PRINCIPLES OF 
PHYSIOLOGY AND HYGIENE 
BY 
GEORGE WELLS FITZ, M.D. 
Sometime Assistant Professor of Physiology 
and Hygiene and Medical Visitor, 
Harvard University 
SECOND EDITION, REVISED 
NEW YORK 
HENRY HOLT AND COMPANY Copyright, 1908, 
BY 
HENRY HOLT AND COMPANY 
THE QUINN & BODEN CO. PRESS 
RAHWAY, N. J. PREFACE 
Many years of experience in teaching physiology1 
have convinced me that the ideal of a text-book should 
be the clearness, accuracy and simplicity obtained by 
viewing the human body as a machine automatically ad- 
justed 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 en- 
vironment; 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 student and thus to give to the 
physiology, and especially to the hygiene, a working 
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. 
1 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. Dellin- 
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, Foster 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. F. 
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. 
Boston, March 3, 1908. 
G. W. F. 
PREFACE TO SECOND EDITION 
The necessity for a second edition has afforded the 
opportunity not only of making certain slight verbal 
changes in the text but of substituting for the modified 
Sylvester method of resuscitation from drowning Scha- 
fer's new prone pressure method, and of adding a table 
of infectious diseases which gives the incubation periods, 
early symptoms, modes of entry, causes and school 
quarantine periods for the several diseases, including 
common diseases of the skin and eyes. 
Boston, January 15, 1909. 
G. W. F. CONTENTS 
CHAPTER I 
PLANT AND ANIMAL LIFE 
PAGE 
Growth-Food of plants and animals-Organisms-Multipli- 
cation of organisms-Organic substances-Building ma- 
terials of animals-A simple type of animal-Reproduc- 
tion by division-Development 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 HUMAN BODY 
Definition of physiology-Man a mammal-Skeleton-Ar- 
rangement of bones and organs-Spinal column-Ver- 
tebrae 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 
CHAPTER III 
( 
BONES, JOINTS AND LIGAMENTS 
Purpose of the skeleton-Composition of bone-Changes 
from infancy to old age-Shapes of bones-Building of 
bone-Growth of long bone in length-Growth in thick- 
ness-Growth of short bone-Growth of flat bone-Ends 
of bones-Structure of a joint-Range of movement- 
Characteristics of a true joint-Kinds of joints-Hinge 
joints-Knee joint-Pivotal joints-Sliding joints- 
Ligaments-Kinds of movement-Joint injuries-Dislo- 
cation-Bone-building materials 26 
CHAPTER IV 
MUSCLES AND TENDONS 
Muscles-Structure-Muscle fibres-Tendon fibres-Union of 
muscle and tendon-Advantages of tendons-Control of 
VII 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-Law 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 fish-Parasites 
in meat-Putrefaction-Meat stews-Soups-Fish-Con- 
diments-Salt-Sugar 73 
CHAPTER IX 
WATER AND OTHER BEVERAGES 
Mineral contents-Organic contents-Wafer supply-Surface 
water-Spring water-Well water-Lake water-Protec- CONTENTS 
IX 
PAGE 
tion of water supply-Sand 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 HYGIENE 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-White 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 CIRCULATION OF THE BLOOD 
System of tubes for the blood-Greater and lesser circuits- 
Heart-Heart muscle-Muscle cells-Ventricles-Auri- 
cles-Auriculo-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 CONTENTS 
X 
PAGE 
CHAPTER XIV 
THE HYGIENE OF THE CIRCULATION 
Vasomotor control of blood distribution-Control by heart 
beat-Faulty distribution-Effects of eating-Causes of 
sleeplessness-Effects 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 
CEIAPTER 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 18$ 
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-Wool-Leather and furs-Thin or thick clothing- 
Bed clothing-Arrangement of bed clothing-Fall in 
body temperature-Alcohol-Freezing-Rise in body 
temperature 211 
CHAPTER XX 
THE NERVOUS SYSTEM 
General arrangement-Nerves-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- 
Cerebrum-Brain convolutions-Gray matter-White 
matter-Protection of brain-Cranial nerves-Reflex 
action-Voluntary action-Habits 219 
CHAPTER XXI 
USE AND CARE OF THE NERVOUS SYSTEM 
Activity of the nervous system-Value of sleep-Amount of 
sleep-Habits of sleep-Nervous breakdown-Value of 
work-Amount of work-Method of work-Meaning of 
pain 241 
CHAPTER XXII 
THE SPECIAL SENSES 
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-siglit-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 
CHAPTER 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 
CHAPTER 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 nar- 
cotic poison-Chronic effects upon structure-Effect 
upon heart-Upon blood-vessels-Upon nervous system- CONTENTS 
XIII 
PAGE 
Systemic effects-Longevity-Experimental proof-Prac- 
tical studies-Economic effects 296 
APPENDIX A 
THE GROWTH OF PLANTS AND ANIMALS 
Food of plants-Oxygen (0) Nitrogen (N)-Carbon dioxide 
(C02 )-Carbon monoxide (CO)-Water (H.2O)-Soil- 
Plant growth-Non-destructibility of matter-Conserva- 
■ tion of energy-Transformation of energy-The animal 
body, an engine 315 
APPENDIX B 
FIRST AID TO THE INJURED 
Wounds-Bruises-Burns-Acids and alkalies-Frost-bite- 
Sprains-Dislocations-Fractures-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 IN FIRST AID 
Triangular bandage-Boiler bandage-Four-tailed bandage 
-Compress-Splints-Sling-Stretcher-Disinfecting so- 
lutions 343 
APPENDIX D 
Table of Infectious Diseases 348 PHYSIOLOGY AND HYGIENE 
CHAPTER I 
PLANT AND ANIMAL LIFE 
Growth.-As we watch plants and animals grow, we 
see how many changes they are making in the world 
about them. The plants are taking the materials which 
they need from the earth, air and water,1 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 within which is 
hidden a minute plant and food prepared by the mother 
plant for its'use. When placed in the moist warm earth, 
the plant awakens and by living upon the stored-up 
food quickly becomes larger 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 large and strong clover plant. The gas and water 
are no longer simply gas and water, but are combined 
1 The soil contributes mainly water containing a small amount 
of salts in solution. The air contributes a colorless gas, carbon 
dioxide (C02), which is produced by the burning and decay of 
wood and other organic materials; and a small amount of nitrogen. 
Water (II2O) consists of 2 parts of hydrogen to 1 of oxygen. For 
a further discussion, see Appendix, p. 315. 2 
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,1 because they 
lead a more or less independent life, 
during which they grow and develop. 
Most organisms begin life compara- 
tively small and weak.2 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 destroyed. 
Fig. 1. Gerininatingpeas, 
growing in water, one 
(7?) deprived of its co- 
tyledons, which con- 
tain the stored-up food. 
(Bergen.) 
1 Literally, an organism is a living unit which possesses organs. 
The term has, however, come to include all plants and animals. 
2 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; moun- 
tains are broken into rocks and loose earth by frost and 
washed down into the valleys 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 
organisms. 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 young individuals, which, after they 
have developed into maturity, again divide. In this 
way, the species is rapidly multiplied, and death and 
decay through old age are avoided. 
In higher forms of plants and animals, the process 
of reproduction consists in the development of the 
young organism as an offshoot or bud from the adult. 
When capable of independent development, it is set 
free as a young plant or animal and thereupon begins 
a new life, in which lies this 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, flour, starch, sugar, coal, coal oil, paraffin 
and natural gas. From animals come such substances as 
flesh, leather, hair, wool 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 various 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.1 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 Dellinger. 
various organs and tissues possessed by the higher ani- 
mals and man. 
A simple type 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 
known 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 
1 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 hardly be seen. Its body of 
protoplasm with its more solid spherical nucleus, makes 
up a single cell.1 
The ameba, like all other animals consisting of but one 
cell, has, in spite of its smallness and simplicity, the be- 
Fig. 3. Ameba progressing (side view). After photo-micrograph by Dellinger. 
ginnings of the faculties and powers 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 may be said to be endless, since 
each healthy adult undergoes division into young twin 
cells of half the original size. These immediately take 
on the characteristics and powers of the older cell, and 
growing rapidly to maturity redivide in their turn. 
Reproduction by division.-This process of division 
begins and is completed in the nucleus before the sur- 
rounding mass of protoplasm, the cytoplasm, changes. 
The cytoplasm then 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- 
1 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- 
Fig. 4. Diagrams illustrating direct cell-division : a, cell-body; b, nucleus; c, 
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,1 and develop the power to do 
1 Differentiation. MULTIPLICATION OF CELLS 
7 
the special work of these organs and tissues,1 they under- 
go marked changes in size, shape and behavior. In our 
study, we are not concerned with their rapid and perplex- 
ing changes, but with the 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 within 
two or three months of the single cell stage. The re- 
Fig. 5. Cleavage or segmentation of an ovum, showing successive division of the 
germ cell (a) into two (d), four (c), and eight (d). Later stages are shown at e 
and/. The first four figures are diagrammatic: e and / are after Hatschek's 
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, are devoted to the enlargement and perfection 
of the organs and tissues 2 already formed in miniature. 
1 Specialization. 
2 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 case it is 
also an organ. PLANT AND ANIMAL LIFE 
8 
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 1 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, 
1 See Appendix, p. 316. FORMS OF CELLS 
9 
it is broader and has the power of shortening itself so 
as to aid in pulling the bones about. In other words, the 
Fig. 6. Various forms of cells found 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 
intricate system of canals, the blood-vessels. The waste 
products of their activity are borne away without effort 
on their part by this same blood supply, which bathes 
all the tissues of the body. 
Demonstrate under the microscope the ameba as found in the 
slime from stagnant pond water. 
DEMONSTRATION 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. 
Fig. 7. Skeletons of gibbon, chimpanzee and man drawn in natural relations of 
size. (After Huxley.) 
Skeleton.-The human body consists of two dis- 
tinct parts, a bony framework called the skeleton, and 
the soft flesh, skin 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.1 By this arrangement, the skeleton 
Fig. 8. Animal with external skeleton (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 are 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, stomach, liver and intestines, which are irregular 
in shape and not in pairs. 
1 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 fundamental part of the skele- 
ton and the only part possessed by some of the lower 
forms of vertebrates is the backbone called the spinal or 
vertebral column. The spinal column 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 vertebra?. These verte- 
bras 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 
vertebrae in the neck must 
move freely. They are there- 
fore comparatively small 
and loosely connected by 
strong bands of gristle, 
the ligaments, and firmly 
held by strong contractile 
bands, the muscles. Move- 
ment beyond a certain 
amount is checked by 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 first of the neck vertebras is so 
shaped as to permit the lower portion of the skull 
which rests upon it to slip readily. To permit the 
Fig. 9. The spinal column, right 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 
Fio. 10. The relation between the 1st and 2nd vertebrse, permitting rotation of 
the head. 
freedom of movement is required, in order that the ribs 
which are attached to the vertebrae may receive ade- 
quate support. The vertebrae 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 vertebrae may be checked. In childhood, the THE VERTEBRAE 
15 
movement permitted is more extensive than in later life, 
owing to the greater looseness of the ligaments and the 
largei' spaces between the processes, but even then the 
movement between adjacent vertebras is slight. 
Of the lower back.-In the lower part of the back, 
the lumbar region, bending is essential. The parts of 
the vertebrae which come together, the articular surfaces, 
Fig. 11. Views of dorsal vertebrae 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 OF 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 movement per- 
Fig. 12. A section through three vertabice, showing structure 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. 
& 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. 
'll 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 L -THE BONES, JOINTS, AND LIGAMENTS. SPINAL INJURIES 
17 
Injuries and deformities.-Because of the great 
strain 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 growth and development due to irregularities in 
the shapes and numbers of the bones, to faulty postures, 
or to the habitual carrying of heavy weights upon one 
Fig. 13. Side and back views of correct and faulty positions at school desks. 
(Tubby.) 
side of the body. Children who carry heavy babies are 
frequently deformed in this way. 
Head.-The spinal column, 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 surmounted 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 OF THE HUMAN BODY 
sternum. The ribs arise from the dorsal vertebras, en- 
circle the chest and are united together in front by the 
Fig. 14. A side view of the skull. 0, 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,1 the 
ribs are of great importance since they enclose and pro- 
tect the heart and lungs. They also make breathing 
Fig. 15. The skeleton of the trunk seen from the front. C, clavicle; S, scapula; 
Oc, pelvic bone attached to the side of the sacrum dorsally. 
possible by furnishing stiff yet movable walls for the 
chest cavity in which the lungs lie. Through the sternum 
1 The axial skeleton is that part of the skeleton which forms the 
central line or axis of the body, STRUCTURE OF THE HUMAN BODY 
20 
Fig. 16. The ribs of the left side, with the dorsal and two lumbar vertebrae, 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 
Fig. 17. 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 
lias 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. Each 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 
Fig. 18. Bones of arm and legFe, femur; Fi, fibula ; II, humerus ; P, patella; 
R, radius ; 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 knee 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- 
Fig. 19. Skeleton of foot of a man (A) and 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 first has two heavier and longer bones, which 
form the big toe. 
The human foot differs markedly from that of man's 
nearest relatives in the animal world, the apes. Tt is 
so firmly knit together that, unlike theirs, it is nearly 
useless for grasping and for climbing. This disadvan- 
tage is more than counterbalanced, however, by the 
fact that its strength enables man to walk firmly upon 
his feet and thereby to maintain an upright posture. 
