and repeating 
 the round. 
 
 A Stove and Jacket. In some cases a jacket is placed 
 around a stove, and a duct from the outer air connects 
 with the lower part of the space inside of the jacket and 
 outside of the stove. Then as the air heated by the stove 
 rises, fresh air is drawn in from outside to be warmed. 
 In this case the direct heat from the stove is shut off from 
 the room. Heat radiates in straight lines. When one 
 holds out his hands beside a stove the heat he receives is 
 radiant heat. Most of the heat from a grate is radiant 
 heat. But in a jacketed stove the heating by air currents 
 is called heating by convection. 
 
 The Furnace. Now a furnace is practically a jacketed 
 stove (almost always placed in a basement). Furnaces 
 have this good feature that they are all the time sending 
 fresh air into a room. 
 
 Foul-air Shafts and Fans. Although in private dwell- 
 ings heated by furnaces there is no special provision for 
 the escape of foul air, there is ordinarily sufficient renewal 
 of the air. But in public buildings there should be escape 
 flues for foul air. 
 
 Frequently a large foul-air shaft is built in some central 
 part of the building, and a small stove placed in it to create 
 a sufficient up-current. In many public buildings the cur- 
 rents created by heat are insufficient to renew the air 
 properly. Fans are used, which force the air, properly 
 heated, into the room. 
 
Il8 rHYS/OLOGY. 
 
 Direct Heating. In heating by steam or hot water, if 
 the radiators are placed in the room they give direct or 
 radiant heat. This system is called direct heating. In 
 itself it has no provision for renewing the air. It gives 
 direct heat, and produces air currents within the room ; 
 and any change in the air is wholly incidental, from escape 
 of heated air in the upper parts of the room and corre- 
 sponding suction of outside air through such openings as 
 the carpenters have left below. 
 
 Indirect Heating. In indirect heating, coils of steam 
 or hot-water pipes are placed in air shafts which lead up 
 to the rooms above, and also have ducts to the outside. 
 As the air is heated by the heat of the pipes it rises into 
 the rooms above, and fresh, cold air presses in through the 
 ducts, to be, in turn/heated and sent up. If there is at 
 the same time a proper escape for the foul air, this makes 
 an excellent system. 
 
 A Combination of Direct and Indirect Heating. In 
 
 many situations the direct and indirect may be advan- 
 tageously combined. Where there is a grate in a room, it 
 serves very well as a foul-air shaft, especially when there 
 is a fire in the grate. It is well to have the flue from the 
 grate in the same chimney with that from the smoke pipe, 
 as then the heat from the smoke will cause a constant up- 
 draft in the grate flue, whether there is a fire going in the 
 grate or not. 
 
 With a grate, in private houses, there is ordinarily no 
 need of other foul-air shaft for any room. But it is very 
 desirable to have at least some "indirect" heat, so that 
 the fresh air introduced will be sufficiently heated. 
 
 If the introduction of air is thus provided for, it is then 
 safe to put on double windows and make the cracks around 
 
DUST AND BACTERIA. 119 
 
 the door very tight. Without any special provision for the 
 renewal of the air these cracks are the means of safety. 
 
 In houses heated by furnaces, steam, or hot water, the 
 floor is likely to be warmer from the escape of heat from 
 the heater itself, and from pipes or air ducts under the 
 floor. 
 
 Double Windows. There is a very common misunder- 
 standing as to the cold felt near a window in cold weather. 
 It seems that air is entering ; but a little reflection will 
 show that even if the window were air-tight this effect 
 would be produced, for the air near the window is cooled 
 by losing heat to the outer air. The air next to the win- 
 dow, thus cooled, is heavier, and falls to the floor ; and if 
 there is any source of heat in the room, this cold air will 
 pass along the floor to that source of heat, up from the 
 heating body to the ceiling, and across the ceiling, and so 
 on around again. There may thus be currents without 
 any appreciable change in the quality of the air. It is 
 economy to use double windows and prevent the loss of 
 heat through the glass. So both economy and comfort 
 suggest to us that we reduce as much as possible cracks 
 around doors and windows, use double windows, make ves- 
 tibules at entrances, and build special ducts by which fresh 
 air may enter, and heat it properly on its way in. 
 
 DEAD DUST. 
 
 The Air is washed by Rain or Snow. Every one 
 will recall how delightfully refreshing the air is after a rain 
 or a snowstorm. This is not due merely to the fact that 
 the air is cool. It is clean because it has been washed. 
 The rain and snow absorb a considerable amount of the 
 various impure gases that are in the air. But raindrops 
 
120 PHYSIOLOGY. 
 
 and snowflakes bring down with them many particles of 
 dust that were floating in the air. Take some of the snow 
 that has fallen in a town. It looks pure in its almost 
 dazzling whiteness. But melt some of it, and you will 
 usually find a decided tinge darkening the water, showing 
 that as the flakes sifted down through the air they caught 
 myriads of particles of dust. 
 
 The Sources of Dust. Where soft coal is used to any 
 large extent it is one abundant source of this dust. In 
 summer dust has many sources. The dust that blows into 
 your face, and perhaps into your mouth, may be made of 
 dry soil. Take a dry clod and drop it ; it falls quickly to 
 the ground. Pulverize it in your hand before dropping it, 
 and considerable of it floats in the air for some time. Any 
 substance that is easily dried. and pulverized may form 
 part of the common dust. The dust that you wipe from 
 your eye, or is caught by the mucus of the nasal passages, 
 may, instead of being made of clean soil, be from the 
 excreta of horses, decayed leaves, wood, grass, etc. In- 
 doors we are constantly making dust by wearing out our 
 clothes. Many of the tiny particles that we see floating in 
 the sunbeams are bits of cotton or woolen fibers. Shake 
 any garment in a beam of light to see how much, and how 
 easily, dust is given off. The worn-off particles of our 
 shoes, books, floors, all contribute to the ever-present 
 dust. 
 
 The Effect of Dust on the Lungs. Now, this dust (so 
 far as it is mere dead, dry matter, not considering it as a 
 poison) is irritating to the lungs and respiratory passages. 
 There is provision, as we have seen, for catching and 
 getting rid of a good deal of it. 
 
 But still much is taken into the lungs. Examination 
 
DUST AND BACTERIA. 121 
 
 shows that the lungs have many black specks from parti- 
 cles of carbon, etc., that have become lodged, and are of 
 no benefit, to say the least. 
 
 LIVE DUST. 
 
 Composition of Live Dust. Bad as this dead dust is, 
 the injury from it is slight compared to that from live dust. 
 We know that certain seeds float in the air, carried along 
 by the wind. But these are comparatively heavy, and soon 
 sink to the ground. 
 
 We all know pollen. At certain seasons it forms, in the 
 vicinity of cornfields, for instance, a considerable part of 
 the dust. This is alive. It will grow if it falls on the 
 right kind of a surface, the stigma of the right plant at the 
 right time. Such dust will not grow in our bodies. We 
 do not furnish a soil in which it can grow. It merely adds 
 to the amount of irritating dust. 
 
 Puffballs and Molds. We have seen puffballs give 
 off a cloud of dust when they are crushed. This dust is 
 composed of live spores that will grow in suitable places 
 and conditions. So, too, from a patch of mold, when 
 brushed, we often see a little cloud of dust. These are a 
 few instances of kinds of living dust that simply act on us 
 like so much dead matter. 
 
 Yeast. If we set a tumbler of cider on a table in a 
 warm room, in a few days it ferments. This is due to 
 yeast that has gotten into it. Boil the cider to kill any 
 yeast that is already in it, and cork it securely so that air 
 cannot get at it, and it will not ferment. Dried yeast 
 germs float in the air, settle into this exposed cider, and 
 cause it to ferment. Cider is a good soil for yeast. 
 
122 PHYSIOLOGY. 
 
 Disease Germs. But there are floating in the air many 
 kinds of spores that may grow in our bodies. We know 
 that many of our contagious diseases are due to the growth 
 in our bodies of some of these spores. Our bodies are a 
 good soil for certain germs. The germs that cause con- 
 sumption, typhoid fever, Asiatic cholera, erysipelas, diph- 
 theria, and some forms of blood poisoning are well known. 
 Microscopists know them when they see them as readily 
 as we know peas from beans. And it is proved beyond 
 all doubt that these germs get into our bodies by being 
 breathed in, or by being eaten in food, or in drinking 
 water, or by introduction into the blood in wounds. We 
 have reason to believe that smallpox, yellow fever, measles, 
 and scarlatina are caused by germs, but these diseases have 
 not been studied so successfully. 
 
 How to avoid Germs. How^can we avoid or get rid 
 of dusts of these kinds ? To exterminate any plant, we 
 try to keep the seeds from ripening, and to kill all that do 
 ripen. Let us take a case that, while not pleasant to con- 
 template, is too terribly true to allow of being called an 
 imagined case. 
 
 The Danger from Consumption. A consumptive ex- 
 pectorates on the pavement. In this sputum are probably 
 hundreds, if not thousands, of germs known as bacilli 
 (Bacillus tuberculosis}. They are alive. Now, so long as 
 they remain on the pavement they do no harm. The 
 sputum dries. But the bacilli are not killed by drying. 
 With other dry material from the pavement they form 
 part of the common dust. Any one of us may breathe 
 some of this kind of matter any day, for there are persons 
 afflicted with this dreaded disease in every community. 
 Our bodies furnish the very best soil for the germs. We 
 
DUST AND BACTERIA. 
 
 12$ 
 
 Bacillus of "Diphtheria (x lOOO) 
 
 Bacillus of Tuberculosis (x 1000) 
 
 Bacillus of Typhoid Fever (x 1200) 
 
 Bacillus of Typhoid Fever (x 1200) 
 showing flagella 
 
 Bacillus (Spirillum) of Asiatic Cholera Bacillus of Hog Cholera (x 1000) 
 
 Fig. 48. Types of Bacilli, showing Morphologic Characters and Arrangement. 
 
124 PHYSIOLOGY. 
 
 do not need to go into the street to be exposed. Who 
 knows what he brings into the house adhering to his 
 clothing ? These germs may be brought into the most 
 cleanly houses in this way, or by the wind. 
 
 How to avoid the Danger. Now, of course, all such 
 material known to be highly dangerous ought to be de- 
 stroyed. If those suffering from such diseases were care- 
 ful to burn all such matter, most of the seeds of this disease 
 would be killed. Thus in time we might stamp out the 
 disease, as a scourge of Canada thistles. But so long as 
 people expectorate upon the floors and pavements it will 
 be difficult to prevent the spread of such germ diseases. 
 
 In hospitals such matters are now looked after with the 
 greatest care, and in private houses where there is intelli- 
 gence on these subjects. And it is encouraging to note 
 the awakening of the public to the significance of the teach- 
 ings of modern science on this subject, as shown by the 
 fact that many of the railroad and street car companies 
 now prohibit spitting on the floors of cars, not merely be- 
 cause it is uncleanly, but on the express ground that it is a 
 means of spreading infectious diseases. 
 
 Bacteria. These disease germs are the smallest and 
 simplest of living things. They are plants ; and while all 
 of them that are well known have their scientific names, 
 just as the larger plants have, they are all included in one 
 general group designated as bacteria. 
 
 How to avoid Dust. We need to learn a good deal 
 more about avoiding and destroying dust, and the things 
 that make dust. 
 
 Towns and cities need more sprinkling to keep the dust 
 down. Much more of the refuse and street sweepings and 
 
DUST AND BACTERIA. 125 
 
 cleanings ought to be burned. The dust of a house should 
 always be burned, as we know not what germs of disease 
 may be in it. If we burn it, we shall surely not have to 
 sweep up that dust again. If we send it out of doors it 
 may come back, and we may have to handle it again and 
 again. 
 
 Sweeping and Dusting. So far as possible let us avoid 
 things that make dust. When we sweep a carpet, a con- 
 siderable share of the dust comes from the carpet itself, 
 especially if the carpet is old. Curtains and tapestries of 
 nearly all sorts not only hold dust, but contribute a good 
 deal to it. Those who write on such subjects recommend 
 hard wood floors with rugs instead of carpets. The rugs 
 can be taken out of doors and shaken, and the floors wiped 
 with a moist cloth, so that little dust is left floating in the 
 air of the room. Compare this with the condition that 
 holds after the ordinary sweeping of a carpeted room with 
 the common broom. The dust fills the air, only to settle 
 back on the floor and furniture. Then comes the whisk 
 broom, the so-called dusting. Well, it is dusting ! It fills 
 the air once more with dust. But do we get rid of it? 
 Wiping off the dust with a moist cloth takes most of it 
 away on the cloth. For those who cannot have hard wood 
 floors a most excellent substitute (and in some respects 
 better) is oilcloth or linoleum. 
 
 Sweeping the Sick Room. - - The improved carpet 
 sweepers are not only convenient, but sanatory. Many a 
 well-meaning person will sweep a carpet in a sick room 
 with an ordinary broom when the patient is suffering from 
 lung disease, thoughtless of the fact that a little dust in 
 sight, and perhaps on the shoes, is of much less signifi- 
 cance than dust in the air we breathe. No one likes dust 
 
126 1'HYSIOLOGY. 
 
 on the floor, but better a thousand times there than in our 
 lungs. 
 
 Lung Diseases. Statistics seem to show that one 
 seventh of the deaths among the civilized races is due to 
 lung diseases. The best authorities are now agreed that 
 consumption is not hereditary. But it appears that there 
 may be inherited a tendency to this disease, so that, if ex- 
 posed, such persons are more likely to contract the disease 
 than those not so predisposed. 
 
 Probably anything that lowers the general vitality makes 
 the system more ready to succumb to any of these con- 
 tagious diseases. We have all noticed what a difference 
 there is among individuals in the readiness with which they 
 " catch " contagious diseases. 
 
 Destruction of Germs by Colorless Corpuscles. It is 
 
 believed by some physiologists that the colorless blood 
 corpuscles may take these germs of disease into their sub- 
 stance, and destroy or change them so that the disease is 
 warded off. In other words, they may be compared to a 
 cat that catches and eats the mice which invade a house. 
 
 How to ward off Contagious Diseases. A good gen- 
 eral condition of the body helps greatly to ward off dis- 
 eases of this nature. A cheerful condition of mind and 
 body should be cultivated. In times of widespread con- 
 tagious disease, if one is terrified into the belief that he is 
 going to have the disease, he is more likely to take it. 
 
 Thorough cleanliness, plenty of direct sunshine, care in 
 diet, and the keeping of the body in good tone, all these 
 reduce the chances of "taking" contagious diseases. 
 
 An open-air life, abundant nutritious food, and freedom 
 from anxiety are probably the best restoratives for incipient 
 consumption. 
 
DUST AND BACTERIA. 127 
 
 The Bacteria of Putrefaction. Besides the disease- 
 producing bacteria, there are others that cause decay and 
 putrefaction of various kinds. They cause our richer foods 
 to " spoil," milk to turn sour, butter to become rancid, etc. 
 
 While these bacteria do not cause disease in the human 
 body, they often make food poisonous. The cases fre- 
 quently reported of poisoning from eating ice cream, 
 cheese, sausage, etc., are in many cases due to bacteria in 
 them. We should, in the first place, be careful to get 
 good, fresh material. In the second place, it should be so 
 kept as to prevent the introduction and development of 
 bacteria in it. Bacteria need heat for their growth (as we 
 so well know is the case with the higher plants). They 
 also need moisture. 
 
 The Preservation of Foods. So our principal modes 
 of keeping foods from spoiling are to keep them in a cold 
 place, or to dry them. Or we heat them, and shut them 
 away from the air, as in our various modes of canning and 
 preserving foods. Salting and smoking meats, etc., preserve 
 them by preventing the growth of bacteria. Cold does 
 not usually kill bacteria. So milk that has been kept in a 
 refrigerator, and that seems sweet, may have in it a stock 
 of bacteria, and after we drink the milk the heat of our 
 bodies favors their development. There are now known 
 ways of killing the bacteria in milk and other liquids, known 
 as " sterilizing," that make us safe from this danger. 
 
 Although the main subject of this chapter is air and 
 ventilation, it has been thought best to touch briefly the 
 subject of bacteria in food, as the bacteria are so widely 
 disseminated by the air. One of the earlier and still in- 
 teresting works on this subject is Tyndall's Floating Matter 
 of the Air. 
 
128 PHYSIOLOGY. 
 
 But let us now turn from the air and respiration to 
 another, yet closely allied subject. 
 
 The Need of the Removal of Waste. When we 
 awaken on a cold winter morning we are likely to find that 
 the fire in our hard coal stove has burned low. Not enough 
 heat is given out. What is the trouble ? Is it merely that 
 more coal is needed ? We put another hod of coal in the 
 magazine (though some usually remains). Does this bring 
 the desired result ? No. We open the draft. Is this suffi- 
 cient? It is not. We must shake down the grate and 
 clean out the clinkers. The removal of waste is often 
 more necessary than the addition of a fresh supply of ma- 
 terial. It is often a more serious matter to have the waste 
 pipe leading to the sewer clogged than to have the water 
 supply cut off. It is often more to be desired that the 
 garbage cart take away decaying matter than that the 
 bread wagon arrive. The demands of nature for the ex- 
 pulsion of excreta are imperative, while we can withstand 
 the cravings of hunger for a while. So we shall turn our 
 attention for the present to the immediate demand for the 
 removal of wastes, and later consider the equally impor- 
 tant, but less importunate, question of supply and renewal. 
 
 READING. (i) Bacteria, (2) Dust and Its Dangers, 
 (3) Drinking Water and Ice Supplies, Prudden ; Ventila- 
 tion and Warming of School Buildings, Morrison; Sanitary 
 Conditions of ScJioolJionses, Lincoln (American Public 
 Health Association); Disinfection, Sternberg (American 
 Public Health Association) ; Micro-Organisms and Disease, 
 Klein ; The Wilderness Cure, Marc Cook. 
 
 Summary. i. Lung diseases usually accompany close confine- 
 ment, but are rare with those living in the open air. 
 
DUST AND BACTERIA. 129 
 
 2. Air in rooms needs constant renewal. 
 
 3. Grates are good ventilators, but not economical heaters. Grates 
 heat very unevenly. 
 
 4. Stoves are economical heaters, but poor ventilators. Stove heat 
 is also very uneven. 
 
 5. All crowded rooms, as schoolrooms and churches, need special 
 inlets for fresh air and outlets for foul air. 
 
 6. The most common means of withdrawing the air is by foul-air 
 shafts. Heat is the force relied on, but the removal of foul air is usually 
 inadequate, on account of the slowness of the current or the narrowness 
 of the outlet, or both combined. 
 
 7. Fans are much more certain to be effectual. 
 
 8. Steam and hot water may heat directly (by radiation) or indi- 
 rectly (placed in flues). A combination of direct and indirect heating 
 favors economy and efficiency. 
 
 9. Dust as mere dry dead matter is irritating. 
 
 10. Disease germs may form part of the dust of the air. 
 
 1 1 . Most of our contagious diseases are known to be due to bacteria. 
 
 12. Burning is the surest method of destroying germs. 
 
 13. Carpets, tapestries, and cloth-upholstered furniture add largely 
 to the dust in houses. 
 
 14. Putrefaction is caused by bacteria. 
 
 15. Preservation of food depends on destroying, or excluding, or 
 retarding the growth of the bacteria of putrefaction . 
 
 Questions. i . How can we renew the air of a room without having 
 unpleasant drafts ? 
 
 2. Should bedroom windows be open at night? Is night air bad? 
 
 3. What dangers in the use of hard coal? 
 
 4. Should there be a damper in the smoke pipe of a hard coal 
 stove? 
 
 5. What do miners mean by " choke damp " ? 
 
 6. What is hay fever? Asthma? Bronchitis? Pneumonia? 
 
 7. Compare stove and furnace heating. 
 
 8. Compare heating by steam and by hot water. 
 
 9. Is the air in the mountains or on the seashore better than else- 
 where ? 
 
 10. What regions are recommended for consumptives ? Why? 
 
CHAPTER VIII. 
 
 EXCRETION. 
 
 Sweat Pore 
 
 Epi- 
 dermis 
 
 Papilla- 
 
 THE SKIN AND ITS FUNCTIONS. 
 
 The Skin throws off Perspiration. The energies of 
 the body heat and motion are produced by the oxida- 
 tion in its tissues. 
 During this process 
 waste products are 
 formed, which if 
 retained in the 
 body would cause 
 very injurious 
 effects. 
 
 How does the 
 body get rid of 
 these substances ? 
 We have learned 
 that the lungs 
 throw off carbon 
 dioxid, water, and 
 certain putrescible 
 organic matter. 
 The skin is constantly throwing off wastes, collectively 
 called sweat, or perspiration. 
 
 The Structure of the Skin. The skin has two layers, 
 the inner, or dermis, and the outer, or epidermis. A 
 bruise often loosens or breaks off a piece of the epidermis, 
 
 130 
 
 Dermis 
 
 Sweat 
 Gland 
 
 Blood 
 Tube 
 
 Bulb 
 
 Fig. 49. Vertical Section of the Skin. 
 
EXCRETION 131 
 
 but seldom removes the dermis. The epidermis is thick 
 over the palms of the han<jls and soles of the feet ; else- 
 where it is thin. Not often seeing the whole thickness of 
 the skin, we do not easily obtain an idea of its real thick- 
 ness. The skin constitutes about one-fifteenth of the 
 body's weight, and if tanned makes a moderately firm and 
 thick leather very much resembling the pigskin used for 
 covering footballs, striking bags, etc. 
 
 Mouth of Sweat Duct 
 
 Horny Epider- 
 mis 
 
 Soft Layer 
 
 Papilla 
 
 Dermis 
 
 \ M 
 Vein Artery 
 
 ,Fig. 50. Section of Epidermis, showing Papilla. (Highly magnified.) 
 
 The Epidermis. The epidermis consists of many 
 layers of cells packed closely together. The deepest cells 
 may be compared to grapes with their cell walls plumply 
 
132 
 
 filled out by the liquids of the cell. Suppose, for the 
 inner layer, grapes set on end, and so closely packed 
 together as to press each other into elongated prisms. 
 Then layers less closely pressed, more nearly spherical ; 
 then layers of cells with less liquid in them, and somewhat 
 shrunken, like raisins; then still dryer cells, flattened 
 parallel with the surface of the skin ; and last, in the outer 
 part, layers of cell walls, dry and empty, pressed flat like 
 empty grapeskins. The flat cell walls come off in flakes 
 (called dandruff from the scalp) from all the surface of 
 the skin, and new cells are continually formed in the 
 deeper layers. 
 
 The Color of the Skin. The pigment, which gives 
 color to the skin, lies in the deeper layers of the epidermis. 
 In albinos this is wanting; in persons with a fair skin it 
 is small in amount, in dark skins more abundant. Where 
 the pigment is irregularly scattered it causes freckles, etc. 
 
 A Blister. A blister is caused by separating the outer, 
 harder layer of the epidermis from the inner, softer, darker 
 layer of the epidermis, as shown at B in Fig. 49. Serum, 
 or blood, fills the space between the separated layers. 
 
 The Dermis. The dermis consists chiefly of tough 
 interlacing fibers. Hence the strength and durability of 
 leather, which is the dermis preserved and prepared. The 
 epidermis is usually removed in tanning. The dermis is 
 richly supplied with blood capillaries and lymph capillaries, 
 but the epidermis has neither. 
 
 Papillae. The outer surface of the dermis has numer- 
 ous conical elevations. Over most of the skin there is no 
 evidence of these papillae, as the epidermis envelops them. 
 But on the palm and sole the papillae are in rows, and 
 these rows are indicated by the fine ridges. 
 
EXCRETION. 
 
 133 
 
 Hairs and Nails. Hairs and nails are outgrowths of 
 the epidermis. Their deeper parts are embedded in the 
 dermis, through which, from the blood, they derive their 
 nourishment. Like the epidermis, they are dead in the 
 outermost part, and are supplied by growth from beneath. 
 
 Examination of the Skin with a Lens. Place a linen tester, or 
 good pocket lens, on the palm of the hand, and note the openings of 
 the ducts of the sweat glands, or sweat pores. Count the pores within 
 the square shown. Measure this square, and then estimate the number 
 of sweat glands to a square inch of the palm. 
 
 Epithelium or Epidermis 
 
 Compound Glands 
 Fig. 51. Evolution of Glands. (After Landois and Stirling.) 
 
 The Sweat Glands. The sweat glands are minute 
 tubes whose inner ends are closed, and whose outer ends 
 open upon the surface of the skin. The tube going 
 inward pursues a corkscrew-like course through the epi- 
 dermis, then becomes straighter, and, having passed 
 
134 PHYSIOLOGY. 
 
 through the dermis, is coiled up in a ball in the connective 
 tissue lying just underneath the inner skin. The cells 
 forming the walls of the coiled part differ from those of 
 the duct, or straighter part of the tube. As the blood 
 flows around the coil it gives off lymph, and from the 
 lymph the cells of the gland take certain waste matters, 
 which are passed out to the surface of the skin. There is 
 also some muscular tissue around the walls of the gland. 
 
 Model of a Sweat Gland. Take a small rubber tube a foot long ; 
 close one end; tie the half with the closed end into a globular knot; 
 around and between the coils place a network of red cord to represent 
 the blood capillaries, as there is a rich supply of these blood tubes 
 around the coil. 
 
 The Essential Features of a Gland. i . Cells lining 
 a cavity, the cells having the power of taking something 
 from the blood (or lymph). 
 
 2. Blood supply or lymph supply. 
 
 3. A duct or tube to pour out on some surface the 
 liquid taken from the lymph. 
 
 4. Nerves to the cells by which their action is controlled. 
 
 5. (Probably) Special nerve centers controlling the 
 various glands. The cells of the glands in many cases 
 so alter the substances taken from the blood that what is 
 produced by the gland differs from anything found in the 
 blood. The gland may be said to manufacture the liquid. 
 
 The Relation between Glands and the Blood 
 Supply. The sweat glands, like all glands, are largely 
 dependent on the amount of blood supply. In exercising, 
 the skin is usually redder from the greater blood supply, 
 and at the same time the glands are more active ; for, 
 during exercise, and immediately after it, there is more 
 waste matter to be thrown out. But the activity of the 
 gland is not a mere filtering process, due to the greater 
 
EXCRETION. 135 
 
 blood pressure. There may be a cold sweat ; i.e. when 
 the skin is pale. Here is evidence that the activity of the 
 glands is, primarily, due to the nerve impulses from some 
 nerve center to the gland cells. 
 
 Sweat Glands are Simple and Excretory. The sweat 
 glands rid the body of certain waste matters that can no 
 longer be used. They are excretory glands. In structure 
 they are simple glands. 
 
 Distribution of Sweat Glands. The sweat glands are 
 thickly distributed over the whole surface of the body, 
 but are especially numerous and large on the palms of the 
 hands and the soles of the feet. In the armpits the glands 
 are very large. 
 
 The Oil Glands. The oil glands of the skin are dis- 
 tributed over all the surface except the palms of the hands 
 and soles of the feet. The oily matter is usually poured 
 out around the hairs as they emerge from the skin. It 
 serves to oil the hair and the skin, and keep them from 
 becoming too dry. 
 
 Composition of Sweat. Sweat is mostly water; about 
 one per cent is solid matter, including salt and certain 
 matters which, like the organic waste matter from the 
 lungs, easily putrefy, and some oily matter from the oil 
 glands of the skin. 
 
 Experiment to show Insensible Perspiration. Thrust the hand 
 into a glass jar, preferably a jar that has been in a cool place. Note 
 the moisture that soon gathers on the inside of the jar from the insen- 
 sible sweat of the hand. A common fruit jar will do for a small hand, 
 but a candy jar is better, having a larger mouth and clear glass. 
 
 Kinds of Perspiration. Ordinarily the sweat is evapo- 
 rated as fast as it is poured out ; in distinction from this 
 insensible^ perspiration, there is the so-called sensible per- 
 
136 PHYSIOLOGY. 
 
 spiration when it accumulates enough to be perceptible. 
 These are not two distinct kinds of sweat, but it is con- 
 venient to distinguish between the perceptible and the 
 imperceptible. Sweat varies greatly in its wateriness, and 
 hence in the relative amount of solid matter contained. 
 
 The Amount of Perspiration. There is about one 
 quart in twenty-four hours. It varies with: 
 
 1. Temperature, dryness, and rate of renewal of air. 
 
 2. Condition of the blood; e.g. if watery from drinking 
 much water. 
 
 3. Muscular exercise. 
 
 4. Certain drugs some exciting perspiration, e.g. 
 camphor ; others diminishing it, e.g. belladonna. 
 
 5. The nerves exercise great influence on the activity of 
 the cells of the gland. 
 
 The Functions of the Skin. 
 
 1 . Protective. 
 
 2. Excretory. 
 
 3. Absorptive. 
 
 4. Sensory organ of touch. 
 
 5. Heat-regulating. 
 
 Next to its excretion, the heat regulation by the skin is 
 the most important for our present consideration. 
 
 Regulation of the Temperature of the Body by the 
 Skin. It is a striking fact that, except in disease, the 
 temperature of the body varies only a little from 98.5 F. 
 in summer and winter, during exercise and rest. The rate 
 of heat production varies greatly. The rate of giving off 
 heat must therefore vary accordingly. 
 
 The Body gives off Heat. In considering the regula- 
 tion of the body's temperature, we must bear in mind that 
 the body is surrounded by air almost always considerably 
 
EXCRETION. 137 
 
 cooler than itself. The body is, therefore, almost always 
 giving off heat. Our clothes do not warm us : we warm 
 them, and they keep us from warming the air too fast ; 
 i.e. keep us from losing too much heat. Indoor heat in 
 winter in the cooler parts of the United States is kept 
 at about 70 F. by artificial heat. This air does not warm 
 us. We, being about 30 F. warmer, are warming it. 
 
 Ways of Giving off Heat. The skin gives off heat by 
 
 1. Radiation: heat is given off in every direction. 
 
 2. Conduction: whatever we touch that is cooler than 
 our bodies is warmed. We warm chairs, clothing, etc. 
 
 3. Convection : the air in contact with the skin is warmed 
 and rises. Our bodily heat is thus carried off by convection. 
 
 4. Evaporation : the evaporation of the sweat is a much 
 more important factor in heat regulation. Any liquid, in 
 evaporating, absorbs heat. The cooling effect of alcohol 
 or ether on the skin is due to the fact that heat is taken 
 from the body in converting the liquid into a gas. 
 
 Experiments in Evaporation. Let the teacher, with a medicine 
 dropper, place a drop of alcohol, ether, or cologne on the back of the 
 hand of each pupil. Notice two facts: (i) It produces a cooling 
 effect. (2) The liquid soon disappears. To prove that it is not 
 merely that the liquid is cool, try the following : Tie a piece of cheese 
 cloth around the bulb of a thermometer ; dip the bulb into a dish of 
 alcohol or ether, and note its temperature (if these are not at hand, 
 gasoline serves very well, or even water, though the evaporation is 
 slower) ; then lift the bulb out of the liquid, and note any change in 
 temperature. The evaporation of the liquid takes heat from the bulb, 
 and causes the thermometer to register a lower temperature. We 
 sponge the face and hands of a feverish patient to reduce the amount of 
 heat. We sprinkle the floor in hot weather, and, by the absorption 
 of heat in evaporating the water, cool the air of the room. 
 
 Heat and Exercise. When we exercise, we produce 
 more heat : we sweat more ; more heat is taken from the 
 
PHYSIOLOGY. 
 
 body to evaporate this sweat. If we are not exercising, 
 and are in cooler air, we sweat less, and less heat is given 
 off. So the temperature of the body is kept uniform. 
 
 This should also be observed : When we exercise, more 
 blood is in the skin, and more heat is given off in the 
 other ways mentioned ; when we exercise less, the skin, 
 especially in a cool air, becomes paler; i.e. has less 
 blood in it, and heat is economized. 
 
 Distribution of Heat in the Body. If more heat is 
 produced in one part of the body than in the others, the 
 circulation of the blood tends to equalize the temperatures 
 of the different parts. So, too, if one part is cooled, 
 that is, is losing heat faster than the others, the blood 
 brings heat from other organs to that part. 
 
 For instance, if one holds his hands in the snow, or puts 
 a piece of ice on his wrist, the whole blood stream is 
 affected. So if the hands and the feet are exposed to the 
 cold, it may do little good to have the rest of the body 
 covered. A pair of wristers and a pair of leggings may 
 often add more to one's comfort than a heavy overcoat. 
 
 Regulation of Bodily Temperature by Food and 
 Clothing. When subject to the influence of cold we eat 
 more ; we choose more heat-producing foods, as fatty food- 
 stuffs ; we take more vigorous exercise ; we put on more 
 clothing, and especially of the non-conducting kinds, 
 woolens. In warmer weather we eat less fatty matter, 
 wear less clothing, and are less disposed to exercise 
 actively ; we fan ourselves to help get rid of heat ; we 
 take ices and cold drinks. For most persons it seems 
 better to wear woolen most of the time, as even in summer 
 we are subject to sudden changes in the air, and with such 
 covering one is less likely to take cold. 
 
EXCRETION. 1 39 
 
 The Effect of Wet Clothing. In getting the clothing 
 wet, the greater loss of heat is not from the coolness of 
 the water, but the loss of heat in evaporating the water 
 from the clothing ; and this goes on for a long time. Of 
 course it is desirable to put on dry clothing as soon as 
 possible ; but a person in good health is not likely to take 
 cold, except in very cold weather, if he continues active 
 exercise till he can change the wet garments for dry ones. 
 Children do not often take cold from wading in water so 
 long as they are barefooted ; but if the shops and stock- 
 ings are wet, they are likely to take cold. 
 
 Sunshine. For good health we need sunshine. We 
 have sunlight indoors, but so do many plants that drag 
 out a sickly existence. We need direct sunlight (not too 
 hot), and many an invalid has been cured by sunbaths. 
 Part of the beneficial effects of sea bathing is due to sun- 
 shine. It is a good thing that it is now the fashion to take 
 a vacation and become well tanned. One of the benefits of 
 the resorts of Colorado (in addition to the climate's mild- 
 ness) is that there are very few cloudy days during the year. 
 
 THE KIDNEYS" 
 
 The Work of the Kidneys. One important part of the 
 work of the lungs, as we have seen, is to throw out carbon 
 dioxid. The skin also throws off certain wastes. The kid- 
 neys have the special task of excreting a waste product of 
 the body called urea. Urea is the nitrogen-containing waste. 
 
 The Parts of the Kidney. The kidneys are attached to the dorsal 
 wall of the abdominal cavity. The depression in the kidney correspond- 
 ing to the stem scar on a bean is called the hilum. From the hilum 
 issues a white tube, the ureter, which conveys the urine to the bladder. 
 
 The Blood Supply of the Kidneys. Entering the kidney along- 
 side the ureter is the renal artery, a branch of the aorta, and from near 
 
140 
 
 PHYSIOLOGY. 
 
 the same point the renal vein returns the blood from the kidneys, and 
 pours it into the postcaval vein. Through the kidneys is pouring a 
 continuous stream of blood, varying in amount at different times and 
 in different conditions. The kidney receives a very large amount of 
 blood for its size, as compared with other organs. The flow to it is 
 made easy by the fact that the renal arteries are relatively wide and 
 short, and take the blood directly from the main current of the aorta. 
 The blood leaving the kidney, especially when in full activity, is still 
 bright red ; it is probably the purest blood in the body. 
 
 Urine. From the kidney, through the ureter, urine is continually 
 passing to the bladder. Urine is mostly water containing urea, salt, and 
 various other substances in small amounts. Urea is a waste matter 
 brought in the blood. If the kidneys are stopped in their action, urea 
 accumulates in the blood, and death soon results ; to just the degree that 
 the kidneys fail in performing their duty, just so far must the body suffer. 
 
 Microscopic Structure of the Kidney. If microscopic sections of 
 the kidney are at hand they should be examined ; but the kidney is so 
 
 complicated in structure that a 
 
 Urinary Cone diagram is needed in connection 
 
 with the sections and the de- 
 scriptions. The unit of struc- 
 ture in the kidney is a tube which 
 takes material from adjacent 
 blood capillaries. The relation 
 of the capillaries to the tube is 
 peculiar. The inner end of the 
 tube is enlarged into a ball ; this 
 ball is deeply depressed opposite 
 the point where the tube leaves 
 it. Into this depres- 
 sion is fitted a globu- 
 lar tuft of capillaries. 
 The arrangement may 
 be illustrated by the 
 common toy known as the " cup 
 and ball." The handle of the 
 cup should be hollow to repre- 
 sent the tube ; the cup should be double walled, the space between 
 the inner and outer layers continuous with the hollow of the handle. 
 
 Cavity of 
 Kidney 
 
 Renal 
 Vein 
 
 Fig. 52. 
 
 U rete r 
 Cross Section of Kidney. 
 
EXCRETION. 
 
 Instead of a solid ball held by one string, there should be a yarn ball 
 with two large strings attached to one side, one representing the artery, 
 the other the vein ; the yarn ball represents the dense cluster of capil- 
 laries. 
 
 Another Illustration. A still better illustration of the urinary tube 
 and capsule may be made thus : Take a thistle tube (used in the chem- 
 ical laboratory), let down into its bulb a rubber balloon or bag of sheet 
 rubber or cloth, fastening the margin around the rim of the bulb ; put 
 a little ball of red yarn in the depression of the bag hanging in the 
 bulb ; have two ends of the yarn projecting to represent the artery 
 entering and the vein leaving the capsule. The vein, soon after it 
 emerges, breaks up into another set of capillaries which extend around 
 the tube. A number of these primary tubes unite, and many of the 
 common ducts open at the apex of each of the urinary pyramids, 
 emptying their secretion into the cavity of the kidney. As the blood 
 flows through the tuft of capillaries in the capsule at the end of the 
 tube, a large amount of water, 
 together with salt and some 
 other substances, pass through 
 the thin partition into the 
 cavity of the capsule, and 
 thence down the tube. The 
 walls of the tube are thicker 
 than, and its cells are different 
 from, those of the capsule. 
 These cells take the urea and 
 some other substances 
 from the blood, and 
 pass them into the tube 
 to join the more watery 
 material from the capsule. 
 
 Artery J 
 
 Vein 
 
 Urinary Tul 
 Fig. 53. Urinary Cone Enlarged. (Diagram.) 
 
 Comparison of the Skin 
 and the Kidneys. The 
 
 kidneys, then, are not very 
 
 different from the skin. 
 
 Imagine a piece of skin rolled up with the outer surface of 
 
 the skin turned inward. Its glands then would pour their 
 
142 PHYSIOLOGY. 
 
 secretion into a cavity where it might accumulate, instead 
 of evaporating as^fast as it is poured out. Of course the 
 kidneys have a somewhat different work from the skin, 
 but in its general plan of working we might say they 
 are skin turned outside in. The kidney unit (the tubular 
 gland) has branches ; i.e. is compound. The kidney is a 
 compound gland of excretion, internal in position. Both 
 skin and kidneys excrete a large amount of water, with 
 salt and some other matter in common. 
 
 Relation between the Work of the Kidneys and that 
 of Skin. There is a very immediate relation between 
 the work of the kidneys and that of the skin. In warm 
 weather, and when exercising actively, we perspire freely, 
 and the amount of urine is reduced ; when we exercise 
 less, and especially in cold weather, we perspire less, and 
 the urine is more abundant. Cold drives the blood from 
 the surface. Consequently more blood goes to the kidneys 
 (as well as to the other internal organs), and they throw 
 off much more water, though probably little if any more 
 urea. The average daily amount of urine is about three 
 pints. The quantity is increased by high blood pressure, 
 copious drinking, by cold air (driving the blood from, the 
 skin), nitrogenous food, certain drugs, etc. It is dimin- 
 ished by a lowered blood pressure, profuse sweating, 
 diarrhea, non-nitrogenous food, and some diseases of the 
 kidneys, etc. 
 
 What is the effect of all the processes thus far studied 
 ,on the weight of the body ? 
 
 READING. The Skin and Its Troubles, D. Appleton 
 & Co. 
 
 Summary. i . The skin throws off sweat, which is water contain- 
 ing waste matter. 
 
EXCRETION. 143 
 
 2. The tubular sweat glands take the wastes from the lymph which 
 soaks out through the walls of the capillaries in the skin. 
 
 3. The activity of the glands is under control of nerves and nerve 
 centers, as is also the supply of blood to the skin. 
 
 4. The amount of sweat depends on temperature, exercise, amount 
 of liquid food taken, drugs, etc. 
 
 5. The temperature of the body is regulated chiefly by the evapora- 
 tion of sweat. 
 
 6. In cold weather we eat more of ' heat-producing foods, such as 
 fats. 
 
 7. The kidneys excrete urea, a nitrogen-containing waste. 
 
 8. There is an intimate relation between the workings of the lungs, 
 skin, and kidneys. 
 
 Questions. i. Does cutting hair make it grow faster ? 
 
 2. Do cows, dogs, and cats sweat ? 
 
 3. Why is thirst relieved by immersion, even in salt water ? 
 
 4. Why should clothing worn during the day be removed at night ? 
 
 5. How does the body lose heat, except by the skin ? 
 
 6. Why should the blood still be red after passing through the 
 kidney ? 
 
 7. What is "skin grafting" ? 
 
 8. Why is it considered a good sign when the skin becomes moist 
 during a fever ? 
 
 9. Can food, medicine, or poison be absorbed through the skin ? 
 
CHAPTER IX. 
 FOODS AND COOKING. 
 
 Necessity of Food. Thus far we have been studying 
 processes by which the body's weight is reduced. We 
 have studied the. oxidation in the tissues and the removal 
 of the wastes. Unless the tissues receive a corresponding 
 supply the heat and energy of the body cannot long be 
 maintained. 
 
 Food Defined. All substances that go to make up the 
 tissues or produce energy are foods. Certain substances 
 that do not become part of any tissues, nor in themselves 
 produce energy,- are useful in aiding the processes going 
 on in the body. These may be called accessory foods, e.g. 
 condiments ; some accessory foods, such as coffee, seem to 
 retard the waste of tissues. 
 
 Foods and Foodstuffs. Most of our articles of food 
 consist of two or more different kinds of materials. For 
 instance, milk consists (i) chiefly of water; in this are (2) 
 the substance that makes cheese (casein); (3) cream, from 
 which we get butter (fat) ; (4) sugar, which gives milk a 
 sweet taste; (5) salts, such as common salt, lime salts, 
 etc. These different materials are foodstuffs. We have 
 many kinds of foods, but few foodstuffs, which we find 
 occurring over and over again, in various forms, in the 
 numerous things we eat. 
 
 144 
 
FOODS. 145 
 
 Kinds of Foodstuffs. 
 
 1. Proteids (exatnple, casein). 4. Water. 
 
 2. Fats. 5. Salts. 
 
 3. Carbohydrates (example, sugar). 6. Oxygen. 
 Oxygen is by some authors called a food, but it is more 
 
 convenient to treat of it elsewhere. 
 
 The Proteids. The chief substance in the white of an 
 egg is albumen, a typical proteid. Of the many proteids 
 some of the more commonly known are casein (the curd of 
 milk), gluten (in. grains), legumin (in peas and beans), 
 fibrin (in blood), myosin (in muscles). Gelatin (obtained 
 from connective tissue and bones by prolonged .boiling) 
 differs considerably from the proteids in composition, but 
 may be counted in with them. It is less valuable as a 
 food than the true proteids, although in certain circum- 
 stances more desirable from the fact that it is very easily 
 digested. 
 
 Characteristics of Proteids. The proteids are 
 
 1. Composed of carbon, hydrogen, oxygen, nitrogen, a 
 little sulphur, and, in some, traces of phosphorus. 
 
 2. Jelly-like, and do not easily diffuse through animal 
 membranes (a characteristic to be kept in mind when 
 studying digestion). 
 
 3. Coagulable (usually) by heat, acids, alcohol, etc. 
 
 4. Easily putrefy when moist and warm. 
 
 Importance of Proteids. The proteids are of special 
 importance as foods because the most active tissues, muscle, 
 nerve, and gland, and the most important liquids of the 
 body, e.g. blood and lymph, have proteid as a chief con- 
 stituent. Proteid food, therefore, must be taken to make 
 good the losses of these tissues during their oxidations. 
 
146 PHYSIOLOGY, 
 
 Proteid-containing Foods. - - The principal proteicl- 
 containing foods are lean meat, fish, eggs, milk, cheese, 
 and some seeds which abound in the vegetable proteids. 
 
 Meat. Lean meat has about twenty per cent of pro- 
 teid, the rest being chiefly water. Beef and mutton are 
 more easily digested than veal and pork. It is better to 
 buy meat from a very fat animal than from a lean one, for, 
 although there is slightly less proteid in the meat from a 
 fat animal, this loss is more than made up by the addition 
 of fat, which takes the place of water in the meat from a 
 lean animal. There is more nourishment in a round steak 
 than in tenderloin. 
 
 Fish. Fish, when fresh, is a good food. Although, 
 as a rule, salted meats are less easily digested than fresh, 
 salted codfish is a nourishing and economical food. 
 
 Eggs. Eggs contain considerable proteid, but their 
 value as food has been overrated. The yolk has a large 
 amount of fat. Although the egg has all the material 
 needed to form a chick, it is not a perfect food for man. 
 
 Milk. Milk, as we have seen, is an ideal food in that 
 it contains all the kinds of foodstuffs, and in the right pro- 
 portion for the young mammal. But the proportions are 
 not right for the adult. An adult would need four quarts 
 and a half daily, and then he would not get enough carbo- 
 hydrates (represented in milk by the sugar). The oily 
 material in milk is in the form of minute globules, which 
 can easily be seen under the microscope. Each of these 
 oil droplets is supposed to be surrounded by a thin en- 
 velope of albuminous matter, by means of which it is 
 enabled to remain suspended for some time instead of 
 rising quickly to the surface. Such a mixture of oil in a 
 
FOODS. 147 
 
 liquid is called an emulsion. When cream is churned the 
 albuminous covering is removed and the butter "gathers." 
 
 Cheese. Cheese is very rich in proteid, much more so 
 than lean meat. Yet, as it is rather difficult of digestion, 
 we do not use it largely as food ; we regard it more as a 
 luxury, while in many parts of Europe it is largely used as 
 food, taking the place of meat. It is a cheap food, and 
 might well be used more extensively, especially by laboring 
 men. When taken with milk it is said to be more readily 
 digested. 
 
 Vegetable Proteids. Peas and beans (dried) contain 
 as much proteid (legumin) as meat, and all the cereals 
 contain some proteid (gluten). 
 
 Fats. Fats are composed of carbon, hydrogen, and 
 oxygen. The oxygen is small in amount, so these foods 
 yield a great amount of energy by the oxidation of their 
 carbon (forming carbon dioxid) and hydrogen (forming 
 water). The fats most used are animal fats, including 
 butter. But some vegetable oils, such as olive and cotton- 
 seed oils, are used. 
 
 The Carbohydrates. Starch and sugar are the chief 
 carbohydrates. Starch is used in larger quantity than any 
 other foodstuff except water. Sugar is usually regarded 
 as a luxury, yet it is an important food. It is quickly 
 absorbed. 
 
 Carbohydrate-containing Foods. The principal car- 
 bohydrate-containing foods are the grains, vegetables, and 
 fruits. 
 
 The Grains. The most important grains are wheat, 
 corn, rice, oats, rye, and barley. 
 
148 PHYSrOLOGY. 
 
 Wheat. Wheat furnishes the principal breadstuff 
 among the more civilized nations. It is especially 
 adapted to the temperate zones. Taking into consid- 
 eration its composition, digestibility, and other charac- 
 teristics, it is the most desirable of all the grains for 
 civilized man. 
 
 Wheat Flour. In ordinary white flour nearly all the 
 gluten has been removed with the bran or " middlings." 
 While wheat or bread made from the whole grain of the 
 wheat may support life, one would starve if he attempted 
 to live on common white bread alone. It is almost en- 
 tirely starch. In the "entire wheat flour" it is claimed 
 that all the gluten is retained, only the very thin outer 
 husk of the grain being removed. It does not make so 
 white a flour, but it is better adapted to use as a food. If 
 we use white bread, having thrown away the nitrogenous 
 part of the wheat, we need to take more proteid from 
 other sources than if we used the entire wheat flour. This 
 is not economy. And it is claimed that the entire wheat 
 bread is more wholesome as well as more nutritious. The 
 part thrown away has in it phosphates as well as the nitrog- 
 enous material. This flour is ground fine so that it has 
 not the coarse particles which are in Graham flour, and 
 which are a source of irritation to the mucous coat of the 
 digestive tube in some persons. 
 
 Corn. Corn is one of the most nutritious of the grains. 
 Professor W. O. Atwater, one of the best authorities in 
 the world on the subject of foods, says that, for a given 
 amount of money, more nutriment can be obtained in corn 
 meal than in any other food known. Corn is said to fur- 
 nish food to a larger part of the human race than any 
 other grain except rice. 
 
FOODS. 149 
 
 Rice. Rice forms a larger part of human food than 
 the product of any other plant, being often an almost ex- 
 clusive diet in India, China, and the Malayan islands. 
 Rice has a larger proportion of starch, and less of fats 
 and albuminoids, than the other grains. It is best adapted 
 for the food of warm climates. 
 
 Oats. This grain was first used as food for man by 
 the Scotch, but the use has extended and become preva- 
 lent in this country. In point of nutrition it is ranked 
 higher by some than ordinary grades of wheat flour. 
 
 Rye. Rye grows farther north than other grains, and is largely 
 used for bread in Russia and parts of Germany. It is a valuable food, 
 though less nutritious and less digestible than the corresponding prepa- 
 rations of wheat. 
 
 Barley. This grain has wide range of cultivation, and, while in- 
 ferior to wheat, is considerably used where other grains cannot be 
 raised. 
 
 Potatoes. Potatoes contain about twenty per cent 
 starch, two per cent of proteid, and no fat, the remainder 
 being chiefly water, with some useful salts, especially 
 potash salts. In spite of its relatively low food value, the 
 potato is our most useful vegetable on account of its 
 abundance, the ease with which it can be preserved, its 
 mild flavor, and the readiness and the variety of ways 
 in which it can be cooked. 
 
 Other Vegetables. The chief nutrient in vegetables 
 is starch, though in many the starch is present in small 
 amounts. The salts and acids present are of value, and 
 care should be observed not to remove too much of these 
 salts in cooking. The fibrous matter, cellulose, while in- 
 digestible, is of value in adding bulk to the mass of food 
 to be digested. Formerly sailors were subject to scurvy ; 
 
150 PHYSIOLOGY. 
 
 this is now attributed to a diet of fat and salt meat, to the 
 exclusion of fresh vegetables, vegetable acids, etc. The 
 disease is avoided by a greater use of vegetables, lime 
 juice, etc. 
 
 Fruits. Many of the fruits, such as bananas and 
 apples, have considerable starch and sugar. But the 
 fruits are probably more useful to us on account of their 
 flavor, due to aromatic bodies, and to their salts and the 
 peculiar fruit acids. 
 
 Water. Water constitutes about two thirds of the 
 entire weight of the body. It constitutes the bulk of the 
 liquids we have studied, blood, lymph, sweat, saliva, bile, 
 etc. Water is the solvent and carrier of all the material 
 of the body. Hence we need a large amount of it ; of 
 course we must remember that we get a good deal of water 
 in most of our solid foods. 
 
 Rain Water. Water, as it comes from the clouds, is 
 pure. After enough rain has fallen to wash the air, rain 
 water is pure, and if caught on a clean roof (especially a 
 slate roof) and kept in a clean cistern, it is good drinking 
 water. 
 
 Well Water. Falling upon the earth, the rain water 
 soaks down until stopped by some impervious layer, such 
 as clay. This water is the supply of our wells and springs. 
 It always has more or less earthy matter in solution, and 
 is therefore more or less " hard." Unless a large amount 
 of mineral matter or some special material is dissolved in 
 it, it is, ordinarily, good drinking water. Such water is 
 not pure, in the strict sense of the word, but is pure for 
 drinking purposes. 
 
FOODS. I 5 1 
 
 Impurities in Water. The great source of danger is 
 from what are called " organic" impurities. Bacteria will 
 not live and grow in pure water. They must have some- 
 thing on which to feed and grow. But in water contain- 
 ing a large amount of decaying animal or vegetable matter 
 they are likely to abound. And the most dangerous 
 sources of contamination are cesspools and sewers. Water 
 may be contaminated by such material and not have bac- 
 teria in it, but is very likely to harbor such foes. 
 
 Contamination from Cesspools. The ordinary cess- 
 pool is a grave source of danger. Because the well may 
 be on higher ground than the cesspool does not give as- 
 surance that the water may not be polluted. Often when 
 the surface of the ground slopes in one direction, the strata 
 underneath may slope in just the opposite direction, and 
 the well may be the reservoir into which the cesspool is 
 drained. 
 
 Good authorities say that a cesspool should not be 
 allowed within a hundred feet of a well. 
 
 Abolish the Cesspool. But it is better and safer to 
 have no cesspool. Where a sewer system is not to be 
 had, it is better to allow no great accumulation of such 
 material. A deep pit in which a quantity of semiliquid 
 matter gathers is not only a nuisance, but a source of 
 danger. Privies should have a very shallow pit, or none, 
 and should be cleaned often. There should be a little 
 dust sprinkled in each day, and occasionally some " chlorid 
 of lime " or sulphate of iron. 
 
 Typhoid Fever. Typhoid fever is now known to be 
 usually caused by drinking water. The dejecta of some 
 one who has had the disease find their way into the source 
 of the drinking water. In many cases this has been clearly 
 
152 PHYSIOLOGY. 
 
 proved. Of course the dejecta of all such patients should 
 be either destroyed or thoroughly disinfected. 
 
 Ice Water. Although bacteria will not develop in a 
 cold place, they are not killed when water freezes, as was 
 formerly supposed. Further, ice, in forming, does not 
 throw out all the impurities, as was formerly stated. So 
 it is not safe to drink water formed from melted ice unless 
 the water of which that ice was made was good water. 
 The ice taken from ponds is not safe. If ice is made 
 artificially from suitable drinking water, of course the 
 melted product will be essentially unchanged so far as the 
 composition is concerned. Water may be cooled by plac- 
 ing any ice around it, and we may have the desired tem- 
 perature without any admixture of a dangerous element. 
 
 Boiling Water. When one cannot get good drinking- 
 water, or when away from home where the water is of 
 doubtful purity, it is better to boil the water before using 
 it, either as a drink or in preparations of food that are not 
 to be thoroughly cooked. It seems to be proved that it 
 is better to heat the water twice nearly to the boiling point 
 than to boil hard once only. The first heating may start 
 the resistant germs into more active life, causing them to 
 sprout (so to speak), and a second heating several hours 
 later may easily kill them ; whereas it has been proved 
 that one hard boiling will not always kill the germs. 
 
 Cautions as to Drinking Water. Or if one uses tea 
 and coffee, it is safer to content one's self with these, and 
 not drink much water till that which is safe, as from deep 
 wells, can be obtained. 
 
 In hot weather, and especially for those who are engaged 
 in hard work, it has been found that a little oatmeal 
 stirred in the water is beneficial. 
 
FOODS. 153 
 
 When overheated, avoid drinking much cold water. Re- 
 peatedly rinse the mouth with cool water, and swallow very 
 little. This is the way trainers manage a horse at a race, 
 and it is sensible to treat a man as carefully. 
 
 Salts. Salts include many substances besides common 
 salt. They aid in the solution of various substances during 
 digestion and in other processes. We cannot live without 
 salt. 
 
 Lime in the form of calcium phosphate and calcium car- 
 bonate is essential, especially in the bones and teeth. Iron 
 is associated with hemoglobin. 
 
