CORNELL 
 
 UNIVERSITY 
 
 LIBRARY 
 
 FROM 
 
 The 'tis tat e of 
 T.R.Vacmilleji 
 
The original of tliis book is in 
 tine Cornell University Library. 
 
 There are no known copyright restrictions in 
 the United States on the use of the text. 
 
 http://www.archive.org/details/cu31924031179959 
 
PRINCIPLES OF 
 
 PHYSIOLOGY AND HYGIENE 
 
 GEORGE WELLS FITZ, M.D. 
 
 Somt'timc .-tssistant ProfrsDor of Physioloffy 
 
 and lli/ifiene and Hfdicat Visitor, 
 
 Harvard VnicersUy 
 
 XEW YORK 
 
 HENRY HOLT AND COMPANY 
 1908 
 
COPTKIGBT. 1908, 
 BY 
 
 HENRY HOLT AND COMPANY 
 
PREFACE 
 
 Many years of experience in teaehiiig physiology ^ 
 have convinced me that the ideal of a High School 
 book should be the clearness, accuracy and simplicity 
 obtained by viewing the human body as a machine auto- 
 matically adjusted to its work and its surroundings. 
 From such a viewpoint, its complex structure is resolved 
 into the definite working parts of a well-regulated 
 mechanism; its varied forms of activity are revealed as 
 organized effort toward development, maintenance and 
 adaptation to environment; and the laws of its health 
 are seen to be the reasonable conditions essential to its 
 effective working. 
 
 Whenever possible, technical terms and names have 
 been omitted for the sake of relieving overburdened 
 memories and of leaving them receptive for the impor- 
 tant practical aspects of the subject. Indeed, the at- 
 tempt throughout has been to utilize and supplement the 
 knowledge of the High School student and thus to give 
 to the physiology, and especially to the hygiene, a work- 
 ing value in his daily thought and life! "When technical 
 terms have of necessity been used, they have been itali- 
 cized, not in every case where they first occur, but where 
 they are most fully explained. This method supple- 
 mented by an accurate index is believed to be preferable 
 to the very inadequate glossary often used. 
 
 ' State Normal School, Oswego, N. Y. ; Cook Co. Normal School, 
 Illinois; Sargent Normal School of Physical Education, Cam- 
 bridge, Mass.; Harvard University, Cambridge, Mass. 
 
iv PREFACE 
 
 While fully realizing and urging the value of experi- 
 mental work, I have, nevertheless, so planned the text 
 that it is independent of the experiments in connection 
 with each chapter. Those schools, therefore, which lack 
 either the time or the equipment for such work, will not 
 find the book less well fitted for their use. By them, the 
 book can be completed in half a year. For those who can 
 carry out the laboratory work, the book offers either a 
 half or a full year's course, depending upon whether 
 the experiments are demonstrated by the teacher or done 
 by the students. 
 
 The experiments and demonstrations should be so 
 planned that, when necessary, the one-hour period may 
 be extended to two hours. In nearly all cases, the experi- 
 ments should precede the text, that the student may be 
 led, in so far as is possible, to make his own observations 
 and conclusions. In order to get the most value from 
 the work, a systematic record of the experiments should 
 be kept in a notebook, to be regularly examined by the 
 teacher. 
 
 Aside from those herewith acknowledged, many of the 
 illustrations are new, being either original or redrawn 
 from the best sources obtainable. To Dr. 0. P. Bellin- 
 ger of Clark University I am indebted for permission to 
 copy his remarkable photographs of the ameba. I am 
 further indebted to the following authors and publishers 
 for permission to use certain cuts from their works: 
 Tigerstedt's Physiology, Mill's Comparative Physiology, 
 Doty's Prompt Aid to the Injured, (D. Appleton and 
 Co.) ; Bergen and Davis' Principles of Botany, Conn's 
 Bacteria, Yeasts and Molds in the Home, Hough and 
 Sedgwick's The Human Mechanism, (Ginn and Co.) ; 
 Gerrish's Anatomy, Hall's Physiology, Egbert's Hy- 
 giene, (Lea Bros, and Co.) ; Martin's Human Body, 
 
PREFACE V 
 
 Barnes' Plant Life, Sedgwick and Wilson's Biology, 
 (Henry Holt and Co.) ; Ziegler's Pathology, Poster and 
 Shore's Physiology, (The Macmillan Co.) ; Scudder and 
 Cotton's Fractures and Dislocations, Quain's Anatomy, 
 ( W. B. Saunders) . 
 
 The manuscript has been read by Professor C. P. 
 Hodge of Clark University, to whom I am much indebted 
 for criticism and suggestion. I am further indebted to • 
 my wife for her invaluable assistance throughout the 
 preparation of the manuscript and the correction of the 
 proofs. 
 
 G. W. P. 
 
 Boston, March 3, 1908. 
 
CONTEXTS 
 
 CH.U»TER I 
 
 PLANT AND ANIMAL LIFE 
 
 PAGE 
 
 Growth— Food of plants and animals — Organisms — ^Jlultipli- 
 cation of or^inisms — Organic substances — Building ma- 
 terials of animals — A simple type of animal — Reproduc- 
 tion by division — Developmeat from the germ cell — 
 Development of organs from cells — ^Differentiation of 
 cells — ^Individuality of cells — Forms of cells — Nutrition 
 of cells 1 
 
 CHAPTER II 
 
 THE GENERAL STRUCTURE OF THE HUilAN BODY 
 
 Definition of physiology — ^Man a mammal — Skeleton — ^Ar- 
 rangement of bones and organs — Spinal column — ^^'er- 
 tebnie of the neck — Of the back— Of the lower back — 
 Sacrum — Coccyx — Flexibility of spine — Injuries and de- 
 formities — ^Head — ^Appendages of the spine — ^Ribs — 
 Shoulder girdle — Arm — Wrist— Hand — Pelvic girdle — 
 Leg — Foot 10 
 
 CHAriER III 
 
 BONES, JOINTS AND LIGAMENTS 
 
 Purpose of tlie skeleton — ^Composition of bone — Changes 
 from infancy to old age — Shapes of bones — Building of 
 bone — Growth of long bone in length — Growth in tliick- 
 ness — Growth of short bone — Growtli of flat bone — ^Ends 
 of bones — Structure of a joint — ^Eange of movement — 
 Characteristics of a true joint — ^Ivinds of joints — Hinge 
 joints — ^Knee joint — Fivotal joints — Sliding joints- 
 Ligaments — Kinds of movement — Joint injuries — ^Dislo- 
 cation — ^Bone-building materials 26 
 
 CHAPTER lY 
 
 MUSCLES AND TENDOJfS 
 
 Muscles — Structure — ^Muscle fibres — Tendon fibres — ^Union of 
 muscle and tendon — Advantages of tendons — Control of 
 
viii CONTENTS 
 
 PAGE 
 
 joint movements — Production of energy — Nerve control — 
 Tonicity — Voluntary muscles — Involuntary muscles — 
 Comparison of voluntary and involuntary muscles — Heart 
 muscle — Effect of work — Influence upon other organs . . 40 
 
 CHAPTER V 
 
 MOTION AND LOCOMOTION 
 
 Simple forms of movement — More complex forms — Definition 
 of lever — hsiw of leverage — Classes of levers — Leverage 
 in animal bodies — Examples of levers of the first class 
 — Examples of the third class — Body as a weight — Power 
 exerted by the muscles — Locomotion^Energy expended 51 
 
 CHAPTER VI 
 
 MUSCULAR WORK 
 
 Influence of muscular activity upon development — Play — Ex- 
 ercise — Work — Disadvantages of work — Fatigue — Rest 
 — Recuperation 61 
 
 CHAPTER VII 
 
 SELECTION AND PREPARATION OF FOODS 
 
 Foods — Carbohydrates — Hydrocarbons — Proteids — Animal 
 manufactures — Diets of animals — Selection of diets — 
 Adjustment of teeth to diet — Of stomach and intestines 
 — Diet of man — Relation of food to muscular energy — 
 Primitive cooking — Boiling — Effects of cooking 65 
 
 CHAPTER VIII 
 
 FOOD MATERIALS 
 
 Plant foods — Bread — Patent breakfast foods — ^Vegetables — 
 Dangers of raw vegetables — Potatoes — Fruits — Preserved 
 fruits — Animal foods: milk — Contamination of milk — 
 Effect of temperature — Eggs — Meats and flsh — Parasites 
 in meat — Putrefaction — Meat stews — Soups — Fish — Con- 
 diments — Salt — Sugar 73 
 
 CHAPTER IX 
 
 WATER AND OTHER BEVERAGES 
 
 Mineral contents— Organic contents— Water supply— Surface 
 water— Spring water — A\'ell water — Lake water— Protec- 
 
COXTENTS 
 
 PAGE 
 
 tion of water supply — Saml filtration — Small filters — 
 Water as a beverage — Cambric tea — Cocoa and chocolate 
 — Tea and coffee — Dangers of tea and coffee — Alcohol — 
 Oxidation of alcohol — Dangers of alcohol 87 
 
 CHAPTER X 
 
 DIGESTION 
 
 Simplest form of digestion — More complex forms — Mouth — 
 Teeth — Permanent set — Development of teeth — ^Roots — 
 Structure — Tongue — Cheeks — Salivary glands — Saliva-^ 
 Pharynx — Esophagus — Stomach — Gastric juice — Exit of 
 chyme from the stomach — Rejection of food — Small in- 
 testine — ^Liver — Pancreas — Digestion of fat — Chyle — 
 Villi — ^Absorption of food — Food after absorption — Un- 
 digested residue — ^Large intestine 96 
 
 CHAPTER XI 
 
 THE HTQIEXE OF DIGESTION 
 
 Food in relation to age — To health — To activity — Variations 
 in diet — Times for meals — ^Appetite as a guide — Its 
 unreliability — Composition of food — ^Necessity for vari- 
 ety — Importance of good teeth 120 
 
 CHAPTER XII 
 
 THE BLOOD 
 
 Red blood corpuscles — Wliite blood corpuscles — ^Platelets — 
 Plasma — Fibrin — Blood as a common carrier — Blood 
 changes — Food elements — Carbohydrates — ^Hydrocarbons 
 — Proteids — Water — Storage of excess food---Starvation 
 • — Internal secretions of glands — Spleen 126 
 
 CHAPTER XIII 
 
 THE CIKCITLATIOX OF THE BLOOD 
 
 System of tubes for the blood — Greater and lesser circuits — 
 Heart — ^Heart muscle — Muscle' cells — ^X'entricles — Auri- 
 cles — Aurlculo-ventricular valves — Exit valves from ven- 
 tricles — Arteries — Functions of arteries — Structure of 
 arterial wall — Control of blood supply — Branching of 
 arteries — Capillaries — Veins — Blood flow in the veins — 
 General function of blood-vessels — ^Pulmonary circula- 
 tion — Travels of a drop of blood — Lymphatics — Function 
 of lymphatic system — Lymph glands — Control of blood 
 supply to tissues 135 
 
X CONTENTS 
 
 PAGE 
 
 CHAPTER XIV 
 
 THE HYGIENE OF THE CIRCULATION 
 
 Vasomotor control of blood distribution — Control by heart 
 beat — Faulty distribution — Efifects of eating — Causes of 
 sleeplessness — EflFeets of alcohol — External pressure — In- 
 juries — Inflammation — Bleeding from arteries — From 
 veins — " Poor " circulation — Fainting 157 
 
 CHAPTER XV 
 
 RESPIRATION 
 
 Air supply of the body — Nose as an air passage — Trachea — 
 Larynx — Bronchial tubes — Air sacs — Structure of lungs — 
 Membrane covering lungs — Relation of lungs to chest cav- 
 ity — Air movement — Inspiration — Expiration — Amount 
 of air breathed — Lungs filled by air pressure — Rapidity 
 of breathing — Effects of exercise — Effects of severe exer- 
 cise — ^Adjustment of respiration and circulation to exer- 
 cise — Effect of training 165 
 
 CHAPTER XVI 
 
 THE HYGIENE OF RESPIRATION 
 
 Effects of respired air — Odor a test of impurity — Amount 
 of fresh air required — ^Ventilation — Heating — Direct 
 method — Use of windows for ventilation — Indirect 
 method — Humidity — Relation of humidity to ventilation 
 — Drafts — Relation of clothing to ventilation — Night 
 air — Malaria — Dust, a source of disease — Coughing — 
 Sewer gas — Care of nose — Catarrh — Adenoids — Enlarged 
 tonsils 182 
 
 CHAPTER XVII 
 
 THE REMOVAL OF WASTE PRODUCTS 
 
 Kidneys — Blood supply — Structure — Excretion — Effect upon 
 blood — Importance of the kidneys — Excretion by the 
 skin — Uses of perspiration 196 
 
 CHAPTER XVIII 
 
 THE SKIN 
 
 The skin, a protection — The skin, a sense organ — Structure — 
 Pigment cells — Color of the skin — Dermis — Connective 
 
CONTENTS xi 
 
 PAGE 
 
 tissue layer — Hair — Nails — Sweat glands — Secretion — 
 " Pores " of the skin — Inadequacy of the skin's protec- 
 tion — Necessity for cleanliness — Bathing — Sea Bathing 
 — Soaps — Skin parasites — Skin eruptions 200 
 
 CHAPTER XIX 
 
 THE HEAT OF THE BODY 
 
 Warm and cold animals — Heat control — Loss of heat — Cloth- 
 ing — ^\\"ooI — Leather and furs — Thin or thick clothing — 
 Bed clothing — Arrangement of bed clothing — Fall in 
 body tempera tui-e — Alcohol — Fi-eezing — Rise in body 
 temperature 211 
 
 CHAPTER XX 
 
 THE KEKVOrS SYSTEM 
 
 General arrangement — Ner\-es — Spinal nerves — Nerve struc- 
 ture — Course of a motor nerve — Neurons — Motor neurons 
 — Course of a sensory nerve — Direction of nervous im- 
 pulses — Spinal cord — Motor impulses from sensory — Re- 
 flex action — Its characteristics — ^Branches of spinal 
 nerves — Sympathetic system — Spinal bulb — Cerebellum — 
 Cenebrum — Brain convolutions — Gray matter — White 
 matter — Protection of brain — Cranial nerves — ^Reflex 
 action — ^'oluntary action — Habits 219 
 
 CHAPTER XXI 
 
 USE AND CARE OF THE XERVOUS SYSTEM 
 
 Activity of the nervous sii-stem- — Value of sleep — ^Amount of 
 sleep — ^Habits of sleep — Nervous breakdown — ^"alue of 
 ■work — Amount of work — Method of work — Meaning of 
 pain 241 
 
 CHAPTER XXII 
 
 THE SPECIAL SEXSES 
 
 Evolution of the special senses — Special senses — Touch — 
 Other dermal senses — Fatigue — End organs — ^Kinds of 
 taste — Structure — Influence upon taste — External ear — 
 Middle ear — ^Eustachian tube — Inner ear — ^Receiving ap- 
 paratus—Sensation of sound — Semicircular canals — ^Na- 
 ture of light — General structure — Detailed structure — 
 Formation of image — Adjustment of lens — Flexibility of 
 
xii CONTENTS 
 
 PAGE 
 lens— Far- and near-sighl^Adjustments to intensity of 
 light— Purpose and structure of retina— Optic nerve- 
 Sensation of sight— Acuteness of vision— Defects of 
 vision— Eye strain— Astigmatism— Perception of dis- 
 tance — Binocular vision— Double vision 246 
 
 CHAPTEE XXIII 
 
 THE CARE OF THE SENSE ORGANS 
 
 Means of protection — Care of the ear — Method of cleaning 
 — Removal of objects — Earache — Effect of noise — Eyes — 
 Removal of objects — Effect of strong light — Weak light 
 — Proper use 272 
 
 CHAPTEE XXIV 
 
 THE VOICE AND SPEECH 
 
 Sound as a means of communication— Larynx and vocal 
 cords — Volume — Pitch — Timbre — Effect of air cavities 
 upon the voice — Vowels — Consonants — Whispering .... 276 
 
 CHAPTER XXV 
 
 HEALTH AND DISEASE 
 
 Health — Conditions of health — Disease— Microbes, a cause 
 of disease — Bacteria, protozoa and molds — Exposure to 
 disease — Generation of toxins — Antibodies — Four stages 
 of disease — Individual differences in resistance — Im- 
 munity — Tuberculosis — Artificial development of anti- 
 bodies — In consumption — Infection — Entrances and exits 
 for microbes — Prevention of disease by personal care — 
 Disinfection — Prevention of disease by municipal hy- 
 giene 281 
 
 CHAPTER XXVI 
 
 STIMULANTS AND NARCOTICS 
 
 Definition — Proper use of narcotics — Improper use — Legal 
 restrictions — Tobacco a narcotic — Method of use — Pres- 
 ence of carbon monoxide (CO) — Extent of use — Indi- 
 vidual susceptibility — Stimulants: tea and coffee — 
 Formation of habit — Alcohol — Production of alcohol — 
 Various beverages — Effects of alcohol — Alcohol, a r;ir- 
 cotic poison — Chronic effects upon structure — Effect 
 upon heart — Upon blood-vessels — Upon nervous system — 
 
CONTENTS xiii 
 
 PAGE 
 
 S>-stemio effects — Txmgevity — Experimental proof — Prac- 
 tical studies — Economio effects 296 
 
 APPENDIX A 
 
 THE QROXTTH OF PLANTS AND ANIMAIS 
 
 Food of plants — Oxygen (0) Xitrogen (X) — Carbon dioxide 
 (CO,) — Carbon "monoxide (CO)— Water (HO) — Soil — 
 Plant growtli — Non-destrnetibility of matter — Conserva- 
 tion of energj- — Transformation of energy — The animal 
 body, an engine 315 
 
 APPENDIX B 
 
 FIRST AID TO THE IXJUKED 
 
 Woimds — Bruises — Burns— Acids and alkalies — Frost-bite — 
 Sprains — ^Dislocations — Fi-actures — Poisons^Drugs and 
 chemicals — Ptomaines and toxins — Stings of insects — 
 Snake bite — Dog bite — Loss of consciousness — Fainting 
 — Convulsions — Epileptic attacks— Apoplexy — Sunstroke 
 — Brain injury — Suffocation and drowning — Artificial 
 respiration— GaS poisoning — Choking — Croup 325 
 
 APPENDIX C 
 
 PRACTICE IX FIRST AID 
 
 Triangular bandage — Roller bandage — Four-tailed bandage 
 — ^Compress — Splints — Sling — Stretcher — Disinfecting so- 
 lutions 343 
 
PHYSIOLOGY AND HYGIENE 
 
 CHAPTER I 
 PLAXT AXD AXIMAL LIFE 
 
 Growth. — As we watch plants and animals grow, we 
 see how many changes they ai-e making in the world 
 about them. The plants are taking the materials which 
 they need from the earth, air and water,^ and are build- 
 ing these materials into themselves. The animals in 
 turn are taking the plant substances and are building 
 their own bodies out of them. 
 
 A clover plant starts from a seed witliin which is 
 hidden a minute plaut and food prepared by the mother 
 plant for its use, AYhen placed in the moist warm earth, 
 the plant awakens and by li\ing upon the stored-up 
 food quickly becomes lai-ger and stronger. After it has 
 thrust its head out of the ground and its roots down 
 into the soil, it is able to take a gas known as carbon 
 dioxide from the air and water, with a small amount of 
 soluble material from the earth. From these, with the 
 aid of the sun"s light and heat, it gradually builds up 
 a lai"ge and strong clover plant. The gas and water 
 are no longer simply gas and water, but are combined 
 
 ' The §oil contributes mainly water containing a small amount 
 of salts in solution. The air contributes a colorless gas, carbon 
 dioxide (CO;V which is produced by the burning and decay of 
 ^rood and other org;\nic materials ; and a small amount of nitrogen. 
 Water (HjO) consists of 2 parts of hydrogen to 1 of oxygen. For 
 a further discussion, see Appendix, p. 311. 
 
PLANT AND ANIMAL LIFE 
 
 and changed to form the woody stem, the luxuriant 
 leaves, the nectar-laden blossoms. A lamb eating the 
 clover changes it so that it is no longer clover, nor yet 
 the gas and water from which the clover was built, 
 but the flesh and bone of the sheep. 
 Food of plants and animals. — 
 The building materials, or food, 
 taken by the plant or the animal 
 are so completely changed that they 
 become a living part of it. If it 
 lives, they live as woody fibre, bone, 
 muscle, or other tissue. If it dies, ' 
 they too are dead, and quickly or 
 slowly decay, returning to the simple 
 chemical compounds which the plant 
 had previously utilized and which 
 thus again become available for 
 other plants and through them for 
 other animals. 
 
 Organisms. — Plants and animals 
 are called organisms,'^ because they 
 lead a more or less independent life, 
 during which they grow and develop. 
 Most organisms begin life compara- 
 tively small and weak.^ They develop 
 rapidly or gradually into the size, strength and per- 
 fection of the adult. They once again become weak in 
 old age, with subsequent death and decay. This se- 
 quence of growth and decay is in marked contrast to 
 the non-living world of things, which cannot grow but 
 instead are changed by being worn away and deigtroyed. 
 
 Fie. 1. Germinatingpeas, 
 growing in water, one 
 (J3) deprived of its co- 
 tyledons, which con- 
 tain the stored-up food. 
 (Bergen.) 
 
 ' Literally, an organism is a living unit which possesses organs. 
 The term has, however, come to include all plants and animals. 
 ' The exceptions are the microscopic plants and animals. 
 
ORGANISMS 3 
 
 The stone, for example, is worn into fine particles of 
 dust by ceaseless grinding against sand and stone ; moiui- 
 taius are broken into rocks and loose earth by frost and 
 waslied down into the valle\-s by rain; wood decays to 
 the carbon dioxide and water from which the plant 
 built it. 
 
 Multiplication of organisms. — Organisms also differ 
 from non-living things in their power to produce new 
 orgajiisms. In the lower forms of both plants and 
 animals, this process of reproducing or continuing life 
 has its simplest example in the division of the adult 
 into two or more >'Oiing individuals, which, after they 
 have developed into maturity, again divide. In this 
 way, the species is rapidly nudtiplied, and death and 
 decay through old age are avoided. 
 
 In higher forms of plants aud animals, the process 
 of repi-oduction consists in the development of the 
 young organism as au offshoot or bud from the adult. 
 "When capable of independent development, it is set 
 free as a young plant or animal aud thereupon begins 
 a new life, in which lies tliis same power of starting 
 young organisms. 
 
 Organic substances. — The substances which plants 
 and animals produce, are called organic substances, since 
 they are dependent for their existence upon the life 
 and activity of plant and animal organisms. From 
 plants come such organic substances as wood, cotton, 
 hemp, oil. tlour. starch, sugar, coal, coal oil, paraffin 
 and natural gas. From animals come such substances as 
 flesli. leather, hair, avooI and silk. 
 
 Inorganic substances. — In contrast to these are inor- 
 ganic substances, which are found in nature independent 
 of plant and animal life, such as air, water, minerals 
 (except coal in its vai'ious forms) and metals. 
 
4 PLANT AND ANIMAL LIFE 
 
 Building materials of animals.— Certain of the or- 
 ganic substances produced by plants, such as starch, oil 
 and sugar, together with such inorganic materials as 
 water, lime and other salts, are used by animals as food 
 and from them they build up their bodies.^ The bodies 
 thus built may be so simple as to consist of but a single 
 speck of living matter or so complicated as to have the 
 
 
 Fig 2. Ameba at rest and branching (viewed from above). After micro-photo- 
 graphs by Delliiiger. 
 
 various organs and tissues possessed by the higher ani- 
 mals and man. 
 
 A simple 15^)6 of animal. — One of the simpler ani- 
 mals which has been most studied because it is commonly 
 found in stagnant waters, is the ameba. The ameba has 
 neither eyes nor ears, nose nor mouth, head nor legs, 
 but is just a minute mass of a living jelly-like substance 
 called protoplasm. Within this is a more solid body 
 Imown as the nucleus. The entire mass is filled with 
 granules and when at rest is more or less spherical in 
 form. When active, it assumes various shapes and is 
 able to move about by throwing out from its body pro- 
 jections which serve as feet. Although it has no mouth, 
 it is able to swallow particles of food when they come 
 in contact with its body and later to expel their undi- 
 gested portions. This bit of independent, self- directing 
 ' Many animals also eat the flesh of other animals. 
 
THE AMEBA 5 
 
 and self-supporting matter is an animal, although it 
 is so small that it can hardlj- be seen. Its body of 
 protoplasm with its more solid spherical nucleus, makes 
 up a single cell.^ 
 
 The ameba, like all other animals consisting of but one 
 cell, has, in spite of its smallness and simplicity, the be- 
 
 Fia. S. Ameba progressing (side view). After micro-photograph by Dellinger. 
 
 ginnings of the faculties and powei-s which are so highly 
 developed in us. The possible exceptions are sight and 
 hearing, although it would seem not entirely to lack 
 even these, since experiments have shown that it is 
 influenced by light and even possibly by sound. Barring 
 accident, their lives maj- be said to be endless, since 
 each healthy adult undergoes division into young twin 
 cells of half the original size. These inunediately take 
 on the characteristics and powei-s of the older cell, and 
 growing rapidly to maturity redi%'ide in their turn. 
 
 Reproduction by division. — This process of division 
 begins and is completed in the nucleus before the sur- 
 rounding fnass of protoplasm, the cytoplasm, changes. 
 The cj-toplasm theu proceeds to divide, and in a short 
 time the two new cells have entered upon an inde- 
 pendent life. This process is called reproduction by divi- 
 
 • Curiously enough, an independent cell somewhat like the ameba 
 is found in large numbers in the blood of the higher animals, and 
 is called a white blood corpuscle. The white blood corpuscles are 
 produced and set free within the body for the purpose of seeking 
 out and destroying any disease germs or other foreign substances 
 which have found a lurking place there. 
 
6 PLANT AND ANIMAL LIFE 
 
 sion and is the final outcome of the growth and develop- 
 ment which have taken place in the cell. It marks 
 the passing of the adult, since its life is now turned over 
 to the young cells which represent it. 
 
 Development from the germ cell. — Nearly all ani- 
 mals, no matter how complicated their structure, be- 
 gin their life as a single cell, the germ cell. The germ 
 cell in the higher animals undergoes a series of rapid 
 divisions into smaller and smaller cells, until a mulberry- 
 
 Vie. 4. Diagrams illi „ JCt cell-division: o, cell-body; J, nucleus; e, 
 
 nucleolus. 
 
 like mass is produced by this process of segmentation. 
 These cells all appear alike at first and are mixed to- 
 gether seemingly without order in a spherical cellular 
 mass. Later, the cells enlarge and are arranged in 
 three definite layers. 
 
 The upper layer develops into the skin of the animal. 
 Through a curious infolding of the cells, it also forms 
 the nervous system. 
 
 The middle and larger layer forms the greater part 
 of the body, namely, the muscles, bones, fibrous tissues, 
 heart, blood vessels and urinary system. 
 
 The lowest layer forms the lining of the gullet, stom- 
 ach, intestines and lungs. 
 
 Development of organs from cells. — As the few 
 primitive cells of the three layers change and grow into 
 the millions of special cells which make up the different or- 
 gans and tissues of the body,^ and develop the power to do 
 
 ' Differentiation. 
 
MULTIPLIcWTION OF CELLS 1 
 
 the special work of these organs and tissues.^ they luider- 
 go marked ehauges in size, shape and behavior. In our 
 study, we are not concerned with their rapid and perplex- 
 ing changes, bvit with tlie cells as finally completed. It 
 will be sufficient for us to realize that these changes in the 
 case of a human being are fairly well established ^^^thin 
 two or three months of the single cell stage. The re- 
 
 FiG 5. Cleavage or se"tnentataon of an OTnm, ehowing snccessive division of the 
 "erm cell (a) into two (*>, four (e), and eight (dl. Later stages are shown at e 
 and f The first four figures are diagrammatic : « and / .ire after UatschetLS 
 figures of the development of a very simple vertebrate (Amphioxus). 
 
 maining six or seven months before birth and eigh- 
 teen or nineteen years of growth and development after 
 birth, ai-e devoted to the enlargement and perfection 
 of the organs and tissues - already formed in miniatui-e. 
 
 ' Spccialhatioii. 
 
 'The term tissue is applied to such parts of the body as are 
 made up of similar cells, as, for example, muscular tissue and 
 nerve tissue. A tissue may do a special work, in which ease it is 
 also an organ. 
 
8 PLANT AND ANIMAL LIFE 
 
 Differentiation of cells.— In animals thus made up 
 of many cells, the cells have fixed positions in the body 
 and are crowded by one another into such permanent 
 shape as best adapts them to their position and work. 
 Unlike the single cell of the ameba, no one cell has the 
 power of doing all the kinds of work required by the 
 body, as moving the limbs, digesting food and breathing, 
 but each group of cells constitutes an organ which does 
 a special part of the body's work. The outer cells, for 
 example, do the work of protecting the inner ones and 
 for this purpose become tough and resistant, 'forming 
 the skin. The inner ones in turn carry on the spe- 
 cial functions of the body, as motion, digestion and 
 respiration. 
 
 Individuality of cells, — Although the cells have thus 
 lost the power of doing more than one kind of work for 
 the body as a whole, they nevertheless resemble the single 
 cell of the ameba in that they can do the various kinds 
 of work necessary to maintain their own existence. For 
 example, each one absorbs and uses the nourishment 
 which it needs to do its work and maintain its health 
 and strength. It takes in the oxygen necessary for the 
 production of energy ^ and throws out carbon dioxide 
 and other waste products. 
 
 Forms of cells. — The cells have further lost the 
 ameba 's power of radically changing their shape and 
 they cannot perpetuate life by mere division of them- 
 selves. Each cell is limited to the shape best adapted 
 to its service in the organism. If, for example, it forms 
 part of the deep layers of the skin, it is small and block- 
 shaped. If it forms a part of the connection between 
 the muscle and its bony attachment, it is long and 
 slender like a silk fibre. If it is a part of the muscle, 
 ' See Appendix, p. 316. 
 
FORMS OF CELLS 
 
 9- 
 
 it is bi-oader and has the power of shortening itself so 
 as to aid in pulling the bones about. lu other words, the 
 
 Connochvc (issue cell^ 
 
 Qtiated epithdial cells 
 
 V-'.-i — Bashc (ibitMS tissue 
 ^ ' ' Sensory nerve cell of spinal coit! 
 
 Motor nerve cell of 
 spinal cord 
 
 Connective tissue 
 
 Cells of a tubular gland 
 
 Fig. t>. Various forms of cells foiiud in the body. 
 
 forms of the various cells are as numerous as their posi- 
 tions and functions in the body. 
 
 Nutrition of cells. — Instead of having the power of 
 independent movement which was necessitated by the 
 ameba's constant search for food suitable to its needs, 
 the cells in the animal body remain relatively stationary, 
 with the exception of the red and white cells of the blood. 
 The stationary cells have food and oxygen prepared for 
 their use and brought to them by the blood through an 
 intxicat<? system of canals, the blood-vessels. The waste 
 products of their activity are borue away without effort 
 on their part by tliis same blood supply, which bathes 
 all the tissues of the body. 
 
 DEilOXSTEATION 
 
 Demonsti"ate under the micixtseope the ameba as found in the 
 slime from stagnant poud water. 
 
CHAPTER II 
 
 THE GENERAL STRUCTURE OF THE HUMAN 
 BODY 
 
 Definition of Physiology. — Although all animals have 
 to procure and digest food, to absorb oxygen and 
 eliminate waste materials, yet the ways in which they 
 accomplish this are so varied as to give rise to many 
 kinds of structure. In accordance with the degree of 
 their complexity, animals may be arranged in a series. 
 At the bottom, we may place the one-celled animal with 
 its simple structure, any part of which is convertible 
 to any use, being interchangeably stomach, lung, foot 
 or excretory organ ; and at the top, man, whose millions 
 of cells are arranged in groups as organs and tissues, 
 each group of which is able to do only its own par- 
 ticular work. The study of the structure of animals is 
 anatomy. The study of the work done by these struc- 
 tures and the way in which it is done is physiology. 
 That branch of physiology devoted to man is human 
 physiology. 
 
 Man a mammal. — Man belongs to the higher class 
 of animals which have a backbone or vertebral column 
 and which are therefore called vertebrates. Man further 
 belongs to the highest division among vertebrates which 
 suckle their young and because of this are called mam- 
 mals. In structure, man differs from some of the other 
 mammals, especially from the higher apes, only in minor 
 details. He has, for example, shorter arms and a larger 
 
 10 
 
THE SKELETON 11 
 
 cranium. His feet are made for walking, not for grasp- 
 ing, and his body is held erect. 
 
 Gibbon Chimpanzee Man 
 
 Fig. 7. Skeletons of gibbon, chimpanzee and man drawn in natnrat relations of 
 size. (.\f tei Huxlej .) 
 
 Skeleton. — The human body consists of two dis- 
 tinct parts, a bony framework called the skeleton, and 
 the soft flesh, slvin and other tissues and organs which 
 clothe it. In many animals, such as crabs and lobsters, 
 
12 STRUCTURE OF THE HUMAN BODY 
 
 the skeleton lies entirely outside of the softer tissues. 
 In vertebrates, on the contrary, the skeleton is entirely 
 covered by the flesh. ^ By this arrangement, the skeleton 
 
 Fio. 8. Animal with external Bkeleton (crab). 
 
 supports and protects the softer tissues and is in turn 
 protected by them. 
 
 Arrangement of bones and organs. — The human 
 skeleton consists of a large number of bones (about 
 208) so arranged and distributed in and about the 
 body's central axis, the spinal column, as to be alike 
 on both sides, that is, bilaterally symmetrical. The two 
 sides are, however, complements of each other in shape 
 and position, that is, rights and lefts. Most of the soft- 
 tissues ate also symmetrically arranged in pairs, as for 
 example the muscles, blood-vessels, nerves, lungs and 
 kidneys. The exceptions to this are such organs as the 
 heart, stoinach, liver and intestines, which are irregular 
 in shape and not in pairs. 
 
 ' The turtle, although a vertebrate, has its backbone and ribs 
 so blended that they form a shell which in certain particulars 
 resembles an outside skeleton. 
 
THE SPINAL COLUMN 
 
 13 
 
 Spinal Column. — The fmidamentalpart of the skeleton 
 and the only part poss(\«ed by some of the lower forms 
 of vertebrates is the spinal or rcrfebral column. The 
 spinal eolnnin varies in form from the simple rod of 
 gristle found in some of the lowest vertebrates, to the 
 many jointed flexible bony structure which distinguishes 
 the higher species. 
 
 Vertebrae of the neck. — In man, the vertebral column 
 consists of 31 short bones, the ccrfciro': These verte- 
 brje vary in form accord- 
 ing to their position in 
 the spine and the work 
 which they have to do. 
 For example, to permit the 
 head to turn and bend 
 in various directions, the 
 vertebnv in the neck must 
 move freely. They are there- 
 fore comparatively small 
 and loosel.v connected by 
 strong bands of gristle, 
 the ligaments, and firmly 
 held by strong contractile 
 bauds, the muscles. Move- 
 meut beyond a certain 
 amount is checked bv the 
 ligaments which at the 
 danger point become tense. 
 As a result, dislocation of 
 the bones of the neck is 
 rare. To allow the head 
 to nod. the upper or fii-st of the neck vertebrse is so 
 shaped as to permit tlie lower portion of the skull 
 which rests upon it to slip readily. To permit the 
 
 Fig. 9. The Bpfna) column, ripht lateral 
 view and dorsal view. (Testut.) 
 
14 
 
 STRUCTURE OF THE HUMAN BODY 
 
 head to turn from side to side, that is to rotate, a pivot 
 projects upward from the second vertebra into a ring 
 on the first vertebra. 
 
 Of the back. — In the upper part of the trunk, or 
 dorsal region, on the contrary, stability rather than 
 
 Surface on which sfciill rests 
 ^Odontoid process of axis 
 Transverse process 
 A'ertebral artery 
 
 Neural arch' 
 
 The Atlas 
 
 Ligament 
 
 Neural canal (for spinal cord) 
 ■Spinous process 
 
 Odontoid process 
 
 (pivot for atlas) 
 
 Articular surface for atlas 
 Vertebral artery 
 
 The Axis 
 ^ the head ''^ relation between the 1st and 2nd vertebra, permitting rotation of 
 
 freedom of movement is required, in order that the ribs 
 which are attached to the vertebra} may receive ade- 
 quate support. The vertebrte of the back are therefore 
 firmly united by additional ligaments and bony exten- 
 sions or processes, in order that any considerable move- 
 ment of the vertebra may be checked. In childhood, the 
 
THE VERTEBR.^ 
 
 15 
 
 movement permitted is more extensive than in latei- life, 
 owing to the greater looseness of the ligaments and the 
 larger spaces between the processes, bnt even then the 
 movement between adjacent vertebiw is slight. 
 
 Of the lower back. — In the lower part of the back, 
 the lumbar region, bending is essential. The parts of 
 tbe vertebnv which come together, the arficular surfaces. 
 
 Neural canal 
 
 Body of vertebra 
 Neural canal 
 Neural arch 
 
 Articular 
 
 3 surfaces for rib 
 Transveree process 
 Spinous process 
 
 Back view 
 
 Top view 
 
 Articular surface for head of rib 
 
 Tticular surface for next 
 
 vertebra above 
 
 ■Articular surfaces for rib 
 
 Articulap surface for next 
 vertebra below 
 ■Articular surface for 
 
 head, of rib 
 Spinous process 
 
 Side view 
 Fig. 11. Views of dorsal vertebrffi showing parts and relations. 
 
 are therefore arranged so that they slip readily upon 
 each other and thus permit free bending backward 
 and forward but only a moderate amount of bending 
 sidewise. 
 
16 
 
 STRUCTURE Or THE HUMAN BODY 
 
 Sacrum. — Below the lumbar region, the greatest 
 strength and stability are required because the weight of 
 the trunk is here transmitted through the hip bones 
 to the legs. Five of the vertebral bones are therefore 
 united to form a single broad strong bone, the sacrum. 
 
 Coccyx. — Below the sacrum are several small bones 
 which constitute the coccyx. They are the sole remnant 
 of a possible prehistoric tail and owing to their exposed 
 position are somewhat frequently injured. 
 
 Flexibility of spine. — As we have seen, the vertebrae 
 form a series of short branching bones knit together by 
 ligaments into the spinal column. The movemeiit per- 
 
 Front ligament.^r^ '^ ''^kii-ftij -!•' 
 
 Back ligaments. 
 
 Body of vertebra 
 Spine of vertebra,- ,'t 
 
 Intervertebral discs 
 of elastic cartilage 
 
 Canal for spinal cO' 
 
 Fig. 12. A section througti tliree vertubrse, sliowing structnre of bone and 
 arrangement of ligaments. 
 
 mitted between each pair of vertebras is slight and the 
 ligaments which bind them together are strong. As a 
 result, the spinal column is firm. Its flexibility is not sac- 
 rificed, however, because there are so many joints that 
 a slight movement on the part of each results in a con- 
 siderable curve of the whole. 
 
EXPLANATION OF PLATE I. 
 
 A front view of an adult human skeleton to illustrate the mode In 
 which the bones are connected at the different joints. 
 
 a Ligaments of the Elbow Joint. 
 
 b The Ligament which is connected with the ventral surfaces of the bodies 
 
 of the Vertebrae. 
 e Ligament connecting the Pelvis to the Spine. 
 f Ligament connecting the Pelvis to the Sacrum. 
 g The Ligaments of the Wrist Joint. 
 h The Membrane which fills up the Interval between the two bones of the 
 
 Forearm. 
 I A similar Membrane between the two bones of the Leg, and, lower down, 
 
 I, ligaments of the Ankle Joint. 
 n Ligaments of the Knee Joint. 
 00 Ligaments of the Toes and Fingers. 
 p Capsular Ligament of the Hip Joint. 
 Q Capsular Ligament of the Shoulder Joint. 
 
PLATE I. — THE BONES, JOINTS, AND UGAMENTS. 
 
SPINAL INJURIES 
 
 17 
 
 Injuries and deformities. — Because of the great 
 stxain to which the spine is often subjected, minor in- 
 juries and deformities are not uncommon. They are 
 caused mainly by wrenching or tearing some of the 
 ligaments, by bruising the articular surfaces, and by one- 
 sided growi;h and development due to irregularities in 
 the sliapes and numbers of the bones, to faulty postures, 
 or to the habitual carrying of heavy weights upon one 
 
 Fio. IS. Side aiid back views of correct aud faulty positions at scliool desks. 
 (Tabby.) 
 
 side of the body. Children who carry heavy babies are 
 frequently deformed in this way. 
 
 Bead. — The spinal coluram, which serves as the axis 
 of the skeleton^ is surmounted by the bones of the head. 
 Here, man's difference from other animals is most pro- 
 nounced, in that the face bones are smaller and the 
 brain cavity, the cranium, is larger. The accompanying 
 illustration shows more accurately than any description 
 the shape and position of the cranial and face bones. 
 
 Appendages of the spine. — In addition to the verte- 
 bral column surmoTinted by the skull, the bony frame- 
 work of the body also includes the shoulder girdle, the 
 ribs and the pelvic girdle. The shoulder girdle carries 
 the arms and consists of two shoulder blades or scapulce, 
 two collar bones or clavicles, and the breast bone or 
 
18 
 
 STRUCTURE OP THE HUMAN BODY 
 
 sternum. The ribs arise from the dorsal vertebrae, en- 
 circle the chest and are united together in front by the 
 
 Tap 
 
 Fig. 14. A side view of tiie pkull. O, occipital bone ; T, temporal ; Pr, parietal ; 
 F, frontal ; S, sphenoid ; Z, malar ; Mx, maxilla ; N, nasal ; E, ethmoid ; L, 
 lachrymal ; Md, Inferior maxilla. 
 
 sternum. The pelvic girdle starts from the sacrum and 
 consists of the broad flaring bones of the hips, to which 
 the legs are attached. 
 
THE CHEST 
 
 19 
 
 Ribs. — Of these appendages of the axial skeleton/ the 
 ribs are of great impoi'tnn^'o since they enclose and pro- 
 tect the heart and lungs. They also make breathing 
 
 Fio. 15. The skeleton of tfie trank seen from the front. C, clavicle ; S, acapnia j 
 Oc, pelvic bone attached to the Bide of the sacram dorsally. 
 
 possible by furnishing stiff yet movable walls for the 
 chest cavitv in which the lungs lie. Through the sternum 
 
 ' The axial skeleton is that part of the skeleton which forms the 
 central line or axis of the body. 
 
20 STRUCTURE OF THE HUMAN BODY 
 
 Fis. 16. The ribs of the left side, with the dorsal and two lambar vertebras, the 
 rib cartilages, and the sternum. 
 
 which unites the ribs in front, they further furnish the 
 necessary bony support for the shoulder girdle and for 
 the muscles which move the arms. 
 
THE SHOULDER 21 
 
 Shoulder girdle. — The shoulder girdle is made up of 
 two parts, one for each side of the body. Each part con- 
 sists of two bones, the scapula and the clavicle. The 
 scapula is broad and flat and lies at the back of the 
 shoulder. The clavicle is long and slender, and connects 
 
 Fis. 1". Articulation of a pair of ribs to a vertebra and to the sternum. 
 
 the tip of the shoulder with the upper portion of the 
 sternum at the root of the neck. Through the clavicle, 
 the shoulder is attached on each side by means of liga- 
 ments to the top of the sternum. It is also held in place 
 by powerful muscles which control the movements of 
 the shoulders and arms. 
 
 Arm. — ^At the upper outer end of the scapula lies a 
 shallow cup, into which the rounded head of the bone 
 of the upper arm fits. The arm itself consists of two 
 parts, the upper arm and the forearm. The upper arm 
 
22 STRUCTURE OF THE HUMAN BODY 
 
 has but one bone, the humerus. The forearm contains 
 two bones, the ulna and the radius. The expanded end 
 of the ulna forms the elbow joint, into which the radius 
 enters only with its small tip. At the wrist, on the 
 contrary, the expanded end of the radius makes up most 
 of the joint, the ulna in turn entering with its small end. 
 This arrangement permits the extensive rotation of the 
 hand which is most important for its free use. 
 
 Wrist. — The wrist is made up of a number of irregu- 
 larly shaped block-like bones. They are small and 
 are knit together by strong ligaments, so that they 
 give considerable freedom of movement without loss 
 of strength. 
 
 Hand. — The palm of the hand is formed of five slender 
 bones, which lead from the wrist bones to the roots 
 of the fingers. The first of these is tipped with two 
 fairly stout bones, which form the thumb. Each of 
 the remaining four bones carries three slender bones, 
 which form the fingers. 
 
 The hand of man resembles that of the higher apes 
 much more closely than does his foot, but it is supe- 
 rior to theirs in the position and flexibility of the thumb. 
 To this, man owes a part of the power of delicately 
 handling objects, which characterizes the use of his 
 hands. 
 
 Pelvic girdle. — The pelvic girdle consists of two broad 
 flaring bones which in front are joined together by liga- 
 ments and behind are also firmly connected by ligaments 
 to the sacrum. In young children, as in many of the 
 lower vertebrates, each of these two bones consists of 
 three distinct bones. Their union gives a much firmer 
 support for the legs and trunk. 
 
 Leg. — The legs are attached to the pelvic girdle by 
 means of the hip joints. Bach leg consists of two main 
 
THE LEG 
 
 23 
 
 parts, the upper or thigh, and the lower or leg. The 
 thigh consists of the longest and strongest bone in the 
 
 Fio. 18. Boiiee of arm and le^ ;— Fe, femnr; Fi, fibula ; H, Immcrus ; P, patella ; 
 R, radins ; T, tibia ; U, ulna. 
 
 human body, the femur. The leg, like the forearm, 
 has two parallel bones, the tibia, which is its main bone ; 
 
24 STRUCTURE OF THE HUMAN BODY 
 
 and the fibula, or slender splint bone. The enlarged 
 ends of the femur and the tibia meet together to form 
 the Imee joint. 
 
 Foot — Connected with the lower ends of the tibia and 
 the fibula by means of the ankle joint are the bones of 
 the ankle. They are a series of strong irregular block- 
 
 Fis. 19. Skeleton of foot of a man (A) Snd a gorilla (B), showing the more 
 flexible ankle and prehensile big toe of the gorilla. 
 
 like bones, which are fastened firmly together by liga- 
 ments. They form the ankle, heel and a portion of the 
 arch of the foot. Jointed to the front of this series there 
 are five slender bones, which complete the arch and reach 
 to the ball of the foot. As in the hand, the ends of the 
 second, third, fourth and fifth of these have three short 
 
THE FOOT 25 
 
 slender bones attached to them, which form the smaller 
 toes. The firet has two heavier and longer bouos, which 
 form the big toe. 
 
 The human foot differs markedly from that of man's 
 nearest relatives in the animal world, the apes. It is 
 so firmly Imit together that, unlike theii-s, it is nearly 
 useless for grasping and for climbing. This disadvan- 
 tage is juore than counterbahuiced, however, by the 
 fact that its strength enables man to walk firiulj' upon 
 his feet and thereby to maintain au upright posture. 
 
 EXPERIMEXTS AXD DEMOXSTRATIOXS 
 
 Materials: Human skeleton; skeletons of monkey, eat (dog or 
 rabbit), bii-d and fish; disseetiou of oat (dog- or rabbit) with 
 all flesh i-emoved; lobster; crab; fly (spider); and elam 
 (mussel) . 
 
 1) Demonstrate the human skeleton as a whole and in detail. 
 
 2) Compai-e the human skeleton with those of a monkey, cat 
 or doar. bird and fish. 
 
 3) Demonstrate the freshly dissected skeleton of a eat. dog, 
 or rabbit, to show bones, ligaments and joints. 
 
 ■1) Compare the skeleton of a vertebrate with those of a lob- 
 ster, ci-ab, fly (spider) and clam (mussel). 
 
 5) Imitate the natural shoulder movements upward, forward 
 and backward, with the skeleton. Carefully compare those 
 made with the body with those made with the skeleton, noticing 
 in detail the movements of clavicle and scapula. 
 
 6) Imitate in bke manner the various movements of the arms 
 and hands. Write them out and illustrate. 
 
CHAPTER III 
 BONES, JOINTS AND LIGAMENTS 
 
 Purpose of the skeleton. — The purpose of a skeleton 
 is to maintain the shape of the body in spite of its weight 
 and the pull of its muscles. To serve this purpose, the 
 bones must be rigid, strong and light. Their strength 
 and rigidity they owe to the material of which they are 
 made. Their lightness in proportion to their strength 
 is due to the fact that they are hollow.^ 
 
 Composition of bone. — Bones contain about sixteen 
 per cent of an animal substance called collagen, which 
 
 Fig. 20. Longitudinal section of long bone (tibia), showing structure. 
 
 when boiled becomes gelatine; thirty-four per cent of 
 earthy matter, chiefly salts of lime; and the remaining 
 fifty per cent, water. To the collagen, the bone owes 
 its toughness ; to the salts of lime, its rigidity and hard- 
 ness. Although bone without moisture might possess the 
 advantage of increased lightness in proportion to its 
 
 ' Hollow stems, like hollow bones, are found throughout nature, 
 as in grass, grains, reeds and bamboo. In manufactures, man has 
 imitated this, as in the bicycle frame, which combines great 
 strength and lightness. 
 
 26 
 
COMPOSITION OF BONE 
 
 27 
 
 strength, yet without moisture the bones could not re- 
 main alive, grow and repair themselves when injured. 
 The collagen represents the part of the bone which has 
 life. The earthy part is simply a deposit of salts of 
 lime made by the living part. 
 
 Changes from infancy to old age.— The composi- 
 tion of bone undergoes certain changes with age. In 
 
 Fig. ai . Greenstlck fracture 
 of bones of left forearm. 
 (Scndder and Cotton.) 
 
 5i>."M 
 
 Fig. 32. Fracture of bones 
 of left forearm. (Scudder 
 and Cotton.) 
 
 childhood, there is more of the animal matter and less 
 of the lime salts than in the adult. The bones of a child 
 are therefore more flexible and less easily broken. Even 
 when a bone is broken, the break usually does not extend 
 across it but makes what is called a greenstick fracture. 
 In adult life, on the contrary, the deposit of earthy 
 
28 BONES, JOINTS AND LIGAMENTS 
 
 matter is sufficient to give a maximum of strength and 
 rigidity to the bone. It therefore requires greater force 
 to break the bones of an adult and the break is com- 
 plete. In old age, the earthy material increases still 
 more in proportion to the animal matter and, as a result, 
 the bones become more brittle and are not apt to heal 
 as readily when broken. 
 
 Shapes of bones. — The forms of bones differ accord- 
 ing to their position and use in the skeleton. Those of 
 the arm, leg, palm, finger, arch of the foot, and toes 
 are called long hones, because they have relatively long 
 shafts. All the long bones have enlarged ends which 
 
 fe'S '-'iT.-MiSMi^M^ Osteoblasts 
 
 Fio. 23. The formation of new bone on the surface of old bone by means of a 
 layer of osteoblasts. 
 
 form joints. The block-shaped bones of the wrist and 
 ankle, on the contrary, have' the enlarged joint ends 
 but no shafts and are therefore called short bones. The 
 vertebrae are essentially short bones but they possess so 
 many extensions or processes that they have earned 
 the name of irregular hones. The sternum and bones 
 of the skull, which are each formed of two dense bony 
 plates united by a layer of spongy (cancellated) bone, 
 are called flat or tahular hones. The ribs are also ordi- 
 narily classed as flat bones in spite of their length, be- 
 cause they are built in the same way. 
 
GROWTH OF BONE 
 
 29 
 
 Building of bone.— The structure of bone cau best 
 be understood, if its growth and development are 
 studied. The long bones take shape in a gristly sub- 
 stance called cartilage, which like collagen yields .gela- 
 tine when boiled. The cartilage is then stiffened by a 
 
 Fie. 34. A small piece of bone, ground very thin and higlily magnified, showing 
 central canals for blood-vessels and bone cells with connccling filaments. 
 
 deposit of lime salts, and at the time of birth this 
 stiffened cartilage constitutes the boue. Soon after birth, 
 this is eaten into by large independent cells,^ which 
 make a sort of honeycomb of it. Another army of cells " 
 builds this honeycomb full of laj^ers of bone, in which 
 many of them become buried. The original cartilage 
 which formed the wall of the honeycomb is also eventu- 
 ally changed into true bone. 
 
 Growth of long bone in length. — The way in which 
 the bones when once formed grow, depends somewhat 
 
 * The osteoclasts. ' The osteoblasts. 
 
30 BONES, JOINTS AND LIGAMENTS 
 
 upon whether they are long, short, or flat. The increase 
 of the long bone in length is provided for by a continu- 
 ous growth of cartilage just within the ends, or epiph- 
 yses, of the bone, which as fast as it grows is honey- 
 combed and built into true bone. At the age of from 
 seventeen to twenty, the cartilage ceases to form and 
 bone growth stops. 
 
 Growth in thickness. — The growth in diameter of 
 the bone from the slenderness of childhood to the thick- 
 ness of the adult, takes place under the tough mem- 
 brane, the periosteum, which encloses the entire bone. 
 The periosteum deposits layers of bone beneath itself, 
 thus building up the outside as it grows in length. As 
 the bone becomes thicker through the deposits by the 
 periosteum, its central portion is hollowed out. The 
 central or medullary canal running through the shaft of 
 each long bone is thus formed and kept proportionate to 
 its size. In this way, the size and strength of the bone 
 are greatly increased, whereas its weight is kept down.^ 
 
 Growth of short bone. — The growth of short bones 
 is in general similar to that of long. Their structure, 
 however, is spongy rather than dense and they have no 
 definite central canal. 
 
 Growth of flat bone.— The flat bones develop chiefly 
 from the periosteum, instead of from the cartilage which 
 forms the starting point of both long and short bones. 
 
 Ends of bones. — The enlarged ends of bones which 
 form joints have a spongy structure with no central 
 canal. When these ends are sawed open, it is seen that 
 the sponginess is due to an arrangement of interlacing 
 
 ' In most animals, the central canal is filled, if the animals are 
 young, with blood-forming tissue, the red marrow; if the animals 
 are mature, with fat, the yellow marrow. In birds, the bones are 
 partially filled with air, thus giving greater lightness. 
 
JOINTS 31 
 
 arches and supporting trusses of bony tissue, which 
 branch out from the dense bone of the shaft. This ex- 
 pansion distributes over a broad surface the pressure 
 between the ends of the bones, and also gives a wide 
 foundation for the attachment of the ligaments and 
 muscles. 
 
 Structure of a joint. — The joint ends of the bone are 
 further adapted to slip easily upon one another and are 
 protected from injury by a thin cushion of smooth 
 elastic cartilage, the articular cartilage. The articular 
 cartilage is kept moist and slippery by a thin fluid, the 
 synovial fluid, which is secreted by a sleeve of mem- 
 brane called the synovial mcmhranc. This membrane, 
 which makes a closed ca\ity of the joint, is so loose 
 that it is not stretched or torn by any movements of 
 the joint. Normally, the amount of fluid secreted is 
 small, but in diseased conditions or after injury the 
 secretion may be so increased as greatly to distend the 
 synovial membrane and the surroimding ligaments. 
 When this happens in the knee joint, it is popularly 
 called water on the knee. 
 
 Range of movement. — Some joints permit but a slight 
 slip, such as that which oeeui-s between the sacrum and 
 the hip bone. Others have a wider but still compara- 
 tively restricted movement, as in the knuckles of the 
 fingers. Still" others have a relatively free movement, 
 as the shoulders. The main exceptions to the presence 
 of joints at the points of contact between bones, are 
 fovuid in the slmll, where the bones are so firmly held, 
 by the interlocking of their jagged edges that all move- 
 ment is made impossible soon after birth ; in the pelvic 
 bones, which in youth become perfectly blended to form 
 the hip bones; and in the sacrum, which, as we have 
 seen, results from the very early fusion of five vertebne. 
 
32 
 
 BONES, JOINTS AND LIGAMENTS 
 
 Characteristics of a true joint. — The three charac- 
 teristics of a true joint are the smooth cartilage-covered 
 ends of the bones ; the synovial membrane ; and the liga- 
 ments, which completely enclose the joint and, while 
 
 Frontal bone 
 
 '^Jv Suture 
 
 'Occipital bone 
 
 Fig. 25. The skull viewed from above, showing arrangement of bones and method 
 of locking together. 
 
 permitting natural movement, are tough and tight 
 enough to prevent any movement harmful either in 
 direction or extent. 
 
 Kinds of joints. — Joints are classified according to 
 their range and character of movement, which depend 
 jipon their shape and the arrangement and tightness 
 of the ligaments. The joints permitting the greatest 
 range are the ball-mid-socket joints, in which the 
 rounded head of one bone moves in the hollow socket of 
 another. Their capsular ligaments are sufficiently loose 
 to allow the ball to move freely in its socket up to the 
 
KINDS OF JOINTS 
 
 33 
 
 point at which it might be pried out, or dislocated. At 
 that point, the ligaments on the farther side of the joint 
 become tight and thereby prevent dislocation. Examples 
 
 Tnceps muscle- 
 Humerus- 
 
 Brachialis muscle 
 (assists biccpii 
 
 Bursa (much distendi 
 Synovial sac ^much■ 
 di^tenui 
 
 Articular cartilages 
 
 Circular ligament of. 
 head of radius 
 
 Tendon of biceps 
 Bursa (much distendedv 
 
 Radius 
 
 Ligament between 
 radius and ulna 
 
 Ulna 
 
 Fi&. 26. Section of elbotv, sliowing botli a hiiige joint (liiimerna and nlna), and a 
 pivot joint (radias and ulna). (The surfaces of ttie elbow joint are shown un- 
 naturally separated, and the synovial sac and bursse injectud with fluid.) 
 
 of ball-and-socket joints are the shoulder and hip and in a 
 measure the knuckles. 
 
34 BONES, JOINTS AND LIGAMENTS 
 
 Hinge joints. — Joints which have free motion in but 
 one direction, as in the elbow, the knee and the first and 
 second joints of the fingers, are called hinge joints. 
 Usually in this class of joints, the ends of the bones have 
 more or less perfect ridges which tend to strengthen 
 the joint against any sidewise slip. They also have 
 strong tight ligaments at the sides. 
 
 Knee joint. — The knee joint, although classed among 
 the hinge joints, is somewhat complicated by the 
 
 Lit^amenl; of patella 
 
 Cu h on of fat 
 
 External aeinilunar cartilage 
 Anterrof crucial Ijgamenl 
 
 Articular surface of 
 
 liead or tibia 
 
 Posterior crucial ligament 
 
 Internal semilunar cdrtilage 
 
 Tenrlon or a flexor muscle 
 
 Fig. 27. Right knee joint, showing the cartilages and ligaments attached to head 
 of tibia. 
 
 various additional structures necessary to protect and 
 strengthen it, because of its exposed position and the 
 heavy weight which it is called upon to bear. Upon 
 either side are loose pads of cartilage,^ which serve to 
 cushion the ends of the bones and protect them against 
 side strain. For further protection, the kneecap or 
 
 ' The semilunar cartilages. 
 
THE KNEE JOINT 
 
 35 
 
 patella ^ is inserted into the tendon which runs from the 
 thigh muscle over the front of the knee to the tibia. 
 The patella is a flattened rounded bone, which protects 
 
 Tendon of muscle 
 extending leg 
 Synovial sac (distended) 
 Patella 
 Bursa 
 
 Tendon of patell 
 
 Posterior cross 
 
 ligament of knee 
 Anterior cross 
 
 ligament of knee 
 
 Articular cartilage— 
 
 Bursa" 
 
 Fig. 28. Cross sectiou of knee, showing the varioas strnctnres which malie np 
 the kuee joint (somewhat diagrammatic), 
 
 the tendon and to some extent the knee joint also. It 
 is, however, itself subject to rather frequent injury on 
 account of its exposed position. 
 
 ' The patella is really a specialized part of the tendon itself, 
 developed for the purpose of making the tendon better able to 
 withstand contact with objects. Similar examples of the develop- 
 ment of bone in tendons is found in other places where tendons 
 are liable to injury, as under the second joint of the big toe. 
 
36 
 
 BONES, JOINTS AND LIGAMENTS 
 
 Humerus 
 Circular iigarhent 
 
 *— Radius 
 
 Ulna 
 
 Fig. 29. Fracture of liumeina. (Scudder 
 and Cotton.) 
 
 Pivotal joints. — Another form of motion in one direc- 
 tion is that permitted by the pivotal joints, in which the 
 
 movement is rotary, 
 as on a pivot. An 
 example of a pivotal 
 joint is that between 
 the first and sec- 
 ond cervical vertebrEe, 
 which permits the 
 head to turn from 
 side to side. An- 
 other example is the 
 joint at the elbow 
 end of the radius, 
 which turns as a 
 pivot within a cir- 
 cular ligament at the side of the ulna and thereby 
 allows the palm of the hand to turn either up or 
 down. 
 
 Sliding joints. — Other forms of joints, such as those 
 between the articular processes of the vertebrse, permit 
 a sliding movement and are therefore called sliding 
 joints. Still others, like the joints between the bodies 
 of the vertebrae, allow merely a slight tipping in all 
 directions. In the case of the vertebra, this would seem 
 to be largely a rocking motion upon the pads of elastic 
 cartilage between the bones, rather than a true slip of 
 the joint surfaces. 
 
 Ligaments. — The supporting ligaments, which are so 
 important in every joint structure, take the form of a 
 sleeve or capsule, which encloses the ends of the bones 
 and is called the capsular ligament. Besides the capsular 
 ligament, most joints have (idditional ligaments which 
 strengthen them where necessary. All ligaments eon- 
 
INJURIES TO JOINTS 
 
 37 
 
 sist of fine fibres of tough, flexible and inelastic tissue, 
 which run from bone to bone across the joint.^ 
 
 Kinds of movement. — The various kinds of move- 
 ment which joints permit us to make with our limbs 
 are chiefly bending, or flexion; straightening, or f.r- 
 tension; turning as on an axis, or rotation; moving away 
 from the middle of tlie body, or abduction; towards the 
 middle line, or adduction; and swinging in a circle, or 
 circumduction. 
 
 Joint injuries.—- Joints are points of weakness iii the 
 skeleton, as shown by the fact that injuries to them 
 are much more numerous than to bones. Their weak- 
 ness is due to the difiBculty 
 of combining freedom of 
 movement with strength. 
 "When a severe wrench is 
 given a joint from which 
 pain and swelling result, it 
 is said to be sprained. In 
 sprains, the fibres of the 
 ligaments are more or less 
 torn and their blood-ves- 
 sels are ruptured. If the 
 injury is severe, there is 
 swelling and subsequent 
 black and blue discolora- 
 tion, due to the blood 
 which has escaped from the ruptured blood-vessels. 
 Sprains heal slowly and may require even more care- 
 ful and prolonged treatment than fractures, in order 
 to prevent permanent stiffness and weakness. - 
 
 ^ Where the capsular ligaments are loose, as at tlie elbow, there 
 is great danger of their being pinched when the joint is flexed or 
 extended. To avoid this, muscle fibres are inserted to pull the 
 loose portion of the capsular ligament out of the joint. 
 
 ' In sprains, the ends of the bones are sometimes fractured. If 
 
 Fia. SO. Dislocation of elbow. 
 (Scndder and Cotton.) 
 
38 BONES, JOINTS, AND LIGAMENTS 
 
 Dislocation. — "When the bones forming a joint are put 
 under such severe strain that they are pried or pulled 
 out of place, the joint is said to be dislocated. In the 
 case of most joints, dislocation is accompanied by more 
 or less tearing of the capsular ligaments, and at times 
 even by injury to the ends of the bones. 
 
 Bone-building materials. — The earthy material for 
 the building of bones is present in all food in small but 
 sufficient quantities for normal growth and constitutes 
 a portion of the ash which remains when food is burned. 
 Although all foods contain a certain amount of bone- 
 building material, some contain more than others.^ It 
 is therefore of the greatest importance, especially dur- 
 ing such a period of rapid growth as early childhood, 
 to have food which will give the bones proper nour- 
 ishment. Although pure milk, for example, is a suffi- 
 cient food for infants, yet when the child at the age 
 of from eight to ten months becomes active and sup- 
 ports his weight by his bones in sitting, standing and 
 walking, milk should be supplemented by cereals and 
 fruit juices. If this is not done, the bones are frequently 
 so poorly built that they bend under the weight of the 
 child and he becomes bow-legged, knock-lmeed, or flat- 
 footed, and may even have deformed arms and a crooked 
 back.^ Plenty of wholesome food, fresh air and sunshine 
 
 this complication is overlooked, as frequently happens, the serious- 
 ness of the sprain is greatly aggravated. 
 
 ' See table of food materials, p. 86. 
 
 ' A similar condition of vi^eakness of bones arises even more 
 frequently when the food of babies is limited to certain infant 
 foods which are largely modified starch and so fail to give the 
 other constituents of a complete diet. Many parents are deceived 
 by the resulting fatness of the baby and do not realize that a child 
 may be fat and yet be weak, because it is being deprived of neces- 
 sary food constituents. The excess of fat is even a great disad- 
 vantage, because it overburdens weak bones, which normally are 
 none too strong in a child who is just beginning to walk. 
 
EXPERIMENTS 39 
 
 will lead to a strong and I'omplete gro^\i:h of the bones 
 and a fine development of the body as a whole. Poor 
 food and bad air have a distinctly stunting effect upon 
 bone as upon other growth. ^ 
 
 EXPERIilEXTS AND DEMONSTRATIONS 
 
 ^[atenals: Bones of the hiud leg of a lamb sawed lengthwise 
 through the .ioints; pieces of fresh ivory hone, such as the thin 
 hones found in the legs of fowls; pieces of dry ivory houe; 
 hydrochloric acid ; ammonia ; piece of sheet iron ; weighing 
 balance; human skeleton such as may be purchased for $25 or 
 $30; microscope. 
 
 1) Strucluir of a long bone: Demonstrate position and ar- 
 rangement of dense (ivory) and cancellated bone; the medul- 
 lary canal; joint ends with epiphyses; ai'ticular cartilage; the 
 periosteum; red and yellow marrow; and the microscopic 
 structure of bone. 
 
 2) Composition of bone: 
 
 a) Boil a piece of fresh bone in water to extract gelatme. 
 
 b) Burn a piece of fresh bone to destroy animal matter. 
 
 c) Put a piece of burned bone and a piece of fresh bone uiio 
 dilute hydrochloric acid (1 part acid to 3 parts water) and let 
 stand 2 days, in order to remove the earthy matter. 
 
 3) Proportions of water and solid in fresh bone: Break a 
 piece of bone iuto smaU fragments, weigh; theu dry in a cur- 
 rent of warm air to a constant weight and determine loss. 
 
 4) Proporti<ins of animal and mineral matter in dry bone: 
 
 a ) Weigh a piece of dry houe, burn on a piece of sheet iron 
 over live coals or over Bunseu burner, and reweigh. 
 
 b) Second method : Weigh, dissolve m 10 per cent hydro- 
 chloric acid, dry. in a warm place for 3 or -i days to obtain a 
 constant weight, and determine loss. 
 
 e) Demonstrate the presence of mineral matter m the solu- 
 tion of b) by precipitating it with ammonia. 
 
 5) Structure of joint: Demonstrate by dissection the cap- 
 sular and reinforcing lig-ameuts ; the syiioWal fluid ; the articular 
 cai'tilage; the function of ligaments. 
 
 ' If the vitiility of the bones is weakened, they seem predisposed 
 to disease. The most common disease of bones in childhood is 
 tuberculosis, which forms destructive abscesses in tlie bones and 
 joints, and thereby causes marked deformities. 
 
CHAPTER IV 
 
 MUSCLES AND TENDONS 
 
 Muscles.— The bones of the skeleton are moved by the 
 muscles, which form the chief bulk of the limbs and of 
 a considerable portion of the trunk and give to the body 
 its rounded graceful form. Many of them are imme- 
 diately under the skin, so that we can feel them as they 
 work. If, for example, we grasp with our left hand 
 the large muscle which lies between the shoulder and 
 the elbow on the front of the arm, the biceps, and then 
 pull and push against some object, we can trace 
 the muscle from its origin in the shoulder to its in- 
 sertion upon the radius. We can also feel the dif- 
 ference between the soft elastic belly of the muscle 
 V; when relaxed and its 
 
 hardness when con- 
 tracted. 
 
 Structure. — The 
 structure of muscle 
 can be studied in the 
 flesh of animals, espe- 
 cially in cross section 
 as in a steak. The 
 mass of muscle is seen 
 to be made up of fairly large sections, an inch or two 
 in diameter, which can be pulled apart easily, since 
 they are held together only by delicate fibres of connec- 
 tive tissue with a certain amount of fat interspersed. 
 
 Muscle fibres. — The large muscle sections are made 
 up of smaller divisions, the fasciculi. Under the micro- 
 
 40 
 
 Fig. 31. A small bit of muscle composed of 
 five primary frtsciculi. A,_ natural size : B, 
 the same magnified, showing the secondary 
 fasciculi of wnich the primary are composed. 
 
MUSCLE STRUCTURE 
 
 41 
 
 scope, the fasciculi are seen to be bundles of fibres 
 packed tightly together. These fibres, when traced 
 throughout their length, are found to be slender hair- 
 like cells about one and a half inches long and one- 
 thousandth of an inch in diameter, crossed by many 
 dark and light bands and covered with a thin mem- 
 brane. Each fibre in turn consists of many much finer 
 contractile threads, the fibrils. 
 
 Tendon fibres.— To one or both ends of each of the 
 muscle fibres is usually attached a fine silkj- thread of 
 
 [■Contractile 
 fibrillae 
 
 -Striae 
 
 -Nucleus 
 of sheath 
 
 -Cement 
 Substance 
 
 -Tenttoi, 
 fibre 
 
 Fig. 3.;. Endof striated (voluntary) 
 luiiscle fibre, showing its att«cli- 
 lueut to tendon fibre. 
 