EXPERIMENTS AND DEMONSTRATIONS 
Materials: Human skeleton; skeletons of monkey, eat (dog or 
rabbit), bird and fish; dissection of cat (dog or rabbit) with 
all flesh removed; lobster; crab; fly (spider); and clam 
(mussel). 
1) Demonstrate the human skeleton as a whole and in detail. 
2) Compare the human skeleton with those of a monkey, cat 
or dog, bird and fish. 
3) Demonstrate the freshly dissected skeleton of a cat, dog, 
or rabbit, to show bones, ligaments and joints. 
4) Compare the skeleton of a vertebrate with those of a lob- 
ster, crab, 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 like 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.1 
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 
1 Hollow stems, like hollow bones, are found throughout nature, 
as in grass, grains, reeds and bamboo, tn 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. 21. Greenstick fracture 
of bones of left forearm. 
(Scudder and Cotton.) 
Fig. 22. 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 adnlt. 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 BONES, JOINTS AND LIGAMENTS 
28 
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 
Fig. 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 bones. 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 tabular bones. 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 can 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 
Fig 34. A small piece of bone, ground very thin and highly magnified, showing 
central canals for blood-vessels and bone cells with connecting filaments. 
deposit of lime salts, and at the time of birth this 
stiffened cartilage constitutes the bone. Soon after birth, 
this is eaten into by large independent cells,1 which 
make a sort of honeycomb of it. Another army of cells 2 
builds this honeycomb full of layers 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 
1 The osteoclasts. 
2 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.1 
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 
1 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 
part-ially 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 membrane. This membrane, 
which makes a closed cavity 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 surrounding 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 occurs 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 
found in the skull, 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 vertebrae. 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 
Fig. 25. The skull viewed from above, allowing 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 
upon their shape and the arrangement and tightness 
of the ligaments. The joints permitting the greatest 
range are the ball-and-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 
Fig. 26. Section of elbow, showing both a hinge joint (humerus and ulna), and a 
pivot joint (radius and ulna). (The surfaces of the elbow joint are shown un- 
naturally separated, and the synovial sac and bursae injected 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 
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,1 which serve to 
cushion the ends of the bones and protect them against 
side strain. For further protection, the kneecap or 
1 The semilunar cartilages. THE KNEE JOINT 
35 
patella 1 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 
Fig. 28. Cross section of knee, showing the various structures which make up 
the knee 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. 
1 The patella is really a specialized part of the tendon itself, 
developed for the purpose of making tile 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 
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 vertebras, 
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 vertebrae, 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 vertebras, 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 additional ligaments which 
strengthen them where necessary. All ligaments con- 
Fig. 29. Fracture of humerus. (Scudder 
and Cotton.) INJURIES TO JOINTS 
37 
sist of fine fibres of tough, flexible and inelastic tissue, 
which run from bone to bone across the joint.1 
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 ex- 
tension; turning as on an axis, or rotation; moving away 
from the middle of the body, or abduction; towards the 
middle line, or adduction; and swinging in a circle, or 
circumduction. 
Joint injuries.-Joints are points of weakness in 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 difficulty 
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.2 
Fig. 30. Dislocation of elbow. 
(Scudder and Cotton.) 
1 Where the capsular ligaments are loose, as at the 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. 
2 In sprains, the ends of the bones are sometimes fractured. If 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.1 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-kneed, or flat- 
footed, and may even have deformed arms and a crooked 
back.2 Plenty of wholesome food, fresh air and sunshine 
this complication is overlooked, as frequently happens, the serious- 
ness of the sprain is greatly aggravated. 
1 See table of food materials, p. 86. 
2 A similar condition of weakness 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 complete growth 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.1 
Materials: Bones of the hind leg of a lamb sawed lengthwise 
through the joints; pieces of fresh ivory bone, such as the thin 
bones found in the legs of fowls; pieces of dry ivory bone; 
hydrochloric acid; ammonia; piece of sheet iron; weighing 
balance; human skeleton such as may be purchased for $25 or 
$30; microscope. 
1) Structure of a long bone: Demonstrate position and ar- 
rangement of dense (ivory) and cancellated bone; the medul- 
lary canal; joint ends with epiphyses; articular 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 gelatine. 
b) Burn a piece of fresh bone to destroy animal matter. 
c) Put a piece of burned bone and a piece of fresh bone into 
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 into small fragments, weigh; then dry in a cur- 
rent of warm air to a constant weight and determine loss. 
4) Proportions of animal and mineral matter in dry bone: 
a) Weigh a piece of dry bone, burn on a piece of sheet iron 
over live coals or over Bunsen burner, and reweigh. 
b) Second method: Weigh, dissolve in 10 per cent hydro- 
chloric acid, dry in a warm place for 3 or 4 days to obtain a 
constant weight, and determine loss. 
c) Demonstrate the presence of mineral matter in the solu- 
tion of b) by precipitating it with ammonia. 
5) Structure of joint: Demonstrate by dissection the cap- 
sular and reinforcing ligaments; the synovial fluid; the articular 
cartilage; the function of ligaments. 
EXPERIMENTS AND DEMONSTRATIONS 
1 If the vitality 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 the 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 
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- 
Fig. 31. A small bit of muscle composed of 
five primary fasciculi. A, natural size; B, 
the same magnified, showing the secondary 
fasciculi of which the primary are composed. 
40 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 silky thread of 
Fig. 33. 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 
coutraction. 
Fig. 32. End of striated (voluntary) 
muscle fibre, showing its attach- 
ment to tendon fibre. 
tough inelastic material, the tendon fibre. Since the 
muscle fibres are usually much shorter than the muscle 
itself, these threads have to run well up 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 
Fig. 34. Back of forearm and hand. 
Fig. 85. Front of right arm, showing 
muscles, tendons, arteries and nerve. 
bones which enter into it is perfectly controlled by the 
pull of the muscles. 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 
Fig. 36. Diagram illustrating 
the muscles (drawn in thick 
black lines) which passbefore 
and behind the joints, and by 
their balanced contraction 
keep the joints rigid and the 
body erect. 
Fig. 37. Flexor and extensor muscles 
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 
45 
such as the shoulder, 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 ready to pull the bone in the oppo- 
site direction. In many cases where powerful action 
is required, the principal pair of opposed muscles is 
reinforced by assisting muscles. Sometimes, there are 
as many as four or five muscles on one or both sides 
of a joint, as in the knee.1 
Production of energy.-During muscular activity, 
animals give off in their breath an increased amount of 
carbon dioxide,2 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 case of the muscles is partly 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.3 
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 unable to work, it becomes soft and 
1 On the front of the thigh, one very large muscle extends the 
leg; at the back, five much smaller muscles flex it. 
2 Carbon dioxide (CO2) equals 1 part of carbon to 2 of oxygen. 
(See Appendix A, p. 316.) 
3 Each cell of the muscle acts as a separate little engine for the 
generation of this power. 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.1 
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 
Fig. 38. Lengthening of biceps when arm 
is extended. 
1 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 warm the body. PLATE IL -THE SUPERFICIAL MUSCLES OF THE FRONT OF THE BODY. EXPLANATION OF PLATE II. 
A view of the muscles situated on the front surface of the body 
seen in 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, Head and Neck : 
1. Muscle of the Forehead. This, together with a muscle at the back of 
the head, has the power of moving the scalp. 
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 figure. 
3, 4, 5. Muscles that raise the Upper Lip and angle of the Mouth. 
6, 7. Muscles that depress the Lower Lip and angle of the Mouth. By the 
action of the muscles which raise the upper lip, and those that depress 
the lower lip, the lips are separated. 
8. 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 teeth in the upper and lower jaws. 
11. Muscle that compresses 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. 
13. 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 beneath 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 (Trapezius Muscle). 
17. Great Muscle of the Chest, which draws the Arm in front of the Chest 
(Great Pectoral Muscle). 
18. Broad Muscle of the Back, which draws the Arm downwards across the 
back of the Body (Latissimus Dorsi). 
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 (Serratus 
magnus). 
At a lower part of the trunk, on each side, may be seen the large 
muscle which, from the oblique direction of its fibres, is called 
20. Outer Oblique Muscle of the Abdomen. EXPLANATION OF PLATE II.-(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 contents 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 and Fingers, and pronate tlie 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 supinate the Forearm 
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 bone 
(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 Sartorius; 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: 
32. 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, lie 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 be seen in the figure. Only one muscle, 36, which 
assists in extending the toes, is placed on the back of the foot. 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. 
Involuntary 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 under voluntary 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, 
Fig. 39. Contraction of biceps to flex 
arm. 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. 
Fig. 40. Isolated 
smooth muscle 
fibres. 
Fig. 41. Smooth or involuntary muscle fibres, 
showing their arrangement. 
Heart muscle.-In addition to these two types of 
muscle structure, there is a third found 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 
quickly than the involuntary and yet not so quickly as 
the voluntary. 
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 from 
the combustion of the food materials furnished by plants 
and animals. A sufficient diet is therefore essential, if 
our muscles are to do their wrork easily and well. Since 
the 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 this 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 (1% drs. 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 slice of meat the cross sections of muscle 
bundles. Also note and sketch the connective tissue in its rela- 
tion to the muscle bundles; the surface tendons; and the inter- 
muscular tendons. 50 
MUSCLES AND TENDONS 
3) Prepare muscle fibre by plunging the leg of a freshly 
killed frog into water at 131° F. 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 weight 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 
by 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 ground 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. 42. 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 
Fig. 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 (poiver) 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 LEVERS 
53 
will be found by careful measurement that, if the two 
children are of exactly equal weight, they 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- 
Fig. 44. Examples of levers of the first class, with analysis of the forces involved. 
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 = fulcrum ; 
P = power ; W = weight. 
tions of the fulcrum, 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 
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 
Fig. 45. Examples of levers of the second class. 
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 found in the nodding of the 
head, in the extension of the elbow by the triceps muscle 
on the back of the arm, and in the raising of the body 
upon the toes by means of the calf muscles. In the lat- 
ter case, the pressure upon the floor by the weight of 
the body is equivalent to the 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.1 
Examples of the third class.-Of the third class of 
levers, we find examples in the 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 draw the arm downward, 
as in hauling or climbing a rope. 
Body as a weight.-A study of the problems in body 
leverage shows that the force exerted by the muscles 
is surprisingly large. It is further greatly increased 
if the body gets heavier without a corresponding in- 
crease in muscle po^ver. For example, if a man weigh- 
ing two hundred 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.2 
1 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 that, 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 them with a force of but fifty pounds! 
2 In this study of leverage, we have considered the mechanical 
relations only in those cases in which the forces act at right angles 
to the length of the lever, in order to make the treatment as simple MOTION AND LOCOMOTION 
56 
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- 
Fig. 47. Analysis 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 alternately supported by first one 
leg and then the other. The leg which supports the 
weight is ordinarily straightened to its full length. At MOTION AND LOCOMOTION 
58 
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.1 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 
1 Thus a man weighing 150 pounds and walking at the rate of 4 
miles per hour, would exert ^X 4 X 5280 ft. = 158,400 foot 
du 
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 
Foot pounds 
per minute 
Foot pounds 
per day 
Bicycle riding, 10 seconds 
Bicycle riding, 60 seconds 
Soldier marching with load 
19,000 
8,750 
, 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 LEVERS 
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 DEMONSTRATIONS 
Apparatus: Lever' apparatus made with 2 spring scales 
weighing up to 24 lbs. and 2 pieces of lath arranged as shown in 
diagram. 
1) Set up apparatus for foot leverage, assuming 1 in. as 
distance from ankle joint (fulcrum) to insertion of tendon of 
Fig. 49. Lever apparatus made of lath and spring balances arranged for foot as 
acted on by calf muscles in rising on toe. The arrangements for arm when flexed 
by biceps muscle and extended by triceps are indicated by the dotted arrows. 
(Figures 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 1% 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 VI 
MUSCULAR WORK 
Influence of muscular activity upon development.- 
The muscular system determines very largely the ac- 
tivity of the other organs 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, lungs, nervous system and every 
other part of the body remain weak and poorly 
developed. If, on the contrary, 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 young 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 full 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 success. 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 amount 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-round 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 work 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- 
down 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 
foi' such games as football and baseball, where exhaustion 
and heart 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 under these conditions, however, a limit is 
set to the working time of the muscles by the fatigue 
of the nervous system, which is often shown by the 
person's inability to keep his 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 
will 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 portions 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 substances 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, are foods. 
The foods which animals need for their growth and ac- 
tivity are manufactured by 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.1 Since they all have twice as much hydrogen 
as oxygen, they are in the right ratio to form water 
(HaO), 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, 
1 Starches (gums and cellulose), C8Hi0O5. 
Sugars (grape sugar, glucose, etc.), C6Hi2O6. 
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,1 and because of this excess of hydrogen they are 
called hydrocarbons. They are much more valuable as 
heat producers than the carbohydrates.2 
Proteids.-The presence of nitrogen and sulphur 
characterizes the third class, examples of which are 
found in the gluten 3 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 iresemble 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.5 
1 Palm oil, CsiHioiOc,. 
2 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. 
3 Gluten is the tenacious gum which remains when raw wheat is 
chewed. 
4 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. 
