PHYSIOLOGY

BRIEFER COURSE

GOLTON

BIOLOGY

LIBRARY

G

.wt

X-RAY PHOTOGRAPH OF HAND

SHOWING SHOT CARRIED FOR TWENTY YEARS

(From Recreation, by permission of G. O. Shields.)

BRIEFER COURSE

PHYSIOLOGY

ILLUSTRATED BY EXPERIMENT

BY

BUEL P. COLTON, A.M.

AUTHOR OF " PHYSIOLOGY, EXPERIMENTAL AND DESCRIPTIVE

"PRACTICAL ZOOLOGY"; AND PROFESSOR OF NATURAL

SCIENCE IN THE ILLINOIS STATE NORMAL

UNIVERSITY

BOSTON, U.S.A.

D. C. HEATH & CO., PUBLISHERS
1900

BIOLOGY

LIBRARY

G

COPYRIGHT, 1899,
BY BUEL P. COLTON.

Nortooob

J. S. Gushing & Co. - Berwick & Smith
Norwood Mass. U.S.A.

PREFACE.

THE author's " Experimental and Descriptive Physiol-
ogy" has been adopted by a large number of schools and
colleges. But there are many schools in which, owing to
the youth of the pupils, the shortness of the time allotted to
the subject, or the meagerness of laboratory facilities, such
a rigorous course cannot be taken. For such schools this
simpler book is written. While it contains considerably
less experiment and dissection than the larger book, it is
still based upon experimental work. No teaching of physi-
. ology is worthy of the name unless it rests upon experi-
ment, observation, and dissection. The ridiculous answers
of the pupil who has learned mere "book physiology"
furnish the standard jest of the educational journal. Try-
ing to teach physiology without experiment is not only in
opposition to modern views of pedagogy and psychology,
but it is equally at variance with the common sense of the
business man's view. Such teaching is a mere mummery
of words — it teaches neither how to know nor to do.

In fitting this work for the less mature mind, special
attention has been paid to conciseness and brevity of state-
ment and to clearness of exposition. Sentences and para-

iii

735021

iv PR El- ACE.

graphs have been made short; chapters are short, with
definite summaries appended.

Function, rather than structure, has been made promi-
nent. Only so much of anatomy as is really needed to
understand the working of the organs has been introduced.
The experimental work and directions for dissection, as
well as some of the more difficult points, have been put in
smaller type, so they may more readily be omitted where
it is not possible to complete all the work in the given
time.

Although hygiene has been given a prominent place,
yet it may be claimed that when the pupil is well grounded
in the functions of the different organs, from observational
and experimental work, many of the rules of hygiene will
readily occur to him as natural inferences. When other
rules for the preservation of health, which might not occur
to him, are suggested, he will see their significance because
he understands the underlying principle ; and he not only
can, but will, obey the rule better because he sees reason
in it, and does not follow it blindly as an arbitrary law
thrust upon him. Questions are given, at the end of each
chapter, to test the pupil's knowledge of principles by
application to new cases.

Some of the more desirable reforms in nomenclature have
been adopted ; among these are the use of the terms ante-
rior, meaning toward the head ; posterior, in the opposite
direction ; dorsal, toward the back ; ventral, toward the
region of the belly. These terms, used instead of " up "

PREFACE. V

and "down," "front" and "back," will do away with
much confusion, especially since we are obliged to use the
structure of horizontal-bodied animals to illustrate human
anatomy. Many Latin terms, such as "vena cava" should
be replaced by English, as caval vein. Postcaval vein and
precaval vein are easier and better than " vena cava infe-
rior " and "vena cava superior." In many cases the
English plural may well replace the Greek or Latin form,
as ganglion, plural ganglions. Blood tube is better than
"bloodvessel." The best authorities say spinal bulb in-
stead of the long "medulla oblongata." Food tube is
simpler than " alimentary canal," especially as the tube is
not canal-like. The rib-bearing vertebras are thoracic, and
are no more "dorsal" than the other parts of the spinal
column.

Effort has been made to lay stress on the more impor-
tant topics, and the skeleton is relegated to a subsidiary
place, as a knowledge of it has so little to do with practical
hygiene. The heart and the stomach receive full treat-
ment, while matters of such slight importance as the hair
and nails are briefly dismissed.

The order of topics is the result of long experience.
For many years the author has sought to find the most
natural sequence of subjects, so that, as the work pro-
gressed, the pupil would find the way best prepared for
him. Without claiming that this is the best sequence, the
writer is sure that it is the " path of least resistance."

The subject of Alcohol has been treated in full com-

vi PREFACE.

pliance with the law. Copious quotations have been taken
from the best authorities on this subject. The same
high-grade illustrations have been used that brought such
favorable comment on the earlier work.

This briefer edition has, too, the full benefit of the
criticism of the eminent authorities whose names are listed
in the larger work.

TO THE TEACHER.

For any practical work in physiology it is very desirable
to have a room furnished with tables and supplied with
water.

Each pupil should make full notes and drawings of the
work done and the organs studied and dissected. Only by
so doing will he firmly fix and retain what he gathers from
day to day.

In the larger work by the author are many experiments
and dissections given in full which are here omitted in
order to present a briefer course. In the larger work there
is also given a list of books which are most helpful in
teaching physiology.

CONTENTS.

CHAPTER I.

PAGE

INTRODUCTION • l

Health. Care of the Body. Hygiene. Physiology. Organ. Func-
tion. Anatomy. Tissues. Cells. Physiological Division of Labor.

CHAPTER II.

MOTION 7

Motion Necessary to Life. Experiments with our Muscles. Action
of Muscle. Structure of Muscle. Connective Tissue. Laws of
Muscle Action. Flexors and Extensors. Symmetry. Muscles and
Bones. Levers. Locomotion. Uses of Bones.

CHAPTER III.

THE GENERAL FUNCTIONS OF THE NERVOUS SYSTEM — SENSATION

AND. MOTION 24

Muscles controlled by Nerves. Voluntary and Involuntary Motion.
The Spinal Cord. The Spinal Nerves. Structure of Nerves.
Function of Nerves. Structure of the Spinal Cord. Ganglions.
Reflex Action of the Spinal Cord. Reflex Action of the Spinal
Cord in the Frog. Function of the Nerve Roots. Importance of
Reflex Action. Inhibition. Nature of a Nervous Impulse. Har-
mony in Muscle Action. Nerves depend on Blood Supply.

CHAPTER IV.

CIRCULATION OF THE BLOOD 39

The Blood and its Work. The Rate of the Heart Beat. Position
and Size of the Heart. The Valves of the Heart. The Blood
Tubes Connected with the Heart. The Action of the Heart. Work
and Rest of the Heart. Action of the Large Arteries. Variation
in Blood Supply. Plain Muscle Fibers in the Walls of the Arteries.

vii

viii CONTENTS.

I'AGK

Circulation of Blood in the \Yel> of the Frog's Foot. Blood Mow in
the Capillaries. The Veins. The Valves in the Veins. F.t'fect of
Pressure on the Veins. Rate of Blood Flow. Nourishment of the
Walls of the Heart. Effect of Gravity on Circulation.

CHAPTER V.

CONTROL OF CIRCULATION. — THE BLOOD AND THE LYMPH .... 64
The Effect of Emotions on Circulation. Rhythmic Action of the
Heart. Nerve Control of the Heart. Sympathetic Nervous System.
The Vagus Nerve. Inhibition. Vaso-motor Nerves. Blushing.
Regulation of the Size of the Arteries. Effect of Exercise on the
Size of the Arteries. Effects of Alcohol on Circulation. The
Bloocl. The Corpuscles of the Blood. The Plasma. Hemoglobin.
Coagulation of Blood. Fibrin. Amount of Blood. Distribution of
Blood. The Lymph Spaces. Lymph Tubes. Lymphatic Glands.
Flow of Lymph. Massage. Transfusion of Blood.

CHAPTER VI.

RESPIRATION 84

The Close Relation between Circulation and Respiration. Organs
of Respiration. Structure of the Lungs. The Windpipe. Cilia.
The Pleura. The Diaphragm. Action of the Diaphragm. Move-
ments of Respiration. Forces of Inspiration. Resistances to Inspi-
ration. Elastic Reactions of Expiration. Forced Respiration. Rate
of Respiration. Modifications of Respiration. Lung Capacity.
Hygiene of Respiration. Breathing through the Mouth. Control
of Respiration. Chemistry of Respiration. Composition of the
Air. Exchanges between the Air and the Blood in the Lungs.
Oxyhemoglobin. The Gases in the Blood. Production of Heat
and Motion in the Body. Oxidation of Live Tissues. Body and
Locomotive Compared. Storage of Oxygen in the Tissues. Re-
breathing Air.

CHAPTER VII.

VENTILATION AND HEATING. — DIST AND BACTERIA 114

Need of Ventilation. Grates. Principles of Ventilation. Stoves.
Furnaces. Foul-air Shafts and Fans. Steam and Hot-water
Heating. Direct and Indirect Heating. Dead Dust. Sources of
Dust. Live Dust. Consumption. Disease Germs. Bacteria. How
to avoid Dust. Sweeping. Contagious Diseases. Putrefaction.
Preservation of Foods. Need of Removal of Waste.

CONTENTS. ix

CHAPTER VIII.

PAGE

EXCRETION 130

The Skin throws off Perspiration. The Structure of the Skin. The
Epidermis. Color of the Skin. The Dermis. Sweat Glands. Es-
sentials of a Gland. Blood Supply of Glands. Oil Glands.
Composition of Sweat. Amount of Perspiration. Functions of the
Skin. Regulation of Bodily Temperature by the Skin. Distribu-
tion of Heat in the Body. Regulation of Bodily Temperature by
Food and Clothing. The Kidneys. Work of the Kidneys. Rela-
tion of the Skin and Kidneys.

CHAPTER IX.

Foons AND COOKING 144

Necessity of Food. Food Defined. Foodstuffs. Proteids. Impor-
tance of Proteids. Meat. Fish. Eggs. Milk. Cheese. Vege-
table Proteids. Carbohydrates. Grains. Wheat. Corn. Rice.
Oats. Potatoes. Vegetables. Fruits. Water. Impurities in
Water. Typhoid Fever. Ice-water. Boiling Water. Salts.
Necessity of a Mixed Diet. Effects of Cold on Appetite for Fats.
Vegetarians. Tea. Coffee. Beef Tea. Cooking. Soups.

CHAPTER X.
THE DIGESTIVE SYSTEM 159

The Object of Food. The Digestive Tube. Organs of Digestion.
The Mouth. The Teeth — Kinds, Structure, Arrangement. Care
of the Teeth. Salivary Glands. Action of Salivary Glands. Saliva
and its Uses. Mucus and Mucous Glands. The Pharynx. Swal-
lowing. The Gullet. The Structure of the Stomach. Gastric
Glands. Blood Supply of the Stomach. Stomach Digestion.
Churning Action of the Stomach. Time of Stomach Digestion.
Chyme. Absorption from the Stomach. The Intestine. The
Liver. The Pancreas. Bile. Pancreatic Juice. The Portal Circu-
lation. Functions of the Bile. Work of the Pancreatic Juice.
Intestinal Juice.

CHAPTER XL

ABSORPTION — DIGESTION COMPLETED 181

Absorption. Villi. Routes of Different Foods after Absorption. Dif-
fusion and Osmosis. Absorption a Vital Process. The Lacteals
and the Lymphatics. Outline of Digestion. The Colon. Work
of the Large Intestine. Constipation. Laxative and Constipating

X CONTENTS.

PAGE

Foods. Hygiene of Digestion. Deliberation in Eating. Thorough
Mastication. Fleets of Repose on Digestion. Conversation at
Meals. Value of Soups and Desserts. Hot Drink at Meals. Time
of Meals. Eating between Meals. Amount of Food Needed.
Errors in Diet.

CHAPTER XII.

NUTRITION 195

Ledger Account of the Body and its Organs. Blood a Mixture of
Good and Bad. Action of Diseased Kidneys. Blood Stream like
Water Pipes and Sewer Combined. A Living Eddy. Importance
of Renewal of Blood and Lymph. Fat as a Tissue. Hibernation.
Respiration and Oxidation of Candle. Glycogen. Muscular Exer-
tion and Excretion of Urea. Metabolism. Indestructibility of
Matter. Indestructibility of Force. Utilization of Energy in the
Body and in Machines. Correlation and Conservation of Energy.

CHAPTER XIII.

ALCOHOL 208

Alcohol and Crime. Alcohol and Energy. Alcohol and Heat. Alco-
hol and Muscular Energy. Arctic Explorers. Alcohol and Train-
ing. Stimulants. Narcotics. Temperance Drinks. Testimony of
Physiologists. Testimony of Army Officers. Testimony of a Natu-
ralist. Physiological Effects of Alcohol.

CHAPTER XIV.

EXERCISE AND BATHING 226

How Exercise is Beneficial. Exercise for General Health. Nature's
Rewards and Punishments. Exercise prolongs Life. Choice of
Exercise. Games of School Children. Tennis. Baseball and
Football. Boxing. Bicycling. Exercise for Middle-aged Men.
Taking Cold. Diarrhea. Bathing. Cold Baths. Bath Mits. Time
for Bathing. Warm Baths vs. Cold Baths. Exercise Arterial Mus-
cles. Habit of Cold Bathing acquired gradually.

CHAPTER XV.

THE BRAIN 235

The Coverings of the Brain. Parts of the Brain. The Cerebrum.
The Cerebellum. ' The Spinal Bulb. Brain of a Cat or Rabbit.
Cranial Nerves and their Functions. Hemispheres of the Cerebrum.
Brain Convolutions and Intelligence. Gray and White Matter of
the Brain. Neuroglia. Functions of the Cerebrum. Pigeon
with Cerebrum Removed. Functions of Cerebral Cortex. Center

CONTENTS. xi

PAGE

of Sensations itself Insensible. Crossed Control of the Body. Lo-
cation of Brain Functions. Left Hemisphere better Developed.
Location of Sensation Centers. Brain Work and Brain Rest.
Sleeplessness. Fatigue. Control of Mind. Habit of Resting the
Brain. Nervous Tissues least Affected by Starvation. Blood Supply
of the Brain. Fainting. Apoplexy. Meningitis. The Water
Cushion of the Brain. Relative Activity of Gray and White Matter.

CHAPTER XVI.

EFFECTS OF ALCOHOL ON THE NERVOUS SYSTEM 250

The Chief Effect of Alcohol is on the Nervous System. Inebriety re-"
garded as a Disease. Moral Deterioration produced by Alcohol.
Narcotics. Opium. Cocaine. Chloral Hydrate. Chloroform.
Tobacco. Cigarette Smoking.

CHAPTER XVII.

GENERAL CONSIDERATIONS CONCERNING THE NERVOUS SYSTEM . . . 261
Nerve Stimuli. Kinds of Nerve Stimuli. Essential Similarity of All
Nerve Fibers. Relation of Stimulus and Sensation. Reaction
Time. Reflex Action. Connection of Brain 'Centers. Nature of
Sensation. Subjective Sensations. The Relative Nature of Sensa-
tion. Induction Currents used in Physiological Experiments.
Dreams. Lingering Effect of Sensations. Habits are Acquired
Reflex Actions. Usefulness of Resting. Nervous System vs. Tele-
graph System. Efferent Currents. Afferent Currents.

CHAPTER XVIII.

THE GENERAL SENSES 271

The Body a Collection of Organs. Influence from the External World.
Classification of the Senses. General Sensations and Special Senses.
The Muscular Sense. Importance of Muscular Sense. Dependence
of Sight on Muscular Sense and Touch. Pain. Pain a General
Sense. Extent of Pain. Use of Pain. Hunger and Thirst.

CHAPTER XIX.

THE SPECIAL SENSES — TOUCH AND TEMPERATURE SENSE .... 278
What we learn by Touching Objects. Cutaneous Sensations. Nerve
Endings in the Skin. Touch Corpuscles. Touch the most General
of the Senses. Pressure Sense. Local Sign. Test by Compass
Points. Reference of Sensation to the Region of the Nerve End-
ings. Temperature Sense.

xil CONTEWS.

CHAPTKR XX.

PAGE

THE SENSE OF SIGHT 285

Protection of the Eye. The Lacrymal Secretion. External Parts of
the Eye. The Conjunctiva. Muscles of the Eyeball. Movements
of the Eye. Coats of the Eye. The Sclerotic Coat. The Choroid
Coat. The Retina. The Cornea. The Iris. The Pupil. Regula-
tion of the Amount of Light admitted into the Eye. The Refract-
ing Media of the Eye. The Aqueous Humor. The Vitreous Humor.
The Crystalline Lens. The Lens Capsule. The Hyaloid Mem-
brane. The Ciliary Muscle. Inversion of the Image. Adjustment
for Distance. Action of the Ciliary Muscle. Defects of Eyesight.
Structure of the Retina. Importance of the Retina. The Blind
Spot. The Optic Nerve not Sensitive to Light. Sympathy between
the Eyes. Pain in the Eyes. Color Sensations. Color Blindness.
Stereoscopic Vision. After-images. Care of the Eyes.

CHAPTER XXI.

TASTE, SMELL, AND HEARING ^01

Uses of the Sense of Taste. The Papilla;. Nerve Supply of the
Tongue. Solution Necessary for Tasting. Flavors. Effect of
Temperature on Taste. The Sense of Smell. Why we Sniff. The
Sense of Bearing. The External Ear. The Tympanum. The
Middle Ear. The Eustachian Tube. The Internal Ear. The Pro-
duction of Sound. The Equilibrium Sense. The Care of the Far.
The Use of the Ears.

CHAPTER XXII.
THE VOICE 309

The Ear and the Voice. What we can learn from our own Throats.
The Vocal Cords. Reinforcement of Sound. Pitch and Voice.
Voice and Speech. Vowels and Consonants. Difference between
Voices. Hoarseness. Whispering. Culture of the Voice.

CHAPTER XXIII.

ACCIDENTS. — WHAT TO DO TILL THE DOCTOR COMES 314

How to stop Flow of Blood from Arteries. Bleeding from the Upper
Arm. Bleeding from the Neck. Wounds in the Thigh. Bleeding
from Veins. Hemorrhage of the Lungs or Stomach. Bleeding from
the Nose. Treatment of Burns. Danger from Burning Clothing.

CONTENTS. xiii

Treatment of Fainting. Broken Bones. Sunstroke. Treatment of
the Drowned. Swimming. Suffoeation in Wells. Bites of Cats,
Dogs, etc. Wounds from Thorns, Rusty Nails, etc. Snake Bites.
Poisons and their Antidotes. Poison Ivy. The Sick-room. Qual-
ities of the Nurse. Care of the Sick.

CHAPTER XXIV.

THE SKELETON 330

Axial Skeleton. Appendicular Skeleton. Uses of the Bones. Study
of a Vertebra. Table of the Bones. The Spinal Column. Articu-
lations of a Vertebra. The Cervical Vertebras. Atlas and Axis.
The Thoracic Vertebras. The Lumbar Vertebras. The Sacrum and
the Coccyx. Flexibility of the Spinal Column. Curves of the Spinal
Column. Cavities of the Skeleton. Pronation and Supination.
Weight of the Bones. Microscopic Structure of Bone. Classifica-
tion of Joints. Sprains and Dislocations.

CHAPTER XXV.

THE MUSCLES 341

The Number of Muscles. The Arrangement of Muscles. Forms of
Muscles. Names of Muscles. Peculiar Muscles. Heart Muscle.
Three kinds of Muscular Fiber Compared. Each Fiber a Cell.
Muscles of Expression. Muscles and Fat. Convulsions. Rigor
Mortis. Some Prominent Muscles. Sculpture and Anatomy.

APPENDIX . . 347

Antidotes. Disinfectants. Vital Statistics.

GLOSSARY 360

INDEX .... 371

PHYSIOLOGY.

CMA.P,TER I. ,'••.::

Health. — Is it not a splendid thing to be well and
strong ? To be full of bounding health ? To " feel one's
life in every limb " ?

Who does not desire to prolong, so far as possible, this
condition characteristic of youth ?

Natural and Artificial Modes of Life. — An animal
living in a state of nature may keep well and live its
natural period of life without knowing anything about the
laws of health. But as students or indoor workers, many
of us lead a sedentary life ; we are not natural, but often
highly artificial, in our mode of living. We move about
but little, whereas the animal abounds in motion. We
concentrate energy upon mental effort, thus diverting a
large share of our sum total of energy away from the pro-
cess of nutrition. We often shut ourselves in rooms nearly
air-tight. We eat poorly chosen and ill-prepared food.
We devour it hastily, often when we are not in fit con-
dition to take food. In short, we frequently disobey the
laws of Nature. Now, Nature punishes every violation of
her laws. She never forgives, never forgets.

1

Value of Knowledge. — The out-of-door worker may
not suffer so much from ignorance in these matters.
From the character of his occupation, he is, »to a certain
•extent, obliged to obey Nature. He gets enough fresh
air. His bodily exertion generally brings a hearty appe-
tite, vigorous digestion, active circulation of the blood.
Still, he would greatly profit by knowing something of the
nature of his food, its wholesomeness or unwholesomeness.
The fact that he has fair health is no proof that he always
does the best thing. His natural mode of life may keep
him in tolerably good condition in spite of his violation of
certain laws V b#t ^(f J-coldd :uXidpubtedly learn how to
economize in the purchase, preparation, and proper com-
bination of foods.

Importance of the Care of the Body. — Any machine
of man's invention must be kept in good running order if
we would have it do good work, or last long. We must
keep a machine clean, well oiled, and not overtax it. Are
not our bodies worth equal care ? If some part of a ma-
chine is broken, we may replace it at moderate expense ;
but none of the vital organs can be replaced. We may
get a new mainspring for a watch, but we cannot obtain a
new stomach or lungs.

Its Admirable Mechanism. — Aside from the above
considerations the human body is worthy of study for its
own sake. Viewed simply as a mechanism, it is wonder-
ful. Each organ is so well adapted to its work, and all
the organs work so harmoniously through their connection
and control by the nervous system, that we never cease to
admire it. We admire a doll, or other toy, so ingeniously
constructed that it can move its eyes or walk a short time
after being wound up. But this live mechanism, which is

INTRODUCTION. 3

self-winding, self-regulating, self-repairing, self-directing,
amazes us.

Hygiene. — We take up the study of the human body
mainly that we may learn how to preserve health ; the
science of health is hygiene.

Physiology. — In order to keep the various organs in
good order we must know what their natural work is, and
how they do it ; the science of the action of the body and
its parts is physiology.

Organ. — Any part, or member, of the body, which has
a special work to do, is called an organ, as the hand, the
eye, or the stomach.

Function. -- The work, or action, of each organ is
its function.

Anatomy. — In order to understand the working of
each organ it is usually necessary to know something
of its construction ; the science of structure is anatomy.
We do not need to go far into anatomy to obtain a fail-
knowledge of the manner in which our organs do their
work. The surgeon, of course, must be able to locate
accurately the various blood tubes, nerves, muscles, etc.
We need to know only the general structure of the body
and, more in detail, some of the more important organs,
such as the heart, the lungs, the larynx, the eye, etc.
It is fortunate for us that these organs in the sheep, pig,
and cow are so nearly like our own that they serve
admirably to enable us to understand ourselves.

Tissues. — Every organ is composed of several different
kinds of material. For instance, in a slice across a ham
we see the skin on the outside, then fat, lean, and bone.

4 I'HYSIOLOGY.

These "primary building materials" of the body we call
tissues. A tissue may be defined as an aggregation of
similar cells devoted to a common work.

Cells. — The whole body is made up of small parts
called cells, comparable to the bricks in a house. These
cells are of various shapes in the different tissues.

In the more active tissues the cells are alive, and each
cell may be compared to the ameba, a little mass of living
jelly-like substance called protoplasm. The ameba is a
protozoan often found in the slime at bottom of stagnant
water. Within this is a small, rounded part called the
nucleus. Most of the cells of the body differ from
the ameba in having a distinct
outer covering or cell wall. A grape
serves very well to show what a cell
is like. The whole body is built up
Nucleus. °f cells, few of them large enough

Fig. i. Epithelial Ceils from to be seen by the naked eye.
Although the cells are closely

packed together, each cell leads, in one sense, an inde-
pendent life. But all work together to maintain the life
of the body. The cell is like the individual in a com-
munity. Each lives primarily for itself, yet all work
together for the good of the whole.

Epithelial Cells from the Inside of the Cheek. — With the blade of
a very dull knife, or the handle of a scalpel, gently scrape the inside of
the cheek. Place a little of the white scraping on a slide in a drop
of water, cover with a cover slip, and examine under a quarter-inch
objective. Many cells will be seen, some of them showing nuclei.
Compare these cells with the accompanying figure.

The Physiological Division of Labor. — We are aware
of the advantages of division of labor in a community. If

INTRODUCTION. 5

each person learns to do one thing well, all together work
economically for the common good, time is saved, and
better goods are produced. In the body there is a division
of labor similar to that of a community. Each organ has
its own work to do, and all work together for the common
welfare. The cells of each tissue have certain properties
and peculiarities of form differing from the form and
properties of the cells of any other tissue. While the
general structure of all cells is essentially the same, and
while they all have certain properties in common, each has
some one kind of work that it can do well, and to which
work it devotes itself. The nerve cells receive impressions
from the outer world, carry nervous impulses, and control
the various activities of the body. The muscle cells have
as their work the production of motion. All the cells
must take food for themselves and grow. Each has a
birth, life, and death, as each individual in a community
of men ; and as the community endures, while the indi-
vidual members are continually changing, so, in the body,
while the form remains about the same from year to year,
the cells are continually changing, some dying, and others
taking their places. .

In an animal of a single cell, like the ameba, the one
cell must do everything for itself. The higher animals all
begin their individual life as an egg, which is, in fact, a
single minute cell. This grows and divides, forming two
cells. By repeated division there accumulates a mass
of cells. These take on the arrangement peculiar to the
kind of animal from which the egg came. But as the cells
increase in number one group of cells takes up one part
of the work of .the body, other cells another part of the
work, and so on.

In studying history (sociology) we have to deal with the

6 J'HYSIOLOGY.

individual, the community, the state, and the nation. The
cell is an individual, the community is a tissue, the state is
an organ, and the nation is one body.

Let us proceed to study the nature of the individual cell,
and the combined actions of these individuals in that com-
munity called the human body.

Summary. — i. Health is essential to comfort and efficiency in
work.

2. Our artificial mode of life is at variance with nature's laws.

3. Only by obeying the laws of nature can we preserve health.

4. We should learn these laws of nature from the advice and ex-
perience of others, and not by the expensive process of suffering from
disobedience.

5. Anatomy is the science of structure. Human anatomy is the
science of the structure of the human body.

6. Physiology is the science of function.

7. Hygiene is the art of preserving health.

8. Cells are the units of structure in the body.

9. A tissue is a group of similar cells having a single function.

10. An organ is a part having a special work or function. The
organs work together for the common good of the whole organism.
This working together results in —

1 1 . The physiological division of labor, in which each organ works
for all the others, and is dependent on all the other organs.

Questions. — i. What are some of the ways in which we most fre-
quently violate the laws of health ?

2. Name the more important organs of the body and their functions.

3. Name the different tissues of one of these organs.

CHAPTER II.
MOTION.

Motion and Life. — Motion is the most manifest sign of
life. While we are sitting still, as we say, there are fre-
quent slight motions of the head, body, and limbs. Even
during sleep the movements of breathing may be seen ;
the hand laid upon the chest may feel .the beating of the
heart, and the finger detect the pulse in a number of
places.

We must move to get our food, or at least to eat and
digest it. Motion is necessary for breathing, for circu-
lating the blood, for getting rid of wastes. We often move
to avoid injury.

Motion is necessary for seeing : we must turn the face
toward the object; we move the eyeballs; within the eye
are motions to regulate the amount of light admitted, and
to adapt the eye for seeing at different distances.

In feeling, we put forth the hand to touch the object.
In tasting, we touch the tongue to the object. In smelling,
we sniff ; and sniffing is a respiratory motion. In hearing
and in speech there is also motion.

How are all these motions produced ?

Experiments with the Muscles in our own Bodies. — i. Clasp
the front of the right upper arm ; draw up the forearm strongly
and as far as possible. Note what changes are felt in the biceps
muscle.

2. Repeat the experiment, and with the thumb and finger feel the
cord, or tendon, at the lower end of the muscle, just within the angle of
the elbow.

7

8 PHYSIOLOGY.

3. Place a weight in the hand, and repeat the act, noting the con-
dition of the muscle during the experiment ; also note the condition
of the tendon.

4. Span the muscle, placing the tips of the fingers in the angle of
the elbow, and the tip of the thumb as far as you can up the arm ; again
bend the arm. What change in the muscle does this show ? Any
muscle that bends a limb, as does the biceps, is called a flexor muscle.

5. Clasp the back of the right upper arm ; forcibly straighten the
arm. The muscle lying along the back of the arm is the triceps muscle.
It is called an extensor muscle because it extends, or straightens, the
arm.

6. Clasp the upper side of the right forearm near the elbow ;
clench the right hand quickly and forcibly ; repeat rapidly.

7. Notice the thick mass of muscle at the base of the thumb ;
pinch the forefinger and thumb strongly together. What changes can
be seen and felt ?

8. Place the hand on the outside of the shoulder ; raise the arm to
a horizontal position; repeat with a weight in the hand.

Fig. 2. The Shortening and Thickening of the Biceps Muscle in raising the
Forearm.

9. Stand erect with the heels close to each other, but not quite
touching; let the arms hang freely by the sides; rise on tiptoes,
without moving otherwise ; repeat ten times.

10. Place the tips of the fingers on the angles of the lower jaw;
shut the teeth firmly on a piece of rubber, and note the bulging of the
masseter muscles.

MOTION. , 9

11. Press the fingers on the temples ; again shut the jaw firmly, and
feel the action of the temporal muscles.

12. Make a narrow band of paper that will snugly fit the forearm
when the hand is open ; now clench the fist strongly.

13. With a tape measure take the circumference of the upper arm
when the arm hangs free ; again when the forearm is strongly flexed.

14. In the same way measure the forearm when the hand is open,
and when the hand is clenched.

By these experiments we learn that when a muscle works it becomes
shorter, thicker, and harder.

Nerves and Muscles of a Rabbit's Leg. — In the hind leg of a
rabbit the sciatic nerve may be found by separating two large
muscles on the sides of the thigh, beginning behind the knee joint.
The shape and connections of the muscles may be learned, and also
the distribution of the nerve.

The Action of Muscle. — The action of muscle is always
a "pull." The muscle shortens, at the same time thick-
ening and hardening. These changes in muscle are
roughly shown in the preceding experiments of feeling
the arm during its action. But the isolated calf muscle of
the frog may be made to prove the characteristic changes
with great clearness.

Action of Frog's Muscle. — A frog may be killed painlessly by put-
ting a teaspoonful of ether into a fruit jar of water, immersing the frog
and capping the jar. When the frog becomes motionless, its head
should be cut off and a wire run down the spinal column to destroy the
spinal cord. After cutting the skin around the base of one thigh the
skin may easily be stripped from the whole hind limb. If the muscles
on the back of the thigh be gently separated there will be found a white
thread running lengthwise, the sciatic nerve. It should be severed
near the hip and carefully turned down upon the calf muscle. It should
not be pinched or dragged. The muscles of the thigh should now all
be cut away, being careful not to sever the nerve near the knee. The
hip joint should be unjointed. With the handle of the scalpel the calf
muscle should be separated from the shin bone, and just below the
knee the shin bone and all the muscles except the calf muscle severed

10

PHYSIOLOGY.

It now the heel cord be cut off below the heel there will remain such a
preparation as is represented in the accompanying figure, consisting of
the thigh bone with the calf muscle hanging from it, and the sciatic

— Femur

Origin ~

Belly of Muscle -

Insertion

Weight

SHORTENED

ELONGATED

Fig. 3. Action of the Calf Muscle of the Frog, showing the Relations of the
Sciatic Nerve.

Origin

Bundle of Muscle Fibers

nerve still connected with the calf muscle. This may be supported by
holding the end of the thigh bone in a clamp on a retort stand. A

light weight should be attached to
the heel cord. The muscle and
nerve should be moistened with
water containing a little salt. On
pinching the free end of the nerve,
or cutting off the least bit with
scissors, the muscle will be made
to act. The shortening and thick-
ening will be plainly seen, and
by taking it between the thumb
and finger the hardening may be
felt.

Muscle Sheath

CROSS SECTION

Tendon

•Insertion
LONGITUDINAL SECTION

Fig. 4. The Structure of Muscle.

Structure of Muscle. —

Chipped beef shows well
the structure of muscle. The

MOTION.

II

white network is the connective tissue. In the meshes
is the red muscular tissue. The partitions which run all
through the muscle are continuous with the muscle sheath,
and both are continuous with the tendons at the ends of
the muscle. In fresh muscle the sheath and the parti-
tions are nearly transparent, and are not easily seen.
When the meat is cooked or salted the connective tissue
becomes white and opaque.

Microscopic Structure of Muscle. — In frog's or rabbit's muscle
observe the thin, transparent membrane covering the muscle, the muscle
sheath. With forceps tear away part of the
muscle sheath. Tear the muscle to pieces,
and note its fibrous structure. A shred of
muscle may be mounted in a drop of nor-
mal saline solution on a slide, and exam-
ined with low power of the microscope. If
examined with a higher power the cross-
markings, or striations, will be seen. Such
muscle is called striated or striped muscle.
All of the muscles used in ordinary motions
are of this kind.

Fig. 5. Two Muscular Fibers
showing the Terminations of
the Nerves.

Effects of Cooking Muscle. — In
well-cooked corned beef the connec-
tive tissue is thoroughly softened,

and the muscle fibers are easily separated. Thorough
cooking, especially slow boiling, will soften the connective
tissue, and may render palatable meat that, cooked other-
wise, would be exceedingly tough on account of the large
amount of connective tissue.

Imitation of Structure of Muscle. — A good way to
represent the structure of muscle is to take a number of
pieces of red cord to represent the muscle fibers. Wrap
each in white tissue paper ; this represents the individual

12

fiber sheath. Lay a number of these side by side ; wrap
all in a common sheath ; let the tissue paper project be-
yond the threads, and here compress it into a compact
cylinder ; this last corresponds to the tendon.

Connective Tissue the Skeleton of Muscle. — If all
the muscular tissue were removed from a muscle, the
sheaths and partitions would remain, just as they do in a
squeezed lemon or orange. The connective tissue forms
a framework for all the soft tissues of the body, and if
their working cells were removed, the connective tissue
would remain, and show more or less completely the form
of the part. Connective tissue, therefore, may be called
the skeleton of the soft tissues. Muscle consists, then,
essentially of a collection of soft, transparent tubes, filled
with the semi-fluid muscle substance. By scraping the
surface of a steak with a dull knife the muscle substance
may be obtained, leaving the connective tissue. This is a
good way to get the nutritious part of beef for an invalid.

Importance of Muscles. — The different materials of
which the body is built up are called tissues. Thus we
find muscular tissue, bony tissue, nervous tissue, etc. The
muscles make up nearly half of the weight of the body.
This fact of itself should lead us to consider the muscles
of high importance. Add to this the facts above noted,
that the muscles are so largely concerned in the nutrition
of the body, the chief agents for its protection, essential
for the reception of ideas, and absolutely indispensable for
the expression of ideas, and we can see the reason for
beginning the study of physiology with the examination
of the muscles and their action.

Laws of Muscle Action. — The chief characteristic of
muscle is its ability to shorten ; incidentally, it at the

MOTION'. 1 3

same time thickens and hardens. But it does its work by
shortening, pulling on the bones by means of the strong,
inelastic tendons, thus producing motion. The action of
the muscle as a whole is the result of the characteristics
of the cells of which it is composed. The individual cells
and fibers shorten, and their combined action is seen in
the muscular movement.

Extent of Muscle Shortening. — A muscle may be
made to shorten one third of its length, but probably
never shortens that much in the living body.

Duration of Muscle Shortening. — A muscle cannot be
kept shortened for any great length of time. If one holds
his arm out horizontally as long as possible he soon feels '
fatigue, later pain, and he may feel soreness in the muscle
for several days. The law of muscle action is to alternate
periods of rest with periods of action. In many exercises,
as in walking, the limbs act alternately, one resting or
recovering position while the other works.

Alternate Action of Flexors and Extensors. — If we

consider the biceps and triceps of the arm, we see that
they are compelled to act alternately if they would do
effective work. They might both shorten at the same
time, and are made to do so in such an attempt as that
of holding the arm rigidly bent at a right angle ; as, for
instance, in wrestling " square hold," in which case one
wishes to prevent his opponent from either pushing or
pulling him. But while the two muscles act, no motion is
produced. When the flexor shortens, the extensor length-
ens, and vice versa.

Normal Condition of Muscle. — The muscles are always
slightly stretched, as shown by the fact that when a cut
is made into a muscle the wound gapes open ; the tension

14 PHYSIOLOGY.

of the muscle is further shown by the fact that when a
bone is broken, as in the upper arm or thigh, the ends
of the bones slip by each other, and the limb has to be
strongly stretched to bring the ends back together. Mus-
cles act better when slightly stretched, and probably need
a slight resistant action of the opponent muscle.

Symmetrical Development of the Muscles; — The mus-
cles of the two sides of the body are the same in number
and arrangement. At birth they are probably about equal
in size, weight, and strength. Most persons early become
right-handed, and the greater use of the right hand and
shoulder makes the muscles of this side larger and heavier.
The muscles pulling on the bones slightly modify them
in shape. The whole body may become noticeably un-
symmetrical. Most persons step harder on one foot than
the other, as shown by the sound of the footstep, and as
shown by the constant wearing of one shoe sole or heel
faster than the other. In many persons one shoulder is
habitually carried higher than the other. Symmetrical
development should be carefully sought, and any tendency
to a one-sided development should, so far as possible, be
avoided. We should use the left hand more. There are
many advantages in being able to use either hand. In
carving, in shaving, in bandaging, in administering medicine,
it may be necessary to use the left hand skillfully. The
pianist and the harpist use the two hands about equally,
while the violinist puts much more skill into his left hand.
Trainers of athletes often begin by developing the left
side of the body till it equals the right in size and strength.

Muscles the Source of Strength. — Our strength de-
pends on our muscles. It is a fine thing to have strong,
well-developed muscles, not only because they give beauty

MOTION, 1 5

of form, but because extra strength and endurance may
be needed in case of accident, to save one's own life or that
of others. In a case of fire the ability to climb, to go up
or down a rope "hand over hand," may be all important.
Any one's life may depend on his ability to run far and
swiftly, to swim, to jump, or to lift a heavy weight.

Skeletal Muscles. — When we look at the skinned car-
cass of an animal in the market, we observe that the mus-
cles almost completely cover the bones. Those which are
attached to the bones are called skeletal muscles. They act
upon them as levers, giving to motion strength, quickness,
and precision. Without bones our motions would be like
those of an earthworm or slug, slow and uncertain. The
muscles, acting through the bones, can lift a weight that
would crush the muscles if laid directly upon them, while
a bone, able to support a heavy weight without being
crushed, has no power in itself. The muscles have active
strength, the bones have passive strength.

Relation of the Muscles and the Bones. — Suspend the skeleton
from the ceiling in the most open space in the room. Let the pupils
study it ; not to learn the names of all the bones, but to get a general
idea of the forms and relations of the parts. It is well to have the
skeleton constantly at hand, to show the location of the various organs
as they are taken up. If possible, supply the class with separate bones
from another skeleton, and let the pupils place each separate bone
alongside the corresponding one in the complete skeleton.

Pass to the skeleton, and locate the biceps muscle. After examining
Fig. 2, show the points of its origin and insertion. Feel the biceps
of your arm. Note that its thickest part is opposite the most slender
part of the bone. But at the enlarged end of the bone the muscle has
narrowed to a slender tendon, which passes over the joint to be attached
to the next bone, thus giving more slenderness, flexibility, and freedom
of motion to the joint. The muscle which closes the mouth, as in
pursing up the lips, is not attached to any bone, but in shortening
reduces the aperture.

1 6 /'//}'S/OUhi}'.

Flexion of the Forearm. — Take the bones of the arm that are
articulated (if there is not an artificial hinge at the elbow, one can
readily be made of wire) ; put a strong rubber band in place of the
biceps muscle ; fasten this to the head of the humerus by cords, and
by the lower end to the radius, where the rough place, an inch or so
from the elbow joint, shows the insertion of the tendon. Have the
rubber stretched so that when not held it will flex the forearm. This
will serve to show the action of the biceps, though we must be careful
to bear in mind that the muscle does not pull the arm up because it has
been stretched, as is the case with the rubber. In the case of the
muscle, we know that the live muscle has the power of shortening when
stimulated, and in this respect is totally unlike the rubber. The live
cells, or units, act in concert.

Levers. — The essentials of a lever are the point about
which the lever turns, called the fulcrum, the place where
the power is applied, called the power, and the part to be
moved, called the weight. In the body, the fulcrum is
some joint, the power is the place where the muscle is
attached, and the weight is the part to be moved.

Kinds of Levers. — In flexing the forearm, the weight
is the hand or the hand and what is in it ; the fulcrum is
the elbow joint ; and the power is the point where the
tendon of the biceps is attached to the radius. This kind
of a lever is what the books call a lever of the third class.
The triceps, on the back of the arm, pulls on the projection
of the ulna (the inner bone of the forearm when the palm
is up), back of the elbow. The elbow is here, also, the
fulcrum, and the hand (or the object to be pushed by the
hand) is the weight. This kind of lever, where the fulcrum
is between the power and the weight, is called a lever of the
first class. In raising the weight of the body, by stand-
ing on tiptoe, we use a lever of the second class. Here
the ball of the foot is the fulcrum. The weight is the
weight of the whole body, resting on the ankle joint, while

MOTION. I/

the power is the calf muscle. We may find many exam-
ples of levers in the body if we look for them.

(1) Tapping on Floor. (2) Rising on Toe. (3) Lifting Weight.

Fig. 6. Three Kinds of Levers as shown by the Foot.

P — Power. W — Weight. F — Fulcrum.

Kinds of Levers shown by the Foot. — The different
classes of levers may be further illustrated by different
motions of the foot. In tapping the toes on the floor
while the heel is lifted, or in pressing down the ball of the
foot while running the treadle of a sewing machine, we
have an example of a first-class lever. In raising the
weight of the body on tiptoes, or as the foot is used in
taking each step, the foot is used as a lever of the second
class. When one lifts a weight with the toes, the foot is
used as a lever of the third class. These three classes of
levers are illustrated in the accompanying figures.

Advantages and Disadvantages of Levers in the Body. — The

action of the bones of the forearm as a lever may perhaps be better
understood by the following considerations : If the arm consisted
merely of the biceps, suspended from the shoulder, it is evident that
its only action would be a straight pull. Suppose the biceps, thus
hanging alone from the shoulder, had a hook at its lower end, it could,
when it shortened, lift a weight just as far as it shortened, and no

i8

PHYSIOLOGY.

farther. It could not swing the wi:ight outward, or push it upward.
But from the way in which the biceps is attached to the forearm, when
the muscle shortens an inch it may move the hand a foot. Of course
the hand moves much faster, and we have a great gain in speed by
reason of this lever arrangement. But we cannot lift so heavy a weight

at this faster rate, as we could at the
elbow. For instance, suppose one were
to carry a heavy basket with a bail
handle by slipping the arm through
the bail up to the elbow. Now. it is
evident that the biceps is supporting
the weight. If it is as heavy as can be
held here, we know that we could not
hold the same weight in the hand with
the elbow bent at a right angle.

Ball

Articular Extremity

Medullary Cavity

— Hard Bone

Study of One of the Long Bones.
— For this, take, preferably, a femur
or a humerus. Let us suppose we ha\ »•
a femur.

1. Observe its shape, — cylindrical,
somewhat curved, enlarged at the ends.

2. The ends have smooth places,
where they fitted other bones.

3. Along the sides, especially near
the ends, are ridges and projections,
where the muscles were attached.

4. There are small holes in the
bone, where blood tubes passed in and
out.

5. Saw a femur in two, lengthwise,
and make a drawing showing : —

(#) The central marrow cavity.

(£) The spongy extremities, noting especially the directions of the
bony plates and fibers.

6. Observe the width of the lower end of the femur, where it rests
on the tibia. Suppose these two bones were as narrow at their ends,
where they meet to form the knee joint, as they are at their centers,
what kind of a joint would they make ? Illustrate by piling up a num-

Spongy Bone

Articular Extremity

r. 7. Longitudinal Section of
Femur.

MOTION.

her of spools on end ; the column is more lightened than it is weak-
ened by the hollowing out of the sides of each spool. And the central
hollow of the spool does not greatly weaken it. A given weight of
material has more strength when in the form of a hollow cylinder. The
bones combine well two very desirable quali-
ties, lightness and strength. If in our col-
umn of spools we place a wide rubber band
around the junction of two spools, we have
something very similar to the capsular liga-
ment, which surrounds the joints.

Joints. — The ends of the bones, where
they fit together in the joints, are covered
with a layer of smooth, elastic, whitish or
transparent cartilage. The motion in the
joints is made still more easy by the synovia,
resembling white of egg. The ends of the
bones are held together by tough bands and
cords of ligament, a form of connective
tissue very much like tendon. Bones are
closely covered by a tough coat of connective
tissue called the periosteum.

All these structures can easily be found
by dissecting a sheep shank gotten from the
butcher, or in the hind leg of a rabbit.

Locomotion. — Locomotion is mov-
ing from place to place and should
be distinguished from mere motion.
By continuing such observations as
we made when we began to study
our motions, we can analyze and
understand many of the common
movements which we habitually
make.

Standing. — Although we are not ordinarily conscious of
the fact, when we are standing still we are using many
muscles. The accompanying figure illustrates how some

Action of the Muscles
in Standing.

20 PHYSIOLOGY.

of the muscles act in keeping the body upright. Our
weight, or, we would better say, the force of gravity, is
continually trying to pull us down to the ground. The
joints are all freely movable, and hence as soon as the
muscles cease to act properly, in balancing against each
other, we lose our equilibrium, and fall if we do not
quickly regain it.

Walking. — In walking, we lean forward, and if we take
no further action we fall. But we keep one foot on the
ground, pushing the body forward, while the other leg is
flexed and carried forward to save us from the fall. We
catch the body on this foot, and repeat the action. To
show how we are really repeatedly falling and catching
ourselves, recall how likely one is to fall if some obstacle
is placed in the way of the foot as it moves forward to
catch the weight of the body.

Running. — In running, the action is more vigorous.
The propulsion by the rear leg is now greater. It gives
such a push as to make the body clear the ground, whereas
in walking, the rear foot is not lifted till the front foot
touches the ground. But in running there is a time when
both feet are off the ground.

Locomotion by Reaction. — Take two broomsticks and place them
crosswise under the ends of a board. Run along the board. This
shows that the direct effort in running is to push one's support from
under him. When a horse plunges forward in the mud, he only thrusts
his feet farther into the mud. Our effort in progression is primarily to
push the earth out from under us, and it is by reaction that we go
forward. It is the same problem with the fish swimming forward by
striking backward and sideways against the water, and with the bird
beating downward and backward upon the air.

Bones combine Lightness and Strength. — The mus-
cles, then, make use of the bones as levers. We carry

MOTION. 21

these levers with us all the time. Hence the desirability
of having them as light as is consistent with the requisite
degree of strength. The body follows the same law of
mechanics that we use outside of the body. A hollow
pillar or hollow tube has a greater strength than the same
amount of material in the form of a solid cylinder. The
long bones of the limbs are hollow, and near their ends,
where we have found that they need to be enlarged, we
find a spongy structure, where lightness and strength are
secured by the interlacing fibers and plates of bony
material.

Uses of Bones. — The part that the bones play is of a
passive nature ; they support the tissues, protect some
parts, and serve as levers on which the muscles act. We
may not call the bones dead tissues, for they receive blood
and grow. But the active muscles use them as a man uses
a crowbar, as a mere tool. It will therefore be more
interesting to return to the muscles, and learn the causes
and conditions of their activity.

What makes Complex Muscular Action Harmoni-
ous.— Have you ever seen two persons, each using the
right hand, try to sew, one holding the cloth, the other
using the needle ? Would they get along well ? Suppose
one were to hold the needle, and the other were to try to
thread it, each using one hand ? Why is it that the right
hands of two persons cannot work so well together as the
right and left hands of one person ? What connection is
there between the two, that one knows just what the other
is doing and when it does it ? Why can two individuals
never, with any amount of practice, work so in unity as the
parts of the individual ?

22 PHYSIOLOGY.

Let us seek the answers to these questions in the follow-
ing lessons.

READING. — How to Get Strong and How to Stay So^
Blaikie ; Sound Bodies for Onr Boys and Girls, Blaikie ;
Physiology of Bodily Exercise, Lagrange.

Summary. — i . Motion is involved in nearly every activity of the
body.

2. The action of muscle is a shortening, accompanied by a thick-
ening and hardening.

3. Muscle consists of fibers with a connective tissue sheath for
each fiber, bundle of fibers, and for the muscle as a whole.

4. The skeletal muscle fibers are striated.

5. The muscles make about half the body's weight.

6. Muscles may shorten one third their length.

7. They cannot remain shortened long at a time.

8. The muscles should be developed symmetrically.

9. In the limbs the muscles are fusiform and have their greatest
diameter opposite the central, or narrower, portions of the bones, con-
cealing the fact that the bones are largest at the ends, as is so manifest
in the skeleton.

10. The bones serve as levers by which the muscles exert their
force.

1 1 . The bones of the limbs are hollow cylinders combining lightness
-and strength.

12. The joints have a smooth motion due to the cartilage and
synovia.

13. Locomotion is brought about by reaction.

Questions. — i . What effect is produced by carrying a heavy satchel
for a long distance without resting?

2. Which is more tiresome, standing still or walking? Why?

3. When the boy, who thinks he can strike a hard blow, says,
•• Feel my muscle,'1 does he usually call attention to the muscle used in
striking?

4. Find other examples of levers in the body.

5. Find examples of the three kinds of levers, not in the body,
which we use often.

MOTION. 23

6. Why is it easier to sit with one leg crossed over the other?

7. What is the effect on muscles of light clothing?

8. How may the arms be used to illustrate the three kinds of
levers ?

9. Analyze and explain jumping, hopping, etc.

10. What is "curvature of the spine"? How caused and how
avoided ?

1 1 . What makes people bow-legged ?

12. Why are the sides of the body often sore after walking on icy
pavements ?

CHAPTER III.

THE GENERAL FUNCTIONS OF THE NERVOUS SYSTEM.
— SENSATION AND MOTION.

What makes Muscles Shorten ? — We have seen that
the muscles have the power of shortening ; that in shorten-
ing they act on the bones as levers to produce our varied
motions. What makes the muscles shorten ?

Voluntary and Involuntary Motions. — Some motions
we will to make. We will to sit, to stand, to walk, to run,
or to stretch out the hand. Such motions, originating in
a brain activity, are called Voluntary. Other motions are
Involuntary. The will does not control the heart beat.
Most persons cannot keep from winking when a quick
motion is made toward the face, even if they know they
will not be hit. But all of these motions, whether volun-
tary or involuntary, are dependent upon the nervous
system.

The Cerebro-spinal Nervous System. — This consists
of the brain, the spinal cord, and the spinal nerves. The
brain will be described later.

The Spinal Cord. — The spinal cord is a cylindrical
body extending from the brain along the cavity of the
spinal column. Its diameter is not uniform throughout.
Between the shoulders is an enlargement called the cer-
vical enlargement, where the large nerves are given off to

24

NERVOUS SYSTEM.

Fig. 9. Diagram showing Arrangement of Nervous System.

26 PHYSIOLOGY.

the arms. In the region of the loins is the lumbar enlarge-
ment, where the nerves are given off to supply the poste-
rior limbs. The cord is not so long as the cavity of the
spinal column, and the space posterior to the cord is occu-
pied by the nerves extending to the posterior limbs, and
these nerves are given off at a very sharp angle, and con-
tinue backward for some distance before they emerge
from the cavity of the spinal column. But in the region
of the shoulders the nerves spring off at about a right
angle with the cord. The outside of the cord is white, but
the central portion consists of what is called gray matter.
The white portion is made up of fibers, but the gray matter
consists of nerve cells as well.

The Spinal Nerves. — These are given off in pairs from
the sides of the spinal cord, passing out between the suc-
cessive vertebrae. In the regions of the shoulders and
loins the spinal nerves are large, as they supply the large
muscles of the limbs ; but in the middle of the back, where
only the muscles of the body wall are supplied, the nerves
are small. We have thirty-one pairs of spinal nerves.

The Roots of the Spinal Nerves. — Each spinal nerve
arises by two roots, one nearer the back, called the dorsal
root, the other nearer the ventral surface, the ventral root.
These two roots soon unite to form one spinal nerve.

The Ganglion of the Dorsal Root. — On the dorsal
root, just before it unites with the ventral root, is a swell-
ing, the ganglion of the dorsal root. Like all ganglions, it
is largely made up of nerve cells, being a center of con-
trol rather than a means of communication.

The Cerebro-spinal Nervous System of the Rabbit or Cat. — It
will prove helpful at this point to examine the nervous system of a

NERVOUS SYSTEM. 2*]

rabbit. The animal may be killed painlessly by shutting it in a tight
box with a sponge holding a teaspoonful of chloroform or ether. The
smaller the box, the less anesthetic necessary. A large glass jar inverted
over the animal is convenient.

For a support, nail a foot of two-by-four scantling edgewise to a base
board. Lay the animal on this and tack out the feet. Slit and pull
aside the skin from the nose along the back to the base of the tail.
Remove the muscle along the sides of the back and neck. Between
the skull and the first vertebra is a space covered by a thin membrane.
This may be cut through with scissors. Then bone forceps may be
employed by inserting the point of a blade on each side of the cord and
cutting through the bone. In this way the whole of the dorsal portion
of the spinal column may be removed, exposing the spinal cord through-
out its entire length. With care the nerves and their roots may be
found. The nerves extending to the anterior limbs are easily traced,
but for the nerves to the posterior limbs more work is needed.

Structure of Nerves. — When we trace the sciatic nerve
outward, we find that it is continually subdividing. This
division continues until the branches are too small to be
seen by the naked eye. Microscopic examination shows
that a nerve is made up of a great number of fibers bound
together in a common sheath of connective tissue, as is
the case with muscle. When the nerve divides there is
ordinarily no true branching or forking, but certain of
the fibers simply separate from the rest, as in the separa-
tion of the fibers in floss silk.

Structure of a Nerve Fiber. — A single nerve fiber is
too small to be seen by the naked eye, being only about
one two-thousandth of an inch in diameter. It consists of
the following parts : —

1. The Axis Cylinder, a central strand, or core, of semi-
transparent, gray material.

2. The Medullary Sheath is a layer of white, oily
material around the axis cylinder.

28 rnvsjoLOGY.

3. The Nerve Fiber Sheath is a thin, transparent outer
sheath of cdnnective tissue.

Function of Nerve Fibers. -The sole function of the
nerve fiber is to convey nerve impulses. The nerve im-
pulse passes along the axis cylinder as an electric current
passes along an insulated wire.

Nerve Fiber Sheath

Axis Cylinder

Medullary Sheath
Fig. 1 0. Structure of a Nerve Fiber.

Gray Nerve Fibers. — In the sympathetic nerves there
are many fibers which have no medullary sheath, but con-
sist simply of the axis cylinder and the nerve-fiber sheath.
These are called gray nerve fibers.

Cross-section of the Spinal Cord. — If a thin slice of
the spinal cord be made as shown in Fig. 11, it will be
seen that the central part is darker in color than the outer
part. The central part is known as the gray matter, in
distinction from the rest, which is called the white matter.
The white matter of the nervous system is made up of
nerve fibers whose structure and use we have just con-
sidered. But the gray matter has a different structure and
a different function. Instead of being made up mainly of
fibers it is composed of cells, one of the forms of which is
represented in Fig. 12. Some of the branches of these
cells are continued, and become the axis cylinders of nerves,
and it is believed that every nerve fiber begins as a branch
of some nerve cell. One of the best places to see these
nerve cells is in the gray matter of the spinal cord, near

NERVOUS SYSTEM. 29

the place where the ventral root of the spinal nerve arises.
This part of the gray matter is called the ventral horn of
the gray matter. If this portion be examined under a
moderately high power of the microscope, there may be
seen a number of cells with radiating branches.

Dorsal or Sensor
Root

Ganglion

i

Ventral or Motor Root

Fig. 1 1 . Cross-section of Spinal Cord.

Functions of the Spinal Cord. — The spinal cord has
two main functions : —

1. Its conducting power, by means of the white fibers
which make up the outer part of the cord. These fibers
may be regarded as connecting the gray matter of the
brain with all parts of the body.

2. The gray matter is the center of the reflex actions of
the cord.

Ganglia. — Masses of nerve cells make up nerve centers,
or ganglia, such as are on the dorsal roots of the spinal
nerves. These also would show under the microscope
that their chief constituent is a collection of nerve cells
which give off one or more branches.

30 /V/KVA >/.(;<;r.

The gray matter of the spinal cord is considered LI col-
lection of ganglions. We see that the outer layer of the
brain is grayish in color. Within is white matter, consist-
ing of nerve fibers that connect the cells of the gray layer

Fig. 12. A Large Nerve Cell from the Gray Matter of the Spinal Cord.

with the various parts of the body through the base of the
brain, the spinal cord, and spinal nerves.

No Sensation without the Brain. — After a fowl's head is cut off it
" flops " around for some time, and it may even jump clear from the
ground. If one takes hold of its feet to pick it up, it may begin to
struggle as if it were trying to escape.

Now, we know that the bird cannot feel anything after its head is
cut off, because the body is completely separated from the brain, which
is the center of sensation. So with the frog. After its head is cut
off, it cannot feel anything.

Reflex Action of the Spinal Cord of the Frog. — A frog may be
killed as directed on p. 9. Cut off its head and suspend the body
from any convenient support, such as the ring of a retort stand.

1. On pinching the toes the foot will be drawn up.

2. The sciatic nerve should now be severed as before directed
(p. 9). At the instant of cutting the nerve the muscles below will
twitch, because the nerve fibers running to them are stimulated.

NERVOUS SYSTEM. 31

3. If the toes are again pinched, it is found that the uninjured leg
will draw up, but not the one whose sciatic nerve has been severed.

4. If a wire be run down the spinal cavity, the spinal cord will- be
destroyed, and during the operation the uninjured leg will act spas-
modically, because the nerve fibers going to its muscles from the cord
are stimulated.

5. Pinching the toes no longer gives response, because the cord,
which acted as the center of this reflex action, is destroyed.

The Gray Matter of the Cord the Center of Reflex
Action. — In simple sensation of touch, pressure on the

Afferent Dorsal Root

Sensor Fiber

Skin

Motor Fiber vv

Efferent Ventrg| Root

Fig. 1 3. Diagram of Reflex Action of the Spinal Cord.
(After Landois and Stirling.)

toes starts a nerve current or nerve impulse which runs up
to the brain. The sensation is in the brain, but is referred
to the foot. Hence we should be careful not to speak of
a sensation being carried. In voluntary muscular action
the impulse starts from the brain, goes to the muscles, and
makes them shorten or relax.

But in reflex action the current runs up the nerve to the
spinal cord. The gray matter of the central part of the
cord receives the message, and sends back a nerve impulse
to the muscles to make them shorten and pull the foot
away from the source of injury.

32 PHYSIOLOGY.

The Parts Essential to Reflex Action of the Spinal
Cord : -

1. A sensitive surface (the skin, for instance).

2. Afferent nerve fibers.

3. A nerve cell, or cells, in the center of the spinal cord.

4. Efferent nerve fibers.

5. Working organ, as muscle or gland.

Phases of Reflex Action. — In the above experiment
on the frog the steps in order were : —

1. Stimulation of the nerve endings in the skin of the
toe.

2. Passage of a nerve impulse up the afferent fibers to
the spinal cord.

Nerve-Cell

Afferent Fiber ^ \ ,_„ _.,

x — Efferent Fiber

Skin — !,

&-- Muscle

Fig. 14. Scheme of Reflex Arc.

3. Reception of the impulse by a cell, or cells, of the
gray matter in the cord.

4. Sending back a nerve impulse

5. Along an efferent fiber, or fibers, to

6. Muscles which shorten and move the foot.

Importance of Reflex Action. — It is important that
we understand the nature of reflex action, for very many
of the processes of the body are regulated by it. Not
only the more manifest motions, such as winking when

NERl/OUS SYSTEM. 33

anything comes quickly toward the eye, dodging, jumping
when suddenly touched by anything hot or when pricked
by a pin, but also the adjustments of the essential processes
of life, circulation, respiration, and digestion, are brought
about through reflex action.

Destination of Nerve Fibers. — The sciatic nerve is
composed of many fibers. If this nerve is traced outward,
it is found to be continually subdividing, and sending small
branches to the muscles, and finally in the muscles one
fine nerve fiber goes to each muscle fiber. (See Fig. 13.)
Many fibers go on past the muscles to the skin. We can
feel in any part of the skin, and we can tell just where we
are touched. These fibers from the skin, then, carry
nerve impulses inward, as those going to the muscles
carry impulses outward.

Nerve Roots and their Functions. — Experiments on
the lower animals, and accidents in the case of man, show
that all the fibers of the nerves that carry currents to the
muscles pass out from the spinal cord into the ventral
root, and that all the fibers that carry currents inward
enter the spinal cord through the dorsal root. Hence, the
dorsal root is often called the afferent root, and the ventral
the efferent root. Since ingoing impulses produce sensa-
tion, the dorsal root is called the sensory root, while the
ventral root, carrying currents outward to produce motion,
is called the motor root.

Effect of Stimulating a Spinal Nerve. — Experiments
have shown that if, in an uninjured animal, a nerve, or
more properly a nerve trunk, — as the sciatic nerve, — be
stimulated, for instance, by a suitable electric shock, two
effects are produced : first, motion in the parts whose

34 PHYSIOLOGY.

muscles are supplied by the nerve ; second, sensation,
which is referred to the parts of the skin supplied by the
branches of the nerve.

Effect of Severing a Spinal Nerve. — If. instead of simply stimu-
lating the nerve, the nerve is severed, the same two effects will he pro-
duced. After severing the nerve, if we stimulate the end of the nerve
still connected with the limb, we get action of the muscles in that limb.
If we stimulate the end of the nerve connected with the body, a sensa-
tion will be produced, and this sensation will be referred to the parts
from which the nerve fibers arise, probably in the skin of the limb.

Effect of Stimulating the Ends of Severed Nerve Roots. — If we
now turn to the roots of the nerve, and make similar experiments, we
obtain the following results : Stimulating the dorsal root causes sensa-
tion referred to some outer surface, and no other effect is noticed.
Cutting the dorsal root also causes sensation. Stimulating the end of
this root still connected with the spinal cord causes sensation: but
stimulating the end of the root connected with the nerve gives no
appreciable result.

Stimulating or cutting the ventral root causes motion in the parts
whose muscles are supplied by fibers from this root. After severing
this root, if the end connected with trie spinal cord be stimulated, no
effect is noticed ; but stimulating the end still connected with the nerve
is followed by shortening of the muscles supplied.

Effect of Severing All the Spinal Nerves. — Severing
all the spinal nerves destroys all power of sensation and
voluntary motion in all parts of the body except the head.
After severing all the dorsal roots, no sensation would be
produced by stimulating any part of the body, and after
severing all the ventral roots no act of the will can cause
any of the muscles of the body to act. Severing all the
nerves, or severing all the roots, cuts off all communication
of the brain with the body, and so far as motion and sensa-
tion in the body generally are concerned, has the same
effect as severing the spinal cord below the head.

NERVOUS SYSTEM. 35

Cramp. — Cramp is a spasmodic shortening of the
muscles, attended with pain.

Tetanus. — Tetanus (or locked jaw) is a spasmodic and
continuous shortening of the muscles, causing rigidity of
the parts they supply. It is due to the disordered and
excessive stimulation of the muscles through the nerves.

Crossing of the Fibers from the Brain to the Spinal
Cord. — Both the brain and the spinal cord consist of two
lateral halves connected by cross fibers. Each half of the
brain is connected with the opposite half of the body.
This is accomplished by the crossing of the fibers. The
fibers that carry nerve impulses outward are now known
to cross as they leave the brain, at the very beginning of
the spinal cord, in the part known as the spinal bulb.
The sensations arising from touching anything with the
right hand, therefore, are in the left half of the brain, and
the right half of the brain controls the left hand.

Voluntary Interference with Reflex Actions. — We

have seen that the jerking of the hand away from a hot
object is due to reflex action of the spinal cord. One
might, by a powerful effort of the will, keep the hand on
an object that is hot enough to burn the skin. One may
command the foot to remain quiet when it is tickled ; but
as soon as the person is asleep, the same stimulations
would be followed by the reflex actions such as we have
considered.

In these cases of interference it is understood that the
brain sends a nerve impulse down to the centers of the
reflex action, and stops or diminishes their operation.
This retarding influence of a group of cells is called inhi-
bition. It is not always due to voluntary interference,
but may be due to reflex interference, as we may see later.

36 rHYSIOLOGY.

The Nature of a Nervous Impulse. — Of the nature
of a nerve impulse we know but little. It is convenient
to compare the nervous system, with its conducting fibers
and central ganglia, to a telegraph system. And electric-
ity is the most convenient stimulus for exciting nerve im-
pulses. Yet a nerve impulse is very different from an
electric current. A nerve fiber is a poor conductor of
electricity. An electric current may travel along a copper
wire at the rate of between 100,000 and 200,000 miles a
second, while a nerve impulse in a motor nerve travels
only 1 70 feet in a second.

Transmission of Motor Impulses. — When a motor fiber is stimu-
lated in the middle of its course we observe only one effect, — the
shortening of the muscle at its lower end. But there is every reason
to believe that the nerve current, or impulse, runs along the nerve in
both directions from its starting point. But while the action of the
muscle at the peripheral extremity manifests the existence of the cur-
rent, there is nothing at the central extremity to give such evidence.