 Fig. 3S. Diagram showing arrange- 
 ment of muscle fibres in relation'to 
 their tendons : A, in muscles con- 
 tracting through a considerable dis- 
 tance ; B, in muscles of shorter and 
 more powerful contraction ; C, in 
 muscles of very short and powerful 
 contraction. 
 
 tough inelastic material, the fetidon fibre. Since the 
 muscle fibres are usually much shorter than the muscle 
 itself, these threads have to run well Tip into the muscle 
 in order to reach the ends of the fibres. By blending 
 together, they form the strong hard continuation of the 
 muscle, the tendon, which joins the muscle to the bone. 
 
42 MUSCLES AND TENDONS 
 
 Union of muscle and tendon.— The large majority 
 of muscles have but one tendon, which is at the outer 
 end, or insertion, of the muscle. The inner end, the 
 origin, of the muscle is attached directly to the bone. At 
 the origin, the muscle fibres are attached to the bone 
 by means of a cement so strong that, in spite of the 
 tremendous pulls to which it is subjected, it seldom or 
 never gives way. The other ends of the muscle fibres 
 are cemented to the tendon fibres, which in turn are 
 cemented to the bone. 
 
 Advantages of tendons. — An important purpose of 
 the tendon is to economize space, since a slender tendon 
 is strong enough to carry the pull of a powerful muscle 
 over a joint or series of joints, as in the case of the mus- 
 cles of the forearm which move the fingers. If it were 
 not for the tendons, bulky muscles would be required 
 wherever movement was necessary, even in the fingers 
 and toes. Tendons are furthermore so flexible and slip- 
 pery that they readily pass around corners, as in the 
 ankle, without any appreciable loss of power through 
 friction. 
 
 An examination of the arms shows that the muscles 
 which move it lie upon the trunk and are not carried 
 by the arm in its movement. The muscles which move 
 the forearm lie upon the upper arm and as close to the 
 shoulder as possible. In like manner, the muscles which 
 move the wrist, palm and fingers are placed not in the 
 hand but upon the forearm close to the elbow. The 
 long tendons make it possible thus to bring the weight 
 of the muscles upon the more slowly moving parts of 
 the limbs. Upon this distribution of weight, ease and 
 quickness of movement depend. 
 
 Control of joint movements. — ^Wherever in the hu- 
 man skeleton a joint is found, the movement of the 
 
MUSCLES OF ARM 
 
 43 
 
 "^' 
 
 Fio. 85. Front of risht arm, showing 
 Fib. 84. Back of forearm and hand. muscles, tendons, arteries and nerve, 
 
 bones wliieli enter into it is perfectly controlled by the 
 puJl of the nrascles. The number of muscles about each 
 
44 
 
 MUSCLES AND TENDONS 
 
 joint depends largely upon the amount of motion per- 
 mitted in it. In a simple joint, for example, such as 
 
 (L: 
 
 Extensor j| 
 muscle 
 of thigh 
 
 Knee cap 
 
 Fig. 36. Diagram illuBtrating 
 the muscles (drawn in thick 
 black lines) which pass before 
 and behind the joints, and by 
 their balanced contraction 
 keep tlie joints rigid and the 
 body erect. 
 
 Tibia 
 
 Fibula 
 
 Fie. 37. Flexor and extensormuscles 
 of the left thigh (somewhat diagram- 
 matic). 
 
 the hinge joint in the finger which permits only flexion 
 and extension, but two controlling muscles are essen- 
 tial, a flexor and an extensor. In a ball-and-socket joint, 
 
MUSCULAR ENERGY 46 
 
 such as the sliouhier, a larger number of muscles is 
 necessary to insure exact and powerful control. In gen- 
 eral, muscles are arranged in pairs, so that each muscle 
 as it lies on one side of the joint has on the other side 
 an opposing muscle read^' to pull the bone in the oppo- 
 site dii'ection. In many eases where powerful action 
 is required, the principal pair of opposed miiscles is 
 reinforced by iissisting muscles. Sometimes, there are 
 as many as four or five muscles on one or both sides 
 of a joint, as in the Iniee.^ 
 
 Production of energy. — During muscular activity, 
 animals give off in their breath an increased amount of 
 carbon dioxide,- which is produced by the union of the 
 oxygen that they breathe with the carbon in the food 
 that they eat. This union is a form of combustion, or 
 oxidation, and like all combustion sets free energy, which 
 in the casse of the muscles is partlj'' muscular energy 
 and partly heat. In addition to the carbon, other food 
 materials are brought to the muscles by the blood- and 
 are oxidized by them for the production of energy.* 
 The muscle is able to convert one-third of the total 
 energy developed by the combustion into a definite pull 
 upon the bones, whereas the best steam engines are able 
 to convert only one-sixth of the total force produced by 
 the combustion of their fuel into effective work. 
 
 Nerve control, — In order that a muscle may develop 
 energy, its cells must be stimulated by their nerves. 
 When the main nerve leading to a muscle is injured or 
 cut, the muscle is imable to work, it becomes soft and 
 
 • On tlie front of tlie thigh, one very large muscle extends the 
 leg; at the back, five much smaller muscles flex it. 
 
 ' Carbon dioxide ( CO ) equals 1 part of carbon to 2 of oxygen. 
 (See Appendix A, p. 316.) 
 
 ' Each cell of the muscle acts as a separate little engine for the 
 generation of this pois'er. 
 
46 
 
 MUSCLES AND TENDONS 
 
 soon begins to waste away, or atrophy. In other words, 
 the muscle is paralyzed and cannot act. 
 
 Tonicity. — In a healthy muscle with its nerve unin- 
 jured, we find a constant slight elastic resistance, or 
 tension, which persists even when the muscle is not con- 
 tracted. This tension is 
 called the tonicity of 
 the muscle, since it 
 gives it the elastic tone . 
 characteristic of health. 
 It is due to a continu- 
 ous but very slight con- 
 traction of the muscle. 
 The contraction is in 
 turn due to a constant 
 slight stimulation of 
 the muscle by its nerve 
 and a consequent con- 
 tinuous setting free of 
 energy by combustion. 
 Each muscle, even when 
 idle, is thus given suf- 
 ficient exercise to keep 
 it in a healthy condition. 
 Moreover, by being kept 
 tense, it is instantly ready for action. The constant 
 combustion is further useful in helping to keep the 
 body warm during inactivity and sleep. ^ 
 
 Voluntary muscles. — Most of our muscles are under 
 our control and can be made to do what we will. Be- 
 cause of this, they are called voluntary muscles. They 
 
 ' When the body is chilled, the shivering which results consists 
 of the rapid contraction of many muscles. Its purpose is to develop 
 heat enough to vi'arm the body. 
 
 Fig. 38. Lengthening of biceps wlien arm 
 is extended. 
 
EXPLANATION OF PLATE II. 
 
 A view of the muscles situated on the front surface of the hody 
 seen la their natural position. It must be understood that beneath 
 these muscles many others are situated, which cannot be represented 
 in the figure. 
 
 Muscles of the Face, Read and Neck : 
 
 1. Muscle of the Forehead. This, together with a muscle at the back of 
 
 ^the head, has the power of movins the soalp. 
 2. -Muscle that closes the Eyelids. The muscle that raises the upper eyelid 
 
 so as to open the eye Is situated within the orbit, and consequently 
 
 cannot be seen in this flgnre. 
 S. 4. 5. Muscles tluit raise the Upper Lip and angle of the Mouth. 
 G, 7. Muscles that depress tlie Lower Lip aud angle of the Month. By the 
 
 action of the muscles which raise the upper lip, and those that depress 
 
 the lower lip, the lips are separated. 
 S. Muscle that draws the Lips together. 
 9. Muscle of the Temple (Temporal Muscle). 
 
 10. Masseter Muscle. 9 and 10 are the two chief muscles of mastication, 
 
 for when they contract the movable lower jaw is elevated, so as to 
 crush the food between the teetli in the upper and lower jaws. 
 
 11. Muscle that compres.ses the Nostril. Close to its outer side is a small 
 
 muscle that dilates the nostril. 
 
 12. Muscle that wrinkles the Skin of the Neck, and assists in depressing 
 
 the lower jaw. 
 IS. Muscle that assists in steadying the Head, and also in moving it from 
 side to side. 
 
 14. Muscles that depress the Windpipe and Organ of Voice. The muscles 
 
 that elevate the same parts are placed l>eneatb the lower jaw, • and 
 cannot be seen in the figure. 
 
 Muscles that connect the upper extremity of the trunk. Portions 
 of four of these muscles are represented in the figure, viz. ; 
 
 15. Muscle that elevates the Shoulder (Traperins Muscle). 
 
 17. Great Muscle of the Chest, which draws the Arm in front of the Chest 
 
 (Great Pectoral Muscle). 
 IS. Broad Muscle of the Back, which draws the Arm downwards across the 
 
 back of the Body (Latlssimus Dorsl). 
 
 19. Serrated Muscle, which extends between the Ribs and Shoulder blade, 
 
 and draws the Shoulder forwards and rotates it. a movement which 
 takes place In the elevation of the arm above the head (Serratns 
 magnus) . 
 
 At a lower part of the trunk, on each side, may he seen the large 
 muscle which, from the oblique direction of its fibres, is called 
 
 20. Outer Oblique Muscle of the Abdomen. 
 
EXPLANATION OP PLATE U.— (Continued) 
 
 Several muscles lie beneath it. The outline of one of these, 
 
 21. Straight Muscle of the Abdomen, may be seen beneath the expanded 
 
 tendon of Insertion of the oblique muscle. These abdominal muscles, 
 by their contraction, possess the power of compressing the eoDtents of 
 the abdomen. 
 
 Muscles of the upper extremity : 
 
 16. Muscle that elevates the Arm (Deltoid Muscle). 
 
 22. Biceps or Two-headed Muscle (see also page 46). 
 
 23. Anterior Muscle of the Arm. This and the Biceps are for the purpose 
 
 of bending the Forearm. 
 
 24. Triceps, or Three-headed Muscle. This counteracts the last two muscles, 
 
 for it extends the Forearm. 
 
 25. Muscles that bend the Wrist anij Fingers, and pronate the Forearm and 
 
 Hand — that is, turn the Hand with the palm downwards. They are 
 called the Flexor and Pronator Muscles. 
 
 26. Muscles that extend* the Wrist and Fingers, and suplnate the Iflorearm 
 
 and Hand — that is, turn the hand with its palm upwards. They are 
 called the Extensor and Supinator Muscles. 
 
 27. Muscles that constitute the ball of the thumb. They move It in differ- 
 
 ent directions. 
 
 28. Muscles that move the Little Finger. 
 
 Muscles which connect the lower extremity to the pelvic hone 
 (several are represented in the figure) : 
 
 29. Muscle usually stated to have the power of crossing one Leg over the 
 
 other, hence called the Tailor's Muscle, or Sartorlus; its real action 
 is to assist In bending the knee. 
 
 30. Muscles that draw the Thighs together (Adductor Muscles). 
 
 31. Muscles that extend or straighten the Leg (Extensor Muscles). The 
 
 muscles that bend the Leg are placed on the back of the thigh, so 
 that they cannot be seen in the figure. 
 
 Muscles of the leg and foot : 
 
 S% Muscles that bend the Foot upon the Leg, and extend the Toes. 
 
 33. Muscles that raise the Heel — these form the prominence of the calf of 
 
 the Leg. 
 
 34. Muscles that turn the Foot outwards. 
 
 35. A band of Membrane which retains In position the tendons which pass 
 
 from the leg to the foot. 
 
 36. A short muscle which extends the Toes. 
 
 The muscles which turn the foot inwards, so as to counteract the 
 last-named muscles, He beneath the great muscles of the calf, which 
 consequently conceal them. The foot possesses numerous muscles, 
 which act upon the toes, so as to move them about in various direc- 
 tions. These are principally placed on the sole of the foot and they 
 cannot therefore he seen in the figure. Only one muscle, 36, which 
 assists in extending the toes, is placed on the hack of the foot. 
 
10 
 
 12 
 
 \ 
 \ 
 
 m 
 
 Zi 
 
 1%M 
 
 -35 ^^^36 
 
VOLUNTARY MUSCLES 
 
 47 
 
 are made up, as we have seen, of slender fibres having 
 a characteristic cross-striped, or striated, appearance. 
 When they contract, their fibres become shorter and 
 thicker, thus shortening and thickening the muscle as a 
 whole. The time required for contraction may be very 
 slow or as quick as one-tenth to one-twentieth of a sec- 
 ond. All muscles con- 
 nected directly or indi- 
 rectly with the bones 
 are classed as voluntary. 
 
 Involuntciry muscles. 
 — The muscles in the 
 walls of the stomach, in- 
 testines and blood-ves- 
 sels are independent of 
 the control of the will 
 and are therefore called 
 involuntary. They dif- 
 fer from the voluntary 
 in that they are comparatively short, are non-striated 
 or "smooth," and require as long as from ten to sixty' 
 seconds for a complete contraction. 
 
 Comparison of voluntary and involuntary muscles. 
 — The distinction between the voluntary and the invol- 
 untary muscles cannot be drawn too closely, since, al- 
 though they differ markedly from each other in size 
 and structure, yet the voluntary muscles may act invol- 
 untarily. A good illustration of this is seen in the 
 movements due to sudden danger, as in winking or 
 starting at a noise. Although the muscles controlling 
 these movements are usually rmder volimtary control, 
 yet in times of danger they may act so quickly for the 
 protection of the body that interference by the will is 
 impossible. This is also true of many other muscles, 
 
 •Humerus 
 
 Contraction of biceps to flex 
 
48 MUSCLES AND TENDONS 
 
 as, for example, those which cause the movements of 
 the chest in respiration. These muscles seem thoroughly 
 under the control of the will, since 
 we can prolong, shorten, or even 
 stop breathing for a time. There is, 
 however, a point where the volun- 
 tary control is mastered by the in- 
 voluntary and we are forced to breathe 
 and not suffocate. 
 
 Fio. 40. Isolated 
 smooth mnscle Pig. 41. Smooth or involnntary mnscle fibres, 
 
 fibres. showing their arrangement. 
 
 Heart muscle. — In addition to these two types of 
 muscle structure, there is a third foiuid only in the 
 heart, which somewhat resembles both. Its cells are 
 striped like those of the voluntary muscles and yet its 
 action is like that of the involuntary muscles, since it is 
 not under the control of the will. It contracts more 
 quicklj^ than the involuntary and yet not so quickly as 
 the volimtary. 
 
 Effect of work.— The muscles do an amount of work 
 far beyond our comprehension, as we shall see in our 
 study of motion and locomotion. They thrive upon hard 
 work and grow larger and stronger as the demands upon 
 them increase, provided only that they are not ex- 
 hausted by overwork. Conversely, when the demands 
 upon them are slight, they become smaller and weaker. 
 Contrary to popular belief, however, they are never 
 completely lost through disuse, because, even when they 
 are idle, there is yet sufficient tonic contraction to main- 
 
MUSCULAR ACTIVITY 49 
 
 tain them. Thus, in spite of thousands of years of dis- 
 use, we still retain the muscles which presumably at 
 some time moved the ears of our ancestors. 
 
 Influence upon other organs. — As we have seen, the 
 muscular energy of animals and man is derived fFom 
 the combustion of the food materials furnished by plants 
 and animals. A sufficient diet is therefore essential, if 
 our muscles are to do their work easily and well. Since 
 tlie muscles constitute a large part of the active tissues 
 of the body^ a correspondingly large proportion of the 
 food which we eat finds its way to them. The digestive 
 system prepares tills food for their use. The blood 
 conveys it to them and takes away the waste products 
 of their activity. The lungs and kidneys remove these 
 waste products from the blood. And, finally, their ac- 
 tivity as a whole is controlled by the nervous system. 
 We can thus see that the muscles are responsible for 
 a large part of the body's activity. As a result, the 
 amount of work which the muscles are called upon to 
 do determines very largely not only the growth and de- 
 velopment of the muscles themselves, but the activity 
 and development of the other organs of the body as 
 well. 
 
 EXPERIMENTS AND DEMONSTRATIONS 
 
 Materials : Frog killed by ether or chloroform ; a slice of meat 
 cut across the grain, such as a low cut of the leg including the 
 bone; normal salt solution (11/2 dre. table salt to 1 qt. water). 
 
 1) Dissect away the skin of frog's leg and note the outlines 
 of muscles; the tendon attachments; and the relation of muscles 
 to joints. Sketch observations. 
 
 2) Examine in a shce of meat the cross sections of muscle 
 bundles. Also note and sketch the connective tissue jn its z-ela- 
 tion to the muscle bundles; the surface tendons; and the inter- 
 muscular tendons. 
 
60 MUSCLES AND TENDONS 
 
 3) Prepare muscle fibre by plunging the leg of a freshly 
 killed frog into water at 131° ¥. and allowing it to cool. 
 Teaze out the muscle fibres with needles in a normal salt solu- 
 tion. Examine under microscope and sketch. 
 
 4) Location of various muscles : Identify 10 of the muscles in 
 Plate II by attempting movement against resistance and then 
 locating the muscles which are contracted. Trace from origin 
 to insertion. 
 
 5) Arrangement of tendons: Using the same method as in 4), 
 determine whether the muscles have tendons at one or at both 
 ends. 
 
CHAPTER V 
 MOTION AND LOCOMOTION 
 
 Simple forms of movement. — The ability to move is 
 a more or less general property of living matter, since 
 it is found in many plants and all animals. One of the 
 most primitive devices for motion we have already seen 
 in the ameba, which moves about by changes of form in 
 its soft elastic body. Many other one-celled plants and 
 animals are able to move by the lashing of hair-like 
 projections from their bodies. Animals which float in 
 water have the advantage of requiring but little effort 
 to produce motion, since their 'sveight is -supported by 
 the water. Some aquatic animals much higher in the 
 scale of development than the ameba, as, for example, 
 certain jelly fishes, are able to get about quite swiftly 
 b}'' hair-like processes similar to those of one-celled 
 plants and animals. 
 
 More complex forms. — Land animals, on the con- 
 trary, must either drag their bodies along on the ground 
 or lift their weight and, therefore, as their bodies in- 
 crease in weight the means of producing motion be- 
 comes more and more complex. In many worms, mo- 
 tion is accomplished by a laborious process of short- 
 ening and lengthening the body. Others attain much 
 greater speed by their many little legs, which lift the 
 body from the groimd and enable them to take definite 
 steps unhindered by its drag. As we get higher in the 
 animal scale, the legs are longer and are stiffened in 
 
 51 
 
52 
 
 MOTION AND LOCOMOTION 
 
 various ways, in order to lift the body and increase the 
 length of the step. In insects, the legs are tubes of 
 horny substance, within which lie the muscles for mov- 
 
 FiG. 43. Angle worm progressing by contracting and extending body. 
 
 ing them. In all the higher animals, the legs are stiffened 
 by bones, which make possible long steps and corre- 
 spondingly rapid progress. The bones are moved by 
 muscles surrounding and protecting them and act as 
 
 ■^"^^^*^8ft#' 
 
 Fio. 43. Measuring worm ready to "step" forward. 
 
 levers greatly to increase the range of movement brought 
 about by the contraction of the muscles. 
 
 Definition of lever. — A lever is a device for the 
 application of force {power) to overcome resistance 
 {weight) by utilizing a third force or support {fulcrum). 
 Thus in every case there must be three forces acting at 
 different points on a lever. 
 
 Law of leverage. — The simplest form of lever is that 
 used by children in a see-saw. The weights of the two 
 children are the two forces acting downward upon the 
 ends of the board, and the support upon which the middle 
 of the board rests is the third force acting upward. It 
 
LEVEES 
 
 53 
 
 will be found by careful measurement that, if the two- 
 children ai'e of exactly equal weight, thej'^ must sit at 
 equal distances from the fulcrum. In other words, the 
 two arms of the lever must be of equal length. If, how- 
 ever, one child is twice the weight of the other, the lighter 
 must sit twice as far from the fulcrum to balance the 
 heavier. 
 
 It is thus seen that the long arm of a lever and a 
 light weight are equal to a short arm and a heavy weight. 
 The fundamental law of leverage is that the forces are 
 inversely proportional to the lengths of the arms on 
 which they act, that is, to their distance from the 
 fulcrum. 
 
 Classes of levers. — Levers are ordinarily divided 
 into three classes, as determined by the relative posi- 
 
 Fie.' 44. Examples of levers of the first class, with analysis of the forces inrolved. 
 The direction of the forces is indicated by the direction of the arrows ; their 
 relative amounts by both the length of the arrows and the figures. F -fnlcrmu ; 
 P = power ; W = weight. 
 
 tions of the fidcrum, the power and the weight. To 
 the first class belongs the lever which has the fulcrum in 
 the middle; to the second, that which has the weight 
 in the middle; to the third, that which has the power in 
 the middle. It will be readily seen that, given the same 
 lengths of arms and the same forces, the balance remains 
 
54 MOTION AND LOCOMOTION 
 
 the same, regardless of whether one end, or the middle, 
 or the other end of the lever is the fulcrum, power, or 
 
 weight. 
 
 Leverage in animal bodies. — In animals, a joint is 
 always the fulcrum and the muscles always furnish the 
 
 Phoo 
 
 Fig. 45. Examples of levers of the second class. 
 
 power. The levers of the animal body are of the first 
 or third class, and, in order to give speed and range of 
 movement, the power arm is short and the weight arm 
 
 > ' i 
 
 
 F 
 
 
 P 
 
 25. 
 
 20 
 
 F| 100 
 
 Wiioo 
 
 200 
 
 r)-- / jT-^ 
 
 Fig. 46. Examples of levers of the third class. 
 
 long. This arrangement necessitates great strength of 
 muscle applied to the short arm, in order to counter- 
 balance the weight applied to the long arm. 
 
BODY LEVERAGE 55 
 
 Examples of levers of the first class. — Examples of 
 the first form of lever are fovuid in the nodding of the 
 head, in the extension of the elbow by the triceps muscle 
 on tlie back of the arm, and in the raising of the body 
 upon the toes by means of tlie calf muscles. In the lat- 
 ter ease, the pressure upon the floor by the weight of 
 the body is equivalent to tlie support, or pressure against 
 the foot, given by the floor. Since the floor support 
 is the external force counterbalanced by the pull of the 
 muscles, it is the weight.^ 
 
 Examples of the third class. — Of tlie third class of 
 levers, we find examples in tlie action' of the biceps in 
 raising weights by the flexion of the elbow ; in the action 
 of the pectorals in drawing the arm inward ; and in the 
 action of the muscles which dx'aw tlie ami downward, 
 as in hauling or climbing a rope. 
 
 Body as a weight. — A studj' of the problems in bodj' 
 leverage shows that the force exerted by the muscles 
 is surprisingly large. It is further greatly increased 
 if the bodj- gets heavier witliout a corresponding in- 
 crease in muscle power. For example, if a man weigh- 
 ing three hiuidred pounds climbs a stair, the quadriceps 
 muscle must exert, when his leg is bent, a pull amount- 
 ing to about a ton. A man weighing but one hundred 
 and fifty pounds would require of his muscle five hun- 
 dred pounds less force.- 
 
 ' Many text-books of physiology analyze this so that the floor 
 becomes the fulcrum and the body the weight applied at the 
 ankle. The error of this is seen when further analysis discloses 
 the fact tliat, were this true, two-thirds of the weight of the body 
 would be supported by the muscle and but one-third upon the 
 floor. In other words a man weighing one hundred and fifty 
 pounds, were he to rise on his toes on weighing scales, would press 
 down upon tliem with a force of but fifty ^unds! 
 
 ' In this study of levei-age. we have considered the mechanical 
 relations only in those cases in which tlie forces act at right angles 
 to the length of the lever, in order to make the treatment as simple 
 
56 
 
 MOTION AND LOCOMOTION 
 
 Power exerted by the muscles. — In walking, the 
 power required of the muscles is that which is necessary 
 to carry the weight of the body, which is borne en- 
 tirely by the muscles of the legs. When a hod-carrier 
 takes up a load of bricks, or the soldier his equipment, 
 the extra power demanded of the leg muscles amounts 
 to not more than a quarter or a half of the regular work 
 of carrying the body 's weight. The arm and trunk mus- 
 
 FiQ. 47. Analjsis of a single step in ordinary walking. (Bradford.) 
 
 cles are able to do a larger amount of work in propor- 
 tion to their weight than the legs, since they do not 
 have to support the weight of the body as a whole. The 
 freedom of the arms for this work is made possible by 
 
 as possible. It is, however, not difficult to convert oblique forces 
 into rectangular forces by the application of the principle that the 
 true lever length for use in a problem involving an oblique force, 
 IS not the full length but is equivalent only to the shortest distance 
 between the fulcrum and the line of action of the weight and of 
 the power. 
 
WALKING 
 
 57 
 
 man's erect posture. In most animals, the four "limbs 
 are adapted chiefly to locomotion, so that their heads and 
 mouths have to do much of the work which we do with 
 our hands. 
 
 Locomotion. — ^Locomotion for man presents more dif- 
 ficulties than for four-footed animals, since the support 
 afforded by the ground is limited to his two feet in- 
 stead of to their widely separated four. As a result, 
 
 Fig. 48. Analysis of a single step in bent-knee walking. (Bradford.) 
 
 the difficulty of maintaining his balance is what makes 
 a baby so slow in learning to stand and walk. In walk- 
 ing, the weight is alternatelj'^ supported by fii"st one 
 leg and then the other. The leg which supports the 
 weight is ordinarily straightened to its full length. At 
 
58 MOTION AND LOCOMOTION 
 
 the end of the step, the leg flexes at the knee and hip 
 and is carried forward in this bent and shortened form. 
 
 Energy expended. — In slow walking, the muscular 
 force required is but little in excess of that required to 
 support the body's weight. It is estimated to be one- 
 twentieth of the weight of the body multiplied by the 
 number of feet walked per hour.^ In walking up or 
 down hill, the amount of power demanded is greatly 
 increased because of the fact that the body weight has 
 to be raised or lowered at every step. In bent-knee 
 walking, which has been experimented with for mili- 
 tary purposes, the body is allowed to fall forward, to be 
 caught by the swinging forward of the other leg. The 
 total effort required in rapid walking is thus some- 
 what reduced. In running, the body is tossed quickly 
 from one foot to the other, in addition to being thrust 
 
 ' Thus a man weighing 150 pounds and walking at the rate of 4 
 
 150 
 miles per hour, would exert -i-x 4 X 5380 ft. = 158,400 foot 
 
 pounds per hour, or 2640 foot pounds per minute. A foot pound 
 equals the energy necessary to raise a weight of 1 pound to a 
 height of 1 foot. Corresponding to this are the units, foot ton, 
 which means the raising of 1 ton to a height of 1 foot; and the 
 French unit, kilogrammeter, which means the raising of 1 kilogram 
 to a height of 1 meter. The energy required to raise 1 pound 10 
 feet is equivalent to that required to raise 10 pounds 1 foot, or 20 
 pounds % foot, and so on. 
 
 Kind of Work ^°°^ pounds Foot pounds 
 
 JiinaoiworK per minute per day 
 
 Bicycle riding, 10 seconds 19,000 
 
 Bicycle riding, 60 seconds 8,750 
 
 Soldier marching with load 5,000 3,000,000 
 
 Climbing stairs for 8 hours 4,032 1,935,360 
 
 Walking for 10 hours 3,987 2,394,000 
 
 Using heavy hammer 5 hours 3,808 1,142,400 
 
 Man pushing on lever in circular 
 
 path 3,667 2,200,000 
 
 Horse pulling on lever 17,166 8,500,000 
 
 Working on treadmill 7 hours . . . 3,360 1,480,000 
 
 Average work of man 3,330 2,000,000 
 
EXPERIMENTS WITH LEVEES 
 
 59 
 
 forward much more rapidly against the resistance of 
 the air. The amount of power required is therefore 
 much greater than for walking. 
 
 EXPERIMENTS AND DEMONSTR.\TIONS 
 
 Apparatus: Lever appwatus made with 2 spring scales 
 weighing np to "24 lbs. and 2 pieces of lath arranged as shown in 
 diagram. 
 
 1) Set np apparatus for foot leverage, assuming 1 in. as 
 distance from ankle joint (fulcrum) to insertion of tendon of 
 
 l^i'i A A AA A <i A i\ <b t ; 
 
 Fig. 49. Lever appar&tas made of latb and spring luilaDCes arranged for foot aa 
 acted on by calf muscles in rising on toe. The arrangements for arm wiien flexed 
 by biceps mnscle and extended by triceps are indicated by tlie dotted arrows. 
 (FigareB indicate half inches.) 
 
 calf muscles [power arm), and 3 in. from ankle joint to ball of 
 foot (weight arm). Use various body weights (taking 1-100 
 of body weight as weight) and determine the muscle pull 
 necessary to balance them. 
 
 2) Set up apparatus to illustrate action of biceps when a 
 weight is lifted in hand, allowing IV2 in. for length of power 
 
60 MOTION AND LOCOMOTION 
 
 arm and 10 in. for length of weight arm. Note the muscle pull 
 for various weights. 
 
 3) Set up apparatus to illustrate action of triceps, when 
 "heel" of hand is used for pushing, as in pushing up a weight. 
 Allow % in. for length of power arm and 10 in. for length of 
 weight arm. 
 
 Problems: (Each pupil should use his own weight and make 
 the necessary measurements on himself or on a skeleton.) 
 
 1, a) How much force do the calf muscles exert in raising 
 heel from floor, when person is standing on one foot, if the 
 ratio between power and weight arms is assumed to be 1 to 3 ? 
 
 b) How much is the pressure in ankle joint? 
 
 2, a) How much does the biceps pull when, by flexing fore- 
 arm, 15 lbs. are raised in palm of hand, if ratio between arm 
 lengths is assumed to be 1 to 7 ? 
 
 b) How much is the pressure in elbow joint? 
 
CHAPTER YI 
 MUSCULAR WORK 
 
 Influence of muscular activity upon development. — 
 The muscular system determines very largely the ac- 
 tivity of tlie other orgsms by its demands for food, oxy- 
 gen and the removal of its waste products. During the 
 years of growth from early infancy to the age of about 
 twenty, the various organs and tissues of the body are 
 being developed and perfected by these demands. If the 
 muscular activity is slight, not only the muscular sys- 
 tem, but the heart, limgs, nervous system and every 
 other part of the body remain weak and poorly 
 developed. If, on the eontraiy. the muscles are given 
 work in proportion to their strength and endurance, 
 every tissue of the body gets a generous and healthy 
 development. 
 
 Play. — All yoimg animals possess an instinct for that 
 muscular development which is essential for their proper 
 growth. The joyous rolling and tumbling of kittens 
 and babies, the apparently aimless racing about and 
 frolicking of puppies and children, the happy play of 
 all growing animals, is nature's provision to insure ac- 
 tivity for the muscles, in order that their bodies may 
 attain fnU strength and complete development in every 
 part. The most valuable forms of play are active games, 
 which develop the strength and endurance demanded for 
 their siiccess. They differ from both exercise and work 
 in that they are full of joyous excitement. During child- 
 
 61 
 
62 MUSCULAR WORK 
 
 hood and youth, pleasurable activity leads to a much 
 more wholesome development of the nervous system than 
 the same amoimt of exercise taken in a sober humdrum 
 fashion. The old adage, "All work and no play makes 
 Jack a dull boy," is truer to-day than ever, when exer- 
 cise is too often made another form of work. 
 
 Exercise. — Exercise differs from play, because it has 
 a definite conscious object, the development of the body. 
 It is planned to supplement the ordinary muscular work 
 of the body, in order to bring about an all-roimd and 
 complete development, which ordinary play and work 
 may not accomplish. 
 
 Work. — Work, in contrast to both play and exercise, 
 ignores the individual's pleasure and development and 
 concerns itself solely with the thing to be accomplished. 
 Throughout the history of the human race, a fair share 
 of hard physical work has been the lot of practically 
 all persons. In very early times, when hardships were 
 many and the conveniences of life few, the keeping of 
 body and soul together was a physical task of no mean 
 proportions and those who survived were hardy and 
 strong. As civilization progressed, physical activity was 
 still essential to success and physical perfection was 
 eagerly sought. In recent years, however, labor-saving 
 invention has progressed so rapidly that the conven- 
 iences of life have been enormously increased. Machines 
 have tended to take the place of the muscular work of 
 men and brain worl? has become the most productive 
 form of activity. As a result, the necessity and the 
 opportunity for physical activity have become for many 
 persons so slight that their bodies do not get the vigor- 
 ous muscular work which they need. The danger of 
 mental work without physical activity during the period 
 of growth is proved to be very real by the tendency 
 
FATIGUE 63 
 
 to weakness, imperfect development and nervous break- 
 do^\-n which is so commonly observed to-day. 
 
 Disadvantages of work. — The disadvantage of work 
 is that it may be so monotonous and prolonged as to cause 
 exhaustion of muscles and nerves. Overwork during 
 the growing period is especially harmful because it 
 interferes seriously with both the strength of the mus- 
 cles and their control by the nerves. It is especially 
 important that this should be considered in the training 
 for such games as football and baseball, where exhaustion 
 and hcEirt strain are not uncommon. 
 
 Fatigue. — Since muscular activity is based upon the 
 combustion of food materials in the muscles, the ex- 
 haustion of these materials or the accumulation of waste 
 products results in fatigue and weakness. In order that 
 the muscles may be able to work for a long time, there- 
 fore, the rate of work must be such as to permit the 
 food supply to be renewed and the waste to be cleared 
 away. Even imder these conditions, however, a limit is 
 set to the working time of the muscles by the fatigue 
 of the nervous system, which is often sho^vn by the 
 person 's inability- to keep bis attention upon his work. 
 
 Rest. — ^Periods of rest are therefore essential to whole- 
 some work. This is" especially true during the growing 
 period when exhaustion of the muscles and nerves leads 
 to their imperfect or unbalanced development. It has 
 been found that a single small muscle may be so com- 
 pletely exhausted by hard work that it will no longer 
 contract, and yet after two hours of complete rest it 
 Avill be as strong as ever. If large groups of muscles are 
 exhausted in this way. however, their recovery from 
 fatigue is much slower. This is apparently due to the 
 much greater quantity of food materials oxidized and 
 of waste products produced. When the waste products 
 
64 MUSCULAR WORK 
 
 are in excessive amounts, they weaken and fatigue the 
 whole body, including even those pjortions which have not 
 shared in the activity. From this more general form of 
 fatigue, prolonged rest in the form of sleep is necessary. 
 Recuperation.— During rest, especially during sleep, 
 the waste products are removed from the body, and the 
 food supplies of the tissues are renewed and built up 
 into the special forms required for quick; combustion, so 
 that the body as a whole is ready to enter upon a new 
 period of activity. If the rest and sleep periods are too 
 short, recovery from fatigue is not complete and growth 
 in the young or full development of strength and effi- 
 ciency in the adult is impeded. 
 
CHAPTER VII 
 SELECTION AND PREPARATION OF FOODS 
 
 Foods. — The development of energy in the body de- 
 pends upon its fuel or food supply. When the food 
 supply gets low, the need of the tissues for more food 
 causes an increasing discomfort until we satisfy our 
 hunger. Those substance's which satisfy hunger by 
 furnishing the energy necessary for the various activi- 
 ties of the body, and which are also wholesome in all 
 their effects when taken in moderate amounts, ^re foods. 
 The foods which animals need for their growth and ac- 
 tivity are manufactured bj^ plants from the simple sub- 
 stances furnished by the air, water and soil. After the 
 plants have built them into their own complex tissues, 
 they are found to be of three principal kinds, namely, 
 carbohydrates, hydrocarbons and proteids. 
 
 Carbohydrates. — To the first group belong cellulose, 
 starch and sugar, which are found in varying amounts 
 in most vegetable tissues and furnish the main food 
 of the majority of animals. They consist of carbon, 
 hydrogen and oxygen in a number of different propor- 
 tions.^ Since they all have twice as much hydrogen 
 as oxygen, they are in the right ratio to form water 
 (11,0), and for this reason they are called carbohy- 
 drates (literally, carbon watered). 
 
 Hydrocarbons. — The second class is represented by 
 the oils obtained from nuts and from the palm, olive, 
 
 ■ Starclies (gums and cellulose), CiHi.Os. 
 Sugars (grape sugar, glucose, etc.), C.HnOe. 
 
 65 
 
66 SELECTION AND PREPARATION OF FOODS 
 
 linseed and cottonseed. In this group, there is more than 
 enough hydrogen to form water with the oxygen pres- 
 ent,^ and because of this excess of hydrogen they are 
 called hydrocarbons. They are much more valuable as 
 heat producers than the carbohydrates.^ 
 
 Proteids. — The presence of nitrogen and sulphur 
 characterizes the third class, examples of which are 
 found in the gluten ^ of wheat and other cereals, and in 
 peas, beans and nuts. These nitrogen-containing sub- 
 stances are called proteids. They have a most com- 
 plex chemical structure, which differs according to the 
 source from which the proteid is obtained.* 
 
 Animal manufactures. — The substances which are 
 found in the bodies of animals closely resemble in chem- 
 ical composition those portions of plants which are used 
 by them for foods and may be similarly classified into 
 carbohydrates, hydrocarbons and proteids. The carbo- 
 hydrates are chiefly represented by milk sugar and by 
 a starch found in the liver called glycogen; the hydro- 
 carbons, by various fats and oils; and the proteids, by 
 flesh, egg albumin and cheese. They differ from the 
 substances found in plants, however, in the much larger 
 proportion of proteids and hydrocarbons and the 
 much. smaller proportion of carbohydrates which they 
 contain.' 
 
 ' Palm oil, CsiH.oiOe. 
 
 ' The hydrogen not already in combination unites with the oxy- 
 gen of the air, as does also the carbon. The result is the pro- 
 duction of much additional heat and energy. 
 
 ' Gluten is the tenacious gum which remains when raw wheat is 
 chewed. 
 
 * On the average, 100 lbs. of ordinary dry proteid contain nearly 
 52 lbs. of carbon, 7 lbs. of hydrogen, 16 lbs. of nitrogen, 2 lbs. of 
 sulphur, 25 lbs. of oxygen and a. certain amount of mineral 
 material. 
 
 » Glycogen, CcHioOd ; milk sugar, CiaHjjOu ; fat (stearin), 
 CstHhoOb ; egg albumin, Cjo.HsjjNsaOaeSj. 
 
DIETS 67 
 
 Diets of animals. — The feeding habits of animals 
 differ greatly. Some animals, as sheep, cows and horses, 
 live entirely upon plants and on this account are called 
 herbivorous. Othei"s, like wolves, lions and tigers, live 
 only upon the flesh of other animals and are therefore 
 called carnivorous. Still others, as birds, apes and men, 
 live upon a mixed diet of plants and animal flesh and are 
 called omnivorous. 
 
 Selection of diets. — The foods chosen by animals 
 have depended upon the kinds obtainable and their lik- 
 ing for them. The food habits of animals as observed 
 to-day are to a large degree the result of a process of 
 natural selection. Those animals which liked the food 
 which made them strong and were fortunate enough to 
 be able to get it, produced strong offspring. These in 
 turn tended to continue the same food habits with the 
 same beneficial results. In the end, their families sur- 
 vived, whereas those which for any reason did not eat 
 wisely perished in the struggle for existence against ene- 
 mies and disease. To-day, therefore, the natural diets 
 of the various species of animals are not tlie result of 
 accident or of mere individual choice, but are rather 
 the final outcome of a long series of experiments to deter- 
 mine the foods best adapted to their needs. 
 
 Adjustment of teeth to diet. — Diiring the long pe- 
 riod of selection, the animal gradually became adapted 
 to the diet chosen. For example, the teeth of herbivorous 
 animals becanie so changed in order to adapt them to 
 the grinding demanded by their diet, that now they could 
 not eat flesh easily, even if they wanted to. Carnivorous 
 animals, on the other hand, have teeth which are perfect 
 for tearing flesh and crushing bone, but which are quite 
 useless for chewing grass and grinding small grains. 
 Those animals, like the ape and man, whose normal diet 
 
68 SELECTION AND PREPARATION OF FOODS 
 
 combines the two, have some teeth adapted for one kind 
 of food and some for the other. 
 
 Of stomach and intestines, — The stomach and intes- 
 tines of animals are also adapted to their diet. The 
 uncooked flesh of animals is the most easily digested of 
 foods and therefore, carnivorous animals have a simple 
 stomach and short intestines. Plant tissues, on the con- 
 trary, are very difficult of digestion and in consequence 
 the majority of herbivoroiis animals have a large and 
 complicated stomach and very long intestines. Animals 
 living upon both a flesh and a vegetable diet have a 
 stomach and intestines the size and structure of which 
 lie between these two extremes. The same is true of 
 animals like squirrels which, although herbivorous, live 
 upon the more easily digested forms of plant substances, 
 as fruits. "^ 
 
 Diet of man. — As man is the most widely distributed 
 animal upon the earth's surface, the different races of 
 men have been for many thousands of years exposed to 
 very different conditions of climate and food supply. 
 The diet of man is therefore as varied as are the con- 
 ditions under which he lives. In the frozen north, his 
 diet is principally fatty animal food; in the equatorial 
 regions, it is largely vegetable; whereas in the tem- 
 perate regions, it ordinarily combines both. 
 
 Relation of food to muscular energy. — In spite of 
 these variations in the kinds of food eaten, it has never- 
 theless been found that in general the amount and funda- 
 mental character of the food required by men depend 
 upon the amount of work which they do. The doing 
 of work depends upon the development of energy. This 
 in turn means that the food eaten must be combined 
 
 ' Technically, fruits include all seeds of plants with their closely 
 related structures, as nuts, grains, pumpkins and apples, 
 
COOKING 69 
 
 in the active tissues with the oxygen breathed, in order 
 that combustion (oxidation) may take phu'o aud energy 
 be thereby developed. Those, tlierefore. who work hard- 
 est require the foods which develop the most energy. 
 If, moreover, they live in a very cold climate where 
 additional energy must be developed in order to keep 
 the body itself wann, then still more food must be eaten. 
 In any case, it is the development of given amounts of 
 energy which determines the amount and composition 
 of the food eaten. For example, a Chinaman, an Italian 
 and an American who do equal amovints of hard work, 
 have been shoA\Ti to eat approximately the same quantity 
 of food made up in general of tlie same proportions of 
 carbohydrates, hydrocarbons and proteids, although the 
 Chinaman may get his from rice and fish, the Italian 
 from macaroni and oil, and the American from potato, 
 meat, bread and butter.^ 
 
 Primitive cooking. — Food substances as furnished by 
 plants and animals were eaten in their raw state by very 
 primitive peoples. The general practice of both primi- 
 tive and civilized nations, however, is to prepare many 
 of them by means of heat. In early times, before the 
 development of cooking utensils,- there were two methods 
 of using heat. -The first was roasting or broiling, which 
 was done on coals or on a spit befoi-e an open fire. The 
 second was baldug, a primitive form of which was the 
 heating of smooth stones by building a fire on them. 
 
 ' That the amount and character of the food required by an 
 individual are determined by the work which he is called upon to do, 
 has been furtlier proved by the experience of the Japanese army 
 and navy in their wars witli China and Russia. The moment that 
 the Japanese, who are light eaters, were called upon to do the 
 heavy work of drilling, marching and fighting, tlie insufficiency of 
 their diet was apparent. To maintain their health and strength, 
 it had to be raised to the European standards both in variety and 
 RnjQunt, 
 
10 SELECTION AND PREPARATION OF FOODS 
 
 When the stones were sufficiently hot, the fire was 
 brushed off, and the food, whether dough, fish, or fowl, 
 was spread upon them. Ultimately, quite elaborate bak- 
 
 Fis. 50. Cells of a raw potato, with starch grains in natural condition. 
 
 ing structures were developed, of which the brick oven 
 used by our grandmothers is an example. 
 
 Boiling. — With the invention of pottery and later 
 of metal vessels which would hold liquids without 
 
 Cellulose 
 envelope 
 Baked 
 slarch 
 
 Fig. 51. Baked potato, showing masses of cooked starch within envelopes of 
 cellulose. (Bulletin of Agricnltural Department.) 
 
 cracking, cooking by boiling was naturally added 
 to roasting and baking. Frying, which is such a com- 
 
VALUE OP COOKING 71 
 
 mon method in modern times, was probably also of later 
 development since it required the use of grease in a 
 metal receptacle. 
 
 Effects of cooking. — Cooking has won favor because 
 the added flavor and delicacy which it imparts to food 
 stimulate tlie appetite and promote digestion. By 
 
 \ 
 
 starch 
 
 . Vx -^^ [Cellulose 
 
 
 envelope 
 
 Single starch 
 ain 
 
 ■'" ^ . _■..■■■-' 
 
 Fis. 63. Haslied boiled potato. (Balletiii of Agricnlturtil Department.) 
 
 means of it, meat becomes tender, hard grains are 
 softened, and fruits which were unwholesome because 
 of their bitterness or acidity are made wholesome and 
 pleasant. Moreover, tlirough the destruction of disease- 
 producing microbes,^ the food is made safe and much 
 disease thereby avoided. 
 
 From the standpoint of cooking, foods fall into two 
 distinct classes, animal and vegetable. In animal tis- 
 sues, the strengthening framework of connective tissue, 
 to Avhich their toughness is largely due. is changed by 
 the cooking to tender soluble gelatine.- In vegetable 
 foods, the binding structure is largely tough hard cellu- 
 lose, which resists chewing and digestion. This becomes 
 
 • See p. 283. 
 
 ' Gelatine itself has little food value. 
 
72 SELECTION AND PREPARATION OF FOODS 
 
 softened through heat and broken by the swelling starch 
 grains, so that mastication and digestion are made easy. 
 
 EXPERIMENTS AND DEMONSTRATIONS 
 
 Materials: Potatoes, raw, baked and boiled; wheat flour; 
 corn meal ; cheap cut of steak, % broiled, % stewed. 
 
 1) Examine scrapings of a raw potato under microscope. 
 Note starch cells, each of which is enclosed in a tough envelope 
 of cellulose. 
 
 2) Examine similarly scrapings from baked and boiled 
 potatoes. 
 
 3) Examine similarly wheat flour, com meal, etc., both 
 cooked and raw. 
 
 4) Compare textures of 2 pieces of the same tough cut of 
 meat, one of which has been broiled or fried quickly over a hot 
 fire, the other slowly cooked for several hours in a small amount 
 of water. 
 
CHAPTER VIII 
 FOOD MATERIALS 
 
 The ordiuary diet of mankind includes both animal 
 aud vegetable food and consists principally of cereals, 
 vegetables, fruit, milk, meat and eggs. In addition to 
 these, many miscellaneous substances such as tea, coffee, 
 chocolate, alcohol and the various condiments whose 
 nutritive value is slight, are used for their stimulating 
 or sedative effects. 
 
 Plant foods. — Cereals deservedly occupy a most im- 
 portant place in all diets, since they furnish more nutri- 
 
 
 FiQ. 53. Section throngh outer piirl of a graiu of wheat. 
 
 ment in proportion to their weight and cost than other 
 food substances. The cereal most generally used the 
 world over is wheat. The grains of wheat ai'e enclosed 
 
 73 
 
74 FOOD MATERIALS 
 
 in an outer covering, or capsule, of hard cellulose. Just 
 within the capsules lies large cells which contain the 
 proteid part of the wheat, the gluten. The rest of the 
 kernel consists mainly of starch cells, which lie in a fine 
 meshwork of cellulose. In addition, each kernel con- 
 tains an embryo plant for which the starch and gluten 
 have been prepared as food and which is itself nutritious. 
 Certain of the cereals, especially wheat, oats and corn, 
 are of special value as foods, because they contain about 
 the right proportions of proteid and starch for a full 
 diet. With the addition of a hydrocarbon in the form 
 of butter or oil, an almost complete food ^ may be 
 obtained. 
 
 Bread. — Bread ^ is a favorite method of using cereals, 
 especially wheat, because of its ease of digestion and its 
 agreeable flavor. Its digestibility depends upon its 
 sponginess, which is due to the myriads of small bubbles 
 caught in the dough because of the tenacity imparted 
 to it by the gluten. The bubbles themselves are ordi- 
 narily produced by yeast, which consists of a large num- 
 ber of microscopic one-celled plants. These develop 
 rapidly in the warm dough and during their growth give 
 off bubbles of carbon dioxide." 
 
 The fact that wheat flour makes a light bread has 
 caused the other cereals which do not make so light a 
 bread, to be undervalued as food, when, as a matter of 
 
 ' A complete food is one that furnishes in their proper pro- 
 portions all the carbohydrate, hydrocarbon and proteid necessary 
 to sustain life and activity. According to recently accepted 
 standards, bread and butter lack only a small amount of proteid. 
 
 ' There are many kinds of bread, both leavened (raised) and un- 
 leavened. A primitive form is a mere flour paste baked by being 
 spread thinly upon a hot stone. Certain hard crackers resemble 
 this. 
 
 ' Carbon dioxide may also be produced by the union of the two 
 chemicals cream of tartar and bicarbonate of soda, as in the best 
 baking powders. 
 
VEGETABLES IS 
 
 fact, they are little, if ioiy inferior and have the ad- 
 vantage in some cases of greater cheapness. Corn is 
 especially valuable because it contains more hydrocarbon 
 than wheat and fully as miieh proteid, although the pro- 
 teid is not in the form of tenacious gluten.^ 
 
 Patent breakfast foods. — In recent years, various 
 preparations of cereals have been exploited in the form 
 of patent breakfast foods. These are mainly prepara- 
 tions of wheat, oats, or corn, which have been steamed, 
 baked, or roasted in such a way as to develop appetizing 
 flavors. Their chief value lies in the fact that in the 
 majority of cases they are easily digested. As far as 
 actual nutriment goes, they are very deceptive, since 
 they are so bulky that one has to pay a good deal for 
 very little nutriment. 
 
 Vegetables. — Certain of the vegetables,^ as white pota- 
 toes, sweet potatoes and tapioca, resemble the cereals in 
 that they are rich in starch. Others, as peas, beans and 
 peanuts, are rich in proteid material. Still others, as 
 beets, are rich in sugar. Some vegetables, however, as 
 cabbages and turnips, consist mainly of cellulose, which 
 is so indigestible as to give little nutriment except when 
 young and tender. All vegetables contain organic salts 
 which are essential to health, as has been abundantly 
 proved by sailors, who when deprived of them for long 
 periods become weak and diseased.^ Vegetables are also 
 
 ' In spite of this, corn is but Httle used by Europeans as food. 
 \\1ien, during a famine in Russia, a large amount of corn was 
 contributed by America, it was necessary both to show the Rus- 
 sians how to use it and to overcome their prejudice against it. 
 
 ' Peas, beans and peanuts, although popularly known as vege- 
 tables, are really fruits. 
 
 ' Scurvy, which used to be the bane of whalers who went on 
 three-year cruises, has been practically obliterated by the use of 
 canned vegetables and fruits, now made compulsory by the various 
 governments. 
 
76 FOOD MATERIALS 
 
 important articles of diet because they contain large 
 amounts of cellulose. Although this cannot be digested, 
 yet it is valuable in that it furnishes a considerable 
 residue in the intestine, thus insuring a regular onward 
 movement of the bowel contents. 
 
 Dangers of raw vegetables. — Raw vegetables, such 
 as radishes, lettuce and celery, are often dangerous to 
 health, more especially in European countries, because 
 animal excretions are used to fertilize them. Many 
 cases of dysentery, typhoid and other diseases have been 
 traced to this source. They should therefore never be 
 eaten unless they have been previously thoroughly 
 washed, or scraped and rinsed under running water. 
 
 Potatoes. — Common or white potatoes have long been 
 recognized as the most valuable of all cheap vegetables, 
 because they contain considerable nutriment and furnish 
 the salts necessary to maintain health. In addition, 
 they are always appetizing and can be kept from one 
 season to the next. 
 
 Fruits. — Besides cereals and vegetables, plants fur- 
 nish us with another most important and attractive kind 
 of food, namely, fruits and nuts. Juicy fruits contain 
 large amounts of fruit or grape sugar, together with 
 a considerable amount of cellulose and some starch. 
 Melons and grapes are particularly rich in sugar, 
 bananas in starch. Nuts contain large amounts of 
 hydrocarbon and proteid and thus resemble meat in 
 composition. Like vegetables, fruits also contain the 
 acids and salts which are so important for health. 
 They should be used freely in all diets, either raw or 
 cooked. 
 
 Preserved fruits. — Fruits are prepared for use out 
 of their season, by being dried, preserved, or canned. 
 Dried fruits are almost as valuable as fresh and are 
 
TRUITS 11 
 
 much cheaper when fresh fruits are out of season. Pre- 
 served fruits are kept from fermentation by the large 
 amount of sugar which is cooked with them. They are 
 less healthful because they are oversweet and they are 
 expensive for the same reason.^ Canned fruits depend 
 for their preservation upon the fact that all microbes 
 which would cause fermentation are killed by cooking, 
 and all others are kept out by the tightness of the cans. 
 They have aboiit the same value as fresh fruits. Unless 
 glass cans with glass tops are used, however, there is 
 always some chance of lead poisoning, through the use 
 of a mixture of tin and lead, instead of pure tin, as a 
 coating for the sheet iron of the cans. On this account, 
 the fruit should never be allowed to remain in a metal 
 can after it has been once opened, since acids develop 
 which attack the coating of the can. 
 
 Animal foods: milk. — Of the foods contributed by 
 animals, milk is more nearly a complete food than any 
 other. It has in solution proteids in the form of albu- 
 min and casein. It also contains sugar {milk sugar) 
 together with fat in the form of minute drops. 
 
 The casein of milk is readily separated out as a flaky 
 solid by adding to the milk a little dilute acid, or rennet 
 from a pig's or calf's stomach. "When properly pressed 
 and dried, it forms cheese. 
 
 The fat of milk rises to the top because of its light- 
 
 ' Many of the commercial preparations contain glucose instead 
 of cane sugar. Glucose is prepared by boiling starch with sul- 
 phuric acid and neutralizing the acid with caustic lime. It is 
 wholesome if the acid is pure and is wholly neutralized by the 
 lime. Unfortunately, the acid sometimes contains poisonous sub- 
 stances, such as arsenic. Glucose is much cheaper than the 
 natural fruit and cane sugars, for which it was formerly sold. 
 As it is considered to be an adulteration of food, the law prescribes 
 that its presence must be stated on the label of the package in 
 which it is sold. To comply with the law and yet avoid the term 
 glucose, corn syrup and other pleasing names are used. 
 
78 POOD MATERIALS 
 
 ness. It becomes butter when the thin membranes which 
 cover the fat drops are broken open by churning. 
 
 After the cream and cheese have been removed from 
 milk, the sugar remains in solution and can be ob- 
 tained by evaporating the water. Milk sugar is a val- 
 uable article of food and is used largely in the feeding 
 
 lO So 
 
 ^9 
 
 o°" a 
 
 
 fat globules^:: °ow.^"o"° 4- ^° 
 
 O c>° O 
 
 Fio. 64. A portion of a drop of eow's milk highly magnified, showing the fat 
 globules. 
 
 of infants. It helps to make cow's milk more like 
 human milk and so makes it better adapted to their 
 digestion. 
 
 Contamination of milk. — Since milk is so valuable a 
 food, it is most unfortunate that it is difficult both to 
 get and to keep it clean and fresh. In the cow itself, 
 on the hands of the milkmen, in the pails, cans and bot- 
 tles, may lurk millions of microbes, some of which are 
 not infrequently productive of disease. Only the milk 
 
MILK 79 
 
 which comes from a clean healthy cow, is milked by 
 a clean pex'son free from disease into carefully boiled 
 (sterilized) vessels, and is not afterward contaminated 
 by handling nor subjected to a temperature higher than 
 40° or 50° F., is so free from microbes as to be absolutely 
 safe. If the cow has some such disease as tuberculosis, 
 the milk, even when fresh, will often contain the germs 
 of the disease and thus be a most dangerous food. Dur- 
 ing the milking process, the microbe-laden dust and dirt 
 on the skins of the cows and on the hands of the milk- 
 men sometimes get into the milk in such quantities 
 that a cubic centimetre of fresh milk contains millions of 
 microbes.^ Fortunately, many or most of these are not 
 ordinarily harmful, but one cannot be sure that this is 
 the case. After milking, the milk may be put into cans 
 which are full of microbes that will hasten its spoil- 
 ing ; the milk cans may even have been washed in water 
 contaminated with typhoid or other disease-producing 
 microbes, or handled by those who are themselves ill, 
 as has only too often been found to be the case in epi- 
 demics of typhoid and scarlet fever. The milk may 
 ' further be left uncovered so that the microbes carried 
 by insects or by the air find ready access to it. In 
 short, milk, because of its large use in the uncooked 
 or raw state, is subject to contamination on every 
 hand. 
 
 Effect of temperature. — In order to keep milk sweet, 
 it must not only be kept clean but in addition it must 
 be chilled as soon as it is milked and thereafter be kept 
 
 * The laws of Massachusetts permit 500,000 microbes to the 
 cu. cm. and consider such milk moderately clean. Of course, 
 these are not supposed to be disease-producing microbes. Their 
 number is considered to be a measure of the cleanliness of the 
 premises, the age of the milk, the care with which it has been 
 handled, and the temperature at which it has been kept. 
 
80 FOOD MATERIALS 
 
 as nearly at the temperature of ice as possible. In this 
 way, the development of microbes, which is exceedingly 
 rapid in warm milk/ may be checked.'' 
 
 Eggs. — Eggs are another important food contributed 
 by animals. Every egg is a package of food especially 
 prepared for the nourishment of the young animal con- 
 tained within it, during its development. It is, therefore, 
 a complete food for an actively growing animal. It 
 consists of a transparent portion, the egg albumin, and 
 a yolk which contains a relatively large amount of fat 
 together with proteid and other substances. As a com- 
 plete food for man, it lacks carbohydrate material. 
 
 Eggs are valuable as food whether eaten raw, slightly 
 cooked or thoroughly boiled. When heated, the white 
 coagulates into a firm hard mass, which when well 
 chewed is not indigestible. Fried eggs are least digesti- 
 ble because the white is made tough by the hot grease. 
 
 Neither milk nor eggs are very economical foods except 
 in the country. The same amount of nutriment, al- 
 though not always in so pleasing or digestible a form, 
 
 ' The development of microbes In milk at different temperatures 
 is about as follows: 
 
 perature 
 
 At end of 24 hrs. 
 
 At end of 48 hre. 
 
 60° 
 68° 
 86° 
 94° 
 
 180,000 
 
 450,000 
 
 1,400,000,000 
 
 25,000,000,000 
 
 28,000,000 
 25,000,000,000 
 
 Below 50°, the development of microbes in milk is comparatively 
 slow. 
 
 ' It was formerly a common practice to get rid of the microbes 
 in milk for infants by heating it to a boiling point {sterilization) , 
 or to a temperature of 150° for 15 minutes (Pasteurization) . In 
 recent years, however, it has been found that to heat milk in this 
 way so changes its character that it lessens its value as food. The 
 best practice therefore seems to be to prevent so far as possible the 
 entrance of microbes into the milk and their subsequent develop- 
 ment, in order that the milk may be safe in its raw state. 
 
MEATS 
 
 81 
 
 can be obtained from such foods as cheap cuts of meat, 
 vegetables and especially cereals. 
 
 Meats and fish. — Meats and fish form a class of ani- 
 mal food which is very rich in proteid material. They 
 average in composition about three-quarters of water 
 and one-quarter of dry proteid and fat. The edible por- 
 tions of both meat and fish consist mainly of the muscu- 
 lar part of the animal. Meat is easily digested and ordi- 
 narily ninety-five per cent is utilized by the body as com- 
 pared with sixty to eighty per cent of plant proteid. It 
 is therefore a more eco- 
 nomical source of pro- 
 teid than its price per 
 pound would indicate, 
 although even with this 
 allowance plant proteid 
 is much cheaper. The 
 cheaper and tougher 
 cuts of meat are just as 
 nutritious as the more 
 expensive ones and if 
 skilfully cooked are often quite as satisfactory. Since 
 flesh contains no carbohydrate material, it is not a com- 
 plete food for man. 
 
 Parasites in meat. — On account of the fact that the 
 flesh of animals is sometimes infested by parasites, 
 meats should always be cooked and never eaten raw, as 
 is done with certain kinds of sausage. The most com- 
 mon parasites found in meats are the tapeivorm from 
 beef and the tricli ina from pork. 
 
 Putrefaction. — Meat which has been kept too long 
 putrefies because of its infection by microbes from the 
 air and from insects. Decaying meat is especially dan- 
 gerous in that it produces severe and often fatal forms 
 
 Muscle fibres EnclosinQ wall (capsule) 
 
 Fie. 55. Trichinse in "measly " pork. 
 (Magnified 60 times.) 
 
82 FOOD MATERIALS 
 
 of poisoning. It should be remembered that after meat 
 has become offensive, no amount of cooking or deodoriz- 
 ing will make it wholesome, since the poisonous products 
 of the microbes, the ptomaines,^ are not destroyed by 
 cooking, although the microbes themselves are. 
 
 Meat stews. — Although meat alone is not a complete 
 food because of its lack of carbohydrate, it may be so 
 combined with vegetables and cereals in stews and pies 
 as to make good this deficiency. Stews and pies are 
 especially valuable in an economical diet because they 
 are cooked so long that cheap tough meats become tender 
 and appetizing. 
 
 Soups.— In marked contrast to stews are thin soups, 
 which consist mostly of water and flavoring materials 
 from meat. Although valuable at the beginning of a meal 
 to increase the appetite, they furnish little nutriment. 
 Bouillon and beef tea are thus stimulants rather than 
 foods and should never be relied upon for nourish- 
 ment, even in the diet of an invalid. 
 
 Fish. — As a food, fish is neither more nor less nutri- 
 tious than meat. It has not the special value as brain 
 food which has been frequently claimed for it. 
 
 Condiments. — Besides bouillons and soups, there are 
 certain condiments or seasonings, such as salt, pepper, 
 mustard, ginger and other spices, which stimulate the 
 appetite by increasing the flavor of the food. This is 
 their sole purpose, as they do not furnish any nutriment. 
 "When used in moderate quantities, they serve to increase 
 the secretion of the digestive fluids and thereby aid the 
 whole process of digestion. In the use of condiments, 
 however, great care must be taken not to use them 
 vmnecessarily or in too large amounts. In normal health, . 
 
 ' Ptomaines are produced by the activity of microbea and are 
 among the most poisonous substances known. 
 
CONDIMENTS 83 
 
 stinralation, aside from that obtained from the natural 
 flavors of the food increased by the addition of a little 
 salt, is ordinarily not needed. 
 
 Salt. — Salt evidently serves a more important purpose 
 in the body than any mere condiment, since many ani- 
 mals, especially the herbivorous whose food is poorest 
 in salt, have such a strong craving for it that they will 
 ignore danger for the sake of reaching salt licks. This 
 is due to the fact that it is essential in the tissues in 
 order that the right proportion of water in them may be 
 maintained. Salt is being constantly lost from the body 
 through perspiration and other excretions, and this loss 
 must be made good through the salt taken as food. In 
 carnivorous animals, the flesh food supplies enough salt 
 in itself, so that they have no craving for an additional 
 supply. 
 
 Sugar. — Sugar is habitually used as a condiment be- 
 cause of its pleasant taste, but it differs from other con- 
 diments in being a valuable food. Sugar, especially in 
 the form of candy, should, however, be used with cau- 
 tion and eaten only at meal times or after other food. 
 If taken at other times, it destroys the appetite for more 
 wholesome food and may even induce painful digestion. 
 The chocolate which is combined with sugar in candy, is 
 also a valuable food, if taken at the proper times and 
 in moderate quantities. 
 
 EXPERIMENTS AND DEMONSTEATIONS 
 
 Materials and apparatus : Yeast cake ; wheat flour ; com, rye 
 and oat meal; breakfast foods; vegetables, as potato, turnip, 
 beet and cabbage; fruits, as apple, banana and orange; milk; 
 egg; meat; glucose (gi'ape juice or raisins stewed in a small 
 amount of water) ; solution of iodine made by diluting 1 dr. 
 tincture of iodine with 1 oz. of water in which 20 grs. of 
 potassic iodide have been dissolved ; solution of copper sulphate, 
 
84 
 
 FOOD MATERIALS 
 
 10 grs. to 1 oz. of water ; solution of sodic hydrate, 20 grs. to 
 1 oz. of water; nitric acid, concentrated; ammonia, strong; 
 gasolene, to be used only in small amounts by teacher; scales; 
 test tubes ; bottles ; microscope. 
 
 
 ^ 
 
 SS 
 
 as 
 
 1 
 
 ID 
 
 'a 
 
 es 
 
 s 
 
 i 
 
 1 
 
 .1 
 
 
 i 
 
 M 
 
 S 
 
 PU 
 
 w 
 
 < 
 
 fq 
 
 ta 
 
 f^ 
 
 n 
 
 Ph 
 
 starch 
 
 
 
 
 
 
 
 
 
 
 
 
 Sngar 
 
 
 
 
 
 
 
 
 
 
 
 
 Proteid 
 
 
 
 
 
 
 
 
 
 
 
 
 Fat 
 
 
 
 
 
 
 
 
 
 
 
 
 S'ote ." The class may be conveniently divided Into groups, to each 
 of which is assigned a given number of substances for test and 
 report. 
 
 1) Prepare a raised dough of each flour to be tested, as 
 wheat, corn, rye and oat. Bake and compare textures of the 
 various breads. 
 
 2) Separate out one cent's worth each of various patent 
 breakfast foods and oatmeal, cracked wheat, rolled oats, etc. 
 Assuming that equal weights have equal nutritive values, how 
 do they compare in cost? 
 
 3) Test for starch: Put one or two drops of iodine solution 
 upon a bit of flour and note result. Boil starch and test 
 similarly. 
 
 Test in Uke manner various meals, breakfast foods, vegetables 
 and fruits, and record as in the accompanying schedule. 
 
 4) Test for fat: Place a few drops of gasolene upon a piece 
 of fat. Apply a drop of the mixture to a piece of paper and to 
 a piece of glass; allow to dry. Caution: Be sure that there is 
 no fire of any sort in the room. 
 
 Test similarly corn and oat meal, wheat flour, crushed nuts, 
 yolk of egg and milk. 
 
 5) Test for sugar ' ; Make a dilute solution of glucose or soak 
 a mashed raisin in water. Put a few drops into a test tube, 
 
 'Ordinary (cane) sugar does not respond to this test. A 
 solution of such sugar must be boiled with g, few drops of acid, as 
 sulphuric. 
 
FOOD EXPERIMENTS 85 
 
 add 1 in. of water and V^ in. of sodio hydrate solution. Then 
 add carefully 1 to 2 drops of copper sulphate solution. Heal 
 the uppei- half of mixture in flame of Buusen burner or alcohol 
 lamp, by holding tube at an angle of 45°. Bring to a boil and 
 note the characteristic change due to the presence of sugar 
 (Trommer's Test). Test similai-ly ' various vegetables, fruits 
 and milk. 
 
 6) Test for proteid (Xantho-proteic reaction) : Put in a test 
 tube Yz ill. of solution of white of egg." Add I/2 in. of con- 
 centrated nitric acid. Heat gently to boiling and continue until 
 a yellow color develops. Let cool and add strong ammonia 
 until the solution is alkaline (turns red litmus paper blue). 
 Note the change to orange color, which is characteristic of 
 proteid reaction. 
 
 Test similarly ' wheat flour, various meals, vegetables, fruits, 
 milk and meats. 
 
 7) Determine the proportion of water in meat, fat, milk, 
 vegetables and fruits, by weighing fresh, chopping fine, drying 
 quickly where they will be warm but not heated and re- 
 weighing.'' 
 
 S, a) Structure of milk: Examine a drop under microscope 
 and sketch the oil globules. 
 
 b) Test for fat: Dry with moderate heat a tablespoonful of 
 milk in a shallow tin vessel. When perfectly dry. pour upou 
 it a small amount of gasolene or ether, being' sure to have 
 no flame of any kind in the room. Put some of the solution 
 
 " upon a glass or piece of paper and allow to evaporate. Note 
 residue. * 
 
 c) Precipitation of casein: Place warmed milk in a small 
 glass. Add drop by di'op a dilute solution of acetic acid 
 (\-inegai-) and stir constantly until a precipitation of casein to- 
 gether with fat is formed. Let settle or filter. Dry precipitate 
 
 ' In case of solid vegetables and fruits, crush, shake in a little 
 water and use tlie clear solution. 
 
 > Cut white of raw egg repeatedly with scissoi-s. Shake in a 
 bottle with 20 parts of water; let settle and filter. Use clear 
 solution. 
 
 * In case of solids, put i^ in. of water into a test tube and add 
 tlie solids to be tested. Proceed as with white of egg solution. 
 
 * Ordinarily drying takes from 24 to 4S hours even under the 
 most favorable circuinstances. 
 
86 
 
 FOOD MATERIALS 
 
 by squeezing out the fluid and spreading out the remainder. 
 When dry, collect in a small vessel and remove fat with gaso- 
 lene or ether. 
 
 d) Test for milk sugar: Test the clear liquid obtained in c) 
 by Trommer's Test. 
 
 e) Test for proteid: Test by Xantho-proteie reaction residue 
 in c) left after fat has been extracted. 
 
 COMPOSITION OF FOOD MATERIALS 
 
 
 Water 
 
 Proteid 
 
 Starch 
 
 Sugar 
 
 Fat 
 
 Salts 
 
 Bread 
 
 37 
 
 15 
 15 
 13 
 15 
 75 
 86 
 37 
 73 
 51 
 72 
 63 
 78 
 77 
 74 
 15 
 
 8 
 11 
 12.6 
 
 6 
 23 
 
 2 
 
 4 
 33 
 19 
 14 
 18 
 16 
 18 
 16 
 14 
 
 47 
 66 
 58 
 79 
 55 
 18 
 
 3 
 3 
 
 5.4 
 
 0.4 
 
 2 
 
 3 
 
 5 
 
 1 
 
 1 
 
 5.6 
 
 0.7 
 
 2 
 
 0.2 
 
 4 
 24 
 
 3 
 29 
 
 5 
 16 
 
 3 
 
 5.5 
 105 
 83 
 
 2 
 
 
 2 
 
 Oatmeal 
 
 Rice 
 
 3 
 
 0.5 
 
 
 2 
 
 
 0.7 
 
 Milk 
 
 0.8 
 
 
 5 
 
 Lean beef 
 
 
 Fat beef 
 
 
 Mutton 
 
 Veal 
 
 
 "White fish 
 
 Salmon 
 
 1.5 
 
 Egg 
 
 Butter 
 
 15 
 3 
 
 
 
CHAPTER IX 
 
 WATER AND OTHER BEVERAGES 
 
 Water is indispensable for animal life, since no food 
 can be absorbed and utilized by the body unless it is 
 in solution. Because of its power to dissolve substances, 
 natural water is never found pure, although fortunatelj' 
 its impiirities are not xisually harmful. Ordinarily, 
 water contains in solution oxygen, carbon dioxide 
 and traces of such salts as nitrates, chlorides and car- 
 bonates. 
 