 Necessity of a Mixed Diet. Our experience, together 
 with the results of the experiments on animals, teaches 
 that we could not live long if fed on any one class of 
 foodstuffs alone. We must take a representative of each 
 of the groups. We have noticed that most of our foods 
 already contain more than one foodstuff. We so combine 
 them as to get suitable proportions. Thus we eat bread 
 and butter (a small amount of fat with a large quantity of 
 starch and a little gluten), meat and potato, crackers and 
 cheese, pork and beans, egg on toast, bread and milk, rice 
 and fowl, macaroni and cheese ; they " go well together " 
 chiefly because they are complementary. 
 
 Disadvantages of a One-sided Diet. In order to get 
 enough nitrogen from bread alone, one would have to eat 
 about four pounds a day ; meanwhile twice as much car- 
 bon as is needed would be taken, thus throwing an undue 
 amount of work upon the digestive organs. Again, one 
 would need to consume about six pounds of meat to get the 
 requisite amount of carbon, and six times as much nitro- 
 gen as is needed would be taken ; to get rid of this extra 
 nitrogen would severely tax the kidneys and liver. 
 
154 
 
 Effect of Cold on Appetite for Fats. In cold el i mates 
 a large amount of fat is consumed, while in the tropics 
 starch is the chief food. Our appetites call for more of the 
 fatty foods during the winter season. 
 
 Proper Diet. While common experience has led people 
 to adopt a mixed diet, the proportions of the different food- 
 stuffs is not always what it should be. The proportions 
 of the foodstuffs (exclusive of water) may be roughly stated 
 as about I part of proteid, i part of fat, 3 parts of carbo- 
 hydrates. But this will vary somewhat with the amount 
 of work done, and other varying conditions. 
 
 Vegetarians. The so-called "vegetarians" recognize 
 the need of proteid food, and most of them seek proteid in 
 eggs, milk, and cheese. But these are animal products, 
 and the name " vegetarian" is inconsistent. They are 
 merely "anti-meat eaters." If they do actually succeed 
 in getting enough proteids from the legumes and the 
 grains, the complete digestion of which is difficult, they 
 are, as Professor Martin says, to be congratulated on having 
 digestive powers that can stand such a strain. That we 
 are adapted for using flesh as part of our food is indicated 
 .in at least two anatomical features: ~(i) we have canine 
 teeth, though not so fully developed as in the carniyora ; 
 (2) the intestine in carnivora is very short, that of the 
 herbivora very long, but in man intermediate. Neverthe- 
 less, it is undoubtedly true that many persons eat too much 
 meat. 
 
 Tea. Tea owes its stimulating effects to a substance 
 called thein. This is a stimulant to the nervous system, 
 but if not too strong is not followed by a subsequent 
 depression. Tea that is too strong is likely to produce 
 nervousness and dyspepsia. Boiling the tea leaves also 
 
FOODS. 155 
 
 brings out the tannic acid that they contain, and produces 
 bad effects. 
 
 Coffee. Coffee owes its stimulating effect to a sub- 
 stance called caff tin, which is considered identical with 
 thein. Coffee acts as a restorative after hard labor, seem- 
 ing to retard the wastes of the tissues and food. It is used 
 in the army (also in penitentiaries), not as a luxury, but as 
 a matter of economy in the matter of food supply. Coffee, 
 used to excess, frequently causes palpitation of the heart. 
 
 Malted Milk. Malted and peptonized milk makes a 
 valuable drink for invalids and dyspeptics. 
 
 Cocoa and Chocolate. Cocoa contains a stimulant 
 called theobromin. But unlike tea and coffee, cocoa and 
 the preparation from cocoa known as chocolate are true 
 foods by virtue of the fat contained. 
 
 Beef Tea. Beef tea and various beef extracts are very 
 beneficial. There is not enough nourishment in them to 
 maintain strength without other food. Their nutritive 
 value has been somewhat overestimated. Their value is 
 probably much more in their stimulating than in their 
 nourishing effect. But many of the soups and drinks 
 made from these preparations are very beneficial. They 
 refresh the tired system wonderfully. If the man who 
 feels " fagged out" and takes a drink of liquor to " brace 
 him up," as he says, were to take a cup of hot bouillon, he 
 would find himself braced up for the time, without any bad 
 reaction, or permanent injury to the system, which follow 
 the use of alcohol. 
 
 Cooking. Cooking is designed to make food more 
 palatable and more digestible. Some foods, such as eggs, 
 
156 PHYSIOLOGY. 
 
 are as digestible before they are cooked as after, often more 
 so, as they are very frequently badly cooked. But many 
 foods in the raw state are unattractive, or even repellent, 
 whereas cooking usually develops an agreeable odor and 
 taste. Cooking should soften the harder and tougher tis- 
 sues, such as cellulose in vegetables, and the connective 
 tissue of animal foods. Cooking starch causes the starch 
 grains to swell and burst, and makes the starch much more 
 digestible. 
 
 Making Soup. If meat be cut into small pieces and 
 put into cold water, and the water gradually warmed, the 
 soluble material of the meat may be extracted, and this is 
 the principle followed in making soups. 
 
 Boiling Meat. But if we wish to cook the meat itself, 
 the juices should be retained instead of withdrawn. For 
 this purpose boiling water is poured over the meat to co- 
 agulate the outer layer, and prevent the extraction of the 
 juices. 
 
 Baking, Roasting, and Broiling. The same principle 
 applies to baking, roasting, and broiling. The outside is 
 subjected to high heat at the beginning of the cooking, 
 which forms a layer nearly impervious to the nutritious 
 material inside. In these modes of cooking it is very de- 
 sirable to reduce the heat applied after the first few min- 
 utes, so that the interior may be more gradually cooked ; 
 this is, perhaps, especially true in broiling. 
 
 Frying. Frying, as ordinarily done, is not a good 
 mode of cooking ; in fact, is often very bad, as the food is 
 frequently penetrated by fat and rendered very indigestible. 
 But true frying, that is, by immersion in boiling fat, is a 
 
FOODS. 157 
 
 good mode of cooking. This coagulates the albuminous 
 substance on the outside, keeps in the nutritious juices, 
 and prevents soaking with the fat. Often the food to be 
 thus cooked is first coated with white of egg, which is 
 very quickly coagulated, and helps form a protecting out- 
 side crust. 
 
 READING. Practical Sanitary and Economic Cooking, 
 Abel (Public Health Association); The Science of Nutri- 
 tion and the Art of Cooking, Atkinson; Chemistry of 
 Cookery, Williams ; Chemistry of Foods and Nutrition, 
 Atwater (Century Magazine, 1887-88; also Department 
 of Agriculture); Eating for Strength, Holbrook; Foods, 
 Smith ; Philosophy of Eating, Bellows ; Handbook of In- 
 valid Cooking, Boland. 
 
 Summary. i . Food builds tissue and maintains energy. 
 
 2. The simpler constituents of foods are called foodstuffs. 
 
 3. The foodstuffs are water, salts, proteids, carbohydrates, and fats. 
 
 4. Water is essential to life, making two thirds of our weight. 
 
 5. Salts are essential to life. 
 
 6. The chief proteids are lean meat, eggs, cheese, gluten, etc. 
 
 7. The chief carbohydrates are starch and sugar, derived from the 
 grains, vegetables, and fruits. 
 
 8. Fats and oils are obtained from plants and animals. 
 
 9. The chief source of impurity in water is from bacteria, which 
 thrive when decaying animal and vegetable matter are present. 
 
 10. Boiling water may destroy these germs of disease. 
 
 11. Ice water is not a wholesome drink. 
 
 12. A mixed diet is necessary, as no one food contains all the 
 needed material in the right proportions to maintain life well. 
 
 13. Tea and coffee are slightly stimulating, but, if used moderately, 
 ordinarily without any bad reaction. 
 
 14. Cooking is to make food more palatable and digestible. 
 
158 rHYSIOLOGY. 
 
 Questions. i. Which class of foodstuffs is most expensive? 
 Why? 
 
 2. Make a list of all the common foods, naming the foodstuffs in 
 them. 
 
 3. Why do we not eat buckwheat cakes and sirup in summer ? 
 
 4. At what price are eggs an expensive food ? 
 
 5. How do flour and potatoes compare in economy at ordinary 
 prices ? 
 
 6. Why are foreigners prejudiced against corn ? 
 
 7. Why is broiling better than frying ? 
 
 8. Why do Englishmen in India so generally suffer from "liver 
 complaint 1 ' ? 
 
CHAPTER X. 
 THE DIGESTIVE SYSTEM. 
 
 The Object of Food. The tissues are worn out by their 
 oxidations. They are built up again by the blood, and 
 the blood is renewed by the food. 
 
 All food must be reduced to the liquid condition, if it 
 is not already liquid. 
 
 The Digestive Tube. The chief organ in this work 
 of liquefying the food is the digestive tube, or " alimentary 
 canal," as it is called. As the food passes through the 
 digestive tube it is subjected to various mechanical and 
 chemical processes which liquefy it and bring it into such 
 a condition that it can be absorbed through the mucous 
 lining of the digestive tube and passed into the blood. 
 
 The Work of the Digestive Tube. To take a special 
 instance, a muscle is in part worn out by the oxidation 
 during its activity ; to replace the loss suppose we take 
 a piece of steak. We cannot substitute this directly in 
 the place of the worn-out tissue. In digesting the steak 
 we must tear it all to pieces, and reduce it to a liquid form 
 by the action of the teeth and by the various liquids from 
 the glands along the digestive tube. In short, the muscle, 
 as such, must be thoroughly destroyed ; in the liquid pro- 
 duced by the digestion of the beef there is no trace what- 
 ever of the structure of the beef. But the blood, taking 
 this material, builds muscle which can hardly, if at all, be 
 distinguished from the original beef. 
 
160 J'HYMOLOUY. 
 
 If the food taken be all ready to build tissue, for exam- 
 ple, certain forms of sugar, liquid, soluble, and of the 
 proper chemical composition, it will not need to go through 
 these changes. 
 
 In order to understand the process of digestion let us 
 first turn our attention to the anatomy of the organs of 
 digestion. 
 
 The Organs of Digestion. The organs of digestion 
 are the digestive tube and the accessory parts, the masti- 
 catory organs, the glands in, and alongside of, the walls 
 of the tube. 
 
 The parts of the digestive tube are the mouth, the 
 pharynx, the gullet (or esophagus), the stomach, the small 
 intestine, the large intestine. 
 
 Brief Description of the Digestive Organs. At the 
 back of the mouth may be seen the soft palate with the 
 cylindrical uvula hanging from its center. Beyond this 
 is the cavity of the pharynx, which narrows below into 
 the gullet, a red-walled, muscular tube, extending along 
 the dorsal side of the windpipe, and close to the spinal 
 column. It extends the length of the thorax, and then 
 passes through the diaphragm and widens into the stomach, 
 at the upper left end of the latter. The stomach is some- 
 what pear-shaped, with the larger end to the left. At the 
 right end it tapers into the small intestine, the first foot 
 or so of which is called the duodenum. Then comes a 
 long coil of the small intestine, which joins the shorter 
 large intestine, ending in the rectum. Just below the 
 diaphragm is the dark-colored liver, overlapping a large 
 portion of the stomach. Between two of the lobes of the 
 liver is the bile sac whose duct enters the duodenum a 
 short distance from the stomach. The pancreas is a pink- 
 
THE DIGESTIVE SYSTEM. 
 
 161 
 
 ish organ of irregular shape lying along the stomach and 
 duodenum. Its duct enters the duodenum at the same 
 point as the bile duct. The intestine is held in place by 
 the mesentery, a thin fold of transparent membrane folded 
 closely around it, and supported from the dorsal wall of 
 the abdominal cavity. Between the two layers of the 
 mesentery are the branches of the artery supplying the 
 walls of the intestines, and the veins that convey the ab- 
 sorbed food from the intestine to the liver. 
 
 Digestive Organs of a Cat or Rabbit. The digestive organs will 
 be much better understood if a cat or rabbit be dissected, as the organs 
 have essentially the same form and relations. The animal may be 
 killed by putting it in a tight box, or under a washbowl with a small 
 sponge holding a tablespoonful of ether or chloroform. It may then 
 be opened by a slit along the middle line of the ventral surface, from 
 the chin to the pelvis. The diaphragm should be noted as forming 
 a partition between the cavity of the chest and that of the abdomen. 
 
 To Illustrate the Mesen- 
 tery. To illustrate the rela- 
 tion of the mesentery to the 
 intestine, suspend the arm in 
 a sling made of a handkerchief; 
 press the two thicknesses of 
 the cloth together just above 
 the arm to represent the two 
 layers of the mesentery. 
 
 Model of Intestine and 
 Mesentery. A more com- 
 plete representation may be 
 made as follows : Material : 
 piece of large (one inch or more 
 in diameter) rubber tubing, 
 eight inches long; sheet of 
 
 thin white court plaster, six inches by twelve inches ; red, blue, and 
 white cord. Lay the tube across the middle of the court plaster; gum 
 the plaster snugly around the tube ; between the two adjacent layers 
 
 Fig. 54. Cross-section of Abdomen. 
 
1 62 rnys/oi.or,y. 
 
 of the court plaster, where they meet after passing around the tube, 
 lay the three kinds of cord, each frayed out at one end, the frayed ends 
 resting upon the tube. Moisten the court plaster and press the layers 
 firmly together. The court plaster should now adhere so closely to 
 the tube as hardly to be seen, and the two layers should seem as one, 
 in which appear the cords representing the arteries, veins, and lacteals. 
 
 The Mouth. In studying the mouth and contained 
 organs, the student should not content himself with mere 
 reading, but should carefully examine his own mouth 
 cavity by means of a hand glass. We are apt to think 
 of the mouth as a cavity of considerable size, as indeed 
 it is when fully opened ; but we are not so likely to think 
 how completely the cavity is obliterated when the mouth 
 is closed. If one notes the sensations from the mouth 
 when it is closed, he will perceive that the tongue almost 
 entirely fills the space, touching the roof of the mouth, and 
 the teeth in front and at the sides. 
 
 The Tongue. The tongue consists chiefly of muscles, 
 extending in different directions, thus giving the tongue 
 a variety of motions. The tongue is the chief organ of 
 taste, and is therefore (with the sense of smell) the gate- 
 keeper of the digestive tube. The tongue has also a keen 
 sense of touch (the keenest of any part of the body), and 
 so is useful in detecting and removing any food particles 
 that may remain on the teeth after a meal. During 
 mastication the tongue, with the lips and cheek, keep the 
 food between the teeth. When the morsel of food is 
 sufficiently masticated, the tongue pushes it back into the 
 pharynx to be swallowed. 
 
 The Teeth. The teacher can usually obtain a lot of 
 teeth from the dentist for the asking. These should be 
 cleaned before using them in the class. Use pearline 
 
THE DIGESTJl'E SYSTEM. 
 
 I6 3 
 
 or any washing soda. If there be enough time, let each 
 pupil make a drawing of one of each of the four kinds of 
 teeth ; and it would be well to draw both a front (outer 
 surface) and a side view (surface adjacent to another 
 tooth) of each of the four kinds. 
 
 Longitudinal Section 
 
 Side View 
 
 Face View 
 
 Crown 
 
 Neck 
 
 Root 
 
 Hole for Blood Tubes and Nerves - 
 Fig. 55. Parts of a Tooth. (Incisor.) 
 
 External Features of a Tooth. Examine one of the 
 front teeth. It has the following parts : 
 
 1. The crown, the part that is above the gum. 
 
 2. The root, the part that was buried beneath the gum. 
 
 3. The neck, a more or less constricted part, dividing 
 the crown from the root ; it is normally at about the sur- 
 face of the gum. 
 
 4. A hole at the tip of the root. 
 
 To make a Section of a Tooth. Let each pupil prepare a longi- 
 tudinal section of a tooth as follows : Imbed a tooth in a little sealing 
 wax on the end of a spool, cork, or block of wood. With a grindstone 
 grind away one half, showing the pulp cavity to the tip of the root as 
 in Fig. 55. Make a drawing of the surface thus exposed, naming the 
 parts. If human teeth cannot be obtained, almost any kind will serve. 
 Let each pupil keep his preparation. 
 
164 rnvsioi.OC,Y. 
 
 Structure of a Tooth. i. The pulp cavity, communi- 
 cating with a hole in the tip of the root, through which 
 the nerve and blood tube entered. 
 
 2. The bulk of the tooth is made up of a substance 
 called dentine (ivory). 
 
 3. The crown of the tooth has a covering of enamel, a 
 very hard substance. 
 
 4. The root is covered with a bony substance called 
 cement. 
 
 The Kinds of Teeth and their Arrangement Begin- 
 ning at the middle of the front of the mouth, there are (in 
 the normal adult) eight teeth in each half jaw : two in- 
 cisors, one canine, two bicuspids (or premolars), and three 
 molars. 
 
 Dental Formula. The kinds and arrangement of teeth 
 are often expressed by a dental formula, in which the nu- 
 merators indicate the upper jaw and the denominators the 
 lower, thus : If, C^, PMf , Mf (for one side of the head). 
 
 Incisors. The crown of an incisor is chisel shaped ; 
 but the root is flattened in the opposite direction, i.e. at 
 right angles to the jaw, instead of parallel to it, as is the 
 case with the crown. Look at a skull from which the 
 teeth have been extracted in order to see the cavities into 
 which the teeth fitted. 
 
 Canines. The canine tooth has a conical crown, and a 
 longer root than the incisor. 
 
 Bicuspids. The bicuspid has two points. 
 
 Molars. The molar has a cuboidal crown, and usually 
 two or three roots. 
 
 The Milk Teeth. The thirty-two teeth of the perma- 
 nent set were preceded by a temporary set of twenty milk 
 
THE DIGESTIVE SYSTEM 
 
 I6 5 
 
 teeth. Because the first set is temporary it should not 
 therefore be neglected. Cavities in these should be filled 
 and the teeth kept clean. Before the temporary set has 
 gone the first of the permanent set appear. The first of 
 
 KINDS OF TEETH 
 Incisors ::: 
 
 Upper 
 
 TIME OF APPEARANCE 
 
 7tb Month 
 
 9th " 
 
 18th " 
 
 TEMPORARY SET 
 Upper 
 
 Lower 
 PERMANENT SET 
 
 Fig. 56. TEETH: Kinds, Arrangements, and Times of Appearance. 
 
 these, often called the " six-year molars," are just back of 
 the hindermost "milk molars." These should receive 
 especial care, as they will never be replaced. Any begin- 
 ning of decay in them ought to receive prompt attention. 
 
1 66 
 
 The Care of the Teeth. The teeth need careful atten- 
 tion. They should be thoroughly brushed at least twice a 
 day, on rising and on going to bed. It would be better to 
 clean them after each meal also. If a tooth powder, recom- 
 mended by a reliable dentist, is not used, a good white 
 castile soap will serve well. It is better to use tepid water. 
 If the teeth are not thoroughly cleansed the particles of 
 food which remain will soon begin to decay. This decay 
 is caused by the growth of germs, usually some kind of 
 bacteria, and the decay thus begun is likely to develop 
 acids which attack the limy material of which the teeth are 
 composed. When it is necessary to take acid medicines, 
 care should be taken not to let them come in contact with 
 the teeth. Sweet substances are very likely to decompose 
 and form acids ; so we must clean the teeth after eating 
 candies. Toothpicks are useful in removing the larger 
 particles. But in using toothpicks care should be taken 
 not to dislodge fillings. The teeth should be examined 
 twice a year by a dentist, and any cavities promptly filled. 
 
 The Salivary Glands. The salivary glands make the 
 saliva and pour it into the mouth. There are three pair of 
 salivary glands the parotid, just back of the angle of the 
 jaw, under the ear ; its duct runs forward under the skin 
 of the cheek, and opens on the inside of the cheek opposite 
 the second molar of the upper jaw. The submaxillary 
 gland lies under the angle of the jaw ; its duct opens under 
 the tongue near the front of the mouth. The sublingual 
 gland is in front of the submaxillary and empties near the 
 same place as the .submaxillary. 
 
 Dissection of the Salivary Glands. The salivary glands of a 
 rabbit or cat may be found near the base of the ear and under the angle 
 of the jaw by removing the skin from the side of the head and neck. 
 
THE DIGESTIVE SYSTEM. 1 67 
 
 Salivary Ducts in Our Mouths. If the inside of one's cheek be 
 examined by the use of a hand mirror, the opening of the duct from the 
 parotid gland may be seen opposite the second molar of the upper jaw. 
 It usually looks like a pink and white spot, resembling a wound of a 
 bee sting. Sometimes saliva may be seen issuing from it. 
 
 Action of the Salivary Glands. The salivary glands 
 pour into the mouth a liquid which they manufacture from 
 materials taken from the blood. In structure the gland 
 may be compared to a bunch of grapes^ the grapes repre- 
 senting the little cavities, with a wall of cells that make 
 
 Mucous Membrane 
 
 Duct of Gland 
 
 Secreting Cells 
 
 Fig. 57. Diagram of a Salivary Gland. (.After Landois and Stirling.) 
 
 the saliva. From these cavities the liquid passes into the 
 individual duct, represented by the stem of a single grape ; 
 many of these unite to form the main stem, which corre- 
 sponds to the main duct. A rich network of capillaries 
 surrounds the gland ; when the gland is at work it receives 
 more blood ; the liquid part of the blood (plasma) soaks 
 out through the capillary walls and surrounds the gland ; 
 it is now called lymph ; from the lymph the gland directly 
 obtains its material. 
 
168 PHYSIOLOGY. 
 
 Nerve Control of Salivary Glands. -The glands are 
 doubly dependent on nerve control : 
 
 1. Through the control of the arterial muscles by the 
 nerves the amount of blood sent to the glands is regulated. 
 
 2. Nerves also go to the cells of the gland to control 
 their activity. When we taste, smell, see, or even when 
 we think of, some delicious food the mouth may "water," 
 as we say, i.e. the salivary glands are, by reflex action, 
 stimulated to activity ; on the other hand, some emotions, 
 such as fear, check the flow of saliva. 
 
 Saliva and its Uses. The saliva is mostly water, and, 
 when we are not eating, serves to keep the mouth moist. 
 The water of the saliva soaks the food during mastication 
 and helps the process of grinding ; it enables us to taste 
 by dissolving any food that is soluble ; it further enables 
 us to swallow what would otherwise be a dry powder. 
 The special element of the saliva, ptyalin, has the power 
 of changing starch to sugar. 
 
 Amount of Saliva. The amount of saliva secreted 
 daily is estimated at three pints. Of course the glands 
 should be allowed to rest between meals. The habit of 
 chewing gum, though supposed to aid digestion, undoubt- 
 edly does far more harm than good. During the resting 
 period the glands accumulate material for the active work 
 of secretion, for there is no sac in which to store the 
 saliva, and it must be made as fast as it is needed. 
 
 Character of Salivary Ferment. " The character of 
 action of salivary ferment is further defined by experi- 
 ments showing : i, that it is destroyed by boiling; 2, that 
 its action is delayed or suspended at a low temperature, 
 most pronounced at about body temperature (37 C); 
 3, that it acts best in a neutral or in a faintly alkaline 
 
THE DIGESTIVE SYSTEM. 169 
 
 medium, not at all in an acid medium, or in too strong an 
 alkaline medium ; 4, that it has almost indefinite power, 
 if the product of its own action (sugar) is not suffered to 
 accumulate. In all these respects, with the exception 
 of the third, the salivary ferment resembles ferments in 
 general, which are destroyed by heat, delayed by cold, 
 and are limited in their action only by the accumulated 
 product of such action." WALLER. 
 
 Enzymes. Ptyalin is a type of a group of bodies 
 called unorganized ferments, or enzymes. These ferments 
 are the agents that produce the peculiar chemical changes 
 that are the chief part of digestion. 
 
 Mucous Glands and Mucus. Besides the salivary 
 glands, there are great numbers of simple glands in the 
 mucous membrane lining the mouth. These secrete a 
 glairy substance called mucus. 
 
 Experiments with Digestive Liquids. It may be proved by 
 experiment that saliva turns starch to grape sugar in an alkaline solu- 
 tion and at the proper temperature. Also that pepsin dissolves proteids 
 in an acid (hydrochloric) at the right temperature. The proteid is 
 turned to peptone, and becomes soluble and diffusible, capable of 
 absorption through the walls of the stomach and intestine. We find 
 that the different elements of the pancreatic juice can, in alkaline solu- 
 tion, and at the right temperature, emulsify fats, turn proteid to pep- 
 tone, and convert starch into grape sugar. 
 
 The Pharynx. The cavity back of the mouth, beyond 
 the soft palate, is the pharynx. The pharynx is a funnel- 
 shaped cavity, communicating above with the passages 
 from the nostrils ; in front it opens into the mouth ; below 
 it connects with the windpipe, through the glottis, and 
 with the gullet, which, as we have seen, lies just back of 
 the windpipe. 
 
PHYSIOLOC.Y. 
 
 Position of Organs during Respiration. In quiet 
 respiration the tongue nearly fills the mouth. The base 
 of the tongue is nearly covered by the soft palate, which 
 curves downward from the hard palate, and by the epi- 
 glottis projecting upward from below. The glottis is 
 open and the gullet is closed. Air enters the nostrils, 
 passes along the nasal passages above the hard palate, 
 back of the soft palate and epiglottis, through the open 
 glottis into the windpipe, and on to the lungs. 
 
 Hard Palate ------ 
 
 Eustachian i ube 
 
 -- Soft Palate, Down 
 
 Pharynx 
 
 - Epiglottis, Raised 
 
 -Gullet, Closed 
 Glottis, Open 
 
 Fig. 58. Diagram, showing the Positions of the Organs of the Mouth and 
 Throat during Breathing. 
 
 The Process of Swallowing. When the morsel of 
 food is ready to be swallowed the tongue pushes it back 
 into the pharynx ; the soft palate is raised to shut off the 
 passage into the nasal cavity ; the larynx is pulled upward 
 and forward ; the epiglottis is pulled down over the glottis, 
 or opening of the windpipe ; and the base of the tongue 
 extends back over the epiglottis ; thus the air passages, 
 above *md below, are shut off, and the food passes over 
 the epiglottis into the gullet. The muscles of the pharynx 
 
THE DIGESTIVE SYSTEM. 
 
 171 
 
 also do their part in pushing the food along. As soon as 
 the food has passed over the epiglottis, the epiglottis rises 
 to its upright position, and the soft palate drops back to 
 its place, leaving the air passages again open. 
 
 Breathing and Swallowing. It is to be observed that 
 the food tube and the air tube cross, and that the pharynx 
 is their crossing. As we are swallowing only a small 
 part of the time, the passageway naturally stands open to 
 the air ; and when we swallow, the parts are, by muscular 
 
 Eustachian Tube 
 
 - Soft Palate, Raised 
 
 - Food 
 
 .... Epiglottis. Down 
 
 - Gullet, Open 
 
 - Glottis, Closed 
 
 Fig. 59. Diagram, showing the Positions of the Organs of the Mouth and 
 Throat during Swallowing. 
 
 effort, temporarily adjusted for this work. There is a 
 spring switch (to borrow a term from the railway) which 
 keeps the track open for the air, which is all the time 
 passing ; but when the food comes along, the switch must 
 be held open for it until it has passed. 
 
 Structure and Action of the Gullet. The gullet has 
 an outer muscular coat and an inner mucous coat. The 
 
172 PHYSIOLOGY. 
 
 muscular coat has two layers, an inner with circularly 
 arranged fibers, and an outer layer with longitudinally 
 arranged fibers. When the food enters the gullet the 
 muscle fibers, especially the circular fibers, shorten, and 
 by a wave-like action push the mass rapidly along into the 
 stomach. The first part of swallowing is voluntary ; but 
 after the bolus has entered the gullet the action is involun- 
 tary. The mucous lining of the gullet has many mucous 
 glands which lubricate the passageway by the mucus which 
 they secrete. 
 
 Illustration of Passage through the Gullet. The passage of the 
 food through the gullet may be illustrated as follows : Let several per- 
 sons hold a large rubber tube with their hands in contact. Put an egg- 
 shaped piece of wet soap in the tube. The first hand is shut and 
 pushes the soap along into the part of the tube held by the next hand ; 
 this hand now compresses the tube, while the first hand remains clinched ; 
 and so, in turn, the object is pushed the whole length of the tube. 
 
 The Stomach. Just beyond the diaphragm the diges- 
 tive tube widens suddenly, forming the stomach ; the 
 stomach is an oval sac lying just beneath the diaphragm, 
 with the large end to the left and the small end to the 
 right. The smaller end, by narrowing, becomes the small 
 intestine. When the stomach is empty it collapses, as its 
 walls are soft and flexible. When distended it may hold 
 three pints, or when abnormally distended even more. 
 
 The Coats of the Stomach. The stomach and intestines have four 
 coats, in the following order, beginning at the outside : the peritoneum, 
 the muscular, the submucous, and the mucous coats. The muscular 
 coat of the stomach consists of three layers, distinguished by the 
 arrangement of the fibers, a circular layer, a longitudinal layer, and an 
 oblique layer. The mucous lining is somewhat loosely attached to 
 the muscular coat by the intervening submucous coat, and when the 
 stomach collapses the mucous coat is thrown into folds, usually running 
 lengthwise. 
 
THE DIGESTIVE SYSTEM. 
 
 173 
 
 The Gastric Glands. In the inner surface of the 
 mucous membrane are many holes. These are the mouths 
 of the ducts of the gastric glands. If a duct is traced 
 inward, it is found to divide into several branches, usually 
 two or three. These gastric glands vary somewhat in their 
 structure in different parts of the stomach. 
 
 The Gastric Juice. The liquid secreted by the differ- 
 ent glands also varies considerably, but the liquid as a 
 whole is called the gastric juice. The gastric juice is 
 
 GULLET 
 
 Fig. 60. Longitudinal Section of Stomach, showing Gastric Glands in Position. 
 (Dorsal View. Mucous Coat Unduly Thickened.) 
 
 chiefly water, containing a ferment, or enzyme, called 
 pepsin, and a small amount of acid. The amount of 
 gastric juice secreted daily has been estimated at from 
 five to ten quarts. Of course, we must bear in mind that 
 nearly all of this is again absorbed from the digestive tube, 
 and is not a permanent loss to the body. 
 
 Blood Supply of the Stomach. The mucous mem- 
 brane is abundantly supplied with blood tubes, but 
 during the time of its rest the blood flow here is 
 
174 
 
 PHYSfOLOGY. 
 
 Mouth of Gland 
 
 Epithelium 
 
 Cells 
 
 diminished, and the membrane is comparatively pale. 
 But as soon as food is introduced into the stomach the 
 blood flow is greatly increased, and the mucous membrane 
 becomes red. This blood supply gives the glands the ma- 
 terials with which they manufacture the gastric juice. At 
 
 the same time the cells of 
 the glands are stimulated 
 to action, and the secre- 
 tion is poured out rapidly. 
 The alkaline saliva also 
 aids in stimulating the 
 i secretion of the gastric 
 juice. 
 
 The Work of the 
 Gastric Juice. The spe- 
 cial work of the gastric 
 juice is accomplished by 
 the pepsin, aided by the 
 acid ; these convert pro- 
 
 teids into a soluble substance, called peptone, which can 
 be absorbed through the walls of the digestive tube into 
 the blood. 
 
 Rennet and Rennin. Rennet, used in cheese making, is a familiar 
 substance obtained from the fourth stomach of the calf. When milk 
 enters the stomach it is curdled ; that is, the casein previously dissolved 
 in the liquid milk is coagulated. This curdling, or coagulation, is at- 
 tributed to a ferment in the gastric juice called rennin, and it seems to 
 be entirely distinct from pepsin. 
 
 Churning Action of the Stomach. At the same time 
 all the food is soaked by the gastric juice, the process being 
 greatly assisted by the churning motion of the stomach 
 caused by the action of the muscular coat. The food is 
 thus gradually re'duced to a pulpy mass called chyme. 
 
 Connective Tissue 
 
 Fig. 6 1 . Three Glands of the Stomach 
 Cardiac Part. 
 
THE DIGESTIVE SYSTEM. 1/5 
 
 During the first part of digestion in the stomach the thick 
 ring of circular fibers called the pylorus (gatekeeper) around 
 the opening of the stomach into the intestine keeps the 
 passage nearly closed, leaving a small orifice for liquids 
 only. But as the food is reduced to the proper condition 
 the pyloric muscles relax and allow the chyme to pass into 
 the intestine. And at last any indigestible substances are 
 usually allowed to pass. 
 
 Sphincter Muscles. Such rings of muscular fibers, 
 guarding openings, are called sphincter muscles. There 
 is a similar one at the anal opening. 
 
 Time of Stomach Digestion. The time required for 
 the digestion of any ordinary meal is from three to four 
 hours, though this may be much longer if very indigestible 
 substances have been eaten, or if the condition of the body 
 or mind is such as to retard the process of digestion. 
 
 Absorption from the Stomach. Some parts of the 
 food that are already digested, or such matters as are sol- 
 uble, e.g. water containing sugar, peptone, salts, etc., may 
 be absorbed immediately through the walls of the mouth 
 and stomach into the blood capillaries. Recent experiments 
 show that the amount of absorption from the stomach is 
 much less than was formerly supposed ; water, for instance, 
 " when taken alone, is practically not absorbed at all in the 
 stomach. As soon as water is introduced into the stomach 
 it begins to pass out into the intestine, being forced out in 
 a series of spurts by the contractions of the stomach." 
 
 Chyme. The rest of the food, now called chyme, is 
 passed on into the small intestine. It is acid, and in a 
 liquid or semiliquid condition. Chyme, as it enters the 
 intestine, is a mixture of digested, partly digested, and un- 
 
1 7 6 
 
 PHYSIOLOGY. 
 
 digested materials. Some of the starch has been changed 
 to sugar, but only a small part, owing to the short time of 
 mastication. The bulk of the starch is unchanged. Some 
 of the proteid is already changed to peptone. Part is still 
 proteid, while part is in an intermediate stage between 
 proteid and peptone. Fat is essentially unchanged, but is 
 melted by the heat of the mouth and stomach, and is more 
 or less divided into small drops by mastication and the 
 movements of the stomach. For instance, in eating bread 
 and butter, the melting butter will be finely mixed with the 
 bread as it is chewed. The water in the chyme was partly 
 taken as such, and partly derived from the saliva and 
 gastric juice. There are also present ptyalin, pepsin, 
 
 mucus, salts, and some indigesti- 
 ble substances. At intervals the 
 sphincter muscles of the pylorus 
 relax, and the contractions of the 
 stomach send the liquid mixture 
 into the intestines by spurts. 
 
 The Intestine. The small in- 
 testine has essentially the same 
 structure as the parts of the diges- 
 tive tube already studied, namely, 
 a mucous lining beset with an im- 
 mense number of tubular glands, 
 called intestinal glands. These 
 
 secrete a liquid collectively called the intestinal juice, whose 
 exact work is not well known, but which may be said to 
 complete the work of the other secretions. The intestine 
 has also a muscular coat with circular and longitudinal 
 fibers. And the muscular coat does the same work of 
 mixing the juices with the food and of moving it along. 
 
 Fig. 62. Horizontal Section 
 through the Mucous Membrane of 
 the Intestine, showing Intestinal 
 Glands in Transverse Section. 
 (Highly Magnified.) 
 
THE DIGESTIVE SYSTEM. 
 
 177 
 
 Bile and Pancreatic Juice. Soon after the chyme 
 enters the small intestine it has poured upon it two liquids, 
 which enter the intestine in one common stream ; these 
 are the bile and the pancreatic juice. These juices come 
 from two large compound glands, the liver and pancreas, 
 
 Fig. 63. Diagram of Portal Circulation. 
 
 that lie close to the stomach. Their ducts join before they 
 enter the intestine into which these juices are emptied a 
 few inches beyond the stomach. 
 
 The Portal Circulation. The liver receives blood 
 from two sources, a branch of the aorta and the portal 
 vein. The portal vein is formed by the union of veins 
 from the stomach, intestine, pancreas, and spleen. Unlike 
 
1/8 PHYSIOLOGY. 
 
 other veins, the portal vein divides and subdivides, forming 
 capillaries which ramify through the liver. The blood is 
 again collected by veins, forming the hepatic vein which 
 empties into the postcaval vein close to the diaphragm. 
 From the blood the liver manufactures at least two impor- 
 tant substances, the bile and liver starch, or glycogen. 
 
 Functions of Bile. The bile is secreted all the time, 
 but more actively during digestion. The part made while 
 digestion is not going on is stored in the bile sac. The 
 functions of the bile are still poorly understood. But the 
 following are believed to be a part of its work : 
 
 1. It is believed to aid in emulsifying the fats. 
 
 2. It is supposed to aid in the absorption of fat. 
 
 3. The bile, to a certain extent, is waste matter ; so the 
 liver is an organ of excretion as well as an organ of secretion. 
 
 4. It is found that if, for any cause, the bile is prevented 
 from entering the intestine, constipation follows, and the 
 contents of the large intestine have a much more fetid 
 odor than usual. The bile itself readily putrefies ; hence 
 it is concluded that the bile has no positive antiseptic 
 properties, but in some indirect way retards putrefaction. 
 
 The liver, from its size, ought certainly to be of great 
 importance in the body ; it is the largest gland in the 
 body, and receives one fourth of the blood. 
 
 The Work of the Pancreatic Juice. The pancreatic 
 juice acts on all the principal classes of foodstuffs : 
 
 1. A ferment in it called amylopsin acts on starches, 
 changing them to sugar, even more energetically than the 
 ptyalin of the saliva. 
 
 2. Another constituent of pancreatic juice is trypsin ; 
 like the pepsin of gastric juice, this ferment has the power 
 of changing proteids to peptones. 
 
THE DIGESTIVE SYSTEM. 179 
 
 3. The pancreatic juice also acts on the fats in two 
 ways : 
 
 (a) It emulsifies them, i.e. the fat is divided into exceed- 
 ingly fine drops, each enveloped in a coating of albuminous 
 substance. An emulsion can be made artificially by shak- 
 ing together water, oil, and white of egg. The shaking 
 breaks the oil into fine drops, which would soon gather 
 again if no other substance were present ; but it is sup- 
 posed that the albumen forms a thin coating around each 
 droplet, enabling it to remain distinct in the liquid. 
 
 (b) The fats are also acted on chemically by steapsin, 
 another ferment of the pancreatic juice ; they are decom- 
 posed with the formation of free fatty acids, and thus 
 more fully prepared to be absorbed and to build up the 
 tissues. These free fatty acids aid in the work of emulsi- 
 fying the rest of the fat. 
 
 Review of Digestive Liquids. Saliva acts only on 
 starch, gastric juice on proteids, bile on fats, whereas 
 pancreatic juice acts on all three, and, probably, more 
 energetically than the above-named liquids. 
 
 Intestinal Juice. The intestinal juice contains a fer- 
 ment, called invertin, which changes cane sugar to dextrose 
 which is a variety 
 of grape sugar. vim 
 
 Acids and Al- 
 kalies in Diges- 
 tion. The bile 
 
 and the pancreatic intestinal cianc-s 
 
 juice are alkaline, 
 
 Fig. 64. Mucous Membrane of Small Intestine 
 
 and overcome the 
 
 acidity of the chyme, as the acidity of the gastric juice 
 
 in the stomach overcame the alkalinity of the saliva. 
 
180 PHYSIOLOGY. 
 
 Summary. I . The chief work in digestion is to render the food 
 liquid, soluble, and in condition to be absorbed and become part of the 
 blood. 
 
 2. The digestive system consists of a long tube, through which 
 the food passes, being subjected to mechanical and chemical processes 
 to liquefy and otherwise make the food ready to become blood. 
 
 3. The teeth grind the food. 
 
 4. The food is soaked and acted on by the saliva, gastric juice, 
 intestinal juice, bile, and pancreatic juice. 
 
 5. These liquids are formed from the blood by glands. A gland 
 is a structure, usually tubular or saclike, surrounded by capillaries, 
 which give off lymph around the gland. The gland cells take part 
 of the lymph and form the "secretion," which is usually poured out 
 on a surface by means of a narrow tube, or duct. 
 
 6. The salivary glands, pancreas, and liver are compound glands. 
 The gastric and intestinal glands are simple. 
 
 7. The first part of swallowing is voluntary. Through the gullet 
 the food is pushed by the shortening of the circular muscle fibers. 
 
 8. The liver receives blood from the hepatic artery and from 
 the portal vein, but is drained by one vein, the hepatic, which empties 
 into the postcaval vein. 
 
 9. Saliva acts only on starch, gastric juice on proteids, bile on 
 fats ; pancreatic juice acts on all three of these foodstuffs. 
 
 Questions. i. Why does the physician examine the tongue of his 
 patient? 
 
 2. What is the "mumps"? 
 
 3. Why is one more likely to choke if he thinks about the process 
 of swallowing? 
 
 4. What are the peculiarities of a cow's stomach? 
 
 5 . What is the meaning of biliousness ? 
 
 6. Why is there a difference in the length of the intestine in a cat 
 and a sheep? 
 
 7. What is colic? 
 
CHAPTER XI. 
 
 Lymph 
 Duct 
 
 ABSORPTION DIGESTION COMPLETED. 
 
 Absorption. The mucous membrane of the small 
 intestine is thrown into ridges, but, unlike those of the 
 stomach, they 
 run transversely. 
 Again, while the 
 folds in the lining 
 of the stomach 
 are temporary, 
 these are perma- 
 nent. They serve 
 to increase the 
 surface of the lin- 
 ing, and to retard 
 
 the passage Of the Mesenterlc 
 . - . Lymph Veins 
 
 food material, and (Fats) 
 so to aid the pro- 
 cess of digestion 
 and of absorption. 
 
 Villi. Fur- 
 ther, the surface 
 of the mucous 
 membrane of the 
 small intestine is thickly beset with little cylindrical pro- 
 jections, like the " pile " on velvet. These projections are 
 
 181 
 
 Lymph 
 Glands """. 
 
 Lacteal s 
 
 Fig. 65. Plan of Absorption. 
 
1 82 PHYSIOLOGY. 
 
 called villi (singular, villus). The villi greatly increase 
 the absorbing surface of the small intestine. In each 
 villus is a network of blood capillaries, and the beginning 
 of lymphatic capillaries called lacteals. 
 
 Routes of Different Foods after Absorption. In the 
 
 villi the largest part of the work of absorption is done. 
 The fats are absorbed by the lymph capillaries, or lacteals, 
 and the rest of the foods by the blood capillaries. It 
 should be carefully noted that nearly all of the foods but 
 the fats go at once to the liver, through the portal vein ; 
 but the fats are carried by the main lymph duct (the 
 thoracic duct) to be emptied into the subclavian vein in 
 the neck ; hence do not directly pass through the liver. 
 
 Diffusion, Osmosis, and Dialysis. If a solution of salt and one 
 of sugar are brought into contact, they will gradually mix by diffusion. 
 If these two solutions are separated by parchment, they will still diffuse 
 through the membrane and mingle. This is osmosis. Since substances 
 differ in the readiness with which they pass through a membrane, they 
 may be thus separated. Such separation is dialysis, and the membrane 
 is called a dialyzing membrane. In the digestive tube the mucous 
 membrane represents the dialyzing membrane with blood or lymph on 
 one side, and the contents of the digestive tube on the other. Soluble 
 materials, such as peptones, sugars, etc., pass through the mucous 
 membrane into the blood. 
 
 Absorption a Vital Process. "The process of osmosis, 
 and to a lesser extent of filtration and imbibition, as they 
 are known to occur outside the body, were supposed to 
 account for the absorption of all the soluble products. 
 This belief has now given way, in large part, to newer 
 views, according to which the living epithelial cells take 
 an active part in absorption, acting under laws peculiar to 
 them as living substances, and different from the laws of 
 diffusion, filtration, etc., established for dead membranes. 
 
ABSORPTION DIGESTION COMPLETED. 
 
 183 
 
 " Unlike sugars and peptones, fats are absorbed chiefly 
 in a solid form that is, in an emulsified condition. 
 There can be no question, in this case, of osmosis. It has 
 been shown by nearly all recent work that the immediate 
 agents in the absorption of fats are again the epithelial 
 cells of the villi of the small intestine. The fat droplets 
 
 Right Lymph Vein .... 
 
 Junction of Thoracic 
 Duct with Left Sub- 
 clavian Vein 
 
 Main Lymph Vein 
 (Thoracic Duct) 
 
 Intestine 
 
 .Lymphatic Glands 
 
 Fig, 66. Lymph Veins Lymphatics. (Ventral View.) 
 
 are taken up by these cells, and can be seen microscopically 
 after digestion in the act of passing, or rather of being 
 passed, through the cell substance. The epithelial cells, 
 in other words, ingest the fat particles lying against their 
 
1 84 
 
 PHYSIOLOGY. 
 
 free ends, and then pass them slowly through their cyto- 
 plasm into the substance of the villus." - - H DWELL. 
 
 The Lacteals and Lymphatics. While the main work 
 of the lymphatics, as we have seen, is the carrying of 
 lymph from the tissues of the body generally to empty into 
 the veins of the neck, the lymphatics of the intestines 
 have another important function. They absorb and carry 
 the fatty portions of the digested food into the general 
 circulation. During most of the time the thoracic duct 
 and the lymphatics of the intestines would hardly be 
 noticed because they are filled with the clear lymph. But 
 after absorption of fatty matter they are filled with a white 
 liquid, called chyle, and are easily seen. 
 
 To show the Thoracic Duct and Lacteals. To show the thoracic 
 duct feed a kitten or puppy on rich milk, and after two or three hours 
 kill it as directed on page 27. As soon as you are sure it is dead, 
 
 Lacteal with Valves Capillaries Muscles Epithelium 
 
 Fig. 67. Elements entering into the Structure of a Villus. 
 
 open the abdominal cavity and spread out the mesentery. The white 
 lacteals, filled with chyle, will be seen radiating through the mesentery. 
 Press on some of these, and it will be seen that they are thin tubes 
 filled with a white liquid. They converge toward the place of attach- 
 ment of the mesentery to the dorsal part of the abdomen. On the 
 dorsal wall of the abdomen, just posterior to the diaphragm, the recep- 
 
ABSORPTION DIGESTION COMPLETED. 185 
 
 tacle of the chyle, or the beginning of the main lymph vein (thoracic 
 duct), should be found. Trace it anteriorly through the chest along- 
 side the aorta to its mouth, near the junction of the left subclavian and 
 jugular veins. 
 
 Action of the Villi. In each villus there are plain 
 muscle fibers. When these shorten they squeeze the 
 chyle, that has already been absorbed, into the lymph 
 tubes of the wall of the intestines, and on into the main 
 
 Epithelial Covering 
 
 Lacteal 
 
 Longitudinal Mus- 
 cular Fibers \ 
 Capillary Network 
 
 Fig. 68. Intestinal Villus. 
 
 lymph duct. The chyle cannot return to the lacteal when 
 the muscles relax, on account of the valves, similar to 
 those of the veins, in the lacteal at the base of the villus. 
 Then, when the muscles relax, the lacteal is empty, and 
 ready to absorb more of the emulsified fat that we call 
 chyle. 
 
 Review of the Digestive Tube. The whole digestive 
 tube may be briefly and roughly described as a muscular 
 tube of varying diameter, lined by mucous membrane. 
 The muscular coat propels the contents and mixes them 
 with liquids ; the mucous coat is beset with glands, making 
 liquids, some of which merely soak the food, others act 
 on it chemically, while mucus serves to lubricate the sur- 
 face. It seems that these myriads of simple glands are 
 not enough, so several large compound glands lie along- 
 side the food tube and empty their secretions into it by 
 
1 86 
 
 PHYSIOLOGY. 
 
 ducts ; these supplementary glands are the salivary glands, 
 the pancreas, and the liver. 
 
 Length of the Intestine. The length of the small 
 intestine is about twenty-five feet, and of the large intestine 
 
 Parotid Sali- 
 vary Gland 
 
 Gullet 
 
 Precaval Vein 
 Postcaval Vein 
 
 Sublingual 
 Salivary Gland 
 
 Submaxillary 
 Salivary Gland 
 
 Hepatic Vein--, 
 
 Mesenteric 
 Vein 
 
 Pancreas and 
 
 Duct 
 
 Receptacle of 
 
 Chyle 
 :n l_acteals 
 
 Mesentery 
 
 Intestine 
 Fig. 69. Diagram of the Organs concerned in the Conversion of Food into Blood. 
 
 five or six feet. The large intestine is not a direct con- 
 tinuation of the small; that is, the small intestine opens 
 at a right angle into the large near the beginning of the 
 latter, so that there is a short blind end called the cecum. 
 
ABSORPTION DIGESTION COMPLETED. 
 
 I8 7 
 
 In some animals this is large and has considerable length, 
 but in man it is very short. It seems to have been longer 
 in man's ancestors, for there is a closed prolongation of 
 the cecum, the vermiform appendix. This appendix is 
 frequently the seat of serious or fatal inflammation, called 
 appendicitis. 
 
 PARTS 
 OF 
 DIGESTIVE 
 TUBE. 
 
 MECHANI- 
 CAL PRO- 
 CESSES. 
 
 GLANDS. 
 
 LIQ- 
 UIDS. 
 
 CHEMICAL 
 CHANGE. 
 
 ABSORPTION. 
 
 MATERIAL 
 
 BY 
 
 MOUTH. 
 
 Cutting 
 and 
 Grinding. 
 
 Salivary. 
 
 Saliva. 
 
 Starch 
 to 
 Sugar. 
 
 
 
 PHARYNX. 
 
 Raising Soft 
 Palate. 
 Depressing 
 Epiglottis. 
 
 
 
 
 
 
 GULLET. 
 
 Food carried 
 to Stomach. 
 
 Mucous. 
 
 Mucus. 
 
 
 
 
 STOMACH. 
 
 Churning 
 and 
 Mixing. 
 
 Gastric. 
 
 Gastric 
 Juice. 
 
 Proteid 
 to 
 Peptone. 
 
 Water. 1 
 Salts. 1 
 Sugars. j 
 Peptones, j 
 
 Blood 
 Capillaries. 
 
 SMALL 
 INTESTINE. 
 
 Mixing 
 and 
 Moving 
 Food, 
 
 Liver. 
 Pancreas. 
 
 Intestinal. 
 
 Bile. 
 Pancreatic 
 Juice. 
 Intestinal 
 Juice. 
 
 f Starch to Sugar. 
 J Proteid to Peptone. 
 1 Fat ^ Emulsified. 
 [ i Decomposed. 
 
 Water. "I 
 Salts. 1 
 Sugar. [ 
 Peptone. J 
 Fats. 
 
 Blood 
 Capillaries 
 
 Lacteals. 
 
 LARGE 
 INTESTINE. 
 
 Food 
 Forced on. 
 
 Mucous. 
 
 Mucus. 
 
 
 Water. 
 
 
 Fig. 70. Outline of Digestion. 
 
 The Colon. The small intestine joins the large near 
 the lower right side of the abdomen. The main part of 
 the large intestine is called the colon. It runs upward 
 (ascending colon), crosses over to the left side (transverse 
 
1 88 PHYSIOLOGY. 
 
 colon), and descends the left side (descending colon), and, 
 after curving somewhat like a letter S (sigmoid flexure), 
 terminates in the rectum. It is well to know the course of 
 the lower bowel, as pressure may be so applied as to push 
 the contents along in case the bowels become torpid. 
 
 The Work of the Large Intestine. Most of the ab- 
 sorption is accomplished in the small intestine ; but as the 
 food passes on into the large intestine the work of digestion 
 and of absorption are carried somewhat farther. If the 
 residue be not soon expelled, there may be absorption of 
 some of the results of putrefactive changes, and a sort of 
 general poisoning of the whole body. Hence the great 
 importance of regularly and thoroughly emptying the 
 lower bowel. The matter thus expelled is largely made 
 up of indigestible material, with some real waste substances. 
 
 Taking up again our comparison of the body and a 
 furnace, we see that the feces are not true waste products, 
 but are rather clinkers, or material that has not been 
 burned or oxidized in the body. The real wastes of the 
 body are the carbon dioxid, urea, water, etc., that are 
 thrown off by the lungs, kidneys, and skin. 
 
 Constipation. This is a very common disorder, and the evils at- 
 tendant upon it are many. Of course, if any trouble is long continued 
 or severe, a physician should be consulted. But it is well known that 
 certain foods tend to bring on such a condition, and that other foods 
 have the opposite tendency. Thus, cracked wheat and oatmeal are 
 generally considered as somewhat laxative in their effects. The fruits 
 generally are laxative. The coarse particles of graham flour, are irri- 
 tating to the mucous lining of the stomach and intestines, and for many 
 persons serve well to stimulate the action of the bowels. But in many 
 persons the mucous coat is so sensitive that it cannot bear such irrita- 
 tion. For these the " entire wheat flour " may serve the same purpose. 
 Of course each person finds out by his own experience what is best for 
 him, and no rules can be laid down that will apply to all cases. But it 
 
ABSORPTION DIGESTION COMPLETED. 
 
 189 
 
 may be well to know what is the usual effect of some of the common 
 articles of food, as perhaps some persons may habitually partake of cer- 
 tain articles and do not suspect that they are the cause of the trouble. 
 The following list is taken from StockhanVs Tokology; 
 
 LAXATIVE. 
 Rolled and cracked wheat bread, 
 
 gems, biscuit, griddlecakes. 
 Crackers and mush from flour of 
 
 the entire wheat and graham 
 
 flour. 
 Granula. 
 
 Bran gruel and jelly. 
 Fruit puddings. 
 Fruit pies. 
 All fresh acid fruits, including 
 
 tropical fruits, like bananas, 
 
 oranges, lemons, etc. 
 Dried fruits. 
 French prunes and prunellas, 
 
 eaten raw. 
 Stewed dried fruits containing 
 
 hydrocyanic acid, of which 
 
 peaches, plums, and prunes are 
 
 the best. 
 
 New Orleans molasses. 
 Rhubarb. 
 Onions. 
 Celery. 
 Tomatoes. 
 Cabbage, raw. 
 Corn. 
 Squash. 
 Cauliflower. 
 Green peas. 
 Spinach. 
 Beets, .etc. 
 Liver. 
 Oysters. 
 Wild game. 
 
 CONSTIPATING. 
 
 Hot bread. 
 
 White bread. 
 
 White crackers. 
 
 Black pepper and spices. 
 
 Pastry made of white flour and 
 lard. 
 
 Bread, rolls, dumplings, etc., made 
 with baking powder. 
 
 Cake. 
 
 All custard puddings. 
 
 Salted meats. 
 
 Salted fish. 
 
 Dried meats. 
 
 Dried fish. 
 
 Smoked meats. 
 
 Poultry. 
 
 Cheese. 
 
 Chocolate. 
 
 Cocoa. 
 
 Boiled milk. 
 
 Tea. 
 
 Coffee. 
 
 Coffee made of wheat, corn, bar- 
 ley, toast, etc. 
 
 Beans (dried). 
 
 Potatoes. 
 
 Farina. 
 
 Sago. 
 
 Starch. 
 
 Tapioca. 
 
 Rice. 
 
 Raspberries. 
 
 Blackberries. 
 
1 90 PHYSIOLOGY. 
 
 Hygiene of Digestion. A prime requisite for a good 
 digestion is a tranquil condition of the whole body, 
 especially of the nervous system. We see that the blood 
 must be massed in the digestive organs at the time of 
 digestion. As there is a limited amount of blood in the 
 body, it is evident that if more is sent to one part, other 
 parts must at the time receive less. If we try to study 
 hard immediately after eating, we are calling the blood 
 away from the organs of digestion, and to that extent in- 
 terfering with the process of digestion. If we exercise 
 the muscles too vigorously soon after eating, we call the 
 blood to the muscles, and so call it away from the stomach 
 and intestines. If, after prolonged study, one is unable to 
 obtain sleep, it may sometimes be efficacious and very de- 
 sirable to eat a little of some very simple food for the pur- 
 pose of drawing off the blood to the stomach, and thus 
 relieving the brain. A little muscular exercise may ac- 
 complish the same result, or a footbath may be employed. 
 For many persons it would probably be better to take a 
 simple lunch than to go to bed hungry, although one 
 should be careful not to abuse the stomach. 
 