Transmission of Sensory Impulses. — Similarly, when a sensor
nerve fiber is stimulated at some intermediate point, we have a sensa-
tion in the brain due to the current brought by the afferent fiber, and
which we refer to the outer end of the nerve fiber. Probably a nerve
impulse passed from the point of stimulation to the outer end of the
fiber ; but as there is nothing at the outer end of the nerve fiber to
interpret it, we get no evidence of such impulse except, by refined
physiological tests.

Harmony in Muscle Action. — In throwing a stone a
number of muscles are used. Each one of these must
shorten in the right way and at the right time or the throw
will not be accurate. Each muscle shortens under the
influence of a nerve impulse started by the brain and
brought by a motor nerve. If any muscle shortens an
instant too soon, or a little too strongly, the stone goes to

NERVOUS SYSTEM. 37

one side. In a tune on a piano we know that the right
keys must be struck ; that each must be struck at the right
time, with the proper degree of force, and held for the
right length of time, or we have discord instead of har-
mony. What the player is to the instrument, the brain
is to the body.

Temporary Loss of Muscular Power. — It may have
happened to you that after sitting long in one position you
attempted to stand, but found that you could not do so.
One leg failed to act at the bidding of your will. When
the foot is " asleep " we get little sensation from it ; we
hardly know whether it is touching the floor or not. Press-
ing on it with the other foot causes no pain.

We try to stand when the foot is asleep, but we are
unable to do so. The brain starts the nerve currents, and
they run along the nerve as far as the compressed part ;
here they stop. They cannot reach the muscles of the
leg below. Hence the muscles do not shorten, and we
do not rise, no matter how strongly we will to do so.

Why is it that the nerves and muscles thus sometimes
lose their ability to perform their natural activities ?

Dependence of Nerves and Muscles. — This has been
explained by saying that owing to external pressure, the
nerve has temporarily lost its power of conducting nerve
currents. But what beside the nerve has been com-
pressed ? What process in the limb has been interfered
with by the pressure due to the position in which one has
been sitting or lying ? What is the temperature of the
benumbed limb ?

On what are the nerves and muscles so dependent for
the maintenance of their activity ?

38 niYSioi.OGY.

READING. — Power through Repose, Call ; The Technique
of Rest, Brackett; Muscles ami Xerres^ Rosenthal.

Summary. — I . Motions are voluntary or involuntary, but all are
under control of the nervous system.

2. The cerebro-spinal nervous system consists of the brain, the
spinal cord, and the spinal nerves.

3. Each spinal nerve has two roots : the dorsal, which is afferent
and sensory ; the ventral, which is efferent and motor.

4. A ganglion is a nerve center largely composed of nerve cells.

5. Nerves are made up of nerve fibers.

6. A nerve fiber consists, of the central core (or axis cylinder),
which conducts the nerve impulse, the medullary sheath, and, outside,
the nerve-fiber sheath.

7. The spinal cord has in its outer part white nerve fibers, in its
center gray nerve cells.

8. These cells are branched, and at least one branch becomes the
axis cylinder of a nerve fiber.

9. The gray matter of the cord is the center of the reflex action.

10. The nerve fibers from each half of the brain connect with the
opposite half of the body.

11. The nervous system is comparable to a telegraph system.

Questions. — i. Name as many involuntary motions as you know.

2. What other cases of reflex action do you know ?

3. The story is told of a young Roman (Mucius Scaevola) that to
show his fortitude he thrust his hand into the fire and held it there
until it was destroyed. What physiological action does this illustrate ?

4. Why is a man partially paralyzed when he has broken his neck
or back ?

5. How does the nervous system differ from a telegraph system?

CHAPTER IV.
CIRCULATION OF THE BLOOD.

The Blood and its Work. — We know that if any animal
is bled freely, it soon becomes weak, then unconscious, and
soon dies, if the escape of blood be not stopped.

We observe the natural difference in color of different
parts of our bodies ; for instance, the lips and cheeks.
We often note varying color, as in blushing and pallor.

We wish to understand these differences and changes ;
also to know what to do in case of fainting or bleeding
from wounds. We may prolong and make more useful
our own lives and those of others by knowing, in a practical
way, something about the causes, prevention, and remedies
of the colds, congestions, and inflammations to which we
are subject.

Nearly every part of the body bleeds when cut. There
is no bleeding when we trim the nails or cut the hair, and
the outer skin has no blood in it. But the inner skin, and
almost every tissue within it, if pierced even by the finest
needle, yields blood. We see a little blood oozing from
the surface of a fresh steak or roast.

What kind of a substance is the blood ? Is it uniformly
distributed through the tissues, like water soaked up into a
cloth, or is it in distinct cavities ? Why is it so essential to
life ? How does it do its work ?

The Rate of the Heart Beat. — The heart beats about
seventy-two times a minute in men ; in women, about

39

4O PHYSIOLOGY.

eighty. At birth the rate is from one hundred and thirty
to one hundred and forty, and gradually decreases till
about the age of twenty, when the average of seventy-two
is reached. This rate holds till old age, when it increases.
The rate is increased by muscular activity, food, external
heat, internal heat (fever), pain, and mental excitement.
Music accelerates the pulse rate. The pulse rate varies
during the twenty-four hours, being lowest during the
night, and highest about 1 1 A.M. Certain diseases increase
the frequency of the pulse. Some drugs quicken the
pulse rate, and others dimmish it.

The Heart Beat and the Pulse. — i . The heart beat, felt at the left
of the breast bone.

2. The pulse, felt at the wrist and at various parts of the body.
Perhaps the most convenient place to study it is at the temple. Lay
the forefinger lightly along the cheek just in front of the ear. Count
the pulsations for a minute.

Let one or two pupils who are quick at figures step to the blackboard
and put down the number of pulsations of each pupil, and divide by the
number thus reporting, to get the average.

1 . Let all in the class count the pulse while sitting. Probably it
will be best to discard the first trial, as there are likely to be several
failures from one cause or another. Then, too, there is usually a slight
excitement at the beginning of a wholly new experiment. Get the aver-
age of the class.

2. Find the pulse while sitting; rise quickly, and immediately begin
to count the pulse. Compare with the pulse as taken while sitting.

3. Compare the pulse before and after meals.

4. With the thumb and finger lightly clasp the windpipe, well back.
The pulse in the carotid arteries will be felt.

The Position of the Heart. — The base of the heart is
in the center of the chest, just back of the breast bone, but
the apex points downward and to the left.

The Covering of the Heart. — The heart is inclosed in
a loosely fitting membranous bag, the pericardium. Within

CIRCULATION OF THE BLOOD. 41

the pericardium and around the heart ivS a small quantity
of liquid, called the pericardial fluid.

The Size of the Heart. — A person's heart is about the
size of his clenched hand.

The External Features of the Heart. — The heart is
cone-shaped and the bulk of it is made up of the ventricles,
the auricles being two ear-like flaps at the base, one on
each side. There is a deep notch between the auricles
and the ventricles. The line of division between the two
ventricles is marked by a groove, which runs obliquely
along the ventral surface. In this groove are blood tubes
and usually considerable fat.

The Internal Structure of the Heart. — The two halves
of the heart are completely separated from one another
by a partition. Each half, in turn, has valves which,
part of the time, separate the cavity of each auricle (at
the base) from the cavity of the corresponding ventricle
(at the apex).

The Valves of the Heart. — Between the auricles and
the ventricles are curtain-like valves, whose upper edges
are attached to the inner surface of the walls at the upper
margin of the ventricle. These flaps are somewhat tri-
angular, and have strong white, tendinous cords extending
from their edges and under surfaces to the walls of the
ventricle below. In the right half of the heart there are
three flaps, and this valve is called the tricuspid valve. In
the left side there are two flaps, which, together, constitute
the mitral valve. In the resting heart these flaps hang
down along the walls of the ventricles so that on opening
the heart one would see only a single cavity in each half
of the heart.

42

The Semilunar Valves. — From the base of the right
ventricle arises the pulmonary artery. Within its base,
just as it leaves the ventricle, are three pocket-like valves,
like " patch-pockets." They are in a circle, with their edges
touching, and thus surround the opening, with their
mouths opening away from the heart. A similar set of
valves are within the base of the aorta, which arises from
the left ventricle. Both these sets of valves are called
semilunar valves.

Dissection of the Heart. — No description (nor even figures) can
give a clear idea of the heart. A good model will be of some assist-
ance. But the heart itself should be examined carefully and then dis-
sected. The heart and lungs of a sheep should be obtained (ask the
butcher to save the "pluck," i.e. the heart and lungs taken out together).
The relations of the heart to the lungs and other organs should first
be studied, and then the pericardium opened. Observe the outside of
the heart, and then cut the heart open to see the points given in the
above description. After the heart is severed from the lungs the auri-
cles may be cut off; then, by pouring water into the ventricle, the
action of the valves between the auricles and the ventricles will be
seen. Pressing on the outer surface of the right ventricle will make
the water escape through the pulmonary artery. If this be split open,
the semilunar valves at its base may be found.

The Blood Tubes connecting the Heart with Other
Organs. — The aorta (the largest artery in the body)
arises from the base of the left ventricle, and supplies
with blood every organ of the body except the lungs.
The pulmonary artery springs from the base of the right
ventricle and sends blood to the right and left lungs.
Two large veins enter the right auricle, the precaval vein
from the anterior regions of the body and the postcaval
vein brings blood from all the organs of the posterior por-
tions of the body. The pulmonary veins return the blood
from the lungs to the left auricle, two from each lung.

CIRCULATION OF THE BLOOD.

43

44

PHYSIOLOGY.

fL External Jugular Vein

Internal Jugular Vein

2 Subclavian Artery
b Subclavian Vein
1 Carotid Artery

i Aorta
in Precaval Vein

IV Postcaval Vein

Gastric Artery
Splenic Artery
Hepatic Artery
Pancreatic Artery

ff Renal Veins
5 Renal Arteries

T Iliac Arteries
i Iliac Veins

Fig. 16. Distribution of Arteries and Veins.

CIRCULATION OF THE BLOOD.

45

The Distribution of the Arteries and Veins. — The

organs of the body receive a supply of blood in propor-
tion to their size and activity. The artery supplying the
blood and the vein which returns it usually lie side by side
(see Fig. 16). The larger arteries are usually deep-seated
and in protected places.

Demonstration of the Action of the Heart. — The heart may be
mounted as shown in Fig. 17, and its action illustrated by compressing
the ventricles with both hands. Instead of the apparatus here shown
two retort stands may be used, though not so convenient.

Capillaries
of the Lungs

Capillaries
of the Body

Fig. 17. Demonstration of the Action of the Heart (Heart Diagrammatic).

The Action of the Heart. - - The -heart consists of
muscle fibers so arranged that they form a thick-walled
bag, which stands expanded when the muscles relax. But
when the fibers shorten the whole heart contracts, and the

46 PHYSIOLOGY.

cavity is much reduced in size, if not entirely obliterated,
and the blood is forced out.

The complete action of the heart consists of three parts,
— the contraction of the auricles, the contraction of the
ventricles, and the pause.

The Pause. — During the pause the blood is steadily
pouring into the auricles ; into the right auricle from the
caval veins, into the left auricle from the pulmonary veins.
At this time the curtain-like valves between the auricles
and the ventricles are open, and their flaps hang loosely
beside the walls of the ventricles. The blood, therefore,
as it passes into the auricles, passes on into the ventricles.
As the ventricle fills, the valves float up, as seen in the
experiment of pouring water into the ventricle.

The Contraction of the Auricle. — When the ventricle
is full, but not stretched, and the auricle partly full, the
auricle suddenly contracts, thus forcing more blood into
the ventricle, and distending it. At the same time the
valves, which were already nearly closed, are tightly closed
by the pressure of the blood which is forced up behind
them. The flaps of the valves are kept from going up too
far by the tendinous cords and by the papillary muscles to
which the cords are attached.

The Contraction of the Ventricle. — Next comes the
contraction of the ventricle, slower, but more powerful
than that of the auricle. As the walls of the ventricle are
drawn together, the blood is subjected to pressure. It
cannot go back into the auricles, for the more it presses
against the valves, the more tightly they are closed. The
semilunar valves are closed by back pressure in the aorta
and pulmonary artery. But the pressure of the blood in
the ventricles is so much greater that the semilunar valves

CIRCULATION OF THE BLOOD,

47

are forced open, and nearly all the blood is driven out of
the ventricles ; from the right ventricle into the pulmonary
artery, and from the left ventricle into the aorta.

While the ventricles are contracting and forcing their
blood out, the auricles are slowly filling by the steady
inflow through the veins.

Systole and Diastole. — The contraction of the heart is
called the systole, and its dilation the diastole.

Dilation of the Ventricle. — As soon as the ventricle
has completed its contraction it dilates, and most of the
blood that has accumulated in the auricle simply falls into
the ventricle. The dilating ventricle exerts a slight suc-
tion, so the blood is in part drawn into the ventricle. Dur-
ing the remainder of the pause the blood accumulates in

Auricle

Fig. 1 8. Diagram of the Heart, showing the Action of the Valves.

the auricle and ventricle till the auricle again contracts and
the cycle is repeated. This is true of both halves of the
heart, which work simultaneously, the right heart pumping
dark blood while the left heart pumps bright blood. The
left ventricle is thicker walled and stronger than the right.

48 PHYSIOLOGY.

Work and Rest of the Heart. — The time taken by the
different parts of the heart beat are about as follows : The
auricle contracts about one eighth of the time and rests
the other seven eighths. The ventricle contracts about
three eighths of the time and dilates during about five
eighths. If we suppose the whole period of the heart beat
to be twenty-four hours (instead of eight tenths of a sec-
ond), we can more easily see how much of the time the
heart is actually at work, and how much of the time the
heart is resting.

Auricle contracting (working) \ of the time — 3 h., resting 21 h.
Ventricle contracting (working) f of the time — 9 h., resting 15 h.

No part of the heart, therefore, is working longer than a
man would who only works nine hours a day. Some ob-
servers state that the resting period is even greater than
these figures would show.

Since the contraction of the ventricles immediately fol-
lows that of the auricles, one half of the time is occupied
by the whole contraction of the heart, and during half the
time the whole heart is resting. This is different from our
usual statements regarding the work of the heart. We
hear it said that the heart never rests. Its work and rest
follow each other at such short intervals that we do not
appreciate the interval of rest that comes between the suc-
cessive impulses that we feel. Suppose a policeman had
the power of sleeping at will, and that he slept thirty min-
utes of each hour, and that in the remaining thirty minutes
he made the rounds of a block. If we saw him passing
regularly once an hour, every hour of the twenty-four, we
might suppose that he did not sleep at all during the entire
time. This ratio of work and rest is fairly constant in
the varying rates of heart beat.

CIRCULATION OF THE BLOOD.

49

The Beat of the Heart. — The apex of the heart is
always in contact with the chest wall. Consequently, it
never strikes it. At each beat it pushes hard against the
chest wall. This push may be felt and seen, and is called
the heart beat.

The Sounds of the Heart. — There are two sounds of
the heart : —

1. A short, sharp sound made by the closing of the semi-
lunar valves.

2. Just preceding this sound a longer, duller sound may
be heard during the contraction of the ventricles. This is
supposed to be due to the vibrations of the walls of the
ventricles and of the large valves.

As soon as

Nucleus

Isolated Fibers

Fibers Joined

Action of the Large Arteries. — The large arteries
have in their walls a yellow elastic tissue. When the
blood is forced into them, they are stretched,
the ventricle ceases to contract,
and sends no more blood into
the arteries, they "stretch back."
We should not say contract, for
it is simply an elastic reaction.
As the artery reacts it presses on
the blood, and hence the blood
tries to escape in every possible
way. It cannot go back, for it
fills the pockets of the semilunar
valves, and closes them with a
click. A rapid wave is sent for-
ward that gives the pulse, and a slower but still rapid
stream flows along the arteries, through the pulmonary
artery to the lungs, and through the aorta and its branches
to all the other parts of the body.

Fig. 1 9. Plain (Unstriated) Muscu-
lar Fibers from the Bladder.

50 PHYSIOLOGY.

The elastic reaction of the arteries thus helps to make
steady the flow of blood, which is intermittent as it leaves
the heart. The medium-sized arteries also have elastic
tissue in their walls, and regulate the blood flow in the
same way.

Variation of the Amount of Blood Needed. — Each
organ requires a supply of blood in proportion to its
activity. An actively working organ, like the brain, de-
mands much more blood than bone, practically inactive.
Further, working tissues, such as the brain and muscles,
need a great deal more blood while they are at work than
when they are resting. An organ needing a constant large
supply of blood might secure this by having a large artery.
But how can the supply be regulated so that an organ
may receive, now more, now less, according to its needs ?

Plain Muscle Fibers in the Walls of the Arteries. —
This is regulated by the medium-sized and small arteries

Connective Tissue

Endothelium

Muscle Fiber

Fig. 20. Plain Muscle Fiber. Isolated and in Wall of Artery.

leading to the parts. In the walls of these arteries are
muscle fibers of a different kind from those of the skele-

CIRCULATION OF THE BLOOD. 51

ton. These fibers are spindle-shaped cells, as shown in
Fig. 19, with a nucleus near the center, and do not have
the cross-markings of the fibers of the skeletal muscles ;
they are in consequence called nonstriated, smooth, or
plain muscle fibers. They are arranged circularly in the
walls of the arteries. These fibers have, in common with
all muscle fibers, the power of shortening. When they
shorten they reduce the size of the artery, and, there-
fore, for the time, less blood can flow through the
artery. When the muscle fibers cease to shorten, the
artery widens, and allows more blood to pass through it.

Illustration of the Action of Muscles in Arterial Walls. — To

illustrate the action of the muscles in the walls of an artery, let the
water run through a hose or large
rubber tube. Now, if a row of per-
sons take hold of this tube, the grip Endotheiium

of their hands is like that of the

muscles. When the hands tighten internal Elastic —

their grip, the caliber of the hose Layer

or tube is diminished, and less water

is allowed to flow through it. When Circular Mus-
cle Fibers
the hands relax, the tube, being

elastic, allows more liquid to flow
through it.

Illustration of a Small Artery.

— To represent a small artery, take
a small, thin-walled rubber tube and
wind a red thread around it. Now,

if the thread could be made to Fl* 21- Coats of a Small Artery.
shorten, it would diminish the cali-
ber of the tube. The representation would be more exact if the thread
were cut into many short pieces, and if each piece were thicker in
the middle, and were then glued to the tube. If the whole were
covered by a layer of tissue paper, the structure of the artery would be
roughly represented.

52 PHYSIOLOGY.

Plain and Striated Muscle Fibers Compared. — These plain mus-
cle fibers are further like those of the skeletal*muscles in that they are
under the control of the nerves, but they are involuntary in their action.

PIGMENT
CELLS

ARTERY
Fig. 22. Part of Frog's Web (low magnifying power).

We cannot interfere with the action of these muscles, no matter how
strongly we may will to do so. Without our thinking about it, more

CIRCULATION OF THE BLOOD.

53

blood goes to the muscles of the legs when we walk, more to the brain
when we are studying, to the digestive organs after eating, etc. The

Walls of Capillari

Tissues of Web

£ \

Fig. 23. Part of Frog's Web (highly magnified).

plain muscle fibers shorten at a much slower rate than the striated
fibers. They are also slower in relaxing. Since the plain muscles are
usually found in the walls of hollow organs such as the heart, blood

54

PHYSIOLOGY.

tubes, digestive tube, etc., they are sometimes called visceral muscles in
distinction from the skeletal muscles.

The Circulation of Blood in the Web of a Frog's Foot. — For this
get a frog with a pale web. Take a piece of shingle six inches long
and three inches wide. Cut a round hole, half an inch in diameter,
near one end of it. Wrap the frog in a wet cloth, with one leg project-
ing, and tie it, thus wrapped, to the shingle. Tie threads around two
of the toes, and stretch the web, but not too tightly, over the hole.
Keep the web moist. Place the shingle firmly on the stage of a micro-
scope. Examine first with a low power. The large tubes which grow
smaller by subdivision are arteries. The large tubes which are
formed by the union of smaller ones are
the veins. The finer tubes, forming a net-
work in every direction, are the capillaries.
They receive the blood from the arteries
and pass it on to the veins.

Put on a higher power, a one-fifth or
one-sixth objective. It may now be seen
that the colored corpuscles float more in
the center of the stream, and with a steady
motion, while the colorless corpuscles keep
close to the walls of the capillary, and seem
to adhere to them, advancing with a hesi-
tant motion, seeming to roll along against
the wall of the capillary.

Close your eyes for a moment, and re-
flect that in all the active tissues of your
body — for example, the muscles, brain, and
digestive organs — there is a similar net-
work of fine tubes with a current of blood

running through them. The current is not so rapid as it seems, for the
microscope magnifies the rate of flow as well as the size of the cor-
puscles. The blood really is moving slowly in the capillaries, and it is
very important that it should be so, for in the capillaries the work of
the blood is done. Part of the liquid of the blood soaks through the
thin walls of the capillaries, and nourishes the surrounding tissues. All
the other parts of the circulatory system exist for the purpose of send-
ing a continuous, slow, and steady stream of blood through the
capillaries. (See pages 72 and 73.)

Fig. 24- Capillary Blood
Tubes of Muscle.

CIRCULATION OF THE BLOOD.

55

Connective

Tissuf

Artery

Fig. 25.

Cross-section of Small Artery
and Vein.

The Blood Flow in the Capillaries. — The arteries

divide and subdivide, and become capillaries, which have

connecting branches, form-
ing a close network of tiny
thin-walled tubes. These
penetrate nearly every tis-
sue of the body. The blood
cannot do its full work till it
is in the tissues/and to reach
the tissues it must soak
through the walls of the
capillaries. The work of
the heart and arteries is to
keep a steady flow of blood

through the capillaries, that the tissues may be constantly

supplied.

How is it that the jerky action of the heart, at each

contraction sending a jet of

blood into the arteries, —

shown by a spurt when an

artery is severed, and also

indicated by the intermit-
tent pulse, — how is this

intermittent flow converted

into the steady, uniform

current that we have seen

in the capillaries ?

Experiments illustrating the
Blood Flow in the Capillaries.—

A few experiments may make this Fig. 26.

Surface View

Longitudinal Section

matter more clear.

Capillaries, composed of a single
layer of cells.

Material : — i . A common rubber syringe.

2. A glass tube three feet long and seven sixteenths of an inch
outside diameter.

56 PHYSIOLOGY.

3. Four inches of the same size glass tubing, for making connec-
tions.

4. Several nozzles, made of the same size glass tubing, all fine, but
of varying degrees of fineness.

5. India-rubber tubing, twelve feet, three eighths of an inch inside
diameter. This should be black, pure gum, rubber which is more
highly elastic than the other kinds.

6. Three feet of rubber tubing, same size as above.

7. Four inches of white rubber tubing, same size as above, for
making connections.

In all the experiments, have one of the students assist by holding
the outlet tube, so that (i) all the members of the class may see the
stream, and (2) that the stream may be suitably directed, as into a pail
or sink.

Count aloud, to mark the exact time of each compression of the
bulb, so the students can compare this with. the time and duration of
the jets of water.

Be very careful to use perfectly clean water, as any fine particles of
sediment drawn into the tube are likely to clog the fine outlet of the
nozzle. And it is well to take the further precaution not to let the
supply tube touch the bottom of the water-supply dish, as some fine
sediment may get in in spite of previous care.

EXPERIMENT i. — Remove the nozzle of the syringe, and put in its
place the long glass tube. Work the syringe, and note that the jet is
jerky, following each contraction of the bulb.

EXPERIMENT 2. — Substitute the rubber tube, three feet long, for
the glass tube. On working the bulb the stream will be found inter-
mittent.

EXPERIMENT 3. — Take off the rubber tube and replace the glass
tube, adding the nozzle. Here the pressure will be so great that it is
likely to push off the nozzle unless the assistant holds it firmly. It
could be tied on, but this takes more time. On working the bulb,
greater effort must be made on account of the resistance caused by the
narrower outlet.

EXPERIMENT 4. — Once more substitute the rubber tube, this time
with a glass nozzle in its end. Now, on working the bulb, resistance
will be felt, and the stream will be constant, or nearly so, and will con-
tinue for some time when the bulb is no longer worked. This is be-
cause the rubber has been stretched, chiefly laterally, and is now

CIRCULATION OF THE BLOOD.

57

" stretching back." That is, by the elastic reaction of the rubber tube
the jerky action of the bulb is converted into the steady flow that we
see. In the first experiment we had a rigid tube and practically no
resistance. In the second, although the tube was elastic, there was no
resistance, so the elasticity was not brought into play. In the third,
there was resistance, but the tube was inelastic. In the fourth, the
resistance brought into play the elasticity of the rubber tube, and the
elastic reaction of the tube continues (so to speak) the action of the bulb
between two successive strokes. In this experiment the pulse can be
felt in the tube.

The Veins. — The capillaries, after penetrating the tis-
sues, reunite to form small veins, which in turn reunite
to form larger ones, till finally two great veins, the caval
veins, precaval and postcaval, return the blood to the
heart. The veins, like the arteries, are smooth inside and
elastic (though less elastic than the arteries). They are
thinner than the arteries, and, in consequence, collapse
when the blood flows out of them, whereas the larger
arteries stand open, after they are emptied of blood.

The Valves in the Veins. — The only valves in the arte-
ries are those which we have seen at the beginning of the
aorta and pulmonary artery.
Many of the veins have
similar pocket-like valves,
though less strong than
those of the arteries. They
are usually in pairs, but some-
times single or in threes. It
is important to note that they
all have the mouths of the
pockets toward the heart, so
that the blood flows freely
toward the heart, but is prevented from flowing the other
way on account of the filling of the valves by the reflow

Open Shut

Fig. 27. Venous Valves.

58 PHYSIOLOGY.

of the blood stream. When the blood is flowing through
the veins toward the heart the valves lie against the walls
of the veins.

The valves are most numerous in the medium-sized veins,
and especially in the veins of the extremities ; more abun-
dant in the leg than in the arm. Valves are absent from the
caval and some other veins, and from the very small veins.

Illustration of Venous Valves. — Make a cloth tube (or take the
lining of a boy's coat sleeve) and sew three patch-pockets on the in-
side, in a circle, i.e. with edges touching each other. Make the pockets
a little " full." Pour sand, shot, or grain through the sleeve first in
one direction and then in the other.

Evidences of Valves in our Veins. — With the forefinger stroke
one of the veins on the hand or wrist toward the tips of the fingers.
The veins swell out. The blood meets resistance in the valves of the
vein. Their location may be determined by their bulging out during
the experiment.

Stroke a vein toward the body, and the blood is pushed along with-
out resistance.

Let the left hand hang by the side. Note the large vein along the
thumb side of the wrist. Place the tip of the second finger on this
vein just above the base of the thumb. Now, while pressing firmly
with the tip of the second finger, let the forefinger, with moderate
pressure, stroke the vein up the wrist. It may be seen that the blood
is pushed on freely, but comes back only part way. It stops where it
reaches the valves, filling the vein full to this point, but leaving it col-
lapsed beyond, as shown by the groove. Remove the second finger,
and the vein immediately fills from the side nearer the tip of the fingers.

These experiments show that the blood in the veins moves freely
toward the body, but cannot flow outward to the extremities.

Dissection of the Valves in a Vein. — The valves may be seen by
dissecting out the jugular vein (or any other large superficial vein) of a
cat, dog, or rabbit. Split the vein and pin it out on a board.

Effect of Pressure on the Veins. — Since the valves in
the veins open toward the heart, any intermittent pressure
on the veins helps to push the blood on toward the heart.

CIRCULATION OF THE BLOOD. 59

The valves are most numerous in the superficial veins and
those of the muscles. The pressure of the muscles during
their action (thickening while shortening) produces pres-
sure on the veins ; and as the muscles act for a short time
only, and then relax, this alternate compression and release
aids very considerably in moving the blood on toward the
heart. It is worthy of remark that this effect is more
pronounced at the time the muscles need the most active
circulation ; namely when they are in action, and are using
the most blood. The heart has power enough to pump
the blood clear around from each ventricle to the auricle
of the other side of the heart ; but this outside aid comes
in good play to relieve the heart at a time when it has an
unusual amount of work to do, as when one is using a
large number of muscles vigorously.

" Every active muscle is a throbbing heart, squeezing
its blood tubes empty while in motion, and relaxing so
as to allow them to fill up anew."

Rate of Blood Flow in the Arteries, Capillaries, and
Veins. — The blood flows most rapidly in the arteries,
slowest in the capillaries. Why is this ?

When an artery divides, the two branches taken together
are larger than the one artery that divided to form them.
Stated more exactly, the sum of the areas of the cross-
sections of the branches is greater than the area of the
cross-section before branching. Hence as the blood flows
on it is continually entering wider and wider channels ;
and we are told that the united cross-section of all the
capillaries fed by the aorta is several hundred times that
of the aorta itself.

The Flow of the Blood compared with the Current of
a Stream. — If we walk along a stream, we see that the

6o

PHYSIOLOGY.

channel varies considerably in width and depth. Where
the channel is large, whether from increased width or depth,
there the current is slower, but wherever the channel is
reduced, the current is more rapid. So the stream in
the relatively narrow artery is swift. In the capillaries,

Pulmonary Vein -

Left Auricle ..

Left Ventricle

Aorta

Digestive Tube

Pulmonary Artery
Lymph Vein

Right Auricle

- Right Ventricle
Caval Vein

- Liver

Fig. 28. Plan of Circulation. (Dorsal View.)

although any individual channel is small, these channels
all together are wide ; the result is the same whether a
river widens out into a single lake, or divides into a great
number of channels running past innumerable islands.

CIRCULATION OF THE BLOOD. 6l

All the tissues of the body may be regarded as so many
islands lying between the capillary streams.

The Blood Flow in the Veins. — When the blood re-
collects in the veins it is entering narrower channels, and
its rate is quickened ; but as the veins are wider than the
arteries, the stream does not enter the heart with the veloc-
ity with which it left that organ. The veins hold more
blood than the arteries, and in dissecting the cat or rabbit
it will be noticed that the arteries are emptied of blood;
that the tissues of most of the organs are fairly free from
blood ; but -that the great veins, such as the caval veins,
are full.

Blood Tubes compared to Two Funnels. — If the blood
tubes leaving the heart could all be united, they would be
best represented by a funnel with its tube connected with
the heart. If another funnel were placed with its mouth
to the mouth of the first, their point of union, the widest
point, would represent the capillaries; and if the second
funnel had a wider tube than the first, it would fairly rep-
resent the veins which return the blood to the heart.

Nourishment of the Walls of the Heart and Blood
Tubes. — The cardiac (coronary) arteries spring from the
aorta just above the semilunar valves, and send blood into
the muscular walls of the heart ; and these arteries, like
others, divide, forming capillaries, through which the heart
muscle is nourished, The cardiac veins return the blood
to the right auricle.

Influence of Gravity on Circulation. — Although the
heart pumps the blood around through the body inde-
pendent of the force of gravity, yet the circulation is influ-
enced by this force. For instance, a person who has

62 PHYSIOLOGY.

fainted should be laid flat on his back, that the heart may
more easily drive blood to the brain. Many persons go to
sleep more readily while sitting than while lying down.
A sore hand feels less pain if held up, as in a sling, than
when hanging by the side, and a sprained ankle does
better rested on a chair, as less blood flows to it. Nearly
every one has noted the pain following the pressure of
blood when a sore hand, or foot, is suddenly lowered.

Experiments illustrating the Effect of Gravity on Circulation. —
Let all the pupils in the class stand. Let one arm hang freely by the
side. Hold the other arm straight up as far as the clothing will readily
permit. Observe : —

1. The difference in the color of the two hands.

2. The difference in fullness, both in the feeling of fullness and in
the prominence of the veins.

3. The difference in temperature ; place the backs of the hands
against the cheeks.

The position largely determines the amount of blood in the hand,
and the amount of blood determines the temperature, the size, and the
color.

Summary. — i. The heart beats about seventy-two times a minute.

2. The pulse is a wave running along an artery.

3. The pulse varies with age, health, food, etc.

4. The heart has two main cavities, one in each half of the heart,
and two independent streams are flowing through it.

5. Valves allow the blood to flow through the heart in one direc-
tion, but prevent a reversal of the current.

6. The heart is a hollow muscle, and. by contraction forces the
blood out into the arteries.

7. The heart works rather less than half the time.

8. The large arteries, by elastic reaction, push the blood on while
the heart is resting.

9. Circular muscle fibers in the walls of the medium-sized arteries
regulate the blood supply to the organs.

10. In the arteries the blood flow is rapid and intermittent, in the
capillaries slow and constant.

CIRCULATION" OF THE BLOOD. 63

11. The thin walls of the capillaries allow the liquid part of the
blood to soak out and nourish the tissues, and to soak back into the
capillaries bearing waste matter.

12. The veins are thin walled, and collapse when empty, while the
arteries are thick walled, and stand open when empty of blood.

13. Arteries carry blood from the heart, while veins carry it toward
the heart.

14. The veins have valves which allow the blood to pass toward
the heart, but not away from it.

15. Any intermittent pressure on the veins aids the blood flow.

1 6. The blood flow is most rapid in the arteries, slower in the veins,
slowest in the capillaries.

17. Gravity influences circulation.

Questions. — i. Why do the large arteries lie deep?

2. In which direction should the limbs be stroked to promote circu-
lation?

3. How does slapping the hands around the body warm the ringers?

4. How can a horse or a cow be comfortable with the head down
for a long time?

5. Why are the walls of the left ventricle thicker than those of the
right ?

CHAPTER V.

CONTROL OF CIRCULATION. — THE BLOOD AND
THE LYMPH.

The Effect of the Emotions on Circulation. — In our
every-day experience we have evidence of the control of
the heart and blood tubes by the nervous system. We know
that certain emotions affect the circulation of the blood ;
for instance, blushing and pallor. Certain emotions may
also quicken or retard the action of the heart. Excessive
grief or joy has produced sudden death by stopping the
beat of the heart.

Let us look a little more closely at that part of the
nervous system that has such intimate relation to the
blood system.

The Rhythmic Action of the Heart. — In the first
place, the action of the heart is automatic. The heart of
the frog continues to beat a long time after it is removed
from the body. This is regarded by many as due to the
action of certain ganglia imbedded in the walls of the
heart, especially in the auricles ; while others say that
since the ventricle, in which no ganglia have been found,
may beat independently of the auricles, rhythmic contrac-
tion is characteristic of heart muscle, and that we are, at
present, unable to explain it.

But while the impulses that originate the action of the
heart arise within the heart itself, still the beat of the heart
is constantly modified by nerve impulses reaching it from
without.

64

Carotid Plexus

Superior Cervical Ganglion

Middle Cervical Ganglion

Pharyngeal Branches

Cardiac Branches

Deep Cardiac Plexus

Superficial Cardiac Plexus

Solar Plexus

Aortic Plexus

Lumbar Ganglia

Fig. 29. Vertical Section of Body, showing Sympathetic Nerves and Ganglia of Right
Sid,e and their Connection with the Cerebro-spinal Nerves.

66

PHYSIOLOGY.

Sympathetic Nerve Chains
GRAY

Sources of the Heart's Nerve Supply. — The heart re-
ceives its nerves from two sources, the sympathetic system
and the vagus (or pneumogastric) nerves.

The Sympathetic Nervous System. — The sympathetic
nervous system consists of two rows of ganglia in the body
cavity, one along each side
of the spinal column, re-
ceiving branches from the
spinal nerves, and sending
branches to all the
internal organs of
the body, — the
heart and lungs in .
the thorax, and the
stomach, intestines, and the
other organs of the abdomi-

Ganglion of
Dorsal Root

Sympathetic
Ganglion

Fig. 30. Relation of Spinal Cord and
Sympathetic Nervous System (Diagram).

nal cavity. In many places
these nerves form a thick
network called a plexus.

One very large plexus is on the dorsal surface of the

stomach, and is called
spinal cord the solar plexus.

Sympathetic
Ganglion

The Vagus Nerves.
— The vagus nerves
are a pair of the cranial
nerves arising from the
sides of the spinal bulb ;
and passing downward,
they give branches to
the pharynx, the gullet,

the stomach, the larynx, the windpipe, the lungs, and the
heart. Now, whatever other function the vagus nerves

Fig- 31. Ideal Cross-section of the Nervous
System. (After Landois and Stirling.)

CONTROL OF THE CIRCULATION.

67

may have, they seem to have the power of retarding, or
stopping altogether, the beat of the heart ; and stimulation
of the vagus nerves may make the heart pause in a relaxed
condition. Other nerves may quicken the heart beat, but
the vagi are regarded as a break on the heart's action.

Inhibition. — This is a case of inhibition. It is well
known that a severe blow over the stomach may cause one
to faint by stopping the heart. This
is due to reflex inhibition of the heart.
The blow sends a nerve impulse by
fibers of the sympathetic system to
the center in the spinal bulb, and
thence an impulse is taken by the
vagus nerves to stop the heart.

Vaso-constrictor Nerves. — In an

experiment with the rabbit's
ear it has been shown that
stimulating the sympathetic
nerve in the neck causes the
ear to become pale. This is
due to the constriction of the
arteries of the ear, because
the nerves have made the
muscle fibers of these arteries
shorten. Such nerve fibers
are called constrictors, or vaso-con-
strictors. They run in the sympa-
thetic nerve, but have their origin
and center in the spinal bulb.

Vaso-dilator Nerves. — Other fibers

may cause the opposite effect, namely, dilation, and are
therefore called vaso-dilators. Examples of these may be

Lungs -

Heart

Stomach

Fig. 32.

Diagram of vagus

Nerve.

68 PHYSIOLOGY.

found running to the arteries of the limbs. When the
muscles of any organ, say the legs, act, they need a greater
supply of blood. Now, at the same time that nerve im-
pulses are sent to the muscles of the legs to make the
muscles shorten, impulses are sent along other fibers of
the same nerves to make the arteries dilate, and allow
more blood to flow to these muscles.

Vaso-motor Nerves. — The vaso-constrictor and the
vaso-dilator nerves taken together are called vaso-motor
nerves.

Centers of Control of Circulation. — The centers of
control of the blood tubes are in the cerebro-spinal nervous
system. There is no evidence that the sympathetic gan-
glia are centers of reflex action.

Blushing. — How is it that the face sometimes flushes
so suddenly ? Because of some emotion, you say. But
how does the emotion bring this about ? We have already
learned about the muscles in the wall of the arteries. We
are now prepared to understand that in the normal condi-
tion nervous impulses are acting on these muscles, keeping
them partly shortened, and so keeping the arteries of a
moderate size. Under the influence of certain emotions,
the caliber of the arteries is suddenly enlarged, and hence
the change in color.

The Regulation of the Size of the Arteries. — Through
the sympathetic system the blood supply of all the organs
of the body is regulated. Any organ needing more blood
sends a message (nerve impulse) to some nerve center, and
in response nerve impulses are sent to the muscle fibers of
the supplying artery, and the amount of blood sent to that
organ is regulated. For instance, a piece of ice is laid

CONTROL OF THE C/RCULATfOJV.

69

upon the skin of the hand. The part becomes pale, as
the arteries have become narrowed. If this action be con-
tinued, there may set in a decided reaction, and the part
become more red than usual, when the reaction has
widened the artery more than it was
before the constriction.

Effect of Exercise on the Size of the
Arteries. — As there is only a certain
amount of blood in the body, it is evi-
dent that if one organ receives
an extra supply, some other sympathetic
organ or organs must, for the Ganglions
time, receive less. For in-
stance, one begins to walk vigorously.
The large muscles of the lower limbs
and trunk become active, and they need
more blood. They therefore send mes-
sages to some nerve center (probably in
the spinal cord), and by reflex action the
arteries supplying the lower limbs are
widened, and these muscles receive more
blood. But these muscles make up a
very considerable part of the weight and
bulk of the body. While in action they
take the lion's share of the blood. The
brain, at such a time, would receive less, Fig. 33. Ventral Vie
and it would be folly to expect the brain
to work at its full capacity while the
blood was called away to other organs.

of Spinal Cord with
Sympathetic Gang-
lions of One Side.

Regulation of the Effects of Exercise. — When we ex-
ercise vigorously, the heart beats faster, and this of itself
would tend to increase the blood supply to all organs.

70 PHYSIOLOGY.

But this mechanism for widening the channel leading to
the working organs, while the arteries to the other organs
are made smaller, or at least are not enlarged, solves the
problem of supplying each part according to a greatly
varying need, while not sending too much to a part not
needing it.

EFFECTS OF ALCOHOL ON THE CIRCULATION.

" Alcohol stimulates the heart, producing increased force
and rapidity of the cardiac beat. It thus tends to increase
the blood pressure by acting on the heart, and to increase
the flow of blood from the arteries into the veins. The
effect on the blood pressure is, however, partly counter-
acted by a coincident dilatation of the blood vessels of the
skin, which thus become flushed, and tends to produce
more sensible perspiration." — Treatise on Hygiene, STE-
VENSON and MURPHY.

"The warm and flushed condition of the skin which
follows the drinking of alcoholic fluids is probably, in a
similar manner, the result of an inhibition of that part
of the vaso-motor center which governs the cutaneous
arteries." • — FOSTER.

The control of the muscles in the walls of the arteries
being thus interfered with, the circular muscles are no
longer made to shorten, and the artery dilates, thus allow-
ing more blood to flow into it.

We may thus account for the flushing of the skin of the
face, which in many individuals quickly betrays indulgence
in alcoholic drink. If this flushing is too often repeated,
the arteries gradually "lose tone," and the condition be-
comes permanent. The circulation in the whites of the
eyes may be affected, making them "bloodshot."

CONTROL OF THE CIRCULATION. ?1

Similar congestion occurs in the mucous membrane of
the stomach from the presence of alcohol, which may
become a permanent inflammation followed in time by
very extensive changes in appearance and function. It
is said that most of the alcohol swallowed is absorbed
directly from the stomach, and hence the intestines are
not so directly affected.

Good authorities state that alcohol arrests the develop-
ment of the corpuscles. It diminishes the size, alters the
form, and reduces the number of the corpuscles. Since
the work of the blood corpuscles is so important this
reduction in their number and efficiency must very
appreciably affect the nutrition of the body as a whole.
When the blood is " out of order" the body is out of order.

The Blood, — The blood is composed of a clear liquid,
the plasma, and the blood cells, or corpuscles. In a drop
of blood under the microscope the plasma occupies the
clear spaces between the corpuscles. The corpuscles
make up one third of the bulk of the blood, and the
plasma two thirds.

Microscopic Examination of the Blood. — To get a drop of blood
from the finger, wind a cord around the finger, beginning at the base,
drawing the cord moderately tight, until the last joint is reached. By
this time the end of the finger is usually well distended with blood.
With a clean needle make a quick, sharp, light puncture near the base
of the nail ; this ordinarily brings a small amount of blood. Put a
small drop on each of several slides and quickly cover with coverslips.
Examine with a high power.

The Colored Corpuscles. — These are often called the
red corpuscles. But while in the mass they give the
blood a red appearance, individually they are faint yellow-
ish red. In shape they are seen to be circular disks, hol-
lowed on each side like a sunken biscuit. As they are

72 PHYSIOLOGY.

hollowed on both sides they are more accurately described
as biconcave. These corpuscles tend to gather side by
side, in rolls, like coins. They are cells without nuclei.

The Colorless Corpuscles. — In the open spaces be-
tween the rolls of colored corpuscles may occasionally
be found some spherical corpuscles. They are usually

White Corpuscles

HIGHLY MAGNIFIED

White Corpuscle

Red Corpuscles
in Rolls

MODERATELY MAGNIFIED
Fig. 34. Red and White Corpuscles of the Blood.

called the white corpuscles, but are better designated as
the colorless corpuscles, since the others have only a slight
color, and these have none. They usually have a dotted
appearance. It is not so easy to distinguish the two kinds
of corpuscles as it is in the case of the frog's blood, for the
two kinds are more nearly of the same size in the human

CONTROL OF THE CIRCULATION. 73

blood ; and, further, when the colored corpuscles of human
blood are seen flatwise they present a circular outline, while
the frog's colored corpuscles are elliptical. But with a
little study the two may be distinguished. As in the frog's
blood, the colorless corpuscles have ameboid movements,
though they are not very marked unless the blood be
warmed to about the temperature of the human body.

Flexibility and Elasticity of the Corpuscles. — It will
be well here to examine again the frog's web. (See p. 54.)
It will occasionally be seen that when one of the colored
corpuscles is pressed against an angle at the forking of
the blood stream, it is sometimes bent, and that as soon as
the pressure is discontinued the corpuscle springs back to
its former shape, showing that it is elastic.

Frog's Blood. — A drop of frog's blood, mounted as the human blood
was, will be helpful, as there is a very decided difference in the size and
shape of the colored and colorless corpuscles. Further, the colorless
corpuscles of the frog will show ameboid movements, i.e. slow changes
of form, if watched a while.

The Plasma. — The plasma consists chiefly of water,
having in solution various salts, including common salt;
it also contains the nourishing materials for the tissues.
These nourishing materials, obtained from the food by
digestion, consist chiefly of proteids, fats, and sugar. The
plasma also contains waste matters, from the working
tissues, on their way out of the body. How the food is pre-
pared for the building of tissue, and how the waste matter
is removed from the body, we shall study a little later.

The Color of Blood. — The difference in color of an in-
dividual corpuscle and the blood in the mass may be better
understood by comparing it with something that we see
more frequently. A tumbler of currant jelly has a rich,

74 PHYSIOLOGY.

red color, but a thin layer of the same jelly, as when one
takes a spoonful on a plate, has a pale color, more yellow-
ish. The colorless plasma with the colored bodies in it
may be compared to a glass dish filled with cranberries
and water.

Hemoglobin. — The coloring matter in the blood, then,
is wholly in the colored corpuscles. Examination of these
corpuscles shows that their color is due to a substance
called hemoglobin. There is a small amount of iron in
the hemoglobin, and the presence of this small quantity
of iron appears to be essential to give the blood its color.
When we come to the study of respiration we shall see
that the hemoglobin in the corpuscles is the chief agent in
picking up the oxygen from the air in the lungs and carry-
ing it to the tissues in the body.

The Coagulation of Blood. — When the blood escapes
from its natural channels it usually changes from a liquid
to a jelly-like condition. This is known as coagulation.
It is due to the formation of threads of fibrin from the
plasma. These threads of fibrin entangle and inclose the
corpuscles, and the two constitute the clot, or coagulum, as
it is more technically termed. The liquid that afterward
separates from the clot is the serum, and differs from the
plasma only in the removal of the fibrin, which is exceed-
ingly small in quantity, though of great importance in its
action. Many experiments have been made, and much
has been written about the coagulation of the blood, and
perhaps its real cause is not yet clear. But we know that
the coagulation often serves to stop the flow of blood from
wounds, and this is its main use.

Fibrin. — If freshly drawn blood be stirred rapidly with
a bundle of wires (perhaps the most convenient stirrer is

CONTROL OF THE CIRCULATION. ?$

a little roll of wire screen), there will soon collect on the
wires a stringy substance. Thorough washing will soon
leave this colorless. It is fibrin. If the stirring has been
done thoroughly, the blood will no longer clot, no matter
how long it may stand.

Liquid Blood and Coagulated Blood. — The following
scheme shows the difference between the liquid blood and
the coagulated blood : —

( Serum

Liquid Blood

Plasma.

( Fibrin

Clot

Coagulated Blood.

Corpuscles

Amount of Blood. — The blood constitutes about one
thirteenth of the weight of the body. In a body weighing
one hundred and fifty pounds this would be about six
quarts.

Chemical Reaction of Blood. — Blood is alkaline.

Specific Gravity of Blood. — Blood is somewhat heavier
than water, owing to the salts and other matters dissolved
in it.

Quantity of Blood in Different Organs (approximately).
— i. One fourth is in the heart and the larger arteries
and veins (including those of the lungs).

2. One fourth in the liver.

3. One fourth in the skeletal muscles.

4. One fourth in the other organs.

The Lymph Spaces. — We have seen that the capillaries
have very thin walls. Through their walls part of the
plasma of the blood soaks out, and is then called lymph.
It passes into irregular cavities in the tissue called lymph
spaces. Most of these lymph spaces are minute chinks or

76 PHYSIOLOGY.

crevices in the connective tissues of the different parts of
the body.

The Lymph Tubes. — Opening out of the lymph spaces
are irregular passage ways called lymph capillaries, and
these lymph capillaries are continuous with thin-walled
tubes, the lymph tubes. These lymph tubes might be
called the lymph veins, since they join still larger tubes,
closely set with valves, similar to those of the veins. But,
unlike the blood veins, the lymph veins do not gradually
increase in size by confluence. They suddenly form a
large tube, the receptacle of the chyle, beginning in the
upper part of the abdomen. This tube soon narrows and
passes through the diaphragm, close to the spinal column,
and up along the column near the aorta, and empties into
the veins of the neck at the junction of the left jugular
and left subclavian veins. This tube is the thoracic duct,
or the main lymph duct. It has numerous valves, and,
like some of the smaller lymph veins, it presents a beaded
appearance, due to the filling and bulging out of the valves.
In the right side of the neck is a short right lymph duct
which receives lymph from the right side of the head,
neck, and thorax, and from the right arm. The lymph
tubes, as a whole, are usually called the "lymphatics."

Lymph Spaces in the Frog. — In dissecting the frog, the looseness
of the skin is very noticeable. The large spaces under the skin are
lymph spaces. Sometimes considerable lymph is found here, so that
in holding up a frog the sagging of the skin from the weight of the
lymph may be easily seen.

Valves at the Mouth of the Lymph Tubes. — There
are valves where these lymph ducts empty into the veins
which prevent any reflow of liquid into the ducts, but allow
the lymph to pass freely into the veins.

CONTROL OF THE CIRCULATION. 77

Muscle Fibers in the Walls of the Lymph Tubes. -

There are plain muscle fibers in the walls of the lymph
ducts.

Lymphatic Glands. — In its course the lymph passes
through many kernel-like masses, the lymphatic glands.
Lymph contains corpuscles which are considered identical
with the colorless blood corpuscles. It is tho'ught that
these corpuscles are formed in the lymphatic glands.

The Flow of Lymph. — The flow of lymph is partly
due to the blood pressure in the capillaries ; this pressure
is caused by the heart. (In the frog there are two small
hearts, — not, however, near the blood-pumping heart,—
and these pump the lymph along.) In our bodies the flow
of lymph is largely aided by any pressure that may be
brought to bear on the lymph veins ; for, on account of
the valves, as in the blood veins, any pressure must push
the liquid toward the heart. Thus the action of the mus-
cles in the limbs, in the chest, in the abdomen, in the
movements of breathing, and in the bending of the body,
etc., all help in this flow, which is always, probably, very
much slower than that in the blood veins.

Relations of Blood Flow and Lymph Flow. — It will
now be seen that while the blood leaves the left ventricle
by one tube, the aorta, it returns to the right auricle, not
merely by the two caval veins, but that a part of the blood
(i.e. of the liquid part of it) does not return by blood veins,
but having left the blood system proper through the thin
walls of the capillaries, it is brought back to the heart by
the lymph veins, which, however, join the blood veins just
before they empty into the heart. There is, in other
words, only one set of distributing tubes, but there are two
sets of collecting or returning tubes.

PHYSIOLOGY.

Left Jugular Vein

Mouth of Lymph ...
Vein

Right Lymph Vein

Right Subclavian
Vein

Precaval Vein

Postcaval Vein

Main Lymph Vein
(Thoracic Duct)

Lymph Capillaries

Blood Capillaries

Fig. 35. Diagram of the Circulation of Blood and Lymph (Dorsal View).

CONTROL OF THE CIRCULATION.

79

Lymph

Capillary

The Lymph. — Lymph is a clear liquid. (Chyle and
the lacteals will be considered when we study digestion.)
It is more watery than the blood plasma, but contains a
share of all its nutritious substances. Lymph may be
defined as "diluted blood minus red corpuscles." The
blood proper never reaches the tissues.

The Cells of the Body live in Lymph. — The cells
of the tissues are bathed in the lymph which fills the
spaces in the connective
tissue (and we have seen
that the connective tissue
pervades nearly all the tis-
sues of the body), as water
may fill the spaces left
between stones built into
a wall. The cells get all
their nourishment from the
lymph, and into the lymph
they throw all their waste
matter. Each cell may be
compared to an individual
ameba, which lives in
water, and takes all its
nourishment from that
water, and throws all its
waste product into the
same water. As water is
the medium in which the

ameba lives, so we may say lymph is the medium in
which the cells of the body live.

Cells of the Body Aquatic. — The cells of the body,
i.e. all the active, working cells, may, therefore, be said

Oxygen

Food

Water

Other
Wastes

Fig. 36. Relation of Blood and Muscle.
(Lymph being Middleman.)

80 PHYSIOLOGY,

to live an aquatic life, and only dead cells, as of hair,
epidermis, etc., live in air. We might also say that not
only the human body, but all animal life is aquatic.

Importance of Lymph. — We can see that the move-
ment and renewal of lymph are as necessary as the circu-
lation of the blood itself ; is, in fact, the most important
part of it.

Lymph Cavities or Serous Cavities. — We have noticed
the pericardial liquid. There is also a small quantity of
similar liquid around the lungs in the pleural cavities, and
in the abdominal or peritoneal cavity, around the digestive
organs ; also in the cavities of the brain. The liquid in
each case is lymph, and these cavities, often called serous
cavities, are lymph cavities. They communicate with the
lymph tubes.

Dropsy. — In health the amount of the liquid in these
cavities is small, but in certain disorders it may accumu-
late. In general, such affections are called "dropsy."
The lymph may also accumulate in the tissues of the
extremities, causing swelling of the limbs.

Variation in the Composition of Lymph. — It is evi-
dent that the materials needed by the cells of the different
tissues are not the same. So, as one tissue takes certain
materials and another tissue others, it is clear that the
lymph will not be of quite the same composition in the
different parts of the body. This difference is further
due to the difference in the waste products thrown out
by the different cells. Hence the composition of the
blood varies considerably in different regions. But the
lymph from all the tissues unites with the blood from all
the tissues in the right heart, and on their way to it in the

CONTROL OF THE CIRCULATION. 8 1

larger veins. So the constant slight differences in com-
position of the blood and lymph in the various tissues are
counterbalanced by the mingling of the currents from
these various parts in the large arteries and veins.

The Spleen. — The function, or functions, of the spleen are not well
understood. It is believed to have something to do with the renova-
tion of the blood, perhaps forming colorless corpuscles and destroying
colored corpuscles. At any rate, the physiologists generally call it a
blood gland. It is unlike true glands in that it has no duct, and forms
no secretion to be poured into any cavity, like the glands of excretion
and secretion. It has been found, in the case of accidents to man, and
by experiment on the lower animals, that life may continue after this
organ has been removed.

Massage. — A system of pressing, rubbing, and knead-
ing the muscles is known as massage. It helps the flow
of the blood and lymph, thus aiding in washing out the
waste products from the muscles and other parts of the
body that are to be reached by pressure. We have seen
that one of the benefits of exercise is to promote the cir-
culation of the blood and of the lymph, and so to help
get rid of the waste matters that are produced by the
activity of the various organs. Many invalids cannot take
active exercise. So this passive exercise may very fairly
take its place, and assist in the nutrition of the tissue by
accelerating the flow of blood and lymph, bringing new
nourishment and carrying away wastes. For students
who do not take sufficient exercise it is a good thing to
rub the body thoroughly and briskly, not only after a
bath, but often with the hands or with a dry towel.

Transfusion of Blood. — Transfusion of blood is the transfer of
blood from the blood vessels of one animal to those of another. Trans-
fusion may be direct or immediate, as when the blood vessels of the
two animals are connected by tubing so that the blood passes from one
to the other without exposure to the air ; in indirect or mediate trans-

82 PHYSIOLOGY.

fusion the blood is first drawn into a receptacle. In indirect transfusion
the blood is often defibrinated before transference. The blood may be
introduced either into an artery or a vein; if -into a vein it is sent in
the direction of the natural flow, i.e. toward the heart ; if into an artery,
in either direction. Soon after the discovery of the circulation of the
blood the operation of transfusion began to be practiced, and high
hopes were indulged in as to its value. But it was soon found to be
attended by so much danger that it is now seldom used. It is resorted
to (i) after great loss of blood, (2) after some forms of poisoning part
of the blood is withdrawn and replaced by fresh blood, and (3) in
certain disordered conditions of the blood. The chief dangers are (i)
the introduction of air which forms minute bubbles and stops the blood-
flow in the capillaries, (2) the introduction sometimes causes coagula-
tion within the blood vessels, and (3) the serum of the introduced
blood sometimes destroys the corpuscles of the blood to which it is
added. In the earlier practice lamb's blood was employed, but now
when transfusion is practiced on man only human blood is used. It
has been found safer and better after great loss of blood from hemor-
rhage, to introduce a salt solution of about the natural degree of salt-
ness of the blood ; this restores the normal volume of circulating liquid,
and avoids most of the dangers except that of introducing air. The
numerous fatal results of this operation have shown that it should not
be resorted to except in cases of extreme necessity.

For directions about stopping the flow of blood from
wounds see Chapter XXIII. and the books named below.

READING. — Prompt Aid to the Injured, Doty ; Emer-
gencies, Dulles; Emergencies, Howe; First Aid to the
Injured, Lawless; First Aid to the Injured, Morton; First
Aid in Illness and Injury, Pilcher ; Sickness and Accidents,
Curran.

What other process keeps pace with the coursing of the
blood through the body, being its running mate, so to
speak ?

Summary. — i . Blushing, and other variations in blood supply, are
under the control of the sympathetic nervous system.

2. The sympathetic nervous system consists of two rows of ganglia

CONTROL OF THE CIRCULATION". 83

in the body cavity near the spinal column, with fibers running to the
internal organs. It is also connected with the cerebro-spinal nervous
system.

3. The heart beat is automatic and rhythmic.

4. The heart beat is regulated by the sympathetic nervous system
and by the vagus nerves.

5. The blood consists of a liquid, the plasma, in which float the
colored and colorless corpuscles.

6. When blood is shed it coagulates, tending to check its own
escape.

7. Lymph is like the blood diluted and lacking the colored cor-
puscles.

8. A set of lymph tubes conveys the lymph into the veins to join
the flow toward the heart.

9. In its course the lymph passes through the lymphatic glands.

Questions. — i. What makes the hands grow red and puff up on
sitting in a warm room after snow balling?

2. How is a mustard plaster effective?

3. Why does light exercise before retiring promote sleep?

4. Why are the feet often cold after studying?

5. How does the application of ice, or cold water, relieve head-
ache?

6. Why should the clothing be changed after getting wet?

7. What is the meaning of humor, in the expressions "good-
humored," " bad-humored " ? Have these expressions a real physio-
logical significance?

CHAPTER VI.

RESPIRATION.

The Close Relation between Circulation and Respira-
tion. — Is it not a very striking fact that we take one
breath for every four heart beats ? That whatever quick-
ens the breathing also quickens the heart, so that the two

always keep in al-
most the same ratio ?
Let us learn what
are the many inti-
mate relations of
the blood pump and
the air pump, the
blood system and
the air system, of
Circulation and Res-
piration.

The Organs of
Respiration.—

1 . The lungs and
air tubes.

2. The structures
which increase and diminish the size of the chest, princi-
pally the diaphragm, and the muscles acting on the ribs.

The Parts of the Lungs. — i. The Air Vesicles, an

immense number of small sacs, which communicate with

84

Fig. 37. The Trachea and Bronchial Tubes, showing
Two Clusters (Alveoli)) of Air Vesicles.

RESPIRATION.

1. Pulmonary Orifice

2. Aortic Orifice

3. Left Auriculo-Ventricular Orifice

4. Right Auriculo-Ventricular Orifice

The heavy black line between the heart and the liver represents the diaphragm.

Fig. 38. Front View of the Thorax. The Ribs and Sternum are represented in

Relation to the Lungs, Heart, and other Internal Organs.

86

PHYSIOLOGY.

the outer air by the bronchial twigs, the bronchi, and the
trachea.

2. The Pulmonary Capillaries, forming a thick network
around and between the air sacs. These capillaries receive
their blood from the pulmonary artery, and return it to the
heart by the pulmonary veins.

Elastic Tissue in the Lungs. — The air vesicles, with
their supplying air tubes and their surrounding blood tubes,
are bound together by elastic tissue, which fills up most of
the intervening space.

The Windpipe or Trachea. — The windpipe has in its
walls C-shaped cartilages, with the open part of the C
on the dorsal surface. These cartilages continue in the
bronchi, and so on until in the smaller twigs they finally
disappear. The cartilages are held together, and the
dorsal gap of the cartilages (the gap would be like that of
a series of horseshoes piled one on top of another) bridged,
by tough fibrous tissue, with much elastic tissue, and
with plain muscle fibers ; the plain muscle fibers are very
abundant in the smaller air tubes.

The Mucous Membrane. — The lining of the trachea

is a mucous mem-
brane. It pours
out on its surface
a substance some-
what like white of
egg, called mucus.
This keeps the air

Fig. 39. Ciliated Cells lining the Air Tubes (x 300).

particles of dust that are in the inspired air. There is a
constant slow current of mucus toward the throat, whence
it is, from time to time, hawked up.

RESI'IRATION.

Cilia. — This current of mucus is caused by the cilia
projecting from the lining cells of the trachea. They are
little hairlike projections, in countless numbers, like a field
of grass, each stalk having the power of bending back and
forth, making a quick stroke toward the throat, then a
slower recover stroke. Thus the united wavelike action
of the myriads of lashing cilia paddles the mucus head-
ward. It is a very common error to suppose that the cilia
produce air currents. This is not their function, and it
can readily be seen that they cannot create currents of air,
as they are wholly submerged, like grass growing on the
bottom of a shallow pond of slimy water.