6 Glycogen, C6Hi0O5 ; milk sugar, C12H22O11 ; fat (stearin), 
CbtHhoOb ; egg albumin,C204H322N62O66S2. DIETS 
67 
Diets of animals.-The feeding habits of animals 
differ greatly. Some animals, as sheep, cows and horses, 
live entirely up'on plants and on this account are called 
herbivorous. Others, 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 the 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.-During the long pe- 
riod of selection, the animal gradually became adapted 
to the diet chosen. For example, the teeth of herbivorous 
animals became 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 herbivorous 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.1 
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 
1 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 place and energy 
be thereby developed. Those, therefore, 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 warm, 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 amounts of hard work, 
have been shown to eat approximately the same quantity 
of food made up in general of the 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.1 
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 before an open fire. The 
second was baking, a primitive form of which was the 
heating of smooth stones by building a fire on them. 
1 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 further proved by the experience of the Japanese army 
and navy in their wars with 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, the 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 
amount. 70 
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- 
Fig. 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 
Fig. 51. Baked potato, showing masses of cooked starch within envelopes of 
cellulose. (Bulletin of Agricultural Department.) 
cracking, cooking by boiling was naturally added 
to roasting and baking. Frying, which is such a com- VALUE OF COOKING 
71 
mon method in modern times, was probably also of later 
development since it required the use of grease in an 
earthen or metal receptacle. 
Effects of cooking.-Cooking has won favor because 
the added flavor and delicacy which it imparts to food 
stimulate the appetite and promote digestion. By 
Fig. 52. Mashed boiled potato. (Bulletin of Agricultural 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, through the destruction of disease- 
producing microbes,1 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 which their toughness is largely due, is changed by 
the cooking to tender soluble gelatine.2 In vegetable 
foods, the binding structure is largely tough hard cellu- 
lose, which resists chewing and digestion. This becomes 
1 See p. 282. 
2 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, corn 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 ordinary diet of mankind includes both animal 
and 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- 
Fig. 53. Section through outer part of a grain 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 are enclosed 
73 74 
FOOD MATERIALS 
in an outer covering, or capsule, of hard cellulose. Just 
within the capsules lie 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 food1 may be 
obtained. 
Bread.-Bread 2 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- 
n>arily 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.3 
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 
1 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. 
2 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. 
3 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 
75 
fact, they are little, if any 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 much proteid, although the pro- 
teid is not in the form of tenacious gluten.1 
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,2 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.3 Vegetables are also 
1 In spite of this, corn is but little used by Europeans as food. 
When, 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. 
2 Peas, beans and peanuts, although popularly known as vege- 
tables, are really fruits. 
3 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 FRUITS 
77 
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.1 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 about 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- 
1 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 
FOOD MATERIALS 
ness. It becomes butter wdien 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 
Fig. 54. A portion of a drop of cow'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 person 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.1 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 
1 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,1 may be checked.2 
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, 
1 The development of microbes in milk at different temperatures 
is about as follows: 
Temperature 
At end of 24 hrs. 
At end of 48 lire. 
60° 
180,000 
28,000,000 
68° 
450,000 
25,000,000,000 
86° 
1,400,000,000 
94° 
25,000,000,000 
Below 50°, the development of microbes in milk is comparatively 
slow. 
2 It was formerly a common practice to get rid of the microbes 
in milk for infants by heating it to a boiling point (sterilization). 
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 the entrance 
of microbes into the milk and their subsequent development, in 
order that the milk may be as safe as possible in its raw state. 
Still greater safety may be insured for infant feeding by heating 
the milk to 150°-160° F. for 15 minutes (Pasteurization), and 
then putting it upon ice. Even pasteurization, however, does not 
protect against the germs of tuberculosis. 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 tapeworm from 
beef and the trichina 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 
Fig. 55. Trichinee 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,1 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 
unnecessarily or in too large amounts. In normal health, 
1 Ptomaines are produced by the activity of microbes and are 
among the most poisonous substances known. CONDIMENTS 
83 
stimulation, 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 DEMONSTRATIONS 
Materials and apparatus: Yeast cake; wheat flour; corn, rye 
and oat meal; breakfast foods; vegetables, as potato, turnip, 
beet and cabbage; fruits, as apple, banana and orange; milk; 
egg; meat; glucose (grape 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. 
Starch 
Sugar 
Proteid 
Fat 
Milk 
Egg 
Meat 
Potato 
Beet 
Apple 
Banana 
Nuts 
Flour 
Bread 
Raisins 
Note: 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 like 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 1; Make a dilute solution of glucose or soak 
a mashed raisin in water. Put a few drops into a test tube, 
1 Ordinary (cane) sugar does not respond to this test. A 
solution of such sugar must be boiled with a few drops of acid, as 
sulphuric. FOOD EXPERIMENTS 
85 
add 1 in. of water and in. of sodic hydrate solution. Then 
add carefully 1 to 2 drops of copper sulphate solution. Heat 
the upper half of mixture in flame of Bunsen 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 
(TrommePs Test). Test similarly 1 various vegetables, fruits 
and milk. 
6) Test for proteid (Xantho-proteic reaction): Put in a test 
tube in. of solution of white of egg.8 Add % 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 3 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.4 
8, 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 upon 
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 drop a dilute solution of acetic acid 
(vinegar) and stir constantly until a precipitation of casein to- 
gether with fat is formed. Let settle or filter. Dry precipitate 
1 In ease of solid vegetables and fruits, crush, shake in a little 
water and use the clear solution. 
2 Cut white of raw egg repeatedly with scissors. Shake in a 
bottle with 20 parts of water; let settle and filter. Use clear 
solution. 
3 In case of solids, put % in. of water into a test tube and add 
the solids to be tested. Proceed as with white of egg solution. 
4 Ordinarily drying takes from 24 to 48 hours even under the 
most favorable circumstances. 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-proteic reaction residue 
in c) left after fat has been extracted. 
COMPOSITION OF FOOD MATERIALS 
Water 
Proteid 
Starch 
Sugar 
Fat 
Salts 
Bread 
37 
8 
47 
3 
1 
2 
Wheat flour 
15 
11 
66 
3 
1 
2 
Oatmeal 
15 
12.6 
58 
5 4 
5.6 
3 
Rice 
13 
6 
79 
0.4 
0.7 
0 5 
Peas 
15 
23 
55 
2 
2 
2 
Potatoes 
75 
2 
18 
3 
0.2 
0.7 
Milk 
86 
4 
5 
4 
0.8 
Cheese 
37 
33 
24 
5 
Lean beef 
72 
19 
3 
1 
Fat beef 
51 
14 
29 
1 
Mutton 
72 
18 
5 
1 
Veal 
63 
16 
16 
1 
White fish 
78 
18 
3 
1 
Salmon 
77 
16 
5.5 
1.5 
Egg 
74 
14 
- 
- 
10 5 
1 5 
Butter 
15 
- 
- 
83 
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 fortunately 
its impurities are not usually 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. Most spring and well 
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 waters 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 WATER 
89 
the spring they had washed down into the stream from 
which the people in the town some distance away got 
their 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 course, 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 contaminated by its surroundings because 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 which may run 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 uncontaminated 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 fiat, 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.1 Many cities,2 
therefore, have constructed large filtering beds to insure 
1 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. 
2 As Philadelphia, Lawrence and Berlin. WATER FILTERS 
91 
the purity of their water supply and thus to protect 
themselves from the epidemics of typhoid which pre- 
vail where the drinking water is impure.1 
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 fluids. 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 
1 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 
dilute 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 well-being and strength, they are un- 
doubtedly doing harm. They then act as goads to prick 
a flagging vitality into exhausting 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 strength 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, until in the end 
he becomes a nervous, irritable dyspeptic. 
Alcohol.-Another 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.1 
The alcohol of wine and cider is derived from the sugar 
in the fruit juices of the grape and apple, acted upon 
by the yeasts present in the dust 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 
1 Sugar-i-yeast = alcohol +carbon dioxide 
C6HijO6+yeast=2 C2H6O+2 CO2. 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 undesirable 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 
Fig. 58. Yeast: a, full-grown 
plant, with a branch (bud) 
partially developed; b, c, 
colonies formed by budding, 
the individuals still attached. 
(Magnified 750 diam.). EXPERIMENTS 
95 
as a drug and not 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.1 
EXPERIMENTS AND DEMONSTRATIONS 
'Materials: Samples of water; yeast cake; iodine solution 
(p. 83); microscope with powers up to 450 diameters; tall 
glass 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, % of which is filled with air. Repeat several times at 
intervals of a few minutes, and 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 general town supply, describe its source and 
the precautions 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 drawings of the cells present. 
b) Add a small drop of iodine solution and again examine. 
1 For a more complete discussion of the effects 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 
96 THE DIGESTIVE TRACT 
97 
for the food and a special organ for its digestion. In 
man, as in the higher animals, the alimentary canal 
Fig. 59. Diagram to illustrate 
the gradual development of 
the alimentary tube as found 
in the lower and higher forms 
of animal structure. (Testut.) 
JFig. 60. Diagram of the alimentary tube 
and its appendages. (Testut.) 
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 teeth and for moving 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 incisor tooth, b, A canine or eye tooth, c, A bicuspid tooth seen 
from its outer side ; the inner cusp is accordingly not visible, 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. 62. Teeth of dog. 
Fig. 63. Teeth ot horse. 
months old. At two years of age, lie 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.1 
Permanent set.--When the child is almost six years 
of age, another molar appears at the back end of each 
Fig. 64. The jaws 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 
come are the incisors, which push their way out from 
under the temporary teeth. The roots of the temporary 
teeth are destroyed by the pressure of the budding teeth 
1 Latin, molere, 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 
Fig. 65. The teetn of the right half of the upper jaw in their sockets, 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, 
wrhere 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 
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 narrowed 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 crown 
of the tooth is capped 
with 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 cement, because it serves to hold 
the teeth firmly in their sockets by wedging their roots 
against the bony walls. 
The cavity within the tooth is filled with blood-vessels 
and nerves, which form the so-called pulp of the tooth 
and enter it through small holes at the tips of the roots. 
They supply the dentine with nourishment and keep it 
Fig. 68. Section through jaw bone and 
tooth 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- 
fulness, 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 
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 cheeks, 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 
submaxillary, 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 1 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 chewing. Of all 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 
1 A ferment or enzyme 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 
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.-When the food reaches the pharynx, its 
muscular walls push it over the top of the trachea into 
the esophagus, which relaxes to receive it. The muscular 
fibres which make up the walls of the esophagus close 
Fio. 69. The stomach and intestines, front view, with the liver turned up and to 
the left. The dotted line shows the normal position of the anterior border 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 
Fig. 70. The stomach 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 STOMACH 
107 
a ferment1 called pepsin. During the digestion of a 
meal, a large amount 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 chyme 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. Sect ion through a 
stomach gland, showing 
its central canal and the 
arrangement of its cells. 
(Gerrish.) 
1 Another ferment called rennin 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 
DIGESTION 
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 pylorus, 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-bladder. 
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- 
Fig. 72. Diagram illustrating 
the muscular contractions of 
a cat's stomach after eating a 
meal just 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 bile. The bile is a thin 
yellow-green alkaline liquid, which is secreted continu- 
ously and is stored in the gall-bladder when digestion 
Fig. 73. Stomach, beginning of small intestine, and entrance of bile and pan- 
creatic duct. (Hough 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 the 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 proteicls 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 
Fig. 74. Diagram showing storage of fat within connective tissue cells. 
are digested in the stomach by the gastric juice, so 
that the fat is 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 
Fig. 75. Small section of wall of intestine showing three villi. In A, artery, vein 
and lacteal with their 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 chyle 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 
known 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 amount 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 
various digestive juices. This residue is passed from the 
small intestine into the large intestine through the con- 
necting ileocecal valve. Occasionally, when masses of 
indigestible material are unable to pass readily through 
this valve, a pronounced distention of the intestine re- 
sults, producing the pain known 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: 
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, lungs and heart, remove them by 
freeing 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. 
c) Follow 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 lacteals 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 vermiform 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 con- 
cavity of the first coil {duodenum} of small intestine: 
Note the pancreas, a thin, branched, glandular mass; the 
portal vein 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 duodenum about 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 length: 116 
DIGESTION 
Note the relative length and diameter of its various parts and 
determine the ratio of its length to the length of body.1 
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. 
Scrape its cut surface and examine cells in normal salt solu- 
tion under microscope. 
Find gall-bladder and trace out its ducts. 
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. 
Digestion 
Materials and apparatus: Sugar; salt; raisins, grapes, cran- 
berries and other fresh fruits, with skins and stems uninjured; 
corn oi' 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; glycerole 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; sodic hydrate solu- 
tion ; copper sulphate solution; water bath for holding test 
tubes (a deep tin containing a wire test tube rack, nearly 
1 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 of a cat or 
dog more nearly resembles the human. DIGESTION EXPERIMENTS 
117 
filled with water and 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; dialyzer, 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 in. in diameter for preparing 
material; six 6 in. test tubes for each student; nests of 3 
beakers of from 4 to 6 oz. capacity; filter papers, 1 package 
3% in. in diameter, a few, 6 oi' 8 in.; litmus paper. 
Experiments 1: 
1) Penetration of membranes by crystalloids (sugar, sait) 
and by peptone: 
a) Place dialyzer obliquely in a glass, so that the membrane- 
covered end does not rest on the bottom. Carefully pour the 
solution to be tested (1 teaspoonful sugar, or salt, to % cup 
water) into open end of dialyzer so that no particle of it is 
spilled. Pour pure water into 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. 
1 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 of 
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 sufficient. 