 Mineral contents. — When water contains much lime 
 or other carbonate, it will not readily dissolve soap 
 and it is therefore said to be hard. ]\Iost spring and weU 
 waters become charged with carbon dioxide from decay- 
 ing vegetation in the upper layers of the soil. The pres- 
 ence of the carbon dioxide gives them the power of dis- 
 solving carbonates from the soil as they filter through it 
 and they are consequently apt to be hard. Surface 
 waters, on the contrary, especially rain water, are rela- 
 tively soft, as are also distilled waters. For drinking 
 purposes, neither the very hard nor yet the soft pure 
 distilled watei-s are good, since the hard waters contain 
 an objectionable amount of carbonate, while distilled 
 water is so pure that it is irritating to the stomach. 
 The best water for drinking, therefore, is one that is 
 neither very hard nor very soft but contains a moderate 
 amount of air in solution together with a moderate 
 amount of carbonates and other earthy salts, including 
 
 87 
 
88 WATER AND OTHER BEVERAGES 
 
 common salt. Such water is not irritating when in con- 
 tact with the delicate tissues of the body. 
 
 Organic contents. — Besides these ordinary contents, 
 surface waters frequently contain minute living plants 
 and animals. Many of these organisms are entirely 
 harmless, since they cannot grow in the bodies of ani- 
 mals. Some of them, however, when introduced into 
 the body thrive and multiply as parasites. The most 
 harmful of these, because of their power to cause disease, 
 are certain kinds of microbes which have been introduced 
 into the water from animals or man. When taken into 
 the body, they multiply at so rapid a rate and develop 
 such powerful poisons that they may even overwhelm 
 and kill the animal which acts as their host. Some of 
 the most dangerous of these are the microbes of typhoid, 
 cholera, dysentery and scarlet fever. They may be in- 
 troduced into the system not only by drinking the 
 water contaminated by them but also by eating raw shell- 
 fish which have lived in the contaminated water, by 
 drinking milk from receptacles washed in it, or by eat- 
 ing raw vegetables watered or washed with it. 
 
 Water supply. — To secure pure drinking water has 
 become one of the great problems of civilized life, espe- 
 cially in the larger towns and cities. The main sources 
 of supply are surface water, spring, well and lake water. 
 
 Surface water. — Surface water, as found in rivers 
 and brooks, is always liable to contamination and should 
 be avoided for drinking purposes, even in sparsely set- 
 tled regions. For example, in a country district in the 
 hilly part of Pennsylvania there was an epidemic of 
 typhoid fever in the spring. It was finally traced to 
 the contamination of the water supply by the excretions 
 of a case of typhoid. These had been thrown out upon 
 the snow on a hillside, and when the snow melted in 
 
DRINKING \YATEK 
 
 89 
 
 the spring they had washed down into the stream from 
 which the people in the town some distance away got 
 tlieir drinking water. 
 
 Spring water. — Spring water, if from the side of a 
 sandy hill through which the water has filtered, is usually 
 safe, provided, of coiu-se, that it is protected from all 
 the surface water which has not been so filtered. 
 
 Well water. — Well water is usually good if the well 
 is entirely protected from the entrance of any water 
 
 Fig. 56. A well contamiuated by iu surruuudinss becnnse of the constant flow 
 of water toward it from all sides, owing to the removal of water from the well 
 itself. 
 
 which has not been slowly filtered through at least ten 
 or fifteen feet of porous air-filled earth. Wells should 
 preferably be at least fifteen feet deep. Those which 
 are driven or bored are ordinarily much safer than open 
 wells because they are more adequately protected from 
 surface drainage. Many small towns obtain an ade- 
 quate and safe water supply from such sources. 
 
 Lake water. — Lake water is frequently used as a 
 source of supply for large cities. Like other surface 
 
90 
 
 WATER AND OTHER BEVERAGES 
 
 waters, it is extremely unsafe, since exposure to the sun 
 and air will not purify it from any contaminating drain- 
 age whicli may rim into it. To be made safe, it must be 
 purified by some such efficient means as sand filtration. 
 
 Protection of water supply. — Various methods of 
 protecting and purifying water have been adopted by 
 cities and towns. If a natural watershed can be pro- 
 tected so that the water which falls upon it and drains 
 off is imcontaminated by human life, it is usually safe 
 for consumption. In mountain regions, such water sup- 
 plies are readily secured without undue expense. Not 
 infrequently, water is thus obtained for cities at great 
 distances from the watershed. 
 
 Sand filtration. — The problem of obtaining pure 
 water for flat, thickly settled regions has been solved 
 
 Fig. 57. Diagram showing arrangement of a filter plant. (Egbert.) 
 
 by the discovery that if the water from lakes and rivers 
 is filtered slowly and intermittently through beds of 
 sand several feet thick, the living organisms are removed 
 from it and the water rendered pure.^ Many cities,^ 
 therefore, have constructed large filtering beds to insure 
 
 '■ This process of purification is due to the action of harmless 
 microbes in the soil, which form a thin film upon the sand grains. 
 They have the power of destroying both the organic substances and 
 the microbes in the water as they pass through it in the process of 
 filtering. Since the soil microbes require air, the passage of the 
 water through the sand has to be intermittent, in order to permit 
 air to enter the sand. 
 
 ' As Philadelphia, Lawrence and Berlin. 
 
WATER FILTERS 91 
 
 the purity of their water stipply and thus to protect 
 themselves from the epidemics of typhoid which pre- 
 vail where the drinking water is impure.^ 
 
 Small filters. — The attempt to render water pure by 
 rapid filtration through small filters attached to faucets, 
 is useless. Slow filtration through unglazed porcelain, 
 as in the Pasteur filter, is effective, but is ordinarily 
 too slow for general use. The most satisfactory method 
 of protecting ourselves against suspicious water is by 
 boiling the water and then shaking it up with air. In 
 this way, the boiled water is made palatable through 
 the restoration of the gases driven out by the heat. 
 
 Water as a beverage. — Water satisfies fully the needs 
 of the body for fiuids. When drunk cold, however, it 
 has for certain persons a depressing effect. Hot water, 
 especially when sipped, does not depress but rather stim- 
 ulates the processes of digestion. Since hot water has not 
 an agreeable flavor, certain substances, as salt, sugar, 
 cocoa, chocolate, tea and coffee, are ordinarily intro- 
 duced. Unfortunately, some of these substances used 
 for flavoring are harmful. 
 
 Cambric tea. — Perhaps the best warm drink is that 
 simple mixture of milk, sugar and water, called cambric 
 tea. This warms and stimulates and has no harmful 
 
 ' The following table shows the death rates from typhoid fever 
 in the city of Lawrence per 10,000 of population, for the 4 years 
 immediately preceding and the 4 years immediately following the 
 introduction in 1893 of sand filtration for the water of the 
 Merrimac River: 
 
 Preceding change Following change 
 
 1889 .12.7 4.7 1894 
 
 1890 13.4 3.1 1895 
 
 1891 11.9 1.9 1896 
 
 1892 10.5 1.6 1897 
 
 During 1893, 1894 and 1895, a considerable number of persons 
 were still using unfiltered water and were responsible for about 
 half the deaths in those years. 
 
92 WATER AND OTHER BEVERAGES 
 
 effects, except that it may lead to the regular use of a 
 hot drink and thus eventually to the use of tea and 
 coffee. 
 
 Cocoa and chocolate.— Cocoa and chocolate are really 
 diute foods, of which chocolate is the richer owing to 
 the fat in the form of cocoa butter contained in it. 
 Otherwise, they are identical in effect. Both contain 
 small amounts of theobromine, which resembles the 
 caffeine of tea and coffee and which in very large doses 
 may be harmful. As found in cocoa and chocolate, how- 
 ever, it has practically no effect. Cocoa and chocolate, 
 if simply prepared and taken in moderate quantities, 
 are ordinarily agreeable and wholesome beverages. For 
 some persons, however, the chocolate especially is too 
 rich. 
 
 Tea and coffee. — The most popular beverages are tea 
 and coffee. Although these have such different flavors, 
 they are almost identical in composition and effect. Both 
 contain a powerful drug, caffeine, which in tea is known 
 as theine, together with a powerful astringent, tannic 
 acid, which is very harmful to the lining membrane of 
 the stomach. ■ The effects of tea and coffee depend to a 
 large extent upon the method of preparation as well as 
 upon the quantity drunk. Caffeine and theine are both 
 quite soluble and are very quickly abstracted by hot 
 water from the finely ground coffee and thin tea leaves. 
 The tannic acid, on the contrary, takes some time to 
 dissolve out and appears in large quantities only when 
 tea and coffee are boiled. They should, therefore, be 
 steeped for only a few minutes. For this, tea balls or 
 small bags are desirable, since in this way the tea leaves 
 or coffee grounds can be removed at the proper time and 
 the solution of tannic acid avoided. If drunk occa- 
 sionally at meals, the amounts of caffeine and theine taken 
 
ALCOHOL 93 
 
 are not thought to be sufficient to do serious harm. As 
 stimulants, they have a considerable value if not taken 
 habitually. 
 
 Dangers of tea and cofFee. — When, however, tea and 
 coffee are used without food for their stimulating effect 
 or when they are regularly depended upon to supply 
 a feeling of weU-being and strength, tliey are un- 
 doubtedly doing harm. They then act as goads to prick 
 a flagging vitality into exliausting itself still further. 
 The slave of tea and coffee is quite as weak and as fool- 
 ish as the victim of alcohol, since he is constantly losing 
 his nervous strengtli and physical vitality in propor- 
 tion to the degree of his indulgence. His nervous 
 strength is weakened, his digestion impaired, and his 
 normal restful sleep seriously lessened, luitil in the end 
 he becomes a nervous, irritable dyspeptic. 
 
 Alcohol. — ^Vnother substance which is extensively 
 used as a beverage in various forms is alcohol. Alcohol 
 is derived from the fermentation of sugar by the action 
 of various forms of microscopic plants called yeasts.^ 
 The alcohol of wine and eider is derived from the sugar 
 in the fruit juices of the grape and apple, acted upon 
 by the yeasts present in the diist upon the fruits. If 
 the process is continued farther, acetic acid (vinegar) 
 is in turn produced from the alcohol. Beers are made 
 in a more roundabout way from the starch of grains, 
 which is first converted into sugar by allowing the 
 grains to sprout. The stronger liquors, as brandy and 
 whiskey, are distilled from the products of previous 
 fermentation, as brandy from wine. Alcohol as found 
 in wines and liquors is in dilute form and is more or less 
 flavored by the substances from which it is made. It 
 
 ' Sugar+yeast= alcohol + carbon dioxide 
 C.H.,06-l-yeast=2 C»HeO+2 CO.. 
 
94 
 
 WATER AND OTHER BEVERAGES 
 
 varies in amount from two to seventy per cent of the 
 total bulk of the solution. 
 
 Oxidation of alcohol. — In its concentrated form, al- 
 cohol is a valuable fuel for cooking and heating pur- 
 poses, because of the large amount of carbon and hydro- 
 gen contained in it. In dilute form, a certain amount 
 of it is oxidized in the animal body and gives rise to 
 carbon dioxide and water. Scientists have long disputed 
 as to whether this combustion is similar to that which 
 food undergoes in the body and whether, as is the case 
 with food, it produces available energy. The essential 
 test has been whether it would 
 replace an equivalent amount 
 of starch and sugar in a diet. 
 At first, it was thought that 
 this was not possible, but re- 
 cent experiments seem to indi- 
 cate that, when taken in mod- 
 erate quantities, it does act as 
 a food. This would seem to be 
 especially true in certain ill- 
 nesses where other foods can- 
 not be properly digested and 
 assimilated. In such cases, di- 
 lute alcohol appears to have the advantage of not re- 
 quiring previous digestion before it is absorbed and 
 utilized. 
 
 Dangers of alcohol. — Although alcohol may occa- 
 sionally have a certain value as food, this is the only thing 
 which can be said in its favor. Its other effects upon 
 animal organisms make it a very imdesirable food, ex- 
 cept in cases of extreme illness. It acts upon the nerv- 
 ous system in such a harmful way, even when taken in 
 comparatively small doses, that it must be considered 
 
 Pio, 58. Yeast 
 plant, 
 
 full-grown 
 with a branch (bud) 
 
 partially developed ; b, 
 colonies formed by budding 
 the individuals still attached 
 (Magnifled 750 diam.). 
 
EXPERIMENTS 95 
 
 as a drug aud uot as a food. It paralyzes the higher 
 nerve centres which are responsible for our ideas of right 
 and wrong, as well as those which control the larger 
 movements of the body. As a result, the person who 
 comes under its influence ceases to be normal in his 
 thoughts or actions.^ 
 
 EXPEEIilEKTS AND DEMONSTRATIONS 
 
 2IatermJs: Samples of Avater; yeast cake; iodiiie solution 
 (p. 83); microscope with powers up to 450 diameters; tall 
 gLiss bottles. 
 
 1) Fill a tall glass with water and allow to settle. Pour off 
 carefully so as to leave sediment undisturbed. Study a drop of 
 the sediment under microscope. 
 
 2) Boil water for 10 minutes. Cool and taste. 
 
 3) Shake up some of the boiled water in 2) in a large clean 
 bottle, 34 of which is filled with air. Repeat several times at 
 intervals of a few minutes, aud compare with the taste of 2). 
 
 4) If your water supply is from well or cistern, draw a 
 diagram of premises to show possible sources of contamination. 
 
 If it is from a genei-al town supply, describe its source and 
 the precautious taken to insure its purity. 
 
 5) Dissolve a small piece of yeast cake in a few drops of 
 water, a) Examine a drop of the fluid under microscope and 
 make drawing's of the cells present. 
 
 b) Add a small drop of iodine solution aud again examine. 
 
 ^ For a move complete discussion of the eflfects of alcohol, see 
 Chapter XXVI. 
 
Chapter x 
 
 DIGESTION 
 
 The development of energy by animals is based, as 
 we have seen, upon the combustion of food materials. 
 In order to bring food to the state in which it can be 
 utilized by their tissues for the production of energy, it 
 must be made soluble by means of digestion. 
 
 Simplest form of digestion. — The process of digestion 
 may be very simple or extremely complex. In the ameba, 
 a particle of food is taken into its body apparently at 
 any point. The nutritious part is then dissolved through 
 the action of certain peculiar substances called enzymes, 
 which are found in the protoplasm. Thus dissolved, it 
 is distributed throughout the body by the flowing and 
 mixing of the protoplasm itself. The part of the- food 
 which cannot be dissolved is finally pushed out through 
 the side of the body. 
 
 More complex forms. — In animals which consist of 
 many cells, a special opening, or mouth, is found through 
 which alone food can enter. Connected with this is a 
 special canal running through the body, within which 
 all undissolved food material is kept. This canal has a 
 definite wall lined with cells, which secrete substances 
 capable of dissolving the food materials. It ends in an 
 opening through which all the undigested parts of the 
 food are expelled. This canal for food, the alimentary 
 canal, is really an infolding of the outside surface of the 
 body, for the double purpose of furnishing a reservoir 
 
THE DIGESTIVE TRACT 
 
 97 
 
 for tlie food and a special organ for its digestion. In 
 man, as in the higher animals, the alimentary canal 
 
 MOirtfl 
 
 Mouth A 
 
 Houtfi 
 
 Fie. 59. Diagram to illnstrete 
 the gradoal developmeDt of 
 the ftJimeDtary tube as fonnd 
 ID the lower and higher fonns 
 of animal 8tractnre. (Testnt.) 
 
 Salivary 
 glands 
 
 Pharynx 
 
 -GuUet 
 
 Stomach 
 Pancreas 
 
 large 
 intestine 
 
 Appendix 
 
 Small 
 intestine 
 
 Fie. 60. Diagram of the alimentary tube 
 and its appendages. (TestnL) 
 
 has become a complicated system of organs, each of 
 which has its own peculiar work to do. 
 
 Mouth. — The first section of the alimentary canal, 
 the mouth, receives the food. It is provided with grind- 
 ing stones, the teeth; with a device for stirring it up, 
 the tongue ; with muscular walls for keeping it between 
 the teetli and for mo\'ing the jaws, the cheeks ; and with 
 glands for moistening it with a digestive fluid, the 
 saliva. 
 
 Teeth. — The teeth are peculiarly adapted to reduc- 
 ing masses of food into the fine particles required for 
 
98 
 
 DIGESTION 
 
 digestion. As soon as the human infant begins to be ac- 
 tive and to require other food than milk, his teeth 
 
 Fig. 61. a, An InciBor tooth. 6, A canine or eye tooth, c, A bicuspid tooth seen 
 from its outer Bide ; the inner cuBp iB accordingly not viBible, d, A molar tooth. 
 
 push their way out through the soft gums from the bones 
 of the jaws in which they have been developing. The 
 first tooth usually comes when the baby is about seven 
 
 Fig. C2. Teeth of dog. 
 
 Fig. 63. Teeth ot horse. 
 
 months old. At two years of age, he should have his 
 first set of twenty teeth. Of these, each jaw contains 
 
THE TEETH 99 
 
 ten, divided into two sets of five on each side. In each 
 of these sets of five, there are found in front two sharp 
 teeth with edges like a chisel for cutting, called incisors. 
 Next to these at the sides is one pointed tooth for tear- 
 ing, called from its resemblance to the corresponding 
 tooth in the dog, the canine. Last of all come two back 
 teeth with broad irregular flat tops for grinding, which 
 are appropriately named molars^ 
 
 Permanent set. — "When the child is almost six years 
 of age, another molar appears at the back end of each 
 
 Central incisor 
 
 Fis. 64. The jawa of a child of seven and a half years, with the external table of 
 bone cut away to show how the teeth of the second set push their way out. 
 (Testut.) 
 
 series of five. These four molars are the first of the 
 permanent teeth. The next of the permanent set to 
 eome are the incisors, which push their way out from 
 under the temporarj^ teeth. The roots of the temporary 
 teeth are destroyed by the pressure of the budding teeth 
 
 • Latin, mokre, to grind. 
 
100 DIGESTION 
 
 beneath, and the teeth themselves fall out when there is 
 • nothing left to hold them in. In this way, all of the tem- 
 porary teeth are displaced one after another by the perma- 
 nent ones, which consist of four sets of eight teeth each. 
 Each set has two incisors, a canine, two bicuspids and 
 
 Fio. 65. The teetn of the right balf of the upper jaw In their soclcete, viewed 
 from below. 
 
 three molars. The bicuspids are so named because they 
 each have two prominences or cusps on their crowns. 
 They are used for crushing and also, like the molars, for 
 grinding. The third molar of each of the four sets, 
 known as the wisdom tooth, develops late and is often 
 deficient in strength and endurance. 
 
 Development of teeth, — The teeth closely resemble 
 bone and are formed as buds within the jawbones, 
 where their roots permanently remain. They are, how- 
 ever, not true bone, as shown by their structure and 
 method of development. They are to be classed rather 
 with the other specialized outgrowths from the skin, such 
 as the nails and hair. 
 
 Roots. — By means of roots, the teeth are rigidly held 
 in the bones of the jaws. The incisors and canines have 
 single roots. Some of the bicuspids have single roots, 
 
STRUCTURE OF TEETH 
 
 101 
 
 Periosteum 
 of socket 
 
 Cemen 
 Bone of jai 
 
 Pulp Cavit' 
 
 whereas others have roots which are forked near the 
 tip. Most of the molars have, three roots. 
 
 Structure. — Each tooth consists of the exposed por- 
 tion, or crown; the narx-owed part enclosed by the edges 
 of the gums, called the 
 neck; and the portion 
 imbedded in the bones, 
 the roots. "When sawed 
 through lengthwise. a 
 tooth is found to consist 
 of a bony portion and an 
 inner cavity. The cro\\-n 
 of the tooth is capped 
 witli the hardest substance 
 found in the human body, 
 a white enamel, which is 
 all of the tooth that we 
 ordinarily see. Enamel is 
 made up of the same 
 earthy material as bone 
 but contains none of the 
 animal matter and but a slight amount of water. 
 
 Within the enamel lies a less hard bony material, the 
 ivory or dentine, which forms the bulk of both crown 
 and root. Dentine also contains less animal matter 
 and less water than bone. The dentine of the root is 
 protected by a substance which closely resembles true 
 bone. It is called cenuni, because it serves to hold 
 the teeth firmly in their sockets by wedging their roots 
 against the bony walls. 
 
 The eavitj' within the tooth is filled, with blood-vessels 
 and nerves, which form the so-called pulp of the tooth 
 and enter it throiigh small holes at the tips of the roots. 
 They supply the dentine with nourishment and keep it 
 
 Fig. 66. Section tlirough jaw bone and 
 tooih of cat. (Waldeyer.) 
 
102 
 
 DIGESTION 
 
 alive. When for any reason they are destroyed, the 
 tooth is dead; but this does not interfere with its use- 
 fuhiess, since a dead tooth, if properly cared for, may 
 remain in the jaw for many years. 
 
 Tongue. — The tongue, which helps to hold and move 
 the food in chewing, consists of a mass of interlacing mus- 
 cular bands, so distributed that they can move the tongue 
 
 Stemo-masto d muscle/ 
 Parotid gland and duct'; 
 Jugular vein 
 Carotid artery^ 
 Submaxillary gland and duct 
 Sublingual gland and duct'' 
 Jaw bone-' 
 Fig. 67. The salivary glands, a portion of lower jaw having been removed. 
 
 to any part of the mouth or curl it up so that its tip can 
 reach to all the teeth. The tongue is richly supplied 
 with blood-vessels and nerves, and is covered with a 
 thick membrane, which contains upon its upper surface 
 the organs of taste. 
 
DIGESTION OF STARCH 103 
 
 Cheeks. — The chccls, which are so necessary for keep- 
 ing the food between the teeth, consist chiefly of power- 
 ful muscles. These draw the lower jaw upward, so as 
 to bring the teeth firmly together for biting and chewing. 
 
 Salivary glands. — The glands of the mouth secrete 
 a large amount of watery fluid, the saliva, which 
 moistens the food as it is chewed. There are three pairs 
 of salivary glands, one pair of which, the sublingual, 
 lies under the sides of the tongue. Another pair, the 
 svlmaxillanj, lies just beneath the angles of the lower 
 jaw, at each side. The third pair, the parotid, lies in 
 the cheeks just in front of the ears. In mumps, the 
 parotids become swollen. 
 
 Saliva. — The saliva is a thin alkaline solution of vari- 
 ous substances, the most important of which is a fer- 
 ment '■ called ptyalin. Ptyalin has the power of chang- 
 ing insoluble starch into a soluble kind of sugar, called 
 maltose, without undergoing any change itself. Since 
 ptyalin, like all other ferments, requires time to do its 
 work, starchy food should not be swallowed without a 
 good deal of che^ang. Of aU foods, starch alone is thus 
 acted upon by the saliva. The others are merely mois- 
 tened, that chewing and swallowing may be made easy. 
 
 Pharynx. — ^When a mouthful of food has been prop- 
 erly chewed, it is reduced to a thin watery mixture. The 
 tongue and the cheeks then squeeze it into the cavity 
 at the back of the mouth, the pharynx, from which it 
 
 ' A ferment or enzynie is a substance produced by living cells, 
 which causes chemical changes in other substances without itself 
 undergoing change. There are many ferments, each one of which 
 can act only upon a single kind of substance, as ptyalin upon 
 starch, pepsin upon proteids, amylopsin of the pancreatic juice 
 upon starch, and lipase of the pancreatic juice upon fat. Many 
 ferments are also found in the various tissues of the body and 
 assist the cells in the oxidation of food and the development of 
 energy therefrom. 
 
104 
 
 DIGESTION 
 
 has been previously kept by a muscular curtain, the soft 
 palate. The pharynx opens into both the mouth and 
 the nose and is the part of the throat which we see when 
 we look into an open mouth. At the bottom of the 
 
 Soft palate 
 Pharynx 
 
 Uvula 
 
 Fig. 68. The upper surface of tongue and the throat. 
 
 pharynx there are two openings. One of these, the wind- 
 pipe or trachea, has a swinging lid which closes during 
 swallowing so as to keep the food out. The other, the 
 gullet or esophagus, is the regular passage for the food 
 and is open only during swallowing. 
 
THE STOMACH 
 
 105 
 
 Esophagus.— ^Yhen tlie food reai-hes the pharynx, its 
 muscular walls push it over the top of tlie trachea into 
 the esophagus, which relaxes to receive it. The muscular 
 fibres which make up the walls of the esophagus close 
 
 Fig. 69. The stomach and intestines, front view, with the liver turned np and to 
 the left. The dotted line shows the normal position of the anterior horder of the 
 liver. (Testut.) 
 
 above the food and, by relaxing in front and contracting 
 behind it, force it quickly into the large food reservoir, 
 the stomach. 
 
 Stomach. — The stomach is a loose muscular elastic 
 bag, which in an adult contains about three pints when 
 normally distended. Its walls consist of several thin 
 
106 
 
 DIGESTION- 
 
 layers, one of which is made up of muscle fibres inter- 
 laced to form a thin elastic coat. This coat can increase 
 or diminish the stomach's capacity by relaxing or con- 
 tracting. The inner layer or lining of the stomach is a 
 thick coat of cells, in which lie the glands for secreting 
 a digestive fluid, the gastric juice. The stomach is 
 shaped like a pear, sharply curved to one side. The 
 
 Oangla of sympathetic system 
 Vena cava inferior 
 
 ^Anenes supplying- 
 tirancbes to stomacft 
 
 Fig. 70. The stomacti and a portion of the small intestine, the remainder of in- 
 testine and liver having been removed. 
 
 esophagus leads into its larger end, and its smaller end 
 is continued into the intestine. 
 
 Gastric juice. — The innumerable small glands which 
 secrete the gastric juice, are embedded in the walls of 
 the stomach, with their mouths opening into its cavity. 
 The gastric juice is composed of hydrochloric acid and 
 
DIGESTION IN STOIIACH 
 
 107 
 
 Inner surface of stomach 
 
 a ferment^ called peps^in. During the digestion of a 
 
 meal, a large amoimt of gastric juice is secreted and is 
 
 thoroughly mixed with the food by the contractions of 
 
 the stomach, forming a grayish acid liquid called chyme. 
 
 The gastric juice changes the pro- 
 
 teids in the food into soluble forms 
 
 which can be readily absorbed, 
 
 called peptones, but it has no 
 
 effect upon the carbohydrates or 
 
 hydrocarbons. 
 
 Exit of ch5niie from the stomach. 
 — During the first hour or so of 
 digestion, the opening from the 
 stomach, the pylorus, is compara- 
 tively small. Only the liquefied 
 contents, such as the starches and 
 sugars and those proteids which 
 have been changed into peptones, 
 are allowed to pass through it in 
 small amounts. During the later 
 period of digestion, when the stom- 
 ach becomes fatigued or consider- 
 ably emptied, the pylorus relaxes 
 more completely and permits 
 particles of considerable size to 
 pass through. The relaxation 
 under the normal conditions of health is sufficient to 
 empty the stomach at the end of from two and a half to 
 three hours. The stomach then enters upon a period of 
 rest, during which the glands are preparing for a subse- 
 quent period of work. 
 
 Fig. 71. Section through a 
 stomach glaud, showing 
 its central canal and the 
 arrangement of its cells. 
 (Gerrifih.) 
 
 ' Another ferment called retjjiin is found in the stomach, es- 
 pecially in babies and other sucking animals. Rennin has the 
 power of coagulating milk as a preliminary to its digestion. 
 
108 
 
 DIGESTIOM 
 
 Rejection of food. — In case the food taken Is irritat- 
 ing to the stomach because of its poisonous nature, or 
 is so excessive in amount as unduly to stretch its walls, 
 the stomach empties itself by sending the food back 
 the way it came. This swal- 
 lowing up, as it may be called, 
 is accomplished on the part of 
 both stomach and esophagus by 
 a reverse process of muscular 
 contraction. The esophagus re- 
 laxes to permit the food's exit, 
 instead of the pylorus. 
 
 Small intestine. — After its 
 exit from the stomach through 
 the pjdorus, the chyme passes 
 into the upper end of the small 
 intestine. This is a tube about 
 twenty feet in length, with mus- 
 cular walls lined with a mucous 
 membrane of closely packed cells. 
 Lying in and beneath this mem- 
 brane are many small glands, 
 which discharge into the intestine a secretion, the in- 
 testinal juice. The intestinal juice contains a number of 
 ferments that have the power of digesting starch and 
 proteid, and of changing cane sugar into grape sugar, in 
 which form only it can be utilized by the body. 
 
 Liver. — Opening into the small intestine near the 
 stomach are two small tubes or ducts. One of these 
 comes from the liver and its reservoir, the gall-hladder. 
 The liver is the largest gland in the body and weighs 
 from three to four pounds. It is reddish-brown in color, 
 firm in consistency but easily torn, and lies across the 
 body at the level of the lower ribs. It has several im- 
 
 Fio. 78. Diagram illustrating 
 the masculur contractions of 
 a cat's stomac b after eating a 
 meal jnst before 11 a. m. By 
 these contractions, the con- 
 tents are squeezed toward the 
 pylorus. (Cannon.) 
 
DIGESTION IN SMALL INTESTINE 
 
 109 
 
 portant functions, two of which are related to digestion. 
 It serves as a storehouse for the excess sugar found in the 
 blood coming from the intestine during digestion, and as 
 a factory for the making of hilc. The bile is a thin 
 yellow-green alkaline liqiaid, which is secreted continu- 
 ously and is stored in the gall-bladder when digestion 
 
 Pancreatic duct 
 
 Flo. 73. Stomach, be^iuninf; of small iutesliue, aud enti-auce of bile and pau- 
 crejitic duct. tUough and Sedgwick.) 
 
 is not going on. "When the acid chyme enters the in- 
 testine, it causes a reflex contraction of the gall-bladder, 
 which thereupon pours out bile through its duct. Un- 
 like the saliva, the gastric juice, and the intestinal juice, 
 bile has no specific action upon starches, sugars, or pro- 
 teids. It is of great use, however, in the digestion and 
 absorption of fat. 
 
 Pancreas. — The other of tlie ducts opening into the 
 small intestine comes from a long gland, the pancreas, 
 which lies at the lower edge of the stomach and along 
 a portion of the intestine. The same stimulation by 
 the acid chyme which causes the gall-bladder to con- 
 tract and force out the bile, also causes the cells of 
 
110 
 
 DIGESTION 
 
 the pancreas to secrete its juice. The pancreatic juice 
 is a thin clear liquid containing several ferments. One 
 of these ferments acts upon proteids and aids in finish- 
 ing the digestion of any part of them not completed 
 by the gastric juice of the stomach. Another finishes the 
 digestion of starch begun in the mouth by the saliva 
 and continued in the stomach until stopped by the acid 
 of the gastric juice. A third ferment acts upon fat, 
 which cannot be acted upon by either the saliva or the 
 gastric juice. 
 
 Digestion of fat. — The fat in animal tissues is in the 
 form of drops of oil which are stored up within the cells 
 of the connective tissue. The walls of these fat cells 
 
 Connective tissue 
 
 Nucleus of connective 
 tissue cell 
 Protoplasm of cell 
 Fat globule within cell 
 
 FiQ. 74. Diagram showing storage of fat within donnective tissue cells. 
 
 are digested in the stomnt^h by the gastric juice, so 
 that the fat ifi free when it enters the intestine. As a 
 result of the action of the pancreatic juice upon it, as- 
 sisted by the alkaline bile, the fat is so changed that 
 it can be readily absorbed through the walls of the in- 
 testine. The action of the pancreatic juice is not com- 
 
ABSORPTION 
 
 111 
 
 pleted immediately but takes place gradually as the 
 food contents are slowly churned forward through the 
 small intestine by the contractions of its walls. 
 
 Chyle. — The bile and the pancreatic juice, when 
 mixed in the intestine with the grayish chyme, make of 
 the fat a soapy solution, or emulsion, and thereby change 
 the chyme into a white alkaline mixture known as 
 chyle. 
 
 Villi. — ^Up to this point, only a small amount of food 
 has been absorbed through the walls of the mouth and 
 
 Network of capillaries 
 Epithelial membrane 
 
 I-acteals 
 
 Level cf inner vail 
 of intestine 
 
 Outer vallfr^: 
 of intesnne 
 
 
 Fio. 75. Small section of wall of intestiue showing three villi. In A, artery, vein 
 and lacteal with tlieir branches are represented; in B, artery, vein and branches ; 
 in C, the lacteal only. (Diagrammatic.) 
 
 stomach into the blood-vessels. The small intestine has 
 a special mechanism by means of which practically all 
 of the digested material in the chvle is absorbed into 
 
112 DIGESTION 
 
 the body before the residue passes into the large in- 
 testine. This mechanism consists of minute finger-like 
 processes, the villi, which project from the inner wall 
 of the intestine into its cavity, where they are bathed 
 by the chyle. The villi are covered with a continuous 
 layer of cells. Within this wall of cells lies a network 
 of connective tissue cells, muscle fibres and blood-vessels. 
 Scattered among these are irregular spaces, into which 
 open the mouths of tube-like channels, called lacteals. 
 
 Absorption of food. — The solutions of food materials 
 absorbed by the villi from the chyle pass into the body 
 in two ways. The peptones and the sugars diffuse di- 
 rectly into the fine blood-vessels in the villi and are 
 thence carried in the blood stream to the liver. The 
 fats, which remain in the villi after the peptones and 
 sugars have been absorbed, are pumped by them into 
 the lacteals, which in turn take them into the blood but 
 not by way of the liver. 
 
 In this process of absorption, it is difficult to see how 
 the solutions get through the cells which form the mem- 
 brane covering the villi. Experiments show conclusively 
 that the cells must have the power of passing the solu- 
 tions of peptones and sugars and the emulsion of fat 
 through themselves. It is true that peptone and sugar 
 can diffuse through animal membrane, but, unless they 
 were assisted by some action of the cells themselves, it 
 would be at a much slower rate. Fats do not seem 
 to be able to pass through animal membranes even slowly 
 and therefore their absorption certainly requires the 
 active assistance of the cells. Indeed, it is probable 
 that the cells even change the fats into soaps in order 
 to facilitate their passage. 
 
 Food after absorption. — As the digested food passes 
 through the membrane covering the villi, its character 
 
THE LARGE INTESTINE 113 
 
 is once again changed. In the blood, peptone is not 
 found, but in its place appear certain forms of albumin 
 and other proteids peculiar to the blood. The emulsion 
 of fat becomes again ordinary fat. The maltose, the spe- 
 cial form of sugar derived from the starches and sugars 
 eaten, alone remains as maltose. "When this reaches 
 the liver, however, most of it also is changed back into 
 a form of starch, the so-called liver or animal starch 
 loiown as glycogen. Thus we see that the main purposes 
 of digestion are to change the food so that it can be 
 readily absorbed and then manufactured, in the case 
 of proteids and fats, into the forms peculiar to the 
 blood. 
 
 Undigested residue. — After the chyle has been ab- 
 sorbed from the small intestine, there still remains a cer- 
 tain amoiuat of undigested material. This ordinarily 
 consists of the cellulose from the vegetables and grains 
 eaten, of the connective tissue from meat, and of any 
 digestible matter which has escaped the action of the 
 ^'arious digestive juices. This residue is passed from the 
 small intestine into the large intestine through the con- 
 necting ileocecal valve. Occasionally, when jnasses of 
 indigestible material are miable to pass readily through 
 this valve, a pronounced distention of the intestine re- 
 sults, producing the pain ImowTi as colic. 
 
 Large intestine. — The large intestine is about five 
 feet long in an adult and varies from one and a half to 
 two and a half inches in diameter. Its walls are made 
 up of a series of pockets, the partitions of which serve 
 to prevent its contents from passing forward too rapidly. 
 In it, a certain amount of digestion and absorption, espe- 
 cially of water, still goes on. As a result, the mass of 
 undigested food and waste becomes firmer and dryer. 
 It passes forward around the partitions in the walls and 
 
114 DIGESTION 
 
 is finally caught as a semi-solid mass in a sharp curve 
 which lies in the left groin. From this, it is ejected at 
 intervals. 
 
 EXPERIMENTS AND DEMONSTRATIONS 
 
 The Alimentary Canal 
 
 Materials: Sound and diseased natural teeth such as can be 
 obtained from a dentist; dilute hydrochloric acid or vinegar; 
 rabbit such as can be bought at a market ; a short piece of the 
 small intestine of a recently killed calf or sheep; alcohol, 50 
 per cent strength; normal salt solution; sheet of fine emery 
 cloth; microscope; fine saw; hand lens. 
 
 1) Teeth: Soak sound teeth in warm water for one or two 
 days; saw some lengthwise, others crosswise and smooth on 
 emery cloth. 
 
 a) Examine the structure. 
 
 b) Demonstrate decayed teeth. 
 
 c) Test the effect of an acid upon a tooth. 
 
 2) Salivary glands: Dissect away the skin from the whole 
 ventral aspect of rabbit and note salivary glands : 
 
 a) Below and back of the ear, the pink mass of the parotid 
 gland. (It is difficult to trace the duct which has its outlet on 
 the inside of the cheek). 
 
 b) Just inside the angles of the lower jaw, the rounded 
 masses of the submaxillary glands. 
 
 c) Farther forward, under the tongue, the narrow sublingual 
 glands. 
 
 3) Mouth and throat: Examine the muscles moving jaw. 
 Cut away the muscles on one side of mouth and neck, exposing 
 cavities of mouth and throat. Identify and sketch the 
 following r 
 
 a) Teeth; tongue; and hard and soft palates. 
 
 b) Cavity at back of mouth and its connection with nasal 
 cavity ; tonsils ; muscular walls of pharynx ; larynx ; epiglottis ; 
 and the opening into esophagus. 
 
 4) Esophagus, stomach and intestines: Carefully cut away 
 the front walls of chest and abdomen. After examining and 
 
ANATOMY OF DIGESTIVE TRACT 115 
 
 sketching the larynx, trachea, hings and heart, remove them by 
 freehig blood-vessels and other attachments: 
 
 a) Trace and sketch the esophagus, stomach, liver and 
 intestines, disturbing their natural positions as little as possible. 
 
 b) Turn liver out of the way and follow esophagus to 
 stomach : 
 
 Note form of stomach; its projection (fundus') to the left 
 of esophagus; its great and small curvatures; its narrower 
 pyloric portion on the right, from which the small intestine 
 proceeds. 
 
 Notice a thin membrane (the omentum) attached to stomach 
 and hanging down over the abdominal contents, ordinarily 
 loaded with fat. 
 
 e) ToUow and unravel the coils of small intestine, spreading 
 out as far as possible the delicate membrane (mesentery) which 
 suspends it from the upper dorsal part of the abdominal cavity. 
 
 Note the blood-vessels and laeteals running in the numerous 
 bands of fat in the mesentery. 
 
 d) Cut open the side of large intestine opposite entrance of 
 small intestine : 
 
 Note the termination of small intestine in the ileocecal valve ; 
 the cecum or blind end of large intestine, projecting beyond the 
 ileocecal valve. 
 
 Compare the position of rermiform appendix and cecum with 
 that in the human body. See pp. 97, 105. 
 
 Follow large intestine through ascending, transverse, and 
 descending colon, sigmoid flexure, and rectum, to its end at anal 
 aperture, cutting away front of pelvis to follow terminal 
 portion. • 
 
 e) Spread out the portion of mesentery lying in the eon- 
 cavity of the first coil (duodenum) of small intestine: 
 
 Note the pancreas, a thin, branched, glandular mass; the 
 portal vem entering the under side of liver by several branches 
 which drain the intestinal tract ; near it the gall duct, formed by 
 the union of two branches and proceeding as a slender tube to 
 open into duqdenum about 1% in. from pyloric orifice of 
 stomach. 
 
 f ) Cut off esophagus and rectum, remove the whole alimen- 
 tary canal, cut away mesentery, and spread the canal out at 
 full lengtli : 
 
116 DIGESTION 
 
 Note the relative length and diameter of its various parts and 
 determine the ratio of its length to the length of body/ 
 
 g) Open stomach along its greater curvature : 
 
 Note character of mucous membrane. 
 
 Examine under water the surface of lining membrane with 
 microscope. 
 
 h) Remove liver : 
 
 Note its general form and relation to body as a whole, to 
 stomach, and to intestine, with special reference to veins and 
 bile duct. 
 
 Find gall-bladder and trace out its ducts. 
 
 Scrape its cut surface and examine cells in normal salt solu- 
 tion under microscope. 
 
 i) Cut out piece of intestine (also of calf or pig), wash inner 
 surface gently with normal salt solution, and examine in the 
 solution with a hand lens. 
 
 j) Place pieces of small intestine in 50 per cent alcohol for 
 24 hours. Then open and examine villi under water with a 
 hand lens. 
 
 Materials and apparatus : Sugar ; salt ; raisins, grapes, cran- 
 berries and other fresh fruits, with skins and stems uninjured; 
 corn or arrowroot starch; olive oil; blood fibrin either fresh or 
 dried and softened in warm water, — or egg albumin coagulated 
 by slowly pouring white of egg, which has been cut up with 
 scissors and forced through cheese cloth, into boiling water 
 acidulated with vinegar; meat juice; milk; bile of pig or other 
 animal, obtained from butcher ; f^yeerole pepsin, Parke, Davis & 
 Co. ; pancreatic extract made by dissolving in 2 oz. warm water, 
 15 grs. dry extract obtained from druggist; saliva collected by 
 chewing paraffin or a piece of rubber and filtered ; hydrochloric 
 acid, 2 per cent solution made by adding 1 teaspoonful com- 
 mercial hydrochloric acid to 1 qt. water; sodio hydrate solu- 
 tion; copper sulphate solution; water bath for holding test 
 tubes (a deep tin containing a wire test tube rack, nearly 
 
 ' It must be remembered that the rabbit is herbivorous and 
 therefore has an alimentary tract quite different in certain 
 particulars from that of man. The alimentary canal pf a cat or 
 dog more nearly resembles the human. 
 
DIGESTION EXPERIMENTS 11'? 
 
 filled with water aud kept at a constant temperature of about 
 99° F. will answer) ; thermometer with scale on stem or in 
 glass tube ; wire test tube racks, each with a capacity of 3 doz. 
 test tubes; one wooden test tube rack with holes and pins for 
 each pair of "students; dialvzer, which may be made from a 
 lamp chimney, the large end being covered with bladder, in- 
 testine, or moist parchment paper; funnels 2 in. in diameter for 
 students' use; funnels 6 or 8 m. in diameter for preparing 
 material; six 6 in. test tubes for each student; nests of 3 
 beakei-s of from 4 to 6 oz. capacity; filter papers, 1 package 
 31 2 iu. ui diameter, a few, 6 or S in. ; litmus paper. 
 
 Experiments '; 
 
 1) Penetration of membranes by crystalloids {sugar, salt) 
 and by peptone: 
 
 a) Place dialyzer obliquely in a glass, so that the membrane- 
 covered eud does not rest on the bottom. Carefully pour the 
 solution to be tested (1 teaspoonful sugar, or salt, to I/2 cup 
 water) into open end of dialyzer so that no particle of it is 
 spilled. Pour pure water mto the glass to exactly the same 
 level as solution in dialyzer and allow to stand over night. 
 Test the water in glass by taste or chemically. 
 
 b) Test peptone and other solutions similarly. 
 
 ' Use a test tube for each experiment beginning with 4. 
 Identify them by slipping bits of paper containing names of 
 students and contents into the open ends. Place the test tube for 
 all digestion experiments in that portion of the water bath 
 reserved for each student. It is best to use small amounts ot 
 substances for digestion, to fill the test tubes about two-thirds 
 full of the solution, and to shake frequently. Two or three drops 
 of the solutions of pepsin and of pancreatic extract are sufiScient. 
 
 The digestion ordinarily requires some time, and it may be 
 necessary in certain eases to prepare the solutions, put tliem in 
 the water bath, and leave them until the next day for examina- 
 tion. If the test tubes are shaken every few minutes, the digestion 
 of starch and of fibrin (or egg albumin) is so rapid that it may 
 be possible to get the proper reactions in half an hour. If the 
 laboratory section extends for two hours, the digestions will be 
 sufliciently completed at the end of that time for all characteristic 
 tests. It is best to have the pupils prepare the digestion test tubes 
 first, then to have the demonstrations and experiments which can 
 be accomplished immediately, and to leave the examination of 
 digestion products until the last. 
 
118 DIGESTION 
 
 2) Non-penetration of membranes hij colloids (starch, al- 
 bumin) except peptone: Proceed as in 1). 
 • 3) Absorption (Osmosis) : 
 
 a) Place 2 grapes, 2 raisins, 2 cranberries or other similar 
 fruit into glasses containing hot water and allow to stand for 
 an hour. Compare the fruits with untreated specimens. 
 
 b) Prepare a syrup of 2 parts of sugar to 1 of water, bring 
 to a boil, and stir in fruit as in a). Let stand for an hour; 
 compare with a) and with untreated fruits. (If difference is 
 not sufficiently obvious, allow to stand over night.) 
 
 Note in both a) and b) changes in size and consistency, and 
 infer what has caused results in each case. Record all obsei-va- 
 tions in schedule form, using the following signs: diminu- 
 tion ( — ); increase (-|-); no change (=) ; solution in water 
 (dissol.). 
 
 In pyrup 
 
 Raisin .... 
 
 Grape 
 
 Cranberry . 
 
 4) Effect of saliva: 
 
 a) Prepare proteid, fat, and boiled and raw starch paste, by 
 mixing in test tubes with water to which 1-3 in bulk of saliva 
 has been added. Place in water bath, shake frequently, and 
 watch progress. 
 
 b) Mix a little saliva with 3 or 4 volumes of thick starch 
 paste and note its immediate effect. 
 
 c) Test results of salivary digestion in a) for starch,^ sugar 
 and peptone." 
 
 5) Effect of artificial gastric juice: 
 
 ' Test by putting 1 drop of solution on a white plate and adding 
 a, drop of the iodine solution. A brownish color indicates dextrin, 
 a partially digested starch. 
 
 ■^ Biuret test for peptones : Put % in. of solution to be tested for 
 peptone into a test tube. Add an equal amount of sodie hydrate 
 solution, mix thoroughly, and then add 1 or 2 drops of very dilute 
 copper sulphate solution. Violet color indicates peptone. 
 
DIGESTION EXPERIMENTS 119 
 
 a) Make gastric juice by adding a few drops of giycerole 
 pepsin to 0.2 per cent hydrochloric acid. Prepare digestion 
 test tubes by adding 1/2 test tube of solution to small amount 
 each of egg albumin (or fibrin) and starch. 
 
 b) Test results of gastric digestion in a) for peptones by 
 means of biuret test. 
 
 6) Effects of pancreatic juice and bile: 
 
 a) Shake sweet oil with an equal amount of solution of 
 pancreatic extract. 
 
 b) Prepare as in a) and add a few drops of bile. Compare 
 with a). Examme a drop under microscope and compare with 
 a drop of milk. 
 
 e) Moisten with bile a filter paper stretched across top of a 
 funnel and add a teaspoonful of oil. Moisten with water 
 another filter paper similarly placed, and apply the same, 
 amount of oil. Note comparative rapidity of penetration. 
 
 4) Make soap by boiling fat or oil with a strong solution of 
 caustic soda. Test result by shaking a few drops with water. 
 
CHAPTER XI 
 THE HYGIENE OF DIGESTION 
 
 Food in relation to age. — The amount of food suffi- 
 cient for the body's needs varies with age and with 
 activity. The active growing child requires food not 
 simply to produce energy but to build up his tissues.. He 
 therefore requires more food in proportion to his weight 
 than the adult, who needs the food principally for the 
 production of energy. The aged person, whose activity 
 is slight and whose tissues are changing but slowly, 
 needs but comparatively little food.^ 
 
 To health. — The amount of food required also varies 
 with the general condition of the body, that is, whether 
 it is healthy or ill. In illness, not only is muscular ac- 
 tivity less, but the ability to digest may be so far reduced 
 
 •Influence of age on diet 
 
 Proteins 
 
 Fats 
 
 Carboliy. 
 drates 
 
 Calories 
 energy 
 
 Children to IJ^ yeare 
 
 Children IJ^ to 6 years 
 
 Children 6 to 15 years 
 Women with light ex- 
 
 (28 gms 
 120-36 " 
 
 (55 
 
 1 36-70 •• 
 
 (75 
 
 170-80 " 
 
 80 
 80 
 
 j 37 gms. 
 1 30^5 '• 
 
 140 
 
 1 3.5-48 " 
 
 (43 
 
 1 37-50 " 
 
 80 
 50 
 
 1 75 gms. 
 1 60-90 •' 
 
 1200 
 
 1 90-250 " 
 
 (323 
 
 1350^00 " 
 
 30O 
 860 
 
 770 
 
 1423 
 
 2048 
 
 2308 
 
 Aged women 
 
 1867 
 
 
 
 The heat units used represent the amount of heat necessary to 
 raise certain amounts of water one degree Centigrade. 
 1 Calorie = 1 kilo water, 1° C. ^ 1 lb. water, 4° F. 
 
 1 calorie = 1 gram water, 1° C. = 0.001 lb. water, 4° F 
 
 1 micro-calorie = 0.001 gram water, 1° C.=0.000001 lb. water, 4° F. 
 1 Calorie is equivalent in mechanical energy to 1.53 foot- tons. 
 
 1 calorie " " " " " " 3.06 foot-pounds. 
 
 120' 
 
VARIATIONS IN DIETS 
 
 121 
 
 that certain foods cannot be used at all. The diet, there- 
 fore, which is proper for a person in good health may- 
 be most injurious for one who is ill. 
 
 To activity.— Another important factor in determin- 
 ing the amount of food necessary for the body is the 
 amount of muscular activity. Of two healthy adults 
 of the same weight imd age, the one who is active re- 
 quires more food than the one who is not, because the 
 former is constantly having to oxidize food materials 
 for the production of energy. ^ If the inactive man 
 should eat and absorb as much as the active one, in- 
 stead of oxidizing it all, he would store the excess as fat. 
 
 Variations in diet. — Between the amoimt of food re- 
 quired by the body and the amount actually eaten, there 
 is often a wide divergence. If a person's appetite is 
 good or if he can aiford to tempt it with luxuries, he 
 may overeat ; if poor, he may fail to have enough to eat. 
 It is probably true that many persons eat too miich pro- 
 teid, especially in the form of meat. Proteid can be 
 stored in the body but slowly, even during the grow- 
 ing period of youth. In adult life, only a comparatively 
 small amount is needed to make good the wear and tear 
 of the active tissues. Since the greater part of it can- 
 not be stored, it is immediately oxidized for the produc- 
 tion of energy, and its waste products of urea and uric 
 acid are removed by the kidneys. Up to a certain point, 
 the kidneys are able easily to do this. If the proteid 
 
 ' Effect of activity on diet 
 
 Proteins 
 
 Fats 
 
 Carbo- 
 liydrates 
 
 Bnergy in 
 calories 
 
 Man at lisht in-door work 
 
 " " " out-of-door work.. 
 " " moderate o u i-o f-d o o r 
 
 worlc 
 
 " " hard out-of-door work 
 " ** very hard out-of-door 
 
 viOTk in winter 
 
 no 
 
 110 
 
 185 
 150 
 
 180 
 
 60 
 100 
 
 125 
 150 
 
 200 
 
 390 
 400 
 
 450 
 500 
 
 600 
 
 8,645 
 3,063 
 
 3,568 
 4,120 
 
 5,026 
 
122 THE HYGIENE OF DIGESTION 
 
 taken is excessive, however, the kidneys may become 
 overburdened, especially if they are weak or diseased. 
 The waste products then tend to clog or even to poison 
 the body.^ 
 
 Times for meals. — The hours at ■which food is taken 
 depend a good deal upon the habits of peoples and of 
 individuals. In America, it is customary to have three 
 quite substantial meals a day. In determining what 
 practice is best for a given individual, the amount of 
 physical work to be done is the main, factor. For the 
 man who is to do a morning's hard muscular work, a 
 substantial breakfast is essential, whereas lighter work 
 requires less food. The test in any case of whether 
 enough food has been taken is the person's condition 
 previous to the next meal. If he feels faint and ex- 
 hausted, with possible headache and even nausea, it 
 shows that his breakfast has been too scanty. He should 
 either have eaten more or have had a luncheon between 
 the two meals. If, on the contrary, he feels dull and 
 sluggish with little appetite for the next meal, he ha:? 
 eaten too much. The same rules apply to the midday 
 meal. If a person is dull and sleepy after it, he should 
 eat more sparingly. At night, the meal should be com- 
 paratively light for children who go to bed soon after 
 it, in order that they may sleep soundly. For those who 
 are active for three or four hours afterwards, a hearty 
 meal may be necessary. The test of whether or not 
 the proper amount is eaten is the soundness of sleep 
 and the appetite for breakfast. 
 
 Appetite as a guide. — For those who are active the 
 
 appetite is a guide as to when food should be taken and 
 
 " Experiments have shown that men can work to advantage on 
 about half as much proteid as the foregoing tables shovif, that is, 
 on from 50 to 70 gms. per day of dry proteid, vifhich is the equiva- 
 lent of 200 to 300 gms. or 7 to 10 oz, of meat, 
 
APPETITE 123 
 
 how much. Under ordinary conditions, however, the ap- 
 petite is for various reasons often misleading. Appetite 
 itself is a diffused sensation of discomfort, which is 
 caused partly by the failure of the tissues to receive 
 as much food as they need and partly by the failure 
 of the stomach to be adequately filled with the food 
 which it has been trained to expect. For the appetite 
 to be a reliable gi^ide, it must be aroused onlj' when 
 the tissues need food and the stomach needs filling. 
 If a person is habitually overeating, the stomach trained 
 to expect food at given intervals, gives the signal through 
 the appetite that it is time for more food, in spite of 
 the fact that the tissues do not need it and so must 
 store the excess as fat. If, on the contrary, a person 
 habitiially eats too little, the stomach acciistomed to ex- 
 pect and to take care of but small amoimts, may fail 
 to produce the appetite for food, although the tissues 
 are actually in need of it. 
 
 Its unreliability. — Another factor which contributes 
 to the unreliability of the appetite is that it often out- 
 lives its cause and so leads to the taking of a larger 
 amount of food than is necessary. The stomach may 
 be filled sufficiently by a meal to satisfy the needs of 
 the tissues and yet the appetite persist, especially if 
 the food has been swallowed without much chewing. 
 If the appetite is further reinforced by pleasure in eat- 
 ing, the probability' of overeating is greatly increased. 
 To avoid this, food should be eaten slowly, that the 
 appetite for it may tend to cease when enough has been 
 eaten. 
 
 A third most important cause of an unreliable appe- 
 tite is eating between meals. This practice not only in- 
 terferes with the rest which the stomach needs but also 
 prevents the proper recurrence of appetite. When for 
 
124 . THE HYGIENE OF DIGESTION 
 
 any reason, as in illness, a proper amount of food can- 
 not be taken at the regular times, the intervals between 
 the meals should be shortened but still kept regular. 
 
 Composition of food. — That food may fully nourish 
 the body, it must not only be taken at the proper time 
 and in the proper amount but it must also be of the 
 right composition, that is, it must combine the right pro- 
 portions of proteid, carbohydrate and hydrocarbon. The 
 amount of proteid which is needed daily by the body has 
 been shown by investigation to be fairly constant and 
 smaller than was formerly thought. The proper amount 
 of carbohydrate and hydrocarbon varies with our ac- 
 tivity. Muscular energy may come from the oxidation of 
 either the carbohydrates or the hydrocarbons, although, 
 as a matter of fact, it is usually derived more largely 
 from the carbohj^drates since the fats are ordinarily 
 eaten in much smaller amounts.^ They are both oxi- 
 dized and their waste products removed in the same 
 way. If taken in excessive amounts, they may both 
 give rise to indigestion. 
 
 Necessity for variety. — The kinds of food which con- 
 tribute the proteids, carbohydrates and hydrocarbons 
 are important, since their proportion may be right and 
 yet the monotony of the food be distinctly injurious, 
 especially if there is a tendency to overeating. Loss 
 of appetite and failure of digestion may result from an 
 unvarying diet. It is necessary therefore to plan to 
 have the kinds of food changed frequently enough to 
 avoid monotony. 
 
 Importance of good teeth However carefully we 
 
 may determine the amount and kind of the food which 
 
 ' In cold climates and in cases of poor nutrition and of tuber- 
 culosis, much larger amounts of fats may sometimes be taken with 
 beneiit, provided they are not used in such a way a-; to make other 
 foods indigestible, as in frying. 
 
CARE OF THE TEETH 125 
 
 we eat, we eamiot be sure of a good digestion unless we 
 take care of such of the digestive organs as are luider 
 our control. Of these, the most important are the teeth. 
 Unless our food is adequately chewed, indigestion almost 
 surely follows. The influence of bad teeth upon the 
 general health has been shown to be so marked that 
 the importance of keeping them clean and of having 
 all cavities, even in the first teeth, attended to by a den- 
 tist, cannot be overestimated. Decayed teeth interfere 
 with proper chewing, and act as lodging places for 
 microbes, which not only make the breath foul but may 
 also infect the glands of the jaw and neck. To keep 
 the teeth clean, they m\ist be brushed after each meal 
 with a good tooth powder or paste. The brushing should 
 be up and down and not across the teeth, as the latter 
 method weai-s the teeth unnecessarily and does not clean 
 between them. A strong silk thread should also be used 
 to remove any particles of food that may have lodged 
 between them. If the thread is moistened and covered 
 with tooth powder, it will keep the sides of the teeth 
 polished and tend to prevent the deposit of tartar. Any 
 discoloration or deposit should be removed by rubbing 
 the teeth with powdered pumice upon the end of a moist- 
 ened pointed stick. 
 
CHAPTER XII 
 
 THE BLOOD 
 
 The products of digestion are received and carried 
 to the tissues by the blood, a red salty liquid which 
 constitutes about eight per cent of the total weight of 
 the body. Upon exposure to the air, the blood quickly 
 
 I corpuscle much enlarged 
 "ross section of red corpuscle 
 
 touleau of red corpuscles 
 iS'i*j~'*'liite corpuscles 
 
 Fibrin 
 
 Fia. 76. Coagulated blood (highly magnified). 
 
 becomes sticky and jelly-like through the formation of 
 clots. "When examined under the low power of a micro- 
 scope, blood is seen to consist of a clear colorless liquid, 
 the plasma, which is thickly packed with small rounded 
 particles, the corpuscles, the majority of which are a 
 
 136 
 
THE CORPUSCLES 127 
 
 pale yellowish-red. When examined under a higher 
 power, the corpuscles are seen to have several different 
 forms. Those which are yellowish-red appear as flat- 
 tened discs. Others which are translucent or "white," 
 are globular and have one or more small rounded granu- 
 lar bodies, the nuclei, within them. Still others are 
 smaller transparent discs. 
 
 Red blood corpuscles. — The blood owes its red color 
 to the yellowish-red discs, which are therefore called 
 red Hood corpuscles. They consist of a clear jelly-like 
 substance, hemoglobin, which readily absorbs oxygen. 
 Their shape makes it possible for them quickly to take 
 up oxygen from the air and give it off to the tissue cells, 
 since they are so flat and broad that each one of them 
 exposes a comparatively large surface for absorption. 
 It has been calculated that in an adult there are 25,000,- 
 000,000,000 red corpuscles and that their total surface 
 equals about 35,000 square feet. In a healthy person, 
 5,000,000 red corpuscles are contained in a drop of 
 blood no bigger than a pin head (1 cu. mm.).^ In bulk, 
 they constitute one-half of the blood. They are devel- 
 oped in the red marrow of the bones and when full 
 grown are set free in the blood current, in which they 
 are carried to all parts of the body. They are destroyed 
 in the liver and spleen. 
 
 White blood corpuscles. — The white blood corpus- 
 cles consist of granular protoplasm containing one or 
 more nuclei. They are nourished by the blood and 
 lymph and behave very much like amebse, in that they 
 are able to change their form and to lead an essentially 
 
 •In cases of anemia (literally, lack of blood), their numbers 
 may be diminished to two-thirds or one-half of this. Consequently, 
 the amount of oxygen necessary for full activity cannot be carried 
 to the tissues, and tlie result is pallor and weakness. 
 
128 
 
 THE BLOOD 
 
 Fio. 77. A white blood-cor- 
 puscle sketched at successive 
 intervals of a ifew seconds to 
 illustrate the changes of form 
 due to its ameboid move- 
 ments. 
 
 independent life. They mal^e their way through minute 
 openings in the walls of the blood-vessels and wander 
 through into the spaces between 
 the cells of the tissues without 
 doing them any harm. By eat- 
 ing up microbes and small par- 
 ticles of foreign matter, they act 
 as scavengers in the body. 
 They are developed in the 
 lymph glands ^ and spleen, 
 from which when mature they 
 are set free in the lymph and 
 blood. 
 
 The white blood corpuscles are present in the blood 
 in the proportion of one white to five himdred red. 
 In certain diseases, however, their number is often in- 
 creased and as a result they are better able to combat 
 the invasion of the harmful microbes to which the 
 disease is due. In abscesses and pustules, many white 
 corpuscles die, either overwhelmed in their attempt to 
 destroy the microbes or smothered as a result of their 
 own overcrowding in the inflamed tissue. The ' ' matter ' ' 
 from abscesses is made up almost entirely of these 
 corpuscles. 
 
 Platelets. — A third kind of blood corpuscle, the 
 platelet, resembles the red blood corpuscle in form but 
 it is smaller, more transparent and so exceedingly deli- 
 cate that it breaks up almost instantly when blood is 
 shed. Practically nothing is known of its functions, ex- 
 cept that it assists in causing the blood to clot. 
 
 Plasma. — When the corpuscles are removed, the fluid 
 of the blood, the plasma, remains as an almost colorless 
 sticky liquid, composed of ninety per cent water and 
 ' See p. 132, 150. 
 
FUNCTION OF BLOOD 129 
 
 ten per cent solids. The solids consist chiefly of pro- 
 teids, together with fat and other organic substances, 
 salts, and a small amount of fibrin-forming substance. 
 
 Fibrin. — Blood plasma vipon its escape from the blood- 
 vessels becomes very quickly a jelly-like mass, or clot, 
 by the rapid formation of a close tangle of slender 
 fibres, Imown as fibrin. "When taken singly, these fibres 
 are so delicate that they can be seen only through a 
 microscope. "When fresh blood is Avhipped with a bun- 
 dle of twigs, the fibrin is caught on the twigs, where it 
 forms very elastic white threads. Since the blood which 
 remains does not clot, it is proved that its coagulation 
 depends upon the formation of these threads, which, 
 although constituting but one two-hundredth part of 
 the blood bulk, are yet so numerous that they completely 
 entangle the water and other constituents of the blood 
 and hold it as a firm, fairly dry jelly. That the blood 
 shoiild be able to coagulate is most .important, since 
 thereby a vein or small artery when cut is quickly 
 plugged and severe bleeding prevented. If a, larger 
 artery is cut, however, the force of the blood is so great 
 as to prevent plugging by the formation of a clot. 
 
 Blood as a common carrier.; — The general work of the 
 blood is that of a common carrier and as such it fur- 
 nishes the only means of transport within the body. It 
 carries in solution to all the tissues their supply of 
 .food, which has been absorbed from the digestive tract, 
 and gathers up from the special organs their secretions, 
 M'hieh it distributes to all parts of the body. It also 
 collects from the cells the waste products of oxidation 
 and carries them to such organs as the lungs and kidneys 
 for disposal. 
 
 Blood changes. — Because of these exchanges with the 
 various tissues of the body, the blood is constantly 
 
130 THE BLOOD 
 
 changed in character. For example, the bright red 
 blood which comes from the lungs is rich in oxygen 
 and fairly poor in carbon dioxide. After its contact with 
 the tissues, the amount of oxygen is diminished, whereas 
 the carbon dioxide has increased. As a result, the blood 
 becomes a dark bluish-red. This blood again passes 
 through the lungs, where it replenishes its supply of 
 oxygen and loses much of its carbon dioxide, thereby 
 regaining its brilliancy. 
 
 Food elements. — The character of the blood is also 
 changed by the rapid absorption of food materials when 
 we eat and drink. Some of these, it stores up and later 
 doles them out to the tissues as they need them for their 
 activity. 
 
 Carbohydrates. — In the storage of the sugar absorbed, 
 the blood is assisted by the liver. The liver takes from 
 the blood the excess sugar which the blood absorbed 
 in the villi during digestion and. stores it in its cells in 
 the form of a starch, called glycogen. As the blood be- 
 comes jjoor in sugar through loss to the tissues, the liver 
 changes the glycogen once again into sugar and restores 
 it to the blood. In this way, the supply of sugar in the 
 blood is kept fairly uniform, provided that meals are 
 taken regularly. 
 
 Hydrocarbons. — The fat absorbed into the blood 
 after each meal remains there until removed by the 
 tissues and oxidized. If, however, an excessive quantity 
 of fat is eaten, the blood is assisted in taking care of 
 it by the various cells of the body, especially those of 
 the connective tissue, which store it within themselves 
 in the form of fat globiiles. 
 
 Proteids. — The proteid material which is absorbed 
 during digestion is retained in the blood until given 
 up to the tissues for repair, growth, or oxidation. Dur- 
 
CONDITIOXS AFFF.CTING BLOOD 131 
 
 ing growth a part of the protoid material is built into 
 the developing tissiies ; the remainder is quickly oxidized 
 for tlie production of energy. After growth censes, the 
 majority of the proteid eaten is oxidized, since none is 
 needed for the building of tissue and but little for tissue 
 repair. 
 
 Water. — AYater, when absorbed from the intestinal 
 tract, dilutes the blood temporarily, but is quickly re- 
 moved by the kidueys. "When water is taten in excessive 
 amounts, there may also be a considerable temporary 
 storage of it in the cells of the tissues. 
 
 Storage of excess food. — If food is taken nt regular 
 intervals, the blood is able to supply the tissues ^nth the 
 nourisliment Mhieh they need in adequate amounts dur- 
 ing the intervals between meals. If excess food is regu- 
 larly taken, the tissues by preference oxidize the pro- 
 teids and carbohydrates, with the result that the fat is 
 left as a permanent storage. 
 
 Starvation. — If too little food is taken, or. as in starva- 
 tion, none at all, we find a marked effort on the part 
 of some of the tissues to keep up the normal composi- 
 tion of the blood. Not only are the stored supplies 
 of fat and carbohydrate gradiially returned to the blood, 
 but additional proteid material is furnished by the sac- 
 rifice of the less active tissues themselves.^ These actu- 
 ally convert themselves into food material for the tissues 
 which must be active in order to preserve life, such as 
 the heart and nervous sj-stem. These are thus enabled 
 
 * Total loss of various tissues in stan-ation: 
 
 Fat >1T.0<-o 
 
 Liver S4.0<~i - 
 
 Mxiscles 30.5% 
 
 Luutp 1S.0'> 
 
 Bones U.O'", 
 
 Nervous system S.2<"c 
 
 Heart . . ." •i.G'"c 
 
132 THE BLOOD 
 
 to continue their activity and the life of the individual 
 is considerably prolonged. 
 
 Internal secretions of glands. — In addition to the 
 food materials, the blood also carries the various products 
 manufactured by the different cells and organs of the 
 body. These materials, although in many cases the waste 
 products of their activity, are yet essential to the health 
 of the other organs and cells to which the blood carries 
 them. Thus the pancreas not only discharges through 
 its duct the pancreatic juice externally into the intestinal 
 tract, but also gives directly to the blood passing through 
 it an internal secretion which enables the cells of the body 
 to oxidize and utilize the sugar brought to them as food 
 by the blood. The kidney also probably does a double 
 work of supplying an internal as well as an external 
 secretion, which it gives to the blood for the benefit of the 
 rest of the body. 
 
 Other internal secretions are those which come from 
 ductless glands such as the thyroid gland, which lies in the 
 neck; the adrenal bodies, which lie just above the kid- 
 neys ; and the pituitary body, which lies at the base of the 
 brain. These secretions have been shown by careful ex- 
 periment to be of the utmost importance to the health 
 of the other cells of the body. 
 
 Spleen. — Secretions are also probably contributed to 
 the blood by the spleen, an organ lying in the left side of 
 the abdominal cavity. Its exact functions, however, are 
 still open to dispute, since it can be removed without 
 serious consequences. The main function clearly be- 
 longing to it is the removal from the blood and the sub- 
 sequent destruction of red blood corpuscles. 
 
EXPEEDIENTS 133 
 
 EXPEEIME^'TS AND DEMONSTRATIONS 
 
 Materials: Alcohol; uitrio acid; deBbviuated blood; blood 
 dot or fresh liver; serum; chisel-poiuted needle; test tubes; 
 blotting papei"; microscope with powei-s up to 450; 2 fruit jars; 
 bundle of twig-s or wires ; tumbler ; platinum foil ; alcohol lamp 
 or Bunseii burner. 
 
 1) Get a di-op of blood from lobe of ear or side of finger by 
 rubbing vigorously, washing with a little alcohol, and piercing 
 when dry to a depth of ^.^ in. with a needle sharpened to a 
 chisel point, soaked in alcohol, and dried. (No pain results 
 from piei"eing.) Spread a drop of blood on a piece of glass, 
 put on a cover glass, and examine under miei'oseope. Note 
 form, size and color of red blood corpuscles; method of cluster- 
 mg; color, form, size and relative number of white blood 
 corpuscles. 
 
 2) Obtain a large drop of blood as above (1) described. 
 Note its physical characteristics (color, opacity, etc.) when it 
 flows fl-om the wound ; its apparent change of color when it is 
 spread very thin on the glass and held over a sheet of white 
 paper; its color when mixed with a teaspoonful or more of 
 water in a test tube; its change of consistency when a drop of 
 nitric acid is added and test tube is heated. 
 