Location of Mucous Membrane. — All the cavities and
passages in the body to which the air has access, such as
the digestive and respiratory passages, etc., are lined by
mucous membrane (not all

Ciliated). Trachea

The Pleura.— The out-
side of each
lung is cov-
ered by a thin
adherent mem-
brane, the pleu-
ra, which com-
pletely invests
it, except at the root of
the lung, where the bron-
chus and blood tubes
enter. Here the pleura
turns toward and adheres to the inner wall of the chest,
forming its lining (still called the pleura), and below passes
over the anterior surface of the diaphragm. The lung is

Pleural Space
(Exaggerated)

Chest Wall- -•

~~~ Pleura

Fig. 40. Diagram of the Lungs and Pleurae.

88 PHYSIOLOGY.

thus free, except at its root, where the air and blood tubes
enter. A very small quantity of liquid moistens the con-
tiguous surfaces of the pleurae on the outside of the lung
and the inside of the chest wall, so they move easily one
upon the other during respiration. As the lungs are
always distended enough to fill the chest cavity, these two
surfaces are always in contact. In pleurisy (inflammation
of the pleurae) pain is felt in breathing from friction or
adhesion of these surfaces.

Important Facts concerning Respiration. — In study-
ing respiration, let us constantly keep in mind these
facts : —

1. The lungs are highly elastic, and

2. Highly porous, each air vesicle being in direct com-
munication with the outer air by means of

3. Air tubes that always stand open

4. And are always moist internally.

5. The pulmonary capillaries closely invest each air
vesicle.

6. The lungs are always expanded enough to fill all
the space in the chest not occupied by other organs, and

7. Freely movable, except at the place of entrance of
the bronchi and blood tubes.

8. The smooth, moist pleurae.

The Diaphragm. — The diaphragm is a thin muscle
making a complete partition between the abdominal cavity
and the chest cavity. It is convex anteriorly, concave pos-
teriorly ; its ventral border is attached to the inside of the
chest wall about opposite the lower end of the breast bone,
thence obliquely along the border of the ribs (as felt in
front), and the dorsal attachment is posterior to the ventral

RESPIRATION'.

89

attachment. Its general position is shown in Figs. 38, 40,
and 43.

To show the Action of the Diaphragm and Lungs. — MATERIAL. —
Bell jar with stopper, sheet of rubber large enough to cover the mouth
of the jar, toy rubber balloon, cork (rubber preferred), glass tube, strong
rubber band (such as boys use for slung shots), marble.

Triangularis Sterni
Internal Mammary Vessels v.

Left Phrenic
Nerve

Pleura
Puimonalis

Pleura Costalis

Mediastinum \ Sympathetic Nerve

( Thoracic Duct

Vena Azygos Major I posterior
, Pneumogastric Nerves )

Fig. 41. A Transverse Section of the Thorax, showing the Relative Position of the
Viscera and Reflections of the Pleurae.

PREPARATION. — Lay the marble on the center of the sheet of rub-
ber, double the rubber over it, stretching the rubber strongly over the
marble, and tie the marble firmly in its place. Stretch the sheet of
rubber over the mouth of the jar with the projection made by the marble
on the outside, and fasten with rubber band. Bore a hole in the cork,

90 PHYSIOLOGY.

and fix the glass tube snugly in it, so that the lower end of the tube will
extend about half-way down the jar. Tie the balloon on the lower end
of the glass tube.

EXPERIMENT i. — Inflate the balloon. Consider that it requires
some expenditure of energy to do this. When the mouth is taken away
from the tube the balloon immediately collapses.

EXPERIMENT 2. — Insert the balloon and tube into the jar, but do
not cork, and repeat Experiment i. The same results as before are
noticed, and it will further be seen, or rather heard and felt, that when
the balloon is inflated some air comes out of the jar around the tube,
and when the balloon collapses air again enters the jar.

EXPERIMENT 3. — Again inflate the balloon, and while it is inflated
tightly cork the jar. If all the parts fit well, the balloon should now
remain inflated. This may at first seem strange, as the mouth is taken
away from the tube, and the tube left entirely open to the air. But it
will be seen that to just the extent that the balloon contracts, so much
more space is left in the jar outside the balloon. This means diminished
pressure, and the pressure of the outer air presses the diaphragm up,
and keeps the balloon partly distended, maintaining equilibrium.

EXPERIMENT 4. — Pull the diaphragm down, using the marble as a
handle. This shows the expansion of the lung by the pressure of the
external air when more space is given by the depression of the dia-
phragm. On releasing the diaphragm, it springs upward, and the
balloon becomes reduced in size, driving out part of the air that was in
it. This shows how expiration is accomplished, so far as the diaphragm
is concerned.

If a bell jar be not at hand, a lamp chimney or a quart bottle may be
used, after cutting off the bottom, as follows : File a deep notch across
near the bottom ; heat an iron rod, and apply the end of it to one end
of the notch, and slowly draw the rod around to the other end of the
notch (the rod may need to be reheated) . After cracking off the bot-
tom of the jar, file the edges so they will not cut the rubber.

Let each pupil make a drawing, showing the position of the parts in
inspiration and in expiration.

Illustration of the Minute Anatomy of the Lung. — To illustrate
the minute anatomy of the lung, take a rubber balloon, a glass tube,
two rubber tubes, one dyed red, the other blue, a bag of netting, with
one side dyed red and the other side blue. Tie the balloon on the end
of the glass tube, slip the bag of netting over the balloon and tie it,

RESPrRATION. 91

with the ends of the rubber tubes on the corresponding sides of the
bag. Slip a short piece of the rubber tube on the end of the glass
tube, and when the balloon is inflated shut the air in by means of a

CILIA I i.BRONCHIAL TUBE.

Fig. 42. Minute Structure of the Lungs, showing Air Vesicles
and Capillaries.

pinchcock. The balloon represents an air vesicle, the glass tube a
bronchial twig, the blue tube a subdivision of the pulmonary artery,
the netting the capillaries around the vesicle, and the red tube one of
the branches of the pulmonary veins.

The Movements of Respiration. — The process of res-
piration consists of two acts, inspiration and expiration.

Two Active Forces in Inspiration. — In inspiration
the principal active forces in the body are, first, the dia-
phragm ; and, second, the muscles which elevate the ribs.

Work of the Diaphragm in Inspiration. — The dia-
phragm is a muscle, and when its fibers shorten, the dia-
phragm is pulled down. In moving down it presses on
the abdominal organs, and makes the abdomen protrude
laterally and ventrally. This lowering of the diaphragm
increases the space in the chest ; the air already in the

PHYSIOLOGY.

chest expands to fill this greater space. When expanded
it exerts less pressure than before, and the air outside,
having greater pressure, enters till equilibrium is produced.
The air enters through the trachea, presses on the inside
of the elastic lungs, and makes their bases extend, follow-
ing the diaphragm in its descent. The bases of the lungs
remain in contact with the upper surface of the diaphragm
all the time.

. . . . Increased Air
Space

Inspiration Expiration

Fig. 43. Diagrammatic Sections of the Body in Inspiration and Expiration.

Work of the Chest Walls in Inspiration. — Certain
muscles of the chest wall elevate the, ribs and breast bone.
This act widens the chest, and the air, as before, presses
in through the open trachea, and keeps the sides of the
lungs in contact with the inner surfaces of the chest walls.

Effort required in Depressing the Diaphragm. -
Inspiration requires considerable effort, because the dia-

RESPIRATION. 93

phragm in its descent presses upon the elastic organs of
the abdomen (stomach, liver, etc.), and these organs, in
turn, are pressed against the elastic walls of the abdomen.
It is somewhat like pressing a pillow down into a rubber
bag; the pillow springs up as soon as the pressure is
stopped, because of its own elasticity as well as that of the
bag. Therefore, as soon as the diaphragm relaxes, the
elastic walls of the abdomen retreat, and the abdominal
organs rise to their former place.

Effort Required in raising the Ribs. — When the ribs
are elevated, the cartilages which connect the ventral ends
of the. bony parts of the ribs with the breast bone are
slightly bent. When the muscles relax, the elasticity of
the rib cartilages helps to bring the ribs back to their
former position, thus reducing the chest to its former
width.

Expiration Easy. — Thus we see why expiration is easy ;
in fact, " does itself " (in ordinary respiration) by elastic
reactions. But inspiration is harder than it would be if it
were not for the fact that the descent of the diaphragm
meets resistance, and the ribs, in rising, have to overcome
resistance in bending the costal cartilages, and in raising
the weight of the chest walls and shoulders.

Potential Energy stored in a Door Spring. — When
one opens a door that has a spring to shut it, he has to
expend more energy to open the door than he would if he
did not have to bend (twist or compress) the spring at the
same time. But no effort is needed to shut the door. The
door was opened and shut at the same time ; i.e. when
the door was opened force was stored in the spring (in the
form of what is called potential energy), and this stored
energy shuts the door while we pass on. We can better

94 PHYSIOLOGY.

afford to employ more energy while opening the door than
to take the extra time to shut it. If, then, a door with such
spring were fastened open, it might remain open for a long
time. When released it flies shut. If one, in this case,
asks, "Who shut the door?" the answer is, "The person
who opened it."

The Storing of Energy during Inspiration. — So in

the act of inspiration we perform a double work in storing
energy by which the expiration is performed without active
muscular effort.

Review of Forces of Respiration : —

FORCES OF INSPIRATION.

1. Depression of the diaphragm.

2. Muscles elevating the ribs.

3. Pressure of the external air.

RESISTANCES TO INSPIRATION.

1. Compression of the abdominal organs and stretching
abdominal walls.

2. Bending the rib cartilages and lifting the chest.

3. Stretching the lungs.

ELASTIC REACTIONS OF EXPIRATION.

1. Elastic reaction of the abdominal walls and contents.

2. Elastic reaction of the rib cartilages.

3. Elastic reaction of the lungs.

Forced Respiration. — Thus far we have been speaking
of ordinary respiration. In forced respiration, as in shout-
ing, many muscles are brought into play to expel the air
rapidly and forcibly. In such an act as coughing there is
vigorous action of the abdominal muscles.

RESPIRATION. 95

Abdominal and Thoracic Respiration. — The main part
of respiration is performed by the diaphragm, and the more
common mode of respiration is therefore called abdominal
or diaphragmatic respiration. In women of the civilized
races respiration is more largely accomplished by the action
of the thoracic muscles, and is called thoracic or costal res-
piration. In children the respiration is of the abdominal
type.

The Rate of Respiration. — The rate of respiration in
the adult varies from sixteen to twenty-four per minute,
the average being about seventeen times a minute ; about
one respiration for every four heart beats. Light is favor-
able to respiratory activity. The rate is affected by the
position of the body, state of activity, temperature, diges-
tion, emotions, age, disease, etc. Ordinary inspiration
takes slightly less time than expiration.

Modifications of Respiration. — Coughing is a forcible expiration,
usually directed through the mouth, and for the purpose of getting rid
of some foreign substance, or caused by irritation. In sneezing there is
first a deep inspiration, and then the current of air is forced out, chiefly
through the nose. Sneezing may be prevented by pressing firmly on
the upper lip. Crying, laughing, sobbing, are modifications of respira-
tion connected with certain emotions. Yawning and sighing are deeper
breathings, caused by etijiui, depressing emotions, or a deficient ventila-
tion. Hiccuping is sudden inspiration, produced by spasmodic action
of the diaphragm, accompanied by sudden closure of the glottis, and is
often caused by some disorder of stomach digestion. Snoring is caused
by breathing through the mouth and setting the soft palate into vibra-
tion. Sniffing is sudden inspiration : the diaphragm is suddenly pulled
down, the air in the nasal cavity is thus drawn downward, and the air
we wish to test, or the odor we wish to inhale, is thus drawn into the
upper nasal cavities ; whereas in ordinary inspiration most of the air
passes along the lower part of the nasal passage. In hawking, the air
is forced out through the narrowed passage between the root of the
tongue and the soft palate to remove mucus. Gargling is forcing air up

96 PHYSIOLOGY.

through liquid held between the tongue and the soft palate. Panting,
whistling, blowing, spitting, sucking, and drinking are also modifica-
tions of respiration. In case of choking it is well to hold the head for-

Jl

II

COMPLEMENTAL AIR.

120 CUBIC INCHES.
AIR THAT CAN BE BUT SELDOM IS TAKEN IN.

TIDAL AIR.— 20 to 30 Cubic Inches Air Taken in
and Sent out at Each Breath.

RESERVE AIR.

100 CUBIC INCHES.

m

^ AIR THAT CAN BE BUT IS SELDOM DRIVEN OUT.

RESIDUAL AIR.

100 CUBIC INCHES.

AIR THAT CANNOT BE DRIVEN OUT.

II

t>

-S -S

-

QU

Figr. 44. Diagram of Lung Capacity.

ward, and perhaps downward. A smart slap between the shoulders
sometimes helps dislodge anything stuck in the throat, and it may be
necessary, in addition, to hold a child with its head downward.

RESPIRATION. 97

Capacity of the Lungs. — Have the class stand, and each pupil raise
his right hand.

1 . Tidal Air. — Let all breathe together, at the ordinary rate and
depth, and let the hand rise about three inches during inspiration, and
fall again during expiration. The amount of air taken in at an ordinary
breath is from 20 to 30 cubic inches, or about a pint. This is called
tidal air.

2. Complemental Air. — As before, let the hand go up and down
with the breathing, but at the end of the third inspiration, instead of
stopping with the usual amount, keep on breathing in as much as pos-
sible, letting the hand rise accordingly. This air that can be taken in
above the ordinary breath is called the complemental air, and it is
estimated to be, on the average, about 120 cubic inches.

3. Reserve Air. — Begin as before, and at what would be the end
of the third expiration continue to drive out as much air as possible,
indicating the degree by correspondingly lowering the hand. This air
that can be breathed out beyond the ordinary expiration is called the
reserve air, and is reckoned at about 100 cubic inches.

4. Residual Air. — The air cannot all be breathed out. The re-
mainder is called the residual air, and is computed to be about 100
cubic inches.

The Vital Capacity. — All the air that can be breathed out after a
full inspiration, i.e. the sum of the complemental, tidal, and reserve
air, would be about 240 to 250 cubic inches, and is called the vital
capacity. Of course these figures represent only the average of cer-
tain experiments and observations. By practice any one can con-
siderably increase his vital capacity.

A Test of the Capacity of the Lungs. — A simple method of
measuring these stages of respiration is to take a gallon bottle and
first carefully graduate it to pints by pouring in water and marking on
the outside with a file. Then invert the bottle in a trough of water,
and inhale from it by means of a rubber tube. Or fill the bottle, in-
vert in water, and exhale into it.

Hygiene of Breathing. — Those persons who take con-
stant exercise in the open air are likely not to suffer much
from deficient respiration. But persons following seden-

98 PHYSIOLOGY.

tary occupations, such as that of the student, not calling
for deep breathing (and often the air taken in is of poor
quality), need to pay especial attention to the matter.

Breathing through the Mouth. — We should breathe
through the nose, and not through the mouth. The nasal
passages are fitted for the introduction of the air (i) by
being narrow, but of large area; (2) by having their lining
membranes richly supplied with blood ; (3) by the abun-
dant secretion of mucus by this membrane. The air,
coming through this narrow channel, is warmed, and a
large part of any dust it may contain is caught by the
sticky mucus that covers all the walls of this passageway.
If we breathe through the mouth (especially out of doors
in cold weather), the air may not be sufficiently warmed
before entering the lungs, and much more dust would be
carried into the lungs. Then, too, the air has a drying
effect on the throat, whereas the mucus of the nasal pas-
sages will moisten the air as it enters. The cilia, which
extend from most of the cells lining the respiratory pas-
sages, are constantly causing the mucus to slowly flow
toward the external opening, so a good share of the dust
is gotten rid of. A further advantage of breathing through
the nose is that we detect odors, and can thus judge of the
quality of the air.

Breathing and Circulation. — The fact has been noted
that breathing directly aids the circulation of the blood.
This is due to the way air pressure is made to affect the
large veins. Breathing also may very considerably aid
the flow of lymph. Every deep inspiration brings pres-
sure to bear on the main lymph duct as the diaphragm
descends. Every forced expiration has the same effect.
We must keep in mind that the tissues are fed directly by

RESPIRATION. 99

the lymph that surrounds them ; that while the lymph is
continually fed by the blood, there is not a great pressure
given in this way. The lymph stream is largely depend-
ent on the pressure of the surrounding organs. When
one takes a good deal of muscular exercise the lymph is
renewed with rapidity enough to supply the tissues with
food, and to carry away their wastes. But in those who
sit quiet a large share of the day, taking no more exercise
than is necessary to take them to and from their places
of business, the lymph becomes too nearly stagnant, the
tissues are not well nourished, and the whole body suffers.

Deep Breathing. — It is a grateful relief to the whole
system to stand, stretch, inhale deeply and slowly several
times, and to repeat this every hour or so. Every one en-
gaged in office work or studying should form this habit,
especially if he does not give an hour daily to exercise in
a gymnasium, or otherwise.

Respiratory Sounds. — During respiration sounds are
produced by which the skilled physician can tell much as
to the condition of the respiratory organs.

The Control of Respiration. — Breathing is an involun-
tary act. Still we can modify it. We can hold the breath
for a time ; but it is stated that one cannot hold the breath
long enough to produce death by suffocation.

The muscles of respiration are under the control of
nerves. The center of respiratory control is believed to
be in the lower portion of the spinal bulb. This respira-
tory center is one of the most vital points in the body, for
if it is destroyed, breathing is completely stopped, and
death ensues. This center is affected by the condition of
the blood. For instance, if the blood going to this center
has not enough oxygen, the center hastens the process

100 PHYSIOLOGY.

of breathing by nerve impulses sent to the muscles of
respiration.

The Control of the Diaphragm. — The diaphragm is
under the control of the phrenic nerves, which arise from
the third, fourth, and fifth cervical nerves. If the neck is
broken above the point where these nerves are given off,
death almost always immediately follows, because the con-
nection of the respiratory center and the diaphragm is
broken.

Composition of Dry Air (by volume) : —

Oxygen . . . . . . .... . 2 1 .00

Nitrogen . . . . . v . . . . . 79.00 .

Carbon Dioxid .04

100.04

Experiments illustrating the Chemistry of Respiration. — EX-
PERIMENT i . — If a piece of phosphorus be burned under a fruit jar
inverted and with the mouth under water (for directions consult any
chemistry), the oxygen will be consumed and water will enter part way
to take its place. The remainder is nitrogen.

EXPERIMENT 2. — If a burning taper be lowered into this nitrogen,
the flame will be extinguished.

EXPERIMENT 3. — If a chemical laboratory is at hand, some carbon
dioxid should be generated and tested to -show that it extinguishes
flame.

EXPERIMENT 4. — Lime water is the test of carbon dioxid, and may
easily be prepared by putting a piece of quicklime the size of a hen's
egg into a quart of water.

EXPERIMENT 5. — Pour a little clear lime water into a jar contain-
ing carbon dioxid, and on shaking the contents the lime water will be
rendered milky.

EXPERIMENT 6. — By means of a tube (a straw will serve) breathe
through a small quantity of lime water to show that there is carbon
dioxid in the expired breath.

EXPERIMENT 7. — If a jar be inverted over a lighted taper, the flame
will soon be extinguished. Test the gas with lime water to see that
carbon dioxid is produced by a burning candle.

RESPIRATION. IOI

EXPERIMENT 8. — By holding a clean, cold tumbler over a burning
taper it will be seen that water vapor is produced by the burning.

EXPERIMENT 9. — Breathing into a clean, cold tumbler shows that
water is produced also in the process of respiration.

EXPERIMENT 10. — A very brilliant experiment and one that is very
instructive at this point is to burn a watch spring in oxygen. In this
process the oxygen unites with the iron, forming iron oxid.

EXPERIMENT n. — If a piece of watch spring be placed in water, it
will soon rust. Rust is also an iron oxid, only the process is slow,
instead of rapid as in the case of combustion, and just as much heat is
given off, but not much at any given instant.

EXPERIMENT 12. — If a short piece of magnesium ribbon can be
obtained, it may be burned in the presence of the class, though it is not
well to look long at the excessively strong while light.

EXPERIMENT 13. — Ma£nMslimi;wild also 'ru^'in water, forming a
white rust, or magnesium oxid, as in burning. , , , ,

EXPERIMENT 14. — If a <fer be ftlz& whVthfi jsScwiy expired breath,
capped tightly, and set in a warm place it will acquire a bad odor.

EXPERIMENT 15. — Hold a thermometer at arm's length. It indi-
cates the temperature of the air — of the air that you are breathing in.
Breathe for a few minutes upon the bulb of the thermometer, and the
fact is clearly shown that the air we breathe out is much warmer than
the air that we breathe in.

EXPERIMENT 16. — With a pair of bellows force the air of the room
through a small quantity of lime water. By continuing this process a
long time it may be shown that there is carbon dioxid in the air, but not
nearly so much as in the expired breath.

Result of Experiments. — These experiments show that
breathed air has gained : —

1. Heat.

2. Water vapor.

3. Carbon dioxid.

4. Waste products, or impurities, having no definite
name, because not well known, highly putrescible, often
called by the general name of ''organic waste matter."

102

PHYSIOLOGY.

IN 10,000 VOLUMES.

i Represented by Largo Square.)

PER CENT.

AMOUNT OF CARBON

DIOXID.

IN

INSPIRED AIR. EXPIRED AIR.

4 400

(Small Square.) (Medium Square).

.04 4

COMMON FRACTION —^~

r

25

20 100

Fig. 45. Amount of Carbon Dioxid in Inspired and Expired Air.

The Composition of Inspired and Expired Air. -

Oxygen. Nitrogen. Carbon Dioxid.
Inspired air ... 21 79 .04

Expired air ... 16 79 4.00

While the amount of nitrogen remains about the same,
some oxygen has disappeared, and its place is taken by
carbon dioxid, while the amount of carbon dioxid has in-
creased a hundred-fold.

RESPIRATION.

103

Exchanges between the Air and the Blood in the
Lungs. — Whatever the air coming from the lungs cen-
tains that was not in the air entering them, it has taken
from the blood, and what the air has lost it has given to
the blood. The air in the air vesicle is separated from the

BRONCHIAL TUBE

FROM PULMONARY ARTERY

TO PULMONARY VEIN

Fig. 46. Exchanges between the Air and the Blood in the Lungs.

blood in the pulmonary capillaries only by the thin wall of
the air vesicle and the thin capillary wall. Carbon dioxid,
water, and other waste matters pass from the blood through
this thin partition into the air vesicle, to be sent out by
later expiration. Oxygen from the air in the vesicle passes

104 PHYSIOLOGY.

through these layers into the plasma, and most of it is
quickly picked up by the colored corpuscles. The colored
corpuscles are the carriers of oxygen.

Hemoglobin and Oxy hemoglobin. — As has already
been stated, the hemoglobin in the colored corpuscles has
an affinity for oxygen. Hemoglobin is of a dark color,
and gives the dark color to the blood which enters the
lungs. When oxygen unites with the hemoglobin it forms
oxyhemoglobin, which is of a bright red color. Hence
the change in the color of the blood in the lungs from a
dark bluish red to a bright scarlet. This bright blood is
usually called "arterial," and the dark "venous"; but it
must be remembered that the blood in the pulmonary
artery is dark, and in the pulmonary veins bright.

Amount of Oxygen Used. —We take into the blood
only about one fourth of the oxygen of the air that passes
through the lungs. In like manner the blood, passing
through the tissues, gives up to those tissues (in ordinary
circumstances) only about half the oxygen it contains (per-
haps holding the remainder as a reserve).

The Gases in the Blood. — If a quart of blood be placed
under the receiver, and the air exhausted, it will be found
that the blood contained about three fifths of a quart of
gas. This gas is a mixture of oxygen, carbon dioxid, and
nitrogen, and the proportions vary according to the kind
of blood taken. If from the left heart, or pulmonary veins,
there will be more oxygen and less carbon dioxid ; if from
the right heart, pulmonary artery, or caval veins, there
will be less oxygen and more carbon dioxid. Oxyhemo-
globin blood ("arterial blood ") contains about one fifth its
volume of oxygen. Hemoglobin blood ("venous blood")
contains about one tenth its volume of oxygen. Oxy-

RESPIRATION.

105

hemoglobin blood holds about two fifths its bulk of carbon
dioxid, while hemoglobin blood has nearly one half its
bulk of carbon dioxid.

, THE GASES IN THE BLOOD.

From 100 volumes of— May be obtained

Oxygen. Carbon dioxid. Nitrogen.

Oxyhemoglobin (arterial) blood . 2ovols. /pvols. ito2vols.

Hemoglobin (venous) blood . . lovols. 46vols. ito2vols.

Illustration of the Changes in the Color of the Blood. — The

changes that take place in the color of the blood, both in the lungs
and in the tissues of the other parts of the body, may be illustrated as

Fig. 47.

follows : Prepare a heart as directed on page 45. Use for the liquid a
strong solutiofl of litmus, neutralized or slightly alkaline ; place in the
throat of each funnel a small sponge. Saturate with ammonia the
sponge in the funnel representing the capillaries of the body, and

106 PHYSIOLOGY.

saturate with hydrochloric acid the one in the funnel representing the
capillaries of the lungs.

Now, on working the heart the liquid will change from red to blue
in the funnel representing the body, and from blue to red in the funnel
representing the lungs.

" Anatomically there are two lungs, and the heart lies between them ;
physiologically, the lungs form a single organ, which is interposed be-
tween the two hearts." — WILDER.

The Changes in the Blood. — What does the blood do
with the oxygen that it gets in the lungs, and where did it
get the carbon dioxid and other impurities that it brings
to the lungs ? Let us follow the blood and see. From
the pulmonary veins the blood goes to the left heart, and
is pumped to all the tissues except the lungs. Let us-
follow a branch of the aorta that leads to a muscle.

The Production of Heat and Motion in the Body. -

When a muscle works it becomes warmer. This has been
repeatedly proved by experiment. We know that we feel
warmer when we exercise. We know that the blood is
flowing more rapidly through the muscle when it is at
work. This more rapid stream brings the muscle more
oxygen. This it needs, for the heat of the muscle is pro-
duced by the oxidation of substance in the muscle. We
have seen that the oxidation of iron produces heat, and it
is the oxidation of the materials in the candle that enable
it to give out heat. But our bodies do not give out the
intense heat of a burning candle, nor do they produce
light, as is the case with the oxidation of iron and magne-
sium when those metals are burned. The slow oxidation
of the metals, in the presence of moisture, is more like
the oxidations in our bodies. It is by the oxidations of
the muscle (or substance in it) that the muscles produce
heat and that form of energy which gives motion. In the

RESPIRATION.

Case of the rusting of the metals there is as much heat pro-
duced as when they are burned, but the heat is so slowly
generated that it is given off about as fast as it is pro-
duced, and we do not notice it. The oxidation produces
the waste matters, just as the burning of the various
substances produces waste.

Oxidation of Live Tissues and Dead Matter. — In our

experiments with oxygen we see that substances which
burn in air will burn still more actively in oxygen. But
we must not infer from this that in our bodies the oxida-
tion of the tissues would be faster in pure oxygen. This
is not the case. The tissues take as much oxygen as they
need (if they can get it), and they will not take any more
than they need, no matter how much is offered them. It
does not injure the body, nor any part of it, to breathe
pure oxygen. It does not make one feverish, it does not
produce any more heat, nor make one "live faster." This
point should be specially noticed,- as it was formerly sup-
posed that the oxidation of the tissues of the body was
just like any combustion of dead material. But the tissues
are alive. They know their own needs. Each cell takes
what it requires and no more, just as it does of food
brought to it by the blood. The amount of oxygen pres-
ent does not determine the degree of muscular activity,
but the degree of muscular activity determines the amount
of oxygen consumed.

Increased Blood Flow is the Result of Exercise. -
When we exercise, the muscles need more oxygen. They
also need to have removed the waste matters that they are
so rapidly producing at this time. How is the oxygen
brought and the waste removed ? By the blood, you
answer. True ; but what makes the blood come and

I08 PHYSIOLOGY.

go faster at this time ? By reflex action, you reply. The
muscles send a message to a nerve center, and this nerve
center sends back a message to the blood tubes, making
them widen, and the heart also may be made to beat
faster. But would it do any good to have the blood flow
through the muscles faster, if it could not bring more oxy-
gen, and take away and get rid of more wastes ? You
will say no. To give the extra oxygen, and take out the
carbon dioxid, the lungs cannot, of themselves, take in and
send out air. The work of pumping air depends on the
muscles of respiration, the diaphragm, and the muscles
that elevate the ribs. These will not work faster unless
they are ordered to do so. A message must be sent to
these telling of the need in the muscles that we are con-
sidering, say one of the large muscles of the lower limbs.
Thus, by a series of reflex actions, all these processes are
kept in harmonious relation to each other. It must be
borne in mind that increased blood flow is the conse-
quence, and not the cause, of the increased activity of the
tissues.

Temperature of the Body. — Insert the bulb of a thermometer into
the mouth, and keep it there three or four minutes to find the tempera-
ture of the inside of the body. For this it is better to use a clinical
thermometer, if one can be obtained. The average temperature of the
tissues within the body is about 98.5° F.

How the Body is like a Stove. — The body may be
compared to a stove. Into one we put fuel and produce
heat. In the other we get heat from food.

How the Body differs from a Stove. — But the body is
not like the stove in burning the fuel (food) directly. The
food is first made into tissues, or " storage compounds " in
the tissues. It is as though we were to build a stove

RESPIRA T1ON. 1 09

entirely of coal, and then start a fire in it. In that case it
would produce heat not merely by burning in one place
within, but would be burning throughout the whole of its
substance. This is the case with the body.

Oxidation in Tissue the Source of Heat in the Body. -

We have seen that the muscles constitute nearly half of
the weight of the body. We know, too, that they are more
active than most of the tissues. We would now naturally
infer, as indeed is the fact, that they are the chief source
of the heat produced in our bodies.

The tissues of the body are oxidizing all the time. But
when they are in vigorous action they oxidize very much
more rapidly.

Next to the muscles, in importance as a heat producer,
is the liver, which is the largest gland in the body, and, as
we shall soon see, one of the most active. The blood, as
it leaves the liver by the hepatic vein, is hotter than
anywhere else in the body.

How the Body is like a Locomotive. — But it will be
better to compare the body to a locomotive, as we produce
not only heat, but motion as well.

If a visitor from another planet, unfamiliar with such
creatures as we are, were to observe closely a man and a
locomotive, he would see several points in common : —

1. Both are warm.

2. Both move.

3. Both use fuel (food or coal).

4. Both take in air, and (if it were a winter day)

5. Both give off smoke (which is essentially the same
in the two, carbon dioxid and water vapor being the chief
constituents).

no PHYSIOLOGY.

How the Body differs from a Locomotive. — By a

closer examination he would find out some of the differ-
ences that we have noticed : —

1. That the body does not get hot enough to burn ; i.e.
the oxidation is relatively slow, and is not combustion.

2. That the oxidation of the body never produces light.

3. That the oxidation here is always in the presence of
moisture.

The Amount of Carbon Dioxid given off. — When the
breath is held for some time, the carbon dioxid in the ex-
pired air may reach 7 or 8 per cent. During violent
exercise the amount of carbon dioxid given off may be
from two to two and a half times as much as when we are
at rest. The amount of carbon dioxid given off is in-
creased in cold weather, and by taking food, and decreased
from one fifth to one fourth during sleep. Oxygen is
carried chiefly in the corpuscles, but the carbon dioxid is
carried in both plasma and corpuscles.

Storage of Oxygen in the Tissues. — The activity of the tissues
from their oxidation does not necessarily mean that the oxidation is
direct ; that is, that the oxygen is used as soon as it is brought to the
tissue. For instance, in the muscles it is believed that the oxygen is
stored in some form, probably in combination, so that it can be used
when needed, perhaps much more rapidly than could be supplied by the
respiration at the time. If we study the chemistry of explosion, we
learn that it is a very rapid combustion. In the explosives are ma-
terials that unite instantaneously, instead of slowly burning, as in the
case of ordinary combustibles.

The Action of Muscles like an Explosion. — Now, many physiolo-
gists hold that a sort of explosive compound is formed in the muscles,
and that when the muscle acts it does so as the result of the explosion,
so to speak, of this material. And, to carry out the figure, the nerve is
compared to the match that ignites the explosive. A little heat is
enough to cause the most violent explosion. So the force that passes

RESTIRA 77 ON. 1 1 1

along a nerve fiber is slight. But it rouses a great amount of energy
that lay dormant in the muscle. It would seem to have "touched off11
a lot of explosive material that was already there, rather than merely
started an action that depends on the comparatively slow process of
respiration at the time. We cannot follow this theory farther, as it
takes us too deep into the study of chemistry in its most difficult
branch, — physiological chemistry.

Summary of Respiration. — The tissues need oxygen ;
air is pumped into the lungs ; this air gives oxygen to the
blood ; the blood carries it to the tissues.

In oxidizing, the tissues produce energy (heat and mo-
tion) and give off waste matter (water, carbon dioxid, etc.);
these the blood carries to the lungs, the lungs give them
to the air, and the air carries them out of the body.

The pumping of the air in and out may be called " me-
chanical respiration." The changes between the air and
the blood in the lungs we will call the " ventilation of the
blood," and the interaction of the blood and the tissues
the "real, or internal respiration."

The Two Breaths. — " Every time you breathe you
breathe two different breaths ; you take in one, you give
out another. The composition of these two breaths is
different. Their effects are different. The breath which
has been breathed out must not be breathed in again. "-
KINGSLEY.

Breathing Expired Air. — The air in the vesicles re-
ceives from the blood carbon dioxid, water vapor, and
other impurities above mentioned. It has been believed
for a number of years that the organic impurities consti-
tute the most dangerous element in expired air. Carbon
dioxid, though to some extent a poison, is not very injuri-
ous in such quantities as ordinarily exist in the air, even in
poorly ventilated rooms ; while the headache and drowsi-

112 rilYSlOLOGY.

ness that one experiences in a close room where there are
a number of people is due to the reabsorption of these or-
ganic matters. It is not due to lack of oxygen, for the
oxygen may be reduced to 13 per cent without causing
discomfort. A person may breathe air containing i per
cent of carbon dioxid, with a corresponding reduction of
oxygen, when the carbon dioxid is generated by ordinary
chemical processes (as in a small room with a large kero-
sene lamp, or a gasoline stove); but air having I per
cent of carbon dioxid produced by breathing is highly in-
jurious, because it contains the organic impurities above
noted, and the term "crowd poison" has been employed
for this material. Later investigators, however, maintain
that there is nothing injurious in the freshly expired breath.

Summary. — i. In the lungs the air and blood are brought very
close together, only the wall of the capillary and that of the air vesicle
intervening.

2. Through these two layers oxygen passes from the air vesicle
into the blood. Carbon dioxid, water vapor, ancj other wastes pass
from the blood into the air vesicle.

3. The mucous membrane of the air passages secretes mucus
which is driven toward the nostrils by the cilia.

4. The chest is lengthened by the depression of the diaphragm,
and widened by the elevation of the ribs, giving greater space, which is
filled by external air expanding the lungs.

5. Inspiration acts in opposition to resistances, whose elastic re-
action performs ordinary expiration without active effort.

6. There are four heart beats for each respiration.

7. The lungs are never emptied.

8. Respiratory capacity may be increased by exercise and practice.

9. Respiration is controlled by the nervous system ; the respiratory
center is in the spinal bulb.

10. Internal respiration is an oxidation in the tissues, illustrated by
the rusting of moist iron.

RES PI R A TION. 1 1 3

11. In passing through the lungs air loses oxygen, and gains water,
carbon dioxid, and other wastes.

12. Oxygen is carried chiefly by the colored corpuscles of the blood ;
it unites with hemoglobin in the corpuscles, forming oxyhemoglobin,
and gives the blood its bright scarlet color.

13. The energy of heat and motion in the body results from the
oxidations in the tissues.

14. Air once breathed is unwholesome. The air of living and sleep-
ing rooms needs constant renewal.

Questions. — i . Is it a good thing to see how long one can hold his
breath ?

2. Should the head be covered by bedclothes ?

3. What are the " lights "" in an animal ?

4. How is respiration affected by a stooping posture ?

5. In what part of the lungs is the best air ? Where the worst ?

6. Can you explain how respiration affects circulation ?

7. Is it easy to determine by the color of blood flowing from a
wound whether it is arterial or venous ? Why ?

8. Of what advantage is it that the cartilages of the windpipe are
C-shaped and not complete rings ?

9. How is it that in respiration 5 per cent of the oxygen disappears
while only 4 per cent of carbon dioxid appears in its place in the ex-
pired breath ? (See p. 102.)

CHAPTER VII.
VENTILATION AND HEATING — DUST AND BACTERIA.

Need of Proper Ventilation. — When one is actively
exercising his muscles he may keep warm outdoors through
our winter days. For the heat of the body depends on its
internal fires, the oxidation of its tissues. But if we are
inactive, these fires burn feebly, and we need outside heat.
While air is free, it really costs a good deal of money to
have it properly warmed.

A Lack of Effective Systems of Ventilation. — Lung
diseases are rare in the regions where the windows and
doors may be kept open most of the days of the year. It
is from shutting ourselves in so closely that we suffer.
This is especially true where many people are housed in a
comparatively small space, as in many public buildings.
But in our private dwellings, even when the owners are
amply able to secure the most sanatory appliances, defec-
tive apparatus is often put in. Any system that does not
provide for a constant renewal of the air is defective.

Grates as Heaters and Ventilators. — Grates will aid
largely in renewing the air. Although in themselves they
merely have provision for sending radiant heat out into the
room and much air up the chimney, yet, without any
special provision for inlet of air to the room, they draw air
in through every crack and crevice. It would probably be
very much better to have special ducts for the admission

114

VENTILATION AND HEATING. 11$

of air, which is suitably warmed while on its way into the
room, and to make the doors shut snugly, and to have
double windows, as then both the admission of fresh air
and the regulation of heat will be better secured. But
it is a serious question whether, with all our modern ap-
pliances, conveniences, and luxuries, we have better air
in our houses, and take cold less frequently, than our
ancestors who depended more on the fireplace, even if
they did " roast on one side while they froze on the other."
Fireplaces are expensive as mere heaters, but they are
excellent ventilators.

Ventilating Flues around a Smoke Flue. — If small
ventilating flues could be built around the flue of the main
heating apparatus, and connected with the various rooms
of the house, air could be drawn from these rooms by
ascending currents created by the heat of the central smoke
flue. Such flues surrounding smoke flues, would have the
added advantage of protecting the house from fire through
the too common " defective flue."

The General Principles of Ventilation. — Of the forces
that operate to renew the air two are natural, diffusion
and the wind ; and two are artificial, warm air shafts and
fan systems.

Diffusion. — Gases tend to mix. We know that if a
bottle containing an odorous substance be opened in
a room where there are no air currents the odor tends to
spread equally through the room. So if a person is in
one corner of a large room, where there are no inlets
or outlets, and no currents, as he uses the oxygen immedi-
ately around him, the oxygen farther away will diffuse
toward him so that he will continue to get oxygen till the
amount of oxygen in the room is nearly exhausted. So,

u6

too, the gases that he breathes out will not remain confined
to the space directly about him, but will spread nearly
evenly throughout the room. The same takes place in the
open air, without wind. So, then, if the windows and
doors are open, the air of the room will, by diffusion, be
renewed.

Wind. — Motion of the air renews faster than mere dif-
fusion. Strong wind forces its way through the cracks
around windows, and when windows are open on opposite
sides of a room there is usually enough breeze to renew the
air. But during the greater part of the year this cannot be
done.

Artificial Renewal of the Air. — The renewal of the
air in most cases depends on the fact that heated air rises.
Heat expands air. It is then lighter, bulk for bulk, than
cooler air. The heavier surrounding air presses the lighter
air upward. If there are outlets above and below, the
heavier, colder air will press in at any opening left below,
and push the lighter, warmer air out above.

The Common Stove. — In the case of the common stove
we very well know that there are currents of heated air
rising above the stove. Children make whirligigs and
various toys to place in these up-currents above stoves.
Air is, at the same time, flowing toward the stove along
the floor and lower part of the room. Cold air can usually
be detected entering around the windows and doors, which
presses downward and toward the source of heat. The
stove does not do much to renew 'the air in the room
except in this general way ; some heated air escapes at
openings in the upper part of the room, and some is passed
out through the stove, taken in as a draft. But in the

VENTILATION AND HEATING. 1 1/

main, the action of the heat of the stove is to make a
current of warm air up from the stove, which current
passes along the ceiling to the more distant corners of the
room, then descends, joining the cold air, and repeating
the round.

A Stove and Jacket. — In some cases a jacket is placed
around a stove, and a duct from the outer air connects
with the lower part of the space inside of the jacket and
outside of the stove. Then as the air heated by the stove
rises, fresh air is drawn in from outside to be warmed.
In this case the direct heat from the stove is shut off from
the room. Heat radiates in straight lines. When one
holds out his hands beside a stove the heat he receives is
radiant heat. Most of the heat from a grate is radiant
heat. But in a jacketed stove the heating by air currents
is called heating by convection.

The Furnace. — Now a furnace is practically a jacketed
stove (almost always placed in a basement). Furnaces
have this good feature that they are all the time sending
fresh air into a room.

Foul-air Shafts and Fans. — Although in private dwell-
ings heated by furnaces there is no special provision for
the escape of foul air, there is ordinarily sufficient renewal
of the air. But in public buildings there should be escape
flues for foul air.

Frequently a large foul-air shaft is built in some central
part of the building, and a small stove placed in it to create
a sufficient up-current. In many public buildings the cur-
rents created by heat are insufficient to renew the air
properly. Fans are used, which force the air, properly
heated, into the room.

Il8 rHYS/OLOGY.

Direct Heating. — In heating by steam or hot water, if
the radiators are placed in the room they give direct or
radiant heat. This system is called direct heating. In
itself it has no provision for renewing the air. It gives
direct heat, and produces air currents within the room ;
and any change in the air is wholly incidental, from escape
of heated air in the upper parts of the room and corre-
sponding suction of outside air through such openings as
the carpenters have left below.

Indirect Heating. — In indirect heating, coils of steam
or hot-water pipes are placed in air shafts which lead up
to the rooms above, and also have ducts to the outside.
As the air is heated by the heat of the pipes it rises into
the rooms above, and fresh, cold air presses in through the
ducts, to be, in turn/heated and sent up. If there is at
the same time a proper escape for the foul air, this makes
an excellent system.

A Combination of Direct and Indirect Heating. — In

many situations the direct and indirect may be advan-
tageously combined. Where there is a grate in a room, it
serves very well as a foul-air shaft, especially when there
is a fire in the grate. It is well to have the flue from the
grate in the same chimney with that from the smoke pipe,
as then the heat from the smoke will cause a constant up-
draft in the grate flue, whether there is a fire going in the
grate or not.

With a grate, in private houses, there is ordinarily no
need of other foul-air shaft for any room. But it is very
desirable to have at least some "indirect" heat, so that
the fresh air introduced will be sufficiently heated.

If the introduction of air is thus provided for, it is then
safe to put on double windows and make the cracks around

DUST AND BACTERIA. 119

the door very tight. Without any special provision for the
renewal of the air these cracks are the means of safety.

In houses heated by furnaces, steam, or hot water, the
floor is likely to be warmer from the escape of heat from
the heater itself, and from pipes or air ducts under the
floor.

Double Windows. — There is a very common misunder-
standing as to the cold felt near a window in cold weather.
It seems that air is entering ; but a little reflection will
show that even if the window were air-tight this effect
would be produced, for the air near the window is cooled
by losing heat to the outer air. The air next to the win-
dow, thus cooled, is heavier, and falls to the floor ; and if
there is any source of heat in the room, this cold air will
pass along the floor to that source of heat, up from the
heating body to the ceiling, and across the ceiling, and so
on around again. There may thus be currents without
any appreciable change in the quality of the air. It is
economy to use double windows and prevent the loss of
heat through the glass. So both economy and comfort
suggest to us that we reduce as much as possible cracks
around doors and windows, use double windows, make ves-
tibules at entrances, and build special ducts by which fresh
air may enter, and heat it properly on its way in.

DEAD DUST.

The Air is washed by Rain or Snow. — Every one
will recall how delightfully refreshing the air is after a rain
or a snowstorm. This is not due merely to the fact that
the air is cool. It is clean because it has been washed.
The rain and snow absorb a considerable amount of the
various impure gases that are in the air. But raindrops

120 PHYSIOLOGY.

and snowflakes bring down with them many particles of
dust that were floating in the air. Take some of the snow
that has fallen in a town. It looks pure in its almost
dazzling whiteness. But melt some of it, and you will
usually find a decided tinge darkening the water, showing
that as the flakes sifted down through the air they caught
myriads of particles of dust.

The Sources of Dust. — Where soft coal is used to any
large extent it is one abundant source of this dust. In
summer dust has many sources. The dust that blows into
your face, and perhaps into your mouth, may be made of
dry soil. Take a dry clod and drop it ; it falls quickly to
the ground. Pulverize it in your hand before dropping it,
and considerable of it floats in the air for some time. Any
substance that is easily dried. and pulverized may form
part of the common dust. The dust that you wipe from
your eye, or is caught by the mucus of the nasal passages,
may, instead of being made of clean soil, be from the
excreta of horses, decayed leaves, wood, grass, etc. In-
doors we are constantly making dust by wearing out our
clothes. Many of the tiny particles that we see floating in
the sunbeams are bits of cotton or woolen fibers. Shake
any garment in a beam of light to see how much, and how
easily, dust is given off. The worn-off particles of our
shoes, books, floors, all contribute to the ever-present
dust.

The Effect of Dust on the Lungs. — Now, this dust (so
far as it is mere dead, dry matter, not considering it as a
poison) is irritating to the lungs and respiratory passages.
There is provision, as we have seen, for catching and
getting rid of a good deal of it.

But still much is taken into the lungs. Examination

DUST AND BACTERIA. 121

shows that the lungs have many black specks from parti-
cles of carbon, etc., that have become lodged, and are of
no benefit, to say the least.

LIVE DUST.

Composition of Live Dust. — Bad as this dead dust is,
the injury from it is slight compared to that from live dust.
We know that certain seeds float in the air, carried along
by the wind. But these are comparatively heavy, and soon
sink to the ground.

We all know pollen. At certain seasons it forms, in the
vicinity of cornfields, for instance, a considerable part of
the dust. This is alive. It will grow if it falls on the
right kind of a surface, the stigma of the right plant at the
right time. Such dust will not grow in our bodies. We
do not furnish a soil in which it can grow. It merely adds
to the amount of irritating dust.

Puffballs and Molds. — We have seen puffballs give
off a cloud of dust when they are crushed. This dust is
composed of live spores that will grow in suitable places
and conditions. So, too, from a patch of mold, when
brushed, we often see a little cloud of dust. These are a
few instances of kinds of living dust that simply act on us
like so much dead matter.

Yeast. — If we set a tumbler of cider on a table in a
warm room, in a few days it ferments. This is due to
yeast that has gotten into it. Boil the cider to kill any
yeast that is already in it, and cork it securely so that air
cannot get at it, and it will not ferment. Dried yeast
germs float in the air, settle into this exposed cider, and
cause it to ferment. Cider is a good soil for yeast.

122 PHYSIOLOGY.

Disease Germs. — But there are floating in the air many
kinds of spores that may grow in our bodies. We know
that many of our contagious diseases are due to the growth
in our bodies of some of these spores. Our bodies are a
good soil for certain germs. The germs that cause con-
sumption, typhoid fever, Asiatic cholera, erysipelas, diph-
theria, and some forms of blood poisoning are well known.
Microscopists know them when they see them as readily
as we know peas from beans. And it is proved beyond
all doubt that these germs get into our bodies by being
breathed in, or by being eaten in food, or in drinking
water, or by introduction into the blood in wounds. We
have reason to believe that smallpox, yellow fever, measles,
and scarlatina are caused by germs, but these diseases have
not been studied so successfully.

How to avoid Germs. — How^can we avoid or get rid
of dusts of these kinds ? To exterminate any plant, we
try to keep the seeds from ripening, and to kill all that do
ripen. Let us take a case that, while not pleasant to con-
template, is too terribly true to allow of being called an
imagined case.

The Danger from Consumption. — A consumptive ex-
pectorates on the pavement. In this sputum are probably
hundreds, if not thousands, of germs known as bacilli
(Bacillus tuberculosis}. They are alive. Now, so long as
they remain on the pavement they do no harm. The
sputum dries. But the bacilli are not killed by drying.
With other dry material from the pavement they form
part of the common dust. Any one of us may breathe
some of this kind of matter any day, for there are persons
afflicted with this dreaded disease in every community.
Our bodies furnish the very best soil for the germs. We

DUST AND BACTERIA.

12$

Bacillus of "Diphtheria (x lOOO)

Bacillus of Tuberculosis (x 1000)

Bacillus of Typhoid Fever (x 1200)

Bacillus of Typhoid Fever (x 1200)
showing flagella

Bacillus (Spirillum) of Asiatic Cholera Bacillus of Hog Cholera (x 1000)

Fig. 48. Types of Bacilli, showing Morphologic Characters and Arrangement.

124 PHYSIOLOGY.

do not need to go into the street to be exposed. Who
knows what he brings into the house adhering to his
clothing ? These germs may be brought into the most
cleanly houses in this way, or by the wind.

How to avoid the Danger. — Now, of course, all such
material known to be highly dangerous ought to be de-
stroyed. If those suffering from such diseases were care-
ful to burn all such matter, most of the seeds of this disease
would be killed. Thus in time we might stamp out the
disease, as a scourge of Canada thistles. But so long as
people expectorate upon the floors and pavements it will
be difficult to prevent the spread of such germ diseases.

In hospitals such matters are now looked after with the
greatest care, and in private houses where there is intelli-
gence on these subjects. And it is encouraging to note
the awakening of the public to the significance of the teach-
ings of modern science on this subject, as shown by the
fact that many of the railroad and street car companies
now prohibit spitting on the floors of cars, not merely be-
cause it is uncleanly, but on the express ground that it is a
means of spreading infectious diseases.

Bacteria. — These disease germs are the smallest and
simplest of living things. They are plants ; and while all
of them that are well known have their scientific names,
just as the larger plants have, they are all included in one
general group designated as bacteria.

How to avoid Dust. — We need to learn a good deal
more about avoiding and destroying dust, and the things
that make dust.

Towns and cities need more sprinkling to keep the dust
down. Much more of the refuse and street sweepings and

DUST AND BACTERIA. 125

cleanings ought to be burned. The dust of a house should
always be burned, as we know not what germs of disease
may be in it. If we burn it, we shall surely not have to
sweep up that dust again. If we send it out of doors it
may come back, and we may have to handle it again and
again.

Sweeping and Dusting. — So far as possible let us avoid
things that make dust. When we sweep a carpet, a con-
siderable share of the dust comes from the carpet itself,
especially if the carpet is old. Curtains and tapestries of
nearly all sorts not only hold dust, but contribute a good
deal to it. Those who write on such subjects recommend
hard wood floors with rugs instead of carpets. The rugs
can be taken out of doors and shaken, and the floors wiped
with a moist cloth, so that little dust is left floating in the
air of the room. Compare this with the condition that
holds after the ordinary sweeping of a carpeted room with
the common broom. The dust fills the air, only to settle
back on the floor and furniture. Then comes the whisk
broom, the so-called dusting. Well, it is dusting ! It fills
the air once more with dust. But do we get rid of it?
Wiping off the dust with a moist cloth takes most of it
away on the cloth. For those who cannot have hard wood
floors a most excellent substitute (and in some respects
better) is oilcloth or linoleum.

Sweeping the Sick Room. - - The improved carpet
sweepers are not only convenient, but sanatory. Many a
well-meaning person will sweep a carpet in a sick room
with an ordinary broom when the patient is suffering from
lung disease, thoughtless of the fact that a little dust in
sight, and perhaps on the shoes, is of much less signifi-
cance than dust in the air we breathe. No one likes dust

126 1'HYSIOLOGY.

on the floor, but better a thousand times there than in our
lungs.

Lung Diseases. — Statistics seem to show that one
seventh of the deaths among the civilized races is due to
lung diseases. The best authorities are now agreed that
consumption is not hereditary. But it appears that there
may be inherited a tendency to this disease, so that, if ex-
posed, such persons are more likely to contract the disease
than those not so predisposed.

Probably anything that lowers the general vitality makes
the system more ready to succumb to any of these con-
tagious diseases. We have all noticed what a difference
there is among individuals in the readiness with which they
" catch " contagious diseases.

Destruction of Germs by Colorless Corpuscles. — It is

believed by some physiologists that the colorless blood
corpuscles may take these germs of disease into their sub-
stance, and destroy or change them so that the disease is
warded off. In other words, they may be compared to a
cat that catches and eats the mice which invade a house.

How to ward off Contagious Diseases. — A good gen-
eral condition of the body helps greatly to ward off dis-
eases of this nature. A cheerful condition of mind and
body should be cultivated. In times of widespread con-
tagious disease, if one is terrified into the belief that he is
going to have the disease, he is more likely to take it.

Thorough cleanliness, plenty of direct sunshine, care in
diet, and the keeping of the body in good tone, all these
reduce the chances of "taking" contagious diseases.

An open-air life, abundant nutritious food, and freedom
from anxiety are probably the best restoratives for incipient
consumption.

DUST AND BACTERIA. 127

The Bacteria of Putrefaction. — Besides the disease-
producing bacteria, there are others that cause decay and
putrefaction of various kinds. They cause our richer foods
to " spoil," milk to turn sour, butter to become rancid, etc.

While these bacteria do not cause disease in the human
body, they often make food poisonous. The cases fre-
quently reported of poisoning from eating ice cream,
cheese, sausage, etc., are in many cases due to bacteria in
them. We should, in the first place, be careful to get
good, fresh material. In the second place, it should be so
kept as to prevent the introduction and development of
bacteria in it. Bacteria need heat for their growth (as we
so well know is the case with the higher plants). They
also need moisture.

The Preservation of Foods. — So our principal modes
of keeping foods from spoiling are to keep them in a cold
place, or to dry them. Or we heat them, and shut them
away from the air, as in our various modes of canning and
preserving foods. Salting and smoking meats, etc., preserve
them by preventing the growth of bacteria. Cold does
not usually kill bacteria. So milk that has been kept in a
refrigerator, and that seems sweet, may have in it a stock
of bacteria, and after we drink the milk the heat of our
bodies favors their development. There are now known
ways of killing the bacteria in milk and other liquids, known
as " sterilizing," that make us safe from this danger.

Although the main subject of this chapter is air and
ventilation, it has been thought best to touch briefly the
subject of bacteria in food, as the bacteria are so widely
disseminated by the air. One of the earlier and still in-
teresting works on this subject is Tyndall's Floating Matter
of the Air.

128 PHYSIOLOGY.

But let us now turn from the air and respiration to
another, yet closely allied subject.

The Need of the Removal of Waste. — When we
awaken on a cold winter morning we are likely to find that
the fire in our hard coal stove has burned low. Not enough
heat is given out. What is the trouble ? Is it merely that
more coal is needed ? We put another hod of coal in the
magazine (though some usually remains). Does this bring
the desired result ? No. We open the draft. Is this suffi-
cient? It is not. We must shake down the grate and
clean out the clinkers. The removal of waste is often
more necessary than the addition of a fresh supply of ma-
terial. It is often a more serious matter to have the waste
pipe leading to the sewer clogged than to have the water
supply cut off. It is often more to be desired that the
garbage cart take away decaying matter than that the
bread wagon arrive. The demands of nature for the ex-
pulsion of excreta are imperative, while we can withstand
the cravings of hunger for a while. So we shall turn our
attention for the present to the immediate demand for the
removal of wastes, and later consider the equally impor-
tant, but less importunate, question of supply and renewal.

READING. — (i) Bacteria, (2) Dust and Its Dangers,
(3) Drinking Water and Ice Supplies, Prudden ; Ventila-
tion and Warming of School Buildings, Morrison; Sanitary
Conditions of ScJioolJionses, Lincoln (American Public
Health Association); Disinfection, Sternberg (American
Public Health Association) ; Micro-Organisms and Disease,
Klein ; The Wilderness Cure, Marc Cook.

Summary. — i. Lung diseases usually accompany close confine-
ment, but are rare with those living in the open air.

DUST AND BACTERIA. 129

2. Air in rooms needs constant renewal.

3. Grates are good ventilators, but not economical heaters. Grates
heat very unevenly.

4. Stoves are economical heaters, but poor ventilators. Stove heat
is also very uneven.

5. All crowded rooms, as schoolrooms and churches, need special
inlets for fresh air and outlets for foul air.

6. The most common means of withdrawing the air is by foul-air
shafts. Heat is the force relied on, but the removal of foul air is usually
inadequate, on account of the slowness of the current or the narrowness
of the outlet, or both combined.

7. Fans are much more certain to be effectual.

8. Steam and hot water may heat directly (by radiation) or indi-
rectly (placed in flues). A combination of direct and indirect heating
favors economy and efficiency.

9. Dust as mere dry dead matter is irritating.

10. Disease germs may form part of the dust of the air.

1 1 . Most of our contagious diseases are known to be due to bacteria.

12. Burning is the surest method of destroying germs.

13. Carpets, tapestries, and cloth-upholstered furniture add largely
to the dust in houses.

14. Putrefaction is caused by bacteria.

15. Preservation of food depends on destroying, or excluding, or
retarding the growth of the bacteria of putrefaction .

Questions. — i . How can we renew the air of a room without having
unpleasant drafts ?

2. Should bedroom windows be open at night? Is night air bad?

3. What dangers in the use of hard coal?

4. Should there be a damper in the smoke pipe of a hard coal
stove?

5. What do miners mean by " choke damp " ?

6. What is hay fever? Asthma? Bronchitis? Pneumonia?

7. Compare stove and furnace heating.

8. Compare heating by steam and by hot water.

9. Is the air in the mountains or on the seashore better than else-
where ?

10. What regions are recommended for consumptives ? Why?

CHAPTER VIII.

EXCRETION.

Sweat Pore

Epi-
dermis

Papilla-

THE SKIN AND ITS FUNCTIONS.

The Skin throws off Perspiration. — The energies of
the body — heat and motion — are produced by the oxida-
tion in its tissues.
During this process
waste products are
formed, which if
retained in the
body would cause
very injurious
effects.

How does the
body get rid of
these substances ?
We have learned
that the lungs
throw off carbon
dioxid, water, and
certain putrescible
organic matter.
The skin is constantly throwing off wastes, collectively
called sweat, or perspiration.

The Structure of the Skin. — The skin has two layers,
the inner, or dermis, and the outer, or epidermis. A
bruise often loosens or breaks off a piece of the epidermis,

130

Dermis

Sweat
Gland

Blood
Tube

Bulb

Fig. 49. Vertical Section of the Skin.

EXCRETION 131

but seldom removes the dermis. The epidermis is thick
over the palms of the han<jls and soles of the feet ; else-
where it is thin. Not often seeing the whole thickness of
the skin, we do not easily obtain an idea of its real thick-
ness. The skin constitutes about one-fifteenth of the
body's weight, and if tanned makes a moderately firm and
thick leather very much resembling the pigskin used for
covering footballs, striking bags, etc.

Mouth of Sweat Duct

Horny Epider-
mis

Soft Layer

Papilla

Dermis

\ M
Vein Artery

,Fig. 50. Section of Epidermis, showing Papilla. (Highly magnified.)

The Epidermis. — The epidermis consists of many
layers of cells packed closely together. The deepest cells
may be compared to grapes with their cell walls plumply

132

filled out by the liquids of the cell. Suppose, for the
inner layer, grapes set on end, and so closely packed
together as to press each other into elongated prisms.
Then layers less closely pressed, more nearly spherical ;
then layers of cells with less liquid in them, and somewhat
shrunken, like raisins; then still dryer cells, flattened
parallel with the surface of the skin ; and last, in the outer
part, layers of cell walls, dry and empty, pressed flat like
empty grapeskins. The flat cell walls come off in flakes
(called dandruff from the scalp) from all the surface of
the skin, and new cells are continually formed in the
deeper layers.

The Color of the Skin.— The pigment, which gives
color to the skin, lies in the deeper layers of the epidermis.
In albinos this is wanting; in persons with a fair skin it
is small in amount, in dark skins more abundant. Where
the pigment is irregularly scattered it causes freckles, etc.

A Blister. — A blister is caused by separating the outer,
harder layer of the epidermis from the inner, softer, darker
layer of the epidermis, as shown at B in Fig. 49. Serum,
or blood, fills the space between the separated layers.

The Dermis. — The dermis consists chiefly of tough
interlacing fibers. Hence the strength and durability of
leather, which is the dermis preserved and prepared. The
epidermis is usually removed in tanning. The dermis is
richly supplied with blood capillaries and lymph capillaries,
but the epidermis has neither.

Papillae. — The outer surface of the dermis has numer-
ous conical elevations. Over most of the skin there is no
evidence of these papillae, as the epidermis envelops them.
But on the palm and sole the papillae are in rows, and
these rows are indicated by the fine ridges.

EXCRETION.

133

Hairs and Nails. — Hairs and nails are outgrowths of
the epidermis. Their deeper parts are embedded in the
dermis, through which, from the blood, they derive their
nourishment. Like the epidermis, they are dead in the
outermost part, and are supplied by growth from beneath.

Examination of the Skin with a Lens. — Place a linen tester, or
good pocket lens, on the palm of the hand, and note the openings of
the ducts of the sweat glands, or sweat pores. Count the pores within
the square shown. Measure this square, and then estimate the number
of sweat glands to a square inch of the palm.

Epithelium or Epidermis

Compound Glands
Fig. 51. Evolution of Glands. (After Landois and Stirling.)

The Sweat Glands. — The sweat glands are minute
tubes whose inner ends are closed, and whose outer ends
open upon the surface of the skin. The tube going
inward pursues a corkscrew-like course through the epi-
dermis, then becomes straighter, and, having passed

134 PHYSIOLOGY.

through the dermis, is coiled up in a ball in the connective
tissue lying just underneath the inner skin. The cells
forming the walls of the coiled part differ from those of
the duct, or straighter part of the tube. As the blood
flows around the coil it gives off lymph, and from the
lymph the cells of the gland take certain waste matters,
which are passed out to the surface of the skin. There is
also some muscular tissue around the walls of the gland.

Model of a Sweat Gland. — Take a small rubber tube a foot long ;
close one end; tie the half with the closed end into a globular knot;
around and between the coils place a network of red cord to represent
the blood capillaries, as there is a rich supply of these blood tubes
around the coil.

The Essential Features of a Gland. — i . Cells lining
a cavity, the cells having the power of taking something
from the blood (or lymph).

2. Blood supply or lymph supply.

3. A duct or tube to pour out on some surface the
liquid taken from the lymph.

4. Nerves to the cells by which their action is controlled.

5. (Probably) Special nerve centers controlling the
various glands. The cells of the glands in many cases
so alter the substances taken from the blood that what is
produced by the gland differs from anything found in the
blood. The gland may be said to manufacture the liquid.

The Relation between Glands and the Blood
Supply. — The sweat glands, like all glands, are largely
dependent on the amount of blood supply. In exercising,
the skin is usually redder from the greater blood supply,
and at the same time the glands are more active ; for,
during exercise, and immediately after it, there is more
waste matter to be thrown out. But the activity of the
gland is not a mere filtering process, due to the greater

EXCRETION. 135

blood pressure. There may be a cold sweat ; i.e. when
the skin is pale. Here is evidence that the activity of the
glands is, primarily, due to the nerve impulses from some
nerve center to the gland cells.

Sweat Glands are Simple and Excretory. — The sweat
glands rid the body of certain waste matters that can no
longer be used. They are excretory glands. In structure
they are simple glands.

Distribution of Sweat Glands. — The sweat glands are
thickly distributed over the whole surface of the body,
but are especially numerous and large on the palms of the
hands and the soles of the feet. In the armpits the glands
are very large.

The Oil Glands. — The oil glands of the skin are dis-
tributed over all the surface except the palms of the hands
and soles of the feet. The oily matter is usually poured
out around the hairs as they emerge from the skin. It
serves to oil the hair and the skin, and keep them from
becoming too dry.

Composition of Sweat. — Sweat is mostly water; about
one per cent is solid matter, including salt and certain
matters which, like the organic waste matter from the
lungs, easily putrefy, and some oily matter from the oil
glands of the skin.

Experiment to show Insensible Perspiration. — Thrust the hand
into a glass jar, preferably a jar that has been in a cool place. Note
the moisture that soon gathers on the inside of the jar from the insen-
sible sweat of the hand. A common fruit jar will do for a small hand,
but a candy jar is better, having a larger mouth and clear glass.

Kinds of Perspiration. — Ordinarily the sweat is evapo-
rated as fast as it is poured out ; in distinction from this
insensible^ perspiration, there is the so-called sensible per-

136 PHYSIOLOGY.

spiration — when it accumulates enough to be perceptible.
These are not two distinct kinds of sweat, but it is con-
venient to distinguish between the perceptible and the