The digestion ordinarily requires some time, and it may be 
necessary in certain cases to prepare the solutions, put them 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 
sufficiently 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. DIGESTION 
118 
2) Non-penetration of membranes by 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 observa- 
tions in schedule form, using the following signs: diminu- 
tion (-); increase (-|-); no change (=); solution in water 
(dissoh). 
In water 
In syrup 
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,1 sugar 
and peptone.2 
5) Effect of artificial gastric juice: 
1 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. 
2 Biuret test for peptones: Put % in. of solution to be tested for 
peptone into a test tube. Add an equal amount of sodic 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 glycerole 
pepsin to 0.2 per cent hydrochloric acid. Prepare digestion 
test tubes by adding % 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). Examine a drop under microscope and compare with 
a drop of milk. 
c) 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.1 
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 
Carbohy- 
drates 
Calories 
energy 
Children to years 
(28 gms. 
120-36 " 
(37 gms. 
I 30-45 " 
(75 gms. 
) 60-90 
770 
Children 1^ to 6 years 
(55 
1 36-70 " 
( 40 
I 35-48 " 
( 200 
1 90-250 " 
1423 
Children 6 to 15 years 
Women with light ex- 
(75 
1 70-80 " 
(43 
137-50 " 
( 325 
(250-400 " 
2048 
ercise 
80 
80 
300 
2308 
Aged women 
80 
50 
260 
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 and 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.1 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 amount 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 afford 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 much 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 
1 Effect of activity on diet 
Proteins 
Fats 
Carbo- 
hydrates 
Energy in 
calories 
Man at light in-door work 
110 
60 
390 
2,645 
" " " out-of-door work.. 
110 
100 
400 
3,063 
" " moderate o u t-o f-d o o r 
work .. 
125 
125 
450 
3,568 
" " hard out-of-door work 
150 
150 
500 
4,120 
" " very hard out-of-door 
work in winter 
180 
200 
600 
5,026 122 
THE HYGIENE OF DIGESTION 
taken is excessive, however, the kidneys may becom1 
overburdened, especially if they are weak or diseased. 
The waste products then tend to clog or even to poison 
the body.1 
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 has 
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 
1 Experiments have shown that men can work to advantage on 
about half as much proteid as the foregoing tables show, that is, 
on from 50 to 70 gms. per day of dry proteid, which 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 guide, it must be aroused only 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 
habitually eats too little, the stomach accustomed to ex- 
pect and to take care of but small amounts, 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 carbohydrates since the fats are ordinarily 
eaten in much smaller amounts.1 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 
1 In cold climates and in cases of poor nutrition and of tuber- 
culosis, much larger amounts of fats may sometimes be taken with 
benefit, provided they are not used in such a way as to make other 
foods indigestible, as in frying. CARE OF THE TEETH 
125 
we eat, we cannot be sure of a good digestion unless we 
take care of such of the digestive organs as are under 
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 must 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 wears 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 
Fig. 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 
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- 
126 THE CORPUSCLES 
127 
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 blood 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.).1 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 amebae, in that they 
are able to change their form and to lead an essentially 
1 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 the result is pallor and weakness. In hook- 
worm disease, which is common in the South and other warm 
countries, the anemia due to the sucking of blood by parasitic 
worms in the intestinal wall, may be so great that there are 
but 1,000,000 cells in a cu. mm. of blood. 128 
THE BLOOD 
independent life. They make 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 glands1 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 hundred 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 
Fig. 77. A white blood-cor- 
puscle sketched at successive 
intervals of a few seconds to 
illustrate the changes of form 
due to its ameboid move- 
ments. 
1 See pp. 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 upon 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, known as fibrin. When taken singly, these fibres 
are so delicate that they can be seen only through a 
microscope. When fresh blood is whipped 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 
should 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, 
which 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 poor 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 globules. 
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- CONDITIONS AFFECTING BLOOD 
131 
ing growth a part of the proteid material is built into 
the developing tissues; the remainder is quickly oxidized 
for the production of energy. After growth ceases, the 
majority of the proteid eaten is oxidized, since none is 
needed for the building of tissue and but little for tissue 
repair. 
Water.--Water, when absorbed from the intestinal 
tract, dilutes the blood temporarily, but is quickly re- 
moved by the kidneys. When water is taken 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 at regular 
intervals, the blood is able to supply the tissues with the 
nourishment which 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- 
teicls 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 gradually returned to the blood, 
but additional proteid material is furnished by the sac- 
rifice of the less active tissues themselves.1 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 system. These are thus enabled 
1 Total loss of various tissues in starvation.: 
Fat 97.0% 
Liver 54.0% 
Muscles 30.5% 
Lungs 18.0% 
Bones 14.0% 
Nervous system 3.2% 
Heart 2.6% 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. EXPERIMENTS 
133 
EXPERIMENTS AND DEMONSTRATIONS 
Materials: Alcohol; nitric acid; defibrinated blood; blood 
clot or fresh liver; serum; chisel-pointed needle; test tubes; 
blotting paper; microscope with powers up to 450; 2 fruit jars; 
bundle of twigs or wires; tumbler; platinum foil; alcohol lamp 
or Bunsen burner. 
1) Get a drop 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 piercing.) Spread a drop of blood on a piece of glass, 
put on a cover glass, and examine under microscope. Note 
form, size and color of red blood corpuscles; method of cluster- 
ing; 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 from 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 drying, cover by inverting over it a glass lined 
with wet blotting paper. 
In 4 or 5 minutes, remove 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 off serum for subsequent tests. 
2) Collect fresh blood in a pail and beat it vigorously with 
twigs for 3 or 4 minutes. Note quantity of stringy elastic 
material (fibrin) collected on twigs. 
Wash fibrin thoroughly in running water and note its color. 
3) Take some of serum and note its physical characteristics. THE BLOOD 
134 
Heat it in a test tube and note change. 
Apply Xantho-proteic 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 body, 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 through 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 
journey 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 known as the lesser, or 
pulmonary, circuit. Neither 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 
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 
137 
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. This contraction and 
relaxation are repeated one or more times a second 
throughout life and cause the heart beat, 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. 
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 the 
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 OE 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 
Fig. 81. Heart, with portion of right auricle and right ventricle cut away to show 
interior. Bristles show passage ways. 
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 THE CIRCULATION OF THE BLOOD 
140 
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 
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 Circulatory 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 ventricle 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. 
6, 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 (10) 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. PLATE IV. -THE CHIEF ARTERIES AND VEINS OF THE BODY. 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 muscle 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 
Fig. 83. Artery and vein, showing structure 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.1 As the arteries become smaller, 
their walls also become thinner and the elastic tissue 
1 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 m 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, which 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 how they 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 all 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 
Fig. 85. Diagram showing the bending of 
red blood corpuscles and the rolling of 
ofl1rSg?°d corpuscle8in thecaPillaries FUNCTION OF BLOOD-VESSELS 
145 
result, the blood is pushed for- 
ward from one section to an- 
other on its way 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 veins, and the method of 
branching of the veins by 
which many other paths are 
open to the returning blood 
in case of obstructingpressure 
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. From 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 
pulmonary veins to the left auricle of the heart. Upon 
Fig. 88. Diagram of the circulation of the arterial and venous blood and the 
lymph. (Arteries have transverse shading; veins longitudinal shading. Lym- 
phatics are represented by black lines.) 
the relaxation of the left ventricle, it enters once 
again through the left auriculo-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 
Fig. 89. Migration of the white blood corpuscles 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,1 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- 
1 Lymph may be seen characteristically under the skin in the 
form of "water blisters." EXPLANATION OF PLATE III. 
A General View of the Lymphatic or Absorbent System 
of 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 hack 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 duct 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 
known as the lacteals is seen at <7 passing from the small intestine e to the thoracic duct f. LYMPHATICS 
149 
stantly 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 
ducts 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 lymphatic system The function of 
the lymphatic system is twofold. It brings the plasma 
of the blood containing the dissolved food materials 
into closer contact with 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. Lacteals and thoracic duct. THE CIRCULATION OF THE BLOOD 
150 
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 
Fig. 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 
151 
masses of small cells, 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 cells 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 tissue 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 THE BLOOD 
oxygen, the nerves cause the muscle fibres to contract. 
The arterioles as a result become smaller ancl less blood 
is allowed to pass. The nerves which control the relaxa- 
Fig. 92. A, Diagram of circulation from artery through capillaries to vein of 
frog. The darker corpuscles show change to venous blood. B, Diagram of cir- 
culation in 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 unpunctured; 
rabbit, freshly killed if possible; glass tube %= in- diameter, 12 
in. long; scalpels; scissors; forceps. 
1) Demonstrate in rabbit, which has been prepared 1 by cut- 
1 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; thence follow it until it enters pericardium. 
b) Trace out veins which vena cava inferior receives from 
liver, spleen, kidneys and diaphragm. 
c) Trace out superior vena cava and its branches. 
d) Notice between ends of two venae cavae 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 pericardial sac.1 Note character of lining 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.2 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 
apex. (This indicates position of partition, or septum, between 
two ventricles.) 
8) Dissect away fat around origins of great arterial trunks 
and around base of ventricles. In fat will be found two 
coronary arteries arising from aorta close to heart, 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 
1 The following dissections are much better carried out upon the 
sheep's heart owing to its larger size. 
2 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 such 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 venas cavae. 
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 % 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 yalve 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 
Materials and apparatus: Frog; 2 sheep's hearts; a piece of 
sheet cork or of thin board with % in. hole cut in it; micro- 
scope; circulation apparatus made from bulb syringe; funnel 
of glass or tin; 2 feet of % in. rubber tubing; 10 inches of 
1 in. sap tubing; several feet of glass tubing, some in., 
some 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,1 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 
efficiency 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. 
1 The frog's red blood corpuscles 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 1 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 kt 
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. 
1 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 per 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 work 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 cases 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 which 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 case of hard muscular work, the reverse 
is true. The muscles draw the blood to themselves and 
so digestion is delayed. EFFECT 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 broken, 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 discoloration 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 
in 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. Compression 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.1 
From veins.-In the case of a vein, the loss of blood 
is much slower and will ordinarily cease through the 
1 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 cases, 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 body against too .great a loss of heat is 
not worn, or that there is some nervous disorder which 
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 fresh 
air and wholesome food. 
Fainting.-The circulation may also be temporarily 
disturbed, especially in weak 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 
and 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 dizzy 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 1 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 
efficiency 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 still 
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. 
1 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 
Fig. 96. Section of face and neck showing passages of nose, mouth and throat. 
(Testut.) 
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.1 
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 within the chest walls and 
are entered by way of the mouth and nose and the wind- 
Fig. 97. Section through 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 lungs 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 
1 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 through 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.1 
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 
1 See p. 276. 168 
RESPIRATION 
the lungs. All of these which have a diameter of more 
thqn 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 
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 
Fig. 99. Two alveoli of lung, considerably magnified, b, b, air sacs ; c, 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 1 of blood to the air 
contained within the air sacs. 
1 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 Jung with distended blood-vessels, highly magnified, c, c, 
partitions between air sacs; b, 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 lines the chest cavity within 
which the lungs lie. This membrane, known as the THE CHEST 
171 
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, 
Fig. 101. Chest, 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 
Fig. 102. Front view of the 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 diminishing 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 ease of stout persons, by the weight of 
the abdominal walls. The diaphragm also relaxes and 
Fig. 103. Diagram illustrating the 
position of the chest in expira- 
tion (A) and inspiration (B). 174 
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.1 
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 
1 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 
sufficient 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 oxygen and from poisoning by an 
accumulation of waste products, as a result of too great 
activity. 176 
RESPIRATION 
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 
Fig. 104. Diagram showing relative amounts of fresh and stale 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 size and EFFECTS OF EXERCISE 
177 
number of the muscles at work. When many large 
muscles are hard at work, as in running 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) Wash surface of mucous 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 yaulted 
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 into 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 muscular 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 not.e position 
of mucus on surface at end of half an hour.1 
Respiration 
Materials: 
Blood clot, defibrinated blood, or piece of liver; lungs of 
rabbit, cat, 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; pinchcock; rubber stopper with double 
perforations, to fit bell jar; 2 pieces of glass tubing, to fit 
perforations of stopper; water-valve respiration apparatus for 
carbon dioxide. 
1) Note the effect of breathing on bulb of a thermometer; on 
a mirror, knife blade, or other polished metallic surface. 
1 Cilia are present in the respiratory 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. 
Fig. 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 (fig. 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.1 
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 
1 Phenolphthalein is pink in alkaline solutions; colorless, in acid. DEMONSTRATION OF RESPIRATION 
181 
b') Shake defibrinated blood in bottle containing oxygen. 
Note result (oxyhemoglobin). 
8) Respiration apparatus: Tie trachea of cat or rat on 
piece of glass tubing which is then passed up inside bell 
jar through one of perforations in stopper. Seat stopper 
firmly in mouth of bell jar. Stretch piece of sheet rubber over 
Fig 106. Diagram of apparatus to demonstrate the action of the diaphragm. A, 
in inspiration diaphragm flattened by contraction ; B, in expiration diaphragm 
relaxed and pushed upward by abdominal contents. Note changes in fullness of 
lungs. 
larger encl 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 membrane down over bowl. 
c) 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 
modern dwelling house, have, however, made it more diff 
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 
182 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 
shown 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 cures 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 know 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 ODOR OF AIR OF AN OCCUPIED ROOM 
Fresh 
Slightly 
close; per- 
c e p t i b 1 e 
odor 
Close; disa- 
greeable 
Very close; 
offensive 
Parts CO., in 10.000 vols. air ... 