 It is exceedingly difficult to lay down general rules in 
 regard to diet. To a certain extent each person must be 
 a law unto himself, for what agrees well with one may act 
 almost as a poison to another. Moderation should always 
 be observed, especially in taking foods to which we are 
 not accustomed. 
 
 Solid Foods digest Slowly. Suppose one were to sit 
 down to eat dinner when ravenously hungry. If in such a 
 condition one begins with solid food, he is likely to eat too 
 fast. Hunger is a demand of the system for food. It 
 takes some time for solid food to go through all the pro- 
 
ABSORPTION DIGESTION COMPLETED. 1 9 1 
 
 cesses of digestion, and be absorbed into the system and 
 appease hunger. 
 
 Value of Soup. But if a soup be first taken, which is 
 readily absorbed, the demand of the system will begin to 
 be met, and there will not be the same tendency to rapid 
 eating. Further, a warm soup stimulates the blood flow 
 in the mucous membrane, and thus prepares for more 
 thorough digestion. It is more easy after a soup to 
 deliberately masticate the solid portion of a meal. 
 
 Desserts. Dessert and sweatmeats, following a meal, 
 are often very helpful by further stimulating the secretion 
 of the glands. Nuts, which are not very digestible, are 
 beneficial if eaten sparingly. The agreeable taste stimu- 
 lates the salivary glands, and the alkalinity of the saliva 
 stimulates the gastric glands to increased activity. The 
 same may be said of cheese. 
 
 " Cheese is a surly elf, 
 Digesting all things but itself.' 1 
 
 Pie. The average pie needs some extra help for its 
 digestion. Donoghue, formerly champion long-distance 
 skater, when asked if he dieted in preparation for a race, 
 said he avoided pastry. If the vigorous digestion of a 
 man skating for hours daily in zero weather cannot profit- 
 ably manage pie, how in the case of sedentary persons ? 
 If pie is eaten, it should be masticated with very great 
 thoroughness. Undoubtedly most persons would be better 
 off if they did not eat puddings and pastries. Fruit is 
 best taken before meals, especially before breakfast. 
 
 Hot Drink at Meals. Hot drink, with a meal, whether 
 it be tea or coffee, or simply hot water, is usually bene- 
 ficial ; especially to a weak digestion when taken before 
 meals. 
 
192 rHYSIOI.()(,\ . 
 
 The Bad Effects of Imperfect Mastication. If we 
 
 swallow food before it is thoroughly ground and mixed 
 with the saliva, the stomach and other parts of the diges- 
 tive organs will require much more time to reduce the 
 food to a liquid form. Further, when eating hastily, we 
 are very apt to eat too much. Thus we may give the 
 stomach a double amount of material to handle, and the 
 material may not be half so well prepared as it should 
 be. The work thus thrown upon the stomach may easily 
 be made fourfold. Of course the organs suffer, and, 
 sooner or later, if this treatment is continued, they must 
 break down. 
 
 Effect of Repose on Digestion. Not only mastication, 
 .but the whole process of digestion, goes on better when 
 the body and mind are at rest and in a peaceful and con- 
 tented condition, as not only the salivary glands, but all 
 the glands, are under the control of the nervous system, 
 and are greatly influenced by the condition of the body. 
 During a meal, and for a short time before and after, all 
 thoughts of one's occupation, and especially all anxiety, 
 should be absolutely dismissed from the mind. For those 
 whose digestion is not strong, it is especially desirable to 
 secure a period of rest after each meal, taking a lounge 
 or easy-chair, closing the eyes, and, as nearly as possible, 
 closing the mind ; for some, even a short nap is very 
 helpful. 
 
 Conversation at Meals. During a meal there should 
 be conversation on topics of general interest. " Chatted 
 food is already half digested." 
 
 Deliberation in Eating. It is said that the people of 
 the United States are nervous, and eat, as they do nearly 
 everything, hastily. Deliberation in eating adds to dignity 
 
ABSORPTION DIGESTION COMPLETED. 193 
 
 as well as health, and properly may be considered an 
 evidence of culture. 
 
 Time of Eating. Probably our almost universal custom 
 of three meals a day, resulting from experience, is well 
 adapted to the needs of our people. Theoretically the 
 chief meal should be near the middle of the day, as is the 
 custom in the country; for the bodily powers are higher 
 than later in the day. But for city people, and others who 
 are very busy in the middle of the day, it is undoubtedly 
 better to take the chief meal after the rush of the day's 
 work is over, when there is time for a deliberate meal and 
 when the mind is free from business cares. For many, too, 
 this is the only time when the whole family can leisurely 
 meet at the table. 
 
 Eating between Meals. The stomach should have 
 time to rest and prepare for the work of digesting another 
 meal. Many find two meals a day sufficient. There are 
 some persons, however, for whom it would be better to 
 have more meals, with less food at each meal. Meals 
 should be regular. 
 
 Amount of Food Needed. This varies greatly with the 
 individual, age, the kind and amount of labor, etc., so that 
 no very helpful rule can be given. Each person must find 
 by experience what is best for himself. It is the opinion 
 of many leading physicians that the majority of man- 
 kind eat too much. The fasting enjoined upon some is 
 undoubtedly hygienic ; and it would be a valuable lesson 
 for more persons to experiment in the line of fasting. 
 
 Errors of Diet. Sir Henry Thompson, one of the 
 foremost authorities in the world on the subject of foods, 
 says : " I have come to the conclusion that more than half 
 
194 PHYSIOLOGY. 
 
 of the disease which embitters the middle and latter part 
 of life is due to avoidable errors of diet ; and that more 
 mischief, in the form of actual disease, of impaired vigor, 
 and of shortened life, accrues to civilized man from 
 erroneous habits of eating than from the habitual use of 
 alcoholic drink, considerable as I know that evil to be." 
 
 READING. Disorders of Digestion, Brunton ; Indiges- 
 tion and Biliousness, Fothergill ; A Plea for a Simpler 
 Life, Keith. 
 
 Summary. i. The hairlike villi lining the small intestine absorb 
 the liquefied food. 
 
 2. Sugars and peptones are carried away by the blood capillaries 
 and pass through the Tiver, but the fats are taken by the lacteals into 
 the lymph stream to join the blood in the subclavian vein. 
 
 3. Digestion is greatly influenced by the condition of the nervous 
 system. 
 
 4. Mastication should be thorough. 
 
 5. Chat at meals is hygienic. 
 
 6. Rest after meals. 
 
 7. Soups and desserts have a physiological justification, though the 
 latter often become harmful. 
 
 8. There is a great amount of suffering from intemperance in eating 
 as well as in drinking. 
 
 Questions. I . What foods are absorbed most quickly ? 
 
 2. Is appendicitis more common than formerly ? 
 
 3. What is the meaning of " laugh and grow fat " ? 
 
CHAPTER XII. 
 NUTRITION. 
 
 Ledger Account of the Body and its Organs. Through 
 the digestive tube and lungs the body receives additions, 
 and there is a corresponding loss through the lungs, skin, 
 kidneys, and intestines. So a ledger account might be 
 kept with the body, and it should balance in the long run, 
 since in adult life the weight remains practically constant. 
 
 So we might take a single organ, say the liver, and 
 balance its accounts. It receives a large amount of blood. 
 To offset what it takes from the blood, it gives to the 
 intestines a large quantity of bile, and to the blood it gives 
 glycogen. 
 
 It is especially interesting to note the losses and gains 
 of the blood as it passes through the various organs of the 
 body. A river, flowing past one State after another, will 
 take some of the soil of each and deposit some of its 
 muddy particles on the banks of each State. Of course, 
 the blood is unlike the river, in that it empties into itself ; 
 i.e. it is truly a circulation. The blood takes something 
 from, and gives something to, each organ as it flows 
 through it. From the intestine the blood gets the chief 
 part of its new material in the newly digested food. To 
 the muscles the blood gives nutritive material and oxygen, 
 and receives water, carbon dioxid, and other waste matters. 
 The account would be similar with the brain. In the skin 
 and the kidneys the blood has great losses and little gains. 
 
196 
 
 PHYSIOLOGY. 
 
 The accompanying diagrams may help in presenting 
 the main points in the blood circuit, and the losses and 
 gains in its course. 
 
 Blood a Mixture of Good and Bad. In the common 
 blood streams are combined the good and the bad. The 
 
 Capillaries 
 
 Vein 
 
 Artery 
 
 Artery 
 
 Vein 
 
 Capillaries 
 Fig. 71. Diagram of the Heart and Blood Tubes (Dorsal View). 
 
 newly digested food is received into a current of impure 
 blood in the postcaval vein. The blood from the kidneys, 
 probably the purest blood in the body, joins the same 
 impure stream. From the aorta, red blood, usually called 
 
NUTRITION. 
 
 197 
 
 pure the same kind that goes to the brain is sent 
 to the kidneys and to the skin to be purified. Yet, as this 
 mixed blood flows through each organ, that organ, so long 
 as it is in health, takes from it only what it should take. 
 
 Lung Capillaric 
 
 Pulmonary Vein 
 
 Left Auricle-- 
 Left Ventricle- 
 
 Body Capillaries 
 
 Fig. 72. Diagram of the Circulation, representing the Right and Left Halves separated 
 (as they are in reality), showing that the Blood makes but One Circuit. 
 
 Action of Diseased Kidneys. The kidney takes, 
 during health, only the waste matters, leaving the valuable 
 nourishing material. But, in disease, the kidneys may 
 
198 
 
 PHYSIOLOGY. 
 
 LUNG 
 
 PULMONARY VEIN 
 LEFT AURICLE 
 
 LEFT VENTRICLE 
 
 PULMONARY ARTERY 
 
 RIGHT VENTRICLE 
 
 RIGHT AURICLE 
 
 Fig. 73. Diagram of the Circulation of the Blood. 
 
NUTRITION. 199 
 
 take out some of the most valuable portions of the nutri- 
 ment. Suppose that in a mill, a workman, whose business 
 is to shovel out wastes, becomes crazy, and shovels wheat 
 or flour out of the mill into the stream below. The dis- 
 eased kidney may be said to have become crazy, and in 
 the disease called "diabetes" throws out sugar, and in 
 " albuminuria " excretes albumen. 
 
 Blood Streams like Water Pipes and Sewer Combined. 
 
 It is as though the water supply of a city house was taken 
 from the sewer ; each organ needing a supply of building 
 material acts like a filter, taking from the blood what it 
 needs, paying no attention to the impurities present, and the 
 organs of excretion select the impurities, allowing the useful 
 substances to pass on to the places where they are needed. 
 
 A Living Eddy. Huxley has very aptly compared the 
 body to an eddy, whose form remains the same, but whose 
 particles are ever changing. 
 
 " To put the matter in the most general shape, the body 
 of the organism is a sort of focus to which certain material 
 particles converge, in which they move for a time, and 
 from which they are expelled in new combinations. 
 
 " The parallel between a whirlpool in a stream and a 
 living being, which has often been drawn, is as just as 
 it is striking. The whirlpool is permanent, but the par- 
 ticles of water which constitute it are incessantly changing. 
 Those which enter it on the one side are whirled around 
 and temporarily constitute a part of its individuality; as 
 they leave it on the other side, their places are made good 
 by new comers. 
 
 " Those who have seen the wonderful whirlpool, three 
 miles below the Falls of Niagara, will not have forgotten 
 the heaped-up wave which tumbles and tosses, a very 
 
200 PHYSIOLOGY. 
 
 embodiment of restless energy, where the swift stream 
 hurrying from the falls is compelled to make a sudden 
 turn toward Lake Ontario. 
 
 " However changeful in the contour of its crest, this 
 wave has been visible, approximately in the same place 
 and with the same general form, for centuries past. Seen 
 from a mile off, it would appear to be a stationary hillock 
 of water. Viewed closely, it is a typical expression of the 
 conflicting impulses generated by a swift rush of material 
 particles. 
 
 " Now, with all our appliances, we cannot get within 
 a good many miles, so to speak, of the living organism. 
 If we could, we should see that it was nothing but the 
 constant form of a similar turmoil of material molecules, 
 which are constantly flowing into the organism on the 
 one side and streaming out on the other." 
 
 Importance of Renewal of Blood and Lymph. It 
 
 will be well here to recall some facts noted in connection 
 with the study of the blood and lymph. We then learned 
 that the lymph (the supply and renewal of which depends 
 upon the blood) surrounds the individual cells which make 
 up the tissues of the body ; and that, to a certain extent, 
 every cell lives an independent life, each taking its nourish- 
 ment directly from the lymph around it. The importance 
 of an abundant supply of good lymph is now more ap- 
 parent. If digestion is not good, or the food be insufficient 
 or of poor quality (whether naturally or from being badly 
 cooked), good blood cannot be made, and the lymph will 
 not be good. The cells are more or less starved, or 
 poisoned if wastes are not properly removed, and the gen- 
 eral tone of the body will soon be lowered ; for the health 
 of the body as a whole depends on the average condition 
 
NUTRITION. 201 
 
 of the cells composing the body, just as the condition of 
 any community depends on the average condition of the 
 individuals of that community. 
 
 Fat as a Tissue. As a tissue fat serves as a stored-up 
 food.' The camel's hump is a well-known instance. In 
 some of the savage races fat is stored in a very similar 
 hump. But in most persons it is distributed more evenly 
 over the body, though there is a tendency to deposit rather 
 more over the abdomen. A fat person can endure starva- 
 tion longer, other things being equal, than a thin person. 
 A layer of fat under the skin serves also as a heat saver. 
 
 Hibernation. Hibernating animals are fat when they enter upon 
 their winter sleep, but are lean when they come out in the spring. 
 Remaining inactive they have produced very little energy, their only 
 motions being a slow and feeble breathing and a correspondingly 
 reduced heart beat. They have consumed the fat, using it mainly in 
 maintaining the necessary heat. In short, they have burned their fat 
 to keep them warm. 
 
 The Hibernation of a Bear. In 'one of Captain Mayne Reid's 
 stories (The Plant Hunters} we are told how the hunters followed a 
 bear into a cave. At the innermost end of this very long cave they 
 finally killed the bear. Just at this time they find that their candles 
 are all burned out, and they are left in complete darkness, lost in the 
 bowels of the earth. Failing to grope their way out, they are at last 
 driven to this expedient : With what combustibles they can gather 
 together, including their gunstocks and some of the fat of the bear, 
 they melt some of the fat, they use the gun barrels for molds, take 
 strips of their clothing for wicks, and make two long candles. With 
 these they finally light their way out to the upper world. 
 
 Respiration and Oxidation of Candle. Now we have seen that 
 when we burn a tallow candle one of the chief products of the combus- 
 tion is carbon dioxid. Another product of the burning is common 
 water. If, then, these hunters had left this bear to his winter's nap, he 
 would have consumed this fat in the slow process of breathing, and 
 it would have given off the same products, as we have proved that two 
 of the waste matters of the expired breath are carbon dioxid and water. 
 
202 PHYSIOLOGY. 
 
 Glycogen. As stated above, glycogen is formed in the 
 liver. This is indicated by the fact that there is more 
 sugar in the blood in the hepatic vein than in the portal 
 vein, except during digestion. Glycogen is formed by and 
 stored in the liver, and is doled out to the tissues. That 
 muscles use sugar in their action is indicated in the fact 
 that the arteries bring to the muscles more sugar than is 
 carried away from them by the veins. As fat is a reserve 
 food, so glycogen serves as a temporary carbohydrate re- 
 serve. 
 
 Nutrition. All the changes that take place between 
 the reception of food and the excretion of waste are 
 
 ANIMAL 
 PROTOPLASM 
 
 INORGANIC WORLD 
 
 Fig. 74. Animal and Vegetable Protoplasm. 
 
 included under the term nutrition. The materials taken 
 as food are usually more complex and unstable, the waste 
 products more simple and stable ; just as the products of 
 combustion are, as a rule, simpler and more stable than 
 fuels. In both combustion and the processes of nutrition 
 the final result is oxidation, more or less direct. 
 
 Muscular Exertion and Excretion of Urea. Since 
 muscles are the engines of motion, and also are largely 
 composed of proteid (nitrogen-containing) material, we 
 would naturally expect that increased muscular exertion 
 would increase the excretion of urea (the only nitrogen- 
 
NUTRITION. 
 
 203 
 
 containing waste). But experiment shows that increased 
 muscular action, such as mountain climbing, hardly in- 
 creases the amount of urea excreted. Such work, how- 
 ever, does largely increase the amount of carbon dioxid 
 excreted. It is thought, therefore, that our energy is 
 largely derived from carbohydrate foods and fats, and this 
 view is strengthened by the fact that our beasts of burden 
 depend chiefly on carbohydrate foods. 
 
 ASSIMILATION^, 
 CIRCULVTION, 
 
 ABSORPTION^ 
 DIGESTION 
 
 VEGETABLE FOOD 
 
 INORGANIC (MINERAL) MATTER 
 
 Fig. 75. Life Processes. 
 
 While increased muscular action does not very per- 
 ceptibly increase the amount of urea excreted, an addition 
 to the amount of proteid food taken does increase the 
 amount of urea. 
 
 Metabolism. The building-up or constructive pro- 
 cesses are included under anabolism, while katabolism 
 designates the tearing down or destructive processes. All 
 the processes of nutrition, both of building up and tearing 
 down, are included in the term metabolism. 
 
 The Indestructibility of Matter. We are agreed that 
 we cannot destroy matter. We may demolish a house, but 
 the material is all there. We may burn it, but if we could 
 gather the ashes and that part of the smoke and gases 
 
204 PHYSIOLOGY. 
 
 furnished by the material of the house, the weight would 
 all be recovered. 
 
 In the continual wasting away of our bodies there is no 
 real loss of matter. Our weight is reduced, but the wastes 
 are still part of the earth or air, and are used again. For 
 instance, a particle of carbon in the carbon dioxid of the 
 expired breath may be taken in through a blade of grass in 
 an adjoining field. A cow may eat the grass, and we may 
 soon take the very same particle of carbon in the flesh or 
 milk of the cow. Or the carbon may be taken by that 
 kind of grass called wheat, and become part of the seed 
 or grain of wheat, and be made into flour and be eaten as 
 bread, and be part of us once more. Or this particle of 
 carbon might be carried by the winds to Florida or Cali- 
 fornia, and become part of an orange, and come again to 
 make part of our bodies. Thus there is a ceaseless round 
 of matter into and out of our bodies. The plants furnish 
 food for us, and we help to make food for them by the 
 wastes of our substance. No one has a monopoly of any 
 portion of matter ; it is now ours, now some one else's. A 
 particle may pass from one animal to another animal, as 
 when we eat flesh or other animal food. But more often 
 the wastes of our bodies go to make part of the air or the 
 soil, and are then taken by some plant before again becom- 
 ing part of our tissues. But we are as unable to destroy 
 matter as we are to create it. 
 
 The Indestructibility of Force. So with energy. We 
 cannot create it and we cannot destroy it. We derive our 
 energy from the food we eat. And this food we get 
 directly or indirectly from the vegetable kingdom. 
 
 An engine gets energy from the combustion of fuel. In 
 the growth of the plant under the influence of sunlight the 
 
NUTRITION. 
 
 2O5 
 
 plant has stored energy. Now that the wood or coal are 
 burned the energy is given out, primarily as heat. But we 
 may convert the heat into electricity, the electricity into 
 light, or back again into heat if we wish. We get our 
 energy from food as the engine gets its energy from fuel. 
 This is saying nothing against the superiority of the 
 human body, and is not in the least degrading. We are 
 
 c o 
 
 N H 
 
 ANIMALS 
 
 AND PLANTS NOT 
 
 POSSESSING CHLOROPHYLL, 
 
 WHICH DISINTEGRATE 
 COMPLEX CHEMICAL COM- 
 POUNDS, LIBERATING 
 ENERGY IN THE 
 
 PROCESS! 
 
 PLANTS 
 POSSESSING CHLOROPHYLL 
 
 INTEGRATE COMPLEX 
 
 CHEMICAL COMPOUNDS, 
 
 STORING UP SOLAR ENERGY 
 
 IN THE PROCESS, 
 
 THEY 
 
 N H. 
 
 Solar Energy 
 
 Energy originally obtained from the sun radiated 
 by the animal (chiefly) into space as heat, and 
 thereby becoming ultimately unavailable 
 
 Fig- 76. Relation of Plants and Animals. 
 
 self-maintaining, self-directing, growing, living machines. 
 Still, starvation soon puts an end to our ability to produce 
 energy of any kind. 
 
 The Utilization of Energy in the Body and in 
 Machines. Now, it is a well-recognized fact that in very 
 many machines only the smaller part of the energy is 
 directed to the end sought. Take a common candle. We 
 wish to get light from it. But most of the energy of the 
 candle is devoted to making heat, which in this case we do 
 not desire. In many machines there is great loss from 
 friction, from radiating heat, etc. Physiologists tell us that 
 the human body utilizes a larger portion of its energy than 
 
206 PHYSIOLOGY. 
 
 most machines. While energy may fail to be used for the 
 desired purpose, it is never destroyed nor really lost. 
 
 CORRELATION AND CONSERVATION OF ENERGY. 
 
 1. The Correlation of Energy. All kinds of energy 
 are so related to one another that energy of any kind can 
 be transformed into energy of any other kind. 
 
 2. The Conservation of Energy. When one form of 
 energy disappears, an exact equivalent of another form 
 of energy always takes its place, so that the sum total of 
 energy is unchanged. 
 
 These two principles constitute the corner stone of phys- 
 ical science, and must be learned and kept in mind if we 
 would understand the actions of our bodies, and our rela- 
 tions to the surrounding parts of the world and the universe 
 in which we live and of which we must consider ourselves 
 a part. 
 
 READING. Foods and Dietaries, Burnet ; Diet in Rela- 
 tion to Age and Activity, Thompson. 
 
 Summary. i . The blood flow is a true circulation ; that is, the 
 blood moves in a circuit, being more or less altered by every organ it 
 passes through. 
 
 2. The body is an eddy into which particles are constantly entering, 
 forming part of it a while, and then passing out. 
 
 3. Fat as tissue is stored food, and consequently stored energy. 
 
 4. Glycogen is a carbohydrate reserve stored temporarily in the 
 liver. 
 
 5. Nutrition includes all the processes of the body from the time 
 matter enters as food until it leaves as waste matter. 
 
 6. The building-up processes of the body are called Anabolism, the 
 tearing down are Katabolism, and both of these are included under 
 Metabolism. 
 
NUTRITION. 207 
 
 7. We can create neither matter nor force, but are dependent on 
 food as the engine is dependent on fuel. 
 
 8. We are dependent on the green plants for our food. 
 
 9. The animal body utilizes more of the energy contained in food 
 than the engine utilizes from fuel. 
 
 Questions. i. Why is it that some persons eat a large amount of 
 food yet remain thin ? 
 
 2. What is meant by "lymphatic temperament" ? 
 
 3. Classify the organs shown in Fig. 73 according to their functions. 
 
 4. What animal is most thoroughly protected from cold by an 
 envelope of fat ? 
 
 5. How are plants and animals dependent one on the other ? 
 
CHAPTER XIII. 
 ALCOHOL. 
 
 Alcohol. Alcohol is not a food. But because it is 
 taken into the digestive tube, and produces its effects, 
 primarily, through the digestive system, it is here pre- 
 sented. 
 
 If we eat a sufficient amount of bread to-day, we do 
 not crave a larger amount to-morrow; but the appetite 
 for alcohol grows ; the law of its use is the law of in- 
 crease, until the terrible alcohol habit is formed. 
 
 Alcohol and Crime. Aside from the fearful effects 
 of the habitual use of alcohol upon the individual himself, 
 statistics show that a large share of the poverty and crime 
 in the world is due to its use. Nearly every child has 
 known of the effects in the family of some drunkard, how 
 the father is feared, how all are ashamed of him, how 
 the children are poorly clothed,- often not sent to school, 
 because not sufficiently supplied with clothes and books ; 
 all these, and the dirt and misery so well known in so 
 many cases, are a sufficient warning not to make the 
 slightest beginning of this habit. History is full of ac- 
 counts of men who thought they could stop when they 
 chose ; the grip of the alcohol habit is almost as relentless 
 as the grip of death. There is one safe rule : " Touch not, 
 taste not, handle not." 
 
 Alcohol and Energy. Some of the best authorities 
 state that alcohol, taken in small doses, is oxidized in the 
 
 208 
 
ALCOHOL. 209 
 
 body, producing energy ; but they do not class it with 
 foods, nor do they recommend its use. 
 
 Alcohol and Heat. As to its power to produce heat, 
 the fact is that, as ordinarily taken, alcohol lowers the tem- 
 perature of the body. It is well known that the face is 
 flushed as the result of taking alcoholic drink. This means 
 that more blood has been sent to the skin. That sending 
 of blood to the skin gives a sensation of heat ; we feel hot 
 when the skin is flushed from other cause, as some emotion. 
 But if the temperature of the body be taken at the time 
 when the body feels warm, in each case it may be found 
 that the temperature is actually lowered ; and we can see 
 the reason for this, for the more blood there is in the skin, 
 the more heat will be given off, and thus the amount of 
 heat in the body diminished. 
 
 Alcohol and Muscular Energy. Neither does alcohol 
 as usually taken increase the energy of the body so far 
 as muscular work is concerned. Experience shows that 
 men can endure more cold and more hard labor without 
 alcohol than with it. This has been repeatedly proved 
 in arctic expeditions, in the army and navy, during the 
 hardships and exposures of forced marches and depriva- 
 tions in all climates. 
 
 Danger in Drinking Alcohol in Cold Climates. - 
 
 Especially if one is to be exposed to severe cold is it 
 dangerous to take alcoholic drink ; many a member of 
 exploring parties has lost his life by disobeying this rule. 
 
 Alcohol and Training. It is a significant fact that 
 men training for athletic contests (no matter what their 
 ordinary habits or principles) let alcoholic drinks alone. 
 One of the famous pugilists said : " I'm no teetotaler, but 
 
210 PHYSIOLOGY. 
 
 when I have business on hand, there's nothing like water 
 and dumb-bells." 
 
 Alcohol as a Stimulant. " Alcohol is a typical stimu- 
 lant ; it acts as a whip, causing a temporary acceleration 
 of physiological activity. Such acceleration must subse- 
 quently be paid for, the extra expenditure brought about 
 by alcohol entailing diminished capacity for further exer- 
 tion. Alcohol is thus of service only for emergencies of 
 short duration ; it is eminently harmful when prolonged 
 exertion and endurance are required. Like all rapid 
 stimulants, alcohol is in large doses a direct depressant." 
 WALLER. 
 
 Alcohol as a Narcotic. Many prefer to call alcohol 
 a narcotic. In large doses it seems to paralyze the mech- 
 anism regulating the caliber of the arteries ; hence the 
 flushing above noted. 
 
 Alcohol and Water. Alcohol has a strong affinity for 
 water, and extracts it from tissues. When we preserve 
 animal tissue in alcohol, the alcohol abstracts the water, 
 thus hardening and preserving the substance. 
 
 Alcohol a Poisonous Drug. Alcohol should be classed 
 with the poisonous drugs (e.g. arsenic, chloroform, bella- 
 donna, strychnin, etc.), the exact nature of whose effects 
 it is exceedingly difficult to determine. We do know that 
 they are very dangerous substances ; and there is one rule 
 that will apply to them all : Never use them except under 
 the advice of a physician. 
 
 The Effects of Drinking Alcohol. " The most serious 
 and widespread derangement of the natural taste is that 
 caused by alcoholic drinks. Alcohol has been demon- 
 strated to be a poison. Its continued use, even in what 
 
ALCOHOL. 211 
 
 is called moderate quantities, will pave the way for many 
 diseases, some of which are sure to overtake those who 
 have the habit of using drinks with alcohol in them. 
 
 " Examples of the effect of the excessive use of alcoholic 
 drinks are numerous and revolting enough in most com- 
 munities to make the strongest appeals against their use. 
 
 "When it is seen that by the use of alcohol an intelli- 
 gent man may act without reason ; that a kind-hearted 
 man may become brutal to his most loved friends ; that 
 it may cause an honorable man to become a dishonorable 
 one ; that it may make a noble nature become one with the 
 most depraved of tastes ; when its use has over and over 
 again been the cause of disappointment, of intense suffer- 
 ing, and of crime, it would seem that vastly stronger 
 reasons existed against its use 'than the mere fact that 
 some slight changes in the tissues occur which might pos- 
 sibly be demonstrated. It is to avoid these serious results 
 that the use of alcohol is to be shunned, and not simply 
 to avoid a differently shaped liver. 
 
 " The physiological effects of poisons are generally much 
 greater than the visible changes which they produce in 
 the tissues would lead us to expect. Indeed, such effects 
 can seldom be detected by changes seen in the tissue cells. 
 
 " Strychnin produces powerful spasms which end in 
 death. It acts, it is said, on the spinal cord, but it would 
 be hard to show any changes that it produces in the cells. 
 And a knowledge of the changes it produces in the cells 
 could not make us fear the poison any more than we do, 
 who know that it results in suffering and death."-- JENKINS. 
 
 Temperance Drinks. Many well-meaning persons use 
 the various preparations called " root beers," perhaps with- 
 out realizing that most, if not all, contain yeast, and in 
 
212 PHYSIOLOGY. 
 
 their preparation undergo fermentation, producing alcohol, 
 though not ordinarily in large amounts. By giving such 
 drinks (often called "temperance drinks") to children, an 
 appetite for alcohol may be cultivated and the beginning 
 of a terrible habit made. (And it may be well here to note 
 the real meaning of the word habit, tJiat which holds us.) 
 
 Cider. Nor is it "advisable to keep cider about a house 
 where there are children. " It is perfectly sweet," you 
 say. Yes, but unless it is all soon consumed it will fer- 
 ment. It is unwise, to say the least, to put temptation 
 in the way of those whose habits are not formed. 
 
 STIMULANTS. 
 
 [WILLIAM H. HOWELL, Ph.D., M.D., Professor of Physiology, Johns Hopkins University, 
 American Text-Book of Physiology.} 
 
 " The well-known stimulating effect of alcohol, tea, 
 coffee, etc., is probably due to a specific action on the 
 nervous system whereby the irritability of the tissue is 
 increased. The physiological effect of tea, coffee, and 
 chocolate is due to the alkaloid caffeine (trimethyl xanthin) 
 and theobromine (dimethyl xanthin). In small doses these 
 substances are oxidized in the body and yield a correspond- 
 ing amount of energy, but their value from this standpoint 
 is altogether unimportant compared with their action as 
 stimulants. Alcohol also, when not taken in too large 
 quantities, may be oxidized in the body, and furnish a not 
 inconsiderable amount of energy. It is, however, a matter 
 of controversy at present whether alcohol in small doses 
 can be considered a true foodstuff, capable of serving as a 
 direct source of energy, and of replacing a corresponding 
 amount of fats or of carbohydrates in the daily diet. The 
 evidence is partly for and partly against such a use of al- 
 
ALCOHOL. 213 
 
 cohol. For example, Reichert finds that moderate doses 
 of alcohol given to a dog do not affect the heat production 
 of the body as measured by a calorimeter. Since the alco- 
 hol is completely, or nearly completely, oxidized in the 
 body, and gives off considerable heat in the process, the 
 fact that the total heat production remains unaltered in- 
 dicates that the oxidation of the alcohol protects an iso- 
 dynamic amount of proteid or non-proteid material in the 
 body from consumption, thus acting as a foodstuff capable 
 of replacing other elements of the food. On the contrary, 
 Miura has arrived at exactly opposite results in a series of 
 experiments made by another method. In these experi- 
 ments Miura brought himself into a condition of nitrogen 
 equilibrium upon a mixed diet. Then for a certain period 
 a portion of the carbohydrates was omitted from the diet, 
 and its place substituted by an isodynamic amount of 
 alcohol. The result was a loss of proteid from the body, 
 showing that the alcohol had not protected the proteid 
 tissue as it should have done if it acts as a food. In a 
 third period the old diet was resumed, and after nitrogen 
 equilibrium had again been established, the same propor- 
 tion of carbohydrate was omitted from the diet, but alcohol 
 was not substituted. When the diet was poor in proteid 
 it was found that less proteid was lost from the body when 
 the alcohol was omitted than when it was used, indicating 
 that, so far from protecting the tissues of the body by its 
 oxidation, the alcohol exercised a directly injurious effect 
 upon proteid consumption. Numerous other researches 
 might be quoted to show that the effect of moderate quan- 
 tities of alcohol upon body metabolism is not yet satisfac- 
 torily understood. Before making any positive statements 
 as to the details of its action, it is wise, therefore, to wait 
 until reliable experimental results have accumulated. The 
 
214 I'JIYS/OLOGV. 
 
 specific action of alcohol on the heart, stomach, and other 
 organs has been investigated more or less completely, but 
 the literature is too great and the results are too uncertain 
 to permit any resume to be given here. When alcohol is 
 taken in excess it produces the familiar symptoms of in- 
 toxication, which may pass subsequently into a condition 
 of stupor or even death, provided the quantity taken is 
 sufficiently great. So, also, the long-continued use of 
 alcohol in large quantities is known to produce serious 
 lesions of the stomach, liver, nerves, blood vessels, and 
 other organs. The effect of alcohol upon the body evi- 
 dently varies greatly with the quantity used. It may 
 perhaps be said with safety that in small quantities it is 
 beneficial, or at least not injurious, barring the danger of 
 acquiring an alcohol habit, while in large quantities it is 
 directly injurious to various tissues." 
 
 [From THOMPSON'S Practical Dietetics.} 
 
 " . . . the following general propositions comprise the 
 belief of many authorities who have devoted careful re- 
 search to this exceedingly important topic : 
 
 " i. The use of alcohol in any shape is wholly unneces- 
 sary for the use of the human organism in health. It does 
 not exist as a natural product. The very lowest types of 
 man Australian and many Polynesian savages know 
 nothing of it, and drink only water and fresh fruit juice, 
 such as that of the cocoanut, although they speedily 
 acquire a fondness for alcohol when it is given them. 
 
 " 2. A large number of persons are undoubtedly better 
 without alcohol, and may prolong their lives by total ab- 
 stinence. 
 
 " 3. The lifelong use of alcohol in moderation, as an 
 occasional beverage with meals, does not necessarily 
 
ALCOHOL. 215 
 
 shorten the duration of life or induce disease in some 
 persons, while in others it undoubtedly produces gradual 
 and permanent changes, chiefly of a cirrhotic character, in 
 the blood vessels and viscera, such as the liver and kidneys. 
 These alterations, which may be slow and subtile in char- 
 acter, may not in themselves materially impair the health 
 or cause an ultimately fatal result, but they tend to weaken 
 vital organs and produce a condition of premature senility ; 
 so that if the patient be overtaken by any severe disease, 
 as, for example, by an acute infection like pneumonia, or 
 a chronic one like pulmonary tuberculosis, the resistance 
 of the body to the force of the disease is materially im- 
 paired, and the danger to the patient is seriously enhanced. 
 
 "4. There are many persons whose constitutional in- 
 heritance is such that they should be particularly warned 
 against the use of alcohol, and in some such cases, as, for 
 example, among those who are subjects of well-marked 
 gouty diathesis, it is better that the use of alcohol should 
 ])e imperatively forbidden. 
 
 "5. The abuse of alcoholic stimulation is invariably 
 injurious, although the extent to which evil influences 
 become manifest depends upon the constitution of the 
 individual, in connection with the two factors of heredity 
 and environment. 
 
 " 6. There are a number of diseases in which the tem- 
 porary use of alcohol is of positive service, and there are a 
 number of cases in which it becomes a necessity in order 
 to prolong life. 
 
 " 7. In many cases of malnutrition and malassimilation 
 of food, alcohol is itself a food, and its consumption under 
 proper direction results in an increase of body weight and 
 strength, and improvement of functional activity. These 
 results are accomplished in part through the action of the 
 
216 
 
 alcohol as a definite food, and in part through its remark- 
 able effect in force production. The latter is due to its 
 own direct combustion, by which in chronic diseases and 
 in critical, acute, and exhausting affections it spares that 
 of the tissues of the body. 
 
 " Although alcohol is such a strong force producer and 
 heat generator, its effect in this direction is very soon 
 counterbalanced by its stronger influence in lowering the 
 general tone of the nervous system, and in producing 
 positive degeneration in the tissues. In the condition of 
 health more food is usually eaten and more force is devel- 
 oped than is actually necessary for the body, and there is 
 constantly a reserve supply of energy on hand which may 
 be utilized for any extraordinary exertion, and hence the 
 constant use of alcohol as a food or stimulant in health is 
 both unnecessary and unadvisable. When alcohol is con- 
 sumed in health in addition to a normal or excessive quan- 
 tity of solid food, by its more ready combustion it prevents 
 the complete oxidation of the latter, and favors the accy 
 mulation of suboxidized waste products, which are always 
 harmful in the system. Excesses in eating are thus doubly 
 aggravated by the effects of alcohol. It is the almost uni- 
 versal testimony of army surgeons, and the experience of 
 those who, like Greely, Stanley, and others, have led long 
 and perilous exploring expeditions involving great fatigue 
 and unusual endurance, that muscular overwork and cli- 
 matic hardships are much better endured if alcohol is 
 entirely abstained from. 
 
 " It has always been found in armies that when good 
 food was at hand the issue of alcohol with the regular 
 ration produced an increased percentage of sick days and 
 of incapacity for work. Colonel Alfred A. Woodhull, 
 surgeon United States army, writes me in regard to this 
 
ALCOHOL. 2i; 
 
 matter : ' I do not think that any of our medical officers 
 would seriously advocate the issue of alcohol as a measure 
 of health, but I believe that its habitual use during the 
 Rebellion was prohibited for reasons of discipline, while it 
 still might have been occasionally issued as if for health. 
 On the rare occasions when it might serve a good purpose, 
 as a temporary stimulant after a long and wet march, the 
 wagons would be in the rear, owing to the same conditions 
 that fatigued the men.' 
 
 " While all this applies to prolonged effort of any kind, 
 and to conditions where other food can be obtained and 
 assimilated, it does not detract from the fact that alcohol 
 is a most helpful food and stimulant in emergencies, when 
 other food cannot be had, or when the body is temporarily 
 endangered from acute disease and the higher rate of 
 combustion in fever, or from failure to assimilate other 
 nourishment. 
 
 " Captain Woodruff, assistant surgeon United States 
 army, says : ' Spirits can never be used in the army as a 
 regular issue ; the practice is thoroughly vicious, and was 
 virtually abandoned sixty years ago. On extraordinary 
 occasions of great fatigue they are allowable in modera- 
 tion. Under such temporary stimulation the men will 
 brace up and perform the necessary work of making earth- 
 works, etc., when without it they would be too exhausted 
 to do anything. Without such stimulation a man is not 
 worth much after he has made a forced march of forty 
 miles.' 
 
 " The problem whether the world as a whole is better or 
 worse for the existence of alcohol, aside from all ethical 
 questions, and viewed merely from the scientific standpoint 
 of the influence of alcohol upon mortality, is difficult of 
 solution ; for to offset the numerous cases of fatal alcohol- 
 
218 
 
 ism, and the still larger number of cases ol diseases which 
 would not presumably be fatal without the existing condi- 
 tion of chronic alcoholic poisoning of the system, are very 
 many cases among both infants and adults in which life is 
 undoubtedly saved by the prompt resort to this food and 
 stimulant, and its energetic use. So long as man is ex- 
 posed to hardships and conditions arising from improper 
 and deficient food supply, as well as to the numerous in- 
 fectious diseases to which he is heir, alcohol must still be 
 regarded rather as a blessing than a curse ; for there is no 
 form of stimulant and food combined, or stimulant alone, 
 which, taken all in all, can be so completely relied upon in 
 cases of emergency. Alcohol, when taken alone, will pro- 
 long life beyond the period at which it terminates from 
 starvation." 
 
 BEVERAGES CONTAINING ALCOHOL. 
 
 [RoHfe, Text-Book of Hygiene.} 
 
 " The physiological action of alcohol has been pretty 
 fully worked out by Binz and his pupils and by other ex- 
 perimenters. From these researches it appears that the 
 first effect of taking alcohol, sufficiently diluted, into the 
 stomach is to increase the flow of saliva and gastric juice. 
 This effect is probably reflex, and results from a stimula- 
 tion of nerve terminations in the stomach. The alcohol is 
 rapidly absorbed, and is carried in the blood, without un- 
 dergoing chemical change, to the nervous centers, lungs, 
 and tissues generally. In the brain the alcohol probably 
 enters into combination with the nervous tissue, modifying 
 the normal activity of the various centers, either increasing 
 the activity, if the alcohol is in small quantity (stimulating 
 effect), or diminishing it, if in larger quantity (depressing 
 
ALCOHOL. 219 
 
 effect), or entirely suspending the activity of the centers 
 if in sufficiently large quantity (paralyzing effect). 
 
 " Alcohol stimulates the vasodilator nerves, causing dila- 
 tation of the smaller vessels ; in consequence of this the 
 blood is largely sent to the periphery of the body, the 
 blood pressure diminishes, and heat radiation is increased. 
 At the same time a portion of the alcohol is used up in the 
 production of animal heat, thus economizing the expendi- 
 ture of fats and proteids, and acting as a true respiratory 
 food. Alcohol does not contribute nutritive material to 
 the body ; it only permits that which is stored up to be 
 saved for other uses, by furnishing easily oxidizable (com- 
 bustible) material for carrying on the respiratory process 
 and supplying animal heat. 
 
 " During the use of alcohol the excretion of urea is 
 diminished. This shows that waste of tissue is retarded 
 in the body. 
 
 " Regarding the statement of some authorities that alco- 
 hol does not undergo any change in the body, but is ex- 
 creted unchanged, Binz asserts that alcohol appears in the 
 urine only when exceptionally large quantities have been 
 taken, and then in very small proportion. It is not excreted 
 by the lungs, the peculiar odor of the breath being due not 
 to the alcohol, but to the volatile aromatic ether, which is 
 oxidized with greater difficulty, and so escapes unchanged. 
 
 " While alcohol produces subjectively an agreeable sen- 
 sation of warmth in the stomach and on the surface of the 
 body, the bodily temperature is not raised. The subjective 
 sensation is due to the dilatation of the blood vessels and 
 the sudden hyperaemia of those parts. 
 
 " During fevers and other exhausting diseases alcohol is in- 
 valuable to prevent waste of tissue and sustain the strength. 
 It does not act merely as a stimulant to the circulation and 
 
220 PHYSIOLOGY. 
 
 nervous system, but, as above pointed out, saves the more 
 stable compounds by furnishing a readily oxidizable res- 
 piratory food. 
 
 " When taken in small doses by healthy persons alcohol 
 diminishes the temperature by increasing heat radiation. 
 When large quantities are taken the bodily temperature is 
 reduced by diminishing heat production, as well as by in- 
 creased radiation. This is shown in the condition known 
 as dead-drunkenness, in which the temperature is some- 
 times depressed as much as 20 degrees F. below the 
 normal. Cases in which the temperature sank to 75 de- 
 grees, 78.8 degrees, and 83 degrees F. have been reported, 
 with recovery in all cases. 
 
 "The constant use of alcohol produces in all the organs 
 an excess of connective tissue, followed by fatty degenera- 
 tion and the condition known as cirrhosis. The organs 
 most frequently affected are the stomach, liver, and kid- 
 neys. Serious pathological alterations also occur in the 
 circulatory, respiratory, and nervous systems. 
 
 "Alcohol is not necessary to persons in good health. 
 Probably most persons, regardless of their state of health, 
 do better without it. Its habitual use, in the form of 
 strong liquors, is to be unreservedly condemned. The 
 lighter wines and malt liquors, if obtained pure, may be 
 consumed in moderate quantities without ill effects. Even 
 in these forms, however, the use of alcohol should be dis- 
 couraged, or perhaps prohibited, in the young. 
 
 " Neither in hot nor in cold climates is alcohol necessary 
 to the preservation of health, and its moderate use even 
 produces more injury than benefit. The polar voyager 
 and the East Indian merchant are alike better off without 
 alcohol than with it. 
 
 " It has long been a prevalent belief that the use of 
 
ALCOHOL. 221 
 
 alcohol enables persons to withstand fatigue better than 
 where no alcohol is used. A large amount of concurrent 
 testimony absolutely negatives this belief. 
 
 "The predisposition to many diseases is greatly in- 
 creased by the habitual use of alcohol. Sunstroke, the 
 acute infectious diseases, and many local organic affec- 
 tions, attack, by preference, the intemperate. A recent 
 collective investigation by the British Medical Association 
 brought out the fact that croupous pneumonia is vastly 
 more fatal among the intemperate than among those- who 
 abstained from the use of alcoholic liquors." 
 
 Testimony of a Naturalist. W. T. Hornaday, author 
 of Two Years in the Jungle, who has had years of ex- 
 perience as collector in many lands, has the following to 
 say as to the use of alcoholic drink : " While a traveler or 
 hunter should never drink brandy or whisky as a bever- 
 age, it is a most excellent thing to have in many cases of 
 sickness or accident, when a powerful stimulant is neces- 
 sary. Above all things, however, which go farthest toward 
 preserving the life of the traveler against diseases and 
 death by accident, and which every naturalist especially 
 should take with him wherever he goes, are Jiabits of strict 
 temperance. In the tropics nothing is so deadly as the 
 drinking habit, for it speedily paves the way to various 
 kinds of disease which are always charged to the account 
 of 'the accursed climate.' If a temperate man falls ill 
 or meets with an accident, his system responds so readily 
 to remedies and moderate stimulants that his chances of 
 recovery are a hundred per cent better than those of the 
 man whose constitution has been undermined by strong 
 drink. There are plenty of men who will say that in the 
 tropics a little liquor is necessary, 'a good thing,' etc.; but 
 
222 PHYSIOLOGY. 
 
 let me tell you it is no such thing, and if necessary I could 
 pile up a mountain of evidence to prove it. The records 
 show most conclusively that it is the men who totally 
 abstain from the use of spirits as a beverage who last 
 longest, have the least sickness, and do the most and best 
 work. As a general rule, an energetic brandy drinker in 
 the ju-ngle is not worth his salt, and as a companion in a 
 serious undertaking, is not even to be regarded as a pos- 
 sible candidate." These statements are made, with no 
 thought of sermonizing, simply as practical advice to 
 collectors. 
 
 [HALLIBURTON, Text-Book of Chemical Physiology and Pathology.} 
 
 " Alcohol. Small quantities of the alcohol taken leave 
 the body by the breath and urine as such, the greater 
 amount is decomposed into simpler products (acetic, oxalic, 
 carbonic acids, and water); the formation of these must 
 give rise to a certain amount of bodily heat. It has been 
 calculated that a man can burn off in his body two ounces 
 of absolute alcohol daily. Alcohol is thus, within narrow 
 limits, a food. It, however, lessens proteid metabolism by 
 about six per cent, and thus ultimately leads to a diminution 
 of the heat produced in the body. It is, moreover, a very 
 uneconomical food ; much more nutriment would have 
 been obtainable from the barley or the grapes from which 
 it was made. The value of alcohol used within moderate 
 limits is not as a food, but as a stimulant not only to 
 digestion, but to the heart and brain." 
 
 [M'KKNDRICK, Text-Book of Physiology.} 
 
 "With regard to alcohol, its exact influence, when taken 
 in moderation by those who use it as an article of diet, 
 cannot be precisely stated. It has been asserted by 
 several observers that alcohol is eliminated from the body 
 
ALCOHOL. 223 
 
 as alcohol by the various excretory channels. The evi- 
 dence of this is doubtful, and it is probable that it is split 
 up into simpler compounds. ... A small part of the 
 alcohol ingested no doubt is exhaled by the mucous mem- 
 brane of the lungs and by the kidneys. The odor of the 
 breath depends on the elimination of oxidation products, 
 such as fusel oil. If oxidized even to a small extent, and 
 the evidence, as already indicated, points to the oxidation 
 of by far the larger proportion of it (95 per cent), alcohol 
 must be regarded, in the scientific sense, as a food. No 
 doubt also its ingestion diminishes the metabolism of pro- 
 teids to the extent of about 6 per cent, as shown by the 
 diminished excretion of urea. Its oxidation will also be 
 attended by the production of heat ; but as, on the other 
 hand, it lessens the production of heat by interfering with 
 the metabolism in proteid tissues, and also by diminishing 
 the oxidation of carbohydrates and fats, the final result 
 is an actual diminution of bodily temperature. While, 
 therefore, alcohol must be classed technically as a food, 
 it is in many respects an unsuitable food, and its place can 
 be taken with great advantage by other substances. In 
 small doses it acts as a local excitant of the digestive 
 mucous membrane, and afterwards as a diffusible stimu- 
 lant upon the circulation and central nervous system. In 
 some cases it may aid the digestive process, but in a state 
 of health it is not only not required, but its use, except in 
 small doses, is positively prejudicial." 
 
 Physiological Effects of Alcohol. These various au- 
 thorities have thus been freely quoted, to show that while 
 there is considerable divergence of opinion in regard to 
 some of the physiological effects of alcohol, they are sub- 
 stantially agreed as to the following points: 
 
224 PHYSIOLOGY. 
 
 1. Alcohol is not needed in health. 
 
 2. While technically it may be called a food, practically 
 it is a poison, and its use is dangerous. 
 
 The danger is especially great where there is a latent 
 hereditary tendency to inebriety or insanity. The danger 
 is also very great when the disease for which alcohol is 
 prescribed is accompanied by melancholy and depression. 
 Many individuals, on finding a drug which exhilarates and 
 banishes the weight of oppression by which they are borne 
 down are tempted beyond their power of resistance, even 
 though the reaction brings them into a worse condition 
 than the one from which they sought relief. 
 
 The Danger of using Alcohol. The pressure of modern 
 life, and the intensity of the struggle for a living, brings 
 about a condition of nervous strain that is fraught with 
 great danger. Every thinking man should see that to use 
 alcoholic drink for the relief of such a condition is like 
 venturing out in a boat above the Falls of Niagara, he 
 knows not when the rushing, mighty power will gain the 
 mastery and dash him to destruction. 
 
 READING. The Temperance Teachings of Science, Pal- 
 mer; The Foundation of Death, a Study of the Drink 
 Question, Gustafson. 
 
 Summary. i. Alcohol is a very dangerous drug and should be 
 used only when prescribed by a physician. 
 
 2. Athletes avoid alcohol when training. 
 
 3. A large per cent of crime is due to alcohol. 
 
 4. On account of its rapid absorption alcohol is a quick recupera- 
 tive after collapse. 
 
 5. In small amounts alcohol is oxidized in the body, producing 
 energy. 
 
ALCOHOL. 225 
 
 6. Alcohol usually lowers the temperature of the body through the 
 increased skin circulation. 
 
 7. It is especially dangerous to take alcoholic drink when exposed 
 to severe cold, as in arctic explorations. 
 
 8. In the army alcoholic drink as a regular ration did more harm 
 than good ; hence was discontinued. 
 
 9. More hard work can be endured without alcohol than with it. 
 10. The precise effects of alcohol are hard to determine. But every- 
 body knows that its effects are generally bad. 
 
 Questions. i . Why do some persons think that alcoholic drink 
 makes them warmer ? 
 
 2. What do statistics show as to "expectation of life" among 
 abstainers and alcohol users ? 
 
CHAPTER XIV. 
 EXERCISE AND BATHING 
 
 How Exercise is Beneficial. -The full significance of 
 the benefits of muscular exercise could not be understood 
 when we studied the muscles, and before we had studied 
 the blood and its work in the tissues of the body generally. 
 Now we can comprehend how exercise stimulates the cells 
 to activity, renews the lymph around the cells both by 
 quickening the blood flow and by pressure on the lymph 
 tubes ; how the glands of excretion are set to work more 
 actively, and the more rapid blood stream brings away the 
 material to be thrown out. 
 
 Exercise for General Health. Exercise is not merely 
 for the muscles. It quickens the action of the whole body 
 by increasing cell activity. It helps clean out the system 
 and clear the brain as well. We read Blaikie's admira- 
 ble book, How to Get Strong, and learn not merely to 
 strengthen the muscles, but how to get strong to do the 
 work we have to do daily, how to feel well every day, how 
 not only to do our work, but to do it gladly, and with a 
 little extra good cheer that may radiate from us and in- 
 spire others. We have no right and no need to carry the 
 sour visage of a devitalized body. Good health is attain- 
 able, and ought to be attained, by nearly all. Attention 
 must be paid to the laws of our being. It takes some 
 effort, mental as well as physical, to adopt and observe 
 
 226 
 
EXERCISE AND BATHING. 22J 
 
 regular hours for exercise and relaxation and to be careful 
 in diet. 
 
 Nature's Rewards and Punishments. But nature 
 rewards for obedience by the delight of a healthy body ; 
 and she never forgets and never forgives, nor fails to pun- 
 ish every violation of every one of her laws. Nature makes 
 no threats beforehand. She does not even tell us her 
 rules. But we may find what they are by careful obser- 
 vation. 
 
 Exercise prolongs Life. Many men would live longer, 
 feel vastly better, and do greater good in the world if they 
 would take regular and systematic exercise or recreation 
 (and this should be, literally, re-creation). It is a short- 
 sighted policy to say, " I cannot afford the time." Not to 
 take time for exercise is to mortgage one's future. Lord 
 Derby says, " He who does not take time for exercise will 
 have to take time for illness." The latter half of every 
 person's life ought in many respects to be by far the most 
 productive of good. But many cut off this half, or render 
 it less productive through breaking down in health as a 
 consequence of violating the laws of hygiene. Thus one 
 defeats his own ends in life, and robs the world of the debt 
 he owes it, that of returning to it, in his riper years, some- 
 thing for the help it gave to him in his early years while 
 he had not yet reached the fullest mental maturity. It is 
 sad enough that so magnificent a structure as the human 
 body must perish and become part of the common clay. 
 But it is infinitely more sad to think that it has not fulfilled 
 its purpose when the end comes in what should be mid- 
 career. Each of us should leave the world better than he 
 found it, and our ability and opportunities for doing this 
 increase as we reach middle life. 
 
228 PHYSIOLOGY. 
 
 Forms of Exercise. In selecting the kind of exercise 
 the old lines fit well : 
 
 " In whate'er you sweat, indulge your taste ; 
 The toil you hate fatigues you soon, 
 And scarce improves your limbs.' 1 
 
 Of course this does not mean that a boy should refuse 
 to saw wood because he dislikes it, and spend all his time 
 playing ball. But for older persons, especially those of 
 sedentary occupation, exercise that exhilarates is far more 
 beneficial than that which is not enjoyed. One may take 
 a walk and carry all his cares and anxieties with him, but 
 he is not likely to think of such matters when playing 
 tennis with a good opponent. Whether it be horseback 
 riding, cycling, boxing, boating, skating, or other form of 
 exercise, choose, whenever a choice is possible, that which 
 you thoroughly enjoy. Exercise should be taken out 
 doors whenever possible. The gymnasium is a substitute 
 in bad weather. 
 
 Games of School Children. Most of the games of 
 school children are excellent kinds of exercise. Cases 
 have been reported of injury from excessive skipping the 
 rope. But in moderate degree it is a good exercise. Tag, 
 snowballing, racing, the various games of ball, jumping, 
 hopping, and other games may be played on the school 
 grounds. 
 
 Tennis. Tennis is a fine game, and suitable for girls 
 as well as boys. It has the great advantage over baseball 
 that it does not require a large ground (which often means 
 going some distance from the school grounds or from 
 home). Two can make up a game, and a little time can 
 be better utilized than with the games requiring more 
 players. The exercise, too, is more evenly distributed. 
 
EXERCISE AND BATHING 2 29 
 
 There is no long waiting, as in some games, but a constant 
 interchange of play, active but not severe, with practically 
 no danger of injury. 
 