 3) Place another large drop of" blood on a clean glass plate. 
 To prevent its dr>-ing. cover by inverting over it a glass lined 
 witJi wet blotting paper. 
 
 In 4 or o minutes, i-emove glass and note condition of blood 
 when manipulated with a needle. 
 
 Replace moist glass and in half an hour examine again. 
 
 Additional Demonstrations at Option of Teacher: 
 
 1) Collect blood at butcher's in a glass jar; set aside until 
 blood clots and carry without shaking. Observe clot and serum 
 next day. Carefully pour oflf serum for subsequent tests. 
 
 2) Collect fresh blood in a pail and beat it ^-igoronsly with 
 twigs for 3 or 4 minutes. Note quantity of struigy elastic 
 material (fibrin) collected on twig-s. 
 
 Wash fibrin thoroughly in running water and note its color. 
 
 3) Take some of serum and note its physical characteristics. 
 
134 THE BLOOD 
 
 Heat it in a test tube and note change. . 
 
 Apply Xantho-proteie test. 
 
 4) Place a small quantity of whipped blood on a piece of 
 platinum foil. Heat in alcohol or gas flame and note that after 
 the drop dries it blackens, showing that it contains much 
 organic matter. 
 
 Continue heating until this is burned away; examine residue 
 of white ash, consisting of mineral constituents of blood. 
 
CHAPTER XIII 
 THE CIRCULATION OF THE BLOOD 
 
 System of tubes for the blood. — In order that the 
 blood may surely find its way from tissue to tissue in 
 the bod,y, a system of tubes and special organs has been 
 developed. This system has a central pumping station, 
 the heart, which furnishes the power by which the blood 
 is pushed forward. A system of tubes, the arteries, veins 
 and capillaries, leads from the heart to the tissues and 
 back to the heart again. These tubes are so constructed 
 and arranged that, although the blood is carried to all 
 parts of the body through their many branches, yet it is 
 all gathered together again and returned to the heart. 
 
 Greater and lesser circuits. — The blood leaves the 
 large cavity on the left side of the heart and goes to 
 the tissues tlirough thick walled tubes, the arteries. It 
 returns by larger and thinner walled tubes, the veins, 
 to the right side of the heart. It is then sent through 
 another set of arteries to the lungs, whence it again 
 returns to the left side of the heart through a second set 
 of veins, and is once again ready for a repetition of its 
 .iourney to the tissues. There is thus the main circu- 
 latory route to and from the tissues comprising the 
 greater, or systemic, circuit: and a secondary route to 
 the lungs and return, which is Imown as the lesser, or 
 piilmonari/, circuit. Xeither of these circuits is in itself 
 complete, since the blood after returning from the tissues 
 can reach the starting point in the heart for its next 
 trip to the tissues only by way of the pulmonary route. 
 
 135 
 
136 
 
 THE CIRCULATION OF THE BLOOD 
 
 Heart. — To provide the power required to drive the 
 blood through the arteries, its pumping organ, the heart, 
 is a strong hollow body, whose thick walls are made up 
 entirely of muscular tissue. In order to keep separate 
 the blood in the two circulatory systems, the heart is 
 divided into two parts with no direct means of com- 
 munication between them. In each part are two cham- 
 bers, an auricle and a ventricle, separated from each 
 other by swinging doors, the valves, which by opening 
 only in one direction prevent the blood from flowing 
 backward. 
 
 Heart muscle. — The muscle which produces the power 
 to push the blood forward, is arranged so- as to form the 
 
 Cavity of auricle 
 ■Auriculo-ventricular valve 
 
 Ctiordae tendinae 
 'Cavity of ventricle' 
 
 ■Papillary muscle 
 
 Fig. 78. Diagram of heart during relaxation and contraction: A, auricle con- 
 tracting to fill ventricle ; B, auricle filling, ventricle emptying into aorta. 
 
 walls and main partitions of the heart. The pumping ac- 
 tion consists in the contraction of the muscular walls 
 of both chambers when they are full of blood, until 
 they become so small that the blood is forced out through 
 the open valves. The valves then close and thereby pre- 
 
THE HEART MUSCLE 
 
 13T 
 
 vent its return. As soon as the blood is forced out, the 
 muscle relaxes and allows another supply of blood to 
 flow in and fill the chambers. T.his contraction and 
 relaxation are repeated one or more times a second 
 throiighout life and cause the heart heat, which can be 
 readily felt on the left side of the front of the chest. 
 
 Muscle cells. — The heart of a human being when con- 
 tracted, is about the size of his clenched fist; when dis- 
 tended with blood, it is nearly twice as large. "When it 
 contracts, the pressure which it ordinarily exerts is suffi- 
 cient to push the blood to a height of about eight feet. 
 At times of severe effort, as in heavy, lifting, it may even 
 be much greater. The heart has therefore to be built 
 in such a way that it is 
 strong enough to generate 
 this amount of power, and 
 firm enough to prevent 
 any of the blood on which 
 it contracts from tearing 
 a way through its walls. 
 For these reasons, its walls 
 are built of short power- 
 ful muscle cells, which are 
 striated like those of the 
 voluntary muscles, but dif- 
 fer markedly from them in 
 that they have squared 
 ends, each of which is ce- 
 mented fast to the ends of the adjoining cells, and lateral 
 branches similarly cemented to other cells. This method 
 of building affords a wall with an interlacing mus- 
 cular meshwork which cannot be split apart by the 
 blood in its attempt to escape as the heart contracts 
 upon it. 
 
 Connecting 
 branch 
 
 Fig. 79. Muscle cells of heart. 
 
138 
 
 THE CIRCULATION OF THE BLOOD 
 
 Ventricles. — Each half of the heart is divided, as we 
 have seen, into two chambers, the thick walled ventricle 
 and its ear-like appendage, the auricle. Of the two ven- 
 tricles, the left pushes the blood into a large artery, 
 the aorta, which leads from it. The left ventricle has to 
 exert great pressure and its walls 
 are therefore thick. The right ven- 
 tricle, on the contrary, has tbe 
 lesser work of sending the blood 
 through the lungs and its walls are 
 correspondingly thinner. 
 
 Auricles. — Of the two auricles, 
 the left receives the blood from the 
 lungs ; the right, from the systemic 
 veins. They then push it for- 
 ward into their respective ventri- 
 cles, when these are relaxed to re- 
 ceive it. The auricles serve mainly 
 as reservoirs for holding the blood 
 while the ventricles are contracting. 
 As they have to do but little work, their muscular walls 
 are comparatively thin. 
 
 Auriculo-ventricular valves. — Lying between each 
 auricle and its corresponding ventricle, there is a strong 
 thin flexible partition which is attached by its outer 
 edge to the wall of the ventricle. It is divided into 
 three flaps on the right side of the heart, into two 
 on the left. Slender tendons arise from the free edges 
 of the flaps and are attached by means of muscular pro- 
 jections, the papillary muscles, to the inner walls of the 
 ventricles. The purpose of these tendons is to hold the 
 flaps in place, so that they will act as valves to prevent 
 the blood from going back into the auricle when the 
 ventricles contract. When the ventricles relax, they 
 
 Fig. 80 Transverse sec- 
 tion through the middle 
 of the ventricles of a 
 dog's heart when full and 
 when contracted. 
 
VALVES OF THE HEART 
 
 139 
 
 offer no resistance to the movement of the blood from 
 the auricles into the ventricles. Because these valves 
 lie-between the auricles and the ventricles, they are called 
 the auriculo-ventricular valves. 
 
 Exit valves from ventricles. — Leading from each 
 ventricle is a large artery. At the beginning of each 
 
 Super or vena cava 
 Pulmonary artery 
 
 Valve flap 
 
 Left auricla 
 ^all of right auricle 
 
 oronary artery 
 
 R ght auriculo- 
 ventricular valve 
 
 -Tendinous cords 
 Papillary muscles 
 
 Wall of right 
 
 ventricle 
 'Inferior vena cava- 
 
 Left ventricle 
 
 Fig. 81. Heart, with portion of right auricle and right ventricle cut away to show 
 interior. Bristles snow passage waya. 
 
 of these two arteries, there is also a valve to prevent the 
 blood from flowing back into the relaxed ventricle. 
 Each valve consists of three thin tough pockets, or valve 
 flaps, which lie flat against the walls of the artery when 
 
140 
 
 THE CIRCULATION OF THE BLOOD 
 
 the blood is passing into it from the ventricle. When, 
 however, the ventricle is emptied and relaxes so that the 
 blood tends to return to it from the artery, they swell 
 
 R]ght carolid 
 Thyroid gland (in front of larynx 
 Right vagus nerve- 
 Vein from the thyroid gi 
 
 Trachea 
 Artefy to right shoulder and arm 
 Vein from head, shoulder and 
 
 Pleura. 
 
 Superior vena cavi- 
 
 Left carotid artery 
 
 vagus nerve Ho hcqrt. 
 stomach, elc-i 
 pti enic nerve do diaphragm] 
 Tforacic duct 
 Artery to left 
 
 shoulder and arm 
 Vein from head 
 
 st)ou[der aniJ arm- 
 Pleura 
 
 dn h or pulmonary artery. 
 
 ■T D of (,n auricle 
 P In-onary artery 
 LcT coronary artery 
 
 Infenor vena ^.a 
 
 Fig. 82. The heart and connecting blood-vessels. 
 
 out with the backward movement of the blood and close 
 the opening. 
 
 Arteries. — Of these two large arteries, one, the aorta, 
 leads from the left ventricle, and its branches reach all 
 parts of the body. The other, the pulmonary artery, 
 leads from the right ventricle, and its branches reach all 
 parts of the lungs. Both the aorta and the pulmonary- 
 artery are tough gristly tubes with highly elastic walls. 
 
EXPLANATION OF PLATE IV. 
 
 The Cibculatoey Organs. 
 
 The arteries (except the pulmonary) and the left side of the heart 
 are colored red; the veins (except the pulmonary) and the right half 
 of the heart, blue. On the limbs of the left side the arteries are 
 omitted and only the superficial veins are shown. 
 
 1. Aorta, near its origin from the left yeutrlcle of the heart. 
 
 2. Lower end of aorta. 
 
 3. Iliac artery. 
 
 4. Femoral artery. 
 
 5. Popliteal artery; the continuation of the femoral which passes behind 
 
 the knee joint. 
 G, 7. The main trunks (anterior and posterior tibial arteries Into which 
 the popliteal divides). 
 
 8. Subclavian artery. 
 
 9. Brachial artery. 
 
 10. Radial artery. 
 
 11. Ulnar artery. 
 
 12. Common carotid artery. 
 
 13. Facial artery. 
 
 14. Temporal artery. 
 
 15. Right side of heart, with superior vena cava Joining It above, and 
 
 Inferior vena cava (16) passing up to it from below. 
 
 17. Innominate vein, formed by the union of subclavian and jugular veins. 
 
 The right and left innominate veins unite to form the superior cava. 
 
 18. Left internal Jugular vein. 
 
 19. Axillary vein. 
 
 20. Basilic vein. 
 
 21. Cephalic vein. 
 
 22. Median vein. 
 
 23. Radial vein. 
 
 24. Ulnar vein. 
 
 25. Median vein. 
 
 26. Iliac vein. 
 
 27. Femoral vein. 
 
 28. Long saphenous vein. 
 
 29. The kidney: attached to It are seen the renal artery and vein. 
 
 30. Branches of the pulmonary arteries and veins In the lung. 
 
ARTERIES 141 
 
 Their numerous branches differ from them mainly in 
 being smaller. 
 
 Functions of arteries. — The arteries form smooth 
 channels through which the blood is guided to all parts 
 of the body. When the left ventricle contracts and 
 pushes the blood into the aorta, the walls of the aorta 
 are stretched out by the extra supply of incoming blood. 
 The elastic recoil of the walls squeezes the blood forward 
 through the branches of the arteries. Before the arteries 
 have a chance to push all the blood that is in them for- 
 ward, they are again filled by the contraction of the left 
 ventricle. The right ventricle also contracts at the same 
 instant and sends its blood into the pulmonary artery, 
 which by its elastic contraction forces it through the 
 lungs. 
 
 Structure of arterial wall. — :The elastic recoil of the 
 walls of the larger arteries is due to a special form of 
 highly elastic tissue which resembles rubber in its ac- 
 tion. Thin overlapping layers of this material lie in 
 the arterial walls. "When the arteries are stretched out 
 by the blood pumped into them, the elastic tissue makes 
 them recoil so that they press upon the blood and thereby 
 push it along. Obviously, the pressure exerted upon the 
 blood is greater when they are distended than when 
 they are but partially filled. As we shall see, this is 
 an important factor in the circulation of the blood. 
 
 Control of blood supply. — In addition to the elastic 
 tissue, the walls of the arteries also contain encircling 
 muscular fibres, which are especially numerous in the 
 very small arteries, the arterioles. These muscular fibres 
 are all of the non-striated variety and are slow in con- 
 traction. In the arterioles, their function is to control 
 the amount of blood passing through them to the tissues. 
 For example, if a tissue is active, these small musclQ 
 
142 
 
 THE CIRCULATION OF THE BLOOD 
 
 fibres, which are usually slightly contracted, relax and 
 thus permit the arterioles to become larger and more 
 blood to pass. If, on the contrary, the tissue's activity 
 
 Connective tissue 
 
 Muscular coat. 
 ,— Elastic coat 
 J-^ Endothelial coaf' 
 Artery 
 
 Fie. 83. Artery and vein, sliowing Btructnre of walls. 
 
 is diminished, they contract so that only the small 
 amount of blood necessary to supply the resting tissues 
 is allowed to pass through. These muscle fibres, under 
 the control of their nerves, thus automatically adjust the 
 supply of blood to the needs of the tissues. 
 
 Branching of arteries. — The arteries divide into 
 smaller and smaller branches and their number be- 
 comes very great. Eventually, they are so small and 
 numerous that they can penetrate nearly every particle 
 of tissue in the body.^ As the arteries become smaller, 
 their walls also become thinner and the elastic tissue 
 
 ' The only exceptions to this are cartilage and certain transpa- 
 rent parts of the eye. In these, sufficient nourishment reaches the 
 very inactive cells by means of the lymph which soaks through 
 from cell to cell. 
 
CAPILLARIES 
 
 143 
 
 diminishes until in the arterioles it disappears com- 
 pletely. The proportion of muscle fibre, on the contrary, 
 increases until the arterioles are reached, when it in turn 
 decreases until none is left. 
 
 Capillaries. — The smallest branches of all, the capil- 
 laries, which are only about half a millimeter in average 
 length, have neither elastic tissue nor muscular fibres. 
 They are the smallest, 
 the most delicate, as 
 well as the most nu- 
 merous of all the blood- 
 vessels. The finest nee- 
 dle point can penetrate 
 scarcely any part of the 
 body without severing 
 some of them. Their 
 walls consist of an ex- 
 ceedingly thin mem- 
 brane, which is made up 
 of flat cells placed edge 
 to edge to form a con- 
 tinuous tube. Their thin- 
 ness permits the blood to come into close contact with 
 the tissue cells, without, however, allowing the red 
 blood corpuscles to escape. The required amount of 
 oxygen freely passes from the red corpuscles to the 
 tissue cells, and the plasma of the blood containing the 
 food material in solution also oozes through in sufficient 
 quantity to nourish them. The blood in the capillaries 
 receives in exchange from the cells their waste products, 
 including carbon dioxide, 'whieh pass readily through 
 their walls into the blood stream. 
 
 Veins. — The capillaries join together at their farther 
 ends to form a second system of larger tubes, the veins. 
 
 Fig. 84. A, diagram of branching capilla- 
 ries, showing liow chey are made, up of a 
 single layer of cells, the edges of which 
 are cemented together to form tubes. 
 B, Cross section of same, showing nuclei 
 in walls. 
 
144 
 
 THE CIRCULATION OF THE BLOOD 
 
 The veins continuously increase in size as they diminish 
 in number, until finally there are but two large tubes 
 which receive the blood from aU the others and pour 
 it into the right auricle of the heart. This second system 
 is known as the venous system. 
 
 Blood flow in the veins. — In structure, the veins 
 closely resemble the arteries, except that their walls are 
 much thinner, since they, do not have to stand any con- 
 siderable pressure. The pressure which in the arteries 
 served to push the blood forward, is not ordinarily trans- 
 mitted to the veins, because it is largely blocked by the 
 contraction of the arterioles. If it were transmitted, the 
 delicate walls of the capillaries would be overstretched 
 
 or even burst by the 
 high pressure of the ar- 
 terial system. The pro- 
 pulsion of the blood back 
 to the heart through the 
 veins must therefore be 
 accomplished by a dif- 
 ferent mechanism from 
 that which pushed it 
 from the heart through 
 the capillaries. The veins 
 have numerous valves 
 which are readily pushed 
 open by the blood flow- 
 ing from the capillaries 
 toward the heart but are 
 closed against its return toward the capillaries. The 
 veins are thus converted into a series of short sections 
 separated by valves. Each section is emptied by the ex- 
 ternal pressure exerted by the muscles, the skin, and 
 the pulsations of the arteries which lie close to it. As a 
 
 Fio. 85. Diagram showing the bending of 
 red blood corpueclee and the rolling of 
 white blood corpasclee in the capillaries 
 of a frog. 
 
FUNCTION OF BLOOD-VESSELS 
 
 145 
 
 result, the blood is pushed for- 
 ward from one section to an- 
 other on its Avay to the heart. 
 The largest veins of the trunk, 
 however, do not have valves. In 
 them, the forward movement of 
 the blood is largely due to the 
 variations in pressure exerted 
 upon them by the movements of 
 the chest in breathing. 
 
 General function of blood- 
 vessels. — The work of the arte- 
 rial system as a whole is thus 
 seen to be to carry the blood in 
 adequate amounts to the capil- 
 laries. The work of the capil- 
 laries is to get the blood into 
 such close contact with the cells 
 of the tissues that oxygen and 
 nourishment may be given to 
 them and waste products re- 
 moved from them. The work of 
 the venous system is to return 
 the used blood back to the oppo- 
 site side of the heart, ready to 
 start on its pulmonary circuit. 
 
 Pulmonary circulation. — In 
 the pulmonary system, the struc- 
 ture and relation of the arteries 
 and veins are similar to those in 
 the systemic. The capillaries in 
 the lungs, however, differ from 
 the systemic capillaries in that 
 they are larger and have a dif- 
 
 FiG. 86. Superficial view of 
 right arm showing the fascia 
 and veinB, and the method of 
 branching of the veins by 
 which many other paths are 
 open to the returning blood 
 in case of obstructiDg pressure 
 or injury to the direct path. 
 
146 
 
 THE CIRCULATION OF THE BLOOD 
 
 ^^ 
 
 ferent arrangement. They cover the walls of the tiny- 
 air sacs in the lungs so thickly that they expose to the 
 purifying and enriching action of the air a layer of blood 
 the thickness of a capillary and. about eight hundred 
 square feet in extent. 
 
 Travels of a drop of blood. — Through this double 
 system of heart, arteries, capillaries and veins, we may 
 
 trace the course of a drop 
 of blood as follows: Start- 
 ing in the left ventricle of 
 the heart, the drop of blood 
 passes through the aortic 
 valve into the aorta. It 
 quickly flows down the 
 aorta into one of its numer- 
 ous arterial branches and 
 finally reaches the capilla- 
 ries, for example, those in 
 a leg muscle. Here a cer- 
 tain amount of plasma and 
 perhaps a few of its white 
 corpuscles pass through the 
 walls of the capillaries into the spaces between the mus- 
 cle cells. Its red corpuscles give up some of their oxy- 
 gen to the muscle cells and its plasma receives carbon 
 dioxide and other waste matters. Thus changed and 
 slightly diminished by its losses, it returns by way of 
 the veins into the right auricle of the heart. It then 
 passes through the right auriculo-ventricular valve into 
 the right ventricle. Prom here, . it is pushed by the 
 contraction of the ventricle through the pulmonary 
 artery and its branches into the capillaries of the lungs 
 which surround the air sacs. Here, some of its car- 
 bon dioxide escapes to the air and a fresh load of oxygen 
 
 Fig. 87. Diagram of valves of veins: 
 A, valve opened by blood passing 
 forward toward heart ; B, valve closed 
 by attempted return of blood ; C, 
 vein opened to show arrangement of 
 valves. 
 
COURSE OF THE BLOOD 
 
 147 
 
 is taken on. Thus renewed, it passes through the 
 puhnonary veins to the left auricle of the heart. Upon 
 
 Arteries to- 
 head, arm 
 and neck 
 
 Pulmonary vein' 
 
 Left auricle 
 Aorta 
 
 Left ventricle 
 
 Arteries to 
 lower part 
 of body 
 
 iStomach and 
 Intestine 
 
 Capillaries 
 
 Lymph duct 
 
 Lungs 
 
 -Veins from head, 
 arm and neck 
 
 Vena cava sup 
 
 Pulmonary artery 
 
 Right auricle 
 
 Right ventricle 
 
 Thoracic duct 
 
 Vena cava inf 
 (from lower part oF body 
 Lacteals 
 
 Liver 
 
 Lymph duct 
 
 Vein from Inteatlne 
 to liver 
 (Portal vein; 
 
 Artery to liver 
 Tissue cells 
 
 Fia. 88. Diagram of the circulation of the arterial and venous blood and the 
 lymph. 
 
 the relaxation of the left ventricle, it enters once 
 again through the left aurieulo-ventricular valve and 
 
148 
 
 THE CIRCULATION OF THE BLOOD 
 
 thus completes the circuit. The shortest time that a 
 drop taking the shortest route can make the circuit is 
 estimated at fifteen seconds. Between one and two min- 
 utes is required for all ^ the blood in the body to pass 
 once through the left ventricle. 
 
 Lymphatics. — The small portion of the blood com- 
 prising the plasma and the white blood corpuscles, which, 
 as we saw, escaped from the capillaries into the space 
 
 White corpuscle 
 penetrating 
 van of capillary 
 
 ^— White corpuscle 
 
 ^ in tissue 
 
 Red corpuscle 
 
 From artery 
 
 To vein 
 
 Fig. 89. Migration of tlie white blood corpiiBclee from the capillaries of a frog 
 into the tissues during inflammation. (After Warren). 
 
 between the muscle cells alone remains to be accounted 
 for. After leaving the capillaries, the plasma and white 
 blood corpuscles are known as lymph,^ because of their 
 clearness and lack of color. The spaces between the cells 
 into which the lymph escapes are irregular in size and 
 shape and have no definite boundaries. They blend to- 
 gether to form communicating spaces of considerable 
 extent. The lymph in these intercellular spaces is con- 
 
 ' Lymph may be seen characteristically under the skjn in the 
 form of "water blisters." 
 
EXPLANATION OP PLATE III. 
 
 A General View op the Lymphatic ok Absorbent Sistbm 
 OP Vessels. 
 
 At e is seen a portion of the small intestine from which lacteals or 
 chyle-conveying vessels, d, proceed ; at f the thoracic duct, into which 
 the lacteals open. This duct passes up the back of the chest, and 
 opens into the great vein at g, on the left side of the neck : here the 
 chyle mingles with the venous blood. In the right upper and lower 
 limbs the superficial lymphatic vessels I I I I, which lie beneath the 
 skin, are represented. In the left upper and lower limbs the deep 
 lymphatic vessels which accompany the deep blood-vessels are shown. 
 The lymphatic vessels of the lower limbs join the thoracic dtict at 
 the spot where the lacteals open into it ; those from the left upper 
 limb and from the left side of the head and neck open into the thoracic 
 duct at the root of the neck. The lymphatics from the right upper 
 limb and from the right side of the head and neck join the great 
 veins at n. At m m are seen the enlargements called lymphatic glands, 
 situated in the course of the lymphatic vessels. 
 
PLATE III.-A GENERAL VIEW OF THE LYMPHATICS OR ABSORBENTS. That portion of them 
 
 knONvn as the lacteals is seen at d, passing from the small intestine e to the thoracic duct/. 
 
LYMPHATICS 
 
 149 
 
 Left 
 
 subclavian vein 
 Thoracic duct 
 
 Lynnph node of 
 lacteal system 
 
 staotly drained away by delicately walled tubes, the 
 lymphatics, whose expanded mouths open into them. 
 The lymphatics join together to form larger lymph 
 canals, very much as the capillaries unite to form the 
 veins. The flow of lymph through the lymphatics is 
 brought about by the exter- 
 nal pressure due to the ac- 
 tivity of the muscles and 
 other tissues lying near 
 them. 
 
 The two large lymphatic 
 duets which result from the 
 union of all the smaller 
 branches, pass respectively 
 into the two large veins 
 under the collar bone on 
 the sides of the neck, 
 through openings pro- 
 tected by valves, so that 
 the blood cannot pass back 
 through the lymphatics. 
 Of these ducts, the left is 
 much the larger and carries, in addition to the lymph, 
 the lacteal flow from the intestinal tract. The total 
 amount discharged from the lymphatics into the veins is 
 estimated to be more than two quarts in every twenty- 
 four hours. 
 
 Function of Ijmiphatic system The function of 
 
 the lymphatic system is twofold. It brings the plasma 
 of the blood containing the dissolved food materials 
 into closer contact ^nth the cells than is possible when 
 the plasma is within the capillaries. By means of the 
 lymph, the tissue cells are bathed in a constant and fresh 
 stream of food-containing fluid, from which they can 
 
 Fig. 90. Lacteale and thoracic dnct. 
 
150 
 
 THE CIRCULATION OF THE BLOOD 
 
 readily absorb what they need. Secondly, it takes away 
 some of the waste products from the active tissues. This 
 it accomplishes in part by the activity of the white 
 
 Nodes of duct5 (valves) 
 
 Fis. 91. Lymph gland and connected lymphatics. 
 
 corpuscles which are carried about in it and are 
 thereby enabled thoroughly to explore the tissues of the 
 body. 
 
 Lymph glands. — The work of drainage is further ac- 
 complished by the establishment of filtering stations 
 called lymph glands. The lymph glands vary in size 
 from a hemp seed to a bean and are scattered at various 
 points along the lymph canals. They are made up of 
 
LYMPH GLANDS 161 
 
 masses of small eells, the function of which, like that of 
 the white blood corpuscles, is to destroy microbes and 
 other foreign substances. They are so constructed that no 
 portion of the lymph can escape passing between a large 
 number of their eells and being exposed to their influence 
 before it continues on its passage towards the veins. If 
 microbes are present in overwhelming numbers, the cells 
 of the first protecting lymph gland may not be able to 
 kill them all or even prevent their development, which 
 then takes place in the overcome gland itself. In this 
 case, the lymph glands next in order in the course block 
 the progress of the microbes and continue to the limit 
 of their ability the good work of exterminating them. 
 In extreme cases, however, an invasion of microbes may 
 overcome gland after gland in the course of the lym- 
 phatics until finally they enter the blood stream and are 
 scattered to all parts of the body. The result is a general 
 infection, or blood poisoning, which always constitutes a 
 grave menace to life. In this way, an infected scratch or 
 cut may eventually have serious results. 
 
 Control of blood supply to tissues. — In order that 
 the tissues may receive as much food and oxygen as they 
 need when active and yet the total amount of the blood 
 be kept as small as possible, the blood is sent to them 
 copiously during activity and sparingly during rest. 
 To accomplish this, a definite and accurate control of 
 the distribution of the blood is required. Certain of the 
 nerves are sensitive to the activity of the tissues and 
 control the muscle fibres in the walls of their arteries. 
 When tissiie cells, because of their activity, require more 
 food and oxygen, the nerves cause the muscle fibres in 
 the walls of their arterioles to relax, thus allowing more 
 blood to pass through them. When, on the contrary, 
 the tissues become quiet and so require less food and 
 
152 
 
 THE CIRCULATION OF TllE BLOOD 
 
 oxygen, the nerves cause the muscle iibres to contract. 
 The arterioles as a result become smaller and less blood 
 is allowed to pass. The nerves which control the relaxa- 
 
 Artery 
 
 B 
 
 Fig. 92. A, Diagram of circulation from artery through capillariee to vein of 
 frog. The dariser corpuscles show change to venons blood. B, Diagram of cir- 
 culation iu congestion, showing dilatation of blood-vessels and crowding of 
 corpuscles. (After Warren.) 
 
 tion and contraction are known as the vasomotor nerves. 
 They are a part of that branch of the nervous system 
 which, because it works automatically, is called the 
 sympathetic system. 
 
 EXPERIMENTS AND DEMONSTRATIONS 
 Anatomy of the Heart 
 
 Materials: Sheep's heart with pericardium unpunetured ; 
 rabbit, freshly killed if possible ; glass tube % in. diameter, 12 
 in. long; scalpels; scissors; forceps. 
 
 1) Demonstrate in rabbit, which has been prepared ' by cut- 
 
 '■ If the chest is carefully punctured with the points of scissors, 
 previous to the removal of the ribs, the entrance of the air will 
 allow the lungs to collapse, so that they will not be injured by 
 subsequent cutting. 
 
ANATOMY OF THE HEART 153 
 
 ting away front ■ of chest with scissors, the relation of 
 diaphragm, heart, lungs, trachea and esophagus. 
 
 2) Expose trachea in neck, cut, and insert glass tube, tying 
 on if necessary. Inflate lungs to natural size, and note their 
 relations to ribs, heart, diaphragm and abdominal organs. 
 
 3) Carefully manipulate heart and lungs : 
 
 a) Find vena cava inferior on under (abdominal) side of 
 diaphragm; thenee follow it until it enters pericardium. 
 
 b) Trace out veins which vena cava inferior receives from 
 liver, spleen, kidneys and diaphragm. 
 
 e) Trace out supei'ior vena cava and its branches, 
 d) Notice between ends of two venae cavee the right pul- 
 monary veins proceeding from lung and entering pericardium. 
 
 4) Turn lung and heart back to their natural positions. 
 Trace out aorta, its arch and branches ; pulmonary artery dor- 
 sal to aorta, and its branches into lungs ; pulmonary veins. 
 
 5) Slit open perieai"dial sac' Note character of Iming mem- 
 brane of cavity ; and character and amount of fluid present. 
 
 6) Cut away pericardium carefully from various vessels at 
 base. Note general form and position of heart and location of 
 vessels connected with its base. 
 
 7) Carefully dissect out entrance of pulmonary veins into 
 heart.* Note on exterior the left and right auricles; the band 
 of fat running around top of ventricles and its offshoot running 
 obliquely down front of heart, thence passing to right of its 
 apes. ( This indicates position of partition, or septum, between 
 two ventricles.) 
 
 8) Dissect away fat around origins of great arterial ti'unks 
 and around base of ventricles. In fat will be found two 
 coronary arteries arising from aorta close to heai't, and the 
 coronary veins which accompany them. 
 
 9) Open right ventricle by passing blade of scalpel through 
 its wall about 1 in. from upper border of ventricle and on right 
 of band of fat, and cut down toward apex. Make a correspond- 
 ing cut through wall of same venticle on its other side. Raise 
 
 ' The following dissections are much better carried out upon the 
 sheep's heart o\\ ing to its larger size. 
 
 ' It will probably seem as if the right pulmonary veins and the 
 inferior cava opened into the same auricle, but it will be found 
 subsequently, ( 14 ) , that sudi is not really the case. 
 
154 THE CIRCULATION OF THE BLOOD 
 
 point of wedge-shaped flap and expose cavity. Cut off pul- 
 monary artery about an inch above its origin and open right 
 auricle by cutting a piece of its wall at left of venae cav». 
 
 a) Pass handle of scalpel from ventricle into auricle, and 
 also from ventricle into pulmonary artery. Study out relations 
 of these openings. 
 
 b) Slit open auricle.* Note fleshy projections on its walls; 
 character of interior surface; apertures of venae cavae; and 
 entrance of coronary sinus below entrance of inferior cava. 
 
 c) Pass probe through aperture along sinus and slit it open. 
 Note muscular layer covering it. 
 
 10) Raise by its apex the flap cut out of ventricular wall, 
 and if necessary prolong cuts toward base of ventricle until 
 divisions of tricuspid valve come into view. Note fleshy 
 columns on wall of ventricle; muscular cord (not found in 
 human heart) stretching across its cavity; and prolongation of 
 ventricular cavity towards aperture of pulmonary artery. 
 
 11) Cut away right auricle. Examine carefully tricuspid 
 valve, composed of three membranous flaps, thinning towards 
 their free edges; and tendinous cords which connect flaps to 
 muscular processes (papillary muscles) of wall of ventricle. 
 
 12) Slit up right ventricle until origin of pulmonary artery 
 is disclosed. Looking carefully for flaps of semilunar valves, 
 prolong cut between two of them so as to open pulmonary 
 artery and spread it out. Note valves; pouch made by each 
 flap ; and slightly dilated wall of artery behind each flap. 
 
 13) Open left ventricle and left auricle similarly. Cut aorta 
 off about 1/2 in. above its origin. Note aperture between auricle 
 and ventricle; passage from ventricle into aorta; entry of 
 pulmonary veins into auricle; septum between auricles; and 
 septum between ventricles. 
 
 14) Pass handle of scalpel from ventricle into auricle; 
 another from ventricle into aorta ; also pass probes into points 
 of entrance of pulmonary veins. Trace possible movements of 
 fluid through auricle, ventricle and aorta, with reference to 
 position and character of valves. 
 
 15) Compare auricles and ventricles as to character of their 
 walls. 
 
 16) Carefully raise wedge-shaped flap of left ventricle, and 
 cut toward base of heart, until valve (mitral) between auricle 
 
HEART ACTION 155 
 
 and ventricle is brought into view. Note that one of its two 
 flaps lies between auriculo-ventricular opening and origin of 
 aorta. 
 
 17) Slit aorta between two semilunar valve flaps: 
 
 a) Compare aorta with pulmonary artery and with larger 
 veins, with special reference to thickness, texture and elasticity. 
 
 b) Note coronary arteries opening into dilatations of aortic 
 wall above semilunar flaps. 
 
 Heart Action 
 
 Ulateiials and apparatus: Frog; 2 sheep's hearts; a piece of 
 sheet cork or of tliin board with % in- hole cut in it; micro- 
 scope; cii-culation apparatus made from bulb syringe; funnel 
 of glass or tin; 2 feet of Vi in- rubber tubing; 10 inches of 
 1 in. sap tubing; several feet of glass tubing, some Vi in-j 
 some ^2 in-; glass nozzle made of glass tubing drawn out in 
 flame; a piece of sheet lead such as comes in tea chests; 
 dissecting instruments; a circular piece of glass 1% in. in 
 diameter, cemented into a short tin tube to form a window; 2 
 basins. 
 
 1) Wrap frog in damp cloth and then in tea lead, leaving 
 one foot outside of lead. Fasten it to perforated sheet cork or 
 board and tie toes to pins so that web foot is spread over hole. 
 Clamp in place on microscope stage and focus carefully on web. 
 Note movement of blood corpuscles; arteries, through which 
 blood is passing toward thin-walled capillaries; veins into which 
 blood from capillaries is passing; rapidity of movement of red 
 blood corpuscles,' their position in blood stream and bending at 
 arterial branches; movement of white blood corpuscles and 
 their behavior in blood stream. 
 
 2) To demonstrate pumping action of heart, carefully re- 
 move sheep's heart from pericardium. 
 
 a) Aortic valve: Cut off aorta 1 in. above valve. Tie into 
 it a piece of glass tubing, down which pour water. Note 
 efSciency of valve. 
 
 Tie a glass or tin funnel into one pulmonary vein and 
 close the other by tying it. Fill funnel with water. Squeeze 
 ventricles with hand and note results. 
 
 ^ The frog's red blood eorpuscles differ from the human in that 
 they are oval and have very large nuclei. 
 
156 THE CIRCULATION OF THE BLOOD 
 
 b) Mitral valve: Tie glass window into left auricle and 
 watch appearance of mitral valve as ventricle is squeezed and 
 released. 
 
 c) Mitral and tricuspid valves: Cut auricles away, taking 
 great care not to injure valves. Hold ventricles apex down, 
 and pour water into them from pitcher held about a foot above. 
 Note movement of valves. 
 
 Cut cords attached to edge of one mitral valve and repeat. 
 
 3) Effect of elasticity of blood-vessels and of change in 
 resistance of arterioles : Take bulb syringe ' and fit outflow tube 
 to receive both a piece of glass tubing about 2 ft. long and a 
 piece of sap tubing ; also prepare nozzle with a hole about A 
 in. in diameter, which is fitted to distal ends of glass and sap 
 tubes. 
 
 a) Put intake tube of syringe into a basin of water, fill 
 syringe, and attach glass tube. Squeeze and release bulb every 
 2 seconds, noting character of outflow. 
 
 b) Attach nozzle to end of glass tube, pump regularly as 
 before, and note character of outflow. 
 
 c) Remove glass tube and attach sap tube. Pump as before, 
 and note character of outflow. 
 
 d) Attach nozzle to sap tube and test as in b). Compare d 
 with a, b, and c, and determine factors contributing to uniform 
 flow. 
 
 ' Instead of this, the more elaborate circulation scheme of Prof. 
 W. T. Porter may be used. It is obtainable from the Harvard 
 Apparatus Co., Medfield, Mass. 
 
CHAPTER XIV 
 THE HYGIENE OF THE CIRCULATION 
 
 Vasomotor control of blood distribution. — The 
 blood in the human body amounts, as we have seen, to 
 only eight pei* cent of its weight, and yet it is so accu- 
 rately distributed to all its parts that each of its tissues 
 never fails of getting the right amount at the right time, 
 in spite of the fact that it wants now more, now less, as 
 its activity increases or diminishes. To accomplish this, 
 two methods are employed. The first is the vasomotor 
 adjustment, by which more blood is allowed to escape 
 into the active tissues through the arterioles which are 
 opened more widely for this purpose. As a result, the 
 distention of the arterial walls is decreased and conse- 
 quently their pressure upon the blood which remains 
 within them is lowered. Less blood therefore is forced 
 through them to the inactive tissues of the body. It is 
 conceivable under this arrangement that so many large 
 organs might be actively at \York at the same time that 
 a large proportion of the blood in the arteries would 
 escape to them. Such a big reduction in the blood pres- 
 sure might result that the other organs of the body 
 would receive less blood than they needed. This would 
 be especially true of the brain, to which the blood has 
 to be sent uphill. 
 
 Control by heart beat. — In order to give complete 
 control of the circulation, the vasomotor control is sup- 
 plemented by variations in the frequency of the heart 
 
 157 
 
158 THE HYGIENE OF THE CIRCULATION 
 
 beat. As the pressure in the arterial system is lowered 
 by the draining away of blood through the active organs, 
 the heart is made to work more quickly, in order to pump 
 the blood faster into the arteries. The arteries are 
 thereby kept well filled and the blood pressure main- 
 tained at a height sufficient to drive the blood through 
 all the tissues in adequate amounts. In this way, the 
 adjustment of the blood supply to the needs of all the 
 organs, including the brain, is made possible within the 
 limits of normal activity. 
 
 Faulty distribution. — "When, however, the body's nor- 
 mal activity is exceeded, as when large numbers of 
 muscles are used at once, both of these methods of 
 adjustment may be inadequate and the blood may be 
 drained out of the arteries faster than the heart can 
 pump it in. The blood pressure then becomes so low 
 that the blood is not forced in sufficient amounts to the 
 brain. The result is dizziness and faintness. Such faulty 
 distribution undoubtedly accounts for the fainting of 
 athletes after a hard run or row. In eases of stomach and 
 intestinal irritation which leads to the abnormal dilata- 
 tion of the abdominal blood-vessels, the arterial blood 
 pressure is similarly lowered, and as a result faintness 
 and dizziness are common accompaniments of these ill- 
 nesses. Similar effects are also produced by considerable 
 losses of blood, or hemorrhage. 
 
 Effects of eating. — These facts make it clear why it 
 is unwise to attempt severe brain or muscular work after 
 a hearty meal. The drowsiness \vhich accompanies the 
 brain work shows that the brain is not getting its full 
 share of blood because of the activity of the digestive 
 organs. In the ease of hard muscular work, the reverse 
 is true. The muscles draw the blood to themselves and 
 so digestion is delayed. 
 
EFPECT OF ALCOHOL 159 
 
 Causes of sleeplessness. — Sleeplessness, on the con- 
 trary, has been shown to be due to an overactive circu- 
 lation in the brain.. The remedy is to reduce by one 
 means or another the amount of blood flowing to the 
 brain. A light meal which draws a portion of it to 
 the stomach, exercise which distributes it to the muscles, 
 a hot water bag which tends to open up the blood- 
 vessels in the feet are all methods of accomplishing 
 this. 
 
 Effects of alcohol, — Another factor which may seri- 
 ously interfere with the economical distribution of blood 
 is the use of alcohol. As a beverage alcohol dilates the 
 blood-vessels in the skin and as a result the blood goes 
 to the skin in larger amounts. In cold weather, this 
 effect opposes the natural adjustment by which the 
 ■ blood within the body is kept away from the skin, in 
 order to protect it against a too rapid loss of heat. Al- 
 though there is a superficial feeling of warmth from 
 the alcohol because of the rush of blood to the skin, yet 
 the total amount of heat in the body is quickly dimin- 
 ished. Many lives have been lost by freezing under 
 these circumstances, and many more by pneumonia and 
 other diseases induced by the severe chill. 
 
 External pressure. — The proper distribution of the 
 blood is subject also to local interference by external 
 pressure, such as that exerted by tight circular garters. 
 External pressure ordinarily interferes with the circu- 
 lation in the lymphatics and veins rather than in the 
 arteries. Unlike the arterial blood, the lymph and the 
 venous blood have not the high pressure necessary to 
 force themselves forward under an obstruction. As a 
 result, the part becomes cold and swollen and the nutri- 
 tion of the tissues is often interfered with. When tight 
 garters are worn, the veins become unduly dilated so 
 
160 THE HYGIENE OF THE CIRCULATION 
 
 that the valves do not close the tubes, and consequently 
 the venous circulation in the legs becomes poor. If per- 
 sisted in, especially in later life, the veins become enor- 
 mously swollen and sometimes even burst through the 
 skin. 
 
 Injuries. — Further instances of local interference with 
 the proper distribution of the blood are seen in such 
 injuries as bruises, sprains and fractures. Small blood- 
 vessels are broken, and bleeding into the tissues occurs; 
 lymph vessels are also brokeij, so that the normal return 
 of the lymph is checked. The collection of the blood and 
 lymph in the tissues causes swelling. Further, as a re- 
 sult of the irritation of the injury, the arterioles in the 
 injured part become dilated so that greater quantities 
 of blood go to them, thereby increasing the swelling 
 and causing throbbing pain. In sprains and bruises, 
 the swelling and dis(;oloration may be largely prevented 
 by working the excess of blood and lymph out through 
 the lymph channels by means of gentle rubbing, or mas- 
 sage. In this way, the force necessary to push the blood 
 and lymph which have escaped from their torn vessels 
 back into the circulation through the lymph channels, 
 is artificially given. Less effective treatment for swelling 
 is heat, which causes contraction of the blood-vessels; 
 cold (ice), which has a similar although less marked 
 effect; or elastic pressure obtained by bandaging the 
 injured part. 
 
 Inflammation. — In inflammation, as in boils and ab- 
 scesses, the blood-vessels are dilated by the irritation of 
 the microbes which have invaded the tissue. Because of 
 this dilatation, the lymph and white blood corpuscles 
 escape more freely into the tissues, where they collect 
 in such great numbers as to clog and distend them. The 
 swollen tissue presses upon the blood-vessels so strongly 
 
INFLAMMATION 
 
 161 
 
 as to stop the circulation in the central part of the in- 
 flamed area. The white blood corpuscles are thus de- 
 prived of nutriment and oxygen by being shut off from 
 the fresh blood and become so 
 weakened that they cannot over- 
 come the invading microbes. As a 
 result, they frequently die in great 
 numbers, together with the tissue 
 in which they are lodged. The 
 white corpuscles, the dead tissue 
 and the microbes are then thrown 
 off as pus. The clogging of the 
 tissue by the white corpuscles 
 has a beneficial result, however, 
 in that it shuts off from the gen- 
 eral circulation the microbes which 
 have caused the disturbance. It is 
 usually considered wise to cut into 
 an actively inflamed area early, in 
 order to get rid of the microbes. 
 The destruction of good tissue 
 and the formation of a large scar 
 are thereby avoided. 
 
 Bleeding from arteries. — In 
 accidents where large arteries are 
 cut, the bleeding is copious be- 
 cause of the high pressure which 
 pushes the blood out in strong 
 spurts. In the case of a large cut 
 iu a fair-sized artery, the whole 
 arterial system may empty itself 
 in a short time and death result. The bleeding can best be 
 stopped by applying pressure to the artery at some point 
 where it comes near the surface in its course from the 
 
 Fig. 93. Diagram showing 
 where important arteries 
 come near enough to sur- 
 face to have pressure 
 applied. 
 
162 THE HYGIENE OF THE CIRCULATION 
 
 heart to the cut. A large pebble or a strip of cloth made 
 into a hard roll, if applied over the artery so as to press 
 it against the bone and then held in place by a tight 
 
 Fig. 94. CompreBSion of femoral artery. 
 
 Fig. 95, Course of artery in arm. 
 
 bandage, will entirely stop the flow of blood through the 
 artery. The points where pressure can be advantage- 
 ously applied are shown in the accompanying illustra- 
 tions. They should be carefully learned by repeated 
 practice, as death has often resulted through the lack of 
 such knowledge."- 
 
 From veins.— In the case of a vein, the loss of blood 
 is much slower and wiU ordinarily cease through the 
 
 '■ In order to develop one's ability to check arterial bleeding, a 
 student should practise finding the pulse in the ankle and wrist 
 and then should press upon the artery above these points until the 
 pulse is stopped. 
 
FAINTING 163 
 
 coagulation of blood in the cut. Bleeding can always be 
 stopped by a light pressure over the wound itself, and 
 can be temporarily treated in an emergency by bandag- 
 ing a small pad firmly over the cut. 
 
 "Poor" circulation. — In many persons, the circula- 
 tion of the blood is said to be poor, because of a tend- 
 ency to cold hands and feet. In most eases, this is due 
 to the fact that not enough exercise is taken for the pro- 
 duction of heat in the body, that clothing warm enough 
 to protect the bodj"^ against too great a loss of heat is 
 not worn, or that there is some nervous disorder whicli 
 leads to a disturbance of the vasomotor control. "What- 
 ever the cause, the result is a chronic spasm of the arte- 
 rioles, which shuts the blood out of the extremities, leav- 
 ing them cold. The remedy depends upon the cause. 
 In many cases, the wearing of warm woolen undercloth- 
 ing is effective, especially if supplemented by frequent 
 periods of brisk exercise and by plenty of good fi-esh 
 air and wholesome food. 
 
 Fainting. — The circulation may also be temporarily 
 disturbed, especially in wealv persons, by such causes as 
 nervous shock, the close warm air of a crowded room, or 
 severe pain. In these cases, the nerve control of the 
 heart is so deranged that the heart beats less forcibly 
 an.d less blood is pumped into the arteries. The blood 
 pressure in them is then too low to push the blood up 
 to the brain against the downward pull of gravity, and 
 the person becomes dizzj^ or even faints. The simple 
 remedy is to place the person thus affected with the 
 head lower than the body and to supply fresh cool air 
 for breathing:, cold water for bathing the face and stim- 
 ulants such as aromatic salts. 
 
164 THE HYGIENE OF THE CIRCULATION 
 
 EXPERIMENTS AND DEMONSTRATIONS 
 
 Materials: Roller bandages of cheese cloth, 2^/2 in. wide, 3 
 yds. long, tightly rolled ; triangular ' or handkerchief bandage. 
 
 1) Locate pulse in wrist; in upper arm at inside edge of 
 biceps muscle ; at back of and below bony prominence of ankle 
 on inside; behind knee; at inner upper part of thigh; at side 
 of larynx in neck ; in front of ear ; and behind collar bone. 
 
 2) Practise shutting off blood current. 
 
 a) In arm, by applying pressure upon arteries in upper arm 
 and back of collar bone. Test effectiveness of pressure by 
 obliteration of wrist pulse. 
 
 b) In leg, by pressure upon large artery in thigh and back 
 of knee. Test effectiveness by obliteration of ankle pulse. 
 
 3) Practise bandaging a pad or stone over pressure points 
 for shutting off arterial blood supply to arm and leg. Test 
 efificieney as in 2). 
 
 4) Adjustment of circulation to activity as shown by heart 
 beat: Test and record rate of pulse on awaking before rising; 
 on first sitting up before standing ; on standing ; after dressing ; 
 seated at table before breakfast; after breakfast while stiU 
 seated ; before and after climbing a flight of stairs ; and before 
 and after running. 
 
 5) Action of valves in veins : 
 
 a) Find large veins on back of hand, and stroke slowly with 
 moderate pressure toward wrist and toward knuckles. Note 
 changes. 
 
 b) Place one finger on end of a vein toward knuckles, and 
 with another finger stroke same vein toward wrist. Carefully 
 compare results with a). Make diagram of veins showing 
 location of valves and direction of action. 
 
 '■ Each pupil should be encouraged to get the printed cloth 
 bandage known as Esmark's Triangular Bandage, for sale at 10 
 cents, by the Society for Instruction in First Aid to the Injured, 
 105 East 22d Street, New York, or by the Health Education League, 
 113 Devonshire St. , Boston. 
 
CHAPTER XV 
 
 RESPIRATION 
 
 Air supply of the body. — ^As we have seen, the 
 venous blood on its return from the tissues must come 
 into contact with the air in the lungs, in order to get 
 
 Vestibu 
 
 Fig. 96. Section of face and neck showing passages of nose, month and throat 
 (Testnt.) 
 
 a fresh supply of oxygen and to remove its burden of 
 carbon dioxide. It is of the utmost importance, there- 
 fore, that the air in the lungs should not fail in purity 
 or abundance. We can live without food for many days, 
 
 165 
 
166 
 
 RESPIRATION 
 
 and without water for a considerable number of days, 
 because of storage within the body; but without air, 
 life is limited to minutes.^ 
 
 Nose as an air passage. — The mechanism for supply- 
 ing oxygen to the blood consists of two elastic bags or 
 reservoirs, the lungs, which lie in the chest walls and are 
 entered by way of the mouth and nose and the wind- 
 
 FiG. 97. SRCtion thi'ough nose, showing how the turbinate bones are arranged to 
 increase the surface over which the air must pass. (Testut.) 
 
 pipe, or trachea. So far as breathing is concerned, the 
 mouth and nose act mainly as canals through which the 
 air passes to the trachea. They are lined with a moist 
 membrane which catches the dust and thus helps to 
 prevent the entrance of irritating particles into the 
 lungs. This membrane also warms and moistens the air, 
 that irritation of the limgs by extreme cold and dryness 
 may be avoided. The nose is especially planned to serve 
 this purpose, in that it is provided with projections, the 
 turbinate bones, which divide the nasal passage into 
 several smaller passages and thus greatly increase the 
 
 ' The longest recorded period of being under water with subse- 
 quent recovery is about fifteen minutes, 
 
THE TRACHEA 167 
 
 surface of warm moist membrane over which the air 
 must pass. 
 
 Trachea. — The windpipe, or trachea, begins at the 
 lower end of the pharynx, that wide shallow chamber 
 at the back of the mouth into which both nose and mouth 
 open. The trachea lies in front of the esophagus and 
 is shut off from it by a lid, which closes during swallow- 
 ing to- keep out particles of food. It is an elastic tube 
 with hoops of cartilage in its walls. The ends of these 
 hoops do not quite meet and tend constantly to spring 
 apart. As a result, the trachea is held widely open 
 so- that the air can always pass throiagh it easily. 
 
 Larynx. — As in every other part of the body each 
 mechanism is made to serve as many purposes as possi- 
 ble, so in the trachea we find the passage of air through 
 it used for the production of voice. A special chamber, 
 the walls of which are stiffened with cartilage, lies near 
 the top of the trachea. It has two membranes which can 
 be made to stretch tightly across the air passage, so as 
 to meet at their edges and shut off the air. When the 
 air passes between their edges, these membranes vibrate 
 and thereby produce sounds which constitute the voice. ^ 
 This chamber is called the larynx and causes the promi- 
 nence in the throat known as "Adam's Apple." 
 
 Bronchial tubes. — At its lower end near the heart, 
 the trachea divides into two short branches, the bronchi, 
 one of which goes toward the right side of the chest, 
 the other toward the left, to connect respectively with 
 the right and left lung. The bronchi are equipped with 
 cartilaginous hoops to keep them open. Upon entering 
 the lungs, they at once multiply into an immense number 
 of smaller branches, the bronchial tubes, which in turn di- 
 vide into smaller ones and thus penetrate to every part of 
 
 ' See p. 276. 
 
168 
 
 RESPIRATION 
 
 the lungs. All of these which have a diameter of more 
 than one-fortieth of an inch are equipped with cartilagi- 
 nous rings. They have in addition a certain number of 
 smooth muscle fibres in their walls. Their lining, like that 
 of the trachea, consists of a mucous membrane made up 
 
 ■Epiglottis. 
 ■Larynx. 
 
 -Thyroid cartilage. 
 
 Fig. 98. Front view of the trachea and its branches. 
 
 of elongated cells, the exposed tips of which carry many 
 cilia for the purpose of whipping dust and mucus out 
 of the lungs. They are also furnished with cells which 
 secrete mucus and thereby keep their surface moist. 
 
 When the bronchial tubes have become as small as 
 one-fortieth of an inch, their walls lose their carti. 
 
THE LUNGS 169 
 
 laginous rings and acquire additional muscle fibres. 
 The lining mucous membrane also loses its cilia and 
 consists of thin broad flat cells. The bronchial tubes 
 
 Fio. 99. Two alveoli of lang, considerably magniflcd. b, b, air eacs ; c, ter- 
 minal branches of bronchial tube. 
 
 themselves are very thin-walled and each leads to sev- 
 eral expanded funnel-shaped soft-walled passages, which 
 serve as entrances to numerous rounded cavities, the 
 air sacs. 
 
 Air sacs. — The thousands of air sacs with their con- 
 necting passages make up the main bulk of the expanded 
 lungs. In an adult, they contain when normally ex- 
 panded about three quarts of air, but are so elastic 
 that they can be stretched to hold one or two quarts 
 more. They have a lining membrane made up of very 
 thin broad cells, which is an extension of that in the 
 bronchial tubes. Under this lining membrane, there is 
 a close meshwork of capillaries, which is so arranged as 
 to expose the largest possible surface ^ of blood to the air 
 contained within the air sacs. 
 
 ' About 800 sq. ft. in extent. 
 
170 
 
 RESPIRATION 
 
 Structure of lungs. — Besides the capillaries with their 
 connected arteries and veins, the air sacs and their 
 connecting passages, the bronchial tubes and bronchi, 
 the lungs consist of but little more than a strengthening 
 framework of soft elastic connective tissue, which holds 
 all the parts together and forms a strong yet highly 
 
 Fia. 100. Section of lung with disLencled blood-vessels, highly magnified, c. c, 
 partitions between air sacs; 6, small artery giving off capillaries to walls of air 
 sacs. 
 
 elastic spongy mass. The bulk of this mass when empty 
 of air occupies but a small fraction of the space which 
 it fills in the chest cavity during life. In other words, 
 the main bulk of the lungs is due to the air which fills 
 the air sacs. 
 
 Membrane covering lungs. — The lungs have for out- 
 side covering an exceedingly thin membrane formed of 
 flattened cells, which also line.s the chest cavity within 
 which the lungs lie. This membrane, known as the 
 
THE CHEST 
 
 111 
 
 pleura, is very smooth and under normal conditions is 
 made slippery by means of a fluid very similar to the 
 synovial fluid of the joints. The two pleural surfaces, 
 
 Superior vena cavi 
 Stern u I 
 Outline of heart (auricles) 
 Boundary between auncli 
 and ventrk-:le 
 
 .Carotid artery 
 Jugular vein 
 Arch of acrta 
 Outline of heart (veniricles) 
 
 lun; 
 Top of diaphragm-«^; 
 
 Lungs 
 
 Portion of heart not 
 covered by lungs 
 Stomach 
 Large inlesline 
 Small intestine 
 
 ¥it_i. luJ. CliL'St, showing position of organs. 
 
 which normally are in contact, are thus made to slip 
 easily over each other during the enlargement and reduc- 
 tion of the chest cavity in the movements of breathing. 
 The inflammation and roughening of these surfaces are 
 what give rise to the discomfort and pain of pleurisy. 
 As a result of pleurisy, the surfaces sometimes grow 
 together, so that the lungs can no longer slip up and 
 down. 
 
 Relation of lungs to chest cavity. — Under the nor- 
 mal conditions of life, the lungs fill all the cavity of the 
 
172 
 
 RESPIRATION 
 
 chest not occupied by the heart and its connected blood- 
 vessels and supporting tissues, by the esophagus and 
 the trachea. As we have seen, the walls of the lungs are 
 in close contact with the inside walls of the chest cavity. 
 Below they are in similar contact with the diaphragm, 
 a partition made up of muscle and tendon, which sepa- 
 rates the chest cavity from the abdominal cavity. All 
 outward and inward movements of the chest wall and 
 
 Aorta 
 
 Central tendon of diaphragrn 
 
 Esophagus 
 
 Pillars of diaphragm 
 
 Fro, 102. Front view of tlie diaphragm and its attachments. 
 
 downward and upward movements of the diaphragm, 
 are accompanied by an equal enlargement and reduction 
 of the lungs, so that there is never any separation of 
 the pleural surfaces. 
 
 Air movement. — Associated with each enlargement of 
 the lung there is an intake, or inspiration, of air; and 
 
INSPIRATION 
 
 173 
 
 with each inward or diminishiag movement there is a 
 corresponding output, or expiration, of air. This air 
 movement is called respiration, and takes place only 
 when the chest wall, or diaphragm, or both are 
 moved. 
 
 Inspiration. — The enlargement of the chest in inspi- 
 ration is caused by the contraction of the muscles which 
 lead from the ribs to the shoulder girdle and to the 
 neck and head. The chest wall is readily lifted by 
 these muscles, because its stiff framework of ribs 
 is jointed at the spine. 
 Moreover, the ribs are con- 
 nected by thin layers of 
 muscle and connective tissue ; 
 hence, when one rib moves, 
 the others are carried with it. 
 The ribs are slanted forward 
 and downward so that, when 
 they are raised by the con- 
 traction of the muscles, the 
 chest cavity is enlarged at 
 the sides as well as in the 
 front. As the chest enlarges, 
 the lungs follow, and their air cavity is correspondingly 
 increased. The enlargement of the chest cavity in in- 
 spiration is further increased by the downward movement 
 of the dome-shaped diaphragm, due to the contraction 
 of its muscle fibres. 
 
 Expiration. — In expiration, the reverse process takes 
 place. The muscles which lifted the chest relax and 
 allow the ribs to descend. Their descent is greatly aided 
 by the weight of the chest walls and shoulders, and, 
 especially in the case of stout persons, by the weight of 
 the abdominal walls. The diaphragm also relaxes and 
 
 Fig. 103. Dinsram illnstratiog the 
 position of the cheat in expira- 
 tion (A) and inspiration (B). 
 
1V4 RESPIRATION 
 
 allows the abdominal contents to push upward against 
 the base of the lungs. 
 
 In forced expiration, as in shouting or blowing upon 
 a horn, the abdominal muscles also contract. They pull 
 down on the ribs and push the abdominal contents with 
 the diaphragm up into the chest cavity, thus strongly 
 pushing the air out of the lungs. 
 
 Amount of air breathed. — The difference in the size 
 of the lungs between an extreme inspiration and an ex- 
 treme expiration is measured by the amount of air 
 which can be blown out after the fullest inspiration.^ 
 It varies much with the size of the individual and the 
 flexibility of his chest wall. It may be as much as two 
 quarts, and as little as two pints if the chest walls are 
 extremely rigid. 
 
 Lungs filled by air pressure. — The entrance of the 
 outside air into the lungs and its exit from them is in 
 accordance with the physical laws governing the move- 
 ment of all gases. It must be remembered that, since 
 we are living at the bottom of a sea of air, we are ex- 
 posed to a constant atmospheric pressure due to the 
 weight of this air of nearly fifteen pounds to the square 
 inch. When the air presses equally upon all side of 
 an object, as upon a thin sheet of rubber, the pressures 
 completely neutralize each other. As a result, the rubber 
 is flaccid and apparently without pressure. If, however, 
 the rubber is held tightly over the open mouth and in- 
 spiration is attempted, the rubber is seen to be pushed 
 inward. This is due to the pushing in of the outside 
 air to fill the increased space made by the enlargement 
 
 " Of course it must be borne in mind that the amount blown out 
 does not represent the total actual capacity of the lungs, since, 
 even after they have been emptied as completely as possible, they 
 still contain two or three pints of air. They are never normally 
 collapsed during life. 
 
VARIATIONS IN BREATHING 175 
 
 of the chest. Just as the air pushes the rubber in, so 
 the air pushes its way through the air passages, dis- 
 tends the walls of the lungs, and presses them against 
 the receding chest wall. 
 
 In expiration, the relaxing muscles permit the ribs to 
 drop, the chest cavity becomes smaller, the elastic lungs 
 contract, and the excess of air in them is pushed out. 
 
 Rapidity of breathing. — Owing to the large bulk of 
 air required to furnish the oxygen necessary for the 
 body's activity and to remove waste products, amounts 
 sufBcient for more than a moment's use cannot be stored 
 up in the body. As a result, constant and fairly rapid 
 breathing is necessary. Its rapidity varies somewhat 
 with age and sex. Women breathe more rapidly than 
 men, and children more rapidly than either. 
 
 Effects of exercise. — Exercise causes a great increase 
 in both the depth and the rate of breathing, because the 
 additional amount of energy expended means a corre- 
 sponding increase in the body's demand for oxygen as 
 well as for the removal of its waste products. If the 
 exercise is mild, an increase in the depth of breathing 
 may at first give all the air necessary. If, however, 
 the exercise is continued and severe, the respiration 
 usually becomes rapid as well as deep, since to get all 
 the air necessary from mere depth of respiration would 
 require such extensive chest movements as would in- 
 terfere with the exercise itself. Thus, when exercise 
 becomes too severe, one has to stop 'to take breath, since 
 the demand for air becomes so imperative and gives 
 rise to so much distress that it cannot be disregarded. 
 The body is thus automatically protected from an in- 
 adequate supply of oxj-^gen and from poisoning by an 
 accumulation of waste products, as a result of too great 
 activity. 
 
116 
 
 EESPIRATION 
 
 Effects of severe exercise. — For those who are weak 
 and habitually inactive and unused to hard work, this 
 feeling of respiratory distress during unusual and severe 
 exercise may be associated with much strain and conse- 
 quent injury to the heart because of its increased labor. 
 The lungs themselves are but rarely injured in this way, 
 although the distress is felt to be respiratory, because 
 
 l^eep 
 breathing 
 
 Moderate 
 breathing 
 
 Quiet 
 breathing 
 
 
 
 
 
 — — 
 
 ' — 
 
 — — — 
 
 
 
 
 
 
 
 
 
 
 
 
 
 ■ Fresh air 
 
 . Air left 
 in lungs 
 
 Fie. 104. Diagram showing relative amounts of fresli and Btale air in lungs at 
 different depths of breathing. 
 
 of the close relation between the nervous control of circu- 
 lation and respiration. 
 
 Adjustment of respiration and circulation to 
 exercise. — "When muscles work, the blood coming from 
 them is, as we have seen, richer in waste products, 
 especially carbon dioxide, and poorer in oxygen and 
 food materials. This change in the blood is directly 
 proportional to the work done by the muscles. The 
 amount of blood thus affected depends on the sige and 
 
EFFECTS OF EXERCISE 177 
 
 number of the muscles at work. "When many large 
 muscles are hard at work, as in riuining or walking 
 upstairs, a comparatively large amount of blood is 
 affected. If under these conditions a more rapid ex- 
 change of waste products were not possible, the blood 
 supply of the entire body would speedily become impure. 
 To avoid this, there is a nervous mechanism by which 
 the condition of the blood is constantly tested to deter- 
 mine its quality. If the quality falls below the stand- 
 ard, this nervous mechanism has the power of quick- 
 ening both the respiratory movements and the heart 
 beat. In consequence, the blood not only gets more 
 oxygen and is more quickly freed of its waste, but it is 
 also sent around faster to supply the larger amounts 
 demanded by the muscles. To aid the heart in the work 
 of pumping this increased amount of blood, the arte- 
 rioles in the active muscles are, as we have seen, relaxed, 
 the blood escapes more freely from the arterioles, the 
 blood pressure in the arterial reservoir is lowered and 
 the left ventricle of the heart has to overcome less re- 
 sistance in opening the aortic valve and emptying its 
 content of blood into it. The work of the heart in 
 pumping the increased amount of blood is thus dimin- 
 ished, and the heart itself is saved from quick exhaustion. 
 Effect of training. — In athletes and in those used to 
 hard work, the nervous control is so perfectly trained 
 for its work that it enables the muscles to exert their 
 greatest effort with little or no strain of the heart. In 
 untrained persons, on the contrary, the automatic mech- 
 anism lacks the skill which comes with practice and so 
 may overdrive the heart in attempting to bring about 
 the proper adjustment between the circulation and res- 
 piration and the muscular activity. This is especially 
 the case in youth, and as a result athletic contests are 
 
178 RESPIRATION 
 
 frequent sources of heart strain. They should be in- 
 dulged in but moderately and under medical advice, at 
 least until the heart is so far developed that its ability 
 safely to do work under conditions of strain has been 
 proved. 
 
 As the perfection of the adjustment between circu- 
 lation and respiration is entirely automatic and beyond 
 the control of the will, the training necessary to attain 
 such perfection can only be gained by frequent active 
 work and exercise. For this reason, during the period of 
 growth and development, children should have much 
 physical activity, in order not only to perfect this con- 
 trol but also through it to attain full development of the 
 heart, lungs and blood-vessels. 
 
 EXPERIMENTS AND DEMONSTRATIONS 
 
 Anatomy of the Respiratory Tract 
 
 Materials: Sheep's lungs with wind-pipe and heart attached 
 (to prevent puncturing of lungs through careless removal of 
 heart) ; rabbit, cat, or rat; frog; normal salt solution; glass and 
 rubber tubing about % in. diameter, 12 in. long; some small 
 object, as a piece of cork or rubber ; microscope.^ 
 
 1) Examine wind-pipe of sheep and trace its division into 
 bronchi. Notice in its wall rings of cartilage, so arranged that 
 dorsal aspect of tube (which lies against esophagus) has no 
 hard parts in it. 
 
 2) Slip rubber tube on end of glass tube and insert other 
 end of glass tube into trachea; tie firmly; blow up lungs and 
 pinch rubber tube to keep distended. 
 
 Note extensibility and elasticity of lungs ; their size and form 
 when distended; concavity of their lower (diaphragm) surface; 
 lobes; pleural membranes; and space occupied by heart. 
 
 3) Trace one bronchus to its lung. 
 
 a) Cut through lung tissue and follow branching bronchi. 
 Note cartilage rings, and lining mucous membrane. 
 
 b) Wf^sh surface Qf muQoug membrane with normal salt 
 
ANATOMY OF THE LUNGS 179 
 
 solution; gently scrape with scalpel and examine scrapings 
 under microscope. 
 
 4) Remove from rabbit its abdominal viscera, cutting away 
 liver and stomach with especial care. Examine vaulted 
 diaphragm and through it the lungs. 
 
 5) Seize diaphragm by its centre and pull it down, imitating 
 its respiratory movements. 
 
 6) Make a free opening uito first one and then the other side 
 of chest and note effect upon lungs. 
 
 7) Cut away front of chest and observe tendinous centre 
 of diaphragm ; its muswilar periphery ; and attachment of peri- 
 cardium to its thoracic side. 
 
 8) Place a recently killed frog on its back; fasten lower jaw 
 wide open. 
 
 a) Place small object on roof of mouth near nose and note 
 movement. 
 
 b) Examine scrapings from roof of frog's mouth in normal 
 salt solution under microscope. 
 
 9) Remove as much of esophagus as possible; split it open 
 and pin out. 
 
 a) Place small object upon it near mouth and note behavior. 
 
 b) Set esophagus aside under moist glass and note position 
 of mucus on surface at end of half an hour.' 
 
 Respiration 
 Materials: 
 
 Blood clot, deflbrinated blood, or piece of liver; lungs of 
 rabbit, eat, or rat; phenolphthalein (a few drops 1 per cent 
 solution) ; lime water; thermometers in tin cases; mirror; tape 
 measure; wide-mouthed bottles; bottle of 1 gal. capacity; pan 
 for water; test tube; glass tubes; rubber tubing; bell jar of 
 2 qts. capacity; heavy pure gum sheet rubber, to tie over 
 bottom of bell jar; pincheock; rubber stopper with double 
 perforations, to fit bell jar; 2 pieces of glass tubing, to fit 
 perforations of stopper; water- valve respiration appai-atus for 
 carbon dioxide. 
 
 1 ) Note the effect of breathing on bulb of a thermometer ; on 
 a miiTor, knife blade, or other polished metallic surface. 
 
 ' Cilia are present in the respii-atoiy passages but not in the 
 esophagus of man. 
 
180 
 
 RESPIRATION 
 
 2) Measure the girths of chest and abdomen at end of in- 
 spiration; at end of expiration. 
 
 3) Measure amount of air which you can blow out after 
 deepest inspiration, by blowing through a piece of tubing into 
 a large bottle filled with water and inverted in a pan of water. 
 
 £ 
 
 
 
 ^ 
 
 ^ 
 
 1 
 
 ¥iGt. 105. Apparatus to demonstrate carbon dioxide in expired air. a, inspiration; 
 b, expiration. 
 
 4) Determine the rate of breathing, that is, the number of 
 inspirations per minute, upon awaking in the morning; upon 
 rising ; after dressing ; after eating ; and after running. 
 
 5) Demonstrate by means of the water-valve respiration ap- 
 paratus (flg. 105) the relative amounts of carbon dioxide in 
 atmospheric air and in expired air, by partly filling bottles with 
 lime water and breathing in and out through mouth tube. 
 