6 
8 
10.5 
13 
Parts COs due to respiratory 
impurity 
2 
4 
6 5 
9 184 
THE HYGIENE OF RESPIRATION 
respiratory 1 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 hour2 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 supply this amount of fresh air 
economically is the problem of ventilation. In summer, 
ventilation is not 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. 
1 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 
1 the amount of air which is necessary. 
2 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 
185 
Heating.-There are two methods 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, unless 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 should 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 OF 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. The openings of these flues should be placed as 
near the floor as possible, in order to get rid of the colder 
impure air of the floor. 
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 dry air takes the 
moisture from our bodies more 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 case, the air is so dry 
that it takes the body's moisture rapidly enough to 
chill it; in the other, the air is so full of moisture that 
it will 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 effects 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 ankles, 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 cases for the spread of disease. In this way, we are 
exposed to hordes of disease germs, which are con- 
stantly lodging in the mucous 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 care 
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 cilia. 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 1 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 are especially frequent in children and make it 
necessary for them to breathe through their mouths. 
The closure of the nose and breathing through the mouth 
1 A proper atomizer and Dobell's solution 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);1 
[Fitz CO2 apparatus2]. 
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 
1 Select cheap tin-eased thermometers hy noting that the three 
scratches on side of glass stem of each coincide respectively with 
the graduations for 32°, G2° 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. 
2 L. E. Knott Apparatus Co., 15 Harcourt Street, Boston, Mass. TESTS OF VENTILATION 
193 
noting presence of odor as none, faint, marked, or strong. 
Record size of room in cu. ft., number of persons occupying it, 
method of heating and ventilating, number of ventilators open 
(windows, doors, registers, transoms, etc.) and movement of 
air through each as to direction 1 and strength. Make diagram 
of essential features. 
[b) By chemical analysis: Use CO2 apparatus according to 
directions accompanying same.2 Make plans of rooms and 
carry out as in a).] 
2) Air currents:3 
a) Direction: By means of the suspended tuft of down, 
determine the direction of air movement in various parts 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 will move with air current in 1 second.4 
c) Amount: Determine by measuring areas 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; divide result by total number of oc- 
cupants; compare with standard requirements (|- cu. ft. per 
sec.). 
3) Humidity of air: Moisten cloth on bulb of psychrometer 
and whirl in air until readings of 2 thermometers are constant. 
1 The best method of detecting currents of air at ventilators is to 
attach a bit of down 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 
the 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. 
2 This method is simple and reliable and does not require a 
knowledge of chemistry. 
3 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. 
4 The seconds are easily measured by means of a metronome or by 
a pendulum consisting of a small lead weight suspended by a cor'd 
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 pendulum as well. 194 
THE HYGIENE OF RESPIRATION 
Record temperatures and subtract the reading of wet bulb from 
that of dry. 
By reference to table, find relative humidity corresponding to 
Fig. 107. Wet and dry bulb thermometers arranged for whirling (Psychrometer) 
to get quick readings. 
air temperature as given by dry bulb thermometer, and to dif- 
ference between readings of 2 thermometers. 
Difference between 
wet and dry bulbs. 
1 
Air temperature (Fahrenheit). 
10° 
. ... 80 
20Q 
86 
30° 
90 
40° 
92 
50° 
93 
60° 
94 
70° 
95 
80° 
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 
10 
. 22 
37 
48 
55 
61 
12 
. 8 
26 
39 
48 
^4 
14 
. 16 
30 
40 
47 
16 
. 5 
21 
33 
41 
18 
. 13 
26 
35 
20 
. 5 
19 
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 OF 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-browm 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 branching 
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- 
Fig. IOS. The kidneys and principal blood-vessels of 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 REMOVAL OF WASTE PRODUCTS 
reservoir, the 'bladder. 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 
Fig. 109. Structure of kidney, showing the secreting mechanism (diagrammatic). 
The arrows indicate the direction of flow of the fluids. 
excreted fluid 1 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 
1 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 kidneys 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 air baths. 
The failure of the kidneys may thus be partially neu- 
tralized by the increased activity of the skin as an ex- 
cretory 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 skin 
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.1 
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-like. 
1 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, which intercepts the rays of the sun and 
thus prevents irritation. In the colored races, these 
cells are more numerous and contain darker pigment 
than in the case of the white races. They are therefore 
Fig. 110. Papillae 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 brunettes, 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 the characteristic color of the skin 
in health and is due to the color of the blood showing 202 
THE SKIN 
through the translucent 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, w'hich 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 
Fig. 111. Section 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 wrinkled. It is for this reason that 
age shows itself most quickly in those who are thin. 
Hair.-Tn 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 larger than the hairs 204 
THE SKIN 
themselves. Here, there is a small root from which the 
hail' 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 layer 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 thickly 
in the skin, especially in the palms of the hands and 
the soles of the feet. Theii' 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 kidneys 
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 known as the pores of the skin, 
and are said to open and close. As a matter of fact, 
they are always wide open. Occasionally, it is true, a 
few 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.-The unbroken 
skin, even when as delicate as in man, forms ordinarily 
an adequate protection against the invasion of the body 
Fig. 112. Magnified view 
of the epidermis, show- 
ing mouths of the sweat 
glands. 206 
THE SKIN 
by disease-producing germs. This protection would bo 
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, boils. 
Fig. 113. Section of the skin 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 own secretions, the 
skin increases the danger of contamination through mi- 
crobes by furnishing a surface to which they adhere and 
on which they develop. The safeguard against this is 
cleanliness. An efficient 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. Microbes 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 water 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 water. 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.1 
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 cat, rabbit, etc.; feathers; fish scales; micro- 
scope ; magnifying glass 2; litmus paper. 
1 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. 
2 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 markings, 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 printers' 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) Compare patterns of markings1 of different fingers of 
same individual and of different individuals. 
3) Moisten back of hand and repeatedly scrape surface 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) With sharp 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 
yarious animals, as dog, cat, cow, fowl, bird, horse, etc. 
6, a) Pull out hair and examine shaft and root in drop of 
water under microscope. Note that root is incomplete. 
b) Compare with hair of dog and horse, with fur of cat and 
rabbit, with feathers, 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 2 as is obtainable, as cow, sheep, pig, horse, alligator, 
snake, etc.) 
9) Dissolve in 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. 
1 Finger prints are so characteristic and so constant as to 
furnish one of the best means of identification. 
2 Leather is skin which has been tanned. The tanning process 
consists in treating the leather with such chemicals as the tannin 
of tan bark, which make insoluble the tissues ^f the skin. THE SKIN 
210 
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 which 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 mechanism. 
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. Tn 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- 
drawal of blood from the 
body's surface is in a meas- 
ure equivalent to putting on 
an overcoat, since it shuts 
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.1 
Fig. 114. Diagram to show distribution 
of blood in the body when heat is 
being saved (A), and is being thrown 
off (B). The black areas represent 
the parts containing blood. The 
innermost white area represents the 
layer of subcutaneous fat; the outer, 
the epidermis. 
1 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 receives great assistance from such further pro- 
tection of the body as is afforded by clothing. Of the 
various materials employed for clothing, the skin of 
animals was probably the first 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 from 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. 
From 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 years 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 workmen who when wet from perspi- 
ration are constantly exposed to cooling drafts, as, for 
example, iron workers and coal stokers. These men wear 
wool all the year around. Those among them who have 
attempted to substitute cotton have almost 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 evaporate 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, whether used as blankets or as filling 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 
Fig. 115. Sleepingin an open shack in cold weather. (Boston Children's Hos- 
pital Report.) 
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.1 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 
1 This leads to curling up in bed, which in children frequently 
results in such bodily deformities as round shoulders, flat chests, 
or even spinal curvature. FREEZING 
217 
and comfort is produced. In reality, even the body's 
reserve heat is being lost through this rush of blood 
to the 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 surface and gives to the person 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 very 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 cases 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. 
l^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. 
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 circulatory system, the n'erV'ons system consists of 
Fig. 116. Right side of brain and upper portion of spinal cord. 
219 220 
THE NERVOUS SYSTEM 
Fig. 117. Diagram illustrating the general arrangement of the nervous system. THE SPINAL CORD 
221 
Fig. 118. Diagrammatic front view of spinal cord and bulb, showing 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 until 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. 
After passing between 
the joints of the spinal 
column, the spinal nerves 
enter the neural canal 
formed by the arches 
which spring from the bodies of the vertebrae. Here 
they split into two parts, 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 
Fig. 119. Formation of a spinal nerve. 
(Testut.) NERVE STRUCTURE 
223 
a large grayish mass of similar composition 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 seen to consist of a large number 
Fig. 120. A, cross section of a nerve, showing 5 bundles of fibres and the sup- 
porting tangle of connective tissue fibres penetrated by blood-vessels. B, 4 fibres 
much more highly 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 are 224 
THE NERVOUS SYSTEM 
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 difficult 
to distinguish them from 
the cell structure itself, 
even with the most power- 
fid microscope. Each axis 
cylinder controls by means 
of its branches the activity 
of a small 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 
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 
Fig. 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). NEURONS 
225 
portion of the spinal cord, where 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 shown by the fact that when the axis 
cylinder is cut off from the cell it dies, whereas the cell 
lives on and may 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 neuron, 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 
nervous impulses, are transmitted along the axis cylin- 
ders of the neurons to the 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 the muscle or gland supplied by their 
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 themselves waste away, since with- 
out the nerve stimulation they are unable 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 the 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 column. Here, instead of passing 
through the ventral root of its spinal nerve, it passes 
into the dorsal root and thence by a short 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. 
Each 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 sensory 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 THE NERVOUS SYSTEM 
228 
to withdraw the hand under the direction of the brain, 
that is voluntarily, would have been from twelve- to 
eighteen-hundredths of a second. 
Fig. 122. Diagram of the spinal cord, showing the mechanism of reflex 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 making 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 
Fig. 123. Diagram showing a part of the reflex mechanism by which heat when 
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. 
From 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. 
Sympathetic 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 
Fig. 124. The sympathetic system of nerves as connected with the spinal nerves 
and distributed to the various organs. (Q'uain.) 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 
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 bulb, 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 
Fig. 126. The brain of a lizard, 
with the cranial tnerves in- 
dicated by numerals. (After 
wiedersheim.) 232 
THE NERVOUS SYSTEM 
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. 
Cerebellu m.- 
Springing from this 
axis and covering the 
spinal bulb is a large 
gray mass, the cere- 
bellum, 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 
Fig. 127. Brain of a pigeon, with the cranial 
nerves indicated by numerals. (After 
Wiedersheim.) THE BRAIN 
233 
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. 
Fig. 128. 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 
Fig. 129. Diagram illustrating the course of nerve fibres within the brain. (After 
Starr.) A, track of nerve fibres running from the frontal convolutions to the 
pons and thence to the cerebellum ; B. 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 are mixed. For example, the cranial nerves by 
means of which we get the nervous impulses which give 
rise to the sensation of sight are sensory, while those 
which control the muscles of the eyes are motor. 
Fig. 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 by the pressure 
upon the lash, travel inward along the sensory nerves to THE NERVOUS SYSTEM 
236 
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 nerves. (Quain.) 
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 
object in the shortest 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 known 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 
communicated 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 consecpience we reach for the 
glass of water. This kind of action which involves the 
higher nerve centres of the cortex, is called voluntary 
action, 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.-If 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 any 
other way. In other words, a habit 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 vertebra?. 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 hrs.1 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 examine with 
microscope. 
6) Dissect away skin and muscles covering cranium of calf's 
or sheep's head. With small saw2 carefully cut bones in 
circular direction, 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 note processes which it sends 
between cerebral hemispheres and between them and cerebellum. 
8) Cut processes away and note a) Glistening inner 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. When brain has become somewhat hardened, 
dissect away pia mater on one side and show, a) Cerebral 
hemispheres and their surface convolutions, b) Cerebellum 
and its foldings, c) Spinal 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) Make 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. 
1 The specimen may preferably be hardened and preserved in a 
solution made of formalin, 2 parts; alcohol, 20 parts; water, 78 
parts. 
2 The skull can be cracked with a light hammer and pieces re- 
moved, without injury to brain. 240 
THE NERVOUS SYSTEM 
Nerve Action 
Materials: Frog; feather; watch with second hand (pref- 
erably stop-watch). 
1) Reflex Action: a) Feign 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 many 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 sufficient regular 
sleep. Sleep is more important even than food or drink, 
since without it life more quickly becomes impossible. 
241 242 
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 overwork. 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 until at ten years of age eleven hours are VALUE OF SLEEP 
243 
enough; 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 acquires. Persons 
who have accustomed 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 persons. It is, however, a matter of fact that those 
who have regularly eight or more hours of sleep out of 
the twenty-four rarely break down nervously, whereas 
those who get less than eight hours, and especially those 
who get less than seven, are very apt to break down 
under mental strain. The safe rule, therefore, is not 
to stint the nervous system in the hours of repair and 
recuperation. 
Nervous breakdown.-Curiously 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- 
ing 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 months 
and even of years may be necessary. The nervous sys- 
tem has made a brave attempt to adapt itself to the 
hardship of too much work 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 tissues of the body, the nerv- 
ous system is developed by exercise, without which its 
growth 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 as 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 not 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 quality, 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 we 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 SKIN 
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 touch 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 
all over the body in 
the papillae 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 
Fig. 132. Section of skin showing two papillae 
of dermis and some deeper cells of epidermis. 