 Baseball and Football. For those who can pursue 
 the more vigorous games of baseball and football they are 
 admirable, and should not be objected to because occa- 
 sional injury comes from them. No vigorous exercise is 
 wholly unattended by risk, though it is usually slight when 
 the proper care is used. All these games calling for great 
 activity and strength develop manly qualities in boys, and 
 do much to make them active, fearless men, men who in 
 time of danger have not only strength and endurance, but 
 well-trained muscles, cool heads, and brave hearts, men 
 who know what to do and how to do it in an accident, as 
 at fires, upsetting of boats, etc. A few strong, cool-headed 
 men, by their presence of mind, often stop a panic and 
 save many lives when there is an alarm of fire, which often 
 proves false. The Duke of Wellington said that it was 
 on the football fields of Eton and Rugby that the battle 
 of Waterloo was won. 
 
 Boxing. Boxing is a splendid exercise. It calls into 
 play nearly every muscle of the body. Many pieces of 
 apparatus in a gymnasium are for the especial purpose 
 of working certain muscles. But a pair of boxing gloves 
 may be said to contain a whole gymnasium. Many kinds 
 of work in a gymnasium are likely to be overdone, espe- 
 cially if not under the direct supervision of a good director. 
 One may overlift or overstrain himself. But in boxing 
 there is little tendency in this direction. Boxing makes 
 one quick on his feet, trains to quick movements of the 
 arms, trains the eye, keeps the body in an erect position, 
 and especially develops the muscles of the legs and back. 
 
230 
 
 bi ings out the chest and shoulders. It develops 
 the "wind," and keeps one in constant action. It teaches 
 control of the temper more than almost any form of exer- 
 cise. It develops a degree of self-reliance that is worth 
 much. Instead of developing a tendency to become in- 
 volved in quarrels, it prevents getting into such disgraceful 
 affairs. The man who knows that he can defend himself 
 when it becomes necessary is far less likely to pay serious 
 attention to idle bluster and slight provocation than one 
 not so trained. And it may prove valuable to know how 
 to defend one's self from the attack of a ruffian, or bully, 
 or drunken brute, or other infuriated animal. The cool- 
 ness of head, the quick judgment, and prompt action of 
 a trained boxer frequently saves one from serious injury, 
 and adds not a little to personal comfort. Like tennis, 
 boxing calls for little apparatus, little space, and only two 
 persons. In many places where ordinary gymnasium 
 work is out of the question, boxing is available. It is 
 indeed a "manly art," and the doctrine taught in Tom 
 Brown s School Days at Rugby is as wholesome as can be 
 given to boys to make them strong and active, to give 
 them physical and moral health. 
 
 Bicycling. This is an excellent exercise, as it is in 
 the open air and exhilarating. There is danger of over- 
 exertion, and it is bad for one to yield to the temptation 
 to make long runs. There is danger of overtaxing the 
 heart. The handle bar should be adjusted to allow a 
 fairly upright position. The saddle should be such as not 
 to sustain the weight on the perineum. 
 
 Exercise for Middle-aged Men. For men in middle life, in most 
 cases, milder exercises are preferable, such as shooting, fishing, and 
 horseback riding. Every person should have some form of exercise 
 that takes him into the open air daily. The English are more given 
 
EXERC/SE AND BATHING. 231 
 
 to their " constitutionals "* than their American cousins, and are the 
 better for it. Doubtless if we paid more attention to these matters, 
 we should lose something of our national reputation as a '"nervous 
 people. 11 English women are noted walkers, and do not seem to pride 
 themselves on the smallness of their feet. The signs of the times 
 would appear to show that we are improving in this respect. Probably 
 Americans make too much use of street cars. Walking is the cheapest 
 exercise, and every one can afford to take it. For those who can 
 afford it horseback riding is admirable. As Dr. Holmes expressed it, 
 "saddle leather is in some respects even preferable to sole leather; 
 the principal objection to it is of a financial character.'' Lord Palmer- 
 ston said "the outside of a horse is the best thing for the inside of 
 a man. 11 Perhaps livery bills would prove cheaper and more agreeable 
 than doctors 1 bills. 
 
 " Taking Cold." So long as one is actively exercising, 
 he is not likely to take cold. But if one rests in a cool 
 place, especially when he is warm, he is, as we all too well 
 know, likely to take cold. As we saw when we were 
 studying the circulation of the blood, the application of 
 cold to the skin causes the arteries (through reflex action) 
 to become smaller. Thus when resting in a cool place the 
 skin becomes pale and cold. 
 
 During a " cold " there is fever. The regulation of the 
 heat by the skin is interfered with. At the same time it 
 is often noticeable that the urine is more abundant than 
 usual. As cold may lead to fatal lung disease, so it may 
 be the beginning of some disease of the kidneys that may, 
 in the end, bring fatal results. 
 
 Diarrhea. Diarrhea, which is a catarrhal condition of the intes- 
 tine, may follow, or be associated with, a cold, and as a result of this 
 the process of absorption is often largely checked. There is a great 
 increase in the secretion of mucus by the mucous glands in the intes- 
 tinal wall. As the various liquids of digestion are all taken from the 
 blood, it is evident that if some returns are not soon made, the system 
 must become bankrupt. It is, then, more easy to understand the ex- 
 
232 PHYSIOLOGY. 
 
 cessive weakness and feeling of utter prostration that we experience 
 during an acute attack of diarrhea. We can now understand where all 
 the material comes from to make the profuse discharges, especially 
 after we have ceased eating for some time. 
 
 It is a significant fact that diarrhea is usually called " summer com- 
 plaint." During the warm summer nights we are tempted to go to 
 sleep with very little covering over our bodies. But it almost always 
 grows cool before morning. The common summer diarrhea is, in 
 many cases, due to bacteria taken in food ; but, on the other hand, may 
 be simply a "cold in the bowels." 
 
 Bathing. One purpose of bathing is to cleanse the 
 skin. For this purpose warm water is best, and it is de- 
 sirable to use soap, especially on those parts which are 
 especially exposed to contamination, such as the hands, 
 the feet, the armpits, and groins. 
 
 Cold Baths. Another important function of bathing 
 is to act as a systemic tonic. For this purpose cold bath- 
 ing is better, but this should not be too long continued, 
 and must be followed by brisk friction to give the skin a 
 ruddy glow. For this kind of bath a tub is not necessary, 
 and hardly desirable. The water may be quickly applied 
 by means of a sponge, and the body thoroughly rubbed 
 with a coarse towel. The whole process should be com- 
 pleted very quickly, especially if the room be not warm. 
 
 Bath Hits. Instead of the sponge and the ordinary 
 form of towel, it may be found more convenient to use 
 bath mits made of Turkish toweling. These are easily 
 made, and are somewhat more convenient, as thus friction 
 may be more readily applied than with a towel, which is 
 apt to slip in the hand. The two hands may be used at 
 the same time, and the whole time of the bath need not 
 exceed two or three minutes. At the beginning of a bath, 
 cold water should be applied to the head and face. 
 
EXERCISE AND BATHING. 233 
 
 Time for Bathing. For students, or others who do 
 not take a great deal of vigorous exercise, which keeps 
 the skin active, this means of keeping the skin active is 
 especially valuable. The use of warm water for cleansing 
 seems best adapted (for busy people) to the time of going 
 to bed. But the best time for the cool bath is on getting 
 up in the morning. 
 
 Warm Baths vs. Cold Baths. Prolonged warm baths 
 are debilitating, and probably increase a tendency to take 
 cold, whereas cold bathing is one of the very best means 
 of fortifying against cold, and especially against the ten- 
 dency to take cold on slight exposure. For most 'persons 
 a cool sponge bath, on rising, will act as a most excellent 
 tonic ; but if it seems to produce neuralgia, it should be 
 used with caution. 
 
 Exercise of Arterial Muscles. We have learned that 
 the blood supply to any organ is regulated by the action 
 of the plain muscle fibers in the walls of the small arter- 
 ies. Now, when we are subject to changes in temperature 
 these muscles get exercise, and one writer has well called 
 the cold bath the gymnastics of the plain muscle fibers, 
 and we can understand how the system can be trained to 
 adjust itself to cold, and enabled to avoid " taking cold" 
 so frequently. 
 
 Habit of Cold Bathing acquired Gradually. There 
 are undoubtedly many persons who do not profit by cold 
 bathing, but probably many of these would soon adapt 
 themselves to it by beginning with tepid water and gradu- 
 ally using cooler. To stand stripped in a cold room, of 
 course, is not a safe thing to do. And the great secret of 
 the benefit that may be expected from the operation, as 
 most people are situated, is to be very brisk, the whole 
 
234 
 
 process occupying only a few minutes. Many are opposed 
 to cold sponge bathing, and condemn it without reserve, 
 when, probably, they have never really given it a fair trial. 
 Let it be repeated, with emphasis, that for students it is 
 one of the very best means of preserving health. 
 
 READING. Baths and Bathing (Health Primers, D. 
 Appleton & Co.). 
 
 Summary. i. Exercise stimulates the activity of all the organs, 
 by promoting cell activity and assisting excretion. 
 
 2. Exercise should be in the open air as much as possible. 
 
 3. Exercise is more beneficial when it exhilarates. 
 
 4. Exercise should be taken regularly. 
 
 5. Warm baths are best for cleansing, and a good time is at bed- 
 time. 
 
 6 Cold baths stimulate the circulation of blood in the skin, and 
 serve as a tonic to the whole system. Just after rising is a good time 
 for the cold bath. 
 
 7. The cold bath fortifies against taking cold. 
 
 Questions. I. Should exercise be carried to the point of fatigue ? 
 
 2. How can one avoid taking cold after exercise ? 
 
 3. Do girls need exercise as much as boys ? 
 
 4. What is the condition of the body during a " cold " ? 
 
 5. How may a cold be caused ? 
 
 6. How may a cold be cured ? 
 
 7. How may a cold be prevented ? 
 
 8. Why do some persons take cold so much more readily than 
 others ? 
 
 9. Why does the same person take cold more readily at one time 
 than at another ? 
 
 10. How often should a person bathe ? 
 
 1 1 . What hour is best for sea bathing ? Why ? 
 
CHAPTER XV. 
 THE BRAIN. 
 
 THE muscles are the executive organs ; but the seat 
 of the will is the brain. 
 
 If models of the brain can be obtained, they should 
 be carefully studied. If not, the accompanying figures 
 may be used in their stead. 
 
 The Coverings of the Brain. There are two readily 
 distinguishable coats of the brain, the dura mater, a tough 
 membrane, adhering more or less closely to the inside 
 of the skull ; and the pia mater, next to the brain, a much 
 thinner membrane, traversed by blood tubes, and dipping 
 down into the grooves between the convolutions of the 
 cerebrum. 
 
 The Parts of the Brain. The larger and upper part 
 of the brain is the cerebrum ; below and back of this is 
 the smaller cerebellum ; the part of the spinal cord within 
 the cranium is generally reckoned as part of the brain. 
 
 The Cerebrum. The cerebrum consists of two lateral 
 hemispheres, separated by a deep median groove. The 
 surface of the cerebrum is in irregular ridges, the con- 
 volutions. The outside of the brain consists of gray 
 matter, whereas the outside of the spinal cord is white. 
 The inner part of the brain is white, and the two halves 
 are connected by a broad band of white matter, which 
 consists of many white fibers. 
 
 2 35 
 
236 PHYSIOLOGY. 
 
 The Cerebellum. The cerebellum is much smaller 
 than the cerebrum, and has fine transverse ridges and 
 grooves in place of the convolutions of the cerebrum. It 
 is also of a deeper color, a reddish gray. The cerebrum 
 overlaps the cerebellum so that the latter could not be 
 seen from above if the whole brain were laid bare. But 
 in the lower animals the parts of the brain are more in 
 a series, one behind the other, and in a line with the 
 spinal cord. 
 
 The Spinal Bulb. The enlarged beginning of the 
 spinal cord, often called the medulla oblongata, is the 
 spinal bulb. It is white like the rest of the cord. 
 
 The Brain of a Cat or Rabbit. The brain of a cat or rabbit may 
 be exposed by first mounting the specimen as directed for showing the 
 spinal cord (see p. 27). After removing the skin from the upper part 
 of the head, the bone should be cut away between the eyes with a pair of 
 bone forceps. Cautiously working backward, the whole of the brain 
 may be unroofed. Great care must be exercised, for here we have one 
 of the softest tissues of the body lying very closely beneath one of the 
 hardest. It is possible to do this with a strong knife, but the bone 
 forceps save a great deal of hard work. The bone must be broken 
 away bit by bit. To remove the brain, it will be necessary to cut 
 through the tough dura mater that covers it. 
 
 Removing this, there will be found an inner covering, the pia mater, 
 a membrane richly supplied with blood tubes, from which the brain 
 gets its nourishment. After the dura mater has been removed, the 
 anterior end of the brain may be gently lifted with the handle of the 
 scalpel and the under surface studied, following the description of 
 the cranial nerves. 
 
 Preservation of the Brain. The brain may be studied while it 
 is fresh, but it is more easily handled after it has been hardened. Lay 
 the brain in weak alcohol, about 25 per cent. It should rest on a layer 
 of cotton, otherwise it may be very much flattened by its own weight. 
 Later transfer it to 50 per cent alcohol, and then to 75 per cent. When 
 it is well hardened, it may be sliced with a sharp scalpel as directed. 
 A better and quicker method is to use a solution of alcohol and forma- 
 
THE BRAIN 237 
 
 lin as follows : 95 per cent alcohol, 60 parts ; .2 per cent formol, 40 
 parts. The liquid need not be changed if used in sufficient volume. 
 
 The Brain of the Rabbit {Alcoholic Specimen}. The brain of 
 a cat or dog is better, being larger. Take a brain well hardened, and 
 review the parts as named above. It is very desirable to have a speci- 
 men in which the arteries have been injected. 
 
 1 . Press down the cerebellum to see the deep groove between it and 
 the cerebrum. The thin membrane covering the brain and dipping 
 into the groove is the pia mater. 
 
 2. Press down the spinal bulb and tear away the pia mater where 
 it passes from the cerebellum to the spinal bulb. Note, between the 
 bulb and the cerebellum, a space covered by a thin membrane. Cut 
 through this membrane ; the cavity is the fourth ventricle of the brain. 
 Observe the two ridges bounding the sides of the fourth ventricle. At 
 the point of their divergence, observe the opening of the central canal 
 of the spinal cord. 
 
 3. Gently separate the cerebral hemispheres, and note the trans- 
 verse band of white fibers connecting them. 
 
 4. Examine the under surface of the brain, and find the roots of the 
 cranial nerve. 
 
 The Cranial Nerves and their Functions. i. The 
 
 olfactory lobes extend forward under the fore part of the 
 cerebral hemispheres. They are the nerves of smell. 
 
 2. The optic netves, or nerves of sight, join each other 
 before reaching the brain. Only the first and second pairs 
 of cranial nerves directly enter the cerebrum. 
 
 3. Back of the optic nerves, near the middle line, is the 
 third pair of nerves. The third, fourth, and sixth pairs 
 of cranial nerves control the muscles of the eyeballs. 
 
 4. The fourth pair extend up on each side into the 
 groove between the cerebrum and the cerebellum. 
 
 5. Back of these is the larger fifth pair, the trigeminal. 
 This pair supplies part of the face, and sends branches to 
 the teeth. It is the nerve affected in neuralgia of the 
 face. Besides being the nerve of sensation for most of the 
 
2 3 8 
 
 PHYSIOLOGY. 
 
 head and face, this nerve has motor fibers which control 
 the muscles of mastication. Unlike the other cranial 
 nerves, the trigeminal resembles the spinal nerves in 
 having two roots, one sensory, the other motor. 
 
 Optic 
 (Sight) 
 
 I, Olfactory 
 
 (Smell) 
 
 Eye Motor, 
 3,4,6 
 
 Hypoglossai, 
 12 (Tongue 
 Motor) 
 
 5, Trigeminal 
 (Face 
 Sensation) 
 
 II, Spinal 
 Accessory 
 
 Fig. 77. The Base of the Brain, showing the Origin of the Cranial Nerves. 
 
 6. Back of and inside of the fifth pair is the sixth pair. 
 
 7. The nerves of the seventh pair are larger, and are 
 farther back and outward. These are the facial nerves, 
 and control the muscles of the face and the facial expres- 
 
 sion. 
 
THE BRAIN. 
 
 239 
 
 8. Close to the seventh are the eighth, or auditory 
 nerves. 
 
 9. The ninth, tenth, and eleventh arise close together, 
 farther back and well up on the sides of the spinal bulb. 
 The ninth supplies the back of the tongue and the pharynx, 
 and is called the glosso-pJiaryngeal nerve. It gives the 
 sense of taste from the base of the tongue. 
 
 Cerebrum 
 
 Fig. 78. Vertical Section of Brain. 
 
 10. The tenth pair, or vagus nerves pass down out of 
 the brain cavity, give off branches to the pharynx and 
 larynx, and are distributed to the heart, lungs, and stomach. 
 The vagus nerves are so widely distributed that their func- 
 tions cannot be briefly stated. 
 
 11. The eleventh pair arise in part from the spinal 
 cord outside of the cranial cavity, enter the skull, and pass 
 
240 
 
 PHYSIOLOGY. 
 
 out again to supply certain muscles of the neck and 
 shoulders. 
 
 12. The last pair of cranial nerves, the twelfth, arise 
 near the middle line of the spinal bulb. This pair supply 
 the muscles of the tongue, and are called the hypoglossal 
 nerves. 
 
 Brain composed of Two Hemispheres. It will be 
 observed that the brain, like the spinal cord, consists of 
 two lateral parts. Cutting sections of the brain length- 
 wise and crosswise shows that the outer part is made up 
 of gray matter and the inner part of white matter. The 
 gray matter is composed of cells essentially similar to those 
 of the spinal cord, while the white 
 matter of the inner part is composed 
 of white fibers like those of the outer 
 part of the spinal cord, or like the 
 nerves. 
 
 Brain Convolutions and Intelli- 
 
 . 79. Pyramidal Nerve gence. The brain of the rabbit has 
 ^wer convolutions than that of the 
 cat, and is nearly smooth. In gen- 
 eral, the lower animals have fewer convolutions, and the 
 lower races of mankind have smoother brains than the 
 higher races. In the earlier stages of development man's 
 brain is smoother, but with growth the convolutions 
 appear, and increase in number with the growth of the 
 brain. As we know that intelligent action depends on 
 the gray matter of the surface of the brain, we infer that 
 to accommodate its increase in the brain case it is thrown 
 into folds, as the surface of the lining of the intestines- is 
 increased by folds and villi. 
 
THE BRAIN. 
 
 241 
 
 Gray and White Matter of the Brain. The gray 
 matter of the convolutions of the adult human brain is 
 about one fifth of an inch thick, the larger part of the 
 brain consisting of the white matter. Sections will show 
 that there are several masses of gray matter in the brain 
 deeper than the con- 
 volutions. These ^.AdfeA^ Gray Matter 
 
 are the ganglia of 
 the brain. The 
 white fibers inside 
 the brain connect 
 the gray matter of G an g iia 
 the convolutions 
 and these ganglia 
 with all parts of 
 the body through 
 the spinal cord. 
 
 Cerebrum 
 
 Cerebellum 
 
 Fig. 80. Diagram of -the Brain, showing the Spinal 
 Cord, Ganglia, and Course of the Fibers. 
 
 Neuroglia. The brain consists of nerve cells and nerve 
 fibers, bound together and supported by a form of connec- 
 tive tissue called neuroglia. 
 
 The Cerebrum and its Functions. If the cerebral 
 hemispheres are removed from a frog, he will sit up about 
 as before, but seems to pay little attention to what is going 
 on around him. If placed on his back ; he will turn over 
 and sit up. If pinched, he may jump away, and may show 
 that he can see by avoiding anything that may come in his 
 way. If placed in the water, he will swim, and if he swims 
 against anything that he can climb upon, will do so and 
 remain quiet. If placed on a board, and the board be 
 slowly tilted, he will move along and keep his equilibrium, 
 climbing over the end of the board if necessary to keep his 
 balance. If left alone, he will not move, but will die in 
 
2 4 2 
 
 PHYSIOLOGY. 
 
 his tracks, though he will eat food if it is put in his mouth. 
 He seems to have lost the power of willing to do anything, 
 or what we call the power of volition. He originates no 
 action. 
 
 A Pigeon with Cerebrum Removed. A pigeon with 
 its cerebrum removed acts in about the same way. It 
 remains quiet, stupid, paying no attention to ordinary 
 
 f- Spinal Cord 
 
 - 1st Spinal Nerve 
 
 - 2d Spinal Nerve 
 
 Fig. 81. Diagram of the Cranial Nerves and Sense Organs. 
 
 events. A sudden loud noise may cause it to start. If its 
 tail be pulled, it moves forward to regain its balance. If 
 thrown in the air, it flies for a distance. It swallows food 
 placed in its mouth, but would starve surrounded by food. 
 
THE URAfN. 243 
 
 Placed on its back, it will right itself, but it does not show 
 the usual degree of intelligence and will power. 
 
 Function of the Cerebral Cortex. " Experimentally, 
 we learn that after the removal of the cortex (gray matter) 
 an intelligent animal is reduced to the state of a non-intelli- 
 gent automaton, responding indeed to stimuli, internal as 
 well as external, but failing to interpret the significance of 
 present events in accordance with bygone experience. A 
 brainless dog is stupid ; he may see a bone in front of his 
 eyes without showing signs that he knows the meaning of 
 a bone or the use to which it may be put ; he may hear the 
 crack of a whip, but he no longer shows signs of fear, 
 for he does not remember its sting ; his former purposeful 
 behavior has entirely disappeared ; in short, he has lost 
 memory and judgment." -WALLER. 
 
 The Center of Sensations itself Insensible. The 
 
 gray matter of the outside of the brain is the central organ 
 of intelligent sensation and motion. The functions of voli- 
 tion, of consciousness, of intelligence, seem to reside in, or 
 rather to depend upon the activities of, the cells of the 
 gray matter of the convolutions of the cerebrum. This we 
 have learned from experiments on the lower animals, and 
 from accidents and disease in the case of man. All sensa- 
 tion seems to be in the gray matter of the convolutions of 
 the cerebrum, and yet it is itself insensible; it may be cut 
 and cause no sensation. But when the nerve impulses 
 from the various parts of the body reach the gray matter 
 of the cerebrum they rouse the cells here to an activity 
 that gives us what we call sensation. It is never a sensa- 
 tion until it reaches this part and is properly interpreted. 
 
 Crossed Control of the Body. While each hemisphere 
 mainly controls the muscles of the opposite half of the 
 
244 
 
 PHYSIOLOGY. 
 
 body, it also, in part, has control of its own side. Paralysis 
 of one side (hemiplegia) is due to injury of the opposite 
 cerebral hemisphere. 
 
 Location of Brain Functions. Much has been learned 
 of late years as to the location of special functions in the 
 brain. Many of the motor centers have been determined 
 
 CENTRAL FISSURE 
 MOTOR AREA x'' 
 
 FISSURE OF SILVIU8 
 
 Fig. 82. Location of Brain Functions. 
 
 in the following manner : In some of the lower animals 
 the brain has been exposed, and on stimulating certain 
 portions with an electric current the movements that fol- 
 lowed were noted. In monkeys, " particular movements 
 of the arm, forearm, hand, and thumb can be produced by 
 excitation of particular spots, almost as regularly as definite 
 notes can be sounded on a piano by touching particular 
 
THE BRAIN. 245 
 
 keys." In the case of man we infer that there is a similar 
 location, and many cases of accident and disease have 
 helped in locating the functions. But these areas are not 
 sharply defined. 
 
 Left Hemisphere Better Developed. The "speech 
 center" is in the left hemisphere; the right eye and ear, 
 which connect with the left brain, are better developed 
 than the left, and in general the left hemisphere seems 
 superior (in right-handed persons) to the right. 
 
 Location of Centers of Sensation. It is not so easy 
 to locate the centers of sensation as those for motion. For 
 we can see the resulting motion, but a sensation can only 
 be felt by the individual in whom it occurs. Still, some of 
 the sensation centers have been located, and it is likely 
 that in time we shall know much more on this subject. 
 The accompanying diagram shows some of these centers. 
 
 The Functions of the Cerebellum. The cerebellum 
 is the center for regulating the actions of the skeletal mus- 
 cles. When we walk or run, or even stand still, a number 
 of muscles must act, and act in concert. The nerve im- 
 pulses originate in the cerebrum, but the cerebellum is the 
 center for harmonizing the action of these various muscles, 
 or coordinating them. When the cerebellum has been re- 
 moved from a pigeon the bird flutters, and, while possess- 
 ing the power to move, does not seem capable of any 
 regular and orderly movement. There is no loss of intelli- 
 gence, no paralysis. Of course, in this experiment there 
 is great disturbance of the system, and perhaps too much 
 is inferred from it. 
 
 Functions of the Spinal Bulb. The spinal bulb is the 
 connection between the spinal cord and the brain. The 
 
246 rUYSIOLOGY. 
 
 bulb may be said to be that part of the spinal cord which 
 is within the cranium. It is enlarged, hence its name, 
 tpinal bulb. From it arise all the cranial nerves except 
 the first five pairs. The spinal bulb is also the center for 
 the control of respiration, of circulation, of deglutition, and 
 perhaps for many other processes. 
 
 Brain Work and Brain Rest. Sleep is not merely 
 rest for the body ; it should be complete rest for the brain. 
 In so far as there are dreams, it would seem to indicate a 
 partial activity ; that is, incomplete rest. The brain worker 
 especially needs plenty of sleep ; excellent authorities say 
 at least eight or nine hours. The brain, like the muscles, 
 needs exercise, and it also needs regular periods of rest. 
 If a nerve cell is not kept active by the passage of nerve 
 impulses through it, it usually atrophies, and may de- 
 generate. 
 
 Sleeplessness. Intense brain work, without sufficient 
 sleep, is likely to lead to sleeplessness, as when one has 
 some subject of special study in hand and either will not 
 or cannot throw it off. Perhaps inventors are as prone to 
 this sort of trouble as any one class of men. Keeping the 
 blood continually in the brain, or in any organ, is likely to 
 lead to a permanent congestion or inflammation that may 
 cause serious, if not fatal, results. 
 
 Fatigue. It is stated that brain workers need more 
 sleep than those who work chiefly with the muscles. Fa- 
 tigue of the voluntary muscles is much more a matter of 
 nervous than of muscular origin. When one is completely 
 " tired out," as he would say, if his mind can be aroused, 
 as by some excitement, he will be found able to expend a 
 good deal more muscular energy. So, too, many persons 
 of slight muscular build, but of great " will power," are 
 
THE BRAIN. 247 
 
 able to do more work with the muscles than others with 
 larger muscles and less will. During fatigue the cell bodies 
 are found to decrease in size, but there is no discernible 
 change in nerve fibers as a result of fatigue. 
 
 Control of Mind. But the brain worker should not 
 only be able to sleep regularly and long enough ; he ought 
 to be able to throw off his mind any subject, and take rest 
 while he is awake. If one allows himself to think about 
 mental work while eating, the process of digestion will not 
 go on well. 
 
 Habit of Resting the Brain. The student should ac- 
 quire the power and cultivate the habit of having, so far 
 as possible, regular hours for work, and of completely 
 throwing aside his work and worry at stated times. In 
 seeking recreation it is well to choose that which will 
 necessitate giving the attention to something entirely dif- 
 ferent from the daily work. For this reason chess may 
 be no real recreation for the student, while a game of 
 tennis, boxing, or other competitive exercise is likely to 
 accomplish this very desirable object. A walk may put 
 the muscles into play, but if the mind is still intent upon 
 the line of work maintained throughout the day, the exercise 
 may prove of little benefit. He may return more tired 
 than when he set out. The exhilaration of horseback rid- 
 ing may prove far better, though perhaps involving much 
 less muscular exertion. 
 
 Nervous Tissue least affected by Starvation. It is 
 worthy of note that in fasting the nervous tissue is less 
 reduced than any other tissue, being scarcely diminished 
 by complete starvation. 
 
 Blood Supply of the Brain. Blood is supplied to the 
 brain through four arteries : the right and left internal 
 
248 PHYSIOLOGY. 
 
 carotid arteries, and the right and left vertebral arteries. 
 These arteries are so connected by cross-branches that 
 if any three of them should be compressed, or the blood 
 flow in them otherwise stopped, the fourth would still be 
 able to give the brain blood enough for its work. When 
 the brain is more active it receives a larger supply of 
 blood. During sleep it is paler. 
 
 Fainting. If the supply of blood to the brain is shut 
 off, unconsciousness quickly follows. In the ordinary 
 faint the blood supply has been reduced, owing to the 
 diminution of the blood pressure or heart's force. It may 
 be due to inhibition of the heart from some emotion, or 
 bad odor, as in a close room ; severe pain may be the 
 cause ; a blow over the pit of the stomach may stop the 
 heart by reflex action. Fresh air should be supplied, 
 and the body laid flat on the back. This position makes 
 it easier for the blood to reach the brain and restore 
 consciousness. Smelling salts (or ammonia) may stimu- 
 late respiration and circulation. Sprinkling a little cold 
 water on the face may have the same effect, but it is 
 not necessary to pour a large quantity of water over the 
 person. Rubbing the limbs toward the heart promotes 
 the flow of blood, and tends to start the heart to activity. 
 
 Apoplexy. Apoplexy is caused by rupture of a blood 
 tube and the formation of a clot that presses on the brain. 
 
 Meningitis. Meningitis is an inflammation of the 
 membranes immediately surrounding the brain or spinal 
 cord or both. 
 
 The Water Cushion of the Brain. Between the coats 
 surrounding the brain and spinal cord there is a layer of 
 liquid, comparable to that around the heart or lungs. 
 When an undue amount of blood is sent to the brain, 
 
THE BRAIN. 249 
 
 it is supposed that part of the cerebrospinal fluid is 
 pressed out into the spinal cavity, thus relieving the pres- 
 sure in the brain cavity. 
 
 Relative Activity of Gray and White Matter. The 
 
 gray matter is, physiologically, more active than the white, 
 and in keeping with this is the fact that the capillary 
 network is closer in the gray matter than in the white. 
 This is true of the spinal cord as well as of the brain. 
 
 READING. Brain-work and Over-work, Wood ; The 
 Brain and its Functions, Luys. 
 
 Summary. i . The outside of the brain consists of gray matter, 
 the inside of white matter. 
 
 2. The twelve pairs of cranial nerves are distributed to the head, 
 with the exception of the tenth and part of the eleventh. 
 
 3. The cranial nerves include all the special senses but that of 
 touch. 
 
 4. Each hemisphere of the brain is connected with, and has chief 
 control of, the opposite half of the body. 
 
 5. The gray matter of the cerebrum is the seat of the will, sensation, 
 thought, and emotion. 
 
 6. The cerebellum regulates voluntary motion. 
 
 7. Many of the cerebral functions have been located. 
 
 8. The brain needs rest. In sleep less blood flows through the 
 brain. 
 
 9. Work reduces the size of nerve cells. During rest they increase 
 again. 
 
 Questions. i. Is there any special reason why the "speech cen- 
 ter " should be in the left cerebral hemisphere ? 
 
 2. Why does a light lunch sometimes enable one to go to sleep 
 after mental work ? 
 
 3. Why is it uncomfortable to hold the head down ? 
 
 4. How does the nervous system resemble a telegraph system ? In 
 what respects are the two unlike ? 
 
 5. Name some remedies for sleeplessness. 
 
CHAPTER XVI. 
 EFFECTS OF ALCOHOL ON THE NERVOUS SYSTEM. 
 
 [Treatise on Hygiene, STEVENSON and MURPHY.] 
 
 " THE physiological effects of alcohol which have been 
 considered are quite subsidiary to its effects on the central 
 nervous system, as there is no doubt that it is for this 
 effect on the brain that alcoholic beverages are so univer- 
 sally taken by mankind. The first effect that alcohol has 
 on the brain is that of a stimulant, and it probably acts as 
 such in two ways ; namely, by increasing the circulation 
 of blood through the brain, which is thus roused to greater 
 vigor, and by directly stimulating the nerve cells of the 
 nerve centers. This stimulating effect is observed chiefly 
 after medium or dietetic doses, and its result is seen in 
 many individuals by an increase of mental and bodily 
 activity, and of acuteness of perception by the special 
 senses. This beneficial physiological effect is, however, 
 soon replaced by poisonous symptoms if the dietetic doses 
 are too often repeated, or a large quantity of alcohol is 
 taken at once ; for alcohol then becomes a depressant and 
 paralyzer of the central nervous system, and symptoms 
 of intoxication appear. This depressant effect is, as Brun- 
 ton points out, one of progressive paralysis. The higher 
 centers of the brain are first affected, then the lower. 
 The perceptive centers are paralyzed, so that correct 
 judgment is no longer possible, while the emotions are 
 uncontrolled and thrown out of working gear, fits of bois- 
 terous hilarity and of emotional depression being common 
 
 250 
 
EFFECTS OF ALCOHOL ON NERVOUS SYSTEM. 251 
 
 symptoms. Speech becomes disordered, and symptoms 
 of incoordination, due probably to an effect on the cere- 
 bellum, appear. The respiratory center in the medulla 
 then becomes affected, and at this stage there is coma 
 with stertorous breathing, while the action of the heart 
 still continues, even after respiration has stopped. There 
 can be no question that alcohol taken in sufficient quanti- 
 ties to depress the higher centers of the brain does an 
 infinite amount of harm." 
 
 Dr. Crothers, author of Diseases of Inebriety, says, " I 
 have often been made impatient in listening to the lecturer 
 presenting the ' scientific aspects of the alcohol question ' 
 to an audience, to see him illustrate extensively with 
 charts, and spend hours to show the effects of alcohol 
 upon the coats of the stomach, and upon the structure of 
 the liver and the kidneys, and never allude once to the 
 brain ; when the fact is, alcohol's principal effect is upon 
 this organ, and the functions of this organ so far transcend 
 the functions of all the others, that I might say, there is 
 no comparison." 
 
 Some authors hold that the alterations in the tissues by 
 alcoholic drinks result from the injury to the nerve centers 
 that preside over these tissues ; for their nutrition depends 
 not merely on the direct effect of the blood and lymph 
 supply, but also upon the direct influences of the nerve 
 centers ; they even go so far as to maintain that there is a 
 special set of nerve fibers devoted to the control of the 
 nutrition of the cells, and these nerve fibers they call 
 "trophic nerves" or "trophic fibers." 
 
 " It is clear that the nervous centers, independently of 
 the ill effects on their nutrition by the blood changes, 
 have a certain chemical attraction for alcohol, which 
 accordingly is found in their tissue." CROTHERS. 
 
252 
 
 Dr. Crothers, in common with many physicians, regards 
 inebriety as a disease. 
 
 Dr. Clum in his work entitled Inebriety, its Causes, its 
 Results, its Remedy, says : " The most important part of 
 man is his nervous system ; the cerebrospinal, sympathetic, 
 and vasomotor being intimately interwoven and connected, 
 composing the whole. The great nervous center, the brain, 
 with its hemispheres, its gray and white matter, is the 
 most complex of all complexities. The nerve fibers not 
 only connect every cell with every other cell, but unite all 
 nervous structures into one, making the entire body a 
 complete whole, and forming close and direct sympathy 
 between the intellect and the physical organization. 
 
 " The mind and body are so intimately connected that 
 exhausting excess of either acts and reacts on the other. 
 Excessive work, either intellectual or physical, the sudden 
 loss of property, intense disappointment, great trouble, un- 
 requited affections, etc., may impart a shock to the senses 
 through the mind, which, extending to the molecules of 
 the brain, disturbs their normal action ; and a sufferer 
 thus worn and debilitated* with the cares of life, with an 
 enfeebled will power, the result of nervous exhaustion, 
 experiences a craving for some form of stimulant to * brace 
 him up.' He is on the verge of inebriety, or of insanity, 
 or both, and if he indulges in alcoholic beverages he 
 becomes an inebriate. Any disease inherited or acquired, 
 acting either directly or indirectly upon the nervous system, 
 may act as the predisposing, exciting, or complicating and 
 protracting cause of alcoholic inebriety." 
 
 " Inebriety is often, too often, observed to flourish in 
 the richest and most promising soil. The clergyman, the 
 lawyer, the editor, the student, and all others -who use 
 their intellectual faculties to excess, as well as the mechanic, 
 
EFFECTS OF ALCOHOL ON NERVOUS SYSTEM. 253 
 
 the laborer, and those who excessively exert their physical 
 system, have unnatural longings for something to restore 
 the exhausted energies of mind and body. 
 
 "The excessive worry of one man, the exhausting ex- 
 cesses of another, and the overwork of others, lead to 
 organic lesions and nervous defects, and the disease 
 inebriety, an ungovernable craving for alcoholic drinks, is 
 the result. 
 
 " When a man drinks to excess, even though forced to 
 do so by a diseased nervous system, Christian communities 
 usually brand him as a criminal, as an outcast, and say, 
 ' We have no sympathy for you ; stop drinking and be a 
 man,' when in reality the man should be cared for, and 
 treated as other diseased human beings. The fact that the 
 desire for alcoholic drinks is often a disease which may be 
 either inherited or acquired is overlooked by those who 
 condemn the drunkard. Our ancestors have for ages been 
 addicted to habits of intoxication, and we, their descend- 
 ants, are tainted with the disease inebriety." 
 
 MORAL DETERIORATION PRODUCED BY ALCOHOL. 
 
 [PROFESSOR H. NEWELL MARTIN.] 
 
 " One result of a single dose of alcohol is that the con- 
 trol of the will over the actions and emotions is temporarily 
 enfeebled ; the slightly tipsy man laughs and talks loudly, 
 says and does rash things, is enraged or delighted without 
 due cause. If the amount of alcohol be increased, further 
 diminution of will power is indicated by loss of control 
 over the muscles. Excessive habitual use of alcohol 
 results in permanent overexcitement of the emotional 
 nature, and enfeeblement of the will; the man's highly 
 emotional state exposes him to special temptations, to 
 
254 
 
 excesses of all kinds, and his weakened will decreases the 
 power of resistance ; the final outcome is a degraded 
 moral condition. He who was prompt in the performance 
 of duty begins to shirk that which is irksome, energy gives 
 place to indifference, truthfulness to lying, integrity to 
 dishonesty ; for even with the best intentions in making 
 promises or pledges there is no strength of will to keep 
 them. In forfeiting the respect of others, respect for self 
 is lost and character is overthrown. Meanwhile the pas- 
 sion for drink grows absorbing ; no sacrifice is too costly 
 which secures it. Swift and swifter is now the downward 
 progress. A mere sot, the man becomes regardless of 
 every duty, and even incapacitated for any which momen- 
 tary shame may make him desire to perform. 
 
 " For such a one there is but one hope, confinement 
 in an asylum, where, if not too late, the diseased craving 
 for drink may be gradually overcome, the prostrated will 
 regain its ascendency, and the man at last gain the victory 
 over the brute." 
 
 NARCOTICS. 
 
 Definitions of Narcotics. Gould's Dictionary of Medi- 
 cine, one of the very best authorities, thus defines narcotic : 
 "A drug that produces narcosis" and narcosis, as "the 
 deadening of pain, or the production of incomplete or com- 
 plete anesthesia by the use of narcotic agents, such as the 
 use of anesthetics, opium, and other drugs." It is common, 
 however, to treat of chloroform, ether, chloral hydrate, etc., 
 in a group by themselves under the designation Anesthetics. 
 
 The Century Dictionary thus defines narcotic : " A sub- 
 stance which directly induces sleep, allaying sensibility and 
 blunting the senses, and which, in large quantities, pro- 
 duces narcotism or complete insensibility. Opium, Cauna- 
 
EFFECTS OF ALCOHOL ON NERVOUS SYSTEM. 255 
 
 bis Indica, hyoscyamus, stramonium, and belladonna are 
 the chief narcotics, of which opium is the most typical. 
 Direct narcotics . . . either produce some specific effect 
 upon the cerebral gray matter, or have a very decided 
 action on the blood supply of the brain." 
 
 Some authorities class alcohol with the narcotics. 
 
 OPIUM. 
 
 Opium. Opium is the dried and thickened juice of the 
 head, or capsule, of a species of poppy. Incisions are 
 made in the partially ripened heads ; the milky juice ex- 
 udes ; after about twenty-four hours the partially dried 
 and thickened material is scraped off with a dull knife. 
 Most of the opium comes to this country from Smyrna, 
 with a smaller quantity from Constantinople. As gathered 
 it is a reddish brown, sticky substance of peculiar odor. 
 It is soluble in water, alcohol, and dilute acids, to all of 
 which it gives a deep brown color. It is a very complex 
 substance, but the chief constituent is morphia, or mor- 
 phine, to which the properties of opium are due. One 
 fourth of a grain of morphine is equal to a grain of opium 
 of the average strength. " Opium was known to the 
 Greeks, but was not much used before the seventeenth 
 century ; at present it is the most important of all medi- 
 cines, and its applications the most multifarious, the chief 
 of them being for the relief of pain and the production of 
 sleep. Its habitual use is disastrous and difficult to break 
 up. It is classed as a stimulant narcotic, acting almost 
 exclusively on the central nervous system when taken in- 
 ternally ; in large quantities it is a powerful narcotic poison, 
 resulting in a coma characterized by great contraction of 
 the pupils, insensibility, and death." Century Dictionary. 
 
256 PHYSIOLOGY. 
 
 Properties and Uses of Opium. The United States 
 Dispensatory makes the following statements as to its 
 medical properties and uses : " Opium is a stimulant nar- 
 cotic. Taken by a healthy person in a moderate dose, it 
 increases the force, fullness, and frequency of the pulse, 
 augments the temperature of the skin, invigorates the 
 muscular system, quickens the senses, animates the spirits, 
 and gives new energy to the intellectual faculties. Its op- 
 eration, while thus extending to all parts of the system, is 
 directed with peculiar force to the brain, the functions of 
 which it excites sometimes even to intoxication or delirium. 
 In a short time this excitation subsides ; a calmness of the 
 corporeal actions, and a delightful placidity of mind suc- 
 ceed ; and the individual, insensible to painful impressions, 
 forgetting all sources o'f care and anxiety, submits himself 
 to a current of undefined and unconnected but pleasing 
 fancies, and is conscious of no other feeling than that of a 
 quiet and vague enjoyment. At the end of half an hour 
 or an hour from the administration of the narcotic, all con- 
 sciousness is lost in sleep. The soporific effect, after hav- 
 ing continued for eight or ten hours, goes off, and is often 
 succeeded by more or less nausea, headache, tremors, and 
 other symptoms of diminished or irregular nervous action, 
 which soon yield to the recuperative energies of the sys- 
 tem, and, unless the dose is frequently repeated, and the 
 powers of nature worn out by overexcitement, no injurious 
 consequences ultimately result. Such is the obvious oper- 
 ation of opium when moderately taken ; but other effects, 
 very important in a remedial point of view, are also ex- 
 perienced. All the secretions, with the exception of that 
 from the skin, are in general either suspended or dimin- 
 ished ; the peristaltic motion of the bowels is lessened ; 
 pain and inordinate muscular contraction, if present, are 
 
EFFECTS OF ALCOHOL ON NERVOUS SYSTEM. 257 
 
 allayed ; and general nervous irritation is composed, if not 
 entirely relieved." 
 
 Cocaine. Cocaine is an alkaloid extract of a shrub 
 native to the Andes. It is much used by the natives for 
 sustenance during long journeys. It is a cerebral stimu- 
 lant, developing a remarkable power of enduring hunger 
 and fatigue. Its effects are similar to those of coffee, but 
 are more intense. Large doses have a narcotic effect and 
 cause hallucinations. Its long-continued use is followed 
 by insomnia, decay of moral and intellectual power, ema- 
 ciation, and death. Locally, it is a powerful anesthetic in 
 a limited area of surface, hence is valuable for minor sur- 
 gical operations. 
 
 Chloral Hydrate. This drug is frequently, but incor- 
 rectly, called chloral. It is a powerful hypnotic, anti- 
 spasmodic, and depressant to the brain and spinal nerve 
 centers, and, to a limited extent, is an anesthetic. It is 
 very useful in fevers accompanied by cerebral excitement, 
 and in convulsions. Its hypnotic effects have led to its 
 use by individuals without a physician's prescription, and 
 often with fatal results. No drugs of this class should be 
 used except under the advice of a physician. 
 
 Chloroform. In a similar way this anesthetic, whose 
 discovery is one of the greatest importance in modern sur- 
 gery, is abused for the sake of its effect on the system, 
 and the hold such a habit gets over the user is similar to 
 that of the alcohol or opium habit. 
 
 The Use of Narcotics. The use of anesthetics and 
 narcotics may all be said to be typified by the use of alco- 
 hol. Not that they are all stimulants, though many of 
 them are, in small doses, or in the earlier stages of their 
 
258 PHYSIOLOGY. 
 
 effects. They all act on the nervous system. They pro- 
 duce a pleasurable effect or they bring relief from pain. 
 The use of many of them is begun during illness, when 
 they are administered to relieve pain, as in neuralgia. 
 The habit, once formed, is hard to break. Others, having 
 heard of the soothing effects of these drugs, are unwise 
 enough to experiment on themselves. Only the confes- 
 sions of such victims, and the degrading effects on char- 
 acter, show how powerful is the sway which this class of 
 drugs gains over those who yield to their influence. Let 
 no one flatter himself that he has a strong will and can 
 control himself. The history of their use is ever the 
 same. They enslave. They destroy. 
 
 Tobacco. The use of tobacco is needless. Man gets 
 along well enough without it. It is injurious to many. It 
 is an expensive habit. Many a man spends enough on 
 tobacco to send a boy through college. With the excellent 
 cheap printing of to-day, many of the very best books may 
 be bought for the money that is paid for as many cigars. 
 Even for those who can abundantly afford it, it seems ex- 
 tremely selfish, when it is needless, and there is so much 
 good that might be done with the money. Another very 
 selfish feature is that so many men do not seem to con- 
 sider the fact that the air is public property, and they 
 have no right to fill the air with any gas or smoke that is 
 offensive to others. Very likely many men derive great 
 comfort from the use of tobacco after they have once 
 formed the habit, but most of these were made sick in 
 learning, showing that the use is unnatural. 
 
 Nicotine. The active material in tobacco is a sub- 
 stance called nicotine. It is a violent poison. A drop of 
 it in concentrated form will kill a dog. 
 
EFFECTS OF ALCOHOL ON NERVOUS SYSTEM. 259 
 
 General Effects of Tobacco on the System. Tobacco 
 usually diminishes the natural appetite for food and inter- 
 feres with digestion. It often affects the stomach and 
 induces a craving for alcoholic drink. The eyes are fre- 
 quently affected. Smoking often irritates the mouth and 
 throat sufficiently to make the voice husky. The heart 
 also is very frequently affected, the beat becoming un- 
 steady. The muscles are in some cases weakened and 
 affected by trembling. 
 
 Cigarette Smoking. It seems to be clearly proved 
 that cigarette smoking is very injurious, especially to boys. 
 And if men smoke cigars, the example is set for the boys 
 to smoke cigarettes. Some of the cigarettes are said to 
 be steeped in preparations of opium, so that the use of 
 cigarettes is often subjecting the user, not only to the 
 tyranny of tobacco, but that of opium as well. 
 
 Perhaps Robinson Crusoe might have been excused for 
 using tobacco, having no one to save money for, no unfor- 
 tunates to aid, no children to educate, no one to whom he 
 might set a bad example, no one whose breath of air he 
 could contaminate, no one to smell his breath, no one to 
 see the offensive results. But a man, living in the society 
 of so many to whom this habit, in all its features, is so 
 disgusting and in every way offensive, ought seriously to 
 consider whether he is doing right in continuing such a 
 practice. 
 
 Many boys seem to think it is manly ; they wish, to do 
 as others do. It is not manly to imitate any one. Do 
 nothing simply because some one else does it. To do this 
 is to be a slave, to be led. And one bad feature of the 
 tobacco habit is that one makes himself a slave to the 
 weed. For, like other narcotics, it has a powerful in- 
 
260 PHYSIOLOGY. 
 
 fluence on the system, and the habit, once formed, is hard 
 to break. 
 
 How many men have been heard to say, " I wish I had 
 never formed the habit." 
 
 Has any one in middle or later life ever been heard to 
 say, " I wish I had formed this habit " ? 
 
 READING. The Nature and Effects of Alcohol and Nar- 
 cotics, Luce ; Diseases of Inebriety, Crothers ; Inebriety, its 
 Causes, its Results, its Remedy, Clum ; Inebriety, Palmer. 
 
 Summary. i. The most important physiological effects of alcohol 
 are on the nervous system. 
 
 2. Many physicians regard inebriety as a disease. 
 
 3. The use of alcohol weakens the will power. 
 
 4. Narcotics produce anesthesia, or loss of feeling. 
 
 5. Hence narcotics are useful in deadening pain, but their use is 
 dangerous. 
 
 6. Opium is one of the most widely used of the narcotics. 
 
 7. Tobacco is needless and in many cases harmful. 
 
 8. Cigarette smoking is very injurious, especially to the young. 
 
 Questions. i . Why is cigarette smoking more injurious than 
 cigar smoking ? 
 
 2. How does the opium habit often begin ? 
 
CHAPTER XVII. 
 
 GENERAL CONSIDERATIONS CONCERNING THE NERVOUS 
 
 SYSTEM. 
 
 Nerve Stimuli. Natural nerve impulses that run out- 
 ward are ordinarily started by the action of some nerve 
 cell or cells, as from the gray matter of the brain or of 
 the spinal cord. 
 
 Nerve impulses coming inward may be started in sev- 
 eral ways. Ordinarily by some one of a few forces that 
 are capable of affecting the nerve endings. Mechanical 
 force, as pressure, acts on the nerve endings of the skin, 
 and starts nerve impulses which are carried to the brain 
 and rouse certain cells to activity, and give us the sensa- 
 tion of touch. The vibrations known as light excite the 
 special nerve endings in the retina, but affect no other 
 nerve endings. Sound is appreciated only by the endings 
 of the auditory nerve. Certain gases or fine particles 
 affect the olfactory nerve endings, and certain substances 
 may give the sense of taste by acting on the ends of nerves 
 in the mouth. Different nerves, then, are adapted to re- 
 ceiving impressions from the action of different forces. 
 
 Kinds of Nerve Stimuli. There are four kinds of 
 nerve stimuli, electrical, mechanical, thermal, and chemi- 
 cal. In experiment, electricity is usually the best stimulus ; 
 mechanical stimuli, as used in the experiments with the 
 muscle-nerve preparation from the frog, by cutting or 
 pinching the nerve, may be employed ; heat, as in touch- 
 
 261 
 
262 PHYSIOLOGY. 
 
 ing the nerve with a hot wire, or holding a hot wire near 
 the nerve, may be used as a stimulus ; chemical stimuli, as 
 acids, strong salt solution, etc., may also be used. 
 
 Essential Similarity of All Nerve Fibers. It is to be 
 noted that while special stimuli act on specially modified 
 nerve endings, all nerve fibers are essentially alike, and 
 the nerve impulse, however started, is probably the same 
 kind of force. For instance, cutting the optic nerve, or 
 severe shock, as a blow on the head, causes a sensation of 
 light not quite so definite, but essentially the same as 
 though light had acted on the retina, and thus started the 
 nerve impulse, instead of a mechanical stimulus acting on 
 the nerve fibers between the retina and the brain. 
 
 Relation of Stimulus and Sensation. If we apply a 
 stimulus of a given intensity, as of an electric current, 
 whose intensity can be measured, it causes a sensation of 
 a certain degree. Doubling the stimulus, or increasing it 
 by a definite amount, does not increase the intensity of the 
 sensation to the same degree. The sensations do not 
 increase at the same rate as the stimuli. To increase the 
 sensations arithmetically, the stimuli must increase geo- 
 metrically. 
 
 Reaction Time. " Reaction time " is the time between 
 the application of a stimulus and the signal given as a 
 response to show that the stimulus has been "felt." Thus 
 a blindfolded person gives a signal as soon as he is touched. 
 This interval between the stimulus and response varies 
 with the individual, mode of stimulation, health, attention, 
 etc. It is from one tenth to one fifth of a second ; is short- 
 est for touch ; longer for sight than for hearing. The total 
 reaction time is occupied by (i) the time of conducting 
 the nerve impulse to the brain, (2) the time occupied in 
 
NERVOUS SYSTEM IN GENERAL. 
 
 263 
 
 the cerebral cortex in the perception of the sensation 
 and the formation of the volition, (3) the time of conduct- 
 ing the motor impulse and giving the signal. The greater 
 part is in the middle interval, i.e. the central elaboration, 
 during which the entering impression gives rise to an out- 
 going impulse. 
 
 Reflex Action. In a previous diagram of reflex action, 
 a single cell was represented as receiving the afferent im- 
 
 Nerve Cells connected by Interlacing Nerve Network 
 
 Afferent Nerve Fibe 
 
 Sensory 
 Epithelium 
 
 Efferent Nerve Fiber 
 
 Muscle 
 
 Fig. 83. Diagram of Reflex Action. 
 
 pulse and sending out an efferent one. It is more proba- 
 ble that at least two cells are concerned in such an act, one 
 receiving the incoming impulse, and influencing, by means 
 of fine connecting branches, a second cell which sends out 
 the motor impulse, as shown in Fig. 83. 
 
 Connection of Brain Centers. We have_seen that the 
 brain functions. are more or less localized. We also know 
 that the cortex receives impressions through the channels 
 
264 
 
 PHYSIOLOGY. 
 
 Writing 
 
 Speech 
 
 of the different sense organs, and we can respond through 
 various channels, speech, writing, facial expression, etc. 
 We would therefore expect, theoretically, that the various 
 parts of the cortex of the brain are connected. As a 
 
 matter of fact, we 
 find anatomically 
 that this is the 
 case. Not only 
 are the cells of 
 the gray mat- 
 ter connected 
 with the various 
 parts of the body, 
 but cells of differ- 
 ent parts of the 
 cortex are in com- 
 munication with 
 each other by what 
 are called " as- 
 sociation fibers." 
 Thus a sensation 
 roused in one part 
 of the brain gives 
 rise to the sending 
 out of an impulse 
 from another part 
 of the brain to 
 produce the re- 
 sponse. 
 
 Fig 84. Connection of Brain Centers by Association 
 Fibers. (After Landois and Stirling.) 
 
 (The dotted lines from the hand, mouth, and eye rep- 
 resent afferent fibers from the skin, muscles, and joints 
 of the hand, lips, orbit, etc.) 
 
 The Nature of Sensation. Of the real nature of sen- 
 sation we know but little. Like consciousness, we call it 
 a condition of the gray matter of the cerebral convolutions. 
 
NERVOUS SYSTEM IN GENERAL. 26$ 
 
 Perhaps the most practical definition of sensation that we 
 can give is that it is the interpretation that the cells of 
 tJie gray matter of the brain give to the nerve impulses 
 that come from without. This will apply to ordinary sen- 
 sations. 
 
 Subjective Sensations. But sensations may be subjec- 
 tive ; that is, they may exist without any corresponding 
 external exciting cause. For some unexplained reason the 
 cells of the brain are active, and their activity, however 
 caused, constitutes what we call a sensation. Certain 
 drugs, such as hashish, may excite an unusual degree of 
 cerebral activity. Here the action is roused through af- 
 ferent nerves, but through unusual channels ; that is, the 
 subject sees, but not through the nerves of sight. Many 
 hallucinations are explainable to a certain degree ;' others 
 we cannot account for. 
 
 The Relative Nature of Sensations. If one hand be 
 held in a basin of hot water and the other in a basin of 
 cold water, and then the two be suddenly plunged into 
 a third basin containing tepid water, a sensation of cold will 
 be received from the hand that was in the hot water, while 
 the hand from the cold water will feel heat. Sensations 
 depend on comparison and contrast. After listening to 
 low sounds, a sudden loud noise is painful ; and after hear- 
 ing loud noises, it is difficult to detect slight sounds. We 
 hardly notice the gradual fading of the light at sunset. 
 And the nose does not usually detect the slow fouling of 
 the air in a room ; but let one come in from the fresh out- 
 side air, and the contrast is striking. A constant current 
 of electricity usually causes a muscular contraction at the 
 time the current enters the muscle and at the time when 
 the current is stopped, that is, at the " making " and the 
 
266 PHYSIO LOG Y. 
 
 "breaking" of the current; but the muscle ordinarily re- 
 mains inactive while the current is passing. 
 