 6) Blow breath through a weak solution of lime water 
 colored with phenolphthalein.' 
 
 7) Cut open blood clot or piece of liver. 
 
 a) Compare freshly cut surface with surface previously ex- 
 posed to air. 
 
 b) Place freshly cut pieces of blood clot or liver in a bottle 
 containing oxygen. Or 
 
 ' Phenolphthalein is pink in alkaline solutions ; colorless, in acid. 
 
DEMONSTRATION OF RESPIRATION 
 
 181 
 
 b) Place freshly init pieces of blood clot or liver in a bottle 
 Note result (oxyhemoglobin). 
 
 8) EcgpiratioH appoiaiua: Tie trachea of cat or rat on 
 piece of glass tubmg which is then passed up inside bell 
 jar through one of perforations in stopper. Seat stopper 
 firmly ui mouth of bell jar. Stretch piece of sheet rubber over 
 
 Pio. 106. Diagrnmof apparatus to demonstrate the action of the diapliragm. A, 
 in inspiration diapliragm flattened l)y coniraction ; B. in expiration diaphragm 
 relaxed and pushed upward by abdominal contents. Note changes in fnUness of 
 longs. 
 
 larger end of bell jar and tie firmly in position. Press this 
 rubber membrane down on top of bowl and close free rubber 
 tube with pinchcock. 
 
 a) To represent inspiration, lift bell jar from bowl, allowing 
 rubber membrane to flatten. 
 
 b) To represent expiration, press membi-ane down over bowl, 
 e) To represent effect of puncture of chest wall, remove 
 
 pinchcock from tube and lift jar from bowl. 
 
CHAPTER XVI 
 THE HYGIENE OF RESPIRATION 
 
 We have seen how dependent the animal organism 
 is upon the air as a source of oxygen and as a means of 
 getting rid of carbon dioxide and other volatile products 
 of the body's activity. In order to serve this purpose, 
 the air breathed must be both rich in oxygen and poor 
 in carbon dioxide. These conditions would be per- 
 fectly fulfilled, if we lived constantly in the open air. 
 The necessity of protecting ourselves from cold and wet, 
 and the consequent living in closed spaces, such as the 
 modem dwelling house, have, however, made it more diffi- 
 cult to get a constant and pure supply of air. Indeed, 
 in many cases, no attempt at all is made to get it. 
 
 Effects of respired air. — ^A study of persons who 
 constantly live and work in close rooms shows that they 
 are pale, weak, with poor appetite, and in a large per- 
 centage of cases, with marked tendencies to consumption, 
 whereas those who work out-of-doors are ruddy and 
 strong. Experiments on animals have also shown the 
 same results from breathing air made impure by respira- 
 tion. For example, a series of cages for mice was ar- 
 ranged with tight sides, so that the only air which 
 reached them came through one end of the series and 
 made its exit at the other. It was found that the ani- 
 mals in the first cages were perfectly well and strong, 
 while those in the others showed weakness and other 
 signs of poisoning, which increased in degree with their 
 distance from the source of the fresh air supply. In the 
 instance of the Black Hole of Calcutta, where a large 
 
 183 
 
IMPURE AIR 
 
 183 
 
 number of prisoners were crowded into a dungeon with 
 but one window, all of the men, except those few who 
 were able to crowd close to the window, were found 
 dead in the morning. The effects of bad air are further 
 sho^^^l by the wonderful improvement in health and 
 strength which a change to out-of-door life in the pure 
 air makes among those who have been confined in close 
 rooms. Even when consumption has obtained a foot- 
 hold, the fresh air life not only stops the progress of 
 the disease but even ciires it. 
 
 Odor a test of impurity. — Careful studies have 
 shown that whenever the air of an occupied room has 
 a close or offensive odor to a person coming into the 
 room from the outside air, it is unwholesome and even 
 poisonous to those breathing it, however unconscious 
 they may be of it. Indeed, the worst danger of bad air 
 lies in the fact that its effects are so general in char- 
 acter and accumulate so slowly from day to day that its 
 victims do not Imow why they are weak, pale and gen- 
 erally miserable. 
 
 Amount of fresh air required. — Many chemical 
 tests have been made of the air of crowded rooms, 
 halls and shops, in which the occupants were sleepy, list- 
 less and given to headaches. The air has invariably 
 been found to be offensive to a person entering from 
 the outside air and to contain large amounts of carbon 
 dioxide from the breath. The presence of 2 parts of 
 
 TEST BY ODOK OF AITS OF AN OCCUPIED ROOM 
 
 Fresh 
 
 Parts CO, in 10 000 vols. air. 
 Parte C0« due to respiratory 
 impurity 
 
 Slightly 
 
 close; per- 
 
 c>e p t i b 1 e 
 
 odor 
 
 Close; disa- 
 greeable 
 
 10.5 
 6.6 
 
 Very close; 
 offensive 
 
184 THE HYGIENE OE RESPIRATION 
 
 respiratory ^ carbon dioxide in 10,000 parts of air indi- 
 cates that the air is as bad as can safely be tolerated 
 by human beings. As expired breath contains 4 per 
 cent of carbon dioxide, or 400 parts in 10,000, each 
 breath must be diluted with at least 200 parts of fresh 
 air to make it safe for breathing. Since the amount of 
 air expired by one person in an hour^ is 15.6 cubic 
 • feet, it is evident that each person in a room must be 
 supplied every hour with about 3,000 cubic feet of 
 fresh air, if he is to avoid the debilitating effects of 
 bad air. 
 
 Ventilation. — To- siipply this amount of fresh air 
 economically is the problem of ventilation. In summer, 
 ventilation is iiot difficult because the windows can be 
 kept open so that the air can circulate throughout the 
 rooms of a house. Under these circumstances, all the 
 air of a room can be changed as frequently as once a 
 minute. In cold weather, when the windows cannot 
 be freely used in this way, special provision has to be 
 made to get rid of the bad air and to introduce in its 
 place air that is fresh and pure. In addition, the air 
 which is thus introduced must be warmed, so that it 
 is customary to consider heating and ventilation to- 
 gether and to provide for them at one and the same 
 time. 
 
 " By respiratory carbon dioxide is meant that which is added to 
 atmospheric air by the breath. Atmospheric air itself contains 
 from 3% to 4 parts of carbon dioxide in 10,000 parts. For ex- 
 ample, when by test 10 parts of carbon dioxide in 10,000 are found 
 in a school-room, 4 parts are the atmospheric carbon dioxide, and 
 the remaining 6 parts are respiratory carbon dioxide. In this 
 case, it is evident that there is being supplied to the room only 
 i the amount of air which is necessary. 
 
 ' In a year, each adult breathes about 10,000 lbs. of air. From 
 it, he takes 657 lbs. of oxygen, and to it he gives 730 lbs. of carbon 
 dioxide. 
 
HEATING AND VENTILATION 186 
 
 Heating. — There are two metliods of heating gener- 
 ally in use. The direct method of heating is by a stove 
 or fireplace, or by a radiator for steam or hot water. 
 The indirect method is by means of a stream of hot air 
 from a furnace or steam coil in the basement. 
 
 Direct method. — The direct method by means of a 
 stove or fireplace gives better ventilation than when a 
 radiator for steam or hot water is used, since the rapid 
 movement of hot air up the chimney draws an equal 
 amount of air into the room through the cracks around 
 the windows and doors, and in the walls and floor. If 
 the house is tightly built, however, or if more than one 
 or two persons are in the room, this amount of fresh 
 air is not ordinarily sufficient and must be supplemented 
 by a proper opening of the windows and doors. If the 
 direct method of heating by means of a radiator is used, 
 no air is drawn out of the room and consequently but 
 little enters through the cracks, imless a heavy wind is 
 blowing. The windows and doors must therefore be used 
 more or less continuously, in order to insure adequate 
 ventilation. 
 
 Use of windows for ventilation. — If windows are to 
 be depended upon for ventilation, they must be intelli- 
 gently used with this end in view. When the wind is 
 blowing, the windows upon the windward side of a room 
 will give entrance to the air because of the wind pres- 
 sure. These windows shoiild be opened more or less, as 
 determined by the force of the wind, and preferably 
 at the top, in order that the air entering may mix with 
 the warm air of the room and not settle as a cold draft 
 near the floor. If there is no fireplace or other means 
 of exit for the air, one or more windows should also be 
 opened at the bottom on the leeward side of the room, 
 to permit the vitiated air to go out. When, as rarely 
 
186 THE HYGIENE OE RESPIRATION 
 
 happens, the wind is not blowing at all, there is, of 
 course, no particular reason for opening one window 
 rather than another. 
 
 When the air of a room is too hot, the windows should 
 be opened at the top -on the leeward side of the room, 
 to allow the hot air, which tends to rise, to escape ; and 
 at the top on the windward side, to allow the cold air 
 to enter in its place. In this way, the air of a room 
 may be quickly changed and cooled, and yet the floor not 
 be chilled. 
 
 Indirect method. — With indirect heating, ventilation 
 is much easier, since the stream of air which carries the 
 heat may and should be a stream of pure fresh air from 
 the outside, which has been carefully kept from con- 
 tamination with bad air, dust, or other impurities. The 
 stream of warm pure air is best admitted near the top 
 of the room so that it will not be mixed with the colder 
 impure air but will spread out and fill the upper part 
 of the room because of its greater lightness. The lower 
 stratum of air should be drawn off by fireplaces or 
 ventilating flues as large or larger than the hot air 
 flues. Their openings should be placed as near the floor 
 as possible, in order not only to get rid of the colder 
 impure air but also to make room for the fresh. 
 
 Humidity. — Aside from the freshness of the air, two 
 of the most important factors in ventilation, are the 
 temperature of the air and the amount of moisture con- 
 tained in it, that is, its humidity. The humidity of any 
 given amount of air depends upon its temperature. The 
 more it is warmed, the more moisture it is able to take 
 up; and, conversely, the colder it becomes, the less 
 moisture it can hold. Thus moist foggy air at 32° F. 
 becomes very dry air at 70° F. ; suddenly cooled to zero, 
 its moisture is so much in excess of what it can hold 
 
HUMIDITY 187 
 
 that it is precipitated as snow. Very di'y air takes the 
 moisture from our bodies moj-e rapidly than that which 
 is humid. Thus we feel chilly in winter when in a dry 
 indoor air at 75° or 80° F. ; in summer at the same tem- 
 perature we feel oppressively hot in the moisture-laden 
 air of the dog days. In the one ease, the air is so dry 
 that it talres the body's moisture rapidly enough to 
 chill it; in the other, the air is so full of moisture that 
 it ^\•ill not take the moisture which, if evaporated, would 
 cool it. It is therefore obvious that a person's comfort 
 depends quite as much upon the humidity as upon the 
 temperature of the air. 
 
 Relation of humidity to ventilation. — In cold cli- 
 mates, such as that of the northern part of the United 
 States, the warming of the air for ventilation often gives 
 it a parching dryness which may equal that of the 
 Sahara desert. Because this excessive dryness causes 
 the moisture on the body's surface to evaporate rapidly, 
 the body is chilled unless the temperature of the room 
 is kept as high as 75° or 80° F. The eyes and the 
 mucous membrane of the respiratory tract also become 
 irritated by undue drying of their surfaces. By adding 
 moisture to the air so as to raise its humidity from 25 
 or 50 per cent to 70 or 75 per cent, the air may be made 
 very comfortable at a temperature of 65° F. and its 
 irritating eifects removed. The addition of moisture not 
 only makes the air more wholesome but saves expense in 
 heating. 
 
 In moist climates, such as are found in coast regions, 
 where the ordinary winter temperature is above freezing, 
 the addition of moisture may not be necessary, except 
 in cold dry weather. It is undoubtedly on this account 
 that in England 60° to 65° F. is accepted as the normal 
 temperature for comfort indoors. 
 
188 THE HYGIENE OF RESPIRATION 
 
 In the New England coast regions, where the extreme 
 ranges in humidity and temperature make the climate 
 like that of almost all other countries in rapid turn, it 
 is necessary to supply moisture only in the clear cold 
 weather when the natural moisture of the air is 
 frozen out. 
 
 Drafts. — One of the greatest difficulties in the way of 
 proper ventilation is a very prevalent fear of drafts. 
 This fear has survived in undiminished strength in spite 
 of the fact that many diseases, notably pneumonia, which 
 were formerly thought to be directly traceable to them, 
 have been proved to have quite a different origin in the 
 invasion of the system by microbes. It is probably true 
 that the exposure to a draft of a limited portion of the 
 body's surface, such as the back of the neck, the wrist, 
 or the anldes, may result in a catarrhal condition of 
 the mucous membranes, especially of the nose and throat, 
 and the development of microbes on their surface be 
 favored thereby. There is every reason to believe, how- 
 ever, that in many of these cases the results are due not 
 so much to exposure to drafts as to the irritation from 
 breathing microbe-laden dust. 
 
 Relation of clothing to ventilation. — Even were 
 drafts, however, responsible for all the ills attributed to 
 them, the sensible thing to do would be to protect the 
 body by proper clothing so that we could have fresh air 
 without injury. In recent years, there has been a grow- 
 ing and most unfortunate tendency in quite the oppo- 
 site direction. "Women and girls especially are dressing 
 more and more thinly, in total disregard of season or 
 climate, and, as a result, they are forced for comfort to 
 keep their houses overheated. Adequate clothing is a 
 most important aid to ventilation. It is the cheapest way 
 of securing comfort with proper ventilation in cold 
 
NIGHT AIR 189 
 
 weather, and it has the further advantage of enabling 
 one to avoid the depressing and weakening effects of 
 overheated rooms. 
 
 Night air. — Another difficulty in the way of ade- 
 quate ventilation, which is fast being overcome, is the 
 fear of night air. Years ago, many persons were accus- 
 tomed to shut their sleeping rooms up tightly, lest "the 
 poison of the night air" should harm them. To-day, 
 however, it is recognized that the night air is as whole- 
 some as that of the day, from which it differs only in 
 temperature. The restfulness and recuperation of sleep 
 depend very largely upon having the freshest air possi- 
 ble in the sleeping room, in order to furnish the tissues 
 with all the oxygen that they need for repairing the 
 inroads which the day's activity has made upon them. 
 For this reason, the bed should always be far enough 
 from the wall to permit the free circulation of air about 
 it, and the windows should be wide enough open to admit 
 perceptible currents of air. In cold weather, the old- 
 fashioned nightcap is most useful, since it protects the 
 head from the drafts which are inseparable from a well- 
 ventilated sleeping room. 
 
 Malaria. — Malaria, which was formerly attributed to 
 the night air, is now known to be due to the transmission 
 of disease germs by the bite of a certain mosquito, the 
 anopheles, which is active at night. The moral, there- 
 fore, is not to keep out the night air but to protect 
 against insects. 
 
 Dust, a source of disease. — Our present knowledge 
 of the way in which disease is spread, has shown us that 
 one of the great menaces to health is the breathing of 
 dust-laden air. The dusty air of cities is so contami- 
 nated by the dried excretions of animals and of human 
 saliva that it is undoubtedly responsible in thousands 
 
190 THE HYGIENE OF RESPIRATION 
 
 of eases for the spread of disease. In this way, we are 
 exposed to hordes of disease germs, which are con- 
 stantly lodging in the raucous membranes of nose, throat 
 and lungs. If we are fortunate, they are thrown out by 
 the cilia or destroyed by the white blood corpuscles. If 
 not, such diseases as colds, consumption, pneumonia and 
 diphtheria result. The problem of diminishing the 
 amount of dust in cities is therefore exceedingly 
 important. 
 
 Coughing. — In addition to the dried particles of 
 microbe-laden sputum and other excretions, air also 
 contains at times particles of moisture which are pro- 
 jected into it by those who cough. These particles are 
 so fine that they quickly dry and float about for some 
 time before settling. Careful examinations have shown 
 that they carry such disease germs as exist in the mucus 
 covering the air passages of the lungs, the bronchi and 
 trachea, the pharynx, nose and throat of those who are 
 coughing or sneezing. Many diseases are directly trans- 
 mitted in this way from diseased to well persons. Thor- 
 ough ventilation and covering the mouth when cough- 
 ing reduce the danger of their transmission very mate- 
 rially, although they do not remove it entirely. Only by 
 the isolation of those diseased, can the danger be 
 eliminated. 
 
 Sewer gas. — Sewer air, which is disagreeable chiefly 
 because of its odor, is not necessarily poisonous, although 
 it may contain poisonous gases such as coal gas and 
 illuminating gas. As we have seen, both coal gas and 
 illuminating gas contain the deadly carbon monoxide 
 (CO) , which has been generated by burning carbon at too 
 low a temperature for complete oxidation. 
 
 Care of nose. — In addition to providing the organs of 
 respiration with as pure air as possible for breathing, 
 
CARE OF NOSE 191 
 
 we have to bestow upon them a certain amount of eare 
 and attention that they may do their work properly. The 
 nose is exposed to all the microbes and dust contained 
 in the air breathed. These are caught upon its moist 
 surface and removed by the eilia. If the mucous mem- 
 brane is not sufficiently moist and the cilia active, or if 
 the dust is excessive or especially irritating, the mucous 
 membrane becomes swollen from the irritation, and 
 secretes large amounts of mucus in its effort to wash 
 the irritating dust away. This constitutes what is popu- 
 larly called a head cold. It is important, therefore, 
 that those who are subject to head colds should remove 
 the dust by spraying the nose with a mild antiseptic 
 solution ^ after such exposure. 
 
 Catarrh. — Persons with sensitive membranes, who 
 have frequent head colds, are liable to get a chronically 
 thickened membrane, which secretes mucus in copious 
 amounts, that is, they have catarrh. Catarrh is not only 
 a very disagreeable ailment in itself but it indicates con- 
 ditions in the nose which may extend to the tube con- 
 necting the throat with the middle ear and produce 
 partial or complete deafness. Head colds, therefore, 
 should be prevented whenever possible, and should re- 
 ceive careful medical attention. 
 
 Adenoids. — In the nasal cavity, the mucous membrane 
 is so delicate that constant irritation, especially by dust, 
 often causes it to become so swollen that it blocks the 
 passage of air through the nose. Repeated irritation 
 tends to produce soft masses of tissue, called adenoids, 
 which ai'e especially frequent in children and make it 
 necessary for tlaem to breathe through their mouths. 
 The closure of the nose and breathing through the mouth 
 
 ^ A proper atomizer and Dgbell's sglutiQP can be bought at any 
 druggist's. 
 
192 THE HYGIENE OF RESPIRATION 
 
 lead to narrowing of the nasal passages, and upper jaw, 
 and eventual closing of the tube to the ear, which re- 
 sults in defective hearing. It is therefore important that 
 adenoids should be removed before the deformities have 
 time to develop. Whenever mouth breathing is habitual 
 or head colds with closure of the nose are frequent, 
 the presence of adenoids should be suspected and a phy- 
 sician consulted. 
 
 Enlarged tonsils. — The throat is affected by much the 
 same conditions as the nose and requires much the same 
 treatment. The tonsils frequently become chronically 
 enlarged, sometimes so much so that swallowing and 
 breathing are difficult. When markedly enlarged, they 
 should be removed, since the general health may suffer 
 greatly through them. 
 
 EXPERIMENTS AND DEMONSTRATIONS 
 
 Materials: Whips or light rods, 5 to 6 ft. long; down or 
 delicate feathers ; spool "A" sewing silk ; ball of lead weighing 
 about 1 oz.; dry and wet bulb thermometers (psychrometer) ; ' 
 [Fitz COa apparatus °]. 
 
 1) Test of purity of air: 
 
 a) By odor: Make an independent test of the air of 2 oc- 
 cupied rooms by entering them from outside fresh air and 
 
 ' Select cheap tin-cased thermometers by noting that the three 
 scratches on side of glass stem of each coincide respectively with 
 the graduations for 32°, 62° and 92°. Match them by putting 
 them into a glass of water of about 60° temperature and selecting 
 the pairs which register the same. A slight variation may be 
 adjusted by sliding one stem up or down on its scale the required 
 amount. Slip thermometers out of tin cases and secure each stem 
 in its proper position on scale by means of sealing wax, applied 
 to back of scale where tip of glass stem projects through. Care- 
 fully cut off lower portion of metal scale where it surrounds bulb 
 and fasten thermometers to a grooved piece of wood, as shown in 
 fig. 107. Upon bulb of one, tie a piece of thin linen cloth and 
 attach a stout cord 12 in. long to top of wooden support so that it 
 can safely be whirled. 
 
 " L, E, Knott Apparatus Co., 15 Harcourt Street, Boston, Mass. 
 
TESTS OF VENTILATION 193 
 
 noting presence of odor as none, faint, marked, or strong. 
 R«cord size of room in cu. ft., number of pereons occupying it, 
 method of heating and ventilating, number of ventilators open 
 (windows, doors, registei-s, transoms, etc.) and movement of 
 air through each as to direction ' and strength. Make diagram 
 of essential features. 
 
 [b) By chemical analj-sis: Use COi appai-atus according to 
 directions accompanying same.' Make plans of rooms and 
 caiTv out as in a).] 
 
 2) Air currents: ' 
 
 a) Direction: By means of the suspended tuft of down, 
 determine the direction of air movement in various pai'ts of a 
 room. Indicate currents upon diagram of room by means of 
 arrows. 
 
 b) Velocity: Determine by measuring distance in feet that 
 a tuft of down wiU move with air current in 1 second. ' 
 
 c) Amount: Determine by measuring ai'eas of air inlets 
 and outlets in square feet and multiplying this by the air 
 velocity in feet per second. 
 
 d) Adequacy of air supply: Add together amounts of air 
 entering inlets of room; di^ade result by total number of oc- 
 cupants; compare with standard requirements {^ cu. ft. per 
 sec.). 
 
 3) Humidity of air: Moisten cloth on bulb of psyehrometer 
 and whirl in air until readiues of 2 thermometers are constant. 
 
 * The best method of detecting currents of air at ventilators is to 
 attach a bit of dowTH or a feather on a silk thread 15 in. in length 
 to the end of a whip or stick long enough to reach to the top of 
 tlie room. This will indicate even a slight draft and show whether 
 it is inward or outward. If the draft is very slight, a candle flame 
 or smoke from a joss stick affords the best means of detection. 
 
 ' This method is simple and reliable and does not require a 
 knowledge of chemistry. 
 
 ' Since the currents of air in a room determine the distribution 
 of the incoming fresh air, their study is important to determine 
 whether the air is distributed evenly throughout the room. 
 
 * The seconds are easily measured by means of a metronome or by 
 a pendulum consisting of a small lead weight suspended by a cord 
 39 in. long from point of suspension to centre of weight, and should 
 be indicated by tapping, so that the one watching the movements 
 of the down may not have his attention distracted by the necessity 
 of watching the pendnlum as well. 
 
194 
 
 THE HYGIENE OF RESPIRATION 
 
 Record temperatures and subtract the reading of wet bijlb from 
 that of dry. 
 By reference to table, find relative humidity corresponding to 
 
 ^ 
 
 Fia. 107. Wet and dry bulb thermometers arranged for whirline (Psychrometer) 
 to get quick readings. s v J > 
 
 air temperature as given by dry bulb thermometer, and to dif- 
 ference between readings of 2 thermometers. 
 
 DifEerence between Air temperature (Fahrenheit). 
 
 wet and dry bulbs. 10" 80= 30° 40° 50° 60° 70° 80° 
 
 1 80 86 90 92 93 94 95 96 
 
 2 60 72 79 84 87 89 90 92 
 
 4 21 44 58 68 74 78 81 83 
 
 6 16 38 52 61 68 72 75 
 
 8 18 37 49 58 64 68 
 
 1'' 22 37 48 55 61 
 
 12 8 26 39 48 54 
 
 W 16 30 40 47 
 
 1° - 5 21 33 41 
 
 1° 13 26 35 
 
 ^0...,,.,,,,,.,,.,..,,, ,,,,,, 5 jg 29 
 
TESTS OF VENTILATION 195 
 
 Repeat test at various times, indoors, outdoors, and at home, 
 making careful notes as to weather conditions. 
 
 4) Heating and ventilating plant: Examine and make 
 sketches showing method of ventilating and heating school; 
 home. 
 
CHAPTER XVII 
 THE REMOVAL Or WASTE PRODUCTS 
 
 As we have seen, the volatile waste products of the 
 body's activity are constantly removed from the blood 
 by the air in the lungs. The non-volatile waste products 
 which are in solution in the blood cannot, however, be 
 got rid of in this way, since they are incapable of pass- 
 ing from the blood to the air. To dispose of them, 
 special organs have been developed, notably the kidneys. 
 
 Kidneys. — The kidneys are two rounded bodies, one 
 of which lies on each side of the spine in the upper part 
 of the abdominal cavity just under the lowest ribs. In 
 size, they are nearly five inches long, two and three- 
 quarters inches wide and one and three-quarters inches 
 thick, and weigh about four ounces each. They are red- 
 dish-brown in color, of firm consistency and covered with 
 a smooth membrane. 
 
 Blood supply. — Each kidney contains two complete 
 systems of tubes. One is made up of the bfanching 
 arteries, capillaries and veins, which carry the arterial 
 blood from the aorta into, through and out of the kid- 
 neys. On leaving the kidneys, the blood enters the large 
 abdominal vein which returns it directly to the heart. 
 Thus a part of the arterial blood is constantly passing 
 through them. 
 
 Structure. — The other system of tubes consists of a 
 very complex meshwork called renal tubules, which 
 begin as tiny cups surrounding tufts of capillaries. 
 
 196 
 
THE KIDNEYS 
 
 197 
 
 These cups are drained by tubes which follow winding 
 paths through the kidney tissue. At one point in their 
 course, they are surrounded by a fine network of capil- 
 
 Esophagus 
 
 aphragnt 
 
 Supra-renal 
 capsule 
 
 Fig. 108. The kidneys and principal blood-veBsels ol abdomen, as seen when 
 intestines are removed. 
 
 laries. They ultimately join together to form large 
 drainage canals, which empty into a cavity on the inner* 
 or concave side of each kidney. This cavity is connected 
 by means of a slender tube, the ureter, with an elastic 
 
198 THE EEMOVAL OF WASTE PRODUCTS 
 
 reservoir, the Madder. At both points of contact be- 
 tween the capillaries and the renal tubules, water and 
 certain waste substances in solution are removed from 
 the blood. 
 
 Excretion,— Since the waste products taken from the 
 blood are to be ejected from the body, the process of 
 removing them from the blood is called excretion. The 
 
 Beginning of 
 
 urinary tubule 
 Tuft of capillaries 
 
 Artery 
 Vein to tubule 
 Vein from tubule 
 
 Urinary tubule 
 
 Capillary mesh 
 
 over tubule 
 
 Artery- 
 Vein 
 
 Fig. 109. Structure of kidney, sliowing the secreting mechiiniBm (diagrammatic). 
 The arrows indicate the direction of flow of the fluids. 
 
 excreted fluid ^ is constantly drained from the kidneys 
 into the bladder, where it is temporarily stored. The 
 amount secreted by the kidneys in twenty-four hours is 
 normally about three pints. 
 
 Effect upon blood. — The kidneys, through their power 
 of eliminating water from the blood, prevent the blood 
 
 ' The total amount in 24 hours is 1500 grams. Its composition 
 is water, 1440 gms.; total solids, 60 gms. (consisting of urea, 35 
 gms.; uric acid, 0.75 gms.; sodium chloride, 16.5 gms.; and other 
 substances as salts of potassium, magnesium and calcium, 7.75 
 gms.). 
 
PERSPIRATION 199 
 
 from being long overdiluted by too much water. If, 
 for any reason, water is drunk in such small quantities 
 that the blood has but little to spare, the amount of water 
 excreted by the kidneys is correspondingly reduced. 
 
 Importance of the kidneys. — The importance of the 
 work of the kidneys is most clearly seen when through 
 disease their action is impeded or stopped. The conse- 
 quent accumulation of waste substances in the blood 
 results in headache, convulsions and even death. 
 
 Excretion by the skin. — The skin, as well as the 
 kidneys, removes a certain amount of waste products 
 in the form of perspiration. The perspiration when 
 analyzed is shown to contain a considerable amount of 
 various salts, especially sodium chloride, some fat and 
 minute traces of other substances which are also found 
 in the kidney excretion. Its bulk consists of water, 
 which under normal conditions is being constantly elimi- 
 nated in this way throughout life. When, through dis- 
 ease, the kidnej's fail to do their work, the urinary sub- 
 stances are found in much greater amounts in the per- 
 spiration. Their excretion may be further increased by 
 inducing copious perspiration through hot baths. The 
 failure of the kidneys may thus be partially neutralized 
 by the increased activity of the skin as an excretory 
 organ. 
 
 Uses of perspiration. — ^Perspiration serves a threefold 
 purpose. It not only aids in removing the excess of 
 water from the blood, but it also keeps the skin both 
 moist and cool, even when the perspiration is so slight 
 in amount that it evaporates as quickly as it is secreted 
 and so is not perceptible or "visible." When perspira- 
 tion fails for any^ reason, as in fever, the skin becomes 
 dry and harsh and the body is no longer properly 
 cooled. 
 
CHAPTER XVIII 
 
 THE SKIN 
 
 The skin, a protection. — Besides aiding in the excre- 
 tion of certain waste products from the body, the sldn 
 serves to enclose the body and thus to protect its more 
 delicate tissues from harmful contact with surrounding 
 objects. For this purpose, it is tough and elastic, and 
 has the power of becoming still thicker and tougher 
 when habitually exposed to hard contact, as in the soles 
 of the feet and the palms of the hands. 
 
 The skin, a sense organ. — The skin is richly supplied 
 with nerves, by means of which information is given of 
 the objects with which contact is made, so that the indi- 
 vidual knows not only when an object is touched but 
 also whether it is warm or cold, large or small, rough 
 or smooth. He is thus able to recognize in general 
 whether the objects touched are harmful or not and to 
 act accordingly.^ 
 
 Structure. — The skin is built up of several layers,, of 
 which the outermost, the epidermis, is solely protective. 
 The epidermis consists of numerous layers of cells, the 
 surface layers of which are flat and scalelike, while the 
 deeper ones are more spherical. The layers of cells 
 on the surface are constantly being worn away and are 
 as constantly being replaced by new cells from the lower 
 layers, which on approaching the surface become flat- 
 tened and scale-liJse. 
 
 ' For a further discussion of the skin as a sense organ, see p. 247. 
 
 200 
 
COLOR 
 
 201 
 
 Pigment cells. — ^In the deepest layers of the epi- 
 dermis are cells containing more or less coloring matter 
 or pigment, whicli intercepts the rays of the sun and 
 thus prevents irritation. In the colored races, these 
 cells ai'e more numerous and contain darker pigment 
 than in the case of the white races. They are therefore 
 
 Fig. 110. Papillse of skin, as seen when epidermis is stripped from dermis. 
 
 much better adapted to hot climates. Among the white 
 races, exposure of the skin to sunshine leads the cells 
 to protect themselves and the body by a rapid increase 
 in the deposit of pigment, which may be uniformly dis- 
 tributed as in tanning, or scattered as in freckling. 
 Freckling is much more common among blondes than 
 among brimettes, because many of their cells have not 
 the power to develop the protective pigment. 
 
 Color of the skin. — The color which results from 
 the presence of pigment must not be confused with the 
 warm glow which is tlie characteristic color of the skin 
 in health and is due to the color of the blood showing 
 
202 THE SKIN 
 
 through the transhicent skin. It is greatly heightened 
 when the blood-vessels dilate in blushing, in exercise, 
 or as a reaction to the cold. A sudden pallor is due 
 to a contraction of the blood-vessels from cold or to 
 a lowering of the blood pressure associated with fear 
 or faintness. Persistent or chronic pallor is frequently 
 due to a chronic contraction of the blood-vessels in the 
 skin, or to a deficiency in the red corpuscles of the 
 blood. The gaining of a good color, therefore, is often 
 dependent upon improving the health by fresh air and 
 exercise, which enrich the color of the blood itself. 
 
 Dermis. — Below the epidermis, we find the true skin, 
 the dermis, which is also made up of numerous layers 
 of cells. The cells of the upper layers are compactly 
 joined together, whereas the deeper ones shade off into 
 soft fibres which blend with the underlying tissue. The 
 dermis is richly supplied with blood-vessels, and con- 
 tains the nerve terminals which receive the impressions 
 of touch. It also contains in part the ducts of the 
 sweat glands and the hair roots. 
 
 Connective tissue layer. — Underneath the dermis, 
 there is a less well-defined layer, consisting largely of 
 loose connective tissue, the spaces of which are more or 
 less filled with fat cells. This layer is of considerable 
 thickness in stout persons. It is made distinct from the 
 underlying muscles and other tissues by a loose mesh- 
 work of connective tissue, such as was found between 
 the large bundles of muscles. Its purpose is to permit 
 the skin to slip freely over the underlying parts, so that 
 it will not interfere with the contraction of the muscles 
 and the bending of the joints. The thickness of the skin 
 when picked up between the thumb and finger is mainly 
 due to this fatty layer, the other layers being com- 
 paratively thin. 
 
STRUCTURE 
 
 203 
 
 Fat is placed in this lower layer of the skin appar- 
 ently for the double purpose of serving as a storage for 
 food supply which can be utilized when needed, and also 
 of forming a thick layer of non-conducting material for 
 the protection of the body against a too rapid loss of 
 
 Shaft of fialr 
 
 Horny byer of skin 
 Dud of s»eal gland 
 
 Capillaries of papillae 
 
 Epidermis'- =sr- 
 
 Dermis - 
 
 SubcularBous tissue- 
 
 LCoous glands 
 :onnective tissue 
 
 ■Erector muscle of hair 
 
 ■Artery 
 
 'Hair follicle 
 
 '.oA of sweat gland 
 
 .rteiy to sweat gland 
 "la of hair 
 innective tissue 
 Fat 
 
 Fig. 111. Sectiou of skin, considerably magnified. 
 
 heat in cold weather. When the partial or complete 
 starvation of prolonged illness, or the partial failure of 
 digestion and assimilation, as in old age, has caused this 
 supply of fat to be used up, the skin is no longer filled 
 out and becomes Avrinkled. It is for this reason that 
 age shows itself most quickly in those who are thin. 
 
 Hair. — In this fatty layer are embedded folds of the 
 epidermis and dermis in which lie the roots of the hairs 
 and nails. The hairs pass from the surface into the fatty 
 layer through tiny canals slightly lai-ger than the hairs 
 
204 THE SKIN 
 
 themselves. Here, there is a small root from which the 
 hair grows. When a hair is pulled out, the portion 
 which is not alive separates from the living root, which 
 remains and builds a new hair. 
 
 Connected with each canal through which a hair passes 
 are several minute glands, the sebaceous glands, which 
 secrete an oil for making the hair glossy and waterproof. 
 Since the hair tends to collect dust and dirt, it should 
 be washed with warm water and mild soap. The natural 
 oil which is removed in washing can be restored when 
 necessary by rubbing a small amount of vaseline into 
 the roots before the hair is dried. 
 
 Nails. — The nails, like the hair, are special modifica- 
 tions of the epidermis. They serve to protect the sensi- 
 tive tips of the fingers and toes, and consist of a trans- 
 lucent horny layep of closely compacted broad cells. 
 They take root in folds of the dermis and epidermis, 
 which dip down through the fatty layer nearly to the 
 bone. The nail is slowly developed and pushed out until 
 it overhangs the end of the finger or toe to which it is 
 attached. When a nail is torn off, a complete new nail 
 is built out from the root in about six months, unless 
 the root itself has been destroyed. 
 
 Since the edges of the nails afford natural lodging 
 places for all kinds of dirt and microbes, it is important 
 from the standpoint of health as well as of beauty that 
 they should be kept clean. They should be trimmed 
 carefully and the crevices around and under them should 
 be cleaned with a pointed stick rubbed in soap. 
 
 Sweat glands. — The sweat glands of the skin have 
 their mouths in the tiny ridges on its surface. Their 
 ducts penetrate in the form of a spiral through the 
 epidermis and dermis into the subcutaneous fatty layer. 
 Here each duct becomes twisted upon itself, and forms 
 
SWEAT GLANDS 
 
 205 
 
 a knotted mass, the gland, which is about one-sixtieth of 
 an inch in diameter. 
 
 Secretion. — The sweat glands are scattered thicldy 
 in the skin, especially in the palms of the hands and 
 the soles of the feet. Their total 
 number is estimated at about 
 2,000,000, and their total secre- 
 tion in twenty-fours hours may be 
 as much as a quart. In warm 
 weather, as a result of vigorous 
 exercise, the secretion may be two 
 or three times as much. It con- 
 sists normally of. water containing 
 a small amount of salt. It is 
 ordinarily more or less mixed 
 with the secretions of the seba- 
 ceous glands. When the Iddneys 
 are not able adequately to do their 
 work, the sweat becomes much 
 richer in the waste products usually eliminated by them. 
 
 "Pores" of the skin. — The mouths of the sweat 
 glands are popularly kno^^na as the pores of the skin, 
 and are said to open and close. As a matter of fact, 
 they are always ^Aide open. Occasionally, it is true, a 
 fe\r of them may be clogged with dirt, with resulting 
 pimples or "black heads." The semi-solid contents of 
 these can be emptied by gentle pressure. The popular 
 term, "opening the pores of the skin," really means 
 increased activity in these glands and visible perspira- 
 tion, or the dilatation of the blood-vessels lying under the 
 skin. 
 
 Inadequacy of the skin's protection. — Theimbroken 
 skin, even when as delicate as in man, forms ordinarily 
 an adequate protection against the invasion of the body 
 
 FiQ. lis. Magnified view 
 of the epidermis, show- 
 ing moatbB of the sweat 
 glands. 
 
206 
 
 THE SKIN 
 
 by disease-producing germs. This protection would be 
 more complete, were it not for the openings of the sweat 
 glands and hair roots, which occasionally afford them 
 entrance and permit their development in the form 
 of small abscesses, pimples, or large abscesses, ioils. 
 
 Fat-laden' 
 connective tissue 
 Blood vessel 
 
 White corpuscles 
 nd bacteria (pus) 
 
 Pis. 113. Section of the Bkin and underlying tissue of the back, showing the 
 spread of pus in a carbuncle. (After Warren.) 
 
 These ordinarily remain in the skin and do not pene- 
 trate into the tissues below. They tend to work out- 
 ward, destroying the skin as they go, until finally they 
 break through the surface. Sometimes, however, when 
 the invading microbes are of a very active form or when 
 they develop in very tough skin, such as that on the back, 
 they tend to work inward and form large spreading ab- 
 scesses called carbuncles. When the skin is broken, 
 microbes are able to find their way into the lymph 
 spaces, where they have a chance for development, pro- 
 vided that they can resist the attacks of the white blood 
 corpuscles. 
 
BATHING 207 
 
 Necessity for cleanliness. — By its owa secretions, the 
 skin increases tlie danger of contamination through mi- 
 crobes by f urnisliing a surface to which they adhere and 
 on which they develop. The safeguard against this is 
 cleanliness. An efScient method of cleaning the skin is 
 by thorough washing with warm water and soap. The 
 soap is dissolved by the warm water and in turn dissolves 
 the oil and grease found upon the skin. ]\Iicrobes and 
 other impurities which have been held to the surface by 
 the oiliness of the skin are in this way carried away 
 by the water. It has been found by tests that this 
 form of cleansing, if followed by rinsing in running 
 water, is ordinarily effective against the transfer of 
 even contagious diseases. Such thorough washing of 
 the hands is a precaution which should always precede 
 eating. 
 
 Bathing. — Washing of the whole body, or bathing, is 
 valuable not only for cleansing the body but also for 
 giving a wholesome stimulation to the nervous system. 
 For this purpose, cold or cool baths are preferable to 
 warm, which have a more relaxing or sedative effect 
 unless immediately followed by a cool shower or sponge 
 bath. To be stimulating, a bath need not be colder 
 than 70° F. Bathing in Avater colder than this has 
 its dangers, chief among which is its liability to increase 
 any tendency to pain or stiffness in the joints. Cold 
 baths should be avoided by those who fail to get a vigor- 
 ous warm reaction or glow after them. 
 
 Sea bathing. — One of the most popular and beneficial 
 forms of cool bathing is sea bathing, principally because 
 of the exercise in the fresh air and sunshine associated 
 with it. Its value, however, is frequently lessened and 
 even changed to actual harm, if prolonged beyond the 
 five or ten minutes which is a safe limit for cool waiter. 
 
208 THE SKIN 
 
 This is especially true if one is fatigued, as then one is 
 liable to cramps of the muscles. 
 
 Soaps. — Some skins are more sensitive than others 
 and become roughened by much washing, especially with 
 strong soaps which contain enough free alkali to be irri- 
 tating. This can be avoided if care is taken to use 
 a neutral soap, such as a good castile, and to replace the 
 oil of the skin by diluted glycerine or other emollient.^ 
 
 Skin parasites. — The skin is sometimes irritated by 
 parasites of both animal and vegetable nature, which, 
 when once established, are difficult to remove. It is 
 therefore important to be cleanly oneself and to avoid 
 contact with those who are not, that such parasites may 
 not get a foothold. 
 
 Skin eruptions. — A number of contagious diseases, 
 such as measles, scarlet fever, small-pox and chicken-pox, 
 are accompanied by eruptions of the skin. All eruptions, 
 therefore, which appear suddenly and are accompanied 
 by such other symptoms of illness as headache, chills, 
 cold in the head and sore throat, should be looked into 
 at once. The person should be isolated, especially from 
 children, until it has been definitely determined by a 
 physician that the cause is not a contagious disease. 
 
 EXPERIMENTS AND DEMONSTRATIONS 
 
 Materials : Piece of glass ; ink roll, or dabber ; printers' ink ; 
 dull and sharp knives; stiff nail brush; soaps — soft, yellow, 
 castile, etc.; vinegar; various kinds of leather; hair of dog, 
 horse, etc. ; fur of eat, rabbit, etc. ; feathers ; fish scales ; micro- 
 scope ; magnifying glass ° ; litmus paper. 
 
 ' Glycerine should be used in a solution of about three or four 
 parts of water to one of glycerine. Emollients are best applied at 
 night, while the skin is still moist after bathing. 
 
 ' In the following experiments, all examinations should be made, 
 if possible, with both a magnifying glass and a microscope. 
 
EXPERIMENTS 209 
 
 1) Examine skin of hand. Compare skin on back with that 
 of palm. Note character of surface and mai"kings, especially 
 on balls of fingers. 
 
 2) Make finger print by rolling ball of finger on a piece of 
 glass upon which a thin film of printei-s' ink has been spread by 
 roller or dabber. Apply finger to smooth white paper. 
 
 a) Examine print with magnifying glass and note white dots 
 (mouths of sweat ducts) on ridges. 
 
 b) Compaie patterns of markings ' of different fingers of 
 same indi\-idual and of different individuals. 
 
 3) Moisten back of hand and repeatedly scrape sui'face with 
 edge of dull knife, as table knife. Collect detritus, place upon 
 glass slide with drop of water, and apply cover glass. Examine 
 under microscope and note flattened cells. 
 
 4) TVith shai'p knife or razor, slice off a thin slip of skin 
 over a callus on palm. Moisten and examine under microscope. 
 Note mouths of sweat ducts and horny character of skin. Dis- 
 tinguish separate cells after prolonged soaking. 
 
 5, a) Make parings of nail, — a narrow strip to show edge, 
 one broad to show surface. Examine under microscope dry 
 and after soaking in water. 
 
 b) Compare shape and general structure with nails of 
 various animals, as dog, cat, cow, fowl, bii'd, horse, etc. 
 
 6, a) PuU out hair and examine shaft and root m drop of 
 water under microscope. Note that root is incomplete. 
 
 b) Compai-e with hair of dog and horse, with fur of cat and 
 rabbit, with feathere, with scales of fish, etc. 
 
 7) Compare human skin with that of various animals, as to 
 general character, texture, thickness, etc. (Make use of such 
 leather ° as is obtainable, as cow, sheep, pig, horse, alligator, 
 snake, etc.) 
 
 9) Dissolve ui separate test tubes pieces of various samples 
 of soap, the size of a lima bean, by shaking gently in 2 tea- 
 spoonfuls of hot water. 
 
 ' Finger prints are so characteristic and so constant as to 
 furnish one of the best means of identification. 
 
 ' Leather is skin which has been tanned. The tanning process 
 consists in treating the leather with such chemicals as the tarniin 
 of tan bark, whicli make insoluble the tissues of the skin. 
 
210 THE SKIN 
 
 a) Test each solution with red litmus paper to determine 
 whether neutral or alkaline. 
 
 b) To determine amount of alkali in each soap, pour table- 
 spoonful of vinegar into glass of water, add slowly to soap 
 solution and gently shake, noting amount required to change 
 soap solution from alkaline to acid. A piece of litmus paper 
 should be floating in each test tube and its change of color 
 carefully watched. 
 
CHAPTER XIX 
 THE HEAT OF THE BODY 
 
 Warm and cold animals.— The heat of the body re- 
 sults from the oxidation of food materials in its tissues. ' 
 The unicellular and lower forms of animals have no 
 means of retaining the heat wliieli they generate within 
 their small bodies, as their skins are so thin and moist 
 as readily to transmit it. Indeed, in many cases, there 
 is but little heat for retention, as their movements are 
 so infrequent or sluggish as to call for but little oxida- 
 tion of food material. As a result, their temperature 
 corresponds to that of the air or water in which they 
 live. They must therefore depend for their warmth 
 upon such external sources as the sun, air and water. 
 In warm-blooded animals, on the contrary, the body 
 is kept at a fairly uniform temperature partly by means' 
 of the protective skin and partly by means of the vaso- 
 motor meehanisjn. 
 
 Heat control. — "When too much heat is generated dur- 
 ing muscular activity and the temperature of the body 
 tends to rise, the excess heat is taken up by the blood, 
 carried away from the active tissues and glands, and 
 distributed throughout the body. In the course of its 
 circulation, the blood reaches the special nerve centre 
 in the upper end of the spinal cord which has to do 
 with the regulation of heat in the body. If, in spite 
 of its distribution, the blood still contains too much 
 heat, this centre at once actively arranges for the re- 
 moval of the superfluous heat by causing the arterioles 
 
 211 
 
212 THE HEAT OF THE BODY 
 
 of the skin to relax. As a result, much more blood is 
 allowed to pass to the surface of the body, where it can 
 be quickly cooled by contact with the air. If the blood 
 is not sufficiently cooled in this way, the sweat glands 
 are also stimulated to activity and secrete a copious 
 amount of perspiration, which they pour upon the sur- 
 face. The heat of the blood then disappears much more 
 rapidly because it is doing the work of evaporating the 
 moisture. In health, the temperature of the body, even 
 in severe exercise, never rises much above the normal 
 point of 98.4° F. 
 
 Loss of heat. — The heat-controlling mechanism has 
 to provide not only against a possible increase of body 
 temperature but also against a too rapid loss of heat 
 from exposure to cold. When there is but little activity 
 on the part of muscles and glands and the air is cold, 
 
 the heat centre causes the 
 arterioles of the skin to 
 contract, so that compara- 
 tively little blood passes 
 through them to be chilled 
 at the surface. This with- 
 
 Fia. 114. Diagram to Bhow distribution drawal of blood from the 
 of blood in ttie body wlien heat '8 
 
 being saved (Ai, and is being thrown bodv 's SUrf ace is in a meas- 
 off (B). Tlie blacli areas represent "^ 
 
 the parts containing blood. The urC equivalent tO putting OU 
 innermost white area represents the ^ r- o 
 
 layer of subcutaneous fat; the outer, an OVCrCOat, sinCC it shutS 
 the epidermis. ' 
 
 the heat inside the fatty 
 layer of the skin. In case this is not sufficient to maintain 
 the normal temperature, the arterioles in the feet and 
 hands, and even those in the legs, arms, ears and nose, also 
 contract to shut the blood within the trunk and thus pre- 
 serve life, even at the sacrifice of these parts by freezing.^ 
 
 " Those who habitually suffer from cold hands and feet simply 
 demonstrate the efficiency of this control and prove that they have 
 
CLOTHING 213 
 
 Clothing. — In cold climates, the heat-regulating mech- 
 anism I'eceives great assistance from such further pro- 
 tection of tlie body as is afforded by clothing. Of the 
 various materials employed for clothing, the skin of 
 animals was probably the fii"st used. "With the develop- 
 ment of weaving and the consequent manufacture of 
 fabric, it became possible to utilize the softer fibrous 
 substances such as the various forms of hair from ani- 
 mals, feathers from birds, silk from the cocoons of worms, 
 and cotton and linen fi'om plants. 
 
 Wool. — Of these materials, hair or its softer finer 
 form, wool, was developed by nature as an outgrowth 
 from the skin to give added protection to animal life. 
 Prom an evolutionary standpoint, therefore, we are 
 forced to regard wool as the best material which nature 
 was capable of developing for that purpose. Thousands 
 of yeai-s of use by man has proved its undoubted claims 
 to superiority as a protection from wet and cold. This 
 superiority seems to be largely due to the fact that the 
 fibres do not soften and become matted down by 
 moisture, but retain their elasticity. As a result, the 
 fabric never loses its porous quality which enables it to 
 remove by absorption a large amount of moisture. By 
 this absorption and removal of moisture from the body's 
 surface, it prevents the chill so noticeable when cotton 
 and linen are used. Wool is the only material which has 
 proved effective for worlcmen who when wet from pei"spi- 
 ration are constantly exposed to cooling drafts, as, for 
 example, iron workere and coal stokers. These men wear 
 wool all the year around. Those among them who have 
 attempted to substitute cotton have abnost invariably be- 
 come crippled by rheumatism. Under such trying con- 
 not sufficient food or exercise to generate a proper amount of heat, 
 or clothing enough to retain it. 
 
214 THE HEAT OF THE BODY 
 
 ditions as these, therefore, the advocates of wool as the 
 most adequate protection against both heat and cold, are 
 fully justified. 
 
 Leather and furs. — The skins of animals, although 
 a most ■ satisfactory protection against wind and cold, 
 lack the power of absorbing moisture and of permitting 
 its evaporation without chill. Instead, they tend to keep 
 the perspiration upon the surface of the body with the 
 result that the clothing worn beneath them becomes wet. 
 Much of this bad effect can be avoided, however, if they 
 are worn loosely enough to permit beneath them the 
 ventilation which will allow for the evaporation of the 
 moisture. 
 
 Thin or thick clothing. — The method of wearing 
 clothing is quite as important as the materials used. 
 Its object is to economize the body's heat and yet per- 
 mit the perspiration to evaporfete freely. To accom- 
 plish this in the most wholesome way, several layers 
 of thinner clothing are preferable to an equal amount 
 in one thick layer. This is especially true if, as is 
 customary, the clothing is worn somewhat loose so that 
 a certain amount of air is enclosed between each layer. 
 The enclosed air warmed by the body not only permits 
 the evaporation of moisture from the body's surface, 
 but also serves in itself to retain the heat. For the 
 same reason, porous underclothing is far superior to 
 that which is tightly woven, since it allows a sufficient 
 change of the enclosed air to permit the evaporation of 
 moisture. 
 
 Bed clothing. — Clothing for sleep is in some measure 
 even more important than that for daytime use, since 
 it cannot be as readily adjusted to sudden changes of 
 temperature. The bed clothing for cold weather should 
 consist, in addition to sheets, of wool blankets of mod- 
 
BED CLOTHING 
 
 215 
 
 erate thickness, or of puffs filled with lamb's wool, 
 eiderdown, or feathers. These should be as light and 
 porous as possible, since heavy clothing is oppressive 
 and interferes with the restfulness of sleep. For this 
 reason, cotton, M'hether used as blankets or as fiUing for 
 puffs and quilts, is much less satisfactory than wool. 
 
 Arrangement of bed clothing. — For getting the 
 greatest warmth out of the least bed clothing, a sleep- 
 ing bag such as hunters use is most effective. Indeed, 
 for children who toss about in bed, several sleeping 
 
 Fis. lis. Sleeping in an open sliack in cold weather. (Boston Children's Hos- 
 pital Repoi t.) 
 
 bags one over another are the only adequate protection. 
 The ordinary bed clothing can be made to imitate a 
 sleeping bag by having it tucked in only at the foot of 
 the bed, and allowing the sides to rest in loose folds 
 closely about the person. The lower part of the body 
 should ordinarily have about twice as much clothing 
 as the upper half, since the feet are most apt to become 
 
216 THE HEAT OF THE BODY 
 
 cold.^ In general, the shoulders and neck should be but 
 lightly covered. Properly to protect the head, a light 
 covering in the shape of a thin hood is also desirable, 
 especially for children, who often cover their heads- with 
 the bed clothes to keep them warm and so half smother 
 themselves. 
 
 Fall in body temperature.— When the body has been 
 exposed to cold or wet without proper protection, the 
 loss of heat may be so great that in spite of the body's 
 effort to increase its heat production, its temperature 
 falls to 94° or even 90°. When the body is chilled, the 
 blood-vessels in the skin and the extremities contract. 
 The extra blood which no longer circulates freely in the 
 exposed parts collects in the large veins, especially those 
 of the abdomen. Under these conditions, the tempera- 
 ture of the skin may be almost if not quite at the freez- 
 ing point, since its sole supply of warmth, the blood, is 
 withdrawn. The quickest relief is afforded by a hot 
 drink, such as soup, tea, coffee, chocolate, or hot milk, 
 which adds heat to the body and stimulates the nerve 
 control to. relax the blood-vessels of the skin and ex- 
 tremities. The warm blood passing freely to the skin 
 raises it at once to a more normal temperature. The 
 nerve ends in the skin are also warmed by the return- 
 ing blood current, and as a result, the person feels warm 
 and comfortable. 
 
 Alcohol. — Alcohol is sometimes used to overcome chill, 
 but, unlike a hot nutritious drink, it has no heat to fur- 
 nish the body. Moreover, it dilates the blood-vessels in 
 the skin, and as a result the blood rushes so strongly to 
 the surface of the body that a false sense of warmth 
 
 ' This leads to curling up in bed, wliieh in children frequently 
 results in such bodily deformities as round shoulders, flat chests, 
 or even spinal curvature. 
 
FREEZING 917 
 
 and comfort is produoed. In reality, even the body's 
 reserve heat is being lost through this rush of blood 
 to tlie surface, and if the exposure to cold continues the 
 subsequent chill is often fatal. 
 
 Freezing. — A similar feeling of warmth comes to a 
 person who is on the point of freezing. As a result of 
 the extreme cold, the heat-controlling mechanism appar- 
 ently becomes fatigued in its effort to retain the blood 
 within the trunk. Consequently, the blood rushes to 
 the siu'faee and gives to the pereon who has been vigor- 
 ously struggling against freezing a grateful feeling of 
 warmth, comfort and drowsiness. ' If he yields to it and 
 stops the exertions upon which his supply of heat 
 depends, he quickly freezes to death. 
 
 Owing to the exposed condition of the fingers, toes, 
 nose and ears, and to the tendency of their blood-vessels 
 to contract in the cold, they are especially liable to be 
 frozen. Before they are actually frozen, vigorous rub- 
 bing will frequently restore the circulation. When 
 frozen, they should be thawed out as soon as possible 
 by applications of verj'' cold water, melting ice, or melt- 
 ing snow. After being thoroughly thawed, the cold 
 applications should be continued, in order to restrain 
 the intense inflammatory reaction which may lead to 
 extensive sloughing of the skin and even to a loss of the 
 frozen parts. The use of warm applications under these 
 conditions serves to aggravate the subsequent inflamma- 
 tion and is therefore most harmful. 
 
 Rise in body temperature. — In fever, we have, in- 
 stead of a decrease in the body's temperature, an in- 
 crease which in extreme eases amounts to as much as 
 seven or eight degrees. This seems to be due both to 
 an increase in the generation of heat by the tissues of 
 the body and to a derangement of the heat-controlling 
 
218 THE HEAT OF THE BODY 
 
 mechanism. More heat than usual is generated in the 
 body because of the poisonous substances developed by 
 the microbes which are responsible for the fever. Be- 
 cause of the derangement of the heat-controlling mech- 
 anism, the secretion of perspiration fails and the blood 
 cannot therefore be cooled by its evaporation. There is 
 therefore an excess of heat to be removed and a de- 
 fective mechanism to accomplish its removal. As a result, 
 much of the heat remains in the body and raises its 
 temperature. 
 
 Since fever has a most harmful effect upon the body, 
 especially upon the nerves and brain, it is important 
 that the body temperature should be kept down as much 
 as possible. To accomplish this, it is customary to give 
 a person with pronounced fever, cooling drinks, appli- 
 cations of ice, and cold baths, in order to aid in removing 
 the excess heat from the body. 
 
 EXPERIMENTS AND DEMONSTRATIONS 
 
 Materials: Clinical thermometer; dairy thermometer; pieces 
 of wool, linen, cotton and silk ; ice ; microscope. 
 
 1) Skin temperature : Place bulb of dairy thermometer on 
 back of hand and cover with piece of dry woolen cloth. Watch 
 mercury column and when it no longer rises (5 or 10 min.) 
 record temperature. 
 
 2) Internal temperature: a) Having carefully shaken mer- 
 cury column of clinical thermometer below 98° F., place bulb 
 under tongue and close lips. Read temperature at end of 5 min. 
 
 b) Hold piece of ice in mouth for a few minutes. Having 
 shaken mercury column down to 90° F., take temperature of 
 mouth. 
 
 3) Examine under microscope fibres of pure linen, silk, cot- 
 ton and wool. Observe and sketch characteristic appearances. 
 
CHAPTER XX 
 
 THE NERVOUS SYSTEM 
 
 General arrangement. — Although there are millions 
 of separate cells in the human body, each doing its indi- 
 vidual task, yet they all work together harmoniously. 
 
 Fis. 116. Right side of brain and npper portion of spinal cord. 
 
 The co-operation of all these minute activities is made 
 possible by means of a master tissue, the nervous system. 
 By its many branches, the nervous system reaches every 
 cell to detect its needs and control its activity. Like 
 the circulatoiy system, the nervous system consists of 
 
 219 
 
220 
 
 THE NERVOUS SYSTEM 
 
 Fia. 117. Diagram illustrating ttie general arrangement of the nerrone eystem. 
 
THE SPINAL CORD 
 
 221 
 
 Sciatic nerve 
 
 Sacral plexus 
 
 Coccygeal plexus 
 
 Fig. 118. Diagrammatic front view of spinal cord and bnlb, Bliowing spinal nerves, 
 one side chain of sympathetic ganglia, and some of cranial nerves. 
 
 a central organ, the brain and spinal cord, and of numer- 
 ous distributing branches, the nerves, which radiate 
 
222 THE NERVOUS SYSTEM 
 
 from it to all parts of the body. In the limbs and to a 
 less extent in the trunk, the larger nerves follow nearly 
 the same courses as the blood-vessels. They can be 
 readily distinguished from them because they appear as 
 solid white cords of considerable strength. 
 
 Nerves. — "When the course of any nerve is traced from 
 its termination in a cell inward toward the brain, it is 
 seen to start as a very fine thread, or nerve fibre, visible 
 only under the microscope, which quickly joins with 
 similar fibres from other cells. Together they form the 
 bundle of fibres known as a nerve. As the nerve passes 
 inward, it constantly grows larger through the addi- 
 tion of many branches luitil a large nerve, or • nerve 
 trunk, is formed. 
 
 Spinal nerves.^ — All the nerves in the body, with the 
 exception of those of the head, are 'finally united into 
 sixty-two nerve trunks, which on approaching the spinal 
 column are called spinal nerves. Two spinal nerves, 
 
 one upon each side, pass 
 into the spinal column at 
 each of its joints. These 
 constitute a pair of spinal 
 nerves, there being thirty- 
 one pairs in all. 
 Ganglion r-^^g^^;^^^)^ After passlug between 
 
 the joints of the spinal 
 column, the spmal nerves 
 
 ^'(TeVtut./"""*"™""""'"*''""^ e^ter the neural canal 
 
 formed by the arches 
 which spring from the bodies of the vertebrae. Here 
 they split into two parfs, or roots, and enter the much 
 larger white tough flexible cord, the spinal cord, which 
 nearly fills the neural canal. The nerve fibres of 
 the spinal cord serve to connect the spinal nerves with 
 
NEEYE STRrCTURE 
 
 223 
 
 a large grayisli mass of similar eoniposition but of much 
 more delicate structure, the brain, which is enclosed 
 within the bony cavity of the skull at the top and back 
 of the head. 
 
 Nerve structure. — "When a nerve is examined under 
 a microscope, it is seai to consist of a large number 
 
 Connective tissue support 
 Sheath of nerve fibre 
 Fatty layer 
 Neiye fil)re (axis cylinder) 
 
 Connective tissue 
 
 Bund'e cf fibres in a nerve 
 
 Fig. 120. A, cross section of .a nerve, showing 5 bnndles of fibres and the sup- 
 porting tangle of connective tissue fibres penetrated by blood-vessels. B, 4fibre- 
 mnch more bighly magnified. 
 
 of very small tubes, or sheaths, which contain fat and 
 carry in their centres the delicate threads which are 
 the true nerve fibres. The sheaths with their fat ar§ 
 
224 
 
 THE NERVOUS SYSTEM 
 
 Motor nerve cell 
 of spinal cord 
 "lendritic branches 
 
 -Axis cylinder 
 Collateral branch 
 
 Medullaiy sheath 
 
 but a means of protecting and strengthening the central 
 nerve fibres. In all nerves, the fibres form the central 
 line, or axis, of the cylindrical sheaths and are there- 
 fore known as axis cylinders. They reach the cells of 
 the various tissues of the body by branching into fine 
 
 short filaments, one of 
 which ordinarily passes 
 into each cell. The fila- 
 ments in turn split up 
 into such fine and delicate 
 branches that it is difScult 
 to distinguish them from 
 the cell structure itself, 
 even with the most power- 
 ful microscope. Each axis 
 cylinder controls by means 
 of its branches the activity 
 of a smaU group of cells. 
 
 Course of a motor nerve. 
 — If we select the axis cyl- 
 inder of a small group 
 of cells in a muscle and 
 trace its course inward, 
 we find that it passes along 
 through its fatty sheath 
 in complete isolation from 
 the many accompanying 
 axis cylinders in their 
 sheaths, which are packed 
 with it in the nerve. It 
 finds its way along the 
 
 Fio. 121 . Diagram of a motor nerve 
 cell from the anterior horn of the 
 spinal cord, and its branches con- 
 nected with a muscle (highly magni- 
 fied except as to length). ~ • 
 
 nerve of which it is a part up to the point where the 
 spinal nerve forms two roots to enter the spinal cord. 
 It then passes through the ventral root into the ventral 
 
NEURONS 225 
 
 portion of the spinal cord, M'here it is seen to be an out- 
 growth from a comparatively large cell. This cell, and 
 not its branch, the axis cylinder, is the real centre of 
 activity, as is sliown by the fact that when tlie axis 
 cylinder is cut off from tlie cell it dies, whereas the cell 
 lives on and m9,y even produce a new and complete axis 
 cylinder. 
 
 Neurons. — From this nerve cell there are also tree- 
 like branches which serve to bring the cell into close 
 relation with other cells. Each cell and its branches, 
 including the axis cylinder, form one unit of the nervous 
 system, a uctirou, of which there are many millions in 
 the brain and spinal cord. 
 
 Motor neurons. — The neurons which terminate in the 
 cells of muscles or glands, control their activity. The 
 contraction of every muscle, the secretion of every gland, 
 is directly due to the stimulations developed in the large 
 central cells of the neurons. These stimulations, or 
 nervotis impuhes, are transmitted along the axis cylin- 
 ders of the neurons to tlie muscles or glands. The neu- 
 rons are therefore called motor neurons, since upon them 
 all activity depends. If motor neurons are injured, 
 as for example by cutting the ventral root of a spinal 
 nerve, the cells of tlie muscle or gland supplied by tlieir 
 fibres become paralyzed. In other words, the cells are 
 powerless to act, because they have ceased to receive 
 nervous impulses. Unless the motor neurons recover so 
 that communication with the cells is restored, the cells 
 of the muscle or gland tliemselves waste away, since ^vith- 
 ont the nerve stimulation they are imable even to take 
 the food which they need from the blood. 
 
 Course of a sensory nerve. — If, instead of selecting 
 an axis cylinder going to a muscle, we had chosen an axis 
 cylinder from tlie cells in the nearby skin and had traced 
 
226 THE NERVOUS SYSTEM 
 
 it inward, we should have found that it followed a course 
 similar to that of the motor fibres, perhaps even in the 
 same nerve and nerve trunks, until it reached the neural 
 canal of the spinal colunm. Here, instead of passing 
 through the ventral root of its spinal nerve, it passes 
 into the dorsal root and thence by a shqrt right-angled 
 branch to the nerve cell of which it is a prolongation. 
 This nerve cell is situated in an enlargement, or ganglion, 
 of the dorsal root of the spinal nerve, which also con- 
 tains the other cells belonging to the similar fibres of 
 this spinal nerve. Each of these ganglion cells sends 
 inward to the spinal cord a branch, which, after enter- 
 ing the spinal cord, divides into numerous branches. 
 Bach ganglion cell with its branches also forms a 
 neuron. These neurons have quite a different function 
 from the motor neurons, in that they are responsible not 
 for our activities but for our sensations. Along them 
 travel the nervous impulses which arise in the skin and 
 which result in our sensations of touch, pressure, heat 
 and cold. They are therefore called sensory neurons. 
 If sensory neurons are injured, as for example by cut- 
 ting the dorsal root of a spinal nerve, there is an imme- 
 diate loss of sensation in the part to which the cut nerves 
 go. That part of the skin may even be pricked or 
 burned, but the person will feel nothing. 
 
 Direction of nervous impulses. — In the case of sen- 
 sation, the nervous impulses start in the skin and pass 
 inward along the sensory nerves to the spinal cord and 
 thence to the brain. In the case of muscle and gland 
 stimulation, on the contrary, the nervous impulses orig- 
 inate in the brain and spinal cord and pass along the 
 motor nerves outward. 
 
 Spinal cord. — The spinal cord is thus seen to con- 
 tain the inner ends of both the motor and sensory neu- 
 
NERVOUS IMPULSES 227 
 
 rons. It also contains still other neurons which are 
 distributed up and down its length. The latter serve to 
 connect the more distant sensory and motor neurons 
 with those which lie in the upper portion of the spinal 
 cord and in the brain. In this way, both sensory and 
 motor nervous impulses are carried to and from the 
 great centre of nervous activity, the brain. 
 
 Motor impulses from sensory. — The spinal cord 
 forms a distinct portion of the nervous system which 
 is responsible for certain activities. If, for example, 
 we accidentally touch a hot object, the irritation of the 
 ends of the nerves in the skin starts nervous impulses, 
 which pass inward along the sensorj' fibres, and thence 
 along the dorsal root of the spinal cord into the branches 
 of the neurons which lie in the cord itself. They then 
 pass along these branches to their many -branched tips, 
 where they come into close relation with many motor 
 cells, which they arouse to activity. The impulses started 
 in the motor cells are then transmitted outward along 
 the motor fibres to the groups of muscle cells controlled 
 by them. As a result, the muscles are caused to contract 
 and the hand is snatched away from the hot object. 
 
 Reflex action. — This kind of nerve activity is called 
 reflex action, and takes place when the sensory impulses 
 are so strong that on their way to the brain they excite 
 the motor nerves in the spinal cord which lie within 
 reach of their branches. Reflex action is involuntary, 
 for the reason that it takes place before the brain has 
 time to know about it and to aid or interfere with it. 
 It is so rapid that the time which elapses between the 
 touching of the skin with a hot object, for example, and 
 its withdrawal is only about six- or seven-hundredths 
 of a second. If touching the object had not been pain- 
 ful and the reaction had not been reflex, the time taken 
 
228 
 
 THE NERVOUS SYSTEM 
 
 to withdraw the hand under the direction of the brain, 
 that is voluntarily, would have been from twelve- to 
 eighteen-hundredths of a second. 
 
 Motor nerve cells 
 of anterior horn 
 
 Sensory cell 
 
 of ganglion 
 
 of dorsal root 
 
 Posterior horn 
 
 ■Connecting 
 branches of 
 sensory cell 
 
 A B 
 
 Fio. 132. Diagram of the spinal cord, showing the mechanism of reilex action ; A, 
 shows how a sensory cell, by means of its branches, may influence many motor 
 cells directly; B, how an intermediate cell, may serve to connect a sensory cell to 
 motor cells, thus malting possible more complicated reactions. (After KOlliker.) 
 
 Its characteristics. — As we study reflex action in its 
 control of muscles, we find that the movements are in 
 general planned to take the part of the body threatened 
 away from danger. For example, the hand is never 
 thrust against the hot object, but always definitely and 
 accurately removed from it. This is true regardless of 
 whether the object is under, above, or on either side 
 of the hand. This means that each sensory nerve is 
 connected by its branches with the particular motor 
 nerves which will cause the proper protective movement 
 and with no others. Thus there is never an opportu- 
 nity for an irritation to start the wrong movement, but 
 
THE SYMPATHETIC SYSTEM 
 
 229 
 
 a given irritation is invariably followed by the correct 
 protective movement. 
 
 Branches of spinal nerves. — In addition to the sys- 
 tem of spinal motor and sensory nerves, there is another 
 system of branches from the spinal nerves which have 
 charge of the parts of the body not under voluntary 
 control, that is the viscera. These branches leave the 
 spinal nerves near the spinal cord and pass into the 
 
 Spinal cord 
 
 Sveat gland 
 
 Motor nerve cells 
 Intermediate nerve ceils 
 Motor (vasodilatar) nerves to blood vessels of skin 
 
 Fis. 133. Diagram showing a part of the reflex mechanism by which heat wlien 
 applied to the skin results in the dilatation of the blood-vessels in the skin and 
 in the secretion of perspiration. 
 
 chest and abdominal cavities. Here they join a chain of 
 ganglia which lie close to the back wall of these cavities. 
 Prom the ganglia issue many nerve branches which pass 
 to the heart and blood-vessels, the lungs, stomach, in- 
 testines and other organs of the chest and abdomen. 
 