At left side are nerve fibres leading to cor- 
puscle. 248 
THE SPECIAL SENSES 
touch corpuscles are found in such 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 
a cold object or even when 
pressed, give a sensation of 
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.1 
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 
Fig. 133. Dingram of a piece 
of skin showing arrangement 
of cold spots (circles); hot 
spots (crosses); and pressure 
spots (dots). 
1 The heat spots are much more difficult to locate than the cold. FATIGUE OF SENSES 
249 
centres are so fatigued that they 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 nerve 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 
direction, 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. They are supposed to arise from nerve 
terminals and bodies resembling touch corpuscles in 
the muscles, tendons and joints. 
SENSE 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 known. 
THE SENSE OF TASTE 
End organs.-The special end organs of taste differ 
markedly 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 taste buds, 
which are distributed over the top and sides of the 250 
THE SPECIAL SENSES 
tongue around the large papillte 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 
Fig. 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, 
sorer 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. For this 
reason, we take bitter medicine in a sweet syrup and 
put 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 
Fig. 135. Diagram showing 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 odors. 
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 
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 ear to a membrane, the ear 
drum or tympanum, which entirely shuts off the inner 
end of the auditory canal from the next cavity, the 
middle ear. The tympanum has a diameter of about a 
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 tympanum 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, anvil 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 middle 
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 bony 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 tympanum, the ear bones, 
the perilymph, the labyrinth and the endolymph. The 
basilar membrane is a long 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 
narrow tip will vibrate sympathetically 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 auditory cells, in which the fibres of the audi- 
tory nerve start. Whenever any part of the basilar 
membrane is set into vibration, the auditory cells of 
that 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. 
SENSE OF EQUILIBRIUM 
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.-Light, 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 luminous 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.1 
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. 
1 The colors lying between the two extremes of reel 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- 
Fig. 138. The right eye cut 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 diminished 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 must 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 our attention is automatically brought into focus. 
Flexibility of lens.-In childhood, the lens is very 
flexible and can be made so convex as to focus objects 
Fig. 140. Diagram illustrating the effect of a convex lens upon rays of light: A, 
when parallel rays are brought to a focus (principal focus); B, when rays from 
a near object are brought to a focus beyond the principal focus; C, when rays 
from an object nearer than the principal focus continue divergent. 
but 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 the 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 by 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 
Fig. 141. Section of front part of eyeball showing the change in the form of the 
lens when near and distant objects are looked at. a, c, b, 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 nearsight. 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, just 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 
Fig. 142. Diagram of a section of the retina, showing groups of rods and cones 
and their 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 structures 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 rdds and cones and the nerve structures 
Fig. 143. The right retina as it would be seen 
if the front part of the eyeball with the 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 
Fig. 144. To find blind spot, hold in front of right eye and close left eye; looking 
steadily at cross, 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 combination 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 the circles appear blacker than 
others, 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 are 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 are necessary. 
With 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 amount 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, first, 
that the eyes should be controlled so as to converge ac- 
Fig. 146. The eye and its muscles. 
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 cases, 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.1 
1 Care should be taken not to exhaust the sense organs by over- 
stimulation. EXPERIMENTS 
267 
c) Study similarly painful points and warm points, using a 
heated point of pencil 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 fingers have remained some time in water. 
b) Withdraw fingers and plunge both immediately into ves- 
sel containing lukewarm water. Compare sensations of two 
fingers. 
Materials: Sugar; salt; dilute vinegar; quinine; dilute am- 
monia, one drop of strong ammonia in glass of water; cabbage; 
onion; carrot. 
Experiments (2 students, one as blindfolded subject, other as 
experimenter) : 
1) Dry tongue, and determine taste of dry sugar. Compare 
with taste of moist sugar. 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. 
Taste and Smell 
Hearing 
Materials: Tuning fork and its resonance chamber; violin 
or stretched cat-gut; violin bow; [apparatus for manometric 
flame]. 
1) Pluck violin string and note dependence of sound upon 
vibration. 
2) Strike tuning fork and note dependence of volume upon 
amplitude of vibrations of prongs. 
3) Place finger on middle of violin string, thus doubling rate 
of vibration. 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 
Fig. 147. Apparatus for analyzing sound by means of manometric flame. 
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 ordinary magnifying glass with cardboard 
diaphragms having central openings of %, V2 an<i 1 in.; 
spectacle lenses, concave and convex of varying strengths; 
candle; 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). 
c) " " " black (shades). 
d) " " " each other. 
5) Color blindness: Give to pupil a set of standard colors 
and their tints and shades. Hold up in succession different 
colors and ask for selection of all pieces resembling them. 
6) Near-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. 270 
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.1 
b) Repeat using other colors. 
[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).] 
1 The color which appears is complementary to the original color. 
White 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 have 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 thrust1 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. 
1 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. 
272 CARE OF THE EAR 
273 
Method of cleaning.-To clean the canal of the ear, a 
rounded object such as the closed end of a hairpin, 
should 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 layers of wax should be 
made, since in normal quantities it is beneficial, not 
harmful. When excessive, it usually works out of itself 
and can then be easily removed. 
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- 
posed arises from 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 inflammation 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 burst through it. The earache which accompanies 
this inflammation should lead one to consult a physician 
at once. 
Effect of noise.-Blows 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 drum 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 from us. The dangers to which 
the eyes are exposed are manifold. Dust,1 cinders and 
1 The irritation due to dust can be relieved by dropping into the 
eyes a small amount of a weak solution (10 grs. to 1 oz. pure 
water) of boracic acid. 274 
THE CARE OF THE SENSE ORGANS 
insects find an easy entrance to them, in spite of the 
quick closure of the eyelids.1 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 
1 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 steadily 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 eyes 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. Most 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 upper 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- 
276 THE LARYNX 
277 
most together and carry with them the vocal cords, 
which are thus stretched tightly across the larynx. In 
this position, they nearly close the air passage through 
the trachea and are made to vibrate by the air as it 
passes over their edges on its way from the lungs. These 
Fig. 149. View of larynx 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 force 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. 278 
THE VOICE AND SPEECH 
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 fundamental 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 
Fig. 150. Diagrams showing 
various positions of the vocal 
cords and their adjustment 
by the muscles 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 harsh. An inflam- 
matory condition of the throat, as in a cold, may result 
in the 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 
mouth, 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 vowels. One 
can readily observe with a mirror the changes involved 
in the production of the sounds a, e, i, o and u. 
Consonants.-The consonants, 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 
b, p, t, d, k and g. If the closure is not complete, the 
result is a hissing sound called an aspirate, as in pro- 
nouncing f, v, w, s, z, I, sell, th, 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 whispering, 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 AND 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 body 
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.-Whenever 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 
Fig. 151. Various forms of bacteria, highly magnified, some of which have flagella 
orcilia: b, bacilli; m, micrococci; s, spirillee. 
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.1 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 which come from 
the animal kingdom and also consist of single cells of 
varying forms, are known as protozoa.2 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, however, they are harmless because of the 
body's ability to destroy them as fast as they find en- 
trance to it. When the body has been weakened, how- 
ever, or when the invading microbes are very numerous 
and virulent, they are able to invade it and to multiply 
1 Defoe's "History of the Plague" gives a vivid picture of the old 
attitude toward infection. 
2 Literally, "first animal." 284 
HEALTH AND DISEASE 
within it. For example, the special bacterium 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 arp able 
to enter and multiply. The result of their activity 
is the disease of the lungs known as pneumonia. 
Generation of toxins.-Like all unicellular 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 toxin. 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 body 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 
greatly 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 HEALTH AND DISEASE 
286 
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,1 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- 
1 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 diphtheria 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 this 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 down and the person quickly 
recovers.1 
In consumption.-Tn 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 fresh 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 
1 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 
Fig. 152. 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 person are the nose and mouth, for the reason 
that streams of air containing microbes are continually 
passing through them. The food entering the mouth also 
forms an 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 great number of persons, it 
is essential that the person 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.- 
Avoid unnecessary contact with others, when either 
they or you are suffering from any acute illness. 
So dispose of all excreta and discharges that no one 
else can come into contact, even remotely, with them. 
The best methods are 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 and drink 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 check 
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 2 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 
1 That is, in a steam-tight vessel. 
2 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 1 by such pre- 
1 Influence of vaccination ii/pon smallpox: 
Before vaccination 
Population Boston 
Cases 
Deaths 
1721 
11,000 
5,989 
850 
1730 
15,000 
4,000 
509 
After vaccination 
1811-1830 .... 
14 
Annual rate of cases per million of inhabitants: 
Sweden 
Before 
2,045 
Optional 
480-155 
Compulsory 
5-0.2 
England 
.... 2,000 
417 
53 
Prussia 
2,000 
300 
4 
Spain 
12,050 
Porto Rico 
600 
0 
Smallpox cases and death rates per 1,000 persons in Sheffield, 
Eng., epidemic: 
Not vaccinated 
Cases 
94 
Deaths 
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 (1894) 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 purity 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° F.) and observe it at 
intervals for 24 hrs., noting carefully its appearance. EXPERIMENTS 
293 
b) At encl of 24 hrs., examine some of sediment1 under 
microscope, using the high power.2 Note yeast cells with their 
buds. Make sketches of characteristic forms and compare with 
forms in the yeast cake. 
c) 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 activity 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 hrs., 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 leave 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 foi'ms 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. 3 
1 The sediment is best obtained by introducing into the liquid a 
glass tube drawn out to a moderately line 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. 
2 The best results are obtained by using a in. oil immersion 
objective, which can probably be borrowed, if necessary, from a 
physician. 
8 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. Moisten 
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 uncovering 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 sddiment. A small piece of 
blotting paper p'lahed up'oh th'e opposite ^icl'e o'f the cover glass will 
assist the flow. EXPERIMENTS 
295 
e) Repeat experiment, using 1 drop of milk (about cu. 
cm.). 
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 aftei' it 
has been washed in soap and warm water. Compare the 
growth after 24 and 48 hrs. 
8) Effect of heat {sterilization') 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 numbei' 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 hrs., 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 scissors 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 grs. of borax; to No. 12, 4 grs. 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 
vrhich 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 and 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 case 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 the 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 reasonably 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 unbearable because of the wealmess, 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 absorbed into 
the system, where it produces its characteristic effect. TOBACCO 
299 
Presence of carbon monoxide (CO).-In 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 nervous 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 with 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 activity which results in their more complete ex- 
haustion. When taken habitually, each period of stimu- 
lation is followed by a period of greater exhaustion,1 
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 leaving 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. 
1 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 overgrowth 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 eases, 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 knobs 
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 well as the liver 
may 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 use 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 under the influence of very small amounts, 
whereas others 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. Unfortunately, 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 years 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 Assurance 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 1 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 of the same 
blood, what is injurious to one cannot be 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 
307 
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 dealers 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 yery atmosphere by which liquor 
dealers 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 find it necessary to call the attention to the rule on 
page 345 of the 'Blue Book' regarding this 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 $5 per thousand extra. 
Wholesale dealers, if apparently 
unaffected by their business Free. 
Restaurant keepers and waiters 
selling liquor $5 per thousand extra. 
(In this whole class the habits, past 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 cases 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 
officers or officials 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 two 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 quickly 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 
otherwise 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." 1 
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, 
1 The Physiological Aspects of the Liquor Problem, Committee 
of Fifty. 310 
STIMULANTS AND NARCOTICS 
many of whose members were total abstainers and the 
rest macle 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 round without perceptible 
harm, fall over with all the symptoms of sunstroke as 
soon as they stepped into the glaring rays of the hot 
sun. ' '1 
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 officers, 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 
1 Practical Hygiene, Harrington. SYSTEMIC EFFECTS 
311 
and cut their own 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 officers 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." 1 
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 officer 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, 
1 The Physiological Aspects of the Liquor Problem, Committee 
of Fifty. 312 
STIMULANTS AND NARCOTICS 
while drunkenness, with its attendant evils, became much 
more common. ' '1 
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: 4 ' 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. " 1 
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 
1 The Physiological Aspects of the Liquor Problem, Committee 
of Fifty. 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 
follow-as well 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 fellow, and will 
sympathize, and sometimes remonstrate with him in his 
being a slave to drink. ' '1 
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. 
1 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 constantly 
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 oxygen, 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 union with other substances, thereby producing 
light and heat. This union is called combustion or 
oxidation.1 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 (CO9) of 
the air into carbon and oxygen, and the water (H2O) 
into hydrogen and oxygen. Oxygen 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 
flesh-forming food of animals. Nitrogen as found in 
1 The chemical compounds formed by oxidation are called oxides. 
Water (H2O) is an oxide of hydrogen; carbon dioxide (CO2), of 
carbon; and iron rust (Fe2O3), 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 (CO3).-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 
317 
stoves, furnaces, charcoal-heaters and from tobacco as 
ordinarily smoked. 
Water (H2O).-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 
they 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 their structure. Moreover, it is only 
when dissolved that food is capable of nourishing them 
and of undergoing 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 about 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 found 
the minerals potassium, calcium, magnesium and phos- 318 
THE GROWTH OF 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. 