 Induction Current used in Physiological Experiment. The in- 
 terrupted current, or induction current, is therefore commonly employed 
 as a stimulus in physiological experiment. A sudden change seems 
 to be requisite for producing the nerve impulse necessary to rouse 
 a sensation in ordinary circumstances. Pressure may be applied so 
 gradually that we fail to notice it. The art of the pickpocket, of the 
 ventriloquist, of the sleight-of-hand performer, depends largely on this 
 fact. Attention is called to something else, and the work is either 
 quickly done when attention is completely absorbed on something else, 
 or the act is so gradual that no sudden change is noted. In smelling 
 it is often necessary to sniff; the sudden rush of particles of air bearing 
 the odorous particles against the surface bearing the nerve endings 
 seems to be necessary. 
 
 Dreams. Dreams, due to more or less perfect brain activity, are 
 often traceable to nerve impulses brought from the digestive tract, from 
 the respiratory organs, from the skin (heat and cold and pressure), 
 from sound, from any internal organ, according to the condition of the 
 blood, pressure, etc. It seems to be well settled that dreams seeming 
 to cover long periods of time really take place in a very short space of 
 time, just as sometimes during waking hours thoughts fly through the 
 mind in countless numbers and with incredible swiftness. 
 
 Ignoring Nerve Currents. Do we have dreams when we recall 
 none? Without attempting to answer this question it is well to note 
 that the brain undoubtedly is constantly receiving nerve currents to 
 which it pays no heed, or at least of which we are not conscious. 
 For instance, our clothing is touching nearly the whole of the surface 
 of our bodies, and, plainly, the surfaces thus touched are affected. 
 Undoubtedly currents go to the brain, but as they are of no significance 
 in ordinary circumstances, we learn to disregard them. If a savage 
 were suddenly clothed as fully as we are, he would, for a long time, 
 be continually conscious of the fact. 
 
 Judgment. In what is called Aristotle's experiment, 
 the experimenter crosses the first and second finger, and 
 feels an object with the fingers thus crossed and eyes shut. 
 
NERVOUS SYSTEM IN GENERAL. 267 
 
 If a marble be rolled about by the two fingers thus crossed, 
 it seems to be two. Here we use judgment with the sen- 
 sation. Ordinarily, we could not feel, at the same time, 
 one simple solid object with the outside of the first and the 
 inside of the second finger. This illustrates how we are 
 constantly using our judgment in interpreting our sen- 
 sations. We see few things as they are in themselves. 
 We see nearly everything in the light of past experiences. 
 
 Lingering Effect of Sensations. We have noted the lingering 
 effects of sensations, how sights and sounds linger and are fused one 
 with the other. So we get continuous light from a series of flashes 
 if they follow each other in sufficiently rapid succession, and continu- 
 ous sound from a series of sounds that would be heard separately if 
 they are more than about a sixteenth of a second apart. So with 
 touch, if the finger be held against the teeth of a revolving wheel, if 
 the wheel revolve slowly, the touch of each tooth may be felt, but when 
 it whirls more rapidly the sensation becomes that of continuous pres- 
 sure. Experience and experiment both go to show that probably 
 nothing is wholly forgotten. Whatever acts upon a cell of nervous 
 matter makes its mark. It may become dim, but it is never completely 
 obliterated. The testimony of persons rescued from drowning, and other 
 similar experiences, goes to show that the record was yet in the mind. 
 We may fail to recollect, but we ever remember. 
 
 Habits are Acquired Reflex Actions. The work of 
 the spinal cord is that of a subordinate officer, whose duty 
 is to relieve his superior, the brain, of many small tasks, 
 and to afford him relief from having all the details con- 
 stantly on his mind. If we learn to do many things me- 
 chanically, we save the effort of doing them by conscious 
 effort and act of will. Whatever we do for the first time 
 requires careful attention. To learn any new muscular 
 action, such as a new step in marching, fingering a musical 
 instrument, or typewriting, requires effort; they produce 
 more or less fatigue. Subsequent effort in doing the same 
 
268 PHYSIOLOGY. 
 
 thing is very much less, showing that, in many cases, 
 fatigue is mental rather than muscular. What we do from 
 habit, and cheerfully, is easily done. Hence the desira- 
 bility of forming good habits, that we may, without un- 
 necessary effort, that is, without loss of energy, do 
 what is needed for our well-being. 
 
 Fatigue from Standing. We are not conscious of 
 expending energy in standing until we begin to be weary ; 
 but the fact that a blow on the head causes one to fall 
 reveals the fact that the brain is constantly sending mes- 
 sages to the muscles to make them act. The shock of the 
 blow has stopped the sending forth of these messages, and 
 so the body is no longer supported. None of the muscles 
 that support the body have been injured or even touched. 
 
 The Usefulness of Resting. We have, in youth, such 
 a boundless store of energy that we do not sufficiently 
 consider these matters. But if one wishes to follow the 
 intellectual life long and successfully, he must learn to 
 economize energy, and to direct his forces into useful 
 channels. And one important part of this knowledge is 
 learning how to rest. It is an art that very few have well 
 learned. 
 
 Nervous System compared to a Telegraph System. - 
 
 The brain is like a telegraph office in both receiving and 
 sending out messages. Unlike the telegraph office, it has 
 one set of fibers to bring currents in (afferent), and another 
 to carry currents outward (efferent). 
 
 Efferent Currents. We have concerned ourselves thus 
 far chiefly with efferent nerve fibers and efferent currents. 
 These efferent currents are sent mainly to muscles, to 
 make them shorten or to relax, or to gland cells, to control 
 
NERVOUS SYSTEM IN GENERAL. 269 
 
 their activity. The only other efferent currents, so far 
 as known, are those which possibly go to the cells of 
 the tissues to regulate their nutrition or their heat pro- 
 duction. 
 
 Having given so much attention to the outgo of nerve 
 impulses, let us ask the question, " What about the in- 
 coming nerve currents ? " 
 
 Afferent Currents. " All life long the never-ceasing 
 changes of the external world continually break as waves 
 on the peripheral endings of the afferent nerves ; all life 
 long nervous impulses, now more, now fewer, are continu- 
 ally sweeping inward toward the center; and the nervous 
 metabolism, which is the basis of nervous action, must be 
 at least as largely dependent on these influences from 
 without as on the mere chemical supply furnished by the 
 blood. We must regard the supereminent activity of the 
 cortex and the characters of the processes taking place in 
 it as due not so much to the intrinsic chemical nature of 
 the nervous substance, which is built up into the cortical 
 gray matter, as to the fact that impulses are continually 
 streaming into it from all parts of the body ; that almost 
 all influences brought to bear on the body make themselves 
 felt by it. To put the matter in a bald way we may ask 
 the question, What would happen in the cortex if, its or- 
 dinary nutritive supply remaining as before, it were cut 
 adrift from afferent impulses of all kinds ? We can hardly 
 doubt but that volitional and other psychical processes 
 would soon come to a standstill, and consciousness vanish. 
 This is, indeed, roughly indicated by the remarkable case 
 of a patient whose almost only communication with the 
 external world was by means of one eye, he being blind in 
 the other eye, deaf of both ears, and suffering from gen- 
 
270 PHYSIOLOGY. 
 
 eral anesthesia. Whenever the sound eye was closed he 
 went to sleep." -FOSTER. 
 
 Let us turn from the consideration of outgoing, or 
 efferent, nerve impulses and their resulting action to the 
 incoming, or afferent, nerve impulses and the activity 
 which they rouse in the gray matter of the cerebrum 
 sensation. 
 
 READING. Wear and Tear, Mitchell ; Power through 
 Repose, Call ; Technique of Rest, Brackett. 
 
 Summary. i. Nerves may be stimulated by mechanical force, 
 chemical action, heat, and electricity. 
 
 2. Electricity is the most convenient nerve stimulus for physiological 
 experiment. The induction current is usually employed. 
 
 3. To increase sensations arithmetically stimuli must increase geo- 
 metrically. 
 
 4. Reaction time is the interval between the application of a stimu- 
 lus and the response. 
 
 5. Sensations are relative. 
 
 6. Habits are acquired reflex actions. 
 
 7. The nervous system is unlike the telegraph system in using one 
 set of fibers for receiving and another for sending messages. 
 
 Questions. i. Is the difference in "reaction time 11 in individuals 
 of any significance ? 
 
 2. Why are slight wounds in a battle often unperceived ? 
 
CHAPTER XVIII. 
 THE GENERAL SENSES. 
 
 The Body a Collection of Organs. We have been 
 considering the body as a collection of organs working 
 together to serve the brain, the mechanism through which 
 the mind operates. 
 
 We have especially studied the muscles as the only 
 means by which the mind manifests itself to the outer 
 world. 
 
 Influences from the External World. But how much 
 mind would we have if we did not receive something from 
 the outer world ? Read the story of Kaspar Hauser. We 
 are continually getting knowledge of the outer world and 
 of the condition of our own bodies through the afferent 
 nerves. We may never know fully what consciousness and 
 thought are, but we can understand that to the brain are 
 continually streaming nerve impulses that convey messages 
 which the brain more or less completely interprets. 
 
 Classification of the Senses. These incoming currents 
 pass along myriads of nerve fibers. But the nerve fibers 
 are all essentially alike. And the kinds of sensations that 
 these currents arouse in the brain are but few. It is diffi- 
 cult to classify the senses, but it will serve our convenience 
 to divide them into two groups. 
 
 General Sensations and Special Senses. In distinc- 
 tion from the special senses, sight, hearing, etc., are the 
 
 271 
 
2/2 PHYSIOLOGY. 
 
 general sensations already referred to, such as hunger, 
 thirst, fatigue, nausea, satiety, faintness, etc. They are 
 often called "common sensations," and Martin designates 
 them as " sensations which we do not mentally attribute to 
 the properties of external objects, but to the conditions of 
 our own bodies." 
 
 General Sensations. Nerve endings in different parts 
 of the body may be affected by the blood and the lymph, 
 and give us sensations of comfort, discomfort, restlessness, 
 fatigue, faintness, etc. These are called general sensa- 
 tions. They are probably due to the condition of the 
 blood, or to the condition of nutrition of the various parts 
 of the body. Thus after muscular exercise the muscles are 
 acid in their reaction, while they are alkaline after resting ; 
 after exercise carbon dioxid accumulates in them to a cer- 
 tain extent. Hunger and thirst come on after abstinence 
 from food and drink, or after work exhausting the tissues. 
 The presence of the various waste products, or the condi- 
 tion of the cells as the result of their activity, acting 
 through the nerve endings in the tissues, keep the nerve 
 centers informed as to the condition of the parts of the body. 
 If these conditions are extreme, we may have definable sen- 
 sations, but ordinarily the sensations are of an undefinable 
 sort which we designate as " general sensations." 
 
 The Muscular Sense. As an example, we will take 
 the case of estimating the weight of an object by holding 
 it in the hand. Our estimate is thought by some to be the 
 result of (i) direct consciousness of the degree of effort 
 put forth ; but probably it is (2) a sensation, or complex of 
 sensations, aroused by nerve impulses from the organs 
 used. There are afferent nerve fibers with endings in 
 (i) the skin, (2) the muscles and tendons, (3) the joints, 
 
THE GENERAL SENSES. 2/3 
 
 In extending the arm and moving it up and down, all three 
 of these sets of nerve endings are probably stimulated, and 
 impulses thence conveyed to the brain. 
 
 Muscular Sense and General Sensibility. It is a 
 matter of doubt, whether or not the impulses from the 
 muscles are predominant, and consequently whether the 
 term " muscular sense " is the most appropriate. Peculiar 
 nerve endings have been found in the tendons, and the 
 joints are believed to have an especially rich nerve supply. 
 It is not necessary that we actively use the muscles to have 
 sensations of this kind. In passive moments, as the rais- 
 ing of the arm by another person, we have a " sense of 
 position" of the parts, a considerable share of which is 
 probably due to the tension of the skin and changes in the 
 joints. There is, of course, some tension of the muscle, 
 even in this passive movement, that might affect nerve 
 endings in it. The muscular sense is closely related to the 
 general sensibility already mentioned, if not a modified 
 form of it. 
 
 Importance of Muscular Sense. It is difficult to real- 
 ize the importance of this sense in our daily experience. 
 We probably underestimate it, and attribute to sight too 
 much of our knowledge of the external world. The funda- 
 mental facts concerning the objects about us are not ob- 
 tained through sight alone. Such knowledge is based on 
 complex judgments concerning the meaning of auditory 
 and visual phenomena, according as they have, in past ex- 
 perience, been interpreted by tactile and muscular percep- 
 tions. That is, when reduced to its simplest terms our 
 most practical and important knowledge of the world is 
 the outgrowth of tactile and muscular perceptions ; by and 
 
2/4 PHYSIOLOGY. 
 
 with them all other sense perceptions have been corrected 
 and compared. 
 
 Dependence of Sight on Muscular Sense and Touch. 
 An illustration of the assistance which touch and the mus- 
 cular sense give to the sense of sight is furnished in the 
 case of a boy who had been blind from birth, and received 
 sight at the age of twelve years by means of a surgical 
 operation. At first he could not distinguish a globe from 
 a circular card of the same color until he had touched them. 
 He knew the peculiar features of the dog and the cat by 
 feeling, but not by sight. Happening one day to pick up 
 the cat he recognized for the first time the connection be- 
 tween the new sense of sight and the old familiar ones of 
 touch and the muscular sense. On putting the cat down 
 he said, "So, puss, I shall know you next time." 
 
 Pain. When a heavy weight is laid on the hand it may 
 cause pain. It would at first seem that the ordinary pres- 
 sure sense, when unduly exaggerated, becomes pain. But 
 there seem good reasons for considering pain as a distinct 
 sense from that of touch intensified. It is thought that 
 there are, throughout all parts of the body, nerves of "com- 
 mon sensibility " or " general sensibility," which keep the 
 nerve centers informed as to the condition of all the various 
 tissues, and that ordinarily we have no sensation resulting 
 from the impulses ; to use the language of the psycholo- 
 gist, " they do not rise above the threshold of conscious- 
 ness." They may have some influence in adjusting the 
 action of the different parts. We have seen how the blood- 
 flow to any part is continually adjusted without our know- 
 ing anything about it. But we are usually more or less 
 conscious of the general condition of the body. We call 
 by the name of " common sensations " such feelings as 
 
THE GENERAL SENSES. 275 
 
 hunger, thirst, nausea, fatigue, depression, melancholy, 
 restlessness, such as many experience preceding a thun- 
 derstorm, the feeling of general discomfort known as 
 malaise, and its opposite, the feeling of general well being. 
 The body seems to have a set of nerves to give information 
 as to the state of nutrition of the body, and as to its condi- 
 tion generally. These nerves, when the system is dis- 
 ordered in any part, may bring messages that cause intense 
 pain. Of course, they are warnings (they are more than 
 mere warnings ; probably if the earlier indications of simple 
 discomfort had been heeded the later more emphatic mes- 
 sages of pain would not have been necessary). These mes- 
 sages of pain demand attention. 
 
 The Extent of Pain. In reference to pain in the skin, 
 it is held that the skin, too, has its nerves of general sensi- 
 bility, and that these are distinct from those of touch and 
 temperature sense. That when they are unduly stimulated 
 they give rise to painful sensations. It is to be noted that 
 the internal organs are ordinarily devoid of feeling, and 
 that the skin is especially sensitive. The skin senses stand 
 guard at the outposts, so to speak, of the body's camp, and 
 give warning of approaching danger. No enemy may 
 enter without being discovered by these keen sentinels, 
 and the alarm is given. If it is not heeded, great harm 
 may follow. And it is a comfort to know that the more 
 severe wounds do not cause pain in proportion to their 
 extent. When a person says his " lungs are sore " the 
 pain is usually in the muscles of the chest from coughing. 
 While there may be acute pain from the lungs, as in pleu- 
 risy, there is often deep-seated lung disease without pain 
 from the lungs themselves. The muscles of the chest and 
 back may be strained by lifting, and the soreness is erro- 
 
2/6 PHYSIOLOGY. 
 
 neously attributed to the lungs or kidneys. Hence there 
 is frequently a wholly needless apprehension of deep- 
 seated disorder, whereas in reality there is merely a strain 
 of superficial muscles. In amputating a limb the chief 
 pain is in cutting through the skin. Some excellent 
 authorities still hold the view that pain is merely the 
 result of intensifying any of the simple sensations ; but it 
 is generally held that it results from the excessive stimula- 
 tion of the nerves of general sensibility ; as Foster puts it, 
 " the constantly smouldering embers of common sensibility 
 may be at any moment fanned into the flame of pain." 
 
 Pain a General Sense. In the real "special senses," 
 sight, hearing, smell, taste, touch, and temperature sense, 
 we refer the sensation to some external object, whereas 
 general sensations are subjective, referred to our bodies. 
 Ordinarily we do not localize the common sensations, and 
 a further indication of the relationship of pain and general 
 sensation is in the lack of complete localization of pain. 
 Slight pain, especially in the skin, may be closely located, 
 but severe pain tends to become indefinite and diffuse. 
 So we may class both the muscular sense and pain with 
 the "general" rather than with the "special" senses. 
 
 Hunger and Thirst. The cause of these sensations in 
 a healthy body is plainly the need of food and water 
 throughout the system generally. The sensation of thirst 
 manifests itself in the throat, and the longing may be tem- 
 porarily relieved by merely moistening the throat. So 
 hunger may, for the time, be appeased by filling the stom- 
 ach with indigestible material. But the sensation soon 
 returns. The system has a crying need, and it is not to be 
 put off by any such frauds. That these sensations are 
 really demands made by the body as a whole may be 
 
THE GENERAL SENSES. 277 
 
 shown by the fact that they are permanently relieved by 
 introducing food and water into the body (by the rectum, 
 for instance), in which case the throat and stomach have 
 nothing given them directly. Since, however, food and 
 drink naturally enter by the throat and stomach, the 
 mucous membrane of these organs has become spokes- 
 man of the body for its demands. 
 
 READING. Pain, Corning. 
 
 Summary. i . Brain action depends, in the long run, upon im- 
 pulses from without. If we had no impressions, we could have no 
 expressions. 
 
 2. General sensations are referred to our bodies and their condition ; 
 special sensations are regarded as attributes of external objects. 
 
 3. The "muscular sense 11 probably depends chiefly on impulses 
 from the tendons and joints. 
 
 4. The muscular sense is necessary for the full interpretation of 
 sight. It enables us to judge of the degree of effort put forth or force 
 resisted. 
 
 5. Pain is a general sensation. It is a warning the cry of a senti- 
 nel that an enemy has passed the picket line. 
 
 6. Hunger and thirst indicate the need of food and drink. They are 
 local signals of a general want. 
 
 Questions. i. If we had no sense of pain, what might result? 
 2. If we pass by a meal time without eating, why does the sense of 
 hunger disappear? 
 
CHAPTER XIX. 
 
 THE SPECIAL SENSES -TOUCH AND TEMPERATURE 
 
 SENSE. 
 
 What we learn by touching Objects. Let one person 
 rest the hand flat on the table, palm upward, and close the 
 eyes. An object placed on the palm, by another person, 
 may give rise to various sensations, so that it may be 
 described as rough or smooth, light or heavy, hot or cold, 
 wet or dry, etc. If the object is very heavy or very hot, it 
 may cause pain. If now the thumb and fingers are raised 
 and applied to the object, more definite information will be 
 gained as to its shape, size, surface, etc. Now raise the 
 object in the hand, and further appreciation will be gained 
 as to its weight. 
 
 These experiments show that several sensations are in- 
 volved in the handling of objects, and that the knowledge 
 so gained is complex. 
 
 Cutaneous Sensations. The sensations from the ob- 
 jects resting on the skin of the passive hand may, proba- 
 bly, all be referred to impressions made on nerve endings 
 in the skin, and are called cutaneous sensations. They 
 include: (i) the pressure sense, or touch proper, (2) the 
 temperature sense, and (3) pain. 
 
 Nerve Endings in the Skin. The skin consists of 
 two layers, the epidermis and the dermis. We need now 
 to recall those conical elevations of the dermis that we caU 
 
 278 
 
THE SENSE OF TOUCH. 
 
 279 
 
 papillae. In these papillae are certain important nerve 
 endings. There are several kinds of nerve endings in the 
 skin and underneath it that receive the impressions which, 
 carried to the brain, give us sensations of touch (and allied 
 sensations to be considered soon). Pressure on the skin 
 affects these nerve endings, and 
 starts impulses that pass along the 
 sensor fibers to some nerve center, 
 probably in the spinal cord, spinal 
 bulb, or brain. 
 
 Nerve 
 
 Fig. 85. Papilla of Skin with 
 Touch Corpuscle. 
 
 Touch Corpuscles. These 
 "touch corpuscles" are not re- 
 garded as essential for producing 
 the sensation of touch, but some 
 nerve endings in the skin do seem 
 necessary ; for if a nerve fiber be 
 touched, not at the end, but some- 
 where along its course, we get, not 
 
 a sensation of touch, but a sensation of pain. Except in 
 the mouth and nose, we get little, if any, sense of touch 
 from any organ but the skin. The lining of the digestive 
 tube and the internal organs generally are devoid of this 
 sense. 
 
 The Sense of Touch. Of the special senses the most 
 general is that of touch. Seeing and hearing, taste and 
 smell, belong to very limited parts of the outside of the 
 body, but we have the power of feeling all over the surface 
 of the body. 
 
 Touch the most General of the Special Senses. 
 
 Not only is the sense of touch the most general in being 
 distributed over the whole of the body, but it is the most 
 widely distributed sense throughout the animal kingdom. 
 
280 PHYSIOLOG } . 
 
 As we descend the animal scale we find many of the lower 
 animals lacking some of the senses that we possess. In 
 many of the simpler forms of animal life there is no evi- 
 dence of a sense of hearing, and it is extremely likely that 
 if they have taste and smell, these senses are in a very 
 rudimentary state of development. But in all these forms 
 it is believed that " feeling " exists. Contact of their exte- 
 rior with foreign objects is so often immediately followed 
 by action that little doubt remains about their having the 
 sense of touch. Even ameba may have, in a rudimentary 
 state, the power to distinguish light, to taste, and to hear. 
 Still we have little or no evidence on these points, while 
 we are pretty sure that it feels. 
 
 The Pressure Sense. The sense of touch, proper, is 
 strictly a pressure sense. If we test the skin to find what 
 regions are able to detect the least pressure, it is found 
 that the forehead is most sensitive, and nearly equally so 
 are the temples, back of the hand, and forearm. 
 
 Ability to detect Differences of Pressure. The 
 
 ability to detect differences of pressure is tested by finding 
 what is the least addition to a weight required to make it 
 seem heavier. For instance, if a weight of 1 1 grains is 
 just perceptibly heavier than one of 10 grains, it does not 
 follow that i grain added to a weight of 100 grains will 
 give any palpable increase. To 100 grains must be added 
 10 grains before additional pressure is felt ; that is, what- 
 ever the weight, there must be the same ratio of increase 
 to increase the sensation. This is part of the law, already 
 stated, of the relation of stimulus and sensation. The law 
 is true only in a general way and will not apply in extreme 
 cases. It is stated that the forehead, the lips, and temples 
 appreciate an increase of one fortieth to one thirtieth of the 
 
THE SENSE OF TOUCH. 28 1 
 
 weight estimated, while the skin of the head, the fingers, 
 and the forearm require an increase of one twentieth to 
 one tenth for its perception. 
 
 After-Pressure. The lingering effect of pressure, or 
 after-pressure, may be noticed after taking off a tight hat, 
 skate strap, shoe, or glove. 
 
 Local Sign. " If a point of the skin is touched, certain 
 tactile corpuscles are irritated; these, in turn, set up im- 
 pulses in sensory nerve fibers, and these impulses are car- 
 ried by the fibers, first to the spinal cord, and then to the 
 brain, where the fibers end in ganglionic masses in the 
 gray matter of the cerebral cortex. There are thus pro- 
 jected, as it were, on the cortex of the brain, tactile centers 
 for the hind leg, fore leg, neck, eye, ear, trunk, etc. ; and 
 it follows that each point of the skin has a corresponding 
 point in the cerebral cortex. Thus for each stimulation of 
 a point of the cerebral cortex there is a local sign, and so 
 we localize tactile impressions." 
 
 Accuracy in locating Touch Sensations. The accu- 
 racy varies, and is ordinarily keenest where the nerves are 
 most numerous. Where the sense of locality seems to be 
 improved by cultivation, this appears to be due to keener 
 discrimination in the brain cells, and not to changes in the 
 nerves or nerve endings. This is indicated in the fact that 
 if the fingers of one hand become more discriminating by 
 practice, it will be found that the fingers of the other hand, 
 without special training, are also improved. 
 
 Test by Compass Points. The delicacy of localizing 
 touch is usually tested in this way. The blunted points of 
 a light pair of compasses are allowed to rest gently on the 
 skin of various parts of the body. If the two points are 
 
282 PHYSIOLOGY. 
 
 very close together, they will be/?// as one pressure. That 
 part which can best distinguish, as two points of touch, 
 these blunt points, is considered the most sensitive. By 
 this test the tip of the tongue is the most sensitive, being 
 able to distinguish, as two separate points of contact, the 
 tips of the compasses when only one twenty-fifth part of 
 an inch apart. Following is the order of degrees of sen- 
 sitiveness : tip of tongue, tips of fingers, lip, tip of nose, 
 eyelid, cheek, forehead, knee, neck; while the middle of 
 the back seems least sensitive, the two points not produc- 
 ing two distinct sensations until they are more than two 
 and a half inches apart. In general those parts which are 
 most used, and those parts which are more freely movable, 
 are most sensitive ; for instance, the knee is much more 
 sensitive than the middle of the thigh or the middle of the 
 leg, and the elbow than the middle of the arm or forearm. 
 If the compass points, about half an inch apart, be passed 
 from the palm to the tips of the fingers, it will at first seem 
 one line gradually separating into two diverging ones, 
 owing to the keener localizing power as the finger tips are 
 approached. . 
 
 Reference of Sensation to the Region of Nerve End- 
 ings. If the " funny bone," or "crazy bone," be hit, i.e. 
 if the ulnar nerve be bruised against the bone, sharp pain 
 may be felt in the wrist and hand, and soreness of these 
 parts may be felt for days, though they are not in the 
 least injured, but only the nerve at the elbow. The cur- 
 rents along this nerve rouse sensation that we have learned 
 to localize at the endings of the nerve fibers. So, too, 
 after amputation of a hand or foot, there may for years 
 be sensations referred to the missing member, probably 
 due to irritation of the nerves of the stump. There is, 
 
THE TEMPERATURE SENSE. 283 
 
 then, no certainty of getting rid of a corn by ampu- 
 tating a toe. 
 
 The Temperature Sense. Many cases are on record 
 in which, from accident or disease, the pressure sense was 
 lost and the temperature sense retained, or vice versa. 
 Such facts have led to the belief that the temperature 
 sense is distinct from that of touch, and has its own nerve 
 fibers and nerve endings. 
 
 Two Sets of Nerve Fibers for Distinguishing Heat and 
 Cold. Since heat and cold are only differences in the 
 degree of heat, we would expect both of these kinds of 
 impressions to be received through one set of nerves. 
 There seems, however, to be good evidence of two sets of 
 nerve fibers, one for heat and the other for cold. In the com- 
 mon experience of the foot " going to sleep" by pressure 
 on the sciatic nerve, or the arm from compression of the 
 brachial nerve, the skin may be found, at a certain stage, 
 to be only slightly sensitive to warmth, while distinctly 
 sensitive to cold. In some diseases of the spinal cord the 
 skin may be affected by warmth, but not by cold. The 
 sensations of cold and pressure seem to be usually lost 
 or retained together, while those of warmth and pain 
 have a similar connection. But more accurate results are 
 obtained by touching the skin with a blunt metal pencil, 
 warmed or cooled. 
 
 Warm Spots and Cold Spots. If this be applied at 
 regular close intervals, it is found that some places feel the 
 warm point, while others feel the cold. In this way the 
 skin has been mapped out into "warm spots" (warmth- 
 perceiving spots) and "cold spots" (cold-perceiving spots), 
 and still other areas seem not sensitive to temperature. 
 
284 PHYSIOLOGY. 
 
 Heat or cold, if applied directly to a nerve trunk, does not 
 rouse sensations of temperature, but, if strong enough, 
 produces pain. If the elbow be dipped into water at the 
 freezing point, a sensation not of cold but of pain is caused, 
 and is felt in the hand. Heat and cold are not felt in the 
 digestive tube except at or near the openings. If very hot 
 liquid be swallowed, it may cause pain in the gullet and 
 stomach. If a considerable quantity of warm liquid be 
 taken, it may give a feeling of warmth from its effect on 
 the skin of the abdomen, by conduction of heat outward. 
 As with other senses, a sudden change in the degree of 
 the stimulus is more certain to rouse sensation than a 
 gradual change. 
 
 READING. The Five Senses of Man, Bernstein. 
 
 * Summary. i. The cutaneous sensations are touch proper, tem- 
 perature sense, and pain. 
 
 2. There are touch corpuscles in the papillae of the dermis. 
 
 3. Touch is the most general of the senses, both in its extent in our 
 bodies, and in the number of animals possessing it. 
 
 4. Touch proper, or pressure sense, is tested by discrimination of 
 additional pressure. 
 
 5. Touch localization is tested by discrimination as to the distance 
 of two points of contact. 
 
 6. Temperature is discerned by a special set of nerve fibers. 
 
 7. Touch and muscular sense are necessary adjuncts of sight to give 
 correct perceptions of size and form. 
 
 Questions. i . What is the explanation of tickling ? 
 
 2. Where does the change occur by which we become more dis- 
 criminating in the sense of touch ? 
 
 3. Why does an emotion, such as shame, make one feel hot ? 
 
CHAPTER XX. 
 THE SENSE OF SIGHT. 
 
 The Sense of Sight. In the fable of the blind man 
 carrying the lame man whose eyes were good, we have an 
 illustration of the dependence of the various organs on 
 each other. We have considered how all our knowledge, 
 both of the condition of our bodies and of the external 
 world, comes through the nervous system. Now, so far 
 as the senses we have studied are concerned, we learn 
 almost nothing of the external world except from actual 
 contact. But sight reveals objects at a distance. With- 
 out the eye the body is comparatively helpless. The lame 
 man that the body carries is a slight burden in comparison 
 with the assistance which he renders. We can well afford 
 to carry with us all the time two of these lame men to 
 keep posted as to the objects beyond our reach. Of course 
 touch is a great aid to our interpretations of what we see. 
 But sight is evidently the main avenue of knowledge, the 
 royal road along which come the messages which bring us 
 the most news, which give us the keenest delight ; which 
 makes us aware of most that we know of this world, and 
 the only means of knowing that there are other worlds 
 than the one we inhabit. 
 
 Protection of the Eye. The eye is set well back in 
 its socket and guarded by three projecting bony promi- 
 nences, the brow, cheek bone, and the bridge of the nose. 
 It is further protected by the eyelids and eyelashes. 
 
 285 
 
286 PHYSIOLOGY. 
 
 The Lacrymal Secretion. The lacrymal gland, or 
 tear gland, is just above the outer angle of the eye, and 
 pours its secretion over the eyeball in weeping, or when 
 there is need of an unusual supply of tears. The lids 
 serve as curtains to admit or shut out light, and, by wink- 
 ing, wash the eye with their own secretion, a fluid mixture 
 of salt water and mucus. It is as though a man were 
 kept all the time in front of a plate-glass window, with 
 water and rubber scraper, to keep it clean and bright. 
 The lacrymal secretion is, ordinarily, carried off as fast as 
 it is made, by two ducts beginning at the inner angle of 
 the eye, one on each lid ; these two ducts soon unite and 
 empty by one outlet into the nasal cavity. If these ducts 
 are stopped, or if the secretion be formed very rapidly, 
 the liquid overflows on the face as tears. 
 
 The External Parts of the Eye. The " white of the 
 eye " is the sclerotic coat. It has blood tubes, but ordina- 
 rily they are not conspicuous. The front part of the eye- 
 ball is covered with the cornea. This is transparent, and 
 the color of the iris shows through the cornea. In the 
 center of the iris is the hole, or pupil, by which Jight enters 
 the interior of the eye. 
 
 The Conjunctiva. The front of the eyeball is covered 
 by a thin, transparent, mucous membrane, the conjunctiva, 
 which turns back and lines the inside of the eyelids. It is 
 highly sensitive. 
 
 The Muscles of the Eyeball. There are six muscles which move 
 the eyeball, four straight muscles (the recti) and two oblique. The 
 four straight muscles arise from the deepest part of the eye socket and 
 pass forward to be attached to the top, bottom, and sides of the ball. 
 Where they are attached, they are flattened out like straps. The in- 
 ferior oblique arises from the inner front part of the orbit and passes 
 outward to attach to the under surface of the eyeball. The superior 
 
THE SENSE OF SIGHT, 287 
 
 oblique arises, like the recti, at the deeper part of the eye socket and 
 passes forward through a fibre-cartilaginous loop or pulley near the 
 inner, upper angle of the orbit, and then runs outward and is attached 
 to the upper surface of the eyeball. 
 
 Movements of the Eye. These six pairs of muscles move the 
 eyes to right and left, up and down, and give rotary movements. 
 Normally the two eyes move in the same direction at the same time, 
 though in looking at near objects the two eyes both point inward, so 
 that one appears cross-eyed, and in looking at an object that is moving 
 away from one, the eyes are gradually diverging, though this is slight. 
 
 Dissection of an Eye. The muscles and external parts of the eye 
 may readily be seen by examining the eye of a rabbit in its natural 
 position and then dissecting it out. A beef eye should be obtained 
 from the butcher and the structure of the eye learned by following the 
 description below. 
 
 The Coats of the Eye. There are three coats, the outer 
 or sclerotic, the middle or choroid, and the inner called the 
 retina. 
 
 The Sclerotic Coat. This is of a dull white color, con- 
 stituting the "white of the eye." It is thick and tough, 
 holding all the contained parts firmly and furnishing suffi- 
 cient strength for the attachment of the muscles that move 
 the eyeball. 
 
 The Choroid Coat. The middle layer of the eye coat 
 is the choroid. It is thinner than the sclerotic and of much 
 more delicate structure. It is permeated by blood tubes, 
 and has an inner lining of dark color to prevent the reflec- 
 tion of light in the eye, just as most optical instruments 
 are painted black on the inside. 
 
 The Retina. The retina is a continuation and expan- 
 sion of the optic nerve and forms an inner coat that lines 
 all but the anterior part of the eye. It is a thin, translu- 
 cent film, somewhat like the film that forms over the white 
 
288 
 
 PHYSIOLOGY. 
 
 of an egg when it is first dropped into hot water. It is 
 exceedingly delicate and easily torn. The retina is the 
 only part of the eye that is sensitive to light, and on it the 
 images must be formed to produce distinct vision. 
 
 The Cornea. The clear front part of the eye is the 
 cornea. It is a continuation of the sclerotic coat and is 
 
 Ciliary Muscle 
 
 Optic Nerve Choroid 
 
 Fig 86. Horizontal Section of Right Eye. 
 
 more bulging than the rest of the front of the eye, as can 
 be seen by taking a side view of the eye, or by noticing 
 some one who closes the eyelids and rolls the eyes about. 
 
 The Iris. This is the part that gives the color to the 
 eye, or if the pigment that gives the color is lacking, the 
 blood gives the pink color seen in albinos. The iris is a 
 forward continuation of the choroid coat. 
 
THE SENSE OF SIGHT. 289 
 
 The Pupil. Most of the light that passes through the 
 transparent cornea is stopped by the opaque iris. But in 
 the center of the iris is a round hole through which light 
 enters the interior of the eye. The pupil looks dark be- 
 cause it is the only opening into a dark room. 
 
 Regulation of the Amount of Light admitted into the Eye. 
 
 Hold a hand glass between the face and a well-lighted window. Note 
 the size of the pupils. Quickly turn toward the darkest part of the 
 room. We see, what we have all noticed in watching the eyes of a cat, 
 that when subject to a bright light the pupil is small, but with less light 
 the pupil is larger. The iris has circular muscle fibers that reduce the 
 pupil when there is too much light for the eye, and when the light is 
 feeble the pupil opens wider. 
 
 The Refracting Media of the Eye. The media that 
 refract the rays of light to form the images on the retina 
 are the cornea, the aqueous humor, the crystalline lens, and 
 the vitreous humor. The cornea has already been described. 
 
 The Aqueous Humor. In looking at the entire eye it 
 is not easy to realize that there is a space between the cor- 
 nea and the iris. In this space is the clear, watery aque- 
 ous humor. 
 
 The Vitreous Humor. All but the front part of the 
 space within the coats of the eye is filled with a clear, 
 jellylike substance, the vitreous humor. 
 
 The Crystalline Lens. Just back of the iris is a double- 
 convex lens, clear as crystal, and of about the consistency 
 of a gumdrop. It is less convex on the front surface. 
 
 The Lens Capsule. The lens is completely enveloped 
 in a thin, transparent membrane called the lens capsule. 
 
 The Hyaloid Membrane. A thin membrane, the hya- 
 loid membrane, lines the inner surface of the retina. As 
 it continues forward toward the lens capsule it is called 
 the suspensory ligament. 
 
290 PHYSIOLOGY. 
 
 The Ciliary Muscle. Arising from the sclerotic coat, 
 just within the outer border of the iris, is the ciliary muscle. 
 It is inserted in the margin of the lens capsule by means 
 of fibrous strands that form an intimate part of the capsule. 
 
 Experiment with Lens to show Inversion of Image. Take a 
 double-convex lens, two ot which are in the common " tripod lens, 1 ' or 
 
 Fig. 87. The Formation of an Image on the Retina. 
 
 any hand magnifier. Hold this up in front of a window and catch the 
 inverted image o/ the window on a piece ot paper held back of the lens. 
 This illustrates how the image ot an external object is formed by the 
 crystalline lens upon the retina ot the eye. If two lenses of different 
 thickness can be obtained, it will be seen that the thicker lens (if both 
 have the same diameter) will make an image closer to the lens than the 
 thinner one. 
 
 Experiments to illustrate the Adjustment for Distance. (i ) Stick 
 a pin at each end of a book cover. Hold the book at about the usual 
 distance for reading, so that the two pins are in a line with the eye. 
 Look closely at the nearer pin, and the second pin will appear indistinct. 
 Now look closely at the head of the farther pin. The nearer one may 
 be seen, but not sharply. (2) Hold the tip of a pencil in a line with any 
 object, say a picture, on a wall opposite. In looking at the tip of the 
 pencil the picture is dim. Now look by the pencil at the picture, and 
 the point of the pencil will be blurred. 
 
 Adjustment of the Lens for Seeing at Different Dis- 
 tances. If we look up from a book we are reading, we 
 do not realize that any change is necessary in the eye for 
 us to see a distant object. But the above experiments 
 prove that we cannot, at the same time, see distinctly a 
 near and a distant object. When the photographer places 
 his camera, he moves the ground-glass plate back and forth 
 till the image is distinctly formed on the plate. We cannot 
 
THE SENSE OF SIGHT. 
 
 291 
 
 move the retina back and forth, so we change the shape of 
 the lens. When we look at a near object the lens becomes 
 thicker, and when we look at a distant object the lens be- 
 comes less thick. This adjustment is called accommodation. 
 
 CILIARY MUSCLE 
 
 FAR NEAR CILIARY PROCESS 
 
 Fig. 88. A Diagram to illustrate Accommodation. 
 
 Action of the Ciliary Muscle. In looking at a near object, the 
 ciliary muscle pulls on the hyaloid membrane, and draws it forward 
 (since the muscle is fastened at the point where the iris joins the 
 cornea). When the hyaloid membrane is pulled forward, the lens is 
 released from pressure that was given it by the lens capsule. Now the 
 lens becomes thicker because it is elastic, and when it is not subject to 
 pressure it tends to become relatively thick. When we look at a dis- 
 tant object the muscle relaxes, and the capsule presses on the front of 
 the lens and flattens it, thus adjusting for far sight. It should be 
 noted that adjustment for near sight is brought about by muscular 
 effort, hence is fatiguing ; whereas adjustment for far sight is accom- 
 plished mechanically, without effort. 
 
 (2) Near-sighted Eye. (I) Normal Eye. (3) Far-sighted Eye. 
 
 Fig. 89. Defects in Eyesight. 
 
 Defects of Eyesight. In old age the lens usually be- 
 comes less elastic, -and cannot adjust for near sight. Since 
 
292 
 
 PHYSIOLOGY. 
 
 it is unable to grow more convex, artificial lenses (eye- 
 glasses) may be used to enable one to see near objects 
 clearly. Most elderly people see fairly well at a distance, 
 but use glasses for reading or any close work. In " near- 
 sighted " eyes, the eyeball is often too long from front to 
 back, so the rays meet in front of the retina. Concave 
 glasses remedy this defect. The eye may also be too 
 short (far-sighted) and need convex glasses. The refract- 
 ing surfaces (cornea and lens) may be unequally curved, 
 causing astigmatism. For most of these defects the 
 oculist can supply suitable glasses. 
 
 Inner or Vitreous Surface 
 
 Internal Limiting Layer 
 Layer of Nerve Fibers 
 Layer of Nerve Cells 
 
 Inner Molecular Layer 
 
 Inner Nuclear Layer 
 Outer Molecular Layer 
 
 Outer Nuclear Layer 
 
 External Limiting Layer 
 
 Layer of Rods and Cones 
 
 ~ Layer of Pigment Cells 
 
 Outer or Choroid Surface 
 
 Fig. 90. Diagrammatic Section of the Human Retina. (Waller.) 
 
 The Structure of the Retina. The retina is very complicated in 
 its structure. No less than eight layers have been distinguished, as 
 shown in Fig. 90. Of these layers the outermost, the layer of the rods 
 and cones, is the one directly concerned in appreciating the differences 
 in the vibrations of the light. The rays of light pass through the 
 
THE SENSE OF SIGHT. 293 
 
 retina, and produce their effect on the rods and cones which constitute 
 the outer (back) layer; and the nerve impulses aroused by the light 
 must return through the thickness of the retina to be conveyed along 
 the nerve fibers of the innermost layer of the retina to the optic nerve. 
 
 Importance of the Retina. The chief structure in the 
 eye is the retina. Without this all else is useless. If 
 light of sufficient strength falls on the retina, it stimulates 
 elements in the outer layer (rods and cones), and the nerve 
 impulses, thus started, pass along the fibers of the optic 
 nerve to the brain, and we have the sensation of sight. 
 But in order to see anything distinctly, the light must fall 
 on the retina in such a way as to form a distinct image of 
 that object. If the lens be removed, or becomes opaque, 
 as in " cataract," we fail to see distinctly, though we may 
 discern light from darkness. The other parts of the eye 
 exist to form images oh the retina. The cornea, lens, and 
 the aqueous and vitreous humors are the parts directly con- 
 cerned in forming the images. Light from an object passes 
 through the cornea, aqueous humor, lens, and vitreous 
 humor, and the rays are so refracted as to form an inverted 
 image. If this image falls on a good retina, we see well. 
 
 The Blind Spot. The retina is much more complicated than any 
 of the other nerve endings. Light must fall on these special structures 
 to have any effect. Falling on the optic nerve itself has no effect in 
 giving a sensation of light. And if the light falls on the spot where 
 the optic nerve enters the eyeball we see nothing. Hence, this spot is 
 called the blind spot. 
 
 Experiment illustrating the Blind Spot. At the left (as looked 
 at by the class) of a long blackboard make a bright circular spot, three 
 inches in diameter, with white or yellow crayon. Beginning at the 
 right of this write the figures i, 2, 3, etc., along the whole length of the 
 board, about eight inches apart. Let each pupil close the right eye and 
 look at the bright spot. Then let each read the figures, passing slowly 
 from one to another in order, at the same time noticing whether the 
 bright spot can be seen. To succeed in this the eye must not be allowed 
 
294 PHYSIOLOGY. 
 
 to waver. Have the pupils tell when the bright spot disappears, then 
 read on, and note when the soot reappears. 
 
 Another Experiment. In this experiment shut the right eye, and 
 be careful not to let the left eye waver. 
 
 . Read this line slowly. Can you see the star all the time ? If the 
 star does not disappear before reaching the end of the line, let the eye 
 travel on across the right-hand page, or hold the book nearer the face. 
 In the human eye the optic nerve enters the eye not in the center, but 
 nearer the nose, so that in turning the left eye toward the right at the 
 proper angle, the image of the star falls upon the spot where the optic 
 nerve enters. As this spot is insensitive to light, the star no longer 
 appears. 
 
 The Optic Nerve not Sensitive. The optic nerve, 
 while capable of carrying nerve impulses that cause sensa- 
 tions of light, is not itself sensitive to light. If the optic 
 nerve be cut, it does not give pain, but gives the sensation 
 of a flash of light. 
 
 Sympathy between the Two Eyes. While most of 
 the fibers from each optic nerve cross to the other side of 
 the brain, some fibers go to the same side of the brain. 
 We can therefore better understand the close sympathy 
 that we know exists between the two eyes. 
 
 Pain in the Eyes. Pain, felt in the eyes, comes from 
 impulses conveyed, not by the optic nerve, but by a branch 
 of the fifth pair of nerves (the nerves of sensation for most 
 of the face). 
 
 Color Sensations. The difference in colors is due to the differ- 
 ences in the rapidity of the vibrations of the waves of light, as in sound 
 differences in the rapidity of the vibrations of the sound waves cause 
 the various degrees of pitch. Many interesting experiments may be 
 made with color sensation, most of which are difficult of explanation. 
 Fasten a bright red wafer or seal on a white card. Look intently at 
 the center of the red spot till the eye is tired. Then quickly look at 
 a point in the white surface. What color appears ? This may be 
 repeated with other colors. 
 
THE SENSE OF SIGHT. 295 
 
 Color Blindness. It is found that some persons can- 
 not distinguish certain colors. Blindness to red and green 
 are most common. This is a matter of importance among 
 railroad men and sailors where it is necessary to distinguish 
 red and green signals. 
 
 Stereoscopic Vision. In looking at an object with one 
 eye more is seen to the side of that eye, while the other 
 eye sees more of the other side, considerable of the object 
 being seen with both eyes. The effects produced on the 
 two eyes are united, and so we better see objects as solids. 
 This is what is termed stereoscopic or binocular vision. 
 
 Duration of Impressions of Light. Most boys have amused them- 
 selves around a bonfire by whirling a stick with a glowing coal on its 
 end. The continuous circle of light thus produced indicates that the 
 impression of light remains for a time, in this case until the stick com- 
 pletes the circle, giving a continuous line of light. Or when riding in a 
 carriage the spokes of the wheels blur together because the impression 
 of each lingers till another has taken its place. 
 
 After-Images. But if we shut the eyes quickly, we may keep dis- 
 tinct the impression of the last positions, and so see them distinct from 
 each other. Better still, shut the eyes while looking at the wheel, then 
 open and shut them as quickly as possible. 
 
 Again, if one looks at a bright lamp and then closes the eyes, there 
 may remain the same appearance as when we looked at the object 
 itself. This is called the Positive After-Image. Or sometimes, espe- 
 cially after looking long at a bright light, we may, on closing the eyes 
 or looking away, see a dark spot of the same shape as the bright one we 
 looked at. This is called the Negative After-Image. 
 
 THE CARE OF THE EYES. 
 
 i. Objectionable Light. In reading we wish light 
 from the printed page. Hence we should avoid light 
 entering the eye from any other source at this time. While 
 reading, then, do not face a window, another light, a mirror, 
 
296 PHYSIOLOGY. 
 
 or white wall, if it can be avoided. White walls are likely 
 to injure the eyes. Choose a dark color for a covering for 
 a reading table. Sewing against the background of a white 
 apron has worked serious harm. Direct sunshine very 
 near the book or table is likely to do harm. 
 
 2. Position in Reference to Light. Preferably have 
 the light from behind and above. Many authors say " from 
 the left," or "over the left shoulder." In writing with the 
 usual slant of the letters this may be desirable. But ver- 
 tical writing is now strongly advocated, as it enables one 
 to sit erect, and have the light from above and equally for 
 the two eyes. Sitting under and a little forward of a hang- 
 ing lamp will thus give the light equally to the two eyes 
 and send no light direct into the face. In reading by day- 
 light avoid cross-lights so far as possible. 
 
 3. Electric Light. The incandescent electric light 
 has an advantage in being readily lighted, without matches, 
 and in giving out little heat ; but owing to its irregular 
 illumination (due to the shadow cast by the wire or fila- 
 ment), it is not well suited for study or other near work. 
 For this purpose an Argand gas or kerosene burner is 
 much to be preferred, since it throws a soft, uniform, and 
 agreeable light upon the work. 
 
 4. Reading Outdoors. Reading out-of-doors is likely 
 to injure the eyes, especially when lying down. To try to 
 read while lying in a hammock is bad in many ways. Too 
 much light directly enters the eye, and often too little falls 
 upon the printed page. 
 
 5. Reading Heavy Books. Do not hold the book or 
 work nearer the eyes than is necessary. " So far as possible 
 avoid continuous reading in large or heavy books by arti- 
 
THE SENSE OF SIGHT, 297 
 
 ficial light. Such books being hard to hold, the elbows 
 gradually settle down against the sides of the body, and 
 thus the book is held too close to the eyes, or at a bad 
 angle, or the body assumes a bad position. 
 
 6. Resting the Eyes. Frequently rest the eyes by 
 looking up and away from the work, especially at some 
 distant object. One may rest the eyes while thinking over 
 each page or paragraph, and thus really gain time instead 
 of losing it. 
 
 7. Strength of Light. Have light that is strong 
 enough. Remember that the law of the intensity of light 
 as affected by distance is that at twice the distance the 
 light is only one fourth as strong. Reading just before 
 sunset is not wise, One is often tempted to go on, not 
 noticing the gradual diminution of light. 
 
 8. Evening Reading. In all ways endeavor to favor 
 the eyes by doing the most difficult reading by daylight, 
 and saving the better print and the books that are easier 
 to hold for work by artificial light. Writing is usually 
 much more trying to the eyes than reading. By carefully 
 planning his work the student may economize eyesight, 
 and it is desirable that persons blessed with good eyes 
 should be careful, as well as those who have a natural 
 weakness in the eyes. It often results that those inherit- 
 ing weak organs, by taking proper care, may outlast and 
 do more and better work than those naturally stronger, 
 but who, through carelessness, injure organs by improper 
 use or wrong use (ab-use). 
 
 9. Artificial Light in the Morning. Reading before 
 breakfast by artificial light is usually bad. 
 
2Q8 PHYSIOLOGY. 
 
 10. Reading during Convalescence. Many eyes are 
 ruined during convalescence. At this time the whole sys- 
 tem is often weak including the eyes. Still, there is a 
 strong temptation to read, perhaps to while away the time, 
 perhaps to make up for lost time in school work. This is 
 a time when a friend may show his friendship. 
 
 u. Irritation of the Eyes. If one finds himself rub- 
 bing his eyes, it is a clear sign that they are irritated. It 
 may be time to stop reading. At any rate, one should find 
 the cause, and not proceed with the work unless the irrita- 
 tion ceases. If any foreign object, as a cinder, lodges in 
 the eye, it is better not to rub the eye, but to draw the lid 
 away from the eyeball and wink repeatedly ; the increased 
 flow of tears may dissolve and wash the matter out. To 
 relieve the feeling that something must be done it may be 
 well to rub the other eye, but of course this gives no posi- 
 tive relief to the affected eye. If it be a sharp cornered 
 cinder, rubbing may merely serve to fix it more firmly in 
 the conjunctiva. If it does not soon come out, the lid may 
 be rolled up over a pencil, taking hold of the lashes or the 
 edge of the lid. The point of a blunt lead pencil is a con- 
 venient and safe instrument with which to remove the par- 
 ticle. Sometimes being out in the wind (especially if un- 
 used to it), together with bright sunlight, may irritate the 
 eyes. If after such exposure one finds lamplight irritating, 
 he will do well to go to bed early, or remain in a dark 
 room. 
 
 12. Keep the Eyes Clean. Be careful to keep the 
 eyes clean. Do not rub the eyes with the fingers. Aside 
 from consideration of rules of etiquette, there is danger of 
 introducing foreign matter that may be very harmful. It 
 is very desirable that each person have his individual face 
 
THE SENSE OF SIGHT. 299 
 
 towel. By not observing this rule certain contagious dis- 
 eases of the eyes often spread rapidly. 
 
 13. Consult a Reliable Oculist. If there is any con 
 tinuous trouble with the eyes, consult a reliable oculist. 
 Many headaches are due to eye-strain, the real cause being 
 unsuspected. If a child has frequent headaches, it is well 
 to have the eyes examined. Many persons injure their 
 eyes by not wearing suitable glasses. On the other hand, 
 do not buy glasses of peddlers nor of any but reliable 
 specialists. One may ruin the eyes by wearing glasses 
 when they are not needed. Sight is priceless. 
 
 READING. Sight, Le Conte. 
 
 Summary. i. Sight, like hearing, acts through space, outstripping 
 the "contact senses " of touch, taste, and smell. 
 
 2. The eye is protected by its bony surroundings, lids, lashes, tears, 
 sensitiveness of the conjunctiva, etc. 
 
 3. The eye is moved by muscles under nerve control. 
 
 4. The eye has three coats sclerotic, choroid, and retina. 
 
 5. The pupil is a hole in the iris, and varies in size to regulate the 
 amount of light admitted. 
 
 6. The refracting media of the eye are the cornea, aqueous humor, 
 lens, and vitreous humor. 
 
 7. These refracting media form an inverted image on the retina. 
 The eye is a camera, darkened on the inside. 
 
 8. The ciliary muscle, acting on the elastic lens, adjusts the lens 
 for seeing at different distances. 
 
 9. Suitable lenses overcome many of the defects in eyesight. 
 
 10. The retina is an expansion of the optic nerve, and is exceed- 
 ingly complicated in its structure. 
 
 11. The blind spot is the place where the optic nerve enters the eye. 
 
 12. The optic nerve is insensitive to light, but injury to it causes 
 sensations of light. 
 
 13. Most of the fibers of the optic nerve cross to the other half of 
 the brain, but some do not cross. 
 
300 PHYSIOLOGY. 
 
 14. Color is due to difference in the rapidity of vibration in the 
 waves of light. 
 
 15. Some eyes do not distinguish these differences and are color 
 blind. 
 
 1 6. Pain in the eyes comes through the fifth pair of nerves, not 
 through the optic nerves. 
 
 17. Binocular vision makes objects "stand out" more distinctly as 
 solid bodies. 
 
 1 8. Impressions of light linger, making after-images. 
 
 19. Defects in eyesight are much more common among civilized 
 men than with the uncivilized men or animals. 
 
 20. The care of the eyes must be made a subject of study and care- 
 ful thought by all reading people. 
 
 Questions. i. What iythe position of the eyeballs during sleep? 
 
 2. What is "cataract"? 
 
 3. What is the cause of " double vision "? 
 
 4. Why does the well eye sympathize with the affected one? 
 
 5. Why does looking at a bright light often cause a person to 
 sneeze ? 
 
 6. Why is weeping associated with grief ? 
 
 7. What is the condition of one who is "cross-eyed"? 
 
 8. Compare the pupils of a man, a cat, and a cow. 
 
 9. Does the color of the eye have any relation to the strength of 
 eyesight ? 
 
 10. Why is one blinded on entering a bright room from the dark? 
 n. Why is one going from a bright room into the dark unable to 
 see at first, but gradually sees more distinctly ? 
 