 S5mipathetic system. — This system of nerves is known 
 as the sympathetic system, because it controls the activi- 
 ties of the viscera automatically through its sensitive- 
 ness to their needs and the needs of the body. For 
 
230 THE NERVOUS SYSTEM 
 
 ''»d^istrTb^^lJ?„Tet'=rir^y„'s"TQ^irr"^^^ ^'"^ «•« «P'-' --s 
 
THE SPINAL BULB 
 
 231 
 
 example, when a muscle is active, the sympathetic sys- 
 tem dilates the blood-vessels in the muscle so as to allow 
 
 more blood to go to it 
 than when it is at rest; 
 when the blood pressure 
 falls, it makes the heart 
 beat faster; when the 
 pressure rises, it makes 
 it beat more slowly; 
 when the skin is hot, it 
 dilates the blood-vessels 
 
 Olfactory nerve 
 
 Forebrain (hemispheres) 
 Midbrain (opt'c lobes) 
 Hindbrain (cerebeflum) 
 Aflerbraln (Medulla oblongata) 
 
 Fig. 125. The brain of a fish. (After 
 Steiner.) 
 
 and starts the secretion of per- 
 spiration; when food enters the 
 stomach, it stimulates its glands 
 and muscles to activity; and so 
 on throughout the unconscious 
 adjustments made in the organs 
 of the body. 
 
 Spinal bulb. — In its upper 
 part, the spinal cord is enlarged 
 into the spinal hulb, or medulla 
 oblongata. The spinal bulb 
 contains several important 
 nerve centres which aid in con- 
 trolling certain of the vital or- 
 gans, as the heart. Since the 
 spinal bulb lies entirely within 
 the skull and its structure is 
 much more complex than that 
 of the cord, it is considered to 
 be a part of the brain. As a 
 
 Spinal cord 
 
 Pig. 136. The brain of alizard, 
 witli the cranial nerves in- 
 dicated by numerals. (After 
 Wiedersheim.) 
 
232 
 
 THE NERVOUS SYSTEM 
 
 Forebrain 
 (hemispHeres) 
 
 matter of fact, however, the brain itself is really but an 
 enlarged and specialized development of the end of the 
 spinal cord and is found fully developed only in the 
 higher animals. The spinal cord may therefore be con- 
 sidered as projecting into the skull and there forming 
 the axis from which the various parts of the brain arise. 
 
 Cerebellum. — 
 Springing from this olfactory lobe- 
 
 axis and covering the 
 spinal bulb is a large 
 gray mass, the cere- 
 iellum, the surface 
 of which is broken 
 up into many ridges. 
 When cut open, it is 
 seen to consist of a 
 thin layer of gray 
 material, which con- 
 tains nerve cells, and 
 a much larger inner 
 white portion made 
 up of nerve fibres in 
 their fatty sheaths. 
 
 Cerebrum. — Arising from the same axis, a short dis- 
 tance in front of the cerebellum, are two large masses 
 of soft gray tissue, the hemispheres, which together con- 
 stitute the largest part of the brain, the cerebrum. 
 When the cerebrum is cut through, the outer gray por- 
 tion, or cortex, is found to be about one-eighth of an inch 
 thick and to be made up of nerve cells. Beneath this is 
 white matter made up of nerve fibres in their fatty sheaths. 
 
 Brain convolutions. — In the case of the higher ani- 
 mals, the extent of the gray matter is greatly increased 
 by furrows, which dip deeply into the brain substance 
 
 Spinal cord- 
 
 FiG. 127. Brain of a pigeon, witli the cranial 
 nerves indicated by numerals. (After 
 Wiederslieim.) 
 
THE Bl^AlN 
 
 233 
 
 ll 
 
 and form the intricate convolutions found upon the 
 brain's exterior. The intelligence of animals has been 
 found to depend more or less upon the number of 
 the convolutions, that is, upon the num- 
 ber of nerve cells contained in the gray 
 matter of the cortex. 
 
 Gray matter. — The gray matter is 
 made up mainly of two kinds of cells, 
 the true nerve cells, and the smaller con- 
 nective tissue cells, the neuroglia, which 
 by their close meshwork support the 
 nerve cells. The nerve cells are con- 
 nected with one another and with other 
 cells in various parts of the brain and 
 the spinal cord, either directly by 
 means of their tree-like branches and 
 axis cylinders, or indirectly by means of 
 intervening neurons. 
 
 White matter. — The white matter of 
 the brain consists, as we have seen, 
 mainly of axis cylinders and their 
 sheaths, together with a certain amount 
 of connective tissue to support them. 
 The axis cylinders tend to follow 
 parallel courses and thus form definite 
 bundles of nerve fibres or tracts of com- 
 munication. 
 
 Protection of brain. — The brain is 
 protected from external injury by the 
 bony case, the skull, in which it lies. It 
 is protected from contact with the skull 
 by a small amount of fluid and by 
 several membranes that both cushion it and help to 
 supply it with blood-vessels for its nutrition. 
 
 White ' 
 
 Fio. 188. Diagram 
 of cortex (gray 
 matter) of Brain, 
 showing nerve 
 cells and their 
 connections. 
 
234 
 
 THE NERVOUS SYSTEM 
 
 Cranial nerves. — From the under side, or base, of the 
 brain are given off twelve pairs of nerves, which supply 
 the two sides of the face and its various organs and mus- 
 cles, such as the nose, ears, eyes, mouth, teeth, tongue, 
 pharynx and the muscles which control them. Two 
 of them also aid in supplying and controlling the organs 
 
 Fi&. 129. Diagram illustrating the course of nerve fibres within (he brain. (After 
 Starr.) A, traclc of nerve fibres running from the frontal convolutions to the 
 pons and thence to the cerebellum ; it, motor tract ; C, sensory tract for touch; 
 D, visual tract; E, auditory tract; F. G, H, tracts to cerebellum. Numerals 
 indicate the cranial nerves. Dotted areas represent the cellular, or gray, matter. 
 
 of the chest, and the stomach and liver. Since they are 
 entirely within the skull, or cranium, they are called 
 the cranial nerves. Each pair of cranial nerves is named 
 according to its function, as, for example, the pair which 
 supply the nose are called olfactory; those which go to 
 the ears are auditory ; those to the eyes are optic; and 
 those to the tongue, gustatory. Some of the cranial 
 nerves are purely sensory, others purely motor, and still 
 
CRANIAL NERVES 
 
 235 
 
 others arc mixed. For example, tlie cranial nerves by 
 means of which wo get the nervous impulses which give 
 rise to the sensation of sight are sensory, while those 
 which control the muscles of the eyes ai"e motor. 
 
 Fie. 130. The base of the brain and the cranial nerves. 
 
 Reflex action. — The cranial nerves, like the spinal 
 nerves, act reflexly as well as voluntarily. For example, 
 if an object touches an eyelash, the lid is instantly 
 closed. The nervous impulses originated hy the pressure 
 upon the lash, travel inward along the sensory ner^^es to 
 
236 
 
 THE NERVOUS SYSTEM 
 
 the branches of the neurons which lie in the base of 
 the brain. They then pass along these branches to their 
 fine many-branched tips, where they come into close 
 proximity with the branches of motor neurons. Here, 
 
 Fig. 131. The cranial uerves. (Qaain.) 
 
 as in the case of the spinal nerves, the nervous impulses, 
 although on their way to higher sensory centres in the 
 cortex of the cerebrum, are strong enough to excite im- 
 pulses in the nearby motor neurons. These impulses are 
 then transmitted outward along the motor fibres to 
 muscle cells. As a result, the muscles controlled by 
 
VOLUNTARY ACTION 237 
 
 them, in this ease the muscles of the lid, contract and 
 the eyelid winks, thus protecting the eyeball from the 
 ob.ieet in the sliortest possible time. 
 
 Voluntary action. — In case the sensory impulses are 
 not strong enough to produce reflex movement, they 
 pass without overflow to the cortex of the brain. There 
 they excite certain of the higher nerve centres, and as 
 a result we are conscious of sensations. These nerve 
 centres in turn excite still other nerve centres, until 
 eventually motor nerve centres are stimulated and motor 
 impulses are transmitted to the muscles, thereby pro- 
 ducing movement. For example, as we sit at the break- 
 fast table, the waves of light reflected from a glass of 
 water pass into the eyes and there start up sensory 
 nervous impulses which travel along the optic nerves to 
 the portion of the cortex kno\m as the visual centre. 
 This nerve centre is excited, with the result that sensa- 
 tions are aroused, that is, we see a glass of water. The 
 sensory impulses from the visual centre may then be 
 conmiunicated through associative nerve fibres to other 
 centres, the excitation of which results in our desiring 
 the water. Thereupon the proper motor nerve centres 
 are stimulated and in consequence we roach for the 
 glass of water. This kind of action which involves the 
 higher nerve centres of the cortex, is called voluntary 
 acfio)i, in contrast with reflex action, which results 
 from the stimulation of motor neurons in the spinal cord 
 or base of the brain because of the overflow of excep- 
 tionally strong impulses. 
 
 Habits. — Tf a voluntary act is repeated many times, 
 it tends to become habitual. The same sensory impulses 
 excite the same nerve centres and the same movements 
 result, until finally it is difficult for them to act in ^y 
 other way. In other words, a haoit has been formed. 
 
238 THE NERVOUS SYSTEM 
 
 Habits, which form so large a share of our daily life, are 
 thus seen to be nothing more nor less than the customary 
 way in which our brain centres act. We do a thing 
 in a given way to-day because we have done it so often 
 in just that way in the past that our brain cells are 
 used to no other way of doing it. We can thus see why 
 it is that habits once formed are hard to break. To 
 change our habits means to change the way in which 
 nerve cells have been trained by constant repetition to 
 work together. If our habitual way of doing things is 
 the best way, habits are our powerful servants, in that 
 through them we can do things easily and quickly. If 
 the opposite is true, they may be evil masters, wasting 
 our time and energy. 
 
 EXPERIMENTS AND DEMONSTRATIONS 
 
 Anatomy of the Nervous System 
 
 Materials : Frog ; ether ; fresh calf's or sheep's head ; piece of 
 spinal cord of lamb, pig, calf, or beef; alcohol, 50 per cent; 
 small saw ; stout scissors ; bone forceps ; microscope. 
 
 1) Kill frog with ether; open abdomen and remove viscera. 
 
 a) Note at back of abdominal cavity a bundle of white cords 
 (nerve trunks) passing to each hind leg. 
 
 b) Trace sciatic nerve into which they unite and dissect it 
 out along its course until it ends in fine branches in muscles. 
 
 2) With stout scissors cut carefully bodies of vertebrae 
 (which will be seen projecting in middle line at back of ab- 
 dominal cavity), until neural canal is laid open and spinal cord 
 exposed. Note a) Origin of nerves from spinal cord. 
 
 b) Their division into ventral and dorsal roots before they 
 join cord. 
 
 c) Ganglionic enlargements on posterior roots. 
 
 3) Turn frog upon abdomen and remove skin and muscles on 
 dorsal side of spinal column. Carefully cut away upper ^ 
 of neural arches of vertebrae. Then remove upper half of 
 
ANATOMY OF NERVOUS SYSTEM 239 
 
 skull. Gently raise brain and spinal cord, divide nerves which 
 spring from them, and lift out whole cerebro-spinal system and 
 place it in alcohol for 24 hre/ Note a) Origin of nerves from 
 both brain and cord, b) Union of brain and cord. 
 
 4) Cut across spinal cord at various levels. Note a) Ar- 
 rangement of gray matter, b) Arrangement of white. 
 
 5) After having hardened spinal cord of lamb or pig in 
 alcohol for "24 hrs., cut thin transverse slices and esamme with 
 microscope. 
 
 6) Dissect away skin and muscles eovermg cranium of calf's 
 or sheep's head. "With small saw ' carefully cut bones in 
 circular dii'ection, so as to loosen top of skull. Carefully re- 
 move top of skull, without injuring the tough protecting mem- 
 brane, the dura mater. 
 
 Demonstrate dura mater enveloping brain. 
 
 7) Cut dura mater away and uote processes which it sends 
 between cerebral hemispheres and between them and cerebellum. 
 
 S) Cut processes away and note a) Glistening mner surface, 
 b) Membrane covering brain and full of blood-vessels (pia 
 mater). 
 
 9) Put specimen aside in alcohol or formalin solution for a 
 day or two. AVhen brain has become somewhat hardened, 
 dissect away pia mater on one side and show, a) Cerebral 
 hemispheres and their surface convolutions, b) Cerebellum 
 aud its foldings, c) Spmal bulb beneath cerebellum. 
 
 10) With bone forceps cut away remainder of sides and roof 
 of skull. Find a) Nerves to eyes, b) Nerves to nose. 
 
 11) Raise brain in front, cut through vessels, nerves, etc., 
 which attach it to base of skull cavity, and remove it from skull 
 cavity. Note a) Cerebral hemispheres, b) Midbrain, c) 
 Stumps of cranial nerves. 
 
 12) ilake sections across brain in different directions and 
 note a) Gray matter spread over most of its surface, b) 
 White matter forming most of its mass, c) Nodules of gray 
 matter imbedded in white, especially in base of brain. 
 
 * The specimen may preferably be hardened and preserved in a 
 solution made of formalin. 2 parts; alcohol, 20 parts; water, 78 
 parts. 
 
 ' The skull can be cracked with a light hammer and pieces re- 
 moved, without injury to brain. 
 
240 THE NEBVOUS SYSTEM 
 
 Nerve Action 
 
 Materials: Frog; feather; watch with second hand (pref- 
 erably stop-watch). 
 
 1) Reflex Action: a) Teign blow at a person's eye, having 
 warned him that he is not to be struck, b) Tickle inside of 
 nose with feather. 
 
 2) Voluntary Reaction: a) Arrange class in a circle so that 
 a signal may be passed from one to another by touching hands. 
 Let instructor, as member of circle, give signal by touching 
 hand of neighbor, who transmits it to next, and so on. Finally, 
 instructor receives signal and determines time of transmission. 
 This time, divided by number in circle, gives average reaction 
 time of its members. 
 
 b) Repeat with such modifications as shutting eyes; whisper- 
 ing a sound instead of touching; dividing class into competing 
 halves, etc. 
 
 3) Place live frog on table and note its reactions (breathing, 
 winking, jumping, etc.) to varying stimulations (touching, 
 turning, feeding, etc.). 
 
CHAPTER XXI 
 
 USE AND CARE OF THE NERVOUS SYSTEM 
 
 Activity of the nervous system. — By means of the 
 nervous system, we get all our information as to the 
 outside world in the form of a constant stream of sen- 
 sations pouring in through each of our sense organs. 
 By means of it, also, our activities from the least to 
 the greatest, from the secretion in a tiny gland to the 
 putting forth of great muscular or mental effort, are 
 started and guided. During our waking hours, there is 
 no second of time when millions of neurons are not 
 actively at work. During our sleep, there is no time 
 when all the neurons are at rest, for the vital processes 
 of the body, the beating of the heart, the movements 
 of breathing, the activity of manj'- glands, the resupply- 
 ing of tissues with food materials and the clearing away 
 of waste, must all be carried on. The nervous system 
 must therefore, in spite of its sensitiveness, be long en- 
 during, and it must further be cared for in such a way 
 as to keep it strong and efficient. Like all the other 
 tissues of the body, it develops strength through use 
 and thrives on good hard work, provided only that the 
 conditions under which it works are wholesome and 
 the work is not too long continued. 
 
 Value of sleep. — The most fundamental condition for 
 the health of the nervous system is sufBeient regular 
 sleep. Sleep is more important even than food or drink, 
 since mthout it life more quickly becomes impossible. 
 
242 USE AND CARE OF THE NERVOUS SYSTEM 
 
 Although during sleep the lower nerve centres, espe- 
 cially those of the sympathetic system, are active, the 
 higher centres of the cerebrum are largely at rest. They 
 are both avoiding exhaustion by further work and re- 
 covering from the work already done by storing up a 
 fresh supply of food and eliminating waste products. 
 Sleep is thus a period of relaxation from outside work, 
 of cleaning up and setting to rights of each cell's house- 
 hold, and of laying in fresh stores of fuel for the mor- 
 row's demands. To deprive the nerve cells of sleep is 
 therefore not only to prevent each cell from recovering 
 its normal amount of strength, but to make it grow 
 weaker and weaker from overworlt. To such abuse 
 there can be but one outcome. Inevitably the nervous 
 system must grow gradually less and less efficient until 
 finally it breaks down. 
 
 Amount of sleep. — Although sleep is required to keep 
 the nervous system in order, yet it has been found that 
 too much sleep is almost as bad as too little, since it 
 results in the nervous system becoming sluggish and 
 inefficient through too little exercise. The cells seem 
 to accumulate an oversupply of food materials and 
 thus become so clogged up that they work much less 
 quickly and easily. The amount of sleep which each 
 person needs depends less upon personal peculiarities' 
 than is generally thought. Rather does it depend upon 
 how old a person is and how hard he works. In early 
 infancy when the brain and other tissues of the body 
 are least developed and are growing most rapidly, the 
 baby spends a very large part of the twenty-four hours 
 in sleep. Gradually the amount of sleep taken grows 
 less, until at the end of a year the child requires but 
 thirteen or fourteen hours. This amount is further 
 diminished tmtil at ten years of age eleven hours are 
 
VALUE OF SLEEP 243 
 
 enougli; at twenty years, from nine to nine and a half; 
 and in adult life, from eight to nine. 
 
 Habits of sleep.^-The nervous system tends to adapt 
 itself to whatever habits of sleep one requires. Persons 
 who have aoeustomed themselves to short sleeping hours 
 are apt to feel that they are exceptions to the general 
 rule in that they require less sleep than the majority 
 of pereons. It is, however, a matter of fact that those 
 who have regularly eight or more houre of sleep out of 
 the twenty-four rarely break do\\'n nervously, whereas 
 those who get less than eight hours, and especially those 
 who get less than seven, are very apt to "break do^vn 
 under mental strain. The safe rule, therefore, is not 
 to stint the nervous system in the houi-s of repair and 
 recuperation. 
 
 Nervous breakdown. — Cux'iously enough, one of the 
 early symptoms of the failing strength of the nervous 
 system is its apparent ability to do hard brain work on 
 but little sleep. Soon, however, as the habit of sleep- 
 ijig less and less increases, the ability to work hard de- 
 creases. Finally, sleeplessness becomes so marked that, 
 in order to avoid a complete breakdown, a rest of montlis 
 and even of yeai-s may be necessary. The nervous sys- 
 tem has made a brave attempt to adapt itself to the 
 hardship of too much woi'k and too little rest and has 
 failed. 
 
 Value of work.— Next to sleep, the most important 
 condition for the health of the nervous system is good 
 wholesome work. Like all the tis.sues of the body, the nerv- 
 ous system is developed by exercise, without which its 
 growtli and power are stunted. To this exercise, all the 
 activity of the body contributes. Even the higher cen- 
 tres of the cortex, which are concerned with the more 
 purely intellectual forms of our activity, with our will- 
 
244 USE AND CARE OF THE NERVOUS SYSTEM 
 
 ing and thinking, are also trained by the work which 
 we do with our muscles. This is especially true of the 
 early years, when the growth of nerve control is entirely 
 dependent upon physical activity. The apparently aim- 
 less kicking and tossing of a baby and the vigorous play 
 of young animals and children are nature's provision to 
 ensure the development of the nervous a§ well as of 
 the muscular system. 
 
 Amount of work. — Work, whatever its nature, should 
 not be continued after a certain degree of fatigue is 
 felt, since the more the nervous system is exhausted, 
 the more uncertain becomes its recovery during rest. 
 For this reason, periods of concentrated study should 
 be made short and be relieved by periods of rest and 
 recreation. The majority of the work should also not 
 be of so exacting a nature that the labor of holding 
 the attention to it is exhausting. The test in any case 
 of whether work is excessive, is the ability of the nerv- 
 ous system fully to recover from its effects by ordinary 
 sleep. 
 
 Method of work. — The way in which we do our work 
 is quite as important for the health of the nervous sys- 
 tem as its character and amount. The same piece of 
 work, whether mental or physical, may result in bene- 
 fit or harm. If we do it with a happy confidence that, 
 since we are doing our best, it must come out well in 
 the end, the effect upon the body and mind is one of 
 exhilaration and strength. The breathing is deeper, the 
 blood courses more vigorously through the vessels, the 
 brain gets a full supply, and every cell of the body is 
 in a condition to do its best work. If, on the contrary, 
 we do our work unwillingly, fretting lest it take too long 
 and not come out right in the end, the effect upon the . 
 body and mind is one of depression. The tissues do riot 
 
PAIN 245 
 
 get as much blood, the breathing is not so deep, the cells 
 are not so well able to work, and the work done is usually 
 less in amount and poorer in qualitj', while the nervous 
 system is exhausted rather than strengthened by the 
 exercise. 
 
 Meaning of pain.— "When the body is not receiving 
 proper care, the nervous system gives danger signals 
 in the form of pain. The pain may come from a defi- 
 nite point, as in earache, and its cause be easily deter- 
 mined. At other times, as in a headache, it may be due 
 to one or more of a number of causes, as eye strain, 
 stomach upset, sleeplessness, or fever. In any case, it is 
 a most important means of guiding us in our care of 
 our bodies and should never be ignored. It indicates 
 that something is out of order, and it is fortunate for 
 us that Ave are made increasingly uncomfortable until 
 we are forced to remedy it. If pain, or fear of pain, had 
 not tended to keep the human race in the straight and 
 narrow path of health, we should probably not be in 
 existence to-day. 
 
CHAPTER XXII 
 
 THE SPECIAL SENSES 
 
 Evolution of the special senses. — In the simple 
 forms of animal life, the special senses of taste, sight, 
 smell and hearing are either lacking entirely or are 
 most rudimentary. The sense of touch, on the contrary, 
 is found in all animals, however simple in structure, and 
 may therefore be considered the fundamental sense from 
 which all the others have been developed. In the next 
 higher forms of animal life, the senses of taste and smell 
 are added to touch, as they require but a fairly simple 
 nervous structure. It is difficult to say at what stage 
 of animal evolution sight and hearing begin. Rudi- 
 mentary organs are found which are probably capable 
 of perceiving noise and light. Hearing and sight of 
 the perfect kind which the higher animals possess is 
 clearly impossible for them, however, since the structure 
 of their ears is too simple to enable them to perceive 
 pitch and quality of sound, nor can their rudimentary 
 eyes build up perfectly formed and colored images of 
 external objects. 
 
 Special senses. — Five distinct or special senses, 
 namely, touch, taste, smell, sight and hearing, have 
 always been recognized. The sensations included under 
 touch have been shown by experiment, however, to con- 
 sist of at least four distinct and different kinds, those 
 of contact or touch, of pain, of heat and of cold. 
 
 246 
 
TOUCH 
 
 247 
 
 THE SENSE ORGANS OF THE SIQN 
 
 Touch. — Of the four senses of the skin, touch alone 
 has a relatively simple mechanism. It consists of spe- 
 cial nerve endings, many of which are located within 
 rounded elongated masses called tmtch corpuscles. Each 
 touch corpuscle is made up of a large number of layers, 
 somewhat after the 
 fashion of an onion, 
 within which are the 
 terminal branches of 
 the nerve. It is about 
 one-twelfth of an 
 inch in length and 
 one twenty-fourth of 
 an inch in diameter, 
 and so very elastic 
 that the slightest 
 touch tends to change 
 its form. The touch 
 corpuscles are found 
 aU over the body in 
 the papilla? of the dermis and are especially numerous on 
 the palms of the hands, on the soles of the feet and on 
 the tongue. 
 
 The touch corpuscles are not the only terminal organs 
 of the sense of touch. "Where there are hairs, for ex- 
 ample, the touch corpuscles are much less frequent, 
 since the hairs themselves serve to transmit pressure 
 to the ends of the nerves, the branches of which sur- 
 round their roots. It has been estimated that there are 
 500.000 points sensitive to touch, including the hairs 
 and the touch corpuscles, scattered over the body's sur- 
 face. In addition, smaller bodies very similar to the 
 
 Section of skin showing two papillse 
 "del 
 
 Fie. la 
 of dermis and some deeper ceUs"of epidermis. 
 At left side are uerve fibres leading to cor- 
 puscle. 
 
248 THE SPECIAL SENSES 
 
 touch corpuscles are found in sach structures as the 
 muscles, tendons and internal organs, and serve the same 
 purpose. 
 
 "When pressure is applied to the skin, the elastic touch 
 corpuscles are so pressed out of shape that they press 
 upon the nerve ends. Nervous impulses are thereby 
 started, which pass up the sensory neurons, until on 
 •reaching the cortex they excite certain of its nerve cells 
 and thus give rise to sensations of touch. 
 
 Other dermal senses. — Although we do not under- 
 stand the mechanisms by which sensations of heat, cold 
 and pain are produced, yet the sensations themselves 
 are so definite as to leave no 
 doubt that each has a special 
 end organ which responds to 
 the application of heat or cold 
 or harmful contact. Distinct 
 points in the skin have been 
 found which, when touched with 
 
 Fig. 133. Diagram of a piece i j i. • i n 
 
 of Bkin Bhowing arrangement a COid ODject Or eVCn whcn 
 
 of cold Bpots (circles) ; hot ■, . , • n 
 
 spots (crossee): and pressure preSSCd, glve a SeUSatlOn 01 
 
 ^^°'^ ° ^ ■ cold. Others when touched 
 
 with a warm object give a sensation of heat; and still 
 others when firmly pressed give a sensation of pain. So 
 definite and specific are these points that pressure by 'a 
 warm point upon a "cold spot" will produce a sensation 
 of cold.^ 
 
 Fatigue. — As in all the special senses, these mechan- 
 isms are so delicate that they quickly get tired out and 
 do not respond to stimulation. For example, a feel- 
 ing of cold or chilliness may be experienced by one who 
 is constantly overclothed, apparently because the heat 
 
 ' The heat spots are much more diflScult to locate than the cold. 
 
FATIGUE OF SENSES 249 
 
 centres are so fatigued that the\- no longer respond. 
 The cold centres, on the other hand, have had so little 
 use that they are oversensitive and respond to the slight- 
 est change of temperature. This is frequently spoken 
 of as a nervous chill and is best corrected by a course of 
 training with cold sponge baths, which serves to restore 
 the equilibrium of the oversensitive nerve ends. In 
 like manner, the nei've end organs of pain may become, 
 oversensitive. This should be corrected by vigorous 
 exercise and massage. 
 
 THE MUSCULAR SENSE 
 
 The means by which we are enabled to judge of the 
 dii-ection, rapidity and extent of movement, the position 
 of the moving: parts, the amount of force exerted, and 
 the weight of objects lifted are grouped under the term, 
 muscular sense. Thej' are supposed to arise from nerve 
 terminals and bodies resembling touch corpuscles in 
 the muscles, tendons and joints. 
 
 SEXSE OF PAIN 
 
 The sensations called pain which do not arise in the 
 skin, are so general that they cannot be localized and the 
 mechanism by which they are produced is not loiown. 
 
 THE SENSE OF TASTE 
 
 End organs. — The special end organs of ta^te differ 
 markedlj' from those of touch, inasmuch as they have 
 to do not with physical contact with external objects, 
 but with substances in solution. The end organs of taste 
 consist of groups of specialized cells, the ta.sfc huds, 
 which are distributed over the top and sides of the 
 
250 
 
 THE SPECIAL SENSES 
 
 tongue around the large papillae found there. The dis- 
 solved substances come into contact with the exposed 
 portions of the taste buds and cause nervous impulses 
 to start inward along the cranial nerves of taste. These 
 
 Fio. 134, A circumvallate papilla. (After Testut.) 
 
 impulses eventually reach the centres in the cortex of 
 the brain and give rise to sensations of taste. 
 
 Kinds of taste. — Careful experiments made by dry- 
 ing the tongue and applying to its surface solutions 
 of different substances, have shown that there are really 
 four different tastes, each, of which probably has a dif- 
 ferent kind of end organ. These tastes are sweet, bitter, 
 sour or acid, and salty. The tip of the tongue is more 
 sensitive to sweetness, the sides to acidity, and the back 
 to bitterness. Sweetness is the most powerful of the 
 tastes and is able to overcome the others, l^'or this 
 reason, we take bitter medicine in a sweet syrup and 
 pat sugar into lemonade. 
 
 THE SENSE OF SMELL 
 
 Structure. — The sense of smell is closely associated 
 with that of taste. The surface which contains the cells 
 sensitive to odors, the olfactory cells, is situated in the 
 
SMELL 
 
 251 
 
 upper part of the cavity of the nose, one half being on 
 each side. It is made up of elongated cells, among 
 which are the pointed olfactory cells, containing the 
 
 'Skull bones 
 
 Ollaclorv bulb 
 Oifjctory nerve 
 Olfactory nerve branches 
 
 I ji,<ji^E/^^^*^: '- Nf'^c ganglion 
 
 ^~ '~'''' -s— Nerve supplying nose 
 
 palate and pharynx 
 ^v Eustachian tube 
 
 Hard palate 
 Soft palate 
 
 Fig. 135. Diagram allowing distribution of olfactory nerve on outer side of nasal 
 cavity. 
 
 ends of the olfactory nerves. "When stimulated by 
 volatile particles 'of substances, the olfactory cells start 
 the nervous impulses which pass up the olfactory nerves 
 to the higher centres in the cortex, thereby producing 
 sensations of odore. 
 
 Influence upon taste. — How much the sense of smell 
 has to do with the flavor of food is readily appre- 
 ciated when the nose is closed by pinching the nostrils 
 or by a head cold. Even such a highly flavored food 
 as an onion cannot be distinguished under these circum- 
 stances from a turnip; and other foods, except those 
 
252 
 
 THE SPECIAL SENSES 
 
 which are sweet, bitter, sour, or salty, become similarly- 
 tasteless. 
 
 THE SENSE OF HEARING 
 
 External ear. — Much more complex than the mechan- 
 isms for touch, taste and.smell, is that of hearing. Within 
 
 Columnar (.mucous) cell 
 Olfactory cell 
 
 Branching of olfactory 
 nerve fibre to 
 supply the cells 
 
 A B 
 
 Fig. 136. Cells from the olfactory surface : A, of the frog ; B, of man. 
 
 each of our ears there is a small complicated structure, 
 which is sensitive to sound vibrations. Although it con- 
 tains thousands of nerve fibres and terminals, it is only 
 the size of a large pea. It is well protected by its posi- 
 tion within one of the hardest bones of the skull and 
 the sole entrance to it from without is a crooked passage, 
 the auditory canal. This canal leads from the vibration- 
 
HEARING 
 
 253 
 
 gathering shell-like external car to a membrane, the ear 
 drum or tympanum, which entirely shuts off the inner 
 end of the auditory caual from the next cavity, the 
 middle ear. The tympanum has a diameter of about a 
 
 Auditory 
 nerve 
 
 Eustachian tube 
 
 Fig. 137. Diagram of a section through the ear, showing the arrangement of 
 its various parts. 
 
 quarter of an inch, is thin, and receives the vibrations 
 of the air in the canal. 
 
 Middle ear. — Imbedded in the tjnnpanum is one end 
 of a tiny bone, the hammer, which is the first of a train 
 of three bones crossing the cavity of the middle ear. 
 These bones, the hammer, anril and stirrup, are called the 
 ear bones. The innermost one, the stirrup, lies against 
 a thin membrane which closes a small opening, the so- 
 called oval window. This window opens into a bony 
 case which contains the real or inner ear. The vibrations 
 of the tympanum are thus transmitted by the ear bones 
 to the inner ear. 
 
254 THE SPECIAL SENSES 
 
 Eustachian tube. — The cavity of the middle ear is 
 connected with the pharynx by a passageway called the 
 Eustachian tube, through which it is filled with air 
 under the same pressure as the outside air. Strain of 
 the delicate tympanum by air pressure from the out- 
 side is thus avoided, and it is free to move with 
 the slightest air vibration. Sometimes, however, the 
 Eustachian tube is closed by the swelling of the mucous 
 membrane of the pharynx. The air supply of the inner 
 ear is thus cut off and the air which it already has is 
 gradually absorbed. As a result, the pressure of air 
 upon the inner surface of the tympanum becomes less 
 than that upon its outer surface ; the tympanum is conse- 
 quently pushed inward and loses some of its sensitiveness 
 to air vibrations. This is the reason why with a head cold 
 we may become temporarily more or less deaf. If the 
 Eustachian tubes are permanently closed for any reason, 
 chronic deafness results. 
 
 Inner ear. — The bony case in which the inner 
 ear lies is coiled like a snail-shell and is therefore called 
 the cochlea or iony labyrinth. The cochlea contains a 
 small amount of fluid, the perilymph, and floating in 
 this fluid, an inner case, shaped like itself but made 
 of membrane, the membranous labyrinth. The en- 
 trance to the membranous labyrinth for vibrations is 
 through the oval window against which, as we have 
 seen, the stirrup lies. The vibrations of the tympanum 
 are thus transmitted through the ear bones, through 
 the oval window, through the perilymph to the mem- 
 branous labyrinth. 
 
 Receiving apparatus. — The membranous labyrinth is 
 itself filled with a thin watery fluid, the endolymph. 
 Stretched across it lies the receptive membrane for the vi- 
 brations, the basilar membrane, to which the vibrations of 
 
THE EAR 255 
 
 the air are transmitted by the tyniptuuini, the ear bones, 
 the perilymph, the labyrinth and the endol.Ninph. The 
 basilar membrane is a lony; strip of thin membrane, 
 broader at one end than at the other, coiled in a spiral 
 form, and stretched between the bony walls of the laby- 
 rinth. Its tension and width are so varied that some 
 portion of its length between the broad end and the 
 nai-row tip will vibrate sympathetieally with all rates 
 not lower than twenty per second and not higher than 
 thirty thousand. 
 
 Sensation of sound. — Standing upon the basilar 
 membrane are various complicated structures. Prom- 
 inent among these are certain slender highly sensitive 
 cells, the axditorii cells, in which the fibi-es of the audi- 
 tory nerve start. "Whenever any part of the basilar 
 membrane is set into vibration, the auditory cells of 
 tJiat part are stimulated to activity. As a result, nerv- 
 ous impulses start inward along the nerve fibres of 
 the auditory nerve to the brain cells in the cortex, and 
 a sensation of sound results. If the vibrations of the air 
 are made up of a number of different rates of vibra- 
 tion, as is usually the case, not one but several regions 
 of the basilar membrane will be agitated, and a corre- 
 sponding number of nervous impulses and of blending 
 sensations will result. 
 
 SEXSK OF EQUILIBRIA 
 
 Semicircular canals. — In close connection with the 
 internal ear are found the semicircular canals. In each 
 ear, there are three of these canals filled with fluid. 
 They are so arranged that any movement of the head 
 will cause movement of the fluid over the surface of the 
 ,wall containing it. This makes the fluid press upon 
 
256 THE SPECIAL SENSES 
 
 the hairs of sensitive cells lying in the wall. Nervous 
 impulses are thereby started which result in our hav- 
 ing a sense of the direction and rapidity of the move- 
 ment of the head. 
 
 THE SENSE OF SIGHT 
 
 Nature of light. — Tiight, upon which our sensations of 
 sight depend, resembles sound in that it is a form of 
 vibration. The vibration, however, is not of the air 
 but of the ether, a gas so extremely thin that it pene- 
 trates bodies and fills all space. Light itself in all its 
 variety of color consists merely of vibrations of ether 
 which pass from hirainous objects at varying rates of 
 speed. Ordinarily, it is a mixture of many different 
 rates which blend together to give us white light. When 
 one rate of vibration prevails in the light which reaches 
 the eye, we perceive the color .characteristic of that 
 rate, as red when the rate is three hundred and ninety- 
 two trillions of vibrations per second, or violet when 
 it is seven hundred and fifty -seven trillions.^ 
 
 General structure. — The mechanism of the eye con- 
 sists essentially of two parts. The first part is an optical 
 instrument corresponding to a camera with lens and 
 screen. Rays of light from external objects are focused 
 upon a screen, the retina, at the back of each eye. The 
 second part is a nervous mechanism in the retina by 
 which the rays of light thus focussed give rise to nervous 
 impulses, and these in turn to our sensations of sight. 
 
 ' The colors lying between the two extremes of red and violet are 
 orange-red, orange, orange-yellow, yellow, yellow-green, green, green- 
 blue, blue and blue-violet. Vibrations which are slower than those 
 giving red or faster than those giving violet are not perceived by 
 the eye, although experiments have proved that they exist. 
 
STRUCTURE OF EYE 
 
 257 
 
 Detailed structure. — The eye is an elongated ball 
 about an inch in diameter, which is covered by a tough 
 coat made up of several membranes. The outer mem- 
 brane forms the white of the eye and covers it except in 
 front, where a transparent membrane, the cornea, per- 
 
 Antdnor cKamber ^ 
 
 (ai^ueous humor 
 
 Iris J' ^ 
 
 , :■■ -■»** 
 Oliar,' muscle 
 
 SjSpen5or>' ligament 
 
 Lens (_^th[n — 
 
 its capisul;'^ 
 ToKion of — - 
 
 mierral ^ 
 iTectus musde 
 
 Vitreous hurnor- 
 
 Oplical a-xis- 
 ( line CI* vision) 
 Layer of 
 
 Central Ar1er> 
 Optic nene 
 
 Fig. 138. The right eye cnt horizontally, viewed from above (somewhat diagram- 
 matic). 
 
 mits light to enter it. After passing through the cornea, 
 the light enters a transparent liquid, the aqueous humor, 
 which fills the front of the eyeball. It then passes 
 through a hard transparent mass, the lens, into a stiff 
 jelly-like transparent substance, the vitreous humor, 
 
258 THE SPECIAL SENSES 
 
 which fills the larger part of the eyeball. It next falls 
 upon the sensitive screen, the retina, which forms the 
 lining coat of the eye. 
 
 Formation of image. — ^In order that we may get a 
 perfect image of an object, it is necessary that the eye 
 should act as a lens to focus upon the retina rays of 
 
 Fig. 139. The formation behind a convex lens of a dlminislied and inverted 
 image of an object placed in front of it. 
 
 light from the object. The cornea receives the rays and 
 makes them converge enough to bring them to a focus 
 behind the retina. The lens then completes the work 
 by focusing them upon the retina. For this purpose, the 
 lens miist be relatively flat if the rays do not require 
 much bending because they come from a distance, or 
 quite convex if they come from nearby objects and so 
 require considerable bending. 
 
 Adjustment of lens. — To enable the lens thus to 
 adjust itself, there is a circle of elastic fibres which 
 radiate out from its edges. These are constantly pulling 
 the edge of the lens outward and thereby flattening its 
 front surface. In addition to the elastic fibres, there is 
 a ring of muscle fibres which encircles the edge of the 
 lens. These muscle fibres, by contracting, relieve the lens 
 of the pull of the elastic fibres and so make it more con- 
 vex. The muscle fibres are controlled automatically 
 
THE LENS 
 
 259 
 
 through their nerves, so that any object upon which we 
 direct out attention is antomatioally brought into focus. 
 
 Flexibility of lens. — In childhood, the lens is very 
 tlexible and can be made so convex as to focus objects 
 
 Pia. 140. Diagram illustrating the effect of a convex len* upon rays of light : A, 
 when parallel rays are brought to a focus (;wtncij«rf/(XM/s); B, when rays from 
 a near object are brought to a focus beyond the principiil focus ; C, wlieu rays 
 from an object nearer than the principal focus continue diver^ut. 
 
 biit three or four inches from the eye. As one grows 
 older, the lens gradually loses its flexibility and tends 
 to become rigid in its flattest form. As a result, we 
 gradually lose tlie power of seeing near objects clearly 
 because their light rays are not brought to a focus 
 on the retina. Ultimately, between the ages of thirty- 
 five and fifty years, a normal person is usually unable 
 to read or thread a needle without strain. He is there- 
 fore forced to aid his eyes liy the use of glass lenses, 
 which by their convexity assist the cornea and lens in 
 
260 THE SPECIAL SENSES 
 
 bringing the rays of light from nearby objects to a focus 
 upon the retina. 
 
 Far- and near-sight. — Flatness of the lens, which 
 brings the rays of light from near objects to a focus 
 beyond the retina, gives rise to far-sight. It can be 
 
 Fia. 141. Section of front part of eyeball showing the change in the fonn of the 
 lens when near and distant objects are looked at. a, c, ft, cornea ; A, lens when 
 near object is looked at ; B, lens when distant object is looked at. 
 
 corrected by convex glasses, which make up the deficiency 
 of the eye and bring the rays to a focus on the retina. 
 In case the eyeball itself is so long that the rays of light 
 from distant objects are focused before they reach the 
 retina, we have a condition of near-sight. Near-sight 
 requires for its correction a concave lens, in order to 
 throw the focus back to the retina. While some eyes 
 are near-sighted from birth, others acquire this con- 
 dition by being used too much upon near objects in 
 childhood. Too early and too long continued attempts 
 at sewing and reading are often responsible for the 
 development of this unfortunate condition. 
 
 Adjustments to intensity of light. — Varying dis- 
 tance is not the only condition to which the eye must 
 be adjusted. Light itself is ever varying in intensity, 
 and the eye must be at once so sensitive as to see ob- 
 
THE RETINA 
 
 261 
 
 jects in a dim light and so protected that it will not 
 be injured by a bright light. To adjust the eye to the 
 strength of light, there is stretched in front of the lens 
 a muscular curtain, the iris, which gives to the eye its 
 characteristic color. In the centre of the iris is an 
 opening, the pupil, through which all the light which 
 enters the eye must pass. The iris is capable of con- 
 tracting to make the pupil smaller or of dilating to 
 make it larger. In this way, jiist enough light is admit- 
 ted to the interior of the eye to give the best vision, 
 but not enough to injure its more sensitive portions. 
 
 Purpose and structure of retina. — ^When the rays of 
 light from objects are focused upon the retina and have 
 
 Fio. 142. Diagram of a section of the retina, showing groups of rods and cones 
 and tteir nerve connections. 
 
 built upon it, as upon a screen, a reduced and inverted 
 picture, no more has been accomplished than is done by 
 the lens and screen of a camera. It still remains to 
 translate this image on the retina into sensations of 
 sight. The retina consists of several layers of nerve 
 
262 
 
 THE SPECIAL SENSES 
 
 and other cells with their branches, a layer of special- 
 ized structiires called rods and cones, which are thought 
 by many to be the real terminals of the nerves, and, 
 deeper still, a layer of dark coloring matter which pre- 
 vents the light from entering the eyeball anywhere 
 except through the pupil and also shuts off reflections 
 within the eyeball itself. 
 
 Optic nerve. — The nerve fibres from all points of the 
 retina pass over its inner surface and converge at one 
 point where they unite to form the optic nerve. The 
 optic nerve then passes out through the wall of the 
 
 eyeball to the brain. 
 At the point of exit 
 of the nerve there is 
 no retina, and rays 
 of light falling up- 
 on it excite no ner- 
 vous impulses. It is 
 therefore called the 
 blind spot. Since the 
 blind spot in the 
 right eye cuts out a 
 portion of the field 
 of vision to the right 
 of the centre, and in 
 the left eye to the 
 left of the centre, we 
 can see with one eye 
 what we cannot see 
 with the other. Vision 
 with two eyes is not, therefore, impaired. 
 
 Sensation of sight. — The excitation of the retina by 
 the exceedingly rapid vibrations which constitute light, 
 excites the rods and cones and the nerve structures 
 
 Fi». 143. The right retina as it would be seen 
 if the front part of the eyeball with tlie lens 
 and vitreous humor were removed. The 
 white disk to the right marks the entry of the 
 optic nerve (blind spot); the lines radiating 
 from this are the retinal arteries and veins. 
 The small central dark patch is the yellow 
 spot, the region of most acute vision. 
 
ACUTENESS OF VISION 263 
 
 connected with them into activity. As a result, multi- 
 tudes of nervous impulses pass through their nerve fibres 
 and thence along the optic nerve to the centre of sight 
 
 Fio. 144. To And blind spot, hold in front of right eye and close left eye; looking 
 steadily at crose, move book nearer and farther from eye until white circle is 
 made to disappear. 
 
 in the cortex of the brain. Here they cause the activity 
 of the nerve cells and as a result we have sensations 
 which we call sight. 
 
 Acuteness of vision. — When we consider the extent 
 of the field of vision pictured upon the small surface 
 of the retina, the delicacy of detail which we perceive 
 seems marvellous. For example, a white thread can be 
 seen on a black blackground at a distance of sixty feet. 
 Since the combiaation of cornea and lens is equivalent 
 to a lens of about three-quarters of an inch focus, the 
 image of the white line upon the retina must be about 
 one two-thousandth of a millimeter in diameter. The end 
 organs of the nerves upon which the image falls must 
 therefore be of extreme fineness and efficiency, 
 
 Defects of vision. — Although the eye serves us so 
 wonderfully well, yet as an optical instrument it has 
 certain marked defects, which are more exaggerated in 
 some persons than in others and are especially noticeable 
 in those who continually use their eyes for close work. 
 In a faint light, as in twilight, when the pupil is large, 
 
264 
 
 THE SPECIAL SENSES 
 
 so much of the lens is uncovered that its defects due 
 to irregularities of curvature and of adjustment be- 
 come apparent and we can no longer see clearly. 
 
 Eye strain. — As long as the adjustments of the eye 
 are reflex and take place accurately enough to give a 
 fair degree of vision, they ordinarily give rise to little 
 or no trouble either directly or indirectly. When, how- 
 ever, they are put to severe use, the attempt to make, 
 in spite of their defects, the constant and complete 
 adjustment necessary for good vision gives rise to eye 
 strain. Eye strain seldom or never shows itself by dis- 
 comfort about the eyes, but rather causes such symp- 
 toms as nervous irritability, headache, dizziness and 
 nausea, which for years may fail of being traced to the 
 eyes. As a result, the ' nervous system often suffers 
 seriously, even to the point of a breakdown. 
 
 Astigmatism. — In addition to far- and near-sight, 
 another defect which causes much eye strain is astig- 
 
 FiG. 145. If certain of the lines or portions of tlie circles appekr blacker than 
 ollierB, astigmatism is present. The test should be made by shutting one eye 
 and then the other. 
 
 ■matism. Astigmatism results when either the cornea or 
 the lens has not a perfectly spherical surface but tends 
 to become curved in one diameter more than in another. 
 
BINOCULAR VISION 
 
 265 
 
 Some rays axe brought to a focus before others and a 
 partial blurring results. Astigmatism may be remedied 
 by glasses of a slightly cylindrical form, which make 
 good the general defect of curvature in the lens. 
 
 Perception of distance. — For the perception of color 
 and form, one eye is enough, but to accurately deter- 
 mine the distance of objects, two eyes ai-e necessary. 
 ^Yith two eyes, we look a little farther around an ob- 
 ject on each side and thereby make it stand out in relief. 
 Besides this, since near objects require a greater con- 
 vergence of the eyes' than distant objects, the anioimt of 
 movement necessary to make the convergence helps us 
 to estimate the distance. 
 
 Binocular vision. — That we may see but one object 
 with the two eyes instead of two. it is necessary, fii-st, 
 that the eyes should be controlled so as to converge ac- 
 
 PuSey of upper rotating rrL^ci^ 
 "Rart of skull iQe s.-vJ;etv 
 Musdc of upper hj 
 
 Uppter rotatir^s 
 
 riuscle himing eve up^^i"^ 
 Muscle turning ^ 
 Muscle turning eye 
 
 Bone 01' s^ve' 
 Optic nene 
 LoTer rotating ""< 
 
 ^^557 
 
 FiQ. U6. The eye and its muscle:?. 
 
 curately upon an object. To accomplish this, there are 
 muscles which pass from the sides of the eyeballs at the 
 front to the back of the eye-sockets. By their contrac- 
 tion, they are able to move the eyes so that they can con- 
 verge upon an object in any direction. It is further 
 
266 THE SPECIAL SENSES 
 
 necessary that the retinas of the two eyes should corre- 
 spond so exactly that the corresponding fibres in each 
 retina may receive the light from exactly the same 
 point in the object. The nervous impulses will then 
 blend in the brain to form a single sensation, that is, 
 we shall see but one object in spite of the two images 
 on the retinas. 
 
 Double vision.' — Where the eyes fail to work together 
 and two images are seen, the fault is probably due to 
 an imperfect control of the convergence of the eyes by 
 their muscles. Extreme instances of this are seen in 
 cross-eyes and in diverging eyes. In all such eases, con- 
 siderable nerve strain may result from the attempt to 
 make the images coincide, and the defect should there- 
 fore be remedied by glasses, or, in more extreme cases, 
 by operation upon the eye muscles. 
 
 EXPERIMENTS AND DEMONSTRATIONS 
 Dermal Senses 
 Materials: Drawing compasses (any form, not too sharp, 
 may be used) ; scale graduated to millimeters; vessels of cold, 
 lukewarm and hot water ; fine horsehair or straight human hair ; 
 pencil; forceps. 
 Experiments (2 students working together) : 
 
 1) Take straight piece of hair in forceps and, by ascertain- 
 ing greatest length which will give rise to sensation of pressure, 
 determine relative sensitiveness of palm; back of hand; fore- 
 head. 
 
 2) Determine least distance that two points of compasses 
 may be separated and still be recognized as two when applied 
 to finger tip ; back of hand ; back of neck ; tongue, etc. 
 
 3, a) Determine sensations caused by slight pressure of pen- 
 cil point on back of hand. 
 
 b) Determine if cold points are constant in their position by 
 testing from day to day.' 
 
 ' Care should be taken not to exhaust the sense organs by over- 
 stimulation. 
 
EXPERIMEXTS 267 
 
 e) Study similarly painful points and warm points, using a 
 heated point of peaicil or wire for latter. 
 
 4, a) Put finger of right hand into warm water and finger of 
 left hand into cold water. Note immediate sensations; changes 
 in sensations after fingei"s have remained some time in water. 
 
 h) "Withdraw fingers and plunge hoth immediately into ves- 
 sel containing lukewarm water. Compai-e sensations of two 
 fingers. 
 
 Taste and Smell 
 
 Materinh: Sugar: salt; dilute vinegar; quinine; dilute am- 
 monia, one drop of strong ammonia in glass of water; cabbage; 
 onion; cari-ot. 
 
 Ex-periments (2 students, one as blindfolded subject, other as 
 expei'imenter) : 
 
 1) Dry tongue, and determine taste of dry sugar. Compare 
 with taste of moist sug'ar. Determine most sensitive part of 
 tongue. 
 
 2) Test similarly with salt and other substances, closing nose 
 to avoid odor. 
 
 3) Determine which have odor. 
 
 4) Determine relative proportions of taste and odor. 
 
 Hearing 
 
 Materials: Tuning fork and its resonance chamber; violin 
 or stretched cat-gut; violin bow; [apparatus for manometric 
 flame] . 
 
 1) Pluck \-iolin string and note dependence of sound upon 
 vibration. 
 
 2) Strike tuning fork and note dependence of volume upon 
 amplitude of \-ibrations of prongs. 
 
 * 3) Place finger on middle of vioUn string, thus doubling rate 
 of \-ibration. Pluck string and compare pitch with that of 
 whole string. 
 
 4) Strike tuning fork and hold prongs over its resonance 
 chamber. 
 
 5) Test acuteness of hearing by determining how far off a 
 watch can be heard. 
 
 6) Test accuracy of sense of direction as determined by hear- 
 
268 
 
 THE SPECIAL SENSES 
 
 Oas chamber 
 Air chamber 
 Vibrating membrane 
 
 Revolving mirror 
 
 Fig. 147. Apparatus for analyzing ijoand by means of manometric flame. 
 
 Image in mirror 
 No sound 
 
 Image produced^ 
 by tuning-fork 
 pitch low C.i-^— 
 
 By tuning-forlc, 
 middle C. 
 
 By atjove forl^s 
 .in unison 
 
 By singing 
 vo*el E, pitch 
 middle C ■ 
 
 Wi 
 
 By vowel 
 middle C. 
 
 Fig. 148. Analysis by means of manometric flames, of the vibrations producing 
 certain sounds. 
 
EXPERIMENTS 269 
 
 ing, by having blindfolded subject point in direction of sounds 
 heard. Close one ear and repeat. 
 
 [7) Demonstrate graphically the varying characteristics of 
 sound waves by projecting tones of voice and cornet into speak- 
 ing tube of apparatus, at same time that revolving mirror is 
 whirled to separate the tongues of flame produced by sound 
 waves.] 
 
 Vision 
 
 Materials: Color top with color disks; set of worsteds for 
 testing color blindness; small glass prism, 60° angles; camera 
 with ground glass, or ovdinary magnifying glass with cardboard 
 diaphragms having central opening's of %, 1,2 and 1 in.; 
 spectacle lenses, couoa^e and convex of varying strengths; 
 caudle ; screen, a piece of cardboard placed in a vertical position 
 on a base : [sharp scalpel ; curved scissors ; forceps] . 
 
 1) Demonstrate formation of image by lens. Use camera 
 with ground glass, or ordinary magnifying glass, and receive 
 image on paper. Note a) Relative sizes of images of near and 
 far objects, b) Relative lengths of focus for near and far 
 objects. 
 
 2) Test effect of different-sized diaphragms on brightness 
 and sharpness of images. 
 
 3) Analyze white light (sunlight) by means of prism throw- 
 ing spectrum on white paper. 
 
 4) Mix colors by means of color top : 
 
 a) Black with white in different proportions (grays). 
 
 b) Various colors with white (tints). 
 e) " " •• black (shades). 
 d) " '■ " each other. 
 
 5) Color blindness: Give to pupil a set of standard colore 
 and their tints and shades. Hold up in succession different 
 colors and ask for selection of all pieces resembling them. 
 
 ■ 6) iXear-sight : Place candle on table; two feet distant, set 
 screen. Place magnifying glass between, so as to throw focus 
 on screen. Move screen away from lens until image is blurred, 
 to imitate the elongated eye of near-sight. Take small piece of 
 paper and locate focus by moving it between lens and screen 
 until image on it is distinct. 
 
2Vo THE SPECIAL SENSES 
 
 Apply in front of magnifying glass the proper spectacle lens 
 to bring focus to screen. 
 
 7) Far-sight: Place candle, glass and screen as in 6), for 
 focusing on screen. Move screen toward lens until image is 
 blurred, to imitate the focal condition of far-sight. 
 
 Apply in front of magnifying glass the proper spectacle lens 
 to bring focus to screen. 
 
 8) Sharpness of vision: a) Determine farthest distance at 
 which white thread on black card can be seen, using one eye; 
 using both eyes. 
 
 b) Determine farthest distance when card is 10° and 20° 
 from line of vision. 
 
 9) Change in iris (2 working together) : a) Have subject 
 sit facing window; cover one eye with hand for 1 min. 
 Quickly uncover eye and note changes in pupil. 
 
 b) Compare size of pupil when looking at distant object 
 with that when looking at object 6 in. away. 
 
 10) Blind spot: Determine distance from eye at which large 
 spot on p. 263 disappears when one looks at cross with right 
 eye. 
 
 11) Accommodation : Determine greatest and least distances 
 at which objects can be seen clearly with left eye; with right 
 eye. 
 
 12) Binocular vision: a) Hold 2 pencils vertically in front 
 of eyes, one at distance of 1 ft., other at 2 ft. When you look 
 at either one with both eyes open, what is appearance of other, 
 and why ? Show by diagram. 
 
 b) Under what conditions do you see "single" when using 
 both eyes? 
 
 13) Determine movements of eyes in changing from far to 
 near vision. 
 
 14) Test visual judgment of 
 
 a)- Sizes of disks of equal diameters but of different colors 
 (black on white, white on black, red on white, etc.). 
 
 b) Lengths of vertical and horizontal lines which appear of 
 same length. 
 
 c) Two halves of a line, one of which is crossed by several 
 short lines. 
 
 15) Fatigue of color sense: a) Place a piece of bright red 
 paper upon sheet of white paper and gaze at it steadily for 
 
EXPERIMENTS 271 
 
 half a minute. Then look steadily at a white surface and note 
 any color changes which appear upon it.' 
 
 b) Repeat using other coloi-s. 
 
 [16) Anatomy of eye: a) Demonstrate muscles of sheep's 
 eye, coats, optic nerve, cornea, iris and pupil. 
 
 b) Cut eye open with scalpel from front to back. Dem- 
 onstrate aqueous humor, anterior chamber, iris, lens, ciliary 
 process, vitreous humor, retina and blind spot (optic nerve).] 
 
 ' The color whicli appears is complemcniarn to the original color. 
 V^liite is made up of the three fundamental colors red, green and 
 violet. When the retina is fatigued for any one of these, the other 
 two preponderate and tinge the white. 
 
CHAPTER XXIII 
 
 THE CARE OF THE SENSE ORGANS 
 
 Means of protection. — The sense organs because of 
 their delicacy have been given careful protection by 
 nature whenever possible. This protection is usually 
 afforded by their location, as in the case of the organs 
 of smell, of taste and of hearing. In the case of the eyes, 
 however, the range of vision is so important that they 
 must be located on the surface of the body. They there- 
 fore hare a special covering, the lids, which act as shut- 
 ters, to be opened for vision and closed for protection. 
 
 Care of the ear. — The ear would seem to be ade- 
 quately guarded by its location in a very deep bone of 
 the skull, where it can be reached only through a long 
 and crooked canal. This canal, however, must be kept 
 open so that sound waves may pass through it, and thus 
 it is the ear's weak point. Through the canal insects 
 may pass and objects may be thrust ^ in spite of the 
 protection afforded it by the growth of hairs. Insects 
 are easily removed by a drop of oil or water. The en- 
 trance of objects we ourselves can control. The drum 
 is so delicate that, were it not for the sake of cleanli- 
 ness,' we might lay down the rule that we should permit 
 nothing whatever to be introduced into its canal. 
 
 ' Recent investigations have shown that many prairie animals, 
 as wolves and coyotes, are deaf because of injury to the ear by the 
 entrance through the canal of the heads of certain grasses. These 
 have actually penetrated the drum and caused an inflammation 
 which has destroyed the inner ear. 
 
 373 
 
CAKE OF THE KAR 2/3 
 
 Method of cleaning.— To cleau the canal of the ear, a 
 TOunded object such as the closed end of a hairpin, 
 sliould be covered with several folds of soft cloth mois- 
 tened in soapy water. This should be rotated in the 
 canal so gently that there is no feeling of pressure. No 
 attempt to remove the deeper layei-s of wax should be 
 made, since in normal quantities it is beneficial, not 
 harmful. "When excessive, it usually works out of itself 
 and cjiu then be easily reuuned. 
 
 Removal of objects. — When an object has become 
 lodged in the canal, no attempt to remove it should be 
 made, since even a slight touch may drive it through 
 the drum. A physician should be consulted immediately. 
 
 Earache. — Another danger to which the ear is ex- 
 jiosed arises fnim the necessity for a canal to the middle 
 ear from the pharynx. This canal may permit inflam- 
 mation of the membrane of the nose and throat to spread 
 TO the middle ear. Such an intlanmiation of the Eusta- 
 chian tube closes it. with the result that the fluid caused 
 by the inflammation swells the drum out and may ulti- 
 mately bui-st through it. The earache which accompanies 
 this inflaimnation should lead one to consult a physician 
 at once. 
 
 Effect of noise. — ^Rlows upon the ear and loud noises, 
 such as the explosion of firearms near the ear, are an- 
 other source of danger, since they may bring such a 
 sudden pressure upon the ear driun as to burst it. 
 
 Eyes. — The organ of sight, being at once the most 
 delicate and the most exposed of the special organs, 
 requires the most care fi-om us. The dangere to which 
 the eyes are exposed are manifold. Dust,^ cinders and 
 
 ^ The irritation due to dust can be relieved by dropping into the 
 eyes a small amount of ii weak solution (10 grs. to 1 oz. pure 
 water) of boraeie acid. 
 
274 THE CARE OF THE SENSE ORGANS 
 
 insects find an easy entrance to them, in spite of the 
 quick closure of the eyelids.^ The light may be so strong 
 as to irritate them or so weak as to make the effort to see, 
 a strain. The nature of the work they are called upon 
 to do may be too exacting and the hours of work too 
 long. 
 
 Removal of objects. — Dust, cinders and other foreign 
 bodies are usually washed out by the copious flow of 
 tears which their irritation causes, especially if the lid 
 is raised so as to free the object from the pressure be- 
 tween lid and eyeball. If the object is not thus removed, 
 it is a simple matter to pull down the lower lid, in case 
 it is lodged there, and wipe it off with the moistened 
 corner of a clean handkerchief. If it is under the upper 
 lid, the lid can be turned back by taking the eyelashes 
 between thumb and finger, raising the edge of the lid 
 outward, upward and finally backward, and at the same 
 time pressing down against the centre of the lid with 
 some slender object, as a match, in order to make the 
 inner surface of the lid turn outward. The object is 
 thus exposed to view and can be removed with the moist 
 corner of a handkerchief. If, in spite of these attempts, 
 the object still remains, a physician should be consulted. 
 
 Effect of strong light. — The eye is protected against 
 too strong a light by the reflex turning of the head 
 or shutting of the lid, which gives the iris time to con- 
 tract and thus make the pupil small. Any light which 
 remains disagreeably bright after this adjustment harms 
 the eye and should be carefully avoided. To look con- 
 tinuously at any bright object, as a lamp or an electric 
 
 ' The muscles controlling the eyelids act more quickly than any 
 others in the body. It takes only about 0.05 of a second to close 
 the lid. If any object touches the tip of an eyelash, therefore, it 
 can get into the eye only if it is going faster than 10 feet per 
 second. 
 
CARE OF THE EYES 275 
 
 light, may result in serious damage to the eye. To look 
 at the sun steadilj^ may actually destroy the spots on 
 the retinas on which its rays are focused. 
 
 Weak light. — Dim light is not in itself harmful to 
 the eye. Only when we attempt to read, sew, or do 
 other fine work, does it do harm. Under these condi- 
 tions, the iris is so wide open that the imperfections 
 of the cornea and lens make it much more difficult to 
 see clearly and therefore add greatly to the strain. 
 
 Proper use. — Under the present conditions of civil- 
 ized life, so much work is exacted of the ej^es that they 
 should be favored in every way possible, especially dur- 
 ing the developing period of childhood. Too early or 
 too long continued use of the eyes for near and fine work, 
 as reading, writing and sewing, should be avoided, since 
 it often produces near-sight. Such work should be done 
 only under the most favorable circumstances. The light 
 should be neither too bright nor too dim; and it should 
 come from the left, in order not to fall directly into the 
 eyes nor to cause a reflection from the page into the 
 eye, as well as to avoid the shadow of the active hand 
 upon the work. The eyes should also have frequent rest 
 by being closed or by being allowed to look at distant 
 objects, that the muscles of accommodation may be re- 
 laxed. Improper use of the eyes often shows itself, not 
 by discomfort of the eyes themselves, but by headache, 
 sleeplessness, nausea and other forms of distress. Under 
 such circumstances, therefore, the eyes should be tested 
 by an oculist to learn if they are at fault. 
 
CHAPTER XXIV 
 THE VOICE AND SPEECH 
 
 Sound as a means of communication. — Because 
 sound penetrates space so rapidly and is so easily pro- 
 duced, it is used by many kinds of animals as a means 
 of communication. The sounds thus used range from 
 the shrilling of insects through various inarticulate coo- 
 ings, gruntings and squealings up to the articulate 
 speech of human beings. The mechanism by which these 
 sounds are produced varies markedly in different ani- 
 mals. Many insects, as the katydid, use their wings 
 by rubbing them against the sides of their bodies. 
 Others, as the locust and cricket, use their legs in a 
 similar fashion. ]\Iost of the higher animals, however, 
 including the birds, use for this purpose the air cur- 
 rents produced by respiration. For this, they have a 
 special organ developed in the trachea for the produc- 
 tion of voice, the larynx. 
 
 Larynx and vocal cords. — The larynx is situated in 
 the tapper part of the trachea, and, as we have seen, is 
 a hollow tube or box made up of several pieces of 
 cartilage, through which the air passes on its way to 
 and from the lungs. Across the larynx are stretched 
 two membranes known as vocal cords. The vocal cords 
 are attached in front and at the sides to the larynx. 
 At the back, they are attached to two small pieces of 
 cartilage which are freely moved by muscles. For the 
 production of voice, these pieces of cartilage swing al- 
 
 376 
 
THE LARYNX 
 
 277 
 
 most togetlier and carry with tliem the vocal cords, 
 which are thus stretched tightly across the larynx. In 
 this position, tliey nearly close the air passage through 
 the trachea and are made to vibrate by the air as it 
 passes over their edges ou its way from the lungs. These 
 
 Vccai cc-i 
 
 CncaJ cartilage 
 
 Fa'^<; \-ccj! cc^ds 
 
 Fie. 149. View of laryirs from above, showing position of vocal cords. 
 
 vibrations cause the air in the larynx to vibrate, and 
 its vibrations are directly transmitted by the air in the 
 throat and mouth to the external air. All the vibrations 
 of which the vocal cords are capable are of a rapidity 
 that comes within the range of the ear and they are 
 therefore perceived by us as sound. 
 
 Volume. — The loudness, or volume, of the sound pro- 
 duced by the vocal cords depends upon the foi'ce with 
 which the air of the lungs is pushed out between them. 
 A gentle voice is the result of very little pressure, 
 whereas a shout requires a sudden vigorous contraction 
 of the expiratory chest and abdominal muscles. 
 
218 
 
 THE VOICE AND SPEECH 
 
 Arytenoid cartilages 
 
 Vocai cords 
 
 Pitch.— The pitch of the voice depends upon the 
 tension of the vocal cords. If they are made very tense 
 by their adjusting muscles, the 
 voice is of high pitch. If, on 
 the contrary, they are but 
 slightly tense, the pitch is low. 
 The range of pitch differs in 
 different individuals. A large 
 larynx with long thick vocal 
 cords results in a deep bass 
 voice ; a smaller larynx with 
 shorter thinner vocal cords re- 
 sults in a tenor voice. In women 
 and children, the larynx is 
 distinctly smaller than in men 
 and their voices are of cor- 
 respondingly higher pitch. In 
 children, as the larynx increases 
 in size, their voices, especially 
 those of boys, become lower 
 pitched. 
 
 Timbre. — The quality, or timbre, of the voice in con- 
 trast to its pitch, depends upon the fact that the vocal 
 cords, like violin and piano strings, vibrate not only as 
 a whole but in halves, quarters and even in shorter 
 lengths. -As a result, the vibration of the whole length, 
 or fundamental vibration, is supplemented by the higher, 
 or overtone, vibrations of the sections. These overtones 
 are octaves of the fimdamental tone. If the vocal cords 
 are smooth and of the same weight and tension, the voice 
 is greatly enriched by the overtones and is musical. If, 
 however, the cords do not vibrate together because of 
 inequality of weight or tension, the vibrations of the two 
 cords do not coincide. In addition, their overtones, not 
 
 Position in 
 
 rapid 
 inspiration 
 
 Fig. ISO. Diagrams showing 
 various positions of tlie vocal 
 cords and their adjustment 
 by the mupcles controlling 
 the arytenoid cartilages. 
 
VOICE 279 
 
 being true octaves, do not blend either with the funda- 
 mental tones or with each other. Under these circum- 
 stances, the voice is unmusical and hnrsh. An inflam- 
 matory condition of the throat, as in a cold, may result 
 in tlie swelling of the vocal cords (laryngitis), which 
 produces the same result. 
 
 Effect of air cavities upon the voice. — It has been 
 found by experiment that the various cavities of the 
 moiith, nose, trachea and lungs have a tendency to act 
 as organ pipes for the reinforcement or increase of the 
 vocal sounds, in just so far as the air within them tends 
 to vibrate in unison with the fundamental vibrations of 
 the vocal cords and of their overtones. In this way, the 
 quality of the voice is made richer and its volume 
 greater. The assistance given by the cavity of the nose, 
 for example, may be readily appreciated by contrasting 
 a person's ordinary voice with the voice produced when 
 the nose cavity is closed by pinching the nostrils or by 
 a head cold. The nasal twang of many voices is due 
 to the fact that the nose is not properly open. 
 
 Vowels. — Besides the increase and reinforcement of 
 the vocal sounds by the air in the various cavities, cer- 
 tain parts of the throat, tongue and lips modify and 
 interrupt the sounds produced. When the air passages 
 are unobstructed so that the movement of the air is 
 continuous, the sounds made are called i-oicels. One 
 can readily observe with a mirror the changes involved 
 in the production of the sounds a, e, i, o and u. 
 
 Consonants. — The consoiianfs, on the contrary, are 
 produced when the air passages are partially or com- 
 pletely obstructed, as by the lips and tongue. If the 
 closure is complete and then is suddenly overcome by 
 air pressure, we get an explosive articular sound, such 
 as is required for the pronunciation of the consonants 
 
280 THE VOICE AND SPEECH 
 
 6, p, i, d, k and g. If the closure is not complete, the 
 result is a hissing sound called an aspirate, as in pro- 
 nouncing /, V, w, s, z, I, sell, til, j, ch and h. Still other 
 sounds, as r, m, n and ng, are produced by the vibration 
 of the tongue or by the resonance of the nose. 
 
 Whispering. — In ivhispering, the larynx is not used, 
 but instead the resonance chambers of the nose together 
 with the articular movements of the lips, tongue and 
 palate, produce the sound. 
 
CHAPTER XXV 
 HEALTH AXD DISEASE 
 
 Health. — We have seen that the ability of our bodies 
 to live and to work depends upon the condition of the 
 millions of cells, the activities of which constitute our 
 life. "When each cell adequately does its share of the 
 work of the body, directed and guided by the nervous 
 system, our physical life runs smoothly and we are said 
 to be in good health. If, on the contrary, any of the 
 cells act sluggishly or fail in any way to do their work, 
 the balanced working of the body as a whole is more or 
 less disturbed, its smooth running ceases and a condi- 
 tion of ill-being or disease exists. 
 
 Conditions of health. — In order that the cells may 
 be in good health, they must inherit a tendency to grow 
 and develop normally and in addition they must be 
 given proper exercise and wholesome conditions. In 
 other words, the body as a whole requires for its per- 
 fect health an abundance of good invigorating exercise, 
 of wholesome food and of pure air. In just so far as 
 any or all of these are lacking, the health of the bodj"^ 
 suffers. Instead of being vigorous and enduring, it is 
 weak and easily succumbs to one or another of the 
 outside influences which stand ready to change weakness 
 into disease. 
 