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,1 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.2 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 plants, 
energy is required to separate out the materials which 
they use and to build them into their proper places in 
1 Growth: Carbon dioxide + water = starch + free oxygen 
6 CO2 + 5H2O=CcH]0O6+ 6O2 
2 Decay: Starch + oxygen = carbon dioxide + water 
C6H10O6+ 6 O2 = 6 CO2 +5 II2O CONSERVATION OF ENERGY 
319 
the plant's tissues. This energy is furnished by the 
sun in the form of light and heat. The same amount of 
energy which is given by the sun to the plant is again 
given out quickly and intensely if the plant is burned, 
or slowly and imperceptibly if the plant decays. Dur- 
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 
known as the conservation of energy.1 
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 they 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 dynamo for the generation 
of electricity. In any case, there is an exact equality,8 
or correlation, between the original heat from the sun, 
the force developed in the engine and the work done 
1 Similai'Iy, the labor (energy) expended in raising building 
materials to their positions in a building, although seemingly lost 
for many years, again becomes active when the materials ulti- 
mately fall to the earth. 
2 All of the sun's heat is not made productive, since a part of it 
escapes as hot gases up the 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 the 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 1 in 
the tissues for the production of heat and muscular 
energy.2 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.3 
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- 
1 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). 
2 Starch 4- oxygen = carb. diox. 4- water 4- heat4- muse, energy 
C6H]0Ob+ 6Os =6 CO2 4-6 II3O 4- " + " 
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. 
3 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 pig, 
103° F.; and in the hen and pigeon, 107° F. EXPERIMENTS 
321 
fortably warm. This excess of heat is thrown off by 
wetting the surface 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 
I 
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 cleared by settling; test tube; 12 in. piece of glass or 
rubber tubing, with about yL in. bore; 12 in. piece of glass 
tubing, % 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 litmus 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 litmus paper with water. Neutral 
reaction. 
d) Test various substances, as soap, ammonia, soda, cream 
of tartar 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 thrusting the 
lighted slivers under its partially 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 carefully 
every change taking place and write out observations. 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 % 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, Vs 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 Vf grain or 1 
centigram (decimal weights preferred); alcohol lamp or Bunsen 
burner; sheet tin. EXPERIMENTS 
323 
1) Oxygen manufacture: 
Put % 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 inverted over holes of perforated shelf. 
Place lighted lamp near trough. Gently heat lower end of test 
tube containing mixed chemicals over flame until gas begins to 
be given off. 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 splinter 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 until 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 wire 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 experiment by demonstrating combustion of 
small bits of magnesium, copper, zinc, etc. 
3) Nitrogen separation:1 
Make a wood float 1 in. by 1 in. by % in. 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 watei' in pneumatic trough. Light phosphorus and 
immediately place over it upon tin shelf of trough an inverted 
1 This is really a method of oxygen elimination by phosphorus 
absorption. The oxygen combines with the phosphorus and the 
resulting oxide is absorbed by the water. The nitrogen is conse- 
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 result 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 and 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 carefully 
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 
amount, is beneficial, since it washes away the microbes 
and has some power of checking their growth. 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- 
325 326 
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 scrub- 
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).1 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 
1 Care should be taken not to bind so 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.-Burns, whether caused by fire, steam, hot 
water, acids and alkalies, 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 blisters should be emptied through small punc- 
tures made with the point of a knife or needle which has 
previously been sterilized.1 The treatment should then 
be the same as for a mild burn. In still more severe 
burns where the skin is destroyed, the skin surrounding 
the 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 alkali 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 
1 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 case 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 
329 
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. 
Treatment: A physician should be called at once, as it 
usually requires experience to replace the bones. There 
should 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 
within 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 serious than simple fractures, as there is a 
probability of infection. 
Treatment: As in a dislocation, a physician should be 
called at once. The treatment depends largely upon 330 
FIRST 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 artery has been 
cut, it will be necessary to apply pressure to check 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 
poisons. 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 are 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 substances 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 vomiting by the use of: 
Finger or feather for tickling the throat. 
Mustard water, tablespoonful of mustard in tumbler of tepid 
water. FIRST AID TO THE INJURED 
332 
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 poison. 
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, 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 
burn. 
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 AND ANTIDOTES 
333 
poison, to form a protective 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: Precipitated oxide of iron. If this cannot be 
immediately obtained, give moistened plaster of wall which will 
mix with the poison and serve to protect the stomach. 
2) Phosphorus (matches, Rough on Rats). 
Antidotes: Emetics and magnesia or plaster from wall. 
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) Acids (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) Opium1 (laudanum, paregoric, morphine, black drops, 
soothing syrups, cholera mixtures, Dover's powder). 
Antidotes: Solution permanganate of potash, 2 grs. dis- 
1 In opium poisoning, a distinguishing symptom is pin-head con- 
traction of the pupils of the eyes. 334 
FIRST AID TO THE INJURED 
solved in water; tannic acid; strong hot coffee; strychnia, 
to gr. 
Keep awake by non-exhansting means, snch as flicking with 
a damp towel, shouting in ear, and making walk. Keep warm 
with hot watei' 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)1: 
Antidotes: Elot coffee and dilute ammonia in small repeated 
doses. Apply first hot and then cold water. Keep patient 
warm. 
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 cases, 
as in the stings of wasps and bees, the poison is irritant 
and results in pain and swelling but is not dangerous 
1 Wood alcohol and denatured alcohol, which contains wood 
alcohol, are extremely dangerous poisons. SNAKE BITE 
335 
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. 
Treatment: 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. Run 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 
head and chest lower than the rest of the body. If there CONVULSIONS 
337 
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 throat 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 attacks may come on 
suddenly, or gradually with symptoms 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 attacks may follow each other 
rapidly. 
Treatment: Keep the patient from injuring 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 stimulants in small quantities. 
These attacks are seldom serious, and it is usually 
unnecessary to do anything except prevent bodily injury. FIRST AID TO THE INJURED 
338 
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: Reduce 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 in 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. 
Artificial respiration.-Prone pressure method (Scha- 
fer).-Wipe out the patient's mouth. Kneel by the side 
of his hips and place hands over the lower ribs. Throw 
your weight forward so as to press strongly though gradu- 
ally upon both sides of the lower ribs for a space of about 
3 seconds. Remove pressure entirely for 3 seconds. 
Again apply pressure as before and release. Keep this 
up at the rate of 10 or 12 times per minute, until the 
patient shows signs of recovery. If, at the end of 2 
hours or more, the patient does not recover and there is 
no perceptible heart beat, the case may be considered 
hopeless. 340 
FIRST AID TO THE INJURED 
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 
Fig. 153. Prone pressure method of artificial respiration-showing, first, position 
of relaxation (inspiration); second, position of pressure (expiration). (After 
Schafer.) 
may tend to keep the blood in circulation and carry 
aerated blood from the lungs 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 
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 
341 
Gas poisoning.-Poisoning by illuminating 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 
choking 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 
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 342 
FIRST AID TO THE INJURED 
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,1 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. 
1 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 knowledge 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,1 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 yds. long, 
which is rolled tightly. To apply the roller, grasp it 
in the right hand so that the loose end points toward 
1 An excellent triangular bandage on which are printed the 
methods 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 
Fig. 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 remains 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 sheeting, of the size necessary 
to cover the part, except in those cases 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 
injuries 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. 
Splints.-Splints consist of light pieces of wood, card- 
board, or any other stiff material. When bandaged on, 
Fig. 155. Padded splints applied to fractured leg for temporary support. 
they serve to hold broken bones and sprained or dislo- 
cated joints in place and thereby relieve pain and pre- 
vent further injury. The accompanying 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. 156. 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- 
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 
Fig. 157. Sling as arranged for left arm. 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 16 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 and 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 
acid in a 3 per cent solution made similarly to lysol; 
sulpho-naphthol {creolin} 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 ereolin, also in a 3 per cent 
solution. Carbolic acid should never be used, as it may 
exert corrosive action upon the skin. 348 
TABLE OF INFECTIOUS DISEASES 
Incubation 
period 
av. ; range 
Usual first symptoms 
Cause 
(Mode of entry) 
Length of quarantine 
(for schools1) 
Choleras 
3 ds.; 2-7 ds. 
diarrhoea, weakness. 
spirillum (food and water, car- 
ried by flies). 
Diphtheria® 
Erysipelas 
Influenza 
2 ds.; 2-15 ds. 
5 ds.; 
3 118.-22 ds. 
3ds.; 1-5 ds. 
fever, pain on swallowing, 
whitish patches in throat, acrid 
discharge from nose. 
chill, fever, red swelling on 
face or neck. 
fever, weakness, backache, etc. 
bacillus (air, food, contact). 
streptococcus (wounds, etc.). 
bacillus (air, contact). 
until 2 negative® cultures 
from nose and throat 48 
hrs. apart. 
Mumps 
Malaria 
15 ds.; 7-30 ds. 
8ds.; 4-60 ds. 
swelling of parotid gland, fever. 
chills, fever, sweating, and 
weakness every 1,2, or 3 ds. 
unknown (air, contact). 
heematozoa (inoculated by 
mosquitoes). 
1 week after all swelling 
and tenderness are gone. 
Measles 
Hydrophobia 
9 ds.; 4-14ds. 
40 ds.; 
13 ds.-2 ys. 
head-cold, white blisters in 
mouth near molar teeth, erup- 
tion (blotches) on face. 
rigidity of neck and jaws, 
spasm on swallowing. 
unknown (air, contact). 
uncertain (wounds). 
after all peeling is over and 
bronchitis is cured. 
Scarlet fever 
4 ds.; 
7 hs.-7 ws. 
fever, sore throat, vomiting, 
eruption (scarlet flush). 
uncertain (air, contact, 
wounds). 
until all fever and all dis- 
charge from nose and ears 
have ceased. 
Small-pox 
Tetanus 
(Lockjaw) 
Typhoid fevers 
12 ds.; 7-15 ds. 
2 ds.; 
2 hs.-35 ds. 
14 ds. 2?-21 ds. 
chill, fever, vomiting, head- 
ache, backache. 
chill, rigid neck and jaws. 
weakness, nosebleed, head- 
ache, fever. 
uncertain (air, contact). 
bacillus (wounds). 
bacillus (food, water, carried 
by flies). 
until all crusts are gone. 
Chicken-pox 
14 ds.; 10-19 ds. 
scattered eruption (pimples, 
then blisters) on face and scalp, 
fever, etc. 
unknown (air, contact). 
until all crusts are gone. 
APPENDIX D-TABLE OF INFECTIOUS DISEASES TABLE OF INFECTIOUS DISEASES 
349 
Whooping- 
cough 
8 ds.; 2-10 ds. 
a cold with peculiar cough re- 
sulting in vomiting. 
unknown (air, contact). 
until cough has stopped. 
Yellow fever 
3 ds.; 2-6 ds. 
chills, headache, fever, vomit- 
ing. 
unknown (injected by mos- 
quitoes). 
Tuberculosis 
? long. 
weakness, wasting, fever, 
cough (?), enlarged glands, 
chronic pimples, bone and joint 
inflammation. 
bacillus (air, food, etc., 
wounds). 
while cough persists. 
Pneumonia 
Id.; ?-2ds. 
chill, fever, pain in chest. 
coccus (air, contact). 
Dysentery 3 
6 ds.; 1-8 ds. 
diarrhoea, pain in rectum. 
ameba or bacillus (water and 
food, carried by flies). 
Conjunctivitis 
(Pink-eye) 
short. 
redness and discharge from eye. 
various bacteria (air (?), con- 
tact, use of infected towels, 
etc.). 
until cured. 
Trachoma 
long. 
granulations of inner surfaces 
of eyelids. 
unknown (contact, use of in- 
fected towels, etc.). 
until cured. 
Scabies (Itch) 
itching and sores on skin from 
scratching. 
animal parasite (contact, use of 
infected towels and clothing). 
until cured (whole family 
must be treated). 
Pedicuh (Lice) 
itching, eggs on hairs, lice in 
hair. 
animal parasite (contact, use 
of infected towels, clothing, 
brushes, combs, etc.). 
until cured. 
Ringworm 
circular, rough, scaly patches 
on skin whicli spread at edges 
and clear at centre. 
vegetable parasite (contact, use 
of infected towels and cloth- 
ing). 
until cured. 
D=day ; h = hour; w=week; m=month ; y=year ; contact maybe either direct or intermediate (when objects infected by the 
touch of a diseased person are handled); air is contaminated by organisms carried in it as dust or by fine particles of discharges 
which float in it after coughing and sneezing. 
1 Lengths of quarantine as suggested by the Medical Committee appointed by the Massachusetts Board of Education, 1907. 
2 A negative culture is one in which no bacilli are found. 
3 A person who has this disease so lightly as to be able to be about or whose recovery has not been proved by negative cultures 
may through carelessness act as a "carrier" of the germs and thus infect others during a long period subsequent to apparent 
recovery. INDEX 
Abduction, 37 
Abscess, 128, 206, 325 
Absorption, 112, 113, 118 
Abstinence, 305, 312 
Accommodation, 260 
Acids, 327 
Activity, 120, 121 
Adduction, 37 
Adenoids, 191 
Adrenal bodies, 132 
Africans, 306 
Age, 120 
Air, 1, 165, 166, 172-175, 182- 
192, 283, 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 
Alimentary canal, 96, 97 
Alkalies, 327 
Alveoli, 169 
Ameba, 4, 8, 51, 96 
Amylopsin, 103 
Anatomy, 10 
Anemia, 127 
Angle worm, 52 
Animal food, 77-82 
Animal heat, 211 
Animal matter, 26 
Animals, 1-10, 51, 67, 211, 315 
Ankle, 24 
Anopheles, 189, 288 
Antibody, 284-287, 290 
Antidotes to poisons, 333, 334 
Antitoxin, 284-287, 291 
Anvil, 253 
Aorta, 136, 139, 140 
Ape, 10, 25 
Apoplexy, 304, 338 
Appetite, 121-124 
Aqueous humor, 257 
Arm, 21 
Arsenic, 77, 333 
Arterial pressure, 158 
Arteries, 135, 140-143, 161, 162, 
326 
Arterioles, 141, 151, 152 
Articular 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 
Auriculo-ventricular valves. 