 12. Why can one not see well when the eye " waters "? 
 
 13. If each eye has a blind spot, why are there 'not blank spaces in 
 the field of vision? 
 
 14. What advantage has a stereoscopic view over a single view? 
 How are stereoscopic views made? 
 
 15. Should the lights which illumine a pulpit or platform be so 
 placed that they can shine into the eyes of the congregation? How 
 should they be arranged? 
 
CHAPTER XXL 
 TASTE, SMELL, AND HEARINGo 
 
 Uses of the Sense of Taste. The sense of taste helps 
 us in judging of the fitness of anything that presents itself 
 as a candidate for election as food. By reflex action the 
 taste of agreeable substances aids in digestion by stimulat- 
 ing the glands, especially the salivary glands. 
 
 The Papillae. The surface of the tongue is covered 
 with papillae. These are of three kinds. Most numerous 
 
 Papillae 
 
 Glosso-pharyngeal 
 Nerve (9th) 
 
 Gustatory Branch of Fifth Nerve 
 Fig. 91. Diagram of Tongue, showing Nerves and Papilla. 
 
 are the filiform papillae, slender, cylindrical projections. 
 Like the papillae of the skin, they seem to be organs of 
 touch. Scattered among the filiform papillae are small, 
 bright red spots which, on examination, are found to be 
 shaped somewhat like a mushroom, the fungiform papillae. 
 Near the base of the tongue are about a dozen larger pa- 
 
 301 
 
302 PHYSIOLOGY. 
 
 pillae, arranged like a letter V with its apex toward the base 
 of the tongue. These are the circumvallate papillae, each 
 having around it a deep circular furrow. 
 
 The Nerve Supply of the Tongue. On the sides of 
 this furrow are small oval bodies, called " taste buds," con- 
 nected with the ends of the nerves of taste. The nerves 
 of taste are the glosso-pharyngeal, or ninth cranial nerves, 
 distributed to the back part of the tongue, and a branch of 
 the fifth pair of nerves, the gustatory, to the front part. 
 
 Although we ordinarily speak of an article of food as 
 "palatable," or "unpalatable," the sense of taste in the 
 palate is only feebly developed. The tip of the tongue 
 seems to be most sensitive to sweets and salines, the back 
 part to bitters, and the sides to acids. 
 
 Solution Necessary for Tasting. Substances must be 
 dissolved before they can be tasted. If the tongue be 
 wiped dry, and a few grains of salt or sugar be placed on 
 it, the taste will not be perceived for a little time. Insol- 
 uble substances give no taste. 
 
 Flavors. What we call flavors affect us more through 
 the sense of smell than through taste. If the nose be held 
 shut, and we are careful about breathing, a piece of onion 
 placed on the tongue does not produce what we usually 
 call the taste of the onion. We may thus get rid of the 
 disagreeable part of taking certain medicines. Let the 
 student experiment with various substances as above in- 
 dicated. 
 
 Effect of Temperature on Taste. It is said that the 
 temperature of about 40 F. is most favorable for tasting, 
 and after rinsing the mouth with very hot or very cold 
 water, such bitter substances as quinine will have only a 
 trace of their usual taste. 
 
TASTE, SMELL, AND HEARING. 
 
 303 
 
 Olfactory Nerves J 
 
 Branches of 
 Fifth Nerve 
 
 Turbinated Bones 
 
 The Sense of Smell. "The sense of odor gives us 
 information as to the quality of food and drink, and more 
 especially as to the quality of the air we breathe. Hence 
 we find the organ placed at the opening of the respiratory 
 passages, and in close proximity to the organs devoted to 
 taste. Taste is at the gateway of the alimentary canal, 
 just as smell is the sentinel of the respiratory tract; and 
 just as taste, when combined with smell to give the sen- 
 sation we call 
 flavor, influ- 
 ences the di- 
 gestive pro- 
 cess, and is 
 influenced by 
 it, so smell 
 influences the 
 respiratory process. The 
 presence of odors influ- 
 ences both the amplitude 
 and the number of the 
 respiratory movements. 
 Thus the smell of winter- 
 green notably increases the 
 
 respiratory work, next comes ylang-ylang, and last rose- 
 mary. The breathing of a fine odor is therefore not only 
 a pleasure, but it increases the amplitude of the respira- 
 tory movements. Just as taste and flavor influence nutri- 
 tion by affecting the digestive process, and as the sight of 
 agreeable or beautiful objects, and the hearing of melo- 
 dious and harmonious sounds react on the body and help 
 physiological well-being, so the odors of the country, or 
 even those of the perfumer, play a beneficent role in the 
 economy of life." M'KENDRICK and SNODGRASS. 
 
 Fig. 92. Nerves of the Outer Wall of the 
 Nasal Cavity. 
 
304 PHYSIOLOGY. 
 
 Why we Sniff. In quiet breathing the air passes 
 along the lower air passages just above the hard palate. 
 The true olfactory passages are higher, but still in com- 
 munication with this lower passage. When we wish to 
 test the quality of the air, we sniff, that is, make a sudden 
 inspiration by jerking the diaphragm down, and air from 
 the outside then rushes into these upper nasal passages, 
 over the walls of which the nerves of smell, the olfactory 
 nerves, are spread in the mucous membrane. The sudden 
 rush of air against this membrane seems to aid greatly in 
 detecting the odor. The nerves have peculiar endings, 
 and it is not known just how the substances produce their 
 effect. The substances must be in a very finely divided 
 state, probably gaseous. The mucous membrane is sup- 
 plied with mucus, and the odorous substance, probably, is 
 first dissolved in the mucus. The lower, or respiratory, 
 passages have a more abundant blood supply, and are 
 redder than the upper. In inflammation, owing to their 
 narrowness, the passages, especially the upper, are often 
 closed by contact of the opposite sides. Substances like 
 ammonia have no odor, but excite the tactile nerves. They 
 are often spoken of as having a " pungent " odor, but are 
 simply irritants. 
 
 The Sense of Hearing. The ear passages are inclosed 
 by the hard bones of the head. The ear is, in consequence, 
 difficult to dissect. It is very desirable to have a model 
 of the ear. The ear may be dissected in a cat or rabbit by 
 following the accompanying description. It will take time 
 and patience to trace all the parts. 
 
 The Parts of the Ear. The ear is a much more com- 
 plicated organ than would naturally be supposed. The 
 parts of the ear are the external, the middle, and the in- 
 ternal ear. 
 
TASTE, SMELL, AND HEARING. 
 
 305 
 
 The External Ear. The external ear gathers the 
 sound waves, and directs them into the opening of the ear, 
 but the loss of the external ear does not seriously interfere 
 with hearing. The passage leading inward from the ear 
 extends about an inch, and is then completely shut off 
 from the cavities beyond by a thin membranous partition, 
 the tympanic membrane or drum skin. The skin of the 
 
 Stirrup Anv 
 
 Semicircular Canals 
 
 COCHLEA 
 
 PHARYNX 
 
 Fig. 93. Diagram of the Ear. 
 
 ear dips into and lines the external tube, and continues as 
 a very thin layer over the membrane of the tympanum. 
 The auditory meatus, as this passageway is called, is 
 guarded by hairs, and is further protected by wax secreted 
 by glands of the lining. 
 
 The Middle Ear. Beyond the membrane of the tym- 
 panum is a cavity called the middle ear. Extending across 
 the cavity of the middle ear is a chain of very small bones, 
 the hammer, anvil, and stirrup, the hammer being attached 
 
306 rnvsiOLOc,\. 
 
 to the inner surface of the membrane of the tympanum, 
 and the stirrup being fastened by its base to the wall of 
 the internal ear. 
 
 The Eustachian Tube. The middle ear communicates 
 with the pharnyx by means of a narrow tube called the 
 eustachian tube. It admits air to equalize the pressure on 
 the two sides of the tympanic membrane. This tube is 
 probably closed most of the time, but opens when we 
 swallow. 
 
 The Internal Ear. The internal ear consists of several 
 complicated cavities and tubes which contain a liquid in 
 which rest the nerves. The principal cavity is the cochlea, 
 or snail-shell cavity, in which the nerve endings are con- 
 nected with an exceedingly complicated apparatus. 
 
 The Production of Sound. Sound waves set the drum 
 skin or membrane of the tympanum in vibration ; the 
 vibrations are conveyed by the chain of bones across 
 the middle ear to the liquid of the inner ear. Through the 
 complicated apparatus of the snail shell the vibrations of 
 the liquid are made to start nerve impulses in the fibers of 
 the auditory nerve, and when these nerve impulses are 
 rightly received and interpreted by the brain, we have a 
 sensation called sound. 
 
 The Equilibrium Sense. Probably most of the senses contribute 
 to the maintaining of the equilibrium of the body by giving information 
 as to position, motion, etc., especially sight and the muscular sense. 
 
 Only that part of the auditory nerve which is distributed in the 
 "snail shell" of the ear is now supposed to have to do with hearing. 
 It is no longer believed that the semicircular canals are concerned with 
 the process of hearing. There seems to be good evidence that the 
 semicircular canals inform us as to changes of the position of the body, 
 and they are regarded as the seat of an "equilibrium sense." The fact 
 that one of these canals is horizontal, and that the two vertical canals 
 
TASTE, SMELL, AND HEARING. 307 
 
 are at right angles to each other, strengthens this belief. It is thought 
 that each of these canals detects movements in its own plane. The 
 experiment has been made of placing a man on a table that easily 
 turned ; with the eyes shut the subject could usually detect fairly well 
 the changes of position from rotation of the table. What is known on 
 the subject comes partly from observation in cases where these parts 
 are diseased (which, in itself, does not cause loss of hearing), and by 
 operating on lower animals ; in both of these lines of observation 
 injury to these parts appears to be followed by dizziness, loss of power 
 to maintain equilibrium, etc. 
 
 The Care of the Ear. In cleaning the ear no hard 
 substance should be used ; even the finger nail is likely to 
 do harm. A moistened cloth should be used. If this is 
 not sufficient, a physician should be consulted. In wash- 
 ing the ear it should be thoroughly dried before being 
 exposed to a wind, especially a cold wind. The rapid 
 evaporation may cool the parts so rapidly as to cause 
 trouble. It is not well to stuff the ears with cotton. If 
 there is any trouble with the hearing, of course a physician 
 should be consulted without delay. 
 
 Colds and Deafness. A cold often produces inflam- 
 mation of the mucous membrane of the pharnyx. This 
 inflammation may extend along the eustachian tube to the 
 middle ear and affect the hearing. 
 
 The Use of the Ears. The existence of an organ of 
 hearing implies the existence of what? Why have we 
 these organs of hearing ? Is it merely a means of protec- 
 tion ? Is it that we may enjoy the music of nature, such 
 as the songs of birds ? Is there not one sound that makes 
 sweeter music than the most gifted of feathered songsters, 
 surpassing all the instruments of man's device, even the 
 violin, with its almost human flexibility and range of 
 expression ? 
 
308 
 
 What sound communicates to us the most of thought 
 and sympathy ? 
 
 What sound was it Robinson Crusoe, in his dreary soli- 
 tude, most longed to hear ? 
 
 READING. The PJiysiology of tlie Senses, M'Kendrick 
 and Snodgrass. 
 
 Summary. i. Taste enables us to judge of the quality of food, 
 and it indirectly influences digestion. 
 
 2. The tongue has two nerves of taste, the fifth pair of cranial nerves 
 supplying the front, and the ninth pair the base. 
 
 3. So-called flavors affect the sense of smell more than that of taste. 
 
 4. The sense of smell tests food and air. 
 
 5. Agreeable odors promote respiration. 
 
 6. The ear consists of the outer, middle, and inner ear. In the inner 
 ear are the endings of the auditory nerve. 
 
 7. The semicircular canals have to do with a sense of equilibrium 
 and not with hearing. 
 
 8. Colds and catarrh often seriously affect hearing. 
 
 Questions. i. How may the sense of taste be blunted ? 
 
 2. What is the effect of inhaling menthol ? 
 
 3. Does a person who is deaf in one ear hear " half as well " as 
 before ? 
 
 4. Which of the senses goes to sleep first when we go to bed ? 
 
 5. In what order do the other senses go to sleep ? 
 
 6. In what order do the senses waken in the morning ? 
 
CHAPTER XXII. 
 THE VOICE. 
 
 The Ear and the Voice. The delicate mechanism and 
 capabilities of the ear are fully matched by the fine adjust- 
 ment and range of the voice. The organ of the voice is 
 well worthy of study, if we look at it merely as a most 
 ingenious contrivance, to say nothing of its importance to 
 us as a means of expressing thought. 
 
 What we can learn from Our Own Throats. We can learn a 
 little from the observation of our own mouths and throats. The pro- 
 jection of the throat known as " Adam's Apple " is one angle of the 
 Thyroid cartilage. A ridge may be felt running downward from the 
 projecting angle. Above the Adam's apple a depression may be felt. 
 Press the tip of the ringer lightly into this depression and perform the 
 act of swallowing. It will be noted that the Adam's apple is drawn up- 
 ward and closer to the bone above the depression. This bone is the 
 Hyoid bone ; it is connected with the larynx below the base of the 
 tongue. Below the thyroid cartilage another cartilage may be felt, 
 the Cricoid cartilage. Below this is the windpipe with its rings of 
 cartilage. The general form of the whole larynx may be felt in a per- 
 son not overburdened with fat. 
 
 By depressing the tongue and looking into the mouth the tip of the 
 epiglottis may possibly be seen at the base of the tongue. Beyond 
 these points we cannot learn much without dissection. A small mirror 
 set obliquely on a handle (like those used by dentists) may be inserted 
 through the mouth so that the larynx can be seen from above. But 
 the meaning of what would be thus seen would not be very clear with- 
 out a careful dissection of the larynx. 
 
 The Vocal Cords. The vocal cords are not very appro- 
 priately named. They are mere ridges projecting from 
 
 39 
 
3io 
 
 PHYSIOLOGY. 
 
 the sides of the larynx. Under the covering of mucous 
 membrane are ligaments and muscles that may be stretched 
 to various degrees and placed in different positions, accord- 
 ing to the sound that is to be produced. 
 
 The Position of the Vocal Cords. While we are 
 
 quietly breathing, the vocal cords, or bands, lie back, like 
 low ridges, against the side of the larynx, and offer nearly 
 the whole channel of the larynx for the free passage of air 
 
 Tiachca 
 
 FROM RIGHT TO LEFT MEDIAN 
 
 Fig. 94. Longitudinal Sections of the Larynx. 
 
 for breathing purposes. But when we wish to produce 
 vocal sound, the vocal cords are made to stand out farther 
 from the side walls, and interfere with the free passage of 
 the air. In examining the larynx, it is seen that the vocal 
 cords are attached close to each other in front, but that at 
 the back of the larynx they diverge widely (in the position 
 of rest), forming a letter V, with the angle of the V in 
 front, just back of Adam's apple. " When changes in the 
 voice or in breathing are being made, the white glistening 
 
THE VOICE. 311 
 
 vocal cords may be seen to come together or to go apart 
 like the blades of a pair of scissors." In a high note the 
 cords are close together and nearly parallel. As the air 
 is forced past the approximated edges of the vocal cords, 
 they are set in vibration, and produce the sound called the 
 voice. 
 
 Illustration of the Vocal Cords. The principle of the action of 
 the vocal cords can be illustrated by the common toy known as the 
 squeaking balloon, or "squawker." Here the air is driven out past a 
 band of rubber stretched across the inner end of the tube. If instead 
 
 Epiglottis 
 False Vocal Cords ... 
 
 True Vocal Cords ~ 
 
 i 
 Glottis Narrowed, High Note Glottis Wider, Quiet Breathing 
 
 Fig. 95. The Larynx, as seen by Means of the Laryngoscope, in Different 
 Conditions of the Glottis. 
 
 of one band with both edges free, we were to tie on the inner end of 
 the tube two bands of rubber, each covering the outer edge of the tube, 
 leaving the inner edge of the rubber free, and with the two bands touch- 
 ing at one end and considerably separated at the other end, we would 
 have a pretty fair resemblance to the larynx. 
 
 Reenforcement of Vocal Sound. As in many musical 
 instruments, the vibrations of the membrane alone would 
 be too feeble to have much effect. In the violin, piano, 
 drum, etc., the vibrations are reenforced by the vibration 
 of a body of air contained within. So here the vibrations 
 of the cords are reenforced and modified by the air spaces 
 above. 
 
 Loudness of Voice. The loudness of the voice depends 
 on the force with which the air is driven past the cords, 
 
312 PHYSIOLOGY. 
 
 together with the size and condition of the cords them- 
 selves. 
 
 Pitch of Voice. Pitch depends on the rapidity of the 
 vibrations, which is determined by the length of the cords 
 and their tension. Other things being equal, the size of 
 the larynx would determine the pitch. 
 
 Voice and Speech. The larynx by itself produces 
 vocal sound merely. In speech the sounds produced in* 
 the larynx are much modified by the lips, tongue, teeth, 
 cheeks, etc. We have voice as soon as born, but we only 
 gradually acquire the power of speech. Mammals, birds, 
 and some of the lower vertebrates have voices, but they 
 have not speech. This distinguishes man from the ani- 
 mals below him, though perhaps some of the higher apes 
 have speech in a slight degree. Dogs can express their 
 wants by barking, growling, snarling, etc., but it is mostly 
 by their tone, with their attitudes, and a slight facial 
 expression (as in snarling). 
 
 Vowels and Consonants. By various positions of the tongue and 
 organs of the throat we make the different vowel sounds. In the con- 
 sonants we more or less shut off (for the time) the passage of air, and 
 so stop, or modify, the sound. This is hardly the place to study and 
 analyze the sounds of our spoken language, yet it may be found profita- 
 ble to watch the different organs as each sound is produced ; for when 
 the structure and relation of the different parts concerned in the pro- 
 duction of these sounds are better known, the definitions and state- 
 ments of the books will be much more fully understood. 
 
 Differences between Voices. Since no two throats 
 are exactly alike, no two voices sound just the same. The 
 size and shape of the pharynx, the shapes and positions of 
 the teeth, lips, the condition of the mucous membrane of 
 the passages generally, all affect the sound, and give it its 
 " quality," by which we distinguish one voice from another, 
 
THE VOICE. 313 
 
 even if they are in the same pitch and have the same 
 degree of loudness. 
 
 Change of Voice. At about the age of fourteen a boy's larynx 
 increases in size and the voice changes, becoming deeper and heavier. 
 During the change the falsetto often breaks in upon the ordinary voice, 
 the voice being said to " crack.' 1 
 
 Hoarseness. If the mucous membrane covering the vocal cords is 
 inflamed, or covered with too much mucous, hoarseness is likely to 
 .result. 
 
 Whispering. As in the animal we have voice without speech, so 
 in whispering we have speech without voice ; that is, there is no vocali- 
 zation. The organs of speech so modify the aspiration as to produce 
 speech. There is no true voice. 
 
 Culture of the Voice. The voice and speech are 
 very susceptible of culture, and nearly all voices may im- 
 prove by proper cultivation. A cultivated voice and care- 
 ful, distinct speech are very desirable accomplishments, 
 and are not nearly so common as they ought to be. We 
 delight in fine singing, and many strive to cultivate this 
 art ; but not so many try to learn to talk so that it is a 
 pleasure to .hear the spoken sound. 
 
 READING. The Throat and the Voice, Cohen. 
 
 Summary. i. The larynx is very complicated. Various muscles 
 move the cartilages and vary the length and tension of the vocal cords, 
 and thus produce the varying degrees of pitch. 
 
 2. The vocal cords are not simple cords, but are band-like ridges 
 on the sides of the larynx. 
 
 3. The higher animals have voice but not speech. 
 
 4. Whispering is speech without voice. 
 
 5. The larynx is affected by " colds " and catarrh. 
 
 Questions. i. Why does one become hoarse from hearing others 
 shouting? 
 
 2. What is ventriloquism? 
 
CHAPTER XXIII. 
 ACCIDENTS. WHAT TO DO TILL THE DOCTOR COMES. 
 
 How to Stop Flow of Blood from Arteries. In case 
 of bleeding from an artery the blood comes in jets. Pres* 
 sure should be applied between the cut and the heart. To 
 know where to apply the pressure, study of the course of 
 the main arteries should be made. By studying Fig. 16 
 it will be seen that the arteries to the arms pass down the 
 inside of the upper arm. Here they come near the sur- 
 face. At the elbow the artery is near the skin in the 
 angle of the elbow. The artery which makes the pulse at 
 the wrist is well known. By putting a baseball under the 
 armpit and pressing the arm down firmly, the artery may 
 be compressed. 
 
 Bleeding from the Upper Arm. In case of a deep 
 cut in the lower part of the arm, a handkerchief should 
 have a knot tied in it, and the knot placed over the artery ; 
 that is, on the inside of the arm just below the armpit. 
 Pass the handkerchief around the arm and tie it loosely. 
 Then run a stick through it, and twist till the knot is drawn 
 tightly against the artery. Instead of a knot, a potato, or 
 anything else to make a firm lump, may be used. (See 
 Figs. 1 6 and 35.) 
 
 Bleeding from the Neck. In studying the pulse, we 
 found the Carotid artery in the neck. If a deep cut has 
 been made in the upper part of the neck, it might be pos- 
 sible to stop the flow by compressing the artery lower 
 down the neck. 
 
 3H 
 
ACCIDENTS. 315 
 
 Wounds in the Thigh. The femoral artery comes 
 near the surface in the groin. Pressure may be applied 
 here in the same way to stop bleeding from a cut farther 
 down the thigh. In the angle back of the knee, pressure 
 may compress the artery supplying the leg. 
 
 In case of severe wounds, pressure should be applied 
 immediately to the wound. Sometimes it is well to make 
 a plug of cloth and press upon the cut. 
 
 Bleeding from Veins. In case of bleeding from veins, 
 holding the part up may check the flow. If necessary to 
 apply pressure, it should be beyond the cut, instead of 
 between it and the heart, as in the case of the artery. 
 
 Hemorrhage of the Lungs or Stomach. Blood from 
 the lungs is bright, frothy, and salty; from the' stomach 
 is dark and sour. In case of bleeding from the lungs or 
 stomach, let the person rest quietly on a lounge or easy- 
 chair. Give him some bits of ice to swallow. 
 
 Bleeding from the Nose. Nosebleed may sometimes 
 be stopped by pressing firmly at the base of the nose. 
 Do not lean forward, as this position aids the flow. Sit 
 up, and hold up the head, and hold a cloth under the nose. 
 Apply cold water or ice to the nose and to the back of the 
 neck. If this does not stop it, inject cold water, with a 
 little salt or soda in it, into the nose. Often the flow may 
 be stopped by pressing firmly on the upper lip at the sides 
 of the nose. If these attempts fail, a long strip of cloth 
 may be used to plug the nostril, pushing the cloth in a 
 little at a time, and leaving the ends so it can be pulled 
 out. This should not be removed till a long time after the 
 flow is checked, as it may start the bleeding afresh. After 
 an attack of this kind avoid blowing the nose, as this often 
 starts bleeding again. 
 
316 PHYSIOLOGY. 
 
 Treatment of Burns. Plunge the burned part into 
 cold water. As soon as possible apply a solution of cook- 
 ing soda (a tablespoonful of bicarbonate of soda to a tea- 
 cup of water) ; or lay a wet cloth on the burned part and 
 put the soda on the cloth. Afterwards apply vaseline, 
 and renew the vaseline till the wound is healed. 
 
 A mixture of equal parts of sweet oil and limewater 
 makes a good liniment for dressing burns. Flour thickly 
 applied gives relief, but is objectionable because it is hard 
 to remove without taking the skin off with it. 
 
 Danger from Burning Clothing. If the clothing takes 
 fire, there is added to the danger of burning the body, the 
 further risk of inhaling the flame and heated air. It is 
 best to lie down and roll or wrap the body in any cloths 
 at hand, rugs, shawls, etc. Running serves to fan the 
 flames. Hence, if a person whose clothing is on fire is 
 seen to be thoroughly frightened, and to have lost presence 
 of mind and be starting to run, the best thing to do usually 
 is to grasp and try to throw him to the ground, putting a 
 wrap of some kind around the body at the same time if 
 possible. Rolling on the ground or floor in itself would 
 very likely put out a small flame. 
 
 Treatment of Fainting. Lay the body flat on the 
 back. Keep the crowd away, and give plenty of fresh air. 
 Loosen the clothing about the neck and waist. Sprinkle 
 cold water on the face, but do not drench the body with a 
 quantity of water. Apply smelling salts (ammonia) to the 
 nostrils ; rub the limbs toward the body. If these reme- 
 dies do not soon restore consciousness, send for a physician. 
 A faint is not usually a serious matter. Bad ventilation, 
 disagreeable odors, or even the oversweet odors of such 
 flowers as the tuberose, may cause fainting. 
 
ACCIDENTS. 317 
 
 Broken Bones. Keep the patient as quiet as possible 
 till the physician arrives. There need be no anxiety if the 
 physician is delayed, as ordinarily no harm comes from 
 waiting. If there is inflammation, cold water may be 
 applied. Cooling applications are desirable in case of 
 severe bruises. If it is necessary to carry the patient, lay 
 him on a board, or at least keep the injured part as quiet 
 as possible ; a cane or umbrella may be tied alongside a leg, 
 and supported by a pillow or a coat. Sometimes the sharp 
 ends of the bones may cut the flesh or even blood tubes. 
 
 Sunstroke. Lay the patient in the shade and pour 
 cold water over the head. 
 
 . 
 
 Fig. 96. Resuscitation from Drowning. (Lincoln, 3 Figures.) 
 (Position 1.) 
 
 TREATMENT OF THE DROWNED. 
 
 (As given by the Michigan Board of Health^) 
 
 RULE I. Remove all obstructions to breathing. Instantly 
 loosen or cut apart all neck and waist bands ; turn the 
 
PHYSIOLOGY. 
 
 patient on his face, with the head down hill ; stand astride 
 the hips with your face toward his head, and, locking your 
 fingers together under his belly, raise the body as high as 
 you can without lifting the forehead off the ground (Fig. 
 96, Position i), and give the body a smart jerk to remove 
 mucus from the throat and water from the windpipe ; hold 
 the body suspended long enough to count slowly, one, 
 
 
 
 
 - Av^i, 
 
 Fig. 97- Resuscitation from Drowning. 
 (Position 2.) 
 
 two, three, four, five, repeating the jerk more gently two 
 or three times. 
 
 RULE 2. Place the patient on the ground face down- 
 ward, and, maintaining all the while your position astride 
 the body, grasp the points of the shoulders by the clothing, 
 or, if the body is naked, thrust your fingers into the arm- 
 pits, clasping your thumbs over the points of the shoulders, 
 and raise the chest as high as you can (Fig. 97, Position 2) 
 
ACCIDENTS. 
 
 319 
 
 without lifting the head quite off the ground, and hold it 
 long enough to count slowly one, two, three. Replace 
 him on the ground, with his forehead on his flexed arm, the 
 neck straightened out, and the mouth and nose free. Place 
 your elbows against your knees, and your hands upon the 
 sides of his chest (Fig. 98, Position 3) over the lower ribs, 
 and press downward and imvard with increasing force long 
 
 Fig. 98. Resuscitation from Drowning. 
 (Position 3.) 
 
 enough to count slowly one, two. Then suddenly let go, 
 grasp the shoulders as before, and raise the chest (Position 
 2), then press upon the ribs, etc. (Position 3). These al- 
 ternate movements should be repeated ten or fifteen times 
 a minute for an hour at least, unless breathing is restored 
 sooner. Use the same regularity as in natural breathing. 
 
 RULE 3. After breathing has commenced, restore the 
 animal heat. Wrap him in warm blankets, apply bottles 
 
320 J'HYSIOLOGY. 
 
 of hot water, hot bricks, or anything to restore heat. Warm 
 tJic head nearly as fast as tJie body lest convulsions come on. 
 Rubbing the body with warm cloths or the hand, and slap- 
 ping the fleshy parts, may assist to restore warmth, and 
 also the breathing. If the patient can surely swallow, give 
 hot coffee, tea, milk, or a little hot sling. Give spirits 
 sparingly, lest they produce depression. Place the patient 
 in a warm bed, and give him plenty of fresh air ; keep him 
 quiet. 
 
 BEWARE ! 
 
 Avoid Delay. A moment may turn the scale for life 
 or death. Dry ground, shelter, warmth, stimulants, etc., 
 at this moment are nothing artificial breathing is 
 everything is the one remedy all others are sec- 
 ondary. 
 
 Do not stop to remove wet clothing. Precious time is 
 wasted, and the patient may be fatally chilled by the ex- 
 posure of the naked body, even in summer. 
 
 First restore Breathing. Give all your attention and 
 effort to restore breathing by forcing air into, and out of, 
 the lungs. If the breathing has just ceased, a smart slap 
 on the face or a vigorous twist of the hair will sometimes 
 start it again, and may be tried incidentally. 
 
 Before natural breathing is fully restored, do not let the 
 patient lie on his back unless some person holds his tongue 
 forward. The tongue by falling backward may close the 
 windpipe and cause fatal choking. 
 
 Prevent friends from crowding around the patient and 
 excluding the fresh air ; also from trying to give stimulants 
 before the patient can swallow. The first causes suffoca- 
 tion ; the second, fatal choking. 
 
ACCIDENTS. 321 
 
 Do not give up too soon : you are working for life. 
 Any time within two hours you may be on the very 
 threshold of success without there being any sign of it. 
 
 Learn to Swim. Of course, persons who cannot swim 
 well ought not to go out in a boat without taking along 
 some sort of a float that may serve as a life-preserver. 
 Some of the rubber cushions serve well for this. 
 
 Every father neglects his duty if he does not teach his 
 children, girls as well as boys, to swim and to float. One 
 cool, trained person may save the lives of a whole boat 
 load. 
 
 When a Boat Upsets. In case an ordinary rowboat is 
 overturned, one should not attempt to climb into it or upon 
 it. It takes very little to float a person in water, as the 
 body is only a little heavier than water ; in fact, if a person 
 fills the lungs and lies back in the water his face and nose 
 will keep above water, and a person (at any rate without 
 clothing) can float in this way for some time if he breathes 
 lightly. The trouble is that the person tries to lift the 
 whole head out of the water. The dog and such animals, 
 when swimming, have little out of the water but the tip of 
 the nose and a little of the top of the head. If we could 
 learn something from them it would be a good thing. The 
 easiest way to float is on the back. Few persons have 
 been taught these facts, and most of those who have 
 learned them lose their presence of mind, and waste their 
 breath and strength in wild and fruitless splashing. If a 
 boat be overturned, those who can swim should help those 
 who cannot to get hold of the edge of the boat, but not 
 permit them to climb upon it. A small plank will float a 
 person if he will not try to lift much of his body out of the 
 water. 
 
322 PHYSIOLOGY. 
 
 Suffocation in Wells. Persons are sometimes suffo- 
 cated by carbon dioxid in wells and cisterns. Before going 
 down into a well, it is a safe precaution to lower a lighted 
 candle. If this is extinguished, a warning is given. If a 
 second person goes down after one who has become un- 
 conscious, great care must be taken that two lives are not 
 lost. A rope should be firmly tied about the body, a hook, 
 attached to another rope, taken to catch into the clothing 
 of the first, and the rescuer should be lowered quickly and 
 brought up immediately. A small rope or large cord 
 might be carried, by pulling which the signal is given to 
 pull up. 
 
 In resuscitating from carbon dioxid suffocation use the 
 same method as after drowning, except the first part, which 
 is to remove water from the windpipe, etc. 
 
 Poisons and their Antidotes. Several of the common 
 drugs and remedies kept about the house are more or less 
 poisonous. The proper antidote for each should be known 
 and kept at hand. In the first place, all such materials 
 should be kept locked up so they will not be taken by 
 children, or by mistake, as in the haste of getting medicine 
 in the night. Again, all grown persons in the family 
 should be instructed as to the effects of each poison, and 
 taught its antidote. As soon as any new poisonous drug 
 is bought, it should be made a point to read up about it, 
 and procure an antidote. Every one should know that 
 strychnin causes spasms, that opium brings on stupor, 
 with contracted pupils, etc. 
 
 Objects of Treatment. Treatment aims at three things, 
 (i) to get rid of the poison, (2) to neutralize what remains 
 and prevent further action, (3) to remedy the effects already 
 produced. 
 
ACCIDENTS. 323 
 
 1. Mustard a Common Emetic. The most common 
 emetic is mustard ; a tablespoonful in a cup of warm water; 
 give half of it, following with free drinking of warm water, 
 then give the rest of the mustard. Do not wait for it to 
 dissolve, but stir quickly and give at once. Provoke vom- 
 iting by tickling the throat with a feather or with the 
 finger. If the mouth of the patient cannot readily be 
 opened, insert the thumbs inside the cheeks and back of 
 the teeth. If mustard is not at hand, a strong solution of 
 table salt will serve. In a few cases, such as poisoning by 
 ammonia, lye, etc., it is considered best not to administer 
 an emetic, but to try to neutralize the effect. 
 
 2. Neutralize the Poison. To neutralize a poison this 
 general rule should be known : an alkali may be neutral- 
 ized by an acid, and vice versa. For example, lye with 
 vinegar, carbolic acid with whiting or magnesia, etc. Some 
 acids and alkalis are always about a house. 
 
 3. Give Something Soothing. After any irritant poi- 
 son some mild and soothing substance should be given, 
 white-of-egg, milk, mucilage and water, flour and water, 
 gruel, olive, or castor-oil. These materials are partly for 
 neutralizing the poison, and are also soothing in their 
 effect. If a patient is drowsy, some stimulant may be 
 given, as strong coffee (after opium). Of course a physi- 
 cian should be sent for immediately, as the after-treatment 
 is of great importance. 
 
 The tables of " Poisons, their Symptoms, Antidotes, and 
 Treatment," in the appendix, are taken from the excellent 
 Text-Book of Nursing by Clara Weeks-Shaw. 
 
 Wounds from Thorns, Rusty Nails. Promote bleed- 
 ing by rubbing and pressing the wound and bathing with 
 
324 
 
 warm water. Or suck the wound. This tends to remove 
 any injurious matter. Apply poultices. 
 
 Bites of Cats, Bogs, etc. If the animal is rabid (mad), 
 suck the wound and cauterize quickly. A poker or nail 
 heated red hot is best for cauterizing. If one cannot do 
 this promptly, get lunar caustic with which to cauterize ; 
 strong acid or alkali, or a coal of fire, may be applied at 
 once to the wound ; the coal on a cigar may be used. Do 
 not kill the animal if there is doubt. Keep it confined, 
 and if it proves a false alarm much anxiety will be saved. 
 
 Snake Bites. Apply ligatures around the part between 
 it and the heart. Suck the wound (there is no danger 
 in this if there are no sores or cracks in the skin of the 
 mouth ; venom is not a stomach poison, though, of course, 
 it should not be swallowed). Then apply caustics, or a 
 live coal. Have the patient drink freely of whiskey or 
 brandy. If ammonia water is at hand, add five teaspoon- 
 fuls to each pint of liquor. 
 
 Ammonium carbonate, ten per cent solution, is also 
 highly recommended. A teaspoonful dose should be 
 given immediately, and repeated twice at intervals of ten 
 minutes. 
 
 Bee Stings. Apply soda, or dilute ammonia. 
 
 Poison Ivy. The itching and discomfort may be 
 relieved by bathing the part in a mixture of- 
 
 Two teaspoons of carbolic acid (pure), 
 
 Two tablespoons of glycerin, 
 
 One half pint of water or rose-water. 
 
 The Sick-room. Every boy and girl ought to learn 
 something about the care of the sick, as any one is 
 likely to be called on to do this kind of work. Good 
 
ACCIDENTS. 325 
 
 nursing is often "half the battle." In the first place, 
 the nurse should faithfully follow the directions of the 
 physician. This obedience should be complete as to admis- 
 sion of visitors, as well as in administering medicine, etc. 
 The nurse often yields to the persuasion of some unwise 
 friend, " It won't do any harm for him to see me." 
 
 Qualities of a Nurse. The nurse should have a quick 
 sympathy, and make the patient feel that all that can be 
 done for his comfort will be done ; yet this sympathy must 
 not lead the nurse to do anything for, or give anything to 
 the patient contrary to the orders of the physician. The 
 nurse should always be cheerful, even when the patient 
 is "impatient" and annoying in his demands. The 
 patient is not "himself," and no attention should be paid 
 to his unnatural irritability. 
 
 The Room should be Cheery. The patient should 
 have a cheerful room, but the bed should be so placed 
 that the light will come not too strongly into his face. 
 Evidence of illness, such as medicine bottles, etc., should 
 be kept out of sight so far as possible. 
 
 Hope. While it is not best to deceive the patient as 
 to his condition, there should at all times be kept up 
 an air of cheerfulness and hope. If the physician can 
 inspire with confidence, and the nurse give unflagging 
 good cheer, the chances of recovery are vastly improved. 
 Nothing sustains like hope. 
 
 Pure Air in the Sick-room. Keep the air of the room 
 pure. Remove excreta and everything offensive just as 
 soon as possible. Do not rely on feeling as to tempera- 
 ture, but keep a thermometer in the room. 
 
 Sympathy with the Patient. One of the necessary 
 characteristics of a good nurse is the power of imagina- 
 
326 PHYSIOLOGY. 
 
 tion. " How would I feel, and what would I like to have 
 done for me, if I were in his place ? " This feeling will 
 lead the nurse frequently to raise the patient's head and 
 turn the pillow the coolness of the other side of the 
 pillow is refreshing ; to give sips of cool water ; to see 
 that the patient does not surfer for want of a bath ; in 
 giving a bath, to do the work thoroughly, as a skillful 
 barber carefully and thoroughly reaches every fold and 
 crevice back of the ear, etc. 
 
 Bathing the Sick. In bathing a weak person only a 
 part of the body should be moistened at a time ; after this 
 part is thoroughly dried, another part may be washed ; 
 it is often necessary to do all this work under the bed 
 clothing. 
 
 Changing the Bedding. In changing the bed clothing 
 move the patient to one side of the bed, push the cloth- 
 ing along close to his body, and place the clean bedding 
 on the other side ; then move the patient back, remove 
 the soiled linen, and smooth out the clean. It is often 
 necessary to warm the sheets first : they should be thor- 
 oughly dry. 
 
 Follow Physician's Directions Faithfully. - - Have 
 the physician's directions written out plainly, as they may 
 be forgotten ; and if there is a change of nurses during 
 the night there is less chance of mistake. Never let your- 
 self get drowsy when acting as nurse. Get up and walk 
 about, get a breath of fresh air, and if inclined to be 
 drowsy do not allow yourself to settle back in an easy- 
 chair. If watching all night, take a good lunch in the 
 middle of the night ; coffee may help to keep you awake. 
 It is not to be expected that one who has worked hard 
 all day out-doors will be likely to keep awake all night. 
 
ACCf DENTS. 327 
 
 There should be day and night watchers, and one wo.uld 
 better not watch more than six hours at a time. 
 
 Sweeping the Sick-room. Do not allow the room to 
 be swept with the ordinary broom. The room should have 
 rugs that can be removed and shaken, and the floor wiped 
 with a moist cloth. If the room is carpeted, it may be 
 swept with moist salt, tea-grounds or coffee-grounds, saw- 
 dust, etc. Any dusting should be avoided ; furniture may 
 be wiped with a damp cloth. 
 
 Do not Whisper. In the effort to be quiet many make 
 a mistake ; do not whisper, as it disturbs more than talking, 
 and also has an air of secrecy that rouses suspicion in the 
 patient. 
 
 Walk Flat-footed. In walking on tiptoe often floors 
 and stairs are made to creak when they would not in ordi- 
 nary circumstances. It takes little reflection to see that 
 in walking on tiptoe one brings more weight than usual 
 on a smaller part of the floor, and is therefore more likely 
 to spring a board in the floor ; it is best to walk flat-footed. 
 Wear an easy pair of shoes ; an old pair are likely to be 
 quiet. 
 
 Food for the Sick. Raise the head with the hand, or 
 bolster the patient up, when giving drink ; or if the patient 
 is very weak, use a rubber tube, so that he will not have to 
 lift the head. The nurse should know how to prepare any 
 food that may be needed during the night. An oil stove 
 or gas stove is very desirable for cooking, or heating poul- 
 tices, as an ordinary wood or coal fire is likely to die down, 
 making it impossible for the nurse to do this work quickly, 
 as is often necessary to take advantage of a favorable 
 time, as when the patient wakens. 
 
328 PHYSIOLOGY. 
 
 Care of Lamps. Most lamps, when turned low, give 
 off a disagreeable gas. It is better to have a very small 
 lamp burning at full height than a large one turned low ; 
 sperm candles are recommended. 
 
 Bandaging, Preparing Food, etc. It is well for every 
 one to know something about bandaging, preparation of 
 food for the sick, etc. Space here will not allow further 
 treatment of these subjects, and the student is referred to 
 treatises on the care of the sick, of which there are several 
 good ones mentioned at the end of this chapter. 
 
 To Prevent Sneezing. It is well known that a sneeze 
 may be prevented by firmly pressing on the upper lip. 
 This may enable a nurse to keep from waking a very sick 
 patient when, at a critical point, sleep is almost a question 
 of life or death. And it is a convenient fact for any one 
 to know. To prevent coughing there are cough drops that 
 will relieve the tickling in the throat. 
 
 For Disinfectants see Appendix. 
 
 In addition to the list of books on Accidents, Emer- 
 gencies, etc., already given, read Hand-Book of Nursing, 
 published under the direction of the Connecticut Training- 
 School for Nurses, State Hospital, New Haven, Conn. ; 
 Text-Book of Nursing, Weeks-Shaw; Nursing: Its Prin- 
 ciples and Practice, Hampton. 
 
 Summary. i . To stop flow of blood from an artery apply pres- 
 sure to the wound, or between the wound and the heart. 
 
 2. To stop flow of blood from a vein apply pressure to the wound or 
 beyond the heart. 
 
 3. Leaning forward promotes, instead of checking, nosebleed. 
 
 4. To burns apply cooking soda. 
 
 5. If the clothing takes fire lie down and roll, or wrap a nig or shawl 
 about the body. 
 
ACCIDENTS. 329 
 
 6. If a person with clothing on fire loses his presence of mind, seize, 
 throw down, and wrap in any woolen clothing. 
 
 7. In case of fainting lay the body flat on the back, loosen clothing, 
 give fresh air, and sprinkle lightly with cold water ; if this does not 
 revive, rub the limbs toward the body, hold to the nostrils smelling- 
 salts (or ammonia) and, last, send for a physician. 
 
 8. Broken bones do not urgently need prompt attention. Keep 
 patient quiet and send for a physician. 
 
 9. For resuscitation from drowning, use artificial respiration, 
 promptly begun and long continued. 
 
 10. Before going down into a well, test the air by lowering a lighted 
 candle. 
 
 1 1 . Learn the antidotes of every poison in your house as soon as it is 
 bought, and keep the antidote at hand. 
 
 12. Volunteer to help take care of sick friends, and learn to do this 
 work well. 
 
 Questions. i. How does holding up the wounded part check- 
 bleeding ? 
 
 2. What other methods of resuscitation from drowning are in 
 use? 
 
 3. What are some of the poisonous substances commonly kept in 
 the house? 
 
CHAPTER XXIV. 
 THE SKELETON. 
 
 The Two Parts of a Skeleton. Observe that the 
 skeleton as a whole consists of two portions, the axial por- 
 tion, consisting of a central axis, the spinal column, to 
 which the head belongs ; and the appendicular portion, 
 the limbs and the bones belonging to them. 
 
 The Uses of the Bones. In the skeleton as a whole 
 observe : 
 
 1. The skeleton shows the form of the body. 
 
 2. It supports the softer tissues. 
 
 3. It protects softer parts, as the brain in the skull, the 
 spinal cord in the spinal column, the heart and lungs in 
 the thorax, etc. 
 
 4. The bones serve as levers in producing motion and 
 locomotion. 
 
 Study of a Vertebra. Take a vertebra from the middle of the 
 spinal column : 
 
 1. Its most solid part is its body, or centrum. 
 
 2. On the dorsal side of this is the neural arch, forming with the 
 body the neural ring, through which the spinal cord passed. 
 
 3. From this arch there extend projections, or processes. Hold the 
 vertebra by the tip of its longest process, and place it beside the cor- 
 responding vertebra in the complete skeleton. Note that : 
 
 (rt) The body is flattened where it fitted against the vertebras 
 anterior and posterior to it ; 
 
 (b) The holes in the vertebrae form a passage for the spinal cord; 
 
 330 
 
THE SKELETON. 
 
 331 
 
 (V) The middle process is the spinous process, and the series of 
 spinous processes form the ridge of the backbone ; 
 
 (d) The two lateral processes are the transverse processes. 
 
 Neural Arch 
 
 Body. 
 
 Transverse Process 
 
 Spinous Process 
 
 Neural Ring 
 Fig. 99- Anterior View of Thoracic Vertebra. 
 
 Demi-Facet for Head of Rib 
 
 Body 
 
 Anterior Articular 
 
 Process 
 
 .... Facet for Tubercle 
 of Rib 
 
 "Transverse Process 
 
 Spinous Process 
 
 Fig. 100. Left Side View of Thoracic Vertebra. 
 
 Fit together two vertebrae in their proper order and observe that : 
 (e) The openings at the sides, through which the spinal nerves 
 passed, are formed by adjacent notches, or grooves, in the contiguous 
 vertebrae. 
 
 (/) The two projections extending anteriorly from the ring of one 
 vertebra fit against two corresponding processes extending posteriorly 
 from the other vertebra. These are the anterior and posterior articu- 
 lating processes. 
 
332 
 
 PHYSIOLOGY. 
 
 Temporal 
 
 Frontal 
 
 Phalanges 
 
 \ Carpus 
 
 Metacarpus Ulna Sternum 
 
 .... . Parietal 
 
 Occipital 
 
 Cervical Vertebrae 
 
 i Tnoracic Vertebrae 
 
 Fumbar Vertebrae 
 
 Sacrum 
 
 Coccyx 
 
 Femur 
 
 Fibula 
 
 Tarsus 
 
 Phalanges.. 
 
 Metatarsus 
 Fig. 101. Side View of the Human Skeleton. 
 
THE SKELETON. 
 
 333 
 
 TABLE OF THE BONES. 
 
 r skuii (8) 
 
 HEAD (28) 
 
 Face (14) 
 
 1 Ears (6) 
 
 CERVICAL REGION (8) 
 THORAX (37 
 
 UPPER EXTREMITIES (64) { Arm. 
 
 Frontal (forehead). 
 
 2 Temporal (temples) . 
 
 2 Parietal (side). 
 "i Occipital (posterior base). 
 | Sphenoid (base). 
 [ Ethmoid (base of nose and between eyes). 
 
 f 2 Superior Maxillae (upper jaw). 
 
 2 Nasal (bridge of nose). 
 
 2 Malar (cheek). 
 
 2 Lacrymal (inner front corner of orbit). 
 
 2 Turbinated (within nostrils). 
 
 2 Palate (posterior hard palate). 
 
 Vomer (nasal partition). 
 ( Inferior Maxilla (lower jaw). 
 
 ( Malleus (hammer). 
 { Stapes (stirrup). 
 I Incus (anvil). 
 
 \ 7 Cervical Vertebrae (neck). 
 | Hyoid Bone (base of tongue). 
 
 ( 14 True, 6 False, 4 Floating Ribs. 
 -1 12 Thoracic Vertebrae (back). 
 I Sternum. 
 
 \ Clavicle (collar-bone). 
 ^ Scapuk (shoulder . blade)i 
 
 ( Humerus (arm). 
 
 Hand. 
 
 f 8 ' 
 
 51 
 I 14 
 
 8 Carpal (wrist). 
 Metacarpal (palm). 
 Phalanges (fingers). 
 
 LUMBAR REGION (5) 
 PELVIS (4) 
 
 LOWER EXTREMITIES (60) 
 
 5 Lumbar Vertebrae (loins). 
 
 ( 2 Innominate. 
 
 \ Sacrum. 
 I Coccyx. 
 
 Thigh. 
 
 Leg. 
 
 Femur. 
 
 f Patella (knee-pan). 
 i Tibia (large bone). 
 I Fibula (outer bone). 
 C 7 Tarsal (instep, heel) 
 -] 5 Metatarsal (arch). 
 I 14 Phalanges (toes). 
 
334 
 
 PHYSIOLOGY. 
 
 The Spinal Column. The central part of the skeleton 
 is the backbone, or spinal column. As a whole it is a 
 column, widening toward the base, composed of a series of 
 separate bones called vertebrae. 
 
 Hole for Blond Tubes 
 
 Body 
 
 Anterior Articular Facet 
 
 ..Neural Arch 
 
 Spinous Process 
 
 '"- Neural Ring 
 
 Fig. 102. Anterior View of Cervical Vertebra. 
 
 Body--- 
 
 Spinous Process 
 
 Fig. 103. Left Side View of Cervical Vertebra. 
 
 Each vertebra has seven processes, four articulating 
 (two anterior and two posterior), two transverse, and one 
 spinous. 
 
 Take a thoracic vertebra and in the presence of the class trim off the 
 processes with a pair of bone-forceps. The vertebra will he seen to be 
 essentially a ring, or padlock, consisting of the body and neural ring or 
 arch. 
 
THE SKELETON. 335 
 
 Articulations of a Vertebra. The smooth places where 
 the articulating processes join are called facets. Observe 
 on each side of the body of the vertebra a facet where the 
 head of the rib articulated. There is also a facet on the 
 transverse process where the tubercle of the rib articulated. 
 
 The Cervical Vertebrae. The seven cervical vertebrae 
 (neck) have holes through their sides, or transverse pro- 
 cesses, for the passage of blood tubes. 
 
 Atlas and Axis. The first vertebra, the atlas, has no 
 body. The second vertebra is the axis. It has a peg, 
 called the odontoid process, which represents the body of 
 the atlas. In shaking the head, the atlas, with the head, 
 turns on the axis. In nodding the head, the head simply 
 rocks back and forth on the atlas. 
 
 The Thoracic Vertebrae. The twelve rib-supporting 
 vertebrae are the thoracic vertebrae. 
 
 The Lumbar Vertebrae. The next five are the lumbar. 
 
 The Sacrum and Coccyx. The sacrum is composed of 
 five vertebrae grown together, and the remaining four are 
 combined in the coccyx. 
 
 Review of the Spinal Column. Let the eye slowly 
 review the whole spinal column, noting what the vertebrae 
 have in common. Note also their differences. 
 
 Flexibility of the Spinal Column. In most articulated 
 skeletons there are pads of felt between the vertebrae. 
 These take the place of the inter-vertebral cartilages, 
 which are a form of connective tissue, possessing the elas- 
 ticity of cartilage and the toughness of fibrous connective 
 tissue, such as ligament and tendon. These inter-vertebral 
 
336 
 
 PHYSIOLOGY. 
 
 cartilages serve both to keep the vertebrae apart and to 
 hold them together. When we bend the shoulders to the 
 right, the right edges of these cartilages are compressed, 
 
 Neural Arch 
 
 Transverse Process 
 
 Body- 
 
 Neural Ring 
 Fig. 104. Anterior View of Lumbar Vertebra. 
 
 Body 
 
 - Spinous 
 Process 
 
 Posterior Articular Process 
 Fig. 105. .Side View of Lumbar Vertebra. 
 
 and the left edges are stretched, as a piece of india rubber 
 would be if it were glued between the ends of two spools, 
 and the whole were slightly bent. 
 
 Curves of the Spinal Column. View the spinal column 
 from the side. Draw a line representing all its curves. 
 
THE SKELETON. 337 
 
 The Cavities of the Skeleton. Examine the cavity o/~ the skull. 
 If the class has not a skull which has been sawed across, look into the 
 skull cavity through the hole where the spinal cord joined the brain. 
 
 Observe the conical shape of the thorax. In the entire body the 
 bones and muscles about the shoulders usually make a reversed cone of 
 the upper part of the trunk. 
 
 Observe that the ribs are connected with the breastbone by carti- 
 lages. 
 
 The upper limbs are articulated with the body only where the inner 
 ends of the collar bones join the breastbone. 
 
 Pronation and Supination. Rest the forearm on the table with the 
 palm up ; keeping the elbow fixed, turn the hand over. Turning the 
 palm up is called supination ; turning it down is pronation. Perform 
 this experiment with the articulated skeleton. 
 
 The Skeleton of a Cat or Rabbit. Examine the skeleton of a cat 
 or rabbit for the sake of comparison. Note especially the skull and 
 spinal column, so that you will know better what to do when dissecting 
 the brain and spinal cord in one of these animals. 
 
 The Weight of Bones. The bones make about one sixth 
 of the weight of the living body. When dried they may 
 lose half of their weight. 
 
 Microscopic Structure of Bone, i . Examine with a hand lens. 
 Hold a mounted cross-section of bone up to the light and examine with 
 a hand lens. The solid part of the bone will be seen to be pierced by 
 many small holes (or if the holes are filled they will appear as black 
 spots). These are the cross-sections of the haversian canals, through 
 which run the blood tubes, mainly lengthwise through the bone. 
 
 2. Examine with the Low Power of a Compound Microscope. 
 Examine the section under the microscope, using a half-inch objective. 
 The bony matter will now be seen to be arranged in circles, lamellae, 
 around the haversian canals, somewhat like the rings seen on the end 
 of a log. 
 
 Between the rings are circles of elongated dark dots. These are 
 lacunae, cavities in which lay the live-bone corpuscles which built up 
 the bone. The bone was, at first, cartilage. Later, mineral matter 
 was deposited, forming true bone. 
 
33* 
 
 PHYSIOLOGY. 
 
 3. Examine with a High Power. Now examine the section 
 under a one-fifth-inch objective. From the lacunae there run out, in 
 every direction, little crevices, appearing as fine black lines. These 
 are the canaliculi. Through the haversian canals, lacunae, and cana- 
 liculi, the nourishing materials of the blood reach all parts of the bone. 
 
 The Chemical Composition of Bone. i . Take a tall, narrow 
 glass jar, called in the chemical laboratory a "graduate,' 1 or a lamp 
 chimney corked at one end answers very well, and nearly fill with 
 
 Lamellae Lacunae 
 
 
 
 \ 
 
 Canaliculi Haversian Canal 
 
 Fig. 106. Cross-section of Bone. (Highly Magnified. 1 ) 
 
 water. Add one sixth as much hydrochloric acid. Put into this a 
 slender, dry bone, such as a fibula or rib. In twenty-four hours take it 
 out, rinse it thoroughly, and examine it. The acid will probably have 
 dissolved out the mineral matter and left the animal matter. 
 
 2. Lay a piece of bone on a shovel, or piece of sheet iron, and place 
 in the fire. The animal matter is burned out, leaving the brittle min- 
 eral matter. 
 
THE SKELETON. 339 
 
 Bone is composed of mineral matter, two thirds, and animal matter, 
 one third ; in childhood the animal matter is in larger proportion, while 
 in old age the mineral matter is in excess. 
 
 The mineral matter is chiefly calcium phosphate, while the animal 
 matter is largely gelatin. 
 
 Joints may be classified according to their structure as 
 follows : 
 
 Classification of Joints. i. Immovable, such as the 
 sutures between the bones of the skull ; 
 
 2. Mixed, such as the joints between the vertebrae ; 
 
 3. Movable, which allow free motion between the parts ; 
 (a} Ball and socket, as in the hip and shoulder ; 
 
 (b) Hinge, as in the knee and elbow ; 
 
 (c) Pivot, as in the forearm, and between the atlas and 
 axis ; 
 
 (d) Gliding, as between the short bones of the wrist, and 
 of the ankle. 
 
 Study of Joints. Examine these joints in the articulated skeleton, 
 and so far as possible, in fresh specimens (of rabbits). Compare the 
 ball and socket joints of the hip and shoulder. Also compare the hinge 
 joints of the knee and elbow. 
 