 Disease. — ^Mienever a tissue is injured or its proper 
 working interfered with, there is said to be disease. 
 Nearly all disease can be traced to some external cause. 
 
 281 
 
282 
 
 HEALTH AND DISEASE 
 
 The cause may be purely mechanical, as in the case of a 
 blow which bruises tissue or breaks bone. It may be 
 chemical, as when a poisonous gas is inhaled or a poison 
 is eaten or drunk. Or it may be some one of the many 
 forms of disease-producing organisms which invade the 
 body and, if the conditions found there are favorable, 
 multiply rapidly as poisonous parasites. 
 
 Microbes, a cause of disease. — The living organisms 
 which are responsible for our infectious diseases, as 
 
 Lactic acid V ijll 
 
 (b) « ;(; 
 
 Diphtheria /Tfe 
 
 
 \^ 
 
 Pus 
 (m) 
 
 Pus 
 (m) 
 
 Tuberculosis 
 
 Cholera 
 (b) 
 
 Influenza 
 (b) 
 
 Typhoid 
 (b) 
 
 Hay 
 (b) 
 
 .'/'/'! ^' I 
 
 
 , , From mouth 
 
 ?(»M From 
 (%»^^ r ditch-water) 
 
 Fig. 151. Variona forms of bacteria, highly magnified, some of which have flagella 
 or cilia: b, bacilli ; m, micrococci ; s, spirilla. 
 
 consumption, cholera, typhoid fever, diphtheria and 
 malaria, come from either the vegetable or the animal 
 kingdom and are so small that they can be seen only 
 
BACTERIA 283 
 
 with a high-powered microscope. On this account, they 
 escaped detection until recently, and the ravages due 
 to them were ascribed to mysterious or supernatural 
 causes.^ By means of the microscope, aided by modern 
 methods of investigation, we now recognize many of 
 these organisms and associate them with the diseases 
 which they cause. 
 
 Bacteria, protozoa and molds. — Each well-defined 
 infectious disease is in all probability caused by its 
 special microscopic organism, or microbe, although in 
 some diseases the particular kind has not as yet been 
 discovered. The microbes which come from the vegeta- 
 ble kingdom and are minute one-celled plants of vary- 
 ing forms are called bacteria. Those ^^•llich come from 
 the animal kingdom and also consist of single cells of 
 varying forms, are kno^\-n as protozoa.- In addition 
 to bacteria and protozoa, certain higher forms of vege- 
 table and animal life are responsible for disease. They 
 are chiefly certain kinds of molds and various forms 
 of animal parasites, as the tapeworm and trichina. 
 
 Exposure to disease. — To many of these varying 
 kinds of disease-producing microbes we are more or less 
 exposed at all times. They may be present in the dust 
 of the air which we breathe, on the food which we eat, 
 or in the water which we drink. They may lurk upon 
 the skin and in the various cavities of the body. In 
 many cases, ho^\'ever, they are harmless because of the 
 body's ability to destroy them as fast as they find en- 
 trance to it. "UHien the bodj' has been weakened, how- 
 ever, or when the invading microbes are very numerous 
 and virulent, they are able to invade it and to multiply 
 
 ' Defoe's "History of the Plague" gives a vivid picture of the old 
 attitude toward infection. 
 ' Literally, "iirst animal." 
 
284 HEALTH AND DISEASE 
 
 within it. For example, the special baeteriTim of pneu- 
 monia is found in almost every one's mouth, where it 
 remains as a harmless parasite, totally unable to force 
 an entrance into the body because of the vigilance of 
 the white blood corpuscles. When, however, through 
 extreme fatigue or a severe chill, the power of the blood 
 corpuscles is greatly reduced, the bacteria find their 
 entrance but weakly contested by them and so are able 
 to enter and multiply. The result of their activity 
 is the disease of the lungs Iniown as pneumonia. 
 
 Generation of toxins. — Like all imicellular organ- 
 isms, microbes multiply by division. The process of 
 division goes on so rapidly that under favorable cir- 
 cumstances one microbe requires but a few hours to 
 become millions. As they increase in numbers, they 
 generate the most active poisons known, the toxins. 
 These poisons are absorbed by the lymph and carried 
 all over the body, with the result that the body is 
 prostrated. 
 
 Antibodies. — In spite of its prostration, the body sets 
 about to resist the poison of the infecting microbes. It 
 is stimulated to increased activity by the toxins, as 
 shown by the fever which is the usual accompaniment 
 of disease. As a result of this activity, there is devel- 
 oped a substance called antibody or antitoxin, which has 
 a threefold power. It neutralizes the poisonous effect 
 of the toxin ; it weakens the invading organisms ; and . 
 it stimulates the white blood corpuscles to destroy them 
 more actively. If the body is able quickly to develop 
 a large amount of antibody, the disease runs an un- 
 usually short course and is said to be aborted. If, on 
 the contrary, the infecting microbes are of overwhelming 
 strength and numbers, the body has little or no chance 
 to develop' an antibody before it is overcome by the 
 
DISEASE 285 
 
 destruction of its tissue and the poison of the toxia. As 
 a result, it quickly succumbs to the disease. 
 
 Four stages of disease. — The ordinary course of any 
 disease is dependent upon the conditions of the inva- 
 sion and the resistance of the body to it. It has 
 four distinct stages. First there is a period of incu- 
 bation, during which the microbes are gaining strength 
 by multiplying in numbers. This period begins at the 
 time of exposure, that is, at the time of the first entrance 
 of the microbes into the body, and ends at the first symp- 
 toms of disease, as nausea, headache and fever. The 
 second stage is a period of development of the disease, 
 due to continued activity and multiplication of the 
 microbes. During this period, the resistance of the body 
 is beginning. During the third period, the fight be- 
 tween the microbes and the bodj' is raging. If the 
 body is able to make a good resistance, the disease ceases 
 to increase and maintains a level. At the end of this 
 period, which may be short or long as determined by 
 the nature of the disease and the body's power of re- 
 sistance, the fourth period commences. The disease 
 either begins to abate, if the body has been successful 
 in its manufacture of antibody; or to increase, if it has 
 been unsuccessful. The decline of the disease may be 
 sudden, as in the crisis of pneumonia, in which case the 
 microbes seem to be speedily and completely over- 
 whelmed; or the decline may be slow, as is much more 
 usual. 
 
 Individual differences in resistance. — The power of 
 the body to develop antibodies to meet disease varies 
 greath' in different individuals. This difference is shown 
 especially in the attitude of the white blood corpus- 
 cles toward the invading microbes. In some persons, 
 they seem to be indifferent to them ; in others, they seize 
 
286 HEALTH AND DISEASE 
 
 upon and destroy them with the greatest eagerness. The 
 latter are those whose cuts heal quickly and who are 
 not troubled with boils and abscesses. 
 
 Immunity. — Certain diseases/ as smallpox and scar- 
 let fever, never attack the same person twice, no matter 
 how often he may be exposed to them. From this fact, 
 we infer that the antibodies developed during the dis- 
 ease persist throughout his life. Consequently, the mi- 
 crobes of the disease can never again gain a foothold 
 and he is said to be immune to the disease. In smallpox, , 
 immunity can also be gained by vaccination with the 
 microbes derived from a modified and much milder form 
 of the disease, cowpox or vaccinia. Such immunity, 
 however, is limited to a period of from six to fifteen 
 years. In such diseases as diphtheria, on the contrary, 
 the immunity acquired by the reaction of the body lasts 
 but a few weeks after the disease has run its course. 
 
 Tuberculosis. — In contrast to these diseases in which 
 the body has the power of curing itself, is that most com- 
 mon disease, consumption or tuberculosis. In consump- 
 tion, the growth and multiplication of the microbes are so 
 slow that they do not give off enough toxin to arouse the 
 body to manufacture an adequate supply of antibodies. 
 The white blood corpuscles seem to remain more or less 
 indifferent to the infecting organisms, and as a result 
 they are not destroyed. If, however, the person is in 
 a condition of very robust health or acquires such health 
 by invigorating out-door life, the body is stimulated to 
 develop antibodies in sufficient amounts and the course 
 of the disease is thereby checked. 
 
 Artificial development of antibodies. — By experi- 
 ments upon animals, it has been found possible to de- 
 
 ' The microbes which cause these diseases have not as yet been 
 established beyond question. 
 
ANTITOXIN 287 
 
 velop antibodies similar to those developed by the body 
 in its struggle with disease. For example, if small doses 
 of the toxin developed by the bacteria of dipMheria are 
 repeatedly injected into a well horse, his tissues will 
 develop the antitoxin which antagonizes diphtheria, so 
 that he will quickly become immune to the disease while 
 retaining perfect health. If tbis process is continued 
 until the maximum amount of antitoxin has been devel- 
 oped, the blood of the horse becomes richly supplied with 
 it. It may then be used to supply antitoxin to a person 
 stricken with diphtheria. The destruction of tissue 
 which goes on while the body itself is preparing anti- 
 toxin is thus avoided, and its presence in sufficient 
 amounts immediately insured. In this way, the microbes 
 are overcome before they have time to overwhelm the 
 body or to cause serious destruction of tissue. As a re- 
 sult, the fever goes do-mi and the person quickly 
 recovers.^ 
 
 In consumption. — In diseases like consumption, where 
 the disease is of such slow progress as to be chronic, 
 there is sufficient time to stimulate the body to produce 
 antibodies. In addition to such improvement in gen- 
 eral health as can be brought about by fresli air and 
 good food, the production of antibodies may be further 
 stimulated by the actual injection into the patient of 
 toxins in the form of the dead bacilli of the disease. 
 The increased amount of toxins in the body stimulates 
 it to make enough antibodies to overcome them. 
 
 Infection. — A disease, to be infectious, must be pro- 
 duced by a microbe which has the power of invading 
 the body, of multiplying therein and of giving rise to 
 
 ' Thus far the method of producing antibodies has been dis- 
 covered for only certain of the infectious diseases, but it is un- 
 doubtedly only a question of time when the list will be greatly 
 extended or even made complete. 
 
288 HEALTH AND DISEASE 
 
 symptoms of disease. The transmission of an infectious 
 disease from one person to another is brought about by 
 the transference of microbes either directly by contact 
 from person to person; or indirectly, through common 
 contact with intermediate objects, as door knobs and 
 furniture, or through inoculation by the bites of in- 
 fected insects. For example, a person with diphtheria 
 may transmit the microbes directly by coughing into 
 another person's face or by touching some part of his 
 skin; or he may transmit them indirectly by leaving 
 
 Anopheles (malaria) 
 
 Anopheles (malaria) Culex (common) Slegomyla (yellow fever) 
 
 Fio. 153. Various types of mosquitoes. (After Howard and Underwood.) 
 
 some of them upon a door knob or chair back which the 
 other person subsequently handles. Had the disease 
 been malaria or yellow fever, the person might have 
 transmitted the microbes indirectly through the bite of 
 a mosquito. The microbes thus transmitted are in a 
 position to enter the body of the well person, provided 
 that they can find a cut in his skin or are conveyed 
 to his mouth. In the case of the insect's bite, they are 
 actually injected under the skin. 
 
 Entrances and exits for microbes. — The main en- 
 trances by which infecting microbes enter the body of a 
 
CONTAGIOUS DISEASE 289 
 
 well pei'son are the uose and mouth, for the reason 
 that streams of air containing microbes are continually 
 passing through them. The food entering the mouth also 
 forms ail excellent means for conveying them into the 
 stomach, provided that the food itself is infected. The 
 main exits for infecting microbes from the body of the 
 diseased person are the discharges from that person, 
 including those of the nose and mouth, as in coughing 
 and sneezing. 
 
 Prevention of disease by personal care. — Since the 
 microbes from one case of infectious disease may so 
 readily be transmitted to a trreat number of persons, it 
 is essential that the pei-son infected should exercise the 
 greatest care to avoid spreading his disease, and that 
 those who are well should similarly exercise the great- 
 est care not to become infected. If each person would 
 follow certain simple rules of hygiene, the number of 
 cases of infectious diseases would be greatly diminished. 
 The more important of these rules may be formulated 
 as follows. — 
 
 Afoid ill) necessary coniact with others, ichen either 
 they or you arc suffering from any acute illness. 
 
 So dispose of all excreta and discharges that no one 
 else can come into contact, cecn remotely, with them. 
 The best methoch arc burning, disinfecting with strong 
 disinfectant solution before putting into sewage, and 
 deep burial (in the country) at a distance from wells 
 and other water supplies. 
 
 Burn or disinfect whatever clothing has come in con- 
 tact with the disease. 
 
 Protect against insects, particularly mosquitoes and 
 flies. 
 
 Protect food against all insects, since they may carry 
 infection upon their feet. 
 
290 HEALTH AND DISEASE 
 
 Do not let any one who is ill assist in preparing food. 
 
 Do not eat or drink from utensils used by others. 
 
 Wash the hands immediately before eating. 
 
 Keep the general health good through proper exercise, 
 fresh air and wholesome food. 
 
 Disinfection. — Since all the microbes producing dis- 
 ease are living organisms which must have favorable con- 
 ditions for their growth and development, it is possible 
 to provide the unfavorable conditions which will cheek 
 their growth or even kill them outright. When the 
 microbes are in the body, this is done, as we have seen, 
 by the development or injection of antibodies. When, 
 however, the microbes are outside of the body, as, for 
 example, in excretions and on clothing and furniture, 
 much more immediate and vigorous measures can be 
 used. The most effective of these is moist heat in the 
 form of steam, especially if the steam is under pressure.' 
 A few minutes' exposure to such steam is sufficient to 
 kill all microbes. Next to steam in efficiency is boiling 
 in water in a closed vessel. For all microbes except those 
 of consumption, ten minutes or so of boiling is sufficient ; 
 for the bacilli of consumption, an hour is necessary. 
 Objects which cannot be either steamed or boiled, have 
 to be treated with such chemicals as will kill the microbes 
 on them. Of these, formaldehyde ^ is the most effective, 
 both in its gaseous and liquid forms. 
 
 Prevention of disease by municipal hygiene. — No 
 matter how much care the individual exercises, it is 
 not possible for him fully to protect himself against 
 the possibility of infection, since in every community 
 
 ' That is, in a steam-tight vessel. 
 
 ' Formalin candles can be obtained of any druggist and when 
 used according to directions afford a most effective and simple 
 means of room and clothing disinfection, provided that penetra- 
 tion of thick clothing, etc., is not required. 
 
MUNICIPAL HYGIENE 291 
 
 some of its members are so careless as to expose others. 
 Moreover, many cases of contagious disease cannot be 
 easily recognized as such in the beginning. Conse- 
 quently, a number of persons may be exposed without 
 knowing it. Against the carelessness of its members, 
 the community as a whole can take certain measures of 
 protection, since no one member has a right to endanger 
 the lives of others. It can, for example, demand the 
 isolation of all cases of contagious disease; the quaran- 
 tine of all those who have been in contact with the 
 disease until it has been proved that they have not caught 
 it ; and the disinfection of the premises at the end of an 
 illness. It can guard against epidemics ' by such pre- 
 
 ' Influence of laccination upon sinaJlpox: 
 
 Before vaccination Population Boston Cases Deaths 
 
 1721 11,000 5,989 850 
 
 1730 15,000 4,000 509 
 
 After vaccination 
 
 1811-1830 1-t 
 
 Annual rate of cases per million of inhabitants : 
 
 Before Optional 'Compulsory 
 
 Sweden 2,045 480-155 5-0.2 
 
 England 2.000 417 53 
 
 Prussia 2,000 300 4 
 
 Spain 12,050 
 
 Porto Rioo 600 
 
 Smallpox cases and death rates per 1,000 persons in Sheffield, 
 Eng., epidemic: 
 
 Ca^es Deaths 
 
 Not vaccinated 94 51 
 
 Once vaccinated 19 1 
 
 Twice vaccinated 3 0.08 
 
 Children under 10 yrs. 
 
 Not vaccinated 101 44 
 
 Vaccinated 5 0.09 
 
 Influence of antitoxin treatment upon diphtheria (at Boston 
 City Hospital) : 
 
 Annual death rate per 1,000 cases for 6 yrs. previous to in- 
 troduction of antitoxin ( 1S94) 400 
 
 Average death rate for 1904 (excluding cases which died 
 
 within 24 hrs.) 69.5 
 
292 HEALTH AND DISEASE 
 
 ventive measures as vaccination in the case of small- 
 pox. It has, further, the right to guard its water 
 supply from all sources of contamination and to make 
 and enforce laws insuring the purjty and healthful- 
 ness of all foods put on sale. It can protect the general 
 health by laws regulating labor in shops and factories, 
 that the conditions of work may be healthful and the 
 hours not excessive. It can institute health inspection 
 in schools, that the spread of contagious diseases may 
 be avoided and such deficiencies as eye and ear trouble 
 be discovered and remedied. It can establish parks, 
 playgrounds and gymnasia, that each one may have the 
 fresh air, sunshine and exercise which might otherwise 
 be denied him. In short, the community can help to 
 protect its members from infection by destroying the 
 sources of disease and by making them better able to 
 resist its attacks. If both the community and the indi- 
 vidual do their duty loyally, the ravages of disease will 
 be lessened with each succeeding year and the horror 
 of epidemics be made impossible. 
 
 EXPERIMENTS AND DEMONSTRATIONS 
 
 Materials : Cake of compressed yeast ; bread ; cheese ; 
 molasses; raw meat; hay; test tubes; perforated stopper for 
 test tube ; delivery tube for perforation in stopper ; cotton-bat- 
 ting; dairy or chemical thermometer; ice box; warm box; 12 
 test tubes of gelatine culture medium, obtained from a dealer 
 in bacteriological supplies ; 6 Petri dishes thoroughly cleansed, 
 covers applied, and baked for % hour in a hot oven, before 
 using for culture experiments (dishes should not be uncovered 
 except as indicated in experiments). 
 
 1) Fermentation by means of yeast: 
 
 a) Put into a test tube 1 part of molasses to 9 parts of 
 water. Add a little compressed yeast rubbed in water. Set 
 aside in a warm place (not above 100° ¥.) and observe it at 
 intervals for 24 hrs., noting carefully its appearance. 
 
EXPERIMENTS 293 
 
 b) At end of 24 hrs., examine some of sediment ' under 
 microscope, using the high power." Note yeast cells with their 
 buds. Make sketches of characteristic forms and compare with 
 forms in the yeast cake. 
 
 e) Collect gas given off by fermentation, by closing mouth of 
 test tube with a cork in which is inserted a bent glass delivery 
 tube, and identify it. 
 
 2) Influence of temperature upon activitii of yeast: 
 
 a) Prepare a test tube similar to 1, a), but put it upon ice 
 for 24 hrs. Compare with 1. a), and note differences. 
 
 b) Prepare 3 test tubes similar to 1, a). Place one in water 
 at 150^ F. for 10 min. ; label and place with 1, a). Place 
 second in water at 175° F. for 10 min.; label and place with 
 other two. Boil third gently for 10 min. ; label and place with 
 others. At end of 24 hi-s., compare 3 test tubes of this experi- 
 ment with test tubes of 1, a) and 2, a). 
 
 3) Presence of yeast in air: 
 
 a) Prepare 3 test tubes similar to 1, a), except that no 
 yeast is added. Put tubes uncovered in various parts of room 
 and lea\e uncovered for a day or two. Note whether there is 
 any fermentation. When bubbling begins, examine sediment 
 under microscope, to detect yeast. 
 
 b) Examine also squirming rods and other forms of microbes 
 present. 
 
 4) Putrefaction through activity of microbes: 
 
 a) Place in a test tube a small piece of raw meat. Add some 
 cold water and set aside in a warm place for 2 or 3 days, noting 
 changes from day to day. At end of time, note odor and ap- 
 pearance' of both meat and fluid. 
 
 b) Examine sediment under microscope and note various 
 forms and degrees of activity of microbes present.' 
 
 '- Tlie sediment is best obtained by introducing into the liquid a 
 glass tube drawn out to a moderately tine point at one end. Hold 
 the other end closed with the finger until the fine end reaches the 
 sediment. Then allow the air to escape from under the finger tip. 
 The sediment will then enter the small tip. 
 
 = The best results are obtained by using a ^ in. oil immersion 
 objective, which can probably be borrowed, if necessary, from a 
 physician. 
 
 » To stain these microbes, which are chiefly bacteria, in order 
 more clearly to show their forms, various coloring fluids may be 
 
294 HEALTH AND DISEASE 
 
 c) Compare putrefaction with fermentation as to odor and 
 general characteristics. It will be found that carbohydrates 
 ferment through action of yeasts and that proteids putrefy 
 through activity of bacteria. 
 
 5) Hay bacillus: 
 
 a) Cut hay into short pieces and pour boiling water upon it. 
 Cover and set aside for several days. Observe carefully from 
 day to day cloudiness and formation of scum, indicating multi- 
 plication of bacteria. 
 
 b) When scum is developed, examine under microscope and 
 note many rod-like bacteria (hay bacilli). 
 
 6) Molds: 
 
 a) Moisten pieces of bread and of cheese, put on plates and 
 cover tightly with tumblers. Leave for several days, observing 
 growth at intervals. 
 
 b) When molds are well developed, examine under micro- 
 scope and note their characteristic forms. 
 
 c) Take up some of mold on point of a needle and touch it to 
 several points on surface of a fresh piece of bread. Mrasten 
 and set aside under tumbler, as before. Note whether mold 
 develops more quickly at points touched than elsewhere. 
 
 7) Determination of number of microbes by culture: 
 
 a) Melt 6 test tubes of gelatine by placing in water at a 
 temperature of about 120° F. When thoroughly melted, re- 
 move the cotton from test tube and, by means of a small glass 
 tube which has been sterilized by boiling or heating in a flame 
 and then cooled, introduce 1 cu. cm. of well or tap water. Re- 
 place cotton and mix water thoroughly by shaking but do not 
 get it upon cotton. Remove cotton and pour into sterilized Petri 
 dish. Cover dish immediately and allow to stand at room 
 temperature for from 24 to 48 hrs. Observe contents of dish 
 from time to time without micovering it. 
 
 b) When small white dots representing colonies of microbes, 
 each of which has grown from a single microbe, are distinctly 
 visible, count them and thus determine number of microbes in 
 cu. cm. of water used. 
 
 used, such as methylene blue and methyl" green. The blue or 
 green is dissolved in a drop of water, which is then allowed to 
 flow under the cover glass into the sediment. A small piece of 
 blotting paper placed upon the opposite side of the cover glass will 
 assist the flow. 
 
EXPERIMENTS 295 
 
 e) Eepeat experiment, using 1 drop of milk (about -^ eu. 
 em.). 
 
 d) Melt 2 tubes of gelatine and pour into Petri dishes. Ex- 
 pose one to air at beginning of school ; the other, after sweeping 
 or dusting. Cover and allow to develop as before. 
 
 e) Prepare 2 Petri dishes and allow to cool. Touch to sur- 
 face of gelatine in one dish some part of skin, as a finger tip, 
 which has not been washed for several hours. Touch to surface 
 of gelatine in other dish the same finger tip immediately after it 
 has been washed in soap and warm water. Compare the 
 growth after 24 and 4S hrs. 
 
 8) Effect of heat {sieriluation) upon bacteria: 
 
 a) Cut some raw meat into small bits. Place a few pieces 
 in a test tube and cover with 2 in. of lukewarm water. Plug it 
 with a tuft of cotton and set aside in a warm place. 
 
 Place an equal number of pieces in another test tube and 
 boil briskly for a half minute. Plug and set aside with former 
 test tube. 
 
 At end of 24 and 48 hre., compare the 2 tubes and note effect 
 of heat. 
 
 b) Place in 2 test tubes 2 in. of milk. Boil one by placing 
 it in a small vessel of boiling water for 5 min. Plug both tubes 
 with cotton and put together in a warm place. Compare at 
 end of 24 and 48 hrs., testing acidity and odor. 
 
 9) Effect of disinfectants upon bacteria: 
 
 a) With scissore cut the white of an egg into 10 times its 
 weight of water. Put 2 in. of the solution into each of 14 test 
 tubes. To No. 1, add nothing. To No. 2, add 4 grs. of salt; 
 to No. 3, 15 grs. To No. 4, add 15 grs. of sugar; to No. 5, 
 45 grs. To No. 6, add 2 drops of 1 to 1000 corrosive sublimate 
 solution ; to No. 7, 6 drops. To No. 8. add 1 drop of formalin, 
 40 per cent solution ; to No. 9, 2 drops ; to No. 10, 3 drops. To 
 No. 11, add 2 gi-s. of borax; to No. 12, 4 gi-s. To No. 13, add 
 4 drops of 5 per cent carbolic acid solution ; to No. 14, 10 drops. 
 
 Shake the 14 test tubes carefully to mix contents, plug firmly 
 with cotton, and set aside in a warm place. Examine daily and 
 note changes in each, in order to determine relative effectiveness 
 of different mixtures as preservatives. 
 
■ CHAPTER XXVI 
 
 STIMULANTS AND NARCOTICS 
 
 Definition. — Aside from the ravages of disease, one 
 of the greatest dangers to human health is the use of 
 certain substances which are not required by the body 
 as food but are taken solely because of the pleasure 
 which they give. These substances are known as stimu- 
 lants and narcotics because they either produce a feel- 
 ing of increased vigor, or partial or complete insensi- 
 bility. The stimulants most commonly used are alco- 
 holic beverages, tea and coffee. The narcotics are the 
 various preparations of opium with its most important 
 derivative morphine, and chloral, cocaine, tobacco and 
 chloroform. 
 
 Proper use of narcotics. — Many of the narcotics, such 
 as morphine, chloral and cocaine, have long been recog- 
 nized as having valuable medicinal properties when 
 given to weak and suffering persons by a cautious phy- 
 sician who fully recognizes their dangers. They are 
 then used for a short time only to tide over an emer- 
 gency. Their use is distinctly the choice of the lesser 
 evil, since, although their after-effects are known to be 
 injurious, yet they are not so injurious as the condi- 
 tion which they correct. For example, a person in in- 
 tense pain would be injured more by sleeplessness and 
 exhaustion than by the after-effects of the narcotic, 
 which, by dulling the pain, brought sleep. In all such 
 cases, however, these substances must be used with ex- 
 
 296 
 
IMPROPER USE 297 
 
 treme caution and their prolonged use for chronic con- 
 ditions avoided. Otherwise, the headache, nervous de- 
 pression ajid exhaustion, indigestion, constipation and 
 weakness of heart and blood-vessels which follow their 
 continued use, may easily become so serious that the 
 original trouble seems trivial by comparison. This is 
 especially true when by their continued and prolonged 
 use the body has so adapted itself to their influence that 
 it demands them. The body is then pledged, as it were, 
 to its own destruction. It is being ruined by their use, 
 and yet so intense is the craving for them that to give 
 them up means intolerable mental and physical distress. 
 Improper use.— In view of the danger lurking in the 
 use of the stronger narcotics, it may be said that for a 
 person to give such a narcotic to himself in any form 
 is in itself improper. The first step in this direction 
 seems most innocent. The person, feels that a few doses 
 can make no difference and that in any ease he himself 
 will be strong enough to resist their effects. In this, 
 he is very apt to overestimate his own strength and 
 underestimate that of tlie drug. Each dose is building 
 up within his body an appetite, a craving for the next 
 dose, and in some moment of pain and depression he may 
 be reasonablj- sure that he will take that dose. As time 
 goes on, the moments of pain and depression become 
 more frequent and the doses necessary to overcome them 
 become larger. The more frequent and larger doses cre- 
 ate more terrible fits of depression, a more irresistible 
 craving for the drug, a weakened resistance to its use. 
 The man has now become the victim of the drug. With- 
 out it his life is mibearable because of the weakness, pain 
 and depression, which are, in turn, largely the result of 
 its use. The man can no longer live without it, yet its 
 use means his mental, moral and physical ruin. 
 
298 STIMULANTS AND NARCOTICS 
 
 Legal restrictions. — Morphine, chloral and cocaine 
 have claimed so many victims that the law recognizes 
 their danger and limits their use as much as possible 
 by restricting their sale except upon a physician 's order. 
 The physician in turn limits his order to the least amount 
 necessary to tide over the emergency which necessitates 
 its use. He further so words his prescription that it is 
 difficult for the patient to know what has been given 
 him or to get a second supply, except upon a new 
 prescription. 
 
 Tobacco a narcotic. — Although of much milder form 
 than the drugs which we have been considering, tobacco 
 has, nevertheless, their narcotic characteristics. It is 
 a sedative, allaying nervousness and- to a certain extent, 
 pain. It produces in habitual users a distinct crav- 
 ing, which is satisfied only by itself. It is not a food 
 and is taken solely for the pleasure which its use 
 gives. 
 
 Method of use. — The physiological effects which to- 
 bacco produces depend upon the manner and extent of 
 its use and the susceptibility of the user. In smoking, 
 the nicotin, which is the essential poison of the drug, 
 is volatilized from the tobacco by the heat. It is then 
 condensed upon the surface of the mouth, or, in the 
 inhalation of cigarette smoking, upon the surface of the 
 throat and bronchi as well. A part of it is lost by burn- 
 ing. In chewing, the nicotin is dissolved by the saliva 
 and absorbed by the mucous membrane of the mouth. 
 In snuff-taking, it is dissolved by the secretions of the 
 nose and is absorbed by its mucous membrane. There 
 is little fundamental difference between these methods, so 
 far as the effects of the drug upon the body are concerned. 
 In each, a certain amount of the nicotin is absoTbed into 
 the system, where it produces its characteristic effect. 
 
TOBACCO 299 
 
 Presence of carbon monoxide (CO). — lu smoking, 
 there are added to the effect of the drug itself the fumes 
 from the ingredients of the tobacco other than the nico- 
 tin, and these are also absorbed into the system. It 
 is supposed that one of these, carbon monoxide, gener- 
 ated because of the low temperature at which the to- 
 bacco is burned, is responsible, in part at least, for the 
 great weakness and deranged heart action which con- 
 firmed smokers, especially of cigarettes, experience. 
 
 Extent of use. — The extent to which tobacco is used 
 is much more important from the standpoint of health 
 than the mode of its use. As in other narcotics, the 
 habit grows fast with repetition. As the habit strength- 
 ens, the size of the dose required to satisfy the desire 
 tends to increase. Owing to the adaptation of the body 
 to its influence, a dose which in the beginning would 
 cause nausea, headache, dizziness, prostration and even 
 death, is often required after a year or two of use to 
 satisfy the daily craving for it. Although the bad 
 effects of its use have thus become less apparent, it 
 cannot be said that they have ceased. Irritation of the 
 mucous membrane lining the throat and mouth, more 
 or less dyspepsia, increased nervo^^s irritability and im- 
 pairment of the heart action are very apt to accompany 
 its persistent use. especially in young persons. 
 
 Individual susceptibility.— The injury which the use 
 of tobacco causes varies greatly vnth individuals, some 
 being much more susceptible to its use than others. This 
 holds true, however, only of those who have passed the 
 developing period. During youth, all are highly sus- 
 ceptible to it. The poison of tobacco is especially injuri- 
 ous to the developing nervous system, the heart and 
 blood-vessels, the lungs and stomach. It not only inter- 
 feres with their growth but even tends to exert first 
 
300 STIMULANTS AND NARCOTICS 
 
 an irritating and then a paralyzing influence upon their 
 functions. As a result, the boy who smokes is apt to be 
 stunted in growth, nervous and lazy. He is poor in his 
 studies and of but little use in athletics. He is indif- 
 ferent to the wholesome ambitions of boyhood and tends 
 to seek the companionship of those who like himself are 
 principally occupied in trying, to have a good time in a 
 more or less questionable way. In short, he is taking the 
 quickest and surest way of ruining his health and his 
 future prospects and of cheating his children of their 
 right to wholesome bodies and minds. 
 
 This has been scientifically demonstrated in studies 
 made by Dr. Seaver of Yale University and by Dr. Hitch- 
 cock of Amherst College, upon the growth of students. 
 These showed that non-smoking students were markedly 
 taller and had larger chest girth and greater lung capac- 
 ity than those who smoked. As to their mental attain- 
 ments, the Hon. Andrew J. White, formerly president of 
 Cornell University, says: 
 
 I never knew a student to smoke cigarettes who did not dis- 
 appoint expectations, or to use our expressive vernacular, 
 "kinder, peter out." I have watched this class of men for 30 
 years, and cannot recall an exception to this rule. Cigarette 
 smoking serves not only to weaken a young man's body, but to 
 undermine his will and to weaken his ambition. In colleges 
 having a large percentage of these futile personages they too 
 often give the student tone ; they set the fashion ; the fashion of 
 overexpenditure, of carelessness as to the real aim and glory 
 of college life. — Cornell Sun, November 11, 1891. 
 
 Stimulants: tea and coffee. — Besides narcotics, the 
 most important substances which are often taken for the 
 feeling of well-being and strength which they give, are 
 stimulants in the form of alcoholic beverages, tea and 
 coffee. As we have already seen in our discussion of 
 food materials, tea and coffee may be occasionally used 
 
TEA AND COFFEE 301 
 
 with benefit to tide over an emergency which involves 
 unusual nervous strain. They give a temporary in- 
 crease of strength, which is later followed by weariness 
 and depression, because they have spurred the tissues 
 to an activitj' which results in their more complete ex- 
 haustion. When taken habitually, each period of stimu- 
 lation is followed by a period of greater exhaustion,^ 
 so that the individual's plane of strength is constantly 
 being lowered. The more he depends upon them for 
 stimulation, the weaker he really becomes, until his 
 nervous system may become more or less shattered and 
 his digestion seriously upset. 
 
 Formation of habit. — As with narcotics, the use of 
 tea and coffee easily becomes a habit, since to leave them 
 off at any time means weakness, restlessness and de- 
 pression. A user of tea and coffee can readily estimate 
 how much he is depending upon them by lea^^ng them 
 off for a few days. If he feels less energetic and com- 
 fortable, it means that his nervous system has suffered 
 from their use. It is then for him to determine whether 
 he wishes to continue the habit at the expense of his 
 nervous system, or to regain a more wholesome condi- 
 tion where the feeling of well-being is not dependent 
 upon artificial stimulation but upon proper amounts of 
 food, exercise, work and sleep. 
 
 Alcohol. — Alcohol differs from tea and coffee, in that 
 like food it is oxidized in the body, thereby producing 
 heat and energy. It cannot, however, be ordinarily con- 
 sidered as a food for the reason that even in small doses 
 it produces a serious effect upon the nervous system. 
 It cannot therefore be safely used in sufficient amounts 
 to get any food value from it. 
 
 ' This is frequently exaggerated by the substitution of tea or 
 coffee for food. 
 
302 STIMULANTS AND NARCOTICS 
 
 Production of alcohol.— Of all forms of drugs, with 
 the exception of tea and coffee, alcohol is the most gen- 
 erally used, doubtless for the reason that it is easily 
 and cheaply made from such common materials as grains 
 and fruits, by the ordinary processes of fermentation 
 or by distillation from the products of fermentation. 
 "When crudely made, however, and not sufficiently aged, 
 the alcoholic beverages from fermentation and especially 
 from distillation contain in addition to ethyl alcohol 
 other much more dangerous forms of alcohol, as fusel 
 oil. ' 
 
 Various beverages. — The alcoholic beverages in com- 
 mon use are of two distinct types, being produced either 
 by fermentation or distillation. Those produced by fer- 
 mentation, as beer, cider and wine, contain from two to 
 twelve per cent of alcohol. Those produced by distilla- 
 tion, as whiskey, brandy and rum, contain from forty 
 to sixty per cent. Certain wines, as port, are strength- 
 ened by the addition of alcohol and are known as forti- 
 fied wines. The alcohol in all cases is the result of the 
 fermentation of sugar, which is present in such fruits as 
 grapes and apples, or is obtained by a malting process 
 from the starch of grains. 
 
 Effects of alcohol.— The effects of alcohol upon the 
 body and especially upon the nervous system depend 
 upon the form, amount and frequency of its use and 
 upon the susceptibility of the individual. In general, 
 its first effect is that of stimulation and excitement. The 
 person's face becomes flushed, his eyes brighten, his re- 
 serve is lost, he becomes animated, confident and talka- 
 tive. In a later stage, the flush becomes more marked, 
 the lack of reserve shows itself in silly loquacity, con- 
 trol of movement is lost and the stagger of drunkenness 
 develops. In a still later stage, the full effects of the 
 
ALCOHOL 303 
 
 poisoning are seen in stupor and inability to move. This 
 last stage may continue for a number of hours or may 
 end in death. 
 
 Alcohol, a narcotic poison. — From a physiological 
 standpoint, alcohol in its effects seems rather to resemble 
 a narcotic than a true stimulant, inasmuch as the period 
 of exhilaration produced by its use appears due not to 
 a stimulation of the brain but rather to a paralysis of 
 its higher functions of caution and judgment. It would 
 further seem that all of its effects are due to a gradual 
 paralysis, first of the higher and then of the lower brain 
 centres, until finally all voluntary action is lost. The 
 automatic processes of organic life, as the beating of the 
 heart and breathing, alone continue and even these feel 
 the paralyzing effect of the poison. 
 
 Chronic effects upon structure. — "When alcoholic bev- 
 erages are used habitually and frequently, other and 
 more chronic effects may be produced, especially if the 
 alcohol is in the concentrated form of wines and liquors. 
 The mucous membrane of the stomach tends to become 
 irritated, producing dyspepsia. The liver, which receives 
 the blood immediately after its absorption from the 
 stomach and intestine, is also irritated. This irritation 
 causes an overgrowi;h of the connective tissue which 
 forms the framework that supports its cells. As a re- 
 sult, its active cells are so pressed for room that they 
 become smaller and less able to do their work. In ex- 
 treme cases, the cells even disappear to a considerable 
 extent, leaving only the connective tissue in their place. 
 This results in so serious a reduction in the amount 
 of work which the liver can do that the person dies. In 
 such cases, the liver when examined is found to be hard 
 and tough and is covered with small projecting Imobs 
 due to the contraction of the masses of connective tissue. 
 
304 STIMULANTS AND NARCOTICS 
 
 Such a liver is called the hobnailed or gin-drinker 's liver, 
 because it is rarely found except among hard drinkers. 
 
 Effect upon heart. — The heart as weU as the liver 
 majr be more or less seriously influenced by the frequent 
 and regular use of alcoholic beverages. The more con- 
 centrated beverages tend to produce deposits of fat about 
 the heart which interfere with its action. Sometimes 
 even, they give rise to a fatty degeneration of its mus- 
 cles. The more dilute beverages, as beer, when taken 
 in excessive amounts throw such an undue bulk of 
 fluid into the circulation that the heart is overtaxed. 
 
 Upon blood-vessels. — The blood-vessels are also fre- 
 quently affected by chronic alcoholism. Their walls may 
 become so weakened that they are unable to withstand 
 the pressure of the blood. This is especially true of the 
 brain, where their bursting results in apoplexy and 
 paralysis. Dilatation of the veins, especially of the 
 face and nose, is also one of the effects of alcoholism, 
 although it is not infrequently due to other causes. 
 
 Upon nervous system. — Whereas the heart, liver 
 and blood-vessels are injured only by the prolonged use 
 of alcohol, the nervous system shows the immediate poi- 
 sonous effects of a single dose, as well as the chronic 
 effect of its continued use. The immediate effect, as we 
 have seen, is largely one of paralysis. The chronic 
 effects are far-reaching and much more serious. They 
 may show themselves as acute pain, due to the inflam- 
 mation of the nerve tracts; as acute mania with hallu- 
 cinations, that is, as delirium tremens; as epilepsy; or 
 as insanity. Often, however, the chronic effects are 
 so intangible that they do not appear until after the 
 system has been weakened by disease. This is especially 
 true in the case of habitual moderate drinkers, who 
 often seem to have escaped all bad effects from the \ise 
 
SYSTEMIC EFFECTS 305 
 
 of alcohol until an illness or accident brings them to 
 light. 
 
 Systemic effects. — Alcohol not only injures the spe- 
 cial organs and tissues of the body but in addition it 
 produces certain more general effects. It is frequently 
 noticed that the powers of resistance to disease in habit- 
 ual moderate users are markedly lessened. Their powers 
 of recovery after accidents or illnesses are also de- 
 creased and in some cases entirely destroyed. These 
 effects vary greatly with different persons. Some dete- 
 riorate rapidly luider the influence of very small amounts, 
 whereas othei-s are seemingly able to withstand large 
 amounts for long periods with but little apparent effect. 
 The latter are simply examples of exceptional resistance 
 to its influence and cannot be cited to prove that alcohol 
 has no injurious effects. One might as well argue that 
 scarlet fever is not contagious because a certain number 
 of persons, although frequently exposed, have failed to 
 catch it. Unfortimately, these resistant cases are rare, 
 whereas the number who bear witness to its injurious 
 effects is overwhelming. 
 
 Longevity. — The effect of the use of alcohol upon 
 length of life is conclusively shown by the statistics of 
 the various life insurance companies, which consider the 
 subject from the unbiased point of view of business. Be- 
 tween the yeai-s 1875 and 1889, the ^Mutual Life Insur- 
 ance Company found that upon the lives of those who had 
 declared themselves to be total abstainers when applying 
 for their policies, the maximum expected loss was $5,455,- 
 669, and the actual loss was $4,251,050. Upon those who 
 acknowledged themselves users of alcoholic beverages the 
 maximum expected loss was $9,829,462, and the actual 
 loss was $9,469,407. 
 
 The experience of the Sceptre Life A§suraace Society, 
 
306 STIMULANTS AND NARCOTICS 
 
 Ltd., of London, for the twenty years from 1884 to 1903, 
 inclusive, gives the following figures : For abstainers, ex- 
 pected deaths, 1,440; actual deaths, 792; being 55% of 
 the expected. Non-abstainers, expected deaths, 2,730; 
 actual deaths, 1,880, or 79% of the expected. 
 
 The experience of the Scottish Temperance Life Assur- 
 ance Company, Ltd., for the twenty years from 1883 to 
 1902, inclusive, gives the following figures : Abstainers, 
 expected deaths, 936; actual deaths, 420, or 45% of the 
 expected. Non-abstainers, expected deaths, 319 ; actual 
 deaths, 225, or 71% of the expected. 
 
 There are many other testimonies ' to the effect that the use 
 of alcoholic stimulants produces an increase in the rate of mor- 
 tality. So destructive has been their effect upon the" lives of 
 the North American Indians, that under United States law it 
 is a penal offense to sell alcoholic beverages to an Indian. The 
 mortality among Africans and South Sea Islanders has also 
 been so increased by the use of alcohol, that simply as a matter 
 of humanity the civilized nations of the world have united in 
 their efforts to stop the sale of liquor in the Congo and in cer- 
 tain islands of the Pacific. While it is doubtless true that the 
 deleterious effects of alcoholic beverages are more apparent 
 among black men and red men than among white men, yet, as 
 we have the assurance that all nations are made of the same 
 blood, what is injurious to one cannot b§ beneficial to another. 
 
 As further proof of the injurious effect of alcoholic bever- 
 ages, as shown in the death rate, I would refer to the statistics 
 which have been published from time to time, showing the 
 percentages of mortality in the various occupations. These 
 statistics have invariably shown a higher death rate among 
 those engaged in the liquor business, from brewers down to 
 bartenders, than among those engaged in other occupations, 
 except such as are clearly defined as specially hazardous. The 
 higher death rate among liquor dealers is so universally recog- 
 
 1 Effects of Total Abstinence on the Death Rate, by Joel G. Van 
 Cise, Actuary of the Equitable Life Assurance Society of the United 
 
 States, 
 
SYSTEMIC EFFECTS SOl 
 
 nized by life assurance companies that a number of them will 
 not issue policies, even on the lives of the richest brewers, upon 
 any terms, and not one of the companies, to my knowledge, 
 admits liquor dealere upon as advantageous conditions as those 
 engaged in other ordinary occupations. 
 
 As an example of the restrictions in this respect, I would 
 quote the rules as given in a circular sent to the agency force 
 of a prominent United States company. This circular reads 
 almost like a temperance document, and yet it is simply sent 
 out as a matter of business, because statistics show that owing 
 to what might be called the very atmosphere by which liquor 
 dealere are surrounded, the mortality among them is higher 
 than among those engaged in occupations which do not involve 
 the handling of alcoholic beverages. This circular reads as 
 follows : 
 
 "The number of applications received from persons engaged 
 in the sale or manufacture of liquor has increased so rapidly 
 that we tuid it necessary to call the attention to the rule on 
 page 345 of the 'Blue Book' reg'arding tliis class of business, in 
 order that unnecessary declinations may be avoided. This rule 
 is as follows : 
 
 Bartenders Not Taken. 
 
 Saloon keepers, generally, not 
 taken, but best of this class may 
 be accepted on 10 or 15 Year En- 
 dowments only. 
 
 Commercial Travelers (Salesmen) $5 per thousand extra. 
 
 Brewers (unless seldom at their 
 breweries) $5 per thousand extra. 
 
 Employees in breweries $o per thousand extra. 
 
 "Wholesale dealers, if apparently 
 unaif ected by their business Free. 
 
 Restaurant keepers and waiters 
 selling liquor $5 per thousand extra. 
 
 (In this whole class the habits, pnst and present, and ap- 
 pearance will be carefully considered. ) 
 
308 STIMULANTS AND NARCOTICS 
 
 Please note that bartenders are positively not taken, and 
 saloon keepers tending bar occasionally are therefore unac- 
 ceptable. Only saloon keepers of the best class, very tem- 
 perate in their habits, not tending bar, and enjoying the best 
 moral surroundings which the business permits, will be taken 
 at all, and only on 10 and 15 Year Endowment G. C. V. 
 policies. It is useless to present eases not falling within these 
 limits, as not only will the applications be declined, but the 
 cost of medical examination may be charged against the agents 
 for their failure to observe the rule. 
 
 It is also noted that there is a growing tendency to present 
 the applications of brewery employees for acceptance with- 
 out extra premium. In order that there may be no misunder- 
 standing on this subject, agents are hereby informed that the 
 only persons employed directly in connection with breweries 
 who will be accepted without extra premium are the financial 
 offieers or oflScials seldom at the breweries, and employees such 
 as book-keepers, etc., whose work is performed in a building 
 apart from the brewery proper, or the place where the product 
 is stored or kept in bulk. 
 
 General store-keepers everywhere, handling liquor at retail 
 as part of their business, if taken at all, will hereafter be 
 limited to dividend accumulation Endowment policies with not 
 more than 20 years to run, but no policies with return of 
 premium or with the Indemnity or Mortuary dividend feature 
 will be issued to this class of applicants. This limitation is 
 made necessary by the very excessive rate of mortality found 
 to exist among persons so employed." 
 
 Experimental proof. — The effects of alcohol upon 
 animal life have been experimentally studied by a num- 
 ber of scientists. One of the most interesting of these 
 studies is that made by Professor Hodge of Clark Uni- 
 versity. He selected four healthy dogs and for four 
 years allowed tvs^o of them to have regular doses of 
 alcohol. The results showed conclusively that the use 
 of alcohol made the dogs weak and timid. They fell 
 ready victims to an epidemic, which they survived only 
 by the most careful nursing. Of their twenty^three 
 
SYSTEMIC EFFECTS 309 
 
 puppies, but four lived to grow up, the rest being born 
 dead or deformed. In marked contrast to them were 
 the other two strong, happy, courageous dogs. When the 
 epidemic came, they were not even ill enough to lose 
 their appetites. Of their forty-five puppies, none were 
 born dead, but four were slightly deformed, while the 
 remaining forty-one were fine and normal. A study 
 by another scientist of ten alcoholic and of ten non- 
 alcoholic families showed that the same conditions held 
 for human beings as for dogs. 
 
 In writing of a somewhat similar experiment upon 
 kittens, Professor Hodge says : " In beginning the experi- 
 ment, it was remarkable how qviickly and completely all 
 the higher psychic characteristics of both the (alcoholic) 
 kittens dropped out. Playfulness, purring, cleanliness 
 and care of coat, interest in mice, fear of dogs, while 
 normally developed before the experiment began, all dis- 
 appeared so suddenly that it could hardly be explained 
 other\vise than as a direct influence of the alcohol upon 
 the higher centres of the brain. They simply ate and 
 slept, and could scarcely have been less active had the 
 greater part of their cerebral hemispheres been removed 
 with the knife. "^ 
 
 Practical studies. — Further proofs of the bad effects 
 of alcohol are to be found in the experiences of men who 
 have watched its use by large numbers of persons. For 
 example, a writer in Manila has remarked pointedly con- 
 cerning the health of the American troops: " 'It is not so 
 much the climate as the glass bottle which injures people 
 out here,' which statement is corroborated by another 
 who had seen actual service as a member of a company, 
 
 • The Physiological Aspects of the Liquor Problem, Committee 
 of Fifty. 
 
310 STIMULANTS AND NARCOTICS 
 
 many of whose members were total abstainers and the 
 rest made up of moderate drinkers and those prone to 
 excesses, the latter constituting 20 to 25 per cent of the 
 whole. Of the latter class, only two returned home in 
 approximately the same condition of health which they 
 enjoyed at the time of enlistment. Of the moderate 
 drinkers who confined themselves to malt liquors, a large 
 majority suffered more or less impairment of general 
 health. But the total abstainers returned almost to a 
 man in excellent health, having endured the same hard- 
 ships of an active campaign. The same correspondent, 
 speaking of the far greater harm induced by the stronger 
 alcoholic drinks, relates that he had repeatedly seen 
 American soldiers, after spending several hours under 
 shelter, drinking round after roimd without perceptible 
 harm, fall over with all the symptoms of sunstroke as 
 soon as they stepped into the glaring rays of the hot 
 sun."' 
 
 Another man who was in the Civil War gives the fol- 
 lowing results of his observation of the soldiers who, as 
 prisoners, were deprived of alcoholic beverages: "During 
 the war I was a prisoner for thirteen months in Louisiana 
 and Texas. Among the prisoners were many men, sol- 
 diers and sailors, but chiefly sailors, who had been ad- 
 dicted to drink. For four or five months the conditions 
 of life were fairly sanitary. On the one hand, the 
 prisoners were in roomy, well-ventilated barracks; they 
 had to police and keep clean their quarters and grounds 
 under their own ofiScers, acting with the cooperation of 
 the Confederate authorities ; they had sufficient food and 
 sufficient means for cooking it properly ; they had saved 
 their clothes when captured ; they were allowed to go out 
 
 ' Practical Hygiene, Harrington, 
 
SYSTEMIC EFFECTS 311 
 
 and cut their pwn wood ; they were marched across Texas 
 from Hempstead to Shreveport, and from Shreveport 
 back to Tyler. On the other hand, there were the confine- 
 ment and depression of imprisonment, the lack of regular 
 work ; a climate they were not accustomed to, and some 
 malarial influences. Notwithstanding the latter condi- 
 tions these men improved physically and mentally in such 
 a marked degree that other ofScers agreed with me, at the 
 time, that enforced total abstinence was the very best 
 condition that could be imposed upon them. 
 
 "And in confirmation of the above, I repeatedly ob- 
 served that many of these men, after they had returned to 
 their homes with all the advantages of civilized life, had 
 run down and did not appear either physically or men- 
 tally to be as fair specimens of manhood as they did while 
 inmates of a Confederate prison camp." ' 
 
 This opinion was further borne out during the same 
 war by the experience of the Federal Authorities. "A 
 daily issue of a gill of whiskey to each ofScer and man of 
 the Army of the Potomac was ordered, half to be given 
 out in the morning and half in the evening. This was 
 brought about by the fact that for several weeks the men 
 had been subjected to unusual hardships and extra duty, 
 and were breaking down under the strain. The issue, 
 which was to continue ' until further orders, ' was greeted 
 with enthusiastic appreciation of the farsightedness of 
 . the authorities responsible for it. ' Until further orders ' 
 proved to be exactly one month, and hot coffee was 
 substituted for the whiskey, the issue of which was 
 ordered to be 'immediately discontinued.' During the 
 month, the general condition of health of the troops was 
 not only in no way improved, but became markedly worse, 
 
 ' The Physiological Aspects of the Liquor Problem, Committee 
 of Fifty. 
 
312 STIMULANTS AND NARCOTICS 
 
 while drunkenness, with its attendant evils, became much 
 more common. ' ' ^ 
 
 That the bad effects of alcohol are not limited to the 
 strenuous life of the soldier but are to be found equally 
 among men in the more peaceful walks of life is borne 
 witness to by a physician of many years' standing, who 
 says : ' ' From my experience during a very active life of 
 twenty -six years of medical practice, I have reached the 
 conclusion that the regular consumption of a moderate or 
 even small quantity of whiskey, wine, or beer is not con- 
 ducive to the most perfect health or the highest working 
 power in my profession or in any walk in life. In the 
 conditions of life in cities, I believe the most effective 
 work is performed by total abstainers from alcohol, but 
 that the greatest harm- is done to men of sedentary pur- 
 suits, and to those who through the stimulus of alcohol 
 consume a larger quantity of nitrogenous food than they 
 would otherwise take. . . . Leaving out of consideration 
 all the harm done by alcohol in excess, the injury done by 
 moderate regular indulgence is incalculable. Almost all 
 the ill health in men beyond forty is associated with 
 alcoholic indulgence and with imprudent or excessive eat- 
 ing in association with it. " ^ 
 
 A man who for many years has had daily evidence of 
 the effects of alcohol, adds his testimony as follows: 
 "From a large experience with drinking men in a line of 
 work for their rescue, covering many years, I find that 
 the drink habit is one that they have formed not through 
 predisposition, but during the years of eighteen to 
 twenty-four from so-called good-fellowship and treating ; 
 then, having acquired a habit, and their system craving 
 
 ' The Physiological Aspects of the Liquor Problem, Committee 
 of Fifi^. 
 
ECONOMIC EFFECTS 313 
 
 alcohol, it became the old story of an uncontrollable 
 appetite. This applies to the millionaires and the sons of 
 the same — who have the means to gratify their wants, and 
 do so till their systems refuse, when mania and death 
 foUow — as weU as to the gutter-snipe who burns for rum 
 and dies the death of a neglected drunkard. Rum levels 
 them both and affects them in the same way — here and 
 hereafter. The curse is in the abuse, but the man, as a 
 rule who is abusing the use of it, does not consider that it 
 applies to himself, but to the other feUow, and will 
 sympathize, and sometimes remonstrate with him in his 
 being a slave to drink. ' ' ^ 
 
 Economic effects. — If the effects of alcohol were lim- 
 ited to physical and moral degeneration, the spectacle 
 would be pitiable enough, but it further brings eco- 
 nomic evils in its train. The expense connected with its 
 use is enormous. The sums of money spent in buying 
 it, although amounting to hundreds of millions yearly, 
 are yet but a small item in the final bill of costs against 
 it. In that must be reckoned the diminished or even 
 destroyed earning power of those who use it, which, if 
 it could be reckoned, would be beyond belief. To its 
 account must also be charged a proportion of the cost 
 of maintaining poorhouses, courts, reformatories and 
 prisons, which are necessitated in part by the crimes 
 committed under its influence. If alcohol could be abol- 
 ished from the world and this immense sum of money 
 spent for the families of its present victims, the world 
 would have made a marvellous step toward the elimina- 
 tion of misery and crime and the development of a more 
 uniformly wholesome, strong and intelligent race. 
 
 ' The Physiological Aspects of the Liquor Problem, Committee 
 of Fifty. 
 
APPENDIX A 
 THE GROWTH OF PLANTS AND ANIMALS 
 
 Food of plants. — ^As plants grow, they are constaatly 
 taking material from the world about them and build- 
 ing it into themselves. The most common source of 
 material for their use is that sea of air called the atmos- 
 phere, at the bottom of which they live. In it are found 
 mainly oxj'gen, nitrogen and carbon dioxide, with slight 
 amounts of such other gases as ammonia and coal gas. 
 
 Oxygen (O). — Oxygen is an invisible gas which 
 forms about 20 per cent of atmospheric air. It is capa- 
 ble of imion with other substances, thereby producing 
 light and heat. This union is called combustion or 
 oxidation.^ Oxygen is given off to the air by plants 
 when, in order to get the carbon and hydrogen which 
 they need, they separate the carbon dioxide (CO,) of 
 the air into carbon and oxygen, and the water (H^O) 
 into hydrogen and oxygen. Oxj'geu is thus a waste 
 product from plant growth. 
 
 Nitrogen (N). — Nitrogen is an invisible gas which 
 forms about 80 per cent of atmospheric air. It serves 
 to dilute the oxygen of the air and thereby prevents 
 over-rapid combustion, which otherwise would mean the 
 destruction of all things. Plants unite nitrogen with 
 carbon, hydrogen and sulphur, and thereby build up the 
 Mesh-forming food of animals. Nitrogen as found in 
 
 ' The chemical compounds formed by oxidation are called oxides. 
 Water (HjO) is an oxide of hydrogen; carbon dioxide (CO,), of 
 carbon; and iron rust (FejOs), of iron. 
 
 315 
 
316 THE GROWTH OF PLANTS AND ANIMALS 
 
 nature cannot be used by animals but must first be built 
 into other compounds by plants. 
 
 Carbon dioxide (COa). — Carbon dioxide consists by 
 measure of one part of the solid, carbon, and two parts 
 of the gas, oxygen, and is present in fresh air only in 
 minute quantities. The burning of coal, wood and oil, 
 and the decay of animal and vegetable substances mean 
 that the oxygen of the air is uniting with the carbon in 
 these substances to form carbon dioxide. It is also gen- 
 erated in the bodies of animals when the food which 
 they eat unites with the oxygen which they breathe. In 
 animals, it is a waste product given off by the breath, 
 but for plants it is a most important building material 
 or food. 
 
 In the remote geologic ages before plants had taken 
 the carbon dioxide from the air and stored up the im- 
 mense quantities of carbon now found in coal and oil 
 fields, the amount of carbon dioxide in the air was much 
 greater than at present. It is probable, however, that 
 the burning of the large quantities of coal and wood now 
 in use is increasing the proportion of carbon dioxide in 
 the air. The air of cities has distinctly more of this 
 gas (0.06 per cent) than that of the country (0.04 per 
 cent), while the sea air contains even less (0.025). 
 
 Carbon monoxide (CO). — Carbon monoxide is an 
 invisible gas which is very poisonous for both plants 
 and animals. It is produced when there is too little 
 oxygen present to furnish the two parts of oxygen to 
 one of carbon necessary for complete combustion into 
 carbon dioxide, or when the temperature is too low 
 to permit of complete oxidation, as in the case of wood 
 or charcoal burning without a flame. It is commonly 
 found in large amounts in illuminating gas, especially 
 in the so-called "water gas," and in the fumes from 
 
WATER 31^ 
 
 stoves, furnaces, charcoal-heaters aud from tobacco as 
 ordinarily smoked. 
 
 Water (HjO). — Of not less importance than air to 
 plants and animals is water. It is formed during the 
 combustion of coal, wood and oil when the hydrogen in 
 them unites with the oxygen of the air. It is also 
 formed in the bodies of animals when the hydrogen in 
 the food which they eat unites with the oxygen which 
 tliey breathe. Water is of great importance for both 
 plants and animals because it dissolves food and waste 
 materials, so that they can be readily carried to and 
 from all parts of tlieir structure. Moreover, it is only 
 when dissolved that food is capable of nourishing them 
 and of imdergoing the various changes necessary for 
 growth and the production of energy by oxidation in 
 animal tissues. 
 
 The demand of living organisms for a definite amount 
 of water is so urgent that animals will seek for it at 
 any cost of exertion or danger. Plants in their help- 
 lessness can only wilt and die. 
 
 The amount of water in the body of a man who weighs 
 150 pounds is about 87 pounds. The daily loss which 
 requires to be made good is aboiit 6 pounds or 6 pints. 
 Of this, 3 pints is usually taken as drink, and the 
 remainder as liquid food. 
 
 Soil. — ^In addition to air and water as sources of food 
 supply for plants, there is the soil. Besides furnishing 
 a firm support for them, the soil is so fine of texture, so 
 filled with decaying organic matter and so well shaded 
 by vegetation that it holds the moisture given it by 
 the rain and gives it back to even the smallest plants. 
 The soil further supplies substances needed by plants of 
 both organic and mineral nature. In it are foimd 
 the minerals potassium, calcium, magnesium and phos- 
 
318 THE GROWTH OP PLANTS AND ANIMALS 
 
 phorus, together with iron, sulphur, chlorine and sodium. 
 They are found, however, only in comparatively small 
 amounts, about 2 to 4 per cent of the plant weight, and 
 constitute the ash or unburned portion of the plant. 
 1 Plant growth. — The most fundamental form of 
 growth, upon which depends the food supply of all 
 animals, is that which takes place in green plants. 
 These require for their growth certain substances as 
 carbon, hydrogen, nitrogen and oxygen. By means of 
 the energy of the sun's light and heat, they are able to 
 separate carbon from its union with oxygen in the carbon 
 dioxide of the air. In the same manner, they are able 
 to separate the hydrogen in water from its union with 
 oxygen. The carbon, hydrogen and oxygen they then 
 transform into such entirely new and complex substances 
 as starch,^ woody fibre or cellulose, and sugar. 
 
 Non-destructibility of matter. — When plants decay 
 or are burned up, the starch, cellulose and sugar are 
 again converted into the original simple substances from 
 which the plants formed them. For example, the carbon 
 in the starch again unites with the oxygen of the air to 
 form carbon dioxide; the hydrogen and oxygen in the 
 starch form water.^ We thus see that the substances used 
 by the plants for their growth and development are not 
 destroyed even by burning or decay, but are used over 
 and over again for thousands of years and will continue 
 to be so used as long as plants grow. 
 
 Conservation of energy. — In the growth of plaiits, 
 energy is required to separate out the materials which 
 they use and to build them into their proper places in 
 
 ' Growth : Carbon dioxide + water = starch + free oxygen 
 
 6 COj +5Hi,0=C,H,„0t+ 6 0, 
 
 'Decay: Starch + oxygen = carbon dioxide + water 
 CeH,oO.+ 6 0j = eCOj +5HaO 
 
CONSERVATION OF ENERGY 319 
 
 the plant's tissues. This energy is furnished by the 
 sun in tlie form of light and heat. The same amount of 
 energy which is given by the sun to the plant is again 
 given out qiiiekly and intensely if the plant is burned, 
 or slowly trnd imperceptibly if the plant decays. Dnr- 
 ing the growth of the plant, the energy is being stored 
 up. The storing up of energy in this way so that it 
 is not lost, although for a longer or shorter time it may 
 seem to disappear, is an example of the natural law 
 kno\\-n as the conservation of energy.^ 
 
 Transformation of energy. — Energy, like matter, can 
 never be destroyed. If, for example, the wood from a 
 tree, which has been built up of carbon and hydrogen ob- 
 tained by the use of the sun 's energy, is burned under a 
 boiler, the energy set free by the burning of the wood 
 causes the little particles of water in the boiler to take on 
 so violent a motion that in their effort to escape from 
 confinement tliey press upon the piston of the engine 
 and drive it vigorously back and forth. As a result, 
 an entirely different form of energy, namely, mechanical 
 energy, is developed. The engine may in turn run a 
 sawmill, a piledriver. or a draamo for the generation 
 of electricity. In any case, there is an exact equality," 
 or correlation, between the original heat from the sun, 
 tlie force developed in the engine and the work done 
 
 'Similarly, the labor (energy) expended in raising building 
 materials to tlieir positions in a building, although seemingly lost 
 for many years, ag:»in becomes active when the materials ulti- 
 mately fall to the earth. 
 
 ' All of the sun's heat is not made producti^'e, since a part of it 
 escapes as hot gases up tlie chimney, a part is radiated from boiler 
 and engine, and a part is neutralized by the friction in the bear- 
 ings of the engine and machinery run thereby. The losses in the 
 ordinary boiler and steam engine amount to about 85 per cent of 
 the heat generated by tlie burning fuel. Thus only 15 per cent of 
 the energy developed from the combustion of the fuel is utilized in 
 useful work. 
 
320 THE GROWTH OF PLANTS AND ANIMALS 
 
 by the sawmill, piledriver, or dynamo. In other words, 
 one form of energy, the sun's heat, has been converted 
 through the processes of growth, burning and the use 
 of machinery, into other forms, such as mechanical and 
 electrical energy. 
 
 The animal body, an engine. — The animal body in its 
 relation to the plant world is in some respects quite 
 in the position of the engine. It too is largely dependent 
 upon plants for the fuel, or food, which is necessary for 
 the development of its energy for growth and work. For 
 example, starch when eaten by animals is burned ^ in 
 the tissues for the production of heat and muscular 
 energy.^ In this process there is just as much energy 
 developed in the form of muscular work and heat as 
 could be developed were the starch burned as fuel in 
 the most perfect steam engine. In fact, the animal body 
 is able to utilize in the form of muscular force, not 15 
 but 30 per cent of the total energy set free. The re- 
 maining 70 per cent takes the form of heat and serves 
 to maintain the temperature of the animal's body.' 
 
 As the muscular work done by animals increases in 
 severity, the amount of heat generated by the oxidation 
 increases in the same ratio. The result is that more 
 heat is generated than is necessary to maintain the 
 body's temperature, and the individual feels uncom- 
 
 ' That is, oxidized, since all burning, whether rapid as in a fire 
 or slow as in decay, is due to the union of the oxygen of the air 
 with the carbon and hydrogen of the fuel ( food ) . 
 
 = Starch + oxygen = carb. diox. + water + heat+ muse, energy 
 
 C,H,„05 + 6 0, =6 CO, +6 H,0 + " + " 
 
 In other words, 1 molecule of starch acted upon by 6 molecules 
 
 (12 atoms) of oxygen forms 6 molecules of carbon dioxide and 6 
 
 of water, and heat or heat and muscular energy are set free in 
 
 the process.^ 
 
 ' In man, the normal temperature is 98.4° F. ; in the horse, 
 about 104° F.; in the ox and dog, 101° F.; in the sheep and pie, 
 103° F.; and in the hen and pigeon, 107° F. ... 
 
EXPERIMENTS 321 
 
 fortably warm. This excess of heat is thrown off by 
 wetting the siirfai-e of the body with perspiration. Here 
 again is another example of the conservation of energy, 
 since the heat is made to disappear as heat in doing the 
 work of changing the liquid water of the perspiration 
 into water vapor. 
 
 EXPERIMENTS AND DEMONSTRATIONS 
 
 Materials : Cellulose in the form of large slivers of soft pine 
 wood ; wide-mouthed bottles with tin or glass covers ; matches ; 
 litmus paper, blue and red; saturated solution of lime water, 
 filtered or cleai-ed by settling ; test tube ; 12 in. piece of glass or 
 rubber tubing, with about ^^ in. bore; 12 in. piece of glass 
 tubing, I's in. opening, bent to S shape and fitted to a rubber 
 stopper; hydrochloric acid, 1 part to 10 parts of water; sheet 
 zinc; small deep tin pan with perforated tin shelf to serve as 
 pneumatic trough; soap; ammonia; soda; cream of tartar; 
 sweet and sour milk. 
 
 1) Acid and alkaline reaction with lit m its paper : 
 
 a) Moisten both blue and red litmus paper with dilute hydro- 
 chloric acid. Acid reaction. 
 
 b) Moisten blue and red litmus paper with lime water. Al- 
 kaline reaction. 
 
 c) Moisten blue and red Htinus paper with water. Neutral 
 reaction. 
 
 d) Test various substances, as soap, ammonia, soda, cream 
 of tai-tar and sweet and sour milk with litmus paper; arrange 
 according to their reactions as acid, alkaline and neutral. 
 
 2) Carbon dioxide manufacture: 
 
 a) Burn cellulose in a wide-mouthed bottle by thrasting the 
 lighted slivei-s under its pai-tially raised cover, keeping the 
 bottle covered as closely as possible in order to avoid the escape 
 of the gas. Continue combustion until the wood will no longer 
 burn. Remove sliver and cover bottle tightly. Note cai-efully 
 every change taking place an^ wj-ite out obs^rvatioug. 
 
322 THE GROWTH OF PLANTS AND ANIMALS 
 
 b) Moisten with water a piece of blue litmus paper and drop 
 it into bottle a). Note the change and make inference. 
 
 3) Carbonate of lime manufacture: 
 
 a) Pour a tablespoonful of lime water into the bottle of 
 2, b) and shake vigorously, keeping the bottle tightly covered. 
 Note the changes and write out observations. 
 
 b) Pour 1 oz. of clear lime water into a clean bottle and 
 blow the breath through it by means of a piece of small tubing. 
 Or, blow breath into the bottle, cover and shake, repeating if 
 necessary until the effect is produced. 
 
 4) Pour carefully a small amount of hydrochloric acid into 
 bottles 2) and 3), so that it will run down their sides. Note 
 the formation of bubbles of carbon dioxide again set free 
 through the decomposition of the carbonate by the acid. 
 
 5) Hydrogen manufacture : 
 
 Place closely coiled strips of sheet zinc in a test tube until 
 it is half full. Cover with dilute hydrochloric acid. Close 
 with a perforated stopper containing S tube. Collect the 
 hydrogen gas in an inverted bottle on the tin shelf of the 
 pneumatic trough. Withdraw the tube while the gas is still 
 coming freely and touch a lighted match to the end of the tube. 
 Note the character and heat of the flame. Hold a piece of cold 
 glass a short distance above the flame and note the condensa- 
 tion of water. Open bottle and apply lighted match. 
 