138-140 
Axial skeleton, 19 
Axis cylinder, 224 
Axis vertebra, 14, 15 
Backbone, 13 
Bacteria, 282-284 
Bad air, 182-185 
Baking powder, 74 
Ball and socket joint, 32, 33, 44 
Banana, 76 
Bandage, 162, 164, 326, 343, 344 
Basilar membrane, 254, 255 
Bathing, 207 
Baths, 163, 199, 207, 218, 248 
Beans, 66, 75 
Bed, 189 
Bed clothing, 214, 215 
Beef-tea, 82 
Beer, 93, 302, 304 
Beets, 75 
Bent-knee walking, 57, 58 
Beverages, 87-95, 302 
Biceps, 40, 59, 60 
351 352 
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, 263 
■Rliqfpr ^97 
Blood, 126-156, 198, 199, 212 
Blood, corpuscles of, 5, 126-128, 
206 
Blood-plasma, 126, 128 
Blood pressure, 157, 158 
Blood-vessels, 37, 135, 145 
Blushing, 202 
Body temperature, 211, 212, 
216-218 
Boiling, 70 
Boils, 206 
Bone, 12, 26-30, 39 
Bony labyrinth, 254 
Bouillon, 82 
Brain, 221, 231-238 
Brain convolutions, 232 
Brain injury, 339 
Brain work, 158 
Brandy, 93, 302 
Bread, 74 
Breakfast foods, 75 
Breastbone, 17 
Breathing, 173, 176, 192 
Brewers, 307 
Broiling, 69 
Bronchi, 167 
Bruises, 160, 326 
Burns, 327 
Butter, 74, 78 
Cabbage, 7 5 
Caffeine, 92 
Calorie, 120, 121 
Cambric tea, 91 
Candy, 83 
Canine teeth, 98 
Canned fruits, 77 
Capacity of lungs, 174 
Capillaries, 111, 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, 206 
Carnivorous animals, 67 
Cartilage, 29, 31, 168 
Casein, 77 
Catarrh, 191 
Celery, 76 
Cells, 5, 6, 7, 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, 125 
Chewing tobacco, 298 
Chill, 284 
Chimpanzee, 11 
Chloral, 296, 298 
Chocolate, 83, 92 
Choking, 341 
Cholera, 88, 282 
Chordae tendineae, 136 
Chyle, 111, 113 
Chyme, 107, 108,. Ill 
Cider, 93, 302 
Cigarettes, 298, 300 
Cilia, 168, 191 
Circulation, 135-164 
Circulatory system, 135-156 
Circumduction, 37 
Circumvallate papillae, 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 
353 
Cochlea, 254 
Cocoa, 92 
Cocoaine, 296, 298 
Coffee, 92, 93, 300, 301 
Cold, sense of, 248 
Cold baths, 207, 218 
Cold feet, 212 
Colds, 190, 191, 279 
Cold spot, 248 
Colic, 113 
Collagen, 26 
Collar bone (clavicle), 17, 21 
Colloids, 118 
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, 82 
Connective tissue, 71, 130, 202, 
303 
Consciousness, loss of, 335, 336 
Conservation of energy, 318, 
319 
Consonants, 279 
Constipation, 297 
Consumption, 183, 190, 282, 
286, 287, 290 
Contagious diseases, 291, 292 
Contraction of heart, 136 
Contraction of muscle, 46 
Contused wound, 326 
Convolutions of the brain, 232 
Convulsions, 337 
Convulsive poisons, 331 
Cooking, 69-71 
Cord, spinal, 221, 227, 228 
Corn, 75 
Cornea, 257, 258, 264 
Corn syrup, 77 
Corpuscles of blood, 5, 126-128, 
206 
Corrosive poisons, 331 
Cotton, 213, 215, 218 
Coughing, 190, 288, 289 
Cow, 79 
Cowpox (vaccinia), 286 
Crab, 11, 12 
Corrosive sublimate, 347 
Cranial nerves, 234 
Cream, 77, 78 
Creolin, 347 
Cross-eyes, 266 
Croup, 342 
Crown of tooth, 101 
Crystalline lens, 257-260, 263 
Crystalloids, 117 
Deafness, 254 
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 eyes, 266 
Dog bite, 335 
Dogs, 308 
Dorsal region, 14 
Drafts, 188 
Dried fruits, 76 
Drowning, 339 
Drugs, 331-334 
Ducts, 108, 109 
Dust, 168, 189-191, 273 
Dysentery, 76, 88 
Ear, 252-256, 272, 273 
Earache, 272 
Ear drum, 253 
Earth, 1 354 
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 
End 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, 61-64, 120-121, 157, 
176-178, 211, 320 
Expiration, 173 
Extension at joints, 37 
External ear, 252 
Eye, 256-266, 273-275 
Eye, foreign bodies in, 274 
Eye, proper use, 275 
Eyeball, 257, 260 
Eyelashes, 274 
Eyelids, 274 
Eye strain, 264 
Fainting, 158, 163, 336 
Far-sight, 260 
Fasciculi of muscles, 40 
Fat, 65, 68, 77-80, 84-86, 110- 
113, 119-121, 124, 130, 131, 
203, 304 
Fatigue, 63, 248, 249, 284 
Femur, 23 
Fermentation, 77, 93, 95, 302 
Ferments, 103,107-110,116-119 
Fever, 217, 218, 285 
Fibril of muscles, 41 
Fibrin, 126, 129 
Fibula, 23, 24 
Filters, 90, 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, 45, 65, 67-86, 94, 
112, 120-124, 130, 131, 158, 
283, 289, 292, 301 
Foods, composition of, 86 
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, 74 
Glycerine, 208 
Glycogen, 113, 130 
Grains, 67, 73, 75, 302 
Grapes, 76 INDEX 
355 
Grape-sugar, 65, 76 
Growth, 1, 29, 131, 178, 299, 
315-318 
Gums, 65 
Gustatory nerves, 234 
Gymnasia, 292 
Habits, 237, 301 
Hair, 203 
Hallucinations, 304 
Hammer, 253 
Hand, 22, 42 
Head, 17 
Headache, 285, 297 
Health, 120, 132, 192, 281-292, 
300-313 
Hearing, sense of, 252-255 
Heart, 136-140, 176-178, 231, 
304 
Heart beat, 137, 157 
Heart muscle, 48, 136, 137 
Heart strain, 63, 178 
Heat, 1, 318 
Heat, sense of, 248 
Heating, 185, 186 
Heat of body, 211-218 
Hemoglobin, 127 
Hemorrhage, 158, 161-163 
Herbivorous animals, 67, 83 
Hinge joints, 34 
Hip-bone, 18 
Hoarseness, 278 
Hookworm disease, 127 
Horse, 287 
Humerus, 22 
Humidity of air, 186 
Hydrocarbons, 65, 69, 74, 76, 
'130 
Hydrochloric acid, 106, 321 
Hydrogen, 1, 315, 317 
Hygiene, 121, 157, 182, 207, 
211, 241, 272, 281-292, 296- 
313 
Ileocecal valve, 113 
Illness, 120, 281 
Illuminating gas, 190 
Image, formation of, 258 
Immunity from disease, 286 
Incisors, 98 
Indians, 306 
Indigestion, 124, 125, 297 
Infection, 282, 287, 291, 292, 326 
Infectious diseases, 348 
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 muscles, 47 
Iris, 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, 113 
Laryngitis, 279 
Larynx, 167, 276-280 
Lead poisoning, 77 
Leather, 3, 214 
Leg, 22, 23 
Lens, 257-260, 263-264 
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, 113, 116, 127, 130, 
303 
Lobster, 11 
Lockjaw (tetanus), 325 
Locomotion, 51-57 
Longevity, 305 
Lumbar region, 15 
Lungs, 165, 166-178 
Lymph, 148-151, 284, 326 
Lymphatics, 148-151, 327 
Lysol, 347 356 
INDEX 
Malaria, 189, 282, 288 
Malt, 302 
Maltose, 103 
Mammal, 10 
Man, 10-11 
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, 160, 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- 
228 231 
Mouth, 96-103, 166, 289 
Mouth breathing, 192 
Movements, 51 
Mucus, 168 
Mumps, 103 
Muscles, 13, 40-50, 54-60, 278 
Muscular sense, 249 
Muscular work, 61-64, 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, 250, 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, 4-7, 61 
Nutrition, 9 
Nuts, 65, 66, 76 
Oils, 65, 66 
Olfactory nerves, 234, 251 
Omnivorous animals, 67 
Optic nerves, 262, 263 
Organic matter, 3 
Organic salts, 75 
Organisms, 2, 3, 88, 282 
Organs, 2, 6, 7, 12 
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, 
111 
Papillae of the tongue, 104, 
250 
Papillary muscles, 138, 139 
Paralysis, 46, 225, 303, 304 
Parasites, 81, 88, 283, 284 
Parks, 292 INDEX 
357 
Parotid glands, 103 
Pasteurization, 80 
Patella (knee-cap),.35 
Peanuts, 75 
Peas, 66, 75 
Pelvic girdle, 17, 18, 22 
Pepsin, 103, 107 
Peptones, 107, 112, 113 
Perilymph, 254 
Periosteum, 30 
Peroxide of hydrogen, 347 
Perspiration, 199, 204, 205, 212, 
214, 321 
Pharynx, 103, 104, 167, 254 
Physiology, 10 
Pigment cells, 201 
Pimples, 205, 206 
Pitch, 278 
Pituitary body, 132 
Pivotal joints, 36 
Plague, 283 
Plants, 1, 51, 67, 315, 318 
Plasma, 126, 128 
Platelets, 128 
Play, 61 
Playgrounds, 292 
Pleura, 171 
Pneumonia, 190, 284 
Poisons, 284, 303, 330-335 
Poor circulation, 163 
Pores of skin, 205 
Potatoes, 75, 76 
Power, 52, 53 
Preserved fruits, 76 
Pressure, 159, 161, 162 
Proteids, 66, 69, 73-77, 81, 107, 
110, 113, 121, 130, 131 
Protoplasm, 4, 127 
Protozoa, 283 
Ptomaines, 82, 334 
Ptyalin, 103 
Pulmonary artery, 140 
Pulmonary circulation, 135, 
145 
Pulp cavity of tooth, 101 
Pulse, 144, 162, 164 
Pupil, 261 
Pus, 161, 206 
Pustule, 128 
Putrefaction, 81 
Pyloris, 107 
Quarantine, 291 
Radish, 76 
Radius, 22 
Rays of light, 258 
Recuperation, 64 
Red blood corpuscles, 126, 127 
Red marrow, 30, 127 
Reflex action, 228-231, 235, 236, 
274 
Renal secretion (urine), 198 
Renal tubules, 196-198 
Rennin, 107 
Reproduction, 3, 5 
Resonance, 279, 280 
Respiration, 165-195 
Respired air, 182-184 
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 
Salivary glands, 103 
Salt, 83 
Sausage, 81 
Scapula (shoulder-blade), 17, 
21 
Scarlet fever, 88, 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, 266-271 
Senses, special, 246-271 358 
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 
359 
Trachea (windpipe), 104, 166, 
167 
Transformation of energy, 319 
Treatment of poisoning, 331- 
334 
Triangular bandage, 164, 343 
Triceps muscle, 60 
Trichina, 81, 283 
Trunk, 14 
Tuberculosis, 183, 282, 286, 287, 
290 
Turbinate bones, 166 
Turnips, 75 
Turtle, 12 
Tympanic membrane, 253, 254 
Typhoid, 76, 88, 91, 282 
Ulna, 22 
Upper arm, 21 
Urea, 121, 198 
Ureter, 197 
Uric acid, 121, 198 
Urine, 198 
Vaccination, 286, 291, 292 
Vaccinia (cowpox), 286 
Valves, 136, 139, 146, 149, 150 
Vasomotor control, 157, 158 
Vasomotor nerves, 152 
Vegetables, 75, 76, 88 
Veins, 135, 143-146 
Ventilating flues, 186 
Ventilation, 184-189 
Ventricles, 136, 138-140 
Vermiform appendix, 97, 115 
Vertebrae, 13 
Vertebral column, 13 
Vertebrate animals, 10 
Villi of small intestine, 111, 
112 
Vision, 263, 265, 266 
Vitreous humor, 257 
Vocal cords, 276, 277 
Voice, 276-280 
Volume of sound, 277 
Voluntary action, 237 
Voluntary muscles, 46-48 
Vomiting, 108 
Vowels; 279 
Walking, 56-58 
Waste products, 196-199 
Warm bath, 207 . 
Water, 1, 87-91, 131, 199, 283, 
292, 317 
Weight, 52-55 
Well water, 89 
Wheat, 66, 73 
Whiskey, 93, 302 
Whispering, 280 
White blood corpuscles, 126- 
128, 206, 284, 286 
White matter of brain, 233 
Windows, 185 
Windpipe, 104, 166, 167 
Wine, 93, 302 
Wood alcohol, 334 
Wool, 213 
Work, 48, 61-64, 69, 121, 122 
243, 244, 292, 320 
Worm, 52 
Wounds, 325, 326 
Wrist, 22 
Yeast, 74, 93, 94 
Yellow fever, 288