 Hygiene of the Bones. Sometimes the bones of chil- 
 dren are deficient in mineral elements, and are unduly soft 
 and flexible. This condition indicates a disease called 
 rickets. Even if the bones are normal, children should 
 not be encouraged to walk early, as bow-legs may result. 
 Most bow-legged persons seem to be active, and probably 
 their muscles developed faster than the bones. Constrained 
 positions or excessive use of special groups of muscles may 
 result in lateral curvature of the spine. The height of 
 seats and desks should be carefully looked after. 
 
 Sprains and Dislocations. Sprains and dislocations 
 are injuries to the joints, and often bring more serious 
 
340 PHYSIOLOGY. 
 
 results than a broken bone. There should, usually, be 
 complete rest until the part can be used without pain. 
 Otherwise a stiffened joint may result. Hot water applied 
 to a sprain or bruise promotes circulation and prevents dis- 
 coloration. But if there is inflammation cold water should 
 be applied. Bandages may be needed for support. 
 
 Summary. i . The skeleton consists of the axial and appendicular 
 portions. 
 
 2. Each vertebra consists of a body, ring (around spinal cord) and 
 processes. 
 
 3. Pads of cartilage connect the vertebrae. 
 
 4. Bone is traversed by tubes and crevices through which it receives 
 its nourishment from the blood. 
 
 5. Bone consists of animal matter with limy matter embedded in it. 
 
 6. Sprains should be treated carefully to avoid stiffened joints. 
 
 Questions. i. Why do the bones of old people break so much 
 more easily than those of children ? 
 
 2. What is the use of the central marrow? 
 
 3. What is the work of the red marrow in the spongy ends of the 
 bones ? 
 
 4. What are " sesamoid " bones ? 
 
CHAPTER XXV. 
 THE MUSCLES. 
 
 The Number of Muscles. There are over five hun- 
 dred muscles in the human body. These vary in size from 
 less than an inch in length, in the ear and in the larynx, 
 to a foot and a half long in the thigh. 
 
 The Arrangement of Muscles. The muscles of the 
 two sides of the body are paired, and normally are about 
 equal in size and strength. The muscles of the limbs are 
 further paired into flexors, which bend, and the extensors, 
 which straighten the limbs. The muscles are also arranged 
 more or less in layers. There is generally a superficial 
 layer and a more deep-seated layer. 
 
 Forms of Muscles. Muscles are of various shapes. 
 The prevailing form in the limbs is spindle-shaped, or fusi- 
 form. This is convenient, as the thicker middle portion 
 of the muscle is opposite the more slender part of the 
 bone, while the tendons at the ends of the muscles are 
 opposite the enlarged ends of the bones at the joints. 
 Some muscles are flat, some have their fibers arranged 
 like the barbs of a feather, and are hence called penni- 
 form. Some muscles have a tendon in the middle which 
 runs through a loop, as in the case of the muscle which 
 depresses the lower jaw. As already stated, muscles 
 which close openings are circular, and are called sphincter 
 muscles. 
 
 34' 
 
342 
 
 PHYSIOLOGY. 
 
 Deltoid 
 
 Serratus Magnus 
 
 Rectus Femoris 
 
 Tibialis Anticu: 
 
 Extensors of the Hand 
 Flexors of the Hand 
 
 Pectoralis Major 
 
 Rectus Abdominalis 
 
 .... Sartorius 
 
 Vastus Externus 
 
 Extensors of the Toes 
 
 Fig. 107. Ventral View of the Superficial Muscles 
 
THE MUSCLES. 
 
 343 
 
 Extensors of the Hand 
 
 Triceps 
 
 Latissimus Dors 
 
 Gluteus Maximus 
 
 Vastus Externus 
 
 Flexors of the Foot 
 
 Trapezius 
 
 Deltoid 
 
 -- Flexors of the Hand 
 
 Biceps Cruris 
 
 Gastrocnemius 
 
 Tendo Achillis 
 
 
 Fig. 108. Dorsal View of the Superficial Muscles. 
 
344 
 
 PHYSIOLOGY. 
 
 Names of Muscles. Some muscles are named from 
 their shape, as the deltoid on the shoulder ; from position, 
 pectoralis major ; from their supposed action, as sartorius 
 and adductor ; direction, as rectus, etc. The biceps and 
 triceps are named from their division at their origins. 
 
 Peculiar Muscles. The diaphragm is a sheet of muscle 
 that forms a partition between the chest and the abdomen. 
 It is arched, and has a clear tendinous center. The ab- 
 dominal muscles form a wall to hold the organs of the 
 abdominal cavity. These muscles also aid in breathing, 
 especially in forced expiration, as after violent exercise 
 and in coughing. The abdominal wall consists of several 
 
 layers of muscle. 
 
 Heart Muscle. The fibers 
 which make up heart muscle 
 are different in appearance from 
 either the striated or smooth 
 muscle fibers. They are more 
 or less branched, as shown in 
 the accompanying figure. No 
 sheath has been found on these 
 fibers. 
 
 The Three Kinds of Muscular 
 Fibers Compared. For the 
 sake of comparison, the striated 
 and unstriated muscle fibers are 
 here shown again, alongside the 
 tschweigger-seideu heart muscle fibers. The stri- 
 
 The nuclei and cell-junctions are only 
 represented on the right hand side ated fibers (of the skeleton) are 
 
 usually called "voluntary," and 
 
 the plain fibers "involuntary." The heart muscle fibers 
 are intermediate, being striated, but involuntary in their 
 
THE MUSCLES. 
 
 345 
 
 action. A striated muscle fiber may be i| inches long and 
 2 -g-0- of an inch wide, though usually less. The heart muscle 
 fiber is narrower than the skeletal fiber, and the plain fiber 
 very much smaller than either. (But the figures do not 
 attempt to give relative proportions with any exactness.) 
 
 Each Muscle Fiber is a Muscle Cell. It is easily seen 
 that each plain muscle fiber is a single cell, having its dis- 
 tinct nucleus. The same is true of the heart muscle fibers, 
 
 Nucleus 
 
 pv.-"- Isolated Fiber 
 
 - Fibers Joined 
 
 Fig. 110. Plain (unstriated) mus- 
 cular fibers from the bladder. 
 
 Fig. 1 1 1. Two striated mus- 
 cular fibers showing the ter- 
 minations of the nerves. 
 
 though they are not so simple, being more or less branched. 
 In the development of striated muscle, when the muscular 
 fibers are about to be formed, the cells from which they 
 develop (called muscle plates) become elongated so that 
 each cell is converted into a long protoplasmic fiber, with 
 many nuclei. Most investigators agree that the striated 
 fibers are produced by the elongation of single cells with 
 multiplication of their nuclei, though some have thought 
 that the fiber is formed by the coalescence of several cells 
 end to end. 
 
 Muscles of Expression. The facial expression is due 
 to the action of the muscles of the face, which in turn are 
 
340 PHYSIOLOGY. 
 
 under control of the cranial nerves. The habitual position 
 becomes somewhat " fixed," so it is true that character 
 is often shown by " the looks." Cultivation of happy 
 thoughts therefore tends to make one better looking. 
 
 Muscles and Fat. Fat fills in space between muscles, 
 and, if abundant, forms a layer over the muscles. One 
 notable instance is the hollow triangular space between 
 the muscles of the cheek. If there is very little fat, a 
 depression is seen, forming the "hollow cheeks.'' But 
 an abundance of fat fnakes a corresponding elevation. 
 
 Convulsions. These spasmodic actions are due to dis- 
 ordered action of the muscles, and, further back, to the 
 disturbed action of the nervous system that controls the 
 muscles. Various disturbances, such as indigestion, may 
 by reflex action bring on convulsions. 
 
 Rigor Mortis. Rigor mortis (death stiffening) is a 
 muscular rigidity due to the coagulation of muscle plasma. 
 It usually sets in not long after death, the time of its 
 appearance and its duration being variable. 
 
 Some Prominent Muscles. The deltoid on the shoul- 
 der is a noticeable muscle. The biceps and triceps have 
 already been studied. The calf muscle is one of the 
 thickest and strongest in the body. The great muscles of 
 the rump are needed to raise and hold the body up. On 
 each side of the front of the neck is a muscle easily ob- 
 served in thin persons. It extends down to the top of the 
 breast bone. 
 
 Sculpture and Anatomy. The sculptor needs to be a 
 thorough student of anatomy, so far as the bones and mus- 
 cles are concerned. If he knows the muscles thoroughly, 
 he can make them " stand out " naturally. Otherwise his 
 work cannot be truly good. 
 
APPENDIX A. 
 
 ANTISEPTICS AND DISINFECTANTS. 
 
 The following is chiefly from Sternberg's Manual of Bacteriology, and 
 embodies part of the report of " The Committee on Disinfectants of the 
 American Public Health Association." 
 
 Antiseptic Defined. An antiseptic is a substance having the power to 
 prevent or destroy putrefaction, or, what is the same -thing, the bacteria upon 
 which putrefaction depends. 
 
 Disinfectant Defined. A disinfectant is a substance that can destroy 
 disease germs. 
 
 Disinfection Defined. Disinfection is the destroying of disease germs by 
 means of heat, chemic substances, fumigation, or by fresh air. 
 
 "The injurious consequences which are likely to result from such misap- 
 prehension and misuse of the word ' disinfectant ' will be appreciated when it 
 is known that recent researches have demonstrated that many of the agents 
 which have been found useful as deodorizers or as antiseptics are entirely 
 without value for the destruction of disease germs." 
 
 An Antiseptic, but not a Disinfectant. " This is true, for example, as 
 regards the sulphate of iron, or copperas, a salt which has been extensively 
 used with the idea that it is a valuable disinfectant. As a matter of fact, 
 sulphate of iron in saturated solution does not destroy the vitality of disease 
 germs, or the infecting power of material containing them. This salt is, 
 nevertheless, a very valuable antiseptic, and its low price makes it one of the 
 most valuable agents for the arrest of putrefactive decomposition." 
 
 EXTRACTS FROM THE ABOVE-MENTIONED REPORT. 
 
 Some Methods of Disinfecting. "The most useful agents for the 
 destruction of spore-containing infectious material are : 
 
 347 
 
3 4 8 PHYSIOLOGY. 
 
 1. Fire ; complete destruction by burning. 
 
 2. Steam under pressure, 105 degrees C. (221 degrees F.), for ten minutes. 
 
 3. Boiling in water for half an hour. 
 
 4. Chloricl of lime ; a four per cent solution. 
 
 5. Mercuric chlorid ; a solution of I : 500. 
 
 For the destruction of material which owes its infecting power to the pres- 
 ence of microorganisms not containing spores, the committee recommends: 
 
 1. Fire; complete destruction by burning. 
 
 2. ISoiling in water for ten minutes. 
 
 3. Dry heat ; no degrees C. (230 degrees F.) for two hours. 
 
 4. Chlorid of lime ; a two per cent solution. 
 
 5. Solution of chlorinated soda ; a ten per cent solution. 
 
 6. Mercuric chlorid ; a solution of I : 2,000. 
 
 7. Carbolic acid ; a five per cent solution. 
 
 8. Sulphate of copper ; a five per cent solution. 
 
 9. Chlorid of zinc ; 'a ten per cent solution. 
 
 10. Sulphur dioxid ; exposure for at least twelve hours to an atmosphere 
 containing at least four volumes per cent of this gas in the presence of 
 moisture. 
 
 Methods of Disinfecting. The committee would make the following 
 recommendations with reference to the practical application of these agents 
 for disinfecting purposes : 
 
 For Excreta. (a) In the sick room : 
 
 1. Chlorid of lime, four per cent. 
 In the absence of spores : 
 
 2. Carbolic acid in solution, five per cent. 
 
 3. Sulphate of copper in solution, five per cent. 
 
 (/>) In privy vaults : 
 
 1. Mercuric chlorid in solution, I : 500. 
 
 2. Carbolic acid in solution, five per cent. 
 
 (c) For the disinfection and deodori/alion of the surface of masses of 
 organic material in privy vaults, etc. : 
 
 Chlorid of lime in powder. 
 
 For Clothing, Bedding, etc. (a) Soiled underclothing, bed linen, etc. 
 
 1. Destruction by fire, if of little value. 
 
 2. Boiling at least half an hour. 
 
ANTISEPTICS AND DISINFECTANTS. 349 
 
 3. Immersion in a solution of mercuric chlorid of the strength of I : 2,000 
 for four hours. 
 
 4. Immersion in a two per cent solution of carbolic acid for four hours. 
 
 (b} Outer garments of wool or silk, and similar articles, which would be 
 injured by immersion in boiling water or in a disinfecting solution : 
 
 1. Exposure in a suitable apparatus to a current of steam for ten minutes. 
 
 2. Exposure to dry heat at a temperature of no degrees C. (230 de- 
 grees F.) for two hours. 
 
 (V) Mattresses and blankets soiled by the discharge of the sick : 
 
 1. Destruction by fire. * 
 
 2. Exposure to superheated steam, 105 degrees C. (221 degrees F.), for 
 ten minutes. (Mattresses to have the cover removed or freely exposed.) 
 
 3. Immersion in boiling water for half an hour. . 
 
 Furniture and Articles of Wood, Leather, and Porcelain. Washing, 
 several times repeated, with : 
 
 I. Solution of carbolic acid, two per cent. 
 
 For the Person. The hands and general surface of the body of attend- 
 ants of the sick, and of convalescents, should be washed with : 
 
 1. Solution of chlorinated soda diluted with nine parts of water, i : 10. 
 
 2. Carbolic acid ; two per cent solution. 
 
 3. Mercuric chlorid, i : l,ooo. 
 
 For the Dead. Envelop the body in a sheet thoroughly saturated 
 with : 
 
 1. Chlorid of lime in solution, four per cent. 
 
 2. Mercuric chlorid in solution, i : 500. 
 
 3. Carbolic acid in solution, five per cent. 
 
 For the Sick Room. (a) While occupied, wash all surfaces with : 
 
 1. Mercuric chlorid in solution, I : 1,000. 
 
 2. Carbolic acid in solution, two per cent. 
 
 (l>) When vacated, fumigate with sulphur dioxid for twelve hours, burning 
 at least three pounds of sulphur for every thousand cubic feet of- air space in 
 the room ; then wash all surfaces with one of the above-mentioned solutions, 
 and afterward with soap and hot water ; finally throw open doors and win- 
 dows, and ventilate freely." 
 
350 
 
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POISONS AND ANTIDOTES. 
 
 35 
 
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352 
 
 LVD ANTIDOTES. 
 
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PO/SONS AND ANTIDOTES. 
 
 353 
 
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354 PHYSIOLOGY. 
 
 Daily Excretions. Sweat, from 1.5 Ibs. to 4.5 Ibs. ; urea, about 
 1 oz. ; organic matter exhaled, :! grains ; urine, 53 oz. 
 
 "Of the entire excreta, 32 per cent pass off by the breath ; 17 per- 
 cent by the skin ; 4C.5 per cent by the kidneys ; 4.5 per cent by the 
 alimentary canal." C'TTTKII. 
 
 Number of Sweat Glands. The number of sweat glands may 
 be as high as 3,500 in a square inch, and the average is estimated at. 
 2,800 per square inch ; as there are about 2,500 square inches of body 
 surface, it is readily computed that there are several millions of sweat, 
 glands. 
 
 Number of Hairs on the Human Head. The average number 
 of hairs on the head is 120,000. They are set obliquely, and are con- 
 trolled by muscles so that they may be made to stand erect, or nearly so, 
 under the influence of certain emotions, as fear, anger, etc. 
 
 Huxley and others have classified the races of men according to the 
 hair, into the Ulotrichi, or crisp or woolly haired division, including 
 the negroes, bushmen, etc. ; and Leiotrichi, or smooth-haired, sub- 
 divided into the Australioid, the Mongoloid, the Xanthochroic, and the 
 Melanochroic. 
 
 In Europeans the hair is oval in cross-section ; in the Japanese 
 and Chinese it is circular. 
 
 Circulation. Rate of blood flow : in the large arteries, from 12 to 
 16 inches a second ; in the caval veins, about 4 inches a second ; in the 
 capillaries, from 1 inch to 1.5 inches a minute. A portion of the blood 
 makes the complete circulation (in a horse) in less than half a minute. 
 This is found by putting some readily detected chemical into one jugular 
 vein, and noting how soon it appears in the other jugular vein. The 
 time necessary for all the blood to pass through the heart is estimated 
 as follows : Each ventricle pumps about six ounces of blood at each 
 stroke. At this rate thirty strokes, 25 to 50 seconds (or less), would 
 have pumped all the blood in the body. Still, some of the blood (from 
 the shorter circuits) may have been pumped twice, and some (from the 
 longer routes) may not yet have been around once. And since the 
 total amount of blood has been only approximately determined, these 
 figures are not very accurate. 
 
 Number of blood corpuscles to the cubic inch, about 83,000,000. 
 
 Dr. Tanner's Forty Days' Fast (Newspaper Account). No 
 Food but "Water Taken. When Dr. Tanner came to New York 
 from Minnesota he weighed 184 pounds. He was six weeks making ar- 
 
VITAL STATISTICS. 
 
 355 
 
 rangernents for his fast; and when lie began his experiment his weight 
 was 157 pounds. He weighed 121 pounds on the day his fast ended. 
 He had therefore lost 62 \ pounds since he came to the city, and 3(3 
 pounds since he began his fast. Dr. Hammond, the well-known New 
 York physician whose assertion that a forty days' fast was a physical 
 impossibility led Dr. Tanner to make the attempt, came out in "a card 
 in the New York papers declaring that he believed the fast had been 
 fairly conducted. 
 
 On each day of his fast Dr. Tanner weighed as follows : 
 
 DAY. 
 
 1st 
 
 POUNDS. 
 
 DAY. 
 
 25th 
 
 POUNDS. 
 
 1314, 
 
 3d 
 
 ... 153 
 
 20th 
 
 . " . . . . I3ld 
 
 5th 
 7th 
 
 . . . 147 
 . 1434 
 
 27th ..... 
 28th . . 
 
 129! 
 
 llth 
 13th 
 14th 
 
 . . . 139| 
 133 
 
 29th ..... 
 30th 
 31st 
 
 130 
 
 16th 
 
 . . . 132 
 
 32d 
 
 1274 
 
 17th (8.30 P.M.) . . 
 17th (HAM) 
 
 135^ 
 
 33d 
 34th 
 
 i2e| 
 
 18th 
 19th 
 
 136 
 
 35th 
 36th . ... 
 
 
 20th (4 P.M.) . . . 
 20th (5 A.M.) . . . 
 21st . 
 
 . . . . 135 
 
 . . . . 1 35 
 
 37th 
 38th 
 39th 
 
 1224 
 
 22d 
 
 1334 
 
 40th 
 
 1214 
 
 26th ...... 
 
 
 
 
 Cavities of the Body. 1. Mucous cavities (open to the external 
 air). Digestive tube, respiratory passages, genito-urinary passages, ex- 
 ternal and middle ear, etc. 
 
 2. Serous cavities (closed). They may all be said to be lymph cav- 
 ities. They are the lymph spaces throughout the body, and the large 
 spaces, called the pleural cavity around the lungs, the pericardial cavity 
 around the heart, the peritoneal cavity in the abdomen, the arachnoid 
 cavity around the brain, and a similar one along the spinal cord. 
 
 3. Synovial cavities in the joints. 
 
 4. Blood cavities, the inside of the heart and blood tubes. 
 
 5. Secretion cavities, the cavities and tubes from the glands ; for 
 example, the bile sac and its duct. 
 
 6. Bone cavities. 
 
356 
 
 PHYSIOLOGY. 
 
 LOSSES OF THE TISSUES DURING STARVATION*. 
 (FROM KXPKRIMEXT ON A CAT.) 
 
 Fat los's:'. per i-Mit. 
 
 Blood .... ;.-> 
 
 Spleen .... "71 " 
 
 Pancreas ... "64 " 
 
 Stomach ... "39 " 
 
 Pharynx, gullet . " 34 " 
 
 Skin " 33 " 
 
 Kidneys. ... "31 " 
 
 Liver . " 52 " 
 
 Heart .... 
 
 Intestines . . . 
 
 Muscles of locomo- 
 tion .... 
 
 Respiratory appa- 
 ratus . . . 
 
 Bones .... 
 
 Eyes 
 
 Nervous system . 
 
 loses 44 per cent. 
 
 " 42 
 
 " 42 " 
 
 " 22 " 
 
 " 16 
 
 " 10 " 
 
 " 2 " 
 
 QUANTITY OF WATER IN 1,000 PARTS. 
 
 Teeth 100 Bile 880 
 
 Bones 130 Milk H87 
 
 Cartilage 550 Pancreatic juice 900 
 
 Muscles 750 Urine 936 
 
 Ligament 768 Lymph 960 
 
 Brain * . . 789 Gastric juice 975 
 
 Blood 795 Sweat 986 
 
 Synovia 805 Saliva W"> 
 
 THE LOSS OF WATER FROM THE BODY. 
 
 From the Alimentary canal (feces) 4 per cent. 
 
 " Lungs 20 
 
 " " Skin (perspiration) 30 " 
 
 " " Kidneys (urine) 46 " 
 
 ELEMENTS IN THE HUMAN BODY. 
 
 Oxygen 72.0 Chlorin .085 
 
 Carbon 13.5 Fluorin 08 
 
 Hydrogen 9.1 Potassium .026 
 
 Nitrogen 2.5 Iron 01 
 
 Calcium 1.3 Magnesium 0012 
 
 Fosforus 1.15 Silicon 0002 
 
 Sulfur 147 Copper, lead, aluminum . (traces) 
 
 Sodium 1 100. 
 
 DAILY RATION OF A U. S. SOLDIER DURING THE LATE WAR. 
 
 Bread or flour 22 oz. 
 
 Fresh or salt beef (or pork or bacon 12 oz.) 20 
 
 Potatoes (three times a week) 16 " 
 
VITAL STATISTICS. 
 
 357 
 
 Rice 
 Coffee (or tea 0-.24 oz.) . . 
 
 
 
 
 . ... 1.6 
 ... 1.6 
 . . . . 2.4 
 
 
 
 
 
 64 
 
 Vinegar 
 Salt 
 
 COMPOSITION OF F< 
 
 WATKU. PROTEIDS. 
 
 
 32 
 
 30DS. 
 
 FATS. 
 
 16 
 
 CARBO- 
 
 
 
 
 
 HYDRATES. 
 
 Beef, lean 
 
 72 
 
 19.3 
 
 3.6 
 
 
 Beef, fat 
 
 51 
 
 14.8 
 
 29.8 
 
 
 Mutton, lean .... 
 
 72 
 
 18.3 
 
 4.9 
 
 
 Mutton, fat .... 
 
 53 
 
 12.4 
 
 31.1 
 
 
 Veal 
 
 63 
 
 16.5 
 
 15.3 
 
 
 Pork, fat 
 
 39 
 
 9.8 
 
 48.9 
 
 
 Poultry 
 
 74 
 
 21 
 
 3.8 
 
 
 Whitefish 
 
 78 
 
 18.1 
 
 2.9 
 
 
 Salmon 
 
 77 
 
 16.1 
 
 5.5 
 
 
 Eels (rich in fat) . . 
 
 75 
 
 9.9 
 
 13.8 
 
 
 Oysters 
 
 75.7 
 
 11.7 
 
 2.4 
 
 
 
 
 
 
 SUGAR. 
 
 Milk 
 
 86 
 
 4.1 
 
 3.9 
 
 5.2 
 
 Buttermilk .... 
 
 88 
 
 4.1 
 
 .7 
 
 6.4 
 
 Cream 
 
 66 
 
 2.7 
 
 26.7 
 
 2.8 
 
 Cheese, full .... 
 
 36 
 
 28.4 
 
 31.1 
 
 . . . 
 
 Cheese, skim .... 
 
 44 
 
 44.8 
 
 6.3 
 
 
 Eggs, white . . . . 
 
 78 
 
 20.4 
 
 
 
 Eggs, yelk . . ... 
 
 52 
 
 16 
 
 30.7 
 
 . . . 
 
 
 
 
 
 STARCH. 
 
 Bread 
 
 37 
 
 8.1 
 
 1.6 
 
 51 
 
 Flour 
 
 15 
 
 10.8 
 
 2 
 
 70.8 
 
 COMPOSITION 
 
 OF THE 
 
 BLOOD. 
 
 
 Water 
 
 
 
 
 
 Solids 
 
 
 
 
 
 Corpuscles .... 
 
 
 
 
 . 130 
 
 Proteids (of serum) 
 
 
 
 
 . 70 
 
 Fibrin (of clot) . . 
 
 
 
 
 2.2 
 
 Fatty matters (of serum) 
 
 1.4 
 
 Inorganic salts . . 
 
 
 
 
 6.0 
 
 Gases, urea, kreatin, 
 
 etc. . . 
 
 
 
 6.4 
 
 gill. 
 
 5.1 
 4.4 
 
 4.8 
 
 4.7 
 2.3 
 1.2 
 1.0 
 1.4 
 2.7 
 2.7 
 
 .8 
 .8 
 4.9 
 4.5 
 4.9 
 1.6 
 1.3 
 
 2.3 
 1.7 
 
 784 
 
 216 
 1000 
 
358 PHYSIOLOGY. 
 
 COMPOSITION OF CASTKK' ,11 K'K. 
 
 Water 99.44 
 
 Solids 
 
 Pepsin 319 
 
 Salts 218 
 
 Hydrochloric acid 02 
 
 .557 
 100 
 
 Fluids of the Body (FORD). 1. Circulating fluids, chyle, 
 lymph, blood. 
 
 2. Fluids for digestion, saliva, gastric juice, pancreatic juice, bile, 
 intestinal juice. 
 
 3. Fluids of closed cavities, of the arachnoid, pleura!, pericardia!, 
 and peritoneal sacs, of joints, of the eye and ear, and of cells. 
 
 4. Secretions for protection, cerumen or wax, tears, fluid of mucous 
 membranes, oily fluids on the surface of the body. 
 
 5. Fluids for discharge, intestinal secretion, renal or kidney se- 
 cretion, perspiration, vapor from the lungs, etc. 
 
 Acids and Alkalies of the Body. Acids, gastric juice, mu- 
 cus, chyme, contents of large intestine. 
 
 Alkalies, saliva (or neutral), pancreatic juice, intestinal juice, 
 bile (or neutral), contents of small intestine, sweat. 
 
 Amount of Digestive Liquids. The amount of saliva secreted 
 daily is estimated at from 1 to 3 pints, of gastric juice from 10 to 20 pints, 
 of bile from 2 to 3 pints. The amount of intestinal and other juices is 
 difficult to estimate. But it is readily seen that a very large amount of 
 liquid is daily separated from the blood to be used in the preparation of 
 the food for absorption into the blood. This is to be looked upon as an 
 investment. It is supposed to be reabsorbed with large returns in addi- 
 tion to the prepared food ; and if anything interferes with the absorp- 
 tion of the food material, especially if the secretion goes on, it is plain 
 that bankruptcy will follow as surely as in the business world whenever 
 there is a continual expenditure without corresponding returns. The 
 condition known as "diarrhea" illustrates this condition, perhaps, as 
 well as any well-known condition of the body. 
 
 Specific Gravity of the Liquids of the Body. As all the 
 liquids of the body have dissolved and suspended in them various salts 
 and other matters, they are all heavier than water. 
 
VITAL STATISTICS. 359 
 
 Alcohol and Longevity. Investigation by Baer has shown that the 
 average expectation of life among users and dealers in alcoholic liquors 
 is very much shortened. The following table gives a comparative view of 
 the expectation of life in those who abstained from and those who used 
 alcohol : 
 
 EXPECTATION OF LIFE. 
 
 AGE. ABSTAINERS. ALCOHOL USERS 
 
 At 25, 32.08 years, 26.23 years. 
 
 "' 35, 25.92 " 20.01 " 
 
 " 45 J 9.92 " * i$.i9 " 
 
 " 55' '4-45 " "- 16 " 
 
 " 65, 9.62 " 8.04 " 
 
 TABLE SHOWING THE INFLUENCE OF ALCOHOL UPON THE 
 MORTALITY FROM VARIOUS DISEASES. 
 
 GENERAL MALE POPULATION. ALCOHOL VENDERS. 
 
 Brain disease, 11.77 P er cent - r 4-43 per cent. 
 
 Tuberculosis, 30.36 " 36.57 " 
 
 Pneumonia and pleuritis, 9.63 " H-44 " 
 
 Heart disease, 1.46 " 3.29 " 
 
 Kidney disease, 1.40 " 2.11 " 
 
 Suicide, 2.99 " 4.02 " 
 
 Cancer, 2.49 " 3.70 " 
 
 Old age, 22.49 " 7-5 " 
 
GLOS BA RY. 
 
 Albumen (al-bu'-meri). The white of an egg. 
 
 Albumin (iil-hi'i'-min). A proteid substance, the chief constituent of 
 the body. Its molecule is highly complex, and varies widely within 
 certain limits in different organs and in different conditions. 
 
 Albuminuria (al-bu'-mi-nu'-ri-a}. The presence of albumin in tin- urine, 
 indicating changes in the blood or in the kidneys. 
 
 Amylopsin (am-i-lop'-xin}. A ferment said to exist in pancreatin. 
 
 Anabolism (an-ab'-o-lizm}. Synthetic or constructive metabolism. 
 Activity and repair of function ; opposed to katabolism. 
 
 Arbor Vitae (ar'-6or vl'-te). A term applied to the branched appear- 
 ance of a section of the cerebellum. 
 
 Argon (ar'-gron). A newly discovered element similar to nitrogen 
 (found in the air). 
 
 Arytenoid (ar-i-te'-noid}. Resembling the mouth of a pitcher, as the 
 arytenoid cartilages of the larynx. 
 
 Atlas (at'-las). The uppermost of the cervical vertebrae (from the 
 mythical Atlas who supported the Earth). 
 
 Auricle (aw'-ri-kl). The auricles of the heart are the two cavities be- 
 tween the veins and the ventricles. Also, the pinna and external 
 meatus of the ear. 
 
 Axis (ak'-sis). The second cervical vertebra, on which the head, with 
 the atlas, turns. 
 
 Bacterium (bak-te'-ri-um}, pi. bacteria. A genus of microscopic fungi 
 characterized by short, linear, inflexible, rod-like forms without 
 tendency to unite into chains or filaments. 
 
 Biceps (bl'-seps}. Biceps brachii, the flexor of the arm. 
 
 Bicuspid (bi-kus'-pid}. Having two points ; the bicuspid or premolar 
 teeth; the bicuspid valve, between the left auricle and the left ven- 
 tricle. 
 
 Brachial (bra'-ke-al or brak'-i-al}. Pertaining to the arm. 
 
 360 
 
GLOSSARY. 361 
 
 Bronchus (brong' -kits'), pi. bronchi. The two tubes into which the tra- 
 chea divides opposite the third thoracic vertebra, called respectively 
 the right and left bronchus. 
 
 Caffein (kaf'-e-in'). An alkaloid that occurs in the leaves and beans of 
 the coffee-tree, in Paraguay tea, etc. 
 
 Canaliculus (kan-a-Uk'-u-lus^), pi. canaliculi. The crevices extending 
 from lacunae, through which nutrition is conveyed to all parts of 
 the bone. 
 
 Canine (ka-nl)i' or ka'-nin*). The conical teeth between the incisors 
 and the premolars. 
 
 Capillary (kap'-i-la-ri or ka-pil'-a-ri). A minute blood-tube connecting 
 the smallest ramification of the arteries with those of the veins. 
 
 Capsule (kap'-auV). A tunic or bag that incloses a part of the body or 
 an organ. 
 
 Carbohydrate (kar-bo-hi'-draf). An organic substance containing six 
 carbon atoms or some multiple of six, and hydrogen and oxygen in 
 the proportion in which they form water; that is, twice as many 
 hydrogen as oxygen atoms. Starches, sugars, and gums are carbo- 
 hydrates. 
 
 Cardiac (kar'-di-ak}. Pertaining to the heart. 
 
 Carotid (ka-rot'-id}. The principal right and left arteries of the neck. 
 
 Carpus (kar'-pus). Belonging to the wrist; as the carpal bones. 
 
 Cartilage (kar'-ti-luj}. Gristle of various kinds, articular, etc. 
 
 Casein (ka'-se-m). A derived albumin, the chief proteid of milk, pre- 
 cipitated by acids and by rennet at 40C. 
 
 Cecum (se'-kum). The large blind pouch or cul-de-sac, in which the 
 large intestine begins. 
 
 Centrum (sen'-trum). The center or middle part ; the body of a verte- 
 bra, exclusive of the bases of the neural arches. 
 
 Cerebellum (ser-e-bel'-um*). The inferior part of the brain, lying below 
 the cerebrum. 
 
 Cerebrum (ser'-e-brum'). The chief portion of the brain, occupying the 
 whole upper part of the cranium. 
 
 Cervical (ser'-m-kal}. Pertaining to the neck, as cervical vertebrae. 
 
 Chordae tendineae (kor'-de}. The tendinous cords connecting the 
 fleshy columns of the heart with the auriculo-ventricular valves. 
 
 Choroid (ko'-roid}. The second or vascular coat of the eye, continu- 
 ous with the iris in front, and lying between the sclerotic and the 
 retina. 
 
362 
 
 Chyle (kll). The milk-white fluid absorbed by tin- lacteals during di- 
 gestion. 
 
 Chyme (kirn'). Food that has undergone gastric digestion, and has not 
 yet been acted upon hy the biliary, pancreatic, and intestinal 
 secretions. 
 
 Cilium (stT-i-um), pi. cilia. The eyelashes; also the hair-like appen- 
 dages of certain epithelial cells, whose function is to propel fluid 
 or particles along the passages that they line. 
 
 Ciliary (sil'-i-a-ri). Pertaining to the eyelid or eyelash ; also by ex- 
 tension to the ciliary apparatus or the structure related to the 
 mechanism of accommodation. Pertaining to the cilia. 
 
 Circumvallate (sir-kum-val'-at). Surrounded by a wall or prominence, 
 as the circumvallate papillae on the tongue. 
 
 Clavicle (klav'-i-kl). The collar-bone. 
 
 Coccyx (kok'-siks). The last bone of the spinal column, formed by the 
 union of four rudimentary vertebrae. 
 
 Cochlea (kok'-le-a). A cavity of the internal ear, resembling a snail- 
 shell. 
 
 Conjunctiva (kon-junyk-ti'-va). The mucous membrane covering the 
 anterior portion of the globe of the eye, reflected on, and extending 
 to, the free edge of the lids. 
 
 Corpus Arantii (kor'-pus). The tubercles, one in the center of each 
 segment of the semilunar valves. 
 
 Corpuscle (kor'-pus-l). A name loosely applied to almost any small, 
 rounded or oval body, as the blood corpuscles. 
 
 Cortex (kor'-teks}. Bark. The outer layer of gray matter of the brain ; 
 the outer layer, cortical substance, of the kidney. 
 
 Cricoid (krl'-koid}. Ring-shaped, as the cricoid cartilage of the 
 larynx. 
 
 Dentine (den'-tin}. The ivory-like substance constituting the bulk of 
 the tooth, lying under the enamel of the crown and the cement 
 of the root. 
 
 Diabetes (di-a-be'-tez*}. The name of two different affections, diuln-t<-x 
 mellitn*, or persistent glycosuria, and diabetes insipidus, or polyu- 
 ria, both characterized, in ordinary cases, by an abnormally large 
 discharge of urine. The former is distinguished by the presence 
 of an excessive quantity of sugar in the urine. 
 
 Dialysis (di-ar-i-*is\ The operation of separating crystalline from 
 colloid substances by means of a porous diaphragm, the former 
 
GLOSSARY. 363 
 
 passing through the diaphragm into the pure water upon which the 
 dialyzer rests. 
 
 Digastric (di-yas'-trik). Having two bellies, as the digastric muscle, 
 enlarged near each end and with a tendon in the middle. 
 
 Duodenum (du-d-de'-num). The first part of the small intestine, begin- 
 ning with the pylorus. 
 
 Emulsion (e-inul'-shun}. Water or other liquid in which oil, in minute 
 subdivision of its particles, is suspended. 
 
 Enamel (eM-am'~el). The hard covering of the crown of a tooth. 
 
 Endothelium (en-do-the'-li-um). The internal lining membrane of 
 serous, synovial, and other internal surfaces, the homolog of epi- 
 thelium. 
 
 Enzyme (en'-zim}. Any chemic or hydrolytic ferment, as distinguished 
 from organized ferments such as yeast; unorganized ferment. 
 
 Epiglottis (ep-i-ylot'-is). A thin fibro-cartilaginous valve that aids in 
 preventing food and drink from passing into the larynx. 
 
 Esophagus (e-8Q/ y -a-grt*). The musculo-membranous tube extending 
 from the pharynx to the stomach. 
 
 Eustachian (u-sta'-ki-an). Eustachian tube, the tube leading from the 
 middle ear to the pharynx. 
 
 Facet (fas'-et}. A small plane surface. The articulating surface of a 
 bone. 
 
 Femur (/e'-mer). The thigh-bone. 
 
 Ferment (fer'-ment}. Any micro-organism, proteid, or other chemic 
 substance capable of producing fermentation, i.e., the oxidation 
 and disorganization of the carbohydrates. 
 
 Fibrin (fi'-brin}. A native albumen or proteid, a substance that, be- 
 coming solid in shed blood, plasma, and lymph, causes coagulation 
 of these fluids. 
 
 Fibula (fib'-u-la}. The smaller or splint bone in the outer part of the 
 leg, articulating above with the tibia, and below with the astraga- 
 lus and tibia. 
 
 Filiform (Jll'-i-forni). Thread-like, as the filiform papillae. 
 
 Frontal (fron'-tal). Belonging to the front, as the frontal bone. 
 
 Fungiform (fun'-ji-form). Having the form of a mushroom, as fungi- 
 form papillae. 
 
 Ganglion (yany'-gli-on\ pi. ganglions or ganglia. A separate and semi- 
 independent nervous center, communicating with other ganglia or 
 nerves, with the central nervous system, and peripheral organs. 
 
364 
 
 Gastric (yas'-trik^). Pertaining to the stomach. 
 
 Gelatin (jel'-a-tin). An albuminoid substance of jelly-like consistence, 
 obtained by boiling skin, connective tissue, and bones of animals 
 in water. The glue of commerce is an impure variety. 
 
 Glosso-pharyngeal (glox'-o-fa-rin'-je-al). Pertaining to the tongue and 
 larynx. 
 
 Gluten (ylo'-ten). A substance resembling albumin, and with which it 
 is probably identified ; it occurs abundantly in the seeds of cereals. 
 
 Glycogen (yll'-ko-jen}. A white amorphous powder, tasteless and odor- 
 less, forming an opalescent solution with water, and insoluble in 
 alcohol. It is commonly known as animal starch. It occurs in the 
 blood and in the liver, by which it is elaborated, and is changed by 
 diastasic ferments into glucose. 
 
 Gustatory (gus'-ta-to-ri}. Pertaining to the special sense of taste and 
 its organs. 
 
 Hashish (JtaM'-etA). A preparation from Indian hemp, Cannabis in- 
 dica. It is a powerful narcotic. 
 
 Haversian (ha-ver'-zian*). Haversian canal, in bone, a central opening 
 for blood-tubes, surrounded by a number of concentric rings, or 
 lamellae, of bone. 
 
 Hemoglobin (hem-o-ylo'-bin}. A substance existing in the corpuscles of 
 the blood, and to which their red color is due. 
 
 Hepatic (he-pat' -ik). Pertaining or belonging to the liver. 
 
 Hilum (hl'-lum}. A small pit, scar, or opening in an organic structure ; 
 the notch on the internal or concave border of the kidney. 
 
 Humerus (hu'-me-rus}. The bone of the upper arm. 
 
 Humor (/m'-wor). Any liquid, or semi-liquid, part of the body. 
 
 Hyoid (hl'-oid}. Having the form of the letter U. The hyoid bone 
 situated between the root of the tongue and the larynx, supporting 
 the tongue and giving attachment to its muscles. 
 
 Hypo-glossal (hi-po-ylos'-al}. Under the tongue. 
 
 Iliac (tT-t-rtJfc). Pertaining to the ilium, or region of the flanks, as iliac 
 artery, vein, etc. 
 
 Incisor (m-sf-sor). The chisel-shaped front teeth. 
 
 Inhibition (in-hi-bish'-un). The act of checking, restraining, or sup- 
 pressing ; any influence that controls, retards, or restrains. Inhib- 
 itory nerves and centers are those intermediating a modification, 
 stoppage, or suppression of a motor or secretory act already in 
 progress. 
 
GLOSSARY. 365 
 
 Innominate (i-nom'-i-nate). Nameless ; a term applied to several parts 
 of the body to which no other definite name has been given, as the 
 innominate bone, artery, vein, etc. 
 
 Invertin (in'-ver-tln\ A ferment found in the intestinal juice, and also 
 produced by several species of plants ; it converts cane-sugar in 
 solution into invert sugar. 
 
 Jugular (jo'-gu-lar^. Pertaining to the throat, as the jugular vein. 
 
 Katabolism (ka-tab'-o-lizm). Analytic or destructive metabolism ; a 
 physiologic disintegration ; opposed to anabolism. 
 
 Lacrymal (lak'-ri-mal}. Having relation to the organs of the secretion, 
 transfer, or excretion of tears. 
 
 Lacuna (la-ku'-na}. A little hollow space ; especially the microscopic 
 cavities in bone occupied by the bone corpuscles, and communicat- 
 ing with one another and with the haversian canals and the sur- 
 faces of the bone through the canaliculi. 
 
 Lamella (fti-mel'-a), pi. lamellae. A thin lamina, scale, or plate ; of 
 bone, the concentric rings surrounding the haversian canals. 
 
 Larynx (lar'-inyks). The upper part of the air passage between the 
 trachea and the base of the tongue ; the voice-box. 
 
 Legumin (le-grw'-rain). A proteid compound in the seeds of many plants 
 belonging to the natural order Leguminosae (peas, beans, lentils, 
 etc.). 
 
 Lumbar (lum'-bcir\ pertaining to the loins, especially to the region 
 about the loins. 
 
 Lymphatic (lim-fat'-ik}. Pertaining to lymph. 
 
 Lymphatics (lim-fat'-iks). The tubes that convey lymph. 
 
 Lymphatic glands. The glands intercalated in the pathway of the 
 lymphatic tubes, through which lymph is filtered. 
 
 Massage (ma-sazh'). A method of effecting changes in the local and 
 general nutrition, action and other functions of the body, by rub- 
 bing, kneading, and other manipulation of the superficial parts of 
 the body by the hand or an instrument. 
 
 Masseter (mas'-e-ter^). A chewing-muscle felt on the angle of the 
 jaw. 
 
 Medullary (med'-u-la-ri}. Pertaining to the medulla, or marrow ; re- 
 sembling marrow. Also pertaining to the white substance of the 
 brain contained within the cortical envelop of gray matter. 
 
 Mesenteric (mez-en-ter'-ik}. Pertaining to the mesentery, as artery, 
 vein, etc. 
 
366 GLOSS. IK}: 
 
 Mesentery ^nez'-cn-lrr-i}. A fold of the peritoneum that connects cer- 
 tain portions of the intestine with the dorsal abdominal wall. 
 
 Metabolism (me-ta&'-d-Jtem). A change in the intimate condition of 
 cells ; (1) constructive or synthetic metabolism is called Anabo- 
 lism ; in anabolism, the substance is becoming more complex and 
 is accumulating force ; (2) destructive or analytic metabolism is 
 called Katabolism : in katabolism there is disintegration, the mate- 
 rial is becoming less complex, and there is loss or expenditure of 
 force. 
 
 Metacarpus (met-a-kirr'-imx). The bones of the palm of the hand. 
 
 Metatarsus (met-a-tar'-ms). The five bones of the arch of the foot, 
 situated between the tarsus and the phalanges. 
 
 Mitral (nil'-trtil). Resembling a miter; mitral valve, with two Hups, 
 between the left auricle and the left ventricle. 
 
 Molar (mo'-far). Mill; the grinding-teeth. 
 
 Mucous (wu'-fctw). A term applied to those tissues that secrete mucus. 
 
 Mucus (mu'-kus). A viscid liquid secretion of mucous membranes, 
 composed essentially of inucin, holding in suspension desquamated 
 epithelial cells, etc. 
 
 Myosin ( wi'-o-sm). A proteid of the globulin class, the chief proteid 
 of muscle. Its coagulation after death causes riyor mortis. 
 
 Narcosis (nar-ko'-sis) . The deadening of pain, or production of incom- 
 plete or complete anesthesia by the use of narcotic agents, such as 
 anesthetics, opium, and other drugs. 
 
 Narcotic (nar-kotf-ic}. A drug that produces narcosis. 
 
 Neural (nu'-ral). Pertaining to the nerves. 
 
 Neuroglia (nu-rog'-li-a*). The reticulated framework or skeleton-work 
 of the substance of the brain and spinal cord. The term is some- 
 times abbreviated to glia. 
 
 Nucleus (nu'-kle-us). The essential part of a typical cell, usually round 
 in outline, and situated in the center. 
 
 Occipital (ok-sip'-i-tal}. Pertaining to the occiput or back part of the 
 head, as the occipital bone. 
 
 Odontoid (o-don'-toid). Resembling a tooth ; the tooth-like process 
 (axis) of the second cervical vertebra, on which the atlas turns. 
 
 Olfactory (ol-fak'-to-ri}. Pertaining to the sense of smell. 
 
 Osmosis (os-wio'-sts)- That property by which liquids and crystalline 
 substances in solution pass through porous septa ; endosmosis and 
 exosmosis. 
 
GLOSSARY. 367 
 
 Oxy-hemoglobin (ok-ai-hem-o-ylo'-bin). Hemoglobin united, molecule 
 for molecule, with oxygen. It is the characteristic constituent of 
 the red corpuscles to which the scarlet color of arterial blood is 
 due. 
 
 Pancreas (pan'-krc-as^. A large racemose gland lying transversely 
 across the dorsal wall of the abdomen. It secretes a clear liquid 
 for the digestion of proteids, fats, and carbohydrates. The sweet- 
 bread of animals, vulgarly called the "belly sweet-bread" in con- 
 tra-distinction to the thymus, or true sweet-bread. 
 
 Pancreatin (pan'-krv-a-t'm}. The active element of the pancreatic juice. 
 
 Papilla (pa-pil'-a}, pi. papillae. Any soft, conical elevation, as papillae 
 of the dermis, tongue, etc. 
 
 Papillary (pap'-i-la-ri}. Pertaining to a papilla; papillary muscles, 
 the conic muscular columns of the heart, to which the chordae 
 tendineae are attached. 
 
 Parietal (pa-ri'-e-tal). Pertaining to the walls, as the parietal bone. 
 
 Parotid (pa-rot'-id). Near the ear, as the parotid salivary glands. 
 
 Patella (pa-tel'-a}. The knee-pan. 
 
 Peptone (pep'-ton}. A proteid body produced by the action of peptic 
 and pancreatic digestion. 
 
 Pericardium (per-i-kar'-di-um}. The closed membranous sac or cover- 
 ing, that envelops the heart. 
 
 Periosteum (per-i-os'-te-um*). A fibrous membrane that invests the 
 surfaces of the bones, except at the points of tendinous and liga- 
 mentary attachments, and on the articular surfaces where cartilage 
 is substituted. 
 
 Peristaltic (per-i-stal'-tik}. The peculiar movement of the intestine 
 and other tubular organs, consisting in a vermicular shortening 
 and narrowing of the tube, thus propelling the contents onward. 
 It is due to the successive contractions of the bundles of longitudi- 
 nal and circular muscular fibers. 
 
 Peritoneal (per-i-to-ne'-al}. Pertaining to the peritoneum. 
 
 Peritoneum (per-l-to-ne'-um*). The serous membrane lining the interior 
 of the abdominal cavity, and surrounding the contained viscera. 
 The peritoneum forms a closed sac, but is rendered complex in its 
 arrangement by numerous foldings produced by its reflection upon 
 the viscera. 
 
 Phalanges (fa-lan'-jez), plural of phalanx (fa'-lanyks~). Any one of 
 the bones of the fingers or toes. 
 
368 GLOSS. 1A'\ \ 
 
 Pharynx ^/'-/m/^- The cavity back of the soft palate. It commu- 
 
 nicates anteriorly with the posterior nares, laterally with the eusta- 
 
 chian tubes, ventrally with the mouth, and posteriorly with the 
 
 gullet and larynx. 
 Plasma (plaz'-ma). The original undifferentiated substance of IUIM rut, 
 
 living matter. The fluid part of the blood and lymph. 
 Pleura (]>Hj'-rii). The serous membrane which envelops the lungs, and 
 
 which, being reflected back, lines the inner surface of the thorax. 
 Plexus (plek'-sus). An aggregation of vessels or nerves forming an 
 
 intricate net-work. 
 Pneumogastric (nu-md-gas'-trik). Pertaining conjointly to the lungs 
 
 and the stomach, or to the pneumogastric or vagus nerve. 
 Portal (por'-tal). Pertaining to the porta (gate) or hi him of an organ, 
 
 especially of the liver, as the portal vein. 
 Postcaval (post-ka'-ioal}. Pertaining to the postcava; the postcaval 
 
 vein, formerly called the inferior vena cava, or vena cava ascendens. 
 Precaval (pre-kaf-mil}. Pertaining to the precava; the anterior caval 
 
 vein, formerly called the superior vena cava, or vena cava de- 
 
 scendens. 
 
 Pronation (pro-na'-shun^). The turning of the palm downward. 
 Protoplasm (pro'-to-plazm). An albuminous substance, ordinarily re- 
 
 sembling the white of an egg, consisting of carbon, oxygen, nitro- 
 
 gen, and hydrogen in extremely complex and unstable molecular 
 
 combination, and capable, under proper conditions, of manifesting 
 
 certain vital phenomena, such as spontaneous motion, sensation, 
 
 assimilation, and reproduction, thus constituting the physical basis 
 
 of life of all plants and animals. 
 Ptyalin (tl'-a-lin}. An amylolytic or diastasic ferment found in saliva, 
 
 having the property of converting starch into dextrin and sugar. 
 Pulmonary (pul'-mo-na-ri). Pertaining to the lungs. 
 Pylorus (pi-lo'-rus). The opening of the stomach into the duodenum. 
 Radius (ra'-di-us). The outer of the bones of the forearm. 
 Renal (re'-naV). Pertaining to the kidneys. 
 Rennin (ren'-w). An enzyme, or ferment, to whose action is due the 
 
 curdling or clotting of milk produced upon the addition of ren- 
 
 net. 
 Retina (ret'-i-na}. The chief and essential peripheral organ of vision; 
 
 the third or internal coat or membrane of the eye, made up of the 
 
 end organs or expansion of the optic nerve within the globe. 
 
GLOSSARY. 369 
 
 Sacrum (sa'-kruni). A curved triangular bone, composed of five con- 
 solidated vertebrae, wedged between the two iliac (pelvic) bones, 
 
 and forming the dorsal boundary of the pelvis. 
 Scapula (skap'-u-la). The shoulder-blade. 
 Sciatic (si-at'-ik}. Pertaining to the ischium; the sciatic nerve, the 
 
 main nerve of the thigh. 
 Sclerotic (skle-rot'-ik). Hard, indurated; pertaining to the outer coat 
 
 of the eye. 
 Semilunar (sem-i-lu'-nar}. Resembling a half-moon in shape; semilu- 
 
 nar valves, pocket-like valves at the beginning of the aorta and 
 
 pulmonary artery. 
 Serous (se'-rus). Pertaining to, characterized by, or having the nature 
 
 of, serum. 
 Serum (se'-rum*). The yellowish fluid separating from the blood after 
 
 the coagulation of the fibrin. 
 
 Solar plexus (so'-lar). Solar, with radiations resembling the sun. 
 Sphincter (sfinyk'-ter'), A muscle surrounding and closing an orifice. 
 Splenic (splen'-ik). Pertaining to the spleen. 
 Steapsin (sep'-,sm). A diastasic ferment which causes fats to combine 
 
 with an additional molecule of water and then split into glycerine 
 
 and their corresponding acids. 
 Sternum (ster'-num}. The breast-bone. 
 Subclavian (sub-kla'-vi-an). Situated under the collar-bone ; subcla- 
 
 vian artery and vein. 
 Sublingual (sub-ling 1 '-ywal). Lying beneath the tongue, as sublingual 
 
 gland. 
 Submaxillary (sub-mak '-si-la-ri}. Lying beneath the lower maxilla, as 
 
 submaxillary salivary gland. 
 
 Supination (su-pi-na'-shun}. The turning of the palm upward. 
 Synovia ($i-no'-vi-a). The lubricating liquid secreted by the synovial 
 
 membranes in the joints. 
 
 Tarsus (ar'-sws). The instep, consisting of seven bones. 
 Temporal (tem'-po-ral). Pertaining to the temples, as temporal artery, 
 
 vein, muscle, etc. 
 Tetanus (tet'-a-nus}. A spasmodic and continuous contraction of the 
 
 muscles, causing rigidity of the parts to which they are attached. 
 Thein (the'-in). An alkaloid found in tea. 
 
 Theobromin (Mr-o-bro'-mm). A feeble alkaloid obtained from cacao- 
 butter ; the essential substance found in cocoa and chocolate. 
 
37O GLOSS A A'\' 
 
 Thyroid (thi'-roid). Shield-shaped, as the thyroid cart ilage of the 
 larynx. 
 
 Tibia (tib'-i-a). The larger (inner) of the two hones of tin- leg, com- 
 monly called the shinbone. 
 
 Trachea (tra-ke'-a or tra'-kc-it). The windpipe. 
 
 Triceps (tri'-seps). Triceps of the arm, the extensor of the arm. lyinu 
 along the back of the humerus. 
 
 Tricuspid (trl-kim'-piil). Having three cusps or points, as the trienspid 
 valve. 
 
 Trypsin (trip'-sin}. The proteolytic ferment of pancreatic juice. 
 
 Ulna (ul'-na). The larger (inner) of the two bones of the forearm. 
 
 Ureter (fi-re'-ter). The tube conveying the urine from the pelvis of the 
 kidney to the bladder. 
 
 Vaso-constrictor (rr/.x'-o-A-on-N/r/A-'-f <>/). Causing a constriction of the 
 blood-vessels. 
 
 Vaso-dilator (a*'-d-cK4a / -tor). Pertaining to the positive dilating mo- 
 tility of the non-striated muscles of the vascular system. 
 
 Vaso-motor (vas-o-ino'-tor). Serving to regulate the tension of the 
 blood-vessels, as vaso-motor nerves ; including vaso-dilator and 
 vaso-constrictor mechanisms. 
 
 Ventricle (ven'-tri-kl). Applied to certain structures having a bellied 
 appearance. The cavities of the heart from which the blood is 
 forced out through the arteries. 
 
 Vesicle (ves'-i-kl}. A small, membranous, bladder-like formation, as 
 air vesicle. 
 
 Villus (wT-its), pi. villi. One of the numerous minute vascular projec- 
 tions from the mucous membrane lining the small intestine, for ab- 
 sorbing digested food. 
 
 Vitreous O*T-re-w). Glass-like, as the clear, jelly-like, vitreous humor 
 of the eye. 
 
INDEX. 
 
 Abdomen, cross section of, i6f. 
 Abdominal respiration, 95. 
 Absorption, 181. 
 
 Of fats, 182, 183. 
 
 From stomach, 175. 
 Accommodation, 291. 
 Acids, indigestion, 179. 
 
 Fatty, 179. 
 
 In poisoning, 323. 
 
 Tasting, 302. 
 Action of large arteries, 49. 
 
 Of gullet, 171. 
 
 Of heart, 45 ; rhythmic, 65. 
 
 Of diseased kidneys, 197. 
 
 Of muscle, 9. 
 
 Of ciliary muscle, 291. 
 
 Reflex, 30, 32, 263. 
 Adam's apple, 309. 
 Adjustment of lens, 290. 
 Afferent currents, 268. 
 