 II 
 
 Materials and apparatus ; % oz. powdered chlorate of potash ; 
 % oz. manganese dioxide; sulphur; small piece of light iron 
 wire or watch spring (broken springs from jeweller) ; small 
 bits of magnesium, copper and zinc; splinters of pine wood; 
 lime water; stick of phosphorus Yz to 1 in. long; matches or 
 candle; ice or cold water; samples of soil; 6 wide-mouthed 
 bottles about 8 oz. ; 6 test tubes with 1 perforated cork or 
 rubber stopper; several pieces of strong glass tubing, Vg in. 
 opening, 12 in. long, bent to S shape and fitted to stopper; 
 small deep pan with perforated tin shelf, to serve as a pneu- 
 matic trough ; tin cup ; scales capable of weighing % grain or 1 
 centigram decimal weights preferred) ; alcohol lamp or Bunsen 
 burner; sheet tin, 
 
EXPERIMENTS 323 
 
 1) Oxygen manufacture: 
 
 Put Yz teaspoonful each of chlorate of potash and manganese 
 dioxide into test tube. Mix and close tightly with stopper 
 carrying bent glass tube. Have ready pneumatic trough filled 
 ■with water, in which several wide-mouthed bottles also filled 
 with water are standing invei-ted over holes of perforated shelf. 
 Place lighted lamp ueai- trovigh. Gently heat lower end of test 
 tube containing mixed chemicals over flame until gas begms to 
 be given oif . Insert open end of delivery tube under shelf of 
 trough so that bubbles of gas will pass up into bottles and dis- 
 place water in them^ In this way, fill several bottles. 
 
 Caution: The heating- must be continued uniformly, and when 
 the gas begins to come very slowly the tube must be withdrawn 
 from the trough quickly enough to prevent the cold water from 
 being sucked back into the test tube. The test tube should then 
 be laid carefully upon something which it will not burn until it 
 is cold enough to be washed out. 
 
 2), Combustion in oxygen: 
 
 a) Thrust end of a burning splmter of pine wood into one 
 of bottles of oxygen covered with a piece of tin. Remove 
 quickly, blow out flame and reintroduce wood with a live coal 
 on its tip. Continue vmtil wood will no longer burn. Test 
 contents of bottle with lime water as in Exp. 3, a), part 1, and 
 compare results with those previously obtained. 
 
 b) Heat end of iron wu-e and melt on it a drop of sulphur. 
 Light sulphur and thrust it into a bottle of oxygen. Note 
 rust (iron oxide) on sides of bottle. 
 
 c) Continue expei'iment by demonstrating combustion of 
 small bits of magnesium, copper, zinc, etc. 
 
 3) Nitrogen separation:^ 
 
 Make a wood float 1 in. by 1 in. by % m. thick. Upon this, 
 place a sq. in. of sheet tin, on centre of which rest a piece of 
 phosphorus the size of a pea. ( The phosphorus should be cut 
 under water and not handled.) Float phosphorus boat on 
 surface of water in pneumatic trough. Light phosphorus and 
 immediately place over it upon tin shelf of trough an inverted 
 
 ' This is really a metliod of oxygen elimmation by phosphorus 
 absorption. The oxygen combines witli the phosphorus and tlie 
 resulting oxide is absorbed by the water. The nitrogen is eonse- 
 quently left pure. 
 
324 THE GROWTH OF PLANTS AND ANIMALS 
 
 tumbler or wide-mouthed bottle filled with air, which should be 
 steadied if it tends to tip. Note formation of phosphorus 
 oxide (PaOs). Allow this to dissolve out, that nitrogen may be 
 left pure. Then cover glass with tin, place it upright and test 
 with lime water and with a burning stick. Compare with car- 
 bon dioxide. 
 
 4) Water manufacture : 
 
 Burn a match, or, better, a candle under bottom of a clean 
 tin cup filled with ice water. Compare with I'esult obtained in 
 5, part 1. 
 
 5) Proportion of organic matter in soil: 
 
 a) Weigh out 1 oz. of each sample of soil, as leaf mold and 
 garden soil, and label each. Dry in oven for several hours, 
 with heat low enough not to burn paper upon which they are 
 placed. Reweigh and explain loss of weight. 
 
 b) Put dried samples in an iron spoon and place in a hot 
 fire until samples have been at red heat for 5 or 10 min. Allow 
 to cool and reweigh. What does loss of weight equal arid of 
 what does residue consist? 
 
APPENDIX B 
 FIRST AID TO THE INJURED 
 
 Wounds. — Injuries which penetrate the skin in any- 
 way are called wounds. They should always be carefuUy 
 dressed, since they remove the protecting coat of the 
 body, the skin, and so afford entrance to the microbes 
 which lie upon its surface or come into contact' with it. 
 These may be the microbes of such diseases as lockjaw 
 (tetanus), abscesses and erysipelas. Many cases of 
 tetanus arise each year as a result of some slight wound 
 such as is often made by the exploding caps of toy 
 pistols, which permits the tetanus germs lying upon 
 the skin to enter. A wound, therefore, may not only 
 be serious in itself but may produce serious results 
 through the entrance of microbes. 
 
 The bleeding associated with wounds, if moderate in 
 amoimt, is beneiicial, since it washes away the microbes 
 and has some power of checking their growi;h. Only, 
 however, in case it is in sufficient amount can it be 
 depended upon to protect the wound from germs. Even 
 in this case, the skin about the wound may be the source 
 of infection. 
 
 Treatment: The proper treatment of any wound in- 
 volves, first, the stopping of the bleeding; and, second, 
 the prevention of infection. If a large artery has not 
 been cut, the bleeding should be stopped by applying 
 a sterile compress (see Appendix C) and a firm band- 
 
 835 
 
326 FIRST AID TO THE INJURED 
 
 age, that the edges of the cut may be held close together. 
 If a large artery has been cut, there should be imme- 
 diately applied an elastic or other tight bandage be- 
 tween the wound and the heart at one or another of 
 the points where the artery can be compressed (see 
 p. 162). Unless it is certain that a wound is super- 
 ficial, a physician should be called at once, since there 
 may be internal bleeding of greater or less seriousness. 
 
 To prevent infection, it is necessary to get rid of the 
 microbes lying upon the skin in the neighborhood of the 
 wound. This is best accomplished by thoroughly scrab- 
 bing the skin with a clean brush and soap and then 
 applying a disinfectant solution (see Appendix C). 
 The person who bandages the wound should first have 
 his hands similarly cleansed. 
 
 Bruises. — Bruises differ from wounds in that the 
 skin is not broken. A combination of a broken skin 
 and a bruise is called a contused wound. A bruise in- 
 volves the crushing of tissues and blood-vessels with 
 more or less internal bleeding. This usually works to 
 the surface in a few hours and produces the dark color 
 characteristic of a bruise. This changes to blue and 
 gradually to yellow, as the pigment of the blood is 
 absorbed. 
 
 Treatment: To prevent blood and lymph from col- 
 lecting in the injured tissues and causing a swelling 
 which retards healing, the bruised part should be imme- 
 diately bound up tightly with a compress and bandage 
 (see Appendix C).^ Hot water or ice may be used 
 as a partial substitute for the bandaging, since cold 
 and especially heat cause contraction of the blood-vessels 
 and thereby check bleeding. Gentle rubbing is also 
 
 » Care should be taken not to bind ao tightly as to check the flow 
 of blood in arteries and veins. 
 
BURNS 327 
 
 most effective in controlling the swelling, discoloration 
 and pain, especially about the head and face. 
 
 Burns.— JSio-H^, whether caused by fire, steam, hot 
 water, acids and allcalies, or by cold, as in frost-bite, 
 resemble wounds in that they remove the barrier to the 
 entrance of microbes, by destroying the skin. They 
 may also cause the irritation of extensive areas of nerve 
 terminals and a consequently profound shock to the 
 nervous system. There may further be an extensive 
 absorption of the detritus of the wounded skin, through 
 the lymphatics. 
 
 Treatment: In mild burns, where the skin is simply 
 reddened, a moist paste of cooking soda is effective in 
 relieving the pain. As a substitute, either a paste of 
 starch or flour, vaseline, sweet oil, lard, or cream may 
 be used. In more severe burns where the skin is blis- 
 tered, the blistere sliould be emptied through small punc- 
 tures made with the point of a knife or needle which has 
 previously been sterilized.^ The treatment should then 
 be the same as for a mild bum. In still more severe 
 burns where the skin is destroj'ed, the skin surrounding 
 tbe burn as well as the hands of the operator should be 
 disinfected. To allay the nerve irritation, soothing ap- 
 plications of sterilized oil should be used. 
 
 Acids and alkalies. — Burns by acids and alkalies 
 require special treatment, because the acid or alliali may 
 continue to destroy the skin if allowed to remain upon 
 it. To remove these chemicals, water should be allowed 
 to flow freely over the injured parts before any other 
 treatment is attempted. As a further precaution in case 
 of burning by an acid, it is well to apply a thin paste 
 of cooking soda, that any remains of the acid may be 
 
 ' Held in boiling water or in alcohol, or heated red hot in a 
 flame and allowed to cool. 
 
328 FIRST AID TO THE INJURED 
 
 neutralized thereby. In ease of burning by an alkali, 
 vinegar should be substituted for the soda. The 
 subsequent treatment should be that prescribed for 
 burns. 
 
 Frost-bite. — The skin frozen by extreme cold should 
 first be gently rubbed with water from melting ice or 
 with melting snow. This treatment should be con- 
 tinued for several hours, in order to avoid the intense 
 inflammatory reaction which is apt to follow freezing. 
 If, in spite of this treatment, the skin becomes inflamed, 
 it should be treated as a. burn. 
 
 In all cases of severe burns, a physician should be 
 immediately summoned, since a burn which involves as 
 much as a quarter of the skin of the body may be quickly 
 fatal. 
 
 Sprains. — Sprains are another frequent form of in- 
 jury and are usually due to a wrenching force applied 
 to a joint. As we have seen in our study of ligaments, 
 a sprain usually involves some tearing of the ligaments 
 about the joint. In severe cases, it may even involve 
 the breaking off of portions of the bones to which the 
 ligaments are attached. 
 
 Treatment : The immediate treatment for a sprain is 
 in general similar to that for a bruise, as the laceration 
 of the tissues leads to bleeding, swelling and pain. In 
 addition to such treatment, a splint (see Appendix C) 
 should be applied to the joint, to prevent pain and the 
 possibility of further injury. Sprains should always 
 be examined by a physician, that the extent of the injury 
 may be definitely determined in the beginning. Serious 
 disability has not infrequently arisen from a neglected 
 sprain, especially of the ankle. 
 
 Dislocations. — Dislocations are ordinarily due to the 
 same causes as sprains. The wrenching force must be 
 
FRACTURES 829 
 
 strong enough, however, to tear away sufficient of the 
 protecting ligaments to allow the ends of the bones 
 to slip by each other. Dislocation can ordinarily be 
 easily detected by the deformity and stiffness of the 
 joint. 
 
 Treat mod: A pliysician sliould be called at once, as it 
 usually requires experience to replace the bones. There 
 sliould be no unnecessary delay, as the subsequent swell- 
 ing makes the operation more difficult. Pending the 
 physician's arrival, the dislocated joint should be pro- 
 tected by support upon a high pillow, in as comfortable 
 an attitude as possible. If a physician cannot be got 
 witliin an hour or so, and if the dislocation is fairly 
 simple, as that of a finger, an ankle, or a shoulder, an 
 attempt should be made to reduce it by pulling the limb, 
 finger, or foot strongly in the direction of its length, with 
 the injured part held in its normal position. Reduction 
 takes place with a snap, which is easily recognized. 
 
 Fractures. — Fractures are more frequent than dislo- 
 cations but ordinarily are not more serious. They 
 usually involve the bones of the limbs, the collar bone, 
 or ribs. Fractures of the spine, pelvis and skull are com- 
 paratively rare. A fracture can usually be easily rec- 
 ognized because the fractured bone becomes movable 
 where there is no joint. The ends of the bones when 
 moved upon each other give a characteristic grating feel- 
 ing. Perforation of the skin may also be caused by the 
 force which produced the fracture or by the projection 
 of the bones through it, in which case the fracture is 
 said to be compound. Compound fractures are usually 
 much more serioiis than simple fractures, as there is a 
 probability of infection. 
 
 Treatment : As in a dislocation, a physician sliould be 
 called at once. The treatment depends largely upon 
 
330 riRST AID TO THE INJURED 
 
 the nature, location and severity of the fracture and 
 the surroundings of the patient. In general, the 
 wounded part should be disturbed as little as possible, 
 if a physician can be secured. For examination, the 
 clothing should be cut, if to remove it means to dis- 
 turb the injured part. The location and nature of the 
 injury should then be determined by a careful and sys- 
 tematic comparison between the injured limb and its 
 mate as to length, deformity and mobility. If, after the 
 fracture has been located and the extent of the injury 
 determined, it is considered necessary to move the pa- 
 tient, it should be done with the least disturbance of 
 the fracture possible. If one of the legs is injured, the 
 person should be placed upon a stretcher (see Appendix 
 C), shutter, or door. If one of the arms is fractured, 
 it should be supported by splints and put up in a sling 
 (see Appendix C). If the collar bone is fractured, the 
 arm on that side should be put up in a sling, in order 
 to relieve the shoulder of its weight. A simple fracture 
 of the ribs permits walking or riding, except where 
 blood is coughed or spit. In that case, the broken rib 
 has punctured the lung and absolute quiet is essential. 
 
 In case a physician cannot be secured, an attempt 
 should be made to set the bone. In case of a simple 
 fracture, the limb may be straightened to the length 
 of its mate by pulling it very gently and evenly in the 
 direction of the part nearest the body. It should then 
 be carefully brought to a position as similar to the nat- 
 ural one as possible and supported by pillows. Tem- 
 porary splints made of canes, laths, or umbrellas padded 
 with cotton or cloth, may then be applied, or folded 
 sheets or pillows bandaged on. In case of a compound 
 fracture, there should also be antiseptic treatment, sim- 
 ilar to that in the case of a wound. If there is bleed- 
 
POISONS 331 
 
 ing copious enough to show that an arteiy has been 
 cut, it will be necessary to apply pressure to cheek it. 
 
 Poisons. — Another frequent source of injury to the 
 tissues or of interference with their functions is found 
 in certain substances which are commonly known as 
 poisois. These may be taken into the body from with- 
 out, as in the case of drugs and chemicals; or they may 
 be developed in the body itself by the action of microbes, 
 as ptomaines and toxins. 
 
 Drugs and chemicals. — Among drugs and chemicals, 
 there are several types of poison which differ widely 
 in their effects upon the body. Some destroy tissue, 
 as strong acids and alkalies, and are called corrosive 
 or irritant poisons. Others, as opium with its deriva- 
 tives and alcohol, produce their harm by benumbing 
 the nervous system and are therefore known as narcotic 
 poisons. A third type, as strychnia, excites the nervous 
 system so much as to destroy its control of the body and 
 thereby cause convulsions. Poisons of this kind are 
 therefore called convulsive. The effects of drugs and 
 chemicals ax-e sometimes very quick or again so slow 
 as to extend over weeks and months, depending largely 
 upon their nature and the quantities in which they are 
 taken. Since many of the siibstances in common use 
 in the household, such as disinfectants, insect powders 
 and the like, are, when taken into the body, violent 
 poisons, every one should be acquainted with them and 
 their antidotes. 
 
 General treatment : 
 
 1) Send for the nearest doctor. 
 
 2) Produce vomitiug by the use of: 
 ringer or feather for tickling the thi-oat. 
 
 Mustai-d water, tablespoonful of mustard in tumbler of tepid 
 water. 
 
332 FIRST AID TO THE INJURED 
 
 Salt water, tablespoonful of salt in tumbler of tepid water. 
 
 Copper sulphate, 10 grs. in 2 oz. of warm water. 
 
 Zinc sulphate, 20 to 30 grs. in half a tumbler of tepid water. 
 
 Ipecac, 2 tablespoonfuls of the wine or syrup. 
 
 Caution: Emetics are useless unless taken immediately after 
 such substances as opium, morphine, carbolic acid, aconite, 
 cocaine, or strong acids and alkalies, which either cause 
 anesthesia of the throat and stomach or destroy their tissues. 
 
 3) Give antidotes: 
 
 Chemical (see Special Poisons), in order to destroy the 
 power of the poispn. 
 
 Physiological, in order to increase the power of the heart 
 and to overcome weakness and depression : 
 
 a) Give stimulants, such as. 
 
 Aromatic spirits of ammonia or common ammonia, table- 
 spoonful in half glass of water ; frequent small doses. 
 
 Pure grain alcohol, 1 or 2 teaspoonfuls in warm water. 
 
 Coffee in strong solution. 
 
 Vapor of ether inhaled or 1 teaspoonful in warm water. 
 
 Tincture of nux vomica, 5 to 10 drops in water. 
 
 Strychnia, ^j- to -^ gr. 
 
 Caution : Since stimulants are not absorbed from the stomach 
 if there is much corrosive action, as in the case of strong acids 
 or alkalies, they should be given by the rectum. 
 
 b) Apply heat by means of warm blankets, hot water bottles, 
 bricks, etc. Caution: In case of loss of consciousness, be 
 especially careful to apply nothing hot enough to cause a 
 btirn. 
 
 c) Give massage, rubbing toward the heart, in order to aid 
 the venous return. Keep the patient in a horizontal position, 
 or, in case of profound depression, with the head and chest 
 lower than the rest of the body. Sudden raising of the head 
 should always be avoided in anyone who is weak. Caution: 
 In case of snake bite, avoid rubbing, since it tends to scatter the 
 poison (see p. 335). 
 
 d) Give diluents, as water, or any harmless fluid, in order 
 to dilute and thereby weaken the power of the poison as well as 
 to delay its absorption. 
 
 e) Give demulcents, as milk, white of egg, or boiled starch, 
 if the poison is corrosive or irritant, in order to coat over the 
 
POISONS AXD ANTIDOTES 333 
 
 poison, to form a pix)teetive coating for the stomach, or to 
 entangle the poison by coagulation. 
 
 Common Poisons and their Antidotes: 
 
 Irritant poisons {more or less corrosive) : 
 
 1) Arsenic (Paris green, Fowler's ■ solution, arsenious acid, 
 and certain vermin killers). 
 
 Antidote: Pi-ecipitated oxide of ii-on. If this cannot be 
 immediately obtained, give moistened plaster of wall which will 
 mis with the poison and serve to protect the stomach. 
 
 2) Phosphorus (matches, Eough on Rats). 
 
 Antidotes: Emetics and magnesia or plaster from waU. 
 Caution: Do not give oily substances, as milk. 
 
 3) Corrosive sublimate (mercuric bichloride, bug poison). 
 Antidotes: Emetics and white of egg. 
 
 4) Iodine (tincture). 
 Antidote: Boiled starch, rice, etc. 
 
 5) Lead (paints, hair dyes). 
 
 Antidotes: Sulphates (Epsom salts, Glauber's salts, alum), 
 emetics, etc. 
 Corrosive Poisons : 
 
 1) Aeids (sulphuric, hydrochloric, nitric). 
 
 Antidotes: Emetics and dilute alkalies, such as lime water, 
 soap solution, tooth powder, chalk, or plaster of wall, followed 
 by demulcents. 
 
 2) Carbolic acid. 
 
 Antidotes: Emetics, water and sulphates (Glauber's or 
 Epsom salts or alum). 
 
 3) Oxalic acid. 
 
 Antidotes: Lime or chalk with stimulants given as needed. 
 
 4) Alkalies (caustic soda, caustic potash, ammonia). 
 Antidotes: Dilute acid, vinegar, hard cider, lemon or orange 
 
 juice, followed by demulcents. 
 Narcotics: 
 
 1) Opium' (laudanum, paregoric, morphine, black drops, 
 soothing s\Tups. cholera mixtures, Dover's powder). 
 
 Antidotes: Solution permanganate of potash, 2 grs. dis- 
 
 ' In opium poisoning, a distinguishing symptom is pin-head con- 
 traction of the pupils of tlie eyes. 
 
334 FIRST AID TO THE INJURED 
 
 solved in water; tannic acid; strong hot coffee; strychnia, ^ij 
 
 to t'o g^- ... 
 
 Keep awake by non-exhausting means, such as flicking with 
 
 a damp towel, shouting in ear, and making walk. Keep warm 
 with hot water bottles, blankets, etc. Perform artificial respira- 
 tion, if necessary. 
 
 2) Chloral hydrate (chloral, knock-out drops). 
 Antidotes: Emetics, stimulants, ammonia. 
 
 Keep body warm with head low. Keep patient awake. Per- 
 form artificial respiration, if necessary. 
 
 3) Alcohol (drunk)': 
 
 Antidotes: Hot coffee and dilute ammonia in small repeated 
 doses. Apply first hot and then cold water. Keep patient 
 
 Ptomaines and toxins. — Ptomaines and toxins arise, 
 as we have seen, from the decomposition of animal and 
 vegetable matter due to the activity of microbes. They 
 may be found in food materials which have not been 
 preserved by cold and even in some, as in ice cream, 
 which have been so preserved. The symptoms of the 
 poisoning are characteristic and include headache, purg- 
 ing and vomiting, fever and abdominal pain. 
 
 Treatment : A doctor should be called at once. The 
 patient should not be allowed to eat but should have 
 plenty of hot water to drink. If a doctor cannot be got 
 without delay, 2 tablespoonfuls of castor oil, a dose of 
 Epsom salts, or a Seidlitz powder should be given, in 
 order to clean out the bowels and intestines. The doctor 
 can then complete the treatment. 
 
 Stings of insects. — The poison injected by insects 
 varies with the nature of the insect. In some eases, 
 as in the stings of wasps and bees, the poison is irritant 
 and results in pain and swelling but is not dangerous 
 
 * Wood alcohol and denatured alcohol, which contains wood 
 alcohol, are extremely dangerous poisons. 
 
SNAKE BITE 336 
 
 when in moderate amount. In other cases, as with 
 scorpions and tarantulas, the poison is often sufficiently 
 virulent to be dangerous. In still others, as with certain 
 mosquitoes, bedbugs and fleas, the poison may be in 
 the form of microbes which infected the insect when it 
 bit a diseased person. 
 
 I'reatmcnt: The treatment varies with each case. For 
 the milder forms of insect bite, a strong solution of 
 ammonia, if applied at once, is fairly effective. The 
 more dangerous forms of poison introduced by scorpions 
 and tarantulas, should be treated like poison from snake 
 bites. 
 
 Snake bite. — Still another form of poison is that in- 
 jected by certain kinds of snake, such as the rattlesnake, 
 moccasin and cobra. The poison is especially virulent 
 and takes effect so quickly that the treatment must be 
 immediate. 
 
 Treatment: Tie a tight bandage around the limb just 
 above the bite, to prevent the transmission of the poison 
 through the body. In this way, the poison is localized 
 in the limb and its effect upon the body as a whole is 
 avoided. Freely slash the skin in which the bite lies, 
 penetrating deeper than the wound, in order to induce 
 a copious bleeding which will wash the poison out of the 
 tissues ; or, burn out the bite with a red-hot iron. Give 
 stimulants as needed to support the strength and prevent 
 shock, but be careful not to make the patient drunk with 
 alcohol, as this tends to increase the paralyzing effect 
 of the poison. A physician should of course be called 
 as quickly as possible. 
 
 Dog bite.— The bite of a mad dog should have the 
 same treatment as a snake bite. 
 
 Loss of consciousness.— Loss of consciousness is a 
 common symptom for many conditions and injuries, such 
 
336 FIRST AID TO THE INJURED 
 
 as fainting, children's convulsions, epileptic attacks, 
 apoplexy, sunstroke, injury of the brain, drowning, and 
 poisoning by illuminating gas, carbolic acid, opium and 
 alcohol. In order to assist a person who is unconscious, 
 one must know the nature of the trouble. Ordinarily, 
 it is possible to discover this and by rendering assistance 
 to prevent more or less serious consequences. 
 
 Treatment: The general treatment for unconscious- 
 ness may be begun while an examination as to its cause 
 is being made. A physician should be sent for at once. 
 The patient should be placed upon his back and the 
 clothing about throat and chest loosened. Give him 
 plenty of fresh air and, if the breathing has ceased 
 although the pulse is still felt, apply artificial respira- 
 tion. Do not give stimulants if the face is flushed or 
 the pulse is strong; in case of brain injury, they may 
 even cause further injury of the brain tissue by continu- 
 ing the hemorrhage. If the temperature of the body is 
 raised, apply wet cloths or ice. 
 
 In making an examination, note if there is fracture 
 of bones, including ribs, collar bone and skull. Eun the 
 fingers down the spine and determine whether there 
 is dislocation or fracture. Lift the lids of both eyes and 
 see whether they are dilated, contracted, or equal in size. 
 In opium and morphine poisoning, they are contracted; 
 in brain injury, they may be dilated or unequal in size. 
 Determine also whether there is an odor to the breath 
 which suggests alcohol, ether, or chloroform. Note 
 whether there is any discoloration of the lips, showing 
 the use of strong acids or alkalies. 
 
 Fainting. — In fainting, the face and lips lose their 
 color and the pulse is weak. 
 
 Treatment: Place the patient upon his back, with the 
 }i?ad and chest lower than the rest of tbe body. If there 
 
CONVULSIONS SSI 
 
 is vomiting:, place him upon his side. Apply smelling 
 salts, or give ammonia or strong coffee. Insure plenty 
 of fresh air by fanning, and avoid excitement. 
 
 Convulsions. — Children frequently lose consciousness 
 through convulsions, as a result of improper diet, fever, 
 worms, constipation, etc. 
 
 Treatment: Keep the child from injuring himself. Put 
 him into a warm bath or wrap him in a blanket dipped 
 in hot water. Keep the head cool by applying cold 
 water or ice. If the convulsions continue, give an emetic, 
 as a teaspoonful of syrup of ipecac, if the child can 
 swallow. Assist vomiting by thrusting the finger down 
 the tliroat or by using a feather. Give injection of 
 soap and warm water, as the seat of irritation may be in 
 the lower bowel. 
 
 Epileptic attacks, — Epileptic attacl^s may come on 
 suddenly, or gradually with s3Tnptoms which the patient 
 recognizes. Loss of consciousness may be accompanied 
 by a peculiar cry, sudden pallor of the face and more 
 or less stiffening of the body. The tongue is some- 
 times bitten and the eyes have a peculiar upward roll- 
 ing motion. An attack usually lasts for a minute or 
 two only, but several attacfe may follow each other 
 rapidly. 
 
 Treatment . -Keep the patient from in juring himself , but 
 do not struggle with him. Allow him to lie flat, and put 
 a piece of folded cloth between the teeth to prevent biting 
 of the tongue. The muscular contractions if prolonged 
 give rise to exhaustion and lameness, but these may be 
 lessened by putting the patient into a bath of warm 
 water. After the attack put him to bed and if necessary 
 use stimiilants in small quantities. 
 
 These attacks are seldom serious, and it is usually 
 unnecessary to do anj-thing except prevent bodily injury. 
 
338 FIRST AID TO THE INJURED 
 
 Apoplexy. —Apoplexy is seldom found in persons 
 under forty years of age. It is due to bleeding from a 
 ruptured blood-vessel in the brain and consequent pres- 
 sure of the blood upon the brain tissue. The nerve cells 
 or nerve fibres when pressed upon, cease to perform^ their 
 functions and more or less unconsciousness and paralysis 
 result. The face is flushed, the pupils of the eyes more 
 or less dilated and perhaps unequal in size, the breathing 
 slow and noisy, the cheeks puffed out and drawn in with 
 the air movement and the pulse slow and full. There 
 may be convulsions and vomiting. An important symp- 
 tom is one-sided paralysis. Notice whether the face 
 is drawn to one side (away from the paralyzed side) 
 or the head kept on one side. 
 
 Treatment: Keep the patient absolutely quiet, lying 
 down, the head moderately raised. Apply cold water or 
 ice to the head and heat to the lower limbs. If the pa- 
 tient can swallow, give castor oil or a dose of salts. The 
 bowels may be emptied by giving an injection of soap and 
 warm water. Do not give stimulants. 
 
 Sunstroke. — When working on a hot sunny day, or 
 on warm days when the air is full of moisture, persons 
 are sometimes overcome with the heat, having headache, 
 weakness and difficulty of vision. The individual quickly 
 becomes unconscious, and may even fall so as to be 
 injured. The body is usually hot to the touch, the skin 
 dry, the face flushed, the pulse full and rapid, but there 
 may be coldness, pallor and weak pulse. Twitchings of 
 the body may also be noticed. 
 
 Treatment : Eeduce the heat of the body as rapidly as 
 possible by throwing cold water over the patient and 
 applying ice to the head. Strip, the body and wrap it 
 in a sheet kept wet by frequent applications of water. 
 Continue until consciousness is regained or the tempera- 
 ture of the body is lowered. Do not send the patient 
 
SUFFOCATION AND DROWNING 339 
 
 to his home or to a hospital until after the treatment 
 has been begun. If the patient does not exhibit symp- 
 toms of high temperature, but shows pallor of face and 
 weak pulse, do not use cold applications, but give rest, 
 quiet, food and stimulants in cautious amounts. 
 
 Brain injury. — Any injury to the brain results iu symp- 
 toms similar to those of apoplexy. In addition, there 
 may be bleeding from one or both ears and even from 
 the eyes, nose and mouth, due to the fracture of the 
 skull. The treatment is also similar to that of apoplexy. 
 
 Suffocation and drowning. — Cases of suffocation and 
 drowning can ordinarily be recognized as such and the 
 proper measures for relief promptly undertaken. 
 
 Treatment: If the natural breathing movements have 
 ceased, as is frequently the case when a person is rescued 
 from drowning, artificial respiration should be applied 
 at once. Turn the person on his face, clasp your hands 
 under the lower chest and raise him from the ground; 
 the pressure upon the lower chest will compress the 
 lungs and tend to empty them of water. Repeat two or 
 three times, taking care not to injure the face by rough 
 handling. Do not, however, delay artificial respiration 
 in the attempt to remove all of the water. 
 
 Wipe out the mouth. Turn the patient over on his 
 back with something under his back and shoulders, so 
 that the head will rest well back. Pass a pin through 
 the tip of the tongue. Draw the tongue out from the 
 mouth; pass a string around it back of the pin, cross 
 it over the chin and tie it behind the head, so that the 
 tongue will be held forward and wiU not close the air 
 passage into the larynx.^ Loosen the clothing and cover 
 it with dry. 
 
 " This is necessary only when no one else is present to hold the 
 tongue. If two are present, friction upon the limbs should also be 
 employed. 
 
340 
 
 FIRST AID TO THE INJURED 
 
 Artificial respiration. — Place yourself at the head o£ 
 the patient, grasp his forearms near the elbow and carry 
 them upward so that they lie parallel at each side of his 
 head. Let them rest there for a moment ; notice that air 
 enters through the nose and mouth. Then carry the arms 
 
 Fig. 153. Sylvester's method of artificial respiration, sliowiiig tlie two movements, 
 inspiration and expiration. A mettiod of fixing the tongue is also shown. 
 
 back and press them upon the chest; notice that air is 
 expelled. Repeat this regularly every 3 or 4 seconds. 
 
 After 5 or 10 minutes of artificial respiration, it may 
 be best, if in winter, to remove the patient to a warm 
 place. During the time of removal continue, if possible, 
 artificial respiration and especially rhythmic pressure in 
 the region of the heart every 1 or 2 seconds, since this 
 may tend to keep the blood in circulation and carry 
 aerated blood from the Itmgs to the tissues. Artificial 
 respiration should be continued for 1 or 2 hours if neces- 
 sary, as there is always hope of saving a person 's life if 
 the pulse or heart beat can be detected. Persons have 
 been saved after being under water as long as 12 or 15 
 minutes. 
 
 In addition to artificial respiration, a hot water bottle 
 may be applied to the heart to stimulate its action ; and 
 warm (105° F.) water may be injected into the rectum, 
 to aid in restoring the heat of the body. Hot cloths, hot 
 water bottles and hot bricks should be freely used as 
 
GAS POISONING 341 
 
 soon as possible, care being taken to avoid burns. Stim- 
 ulants may be given by the mouth, if the patient is able 
 to swallow ; if not, they may be given by the rectum, in 
 which case they will be absorbed and carried by the 
 blood to the respiratory and cardiac centres. 
 
 After the crisis is past, shock should be avoided by 
 keeping the patient quiet in bed, and his strength should 
 be built up by the use of food and stimulants as needed. 
 
 Gas poisoning. — Poisoning by iUuminating or coal 
 gas results in headache, dizziness, ringing in the ears and 
 gradual loss of consciousness. The skin is pale and 
 bluish and the respiration irregular. 
 
 Treatment: Remove the patient into the fresh air. 
 Dash cold water into the face, slap the chest, and tickle 
 the nose. Hold ammonia under the nostrils or take 
 the tongue in a dry handkerchief and every 4 seconds 
 draw it out with moderate force. If these measures fail 
 to re-establish breathing, artificial respiration must be 
 immediately undertaken. 
 
 Choking. — ^Unconsciousness may further be due to 
 choTxing or suffocation. Choking is usually due to the 
 presence of objects too large to be swallowed, which 
 become wedged against the larynx and thereby . inter- 
 fere with the passage of air. It may also be due to 
 the presence of foreign bodies in the air passages, or 
 to irritating gases the inhalation of which causes spasm. 
 The result may be more or less complete but usually tem- 
 porary suffocation. Distress and violent coughing are 
 prominent symptoms. 
 
 Treatment: Strike the patient strongly with the flat 
 of the hand on the back. Lay him on a bed or chairs 
 with the head and upper part of the chest hanging over. 
 Let him take a full breath and then press on his back 
 as the air goes out. In a child, raising by the feet may 
 
342 FIRST AID TO THE INJURED 
 
 aid in dislodging the object. If ineffective, do not waste 
 time, but pass the finger down the throat, taking the 
 precaution to insert a folded handkerchief between the 
 teeth to avoid being bitten. An ordinary finger is long 
 enough to reach to the larynx, and the object may be 
 felt and removed. An emetic of mustard water is some- 
 times effective if the object has not passed too far. Avoid 
 exhaustion of patient in the attempts at removal, since 
 objects which can pass through the esophagus by the 
 larynx usually do no harm, if they are assisted in their 
 passage by masses of food with large waste, as potato 
 and turnip. 
 
 Croup. — At times, children are taken suddenly with 
 croup, '^ the symptoms of which resemble those of chok- 
 ing. Give the child warm water, or, better, a teaspoon- 
 ful of syrup of ipecac, and repeat until vomiting occurs. 
 Apply hot water, ice, or mustard plasters to the throat. 
 Send for the doctor. 
 
 ' What used to be known as malignant croup is now recognized 
 to be diphtheria. 
 
APPENDIX C 
 PRACTICE IN FIRST AID 
 
 In order to render effective first aid, a certain amount 
 of practice in the application of bandages, compresses, 
 splints and slings and in the proper handling of the 
 body when injured, is necessary. To this must be added 
 a practical Imowledge -of the methods of disinfecting 
 wounds. 
 
 Triangular bandage. — There are three principal forms 
 of bandages with which a first-aid student should be 
 familiar, namely, the triangular,^ the roller and the 
 four-tailed. The triangular bandage is made of fairly 
 stout sheeting in the form of a triangle. The simplest 
 way to make it is to take a piece of cloth from 30 to 
 36 in. square, and either to fold or cut it along the 
 diagonal. This bandage is most useful as a protective 
 bandage or to hold a compress in place but ordinarily 
 is not very effective in applying pressure. 
 
 Roller bandage. — The bandage which applies pressure 
 best is the roller bandage. This consists of a strip of 
 cheesecloth 1 to 5 in. wide and from 4 to 10 j'ds. long, 
 which is rolled tightly. To apply the roller, grasp it 
 in the right hand so that the loose end points toward 
 
 ' An excellent triangular bandage on which are printed the 
 metliods of applying, can be obtained for 10 cents from The Society 
 for Instruction in First Aid to the Injured, 105 East 22d Street, 
 New York, or from The Health Education League, 113 Devonshire 
 Street, Boston. The directions for use are given so simply by 
 means of illustrations on the bandage that they are omitted from 
 this discussion. It is hoped that each pupil will own one of these 
 bandages. 
 
 343 
 
344 
 
 PRACTICE IN FIRST AID 
 
 the left as it comes from underneath the roller. With 
 the thumb of the left hand, gently hold the loose end 
 upon the part to be bandaged. At the same time, run 
 the roller around the limb and bring it firmly over the 
 thumb which holds the loose end, so that when the thumb 
 is withdrawn the loose end remains in place. Continue 
 to roll the bandage upon the limb, keeping it taut so that 
 it will not slip or give uneven pressure. After the 
 bandaging is complete, double under the end and fasten 
 
 FiQ. 154. A and B, Four-tailed bandage as applied to the head. C, Handkerchief 
 bandage as applied to the chin in case of injury to the lower jaw. 
 
 it with a small safety pin, or split the end and tie the 
 parts together around the limb. In applying the 
 bandage, too severe pressure must be avoided, as other- 
 wise the circulation may be stopped and even gangrene 
 eventually result if the bandage j-emains on long enough. 
 To test the amount of pressure, examine the limb after 
 the bandage has been on for an hour or so. If it shows 
 swelling beyond the bandage or is cold and bluish, the 
 bandage is too tight and should be loosened. The roller 
 bandage will be found to be more generally useful than 
 any other. 
 
 Four-tailed bandage. — The four-tailed bandage is 
 made of a piece of cotton cloth about 36 in. long and 
 
BANDAGES 
 
 345 
 
 from 6 to 10 in. wide, the two ends of which are slit 
 equally toward the middle, leaving only about 6 or 8 
 in. intact. It is most useful for bandaging the head 
 and should be applied as shown in the accompanying 
 illustrations. 
 
 Compress. — Compresses are made of 10 to 15 lay- 
 ers of cheesecloth or soft slieeting, of the size necessary 
 to cover the part, except in those eases where it is 
 easier to use several compresses of a smaller size. They 
 may be used dry for pressure, or moistened with hot 
 water or antiseptic solutions. Compresses are used to 
 apply pressure, heat, or medication to sprained joints or 
 in,iuries where the skin is not broken. In case of wounds, 
 the compresses may be freed from microbes (sterilized) 
 by baking to a light brown in an oven or by steaming 
 for fifteen minutes. They may then be safely applied to 
 the cut surface to check bleeding and to prevent 
 infection. 
 
 Splmts.^S pi infs consist of light pieces of wood, card- 
 board, or any other stiff material. When bandaged on, 
 
 Fig. 155. Padiled splints applied to fractured leg for temporary support. 
 
 they serve to hold broken bones and sprained or dislo- 
 cated .ioints in place and thereby relieve pain and pre- 
 vent further injury. The aeeompanying illustrations 
 show several methods of utilizing splints. It will be 
 
346 PRACTICE IN FIRST AID 
 
 seen that the essential point is to give such full support 
 that the movements of the patient will not jar the in- 
 
 FiG. 166. Pillow used as an emergency splint. 
 
 jured part. In bandaging the splint, care must be 
 taken to avoid such pressure as would interfere with 
 circulation. 
 
 Sling. — ^When the arm or shoulder is injured, it is 
 important to support the weight of the arm. For this 
 purpose, a sling is used, which consists of a large tri- 
 
 Fie. 167. Sling as arranged for left arm. 
 
 angle of cloth of sufficient length to permit the forearm 
 to hang in a horizontal position. The middle of the 
 base of the triangle is placed at the finger tips, while 
 the apex lies behind the elbow. The long ends are then 
 carried around the neck, the outer one toward the farther 
 
DISINFECTION 347 
 
 shoulder, and are tied behind the neck. The apex is 
 pinned behind the elbow. 
 
 Stretcher. — A stretcher on which to carry an injured 
 person may be made of two stout poles, 7 to 8 ft. long, 
 slipped through hems in the sides of a piece of canvas 
 6 ft. long by 1 6 in. wide. As a substitute for the canvas 
 in an emergency, two coats buttoned together over 
 poles may be used. A wide board, door, shutter, or 
 similar object may also be substituted. If nothing of 
 this sort is available, it is possible for a number of per- 
 sons so to carry an injured man as to avoid increased 
 injury ajid pain. In this case, no part should be allowed 
 to sag and there should therefore be as many supporting 
 points as possible. The lifting should be done by all 
 simultaneously, so that jar is avoided. 
 
 Disinfecting solutions. — For the disinfection of 
 wounds, several antiseptics are available, such as cor- 
 rosive sublimate, of the strength of 1 part to 1,000 parts 
 of water ; lysol in a 3 per cent solution, made by adding 
 f of a cup of water to a teaspoonful of lysol; carbolic 
 aeid in a 3 per cent solution made similarly to lysol; 
 sulpha- naphthol (creoliii) in a 3 per cent solution, 
 similarly prepared ; and peroxide of hydrogen used full 
 strength as sold by druggists. In the absence of other 
 antiseptics, alcohol diluted with half as much water may 
 be used. "Washing soap is antiseptic to a certain extent 
 and may be used in strong solution for thoroughly scrub- 
 bing around the wound. 
 
 Of these disinfectants, the best for use in wet com- 
 presses are corrosive sublimate, 1 to 2,000; lysol in a 
 3 per cent solution; and creolin, also in a 3 per cent 
 solution. Carbolic acid should never be used, as it may 
 exert corrosive action upon the skin. 
 
INDEX 
 
 Abduction, 37 
 
 Abscess. 128, 206, ;V25 
 
 Absorption, 112, 113, US 
 
 Abstinence, 305, 312 
 
 Accommodation, 200 
 
 Acids, 327 
 
 Activity, 120, 121 
 
 Adduction, 37 
 
 Adenoids, 191 
 
 Adrenal bodies, 132 
 
 Africans, 300 
 
 Age, 120 
 
 Air, 1, 165, 166, 172-175. 1S2- 
 
 192, 2S3, 316 
 Air pressure, 174 
 Air sacs, 169 
 
 Air tests, 183, 184, 193, 194 
 Albumin, 77 
 Alcohol, 93-95, 159, 216, 217, 
 
 301-313, 334. 347 
 Alcoholism, 304, 312 
 Alimentarv canal. 96, 07 
 Alkalies, 327 
 Ah-eoli, 169 
 Ameba, 4, 8, 51, 96 
 Amylopsin, 103 
 Anatomy, 10 
 Anemia, 127 
 Angle worm, 52 
 Animal food, 77-82 
 Animal heat, 211 
 Animal matter, 262 
 Animals, 1, 10, 51, 67, 211. 315 
 Ankle, 24 
 
 Anopheles, 189, 2SS 
 Antibody, 284-287, 290 
 Antidotes to poisons, 333, 334 
 Antitoxin, 284-287, 290, 291 
 Anvil, 253 
 Aorta, 136. 139, 140 
 Ape, 10, 25 
 Apoplexy, 304, 338 
 
 Appetite, 121-124 
 
 Aqueous humor, 257 
 
 Arm. 21 
 
 Arsenic, 77 
 
 Arterial pressure, 158 
 
 Arteries, 135. 140-143, 161, 162, 
 
 320 
 Arterioles, 141 
 Artieular cartilage, 31 
 Articular surfaces. 15 
 Artificial respiration, 339, 340 
 Astigmatism, 264 
 Atlas, 14 
 Atrophy, 46 
 Auditory canal, 252 
 Auditory nerve, 234, 255 
 Auricles, 136, 138-140 
 Aurieulo-ventricular valves, 
 
 138-140 
 Axial skeleton, 19 
 Axis cylinder, 224 
 Axis vertebra, 14, 15 
 
 Backbone, 13 
 
 Bacteria, 2S2-2S4 
 
 Bad air, 182-185 
 
 Baking powder, 74 
 
 Ball and socket joint, 32, 33, 44 
 
 Banana, 76 
 
 Bandage, 162, 164, 320, 343, 344 
 
 Basilar membrane, 254. 255 
 
 Batliing, 207 
 
 Baths, 207 
 
 Beans, 66, 75 
 
 Bed, 189 
 
 Bed clotliing, 214, 215 
 
 Beef-tea, 82 
 
 Beer, 93, 302. 304 
 
 Beets, 75 
 
 Bent-knee walking. 57. 5S 
 
 Beverages, 87-95, 302 
 
 Biceps, 40, 59, 60 
 
 349 
 
350 
 
 INDEX 
 
 Bicuspids, 98 
 
 Bile, 109-111 
 
 Bile duct, 108, 109 
 
 Binocular vision, 265 
 
 Biuret test, 118 
 
 Bladder, 198 
 
 Blankets, 214, 215 
 
 Bleeding, 158, 160, 161, 163, 325 
 
 Blind spot, 262 
 
 Blister, 327 
 
 Blood, 126-156, 198, 199, 212 
 
 Blood, corpuscles of, 5, 126-128, 
 
 206 
 Blood-plasma, 126, 128 
 Blood pressure, 158 
 Blood-vessels, 37, 135, 136 
 Blushing, 141-148, 304 
 Body temperature, 211, 212, 
 
 216-218 
 Boiling, 70 
 Boils, 206 
 Bone, 12, 26-30, 39 
 Bony labyrinth, 254 
 Bouillon, 82 
 Brain, 221, 232-238 
 Brain convolutions, 232 
 Brain injury, 339 
 Brain work, 158 
 Brandy, 93, 302 
 Bread, 74 
 
 Breakfast foods, 75 
 Breastbone, 17 
 Breathing, 175, 176, 192 
 Brewers, 307 
 Broiling, 69 
 Bronchi, 167 
 Bruises, 160, 326 
 Burns, 327 
 Butter, 74, 78 
 
 Cabbage, 75 
 
 Caffeine, 92 
 
 Calorie, 120, 121 
 
 Cambric tea, 91 
 
 Candy, 84 
 
 Canine teeth, 98 
 
 Canned fruits, 77 
 
 Capacity of lungs, 174 
 
 Capillaries, 135, 143, 144, 196, 
 
 197 
 Capsular ligament, 36, 37 
 
 Carbohydrates, 65, 69, 121, 130 
 
 Carbolic acid, 347 
 
 Carbon dioxide, 1, 45, 74, 130, 
 165, 183, 184, 315, 316 
 
 Carbon monoxide, 299, 316 
 
 Carbuncles, 2.06 
 
 Carnivorous animals, 67 
 
 Cartilage, 29, 168 
 
 Casein, 77 
 
 Catarrh, 191 
 
 Celery, 76 
 
 Cells, 5, 6, 8, 9, 112, 201, 281, 
 303 
 
 Cellulose, 71, 75, 318 
 
 Cement, 42 
 
 Cement of teeth, 101 
 
 Cereals, 66, 73, 75 
 
 Cerebellum, 232 
 
 Cerebral hemispheres, 232 
 
 Cerebrum, 232 
 
 Cheeks, 103 
 
 Cheese, 77 
 
 Chemicals, 331-334 
 
 Chest, 171-173, 300 
 
 Chewing, 103 
 
 Chewing tobacco, 298 
 
 Chill, 284 
 
 Chimpanzee, 11 
 
 Chloral, 296, 298 
 
 Chocolate, 84, 92 
 
 Choking, 341 
 
 Cholera, 88, 282 
 
 Chordse tendinese, 137 
 
 Chyle, 111, 113 
 
 Chyme, 107, 108, 111 
 
 Cider, 93, 302 
 
 Cigarettes, 298, 300 
 
 Cilia, 168, 191 
 
 Circulation, 135-164 
 
 Circulatory system, 135-156 
 
 Circumduction, 37 
 
 Circumvallate papillse, 250 
 
 Clavicle (collar-bone), 17, 21 
 
 Cleanliness, 207 
 
 Climates, 187, 188 
 
 Clothing, 188, 213, 214 
 
 Clotting of blood (see Coagula- 
 tion) 
 
 Coagulation of blood, 126, 128 
 
 Coal gas, 190 
 
 Coccyx, 16 
 
INDEX 
 
 351 
 
 Cochlea, 254 
 
 Cocoa. 0-2 
 
 Cocoaiiie, 2!Hi, 20S 
 
 Coffee. 02, 93, 300, 301 
 
 Cold, sense of. 24S 
 
 Cold baths, 207, 21S 
 
 Cold feet. 212 
 
 Colds, 190. 191. 279 
 
 Cold spot, 248 
 
 Colic. 113 
 
 Collagen, 2G 
 
 Collar bone (clavicle), 17, 21 
 
 Colloids, US 
 
 Color. 256 
 
 Colored races, 201 
 
 Color of skin. 201, 202 
 
 Combustion, 45, 315 
 
 Common poisons, 333, 334 
 
 Composition of foods, 86 
 
 Compress, 325, 345 
 
 Condiments. S2 
 
 Connective tissue, 71, 130. 202, 
 
 303 
 Consciousness, loss of, 335, 336 
 Conservation of energ\-, 318, 
 
 319 
 Consonants, 279 
 Constipation, 297 
 Consumption, 1S3, 190, 2S2. 
 
 286, 2S7, 290 
 Contagious diseases. 291. 292 
 Contraction of heart. 136 
 Contraction of muscle, 46 
 Contused wound, 326 
 Convolutions of the bi-ain, 232 
 Convulsions, 337 
 ComTilsive poisons. 331 
 Cooking, 69-71 
 Cord, spinal, 221, 227, 228 
 Corn, 75 
 
 Cornea, 257, 258, 203 
 Corn syrup, 77 
 Corpuscles of blood, 5, 126-128. 
 
 206 
 Corrosive poisons. 331 
 Cotton, 215 
 
 Coughing, 190, 288, 289 
 Cow, 79 
 
 Cowpox (vaccinia), 286 
 Crsib, 11. 12 
 Con-osive sublimate, 347 
 
 Cranial nerves, 234 
 
 Cream. 77, 78 
 
 Creolin, 347 
 
 Cross-eves. 266 
 
 Croup, ' 342 
 
 Crown of tooth, 101 
 
 Crystalline lens, 257-260, 263 
 
 Crystalloids, 117 
 
 Deafness, 271 
 
 Decay, 318 
 
 Deformities, 17 
 
 Delirium tremens, 304 
 
 Denatured alcohol, 334 
 
 Dentine, 101 
 
 Dermal senses, 248 
 
 Dermis, 202 
 
 Dextrin, 118 
 
 Dialysis (osmosis), 117, 118 
 
 Diaphragm, 172-174 
 
 Diet, 67-69, 73, 121 
 
 Differentiation, 6, 8 
 
 Digestion, 96-125 
 
 Diphtheria, 190, 282, 286, 287, 
 
 291, 342 
 Discharges, 289 
 Disease," 189, 190. 281-292 
 Disease germs, 190, 282-292 
 Disinfecting solutions, 347 
 Disinfection, 289, 290 
 Dislocations, 33, 37, 328 
 Distance, perception of, 265 
 Distillation, 93, 302 
 Dizziness, 158 
 Diverging eves, 266 
 Dog bite, 335 
 Dogs. 308 
 Dorsal region, 14 
 Drafts, 188 
 Dried fruits, 76 
 Drownins;. 339 
 Drugs, 331-334 
 Ducts, 108, 109 
 Dust, 168. 189-191. 273 
 Dysentery, 76. 88 
 
 Ear, 256, 272, 273 
 Earache, 272 
 Ear drum, 253 
 Earth, I 
 
352 
 
 INDEX 
 
 Earthy matter, 26 
 
 Economic effects of alcohol, 313 
 
 Egg albumin, 80 
 
 Eggs, 80 
 
 Elbow, 22, 33 
 
 Emollients, 208 
 
 Emulsion, 111, 113 
 
 Enamel, 101 
 
 Endolymph, 254 
 
 ]Ond organs, 249 
 
 Energy, 8, 45, 58, 65, 68, 69, 
 
 124, 131, 319-320 
 Engine, 319, 320 
 Enzyme, 103 
 Epidemics, 291, 292 
 Epidermis, 200 
 Epilepsy, 304, 337 
 Epiphysis, 30 
 Equilibrium, sense of, 255 
 Erysipelas, 325 
 Esophagus, 104, 105 
 Ether, 256 
 
 Eustachian tube, 254 
 Excretion, 198 
 Excretions, 289, 290 
 Exercise, 62, 176-178 
 Expiration, 173 
 Extension at joints, 37 
 External ear, 252 
 Eye, 256-266, 273-275 
 Eye, foreign bodies in, 274 
 Eye, proper use, 275 
 Eyeball, 258, 262 
 Eyelashes, 274 
 Eyelids, 274 
 Eye strain, 264 
 
 Fainting, 158, 163, 336 
 
 Far-sight, 260 
 
 Fasciculi of muscles, 40 
 
 Fat, 203, 304 
 
 Fatigue, 63, 248, 249, 284 
 
 Fats, 65, 110, 113, 121, 123, 
 
 130 
 Femur, 23 
 
 Fermentation, 77, 93, 95, 302 
 Ferments, 103 
 Fever, 217, 218, 285 
 Fibril of muscles, 41 
 Fibrin, 126, 129 
 Fibula, 24 
 
 Filters, 91 
 
 Filtration of water, 90 
 
 Finger, 22 
 
 Fireplaces, 186 
 
 First aid, 325-347 
 
 Fish, 81, 82 
 
 Flavor, 251 
 
 Flexion at joints, 37 
 
 Focus, 259, 260 
 
 Food, 1, 2, 65, 67-86, 94, 112, 
 
 120-124, 130, 158, 283, 289, 
 
 292, 301 
 Foods, composition of, 83 
 Foot, 24 
 Foot-pound, 120 
 Foot- ton, 120 
 Forearm, 21, 42 
 Formaldehyde, 290 
 Four-tailed bandage, 344 
 Fractures, 27, 37, 329, 330 
 Freezing, 217 
 Fresh air, 183, 184 
 Frost bite, 328 
 Fruits, 76, 302 
 Frying, 70 
 Fulcrum, 52, 53 
 Fundamental tone, 278 
 Fur, 214 
 Fusel oil, 302 
 
 Gall (see Bile) 
 
 Gall-bladder, 108, 109 
 
 Games, 61 
 
 Ganglia, 226 
 
 Gases, 190 
 
 Gas poisoning, 341 
 
 Gastric glands, 106, 107 
 
 Gastric juice, 106, 110 
 
 Gelatine, 26, 71 
 
 Germ cell, 6 
 
 Germs, 5, 190 
 
 Gibbon, 11 
 
 Glands, 103, 106, 107, 132, 150, 
 
 151, 204, 205 
 Glucose, 65, 77 
 Gluten, 66 
 Glycerine, 208 
 Glycogen, 113, 130 
 Grains, 66, 73, 75, 302 
 Grapes, 76 
 Grape-sugar, 65, 76 
 
INDEX 
 
 353 
 
 Growth, 1, 29, 131, 178, 299, 
 
 315-318 
 Gums, 65 
 
 Gustatory nerves, 235 
 Gymnasia, 292 
 
 Habits, 237, 301 
 
 Hair, 203 
 
 Hallucinations, 304 
 
 Hammer. 253 
 
 Hand, 22. 42 
 
 Head, 17 
 
 Headaclie. 285, 297 
 
 Healtli, 120, 132, 102, 281. 286, 
 
 300 
 Hearing, sense of, 252-255 
 Heart, 130-140, 231, 304 
 Heart beat, 137, 157 
 Heart muscle, 48, 136, 137 
 Heart strain, 178 
 Heat. 1, 318 
 Heat, sense of, 248 
 Heating, 185, 186 
 Heat of body, 211, 212, 216- 
 
 218 
 Hemoglobin, 127 
 Hemorrhage, 15S, 161-163 
 Herbivorous animals, 67, 83 
 Hinge joints, 34 
 Hip-bone, 18 
 Hoarseness, 278 
 Horse, 287 
 Humerus, 22 
 Humidity of air, 186 
 Hydrocarbons, 65, 69. 76, 130 
 Hydrochloric acid, 321 
 Hvdrogen, 1 
 Hygiene, rules of, 289. 290 
 
 Ileocecal valve, 113 
 Illness, 120 
 
 Illuminating gas, 190 
 Image, formation of, 258 
 Immunity from disease, 286 
 Incisors, 98 
 Indians, 306 
 Indigestion, 124, 297 
 Infection, 282. 287. 291, 292, 
 
 326 
 Inflammation, 160, 161 
 Injuries, 17, 160 
 
 Inner ear, 254 
 
 Inoculation, 288 
 
 Inorganic matter, 3 
 
 Insanity, 304 
 
 Insects, 288, 334 
 
 Inspiration, 172-174 
 
 Insurance, 305-308 
 
 Internal secretion of glands, 
 
 132 
 Intestinal digestion, 108-113 
 Intestinal juice, 108 
 Intestines, small, 68, 108-114 
 Involuntary muatsles, 47 
 Ivis, 257, 261 
 Irritant poisons, 331 
 
 Joints, 31-37, 42 
 
 Kidneys, 121, 122, 131, 132, 
 
 196," 199 
 Kittens, 309 
 Knee-cap ( patella ) , 34 
 Knee-joint, 34 
 
 Lacteals, 111, 112, 149 
 
 Lake water, 89 
 
 Large intestine, 112, 113 
 
 Laryngitis, 279 
 
 Larynx, 167, 276-278, 280 
 
 Lead poisoning, 77 
 
 Leather, 214 
 
 Leg, 22. 23 
 
 Lens, 257-260, 263 
 
 Lettuce, 76 
 
 Levers, 52-55, 59 
 
 Ligaments. 13, 33, 36. 328, 329 
 
 Light, 1, 256, 262. 274, 275, 318 
 
 Lime salts, 26, 27, 29 
 
 Lipase, 103 
 
 Liver, 108, 112, 127, 130, 303 
 
 Tjobster, 11 
 
 Lockjaw (tetanus), 325 
 
 Locomotion, 51, 57 
 
 Longevity, 305 
 
 Lumbar region, 15 
 
 Lungs, 165, 166, 170, 171, 173- 
 
 178 
 Lvmph, 148-151. 284 
 Lymphatics, 148-151, 327 
 Lysol, 347 
 
354 
 
 INDEX 
 
 Malaria, 189, 282, 288 
 
 Malt, 302 
 
 Maltose, 103 
 
 Mammal, 10 
 
 Man, 9-11 
 
 Mania, 304 
 
 Marrow, 30, 127 
 
 Meals, 122, 158 
 
 Measuring worm, 52 
 
 Meats, 81, 82 
 
 Medulla oblongata, 231 
 
 Medullary canal, 30 
 
 Melons, 76 
 
 Membranous labyrinth, 254 
 
 Microbes, 78-80, 82, 88, 128, 
 
 151, 161, 190, 191, 206, 207, 
 
 218, 282-292, 325 
 Middle ear, 253 
 Milk, 77, 80, 88 
 Milk sugar, 77 
 Moisture of air, 186 
 Molar teeth, 99 
 Molds, 283 
 Morphine, 296, 298 
 Mosquito, 189, 288 
 Motor (efferent) nerves, 224- 
 
 228 2^1 
 Mouth, 96-103, 166, 289 
 Mouth breathing, 192 
 Movements, 51 
 Mucus, 168 
 Mumps, 103 
 
 Muscles, 13, 40, 44-48, 56, 278 
 Muscular sense, 249 
 Muscular work, 61, 120-122, 
 
 124, 158, 176-178, 320 
 
 Nails, 204 
 
 Narcotic poisons, 331 
 Narcotics, 296-313 
 Nasal tones, 279 
 Nausea, 285 
 Near-sight, 260, 275 
 Neck, 13 
 
 Neck of tooth, 101 
 Nerve control, 45 
 Nerve fibres, 223 
 Nerve filament, 224 
 Nerve ganglia, 226 
 Nerves, 221-245 
 Nerve sheath, 223 
 
 Nerve trunks, 222 
 Nervous breakdown, 243 
 Nervous impulses, 225, 227, 
 
 248, 249, 251, 255, 256, 263 
 Nervous system, 6, 62, 219-245, 
 
 302, 304 
 Neural canal, 15 
 Neuroglia, 233 
 Neuron, 225 
 Nicotin, 298 
 Night air, 189 
 Night-cap, 189, 216 
 Nitrogen, 66, 315 
 Noise, 273 
 Non-destructibility of matter, 
 
 318 
 Nose, 166, 190, 279, 280, 289 
 Nucleus, 4, 61 
 Nutrition, 9 
 Nuts, 65, 66, 76 
 
 Oils, 65, 66 
 
 Olfactory nerves, 234, 251 
 Omnivorous animals, 67 
 Optic nerves, 262, 263 
 Organ, 12 
 Organic matter, 3 
 Organic salts, 75 
 Organisms, 2, 3, 88, 282 
 Organs, 6 
 Osmosis, 118, 119 
 Osteoblasts, 29 
 Osteoclasts, 29 
 Oval window, 253 
 Overtones, 278, 279 
 Overwork, 63 
 Oxidation, 45, 315 
 Oxygen, 1, 127, 130, 165, 315 
 
 Pain, 245, 296 
 
 Pain, sense of, 248, 249 
 
 Palate, 104 
 
 Pancreas, 109, 132 
 
 Pancreatic secretion, 103, 110, 
 
 11] 
 PapilliE of the tongue, 104, 250 
 Papillary muscles, 138, 139 
 Paralysis, 46, 225, 303, 304 
 Parasites, 81, 88, 283, 284 
 Parks, 292 
 Parotid glands, 103 
 
INDEX 
 
 35S 
 
 Pasteuiizntioii, 80 
 
 Patella (knee-cap) . 35 
 
 Peanuts, 7.) 
 
 Peas, 66, 75 
 
 Pelvic girdle, 17, 18, 22 
 
 Pepsin, 103, 107 
 
 Peptones, 107. 112, 113 
 
 Periljinph, 254 
 
 Periosteum, 30 
 
 Pei-oxide of hvdrogen, 347 
 
 Perspiration, 199, 204, 20,>, 212, 
 
 214, 321 
 Pharynx, 103,' 104, 167, 2o4 
 Physiology, 10 
 Pigment cells, 201 
 Pimples, 20o, 206 
 Pitdi, 27 S 
 Pituitary body, 132 
 Pivotal joints, 36 
 Plague, 2S3 
 
 Plants, 1, 51, 07, 315, 318 
 Plasma, 126, 12S 
 Platelets, 128 
 Play, 61 
 
 Playgrounds, 292 
 Pleura, 171 
 Pneumonia, 190, 2S4 
 Poisoning, 331, 332 
 Poisons, 284, 303, 330-335 
 Poor circulation, 163 
 Pores of skin, 205 
 Potatoes, 75, 76 
 Power, 52. 53 
 Preserved fruits, 7t! 
 Pressure, 159. 161. 162 
 Proteids, 66. l!9. 76, 81, 107, 
 
 110, 113, 121, 130, 131 
 Protoplasm, 4, 127 
 Protozoa, 283 
 Ptomaines, S2, 334 
 Ptialin, 103 
 Pulmonary artery, 140 
 Pulmonarv circulation, 135, 
 
 145 
 Pulp cavitv of tooth. 101 
 Pulse, 144", 162. 164 
 Pupil. 261 
 Pus, 161 
 Pustule, 128 
 Putrefaction, 81 
 Pyloris, 107 
 
 Quarantine, 291 
 
 Radish, 76 
 
 Radius. 22 
 
 Rays of light, 258 
 
 Recuperation, 64 
 
 Red blood corpuscles, 120, 127 
 
 Red marrow, 30, 127 
 
 Reflex action, 228-231. 235, 236, 
 
 274 
 Renal secretion (urine), 198 
 Renal tubules, 196 
 Rennin, 107 
 Reproduction, 3, 5 
 Resonance, 279. 280 
 Respiration, 165-195 
 Respii-ed air, 1S2-184 
 Rest, 63 
 
 Retina, 257. 258. 261 
 Ribs, 17-20, 173 
 Rice, 86 
 River water, 88 
 Roasting, 69 
 Rods (and cones), 262 
 Roller bandage, 343 
 Room, ventilation of, 185, 186 
 Roots of teeth, 100 
 Rotation of joints, 37 
 Rules of hygiene, 289, 290 
 Rum, 302 
 Running, 58 
 
 Sacrum, 16 
 
 Saliva, 103 
 
 Salivarv glands, 103 
 
 Salt. S3 
 
 Sausage, 81 
 
 Scapula (shoulder-blade), 17. 
 
 21 
 Scarlet fever, S8. 286 
 Scurvy, 75 
 Sea bathing, 207 
 Seasonings, 82 
 Sebaceous glands (oil glands), 
 
 204 
 Segmentation, 6 
 Semicircular canals, 255 
 Semilunar cartilage, 34 
 Sensations, 248-251, 255. 256, 
 
 261-263 
 Senses, special, 246-271 
 
356 
 
 INDEX 
 
 Sensory (afferent) nerves, 225- 
 228, 231 
 
 Sewer gas, 190 
 
 Shell fish, 88 
 
 Shock, 327 
 
 Shoulder, 21 
 
 Shoulder girdle, 17, 21 
 
 Sight, sense of, 256-266 
 
 Skeleton, 11, 12, 26 
 
 Skin, 6, 200-210, 283, 325, 327 
 
 Skull, 18 
 
 Sleep, 64, 122, 189, 241-243 
 
 Sleeping bag, 215 
 
 Sleeplessness, 159, 243, 296 
 
 Sliding joint, 36 
 
 Slings, 346 
 
 Small intestine, 108, 113 
 
 Smallpox, 286, 291 
 
 Smell, sense of, 250, 251 
 
 Smoking tobacco, 298 
 
 Smooth muscular tissue, 48 
 
 Snake bite, 335 
 
 Sneezing, 289 
 
 Snuff, 298 
 
 Soap, 112, 119, 207, 208, 347 
 
 Soft palate, 104 
 
 Soil, 1, 317 
 
 Sound, 255, 276 
 
 Soup, 82 
 
 South Sea Islanders, 306 
 
 Specialization, 7 
 
 Special senses, 246-271 
 
 Speech, 276 
 
 Spinal bulb, 231 
 
 Spinal column, 13 
 
 Spinal cord, 221, 227, 228 
 
 Spinal nerves, 222 
 
 Spleen, 127, 132 
 
 Splints, 345, 346 
 
 Sprains, 37, 160, 328, 329 
 
 Spring water, 89 
 
 Starch, 65, 70, 72, 93, 103, 107, 
 
 110, 113, 318 
 Starvation, 131 
 Sterilization, 80, 327 
 Sternum (breast-bone), 18 
 Stew, 82 
 
 Stimulants, 296-313 
 Stings, 334 
 Stirrup, 253 
 Stomach, 68, 105-108, 303 
 
 Storage of food, 131 
 
 Stretcher, 330, 347 
 
 Striped muscle, 47 
 
 Sublingual glands, 103 
 
 Submaxillary glands, 103 
 
 Suffocation, 339, 341 
 
 Sugar, 65, 77, 83, 84, 93, 107, 
 
 109, 112, 113, 130, 302, 318 
 Sulpho-naphthol (creolin), 347 
 Sulphur, 66 
 Sun, 1, 318, 319 
 Sunstroke, 338 
 Swallowing, 104, -105 
 Sweat, 205, 214 
 Sweat glands, 204, 205, 212, 
 
 231 
 Sympathetic system, 152, 229 
 Synovial fluid, 31 
 Synovial membrane, 31 
 Systemic circulation, 135 
 
 Tannic acid, 92 
 
 Tapeworm, 81, 283 
 
 Tapioca, 75 
 
 Taste, sense of, 249, 250 
 
 Taste buds, 249, 250 
 
 Tea, 92, 93, 300, 301 
 
 Teeth, 67, 97-102, 124, 125 
 
 Temperature, 79, 80, 216-218 
 
 Temperature sense, 248, 249 
 
 Tendon, 35, 40 
 
 Tetanus, 325 
 
 Theine, 92 
 
 Theobromine, 92 
 
 Thermometer, 218 
 
 Thigh, 23 
 
 Thoracic duct, 149 
 
 Thumb, 22 
 
 Thyroid gland, 132 
 
 Tibia, 23 
 
 Timbre, 278 
 
 Tissues, 6, 7, 71 
 
 Tobacco, 298-300 
 
 Toe, 25 
 
 Tongue, 102, 250 
 
 Tonicity, 46 
 
 Tonsils, 192 
 
 Total abstinence, 305, 306, 312 
 
 Touch, 247, 248 
 
 Touch corpuscle, 247 
 
 Toxins, 284, 286, 287, 334 
 
INDEX 
 
 357 
 
 Ti-achea (windpipe), 104, 16(j, 
 
 167 
 Transformation of energj-, ^^\'^ 
 Treatment of poisoning, 331, 
 
 332 
 Triangular bandage, 104, 343 
 Triceps muscle, 60 
 Trichina, 81, 283 
 Trunk, 14 
 Tuberculosis, 183, 2S2. 280, 287, 
 
 290 
 Turbinate Iwnes, 166 
 Turnips. 75 
 Turtle, 12 
 
 Tympanic membrane, 253, 254 
 T)'phoid, 70, 88, 91, 282 
 
 Ulna, 22 
 Upper arm, 21 
 Urea, 121 
 Ureter, 197 
 Uric acid, 121 
 Urine, 198 
 
 Vaccination, 280, 291, 202 
 Vaccinia (cowpox), 280 
 Valves, 136, 139, 146 
 Vasomotor control, 157, 158 
 Vasomotor ner\-es, 152 
 Vea^>tables, 75, 70, 88 
 Veins, 135, 143-146 
 Venous system, 144 
 Ventilating flues, 186 
 Ventilation, 184-189 
 Ventricles. 136, 138-140 
 ^>rmifo^m appendix, 97, 115 
 \>rtebrsp, 13 
 Vertebral colunm, 13 
 Vertebrate animals, 19 
 
 A'illi of small intestine, 111, 
 
 112 
 Vision, 203, 205, 200 
 Mtroous humor, 2o7 
 Vooal cords, 270, 277 
 Voice, 270-278 
 Volume of sound, 277 
 A'olimtary action, 237 
 A'oluntary muscles, 46 
 \'omiting, 108 
 N'owels, 279 
 
 Walking, 50, 58 
 
 Waste pi-oducts, 196 
 
 Warm bath, 207 
 
 Water, 1, 87-91, 131, 199, 283, 
 
 202, 316 
 Weight. 52. 53 
 \\ell water, 89 
 Wheat, 66, 73 
 Whiskey. 93, 302 
 Whispering, 280 
 White blood corpuscles, 126- 
 
 128. 206. 2S4. 286 
 \^'hite matter of brain, 233 
 Windows, 185 
 Windpipe, 104, 166, 167 
 Wine, 93. 302 
 Wood alcohol, 334 
 Wool, 213 
 Work, 48, 61-63, 69, 121, 122, 
 
 243, 244, 292, 320 
 Worm, 52 
 Wounds, 325, 326 
 Wrist, 22 
 
 Yeast, 74, 93, 94 
 Yellow fever, 288 
 
arV135 ^°"'^" ''"'"erslty Library 
 
 ''iiiiii?ite,.,!?Lfi!3n'°!Psy...and 
 
 olin.anx 
 
 3 1924 031 179 959