imperceptible. Sweat varies greatly in its wateriness, and
hence in the relative amount of solid matter contained.

The Amount of Perspiration. — There is about one
quart in twenty-four hours. It varies with: —

1. Temperature, dryness, and rate of renewal of air.

2. Condition of the blood; e.g. if watery from drinking
much water.

3. Muscular exercise.

4. Certain drugs — some exciting perspiration, e.g.
camphor ; others diminishing it, e.g. belladonna.

5. The nerves exercise great influence on the activity of
the cells of the gland.

The Functions of the Skin.

1 . Protective.

2. Excretory.

3. Absorptive.

4. Sensory — organ of touch.

5. Heat-regulating.

Next to its excretion, the heat regulation by the skin is
the most important for our present consideration.

Regulation of the Temperature of the Body by the
Skin. — It is a striking fact that, except in disease, the
temperature of the body varies only a little from 98.5° F.
in summer and winter, during exercise and rest. The rate
of heat production varies greatly. The rate of giving off
heat must therefore vary accordingly.

The Body gives off Heat. — In considering the regula-
tion of the body's temperature, we must bear in mind that
the body is surrounded by air almost always considerably

EXCRETION. 137

cooler than itself. The body is, therefore, almost always
giving off heat. Our clothes do not warm us : we warm
them, and they keep us from warming the air too fast ;
i.e. keep us from losing too much heat. Indoor heat in
winter in the cooler parts of the United States is kept
at about 70° F. by artificial heat. This air does not warm
us. We, being about 30° F. warmer, are warming it.

Ways of Giving off Heat. — The skin gives off heat by—

1. Radiation: heat is given off in every direction.

2. Conduction: whatever we touch that is cooler than
our bodies is warmed. We warm chairs, clothing, etc.

3. Convection : the air in contact with the skin is warmed
and rises. Our bodily heat is thus carried off by convection.

4. Evaporation : the evaporation of the sweat is a much
more important factor in heat regulation. Any liquid, in
evaporating, absorbs heat. The cooling effect of alcohol
or ether on the skin is due to the fact that heat is taken
from the body in converting the liquid into a gas.

Experiments in Evaporation. — Let the teacher, with a medicine
dropper, place a drop of alcohol, ether, or cologne on the back of the
hand of each pupil. Notice two facts: (i) It produces a cooling
effect. (2) The liquid soon disappears. To prove that it is not
merely that the liquid is cool, try the following : Tie a piece of cheese
cloth around the bulb of a thermometer ; dip the bulb into a dish of
alcohol or ether, and note its temperature (if these are not at hand,
gasoline serves very well, or even water, though the evaporation is
slower) ; then lift the bulb out of the liquid, and note any change in
temperature. The evaporation of the liquid takes heat from the bulb,
and causes the thermometer to register a lower temperature. We
sponge the face and hands of a feverish patient to reduce the amount of
heat. We sprinkle the floor in hot weather, and, by the absorption
of heat in evaporating the water, cool the air of the room.

Heat and Exercise. — When we exercise, we produce
more heat : we sweat more ; more heat is taken from the

PHYSIOLOGY.

body to evaporate this sweat. If we are not exercising,
and are in cooler air, we sweat less, and less heat is given
off. So the temperature of the body is kept uniform.

This should also be observed : When we exercise, more
blood is in the skin, and more heat is given off in the
other ways mentioned ; when we exercise less, the skin,
especially in a cool air, becomes paler; i.e. has less
blood in it, and heat is economized.

Distribution of Heat in the Body. — If more heat is
produced in one part of the body than in the others, the
circulation of the blood tends to equalize the temperatures
of the different parts. So, too, if one part is cooled, —
that is, is losing heat faster than the others, — the blood
brings heat from other organs to that part.

For instance, if one holds his hands in the snow, or puts
a piece of ice on his wrist, the whole blood stream is
affected. So if the hands and the feet are exposed to the
cold, it may do little good to have the rest of the body
covered. A pair of wristers and a pair of leggings may
often add more to one's comfort than a heavy overcoat.

Regulation of Bodily Temperature by Food and
Clothing. — When subject to the influence of cold we eat
more ; we choose more heat-producing foods, as fatty food-
stuffs ; we take more vigorous exercise ; we put on more
clothing, and especially of the non-conducting kinds, —
woolens. In warmer weather we eat less fatty matter,
wear less clothing, and are less disposed to exercise
actively ; we fan ourselves to help get rid of heat ; we
take ices and cold drinks. For most persons it seems
better to wear woolen most of the time, as even in summer
we are subject to sudden changes in the air, and with such
covering one is less likely to take cold.

EXCRETION. 1 39

The Effect of Wet Clothing. — In getting the clothing
wet, the greater loss of heat is not from the coolness of
the water, but the loss of heat in evaporating the water
from the clothing ; and this goes on for a long time. Of
course it is desirable to put on dry clothing as soon as
possible ; but a person in good health is not likely to take
cold, except in very cold weather, if he continues active
exercise till he can change the wet garments for dry ones.
Children do not often take cold from wading in water so
long as they are barefooted ; but if the shops and stock-
ings are wet, they are likely to take cold.

Sunshine. — For good health we need sunshine. We
have sunlight indoors, but so do many plants that drag
out a sickly existence. We need direct sunlight (not too
hot), and many an invalid has been cured by sunbaths.
Part of the beneficial effects of sea bathing is due to sun-
shine. It is a good thing that it is now the fashion to take
a vacation and become well tanned. One of the benefits of
the resorts of Colorado (in addition to the climate's mild-
ness) is that there are very few cloudy days during the year.

THE KIDNEYS"

The Work of the Kidneys. — One important part of the
work of the lungs, as we have seen, is to throw out carbon
dioxid. The skin also throws off certain wastes. The kid-
neys have the special task of excreting a waste product of
the body called urea. Urea is the nitrogen-containing waste.

The Parts of the Kidney. — The kidneys are attached to the dorsal
wall of the abdominal cavity. The depression in the kidney correspond-
ing to the stem scar on a bean is called the hilum. From the hilum
issues a white tube, the ureter, which conveys the urine to the bladder.

The Blood Supply of the Kidneys. — Entering the kidney along-
side the ureter is the renal artery, a branch of the aorta, and from near

140

PHYSIOLOGY.

the same point the renal vein returns the blood from the kidneys, and
pours it into the postcaval vein. Through the kidneys is pouring a
continuous stream of blood, varying in amount at different times and
in different conditions. The kidney receives a very large amount of
blood for its size, as compared with other organs. The flow to it is
made easy by the fact that the renal arteries are relatively wide and
short, and take the blood directly from the main current of the aorta.
The blood leaving the kidney, especially when in full activity, is still
bright red ; it is probably the purest blood in the body.

Urine. — From the kidney, through the ureter, urine is continually
passing to the bladder. Urine is mostly water containing urea, salt, and
various other substances in small amounts. Urea is a waste matter
brought in the blood. If the kidneys are stopped in their action, urea
accumulates in the blood, and death soon results ; to just the degree that
the kidneys fail in performing their duty, just so far must the body suffer.

Microscopic Structure of the Kidney. — If microscopic sections of
the kidney are at hand they should be examined ; but the kidney is so

complicated in structure that a

Urinary Cone diagram is needed in connection

with the sections and the de-
scriptions. The unit of struc-
ture in the kidney is a tube which
takes material from adjacent
blood capillaries. The relation
of the capillaries to the tube is
peculiar. The inner end of the
tube is enlarged into a ball ; this
ball is deeply depressed opposite
the point where the tube leaves
it. Into this depres-
sion is fitted a globu-
lar tuft of capillaries.
The arrangement may
be illustrated by the
common toy known as the " cup
and ball." The handle of the
cup should be hollow to repre-
sent the tube ; the cup should be double walled, the space between
the inner and outer layers continuous with the hollow of the handle.

Cavity of —
Kidney

Renal
Vein

Fig. 52.

U rete r
Cross Section of Kidney.

EXCRETION.

Instead of a solid ball held by one string, there should be a yarn ball
with two large strings attached to one side, one representing the artery,
the other the vein ; the yarn ball represents the dense cluster of capil-
laries.

Another Illustration. —A still better illustration of the urinary tube
and capsule may be made thus : Take a thistle tube (used in the chem-
ical laboratory), let down into its bulb a rubber balloon or bag of sheet
rubber or cloth, fastening the margin around the rim of the bulb ; put
a little ball of red yarn in the depression of the bag hanging in the
bulb ; have two ends of the yarn projecting to represent the artery
entering and the vein leaving the capsule. The vein, soon after it
emerges, breaks up into another set of capillaries which extend around
the tube. A number of these primary tubes unite, and many of the
common ducts open at the apex of each of the urinary pyramids,
emptying their secretion into the cavity of the kidney. As the blood
flows through the tuft of capillaries in the capsule at the end of the
tube, a large amount of water,
together with salt and some
other substances, pass through
the thin partition into the
cavity of the capsule, and
thence down the tube. The
walls of the tube are thicker
than, and its cells are different
from, those of the capsule.
These cells take the urea and
some other substances
from the blood, and
pass them into the tube
to join the more watery
material from the capsule.

Artery J

— Vein

Urinary Tul
Fig. 53. Urinary Cone Enlarged. (Diagram.)

Comparison of the Skin
and the Kidneys. — The

kidneys, then, are not very

different from the skin.

Imagine a piece of skin rolled up with the outer surface of

the skin turned inward. Its glands then would pour their

142 PHYSIOLOGY.

secretion into a cavity where it might accumulate, instead
of evaporating as^fast as it is poured out. Of course the
kidneys have a somewhat different work from the skin,
but in its general plan of working we might say they
are skin turned outside in. The kidney unit (the tubular
gland) has branches ; i.e. is compound. The kidney is a
compound gland of excretion, internal in position. Both
skin and kidneys excrete a large amount of water, with
salt and some other matter in common.

Relation between the Work of the Kidneys and that
of Skin. — There is a very immediate relation between
the work of the kidneys and that of the skin. In warm
weather, and when exercising actively, we perspire freely,
and the amount of urine is reduced ; when we exercise
less, and especially in cold weather, we perspire less, and
the urine is more abundant. Cold drives the blood from
the surface. Consequently more blood goes to the kidneys
(as well as to the other internal organs), and they throw
off much more water, though probably little if any more
urea. The average daily amount of urine is about three
pints. The quantity is increased by high blood pressure,
copious drinking, by cold air (driving the blood from, the
skin), nitrogenous food, certain drugs, etc. It is dimin-
ished by a lowered blood pressure, profuse sweating,
diarrhea, non-nitrogenous food, and some diseases of the
kidneys, etc.

What is the effect of all the processes thus far studied
,on the weight of the body ?

READING. — The Skin and Its Troubles, D. Appleton
& Co.

Summary. — i . The skin throws off sweat, which is water contain-
ing waste matter.

EXCRETION. 143

2. The tubular sweat glands take the wastes from the lymph which
soaks out through the walls of the capillaries in the skin.

3. The activity of the glands is under control of nerves and nerve
centers, as is also the supply of blood to the skin.

4. The amount of sweat depends on temperature, exercise, amount
of liquid food taken, drugs, etc.

5. The temperature of the body is regulated chiefly by the evapora-
tion of sweat.

6. In cold weather we eat more of ' heat-producing foods, such as
fats.

7. The kidneys excrete urea, a nitrogen-containing waste.

8. There is an intimate relation between the workings of the lungs,
skin, and kidneys.

Questions. — i. Does cutting hair make it grow faster ?

2. Do cows, dogs, and cats sweat ?

3. Why is thirst relieved by immersion, even in salt water ?

4. Why should clothing worn during the day be removed at night ?

5. How does the body lose heat, except by the skin ?

6. Why should the blood still be red after passing through the
kidney ?

7. What is "skin grafting" ?

8. Why is it considered a good sign when the skin becomes moist
during a fever ?

9. Can food, medicine, or poison be absorbed through the skin ?

CHAPTER IX.
FOODS AND COOKING.

Necessity of Food. — Thus far we have been studying
processes by which the body's weight is reduced. We
have studied the. oxidation in the tissues and the removal
of the wastes. Unless the tissues receive a corresponding
supply the heat and energy of the body cannot long be
maintained.

Food Defined. — All substances that go to make up the
tissues or produce energy are foods. Certain substances
that do not become part of any tissues, nor in themselves
produce energy,- are useful in aiding the processes going
on in the body. These may be called accessory foods, e.g.
condiments ; some accessory foods, such as coffee, seem to
retard the waste of tissues.

Foods and Foodstuffs. — Most of our articles of food
consist of two or more different kinds of materials. For
instance, milk consists (i) chiefly of water; in this are (2)
the substance that makes cheese (casein); (3) cream, from
which we get butter (fat) ; (4) sugar, which gives milk a
sweet taste; (5) salts, such as common salt, lime salts,
etc. These different materials are foodstuffs. We have
many kinds of foods, but few foodstuffs, which we find
occurring over and over again, in various forms, in the
numerous things we eat.

144

FOODS. 145

Kinds of Foodstuffs.

1. Proteids (exatnple, casein). 4. Water.

2. Fats. 5. Salts.

3. Carbohydrates (example, sugar). 6. Oxygen.
Oxygen is by some authors called a food, but it is more

convenient to treat of it elsewhere.

The Proteids. — The chief substance in the white of an
egg is albumen, a typical proteid. Of the many proteids
some of the more commonly known are casein (the curd of
milk), gluten (in. grains), legumin (in peas and beans),
fibrin (in blood), myosin (in muscles). Gelatin (obtained
from connective tissue and bones by prolonged .boiling)
differs considerably from the proteids in composition, but
may be counted in with them. It is less valuable as a
food than the true proteids, although in certain circum-
stances more desirable from the fact that it is very easily
digested.

Characteristics of Proteids. — The proteids are —

1. Composed of carbon, hydrogen, oxygen, nitrogen, a
little sulphur, and, in some, traces of phosphorus.

2. Jelly-like, and do not easily diffuse through animal
membranes (a characteristic to be kept in mind when
studying digestion).

3. Coagulable (usually) by heat, acids, alcohol, etc.

4. Easily putrefy when moist and warm.

Importance of Proteids. — The proteids are of special
importance as foods because the most active tissues, muscle,
nerve, and gland, and the most important liquids of the
body, e.g. blood and lymph, have proteid as a chief con-
stituent. Proteid food, therefore, must be taken to make
good the losses of these tissues during their oxidations.

146 PHYSIOLOGY,

Proteid-containing Foods. - - The principal proteicl-
containing foods are lean meat, fish, eggs, milk, cheese,
and some seeds which abound in the vegetable proteids.

Meat. — Lean meat has about twenty per cent of pro-
teid, the rest being chiefly water. Beef and mutton are
more easily digested than veal and pork. It is better to
buy meat from a very fat animal than from a lean one, for,
although there is slightly less proteid in the meat from a
fat animal, this loss is more than made up by the addition
of fat, which takes the place of water in the meat from a
lean animal. There is more nourishment in a round steak
than in tenderloin.

Fish. — Fish, when fresh, is a good food. Although,
as a rule, salted meats are less easily digested than fresh,
salted codfish is a nourishing and economical food.

Eggs. — Eggs contain considerable proteid, but their
value as food has been overrated. The yolk has a large
amount of fat. Although the egg has all the material
needed to form a chick, it is not a perfect food for man.

Milk. — Milk, as we have seen, is an ideal food in that
it contains all the kinds of foodstuffs, and in the right pro-
portion for the young mammal. But the proportions are
not right for the adult. An adult would need four quarts
and a half daily, and then he would not get enough carbo-
hydrates (represented in milk by the sugar). The oily
material in milk is in the form of minute globules, which
can easily be seen under the microscope. Each of these
oil droplets is supposed to be surrounded by a thin en-
velope of albuminous matter, by means of which it is
enabled to remain suspended for some time instead of
rising quickly to the surface. Such a mixture of oil in a

FOODS. 147

liquid is called an emulsion. When cream is churned the
albuminous covering is removed and the butter "gathers."

Cheese. — Cheese is very rich in proteid, much more so
than lean meat. Yet, as it is rather difficult of digestion,
we do not use it largely as food ; we regard it more as a
luxury, while in many parts of Europe it is largely used as
food, taking the place of meat. It is a cheap food, and
might well be used more extensively, especially by laboring
men. When taken with milk it is said to be more readily
digested.

Vegetable Proteids. — Peas and beans (dried) contain
as much proteid (legumin) as meat, and all the cereals
contain some proteid (gluten).

Fats. — Fats are composed of carbon, hydrogen, and
oxygen. The oxygen is small in amount, so these foods
yield a great amount of energy by the oxidation of their
carbon (forming carbon dioxid) and hydrogen (forming
water). The fats most used are animal fats, including
butter. But some vegetable oils, such as olive and cotton-
seed oils, are used.

The Carbohydrates. — Starch and sugar are the chief
carbohydrates. Starch is used in larger quantity than any
other foodstuff except water. Sugar is usually regarded
as a luxury, yet it is an important food. It is quickly
absorbed.

Carbohydrate-containing Foods. — The principal car-
bohydrate-containing foods are the grains, vegetables, and
fruits.

The Grains. — The most important grains are wheat,
corn, rice, oats, rye, and barley.

148 PHYSrOLOGY.

Wheat. — Wheat furnishes the principal breadstuff
among the more civilized nations. It is especially
adapted to the temperate zones. Taking into consid-
eration its composition, digestibility, and other charac-
teristics, it is the most desirable of all the grains for
civilized man.

Wheat Flour. — In ordinary white flour nearly all the
gluten has been removed with the bran or " middlings."
While wheat or bread made from the whole grain of the
wheat may support life, one would starve if he attempted
to live on common white bread alone. It is almost en-
tirely starch. In the "entire wheat flour" it is claimed
that all the gluten is retained, only the very thin outer
husk of the grain being removed. It does not make so
white a flour, but it is better adapted to use as a food. If
we use white bread, having thrown away the nitrogenous
part of the wheat, we need to take more proteid from
other sources than if we used the entire wheat flour. This
is not economy. And it is claimed that the entire wheat
bread is more wholesome as well as more nutritious. The
part thrown away has in it phosphates as well as the nitrog-
enous material. This flour is ground fine so that it has
not the coarse particles which are in Graham flour, and
which are a source of irritation to the mucous coat of the
digestive tube in some persons.

Corn. — Corn is one of the most nutritious of the grains.
Professor W. O. Atwater, one of the best authorities in
the world on the subject of foods, says that, for a given
amount of money, more nutriment can be obtained in corn
meal than in any other food known. Corn is said to fur-
nish food to a larger part of the human race than any
other grain except rice.

FOODS. 149

Rice. — Rice forms a larger part of human food than
the product of any other plant, being often an almost ex-
clusive diet in India, China, and the Malayan islands.
Rice has a larger proportion of starch, and less of fats
and albuminoids, than the other grains. It is best adapted
for the food of warm climates.

Oats. — This grain was first used as food for man by
the Scotch, but the use has extended and become preva-
lent in this country. In point of nutrition it is ranked
higher by some than ordinary grades of wheat flour.

Rye. — Rye grows farther north than other grains, and is largely
used for bread in Russia and parts of Germany. It is a valuable food,
though less nutritious and less digestible than the corresponding prepa-
rations of wheat.

Barley. — This grain has wide range of cultivation, and, while in-
ferior to wheat, is considerably used where other grains cannot be
raised.

Potatoes. — Potatoes contain about twenty per cent
starch, two per cent of proteid, and no fat, the remainder
being chiefly water, with some useful salts, especially
potash salts. In spite of its relatively low food value, the
potato is our most useful vegetable on account of its
abundance, the ease with which it can be preserved, its
mild flavor, and the readiness and the variety of ways
in which it can be cooked.

Other Vegetables. — The chief nutrient in vegetables
is starch, though in many the starch is present in small
amounts. The salts and acids present are of value, and
care should be observed not to remove too much of these
salts in cooking. The fibrous matter, cellulose, while in-
digestible, is of value in adding bulk to the mass of food
to be digested. Formerly sailors were subject to scurvy ;

150 PHYSIOLOGY.

this is now attributed to a diet of fat and salt meat, to the
exclusion of fresh vegetables, vegetable acids, etc. The
disease is avoided by a greater use of vegetables, lime
juice, etc.

Fruits. — Many of the fruits, such as bananas and
apples, have considerable starch and sugar. But the
fruits are probably more useful to us on account of their
flavor, due to aromatic bodies, and to their salts and the
peculiar fruit acids.

Water. — Water constitutes about two thirds of the
entire weight of the body. It constitutes the bulk of the
liquids we have studied, blood, lymph, sweat, saliva, bile,
etc. Water is the solvent and carrier of all the material
of the body. Hence we need a large amount of it ; of
course we must remember that we get a good deal of water
in most of our solid foods.

Rain Water. — Water, as it comes from the clouds, is
pure. After enough rain has fallen to wash the air, rain
water is pure, and if caught on a clean roof (especially a
slate roof) and kept in a clean cistern, it is good drinking
water.

Well Water. — Falling upon the earth, the rain water
soaks down until stopped by some impervious layer, such
as clay. This water is the supply of our wells and springs.
It always has more or less earthy matter in solution, and
is therefore more or less " hard." Unless a large amount
of mineral matter or some special material is dissolved in
it, it is, ordinarily, good drinking water. Such water is
not pure, in the strict sense of the word, but is pure for
drinking purposes.

FOODS. I 5 1

Impurities in Water. — The great source of danger is
from what are called " organic" impurities. Bacteria will
not live and grow in pure water. They must have some-
thing on which to feed and grow. But in water contain-
ing a large amount of decaying animal or vegetable matter
they are likely to abound. And the most dangerous
sources of contamination are cesspools and sewers. Water
may be contaminated by such material and not have bac-
teria in it, but is very likely to harbor such foes.

Contamination from Cesspools. — The ordinary cess-
pool is a grave source of danger. Because the well may
be on higher ground than the cesspool does not give as-
surance that the water may not be polluted. Often when
the surface of the ground slopes in one direction, the strata
underneath may slope in just the opposite direction, and
the well may be the reservoir into which the cesspool is
drained.

Good authorities say that a cesspool should not be
allowed within a hundred feet of a well.

Abolish the Cesspool. — But it is better and safer to
have no cesspool. Where a sewer system is not to be
had, it is better to allow no great accumulation of such
material. A deep pit in which a quantity of semiliquid
matter gathers is not only a nuisance, but a source of
danger. Privies should have a very shallow pit, or none,
and should be cleaned often. There should be a little
dust sprinkled in each day, and occasionally some " chlorid
of lime " or sulphate of iron.

Typhoid Fever. — Typhoid fever is now known to be
usually caused by drinking water. The dejecta of some
one who has had the disease find their way into the source
of the drinking water. In many cases this has been clearly

152 PHYSIOLOGY.

proved. Of course the dejecta of all such patients should
be either destroyed or thoroughly disinfected.

Ice Water. — Although bacteria will not develop in a
cold place, they are not killed when water freezes, as was
formerly supposed. Further, ice, in forming, does not
throw out all the impurities, as was formerly stated. So
it is not safe to drink water formed from melted ice unless
the water of which that ice was made was good water.
The ice taken from ponds is not safe. If ice is made
artificially from suitable drinking water, of course the
melted product will be essentially unchanged so far as the
composition is concerned. Water may be cooled by plac-
ing any ice around it, and we may have the desired tem-
perature without any admixture of a dangerous element.

Boiling Water. — When one cannot get good drinking-
water, or when away from home where the water is of
doubtful purity, it is better to boil the water before using
it, either as a drink or in preparations of food that are not
to be thoroughly cooked. It seems to be proved that it
is better to heat the water twice nearly to the boiling point
than to boil hard once only. The first heating may start
the resistant germs into more active life, causing them to
sprout (so to speak), and a second heating several hours
later may easily kill them ; whereas it has been proved
that one hard boiling will not always kill the germs.

Cautions as to Drinking Water. — Or if one uses tea
and coffee, it is safer to content one's self with these, and
not drink much water till that which is safe, as from deep
wells, can be obtained.

In hot weather, and especially for those who are engaged
in hard work, it has been found that a little oatmeal
stirred in the water is beneficial.

FOODS. 153

When overheated, avoid drinking much cold water. Re-
peatedly rinse the mouth with cool water, and swallow very
little. This is the way trainers manage a horse at a race,
and it is sensible to treat a man as carefully.

Salts. — Salts include many substances besides common
salt. They aid in the solution of various substances during
digestion and in other processes. We cannot live without
salt.

Lime in the form of calcium phosphate and calcium car-
bonate is essential, especially in the bones and teeth. Iron
is associated with hemoglobin.

Necessity of a Mixed Diet. — Our experience, together
with the results of the experiments on animals, teaches
that we could not live long if fed on any one class of
foodstuffs alone. We must take a representative of each
of the groups. We have noticed that most of our foods
already contain more than one foodstuff. We so combine
them as to get suitable proportions. Thus we eat bread
and butter (a small amount of fat with a large quantity of
starch and a little gluten), meat and potato, crackers and
cheese, pork and beans, egg on toast, bread and milk, rice
and fowl, macaroni and cheese ; they " go well together "
chiefly because they are complementary.

Disadvantages of a One-sided Diet. — In order to get
enough nitrogen from bread alone, one would have to eat
about four pounds a day ; meanwhile twice as much car-
bon as is needed would be taken, thus throwing an undue
amount of work upon the digestive organs. Again, one
would need to consume about six pounds of meat to get the
requisite amount of carbon, and six times as much nitro-
gen as is needed would be taken ; to get rid of this extra
nitrogen would severely tax the kidneys and liver.

154

Effect of Cold on Appetite for Fats. — In cold el i mates
a large amount of fat is consumed, while in the tropics
starch is the chief food. Our appetites call for more of the
fatty foods during the winter season.

Proper Diet. — While common experience has led people
to adopt a mixed diet, the proportions of the different food-
stuffs is not always what it should be. The proportions
of the foodstuffs (exclusive of water) may be roughly stated
as about I part of proteid, i part of fat, 3 parts of carbo-
hydrates. But this will vary somewhat with the amount
of work done, and other varying conditions.

Vegetarians. — The so-called "vegetarians" recognize
the need of proteid food, and most of them seek proteid in
eggs, milk, and cheese. But these are animal products,
and the name " vegetarian" is inconsistent. They are
merely "anti-meat eaters." If they do actually succeed
in getting enough proteids from the legumes and the
grains, the complete digestion of which is difficult, they
are, as Professor Martin says, to be congratulated on having
digestive powers that can stand such a strain. That we
are adapted for using flesh as part of our food is indicated
.in at least two anatomical features: ~(i) we have canine
teeth, though not so fully developed as in the carniyora ;
(2) the intestine in carnivora is very short, that of the
herbivora very long, but in man intermediate. Neverthe-
less, it is undoubtedly true that many persons eat too much
meat.

Tea. — Tea owes its stimulating effects to a substance
called thein. This is a stimulant to the nervous system,
but if not too strong is not followed by a subsequent
depression. Tea that is too strong is likely to produce
nervousness and dyspepsia. Boiling the tea leaves also

FOODS. 155

brings out the tannic acid that they contain, and produces
bad effects.

Coffee. — Coffee owes its stimulating effect to a sub-
stance called caff tin, which is considered identical with
thein. Coffee acts as a restorative after hard labor, seem-
ing to retard the wastes of the tissues and food. It is used
in the army (also in penitentiaries), not as a luxury, but as
a matter of economy in the matter of food supply. Coffee,
used to excess, frequently causes palpitation of the heart.

Malted Milk. — Malted and peptonized milk makes a
valuable drink for invalids and dyspeptics.

Cocoa and Chocolate. — Cocoa contains a stimulant
called theobromin. But unlike tea and coffee, cocoa and
the preparation from cocoa known as chocolate are true
foods by virtue of the fat contained.

Beef Tea. — Beef tea and various beef extracts are very
beneficial. There is not enough nourishment in them to
maintain strength without other food. Their nutritive
value has been somewhat overestimated. Their value is
probably much more in their stimulating than in their
nourishing effect. But many of the soups and drinks
made from these preparations are very beneficial. They
refresh the tired system wonderfully. If the man who
feels " fagged out" and takes a drink of liquor to " brace
him up," as he says, were to take a cup of hot bouillon, he
would find himself braced up for the time, without any bad
reaction, or permanent injury to the system, which follow
the use of alcohol.

Cooking. — Cooking is designed to make food more
palatable and more digestible. Some foods, such as eggs,

156 PHYSIOLOGY.

are as digestible before they are cooked as after, often more
so, as they are very frequently badly cooked. But many
foods in the raw state are unattractive, or even repellent,
whereas cooking usually develops an agreeable odor and
taste. Cooking should soften the harder and tougher tis-
sues, such as cellulose in vegetables, and the connective
tissue of animal foods. Cooking starch causes the starch
grains to swell and burst, and makes the starch much more
digestible.

Making Soup. — If meat be cut into small pieces and
put into cold water, and the water gradually warmed, the
soluble material of the meat may be extracted, and this is
the principle followed in making soups.

Boiling Meat. — But if we wish to cook the meat itself,
the juices should be retained instead of withdrawn. For
this purpose boiling water is poured over the meat to co-
agulate the outer layer, and prevent the extraction of the
juices.

Baking, Roasting, and Broiling. — The same principle
applies to baking, roasting, and broiling. The outside is
subjected to high heat at the beginning of the cooking,
which forms a layer nearly impervious to the nutritious
material inside. In these modes of cooking it is very de-
sirable to reduce the heat applied after the first few min-
utes, so that the interior may be more gradually cooked ;
this is, perhaps, especially true in broiling.

Frying. — Frying, as ordinarily done, is not a good
mode of cooking ; in fact, is often very bad, as the food is
frequently penetrated by fat and rendered very indigestible.
But true frying, that is, by immersion in boiling fat, is a

FOODS. 157

good mode of cooking. This coagulates the albuminous
substance on the outside, keeps in the nutritious juices,
and prevents soaking with the fat. Often the food to be
thus cooked is first coated with white of egg, which is
very quickly coagulated, and helps form a protecting out-
side crust.

READING. — Practical Sanitary and Economic Cooking,
Abel (Public Health Association); The Science of Nutri-
tion and the Art of Cooking, Atkinson; Chemistry of
Cookery, Williams ; Chemistry of Foods and Nutrition,
Atwater (Century Magazine, 1887-88; also Department
of Agriculture); Eating for Strength, Holbrook; Foods,
Smith ; Philosophy of Eating, Bellows ; Handbook of In-
valid Cooking, Boland.

Summary. — i . Food builds tissue and maintains energy.

2. The simpler constituents of foods are called foodstuffs.

3. The foodstuffs are water, salts, proteids, carbohydrates, and fats.

4. Water is essential to life, making two thirds of our weight.

5. Salts are essential to life.

6. The chief proteids are lean meat, eggs, cheese, gluten, etc.

7. The chief carbohydrates are starch and sugar, derived from the
grains, vegetables, and fruits.

8. Fats and oils are obtained from plants and animals.

9. The chief source of impurity in water is from bacteria, which
thrive when decaying animal and vegetable matter are present.

10. Boiling water may destroy these germs of disease.

11. Ice water is not a wholesome drink.

12. A mixed diet is necessary, as no one food contains all the
needed material in the right proportions to maintain life well.

13. Tea and coffee are slightly stimulating, but, if used moderately,
ordinarily without any bad reaction.

14. Cooking is to make food more palatable and digestible.

158 rHYSIOLOGY.

Questions. — i. Which class of foodstuffs is most expensive?
Why?

2. Make a list of all the common foods, naming the foodstuffs in
them.

3. Why do we not eat buckwheat cakes and sirup in summer ?

4. At what price are eggs an expensive food ?

5. How do flour and potatoes compare in economy at ordinary
prices ?

6. Why are foreigners prejudiced against corn ?

7. Why is broiling better than frying ?

8. Why do Englishmen in India so generally suffer from "liver
complaint1' ?

CHAPTER X.
THE DIGESTIVE SYSTEM.

The Object of Food. — The tissues are worn out by their
oxidations. They are built up again by the blood, and
the blood is renewed by the food.

All food must be reduced to the liquid condition, if it
is not already liquid.

The Digestive Tube. — The chief organ in this work
of liquefying the food is the digestive tube, or " alimentary
canal," as it is called. As the food passes through the
digestive tube it is subjected to various mechanical and
chemical processes which liquefy it and bring it into such
a condition that it can be absorbed through the mucous
lining of the digestive tube and passed into the blood.

The Work of the Digestive Tube. — To take a special
instance, a muscle is in part worn out by the oxidation
during its activity ; to replace the loss suppose we take
a piece of steak. We cannot substitute this directly in
the place of the worn-out tissue. In digesting the steak
we must tear it all to pieces, and reduce it to a liquid form
by the action of the teeth and by the various liquids from
the glands along the digestive tube. In short, the muscle,
as such, must be thoroughly destroyed ; in the liquid pro-
duced by the digestion of the beef there is no trace what-
ever of the structure of the beef. But the blood, taking
this material, builds muscle which can hardly, if at all, be
distinguished from the original beef.

160 J'HYMOLOUY.

If the food taken be all ready to build tissue, for exam-
ple, certain forms of sugar, liquid, soluble, and of the
proper chemical composition, it will not need to go through
these changes.

In order to understand the process of digestion let us
first turn our attention to the anatomy of the organs of
digestion.

The Organs of Digestion. — The organs of digestion
are the digestive tube and the accessory parts, the masti-
catory organs, the glands in, and alongside of, the walls
of the tube.

The parts of the digestive tube are the mouth, the
pharynx, the gullet (or esophagus), the stomach, the small
intestine, the large intestine.

Brief Description of the Digestive Organs. — At the
back of the mouth may be seen the soft palate with the
cylindrical uvula hanging from its center. Beyond this
is the cavity of the pharynx, which narrows below into
the gullet, a red-walled, muscular tube, extending along
the dorsal side of the windpipe, and close to the spinal
column. It extends the length of the thorax, and then
passes through the diaphragm and widens into the stomach,
at the upper left end of the latter. The stomach is some-
what pear-shaped, with the larger end to the left. At the
right end it tapers into the small intestine, the first foot
or so of which is called the duodenum. Then comes a
long coil of the small intestine, which joins the shorter
large intestine, ending in the rectum. Just below the
diaphragm is the dark-colored liver, overlapping a large
portion of the stomach. Between two of the lobes of the
liver is the bile sac whose duct enters the duodenum a
short distance from the stomach. The pancreas is a pink-

THE DIGESTIVE SYSTEM.

161

ish organ of irregular shape lying along the stomach and
duodenum. Its duct enters the duodenum at the same
point as the bile duct. The intestine is held in place by
the mesentery, a thin fold of transparent membrane folded
closely around it, and supported from the dorsal wall of
the abdominal cavity. Between the two layers of the
mesentery are the branches of the artery supplying the
walls of the intestines, and the veins that convey the ab-
sorbed food from the intestine to the liver.

Digestive Organs of a Cat or Rabbit. — The digestive organs will
be much better understood if a cat or rabbit be dissected, as the organs
have essentially the same form and relations. The animal may be
killed by putting it in a tight box, or under a washbowl with a small
sponge holding a tablespoonful of ether or chloroform. It may then
be opened by a slit along the middle line of the ventral surface, from
the chin to the pelvis. The diaphragm should be noted as forming
a partition between the cavity of the chest and that of the abdomen.

To Illustrate the Mesen-
tery.— To illustrate the rela-
tion of the mesentery to the
intestine, suspend the arm in
a sling made of a handkerchief;
press the two thicknesses of
the cloth together just above
the arm to represent the two
layers of the mesentery.

Model of Intestine and
Mesentery. — A more com-
plete representation may be
made as follows : Material :
piece of large (one inch or more
in diameter) rubber tubing,
eight inches long; sheet of

thin white court plaster, six inches by twelve inches ; red, blue, and
white cord. Lay the tube across the middle of the court plaster; gum
the plaster snugly around the tube ; between the two adjacent layers

Fig. 54. Cross-section of Abdomen.

1 62 rnys/oi.or,y.

of the court plaster, where they meet after passing around the tube,
lay the three kinds of cord, each frayed out at one end, the frayed ends
resting upon the tube. Moisten the court plaster and press the layers
firmly together. The court plaster should now adhere so closely to
the tube as hardly to be seen, and the two layers should seem as one,
in which appear the cords representing the arteries, veins, and lacteals.

The Mouth. — In studying the mouth and contained
organs, the student should not content himself with mere
reading, but should carefully examine his own mouth
cavity by means of a hand glass. We are apt to think
of the mouth as a cavity of considerable size, as indeed
it is when fully opened ; but we are not so likely to think
how completely the cavity is obliterated when the mouth
is closed. If one notes the sensations from the mouth
when it is closed, he will perceive that the tongue almost
entirely fills the space, touching the roof of the mouth, and
the teeth in front and at the sides.

The Tongue. — The tongue consists chiefly of muscles,
extending in different directions, thus giving the tongue
a variety of motions. The tongue is the chief organ of
taste, and is therefore (with the sense of smell) the gate-
keeper of the digestive tube. The tongue has also a keen
sense of touch (the keenest of any part of the body), and
so is useful in detecting and removing any food particles
that may remain on the teeth after a meal. During
mastication the tongue, with the lips and cheek, keep the
food between the teeth. When the morsel of food is
sufficiently masticated, the tongue pushes it back into the
pharynx to be swallowed.

The Teeth. — The teacher can usually obtain a lot of
teeth from the dentist for the asking. These should be
cleaned before using them in the class. Use pearline

THE DIGESTJl'E SYSTEM.

I63

or any washing soda. If there be enough time, let each
pupil make a drawing of one of each of the four kinds of
teeth ; and it would be well to draw both a front (outer
surface) and a side view (surface adjacent to another
tooth) of each of the four kinds.

Longitudinal Section

Side View

Face View

Crown

Neck

Root

Hole for Blood Tubes and Nerves -
Fig. 55. Parts of a Tooth. (Incisor.)

External Features of a Tooth. — Examine one of the
front teeth. It has the following parts : —

1. The crown, the part that is above the gum.

2. The root, the part that was buried beneath the gum.

3. The neck, a more or less constricted part, dividing
the crown from the root ; it is normally at about the sur-
face of the gum.

4. A hole at the tip of the root.

To make a Section of a Tooth. — Let each pupil prepare a longi-
tudinal section of a tooth as follows : Imbed a tooth in a little sealing
wax on the end of a spool, cork, or block of wood. With a grindstone
grind away one half, showing the pulp cavity to the tip of the root as
in Fig. 55. Make a drawing of the surface thus exposed, naming the
parts. If human teeth cannot be obtained, almost any kind will serve.
Let each pupil keep his preparation.

164 rnvsioi.OC,Y.

Structure of a Tooth. — i. The pulp cavity, communi-
cating with a hole in the tip of the root, through which
the nerve and blood tube entered.

2. The bulk of the tooth is made up of a substance
called dentine (ivory).

3. The crown of the tooth has a covering of enamel, a
very hard substance.

4. The root is covered with a bony substance called
cement.

The Kinds of Teeth and their Arrangement — Begin-
ning at the middle of the front of the mouth, there are (in
the normal adult) eight teeth in each half jaw : two in-
cisors, one canine, two bicuspids (or premolars), and three
molars.

Dental Formula. — The kinds and arrangement of teeth
are often expressed by a dental formula, in which the nu-
merators indicate the upper jaw and the denominators the
lower, thus : If, C^, PMf , Mf (for one side of the head).

Incisors. — The crown of an incisor is chisel shaped ;
but the root is flattened in the opposite direction, i.e. at
right angles to the jaw, instead of parallel to it, as is the
case with the crown. Look at a skull from which the
teeth have been extracted in order to see the cavities into
which the teeth fitted.

Canines. — The canine tooth has a conical crown, and a
longer root than the incisor.

Bicuspids. — The bicuspid has two points.

Molars. — The molar has a cuboidal crown, and usually
two or three roots.

The Milk Teeth. — The thirty-two teeth of the perma-
nent set were preceded by a temporary set of twenty milk

THE DIGESTIVE SYSTEM

I65

teeth. Because the first set is temporary it should not
therefore be neglected. Cavities in these should be filled
and the teeth kept clean. Before the temporary set has
gone the first of the permanent set appear. The first of

KINDS OF TEETH
Incisors :::••—

Upper

TIME OF APPEARANCE

7tb Month

9th "

18th "

TEMPORARY SET
Upper

Lower
PERMANENT SET

Fig. 56. TEETH: Kinds, Arrangements, and Times of Appearance.

these, often called the " six-year molars," are just back of
the hindermost "milk molars." These should receive
especial care, as they will never be replaced. Any begin-
ning of decay in them ought to receive prompt attention.

1 66

The Care of the Teeth. — The teeth need careful atten-
tion. They should be thoroughly brushed at least twice a
day, on rising and on going to bed. It would be better to
clean them after each meal also. If a tooth powder, recom-
mended by a reliable dentist, is not used, a good white
castile soap will serve well. It is better to use tepid water.
If the teeth are not thoroughly cleansed the particles of
food which remain will soon begin to decay. This decay
is caused by the growth of germs, usually some kind of
bacteria, and the decay thus begun is likely to develop
acids which attack the limy material of which the teeth are
composed. When it is necessary to take acid medicines,
care should be taken not to let them come in contact with
the teeth. Sweet substances are very likely to decompose
and form acids ; so we must clean the teeth after eating
candies. Toothpicks are useful in removing the larger
particles. But in using toothpicks care should be taken
not to dislodge fillings. The teeth should be examined
twice a year by a dentist, and any cavities promptly filled.

The Salivary Glands. — The salivary glands make the
saliva and pour it into the mouth. There are three pair of
salivary glands — the parotid, just back of the angle of the
jaw, under the ear ; its duct runs forward under the skin
of the cheek, and opens on the inside of the cheek opposite
the second molar of the upper jaw. The submaxillary
gland lies under the angle of the jaw ; its duct opens under
the tongue near the front of the mouth. The sublingual
gland is in front of the submaxillary and empties near the
same place as the .submaxillary.

Dissection of the Salivary Glands. — The salivary glands of a
rabbit or cat may be found near the base of the ear and under the angle
of the jaw by removing the skin from the side of the head and neck.

THE DIGESTIVE SYSTEM. 1 67

Salivary Ducts in Our Mouths. — If the inside of one's cheek be
examined by the use of a hand mirror, the opening of the duct from the
parotid gland may be seen opposite the second molar of the upper jaw.
It usually looks like a pink and white spot, resembling a wound of a
bee sting. Sometimes saliva may be seen issuing from it.

Action of the Salivary Glands. — The salivary glands
pour into the mouth a liquid which they manufacture from
materials taken from the blood. In structure the gland
may be compared to a bunch of grapes^ the grapes repre-
senting the little cavities, with a wall of cells that make

Mucous Membrane

Duct of Gland

Secreting Cells

Fig. 57. Diagram of a Salivary Gland. (.After Landois and Stirling.)

the saliva. From these cavities the liquid passes into the
individual duct, represented by the stem of a single grape ;
many of these unite to form the main stem, which corre-
sponds to the main duct. A rich network of capillaries
surrounds the gland ; when the gland is at work it receives
more blood ; the liquid part of the blood (plasma) soaks
out through the capillary walls and surrounds the gland ;
it is now called lymph ; from the lymph the gland directly
obtains its material.

168 PHYSIOLOGY.

Nerve Control of Salivary Glands. -The glands are
doubly dependent on nerve control : —

1. Through the control of the arterial muscles by the
nerves the amount of blood sent to the glands is regulated.

2. Nerves also go to the cells of the gland to control
their activity. When we taste, smell, see, or even when
we think of, some delicious food the mouth may "water,"
as we say, i.e. the salivary glands are, by reflex action,
stimulated to activity ; on the other hand, some emotions,
such as fear, check the flow of saliva.

Saliva and its Uses. — The saliva is mostly water, and,
when we are not eating, serves to keep the mouth moist.
The water of the saliva soaks the food during mastication
and helps the process of grinding ; it enables us to taste
by dissolving any food that is soluble ; it further enables
us to swallow what would otherwise be a dry powder.
The special element of the saliva, ptyalin, has the power
of changing starch to sugar.

Amount of Saliva. — The amount of saliva secreted
daily is estimated at three pints. Of course the glands
should be allowed to rest between meals. The habit of
chewing gum, though supposed to aid digestion, undoubt-
edly does far more harm than good. During the resting
period the glands accumulate material for the active work
of secretion, for there is no sac in which to store the
saliva, and it must be made as fast as it is needed.

Character of Salivary Ferment. — " The character of
action of salivary ferment is further defined by experi-
ments showing : i, that it is destroyed by boiling; 2, that
its action is delayed or suspended at a low temperature,
most pronounced at about body temperature (37° C);
3, that it acts best in a neutral or in a faintly alkaline

THE DIGESTIVE SYSTEM. 169

medium, not at all in an acid medium, or in too strong an
alkaline medium ; 4, that it has almost indefinite power,
if the product of its own action (sugar) is not suffered to
accumulate. In all these respects, with the exception
of the third, the salivary ferment resembles ferments in
general, which are destroyed by heat, delayed by cold,
and are limited in their action only by the accumulated
product of such action." — WALLER.

Enzymes. — Ptyalin is a type of a group of bodies
called unorganized ferments, or enzymes. These ferments
are the agents that produce the peculiar chemical changes
that are the chief part of digestion.

Mucous Glands and Mucus. — Besides the salivary
glands, there are great numbers of simple glands in the
mucous membrane lining the mouth. These secrete a
glairy substance called mucus.

Experiments with Digestive Liquids. — It may be proved by
experiment that saliva turns starch to grape sugar in an alkaline solu-
tion and at the proper temperature. Also that pepsin dissolves proteids
in an acid (hydrochloric) at the right temperature. The proteid is
turned to peptone, and becomes soluble and diffusible, capable of
absorption through the walls of the stomach and intestine. We find
that the different elements of the pancreatic juice can, in alkaline solu-
tion, and at the right temperature, emulsify fats, turn proteid to pep-
tone, and convert starch into grape sugar.

The Pharynx. — The cavity back of the mouth, beyond
the soft palate, is the pharynx. The pharynx is a funnel-
shaped cavity, communicating above with the passages
from the nostrils ; in front it opens into the mouth ; below
it connects with the windpipe, through the glottis, and
with the gullet, which, as we have seen, lies just back of
the windpipe.

PHYSIOLOC.Y.

Position of Organs during Respiration. — In quiet
respiration the tongue nearly fills the mouth. The base
of the tongue is nearly covered by the soft palate, which
curves downward from the hard palate, and by the epi-
glottis projecting upward from below. The glottis is
open and the gullet is closed. Air enters the nostrils,
passes along the nasal passages above the hard palate,
back of the soft palate and epiglottis, through the open
glottis into the windpipe, and on to the lungs.

Hard Palate ------

Eustachian i ube

•-- Soft Palate, Down

Pharynx

- Epiglottis, Raised

-—Gullet, Closed
Glottis, Open

Fig. 58. Diagram, showing the Positions of the Organs of the Mouth and
Throat during Breathing.

The Process of Swallowing. — When the morsel of
food is ready to be swallowed the tongue pushes it back
into the pharynx ; the soft palate is raised to shut off the
passage into the nasal cavity ; the larynx is pulled upward
and forward ; the epiglottis is pulled down over the glottis,
or opening of the windpipe ; and the base of the tongue
extends back over the epiglottis ; thus the air passages,
above *md below, are shut off, and the food passes over
the epiglottis into the gullet. The muscles of the pharynx

THE DIGESTIVE SYSTEM.

171

also do their part in pushing the food along. As soon as
the food has passed over the epiglottis, the epiglottis rises
to its upright position, and the soft palate drops back to
its place, leaving the air passages again open.

Breathing and Swallowing. — It is to be observed that
the food tube and the air tube cross, and that the pharynx
is their crossing. As we are swallowing only a small
part of the time, the passageway naturally stands open to
the air ; and when we swallow, the parts are, by muscular

Eustachian Tube

- Soft Palate, Raised

- Food

.... Epiglottis. Down

- Gullet, Open

•- Glottis, Closed

Fig. 59. Diagram, showing the Positions of the Organs of the Mouth and
Throat during Swallowing.

effort, temporarily adjusted for this work. There is a
spring switch (to borrow a term from the railway) which
keeps the track open for the air, which is all the time
passing ; but when the food comes along, the switch must
be held open for it until it has passed.

Structure and Action of the Gullet. — The gullet has
an outer muscular coat and an inner mucous coat. The

172 PHYSIOLOGY.

muscular coat has two layers, an inner with circularly
arranged fibers, and an outer layer with longitudinally
arranged fibers. When the food enters the gullet the
muscle fibers, especially the circular fibers, shorten, and
by a wave-like action push the mass rapidly along into the
stomach. The first part of swallowing is voluntary ; but
after the bolus has entered the gullet the action is involun-
tary. The mucous lining of the gullet has many mucous
glands which lubricate the passageway by the mucus which
they secrete.

Illustration of Passage through the Gullet. — The passage of the
food through the gullet may be illustrated as follows : Let several per-
sons hold a large rubber tube with their hands in contact. Put an egg-
shaped piece of wet soap in the tube. The first hand is shut and
pushes the soap along into the part of the tube held by the next hand ;
this hand now compresses the tube, while the first hand remains clinched ;
and so, in turn, the object is pushed the whole length of the tube.

The Stomach. — Just beyond the diaphragm the diges-
tive tube widens suddenly, forming the stomach ; the
stomach is an oval sac lying just beneath the diaphragm,
with the large end to the left and the small end to the
right. The smaller end, by narrowing, becomes the small
intestine. When the stomach is empty it collapses, as its
walls are soft and flexible. When distended it may hold
three pints, or when abnormally distended even more.

The Coats of the Stomach. — The stomach and intestines have four
coats, in the following order, beginning at the outside : the peritoneum,
the muscular, the submucous, and the mucous coats. The muscular
coat of the stomach consists of three layers, distinguished by the
arrangement of the fibers, a circular layer, a longitudinal layer, and an
oblique layer. The mucous lining is somewhat loosely attached to
the muscular coat by the intervening submucous coat, and when the
stomach collapses the mucous coat is thrown into folds, usually running
lengthwise.

THE DIGESTIVE SYSTEM.

173

The Gastric Glands. — In the inner surface of the
mucous membrane are many holes. These are the mouths
of the ducts of the gastric glands. If a duct is traced
inward, it is found to divide into several branches, usually
two or three. These gastric glands vary somewhat in their
structure in different parts of the stomach.

The Gastric Juice. — The liquid secreted by the differ-
ent glands also varies considerably, but the liquid as a
whole is called the gastric juice. The gastric juice is

GULLET

Fig. 60. Longitudinal Section of Stomach, showing Gastric Glands in Position.
(Dorsal View. Mucous Coat Unduly Thickened.)

chiefly water, containing a ferment, or enzyme, called
pepsin, and a small amount of acid. The amount of
gastric juice secreted daily has been estimated at from
five to ten quarts. Of course, we must bear in mind that
nearly all of this is again absorbed from the digestive tube,
and is not a permanent loss to the body.

Blood Supply of the Stomach. — The mucous mem-
brane is abundantly supplied with blood tubes, but
during the time of its rest the blood flow here is

174

PHYSfOLOGY.

Mouth of Gland

Epithelium

Cells

diminished, and the membrane is comparatively pale.
But as soon as food is introduced into the stomach the
blood flow is greatly increased, and the mucous membrane
becomes red. This blood supply gives the glands the ma-
terials with which they manufacture the gastric juice. At

the same time the cells of
the glands are stimulated
to action, and the secre-
tion is poured out rapidly.
The alkaline saliva also
aids in stimulating the
i secretion of the gastric
juice.

The Work of the
Gastric Juice. — The spe-
cial work of the gastric
juice is accomplished by
the pepsin, aided by the
acid ; these convert pro-

teids into a soluble substance, called peptone, which can
be absorbed through the walls of the digestive tube into
the blood.

Rennet and Rennin. — Rennet, used in cheese making, is a familiar
substance obtained from the fourth stomach of the calf. When milk
enters the stomach it is curdled ; that is, the casein previously dissolved
in the liquid milk is coagulated. This curdling, or coagulation, is at-
tributed to a ferment in the gastric juice called rennin, and it seems to
be entirely distinct from pepsin.

Churning Action of the Stomach. — At the same time
all the food is soaked by the gastric juice, the process being
greatly assisted by the churning motion of the stomach
caused by the action of the muscular coat. The food is
thus gradually re'duced to a pulpy mass called chyme.

Connective Tissue

Fig. 6 1 . Three Glands of the Stomach —
Cardiac Part.

THE DIGESTIVE SYSTEM. 1/5

During the first part of digestion in the stomach the thick
ring of circular fibers called the pylorus (gatekeeper) around
the opening of the stomach into the intestine keeps the
passage nearly closed, leaving a small orifice for liquids
only. But as the food is reduced to the proper condition
the pyloric muscles relax and allow the chyme to pass into
the intestine. And at last any indigestible substances are
usually allowed to pass.

Sphincter Muscles. — Such rings of muscular fibers,
guarding openings, are called sphincter muscles. There
is a similar one at the anal opening.

Time of Stomach Digestion. — The time required for
the digestion of any ordinary meal is from three to four
hours, though this may be much longer if very indigestible
substances have been eaten, or if the condition of the body
or mind is such as to retard the process of digestion.

Absorption from the Stomach. — Some parts of the
food that are already digested, or such matters as are sol-
uble, e.g. water containing sugar, peptone, salts, etc., may
be absorbed immediately through the walls of the mouth
and stomach into the blood capillaries. Recent experiments
show that the amount of absorption from the stomach is
much less than was formerly supposed ; water, for instance,
" when taken alone, is practically not absorbed at all in the
stomach. As soon as water is introduced into the stomach
it begins to pass out into the intestine, being forced out in
a series of spurts by the contractions of the stomach."

Chyme. — The rest of the food, now called chyme, is
passed on into the small intestine. It is acid, and in a
liquid or semiliquid condition. Chyme, as it enters the
intestine, is a mixture of digested, partly digested, and un-

1 76

PHYSIOLOGY.

digested materials. Some of the starch has been changed
to sugar, but only a small part, owing to the short time of
mastication. The bulk of the starch is unchanged. Some
of the proteid is already changed to peptone. Part is still
proteid, while part is in an intermediate stage between
proteid and peptone. Fat is essentially unchanged, but is
melted by the heat of the mouth and stomach, and is more
or less divided into small drops by mastication and the
movements of the stomach. For instance, in eating bread
and butter, the melting butter will be finely mixed with the
bread as it is chewed. The water in the chyme was partly
taken as such, and partly derived from the saliva and
gastric juice. There are also present ptyalin, pepsin,

mucus, salts, and some indigesti-
ble substances. At intervals the
sphincter muscles of the pylorus
relax, and the contractions of the
stomach send the liquid mixture
into the intestines by spurts.

The Intestine. — The small in-
testine has essentially the same
structure as the parts of the diges-
tive tube already studied, namely,
a mucous lining beset with an im-
mense number of tubular glands,
called intestinal glands. These

secrete a liquid collectively called the intestinal juice, whose
exact work is not well known, but which may be said to
complete the work of the other secretions. The intestine
has also a muscular coat with circular and longitudinal
fibers. And the muscular coat does the same work of
mixing the juices with the food and of moving it along.

Fig. 62. Horizontal Section
through the Mucous Membrane of
the Intestine, showing Intestinal
Glands in Transverse Section.
(Highly Magnified.)

THE DIGESTIVE SYSTEM.

177

Bile and Pancreatic Juice. — Soon after the chyme
enters the small intestine it has poured upon it two liquids,
which enter the intestine in one common stream ; these
are the bile and the pancreatic juice. These juices come
from two large compound glands, the liver and pancreas,

Fig. 63. Diagram of Portal Circulation.

that lie close to the stomach. Their ducts join before they
enter the intestine into which these juices are emptied a
few inches beyond the stomach.

The Portal Circulation. — The liver receives blood
from two sources, — a branch of the aorta and the portal
vein. The portal vein is formed by the union of veins
from the stomach, intestine, pancreas, and spleen. Unlike

1/8 PHYSIOLOGY.

other veins, the portal vein divides and subdivides, forming
capillaries which ramify through the liver. The blood is
again collected by veins, forming the hepatic vein which
empties into the postcaval vein close to the diaphragm.
From the blood the liver manufactures at least two impor-
tant substances, — the bile and liver starch, or glycogen.

Functions of Bile. — The bile is secreted all the time,
but more actively during digestion. The part made while
digestion is not going on is stored in the bile sac. The
functions of the bile are still poorly understood. But the
following are believed to be a part of its work : —

1. It is believed to aid in emulsifying the fats.

2. It is supposed to aid in the absorption of fat.

3. The bile, to a certain extent, is waste matter ; so the
liver is an organ of excretion as well as an organ of secretion.

4. It is found that if, for any cause, the bile is prevented
from entering the intestine, constipation follows, and the
contents of the large intestine have a much more fetid
odor than usual. The bile itself readily putrefies ; hence
it is concluded that the bile has no positive antiseptic
properties, but in some indirect way retards putrefaction.

The liver, from its size, ought certainly to be of great
importance in the body ; it is the largest gland in the
body, and receives one fourth of the blood.

The Work of the Pancreatic Juice. — The pancreatic
juice acts on all the principal classes of foodstuffs : —

1. A ferment in it called amylopsin acts on starches,
changing them to sugar, even more energetically than the
ptyalin of the saliva.

2. Another constituent of pancreatic juice is trypsin ;
like the pepsin of gastric juice, this ferment has the power
of changing proteids to peptones.

THE DIGESTIVE SYSTEM. 179

3. The pancreatic juice also acts on the fats in two
ways : —

(a) It emulsifies them, i.e. the fat is divided into exceed-
ingly fine drops, each enveloped in a coating of albuminous
substance. An emulsion can be made artificially by shak-
ing together water, oil, and white of egg. The shaking
breaks the oil into fine drops, which would soon gather
again if no other substance were present ; but it is sup-
posed that the albumen forms a thin coating around each
droplet, enabling it to remain distinct in the liquid.

(b) The fats are also acted on chemically by steapsin,
another ferment of the pancreatic juice ; they are decom-
posed with the formation of free fatty acids, and thus
more fully prepared to be absorbed and to build up the
tissues. These free fatty acids aid in the work of emulsi-
fying the rest of the fat.

Review of Digestive Liquids. — Saliva acts only on
starch, gastric juice on proteids, bile on fats, whereas
pancreatic juice acts on all three, and, probably, more
energetically than the above-named liquids.

Intestinal Juice. — The intestinal juice contains a fer-
ment, called invertin, which changes cane sugar to dextrose
which is a variety
of grape sugar. vim

Acids and Al-
kalies in Diges-
tion. — The bile

and the pancreatic intestinal cianc-s

juice are alkaline,

Fig. 64. Mucous Membrane of Small Intestine

and overcome the

acidity of the chyme, as the acidity of the gastric juice

in the stomach overcame the alkalinity of the saliva.

180 PHYSIOLOGY.

Summary. — I . The chief work in digestion is to render the food
liquid, soluble, and in condition to be absorbed and become part of the
blood.

2. The digestive system consists of a long tube, through which
the food passes, being subjected to mechanical and chemical processes
to liquefy and otherwise make the food ready to become blood.

3. The teeth grind the food.

4. The food is soaked and acted on by the saliva, gastric juice,
intestinal juice, bile, and pancreatic juice.

5. These liquids are formed from the blood by glands. A gland
is a structure, usually tubular or saclike, surrounded by capillaries,
which give off lymph around the gland. The gland cells take part
of the lymph and form the "secretion," which is usually poured out
on a surface by means of a narrow tube, or duct.

6. The salivary glands, pancreas, and liver are compound glands.
The gastric and intestinal glands are simple.

7. The first part of swallowing is voluntary. Through the gullet
the food is pushed by the shortening of the circular muscle fibers.

8. The liver receives blood from the hepatic artery and from
the portal vein, but is drained by one vein, the hepatic, which empties
into the postcaval vein.

9. Saliva acts only on starch, gastric juice on proteids, bile on
fats ; pancreatic juice acts on all three of these foodstuffs.

Questions. — i. Why does the physician examine the tongue of his
patient?

2. What is the "mumps"?

3. Why is one more likely to choke if he thinks about the process
of swallowing?

4. What are the peculiarities of a cow's stomach?

5 . What is the meaning of biliousness ?

6. Why is there a difference in the length of the intestine in a cat
and a sheep?

7. What is colic?

CHAPTER XI.

Lymph
Duct

ABSORPTION — DIGESTION COMPLETED.

Absorption. — The mucous membrane of the small
intestine is thrown into ridges, but, unlike those of the
stomach, they
run transversely.
Again, while the
folds in the lining
of the stomach
are temporary,
these are perma-
nent. They serve
to increase the
surface of the lin-
ing, and to retard

the passage Of the Mesenterlc
. - . Lymph Veins

food material, and (Fats)
so to aid the pro-
cess of digestion
and of absorption.

Villi. — Fur-
ther, the surface
of the mucous
membrane of the
small intestine is thickly beset with little cylindrical pro-
jections, like the " pile " on velvet. These projections are

181

Lymph
Glands ""•".

Lacteal s

Fig. 65. Plan of Absorption.

1 82 PHYSIOLOGY.

called villi (singular, villus). The villi greatly increase
the absorbing surface of the small intestine. In each
villus is a network of blood capillaries, and the beginning
of lymphatic capillaries called lacteals.

Routes of Different Foods after Absorption. — In the

villi the largest part of the work of absorption is done.
The fats are absorbed by the lymph capillaries, or lacteals,
and the rest of the foods by the blood capillaries. It
should be carefully noted that nearly all of the foods but
the fats go at once to the liver, through the portal vein ;
but the fats are carried by the main lymph duct (the
thoracic duct) to be emptied into the subclavian vein in
the neck ; hence do not directly pass through the liver.

Diffusion, Osmosis, and Dialysis. — If a solution of salt and one
of sugar are brought into contact, they will gradually mix by diffusion.
If these two solutions are separated by parchment, they will still diffuse
through the membrane and mingle. This is osmosis. Since substances
differ in the readiness with which they pass through a membrane, they
may be thus separated. Such separation is dialysis, and the membrane
is called a dialyzing membrane. In the digestive tube the mucous
membrane represents the dialyzing membrane with blood or lymph on
one side, and the contents of the digestive tube on the other. Soluble
materials, such as peptones, sugars, etc., pass through the mucous
membrane into the blood.

Absorption a Vital Process. — "The process of osmosis,
and to a lesser extent of filtration and imbibition, as they
are known to occur outside the body, were supposed to
account for the absorption of all the soluble products.
This belief has now given way, in large part, to newer
views, according to which the living epithelial cells take
an active part in absorption, acting under laws peculiar to
them as living substances, and different from the laws of
diffusion, filtration, etc., established for dead membranes.

ABSORPTION— DIGESTION COMPLETED.

183

" Unlike sugars and peptones, fats are absorbed chiefly
in a solid form — that is, in an emulsified condition.
There can be no question, in this case, of osmosis. It has
been shown by nearly all recent work that the immediate
agents in the absorption of fats are again the epithelial
cells of the villi of the small intestine. The fat droplets

Right Lymph Vein ....

Junction of Thoracic
Duct with Left Sub-
clavian Vein

Main Lymph Vein
(Thoracic Duct)

— Intestine

.Lymphatic Glands

Fig, 66. Lymph Veins — Lymphatics. (Ventral View.)

are taken up by these cells, and can be seen microscopically
after digestion in the act of passing, or rather of being
passed, through the cell substance. The epithelial cells,
in other words, ingest the fat particles lying against their

1 84

PHYSIOLOGY.

free ends, and then pass them slowly through their cyto-
plasm into the substance of the villus." - - H DWELL.

The Lacteals and Lymphatics. — While the main work
of the lymphatics, as we have seen, is the carrying of
lymph from the tissues of the body generally to empty into
the veins of the neck, the lymphatics of the intestines
have another important function. They absorb and carry
the fatty portions of the digested food into the general
circulation. During most of the time the thoracic duct
and the lymphatics of the intestines would hardly be
noticed because they are filled with the clear lymph. But
after absorption of fatty matter they are filled with a white
liquid, called chyle, and are easily seen.

To show the Thoracic Duct and Lacteals. — To show the thoracic
duct feed a kitten or puppy on rich milk, and after two or three hours
kill it as directed on page 27. As soon as you are sure it is dead,

Lacteal with Valves Capillaries Muscles Epithelium

Fig. 67. Elements entering into the Structure of a Villus.

open the abdominal cavity and spread out the mesentery. The white
lacteals, filled with chyle, will be seen radiating through the mesentery.
Press on some of these, and it will be seen that they are thin tubes
filled with a white liquid. They converge toward the place of attach-
ment of the mesentery to the dorsal part of the abdomen. On the
dorsal wall of the abdomen, just posterior to the diaphragm, the recep-

ABSORPTION— DIGESTION COMPLETED. 185

tacle of the chyle, or the beginning of the main lymph vein (thoracic
duct), should be found. Trace it anteriorly through the chest along-
side the aorta to its mouth, near the junction of the left subclavian and
jugular veins.

Action of the Villi. — In each villus there are plain