 Nerve fibers, 27, 28, 32. 
 
 Nerve roots, 33, 31. 
 After-images, 295. 
 
 Negative, 295 ; Positive, 295. 
 After-pressure, 281. 
 Air, complemental, 96, 97. 
 
 Composition of, 100. 
 
 Currents about stoves, 116. 
 
 Expired, 102. 
 
 Reserve, 96, 97. 
 
 Residual, 96, 97. 
 
 Sacs, 84, 91. 
 
 In the sickroom, 325. 
 
 Tidal, 96, 97. 
 
 Vesicles, 84, 91, 103. 
 
 Washed, 119. 
 Albinos, 288. 
 Albumen, 145. 
 
 Albuminuria, 199. 
 Alcohol, 208. 
 
 In the army, 216, 217. 
 
 Binz, 218. 
 
 Brunton, 250. 
 
 And circulation, 70. 
 
 Clum, 252. 
 
 And cold climates, 209. 
 
 And crime, 208. 
 
 Crothers, 251. 
 
 Effects of, 210, 223. 
 
 And energy, 208, 212. 
 
 And excesses, 252. 
 
 Greely, 216. 
 
 Halliburton, 222. 
 
 And heat, 209. 
 
 Hornaday, 221. 
 
 Howell, 212. 
 
 Luce, 260. 
 
 Martin, 253. 
 
 M'Kendrick, 222. 
 
 Miura, 213. 
 
 Moral deterioration, 253. 
 
 As a narcotic, 210. 
 
 And nerve centers, 251. 
 
 And nervous system, 250. 
 
 As a poison, 210. 
 
 Reichert, 213. 
 
 Rohe, 218. 
 
 Stanley, 216. 
 
 Stevenson and Murphy, 250. 
 
 As a stimulant, 210. 
 
 Thompson, 214. 
 
 And training, 209. 
 
 In the tropics, 221. 
 
 And water, 210. 
 
 Woodhull, 216. 
 
 Woodruff, 217. 
 
 371 
 
372 
 
 INDEX. 
 
 Alcoholic beverages, 218. 
 Alkalies, in digestion, 179. 
 
 In poisoning, 323. 
 Alveoli, of the lungs, 84. 
 Ameba, 5. 
 Amount of blood, 75. 
 
 Of food needed, 193. 
 
 Of perspiration, 136. 
 
 Of saliva, 168. 
 Amylopsin, 178. 
 Anabolism, 203. 
 Anatomy defined, 3. 
 
 And sculpture, 346. 
 Anesthetics, 254. 
 Animal matter, 338, 339. 
 
 Protoplasm, 202. 
 Animals and plants, 205. 
 Antidotes to poisons, 322, 347. 
 Aorta, 44, 177. 
 Apex beat of heart, 49. 
 Apoplexy, 248. 
 Appendicular skeleton, 330. 
 Appendix, vermiform, 187. 
 Aqueous humor, 288, 289. 
 Arch, neural, 330, 331. 
 Aristotle's experiment, 266. 
 Arm, bleeding from, 314. 
 Arrangement of teeth, 164. 
 
 Of muscles, 341, 
 
 Arterial muscle, exercise of, 233. 
 Arteries, large, action of, 49. 
 
 Bleeding from, 314. 
 
 Distribution of, 44. 
 
 And exercise, 69. 
 
 Regulation of size, 68. 
 
 Structure of, 51. 
 Artery, carotid, 44, 314. 
 
 Gastric, 44. 
 
 Hepatic, 44, 177. 
 
 Iliac, 44. 
 
 Mesenteric, 177. 
 
 Pancreatic, 44. 
 
 Pulmonary, 42, 43. 
 
 Renal, 44. 
 
 Splenic, 44. 
 
 Subclavian, 44. 
 Articulating process, 331. 
 Articulations of vertebra, 335. 
 Artificial life, i. 
 
 Renewal of air, 116. 
 
 Auditory center, 244, 264. 
 
 Nerve, 239, 238, 305. 
 Auricles of heart, 41, 47. 
 
 Contraction of, 46. 
 Asiatic cholera, Bacillus of, 123. 
 Association fibers, 264. 
 Astigmatism, 292. 
 Atlas, 335. 
 Axial skeleton, 330. 
 Axis, 335 ; axis cylinder, 27, 28. 
 
 Bacilli, types of, 123. 
 
 Bacillus, of Asiatic cholera, 123. 
 
 Of diphtheria, 123. 
 
 Of hog cholera, 123. 
 
 Tuberculosis, 122, 123 
 
 Of typhoid fever, 123. 
 Bacteria, 124. 
 
 Of putrefaction, 127. 
 Baking meat, 156. 
 
 Powder bread, 189. 
 Ball and socket joint, 339. 
 Bandaging, 328. 
 Barley, 149. 
 Baseball, 229. 
 Bathing, 232. 
 
 The sick, 326; Time for, 233. 
 Bath mils. 232. 
 Baths, cold, 232; warm, 233. 
 Beans, dried, 189. 
 Bear, hibernation of, 201. 
 Bedding, changing in sickroom. 326. 
 Bee-stings, 324. 
 Beef extract, 155. 
 
 Tea, 155. 
 Beets, 189. 
 
 Beverages containing alcohol, 218. 
 Biceps, 8, 15. 
 Bicuspid teeth, 164. 
 Bicycling, 230. 
 Bile, 177. 
 
 Duct, 186, 177. 
 
 Functions of, 178. 
 
 Sac, 160, 186. 
 
 Bites of cats, 324; dogs, 324; snakes, 324. 
 Bitters, taste of, 302. 
 Blackberries, 189. 
 
 Bleeding from arm, 314; arteries, 314; 
 neck, 314; nose, 315; veins, 315. 
 Blind spot, 293. 
 
INDEX. 
 
 373 
 
 Blindness, color, 295. 
 
 Blister, 132. 
 
 Blood, amount of, 75. 
 
 Changes in, 106. 
 
 Chemical reaction of, 75. 
 
 Coagulation of, 74. 
 
 Color of, 73. 
 
 Composition of, 71. 
 
 Of frog, 73. 
 
 Gases of, 104. 
 
 And glands, 134. 
 
 Mixture of good and bad, 196. 
 
 Quantity in different organs, 75. 
 
 Renewal of, 200. 
 
 And river, 195. 
 
 Specific gravity of, 75. 
 
 Transfusion of, 81. 
 
 Work of, 39. 
 Blood-flow, and exercise, 107. 
 
 And lymph-flow, 77, 78. 
 
 Rate of, 59. 
 
 Blood-pressure, of ventricle, 46. 
 Blood-stream and sewer, 199. 
 Blood-supply of brain, 247. 
 
 Of stomach, 173. 
 Blood-tubes joining heart, 42. 
 Blowing, 96. 
 Blushing, 68. 
 Boats upsetting, 321. 
 Body, care of, 2. 
 
 And locomotive, 109. 
 
 Temperature of, 108. 
 Boiled milk, 189. 
 
 Boiling meat, 156 ; boiling water, 152. 
 Bone, composition of, 338. 
 
 Corpuscles, 337. 
 
 Lamellae of, 337. 
 Bone, structure of, 18, 337. 
 Bones, broken, 317. 
 
 Of ear, 305, 306. 
 
 Hygiene of, 339. 
 
 Lightness and strength of, 20. 
 
 Relation to muscles, 15. 
 
 Table of, 333. 
 
 Uses of, 21, 330. 
 
 Weight of, 337. 
 Bow-legs, 339. 
 Boxing, 229. 
 Brain, 235. 
 
 Blood-supply of, 247. 
 
 Brain centers, connection of, 263. 
 
 Convolutions and intelligence, 240. 
 
 Ganglia of, 241. 
 
 Gray matter of, 241. 
 
 Hemispheres of, 240. 
 
 Location of functions, 244. 
 
 Parts of, 235. 
 
 Preservation of, 236. 
 
 Rest, 246, 247. 
 
 And sensation, 30, 243. 
 
 The water-cushion of, 248. 
 
 White matter of, 241. 
 
 Work, 246. 
 Bread, hot, 189. 
 Breathing, effect on circulation, 98. 
 
 Deep, 97, 98. 
 
 Hygiene of, 97. 
 
 Through mouth, 98. 
 
 Restoring, 320. 
 
 And swallowing, 170, 171. 
 Broiling meat, 156. 
 Broken bones, 317. 
 Bronchi, 43. 
 Bruises, 340. 
 Bulb, hair, 130. 
 
 Olfactory, 303. 
 
 Spinal, 245, 246. 
 Burning clothing, 316. 
 Burns, treatment of, 316. 
 
 Cabbage, 189. 
 
 Caffein, 155. 
 
 Cake, 189. 
 
 Calf muscle of frog, 9. 
 
 Camel's hump, 201. 
 
 Canaliculi, 338. 
 
 Canals, haversian, 337, 338. 
 
 Canals, semicircular, 305, 306. 
 
 Candle, heat of, 205. 
 And respiration, 201. 
 
 Cane sugar, 179. 
 
 Canine teeth, 164. 
 
 Capacity of lungs, 97, 96. 
 Vital, 97. 
 
 Capillaries, blood-flow in, 55 ; of frog's 
 web, 52, 53 ; of lung, 91 ; of 
 muscle, 54 ; pulmonary, 86. 
 
 Capsule of lens, 289. 
 
 Carbohydrate food, 147. 
 
 Carbohydrates, 147. 
 
374 
 
 Carbon dioxid of air, 100, 102; in blood, 
 i<xj ; in bivatli, 102; in wells, 322. 
 Care of body, importance of, 2. 
 
 Of ears, 307. 
 
 Of eyes, 295. 
 
 Of lamps in sickroom, 328. 
 
 Of the sick, 324, 325. 
 
 Of teeth, 166. 
 Carotid artery, 44, 314. 
 Carpal bones, 333. 
 Carpus, 332, 333. 
 Cartilage, 19. 
 
 Cricoid, 309. 
 
 Intervertebral, 335. 
 
 Thyroid, 309. 
 Cartilages of windpipe, 86. 
 Casein, 144, 145. 
 Cataract, 293. 
 Cats, bites from, 324. 
 Cauliflower, 189. 
 Cauterizing, 324. 
 Cavities, lymph, 80. 
 
 Serous, 80. 
 
 Of skeleton, 337. 
 Cavity, pulp, 163, 164. 
 Cecum, 1 86. 
 Celery, 189. 
 Cells, aquatic, 79. 
 
 Ciliated, 86. 
 
 Division of, 5. 
 
 Of epidermis, 53. 
 
 Epithelial, 4. 
 
 Fat, 130. 
 Cells and lymph, 79, 200. 
 
 Muscle, 5, 345. 
 
 Nerve, 5, 28. 
 
 And oxygen, 107. 
 
 Pigment, 52, 53. 
 
 Poisoning of, 200. 
 
 Starvation of, 200. 
 
 Structure of, 4. 
 Center of control of circulation, 68. 
 
 For hearing, 244, 264. 
 
 Respiratory, 99. 
 
 Of sensation, 243, 245. 
 
 For speech, 245, 264. 
 
 For vision, 264. 
 Centrum, 330. 
 Cerebellum, 236, 245. 
 Cerebral cortex, functions of, 243. 
 
 Cerebro-spinal system, cat, 26. 
 
 Of man, 24, 25. 
 Cerebrum, 235, 241. 
 Cervical vertebrae, 332, 333. 
 Cesspools, 151. 
 Change of voice, 313. 
 Cheese, 147, 189, 191. 
 Chemical composition of bone, 338. 
 Chemistry of respiration, too. 
 Children, exercise of, 228. 
 Chloral hydrate, 257. 
 Chloroform, 257. 
 Chocolate, 155, 189, 212. 
 Choking, 96. 
 Cholera, Asiatic, bacillus of, 123. 
 
 Hog, bacillus of, 123. 
 Choroid coat, 287. 
 Churning in the stomach, 174. 
 Chyle, receptacle of, 184, 186. 
 Chyme, 175. 
 
 Cider, 212; fermentation of, 121, 212. 
 Cigarettes, 259. 
 Cigars, 258. 
 Cilia, 87. 
 Ciliary muscle, 290, 291. 
 
 Process, 288. 
 Ciliated cells, 86. 
 Circulation and alcohol, 70. . 
 
 Control of, 64. 
 
 Diagram of, 60, 196, 197, 198. 
 
 In frog's web, 52, 53, 54. 
 
 In gray matter, 249. 
 
 In muscle, 54. 
 
 Plan of, 60. 
 
 Portal, 177. 
 
 In white matter, 249. 
 Circumvallate papillae, 302. 
 Classification of senses, 271. 
 Clavicle, 332, 333. 
 Cleanliness of eyes, 298. 
 Climate and alcohol, 209. 
 Clothing, regulating heat, 138. 
 
 Effect of wet, 139. 
 Coagulation of blood, 74. 
 
 Of muscle plasma, 346. 
 Coat, choroid, 287. 
 
 Sclerotic, 287. 
 
 Coats of eye, 287 ; of stomach, 172. 
 Cocaine, 257. 
 Coccyx, 332, 333, 335. 
 
INDEX. 
 
 375 
 
 Cochlea, 305, 306. 
 Cocoa, 155, 189. 
 Coffee, 155, 189, 212. 
 Cold baths, 232. 
 
 Spots, 283. 
 
 Taking, 231. 
 Colds and deafness, 307. 
 Colon, 187. 
 Color blindness, 295. 
 
 Of blood, 73, 105. 
 
 Sensations, 294. 
 
 Of skin, 132. 
 Colored corpuscles, 71. 
 Colorless corpuscles, 72. 
 
 As germ destroyers, 126. 
 Column, spinal, 334. 
 Common sensations, 272. 
 Compass points and touch, 281. 
 Complemental air, 97. 
 Composition of air, 100. 
 
 Of blood, 71. 
 
 Of bone, 338. 
 
 Of sweat, 135. 
 Conduction of heat, 137. 
 Cones and rods, 293, 292. 
 Conjunctiva, 286. 
 Connective tissue, n, 12. 
 Consciousness, 243. 
 Conservation of energy, 206. 
 Consonants and vowels, 312. 
 Constipating foods, 189. 
 Constipation, 178, 188. 
 Consumption, danger from, 122. 
 Contraction of auricle, 46. 
 
 Of ventricle, 46. 
 Control of diaphragm, 100. 
 
 Of mind, 247. 
 
 Of respiration, 99. 
 Convalescence and reading, 298. 
 Convection of heat, 137. 
 Conversation at meals, 192. 
 Convolutions of brain, 235, 240. 
 
 And intelligence, 240. 
 Convulsions, 346. 
 Cooking, 155. 
 Coordination, 245. 
 
 Cord, spinal, 24 ; reflex action of, 30, 32. 
 Cords, tendinous, 41, 46 ; vocal, 309. 
 Corn, 148, 189. 
 Cornea, 288. 
 
 Corpuscles of blood, 72, 53. 
 
 Bone, 337. 
 
 Colored, 71, 72, 104. 
 
 Colorless, 72, 126. 
 
 Touch, 279. 
 
 Correlation of energy, 206. 
 Cortex, cerebral, functions of, 243. 
 Coughing, 95. 
 
 Covering of brain, 235 ; of heart, 40. 
 Cracked wheat, 189. 
 Crackers, 189. 
 Cramps, 35. 
 
 Cranial nerves, 237, 242. 
 Cream, 144. 
 Cricoid cartilage, 309. 
 Crime and alcohol, 208. 
 Crossing of nerve fibers, 35, 243. 
 Crown of tooth, 163. 
 Crying, 95. 
 
 Crystalline lens, 288, 289. 
 Culture of voice, 313. 
 Curdling in stomach, 174. 
 Currents, afferent, 268, 269; efferent, 
 
 268; induction, 266. 
 Curvature of spine, 339. 
 Custard, 189. 
 
 Cutaneous sensations, 278. 
 Cylinder, axis, 27. 
 
 Danger of consumption, 122. 
 
 Dead dust, 119. 
 
 Deafness and colds, 307. 
 
 Deep breathing, 99. 
 
 Defects in eyesight, 291. 
 
 Deliberation in eating, 192. 
 
 Dental formula, 164. 
 
 Dentine, 163, 164. 
 
 Dermis, 132. 
 
 Desserts, 191. 
 
 Dextrose, 179. 
 
 Diabetes, 199. 
 
 Dialysis, 182. 
 
 Diaphragm, 85, 87, 88, 177, 344. 
 
 Control of, 99. 
 Diarrhea, 231. 
 Diastole, 47. 
 
 Diet, errors of, 193; mixed, 153; one- 
 sided, 153; proper, 154. 
 Diffusion of gases, 115; of liquids, 182. 
 Digestion, hygiene of, 190. 
 
3/6 
 
 Digestion, organs of, 160. 
 
 Outline of, 187. 
 
 Time in stomach, 175. 
 Digestive tube, 159. 
 Dilation of ventricle, 47. 
 Diphtheria, bacillus of, 123. 
 Direct heating, 118. 
 Disease germs, 122. 
 
 Of lungs, 126. 
 
 Prevention of, 126. 
 Dislocations, 339. 
 Distribution of arteries, 44 ; of veins, 44. 
 
 Of heat, 138. 
 Division of cells, 5. 
 
 Of labor, physiological, 4. 
 Dogs, bites from, 324. 
 Double windows, 119. 
 Dreams, 266. 
 Dried fish, 189. 
 Drink, hot, 191. 
 Drinking, 96. 
 
 Water, 152. 
 Dropsy, 80. 
 
 Drowned, treatment of, 317. 
 Drowning, resuscitation from, 317. 
 Duodenum, 160. 
 Dura mater, 235. 
 Dust, avoiding, 124. 
 
 Dead, 119; live, 121. 
 
 And lungs, 120. 
 
 Sources of, 120. 
 Dusting, 125. 
 
 Ear, bones of, 305, 306. 
 
 Care of, 307. 
 
 External, 305. 
 
 Internal, 306. 
 
 Middle, 305. 
 
 Parts of, 305. 
 
 Use of, 307. 
 Eating between meals, 193. 
 
 Deliberation in, 192. 
 
 Time of, 193. 
 Eddy, living, 199. 
 Efferent nerve currents, 268. 
 
 Nerve fibers, 27, 32, 33. 
 Eggs, 146. 
 Electric light, 296. 
 Emetic, mustard, 323. 
 Emulsion, 147, 179. 
 
 Enamel, 163, 164. 
 Energy and alcohol, 208. 
 
 Conservation of, 206. 
 
 Correlation of, 206. 
 
 From food, 204. 
 
 Utilization of, 205. 
 Ennui, 95. 
 
 Entire wheat flour, 148. 
 Enzymes, 169. 
 Epidermis, 53, 131. 
 I Epiglottis, 170, 171, 310. 
 Epithelial cells, 4. 
 Equilibrium sense, 306. 
 Errors in diet, 193. 
 Essentials of reflex action, 32. 
 Ethmoid bone, 333. 
 Eustachian tube, 306, 305, 170, 171. 
 Evaporation of sweat, 137. 
 Evening reading, 297. 
 Excretion, 130; of urea, 202. 
 Exercise of arterial muscles, 233. 
 
 And bathing, 226. 
 
 And blood-flow, 107. 
 
 Forms of, 228. 
 
 And health, 226. 
 
 And heat, 137. 
 
 And long life, 227. 
 
 And size of arteries, 69. 
 Expiration, elastic reactions of, 94. 
 Explosion in muscles, no. 
 Expression, muscles of, 345. 
 Extensor muscle, 8. 
 External ear, 305. 
 Extract of beef, 155. 
 Eye, coats of, 287. 
 
 Dissection of, 287. 
 
 External parts of, 286. 
 
 Movements of, 287. 
 
 Muscles, 286, 288. 
 
 Protection of, 285. 
 
 Section of, 288. 
 
 Structure of, 288. 
 Eyes, of albinos, 288. 
 
 Care of, 295. 
 
 Cleanliness of, 298. 
 
 Irritation of, 298. 
 
 Pain in, 294. 
 
 Pigment in, 288. 
 
 Resting, 297. 
 
 Sympathy between, 294. 
 
INDEX, 
 
 377 
 
 Eyeball, muscles of, 286. 
 Eyeglasses, 292. 
 Eyesight, defects of, 291. 
 Eyestrain, 299. 
 
 Facial expression, 345. 
 
 Nerves, 238. 
 Fainting, 316, 248. 
 Fans, ventilating, 117. 
 Far-sight, 291, 292. 
 Farina, 189. 
 Fat cells, 130. 
 
 And muscles, 346. 
 
 As a tissue, 201. 
 Fats, 147. 
 Fatty acids, 179. 
 
 Fatigue, 246, 272 ; from standing, 268. 
 Femur, 18, 332, 333. 
 Fever, typhoid, 151. 
 Fiber, muscle, plain, 50, 344. 
 
 Muscle, striated, n, 12, 344. 
 
 Nerve, 28. 
 
 Fibers, association, 264. 
 Fibrin, 74, 145. 
 Fibula, 333. 
 Filiform papillae, 301. 
 Fish, 146; dried fish, 189. 
 Flavors, 302. 
 
 Flexibility of spinal column, 335. 
 Flexion of forearm, 16. 
 Flexor muscle, 8, 13. 
 Flexure, sigmoid, 188. 
 Floating, 321. 
 
 Flour, entire wheat, 148; Graham, 148. 
 Flow of lymph, 77. 
 Flues, ventilating, 115. 
 Food, amount needed, 193. 
 
 Object of, 159. 
 
 Regulating temperature, 138. 
 
 For the sick, 327. 
 
 Source of energy, 204. 
 Foods, 144. 
 
 Constipating, 189 ; laxative, 189. 
 
 Preservation of, 127. 
 Foodstuffs, 144, 145. 
 Foot asleep, 37 ; as kind of lever, 17. 
 Football, 229. 
 
 Force, indestructibility of, 204. 
 Forced respiration, 94. 
 Forms of exercise, 228 ; of muscles, 341. 
 
 Formula, dental, 164. 
 Foul air shafts, 117. 
 Frog, blood of, 73. 
 
 Without cerebrum, 241. 
 
 Muscle action of, 9. 
 Frontal bone, 332, 333. 
 Fruits, 150. 
 
 Acid, 189. 
 
 Pies, 189. 
 
 Puddings, 189. 
 Frying, 156. 
 Fulcrum, 16. 
 Function, defined, 3. 
 
 Of cerebellum, 245. 
 
 Of cerebral cortex, 243. 
 
 Of cerebrum, 241. 
 
 Of nerve fibers, 28. 
 
 Of nerve roots, 33. 
 
 Of skin, 136. 
 
 Of spinal bulb, 245. 
 
 Of spinal cord, 29. 
 Fungiform papillae, 301. 
 Furnaces, 117. 
 
 Gain and loss of body, 195. 
 Game, wild, 189. 
 Games of children, 228. 
 Ganglia, 29; of brain, 241. 
 
 Sympathetic, 65. 
 Ganglion of dorsal root, 26, 29. 
 Gargling, 95. 
 Gases of blood, 104. 
 
 Diffusion of, 115. 
 
 Gastric glands, 173 ; juice, 173, 174. 
 Gelatin, 145. 
 
 General sensations, 271, 272. 
 Germs of disease, 122. 
 Glands and blood supply, 134. 
 
 Compound, 133. 
 
 Essentials of, 134. 
 
 Gastric, 173. 
 
 Intestinal, 176. 
 
 Lacrymal, 286. 
 
 Lymphatic, 77, 183. 
 
 Mucous, 169. 
 
 Oil, 130. 
 
 Salivary, 166. 
 
 Simple, 133, 135. 
 
 Sweat, 133. 
 Glasses, wearing, 299. 
 
3/8 
 
 INDEX. 
 
 Gliding joints, 339. 
 Glossopharyngeal nerves, 239. 
 Glottis, 170, 171. 
 Gluten, 145. 
 Glycogen, 178, 202. 
 Graham flour, 148. 
 Grains, 147. 
 Granula, 189. 
 Grape sugar, 179. 
 Grates as ventilators, 114. 
 Gravity and circulation, 61. 
 Gray matter of brain, 241. 
 
 Matter, circulation in, 249. 
 
 Matter of spinal cord, 28, 29, 31. 
 Gray nerve fibers, 28. 
 Gullet, 160, 170, 171, 186. 
 
 Habit, 212. 
 
 Acquired reflex action, 267. 
 Hair, 130, 133 ; bulb, 130. 
 Hammer bone, 333. 
 Hard palate, 170. 
 Harmony in muscle action, 21, 36. 
 Hauser, Kaspar, 271. 
 Haversian canals, 337. 
 Hawking, 95. 
 
 Headaches from eyestrain, 299. 
 Health, i. 
 Hearing, 304. 
 Heart, action of, 45 ; rhythmic, 64. 
 
 Auricles of, 41, 46. 
 
 Beat of, 39, 49. 
 
 Blood tubes joining, 42. 
 
 Covering, 40. 
 
 Dissection of, 42. 
 
 Muscle, 344. 
 
 Nourishment of, 61. 
 
 Position of, 40. 
 
 Size of, 41. 
 
 Sounds of, 49. 
 
 Structure of, 41. 
 
 Valves of, 41. 
 
 Ventricles of, 41, 46. 
 
 Work and rest of, 48. 
 Heat and alcohol, 209. 
 
 Conduction of, 137. 
 
 Convection of, 137. 
 
 Distribution of, 138. 
 
 And exercise, 137. 
 
 From oxidation, 109. 
 
 Heat, production of, 106. 
 
 Radiation of, 137. 
 
 Ways of giving off, 137. 
 Heating, direct, 118; indirect, 118. 
 Hemispheres of brain, 235, 240. 
 Hemoglobin, 74, 104. 
 Hemorrhage of lungs, 315. 
 
 Of stomach, 315. 
 
 Hepatic arteries, 177 ; veins, 177, 186. 
 Hibernation, 201. 
 Hiccuping, 95. 
 Hinge joint, 339. 
 Hoarseness, 313. 
 Hog cholera, bacillus of, 123. 
 Hope in illness, 325. 
 Hot drink, 191. 
 Humerus, 332, 333. 
 Humor, aqueous, 288, 289. 
 
 Vitreous, 288, 289. 
 Hump, camel's, 201. 
 Hunger, 276. 
 Hyaloid membrane, 289. 
 Hygiene of bones, 339. 
 
 Of breathing, 97. 
 
 Defined, 3. 
 
 Of digestion, 190. 
 Hyoid bone, 333. 
 Hypoglossal nerve, 240. 
 
 Ice water, 152. 
 
 Ignoring nerve currents, 266. 
 Iliac arteries, 44 ; veins, 44. 
 Image, inversion of, 290. 
 Immovable joints, 339. 
 Importance of retina, 293. 
 Impulse, nerve, 28, 36. 
 
 Transmission of, 36. 
 Impurities in water, 151. 
 Incisor, 164. 
 Incus, 333. 
 Indestructibility of force, 204. 
 
 Of matter, 203. 
 Indirect heating, 118. 
 Induction current, 266. 
 Inebriety, Clum, 260; Crothers, 260. 
 
 A disease, 253. 
 
 Palmer, 260. 
 Inhibition, 67. 
 Innominate bones, 333. 
 Insertion of muscle, 10, 15. 
 
INDEX. 
 
 379 
 
 Inspiration, 91 ; and expiration, 92. 
 
 Forces of, 94. 
 
 Resistances to, 94. 
 
 Intelligence, 243; and convolutions, 240. 
 Interference with reflex action, 35. 
 I ntervertebral cartilages, 335. 
 Intestine, 176, 177. 
 
 Large, 186, 188 ; small, 160, 176, 186. 
 Intestinal glands, 176, 179. 
 Inversion of image, 290. 
 Invertin, 179. 
 Iris, 288. 
 
 Iron, in blood, 74. 
 Irritant poisons, 323. 
 Irritation of eye, 298. 
 Ivy poisoning, 324. 
 
 Jacketed stoves, 117. 
 Joints, 19, 339. 
 Judgment, 266. 
 Jugular vein, 44. 
 Juice, gastric, 173. 
 
 Intestinal, 179. 
 
 Lime, 150. 
 
 Pancreatic, 177. 
 
 Kaspar Hauser, 271. 
 Katabolism, 203. 
 Kidneys, 139. 
 
 Diseased, 197. 
 
 And skin, 141, 142. 
 Kinds of teeth, 164. 
 
 Labor, physiological division of, 4. 
 Lacrymal bone, 333 ; gland, 286. 
 Lacteals, 181, 184, 186. 
 Lacunoe of bone, 337. 
 Lamellae, of bone, 337. 
 Lamps, in sickroom, 328. 
 Larynx, from above, 311. 
 
 Structure of, 310. 
 Lateral process, 331. 
 Laughing, 95. 
 Laxative foods, 189. 
 Leather, 132. 
 Ledger of body, 195. 
 Legumin, 145. 
 Lens capsule, 289. 
 
 Crystalline. 288, 289. 
 
 Levers, 16, 17. 
 
 Life, artificial, i ; natural, I. 
 
 Processes, 203. 
 Ligament, suspensory, 288. 
 Ligaments, 19. 
 Light, electric, 296. 
 
 In sickroom, 325. 
 
 Strength of, 297. 
 Lingering of sensations, 267. 
 Live dust, 121. 
 Liver, 177, 160. 
 
 As food, 189. 
 
 Position, 85. 
 
 Starch, 178. 
 Lobes, olfactory, 237. 
 Local sign, 281. 
 
 Location of brain functions, 244. 
 Locomotion, 19; by reaction, 20. 
 Loss and gain of body, 195. 
 Loudness of voice, 311. 
 Lumbar vertebrae, 332, 333, 335. 
 Lung diseases, 126. 
 Lungs, 87. 
 . Parts of, 84. 
 
 Capacity of, 97. 
 
 Dorsal view of, 43. 
 
 Hemorrhage of, 315. 
 Lymph, 79. 
 
 Cavities, 80. 
 
 Flow of, 77. 
 
 Importance of, 80. 
 
 Renewal of, 200. 
 
 Spaces, 75. 
 
 Tubes, 76. 
 
 Variations in, 80. 
 Lymphatic glands, 77, 183. 
 Lymphatics, 183, 184. 
 
 Malar bone, 333. 
 
 Malleus, 333. 
 
 Malted milk, 155. 
 
 Massage, 81. 
 
 Masseter muscle, 8. 
 
 Mastication, imperfect, 192. 
 
 Matter, animal, in bone, 338, 339. 
 
 Indestructibility of, 203. 
 
 Mineral in bone, 338, 339. 
 Maxilla, inferior, 333. 
 
 Superior, 333. 
 Meals, conversation at, 192. 
 
INDEX. 
 
 Meat, 146; baking, 1^6; boiling, 156; 
 broiling, 156 ; roasting, 156 ; salted, 
 189 ; smoked, 189. 
 Mechanism, of body, 2. 
 Media, refracting of eye, 289. 
 Medullary sheath, 27. 
 Membrane, hyaloid, 289. 
 Memory, 267. 
 Meningitis, 248. 
 Mesentery, 161, 186. 
 Mesenteric artery, 177 ; vein, 186. 
 Metabolism, 203. 
 Metacarpus, 333, 334. 
 Metatarsal bones, 333. 
 Metatarsus, 332, 333. 
 Middle ear, 305. 
 Milk, 144, 146. 
 
 Boiled, 189; Malted, 155. 
 
 Souring of, 127. 
 
 Teeth, 164. 
 Mind, control of, 247. 
 Mineral matter in bone, 338, 339. 
 Mitral valve, 41. 
 Mixed diet, 153. 
 
 Joints, 339. 
 
 Modification of respiration, 95. 
 Molars, 164. 
 Molds, 121. 
 Morphia, 255. 
 Morphine, 255. 
 Motion, experiments with, 7. 
 
 Involuntary, 24. 
 
 And locomotion, 19. 
 
 Production of, 106. 
 
 Voluntary, 24. 
 
 Mouth, 162 ; breathing through, 98. 
 Movable joints, 339. 
 Movements of eye, 287. 
 
 Of respiration, 91. 
 
 Mucous glands, 169; Membrane, 86, 87. 
 Mucus, 169. 
 Muscle, action of, 9. 
 
 Capillaries of, 54. 
 
 Explosion in, no. 
 
 Insertion of, 10, 15. 
 
 Normal condition of, 13. 
 
 Origin of, 10, 15. 
 
 Shortening, 13, 24. 
 
 Structure of, 10, n. 
 Muscle-action, harmony in, 36. 
 
 Muscle-action, laws of, 12. 
 Muscle-cells, 5, 345; of heart, 344. 
 Muscle-fiber, a cell, 345. 
 Muscle-fibers compared, 344. 
 
 Plain, in artery, 50. 
 
 Plain and striated, 52, 344. 
 
 In lymph tubes, 77. 
 Muscle-plasma, coagulation of, 346. 
 Muscles, arrangement of, 341. 
 
 Arterial, exercise of, 233. 
 
 Biceps, 8. 
 
 Ciliary, 290, 291. 
 
 Of expression, 345. 
 
 Of eyeball, 286, 288. 
 
 And fat, 346. 
 
 Forms of, 341. 
 
 Importance of, 12. 
 
 Names of, 344. 
 
 Number of, 341. 
 
 Papillary, 46. 
 
 Relation to bone, 15. 
 
 Size of, 341. 
 
 Skeletal, 15. 
 
 Sphincter, 175. 
 
 Superficial, 342, 343. 
 
 Symmetrical development of, 14. 
 
 Temporal, 9. 
 
 Triceps, 8. 
 Muscular exertion and urea, 202. 
 
 Power, loss of, 37. 
 
 Sense, 272. 
 
 Sense and sight, 274. 
 Myosin, 145. 
 
 Nails, 133. 
 
 Rusty, wounds from, 323. 
 Names of muscles, 344. 
 Narcosis, 254. 
 Narcotics, 254, 257. 
 Nasal bones, 333. 
 Nature, punishments, i, 227. 
 
 Of sensation, 264. 
 Nausea, 272. 
 Near sight, 291, 292. 
 Neck, bleeding from, 314. 
 
 Of tooth, 163, 164. 
 Negative after-images, 295. 
 Nerve cells, 5, 28. 
 
 Centers, 29. 
 
 Currents afferent and efferent, 268, 269. 
 
INDEX. 
 
 Nerve, currents ignoring, 266. 
 
 Endings, in skin, 278. 
 
 Fibers, crossing of, 35, 243. 
 
 Fibers, destination of, 33. 
 
 Fibers, function of, 28. 
 
 Fibers, gray, 28. 
 
 Fibers, sheath of, 28. 
 
 Fibers, similarity of, 262. 
 
 Fibers, structure of, 27, 28. 
 
 Impulse, 28, 36. 
 
 Roots, functions of, 33. 
 
 Stimuli, 261. 
 
 Supply of heart, 66. 
 
 Supply of tongue, 302. 
 Nerves, Auditory, 239, 305. 
 
 Cranial, 237, 242. 
 
 Of diaphragm, 100. 
 
 Effect of pressure, 37. 
 
 Facial, 238. 
 
 Glossopharyngeal, 239. 
 
 Of hearing, 242, 305. 
 
 Of heart, 66. 
 
 Hypoglossal, 240. 
 
 Olfactory, 238, 303. 
 
 Optic, 237, 238, 288. 
 
 Pneumogastric (see vagus). 
 
 Sciatic of frog, 9. 
 
 Of smell, 303. 
 
 Spinal, 26. 
 
 Structure of, 27. 
 
 Of taste, 302, 301. 
 
 Trigeminal, 237. 
 
 Trophic, 251. 
 
 Vagus, 66, 239. 
 
 Vaso-constrictor, 67. 
 
 Vaso-dilator, 67. 
 
 Vaso-motor, 68. 
 
 Nervous impulse, nature of, 28, 36. 
 Nervous system and alcohol, 250. 
 
 Cerebro-spinal, 24. 
 
 Sympathetic, 65, 66. 
 
 And telegraph, 268. 
 Nervous tissue and starvation, 247. 
 Neural arch, 330; ring, 330. 
 Neuralgia and cold baths, 233. 
 Neuroglia, 241. 
 Nicotine, 258. 
 Nitrogen in air, 100. 
 Nose, bleeding from, 315. 
 Nourishment of heart, 61. 
 
 Nucleus, 4; of ciliated cell, 86; of epi- 
 dermic cell, 53. 
 Nurse, qualities of, 325. 
 Nursing, 325 ; books on, 328. 
 Nutrition, 202. 
 Nuts, 191. 
 
 Oats, 149. 
 
 Occipital bone, 332. 333. 
 
 Oculist, consultation of, 299. 
 
 Odontoid process, 335. 
 
 Oil gland, 130. 
 
 Olfactory bulb, 303, 238, 242. 
 
 Lobes, 237, 242. 
 
 Nerves, 303, 242, 238. 
 Onions, 189. 
 Opium, 255. 
 
 Optic nerves, 237, 242, 288, 297. 
 Organ, defined, 3. 
 Organs of digestion, 160. 
 
 Ledger account of, 195. 
 Origin, of muscle, 10, 15. 
 Osmosis, 182. 
 Outline of digestion, 187. 
 Oxidation, source of heat, 109. 
 
 Of tissues, 107. 
 Oxygen in the air, 100. 
 
 Amount used, 104. 
 
 In blood, 104. 
 
 Storage in tissues, no. 
 Oxy-hemoglogin, 104. 
 Oysters, 189. 
 
 Pain, 274; extent of, 275. 
 
 In eyes, 294. 
 
 A general sense, 276. 
 Palate bone, 333. 
 
 Hard, 170, 171. 
 
 Sense of taste in, 302. 
 
 Soft, 160, 170, 171. 
 Pancreas, 160, 177, 186. 
 Pancreatic duct, 186. 
 
 Juice, 177, 178. 
 Panting, 96. 
 Papillae, circumvallate, 303. 
 
 Filiform, 301. 
 
 Fungiform, 301. 
 
 Of skin, 130, 131, 279. 
 
 Of tongue, 301. 
 Papillary muscles, 46. 
 
382 
 
 INDEX. 
 
 Parietal bone, 332, 333. 
 
 Parotid salivary gland, 186. 
 
 Pastry, 189. 
 
 Patella, 332, 333. 
 
 Peaches, 189. 
 
 Peas, green, 189. 
 
 Pepper, 189. 
 
 Pepsin, 173. 
 
 Peptone, 176. 
 
 Periosteum, 19. 
 
 Peritoneum, 161. 
 
 Perspiration, 130; amount of, 136. 
 
 Insensible, 135; sensible, 135. 
 Phalanges, 333, 334. 
 Pharynx, 160, 169. 
 Physician's directions, 326. 
 Physiology defined, 3. 
 Pia mater, 235. 
 Pie, 191. 
 
 Pigeon without cerebrum, 241. 
 Pigment cells, 52, 53. 
 
 Of eye, 288. 
 
 Of human skin, 132. 
 Pitch of voice, 312. 
 Pivot joint, 339. 
 
 Plain muscle fibers, 49, 50, 344. 
 Plants, relation to animals, 205. 
 Plasma, 73. 
 Pleura, 87. 
 Plexus, solar, 66. 
 Plums, 189. 
 Poison ivy, 324. 
 Poisons, 322, 347. 
 
 Irritant, 323; neutralizing, 323. 
 Pollen, 121. 
 Pores, sweat, 130. 
 Portal circulation, 177; Vein, 177. 
 Positive after-images, 295. 
 Postcaval vein, 42, 44, 177, 186. 
 Potatoes, 149, 189. 
 Potential energy, in respiration, 93. 
 Poultry, 189. 
 Power, of levers, 16. 
 Precaval vein, 42, 44, 186. 
 Premolars, 164. 
 Preservation of food, 127. 
 Pressure sense, 280. 
 
 Effect on nerves, 37 ; on veins, 58. 
 Prevention of sneezing, 328. 
 Process, articulating, 331 ; lateral, 331. 
 
 Process, odontoid, 335. 
 
 Spinous, 331. 
 
 Processes, of vertebra, 330. 
 Production of heat, 106; of sound, 306. 
 1'ronation, 337. 
 Protection of eye, 285. 
 Proteid food, 146. 
 Proteids, 145; importance of, 145. 
 
 Vegetable, 147. 
 
 Protoplasm, 4; animal, 202; vegetal, 202. 
 Ptyalin, 168, 176. 
 Puff-balls, 121. 
 Pulmonary arterv, 42 ; veins, 42, 43. 
 
 Capillaries, 86. 
 Pulp-cavity, 163, 164. 
 Pulse, 40. 
 
 Punishment, by nature, 227. 
 Pupil, 288, 289. 
 Putrefaction, bacteria of, 127. 
 Pylorus, 175. 
 
 Quality of voice, 312. 
 
 Quantity of blood in organs, 75. 
 
 Rabbit, muscles of leg, 9. 
 
 Nerves of leg, 9. 
 Radiation of heat, 137. 
 Radius, 332, 333. 
 Rainwater, 150. 
 Raspberries, 189. 
 Rate of blood-flo\v, 59. 
 
 Of heart beat, 39. 
 
 Of respiration, 95. 
 Reaction of blood, 75. 
 
 Time, 262. 
 
 Reading in convalescence, 298 ; heavy 
 books, 296; mornings, 297; even- 
 ings, 297 ; outdoors, 296. 
 Receptacle of chyle, 186. 
 Rectum, 188. 
 
 Reference in sensation, 282. 
 Reflex action, 30, 32, 263. 
 
 Essentials of, 32. 
 
 And habit, 267. 
 
 Importance of, 32. 
 
 Of spinal cord of frog, 30. 
 Refracting media of eye, 289. 
 Regulation of blood-flow, 68, 69, 107. 
 
 Of hearl beat, 66, 67. 
 
 Of lymph-flow, 77. 
 
INDEX. 
 
 Regulation of respiration, 99, 108. 
 
 Of temperature, 136. 
 Renal arteries, 44; veins, 44. 
 Renewal of blood and lymph, 200. 
 Rennet, 174. 
 Rennin, 174. 
 
 Repose, effeet on digestion, 192. 
 Reserve air, 97. 
 Residual air, 97. 
 Respiration, abdominal, 95. 
 
 And candle, 201. 
 
 Chemistry of, 100. 
 
 Control of, 99. 
 
 Forced, 94. 
 
 Modifications of, 95. 
 
 Movements of, 91. 
 
 Organs of, 84. 
 
 And oxidation, 201. 
 
 Rate of, 95. 
 
 Thoracic, 95. 
 
 Respiratory center, 99 ; sounds, 99. 
 Rest of brain, 246, 247. 
 
 Of eyes, 297. 
 
 Of heart, 48. 
 
 Usefulness of, 268. 
 Restoring breathing, 320. 
 Resuscitation from carbon dioxid, 322. 
 
 From drowning, 317. 
 Retina, 287, 292, 293. 
 Rhubarb, 189. 
 
 Ribs, 332, 333; in respiration, 92. 
 Rice, 149, 189. 
 Rickets, 339. 
 Rigor mortis, 346. 
 Ring, neural, 330. 
 River and blood-flow, 195. 
 Roasting meat, 156. 
 Rods and cones, 293, 292. 
 Roots of spinal nerves, 26, 29, 31. 
 Running, 20. 
 Rye, 149. 
 
 Sacrum, 333, 334, 335. 
 
 Sago, 189. 
 
 Salines, 302. 
 
 Saliva, amount of, 168; uses of, 168. 
 
 Salivary glands, 166, 186. 
 
 Salted meat, 189. 
 
 Salts, 153. 
 
 Satiety, 272. 
 
 Scapula, 332, 333. 
 Sciatic nerve of frog, 9. 
 Sclerotic coat, 287, 288. 
 Sculpture and anatomy, 346. 
 Semicircular canals, 305, 306. 
 Semilunar valves, 42. 
 Sensation centers, 243, 245 
 
 Defined, 265. 
 
 Nature of, 264. 
 
 And stimulus, 262. 
 Sensations and brain, 30. 
 
 Of color, 294. 
 
 Common, 272. 
 
 Cutaneous, 278. 
 
 General, 271. 
 
 Lingering, 267. 
 
 Referred to nerve ends, 282. 
 
 Relative, 265. 
 
 Subjective, 265. 
 Sense of equilibrium, 306. 
 
 Of hearing, 304. 
 
 Muscular, 272. 
 
 Of sight, 285. 
 
 Of smell, 303. 
 
 Of taste, 301. 
 
 Temperature, 283. 
 
 Of touch, 279. 
 
 Senses, classification of, 271. 
 Serous cavities, 80. 
 Sewer and water pipes, 199. 
 Sheath, medullary, 27. 
 
 Of muscle fiber, u, 12. 
 
 Of nerve fiber, 28. 
 Sick, care of, 325 ; food for, 327. 
 Sickroom, 324. 
 
 Sweeping, 125, 327. 
 
 Temperature of, 325. 
 Sighing, 95. 
 Sight, 285. 
 
 Sigmoid flexure, 188. 
 Sign, local, 281. 
 Skeleton, 330. 
 
 Appendicular, 330. 
 
 Axial, 330. 
 
 Cavities of, 337. 
 Skeleton, side view of, 332. 
 Skin, color of, 132. 
 
 Functions of, 130, 136. 
 
 And kidneys, 141. 
 
 Papilla; of, 279. 
 
INDEX. 
 
 Skin, structure of, 130. 
 
 Skull, 332, 333. 
 
 Sleeplessness, 246. 
 
 Small intestine, 160. 
 
 Smell, 303. 
 
 Smoked meat, 189. 
 
 Snake bites, 324. 
 
 Sneezing, 95 ; prevention of, 328. 
 
 Sniffing, 95, 304. 
 
 Snoring, 95. 
 
 Sobbing, 95. 
 
 Socket-joint, 339. 
 
 Soft palate, 160. 
 
 Solar plexus, 66. 
 
 Sound, 306. 
 
 Sounds of heart, 49. 
 
 Respiratory, 99. 
 Soup, 156; value of, 191. 
 Special senses, 271, 278. 
 Specific gravity of blood, 75. 
 Speech center, 245, 264. 
 
 And voice, 312. 
 Sphenoid bone, 333. 
 Sphincter muscles, 175. 
 Spices, 189. 
 Spinach, 189. 
 Spinal bulb, 236, 245, 246. 
 Spinal column, 334; flexibility of, 335. 
 Spinal cord, 24. 
 
 Cross section of, 28. 
 
 Figure of, 29. 
 
 Functions of, 29. 
 
 Reflex action of, 30. 
 Spinal nerves, 26. 
 
 Roots of, 26, 29. 
 
 Effect of severing, 34. 
 Spine, curvature of, 339. 
 Spinous process, 331. 
 Spirillum, of Asiatic cholera, 123. 
 Spitting, 96. 
 Spleen, 81. 
 Spot, blind, 293. 
 
 Yellow, 288. 
 
 Spots, cold, 283 ; warm, 283. 
 Sprains, 339. 
 Squash, 189. 
 Standing, 19. 
 Stapes, 333. 
 Starch, 189. 
 Starvation of cells, 200. 
 
 Starvation of nervous system, 247. 
 
 Steapsin, 179. 
 
 Stereoscopic vision, 295. 
 
 Sternum, 332, 333. 
 
 Stiffened joints, 340. 
 
 Stimulants, 210, 212 ; in resuscitation, 320. 
 
 Stimulating nerve roots, 34. 
 
 Spinal nerves, 33. 
 Stimuli of nerves, 261. 
 Stimulus and sensation, 262. 
 Stings of bees, 324. 
 Stirrup bones, 333. 
 Stomach, 160, 172, 186. 
 
 Absorption from, 175. 
 
 Blood-supply of, 173. 
 
 Coats of, 172. 
 
 Churning, 174. 
 
 Digestion, time of, 175. 
 
 Hemorrhage of, 315. 
 
 Position, 85, 160, 172, 186. 
 
 Structure of, 172. 
 Storage of oxygen, no. 
 Stove, 116; with jacket, 117. 
 Strength of light, 297. 
 
 Source of, 14. 
 Structure of artery, 51. 
 
 Of bone, 18, 337. 
 
 Of brain, 238, 239, 241. 
 
 Of eye, 288. 
 
 Of gullet, 171. 
 
 Of heart, 41. 
 
 Of kidney, 139, 140. 
 
 Of larynx, 310. 
 
 Of muscle, 10, n. 
 
 Of nerves, 27. 
 
 Of retina, 292. 
 
 Of skin, 130. 
 Structure of stomach, 172; of tooth, 163, 
 
 164. 
 
 Subclavian vein, 44, 186. 
 Subjective sensations, 265. 
 Sublingual salivary gland, 166, 186. 
 Submaxillary salivary gland, 166, 186. 
 Sucking, 96. 
 
 Suffocation in wells, 322. 
 Sugar, 144 ; cane, 179 ; grape, 179. 
 
 In diabetes, 199. 
 Sunshine, 139. 
 Sunstroke, 317. 
 Supination, 337. 
 
INDEX. 
 
 Suspensory ligament, 288. 
 
 Swallowing, 171 ; and breathing, 170, 171. 
 
 Sweat, 130. 
 
 Composition of, 135. 
 
 Evaporation of, 137. 
 
 Glands, 130, 133, 135. 
 
 Pores, 130. 
 Sweeping, 125. 
 
 Sickroom, 125, 327. 
 Sweetmeats, 191. 
 Sweets, where tasted, 302. 
 Swimming, 321. 
 
 Sympathetic nervous system, 65, 66. 
 Sympathy between eyes, 294. 
 
 In nursing, 325. 
 Synovia, 19. 
 Systole, 47. 
 
 Table of bones, 333. 
 
 Tapioca, 189. 
 
 Tarsal bones, 333. 
 
 Tarsus, 332, 333. 
 
 Taste, 301. 
 
 Tasting, conditions of, 302. 
 
 Tea, 154, 189, 212 ; beef, 155. 
 
 Tears, 286. 
 
 Teeth, 162, 163. 
 
 Arrangement of, 164. 
 
 Care of, 166. 
 
 Kinds, 164. 
 
 Milk, 164. 
 
 Temperance drinks, 211. 
 Temperature of body, 108. 
 Temperature, regulation of, 136. 
 
 Sense, 283. 
 
 Of sickroom, 325. 
 
 Effect on taste, 302. 
 Temporal bone, 332, 333 ; muscle, 9. 
 Tendinous cords, 41, 46. 
 Tendon, 7, 10, n, 15. 
 Tennis, 228. 
 Tetanus, 35. 
 Thein, 154. 
 Theobromin, 155. 
 Thermometer in sickroom, 325. 
 Thigh, wounds in, 315. 
 Thirst, 276, 272. 
 Thoracic duct, 183. 
 
 Respiration, 95. 
 
 Vertebra, 331, 335. 
 
 Thorax, cross section of, 89. 
 
 Thorns, wounds from, 323. 
 
 Thyroid cartilage, 309. 
 
 Tibia, 332, 333. 
 
 Tidal air, 97. 
 
 Time for bathing, 233 ; of eating, 193. 
 
 Tissue defined, 3. 
 
 Connective, n, 12. 
 
 Fatty, 201. 
 
 Tissues, oxidation of, 107. 
 Tobacco, 258. 
 Tomatoes, 189. 
 Tongue, 162. 
 
 Nerves of, 301. 
 
 Papillae of, 301. 
 Tooth, structure of, 163, 164. 
 Touch, sense of, 279. 
 
 Corpuscles of, 279. 
 Trachea, 43, 86. 
 Training and alcohol, 209. 
 Transfusion of blood, 81. 
 Transmission of nerve impulse, 36. 
 Treatment of burns, 316. 
 
 Of the drowned, 317. 
 
 Of fainting, 316. 
 
 In poisoning, 322, 347. 
 Triceps muscle, 8. 
 Tricuspid valve, 41. 
 Trigeminal nerve, 237. 
 Trophic nerves, 251. 
 Trypsin, 178. 
 Tube, digestive, 159. 
 
 Eustachian, 305, 306. 
 Tubes, lymph, 76. 
 Tuberculosis, bacillus of, 123. 
 Turbinated bones, 333. 
 Typhoid fever, 151 ; bacillus of, 123. 
 
 Ulna, 332, 333. 
 
 Upsetting of boats, 321. 
 
 Urea, 139; and muscular exertion, 202. 
 
 Uses of bones, 330. 
 
 Utilization of energy, 205. 
 
 Uvula, 160. 
 
 Vagus nerves, 66, 239. 
 
 Valve, mitral, 41 ; tricuspid, 41. 
 
 Valves of heart, 41. 
 
 Of lymph tubes, 76. 
 
 Semilunar, 42, 46. 
 
386 
 
 INDEX. 
 
 Valves of veins, 57. 
 Variation of blood-supply, 50. 
 Vaso-constrictor nerves, 67. 
 
 -dilator nerves, 67. 
 
 -motor nerves, 68. 
 Vegetable proteid, 147. 
 Vegetables, 149. 
 Vegetal protoplasm, 202. 
 Vegetarians, 154. 
 Veins, 57. 
 
 Bleeding from, 315. 
 
 Distribution of, 44. 
 
 Flow in, 61. 
 
 Hepatic, 177, 186. 
 
 Iliac, 44. 
 
 Jugular, 44. 
 
 Mesenteric, 186. 
 
 Portal, 177. 
 
 Postcaval, 42, 44, 177, 186. 
 
 Precaval, 42, 44, 186. 
 
 Effect of pressure on, 58. 
 
 Pulmonary, 42, 43. 
 
 Renal, 44. 
 
 Subclavian, 44, 286. 
 
 Valves in, 57. 
 Ventilating flues, 115. 
 Ventilation, need of, 114. 
 
 Principles of, 115. 
 Ventricle, contraction of, 46. 
 
 Dilation of, 47. 
 
 Of heart, 41. 
 
 Vermiform appendix, 187. 
 Vertebra, articulations of, 335. 
 
 Parts of, 330. 
 
 Processes of, 330. 
 Vertebrae, cervical, -332, 333, 334. 
 
 Lumbar, 335. 
 
 Thoracic, 331, 332, 333, 335. 
 Vesicles, air, 84. 
 Villi, 179, 181, 184, 185. 
 Vision, stereoscopic, 295. 
 Visual center, 264. 
 Vital capacity, 97. 
 Vitreous humor, 288, 289. 
 Vocal cords, 309. 
 Voice, 309. 
 
 Change of, 313. 
 
 Culture of, 313. 
 
 I^oudness of, 311. 
 
 Pitch of, 312. 
 
 Voice, quality of, 312. 
 
 And speech, 312. 
 Volition, 242, 243. 
 Voluntary inhibition. 35. 
 Vomer, 333. 
 Yourls and consonants, 312. 
 
 \Yalking, 20; in sickroom, 327. 
 Warm baths, 233. 
 
 Spots, 283. 
 
 Watching in sickroom, 326. 
 Water, 150. 
 
 Boiling, 152. 
 
 Drinking, 152. 
 
 Ice, 152. 
 
 Impurities in, 151, 
 
 Rain, 150. 
 
 Well, 150. 
 
 Water-cushion of brain, 248. 
 Water-pipes and bloodstream, 199. 
 
 And sewer, 199. 
 Wearing glasses, 299. 
 Web of frog's foot, 52, 53. 
 Weight of bones, 337. 
 
 In levers, 16. 
 Well-water, 150. 
 Wheat, 148. 
 
 Flour, 148. 
 
 Whispering, 313 ; in sickroom, 327. 
 Whistling, 96. 
 White matter of brain, 241. 
 
 Circulation in, 249. 
 
 Of spinal cord, 28, 29. 
 Wild game, 189. 
 Wind, 116. 
 
 Windows, double, 119. 
 Windpipe, 86. 
 Work of blood, 39. 
 
 Brain, 246. 
 
 Of heart, 48. 
 Worker, outdoor, 2. 
 
 Wounds from rusty nails, 323; from 
 thorns, 323. 
 
 In thigh, 315. 
 
 Yawning, 95. 
 Yeast, 121. 
 Yellow spot, 288. 
 
BIOLOGY 
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 UNIVERSITY OF CALIFORNIA LIBRARY