muscle fibers. When these shorten they squeeze the
chyle, that has already been absorbed, into the lymph
tubes of the wall of the intestines, and on into the main

Epithelial Covering

Lacteal

Longitudinal Mus-
cular Fibers \
Capillary Network

Fig. 68. Intestinal Villus.

lymph duct. The chyle cannot return to the lacteal when
the muscles relax, on account of the valves, similar to
those of the veins, in the lacteal at the base of the villus.
Then, when the muscles relax, the lacteal is empty, and
ready to absorb more of the emulsified fat that we call
chyle.

Review of the Digestive Tube. — The whole digestive
tube may be briefly and roughly described as a muscular
tube of varying diameter, lined by mucous membrane.
The muscular coat propels the contents and mixes them
with liquids ; the mucous coat is beset with glands, making
liquids, some of which merely soak the food, others act
on it chemically, while mucus serves to lubricate the sur-
face. It seems that these myriads of simple glands are
not enough, so several large compound glands lie along-
side the food tube and empty their secretions into it by

1 86

PHYSIOLOGY.

ducts ; these supplementary glands are the salivary glands,
the pancreas, and the liver.

Length of the Intestine. — The length of the small
intestine is about twenty-five feet, and of the large intestine

Parotid Sali-
vary Gland

Gullet

Precaval Vein
Postcaval Vein

Sublingual
Salivary Gland

Submaxillary
Salivary Gland

Hepatic Vein--,

Mesenteric
Vein

Pancreas and

Duct

Receptacle of

Chyle
:nl_acteals

Mesentery

Intestine
Fig. 69. Diagram of the Organs concerned in the Conversion of Food into Blood.

five or six feet. The large intestine is not a direct con-
tinuation of the small; that is, the small intestine opens
at a right angle into the large near the beginning of the
latter, so that there is a short blind end called the cecum.

ABSORPTION— DIGESTION COMPLETED.

I87

In some animals this is large and has considerable length,
but in man it is very short. It seems to have been longer
in man's ancestors, for there is a closed prolongation of
the cecum, the vermiform appendix. This appendix is
frequently the seat of serious or fatal inflammation, called
appendicitis.

PARTS
OF
DIGESTIVE
TUBE.

MECHANI-
CAL PRO-
CESSES.

GLANDS.

LIQ-
UIDS.

CHEMICAL
CHANGE.

ABSORPTION.

MATERIAL

BY

MOUTH.

Cutting
and
Grinding.

Salivary.

Saliva.

Starch
to
Sugar.

PHARYNX.

Raising Soft
Palate.
Depressing
Epiglottis.

GULLET.

Food carried
to Stomach.

Mucous.

Mucus.

STOMACH.

Churning
and
Mixing.

Gastric.

Gastric
Juice.

Proteid
to
Peptone.

Water. 1
Salts. 1
Sugars. j
Peptones, j

Blood
Capillaries.

SMALL
INTESTINE.

Mixing
and
Moving
Food,

Liver.
Pancreas.

Intestinal.

Bile.
Pancreatic
Juice.
Intestinal
Juice.

f Starch to Sugar.
J Proteid to Peptone.
1 Fat ^ Emulsified.
[ i Decomposed.

Water. "I
Salts. 1
Sugar. [
Peptone. J
Fats.

Blood
Capillaries

Lacteals.

LARGE
INTESTINE.

Food
Forced on.

Mucous.

Mucus.

Water.

Fig. 70. Outline of Digestion.

The Colon. — The small intestine joins the large near
the lower right side of the abdomen. The main part of
the large intestine is called the colon. It runs upward
(ascending colon), crosses over to the left side (transverse

1 88 PHYSIOLOGY.

colon), and descends the left side (descending colon), and,
after curving somewhat like a letter S (sigmoid flexure),
terminates in the rectum. It is well to know the course of
the lower bowel, as pressure may be so applied as to push
the contents along in case the bowels become torpid.

The Work of the Large Intestine. — Most of the ab-
sorption is accomplished in the small intestine ; but as the
food passes on into the large intestine the work of digestion
and of absorption are carried somewhat farther. If the
residue be not soon expelled, there may be absorption of
some of the results of putrefactive changes, and a sort of
general poisoning of the whole body. Hence the great
importance of regularly and thoroughly emptying the
lower bowel. The matter thus expelled is largely made
up of indigestible material, with some real waste substances.

Taking up again our comparison of the body and a
furnace, we see that the feces are not true waste products,
but are rather clinkers, or material that has not been
burned or oxidized in the body. The real wastes of the
body are the carbon dioxid, urea, water, etc., that are
thrown off by the lungs, kidneys, and skin.

Constipation. — This is a very common disorder, and the evils at-
tendant upon it are many. Of course, if any trouble is long continued
or severe, a physician should be consulted. But it is well known that
certain foods tend to bring on such a condition, and that other foods
have the opposite tendency. Thus, cracked wheat and oatmeal are
generally considered as somewhat laxative in their effects. The fruits
generally are laxative. The coarse particles of graham flour, are irri-
tating to the mucous lining of the stomach and intestines, and for many
persons serve well to stimulate the action of the bowels. But in many
persons the mucous coat is so sensitive that it cannot bear such irrita-
tion. For these the " entire wheat flour " may serve the same purpose.
Of course each person finds out by his own experience what is best for
him, and no rules can be laid down that will apply to all cases. But it

ABSORPTION— DIGESTION COMPLETED.

189

may be well to know what is the usual effect of some of the common
articles of food, as perhaps some persons may habitually partake of cer-
tain articles and do not suspect that they are the cause of the trouble.
The following list is taken from StockhanVs Tokology; —

LAXATIVE.
Rolled and cracked wheat bread,

gems, biscuit, griddlecakes.
Crackers and mush from flour of

the entire wheat and graham

flour.
Granula.

Bran gruel and jelly.
Fruit puddings.
Fruit pies.
All fresh acid fruits, including

tropical fruits, like bananas,

oranges, lemons, etc.
Dried fruits.
French prunes and prunellas,

eaten raw.
Stewed dried fruits containing

hydrocyanic acid, of which

peaches, plums, and prunes are

the best.

New Orleans molasses.
Rhubarb.
Onions.
Celery.
Tomatoes.
Cabbage, raw.
Corn.
Squash.
Cauliflower.
Green peas.
Spinach.
Beets, .etc.
Liver.
Oysters.
Wild game.

CONSTIPATING.

Hot bread.

White bread.

White crackers.

Black pepper and spices.

Pastry made of white flour and
lard.

Bread, rolls, dumplings, etc., made
with baking powder.

Cake.

All custard puddings.

Salted meats.

Salted fish.

Dried meats.

Dried fish.

Smoked meats.

Poultry.

Cheese.

Chocolate.

Cocoa.

Boiled milk.

Tea.

Coffee.

Coffee made of wheat, corn, bar-
ley, toast, etc.

Beans (dried).

Potatoes.

Farina.

Sago.

Starch.

Tapioca.

Rice.

Raspberries.

Blackberries.

1 90 PHYSIOLOGY.

Hygiene of Digestion. — A prime requisite for a good
digestion is a tranquil condition of the whole body,
especially of the nervous system. We see that the blood
must be massed in the digestive organs at the time of
digestion. As there is a limited amount of blood in the
body, it is evident that if more is sent to one part, other
parts must at the time receive less. If we try to study
hard immediately after eating, we are calling the blood
away from the organs of digestion, and to that extent in-
terfering with the process of digestion. If we exercise
the muscles too vigorously soon after eating, we call the
blood to the muscles, and so call it away from the stomach
and intestines. If, after prolonged study, one is unable to
obtain sleep, it may sometimes be efficacious and very de-
sirable to eat a little of some very simple food for the pur-
pose of drawing off the blood to the stomach, and thus
relieving the brain. A little muscular exercise may ac-
complish the same result, or a footbath may be employed.
For many persons it would probably be better to take a
simple lunch than to go to bed hungry, although one
should be careful not to abuse the stomach.

It is exceedingly difficult to lay down general rules in
regard to diet. To a certain extent each person must be
a law unto himself, for what agrees well with one may act
almost as a poison to another. Moderation should always
be observed, especially in taking foods to which we are
not accustomed.

Solid Foods digest Slowly. — Suppose one were to sit
down to eat dinner when ravenously hungry. If in such a
condition one begins with solid food, he is likely to eat too
fast. Hunger is a demand of the system for food. It
takes some time for solid food to go through all the pro-

ABSORPTION— DIGESTION COMPLETED. 1 9 1

cesses of digestion, and be absorbed into the system and
appease hunger.

Value of Soup. — But if a soup be first taken, which is
readily absorbed, the demand of the system will begin to
be met, and there will not be the same tendency to rapid
eating. Further, a warm soup stimulates the blood flow
in the mucous membrane, and thus prepares for more
thorough digestion. It is more easy after a soup to
deliberately masticate the solid portion of a meal.

Desserts. — Dessert and sweatmeats, following a meal,
are often very helpful by further stimulating the secretion
of the glands. Nuts, which are not very digestible, are
beneficial if eaten sparingly. The agreeable taste stimu-
lates the salivary glands, and the alkalinity of the saliva
stimulates the gastric glands to increased activity. The
same may be said of cheese.

" Cheese is a surly elf,
Digesting all things but itself.'1

Pie. — The average pie needs some extra help for its
digestion. Donoghue, formerly champion long-distance
skater, when asked if he dieted in preparation for a race,
said he avoided pastry. If the vigorous digestion of a
man skating for hours daily in zero weather cannot profit-
ably manage pie, how in the case of sedentary persons ?
If pie is eaten, it should be masticated with very great
thoroughness. Undoubtedly most persons would be better
off if they did not eat puddings and pastries. Fruit is
best taken before meals, especially before breakfast.

Hot Drink at Meals. — Hot drink, with a meal, whether
it be tea or coffee, or simply hot water, is usually bene-
ficial ; especially to a weak digestion when taken before
meals.

192 rHYSIOI.()(,\ .

The Bad Effects of Imperfect Mastication. — If we

swallow food before it is thoroughly ground and mixed
with the saliva, the stomach and other parts of the diges-
tive organs will require much more time to reduce the
food to a liquid form. Further, when eating hastily, we
are very apt to eat too much. Thus we may give the
stomach a double amount of material to handle, and the
material may not be half so well prepared as it should
be. The work thus thrown upon the stomach may easily
be made fourfold. Of course the organs suffer, and,
sooner or later, if this treatment is continued, they must
break down.

Effect of Repose on Digestion. — Not only mastication,
.but the whole process of digestion, goes on better when
the body and mind are at rest and in a peaceful and con-
tented condition, as not only the salivary glands, but all
the glands, are under the control of the nervous system,
and are greatly influenced by the condition of the body.
During a meal, and for a short time before and after, all
thoughts of one's occupation, and especially all anxiety,
should be absolutely dismissed from the mind. For those
whose digestion is not strong, it is especially desirable to
secure a period of rest after each meal, taking a lounge
or easy-chair, closing the eyes, and, as nearly as possible,
closing the mind ; for some, even a short nap is very
helpful.

Conversation at Meals. — During a meal there should
be conversation on topics of general interest. " Chatted
food is already half digested."

Deliberation in Eating. — It is said that the people of
the United States are nervous, and eat, as they do nearly
everything, hastily. Deliberation in eating adds to dignity

ABSORPTION— DIGESTION COMPLETED. 193

as well as health, and properly may be considered an
evidence of culture.

Time of Eating. — Probably our almost universal custom
of three meals a day, resulting from experience, is well
adapted to the needs of our people. Theoretically the
chief meal should be near the middle of the day, as is the
custom in the country; for the bodily powers are higher
than later in the day. But for city people, and others who
are very busy in the middle of the day, it is undoubtedly
better to take the chief meal after the rush of the day's
work is over, when there is time for a deliberate meal and
when the mind is free from business cares. For many, too,
this is the only time when the whole family can leisurely
meet at the table.

Eating between Meals. — The stomach should have
time to rest and prepare for the work of digesting another
meal. Many find two meals a day sufficient. There are
some persons, however, for whom it would be better to
have more meals, with less food at each meal. Meals
should be regular.

Amount of Food Needed. — This varies greatly with the
individual, age, the kind and amount of labor, etc., so that
no very helpful rule can be given. Each person must find
by experience what is best for himself. It is the opinion
of many leading physicians that the majority of man-
kind eat too much. The fasting enjoined upon some is
undoubtedly hygienic ; and it would be a valuable lesson
for more persons to experiment in the line of fasting.

Errors of Diet. — Sir Henry Thompson, one of the
foremost authorities in the world on the subject of foods,
says : " I have come to the conclusion that more than half

194 PHYSIOLOGY.

of the disease which embitters the middle and latter part
of life is due to avoidable errors of diet ; and that more
mischief, in the form of actual disease, of impaired vigor,
and of shortened life, accrues to civilized man from
erroneous habits of eating than from the habitual use of
alcoholic drink, considerable as I know that evil to be."

READING. — Disorders of Digestion, Brunton ; Indiges-
tion and Biliousness, Fothergill ; A Plea for a Simpler
Life, Keith.

Summary. — i. The hairlike villi lining the small intestine absorb
the liquefied food.

2. Sugars and peptones are carried away by the blood capillaries
and pass through the Tiver, but the fats are taken by the lacteals into
the lymph stream to join the blood in the subclavian vein.

3. Digestion is greatly influenced by the condition of the nervous
system.

4. Mastication should be thorough.

5. Chat at meals is hygienic.

6. Rest after meals.

7. Soups and desserts have a physiological justification, though the
latter often become harmful.

8. There is a great amount of suffering from intemperance in eating
as well as in drinking.

Questions. — I . What foods are absorbed most quickly ?

2. Is appendicitis more common than formerly ?

3. What is the meaning of " laugh and grow fat " ?

CHAPTER XII.
NUTRITION.

Ledger Account of the Body and its Organs. — Through
the digestive tube and lungs the body receives additions,
and there is a corresponding loss through the lungs, skin,
kidneys, and intestines. So a ledger account might be
kept with the body, and it should balance in the long run,
since in adult life the weight remains practically constant.

So we might take a single organ, say the liver, and
balance its accounts. It receives a large amount of blood.
To offset what it takes from the blood, it gives to the
intestines a large quantity of bile, and to the blood it gives
glycogen.

It is especially interesting to note the losses and gains
of the blood as it passes through the various organs of the
body. A river, flowing past one State after another, will
take some of the soil of each and deposit some of its
muddy particles on the banks of each State. Of course,
the blood is unlike the river, in that it empties into itself ;
i.e. it is truly a circulation. The blood takes something
from, and gives something to, each organ as it flows
through it. From the intestine the blood gets the chief
part of its new material in the newly digested food. To
the muscles the blood gives nutritive material and oxygen,
and receives water, carbon dioxid, and other waste matters.
The account would be similar with the brain. In the skin
and the kidneys the blood has great losses and little gains.

196

PHYSIOLOGY.

The accompanying diagrams may help in presenting
the main points in the blood circuit, and the losses and
gains in its course.

Blood a Mixture of Good and Bad. — In the common
blood streams are combined the good and the bad. The

Capillaries

Vein

Artery

Artery

Vein

Capillaries
Fig. 71. Diagram of the Heart and Blood Tubes (Dorsal View).

newly digested food is received into a current of impure
blood in the postcaval vein. The blood from the kidneys,
probably the purest blood in the body, joins the same
impure stream. From the aorta, red blood, usually called

NUTRITION.

197

pure — the same kind that goes to the brain — is sent
to the kidneys and to the skin to be purified. Yet, as this
mixed blood flows through each organ, that organ, so long
as it is in health, takes from it only what it should take.

Lung Capillaric

Pulmonary Vein

Left Auricle--
Left Ventricle-

Body Capillaries

Fig. 72. Diagram of the Circulation, representing the Right and Left Halves separated
(as they are in reality), showing that the Blood makes but One Circuit.

Action of Diseased Kidneys. — The kidney takes,
during health, only the waste matters, leaving the valuable
nourishing material. But, in disease, the kidneys may

198

PHYSIOLOGY.

LUNG

PULMONARY VEIN
LEFT AURICLE

LEFT VENTRICLE

PULMONARY ARTERY

RIGHT VENTRICLE

RIGHT AURICLE

Fig. 73. Diagram of the Circulation of the Blood.

NUTRITION. 199

take out some of the most valuable portions of the nutri-
ment. Suppose that in a mill, a workman, whose business
is to shovel out wastes, becomes crazy, and shovels wheat
or flour out of the mill into the stream below. The dis-
eased kidney may be said to have become crazy, and in
the disease called "diabetes" throws out sugar, and in
" albuminuria " excretes albumen.

Blood Streams like Water Pipes and Sewer Combined.

— It is as though the water supply of a city house was taken
from the sewer ; each organ needing a supply of building
material acts like a filter, taking from the blood what it
needs, paying no attention to the impurities present, and the
organs of excretion select the impurities, allowing the useful
substances to pass on to the places where they are needed.

A Living Eddy. — Huxley has very aptly compared the
body to an eddy, whose form remains the same, but whose
particles are ever changing.

" To put the matter in the most general shape, the body
of the organism is a sort of focus to which certain material
particles converge, in which they move for a time, and
from which they are expelled in new combinations.

" The parallel between a whirlpool in a stream and a
living being, which has often been drawn, is as just as
it is striking. The whirlpool is permanent, but the par-
ticles of water which constitute it are incessantly changing.
Those which enter it on the one side are whirled around
and temporarily constitute a part of its individuality; as
they leave it on the other side, their places are made good
by new comers.

" Those who have seen the wonderful whirlpool, three
miles below the Falls of Niagara, will not have forgotten
the heaped-up wave which tumbles and tosses, a very

200 PHYSIOLOGY.

embodiment of restless energy, where the swift stream
hurrying from the falls is compelled to make a sudden
turn toward Lake Ontario.

" However changeful in the contour of its crest, this
wave has been visible, approximately in the same place
and with the same general form, for centuries past. Seen
from a mile off, it would appear to be a stationary hillock
of water. Viewed closely, it is a typical expression of the
conflicting impulses generated by a swift rush of material
particles.

" Now, with all our appliances, we cannot get within
a good many miles, so to speak, of the living organism.
If we could, we should see that it was nothing but the
constant form of a similar turmoil of material molecules,
which are constantly flowing into the organism on the
one side and streaming out on the other."

Importance of Renewal of Blood and Lymph. — It

will be well here to recall some facts noted in connection
with the study of the blood and lymph. We then learned
that the lymph (the supply and renewal of which depends
upon the blood) surrounds the individual cells which make
up the tissues of the body ; and that, to a certain extent,
every cell lives an independent life, each taking its nourish-
ment directly from the lymph around it. The importance
of an abundant supply of good lymph is now more ap-
parent. If digestion is not good, or the food be insufficient
or of poor quality (whether naturally or from being badly
cooked), good blood cannot be made, and the lymph will
not be good. The cells are more or less starved, or
poisoned if wastes are not properly removed, and the gen-
eral tone of the body will soon be lowered ; for the health
of the body as a whole depends on the average condition

NUTRITION. 201

of the cells composing the body, just as the condition of
any community depends on the average condition of the
individuals of that community.

Fat as a Tissue. — As a tissue fat serves as a stored-up
food.' The camel's hump is a well-known instance. In
some of the savage races fat is stored in a very similar
hump. But in most persons it is distributed more evenly
over the body, though there is a tendency to deposit rather
more over the abdomen. A fat person can endure starva-
tion longer, other things being equal, than a thin person.
A layer of fat under the skin serves also as a heat saver.

Hibernation. — Hibernating animals are fat when they enter upon
their winter sleep, but are lean when they come out in the spring.
Remaining inactive they have produced very little energy, their only
motions being a slow and feeble breathing and a correspondingly
reduced heart beat. They have consumed the fat, using it mainly in
maintaining the necessary heat. In short, they have burned their fat
to keep them warm.

The Hibernation of a Bear. — In 'one of Captain Mayne Reid's
stories (The Plant Hunters} we are told how the hunters followed a
bear into a cave. At the innermost end of this very long cave they
finally killed the bear. Just at this time they find that their candles
are all burned out, and they are left in complete darkness, lost in the
bowels of the earth. Failing to grope their way out, they are at last
driven to this expedient : With what combustibles they can gather
together, including their gunstocks and some of the fat of the bear,
they melt some of the fat, they use the gun barrels for molds, take
strips of their clothing for wicks, and make two long candles. With
these they finally light their way out to the upper world.

Respiration and Oxidation of Candle. — Now we have seen that
when we burn a tallow candle one of the chief products of the combus-
tion is carbon dioxid. Another product of the burning is common
water. If, then, these hunters had left this bear to his winter's nap, he
would have consumed this fat in the slow process of breathing, and
it would have given off the same products, as we have proved that two
of the waste matters of the expired breath are carbon dioxid and water.

202 PHYSIOLOGY.

Glycogen. — As stated above, glycogen is formed in the
liver. This is indicated by the fact that there is more
sugar in the blood in the hepatic vein than in the portal
vein, except during digestion. Glycogen is formed by and
stored in the liver, and is doled out to the tissues. That
muscles use sugar in their action is indicated in the fact
that the arteries bring to the muscles more sugar than is
carried away from them by the veins. As fat is a reserve
food, so glycogen serves as a temporary carbohydrate re-
serve.

Nutrition. — All the changes that take place between
the reception of food and the excretion of waste are

ANIMAL
PROTOPLASM

INORGANIC WORLD

Fig. 74. Animal and Vegetable Protoplasm.

included under the term nutrition. The materials taken
as food are usually more complex and unstable, the waste
products more simple and stable ; just as the products of
combustion are, as a rule, simpler and more stable than
fuels. In both combustion and the processes of nutrition
the final result is oxidation, more or less direct.

Muscular Exertion and Excretion of Urea. — Since
muscles are the engines of motion, and also are largely
composed of proteid (nitrogen-containing) material, we
would naturally expect that increased muscular exertion
would increase the excretion of urea (the only nitrogen-

NUTRITION.

203

containing waste). But experiment shows that increased
muscular action, such as mountain climbing, hardly in-
creases the amount of urea excreted. Such work, how-
ever, does largely increase the amount of carbon dioxid
excreted. It is thought, therefore, that our energy is
largely derived from carbohydrate foods and fats, and this
view is strengthened by the fact that our beasts of burden
depend chiefly on carbohydrate foods.

ASSIMILATION^,
CIRCULVTION,

ABSORPTION^
DIGESTION

VEGETABLE FOOD

INORGANIC (MINERAL) MATTER

Fig. 75. Life Processes.

While increased muscular action does not very per-
ceptibly increase the amount of urea excreted, an addition
to the amount of proteid food taken does increase the
amount of urea.

Metabolism. — The building-up or constructive pro-
cesses are included under anabolism, while katabolism
designates the tearing down or destructive processes. All
the processes of nutrition, both of building up and tearing
down, are included in the term metabolism.

The Indestructibility of Matter. — We are agreed that
we cannot destroy matter. We may demolish a house, but
the material is all there. We may burn it, but if we could
gather the ashes and that part of the smoke and gases

204 PHYSIOLOGY.

furnished by the material of the house, the weight would
all be recovered.

In the continual wasting away of our bodies there is no
real loss of matter. Our weight is reduced, but the wastes
are still part of the earth or air, and are used again. For
instance, a particle of carbon in the carbon dioxid of the
expired breath may be taken in through a blade of grass in
an adjoining field. A cow may eat the grass, and we may
soon take the very same particle of carbon in the flesh or
milk of the cow. Or the carbon may be taken by that
kind of grass called wheat, and become part of the seed
or grain of wheat, and be made into flour and be eaten as
bread, and be part of us once more. Or this particle of
carbon might be carried by the winds to Florida or Cali-
fornia, and become part of an orange, and come again to
make part of our bodies. Thus there is a ceaseless round
of matter into and out of our bodies. The plants furnish
food for us, and we help to make food for them by the
wastes of our substance. No one has a monopoly of any
portion of matter ; it is now ours, now some one else's. A
particle may pass from one animal to another animal, as
when we eat flesh or other animal food. But more often
the wastes of our bodies go to make part of the air or the
soil, and are then taken by some plant before again becom-
ing part of our tissues. But we are as unable to destroy
matter as we are to create it.

The Indestructibility of Force. — So with energy. We
cannot create it and we cannot destroy it. We derive our
energy from the food we eat. And this food we get
directly or indirectly from the vegetable kingdom.

An engine gets energy from the combustion of fuel. In
the growth of the plant under the influence of sunlight the

NUTRITION.

2O5

plant has stored energy. Now that the wood or coal are
burned the energy is given out, primarily as heat. But we
may convert the heat into electricity, the electricity into
light, or back again into heat if we wish. We get our
energy from food as the engine gets its energy from fuel.
This is saying nothing against the superiority of the
human body, and is not in the least degrading. We are

c o

N H

ANIMALS

AND PLANTS NOT

POSSESSING CHLOROPHYLL,

WHICH DISINTEGRATE
COMPLEX CHEMICAL COM-
POUNDS, LIBERATING
ENERGY IN THE

PROCESS!

PLANTS
POSSESSING CHLOROPHYLL

INTEGRATE COMPLEX

CHEMICAL COMPOUNDS,

STORING UP SOLAR ENERGY

IN THE PROCESS,

THEY

N H.

Solar Energy

Energy originally obtained from the sun radiated
by the animal (chiefly) into space as heat, and
thereby becoming ultimately unavailable

Fig- 76. Relation of Plants and Animals.

self-maintaining, self-directing, growing, living machines.
Still, starvation soon puts an end to our ability to produce
energy of any kind.

The Utilization of Energy in the Body and in
Machines. — Now, it is a well-recognized fact that in very
many machines only the smaller part of the energy is
directed to the end sought. Take a common candle. We
wish to get light from it. But most of the energy of the
candle is devoted to making heat, which in this case we do
not desire. In many machines there is great loss from
friction, from radiating heat, etc. Physiologists tell us that
the human body utilizes a larger portion of its energy than

206 PHYSIOLOGY.

most machines. While energy may fail to be used for the
desired purpose, it is never destroyed nor really lost.

CORRELATION AND CONSERVATION OF ENERGY.

1. The Correlation of Energy. — All kinds of energy
are so related to one another that energy of any kind can
be transformed into energy of any other kind.

2. The Conservation of Energy. — When one form of
energy disappears, an exact equivalent of another form
of energy always takes its place, so that the sum total of
energy is unchanged.

These two principles constitute the corner stone of phys-
ical science, and must be learned and kept in mind if we
would understand the actions of our bodies, and our rela-
tions to the surrounding parts of the world and the universe
in which we live and of which we must consider ourselves
a part.

READING. — Foods and Dietaries, Burnet ; Diet in Rela-
tion to Age and Activity, Thompson.

Summary. — i . The blood flow is a true circulation ; that is, the
blood moves in a circuit, being more or less altered by every organ it
passes through.

2. The body is an eddy into which particles are constantly entering,
forming part of it a while, and then passing out.

3. Fat as tissue is stored food, and consequently stored energy.

4. Glycogen is a carbohydrate reserve stored temporarily in the
liver.

5. Nutrition includes all the processes of the body from the time
matter enters as food until it leaves as waste matter.

6. The building-up processes of the body are called Anabolism, the
tearing down are Katabolism, and both of these are included under
Metabolism.

NUTRITION. 207

7. We can create neither matter nor force, but are dependent on
food as the engine is dependent on fuel.

8. We are dependent on the green plants for our food.

9. The animal body utilizes more of the energy contained in food
than the engine utilizes from fuel.

Questions. — i. Why is it that some persons eat a large amount of
food yet remain thin ?

2. What is meant by "lymphatic temperament" ?

3. Classify the organs shown in Fig. 73 according to their functions.

4. What animal is most thoroughly protected from cold by an
envelope of fat ?

5. How are plants and animals dependent one on the other ?

CHAPTER XIII.
ALCOHOL.

Alcohol. — Alcohol is not a food. But because it is
taken into the digestive tube, and produces its effects,
primarily, through the digestive system, it is here pre-
sented.

If we eat a sufficient amount of bread to-day, we do
not crave a larger amount to-morrow; but the appetite
for alcohol grows ; the law of its use is the law of in-
crease, until the terrible alcohol habit is formed.

Alcohol and Crime. — Aside from the fearful effects
of the habitual use of alcohol upon the individual himself,
statistics show that a large share of the poverty and crime
in the world is due to its use. Nearly every child has
known of the effects in the family of some drunkard, how
the father is feared, how all are ashamed of him, how
the children are poorly clothed,- often not sent to school,
because not sufficiently supplied with clothes and books ;
all these, and the dirt and misery so well known in so
many cases, are a sufficient warning not to make the
slightest beginning of this habit. History is full of ac-
counts of men who thought they could stop when they
chose ; the grip of the alcohol habit is almost as relentless
as the grip of death. There is one safe rule : " Touch not,
taste not, handle not."

Alcohol and Energy. — Some of the best authorities
state that alcohol, taken in small doses, is oxidized in the

208

ALCOHOL. 209

body, producing energy ; but they do not class it with
foods, nor do they recommend its use.

Alcohol and Heat. — As to its power to produce heat,
the fact is that, as ordinarily taken, alcohol lowers the tem-
perature of the body. It is well known that the face is
flushed as the result of taking alcoholic drink. This means
that more blood has been sent to the skin. That sending
of blood to the skin gives a sensation of heat ; we feel hot
when the skin is flushed from other cause, as some emotion.
But if the temperature of the body be taken at the time
when the body feels warm, in each case it may be found
that the temperature is actually lowered ; and we can see
the reason for this, for the more blood there is in the skin,
the more heat will be given off, and thus the amount of
heat in the body diminished.

Alcohol and Muscular Energy. — Neither does alcohol
as usually taken increase the energy of the body so far
as muscular work is concerned. Experience shows that
men can endure more cold and more hard labor without
alcohol than with it. This has been repeatedly proved
in arctic expeditions, in the army and navy, during the
hardships and exposures of forced marches and depriva-
tions in all climates.

Danger in Drinking Alcohol in Cold Climates. -

Especially if one is to be exposed to severe cold is it
dangerous to take alcoholic drink ; many a member of
exploring parties has lost his life by disobeying this rule.

Alcohol and Training. — It is a significant fact that
men training for athletic contests (no matter what their
ordinary habits or principles) let alcoholic drinks alone.
One of the famous pugilists said : " I'm no teetotaler, but

210 PHYSIOLOGY.

when I have business on hand, there's nothing like water
and dumb-bells."

Alcohol as a Stimulant. — " Alcohol is a typical stimu-
lant ; it acts as a whip, causing a temporary acceleration
of physiological activity. Such acceleration must subse-
quently be paid for, the extra expenditure brought about
by alcohol entailing diminished capacity for further exer-
tion. Alcohol is thus of service only for emergencies of
short duration ; it is eminently harmful when prolonged
exertion and endurance are required. Like all rapid
stimulants, alcohol is in large doses a direct depressant."
— WALLER.

Alcohol as a Narcotic. — Many prefer to call alcohol
a narcotic. In large doses it seems to paralyze the mech-
anism regulating the caliber of the arteries ; hence the
flushing above noted.

Alcohol and Water. — Alcohol has a strong affinity for
water, and extracts it from tissues. When we preserve
animal tissue in alcohol, the alcohol abstracts the water,
thus hardening and preserving the substance.

Alcohol a Poisonous Drug. — Alcohol should be classed
with the poisonous drugs (e.g. arsenic, chloroform, bella-
donna, strychnin, etc.), the exact nature of whose effects
it is exceedingly difficult to determine. We do know that
they are very dangerous substances ; and there is one rule
that will apply to them all : Never use them except under
the advice of a physician.

The Effects of Drinking Alcohol. — " The most serious
and widespread derangement of the natural taste is that
caused by alcoholic drinks. Alcohol has been demon-
strated to be a poison. Its continued use, even in what

ALCOHOL. 211

is called moderate quantities, will pave the way for many
diseases, some of which are sure to overtake those who
have the habit of using drinks with alcohol in them.

" Examples of the effect of the excessive use of alcoholic
drinks are numerous and revolting enough in most com-
munities to make the strongest appeals against their use.

"When it is seen that by the use of alcohol an intelli-
gent man may act without reason ; that a kind-hearted
man may become brutal to his most loved friends ; that
it may cause an honorable man to become a dishonorable
one ; that it may make a noble nature become one with the
most depraved of tastes ; when its use has over and over
again been the cause of disappointment, of intense suffer-
ing, and of crime, — it would seem that vastly stronger
reasons existed against its use 'than the mere fact that
some slight changes in the tissues occur which might pos-
sibly be demonstrated. It is to avoid these serious results
that the use of alcohol is to be shunned, and not simply
to avoid a differently shaped liver.

" The physiological effects of poisons are generally much
greater than the visible changes which they produce in
the tissues would lead us to expect. Indeed, such effects
can seldom be detected by changes seen in the tissue cells.

" Strychnin produces powerful spasms which end in
death. It acts, it is said, on the spinal cord, but it would
be hard to show any changes that it produces in the cells.
And a knowledge of the changes it produces in the cells
could not make us fear the poison any more than we do,
who know that it results in suffering and death."-- JENKINS.

Temperance Drinks. — Many well-meaning persons use
the various preparations called " root beers," perhaps with-
out realizing that most, if not all, contain yeast, and in

212 PHYSIOLOGY.

their preparation undergo fermentation, producing alcohol,
though not ordinarily in large amounts. By giving such
drinks (often called "temperance drinks") to children, an
appetite for alcohol may be cultivated and the beginning
of a terrible habit made. (And it may be well here to note
the real meaning of the word habit, tJiat which holds us.)

Cider. — Nor is it "advisable to keep cider about a house
where there are children. " It is perfectly sweet," you
say. Yes, but unless it is all soon consumed it will fer-
ment. It is unwise, to say the least, to put temptation
in the way of those whose habits are not formed.

STIMULANTS.

[WILLIAM H. HOWELL, Ph.D., M.D., Professor of Physiology, Johns Hopkins University,
American Text-Book of Physiology.}

" The well-known stimulating effect of alcohol, tea,
coffee, etc., is probably due to a specific action on the
nervous system whereby the irritability of the tissue is
increased. The physiological effect of tea, coffee, and
chocolate is due to the alkaloid caffeine (trimethyl xanthin)
and theobromine (dimethyl xanthin). In small doses these
substances are oxidized in the body and yield a correspond-
ing amount of energy, but their value from this standpoint
is altogether unimportant compared with their action as
stimulants. Alcohol also, when not taken in too large
quantities, may be oxidized in the body, and furnish a not
inconsiderable amount of energy. It is, however, a matter
of controversy at present whether alcohol in small doses
can be considered a true foodstuff, capable of serving as a
direct source of energy, and of replacing a corresponding
amount of fats or of carbohydrates in the daily diet. The
evidence is partly for and partly against such a use of al-

ALCOHOL. 213

cohol. For example, Reichert finds that moderate doses
of alcohol given to a dog do not affect the heat production
of the body as measured by a calorimeter. Since the alco-
hol is completely, or nearly completely, oxidized in the
body, and gives off considerable heat in the process, the
fact that the total heat production remains unaltered in-
dicates that the oxidation of the alcohol protects an iso-
dynamic amount of proteid or non-proteid material in the
body from consumption, thus acting as a foodstuff capable
of replacing other elements of the food. On the contrary,
Miura has arrived at exactly opposite results in a series of
experiments made by another method. In these experi-
ments Miura brought himself into a condition of nitrogen
equilibrium upon a mixed diet. Then for a certain period
a portion of the carbohydrates was omitted from the diet,
and its place substituted by an isodynamic amount of
alcohol. The result was a loss of proteid from the body,
showing that the alcohol had not protected the proteid
tissue as it should have done if it acts as a food. In a
third period the old diet was resumed, and after nitrogen
equilibrium had again been established, the same propor-
tion of carbohydrate was omitted from the diet, but alcohol
was not substituted. When the diet was poor in proteid
it was found that less proteid was lost from the body when
the alcohol was omitted than when it was used, indicating
that, so far from protecting the tissues of the body by its
oxidation, the alcohol exercised a directly injurious effect
upon proteid consumption. Numerous other researches
might be quoted to show that the effect of moderate quan-
tities of alcohol upon body metabolism is not yet satisfac-
torily understood. Before making any positive statements
as to the details of its action, it is wise, therefore, to wait
until reliable experimental results have accumulated. The

214 I'JIYS/OLOGV.

specific action of alcohol on the heart, stomach, and other
organs has been investigated more or less completely, but
the literature is too great and the results are too uncertain
to permit any resume to be given here. When alcohol is
taken in excess it produces the familiar symptoms of in-
toxication, which may pass subsequently into a condition
of stupor or even death, provided the quantity taken is
sufficiently great. So, also, the long-continued use of
alcohol in large quantities is known to produce serious
lesions of the stomach, liver, nerves, blood vessels, and
other organs. The effect of alcohol upon the body evi-
dently varies greatly with the quantity used. It may
perhaps be said with safety that in small quantities it is
beneficial, or at least not injurious, barring the danger of
acquiring an alcohol habit, while in large quantities it is
directly injurious to various tissues."

[From THOMPSON'S Practical Dietetics.}

" . . . the following general propositions comprise the
belief of many authorities who have devoted careful re-
search to this exceedingly important topic : —

" i. The use of alcohol in any shape is wholly unneces-
sary for the use of the human organism in health. It does
not exist as a natural product. The very lowest types of
man — Australian and many Polynesian savages — know
nothing of it, and drink only water and fresh fruit juice,
such as that of the cocoanut, although they speedily
acquire a fondness for alcohol when it is given them.

" 2. A large number of persons are undoubtedly better
without alcohol, and may prolong their lives by total ab-
stinence.

" 3. The lifelong use of alcohol in moderation, as an
occasional beverage with meals, does not necessarily

ALCOHOL. 215

shorten the duration of life or induce disease in some
persons, while in others it undoubtedly produces gradual
and permanent changes, chiefly of a cirrhotic character, in
the blood vessels and viscera, such as the liver and kidneys.
These alterations, which may be slow and subtile in char-
acter, may not in themselves materially impair the health
or cause an ultimately fatal result, but they tend to weaken
vital organs and produce a condition of premature senility ;
so that if the patient be overtaken by any severe disease,
as, for example, by an acute infection like pneumonia, or
a chronic one like pulmonary tuberculosis, the resistance
of the body to the force of the disease is materially im-
paired, and the danger to the patient is seriously enhanced.

"4. There are many persons whose constitutional in-
heritance is such that they should be particularly warned
against the use of alcohol, and in some such cases, as, for
example, among those who are subjects of well-marked
gouty diathesis, it is better that the use of alcohol should
])e imperatively forbidden.

"5. The abuse of alcoholic stimulation is invariably
injurious, although the extent to which evil influences
become manifest depends upon the constitution of the
individual, in connection with the two factors of heredity
and environment.

" 6. There are a number of diseases in which the tem-
porary use of alcohol is of positive service, and there are a
number of cases in which it becomes a necessity in order
to prolong life.

" 7. In many cases of malnutrition and malassimilation
of food, alcohol is itself a food, and its consumption under
proper direction results in an increase of body weight and
strength, and improvement of functional activity. These
results are accomplished in part through the action of the

216

alcohol as a definite food, and in part through its remark-
able effect in force production. The latter is due to its
own direct combustion, by which in chronic diseases and
in critical, acute, and exhausting affections it spares that
of the tissues of the body.

" Although alcohol is such a strong force producer and
heat generator, its effect in this direction is very soon
counterbalanced by its stronger influence in lowering the
general tone of the nervous system, and in producing
positive degeneration in the tissues. In the condition of
health more food is usually eaten and more force is devel-
oped than is actually necessary for the body, and there is
constantly a reserve supply of energy on hand which may
be utilized for any extraordinary exertion, and hence the
constant use of alcohol as a food or stimulant in health is
both unnecessary and unadvisable. When alcohol is con-
sumed in health in addition to a normal or excessive quan-
tity of solid food, by its more ready combustion it prevents
the complete oxidation of the latter, and favors the accy
mulation of suboxidized waste products, which are always
harmful in the system. Excesses in eating are thus doubly
aggravated by the effects of alcohol. It is the almost uni-
versal testimony of army surgeons, and the experience of
those who, like Greely, Stanley, and others, have led long
and perilous exploring expeditions involving great fatigue
and unusual endurance, that muscular overwork and cli-
matic hardships are much better endured if alcohol is
entirely abstained from.

" It has always been found in armies that when good
food was at hand the issue of alcohol with the regular
ration produced an increased percentage of sick days and
of incapacity for work. Colonel Alfred A. Woodhull,
surgeon United States army, writes me in regard to this

ALCOHOL. 2i;

matter : ' I do not think that any of our medical officers
would seriously advocate the issue of alcohol as a measure
of health, but I believe that its habitual use during the
Rebellion was prohibited for reasons of discipline, while it
still might have been occasionally issued as if for health.
On the rare occasions when it might serve a good purpose,
as a temporary stimulant after a long and wet march, the
wagons would be in the rear, owing to the same conditions
that fatigued the men.'

" While all this applies to prolonged effort of any kind,
and to conditions where other food can be obtained and
assimilated, it does not detract from the fact that alcohol
is a most helpful food and stimulant in emergencies, when
other food cannot be had, or when the body is temporarily
endangered from acute disease and the higher rate of
combustion in fever, or from failure to assimilate other
nourishment.

" Captain Woodruff, assistant surgeon United States
army, says : ' Spirits can never be used in the army as a
regular issue ; the practice is thoroughly vicious, and was
virtually abandoned sixty years ago. On extraordinary
occasions of great fatigue they are allowable in modera-
tion. Under such temporary stimulation the men will
brace up and perform the necessary work of making earth-
works, etc., when without it they would be too exhausted
to do anything. Without such stimulation a man is not
worth much after he has made a forced march of forty
miles.'

" The problem whether the world as a whole is better or
worse for the existence of alcohol, aside from all ethical
questions, and viewed merely from the scientific standpoint
of the influence of alcohol upon mortality, is difficult of
solution ; for to offset the numerous cases of fatal alcohol-

218

ism, and the still larger number of cases ol diseases which
would not presumably be fatal without the existing condi-
tion of chronic alcoholic poisoning of the system, are very
many cases among both infants and adults in which life is
undoubtedly saved by the prompt resort to this food and
stimulant, and its energetic use. So long as man is ex-
posed to hardships and conditions arising from improper
and deficient food supply, as well as to the numerous in-
fectious diseases to which he is heir, alcohol must still be
regarded rather as a blessing than a curse ; for there is no
form of stimulant and food combined, or stimulant alone,
which, taken all in all, can be so completely relied upon in
cases of emergency. Alcohol, when taken alone, will pro-
long life beyond the period at which it terminates from
starvation."

BEVERAGES CONTAINING ALCOHOL.

[RoHfe, Text-Book of Hygiene.}

" The physiological action of alcohol has been pretty
fully worked out by Binz and his pupils and by other ex-
perimenters. From these researches it appears that the
first effect of taking alcohol, sufficiently diluted, into the
stomach is to increase the flow of saliva and gastric juice.
This effect is probably reflex, and results from a stimula-
tion of nerve terminations in the stomach. The alcohol is
rapidly absorbed, and is carried in the blood, without un-
dergoing chemical change, to the nervous centers, lungs,
and tissues generally. In the brain the alcohol probably
enters into combination with the nervous tissue, modifying
the normal activity of the various centers, either increasing
the activity, if the alcohol is in small quantity (stimulating
effect), or diminishing it, if in larger quantity (depressing

ALCOHOL. 219

effect), or entirely suspending the activity of the centers
if in sufficiently large quantity (paralyzing effect).

" Alcohol stimulates the vasodilator nerves, causing dila-
tation of the smaller vessels ; in consequence of this the
blood is largely sent to the periphery of the body, the
blood pressure diminishes, and heat radiation is increased.
At the same time a portion of the alcohol is used up in the
production of animal heat, thus economizing the expendi-
ture of fats and proteids, and acting as a true respiratory
food. Alcohol does not contribute nutritive material to
the body ; it only permits that which is stored up to be
saved for other uses, by furnishing easily oxidizable (com-
bustible) material for carrying on the respiratory process
and supplying animal heat.

" During the use of alcohol the excretion of urea is
diminished. This shows that waste of tissue is retarded
in the body.

" Regarding the statement of some authorities that alco-
hol does not undergo any change in the body, but is ex-
creted unchanged, Binz asserts that alcohol appears in the
urine only when exceptionally large quantities have been
taken, and then in very small proportion. It is not excreted
by the lungs, the peculiar odor of the breath being due not
to the alcohol, but to the volatile aromatic ether, which is
oxidized with greater difficulty, and so escapes unchanged.

" While alcohol produces subjectively an agreeable sen-
sation of warmth in the stomach and on the surface of the
body, the bodily temperature is not raised. The subjective
sensation is due to the dilatation of the blood vessels and
the sudden hyperaemia of those parts.

" During fevers and other exhausting diseases alcohol is in-
valuable to prevent waste of tissue and sustain the strength.
It does not act merely as a stimulant to the circulation and

220 PHYSIOLOGY.

nervous system, but, as above pointed out, saves the more
stable compounds by furnishing a readily oxidizable res-
piratory food.

" When taken in small doses by healthy persons alcohol
diminishes the temperature by increasing heat radiation.
When large quantities are taken the bodily temperature is
reduced by diminishing heat production, as well as by in-
creased radiation. This is shown in the condition known
as dead-drunkenness, in which the temperature is some-
times depressed as much as 20 degrees F. below the
normal. Cases in which the temperature sank to 75 de-
grees, 78.8 degrees, and 83 degrees F. have been reported,
with recovery in all cases.

"The constant use of alcohol produces in all the organs
an excess of connective tissue, followed by fatty degenera-
tion and the condition known as cirrhosis. The organs
most frequently affected are the stomach, liver, and kid-
neys. Serious pathological alterations also occur in the
circulatory, respiratory, and nervous systems.

"Alcohol is not necessary to persons in good health.
Probably most persons, regardless of their state of health,
do better without it. Its habitual use, in the form of
strong liquors, is to be unreservedly condemned. The
lighter wines and malt liquors, if obtained pure, may be
consumed in moderate quantities without ill effects. Even
in these forms, however, the use of alcohol should be dis-
couraged, or perhaps prohibited, in the young.

" Neither in hot nor in cold climates is alcohol necessary
to the preservation of health, and its moderate use even
produces more injury than benefit. The polar voyager
and the East Indian merchant are alike better off without
alcohol than with it.

" It has long been a prevalent belief that the use of

ALCOHOL. 221

alcohol enables persons to withstand fatigue better than
where no alcohol is used. A large amount of concurrent
testimony absolutely negatives this belief.

"The predisposition to many diseases is greatly in-
creased by the habitual use of alcohol. Sunstroke, the
acute infectious diseases, and many local organic affec-
tions, attack, by preference, the intemperate. A recent
collective investigation by the British Medical Association
brought out the fact that croupous pneumonia is vastly
more fatal among the intemperate than among those- who
abstained from the use of alcoholic liquors."

Testimony of a Naturalist. — W. T. Hornaday, author
of Two Years in the Jungle, who has had years of ex-
perience as collector in many lands, has the following to
say as to the use of alcoholic drink : " While a traveler or
hunter should never drink brandy or whisky as a bever-
age, it is a most excellent thing to have in many cases of
sickness or accident, when a powerful stimulant is neces-
sary. Above all things, however, which go farthest toward
preserving the life of the traveler against diseases and
death by accident, and which every naturalist especially
should take with him wherever he goes, are Jiabits of strict
temperance. In the tropics nothing is so deadly as the
drinking habit, for it speedily paves the way to various
kinds of disease which are always charged to the account
of 'the accursed climate.' If a temperate man falls ill
or meets with an accident, his system responds so readily
to remedies and moderate stimulants that his chances of
recovery are a hundred per cent better than those of the
man whose constitution has been undermined by strong
drink. There are plenty of men who will say that in the
tropics a little liquor is necessary, 'a good thing,' etc.; but

222 PHYSIOLOGY.

let me tell you it is no such thing, and if necessary I could
pile up a mountain of evidence to prove it. The records
show most conclusively that it is the men who totally
abstain from the use of spirits as a beverage who last
longest, have the least sickness, and do the most and best
work. As a general rule, an energetic brandy drinker in
the ju-ngle is not worth his salt, and as a companion in a
serious undertaking, is not even to be regarded as a pos-
sible candidate." These statements are made, with no
thought of sermonizing, simply as practical advice to
collectors.

[HALLIBURTON, Text-Book of Chemical Physiology and Pathology.}

" Alcohol. — Small quantities of the alcohol taken leave
the body by the breath and urine as such, the greater
amount is decomposed into simpler products (acetic, oxalic,
carbonic acids, and water); the formation of these must
give rise to a certain amount of bodily heat. It has been
calculated that a man can burn off in his body two ounces
of absolute alcohol daily. Alcohol is thus, within narrow
limits, a food. It, however, lessens proteid metabolism by
about six per cent, and thus ultimately leads to a diminution
of the heat produced in the body. It is, moreover, a very
uneconomical food ; much more nutriment would have
been obtainable from the barley or the grapes from which
it was made. The value of alcohol used within moderate
limits is not as a food, but as a stimulant not only to
digestion, but to the heart and brain."

[M'KKNDRICK, Text-Book of Physiology.}

"With regard to alcohol, its exact influence, when taken
in moderation by those who use it as an article of diet,
cannot be precisely stated. It has been asserted by
several observers that alcohol is eliminated from the body

ALCOHOL. 223

as alcohol by the various excretory channels. The evi-
dence of this is doubtful, and it is probable that it is split
up into simpler compounds. ... A small part of the
alcohol ingested no doubt is exhaled by the mucous mem-
brane of the lungs and by the kidneys. The odor of the
breath depends on the elimination of oxidation products,
such as fusel oil. If oxidized even to a small extent, and
the evidence, as already indicated, points to the oxidation
of by far the larger proportion of it (95 per cent), alcohol
must be regarded, in the scientific sense, as a food. No
doubt also its ingestion diminishes the metabolism of pro-
teids to the extent of about 6 per cent, as shown by the
diminished excretion of urea. Its oxidation will also be
attended by the production of heat ; but as, on the other
hand, it lessens the production of heat by interfering with
the metabolism in proteid tissues, and also by diminishing
the oxidation of carbohydrates and fats, the final result
is an actual diminution of bodily temperature. While,
therefore, alcohol must be classed technically as a food,
it is in many respects an unsuitable food, and its place can
be taken with great advantage by other substances. In
small doses it acts as a local excitant of the digestive
mucous membrane, and afterwards as a diffusible stimu-
lant upon the circulation and central nervous system. In
some cases it may aid the digestive process, but in a state
of health it is not only not required, but its use, except in
small doses, is positively prejudicial."

Physiological Effects of Alcohol. — These various au-
thorities have thus been freely quoted, to show that while
there is considerable divergence of opinion in regard to
some of the physiological effects of alcohol, they are sub-
stantially agreed as to the following points: —

224 PHYSIOLOGY.

1. Alcohol is not needed in health.

2. While technically it may be called a food, practically
it is a poison, and its use is dangerous.

The danger is especially great where there is a latent
hereditary tendency to inebriety or insanity. The danger
is also very great when the disease for which alcohol is
prescribed is accompanied by melancholy and depression.
Many individuals, on finding a drug which exhilarates and
banishes the weight of oppression by which they are borne
down are tempted beyond their power of resistance, even
though the reaction brings them into a worse condition
than the one from which they sought relief.

The Danger of using Alcohol. — The pressure of modern
life, and the intensity of the struggle for a living, brings
about a condition of nervous strain that is fraught with
great danger. Every thinking man should see that to use
alcoholic drink for the relief of such a condition is like
venturing out in a boat above the Falls of Niagara, — he
knows not when the rushing, mighty power will gain the
mastery and dash him to destruction.

READING. — The Temperance Teachings of Science, Pal-
mer; The Foundation of Death, a Study of the Drink
Question, Gustafson.

Summary. — i. Alcohol is a very dangerous drug and should be
used only when prescribed by a physician.

2. Athletes avoid alcohol when training.

3. A large per cent of crime is due to alcohol.

4. On account of its rapid absorption alcohol is a quick recupera-
tive after collapse.

5. In small amounts alcohol is oxidized in the body, producing
energy.

ALCOHOL. 225

6. Alcohol usually lowers the temperature of the body through the
increased skin circulation.

7. It is especially dangerous to take alcoholic drink when exposed
to severe cold, as in arctic explorations.

8. In the army alcoholic drink as a regular ration did more harm
than good ; hence was discontinued.

9. More hard work can be endured without alcohol than with it.
10. The precise effects of alcohol are hard to determine. But every-
body knows that its effects are generally bad.

Questions. — i . Why do some persons think that alcoholic drink
makes them warmer ?

2. What do statistics show as to "expectation of life" among
abstainers and alcohol users ?

CHAPTER XIV.
EXERCISE AND BATHING

How Exercise is Beneficial. -The full significance of
the benefits of muscular exercise could not be understood
when we studied the muscles, and before we had studied
the blood and its work in the tissues of the body generally.
Now we can comprehend how exercise stimulates the cells
to activity, renews the lymph around the cells both by
quickening the blood flow and by pressure on the lymph
tubes ; how the glands of excretion are set to work more
actively, and the more rapid blood stream brings away the
material to be thrown out.

Exercise for General Health. — Exercise is not merely
for the muscles. It quickens the action of the whole body
by increasing cell activity. It helps clean out the system
and clear the brain as well. We read Blaikie's admira-
ble book, How to Get Strong, and learn not merely to
strengthen the muscles, but how to get strong to do the
work we have to do daily, how to feel well every day, how
not only to do our work, but to do it gladly, and with a
little extra good cheer that may radiate from us and in-
spire others. We have no right and no need to carry the
sour visage of a devitalized body. Good health is attain-
able, and ought to be attained, by nearly all. Attention
must be paid to the laws of our being. It takes some
effort, mental as well as physical, to adopt and observe

226

EXERCISE AND BATHING. 22J

regular hours for exercise and relaxation and to be careful
in diet.

Nature's Rewards and Punishments. — But nature
rewards for obedience by the delight of a healthy body ;
and she never forgets and never forgives, nor fails to pun-
ish every violation of every one of her laws. Nature makes
no threats beforehand. She does not even tell us her
rules. But we may find what they are by careful obser-
vation.

Exercise prolongs Life. — Many men would live longer,
feel vastly better, and do greater good in the world if they
would take regular and systematic exercise or recreation
(and this should be, literally, re-creation). It is a short-
sighted policy to say, " I cannot afford the time." Not to
take time for exercise is to mortgage one's future. Lord
Derby says, " He who does not take time for exercise will
have to take time for illness." The latter half of every
person's life ought in many respects to be by far the most
productive of good. But many cut off this half, or render
it less productive through breaking down in health as a
consequence of violating the laws of hygiene. Thus one
defeats his own ends in life, and robs the world of the debt
he owes it, that of returning to it, in his riper years, some-
thing for the help it gave to him in his early years while
he had not yet reached the fullest mental maturity. It is
sad enough that so magnificent a structure as the human
body must perish and become part of the common clay.
But it is infinitely more sad to think that it has not fulfilled
its purpose when the end comes in what should be mid-
career. Each of us should leave the world better than he
found it, and our ability and opportunities for doing this
increase as we reach middle life.

228 PHYSIOLOGY.

Forms of Exercise. — In selecting the kind of exercise
the old lines fit well : —

" In whate'er you sweat, indulge your taste ;
The toil you hate fatigues you soon,
And scarce improves your limbs.'1

Of course this does not mean that a boy should refuse
to saw wood because he dislikes it, and spend all his time
playing ball. But for older persons, especially those of
sedentary occupation, exercise that exhilarates is far more
beneficial than that which is not enjoyed. One may take
a walk and carry all his cares and anxieties with him, but
he is not likely to think of such matters when playing
tennis with a good opponent. Whether it be horseback
riding, cycling, boxing, boating, skating, or other form of
exercise, choose, whenever a choice is possible, that which
you thoroughly enjoy. Exercise should be taken out
doors whenever possible. The gymnasium is a substitute
in bad weather.

Games of School Children. — Most of the games of
school children are excellent kinds of exercise. Cases
have been reported of injury from excessive skipping the
rope. But in moderate degree it is a good exercise. Tag,
snowballing, racing, the various games of ball, jumping,
hopping, and other games may be played on the school
grounds.

Tennis. — Tennis is a fine game, and suitable for girls
as well as boys. It has the great advantage over baseball
that it does not require a large ground (which often means
going some distance from the school grounds or from
home). Two can make up a game, and a little time can
be better utilized than with the games requiring more
players. The exercise, too, is more evenly distributed.

EXERCISE AND BATHING 2 29

There is no long waiting, as in some games, but a constant
interchange of play, active but not severe, with practically
no danger of injury.

Baseball and Football. — For those who can pursue
the more vigorous games of baseball and football they are
admirable, and should not be objected to because occa-
sional injury comes from them. No vigorous exercise is
wholly unattended by risk, though it is usually slight when
the proper care is used. All these games calling for great
activity and strength develop manly qualities in boys, and
do much to make them active, fearless men, men who in
time of danger have not only strength and endurance, but
well-trained muscles, cool heads, and brave hearts, men
who know what to do and how to do it in an accident, as
at fires, upsetting of boats, etc. A few strong, cool-headed
men, by their presence of mind, often stop a panic and
save many lives when there is an alarm of fire, which often
proves false. The Duke of Wellington said that it was
on the football fields of Eton and Rugby that the battle
of Waterloo was won.

Boxing. — Boxing is a splendid exercise. It calls into
play nearly every muscle of the body. Many pieces of
apparatus in a gymnasium are for the especial purpose
of working certain muscles. But a pair of boxing gloves
may be said to contain a whole gymnasium. Many kinds
of work in a gymnasium are likely to be overdone, espe-
cially if not under the direct supervision of a good director.
One may overlift or overstrain himself. But in boxing
there is little tendency in this direction. Boxing makes
one quick on his feet, trains to quick movements of the
arms, trains the eye, keeps the body in an erect position,
and especially develops the muscles of the legs and back.

230

bi ings out the chest and shoulders. It develops
the "wind," and keeps one in constant action. It teaches
control of the temper more than almost any form of exer-
cise. It develops a degree of self-reliance that is worth
much. Instead of developing a tendency to become in-
volved in quarrels, it prevents getting into such disgraceful
affairs. The man who knows that he can defend himself
when it becomes necessary is far less likely to pay serious
attention to idle bluster and slight provocation than one
not so trained. And it may prove valuable to know how
to defend one's self from the attack of a ruffian, or bully,
or drunken brute, or other infuriated animal. The cool-
ness of head, the quick judgment, and prompt action of
a trained boxer frequently saves one from serious injury,
and adds not a little to personal comfort. Like tennis,
boxing calls for little apparatus, little space, and only two
persons. In many places where ordinary gymnasium
work is out of the question, boxing is available. It is
indeed a "manly art," and the doctrine taught in Tom
Brown s School Days at Rugby is as wholesome as can be
given to boys to make them strong and active, to give
them physical and moral health.

Bicycling. — This is an excellent exercise, as it is in
the open air and exhilarating. There is danger of over-
exertion, and it is bad for one to yield to the temptation
to make long runs. There is danger of overtaxing the
heart. The handle bar should be adjusted to allow a
fairly upright position. The saddle should be such as not
to sustain the weight on the perineum.

Exercise for Middle-aged Men. — For men in middle life, in most
cases, milder exercises are preferable, such as shooting, fishing, and
horseback riding. Every person should have some form of exercise
that takes him into the open air daily. The English are more given

EXERC/SE AND BATHING. 231

to their " constitutionals "* than their American cousins, and are the
better for it. Doubtless if we paid more attention to these matters,
we should lose something of our national reputation as a '"nervous
people.11 English women are noted walkers, and do not seem to pride
themselves on the smallness of their feet. The signs of the times
would appear to show that we are improving in this respect. Probably
Americans make too much use of street cars. Walking is the cheapest
exercise, and every one can afford to take it. For those who can
afford it horseback riding is admirable. As Dr. Holmes expressed it,
"saddle leather is in some respects even preferable to sole leather;
the principal objection to it is of a financial character.'' Lord Palmer-
ston said "the outside of a horse is the best thing for the inside of
a man.11 Perhaps livery bills would prove cheaper and more agreeable
than doctors1 bills.

" Taking Cold." — So long as one is actively exercising,
he is not likely to take cold. But if one rests in a cool
place, especially when he is warm, he is, as we all too well
know, likely to take cold. As we saw when we were
studying the circulation of the blood, the application of
cold to the skin causes the arteries (through reflex action)
to become smaller. Thus when resting in a cool place the
skin becomes pale and cold.

During a " cold " there is fever. The regulation of the
heat by the skin is interfered with. At the same time it
is often noticeable that the urine is more abundant than
usual. As cold may lead to fatal lung disease, so it may
be the beginning of some disease of the kidneys that may,
in the end, bring fatal results.

Diarrhea. — Diarrhea, which is a catarrhal condition of the intes-
tine, may follow, or be associated with, a cold, and as a result of this
the process of absorption is often largely checked. There is a great
increase in the secretion of mucus by the mucous glands in the intes-
tinal wall. As the various liquids of digestion are all taken from the
blood, it is evident that if some returns are not soon made, the system
must become bankrupt. It is, then, more easy to understand the ex-

232 PHYSIOLOGY.

cessive weakness and feeling of utter prostration that we experience
during an acute attack of diarrhea. We can now understand where all
the material comes from to make the profuse discharges, especially
after we have ceased eating for some time.

It is a significant fact that diarrhea is usually called " summer com-
plaint." During the warm summer nights we are tempted to go to
sleep with very little covering over our bodies. But it almost always
grows cool before morning. The common summer diarrhea is, in
many cases, due to bacteria taken in food ; but, on the other hand, may
be simply a "cold in the bowels."

Bathing. — One purpose of bathing is to cleanse the
skin. For this purpose warm water is best, and it is de-
sirable to use soap, especially on those parts which are
especially exposed to contamination, such as the hands,
the feet, the armpits, and groins.

Cold Baths. — Another important function of bathing
is to act as a systemic tonic. For this purpose cold bath-
ing is better, but this should not be too long continued,
and must be followed by brisk friction to give the skin a
ruddy glow. For this kind of bath a tub is not necessary,
and hardly desirable. The water may be quickly applied
by means of a sponge, and the body thoroughly rubbed
with a coarse towel. The whole process should be com-
pleted very quickly, especially if the room be not warm.

Bath Hits. — Instead of the sponge and the ordinary
form of towel, it may be found more convenient to use
bath mits made of Turkish toweling. These are easily
made, and are somewhat more convenient, as thus friction
may be more readily applied than with a towel, which is
apt to slip in the hand. The two hands may be used at
the same time, and the whole time of the bath need not
exceed two or three minutes. At the beginning of a bath,
cold water should be applied to the head and face.

EXERCISE AND BATHING. 233

Time for Bathing. — For students, or others who do
not take a great deal of vigorous exercise, which keeps
the skin active, this means of keeping the skin active is
especially valuable. The use of warm water for cleansing
seems best adapted (for busy people) to the time of going
to bed. But the best time for the cool bath is on getting
up in the morning.

Warm Baths vs. Cold Baths. — Prolonged warm baths
are debilitating, and probably increase a tendency to take
cold, whereas cold bathing is one of the very best means
of fortifying against cold, and especially against the ten-
dency to take cold on slight exposure. For most 'persons
a cool sponge bath, on rising, will act as a most excellent
tonic ; but if it seems to produce neuralgia, it should be
used with caution.

Exercise of Arterial Muscles. — We have learned that
the blood supply to any organ is regulated by the action
of the plain muscle fibers in the walls of the small arter-
ies. Now, when we are subject to changes in temperature
these muscles get exercise, and one writer has well called
the cold bath the gymnastics of the plain muscle fibers,
and we can understand how the system can be trained to
adjust itself to cold, and enabled to avoid " taking cold"
so frequently.

Habit of Cold Bathing acquired Gradually. — There
are undoubtedly many persons who do not profit by cold
bathing, but probably many of these would soon adapt
themselves to it by beginning with tepid water and gradu-
ally using cooler. To stand stripped in a cold room, of
course, is not a safe thing to do. And the great secret of
the benefit that may be expected from the operation, as
most people are situated, is to be very brisk, the whole

234

process occupying only a few minutes. Many are opposed
to cold sponge bathing, and condemn it without reserve,
when, probably, they have never really given it a fair trial.
Let it be repeated, with emphasis, that for students it is
one of the very best means of preserving health.

READING. — Baths and Bathing (Health Primers, D.
Appleton & Co.).

Summary. — i. Exercise stimulates the activity of all the organs,
by promoting cell activity and assisting excretion.

2. Exercise should be in the open air as much as possible.

3. Exercise is more beneficial when it exhilarates.

4. Exercise should be taken regularly.

5. Warm baths are best for cleansing, and a good time is at bed-
time.

6 Cold baths stimulate the circulation of blood in the skin, and
serve as a tonic to the whole system. Just after rising is a good time
for the cold bath.

7. The cold bath fortifies against taking cold.

Questions. — I. Should exercise be carried to the point of fatigue ?

2. How can one avoid taking cold after exercise ?

3. Do girls need exercise as much as boys ?

4. What is the condition of the body during a " cold " ?

5. How may a cold be caused ?

6. How may a cold be cured ?

7. How may a cold be prevented ?

8. Why do some persons take cold so much more readily than
others ?

9. Why does the same person take cold more readily at one time
than at another ?

10. How often should a person bathe ?

1 1 . What hour is best for sea bathing ? Why ?

CHAPTER XV.
THE BRAIN.

THE muscles are the executive organs ; but the seat
of the will is the brain.

If models of the brain can be obtained, they should
be carefully studied. If not, the accompanying figures
may be used in their stead.

The Coverings of the Brain. — There are two readily
distinguishable coats of the brain, the dura mater, a tough
membrane, adhering more or less closely to the inside
of the skull ; and the pia mater, next to the brain, a much
thinner membrane, traversed by blood tubes, and dipping
down into the grooves between the convolutions of the
cerebrum.

The Parts of the Brain. — The larger and upper part
of the brain is the cerebrum ; below and back of this is
the smaller cerebellum ; the part of the spinal cord within
the cranium is generally reckoned as part of the brain.

The Cerebrum. — The cerebrum consists of two lateral
hemispheres, separated by a deep median groove. The
surface of the cerebrum is in irregular ridges, the con-
volutions. The outside of the brain consists of gray
matter, whereas the outside of the spinal cord is white.
The inner part of the brain is white, and the two halves
are connected by a broad band of white matter, which
consists of many white fibers.

235

236 PHYSIOLOGY.

The Cerebellum. — The cerebellum is much smaller
than the cerebrum, and has fine transverse ridges and
grooves in place of the convolutions of the cerebrum. It
is also of a deeper color, a reddish gray. The cerebrum
overlaps the cerebellum so that the latter could not be
seen from above if the whole brain were laid bare. But
in the lower animals the parts of the brain are more in
a series, one behind the other, and in a line with the
spinal cord.

The Spinal Bulb. — The enlarged beginning of the
spinal cord, often called the medulla oblongata, is the
spinal bulb. It is white like the rest of the cord.

The Brain of a Cat or Rabbit. — The brain of a cat or rabbit may
be exposed by first mounting the specimen as directed for showing the
spinal cord (see p. 27). After removing the skin from the upper part
of the head, the bone should be cut away between the eyes with a pair of
bone forceps. Cautiously working backward, the whole of the brain
may be unroofed. Great care must be exercised, for here we have one
of the softest tissues of the body lying very closely beneath one of the
hardest. It is possible to do this with a strong knife, but the bone
forceps save a great deal of hard work. The bone must be broken
away bit by bit. To remove the brain, it will be necessary to cut
through the tough dura mater that covers it.

Removing this, there will be found an inner covering, the pia mater,
a membrane richly supplied with blood tubes, from which the brain
gets its nourishment. After the dura mater has been removed, the
anterior end of the brain may be gently lifted with the handle of the
scalpel and the under surface studied, following the description of
the cranial nerves.

Preservation of the Brain. — The brain may be studied while it
is fresh, but it is more easily handled after it has been hardened. Lay
the brain in weak alcohol, about 25 per cent. It should rest on a layer
of cotton, otherwise it may be very much flattened by its own weight.
Later transfer it to 50 per cent alcohol, and then to 75 per cent. When
it is well hardened, it may be sliced with a sharp scalpel as directed.
A better and quicker method is to use a solution of alcohol and forma-

THE BRAIN 237

lin as follows : 95 per cent alcohol, 60 parts ; .2 per cent formol, 40
parts. The liquid need not be changed if used in sufficient volume.

The Brain of the Rabbit {Alcoholic Specimen}. — The brain of
a cat or dog is better, being larger. Take a brain well hardened, and
review the parts as named above. It is very desirable to have a speci-
men in which the arteries have been injected.

1 . Press down the cerebellum to see the deep groove between it and
the cerebrum. The thin membrane covering the brain and dipping
into the groove is the pia mater.

2. Press down the spinal bulb and tear away the pia mater where
it passes from the cerebellum to the spinal bulb. Note, between the
bulb and the cerebellum, a space covered by a thin membrane. Cut
through this membrane ; the cavity is the fourth ventricle of the brain.
Observe the two ridges bounding the sides of the fourth •ventricle. At
the point of their divergence, observe the opening of the central canal
of the spinal cord.

3. Gently separate the cerebral hemispheres, and note the trans-
verse band of white fibers connecting them.

4. Examine the under surface of the brain, and find the roots of the
cranial nerve.

The Cranial Nerves and their Functions. — i. The

olfactory lobes extend forward under the fore part of the
cerebral hemispheres. They are the nerves of smell.

2. The optic netves, or nerves of sight, join each other
before reaching the brain. Only the first and second pairs
of cranial nerves directly enter the cerebrum.

3. Back of the optic nerves, near the middle line, is the
third pair of nerves. The third, fourth, and sixth pairs
of cranial nerves control the muscles of the eyeballs.

4. The fourth pair extend up on each side into the
groove between the cerebrum and the cerebellum.

5. Back of these is the larger fifth pair, the trigeminal.
This pair supplies part of the face, and sends branches to
the teeth. It is the nerve affected in neuralgia of the
face. Besides being the nerve of sensation for most of the

238

PHYSIOLOGY.

head and face, this nerve has motor fibers which control
the muscles of mastication. Unlike the other cranial
nerves, the trigeminal resembles the spinal nerves in
having two roots, one sensory, the other motor.

Optic
(Sight)

I, Olfactory

(Smell)

Eye Motor,
3,4,6

Hypoglossai,
12 (Tongue
Motor)

5, Trigeminal
(Face
Sensation)

II, Spinal
Accessory

Fig. 77. The Base of the Brain, showing the Origin of the Cranial Nerves.

6. Back of and inside of the fifth pair is the sixth pair.

7. The nerves of the seventh pair are larger, and are
farther back and outward. These are the facial nerves,
and control the muscles of the face and the facial expres-

sion.

THE BRAIN.

239

8. Close to the seventh are the eighth, or auditory
nerves.

9. The ninth, tenth, and eleventh arise close together,
farther back and well up on the sides of the spinal bulb.
The ninth supplies the back of the tongue and the pharynx,
and is called the glosso-pJiaryngeal nerve. It gives the
sense of taste from the base of the tongue.

Cerebrum

Fig. 78. Vertical Section of Brain.

10. The tenth pair, or vagus nerves pass down out of
the brain cavity, give off branches to the pharynx and
larynx, and are distributed to the heart, lungs, and stomach.
The vagus nerves are so widely distributed that their func-
tions cannot be briefly stated.

11. The eleventh pair arise in part from the spinal
cord outside of the cranial cavity, enter the skull, and pass

240

PHYSIOLOGY.

out again to supply certain muscles of the neck and
shoulders.

12. The last pair of cranial nerves, the twelfth, arise
near the middle line of the spinal bulb. This pair supply
the muscles of the tongue, and are called the hypoglossal
nerves.

Brain composed of Two Hemispheres. — It will be
observed that the brain, like the spinal cord, consists of
two lateral parts. Cutting sections of the brain length-
wise and crosswise shows that the outer part is made up
of gray matter and the inner part of white matter. The
gray matter is composed of cells essentially similar to those
of the spinal cord, while the white
matter of the inner part is composed
of white fibers like those of the outer
part of the spinal cord, or like the
nerves.

Brain Convolutions and Intelli-

. 79. Pyramidal Nerve gence. — The brain of the rabbit has
^wer convolutions than that of the
cat, and is nearly smooth. In gen-
eral, the lower animals have fewer convolutions, and the
lower races of mankind have smoother brains than the
higher races. In the earlier stages of development man's
brain is smoother, but with growth the convolutions
appear, and increase in number with the growth of the
brain. As we know that intelligent action depends on
the gray matter of the surface of the brain, we infer that
to accommodate its increase in the brain case it is thrown
into folds, as the surface of the lining of the intestines- is
increased by folds and villi.

THE BRAIN.

241

Gray and White Matter of the Brain. — The gray
matter of the convolutions of the adult human brain is
about one fifth of an inch thick, the larger part of the
brain consisting of the white matter. Sections will show
that there are several masses of gray matter in the brain
deeper than the con-
volutions. These ^.AdfeA^ Gray Matter

are the ganglia of
the brain. The
white fibers inside
the brain connect
the gray matter of Gangiia
the convolutions
and these ganglia
with all parts of
the body through
the spinal cord.

Cerebrum

Cerebellum

Fig. 80. Diagram of -the Brain, showing the Spinal
Cord, Ganglia, and Course of the Fibers.

Neuroglia. — The brain consists of nerve cells and nerve
fibers, bound together and supported by a form of connec-
tive tissue called neuroglia.

The Cerebrum and its Functions. — If the cerebral
hemispheres are removed from a frog, he will sit up about
as before, but seems to pay little attention to what is going
on around him. If placed on his back; he will turn over
and sit up. If pinched, he may jump away, and may show
that he can see by avoiding anything that may come in his
way. If placed in the water, he will swim, and if he swims
against anything that he can climb upon, will do so and
remain quiet. If placed on a board, and the board be
slowly tilted, he will move along and keep his equilibrium,
climbing over the end of the board if necessary to keep his
balance. If left alone, he will not move, but will die in

242

PHYSIOLOGY.

his tracks, though he will eat food if it is put in his mouth.
He seems to have lost the power of willing to do anything,
or what we call the power of volition. He originates no
action.

A Pigeon with Cerebrum Removed. — A pigeon with
its cerebrum removed acts in about the same way. It
remains quiet, stupid, paying no attention to ordinary

f- Spinal Cord

- 1st Spinal Nerve

- 2d Spinal Nerve

Fig. 81. Diagram of the Cranial Nerves and Sense Organs.

events. A sudden loud noise may cause it to start. If its
tail be pulled, it moves forward to regain its balance. If
thrown in the air, it flies for a distance. It swallows food
placed in its mouth, but would starve surrounded by food.

THE URAfN. 243

Placed on its back, it will right itself, but it does not show
the usual degree of intelligence and will power.

Function of the Cerebral Cortex. — " Experimentally,
we learn that after the removal of the cortex (gray matter)
an intelligent animal is reduced to the state of a non-intelli-
gent automaton, responding indeed to stimuli, internal as
well as external, but failing to interpret the significance of
present events in accordance with bygone experience. A
brainless dog is stupid ; he may see a bone in front of his
eyes without showing signs that he knows the meaning of
a bone or the use to which it may be put ; he may hear the
crack of a whip, but he no longer shows signs of fear,
for he does not remember its sting ; his former purposeful
behavior has entirely disappeared ; in short, he has lost
memory and judgment." -WALLER.

The Center of Sensations itself Insensible. — The

gray matter of the outside of the brain is the central organ
of intelligent sensation and motion. The functions of voli-
tion, of consciousness, of intelligence, seem to reside in, or
rather to depend upon the activities of, the cells of the
gray matter of the convolutions of the cerebrum. This we
have learned from experiments on the lower animals, and
from accidents and disease in the case of man. All sensa-
tion seems to be in the gray matter of the convolutions of
the cerebrum, and yet it is itself insensible; it may be cut
and cause no sensation. But when the nerve impulses
from the various parts of the body reach the gray matter
of the cerebrum they rouse the cells here to an activity
that gives us what we call sensation. It is never a sensa-
tion until it reaches this part and is properly interpreted.

Crossed Control of the Body. — While each hemisphere
mainly controls the muscles of the opposite half of the

244

PHYSIOLOGY.

body, it also, in part, has control of its own side. Paralysis
of one side (hemiplegia) is due to injury of the opposite
cerebral hemisphere.

Location of Brain Functions. — Much has been learned
of late years as to the location of special functions in the
brain. Many of the motor centers have been determined

CENTRAL FISSURE
MOTOR AREA x''

FISSURE OF SILVIU8

Fig. 82. Location of Brain Functions.

in the following manner : In some of the lower animals
the brain has been exposed, and on stimulating certain
portions with an electric current the movements that fol-
lowed were noted. In monkeys, " particular movements
of the arm, forearm, hand, and thumb can be produced by
excitation of particular spots, almost as regularly as definite
notes can be sounded on a piano by touching particular

THE BRAIN. 245

keys." In the case of man we infer that there is a similar
location, and many cases of accident and disease have
helped in locating the functions. But these areas are not
sharply defined.

Left Hemisphere Better Developed. — The "speech
center" is in the left hemisphere; the right eye and ear,
which connect with the left brain, are better developed
than the left, and in general the left hemisphere seems
superior (in right-handed persons) to the right.

Location of Centers of Sensation. — It is not so easy
to locate the centers of sensation as those for motion. For
we can see the resulting motion, but a sensation can only
be felt by the individual in whom it occurs. Still, some of
the sensation centers have been located, and it is likely
that in time we shall know much more on this subject.
The accompanying diagram shows some of these centers.

The Functions of the Cerebellum. — The cerebellum
is the center for regulating the actions of the skeletal mus-
cles. When we walk or run, or even stand still, a number
of muscles must act, and act in concert. The nerve im-
pulses originate in the cerebrum, but the cerebellum is the
center for harmonizing the action of these various muscles,
or coordinating them. When the cerebellum has been re-
moved from a pigeon the bird flutters, and, while possess-
ing the power to move, does not seem capable of any
regular and orderly movement. There is no loss of intelli-
gence, no paralysis. Of course, in this experiment there
is great disturbance of the system, and perhaps too much
is inferred from it.

Functions of the Spinal Bulb. — The spinal bulb is the
connection between the spinal cord and the brain. The

246 rUYSIOLOGY.

bulb may be said to be that part of the spinal cord which
is within the cranium. It is enlarged, hence its name,
tpinal bulb. From it arise all the cranial nerves except
the first five pairs. The spinal bulb is also the center for
the control of respiration, of circulation, of deglutition, and
perhaps for many other processes.

Brain Work and Brain Rest. — Sleep is not merely
rest for the body ; it should be complete rest for the brain.
In so far as there are dreams, it would seem to indicate a
partial activity ; that is, incomplete rest. The brain worker
especially needs plenty of sleep ; excellent authorities say
at least eight or nine hours. The brain, like the muscles,
needs exercise, and it also needs regular periods of rest.
If a nerve cell is not kept active by the passage of nerve
impulses through it, it usually atrophies, and may de-
generate.

Sleeplessness. — Intense brain work, without sufficient
sleep, is likely to lead to sleeplessness, as when one has
some subject of special study in hand and either will not
or cannot throw it off. Perhaps inventors are as prone to
this sort of trouble as any one class of men. Keeping the
blood continually in the brain, or in any organ, is likely to
lead to a permanent congestion or inflammation that may
cause serious, if not fatal, results.

Fatigue. — It is stated that brain workers need more
sleep than those who work chiefly with the muscles. Fa-
tigue of the voluntary muscles is much more a matter of
nervous than of muscular origin. When one is completely
" tired out," as he would say, if his mind can be aroused,
as by some excitement, he will be found able to expend a
good deal more muscular energy. So, too, many persons
of slight muscular build, but of great " will power," are

THE BRAIN. 247

able to do more work with the muscles than others with
larger muscles and less will. During fatigue the cell bodies
are found to decrease in size, but there is no discernible
change in nerve fibers as a result of fatigue.

Control of Mind. — But the brain worker should not
only be able to sleep regularly and long enough ; he ought
to be able to throw off his mind any subject, and take rest
while he is awake. If one allows himself to think about
mental work while eating, the process of digestion will not
go on well.

Habit of Resting the Brain. — The student should ac-
quire the power and cultivate the habit of having, so far
as possible, regular hours for work, and of completely
throwing aside his work and worry at stated times. In
seeking recreation it is well to choose that which will
necessitate giving the attention to something entirely dif-
ferent from the daily work. For this reason chess may
be no real recreation for the student, while a game of
tennis, boxing, or other competitive exercise is likely to
accomplish this very desirable object. A walk may put
the muscles into play, but if the mind is still intent upon
the line of work maintained throughout the day, the exercise
may prove of little benefit. He may return more tired
than when he set out. The exhilaration of horseback rid-
ing may prove far better, though perhaps involving much
less muscular exertion.

Nervous Tissue least affected by Starvation. — It is
worthy of note that in fasting the nervous tissue is less
reduced than any other tissue, being scarcely diminished
by complete starvation.

Blood Supply of the Brain. — Blood is supplied to the
brain through four arteries : the right and left internal

248 PHYSIOLOGY.

carotid arteries, and the right and left vertebral arteries.
These arteries are so connected by cross-branches that
if any three of them should be compressed, or the blood
flow in them otherwise stopped, the fourth would still be
able to give the brain blood enough for its work. When
the brain is more active it receives a larger supply of
blood. During sleep it is paler.

Fainting. — If the supply of blood to the brain is shut
off, unconsciousness quickly follows. In the ordinary
faint the blood supply has been reduced, owing to the
diminution of the blood pressure or heart's force. It may
be due to inhibition of the heart from some emotion, or
bad odor, as in a close room ; severe pain may be the
cause ; a blow over the pit of the stomach may stop the
heart by reflex action. Fresh air should be supplied,
and the body laid flat on the back. This position makes
it easier for the blood to reach the brain and restore
consciousness. Smelling salts (or ammonia) may stimu-
late respiration and circulation. Sprinkling a little cold
water on the face may have the same effect, but it is
not necessary to pour a large quantity of water over the
person. Rubbing the limbs toward the heart promotes
the flow of blood, and tends to start the heart to activity.

Apoplexy. — Apoplexy is caused by rupture of a blood
tube and the formation of a clot that presses on the brain.

Meningitis. — Meningitis is an inflammation of the
membranes immediately surrounding the brain or spinal
cord or both.

The Water Cushion of the Brain. — Between the coats
surrounding the brain and spinal cord there is a layer of
liquid, comparable to that around the heart or lungs.
When an undue amount of blood is sent to the brain,

THE BRAIN. 249

it is supposed that part of the cerebrospinal fluid is
pressed out into the spinal cavity, thus relieving the pres-
sure in the brain cavity.

Relative Activity of Gray and White Matter. — The

gray matter is, physiologically, more active than the white,
and in keeping with this is the fact that the capillary
network is closer in the gray matter than in the white.
This is true of the spinal cord as well as of the brain.

READING. — Brain-work and Over-work, Wood ; The
Brain and its Functions, Luys.

Summary. — i . The outside of the brain consists of gray matter,
the inside of white matter.

2. The twelve pairs of cranial nerves are distributed to the head,
with the exception of the tenth and part of the eleventh.

3. The cranial nerves include all the special senses but that of
touch.

4. Each hemisphere of the brain is connected with, and has chief
control of, the opposite half of the body.

5. The gray matter of the cerebrum is the seat of the will, sensation,
thought, and emotion.

6. The cerebellum regulates voluntary motion.

7. Many of the cerebral functions have been located.

8. The brain needs rest. In sleep less blood flows through the
brain.

9. Work reduces the size of nerve cells. During rest they increase
again.

Questions. — i. Is there any special reason why the "speech cen-
ter " should be in the left cerebral hemisphere ?

2. Why does a light lunch sometimes enable one to go to sleep
after mental work ?

3. Why is it uncomfortable to hold the head down ?

4. How does the nervous system resemble a telegraph system ? In
what respects are the two unlike ?

5. Name some remedies for sleeplessness.

CHAPTER XVI.
EFFECTS OF ALCOHOL ON THE NERVOUS SYSTEM.

[Treatise on Hygiene, STEVENSON and MURPHY.]

" THE physiological effects of alcohol which have been
considered are quite subsidiary to its effects on the central
nervous system, as there is no doubt that it is for this
effect on the brain that alcoholic beverages are so univer-
sally taken by mankind. The first effect that alcohol has
on the brain is that of a stimulant, and it probably acts as
such in two ways ; namely, by increasing the circulation
of blood through the brain, which is thus roused to greater
vigor, and by directly stimulating the nerve cells of the
nerve centers. This stimulating effect is observed chiefly
after medium or dietetic doses, and its result is seen in
many individuals by an increase of mental and bodily
activity, and of acuteness of perception by the special
senses. This beneficial physiological effect is, however,
soon replaced by poisonous symptoms if the dietetic doses
are too often repeated, or a large quantity of alcohol is
taken at once ; for alcohol then becomes a depressant and
paralyzer of the central nervous system, and symptoms
of intoxication appear. This depressant effect is, as Brun-
ton points out, one of progressive paralysis. The higher
centers of the brain are first affected, then the lower.
The perceptive centers are paralyzed, so that correct
judgment is no longer possible, while the emotions are
uncontrolled and thrown out of working gear, fits of bois-
terous hilarity and of emotional depression being common

250

EFFECTS OF ALCOHOL ON NERVOUS SYSTEM. 251

symptoms. Speech becomes disordered, and symptoms
of incoordination, due probably to an effect on the cere-
bellum, appear. The respiratory center in the medulla
then becomes affected, and at this stage there is coma
with stertorous breathing, while the action of the heart
still continues, even after respiration has stopped. There
can be no question that alcohol taken in sufficient quanti-
ties to depress the higher centers of the brain does an
infinite amount of harm."

Dr. Crothers, author of Diseases of Inebriety, says, " I
have often been made impatient in listening to the lecturer
presenting the ' scientific aspects of the alcohol question '
to an audience, to see him illustrate extensively with
charts, and spend hours to show the effects of alcohol
upon the coats of the stomach, and upon the structure of
the liver and the kidneys, and never allude once to the
brain ; when the fact is, alcohol's principal effect is upon
this organ, and the functions of this organ so far transcend
the functions of all the others, that I might say, there is
no comparison."

Some authors hold that the alterations in the tissues by
alcoholic drinks result from the injury to the nerve centers
that preside over these tissues ; for their nutrition depends
not merely on the direct effect of the blood and lymph
supply, but also upon the direct influences of the nerve
centers ; they even go so far as to maintain that there is a
special set of nerve fibers devoted to the control of the
nutrition of the cells, and these nerve fibers they call
"trophic nerves" or "trophic fibers."

" It is clear that the nervous centers, independently of
the ill effects on their nutrition by the blood changes,
have a certain chemical attraction for alcohol, which
accordingly is found in their tissue." —CROTHERS.

252

Dr. Crothers, in common with many physicians, regards
inebriety as a disease.

Dr. Clum in his work entitled Inebriety, its Causes, its
Results, its Remedy, says : " The most important part of
man is his nervous system ; the cerebrospinal, sympathetic,
and vasomotor being intimately interwoven and connected,
composing the whole. The great nervous center, the brain,
with its hemispheres, its gray and white matter, is the
most complex of all complexities. The nerve fibers not
only connect every cell with every other cell, but unite all
nervous structures into one, making the entire body a
complete whole, and forming close and direct sympathy
between the intellect and the physical organization.

" The mind and body are so intimately connected that
exhausting excess of either acts and reacts on the other.
Excessive work, either intellectual or physical, the sudden
loss of property, intense disappointment, great trouble, un-
requited affections, etc., may impart a shock to the senses
through the mind, which, extending to the molecules of
the brain, disturbs their normal action ; and a sufferer
thus worn and debilitated* with the cares of life, with an
enfeebled will power, the result of nervous exhaustion,
experiences a craving for some form of stimulant to * brace
him up.' He is on the verge of inebriety, or of insanity,
or both, and if he indulges in alcoholic beverages he
becomes an inebriate. Any disease inherited or acquired,
acting either directly or indirectly upon the nervous system,
may act as the predisposing, exciting, or complicating and
protracting cause of alcoholic inebriety."

" Inebriety is often, too often, observed to flourish in
the richest and most promising soil. The clergyman, the
lawyer, the editor, the student, and all others -who use
their intellectual faculties to excess, as well as the mechanic,

EFFECTS OF ALCOHOL ON NERVOUS SYSTEM. 253

the laborer, and those who excessively exert their physical
system, have unnatural longings for something to restore
the exhausted energies of mind and body.

"The excessive worry of one man, the exhausting ex-
cesses of another, and the overwork of others, lead to
organic lesions and nervous defects, and the disease
inebriety, an ungovernable craving for alcoholic drinks, is
the result.

" When a man drinks to excess, even though forced to
do so by a diseased nervous system, Christian communities
usually brand him as a criminal, as an outcast, and say,
' We have no sympathy for you ; stop drinking and be a
man,' when in reality the man should be cared for, and
treated as other diseased human beings. The fact that the
desire for alcoholic drinks is often a disease which may be
either inherited or acquired is overlooked by those who
condemn the drunkard. Our ancestors have for ages been
addicted to habits of intoxication, and we, their descend-
ants, are tainted with the disease inebriety."

MORAL DETERIORATION PRODUCED BY ALCOHOL.

[PROFESSOR H. NEWELL MARTIN.]

" One result of a single dose of alcohol is that the con-
trol of the will over the actions and emotions is temporarily
enfeebled ; the slightly tipsy man laughs and talks loudly,
says and does rash things, is enraged or delighted without
due cause. If the amount of alcohol be increased, further
diminution of will power is indicated by loss of control
over the muscles. Excessive habitual use of alcohol
results in permanent overexcitement of the emotional
nature, and enfeeblement of the will; the man's highly
emotional state exposes him to special temptations, to

254

excesses of all kinds, and his weakened will decreases the
power of resistance ; the final outcome is a degraded
moral condition. He who was prompt in the performance
of duty begins to shirk that which is irksome, energy gives
place to indifference, truthfulness to lying, integrity to
dishonesty ; for even with the best intentions in making
promises or pledges there is no strength of will to keep
them. In forfeiting the respect of others, respect for self
is lost and character is overthrown. Meanwhile the pas-
sion for drink grows absorbing ; no sacrifice is too costly
which secures it. Swift and swifter is now the downward
progress. A mere sot, the man becomes regardless of
every duty, and even incapacitated for any which momen-
tary shame may make him desire to perform.

" For such a one there is but one hope, — confinement
in an asylum, where, if not too late, the diseased craving
for drink may be gradually overcome, the prostrated will
regain its ascendency, and the man at last gain the victory
over the brute."

NARCOTICS.

Definitions of Narcotics. — Gould's Dictionary of Medi-
cine, one of the very best authorities, thus defines narcotic :
"A drug that produces narcosis" and narcosis, as "the
deadening of pain, or the production of incomplete or com-
plete anesthesia by the use of narcotic agents, such as the
use of anesthetics, opium, and other drugs." It is common,
however, to treat of chloroform, ether, chloral hydrate, etc.,
in a group by themselves under the designation Anesthetics.

The Century Dictionary thus defines narcotic : " A sub-
stance which directly induces sleep, allaying sensibility and
blunting the senses, and which, in large quantities, pro-
duces narcotism or complete insensibility. Opium, Cauna-

EFFECTS OF ALCOHOL ON NERVOUS SYSTEM. 255

bis Indica, hyoscyamus, stramonium, and belladonna are
the chief narcotics, of which opium is the most typical.
Direct narcotics . . . either produce some specific effect
upon the cerebral gray matter, or have a very decided
action on the blood supply of the brain."

Some authorities class alcohol with the narcotics.

OPIUM.

Opium. — Opium is the dried and thickened juice of the
head, or capsule, of a species of poppy. Incisions are
made in the partially ripened heads ; the milky juice ex-
udes ; after about twenty-four hours the partially dried
and thickened material is scraped off with a dull knife.
Most of the opium comes to this country from Smyrna,
with a smaller quantity from Constantinople. As gathered
it is a reddish brown, sticky substance of peculiar odor.
It is soluble in water, alcohol, and dilute acids, to all of
which it gives a deep brown color. It is a very complex
substance, but the chief constituent is morphia, or mor-
phine, to which the properties of opium are due. One
fourth of a grain of morphine is equal to a grain of opium
of the average strength. " Opium was known to the
Greeks, but was not much used before the seventeenth
century ; at present it is the most important of all medi-
cines, and its applications the most multifarious, the chief
of them being for the relief of pain and the production of
sleep. Its habitual use is disastrous and difficult to break
up. It is classed as a stimulant narcotic, acting almost
exclusively on the central nervous system when taken in-
ternally ; in large quantities it is a powerful narcotic poison,
resulting in a coma characterized by great contraction of
the pupils, insensibility, and death." — Century Dictionary.

256 PHYSIOLOGY.

Properties and Uses of Opium. — The United States
Dispensatory makes the following statements as to its
medical properties and uses : " Opium is a stimulant nar-
cotic. Taken by a healthy person in a moderate dose, it
increases the force, fullness, and frequency of the pulse,
augments the temperature of the skin, invigorates the
muscular system, quickens the senses, animates the spirits,
and gives new energy to the intellectual faculties. Its op-
eration, while thus extending to all parts of the system, is
directed with peculiar force to the brain, the functions of
which it excites sometimes even to intoxication or delirium.
In a short time this excitation subsides ; a calmness of the
corporeal actions, and a delightful placidity of mind suc-
ceed ; and the individual, insensible to painful impressions,
forgetting all sources o'f care and anxiety, submits himself
to a current of undefined and unconnected but pleasing
fancies, and is conscious of no other feeling than that of a
quiet and vague enjoyment. At the end of half an hour
or an hour from the administration of the narcotic, all con-
sciousness is lost in sleep. The soporific effect, after hav-
ing continued for eight or ten hours, goes off, and is often
succeeded by more or less nausea, headache, tremors, and
other symptoms of diminished or irregular nervous action,
which soon yield to the recuperative energies of the sys-
tem, and, unless the dose is frequently repeated, and the
powers of nature worn out by overexcitement, no injurious
consequences ultimately result. Such is the obvious oper-
ation of opium when moderately taken ; but other effects,
very important in a remedial point of view, are also ex-
perienced. All the secretions, with the exception of that
from the skin, are in general either suspended or dimin-
ished ; the peristaltic motion of the bowels is lessened ;
pain and inordinate muscular contraction, if present, are

EFFECTS OF ALCOHOL ON NERVOUS SYSTEM. 257

allayed ; and general nervous irritation is composed, if not
entirely relieved."

Cocaine. — Cocaine is an alkaloid extract of a shrub
native to the Andes. It is much used by the natives for
sustenance during long journeys. It is a cerebral stimu-
lant, developing a remarkable power of enduring hunger
and fatigue. Its effects are similar to those of coffee, but
are more intense. Large doses have a narcotic effect and
cause hallucinations. Its long-continued use is followed
by insomnia, decay of moral and intellectual power, ema-
ciation, and death. Locally, it is a powerful anesthetic in
a limited area of surface, hence is valuable for minor sur-
gical operations.

Chloral Hydrate. — This drug is frequently, but incor-
rectly, called chloral. It is a powerful hypnotic, anti-
spasmodic, and depressant to the brain and spinal nerve
centers, and, to a limited extent, is an anesthetic. It is
very useful in fevers accompanied by cerebral excitement,
and in convulsions. Its hypnotic effects have led to its
use by individuals without a physician's prescription, and
often with fatal results. No drugs of this class should be
used except under the advice of a physician.

Chloroform. — In a similar way this anesthetic, whose
discovery is one of the greatest importance in modern sur-
gery, is abused for the sake of its effect on the system,
and the hold such a habit gets over the user is similar to
that of the alcohol or opium habit.

The Use of Narcotics. — The use of anesthetics and
narcotics may all be said to be typified by the use of alco-
hol. Not that they are all stimulants, though many of
them are, in small doses, or in the earlier stages of their

258 PHYSIOLOGY.

effects. They all act on the nervous system. They pro-
duce a pleasurable effect or they bring relief from pain.
The use of many of them is begun during illness, when
they are administered to relieve pain, as in neuralgia.
The habit, once formed, is hard to break. Others, having
heard of the soothing effects of these drugs, are unwise
enough to experiment on themselves. Only the confes-
sions of such victims, and the degrading effects on char-
acter, show how powerful is the sway which this class of
drugs gains over those who yield to their influence. Let
no one flatter himself that he has a strong will and can
control himself. The history of their use is ever the
same. They enslave. They destroy.

Tobacco. — The use of tobacco is needless. Man gets
along well enough without it. It is injurious to many. It
is an expensive habit. Many a man spends enough on
tobacco to send a boy through college. With the excellent
cheap printing of to-day, many of the very best books may
be bought for the money that is paid for as many cigars.
Even for those who can abundantly afford it, it seems ex-
tremely selfish, when it is needless, and there is so much
good that might be done with the money. Another very
selfish feature is that so many men do not seem to con-
sider the fact that the air is public property, and they
have no right to fill the air with any gas or smoke that is
offensive to others. Very likely many men derive great
comfort from the use of tobacco after they have once
formed the habit, but most of these were made sick in
learning, showing that the use is unnatural.

Nicotine. — The active material in tobacco is a sub-
stance called nicotine. It is a violent poison. A drop of
it in concentrated form will kill a dog.

EFFECTS OF ALCOHOL ON NERVOUS SYSTEM. 259

General Effects of Tobacco on the System. — Tobacco
usually diminishes the natural appetite for food and inter-
feres with digestion. It often affects the stomach and
induces a craving for alcoholic drink. The eyes are fre-
quently affected. Smoking often irritates the mouth and
throat sufficiently to make the voice husky. The heart
also is very frequently affected, the beat becoming un-
steady. The muscles are in some cases weakened and
affected by trembling.

Cigarette Smoking. — It seems to be clearly proved
that cigarette smoking is very injurious, especially to boys.
And if men smoke cigars, the example is set for the boys
to smoke cigarettes. Some of the cigarettes are said to
be steeped in preparations of opium, so that the use of
cigarettes is often subjecting the user, not only to the
tyranny of tobacco, but that of opium as well.

Perhaps Robinson Crusoe might have been excused for
using tobacco, having no one to save money for, no unfor-
tunates to aid, no children to educate, no one to whom he
might set a bad example, no one whose breath of air he
could contaminate, no one to smell his breath, no one to
see the offensive results. But a man, living in the society
of so many to whom this habit, in all its features, is so
disgusting and in every way offensive, ought seriously to
consider whether he is doing right in continuing such a
practice.

Many boys seem to think it is manly ; they wish, to do
as others do. It is not manly to imitate any one. Do
nothing simply because some one else does it. To do this
is to be a slave, to be led. And one bad feature of the
tobacco habit is that one makes himself a slave to the
weed. For, like other narcotics, it has a powerful in-

260 PHYSIOLOGY.

fluence on the system, and the habit, once formed, is hard
to break.

How many men have been heard to say, " I wish I had
never formed the habit."

Has any one in middle or later life ever been heard to
say, " I wish I had formed this habit " ?

READING. — The Nature and Effects of Alcohol and Nar-
cotics, Luce ; Diseases of Inebriety, Crothers ; Inebriety, its
Causes, its Results, its Remedy, Clum ; Inebriety, Palmer.

Summary. — i. The most important physiological effects of alcohol
are on the nervous system.

2. Many physicians regard inebriety as a disease.

3. The use of alcohol weakens the will power.

4. Narcotics produce anesthesia, or loss of feeling.

5. Hence narcotics are useful in deadening pain, but their use is
dangerous.

6. Opium is one of the most widely used of the narcotics.

7. Tobacco is needless and in many cases harmful.

8. Cigarette smoking is very injurious, especially to the young.

Questions. — i . Why is cigarette smoking more injurious than
cigar smoking ?

2. How does the opium habit often begin ?

CHAPTER XVII.

GENERAL CONSIDERATIONS CONCERNING THE NERVOUS

SYSTEM.

Nerve Stimuli. — Natural nerve impulses that run out-
ward are ordinarily started by the action of some nerve
cell or cells, as from the gray matter of the brain or of
the spinal cord.

Nerve impulses coming inward may be started in sev-
eral ways. Ordinarily by some one of a few forces that
are capable of affecting the nerve endings. Mechanical
force, as pressure, acts on the nerve endings of the skin,
and starts nerve impulses which are carried to the brain
and rouse certain cells to activity, and give us the sensa-
tion of touch. The vibrations known as light excite the
special nerve endings in the retina, but affect no other
nerve endings. Sound is appreciated only by the endings
of the auditory nerve. Certain gases or fine particles
affect the olfactory nerve endings, and certain substances
may give the sense of taste by acting on the ends of nerves
in the mouth. Different nerves, then, are adapted to re-
ceiving impressions from the action of different forces.

Kinds of Nerve Stimuli. — There are four kinds of
nerve stimuli, — electrical, mechanical, thermal, and chemi-
cal. In experiment, electricity is usually the best stimulus ;
mechanical stimuli, as used in the experiments with the
muscle-nerve preparation from the frog, by cutting or
pinching the nerve, may be employed ; heat, as in touch-

261

262 PHYSIOLOGY.

ing the nerve with a hot wire, or holding a hot wire near
the nerve, may be used as a stimulus ; chemical stimuli, as
acids, strong salt solution, etc., may also be used.

Essential Similarity of All Nerve Fibers. — It is to be
noted that while special stimuli act on specially modified
nerve endings, all nerve fibers are essentially alike, and
the nerve impulse, however started, is probably the same
kind of force. For instance, cutting the optic nerve, or
severe shock, as a blow on the head, causes a sensation of
light not quite so definite, but essentially the same as
though light had acted on the retina, and thus started the
nerve impulse, instead of a mechanical stimulus acting on
the nerve fibers between the retina and the brain.

Relation of Stimulus and Sensation. — If we apply a
stimulus of a given intensity, as of an electric current,
whose intensity can be measured, it causes a sensation of
a certain degree. Doubling the stimulus, or increasing it
by a definite amount, does not increase the intensity of the
sensation to the same degree. The sensations do not
increase at the same rate as the stimuli. To increase the
sensations arithmetically, the stimuli must increase geo-
metrically.

Reaction Time. — " Reaction time " is the time between
the application of a stimulus and the signal given as a
response to show that the stimulus has been "felt." Thus
a blindfolded person gives a signal as soon as he is touched.
This interval between the stimulus and response varies
with the individual, mode of stimulation, health, attention,
etc. It is from one tenth to one fifth of a second ; is short-
est for touch ; longer for sight than for hearing. The total
reaction time is occupied by (i) the time of conducting
the nerve impulse to the brain, (2) the time occupied in

NERVOUS SYSTEM IN GENERAL.

263

the cerebral cortex in the perception of the sensation
and the formation of the volition, (3) the time of conduct-
ing the motor impulse and giving the signal. The greater
part is in the middle interval, i.e. the central elaboration,
during which the entering impression gives rise to an out-
going impulse.

Reflex Action. — In a previous diagram of reflex action,
a single cell was represented as receiving the afferent im-

Nerve Cells connected by Interlacing Nerve Network

Afferent Nerve Fibe

Sensory
Epithelium

Efferent Nerve Fiber

Muscle

Fig. 83. Diagram of Reflex Action.

pulse and sending out an efferent one. It is more proba-
ble that at least two cells are concerned in such an act, one
receiving the incoming impulse, and influencing, by means
of fine connecting branches, a second cell which sends out
the motor impulse, as shown in Fig. 83.

Connection of Brain Centers. — We have_seen that the
brain functions. are more or less localized. We also know
that the cortex receives impressions through the channels

264

PHYSIOLOGY.

Writing

Speech

of the different sense organs, and we can respond through
various channels, — speech, writing, facial expression, etc.
We would therefore expect, theoretically, that the various
parts of the cortex of the brain are connected. As a

matter of fact, we
find anatomically
that this is the
case. Not only
are the cells of
the gray mat-
ter connected
with the various
parts of the body,
but cells of differ-
ent parts of the
cortex are in com-
munication with
each other by what
are called " as-
sociation fibers."
Thus a sensation
roused in one part
of the brain gives
rise to the sending
out of an impulse
from another part
of the brain to
produce the re-
sponse.

Fig 84. Connection of Brain Centers by Association
Fibers. (After Landois and Stirling.)

(The dotted lines from the hand, mouth, and eye rep-
resent afferent fibers from the skin, muscles, and joints
of the hand, lips, orbit, etc.)

The Nature of Sensation. — Of the real nature of sen-
sation we know but little. Like consciousness, we call it
a condition of the gray matter of the cerebral convolutions.

NERVOUS SYSTEM IN GENERAL. 26$

Perhaps the most practical definition of sensation that we
can give is that it is the interpretation that the cells of
tJie gray matter of the brain give to the nerve impulses
that come from without. This will apply to ordinary sen-
sations.

Subjective Sensations. — But sensations may be subjec-
tive ; that is, they may exist without any corresponding
external exciting cause. For some unexplained reason the
cells of the brain are active, and their activity, however
caused, constitutes what we call a sensation. Certain
drugs, such as hashish, may excite an unusual degree of
cerebral activity. Here the action is roused through af-
ferent nerves, but through unusual channels ; that is, the
subject sees, but not through the nerves of sight. Many
hallucinations are explainable to a certain degree ;' others
we cannot account for.

The Relative Nature of Sensations. — If one hand be
held in a basin of hot water and the other in a basin of
cold water, and then the two be suddenly plunged into
a third basin containing tepid water, a sensation of cold will
be received from the hand that was in the hot water, while
the hand from the cold water will feel heat. Sensations
depend on comparison and contrast. After listening to
low sounds, a sudden loud noise is painful ; and after hear-
ing loud noises, it is difficult to detect slight sounds. We
hardly notice the gradual fading of the light at sunset.
And the nose does not usually detect the slow fouling of
the air in a room ; but let one come in from the fresh out-
side air, and the contrast is striking. A constant current
of electricity usually causes a muscular contraction at the
time the current enters the muscle and at the time when
the current is stopped, that is, at the " making " and the

266 PHYSIO LOG Y.

"breaking" of the current; but the muscle ordinarily re-
mains inactive while the current is passing.

Induction Current used in Physiological Experiment. — The in-
terrupted current, or induction current, is therefore commonly employed
as a stimulus in physiological experiment. A sudden change seems
to be requisite for producing the nerve impulse necessary to rouse
a sensation in ordinary circumstances. Pressure may be applied so
gradually that we fail to notice it. The art of the pickpocket, of the
ventriloquist, of the sleight-of-hand performer, depends largely on this
fact. Attention is called to something else, and the work is either
quickly done when attention is completely absorbed on something else,
or the act is so gradual that no sudden change is noted. In smelling
it is often necessary to sniff; the sudden rush of particles of air bearing
the odorous particles against the surface bearing the nerve endings
seems to be necessary.

Dreams. — Dreams, due to more or less perfect brain activity, are
often traceable to nerve impulses brought from the digestive tract, from
the respiratory organs, from the skin (heat and cold and pressure),
from sound, from any internal organ, according to the condition of the
blood, pressure, etc. It seems to be well settled that dreams seeming
to cover long periods of time really take place in a very short space of
time, just as sometimes during waking hours thoughts fly through the
mind in countless numbers and with incredible swiftness.

Ignoring Nerve Currents. — Do we have dreams when we recall
none? Without attempting to answer this question it is well to note
that the brain undoubtedly is constantly receiving nerve currents to
which it pays no heed, or at least of which we are not conscious.
For instance, our clothing is touching nearly the whole of the surface
of our bodies, and, plainly, the surfaces thus touched are affected.
Undoubtedly currents go to the brain, but as they are of no significance
in ordinary circumstances, we learn to disregard them. If a savage
were suddenly clothed as fully as we are, he would, for a long time,
be continually conscious of the fact.

Judgment. — In what is called Aristotle's experiment,
the experimenter crosses the first and second finger, and
feels an object with the fingers thus crossed and eyes shut.

NERVOUS SYSTEM IN GENERAL. 267

If a marble be rolled about by the two fingers thus crossed,
it seems to be two. Here we use judgment with the sen-
sation. Ordinarily, we could not feel, at the same time,
one simple solid object with the outside of the first and the
inside of the second finger. This illustrates how we are
constantly using our judgment in interpreting our sen-
sations. We see few things as they are in themselves.
We see nearly everything in the light of past experiences.

Lingering Effect of Sensations. — We have noted the lingering
effects of sensations, how sights and sounds linger and are fused one
with the other. So we get continuous light from a series of flashes
if they follow each other in sufficiently rapid succession, and continu-
ous sound from a series of sounds that would be heard separately if
they are more than about a sixteenth of a second apart. So with
touch, if the finger be held against the teeth of a revolving wheel, if
the wheel revolve slowly, the touch of each tooth may be felt, but when
it whirls more rapidly the sensation becomes that of continuous pres-
sure. Experience and experiment both go to show that probably
nothing is wholly forgotten. Whatever acts upon a cell of nervous
matter makes its mark. It may become dim, but it is never completely
obliterated. The testimony of persons rescued from drowning, and other
similar experiences, goes to show that the record was yet in the mind.
We may fail to recollect, but we ever remember.

Habits are Acquired Reflex Actions. — The work of
the spinal cord is that of a subordinate officer, whose duty
is to relieve his superior, the brain, of many small tasks,
and to afford him relief from having all the details con-
stantly on his mind. If we learn to do many things me-
chanically, we save the effort of doing them by conscious
effort and act of will. Whatever we do for the first time
requires careful attention. To learn any new muscular
action, such as a new step in marching, fingering a musical
instrument, or typewriting, requires effort; they produce
more or less fatigue. Subsequent effort in doing the same

268 PHYSIOLOGY.

thing is very much less, showing that, in many cases,
fatigue is mental rather than muscular. What we do from
habit, and cheerfully, is easily done. Hence the desira-
bility of forming good habits, that we may, without un-
necessary effort, — that is, without loss of energy, — do
what is needed for our well-being.

Fatigue from Standing. — We are not conscious of
expending energy in standing until we begin to be weary ;
but the fact that a blow on the head causes one to fall
reveals the fact that the brain is constantly sending mes-
sages to the muscles to make them act. The shock of the
blow has stopped the sending forth of these messages, and
so the body is no longer supported. None of the muscles
that support the body have been injured or even touched.

The Usefulness of Resting. — We have, in youth, such
a boundless store of energy that we do not sufficiently
consider these matters. But if one wishes to follow the
intellectual life long and successfully, he must learn to
economize energy, and to direct his forces into useful
channels. And one important part of this knowledge is
learning how to rest. It is an art that very few have well
learned.

Nervous System compared to a Telegraph System. -

The brain is like a telegraph office in both receiving and
sending out messages. Unlike the telegraph office, it has
one set of fibers to bring currents in (afferent), and another
to carry currents outward (efferent).

Efferent Currents. — We have concerned ourselves thus
far chiefly with efferent nerve fibers and efferent currents.
These efferent currents are sent mainly to muscles, to
make them shorten or to relax, or to gland cells, to control

NERVOUS SYSTEM IN GENERAL. 269

their activity. The only other efferent currents, so far
as known, are those which possibly go to the cells of
the tissues to regulate their nutrition or their heat pro-
duction.

Having given so much attention to the outgo of nerve
impulses, let us ask the question, " What about the in-
coming nerve currents ? "

Afferent Currents. — " All life long the never-ceasing
changes of the external world continually break as waves
on the peripheral endings of the afferent nerves ; all life
long nervous impulses, now more, now fewer, are continu-
ally sweeping inward toward the center; and the nervous
metabolism, which is the basis of nervous action, must be
at least as largely dependent on these influences from
without as on the mere chemical supply furnished by the
blood. We must regard the supereminent activity of the
cortex and the characters of the processes taking place in
it as due not so much to the intrinsic chemical nature of
the nervous substance, which is built up into the cortical
gray matter, as to the fact that impulses are continually
streaming into it from all parts of the body ; that almost
all influences brought to bear on the body make themselves
felt by it. To put the matter in a bald way we may ask
the question, What would happen in the cortex if, its or-
dinary nutritive supply remaining as before, it were cut
adrift from afferent impulses of all kinds ? We can hardly
doubt but that volitional and other psychical processes
would soon come to a standstill, and consciousness vanish.
This is, indeed, roughly indicated by the remarkable case
of a patient whose almost only communication with the
external world was by means of one eye, he being blind in
the other eye, deaf of both ears, and suffering from gen-

270 PHYSIOLOGY.

eral anesthesia. Whenever the sound eye was closed he
went to sleep." -FOSTER.

Let us turn from the consideration of outgoing, or
efferent, nerve impulses and their resulting action to the
incoming, or afferent, nerve impulses and the activity
which they rouse in the gray matter of the cerebrum —
sensation.

READING. — Wear and Tear, Mitchell ; Power through
Repose, Call ; Technique of Rest, Brackett.

Summary. — i. Nerves may be stimulated by mechanical force,
chemical action, heat, and electricity.

2. Electricity is the most convenient nerve stimulus for physiological
experiment. The induction current is usually employed.

3. To increase sensations arithmetically stimuli must increase geo-
metrically.

4. Reaction time is the interval between the application of a stimu-
lus and the response.

5. Sensations are relative.

6. Habits are acquired reflex actions.

7. The nervous system is unlike the telegraph system in using one
set of fibers for receiving and another for sending messages.

Questions. — i. Is the difference in "reaction time11 in individuals
of any significance ?

2. Why are slight wounds in a battle often unperceived ?

CHAPTER XVIII.
THE GENERAL SENSES.

The Body a Collection of Organs. — We have been
considering the body as a collection of organs working
together to serve the brain, the mechanism through which
the mind operates.

We have especially studied the muscles as the only
means by which the mind manifests itself to the outer
world.

Influences from the External World. — But how much
mind would we have if we did not receive something from
the outer world ? Read the story of Kaspar Hauser. We
are continually getting knowledge of the outer world and
of the condition of our own bodies through the afferent
nerves. We may never know fully what consciousness and
thought are, but we can understand that to the brain are
continually streaming nerve impulses that convey messages
which the brain more or less completely interprets.

Classification of the Senses. — These incoming currents
pass along myriads of nerve fibers. But the nerve fibers
are all essentially alike. And the kinds of sensations that
these currents arouse in the brain are but few. It is diffi-
cult to classify the senses, but it will serve our convenience
to divide them into two groups.

General Sensations and Special Senses. — In distinc-
tion from the special senses, sight, hearing, etc., are the

271

2/2 PHYSIOLOGY.

general sensations already referred to, such as hunger,
thirst, fatigue, nausea, satiety, faintness, etc. They are
often called "common sensations," and Martin designates
them as " sensations which we do not mentally attribute to
the properties of external objects, but to the conditions of
our own bodies."

General Sensations. — Nerve endings in different parts
of the body may be affected by the blood and the lymph,
and give us sensations of comfort, discomfort, restlessness,
fatigue, faintness, etc. These are called general sensa-
tions. They are probably due to the condition of the
blood, or to the condition of nutrition of the various parts
of the body. Thus after muscular exercise the muscles are
acid in their reaction, while they are alkaline after resting ;
after exercise carbon dioxid accumulates in them to a cer-
tain extent. Hunger and thirst come on after abstinence
from food and drink, or after work exhausting the tissues.
The presence of the various waste products, or the condi-
tion of the cells as the result of their activity, acting
through the nerve endings in the tissues, keep the nerve
centers informed as to the condition of the parts of the body.
If these conditions are extreme, we may have definable sen-
sations, but ordinarily the sensations are of an undefinable
sort which we designate as " general sensations."

The Muscular Sense. — As an example, we will take
the case of estimating the weight of an object by holding
it in the hand. Our estimate is thought by some to be the
result of (i) direct consciousness of the degree of effort
put forth ; but probably it is (2) a sensation, or complex of
sensations, aroused by nerve impulses from the organs
used. There are afferent nerve fibers with endings in
(i) the skin, (2) the muscles and tendons, (3) the joints,

THE GENERAL SENSES. 2/3

In extending the arm and moving it up and down, all three
of these sets of nerve endings are probably stimulated, and
impulses thence conveyed to the brain.

Muscular Sense and General Sensibility. — It is a
matter of doubt, whether or not the impulses from the
muscles are predominant, and consequently whether the
term " muscular sense " is the most appropriate. Peculiar
nerve endings have been found in the tendons, and the
joints are believed to have an especially rich nerve supply.
It is not necessary that we actively use the muscles to have
sensations of this kind. In passive moments, as the rais-
ing of the arm by another person, we have a " sense of
position" of the parts, a considerable share of which is
probably due to the tension of the skin and changes in the
joints. There is, of course, some tension of the muscle,
even in this passive movement, that might affect nerve
endings in it. The muscular sense is closely related to the
general sensibility already mentioned, if not a modified
form of it.

Importance of Muscular Sense. — It is difficult to real-
ize the importance of this sense in our daily experience.
We probably underestimate it, and attribute to sight too
much of our knowledge of the external world. The funda-
mental facts concerning the objects about us are not ob-
tained through sight alone. Such knowledge is based on
complex judgments concerning the meaning of auditory
and visual phenomena, according as they have, in past ex-
perience, been interpreted by tactile and muscular percep-
tions. That is, when reduced to its simplest terms our
most practical and important knowledge of the world is
the outgrowth of tactile and muscular perceptions ; by and

2/4 PHYSIOLOGY.

with them all other sense perceptions have been corrected
and compared.

Dependence of Sight on Muscular Sense and Touch. —
An illustration of the assistance which touch and the mus-
cular sense give to the sense of sight is furnished in the
case of a boy who had been blind from birth, and received
sight at the age of twelve years by means of a surgical
operation. At first he could not distinguish a globe from
a circular card of the same color until he had touched them.
He knew the peculiar features of the dog and the cat by
feeling, but not by sight. Happening one day to pick up
the cat he recognized for the first time the connection be-
tween the new sense of sight and the old familiar ones of
touch and the muscular sense. On putting the cat down
he said, "So, puss, I shall know you next time."

Pain. — When a heavy weight is laid on the hand it may
cause pain. It would at first seem that the ordinary pres-
sure sense, when unduly exaggerated, becomes pain. But
there seem good reasons for considering pain as a distinct
sense from that of touch intensified. It is thought that
there are, throughout all parts of the body, nerves of "com-
mon sensibility " or " general sensibility," which keep the
nerve centers informed as to the condition of all the various
tissues, and that ordinarily we have no sensation resulting
from the impulses ; to use the language of the psycholo-
gist, " they do not rise above the threshold of conscious-
ness." They may have some influence in adjusting the
action of the different parts. We have seen how the blood-
flow to any part is continually adjusted without our know-
ing anything about it. But we are usually more or less
conscious of the general condition of the body. We call
by the name of " common sensations " such feelings as

THE GENERAL SENSES. 275

hunger, thirst, nausea, fatigue, depression, melancholy,
restlessness, such as many experience preceding a thun-
derstorm, the feeling of general discomfort known as
malaise, and its opposite, the feeling of general well being.
The body seems to have a set of nerves to give information
as to the state of nutrition of the body, and as to its condi-
tion generally. These nerves, when the system is dis-
ordered in any part, may bring messages that cause intense
pain. Of course, they are warnings (they are more than
mere warnings ; probably if the earlier indications of simple
discomfort had been heeded the later more emphatic mes-
sages of pain would not have been necessary). These mes-
sages of pain demand attention.

The Extent of Pain. — In reference to pain in the skin,
it is held that the skin, too, has its nerves of general sensi-
bility, and that these are distinct from those of touch and
temperature sense. That when they are unduly stimulated
they give rise to painful sensations. It is to be noted that
the internal organs are ordinarily devoid of feeling, and
that the skin is especially sensitive. The skin senses stand
guard at the outposts, so to speak, of the body's camp, and
give warning of approaching danger. No enemy may
enter without being discovered by these keen sentinels,
and the alarm is given. If it is not heeded, great harm
may follow. And it is a comfort to know that the more
severe wounds do not cause pain in proportion to their
extent. When a person says his " lungs are sore " the
pain is usually in the muscles of the chest from coughing.
While there may be acute pain from the lungs, as in pleu-
risy, there is often deep-seated lung disease without pain
from the lungs themselves. The muscles of the chest and
back may be strained by lifting, and the soreness is erro-

2/6 PHYSIOLOGY.

neously attributed to the lungs or kidneys. Hence there
is frequently a wholly needless apprehension of deep-
seated disorder, whereas in reality there is merely a strain
of superficial muscles. In amputating a limb the chief
pain is in cutting through the skin. Some excellent
authorities still hold the view that pain is merely the
result of intensifying any of the simple sensations ; but it
is generally held that it results from the excessive stimula-
tion of the nerves of general sensibility ; as Foster puts it,
" the constantly smouldering embers of common sensibility
may be at any moment fanned into the flame of pain."

Pain a General Sense. — In the real "special senses,"
— sight, hearing, smell, taste, touch, and temperature sense,
— we refer the sensation to some external object, whereas
general sensations are subjective, referred to our bodies.
Ordinarily we do not localize the common sensations, and
a further indication of the relationship of pain and general
sensation is in the lack of complete localization of pain.
Slight pain, especially in the skin, may be closely located,
but severe pain tends to become indefinite and diffuse.
So we may class both the muscular sense and pain with
the "general" rather than with the "special" senses.

Hunger and Thirst. — The cause of these sensations in
a healthy body is plainly the need of food and water
throughout the system generally. The sensation of thirst
manifests itself in the throat, and the longing may be tem-
porarily relieved by merely moistening the throat. So
hunger may, for the time, be appeased by filling the stom-
ach with indigestible material. But the sensation soon
returns. The system has a crying need, and it is not to be
put off by any such frauds. That these sensations are
really demands made by the body as a whole may be

THE GENERAL SENSES. 277

shown by the fact that they are permanently relieved by
introducing food and water into the body (by the rectum,
for instance), in which case the throat and stomach have
nothing given them directly. Since, however, food and
drink naturally enter by the throat and stomach, the
mucous membrane of these organs has become spokes-
man of the body for its demands.

READING. — Pain, Corning.

Summary. — i . Brain action depends, in the long run, upon im-
pulses from without. If we had no impressions, we could have no
expressions.

2. General sensations are referred to our bodies and their condition ;
special sensations are regarded as attributes of external objects.

3. The "muscular sense11 probably depends chiefly on impulses
from the tendons and joints.

4. The muscular sense is necessary for the full interpretation of
sight. It enables us to judge of the degree of effort put forth or force
resisted.

5. Pain is a general sensation. It is a warning — the cry of a senti-
nel that an enemy has passed the picket line.

6. Hunger and thirst indicate the need of food and drink. They are
local signals of a general want.

Questions. — i. If we had no sense of pain, what might result?
2. If we pass by a meal time without eating, why does the sense of
hunger disappear?

CHAPTER XIX.

THE SPECIAL SENSES -TOUCH AND TEMPERATURE

SENSE.

What we learn by touching Objects. — Let one person
rest the hand flat on the table, palm upward, and close the
eyes. An object placed on the palm, by another person,
may give rise to various sensations, so that it may be
described as rough or smooth, light or heavy, hot or cold,
wet or dry, etc. If the object is very heavy or very hot, it
may cause pain. If now the thumb and fingers are raised
and applied to the object, more definite information will be
gained as to its shape, size, surface, etc. Now raise the
object in the hand, and further appreciation will be gained
as to its weight.

These experiments show that several sensations are in-
volved in the handling of objects, and that the knowledge
so gained is complex.

Cutaneous Sensations. — The sensations from the ob-
jects resting on the skin of the passive hand may, proba-
bly, all be referred to impressions made on nerve endings
in the skin, and are called cutaneous sensations. They
include: (i) the pressure sense, or touch proper, (2) the
temperature sense, and (3) pain.

Nerve Endings in the Skin. — The skin consists of
two layers, the epidermis and the dermis. We need now
to recall those conical elevations of the dermis that we caU

278

THE SENSE OF TOUCH.

279

papillae. In these papillae are certain important nerve
endings. There are several kinds of nerve endings in the
skin and underneath it that receive the impressions which,
carried to the brain, give us sensations of touch (and allied
sensations to be considered soon). Pressure on the skin
affects these nerve endings, and
starts impulses that pass along the
sensor fibers to some nerve center,
probably in the spinal cord, spinal
bulb, or brain.

Nerve

Fig. 85. Papilla of Skin with
Touch Corpuscle.

Touch Corpuscles. — These
"touch corpuscles" are not re-
garded as essential for producing
the sensation of touch, but some
nerve endings in the skin do seem
necessary ; for if a nerve fiber be
touched, not at the end, but some-
where along its course, we get, not

a sensation of touch, but a sensation of pain. Except in
the mouth and nose, we get little, if any, sense of touch
from any organ but the skin. The lining of the digestive
tube and the internal organs generally are devoid of this
sense.

The Sense of Touch. — Of the special senses the most
general is that of touch. Seeing and hearing, taste and
smell, belong to very limited parts of the outside of the
body, but we have the power of feeling all over the surface
of the body.

Touch the most General of the Special Senses. —

Not only is the sense of touch the most general in being
distributed over the whole of the body, but it is the most
widely distributed sense throughout the animal kingdom.

280 PHYSIOLOG } .

As we descend the animal scale we find many of the lower
animals lacking some of the senses that we possess. In
many of the simpler forms of animal life there is no evi-
dence of a sense of hearing, and it is extremely likely that
if they have taste and smell, these senses are in a very
rudimentary state of development. But in all these forms
it is believed that " feeling " exists. Contact of their exte-
rior with foreign objects is so often immediately followed
by action that little doubt remains about their having the
sense of touch. Even ameba may have, in a rudimentary
state, the power to distinguish light, to taste, and to hear.
Still we have little or no evidence on these points, while
we are pretty sure that it feels.

The Pressure Sense. — The sense of touch, proper, is
strictly a pressure sense. If we test the skin to find what
regions are able to detect the least pressure, it is found
that the forehead is most sensitive, and nearly equally so
are the temples, back of the hand, and forearm.

Ability to detect Differences of Pressure. — The

ability to detect differences of pressure is tested by finding
what is the least addition to a weight required to make it
seem heavier. For instance, if a weight of 1 1 grains is
just perceptibly heavier than one of 10 grains, it does not
follow that i grain added to a weight of 100 grains will
give any palpable increase. To 100 grains must be added
10 grains before additional pressure is felt ; that is, what-
ever the weight, there must be the same ratio of increase
to increase the sensation. This is part of the law, already
stated, of the relation of stimulus and sensation. The law
is true only in a general way and will not apply in extreme
cases. It is stated that the forehead, the lips, and temples
appreciate an increase of one fortieth to one thirtieth of the

THE SENSE OF TOUCH. 28 1

weight estimated, while the skin of the head, the fingers,
and the forearm require an increase of one twentieth to
one tenth for its perception.

After-Pressure. — The lingering effect of pressure, or
after-pressure, may be noticed after taking off a tight hat,
skate strap, shoe, or glove.

Local Sign. — " If a point of the skin is touched, certain
tactile corpuscles are irritated; these, in turn, set up im-
pulses in sensory nerve fibers, and these impulses are car-
ried by the fibers, first to the spinal cord, and then to the
brain, where the fibers end in ganglionic masses in the
gray matter of the cerebral cortex. There are thus pro-
jected, as it were, on the cortex of the brain, tactile centers
for the hind leg, fore leg, neck, eye, ear, trunk, etc. ; and
it follows that each point of the skin has a corresponding
point in the cerebral cortex. Thus for each stimulation of
a point of the cerebral cortex there is a local sign, and so
we localize tactile impressions."

Accuracy in locating Touch Sensations. — The accu-
racy varies, and is ordinarily keenest where the nerves are
most numerous. Where the sense of locality seems to be
improved by cultivation, this appears to be due to keener
discrimination in the brain cells, and not to changes in the
nerves or nerve endings. This is indicated in the fact that
if the fingers of one hand become more discriminating by
practice, it will be found that the fingers of the other hand,
without special training, are also improved.

Test by Compass Points. — The delicacy of localizing
touch is usually tested in this way. The blunted points of
a light pair of compasses are allowed to rest gently on the
skin of various parts of the body. If the two points are

282 PHYSIOLOGY.

very close together, they will be/?// as one pressure. That
part which can best distinguish, as two points of touch,
these blunt points, is considered the most sensitive. By
this test the tip of the tongue is the most sensitive, being
able to distinguish, as two separate points of contact, the
tips of the compasses when only one twenty-fifth part of
an inch apart. Following is the order of degrees of sen-
sitiveness : tip of tongue, tips of fingers, lip, tip of nose,
eyelid, cheek, forehead, knee, neck; while the middle of
the back seems least sensitive, the two points not produc-
ing two distinct sensations until they are more than two
and a half inches apart. In general those parts which are
most used, and those parts which are more freely movable,
are most sensitive ; for instance, the knee is much more
sensitive than the middle of the thigh or the middle of the
leg, and the elbow than the middle of the arm or forearm.
If the compass points, about half an inch apart, be passed
from the palm to the tips of the fingers, it will at first seem
one line gradually separating into two diverging ones,
owing to the keener localizing power as the finger tips are
approached. .

Reference of Sensation to the Region of Nerve End-
ings.— If the " funny bone," or "crazy bone," be hit, i.e.
if the ulnar nerve be bruised against the bone, sharp pain
may be felt in the wrist and hand, and soreness of these
parts may be felt for days, though they are not in the
least injured, but only the nerve at the elbow. The cur-
rents along this nerve rouse sensation that we have learned
to localize at the endings of the nerve fibers. So, too,
after amputation of a hand or foot, there may for years
be sensations referred to the missing member, probably
due to irritation of the nerves of the stump. There is,

THE TEMPERATURE SENSE. 283

then, no certainty of getting rid of a corn by ampu-
tating a toe. •

The Temperature Sense. — Many cases are on record
in which, from accident or disease, the pressure sense was
lost and the temperature sense retained, or vice versa.
Such facts have led to the belief that the temperature
sense is distinct from that of touch, and has its own nerve
fibers and nerve endings.

Two Sets of Nerve Fibers for Distinguishing Heat and
Cold. — Since heat and cold are only differences in the
degree of heat, we would expect both of these kinds of
impressions to be received through one set of nerves.
There seems, however, to be good evidence of two sets of
nerve fibers, one for heat and the other for cold. In the com-
mon experience of the foot " going to sleep" by pressure
on the sciatic nerve, or the arm from compression of the
brachial nerve, the skin may be found, at a certain stage,
to be only slightly sensitive to warmth, while distinctly
sensitive to cold. In some diseases of the spinal cord the
skin may be affected by warmth, but not by cold. The
sensations of cold and pressure seem to be usually lost
or retained together, while those of warmth and pain
have a similar connection. But more accurate results are
obtained by touching the skin with a blunt metal pencil,
warmed or cooled.

Warm Spots and Cold Spots. — If this be applied at
regular close intervals, it is found that some places feel the
warm point, while others feel the cold. In this way the
skin has been mapped out into "warm spots" (warmth-
perceiving spots) and "cold spots" (cold-perceiving spots),
and still other areas seem not sensitive to temperature.

284 PHYSIOLOGY.

Heat or cold, if applied directly to a nerve trunk, does not
rouse sensations of temperature, but, if strong enough,
produces pain. If the elbow be dipped into water at the
freezing point, a sensation not of cold but of pain is caused,
and is felt in the hand. Heat and cold are not felt in the
digestive tube except at or near the openings. If very hot
liquid be swallowed, it may cause pain in the gullet and
stomach. If a considerable quantity of warm liquid be
taken, it may give a feeling of warmth from its effect on
the skin of the abdomen, by conduction of heat outward.
As with other senses, a sudden change in the degree of
the stimulus is more certain to rouse sensation than a
gradual change.

READING. — The Five Senses of Man, Bernstein.

* Summary. — i. The cutaneous sensations are touch proper, tem-
perature sense, and pain.

2. There are touch corpuscles in the papillae of the dermis.

3. Touch is the most general of the senses, both in its extent in our
bodies, and in the number of animals possessing it.

4. Touch proper, or pressure sense, is tested by discrimination of
additional pressure.

5. Touch localization is tested by discrimination as to the distance
of two points of contact.

6. Temperature is discerned by a special set of nerve fibers.

7. Touch and muscular sense are necessary adjuncts of sight to give
correct perceptions of size and form.

Questions. — i . What is the explanation of tickling ?

2. Where does the change occur by which we become more dis-
criminating in the sense of touch ?

3. Why does an emotion, such as shame, make one feel hot ?

CHAPTER XX.
THE SENSE OF SIGHT.

The Sense of Sight. — In the fable of the blind man
carrying the lame man whose eyes were good, we have an
illustration of the dependence of the various organs on
each other. We have considered how all our knowledge,
both of the condition of our bodies and of the external
world, comes through the nervous system. Now, so far
as the senses we have studied are concerned, we learn
almost nothing of the external world except from actual
contact. But sight reveals objects at a distance. With-
out the eye the body is comparatively helpless. The lame
man that the body carries is a slight burden in comparison
with the assistance which he renders. We can well afford
to carry with us all the time two of these lame men to
keep posted as to the objects beyond our reach. Of course
touch is a great aid to our interpretations of what we see.
But sight is evidently the main avenue of knowledge, the
royal road along which come the messages which bring us
the most news, which give us the keenest delight ; which
makes us aware of most that we know of this world, and
the only means of knowing that there are other worlds
than the one we inhabit.

Protection of the Eye. — The eye is set well back in
its socket and guarded by three projecting bony promi-
nences, — the brow, cheek bone, and the bridge of the nose.
It is further protected by the eyelids and eyelashes.

285

286 PHYSIOLOGY.

The Lacrymal Secretion. — The lacrymal gland, or
tear gland, is just above the outer angle of the eye, and
pours its secretion over the eyeball in weeping, or when
there is need of an unusual supply of tears. The lids
serve as curtains to admit or shut out light, and, by wink-
ing, wash the eye with their own secretion, a fluid mixture
of salt water and mucus. It is as though a man were
kept all the time in front of a plate-glass window, with
water and rubber scraper, to keep it clean and bright.
The lacrymal secretion is, ordinarily, carried off as fast as
it is made, by two ducts beginning at the inner angle of
the eye, one on each lid ; these two ducts soon unite and
empty by one outlet into the nasal cavity. If these ducts
are stopped, or if the secretion be formed very rapidly,
the liquid overflows on the face as tears.

The External Parts of the Eye.— The " white of the
eye " is the sclerotic coat. It has blood tubes, but ordina-
rily they are not conspicuous. The front part of the eye-
ball is covered with the cornea. This is transparent, and
the color of the iris shows through the cornea. In the
center of the iris is the hole, or pupil, by which Jight enters
the interior of the eye.

The Conjunctiva. — The front of the eyeball is covered
by a thin, transparent, mucous membrane, the conjunctiva,
which turns back and lines the inside of the eyelids. It is
highly sensitive.

The Muscles of the Eyeball. — There are six muscles which move
the eyeball, — four straight muscles (the recti) and two oblique. The
four straight muscles arise from the deepest part of the eye socket and
pass forward to be attached to the top, bottom, and sides of the ball.
Where they are attached, they are flattened out like straps. The in-
ferior oblique arises from the inner front part of the orbit and passes
outward to attach to the under surface of the eyeball. The superior

THE SENSE OF SIGHT, 287

oblique arises, like the recti, at the deeper part of the eye socket and
passes forward through a fibre-cartilaginous loop or pulley near the
inner, upper angle of the orbit, and then runs outward and is attached
to the upper surface of the eyeball.

Movements of the Eye. — These six pairs of muscles move the
eyes to right and left, up and down, and give rotary movements.
Normally the two eyes move in the same direction at the same time,
though in looking at near objects the two eyes both point inward, so
that one appears cross-eyed, and in looking at an object that is moving
away from one, the eyes are gradually diverging, though this is slight.

Dissection of an Eye. — The muscles and external parts of the eye
may readily be seen by examining the eye of a rabbit in its natural
position and then dissecting it out. A beef eye should be obtained
from the butcher and the structure of the eye learned by following the
description below.

The Coats of the Eye. — There are three coats, the outer
or sclerotic, the middle or choroid, and the inner called the
retina.

The Sclerotic Coat. — This is of a dull white color, con-
stituting the "white of the eye." It is thick and tough,
holding all the contained parts firmly and furnishing suffi-
cient strength for the attachment of the muscles that move
the eyeball.

The Choroid Coat. — The middle layer of the eye coat
is the choroid. It is thinner than the sclerotic and of much
more delicate structure. It is permeated by blood tubes,
and has an inner lining of dark color to prevent the reflec-
tion of light in the eye, just as most optical instruments
are painted black on the inside.

The Retina. — The retina is a continuation and expan-
sion of the optic nerve and forms an inner coat that lines
all but the anterior part of the eye. It is a thin, translu-
cent film, somewhat like the film that forms over the white

288

PHYSIOLOGY.

of an egg when it is first dropped into hot water. It is
exceedingly delicate and easily torn. The retina is the
only part of the eye that is sensitive to light, and on it the
images must be formed to produce distinct vision.

The Cornea. — The clear front part of the eye is the
cornea. It is a continuation of the sclerotic coat and is

Ciliary Muscle

Optic Nerve Choroid

Fig 86. Horizontal Section of Right Eye.

more bulging than the rest of the front of the eye, as can
be seen by taking a side view of the eye, or by noticing
some one who closes the eyelids and rolls the eyes about.

The Iris. — This is the part that gives the color to the
eye, or if the pigment that gives the color is lacking, the
blood gives the pink color seen in albinos. The iris is a
forward continuation of the choroid coat.

THE SENSE OF SIGHT. 289

The Pupil. — Most of the light that passes through the
transparent cornea is stopped by the opaque iris. But in
the center of the iris is a round hole through which light
enters the interior of the eye. The pupil looks dark be-
cause it is the only opening into a dark room.

Regulation of the Amount of Light admitted into the Eye.—

Hold a hand glass between the face and a well-lighted window. Note
the size of the pupils. Quickly turn toward the darkest part of the
room. We see, what we have all noticed in watching the eyes of a cat,
that when subject to a bright light the pupil is small, but with less light
the pupil is larger. The iris has circular muscle fibers that reduce the
pupil when there is too much light for the eye, and when the light is
feeble the pupil opens wider.

The Refracting Media of the Eye. — The media that
refract the rays of light to form the images on the retina
are the cornea, the aqueous humor, the crystalline lens, and
the vitreous humor. The cornea has already been described.

The Aqueous Humor. — In looking at the entire eye it
is not easy to realize that there is a space between the cor-
nea and the iris. In this space is the clear, watery aque-
ous humor.

The Vitreous Humor. — All but the front part of the
space within the coats of the eye is filled with a clear,
jellylike substance, the vitreous humor.

The Crystalline Lens. — Just back of the iris is a double-
convex lens, clear as crystal, and of about the consistency
of a gumdrop. It is less convex on the front surface.

The Lens Capsule. — The lens is completely enveloped
in a thin, transparent membrane called the lens capsule.

The Hyaloid Membrane. — A thin membrane, the hya-
loid membrane, lines the inner surface of the retina. As
it continues forward toward the lens capsule it is called
the suspensory ligament.

290 PHYSIOLOGY.

The Ciliary Muscle. — Arising from the sclerotic coat,
just within the outer border of the iris, is the ciliary muscle.
It is inserted in the margin of the lens capsule by means
of fibrous strands that form an intimate part of the capsule.

Experiment with Lens to show Inversion of Image. — Take a
double-convex lens, two ot which are in the common " tripod lens,1' or

Fig. 87. The Formation of an Image on the Retina.

any hand magnifier. Hold this up in front of a window and catch the
inverted image o/ the window on a piece ot paper held back of the lens.
This illustrates how the image ot an external object is formed by the
crystalline lens upon the retina ot the eye. If two lenses of different
thickness can be obtained, it will be seen that the thicker lens (if both
have the same diameter) will make an image closer to the lens than the
thinner one.

Experiments to illustrate the Adjustment for Distance. — (i ) Stick
a pin at each end of a book cover. Hold the book at about the usual
distance for reading, so that the two pins are in a line with the eye.
Look closely at the nearer pin, and the second pin will appear indistinct.
Now look closely at the head of the farther pin. The nearer one may
be seen, but not sharply. (2) Hold the tip of a pencil in a line with any
object, say a picture, on a wall opposite. In looking at the tip of the
pencil the picture is dim. Now look by the pencil at the picture, and
the point of the pencil will be blurred.

Adjustment of the Lens for Seeing at Different Dis-
tances. — If we look up from a book we are reading, we
do not realize that any change is necessary in the eye for
us to see a distant object. But the above experiments
prove that we cannot, at the same time, see distinctly a
near and a distant object. When the photographer places
his camera, he moves the ground-glass plate back and forth
till the image is distinctly formed on the plate. We cannot

THE SENSE OF SIGHT.

291

move the retina back and forth, so we change the shape of
the lens. When we look at a near object the lens becomes
thicker, and when we look at a distant object the lens be-
comes less thick. This adjustment is called accommodation.

CILIARY MUSCLE

FAR NEAR CILIARY PROCESS

Fig. 88. A Diagram to illustrate Accommodation. »

Action of the Ciliary Muscle. — In looking at a near object, the
ciliary muscle pulls on the hyaloid membrane, and draws it forward
(since the muscle is fastened at the point where the iris joins the
cornea). When the hyaloid membrane is pulled forward, the lens is
released from pressure that was given it by the lens capsule. Now the
lens becomes thicker because it is elastic, and when it is not subject to
pressure it tends to become relatively thick. When we look at a dis-
tant object the muscle relaxes, and the capsule presses on the front of
the lens and flattens it, thus adjusting for far sight. It should be
noted that adjustment for near sight is brought about by muscular
effort, hence is fatiguing ; whereas adjustment for far sight is accom-
plished mechanically, without effort.

(2) Near-sighted Eye. (I) Normal Eye. (3) Far-sighted Eye.

Fig. 89. Defects in Eyesight.

Defects of Eyesight. — In old age the lens usually be-
comes less elastic, -and cannot adjust for near sight. Since

292

PHYSIOLOGY.

it is unable to grow more convex, artificial lenses (eye-
glasses) may be used to enable one to see near objects
clearly. Most elderly people see fairly well at a distance,
but use glasses for reading or any close work. In " near-
sighted " eyes, the eyeball is often too long from front to
back, so the rays meet in front of the retina. Concave
glasses remedy this defect. The eye may also be too
short (far-sighted) and need convex glasses. The refract-
ing surfaces (cornea and lens) may be unequally curved,
causing astigmatism. For most of these defects the
oculist can supply suitable glasses.

Inner or Vitreous Surface

Internal Limiting Layer
Layer of Nerve Fibers
Layer of Nerve Cells

Inner Molecular Layer

Inner Nuclear Layer
Outer Molecular Layer

— Outer Nuclear Layer

External Limiting Layer

Layer of Rods and Cones

~ Layer of Pigment Cells

Outer or Choroid Surface

Fig. 90. Diagrammatic Section of the Human Retina. (Waller.)

The Structure of the Retina. — The retina is very complicated in
its structure. No less than eight layers have been distinguished, as
shown in Fig. 90. Of these layers the outermost, the layer of the rods
and cones, is the one directly concerned in appreciating the differences
in the vibrations of the light. The rays of light pass through the

THE SENSE OF SIGHT. 293

retina, and produce their effect on the rods and cones which constitute
the outer (back) layer; and the nerve impulses aroused by the light
must return through the thickness of the retina to be conveyed along
the nerve fibers of the innermost layer of the retina to the optic nerve.

Importance of the Retina. — The chief structure in the
eye is the retina. Without this all else is useless. If
light of sufficient strength falls on the retina, it stimulates
elements in the outer layer (rods and cones), and the nerve
impulses, thus started, pass along the fibers of the optic
nerve to the brain, and we have the sensation of sight.
But in order to see anything distinctly, the light must fall
on the retina in such a way as to form a distinct image of
that object. If the lens be removed, or becomes opaque,
as in " cataract," we fail to see distinctly, though we may
discern light from darkness. The other parts of the eye
exist to form images oh the retina. The cornea, lens, and
the aqueous and vitreous humors are the parts directly con-
cerned in forming the images. Light from an object passes
through the cornea, aqueous humor, lens, and vitreous
humor, and the rays are so refracted as to form an inverted
image. If this image falls on a good retina, we see well.

The Blind Spot.— The retina is much more complicated than any
of the other nerve endings. Light must fall on these special structures
to have any effect. Falling on the optic nerve itself has no effect in
giving a sensation of light. And if the light falls on the spot where
the optic nerve enters the eyeball we see nothing. Hence, this spot is
called the blind spot.

Experiment illustrating the Blind Spot. — At the left (as looked
at by the class) of a long blackboard make a bright circular spot, three
inches in diameter, with white or yellow crayon. Beginning at the
right of this write the figures i, 2, 3, etc., along the whole length of the
board, about eight inches apart. Let each pupil close the right eye and
look at the bright spot. Then let each read the figures, passing slowly
from one to another in order, at the same time noticing whether the
bright spot can be seen. To succeed in this the eye must not be allowed

294 PHYSIOLOGY.

to waver. Have the pupils tell when the bright spot disappears, then
read on, and note when the soot reappears.

Another Experiment. — In this experiment shut the right eye, and
be careful not to let the left eye waver.

. Read this line slowly. Can you see the star all the time ? If the
star does not disappear before reaching the end of the line, let the eye
travel on across the right-hand page, or hold the book nearer the face.
In the human eye the optic nerve enters the eye not in the center, but
nearer the nose, so that in turning the left eye toward the right at the
proper angle, the image of the star falls upon the spot where the optic
nerve enters. As this spot is insensitive to light, the star no longer
appears.

The Optic Nerve not Sensitive. — The optic nerve,
while capable of carrying nerve impulses that cause sensa-
tions of light, is not itself sensitive to light. If the optic
nerve be cut, it does not give pain, but gives the sensation
of a flash of light.

Sympathy between the Two Eyes. —While most of
the fibers from each optic nerve cross to the other side of
the brain, some fibers go to the same side of the brain.
We can therefore better understand the close sympathy
that we know exists between the two eyes.

Pain in the Eyes. — Pain, felt in the eyes, comes from
impulses conveyed, not by the optic nerve, but by a branch
of the fifth pair of nerves (the nerves of sensation for most
of the face).

Color Sensations. — The difference in colors is due to the differ-
ences in the rapidity of the vibrations of the waves of light, as in sound
differences in the rapidity of the vibrations of the sound waves cause
the various degrees of pitch. Many interesting experiments may be
made with color sensation, most of which are difficult of explanation.
Fasten a bright red wafer or seal on a white card. Look intently at
the center of the red spot till the eye is tired. Then quickly look at
a point in the white surface. What color appears ? This may be
repeated with other colors.

THE SENSE OF SIGHT. 295

Color Blindness. — It is found that some persons can-
not distinguish certain colors. Blindness to red and green
are most common. This is a matter of importance among
railroad men and sailors where it is necessary to distinguish
red and green signals.

Stereoscopic Vision. — In looking at an object with one
eye more is seen to the side of that eye, while the other
eye sees more of the other side, considerable of the object
being seen with both eyes. The effects produced on the
two eyes are united, and so we better see objects as solids.
This is what is termed stereoscopic or binocular vision.

Duration of Impressions of Light. — Most boys have amused them-
selves around a bonfire by whirling a stick with a glowing coal on its
end. The continuous circle of light thus produced indicates that the
impression of light remains for a time, in this case until the stick com-
pletes the circle, giving a continuous line of light. Or when riding in a
carriage the spokes of the wheels blur together because the impression
of each lingers till another has taken its place.

After-Images. — But if we shut the eyes quickly, we may keep dis-
tinct the impression of the last positions, and so see them distinct from
each other. Better still, shut the eyes while looking at the wheel, then
open and shut them as quickly as possible.

Again, if one looks at a bright lamp and then closes the eyes, there
may remain the same appearance as when we looked at the object
itself. This is called the Positive After-Image. Or sometimes, espe-
cially after looking long at a bright light, we may, on closing the eyes
or looking away, see a dark spot of the same shape as the bright one we
looked at. This is called the Negative After-Image.

THE CARE OF THE EYES.

i. Objectionable Light. — In reading we wish light
from the printed page. Hence we should avoid light
entering the eye from any other source at this time. While
reading, then, do not face a window, another light, a mirror,

296 PHYSIOLOGY.

or white wall, if it can be avoided. White walls are likely
to injure the eyes. Choose a dark color for a covering for
a reading table. Sewing against the background of a white
apron has worked serious harm. Direct sunshine very
near the book or table is likely to do harm.

2. Position in Reference to Light. — Preferably have
the light from behind and above. Many authors say " from
the left," or "over the left shoulder." In writing with the
usual slant of the letters this may be desirable. But ver-
tical writing is now strongly advocated, as it enables one
to sit erect, and have the light from above and equally for
the two eyes. Sitting under and a little forward of a hang-
ing lamp will thus give the light equally to the two eyes
and send no light direct into the face. In reading by day-
light avoid cross-lights so far as possible.

3. Electric Light. — The incandescent electric light
has an advantage in being readily lighted, without matches,
and in giving out little heat ; but owing to its irregular
illumination (due to the shadow cast by the wire or fila-
ment), it is not well suited for study or other near work.
For this purpose an Argand gas or kerosene burner is
much to be preferred, since it throws a soft, uniform, and
agreeable light upon the work.

4. Reading Outdoors. — Reading out-of-doors is likely
to injure the eyes, especially when lying down. To try to
read while lying in a hammock is bad in many ways. Too
much light directly enters the eye, and often too little falls
upon the printed page.

5. Reading Heavy Books. — Do not hold the book or
work nearer the eyes than is necessary. " So far as possible
avoid continuous reading in large or heavy books by arti-

THE SENSE OF SIGHT, 297

ficial light. Such books being hard to hold, the elbows
gradually settle down against the sides of the body, and
thus the book is held too close to the eyes, or at a bad
angle, or the body assumes a bad position.

6. Resting the Eyes. — Frequently rest the eyes by
looking up and away from the work, especially at some
distant object. One may rest the eyes while thinking over
each page or paragraph, and thus really gain time instead
of losing it.

7. Strength of Light. — Have light that is strong
enough. Remember that the law of the intensity of light
as affected by distance is that at twice the distance the
light is only one fourth as strong. Reading just before
sunset is not wise, One is often tempted to go on, not
noticing the gradual diminution of light.

8. Evening Reading. — In all ways endeavor to favor
the eyes by doing the most difficult reading by daylight,
and saving the better print and the books that are easier
to hold for work by artificial light. Writing is usually
much more trying to the eyes than reading. By carefully
planning his work the student may economize eyesight,
and it is desirable that persons blessed with good eyes
should be careful, as well as those who have a natural
weakness in the eyes. It often results that those inherit-
ing weak organs, by taking proper care, may outlast and
do more and better work than those naturally stronger,
but who, through carelessness, injure organs by improper
use or wrong use (ab-use).

9. Artificial Light in the Morning. — Reading before
breakfast by artificial light is usually bad.

2Q8 PHYSIOLOGY.

10. Reading during Convalescence. — Many eyes are
ruined during convalescence. At this time the whole sys-
tem is often weak — including the eyes. Still, there is a
strong temptation to read, perhaps to while away the time,
perhaps to make up for lost time in school work. This is
a time when a friend may show his friendship.

u. Irritation of the Eyes. — If one finds himself rub-
bing his eyes, it is a clear sign that they are irritated. It
may be time to stop reading. At any rate, one should find
the cause, and not proceed with the work unless the irrita-
tion ceases. If any foreign object, as a cinder, lodges in
the eye, it is better not to rub the eye, but to draw the lid
away from the eyeball and wink repeatedly ; the increased
flow of tears may dissolve and wash the matter out. To
relieve the feeling that something must be done it may be
well to rub the other eye, but of course this gives no posi-
tive relief to the affected eye. If it be a sharp cornered
cinder, rubbing may merely serve to fix it more firmly in
the conjunctiva. If it does not soon come out, the lid may
be rolled up over a pencil, taking hold of the lashes or the
edge of the lid. The point of a blunt lead pencil is a con-
venient and safe instrument with which to remove the par-
ticle. Sometimes being out in the wind (especially if un-
used to it), together with bright sunlight, may irritate the
eyes. If after such exposure one finds lamplight irritating,
he will do well to go to bed early, or remain in a dark
room.

12. Keep the Eyes Clean. — Be careful to keep the
eyes clean. Do not rub the eyes with the fingers. Aside
from consideration of rules of etiquette, there is danger of
introducing foreign matter that may be very harmful. It
is very desirable that each person have his individual face

THE SENSE OF SIGHT. 299

towel. By not observing this rule certain contagious dis-
eases of the eyes often spread rapidly.

13. Consult a Reliable Oculist. — If there is any con
tinuous trouble with the eyes, consult a reliable oculist.
Many headaches are due to eye-strain, the real cause being
unsuspected. If a child has frequent headaches, it is well
to have the eyes examined. Many persons injure their
eyes by not wearing suitable glasses. On the other hand,
do not buy glasses of peddlers nor of any but reliable
specialists. One may ruin the eyes by wearing glasses
when they are not needed. Sight is priceless.

READING. — Sight, Le Conte.

Summary. — i. Sight, like hearing, acts through space, outstripping
the "contact senses " of touch, taste, and smell.

2. The eye is protected by its bony surroundings, lids, lashes, tears,
sensitiveness of the conjunctiva, etc.

3. The eye is moved by muscles under nerve control.

4. The eye has three coats — sclerotic, choroid, and retina.

5. The pupil is a hole in the iris, and varies in size to regulate the
amount of light admitted.

6. The refracting media of the eye are the cornea, aqueous humor,
lens, and vitreous humor.

7. These refracting media form an inverted image on the retina.
The eye is a camera, darkened on the inside.

8. The ciliary muscle, acting on the elastic lens, adjusts the lens
for seeing at different distances.

9. Suitable lenses overcome many of the defects in eyesight.

10. The retina is an expansion of the optic nerve, and is exceed-
ingly complicated in its structure.

11. The blind spot is the place where the optic nerve enters the eye.

12. The optic nerve is insensitive to light, but injury to it causes
sensations of light.

13. Most of the fibers of the optic nerve cross to the other half of
the brain, but some do not cross.

300 PHYSIOLOGY.

14. Color is due to difference in the rapidity of vibration in the
waves of light.

15. Some eyes do not distinguish these differences and are color
blind.

1 6. Pain in the eyes comes through the fifth pair of nerves, not
through the optic nerves.

17. Binocular vision makes objects "stand out" more distinctly as
solid bodies.

1 8. Impressions of light linger, making after-images.

19. Defects in eyesight are much more common among civilized
men than with the uncivilized men or animals.

20. The care of the eyes must be made a subject of study and care-
ful thought by all reading people.

Questions. — i. What iythe position of the eyeballs during sleep?

2. What is "cataract"?

3. What is the cause of " double vision "?

4. Why does the well eye sympathize with the affected one?

5. Why does looking at a bright light often cause a person to
sneeze ?

6. Why is weeping associated with grief ?

7. What is the condition of one who is "cross-eyed"?

8. Compare the pupils of a man, a cat, and a cow.

9. Does the color of the eye have any relation to the strength of
eyesight ?

10. Why is one blinded on entering a bright room from the dark?
n. Why is one going from a bright room into the dark unable to
see at first, but gradually sees more distinctly ?

12. Why can one not see well when the eye " waters "?

13. If each eye has a blind spot, why are there 'not blank spaces in
the field of vision?

14. What advantage has a stereoscopic view over a single view?
How are stereoscopic views made?

15. Should the lights which illumine a pulpit or platform be so
placed that they can shine into the eyes of the congregation? How
should they be arranged?

CHAPTER XXL
TASTE, SMELL, AND HEARINGo

Uses of the Sense of Taste. —The sense of taste helps
us in judging of the fitness of anything that presents itself
as a candidate for election as food. By reflex action the
taste of agreeable substances aids in digestion by stimulat-
ing the glands, especially the salivary glands.

The Papillae. — The surface of the tongue is covered
with papillae. These are of three kinds. Most numerous

Papillae

Glosso-pharyngeal
Nerve (9th)

Gustatory Branch of Fifth Nerve
Fig. 91. Diagram of Tongue, showing Nerves and Papilla.

are the filiform papillae, slender, cylindrical projections.
Like the papillae of the skin, they seem to be organs of
touch. Scattered among the filiform papillae are small,
bright red spots which, on examination, are found to be
shaped somewhat like a mushroom, the fungiform papillae.
Near the base of the tongue are about a dozen larger pa-

301

302 PHYSIOLOGY.

pillae, arranged like a letter V with its apex toward the base
of the tongue. These are the circumvallate papillae, each
having around it a deep circular furrow.

The Nerve Supply of the Tongue. — On the sides of
this furrow are small oval bodies, called " taste buds," con-
nected with the ends of the nerves of taste. The nerves
of taste are the glosso-pharyngeal, or ninth cranial nerves,
distributed to the back part of the tongue, and a branch of
the fifth pair of nerves, the gustatory, to the front part.

Although we ordinarily speak of an article of food as
"palatable," or "unpalatable," the sense of taste in the
palate is only feebly developed. The tip of the tongue
seems to be most sensitive to sweets and salines, the back
part to bitters, and the sides to acids.

Solution Necessary for Tasting. — Substances must be
dissolved before they can be tasted. If the tongue be
wiped dry, and a few grains of salt or sugar be placed on
it, the taste will not be perceived for a little time. Insol-
uble substances give no taste.

Flavors. — What we call flavors affect us more through
the sense of smell than through taste. If the nose be held
shut, and we are careful about breathing, a piece of onion
placed on the tongue does not produce what we usually
call the taste of the onion. We may thus get rid of the
disagreeable part of taking certain medicines. Let the
student experiment with various substances as above in-
dicated.

Effect of Temperature on Taste. — It is said that the
temperature of about 40° F. is most favorable for tasting,
and after rinsing the mouth with very hot or very cold
water, such bitter substances as quinine will have only a
trace of their usual taste.

TASTE, SMELL, AND HEARING.

303

Olfactory Nerves J

Branches of
Fifth Nerve

Turbinated Bones

The Sense of Smell. — "The sense of odor gives us
information as to the quality of food and drink, and more
especially as to the quality of the air we breathe. Hence
we find the organ placed at the opening of the respiratory
passages, and in close proximity to the organs devoted to
taste. Taste is at the gateway of the alimentary canal,
just as smell is the sentinel of the respiratory tract; and
just as taste, when combined with smell to give the sen-
sation we call
flavor, influ-
ences the di-
gestive pro-
cess, and is
influenced by
it, so smell
influences the
respiratory process. The
presence of odors influ-
ences both the amplitude
and the number of the
respiratory movements.
Thus the smell of winter-
green notably increases the

respiratory work, next comes ylang-ylang, and last rose-
mary. The breathing of a fine odor is therefore not only
a pleasure, but it increases the amplitude of the respira-
tory movements. Just as taste and flavor influence nutri-
tion by affecting the digestive process, and as the sight of
agreeable or beautiful objects, and the hearing of melo-
dious and harmonious sounds react on the body and help
physiological well-being, so the odors of the country, or
even those of the perfumer, play a beneficent role in the
economy of life." — M'KENDRICK and SNODGRASS.

Fig. 92. Nerves of the Outer Wall of the
Nasal Cavity.

304 PHYSIOLOGY.

Why we Sniff. — In quiet breathing the air passes
along the lower air passages just above the hard palate.
The true olfactory passages are higher, but still in com-
munication with this lower passage. When we wish to
test the quality of the air, we sniff, that is, make a sudden
inspiration by jerking the diaphragm down, and air from
the outside then rushes into these upper nasal passages,
over the walls of which the nerves of smell, the olfactory
nerves, are spread in the mucous membrane. The sudden
rush of air against this membrane seems to aid greatly in
detecting the odor. The nerves have peculiar endings,
and it is not known just how the substances produce their
effect. The substances must be in a very finely divided
state, probably gaseous. The mucous membrane is sup-
plied with mucus, and the odorous substance, probably, is
first dissolved in the mucus. The lower, or respiratory,
passages have a more abundant blood supply, and are
redder than the upper. In inflammation, owing to their
narrowness, the passages, especially the upper, are often
closed by contact of the opposite sides. Substances like
ammonia have no odor, but excite the tactile nerves. They
are often spoken of as having a " pungent " odor, but are
simply irritants.

The Sense of Hearing. — The ear passages are inclosed
by the hard bones of the head. The ear is, in consequence,
difficult to dissect. It is very desirable to have a model
of the ear. The ear may be dissected in a cat or rabbit by
following the accompanying description. It will take time
and patience to trace all the parts.

The Parts of the Ear. — The ear is a much more com-
plicated organ than would naturally be supposed. The
parts of the ear are the external, the middle, and the in-
ternal ear.

TASTE, SMELL, AND HEARING.

305

The External Ear. — The external ear gathers the
sound waves, and directs them into the opening of the ear,
but the loss of the external ear does not seriously interfere
with hearing. The passage leading inward from the ear
extends about an inch, and is then completely shut off
from the cavities beyond by a thin membranous partition,
the tympanic membrane or drum skin. The skin of the

Stirrup Anv

Semicircular Canals

COCHLEA

PHARYNX

Fig. 93. Diagram of the Ear.

ear dips into and lines the external tube, and continues as
a very thin layer over the membrane of the tympanum.
The auditory meatus, as this passageway is called, is
guarded by hairs, and is further protected by wax secreted
by glands of the lining.

The Middle Ear. — Beyond the membrane of the tym-
panum is a cavity called the middle ear. Extending across
the cavity of the middle ear is a chain of very small bones,
the hammer, anvil, and stirrup, the hammer being attached

306 rnvsiOLOc,\.

to the inner surface of the membrane of the tympanum,
and the stirrup being fastened by its base to the wall of
the internal ear.

The Eustachian Tube. — The middle ear communicates
with the pharnyx by means of a narrow tube called the
eustachian tube. It admits air to equalize the pressure on
the two sides of the tympanic membrane. This tube is
probably closed most of the time, but opens when we
swallow.

The Internal Ear. — The internal ear consists of several
complicated cavities and tubes which contain a liquid in
which rest the nerves. The principal cavity is the cochlea,
or snail-shell cavity, in which the nerve endings are con-
nected with an exceedingly complicated apparatus.

The Production of Sound. — Sound waves set the drum
skin or membrane of the tympanum in vibration ; the
vibrations are conveyed by the chain of bones across
the middle ear to the liquid of the inner ear. Through the
complicated apparatus of the snail shell the vibrations of
the liquid are made to start nerve impulses in the fibers of
the auditory nerve, and when these nerve impulses are
rightly received and interpreted by the brain, we have a
sensation called sound.

The Equilibrium Sense. — Probably most of the senses contribute
to the maintaining of the equilibrium of the body by giving information
as to position, motion, etc., especially sight and the muscular sense.

Only that part of the auditory nerve which is distributed in the
"snail shell" of the ear is now supposed to have to do with hearing.
It is no longer believed that the semicircular canals are concerned with
the process of hearing. There seems to be good evidence that the
semicircular canals inform us as to changes of the position of the body,
and they are regarded as the seat of an "equilibrium sense." The fact
that one of these canals is horizontal, and that the two vertical canals

TASTE, SMELL, AND HEARING. 307

are at right angles to each other, strengthens this belief. It is thought
that each of these canals detects movements in its own plane. The
experiment has been made of placing a man on a table that easily
turned ; with the eyes shut the subject could usually detect fairly well
the changes of position from rotation of the table. What is known on
the subject comes partly from observation in cases where these parts
are diseased (which, in itself, does not cause loss of hearing), and by
operating on lower animals ; in both of these lines of observation
injury to these parts appears to be followed by dizziness, loss of power
to maintain equilibrium, etc.

The Care of the Ear. — In cleaning the ear no hard
substance should be used ; even the finger nail is likely to
do harm. A moistened cloth should be used. If this is
not sufficient, a physician should be consulted. In wash-
ing the ear it should be thoroughly dried before being
exposed to a wind, especially a cold wind. The rapid
evaporation may cool the parts so rapidly as to cause
trouble. It is not well to stuff the ears with cotton. If
there is any trouble with the hearing, of course a physician
should be consulted without delay.

Colds and Deafness. — A cold often produces inflam-
mation of the mucous membrane of the pharnyx. This
inflammation may extend along the eustachian tube to the
middle ear and affect the hearing.

The Use of the Ears. — The existence of an organ of
hearing implies the existence of what? Why have we
these organs of hearing ? Is it merely a means of protec-
tion ? Is it that we may enjoy the music of nature, such
as the songs of birds ? Is there not one sound that makes
sweeter music than the most gifted of feathered songsters,
surpassing all the instruments of man's device, even the
violin, with its almost human flexibility and range of
expression ?

308

What sound communicates to us the most of thought
and sympathy ?

What sound was it Robinson Crusoe, in his dreary soli-
tude, most longed to hear ?

READING. — The PJiysiology of tlie Senses, M'Kendrick
and Snodgrass.

Summary. — i. Taste enables us to judge of the quality of food,
and it indirectly influences digestion.

2. The tongue has two nerves of taste, the fifth pair of cranial nerves
supplying the front, and the ninth pair the base.

3. So-called flavors affect the sense of smell more than that of taste.

4. The sense of smell tests food and air.

5. Agreeable odors promote respiration.

6. The ear consists of the outer, middle, and inner ear. In the inner
ear are the endings of the auditory nerve.

7. The semicircular canals have to do with a sense of equilibrium
and not with hearing.

8. Colds and catarrh often seriously affect hearing.

Questions. — i. How may the sense of taste be blunted ?

2. What is the effect of inhaling menthol ?

3. Does a person who is deaf in one ear hear " half as well " as
before ?

4. Which of the senses goes to sleep first when we go to bed ?

5. In what order do the other senses go to sleep ?

6. In what order do the senses waken in the morning ?

CHAPTER XXII.
THE VOICE.

The Ear and the Voice. — The delicate mechanism and
capabilities of the ear are fully matched by the fine adjust-
ment and range of the voice. The organ of the voice is
well worthy of study, if we look at it merely as a most
ingenious contrivance, to say nothing of its importance to
us as a means of expressing thought.

What we can learn from Our Own Throats. — We can learn a
little from the observation of our own mouths and throats. The pro-
jection of the throat known as " Adam's Apple " is one angle of the
Thyroid cartilage. A ridge may be felt running downward from the
projecting angle. Above the Adam's apple a depression may be felt.
Press the tip of the ringer lightly into this depression and perform the
act of swallowing. It will be noted that the Adam's apple is drawn up-
ward and closer to the bone above the depression. This bone is the
Hyoid bone ; it is connected with the larynx below the base of the
tongue. Below the thyroid cartilage another cartilage may be felt,
the Cricoid cartilage. Below this is the windpipe with its rings of
cartilage. The general form of the whole larynx may be felt in a per-
son not overburdened with fat.

By depressing the tongue and looking into the mouth the tip of the
epiglottis may possibly be seen at the base of the tongue. Beyond
these points we cannot learn much without dissection. A small mirror
set obliquely on a handle (like those used by dentists) may be inserted
through the mouth so that the larynx can be seen from above. But
the meaning of what would be thus seen would not be very clear with-
out a careful dissection of the larynx.

The Vocal Cords. — The vocal cords are not very appro-
priately named. They are mere ridges projecting from

3°9

3io

PHYSIOLOGY.

the sides of the larynx. Under the covering of mucous
membrane are ligaments and muscles that may be stretched
to various degrees and placed in different positions, accord-
ing to the sound that is to be produced.

The Position of the Vocal Cords. — While we are

quietly breathing, the vocal cords, or bands, lie back, like
low ridges, against the side of the larynx, and offer nearly
the whole channel of the larynx for the free passage of air

— Tiachca

FROM RIGHT TO LEFT MEDIAN

Fig. 94. Longitudinal Sections of the Larynx.

for breathing purposes. But when we wish to produce
vocal sound, the vocal cords are made to stand out farther
from the side walls, and interfere with the free passage of
the air. In examining the larynx, it is seen that the vocal
cords are attached close to each other in front, but that at
the back of the larynx they diverge widely (in the position
of rest), forming a letter V, with the angle of the V in
front, just back of Adam's apple. " When changes in the
voice or in breathing are being made, the white glistening

THE VOICE. 311

vocal cords may be seen to come together or to go apart
like the blades of a pair of scissors." In a high note the
cords are close together and nearly parallel. As the air
is forced past the approximated edges of the vocal cords,
they are set in vibration, and produce the sound called the
voice.

Illustration of the Vocal Cords. — The principle of the action of
the vocal cords can be illustrated by the common toy known as the
squeaking balloon, or "squawker." Here the air is driven out past a
band of rubber stretched across the inner end of the tube. If instead

Epiglottis
False Vocal Cords ...

True Vocal Cords ~

i
Glottis Narrowed, High Note Glottis Wider, Quiet Breathing

Fig. 95. The Larynx, as seen by Means of the Laryngoscope, in Different
Conditions of the Glottis.

of one band with both edges free, we were to tie on the inner end of
the tube two bands of rubber, each covering the outer edge of the tube,
leaving the inner edge of the rubber free, and with the two bands touch-
ing at one end and considerably separated at the other end, we would
have a pretty fair resemblance to the larynx.

Reenforcement of Vocal Sound. — As in many musical
instruments, the vibrations of the membrane alone would
be too feeble to have much effect. In the violin, piano,
drum, etc., the vibrations are reenforced by the vibration
of a body of air contained within. So here the vibrations
of the cords are reenforced and modified by the air spaces
above.

Loudness of Voice. — The loudness of the voice depends
on the force with which the air is driven past the cords,

312 PHYSIOLOGY.

together with the size and condition of the cords them-
selves.

Pitch of Voice. — Pitch depends on the rapidity of the
vibrations, which is determined by the length of the cords
and their tension. Other things being equal, the size of
the larynx would determine the pitch.

Voice and Speech. — The larynx by itself produces
vocal sound merely. In speech the sounds produced in*
the larynx are much modified by the lips, tongue, teeth,
cheeks, etc. We have voice as soon as born, but we only
gradually acquire the power of speech. Mammals, birds,
and some of the lower vertebrates have voices, but they
have not speech. This distinguishes man from the ani-
mals below him, though perhaps some of the higher apes
have speech in a slight degree. Dogs can express their
wants by barking, growling, snarling, etc., but it is mostly
by their tone, with their attitudes, and a slight facial
expression (as in snarling).

Vowels and Consonants. — By various positions of the tongue and
organs of the throat we make the different vowel sounds. In the con-
sonants we more or less shut off (for the time) the passage of air, and
so stop, or modify, the sound. This is hardly the place to study and
analyze the sounds of our spoken language, yet it may be found profita-
ble to watch the different organs as each sound is produced ; for when
the structure and relation of the different parts concerned in the pro-
duction of these sounds are better known, the definitions and state-
ments of the books will be much more fully understood.

Differences between Voices. — Since no two throats
are exactly alike, no two voices sound just the same. The
size and shape of the pharynx, the shapes and positions of
the teeth, lips, the condition of the mucous membrane of
the passages generally, all affect the sound, and give it its
" quality," by which we distinguish one voice from another,

THE VOICE. 313

even if they are in the same pitch and have the same
degree of loudness.

Change of Voice. — At about the age of fourteen a boy's larynx
increases in size and the voice changes, becoming deeper and heavier.
During the change the falsetto often breaks in upon the ordinary voice,
the voice being said to " crack.'1

Hoarseness. — If the mucous membrane covering the vocal cords is
inflamed, or covered with too much mucous, hoarseness is likely to
.result.

Whispering. — As in the animal we have voice without speech, so
in whispering we have speech without voice ; that is, there is no vocali-
zation. The organs of speech so modify the aspiration as to produce
speech. There is no true voice.

Culture of the Voice. — The voice and speech are
very susceptible of culture, and nearly all voices may im-
prove by proper cultivation. A cultivated voice and care-
ful, distinct speech are very desirable accomplishments,
and are not nearly so common as they ought to be. We
delight in fine singing, and many strive to cultivate this
art ; but not so many try to learn to talk so that it is a
pleasure to .hear the spoken sound.

READING. — The Throat and the Voice, Cohen.

Summary. — i. The larynx is very complicated. Various muscles
move the cartilages and vary the length and tension of the vocal cords,
and thus produce the varying degrees of pitch.

2. The vocal cords are not simple cords, but are band-like ridges
on the sides of the larynx.

3. The higher animals have voice but not speech.

4. Whispering is speech without voice.

5. The larynx is affected by " colds " and catarrh.

Questions. — i. Why does one become hoarse from hearing others
shouting?

2. What is ventriloquism?

CHAPTER XXIII.
ACCIDENTS.— WHAT TO DO TILL THE DOCTOR COMES.

How to Stop Flow of Blood from Arteries. — In case
of bleeding from an artery the blood comes in jets. Pres*
sure should be applied between the cut and the heart. To
know where to apply the pressure, study of the course of
the main arteries should be made. By studying Fig. 16
it will be seen that the arteries to the arms pass down the
inside of the upper arm. Here they come near the sur-
face. At the elbow the artery is near the skin in the
angle of the elbow. The artery which makes the pulse at
the wrist is well known. By putting a baseball under the
armpit and pressing the arm down firmly, the artery may
be compressed.

Bleeding from the Upper Arm. — In case of a deep
cut in the lower part of the arm, a handkerchief should
have a knot tied in it, and the knot placed over the artery ;
that is, on the inside of the arm just below the armpit.
Pass the handkerchief around the arm and tie it loosely.
Then run a stick through it, and twist till the knot is drawn
tightly against the artery. Instead of a knot, a potato, or
anything else to make a firm lump, may be used. (See
Figs. 1 6 and 35.)

Bleeding from the Neck. — In studying the pulse, we
found the Carotid artery in the neck. If a deep cut has
been made in the upper part of the neck, it might be pos-
sible to stop the flow by compressing the artery lower
down the neck.

3H

ACCIDENTS. 315

Wounds in the Thigh. — The femoral artery comes
near the surface in the groin. Pressure may be applied
here in the same way to stop bleeding from a cut farther
down the thigh. In the angle back of the knee, pressure
may compress the artery supplying the leg.

In case of severe wounds, pressure should be applied
immediately to the wound. Sometimes it is well to make
a plug of cloth and press upon the cut.

Bleeding from Veins. — In case of bleeding from veins,
holding the part up may check the flow. If necessary to
apply pressure, it should be beyond the cut, instead of
between it and the heart, as in the case of the artery.

Hemorrhage of the Lungs or Stomach. — Blood from
the lungs is bright, frothy, and salty; from the' stomach
is dark and sour. In case of bleeding from the lungs or
stomach, let the person rest quietly on a lounge or easy-
chair. Give him some bits of ice to swallow.

Bleeding from the Nose. — Nosebleed may sometimes
be stopped by pressing firmly at the base of the nose.
Do not lean forward, as this position aids the flow. Sit
up, and hold up the head, and hold a cloth under the nose.
Apply cold water or ice to the nose and to the back of the
neck. If this does not stop it, inject cold water, with a
little salt or soda in it, into the nose. Often the flow may
be stopped by pressing firmly on the upper lip at the sides
of the nose. If these attempts fail, a long strip of cloth
may be used to plug the nostril, pushing the cloth in a
little at a time, and leaving the ends so it can be pulled
out. This should not be removed till a long time after the
flow is checked, as it may start the bleeding afresh. After
an attack of this kind avoid blowing the nose, as this often
starts bleeding again.

316 PHYSIOLOGY.

Treatment of Burns. — Plunge the burned part into
cold water. As soon as possible apply a solution of cook-
ing soda (a tablespoonful of bicarbonate of soda to a tea-
cup of water) ; or lay a wet cloth on the burned part and
put the soda on the cloth. Afterwards apply vaseline,
and renew the vaseline till the wound is healed.

A mixture of equal parts of sweet oil and limewater
makes a good liniment for dressing burns. Flour thickly
applied gives relief, but is objectionable because it is hard
to remove without taking the skin off with it.

Danger from Burning Clothing. — If the clothing takes
fire, there is added to the danger of burning the body, the
further risk of inhaling the flame and heated air. It is
best to lie down and roll or wrap the body in any cloths
at hand, — rugs, shawls, etc. Running serves to fan the
flames. Hence, if a person whose clothing is on fire is
seen to be thoroughly frightened, and to have lost presence
of mind and be starting to run, the best thing to do usually
is to grasp and try to throw him to the ground, putting a
wrap of some kind around the body at the same time if
possible. Rolling on the ground or floor in itself would
very likely put out a small flame.

Treatment of Fainting. — Lay the body flat on the
back. Keep the crowd away, and give plenty of fresh air.
Loosen the clothing about the neck and waist. Sprinkle
cold water on the face, but do not drench the body with a
quantity of water. Apply smelling salts (ammonia) to the
nostrils ; rub the limbs toward the body. If these reme-
dies do not soon restore consciousness, send for a physician.
A faint is not usually a serious matter. Bad ventilation,
disagreeable odors, or even the oversweet odors of such
flowers as the tuberose, may cause fainting.

ACCIDENTS. 317

Broken Bones. — Keep the patient as quiet as possible
till the physician arrives. There need be no anxiety if the
physician is delayed, as ordinarily no harm comes from
waiting. If there is inflammation, cold water may be
applied. Cooling applications are desirable in case of
severe bruises. If it is necessary to carry the patient, lay
him on a board, or at least keep the injured part as quiet
as possible ; a cane or umbrella may be tied alongside a leg,
and supported by a pillow or a coat. Sometimes the sharp
ends of the bones may cut the flesh or even blood tubes.

Sunstroke. — Lay the patient in the shade and pour
cold water over the head.

.

Fig. 96. Resuscitation from Drowning. (Lincoln, 3 Figures.)
(Position 1.)

TREATMENT OF THE DROWNED.

(As given by the Michigan Board of Health^)

RULE I. Remove all obstructions to breathing. Instantly
loosen or cut apart all neck and waist bands ; turn the

PHYSIOLOGY.

patient on his face, with the head down hill ; stand astride
the hips with your face toward his head, and, locking your
fingers together under his belly, raise the body as high as
you can without lifting the forehead off the ground (Fig.
96, Position i), and give the body a smart jerk to remove
mucus from the throat and water from the windpipe ; hold
the body suspended long enough to count slowly, one,

- Av^i,

Fig. 97- Resuscitation from Drowning.
(Position 2.)

two, three, four, five, repeating the jerk more gently two
or three times.

RULE 2. Place the patient on the ground face down-
ward, and, maintaining all the while your position astride
the body, grasp the points of the shoulders by the clothing,
or, if the body is naked, thrust your fingers into the arm-
pits, clasping your thumbs over the points of the shoulders,
and raise the chest as high as you can (Fig. 97, Position 2)

ACCIDENTS.

319

without lifting the head quite off the ground, and hold it
long enough to count slowly one, two, three. Replace
him on the ground, with his forehead on his flexed arm, the
neck straightened out, and the mouth and nose free. Place
your elbows against your knees, and your hands upon the
sides of his chest (Fig. 98, Position 3) over the lower ribs,
and press downward and imvard with increasing force long

Fig. 98. Resuscitation from Drowning.
(Position 3.)

enough to count slowly one, two. Then suddenly let go,
grasp the shoulders as before, and raise the chest (Position
2), then press upon the ribs, etc. (Position 3). These al-
ternate movements should be repeated ten or fifteen times
a minute for an hour at least, unless breathing is restored
sooner. Use the same regularity as in natural breathing.

RULE 3. After breathing has commenced, restore the
animal heat. Wrap him in warm blankets, apply bottles

320 J'HYSIOLOGY.

of hot water, hot bricks, or anything to restore heat. Warm
tJic head nearly as fast as tJie body lest convulsions come on.
Rubbing the body with warm cloths or the hand, and slap-
ping the fleshy parts, may assist to restore warmth, and
also the breathing. If the patient can surely swallow, give
hot coffee, tea, milk, or a little hot sling. Give spirits
sparingly, lest they produce depression. Place the patient
in a warm bed, and give him plenty of fresh air ; keep him
quiet.

BEWARE !

Avoid Delay. A moment may turn the scale for life
or death. Dry ground, shelter, warmth, stimulants, etc.,
at this moment are nothing — artificial breathing is
everything — is the one remedy — all others are sec-
ondary.

Do not stop to remove wet clothing. Precious time is
wasted, and the patient may be fatally chilled by the ex-
posure of the naked body, even in summer.

First restore Breathing. — Give all your attention and
effort to restore breathing by forcing air into, and out of,
the lungs. If the breathing has just ceased, a smart slap
on the face or a vigorous twist of the hair will sometimes
start it again, and may be tried incidentally.

Before natural breathing is fully restored, do not let the
patient lie on his back unless some person holds his tongue
forward. The tongue by falling backward may close the
windpipe and cause fatal choking.

Prevent friends from crowding around the patient and
excluding the fresh air ; also from trying to give stimulants
before the patient can swallow. The first causes suffoca-
tion ; the second, fatal choking.

ACCIDENTS. 321

Do not give up too soon : you are working for life.
Any time within two hours you may be on the very
threshold of success without there being any sign of it.

Learn to Swim. — Of course, persons who cannot swim
well ought not to go out in a boat without taking along
some sort of a float that may serve as a life-preserver.
Some of the rubber cushions serve well for this.

Every father neglects his duty if he does not teach his
children, girls as well as boys, to swim and to float. One
cool, trained person may save the lives of a whole boat
load.

When a Boat Upsets. — In case an ordinary rowboat is
overturned, one should not attempt to climb into it or upon
it. It takes very little to float a person in water, as the
body is only a little heavier than water ; in fact, if a person
fills the lungs and lies back in the water his face and nose
will keep above water, and a person (at any rate without
clothing) can float in this way for some time if he breathes
lightly. The trouble is that the person tries to lift the
whole head out of the water. The dog and such animals,
when swimming, have little out of the water but the tip of
the nose and a little of the top of the head. If we could
learn something from them it would be a good thing. The
easiest way to float is on the back. Few persons have
been taught these facts, and most of those who have
learned them lose their presence of mind, and waste their
breath and strength in wild and fruitless splashing. If a
boat be overturned, those who can swim should help those
who cannot to get hold of the edge of the boat, but not
permit them to climb upon it. A small plank will float a
person if he will not try to lift much of his body out of the
water.

322 PHYSIOLOGY.

Suffocation in Wells. — Persons are sometimes suffo-
cated by carbon dioxid in wells and cisterns. Before going
down into a well, it is a safe precaution to lower a lighted
candle. If this is extinguished, a warning is given. If a
second person goes down after one who has become un-
conscious, great care must be taken that two lives are not
lost. A rope should be firmly tied about the body, a hook,
attached to another rope, taken to catch into the clothing
of the first, and the rescuer should be lowered quickly and
brought up immediately. A small rope or large cord
might be carried, by pulling which the signal is given to
pull up.

In resuscitating from carbon dioxid suffocation use the
same method as after drowning, except the first part, which
is to remove water from the windpipe, etc.

Poisons and their Antidotes. — Several of the common
drugs and remedies kept about the house are more or less
poisonous. The proper antidote for each should be known
and kept at hand. In the first place, all such materials
should be kept locked up so they will not be taken by
children, or by mistake, as in the haste of getting medicine
in the night. Again, all grown persons in the family
should be instructed as to the effects of each poison, and
taught its antidote. As soon as any new poisonous drug
is bought, it should be made a point to read up about it,
and procure an antidote. Every one should know that
strychnin causes spasms, that opium brings on stupor,
with contracted pupils, etc.

Objects of Treatment. — Treatment aims at three things,
(i) to get rid of the poison, (2) to neutralize what remains
and prevent further action, (3) to remedy the effects already
produced.

ACCIDENTS. 323

1. Mustard a Common Emetic. — The most common
emetic is mustard ; a tablespoonful in a cup of warm water;
give half of it, following with free drinking of warm water,
then give the rest of the mustard. Do not wait for it to
dissolve, but stir quickly and give at once. Provoke vom-
iting by tickling the throat with a feather or with the
finger. If the mouth of the patient cannot readily be
opened, insert the thumbs inside the cheeks and back of
the teeth. If mustard is not at hand, a strong solution of
table salt will serve. In a few cases, such as poisoning by
ammonia, lye, etc., it is considered best not to administer
an emetic, but to try to neutralize the effect.

2. Neutralize the Poison. — To neutralize a poison this
general rule should be known : an alkali may be neutral-
ized by an acid, and vice versa. For example, lye with
vinegar, carbolic acid with whiting or magnesia, etc. Some
acids and alkalis are always about a house.

3. Give Something Soothing. — After any irritant poi-
son some mild and soothing substance should be given, —
white-of-egg, milk, mucilage and water, flour and water,
gruel, olive, or castor-oil. These materials are partly for
neutralizing the poison, and are also soothing in their
effect. If a patient is drowsy, some stimulant may be
given, as strong coffee (after opium). Of course a physi-
cian should be sent for immediately, as the after-treatment
is of great importance.

The tables of " Poisons, their Symptoms, Antidotes, and
Treatment," in the appendix, are taken from the excellent
Text-Book of Nursing by Clara Weeks-Shaw.

Wounds from Thorns, Rusty Nails. — Promote bleed-
ing by rubbing and pressing the wound and bathing with

324

warm water. Or suck the wound. This tends to remove
any injurious matter. Apply poultices.

Bites of Cats, Bogs, etc. — If the animal is rabid (mad),
suck the wound and cauterize quickly. A poker or nail
heated red hot is best for cauterizing. If one cannot do
this promptly, get lunar caustic with which to cauterize ;
strong acid or alkali, or a coal of fire, may be applied at
once to the wound ; the coal on a cigar may be used. Do
not kill the animal if there is doubt. Keep it confined,
and if it proves a false alarm much anxiety will be saved.

Snake Bites. — Apply ligatures around the part between
it and the heart. Suck the wound (there is no danger
in this if there are no sores or cracks in the skin of the
mouth ; venom is not a stomach poison, though, of course,
it should not be swallowed). Then apply caustics, or a
live coal. Have the patient drink freely of whiskey or
brandy. If ammonia water is at hand, add five teaspoon-
fuls to each pint of liquor.

Ammonium carbonate, ten per cent solution, is also
highly recommended. A teaspoonful dose should be
given immediately, and repeated twice at intervals of ten
minutes.

Bee Stings. — Apply soda, or dilute ammonia.

Poison Ivy. — The itching and discomfort may be
relieved by bathing the part in a mixture of-

Two teaspoons of carbolic acid (pure),

Two tablespoons of glycerin,

One half pint of water or rose-water.

The Sick-room. — Every boy and girl ought to learn
something about the care of the sick, as any one is
likely to be called on to do this kind of work. Good

ACCIDENTS. 325

nursing is often "half the battle." In the first place,
the nurse should faithfully follow the directions of the
physician. This obedience should be complete as to admis-
sion of visitors, as well as in administering medicine, etc.
The nurse often yields to the persuasion of some unwise
friend, " It won't do any harm for him to see me."

Qualities of a Nurse. — The nurse should have a quick
sympathy, and make the patient feel that all that can be
done for his comfort will be done ; yet this sympathy must
not lead the nurse to do anything for, or give anything to
the patient contrary to the orders of the physician. The
nurse should always be cheerful, even when the patient
is "impatient" and annoying in his demands. The
patient is not "himself," and no attention should be paid
to his unnatural irritability.

The Room should be Cheery. — The patient should
have a cheerful room, but the bed should be so placed
that the light will come not too strongly into his face.
Evidence of illness, such as medicine bottles, etc., should
be kept out of sight so far as possible.

Hope. — While it is not best to deceive the patient as
to his condition, there should at all times be kept up
an air of cheerfulness and hope. If the physician can
inspire with confidence, and the nurse give unflagging
good cheer, the chances of recovery are vastly improved.
Nothing sustains like hope.

Pure Air in the Sick-room. — Keep the air of the room
pure. Remove excreta and everything offensive just as
soon as possible. Do not rely on feeling as to tempera-
ture, but keep a thermometer in the room.

Sympathy with the Patient. — One of the necessary
characteristics of a good nurse is the power of imagina-

326 PHYSIOLOGY.

tion. " How would I feel, and what would I like to have
done for me, if I were in his place ? " This feeling will
lead the nurse frequently to raise the patient's head and
turn the pillow — the coolness of the other side of the
pillow is refreshing ; to give sips of cool water ; to see
that the patient does not surfer for want of a bath ; in
giving a bath, to do the work thoroughly, as a skillful
barber carefully and thoroughly reaches every fold and
crevice back of the ear, etc.

Bathing the Sick. — In bathing a weak person only a
part of the body should be moistened at a time ; after this
part is thoroughly dried, another part may be washed ;
it is often necessary to do all this work under the bed
clothing.

Changing the Bedding. — In changing the bed clothing
move the patient to one side of the bed, push the cloth-
ing along close to his body, and place the clean bedding
on the other side ; then move the patient back, remove
the soiled linen, and smooth out the clean. It is often
necessary to warm the sheets first : they should be thor-
oughly dry.

Follow Physician's Directions Faithfully. - - Have
the physician's directions written out plainly, as they may
be forgotten ; and if there is a change of nurses during
the night there is less chance of mistake. Never let your-
self get drowsy when acting as nurse. Get up and walk
about, get a breath of fresh air, and if inclined to be
drowsy do not allow yourself to settle back in an easy-
chair. If watching all night, take a good lunch in the
middle of the night ; coffee may help to keep you awake.
It is not to be expected that one who has worked hard
all day out-doors will be likely to keep awake all night.

ACCf DENTS. 327

There should be day and night watchers, and one wo.uld
better not watch more than six hours at a time.

Sweeping the Sick-room. — Do not allow the room to
be swept with the ordinary broom. The room should have
rugs that can be removed and shaken, and the floor wiped
with a moist cloth. If the room is carpeted, it may be
swept with moist salt, tea-grounds or coffee-grounds, saw-
dust, etc. Any dusting should be avoided ; furniture may
be wiped with a damp cloth.

Do not Whisper. — In the effort to be quiet many make
a mistake ; do not whisper, as it disturbs more than talking,
and also has an air of secrecy that rouses suspicion in the
patient.

Walk Flat-footed. — In walking on tiptoe often floors
and stairs are made to creak when they would not in ordi-
nary circumstances. It takes little reflection to see that
in walking on tiptoe one brings more weight than usual
on a smaller part of the floor, and is therefore more likely
to spring a board in the floor ; it is best to walk flat-footed.
Wear an easy pair of shoes ; an old pair are likely to be
quiet.

Food for the Sick. — Raise the head with the hand, or
bolster the patient up, when giving drink ; or if the patient
is very weak, use a rubber tube, so that he will not have to
lift the head. The nurse should know how to prepare any
food that may be needed during the night. An oil stove
or gas stove is very desirable for cooking, or heating poul-
tices, as an ordinary wood or coal fire is likely to die down,
making it impossible for the nurse to do this work quickly,
as is often necessary to take advantage of a favorable
time, as when the patient wakens.

328 PHYSIOLOGY.

Care of Lamps. — Most lamps, when turned low, give
off a disagreeable gas. It is better to have a very small
lamp burning at full height than a large one turned low ;
sperm candles are recommended.

Bandaging, Preparing Food, etc. — It is well for every
one to know something about bandaging, preparation of
food for the sick, etc. Space here will not allow further
treatment of these subjects, and the student is referred to
treatises on the care of the sick, of which there are several
good ones mentioned at the end of this chapter.

To Prevent Sneezing. — It is well known that a sneeze
may be prevented by firmly pressing on the upper lip.
This may enable a nurse to keep from waking a very sick
patient when, at a critical point, sleep is almost a question
of life or death. And it is a convenient fact for any one
to know. To prevent coughing there are cough drops that
will relieve the tickling in the throat.

For Disinfectants see Appendix.

In addition to the list of books on Accidents, Emer-
gencies, etc., already given, read Hand-Book of Nursing,
published under the direction of the Connecticut Training-
School for Nurses, State Hospital, New Haven, Conn. ;
Text-Book of Nursing, Weeks-Shaw; Nursing: Its Prin-
ciples and Practice, Hampton.

Summary. — i . To stop flow of blood from an artery apply pres-
sure to the wound, or between the wound and the heart.

2. To stop flow of blood from a vein apply pressure to the wound or
beyond the heart.

3. Leaning forward promotes, instead of checking, nosebleed.

4. To burns apply cooking soda.

5. If the clothing takes fire lie down and roll, or wrap a nig or shawl
about the body.

ACCIDENTS. 329

6. If a person with clothing on fire loses his presence of mind, seize,
throw down, and wrap in any woolen clothing.

7. In case of fainting lay the body flat on the back, loosen clothing,
give fresh air, and sprinkle lightly with cold water ; if this does not
revive, rub the limbs toward the body, hold to the nostrils smelling-
salts (or ammonia) and, last, send for a physician.

8. Broken bones do not urgently need prompt attention. Keep
patient quiet and send for a physician.

9. For resuscitation from drowning, use artificial respiration,
promptly begun and long continued.

10. Before going down into a well, test the air by lowering a lighted
candle.

1 1 . Learn the antidotes of every poison in your house as soon as it is
bought, and keep the antidote at hand.

12. Volunteer to help take care of sick friends, and learn to do this
work well.

Questions. — i. How does holding up the wounded part check-
bleeding ?

2. What other methods of resuscitation from drowning are in
use?

3. What are some of the poisonous substances commonly kept in
the house?

CHAPTER XXIV.
THE SKELETON.

The Two Parts of a Skeleton. — Observe that the
skeleton as a whole consists of two portions, the axial por-
tion, consisting of a central axis, the spinal column, to
which the head belongs ; and the appendicular portion,
the limbs and the bones belonging to them.

The Uses of the Bones. — In the skeleton as a whole
observe : —

1. The skeleton shows the form of the body.

2. It supports the softer tissues.

3. It protects softer parts, as the brain in the skull, the
spinal cord in the spinal column, the heart and lungs in
the thorax, etc.

4. The bones serve as levers in producing motion and
locomotion.

Study of a Vertebra. — Take a vertebra from the middle of the
spinal column : —

1. Its most solid part is its body, or centrum.

2. On the dorsal side of this is the neural arch, forming with the
body the neural ring, through which the spinal cord passed.

3. From this arch there extend projections, or processes. Hold the
vertebra by the tip of its longest process, and place it beside the cor-
responding vertebra in the complete skeleton. Note that : —

(rt) The body is flattened where it fitted against the vertebras
anterior and posterior to it ;

(b) The holes in the vertebrae form a passage for the spinal cord;

330

THE SKELETON.

331

(V) The middle process is the spinous process, and the series of
spinous processes form the ridge of the backbone ;

(d) The two lateral processes are the transverse processes.

Neural Arch

Body.

Transverse Process

Spinous Process

Neural Ring
Fig. 99- Anterior View of Thoracic Vertebra.

Demi-Facet for Head of Rib

Body

Anterior Articular

Process

.... Facet for Tubercle
of Rib

"•Transverse Process

— Spinous Process

Fig. 100. Left Side View of Thoracic Vertebra.

Fit together two vertebrae in their proper order and observe that : —
(e) The openings at the sides, through which the spinal nerves
passed, are formed by adjacent notches, or grooves, in the contiguous
vertebrae.

(/) The two projections extending anteriorly from the ring of one
vertebra fit against two corresponding processes extending posteriorly
from the other vertebra. These are the anterior and posterior articu-
lating processes.

332

PHYSIOLOGY.

Temporal

Frontal

Phalanges

\ Carpus

Metacarpus Ulna Sternum

.... . Parietal

Occipital

Cervical Vertebrae

i Tnoracic Vertebrae

Fumbar Vertebrae

Sacrum

Coccyx

Femur

Fibula

Tarsus

Phalanges..

Metatarsus
Fig. 101. Side View of the Human Skeleton.

THE SKELETON.

333

TABLE OF THE BONES.

r skuii (8)

HEAD (28) •

Face (14)

1 Ears (6)

CERVICAL REGION (8)
THORAX (37

UPPER EXTREMITIES (64) { Arm.

Frontal (forehead).

2 Temporal (temples) .

2 Parietal (side).
"i Occipital (posterior base).
| Sphenoid (base).
[ Ethmoid (base of nose and between eyes).

f 2 Superior Maxillae (upper jaw).

2 Nasal (bridge of nose).

2 Malar (cheek).

2 Lacrymal (inner front corner of orbit).

2 Turbinated (within nostrils).

2 Palate (posterior hard palate).

Vomer (nasal partition).
( Inferior Maxilla (lower jaw).

( Malleus (hammer).
{ Stapes (stirrup).
I Incus (anvil).

\ 7 Cervical Vertebrae (neck).
| Hyoid Bone (base of tongue).

( 14 True, 6 False, 4 Floating Ribs.
-1 12 Thoracic Vertebrae (back).
I Sternum.

\ Clavicle (collar-bone).
^ Scapuk (shoulder.blade)i

( Humerus (arm).

Hand.

f8'

51
I 14

8 Carpal (wrist).
Metacarpal (palm).
Phalanges (fingers).

LUMBAR REGION (5)
PELVIS (4)

LOWER EXTREMITIES (60)

5 Lumbar Vertebrae (loins).

( 2 Innominate.

\ Sacrum.
I Coccyx.

Thigh.

Leg.

Femur.

f Patella (knee-pan).
i Tibia (large bone).
I Fibula (outer bone).
C 7 Tarsal (instep, heel)
-] 5 Metatarsal (arch).
I 14 Phalanges (toes).

334

PHYSIOLOGY.

The Spinal Column. — The central part of the skeleton
is the backbone, or spinal column. As a whole it is a
column, widening toward the base, composed of a series of
separate bones called vertebrae.

Hole for Blond Tubes

Body

Anterior Articular Facet

..Neural Arch

Spinous Process

'"•-» Neural Ring

Fig. 102. Anterior View of Cervical Vertebra.

Body---

Spinous Process

Fig. 103. Left Side View of Cervical Vertebra.

Each vertebra has seven processes, four articulating
(two anterior and two posterior), two transverse, and one
spinous.

Take a thoracic vertebra and in the presence of the class trim off the
processes with a pair of bone-forceps. The vertebra will he seen to be
essentially a ring, or padlock, consisting of the body and neural ring or
arch.

THE SKELETON. 335

Articulations of a Vertebra. — The smooth places where
the articulating processes join are called facets. Observe
on each side of the body of the vertebra a facet where the
head of the rib articulated. There is also a facet on the
transverse process where the tubercle of the rib articulated.

The Cervical Vertebrae. — The seven cervical vertebrae
(neck) have holes through their sides, or transverse pro-
cesses, for the passage of blood tubes.

Atlas and Axis. — The first vertebra, the atlas, has no
body. The second vertebra is the axis. It has a peg,
called the odontoid process, which represents the body of
the atlas. In shaking the head, the atlas, with the head,
turns on the axis. In nodding the head, the head simply
rocks back and forth on the atlas.

The Thoracic Vertebrae. — The twelve rib-supporting
vertebrae are the thoracic vertebrae.

The Lumbar Vertebrae. — The next five are the lumbar.

The Sacrum and Coccyx. — The sacrum is composed of
five vertebrae grown together, and the remaining four are
combined in the coccyx.

Review of the Spinal Column. — Let the eye slowly
review the whole spinal column, noting what the vertebrae
have in common. Note also their differences.

Flexibility of the Spinal Column. — In most articulated
skeletons there are pads of felt between the vertebrae.
These take the place of the inter-vertebral cartilages,
which are a form of connective tissue, possessing the elas-
ticity of cartilage and the toughness of fibrous connective
tissue, such as ligament and tendon. These inter-vertebral

336

PHYSIOLOGY.

cartilages serve both to keep the vertebrae apart and to
hold them together. When we bend the shoulders to the
right, the right edges of these cartilages are compressed,

Neural Arch

Transverse Process

Body- —

Neural Ring
Fig. 104. Anterior View of Lumbar Vertebra.

Body

- Spinous
Process

Posterior Articular Process
Fig. 105. .Side View of Lumbar Vertebra.

and the left edges are stretched, as a piece of india rubber
would be if it were glued between the ends of two spools,
and the whole were slightly bent.

Curves of the Spinal Column. — View the spinal column
from the side. Draw a line representing all its curves.

THE SKELETON. 337

The Cavities of the Skeleton. — Examine the cavity o/~ the skull.
If the class has not a skull which has been sawed across, look into the
skull cavity through the hole where the spinal cord joined the brain.

Observe the conical shape of the thorax. In the entire body the
bones and muscles about the shoulders usually make a reversed cone of
the upper part of the trunk.

Observe that the ribs are connected with the breastbone by carti-
lages.

The upper limbs are articulated with the body only where the inner
ends of the collar bones join the breastbone.

Pronation and Supination. — Rest the forearm on the table with the
palm up ; keeping the elbow fixed, turn the hand over. Turning the
palm up is called supination ; turning it down is pronation. Perform
this experiment with the articulated skeleton.

The Skeleton of a Cat or Rabbit. — Examine the skeleton of a cat
or rabbit for the sake of comparison. Note especially the skull and
spinal column, so that you will know better what to do when dissecting
the brain and spinal cord in one of these animals.

The Weight of Bones. — The bones make about one sixth
of the weight of the living body. When dried they may
lose half of their weight.

Microscopic Structure of Bone, i . Examine with a hand lens. —
Hold a mounted cross-section of bone up to the light and examine with
a hand lens. The solid part of the bone will be seen to be pierced by
many small holes (or if the holes are filled they will appear as black
spots). These are the cross-sections of the haversian canals, through
which run the blood tubes, mainly lengthwise through the bone.

2. Examine with the Low Power of a Compound Microscope.—
Examine the section under the microscope, using a half-inch objective.
The bony matter will now be seen to be arranged in circles, lamellae,
around the haversian canals, somewhat like the rings seen on the end
of a log.

Between the rings are circles of elongated dark dots. These are
lacunae, cavities in which lay the live-bone corpuscles which built up
the bone. The bone was, at first, cartilage. Later, mineral matter
was deposited, forming true bone.

33*

PHYSIOLOGY.

3. Examine with a High Power. — Now examine the section
under a one-fifth-inch objective. From the lacunae there run out, in
every direction, little crevices, appearing as fine black lines. These
are the canaliculi. Through the haversian canals, lacunae, and cana-
liculi, the nourishing materials of the blood reach all parts of the bone.

The Chemical Composition of Bone. — i . Take a tall, narrow
glass jar, called in the chemical laboratory a "graduate,'1 or a lamp
chimney corked at one end answers very well, and nearly fill with

Lamellae Lacunae

\

Canaliculi Haversian Canal

Fig. 106. Cross-section of Bone. (Highly Magnified.1)

water. Add one sixth as much hydrochloric acid. Put into this a
slender, dry bone, such as a fibula or rib. In twenty-four hours take it
out, rinse it thoroughly, and examine it. The acid will probably have
dissolved out the mineral matter and left the animal matter.

2. Lay a piece of bone on a shovel, or piece of sheet iron, and place
in the fire. The animal matter is burned out, leaving the brittle min-
eral matter.

THE SKELETON. 339

Bone is composed of mineral matter, two thirds, and animal matter,
one third ; in childhood the animal matter is in larger proportion, while
in old age the mineral matter is in excess.

The mineral matter is chiefly calcium phosphate, while the animal
matter is largely gelatin.

Joints may be classified according to their structure as
follows : —

Classification of Joints. — i. Immovable, such as the
sutures between the bones of the skull ;

2. Mixed, such as the joints between the vertebrae ;

3. Movable, which allow free motion between the parts ;
(a} Ball and socket, as in the hip and shoulder ;

(b) Hinge, as in the knee and elbow ;

(c) Pivot, as in the forearm, and between the atlas and
axis ;

(d) Gliding, as between the short bones of the wrist, and
of the ankle.

Study of Joints. — Examine these joints in the articulated skeleton,
and so far as possible, in fresh specimens (of rabbits). Compare the
ball and socket joints of the hip and shoulder. Also compare the hinge
joints of the knee and elbow.

Hygiene of the Bones. — Sometimes the bones of chil-
dren are deficient in mineral elements, and are unduly soft
and flexible. This condition indicates a disease called
rickets. Even if the bones are normal, children should
not be encouraged to walk early, as bow-legs may result.
Most bow-legged persons seem to be active, and probably
their muscles developed faster than the bones. Constrained
positions or excessive use of special groups of muscles may
result in lateral curvature of the spine. The height of
seats and desks should be carefully looked after.

Sprains and Dislocations. — Sprains and dislocations
are injuries to the joints, and often bring more serious

340 PHYSIOLOGY.

results than a broken bone. There should, usually, be
complete rest until the part can be used without pain.
Otherwise a stiffened joint may result. Hot water applied
to a sprain or bruise promotes circulation and prevents dis-
coloration. But if there is inflammation cold water should
be applied. Bandages may be needed for support.

Summary. — i . The skeleton consists of the axial and appendicular
portions.

2. Each vertebra consists of a body, ring (around spinal cord) and
processes.

3. Pads of cartilage connect the vertebrae.

4. Bone is traversed by tubes and crevices through which it receives
its nourishment from the blood.

5. Bone consists of animal matter with limy matter embedded in it.

6. Sprains should be treated carefully to avoid stiffened joints.

Questions. — i. Why do the bones of old people break so much
more easily than those of children ?

2. What is the use of the central marrow?

3. What is the work of the red marrow in the spongy ends of the
bones ?

4. What are " sesamoid " bones ?

CHAPTER XXV.
THE MUSCLES.

The Number of Muscles. — There are over five hun-
dred muscles in the human body. These vary in size from
less than an inch in length, in the ear and in the larynx,
to a foot and a half long in the thigh.

The Arrangement of Muscles. — The muscles of the
two sides of the body are paired, and normally are about
equal in size and strength. The muscles of the limbs are
further paired into flexors, which bend, and the extensors,
which straighten the limbs. The muscles are also arranged
more or less in layers. There is generally a superficial
layer and a more deep-seated layer.

Forms of Muscles. — Muscles are of various shapes.
The prevailing form in the limbs is spindle-shaped, or fusi-
form. This is convenient, as the thicker middle portion
of the muscle is opposite the more slender part of the
bone, while the tendons at the ends of the muscles are
opposite the enlarged ends of the bones at the joints.
Some muscles are flat, some have their fibers arranged
like the barbs of a feather, and are hence called penni-
form. Some muscles have a tendon in the middle which
runs through a loop, as in the case of the muscle which
depresses the lower jaw. As already stated, muscles
which close openings are circular, and are called sphincter
muscles.

34'

342

PHYSIOLOGY.

Deltoid

Serratus Magnus

Rectus Femoris

Tibialis Anticu:

Extensors of the Hand
Flexors of the Hand

Pectoralis Major

Rectus Abdominalis

.... Sartorius

Vastus Externus

Extensors of the Toes

Fig. 107. Ventral View of the Superficial Muscles

THE MUSCLES.

343

Extensors of the Hand

Triceps

Latissimus Dors

Gluteus Maximus

Vastus Externus

Flexors of the Foot —

Trapezius

Deltoid

-- Flexors of the Hand

•Biceps Cruris

Gastrocnemius

Tendo Achillis

Fig. 108. Dorsal View of the Superficial Muscles.

344

PHYSIOLOGY.

Names of Muscles. — Some muscles are named from
their shape, as the deltoid on the shoulder ; from position,
pectoralis major ; from their supposed action, as sartorius
and adductor ; direction, as rectus, etc. The biceps and
triceps are named from their division at their origins.

Peculiar Muscles. — The diaphragm is a sheet of muscle
that forms a partition between the chest and the abdomen.
It is arched, and has a clear tendinous center. The ab-
dominal muscles form a wall to hold the organs of the
abdominal cavity. These muscles also aid in breathing,
especially in forced expiration, as after violent exercise
and in coughing. The abdominal wall consists of several

layers of muscle.

Heart Muscle. — The fibers
which make up heart muscle
are different in appearance from
either the striated or smooth
muscle fibers. They are more
or less branched, as shown in
the accompanying figure. No
sheath has been found on these
fibers.

The Three Kinds of Muscular
Fibers Compared. — For the
sake of comparison, the striated
and unstriated muscle fibers are
here shown again, alongside the
tschweigger-seideu heart muscle fibers. The stri-

The nuclei and cell-junctions are only
represented on the right hand side ated fibers (of the skeleton) are

usually called "voluntary," and

the plain fibers "involuntary." The heart muscle fibers
are intermediate, being striated, but involuntary in their

THE MUSCLES.

345

action. A striated muscle fiber may be i| inches long and
•2-g-0- of an inch wide, though usually less. The heart muscle
fiber is narrower than the skeletal fiber, and the plain fiber
very much smaller than either. (But the figures do not
attempt to give relative proportions with any exactness.)

Each Muscle Fiber is a Muscle Cell. — It is easily seen
that each plain muscle fiber is a single cell, having its dis-
tinct nucleus. The same is true of the heart muscle fibers,

Nucleus

pv.-"»- Isolated Fiber

•- Fibers Joined

Fig. 110. — Plain (unstriated) mus-
cular fibers from the bladder.

Fig. 1 1 1. — Two striated mus-
cular fibers showing the ter-
minations of the nerves.

though they are not so simple, being more or less branched.
In the development of striated muscle, when the muscular
fibers are about to be formed, the cells from which they
develop (called muscle plates) become elongated so that
each cell is converted into a long protoplasmic fiber, with
many nuclei. Most investigators agree that the striated
fibers are produced by the elongation of single cells with
multiplication of their nuclei, though some have thought
that the fiber is formed by the coalescence of several cells
end to end.

Muscles of Expression. — The facial expression is due
to the action of the muscles of the face, which in turn are

340 PHYSIOLOGY.

under control of the cranial nerves. The habitual position
becomes somewhat " fixed," so it is true that character
is often shown by " the looks." Cultivation of happy
thoughts therefore tends to make one better looking.

Muscles and Fat. — Fat fills in space between muscles,
and, if abundant, forms a layer over the muscles. One
notable instance is the hollow triangular space between
the muscles of the cheek. If there is very little fat, a
depression is seen, forming the "hollow cheeks.'' But
an abundance of fat fnakes a corresponding elevation.

Convulsions. — These spasmodic actions are due to dis-
ordered action of the muscles, and, further back, to the
disturbed action of the nervous system that controls the
muscles. Various disturbances, such as indigestion, may
by reflex action bring on convulsions.

Rigor Mortis. — Rigor mortis (death stiffening) is a
muscular rigidity due to the coagulation of muscle plasma.
It usually sets in not long after death, the time of its
appearance and its duration being variable.

Some Prominent Muscles. — The deltoid on the shoul-
der is a noticeable muscle. The biceps and triceps have
already been studied. The calf muscle is one of the
thickest and strongest in the body. The great muscles of
the rump are needed to raise and hold the body up. On
each side of the front of the neck is a muscle easily ob-
served in thin persons. It extends down to the top of the
breast bone.

Sculpture and Anatomy. — The sculptor needs to be a
thorough student of anatomy, so far as the bones and mus-
cles are concerned. If he knows the muscles thoroughly,
he can make them " stand out " naturally. Otherwise his
work cannot be truly good.

APPENDIX A.

ANTISEPTICS AND DISINFECTANTS.

The following is chiefly from Sternberg's Manual of Bacteriology, and
embodies part of the report of " The Committee on Disinfectants of the
American Public Health Association."

Antiseptic Defined. — An antiseptic is a substance having the power to
prevent or destroy putrefaction, or, what is the same -thing, the bacteria upon
which putrefaction depends.

Disinfectant Defined. — A disinfectant is a substance that can destroy
disease germs.

Disinfection Defined. — Disinfection is the destroying of disease germs by
means of heat, chemic substances, fumigation, or by fresh air.

"The injurious consequences which are likely to result from such misap-
prehension and misuse of the word ' disinfectant ' will be appreciated when it
is known that recent researches have demonstrated that many of the agents
which have been found useful as deodorizers or as antiseptics are entirely
without value for the destruction of disease germs."

An Antiseptic, but not a Disinfectant. — " This is true, for example, as
regards the sulphate of iron, or copperas, a salt which has been extensively
used with the idea that it is a valuable disinfectant. As a matter of fact,
sulphate of iron in saturated solution does not destroy the vitality of disease
germs, or the infecting power of material containing them. This salt is,
nevertheless, a very valuable antiseptic, and its low price makes it one of the
most valuable agents for the arrest of putrefactive decomposition."

EXTRACTS FROM THE ABOVE-MENTIONED REPORT.

Some Methods of Disinfecting. — "The most useful agents for the
destruction of spore-containing infectious material are : —

347

348 PHYSIOLOGY.

1. Fire ; complete destruction by burning.

2. Steam under pressure, 105 degrees C. (221 degrees F.), for ten minutes.

3. Boiling in water for half an hour.

4. Chloricl of lime ; a four per cent solution.

5. Mercuric chlorid ; a solution of I : 500.

For the destruction of material which owes its infecting power to the pres-
ence of microorganisms not containing spores, the committee recommends: —

1. Fire; complete destruction by burning.

2. ISoiling in water for ten minutes.

3. Dry heat ; no degrees C. (230 degrees F.) for two hours.

4. Chlorid of lime ; a two per cent solution.

5. Solution of chlorinated soda ; a ten per cent solution.

6. Mercuric chlorid ; a solution of I : 2,000.

7. Carbolic acid ; a five per cent solution.

8. Sulphate of copper ; a five per cent solution.

9. Chlorid of zinc ; 'a ten per cent solution.

10. Sulphur dioxid ; exposure for at least twelve hours to an atmosphere
containing at least four volumes per cent of this gas in the presence of
moisture.

Methods of Disinfecting. — The committee would make the following
recommendations with reference to the practical application of these agents
for disinfecting purposes : —

For Excreta. — (a) In the sick room : —

1. Chlorid of lime, four per cent.
In the absence of spores : —

2. Carbolic acid in solution, five per cent.

3. Sulphate of copper in solution, five per cent.

(/>) In privy vaults : —

1. Mercuric chlorid in solution, I : 500.

2. Carbolic acid in solution, five per cent.

(c) For the disinfection and deodori/alion of the surface of masses of
organic material in privy vaults, etc. : —

Chlorid of lime in powder.

For Clothing, Bedding, etc. — (a) Soiled underclothing, bed linen, etc.

1. Destruction by fire, if of little value.

2. Boiling at least half an hour.

ANTISEPTICS AND DISINFECTANTS. 349

3. Immersion in a solution of mercuric chlorid of the strength of I : 2,000
for four hours.

4. Immersion in a two per cent solution of carbolic acid for four hours.

(b} Outer garments of wool or silk, and similar articles, which would be
injured by immersion in boiling water or in a disinfecting solution : —

1. Exposure in a suitable apparatus to a current of steam for ten minutes.

2. Exposure to dry heat at a temperature of no degrees C. (230 de-
grees F.) for two hours.

(V) Mattresses and blankets soiled by the discharge of the sick : —

1. Destruction by fire. *

2. Exposure to superheated steam, 105 degrees C. (221 degrees F.), for
ten minutes. (Mattresses to have the cover removed or freely exposed.)

3. Immersion in boiling water for half an hour. .

Furniture and Articles of Wood, Leather, and Porcelain. — Washing,
several times repeated, with : —

I. Solution of carbolic acid, two per cent.

For the Person. — The hands and general surface of the body of attend-
ants of the sick, and of convalescents, should be washed with : —

1. Solution of chlorinated soda diluted with nine parts of water, i : 10.

2. Carbolic acid ; two per cent solution.

3. Mercuric chlorid, i : l,ooo.

For the Dead. — Envelop the body in a sheet thoroughly saturated
with : —

1. Chlorid of lime in solution, four per cent.

2. Mercuric chlorid in solution, i : 500.

3. Carbolic acid in solution, five per cent.

For the Sick Room. — (a) While occupied, wash all surfaces with : —

1. Mercuric chlorid in solution, I : 1,000.

2. Carbolic acid in solution, two per cent.

(l>) When vacated, fumigate with sulphur dioxid for twelve hours, burning
at least three pounds of sulphur for every thousand cubic feet of- air space in
the room ; then wash all surfaces with one of the above-mentioned solutions,
and afterward with soap and hot water ; finally throw open doors and win-
dows, and ventilate freely."

350

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PO/SONS AND ANTIDOTES.

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354 PHYSIOLOGY.

Daily Excretions. — Sweat, from 1.5 Ibs. to 4.5 Ibs. ; urea, about
1 oz. ; organic matter exhaled, :! grains ; urine, 53 oz.

"Of the entire excreta, 32 per cent pass off by the breath ; 17 per-
cent by the skin ; 4C.5 per cent by the kidneys ; 4.5 per cent by the
alimentary canal." — C'TTTKII.

Number of Sweat Glands. — The number of sweat glands may
be as high as 3,500 in a square inch, and the average is estimated at.
2,800 per square inch ; as there are about 2,500 square inches of body
surface, it is readily computed that there are several millions of sweat,
glands.

Number of Hairs on the Human Head. — The average number
of hairs on the head is 120,000. They are set obliquely, and are con-
trolled by muscles so that they may be made to stand erect, or nearly so,
under the influence of certain emotions, as fear, anger, etc.

Huxley and others have classified the races of men according to the
hair, into the Ulotrichi, or crisp or woolly haired division, including
the negroes, bushmen, etc. ; and Leiotrichi, or smooth-haired, sub-
divided into the Australioid, the Mongoloid, the Xanthochroic, and the
Melanochroic.

In Europeans the hair is oval in cross-section ; in the Japanese
and Chinese it is circular.

Circulation. — Rate of blood flow : in the large arteries, from 12 to
16 inches a second ; in the caval veins, about 4 inches a second ; in the
capillaries, from 1 inch to 1.5 inches a minute. A portion of the blood
makes the complete circulation (in a horse) in less than half a minute.
This is found by putting some readily detected chemical into one jugular
vein, and noting how soon it appears in the other jugular vein. The
time necessary for all the blood to pass through the heart is estimated
as follows : Each ventricle pumps about six ounces of blood at each
stroke. At this rate thirty strokes, 25 to 50 seconds (or less), would
have pumped all the blood in the body. Still, some of the blood (from
the shorter circuits) may have been pumped twice, and some (from the
longer routes) may not yet have been around once. And since the
total amount of blood has been only approximately determined, these
figures are not very accurate.

Number of blood corpuscles to the cubic inch, about 83,000,000.

Dr. Tanner's Forty Days' Fast (Newspaper Account). No
Food but "Water Taken. — When Dr. Tanner came to New York
from Minnesota he weighed 184 pounds. He was six weeks making ar-

VITAL STATISTICS.

355

rangernents for his fast; and when lie began his experiment his weight
was 157£ pounds. He weighed 121 £ pounds on the day his fast ended.
He had therefore lost 62 \ pounds since he came to the city, and 3(3
pounds since he began his fast. Dr. Hammond, the well-known New
York physician whose assertion that a forty days' fast was a physical
impossibility led Dr. Tanner to make the attempt, came out in "a card
in the New York papers declaring that he believed the fast had been
fairly conducted.

On each day of his fast Dr. Tanner weighed as follows : —

DAY.

1st

POUNDS.

DAY.

25th

POUNDS.

1314,

3d

... 153

20th

. " . . . . I3ld

5th
7th

. . . 147£
. 1434

27th .....
28th . .

129!

llth
13th
14th

. . . 139|
133

29th .....
30th
31st

130

16th

. . . 132

32d

1274

17th (8.30 P.M.) . .
17th (HAM)

135^

33d
34th

i2e|

18th
19th

136

35th
36th . ...

20th (4 P.M.) . . .
20th (5 A.M.) . . .
21st .

. . . . 135

. . . . 1 35

37th
38th
39th

1224

22d

1334

40th

1214

26th ......

Cavities of the Body. — 1. Mucous cavities (open to the external
air). Digestive tube, respiratory passages, genito-urinary passages, ex-
ternal and middle ear, etc.

2. Serous cavities (closed). They may all be said to be lymph cav-
ities. They are the lymph spaces throughout the body, and the large
spaces, called the pleural cavity around the lungs, the pericardial cavity
around the heart, the peritoneal cavity in the abdomen, the arachnoid
cavity around the brain, and a similar one along the spinal cord.

3. Synovial cavities in the joints.

4. Blood cavities, — the inside of the heart and blood tubes.

5. Secretion cavities, — the cavities and tubes from the glands ; for
example, the bile sac and its duct.

6. Bone cavities.

356

PHYSIOLOGY.

LOSSES OF THE TISSUES DURING STARVATION*.
(FROM KXPKRIMEXT ON A CAT.)

Fat los«'s«»:'. per i-»Mit.

Blood .... ••;.->

Spleen .... "71 "

Pancreas ... "64 "

Stomach ... "39 "

Pharynx, gullet . " 34 "

Skin " 33 "

Kidneys. ... "31 "

Liver . " 52 "

Heart ....

Intestines . . .

Muscles of locomo-
tion ....

Respiratory appa-
ratus . . .

Bones ....

Eyes

Nervous system .

loses 44 per cent.

" 42

" 42 "

" 22 "

" 16

" 10 "

" 2 "

QUANTITY OF WATER IN 1,000 PARTS.

Teeth 100 Bile 880

Bones 130 Milk H87

Cartilage 550 Pancreatic juice 900

Muscles 750 Urine 936

Ligament 768 Lymph 960

Brain * . . 789 Gastric juice 975

Blood 795 Sweat 986

Synovia 805 Saliva W">

THE LOSS OF WATER FROM THE BODY.

From the Alimentary canal (feces) 4 per cent.

" Lungs 20

" " Skin (perspiration) 30 "

" " Kidneys (urine) 46 "

ELEMENTS IN THE HUMAN BODY.

Oxygen 72.0 Chlorin .085

Carbon 13.5 Fluorin 08

Hydrogen 9.1 Potassium .026

Nitrogen 2.5 Iron 01

Calcium 1.3 Magnesium 0012

Fosforus 1.15 Silicon 0002

Sulfur 147 Copper, lead, aluminum . (traces)

Sodium 1 100.

DAILY RATION OF A U. S. SOLDIER DURING THE LATE WAR.

Bread or flour 22 oz.

Fresh or salt beef (or pork or bacon 12 oz.) 20

Potatoes (three times a week) 16 "

VITAL STATISTICS.

357

Rice
Coffee (or tea 0-.24 oz.) . .

. ... 1.6
... 1.6
. . . . 2.4

64

Vinegar • •
Salt •

COMPOSITION OF F<

WATKU. PROTEIDS.

32

30DS.

FATS.

16

CARBO-

HYDRATES.

Beef, lean

72

19.3

3.6

Beef, fat

51

14.8

29.8

Mutton, lean ....

72

18.3

4.9

Mutton, fat ....

53

12.4

31.1

Veal

63

16.5

15.3

Pork, fat

39

9.8

48.9

Poultry

74

21

3.8

Whitefish

78

18.1

2.9

Salmon

77

16.1

5.5

Eels (rich in fat) . .

75

9.9

13.8

Oysters

75.7

11.7

2.4

SUGAR.

Milk

86

4.1

3.9

5.2

Buttermilk ....

88

4.1

.7

6.4

Cream

66

2.7

26.7

2.8

Cheese, full ....

36

28.4

31.1

. . .

Cheese, skim ....

44

44.8

6.3

Eggs, white . . . .

78

20.4

Eggs, yelk . . ...

52

16

30.7

. . .

STARCH.

Bread

37

8.1

1.6

51

Flour

15

10.8

2

70.8

COMPOSITION

OF THE

BLOOD.

Water

Solids —

Corpuscles ....

. 130

Proteids (of serum)

. 70

Fibrin (of clot) . .

2.2

Fatty matters (of serum)

1.4

Inorganic salts . .

6.0

Gases, urea, kreatin,

etc. . .

6.4

gill.

5.1
4.4

4.8

4.7
2.3
1.2
1.0
1.4
2.7
2.7

.8
.8
4.9
4.5
4.9
1.6
1.3

2.3
1.7

784

216
1000

358 PHYSIOLOGY.

COMPOSITION OF CASTKK' ,11 K'K.

Water 99.44

Solids —

Pepsin 319

Salts 218

Hydrochloric acid 02

.557
100

Fluids of the Body (FORD). — 1. Circulating fluids, — chyle,
lymph, blood.

2. Fluids for digestion, — saliva, gastric juice, pancreatic juice, bile,
intestinal juice.

3. Fluids of closed cavities, — of the arachnoid, pleura!, pericardia!,
and peritoneal sacs, of joints, of the eye and ear, and of cells.

4. Secretions for protection, — cerumen or wax, tears, fluid of mucous
membranes, oily fluids on the surface of the body.

5. Fluids for discharge, — intestinal secretion, renal or kidney se-
cretion, perspiration, vapor from the lungs, etc.

Acids and Alkalies of the Body. — Acids, — gastric juice, mu-
cus, chyme, contents of large intestine.

Alkalies, — saliva (or neutral), pancreatic juice, intestinal juice,
bile (or neutral), contents of small intestine, sweat.

Amount of Digestive Liquids. — The amount of saliva secreted
daily is estimated at from 1 to 3 pints, of gastric juice from 10 to 20 pints,
of bile from 2 to 3 pints. The amount of intestinal and other juices is
difficult to estimate. But it is readily seen that a very large amount of
liquid is daily separated from the blood to be used in the preparation of
the food for absorption into the blood. This is to be looked upon as an
investment. It is supposed to be reabsorbed with large returns in addi-
tion to the prepared food ; and if anything interferes with the absorp-
tion of the food material, especially if the secretion goes on, it is plain
that bankruptcy will follow as surely as in the business world whenever
there is a continual expenditure without corresponding returns. The
condition known as "diarrhea" illustrates this condition, perhaps, as
well as any well-known condition of the body.

Specific Gravity of the Liquids of the Body. — As all the
liquids of the body have dissolved and suspended in them various salts
and other matters, they are all heavier than water.

VITAL STATISTICS. 359

Alcohol and Longevity. — Investigation by Baer has shown that the
average expectation of life among users and dealers in alcoholic liquors
is very much shortened. The following table gives a comparative view of
the expectation of life in those who abstained from and those who used
alcohol : —

EXPECTATION OF LIFE.

AGE. ABSTAINERS. ALCOHOL USERS

At 25, 32.08 years, 26.23 years.

"' 35, 25.92 " 20.01 "

" 45 J9.92 " * i$.i9 "

" 55' '4-45 " "-16 "

" 65, 9.62 " 8.04 "

TABLE SHOWING THE INFLUENCE OF ALCOHOL UPON THE
MORTALITY FROM VARIOUS DISEASES.

GENERAL MALE POPULATION. ALCOHOL VENDERS.

Brain disease, 11.77 Per cent- r4-43 per cent.

Tuberculosis, 30.36 " 36.57 "

Pneumonia and pleuritis, 9.63 " H-44 "

Heart disease, 1.46 " 3.29 "

Kidney disease, 1.40 " 2.11 "

Suicide, 2.99 " 4.02 "

Cancer, 2.49 " 3.70 "

Old age, 22.49 " 7-°5 "

GLOS BA RY.

Albumen (al-bu'-meri). The white of an egg.

Albumin (iil-hi'i'-min). A proteid substance, the chief constituent of
the body. Its molecule is highly complex, and varies widely within
certain limits in different organs and in different conditions.

Albuminuria (al-bu'-mi-nu'-ri-a}. The presence of albumin in tin- urine,
indicating changes in the blood or in the kidneys.

Amylopsin (am-i-lop'-xin}. A ferment said to exist in pancreatin.

Anabolism (an-ab'-o-lizm}. Synthetic or constructive metabolism.
Activity and repair of function ; opposed to katabolism.

Arbor Vitae (ar'-6or vl'-te). A term applied to the branched appear-
ance of a section of the cerebellum.

Argon (ar'-gron). A newly discovered element similar to nitrogen
(found in the air).

Arytenoid (ar-i-te'-noid}. Resembling the mouth of a pitcher, as the
arytenoid cartilages of the larynx.

Atlas (at'-las). The uppermost of the cervical vertebrae (from the
mythical Atlas who supported the Earth).

Auricle (aw'-ri-kl). The auricles of the heart are the two cavities be-
tween the veins and the ventricles. Also, the pinna and external
meatus of the ear.

Axis (ak'-sis). The second cervical vertebra, on which the head, with
the atlas, turns.

Bacterium (bak-te'-ri-um}, pi. bacteria. A genus of microscopic fungi
characterized by short, linear, inflexible, rod-like forms — without
tendency to unite into chains or filaments.

Biceps (bl'-seps}. Biceps brachii, the flexor of the arm.

Bicuspid (bi-kus'-pid}. Having two points ; the bicuspid or premolar
teeth; the bicuspid valve, between the left auricle and the left ven-
tricle.

Brachial (bra'-ke-al or brak'-i-al}. Pertaining to the arm.

360

GLOSSARY. 361

Bronchus (brong' -kits'), pi. bronchi. The two tubes into which the tra-
chea divides opposite the third thoracic vertebra, called respectively
the right and left bronchus.

Caffein (kaf'-e-in'). An alkaloid that occurs in the leaves and beans of
the coffee-tree, in Paraguay tea, etc.

Canaliculus (kan-a-Uk'-u-lus^), pi. canaliculi. The crevices extending
from lacunae, through which nutrition is conveyed to all parts of
the bone.

Canine (ka-nl)i' or ka'-nin*). The conical teeth between the incisors
and the premolars.

Capillary (kap'-i-la-ri or ka-pil'-a-ri). A minute blood-tube connecting
the smallest ramification of the arteries with those of the veins.

Capsule (kap'-auV). A tunic or bag that incloses a part of the body or
an organ.

Carbohydrate (kar-bo-hi'-draf). An organic substance containing six
carbon atoms or some multiple of six, and hydrogen and oxygen in
the proportion in which they form water; that is, twice as many
hydrogen as oxygen atoms. Starches, sugars, and gums are carbo-
hydrates.

Cardiac (kar'-di-ak}. Pertaining to the heart.

Carotid (ka-rot'-id}. The principal right and left arteries of the neck.

Carpus (kar'-pus). Belonging to the wrist; as the carpal bones.

Cartilage (kar'-ti-luj}. Gristle of various kinds, articular, etc.

Casein (ka'-se-m). A derived albumin, the chief proteid of milk, pre-
cipitated by acids and by rennet at 40°C.

Cecum (se'-kum). The large blind pouch or cul-de-sac, in which the
large intestine begins.

Centrum (sen'-trum). The center or middle part ; the body of a verte-
bra, exclusive of the bases of the neural arches.

Cerebellum (ser-e-bel'-um*). The inferior part of the brain, lying below
the cerebrum.

Cerebrum (ser'-e-brum'). The chief portion of the brain, occupying the
whole upper part of the cranium.

Cervical (ser'-m-kal}. Pertaining to the neck, as cervical vertebrae.

Chordae tendineae (kor'-de}. The tendinous cords connecting the
fleshy columns of the heart with the auriculo-ventricular valves.

Choroid (ko'-roid}. The second or vascular coat of the eye, continu-
ous with the iris in front, and lying between the sclerotic and the
retina.

362

Chyle (kll). The milk-white fluid absorbed by tin- lacteals during di-
gestion.

Chyme (kirn'). Food that has undergone gastric digestion, and has not
yet been acted upon hy the biliary, pancreatic, and intestinal
secretions.

Cilium (stT-i-um), pi. cilia. The eyelashes; also the hair-like appen-
dages of certain epithelial cells, whose function is to propel fluid
or particles along the passages that they line.

Ciliary (sil'-i-a-ri). Pertaining to the eyelid or eyelash ; also by ex-
tension to the ciliary apparatus or the structure related to the
mechanism of accommodation. Pertaining to the cilia.

Circumvallate (sir-kum-val'-at). Surrounded by a wall or prominence,
as the circumvallate papillae on the tongue.

Clavicle (klav'-i-kl). The collar-bone.

Coccyx (kok'-siks). The last bone of the spinal column, formed by the
union of four rudimentary vertebrae.

Cochlea (kok'-le-a). A cavity of the internal ear, resembling a snail-
shell.

Conjunctiva (kon-junyk-ti'-va). The mucous membrane covering the
anterior portion of the globe of the eye, reflected on, and extending
to, the free edge of the lids.

Corpus Arantii (kor'-pus). The tubercles, one in the center of each
segment of the semilunar valves.

Corpuscle (kor'-pus-l). A name loosely applied to almost any small,
rounded or oval body, as the blood corpuscles.

Cortex (kor'-teks}. Bark. The outer layer of gray matter of the brain ;
the outer layer, cortical substance, of the kidney.

Cricoid (krl'-koid}. Ring-shaped, as the cricoid cartilage of the
larynx.

Dentine (den'-tin}. The ivory-like substance constituting the bulk of
the tooth, lying under the enamel of the crown and the cement
of the root.

Diabetes (di-a-be'-tez*}. The name of two different affections, diuln-t<-x
mellitn*, or persistent glycosuria, and diabetes insipidus, or polyu-
ria, both characterized, in ordinary cases, by an abnormally large
discharge of urine. The former is distinguished by the presence
of an excessive quantity of sugar in the urine.

Dialysis (di-ar-i-*is\ The operation of separating crystalline from
colloid substances by means of a porous diaphragm, the former

GLOSSARY. 363

passing through the diaphragm into the pure water upon which the
dialyzer rests.

Digastric (di-yas'-trik). Having two bellies, as the digastric muscle,
enlarged near each end and with a tendon in the middle.

Duodenum (du-d-de'-num). The first part of the small intestine, begin-
ning with the pylorus.

Emulsion (e-inul'-shun}. Water or other liquid in which oil, in minute
subdivision of its particles, is suspended.

Enamel (eM-am'~el). The hard covering of the crown of a tooth.

Endothelium (en-do-the'-li-um). The internal lining membrane of
serous, synovial, and other internal surfaces, the homolog of epi-
thelium.

Enzyme (en'-zim}. Any chemic or hydrolytic ferment, as distinguished
from organized ferments such as yeast; unorganized ferment.

Epiglottis (ep-i-ylot'-is). A thin fibro-cartilaginous valve that aids in
preventing food and drink from passing into the larynx.

Esophagus (e-8Q/y-a-grt*«). The musculo-membranous tube extending
from the pharynx to the stomach.

Eustachian (u-sta'-ki-an). Eustachian tube, the tube leading from the
middle ear to the pharynx.

Facet (fas'-et}. A small plane surface. The articulating surface of a
bone.

Femur (/e'-mer). The thigh-bone.

Ferment (fer'-ment}. Any micro-organism, proteid, or other chemic
substance capable of producing fermentation, i.e., the oxidation
and disorganization of the carbohydrates.

Fibrin (fi'-brin}. A native albumen or proteid, a substance that, be-
coming solid in shed blood, plasma, and lymph, causes coagulation
of these fluids.

Fibula (fib'-u-la}. The smaller or splint bone in the outer part of the
leg, articulating above with the tibia, and below with the astraga-
lus and tibia.

Filiform (Jll'-i-forni). Thread-like, as the filiform papillae.

Frontal (fron'-tal). Belonging to the front, as the frontal bone.

Fungiform (fun'-ji-form). Having the form of a mushroom, as fungi-
form papillae.

Ganglion (yany'-gli-on\ pi. ganglions or ganglia. A separate and semi-
independent nervous center, communicating with other ganglia or
nerves, with the central nervous system, and peripheral organs.

364

Gastric (yas'-trik^). Pertaining to the stomach.

Gelatin (jel'-a-tin). An albuminoid substance of jelly-like consistence,
obtained by boiling skin, connective tissue, and bones of animals
in water. The glue of commerce is an impure variety.

Glosso-pharyngeal (glox'-o-fa-rin'-je-al). Pertaining to the tongue and
larynx.

Gluten (ylo'-ten). A substance resembling albumin, and with which it
is probably identified ; it occurs abundantly in the seeds of cereals.

Glycogen (yll'-ko-jen}. A white amorphous powder, tasteless and odor-
less, forming an opalescent solution with water, and insoluble in
alcohol. It is commonly known as animal starch. It occurs in the
blood and in the liver, by which it is elaborated, and is changed by
diastasic ferments into glucose.

Gustatory (gus'-ta-to-ri}. Pertaining to the special sense of taste and
its organs.

Hashish (JtaM'-etA). A preparation from Indian hemp, Cannabis in-
dica. It is a powerful narcotic.

Haversian (ha-ver'-zian*). Haversian canal, in bone, a central opening
for blood-tubes, surrounded by a number of concentric rings, or
lamellae, of bone.

Hemoglobin (hem-o-ylo'-bin}. A substance existing in the corpuscles of
the blood, and to which their red color is due.

Hepatic (he-pat' -ik). Pertaining or belonging to the liver.

Hilum (hl'-lum}. A small pit, scar, or opening in an organic structure ;
the notch on the internal or concave border of the kidney.

Humerus (hu'-me-rus}. The bone of the upper arm.

Humor (/m'-wor). Any liquid, or semi-liquid, part of the body.

Hyoid (hl'-oid}. Having the form of the letter U. The hyoid bone
situated between the root of the tongue and the larynx, supporting
the tongue and giving attachment to its muscles.

Hypo-glossal (hi-po-ylos'-al}. Under the tongue.

Iliac (tT-t-rtJfc). Pertaining to the ilium, or region of the flanks, as iliac
artery, vein, etc.

Incisor (m-sf-sor). The chisel-shaped front teeth.

Inhibition (in-hi-bish'-un). The act of checking, restraining, or sup-
pressing ; any influence that controls, retards, or restrains. Inhib-
itory nerves and centers are those intermediating a modification,
stoppage, or suppression of a motor or secretory act already in
progress.

GLOSSARY. 365

Innominate (i-nom'-i-nate). Nameless ; a term applied to several parts
of the body to which no other definite name has been given, as the
innominate bone, artery, vein, etc.

Invertin (in'-ver-tln\ A ferment found in the intestinal juice, and also
produced by several species of plants ; it converts cane-sugar in
solution into invert sugar.

Jugular (jo'-gu-lar^. Pertaining to the throat, as the jugular vein.

Katabolism (ka-tab'-o-lizm). Analytic or destructive metabolism ; a
physiologic disintegration ; opposed to anabolism.

Lacrymal (lak'-ri-mal}. Having relation to the organs of the secretion,
transfer, or excretion of tears.

Lacuna (la-ku'-na}. A little hollow space ; especially the microscopic
cavities in bone occupied by the bone corpuscles, and communicat-
ing with one another and with the haversian canals and the sur-
faces of the bone through the canaliculi.

Lamella (fti-mel'-a), pi. lamellae. A thin lamina, scale, or plate ; of
bone, the concentric rings surrounding the haversian canals.

Larynx (lar'-inyks). The upper part of the air passage between the
trachea and the base of the tongue ; the voice-box.

Legumin (le-grw'-rain). A proteid compound in the seeds of many plants
belonging to the natural order Leguminosae (peas, beans, lentils,
etc.).

Lumbar (lum'-bcir\ pertaining to the loins, especially to the region
about the loins.

Lymphatic (lim-fat'-ik}. Pertaining to lymph.

Lymphatics (lim-fat'-iks). The tubes that convey lymph.

Lymphatic glands. The glands intercalated in the pathway of the
lymphatic tubes, through which lymph is filtered.

Massage (ma-sazh'). A method of effecting changes in the local and
general nutrition, action and other functions of the body, by rub-
bing, kneading, and other manipulation of the superficial parts of
the body by the hand or an instrument.

Masseter (mas'-e-ter^). A chewing-muscle felt on the angle of the
jaw.

Medullary (med'-u-la-ri}. Pertaining to the medulla, or marrow ; re-
sembling marrow. Also pertaining to the white substance of the
brain contained within the cortical envelop of gray matter.

Mesenteric (mez-en-ter'-ik}. Pertaining to the mesentery, as artery,
vein, etc.

366 GLOSS. IK}:

Mesentery ^nez'-cn-lrr-i}. A fold of the peritoneum that connects cer-
tain portions of the intestine with the dorsal abdominal wall.

Metabolism (me-ta&'-d-Jtem). A change in the intimate condition of
cells ; (1) constructive or synthetic metabolism is called Anabo-
lism ; in anabolism, the substance is becoming more complex and
is accumulating force ; (2) destructive or analytic metabolism is
called Katabolism : in katabolism there is disintegration, the mate-
rial is becoming less complex, and there is loss or expenditure of
force.

Metacarpus (met-a-kirr'-imx). The bones of the palm of the hand.

Metatarsus (met-a-tar'-ms). The five bones of the arch of the foot,
situated between the tarsus and the phalanges.

Mitral (nil'-trtil). Resembling a miter; mitral valve, with two Hups,
between the left auricle and the left ventricle.

Molar (mo'-far). Mill; the grinding-teeth.

Mucous (wu'-fctw). A term applied to those tissues that secrete mucus.

Mucus (mu'-kus). A viscid liquid secretion of mucous membranes,
composed essentially of inucin, holding in suspension desquamated
epithelial cells, etc.

Myosin ( wi'-o-sm). A proteid of the globulin class, — the chief proteid
of muscle. Its coagulation after death causes riyor mortis.

Narcosis (nar-ko'-sis) . The deadening of pain, or production of incom-
plete or complete anesthesia by the use of narcotic agents, such as
anesthetics, opium, and other drugs.

Narcotic (nar-kotf-ic}. A drug that produces narcosis.

Neural (nu'-ral). Pertaining to the nerves.

Neuroglia (nu-rog'-li-a*). The reticulated framework or skeleton-work
of the substance of the brain and spinal cord. The term is some-
times abbreviated to glia.

Nucleus (nu'-kle-us). The essential part of a typical cell, usually round
in outline, and situated in the center.

Occipital (ok-sip'-i-tal}. Pertaining to the occiput or back part of the
head, as the occipital bone.

Odontoid (o-don'-toid). Resembling a tooth ; the tooth-like process
(axis) of the second cervical vertebra, on which the atlas turns.

Olfactory (ol-fak'-to-ri}. Pertaining to the sense of smell.

Osmosis (os-wio'-sts)- That property by which liquids and crystalline
substances in solution pass through porous septa ; endosmosis and
exosmosis.

GLOSSARY. 367

Oxy-hemoglobin (ok-ai-hem-o-ylo'-bin). Hemoglobin united, molecule
for molecule, with oxygen. It is the characteristic constituent of
the red corpuscles to which the scarlet color of arterial blood is
due.

Pancreas (pan'-krc-as^. A large racemose gland lying transversely
across the dorsal wall of the abdomen. It secretes a clear liquid
for the digestion of proteids, fats, and carbohydrates. The sweet-
bread of animals, vulgarly called the "belly sweet-bread" in con-
tra-distinction to the thymus, or true sweet-bread.

Pancreatin (pan'-krv-a-t'm}. The active element of the pancreatic juice.

Papilla (pa-pil'-a}, pi. papillae. Any soft, conical elevation, as papillae
of the dermis, tongue, etc.

Papillary (pap'-i-la-ri}. Pertaining to a papilla; papillary muscles, —
the conic muscular columns of the heart, to which the chordae
tendineae are attached.

Parietal (pa-ri'-e-tal). Pertaining to the walls, as the parietal bone.

Parotid (pa-rot'-id). Near the ear, as the parotid salivary glands.

Patella (pa-tel'-a}. The knee-pan.

Peptone (pep'-ton}. A proteid body produced by the action of peptic
and pancreatic digestion.

Pericardium (per-i-kar'-di-um}. The closed membranous sac or cover-
ing, that envelops the heart.

Periosteum (per-i-os'-te-um*). A fibrous membrane that invests the
surfaces of the bones, except at the points of tendinous and liga-
mentary attachments, and on the articular surfaces where cartilage
is substituted.

Peristaltic (per-i-stal'-tik}. The peculiar movement of the intestine
and other tubular organs, consisting in a vermicular shortening
and narrowing of the tube, thus propelling the contents onward.
It is due to the successive contractions of the bundles of longitudi-
nal and circular muscular fibers.

Peritoneal (per-i-to-ne'-al}. Pertaining to the peritoneum.

Peritoneum (per-l-to-ne'-um*). The serous membrane lining the interior
of the abdominal cavity, and surrounding the contained viscera.
The peritoneum forms a closed sac, but is rendered complex in its
arrangement by numerous foldings produced by its reflection upon
the viscera.

Phalanges (fa-lan'-jez), plural of phalanx (fa'-lanyks~). Any one of
the bones of the fingers or toes.

368 GLOSS. 1A'\ \

Pharynx ^/•'-/m/^- The cavity back of the soft palate. It commu-

nicates anteriorly with the posterior nares, laterally with the eusta-

chian tubes, ventrally with the mouth, and posteriorly with the

gullet and larynx.
Plasma (plaz'-ma). The original undifferentiated substance of IUIM rut,

living matter. The fluid part of the blood and lymph.
Pleura (]>Hj'-rii). The serous membrane which envelops the lungs, and

which, being reflected back, lines the inner surface of the thorax.
Plexus (plek'-sus). An aggregation of vessels or nerves forming an

intricate net-work.
Pneumogastric (nu-md-gas'-trik). Pertaining conjointly to the lungs

and the stomach, or to the pneumogastric or vagus nerve.
Portal (por'-tal). Pertaining to the porta (gate) or hi him of an organ,

especially of the liver, as the portal vein.
Postcaval (post-ka'-ioal}. Pertaining to the postcava; the postcaval

vein, formerly called the inferior vena cava, or vena cava ascendens.
Precaval (pre-kaf-mil}. Pertaining to the precava; the anterior caval

vein, formerly called the superior vena cava, or vena cava de-

scendens.

Pronation (pro-na'-shun^). The turning of the palm downward.
Protoplasm (pro'-to-plazm). An albuminous substance, ordinarily re-

sembling the white of an egg, consisting of carbon, oxygen, nitro-

gen, and hydrogen in extremely complex and unstable molecular

combination, and capable, under proper conditions, of manifesting

certain vital phenomena, such as spontaneous motion, sensation,

assimilation, and reproduction, thus constituting the physical basis

of life of all plants and animals.
Ptyalin (tl'-a-lin}. An amylolytic or diastasic ferment found in saliva,

having the property of converting starch into dextrin and sugar.
Pulmonary (pul'-mo-na-ri). Pertaining to the lungs.
Pylorus (pi-lo'-rus). The opening of the stomach into the duodenum.
Radius (ra'-di-us). The outer of the bones of the forearm.
Renal (re'-naV). Pertaining to the kidneys.
Rennin (ren'-w). An enzyme, or ferment, to whose action is due the

curdling or clotting of milk produced upon the addition of ren-

net.
Retina (ret'-i-na}. The chief and essential peripheral organ of vision;

the third or internal coat or membrane of the eye, made up of the

end organs or expansion of the optic nerve within the globe.

GLOSSARY. 369

Sacrum (sa'-kruni). A curved triangular bone, composed of five con-
solidated vertebrae, wedged between the two iliac (pelvic) bones,

and forming the dorsal boundary of the pelvis.
Scapula (skap'-u-la). The shoulder-blade.
Sciatic (si-at'-ik}. Pertaining to the ischium; the sciatic nerve, the

main nerve of the thigh.
Sclerotic (skle-rot'-ik). Hard, indurated; pertaining to the outer coat

of the eye.
Semilunar (sem-i-lu'-nar}. Resembling a half-moon in shape; semilu-

nar valves, pocket-like valves at the beginning of the aorta and

pulmonary artery.
Serous (se'-rus). Pertaining to, characterized by, or having the nature

of, serum.
Serum (se'-rum*). The yellowish fluid separating from the blood after

the coagulation of the fibrin.

Solar plexus (so'-lar). Solar, with radiations resembling the sun.
Sphincter (sfinyk'-ter'), A muscle surrounding and closing an orifice.
Splenic (splen'-ik). Pertaining to the spleen.
Steapsin (s£ep'-,sm). A diastasic ferment which causes fats to combine

with an additional molecule of water and then split into glycerine

and their corresponding acids.
Sternum (ster'-num}. The breast-bone.
Subclavian (sub-kla'-vi-an). Situated under the collar-bone ; subcla-

vian artery and vein.
Sublingual (sub-ling1 '-ywal). Lying beneath the tongue, as sublingual

gland.
Submaxillary (sub-mak '-si-la-ri}. Lying beneath the lower maxilla, as

submaxillary salivary gland.

Supination (su-pi-na'-shun}. The turning of the palm upward.
Synovia ($i-no'-vi-a). The lubricating liquid secreted by the synovial

membranes in the joints.

Tarsus (£ar'-sws). The instep, consisting of seven bones.
Temporal (tem'-po-ral). Pertaining to the temples, as temporal artery,

vein, muscle, etc.
Tetanus (tet'-a-nus}. A spasmodic and continuous contraction of the

muscles, causing rigidity of the parts to which they are attached.
Thein (the'-in). An alkaloid found in tea.

Theobromin (Mr-o-bro'-mm). A feeble alkaloid obtained from cacao-
butter ; the essential substance found in cocoa and chocolate.

37O GLOSS A A'\'

Thyroid (thi'-roid). Shield-shaped, as the thyroid cart ilage of the
larynx.

Tibia (tib'-i-a). The larger (inner) of the two hones of tin- leg, com-
monly called the shinbone.

Trachea (tra-ke'-a or tra'-kc-it). The windpipe.

Triceps (tri'-seps). Triceps of the arm, the extensor of the arm. lyinu
along the back of the humerus.

Tricuspid (trl-kim'-piil). Having three cusps or points, as the trienspid
valve.

Trypsin (trip'-sin}. The proteolytic ferment of pancreatic juice.

Ulna (ul'-na). The larger (inner) of the two bones of the forearm.

Ureter (fi-re'-ter). The tube conveying the urine from the pelvis of the
kidney to the bladder.

Vaso-constrictor (rr/.x'-o-A-on-N/r/A-'-f <>/•). Causing a constriction of the
blood-vessels.

Vaso-dilator («a*'-d-cK4a/-tor). Pertaining to the positive dilating mo-
tility of the non-striated muscles of the vascular system.

Vaso-motor (vas-o-ino'-tor). Serving to regulate the tension of the
blood-vessels, as vaso-motor nerves ; including vaso-dilator and
vaso-constrictor mechanisms.

Ventricle (ven'-tri-kl). Applied to certain structures having a bellied
appearance. The cavities of the heart from which the blood is
forced out through the arteries.

Vesicle (ves'-i-kl}. A small, membranous, bladder-like formation, as
air vesicle.

Villus (wT-its), pi. villi. One of the numerous minute vascular projec-
tions from the mucous membrane lining the small intestine, for ab-
sorbing digested food.

Vitreous O*T-re-w«). Glass-like, as the clear, jelly-like, vitreous humor
of the eye.

INDEX.

Abdomen, cross section of, i6f.
Abdominal respiration, 95.
Absorption, 181.

Of fats, 182, 183.

From stomach, 175.
Accommodation, 291.
Acids, indigestion, 179.

Fatty, 179.

In poisoning, 323.

Tasting, 302.
Action of large arteries, 49.

Of gullet, 171.

Of heart, 45 ; rhythmic, 65.

Of diseased kidneys, 197.

Of muscle, 9.

Of ciliary muscle, 291.

Reflex, 30, 32, 263.
Adam's apple, 309.
Adjustment of lens, 290.
Afferent currents, 268.

Nerve fibers, 27, 28, 32.

Nerve roots, 33, 31.
After-images, 295.

Negative, 295 ; Positive, 295.
After-pressure, 281.
Air, complemental, 96, 97.

Composition of, 100.

Currents about stoves, 116.

Expired, 102.

Reserve, 96, 97.

Residual, 96, 97.

Sacs, 84, 91.

In the sickroom, 325.

Tidal, 96, 97.

Vesicles, 84, 91, 103.

Washed, 119.
Albinos, 288.
Albumen, 145.

Albuminuria, 199.
Alcohol, 208.

In the army, 216, 217.

Binz, 218.

Brunton, 250.

And circulation, 70.

Clum, 252.

And cold climates, 209.

And crime, 208.

Crothers, 251.

Effects of, 210, 223.

And energy, 208, 212.

And excesses, 252.

Greely, 216.

Halliburton, 222.

And heat, 209.

Hornaday, 221.

Howell, 212.

Luce, 260.

Martin, 253.

M'Kendrick, 222.

Miura, 213.

Moral deterioration, 253.

As a narcotic, 210.

And nerve centers, 251.

And nervous system, 250.

As a poison, 210.

Reichert, 213.

Rohe, 218.

Stanley, 216.

Stevenson and Murphy, 250.

As a stimulant, 210.

Thompson, 214.

And training, 209.

In the tropics, 221.

And water, 210.

Woodhull, 216.

Woodruff, 217.

371

372

INDEX.

Alcoholic beverages, 218.
Alkalies, in digestion, 179.

In poisoning, 323.
Alveoli, of the lungs, 84.
Ameba, 5.
Amount of blood, 75.

Of food needed, 193.

Of perspiration, 136.

Of saliva, 168.
Amylopsin, 178.
Anabolism, 203.
Anatomy defined, 3.

And sculpture, 346.
Anesthetics, 254.
Animal matter, 338, 339.

Protoplasm, 202.
Animals and plants, 205.
Antidotes to poisons, 322, 347.
Aorta, 44, 177.
Apex beat of heart, 49.
Apoplexy, 248.
Appendicular skeleton, 330.
Appendix, vermiform, 187.
Aqueous humor, 288, 289.
Arch, neural, 330, 331.
Aristotle's experiment, 266.
Arm, bleeding from, 314.
Arrangement of teeth, 164.

Of muscles, 341,

Arterial muscle, exercise of, 233.
Arteries, large, action of, 49.

Bleeding from, 314.

Distribution of, 44.

And exercise, 69.

Regulation of size, 68.

Structure of, 51.
Artery, carotid, 44, 314.

Gastric, 44.

Hepatic, 44, 177.

Iliac, 44.

Mesenteric, 177.

Pancreatic, 44.

Pulmonary, 42, 43.

Renal, 44.

Splenic, 44.

Subclavian, 44.
Articulating process, 331.
Articulations of vertebra, 335.
Artificial life, i.

Renewal of air, 116.

Auditory center, 244, 264.

Nerve, 239, 238, 305.
Auricles of heart, 41, 47.

Contraction of, 46.
Asiatic cholera, Bacillus of, 123.
Association fibers, 264.
Astigmatism, 292.
Atlas, 335.
Axial skeleton, 330.
Axis, 335 ; axis cylinder, 27, 28.

Bacilli, types of, 123.

Bacillus, of Asiatic cholera, 123.

Of diphtheria, 123.

Of hog cholera, 123.

Tuberculosis, 122, 123

Of typhoid fever, 123.
Bacteria, 124.

Of putrefaction, 127.
Baking meat, 156.

Powder bread, 189.
Ball and socket joint, 339.
Bandaging, 328.
Barley, 149.
Baseball, 229.
Bathing, 232.

The sick, 326; Time for, 233.
Bath mils. 232.
Baths, cold, 232; warm, 233.
Beans, dried, 189.
Bear, hibernation of, 201.
Bedding, changing in sickroom. 326.
Bee-stings, 324.
Beef extract, 155.

Tea, 155.
Beets, 189.

Beverages containing alcohol, 218.
Biceps, 8, 15.
Bicuspid teeth, 164.
Bicycling, 230.
Bile, 177.

Duct, 186, 177.

Functions of, 178.

Sac, 160, 186.

Bites of cats, 324; dogs, 324; snakes, 324.
Bitters, taste of, 302.
Blackberries, 189.

Bleeding from arm, 314; arteries, 314;
neck, 314; nose, 315; veins, 315.
Blind spot, 293.

INDEX.

373

Blindness, color, 295.

Blister, 132.

Blood, amount of, 75.

Changes in, 106.

Chemical reaction of, 75.

Coagulation of, 74.

Color of, 73.

Composition of, 71.

Of frog, 73.

Gases of, 104.

And glands, 134.

Mixture of good and bad, 196.

Quantity in different organs, 75.

Renewal of, 200.

And river, 195.

Specific gravity of, 75.

Transfusion of, 81.

Work of, 39.
Blood-flow, and exercise, 107.

And lymph-flow, 77, 78.

Rate of, 59.

Blood-pressure, of ventricle, 46.
Blood-stream and sewer, 199.
Blood-supply of brain, 247.

Of stomach, 173.
Blood-tubes joining heart, 42.
Blowing, 96.
Blushing, 68.
Boats upsetting, 321.
Body, care of, 2.

And locomotive, 109.

Temperature of, 108.
Boiled milk, 189.

Boiling meat, 156 ; boiling water, 152.
Bone, composition of, 338.

Corpuscles, 337.

Lamellae of, 337.
Bone, structure of, 18, 337.
Bones, broken, 317.

Of ear, 305, 306.

Hygiene of, 339.

Lightness and strength of, 20.

Relation to muscles, 15.

Table of, 333.

Uses of, 21, 330.

Weight of, 337.
Bow-legs, 339.
Boxing, 229.
Brain, 235.

Blood-supply of, 247.

Brain centers, connection of, 263.

Convolutions and intelligence, 240.

Ganglia of, 241.

Gray matter of, 241.

Hemispheres of, 240.

Location of functions, 244.

Parts of, 235.

Preservation of, 236.

Rest, 246, 247.

And sensation, 30, 243.

The water-cushion of, 248.

White matter of, 241.

Work, 246.
Bread, hot, 189.
Breathing, effect on circulation, 98.

Deep, 97, 98.

Hygiene of, 97.

Through mouth, 98.

Restoring, 320.

And swallowing, 170, 171.
Broiling meat, 156.
Broken bones, 317.
Bronchi, 43.
Bruises, 340.
Bulb, hair, 130.

Olfactory, 303.

Spinal, 245, 246.
Burning clothing, 316.
Burns, treatment of, 316.

Cabbage, 189.

Caffein, 155.

Cake, 189.

Calf muscle of frog, 9.

Camel's hump, 201.

Canaliculi, 338.

Canals, haversian, 337, 338.

Canals, semicircular, 305, 306.

Candle, heat of, 205.
And respiration, 201.

Cane sugar, 179.

Canine teeth, 164.

Capacity of lungs, 97, 96.
Vital, 97.

Capillaries, blood-flow in, 55 ; of frog's
web, 52, 53 ; of lung, 91 ; of
muscle, 54 ; pulmonary, 86.

Capsule of lens, 289.

Carbohydrate food, 147.

Carbohydrates, 147.

374

Carbon dioxid of air, 100, 102; in blood,
i<xj ; in bivatli, 102; in wells, 322.
Care of body, importance of, 2.

Of ears, 307.

Of eyes, 295.

Of lamps in sickroom, 328.

Of the sick, 324, 325.

Of teeth, 166.
Carotid artery, 44, 314.
Carpal bones, 333.
Carpus, 332, 333.
Cartilage, 19.

Cricoid, 309.

Intervertebral, 335.

Thyroid, 309.
Cartilages of windpipe, 86.
Casein, 144, 145.
Cataract, 293.
Cats, bites from, 324.
Cauliflower, 189.
Cauterizing, 324.
Cavities, lymph, 80.

Serous, 80.

Of skeleton, 337.
Cavity, pulp, 163, 164.
Cecum, 1 86.
Celery, 189.
Cells, aquatic, 79.

Ciliated, 86.

Division of, 5.

Of epidermis, 53.

Epithelial, 4.

Fat, 130.
Cells and lymph, 79, 200.

Muscle, 5, 345.

Nerve, 5, 28.

And oxygen, 107.

Pigment, 52, 53.

Poisoning of, 200.

Starvation of, 200.

Structure of, 4.
Center of control of circulation, 68.

For hearing, 244, 264.

Respiratory, 99.

Of sensation, 243, 245.

For speech, 245, 264.

For vision, 264.
Centrum, 330.
Cerebellum, 236, 245.
Cerebral cortex, functions of, 243.

Cerebro-spinal system, cat, 26.

Of man, 24, 25.
Cerebrum, 235, 241.
Cervical vertebrae, 332, 333.
Cesspools, 151.
Change of voice, 313.
Cheese, 147, 189, 191.
Chemical composition of bone, 338.
Chemistry of respiration, too.
Children, exercise of, 228.
Chloral hydrate, 257.
Chloroform, 257.
Chocolate, 155, 189, 212.
Choking, 96.
Cholera, Asiatic, bacillus of, 123.

Hog, bacillus of, 123.
Choroid coat, 287.
Churning in the stomach, 174.
Chyle, receptacle of, 184, 186.
Chyme, 175.

Cider, 212; fermentation of, 121, 212.
Cigarettes, 259.
Cigars, 258.
Cilia, 87.
Ciliary muscle, 290, 291.

Process, 288.
Ciliated cells, 86.
Circulation and alcohol, 70. .

Control of, 64.

Diagram of, 60, 196, 197, 198.

In frog's web, 52, 53, 54.

In gray matter, 249.

In muscle, 54.

Plan of, 60.

Portal, 177.

In white matter, 249.
Circumvallate papillae, 302.
Classification of senses, 271.
Clavicle, 332, 333.
Cleanliness of eyes, 298.
Climate and alcohol, 209.
Clothing, regulating heat, 138.

Effect of wet, 139.
Coagulation of blood, 74.

Of muscle plasma, 346.
Coat, choroid, 287.

Sclerotic, 287.

Coats of eye, 287 ; of stomach, 172.
Cocaine, 257.
Coccyx, 332, 333, 335.

INDEX.

375

Cochlea, 305, 306.
Cocoa, 155, 189.
Coffee, 155, 189, 212.
Cold baths, 232.

Spots, 283.

Taking, 231.
Colds and deafness, 307.
Colon, 187.
Color blindness, 295.

Of blood, 73, 105.

Sensations, 294.

Of skin, 132.
Colored corpuscles, 71.
Colorless corpuscles, 72.

As germ destroyers, 126.
Column, spinal, 334.
Common sensations, 272.
Compass points and touch, 281.
Complemental air, 97.
Composition of air, 100.

Of blood, 71.

Of bone, 338.

Of sweat, 135.
Conduction of heat, 137.
Cones and rods, 293, 292.
Conjunctiva, 286.
Connective tissue, n, 12.
Consciousness, 243.
Conservation of energy, 206.
Consonants and vowels, 312.
Constipating foods, 189.
Constipation, 178, 188.
Consumption, danger from, 122.
Contraction of auricle, 46.

Of ventricle, 46.
Control of diaphragm, 100.

Of mind, 247.

Of respiration, 99.
Convalescence and reading, 298.
Convection of heat, 137.
Conversation at meals, 192.
Convolutions of brain, 235, 240.

And intelligence, 240.
Convulsions, 346.
Cooking, 155.
Coordination, 245.

Cord, spinal, 24 ; reflex action of, 30, 32.
Cords, tendinous, 41, 46 ; vocal, 309.
Corn, 148, 189.
Cornea, 288.

Corpuscles of blood, 72, 53.

Bone, 337.

Colored, 71, 72, 104.

Colorless, 72, 126.

Touch, 279.

Correlation of energy, 206.
Cortex, cerebral, functions of, 243.
Coughing, 95.

Covering of brain, 235 ; of heart, 40.
Cracked wheat, 189.
Crackers, 189.
Cramps, 35.

Cranial nerves, 237, 242.
Cream, 144.
Cricoid cartilage, 309.
Crime and alcohol, 208.
Crossing of nerve fibers, 35, 243.
Crown of tooth, 163.
Crying, 95.

Crystalline lens, 288, 289.
Culture of voice, 313.
Curdling in stomach, 174.
Currents, afferent, 268, 269; efferent,

268; induction, 266.
Curvature of spine, 339.
Custard, 189.

Cutaneous sensations, 278.
Cylinder, axis, 27.

Danger of consumption, 122.

Dead dust, 119.

Deafness and colds, 307.

Deep breathing, 99.

Defects in eyesight, 291.

Deliberation in eating, 192.

Dental formula, 164.

Dentine, 163, 164.

Dermis, 132.

Desserts, 191.

Dextrose, 179.

Diabetes, 199.

Dialysis, 182.

Diaphragm, 85, 87, 88, 177, 344.

Control of, 99.
Diarrhea, 231.
Diastole, 47.

Diet, errors of, 193; mixed, 153; one-
sided, 153; proper, 154.
Diffusion of gases, 115; of liquids, 182.
Digestion, hygiene of, 190.

3/6

Digestion, organs of, 160.

Outline of, 187.

Time in stomach, 175.
Digestive tube, 159.
Dilation of ventricle, 47.
Diphtheria, bacillus of, 123.
Direct heating, 118.
Disease germs, 122.

Of lungs, 126.

Prevention of, 126.
Dislocations, 339.
Distribution of arteries, 44 ; of veins, 44.

Of heat, 138.
Division of cells, 5.

Of labor, physiological, 4.
Dogs, bites from, 324.
Double windows, 119.
Dreams, 266.
Dried fish, 189.
Drink, hot, 191.
Drinking, 96.

Water, 152.
Dropsy, 80.

Drowned, treatment of, 317.
Drowning, resuscitation from, 317.
Duodenum, 160.
Dura mater, 235.
Dust, avoiding, 124.

Dead, 119; live, 121.

And lungs, 120.

Sources of, 120.
Dusting, 125.

Ear, bones of, 305, 306.

Care of, 307.

External, 305.

Internal, 306.

Middle, 305.

Parts of, 305.

Use of, 307.
Eating between meals, 193.

Deliberation in, 192.

Time of, 193.
Eddy, living, 199.
Efferent nerve currents, 268.

Nerve fibers, 27, 32, 33.
Eggs, 146.
Electric light, 296.
Emetic, mustard, 323.
Emulsion, 147, 179.

Enamel, 163, 164.
Energy and alcohol, 208.

Conservation of, 206.

Correlation of, 206.

From food, 204.

Utilization of, 205.
Ennui, 95.

Entire wheat flour, 148.
Enzymes, 169.
Epidermis, 53, 131.
I Epiglottis, 170, 171, 310.
Epithelial cells, 4.
Equilibrium sense, 306.
Errors in diet, 193.
Essentials of reflex action, 32.
Ethmoid bone, 333.
Eustachian tube, 306, 305, 170, 171.
Evaporation of sweat, 137.
Evening reading, 297.
Excretion, 130; of urea, 202.
Exercise of arterial muscles, 233.

And bathing, 226.

And blood-flow, 107.

Forms of, 228.

And health, 226.

And heat, 137.

And long life, 227.

And size of arteries, 69.
Expiration, elastic reactions of, 94.
Explosion in muscles, no.
Expression, muscles of, 345.
Extensor muscle, 8.
External ear, 305.
Extract of beef, 155.
Eye, coats of, 287.

Dissection of, 287.

External parts of, 286.

Movements of, 287.

Muscles, 286, 288.

Protection of, 285.

Section of, 288.

Structure of, 288.
Eyes, of albinos, 288.

Care of, 295.

Cleanliness of, 298.

Irritation of, 298.

Pain in, 294.

Pigment in, 288.

Resting, 297.

Sympathy between, 294.

INDEX,

377

Eyeball, muscles of, 286.
Eyeglasses, 292.
Eyesight, defects of, 291.
Eyestrain, 299.

Facial expression, 345.

Nerves, 238.
Fainting, 316, 248.
Fans, ventilating, 117.
Far-sight, 291, 292.
Farina, 189.
Fat cells, 130.

And muscles, 346.

As a tissue, 201.
Fats, 147.
Fatty acids, 179.

Fatigue, 246, 272 ; from standing, 268.
Femur, 18, 332, 333.
Fever, typhoid, 151.
Fiber, muscle, plain, 50, 344.

Muscle, striated, n, 12, 344.

Nerve, 28.

Fibers, association, 264.
Fibrin, 74, 145.
Fibula, 333.
Filiform papillae, 301.
Fish, 146; dried fish, 189.
Flavors, 302.

Flexibility of spinal column, 335.
Flexion of forearm, 16.
Flexor muscle, 8, 13.
Flexure, sigmoid, 188.
Floating, 321.

Flour, entire wheat, 148; Graham, 148.
Flow of lymph, 77.
Flues, ventilating, 115.
Food, amount needed, 193.

Object of, 159.

Regulating temperature, 138.

For the sick, 327.

Source of energy, 204.
Foods, 144.

Constipating, 189 ; laxative, 189.

Preservation of, 127.
Foodstuffs, 144, 145.
Foot asleep, 37 ; as kind of lever, 17.
Football, 229.

Force, indestructibility of, 204.
Forced respiration, 94.
Forms of exercise, 228 ; of muscles, 341.

Formula, dental, 164.
Foul air shafts, 117.
Frog, blood of, 73.

Without cerebrum, 241.

Muscle action of, 9.
Frontal bone, 332, 333.
Fruits, 150.

Acid, 189.

Pies, 189.

Puddings, 189.
Frying, 156.
Fulcrum, 16.
Function, defined, 3.

Of cerebellum, 245.

Of cerebral cortex, 243.

Of cerebrum, 241.

Of nerve fibers, 28.

Of nerve roots, 33.

Of skin, 136.

Of spinal bulb, 245.

Of spinal cord, 29.
Fungiform papillae, 301.
Furnaces, 117.

Gain and loss of body, 195.
Game, wild, 189.
Games of children, 228.
Ganglia, 29; of brain, 241.

Sympathetic, 65.
Ganglion of dorsal root, 26, 29.
Gargling, 95.
Gases of blood, 104.

Diffusion of, 115.

Gastric glands, 173 ; juice, 173, 174.
Gelatin, 145.

General sensations, 271, 272.
Germs of disease, 122.
Glands and blood supply, 134.

Compound, 133.

Essentials of, 134.

Gastric, 173.

Intestinal, 176.

Lacrymal, 286.

Lymphatic, 77, 183.

Mucous, 169.

Oil, 130.

Salivary, 166.

Simple, 133, 135.

Sweat, 133.
Glasses, wearing, 299.

3/8

INDEX.

Gliding joints, 339.
Glossopharyngeal nerves, 239.
Glottis, 170, 171.
Gluten, 145.
Glycogen, 178, 202.
Graham flour, 148.
Grains, 147.
Granula, 189.
Grape sugar, 179.
Grates as ventilators, 114.
Gravity and circulation, 61.
Gray matter of brain, 241.

Matter, circulation in, 249.

Matter of spinal cord, 28, 29, 31.
Gray nerve fibers, 28.
Gullet, 160, 170, 171, 186.

Habit, 212.

Acquired reflex action, 267.
Hair, 130, 133 ; bulb, 130.
Hammer bone, 333.
Hard palate, 170.
Harmony in muscle action, 21, 36.
Hauser, Kaspar, 271.
Haversian canals, 337.
Hawking, 95.

Headaches from eyestrain, 299.
Health, i.
Hearing, 304.
Heart, action of, 45 ; rhythmic, 64.

Auricles of, 41, 46.

Beat of, 39, 49.

Blood tubes joining, 42.

Covering, 40.

Dissection of, 42.

Muscle, 344.

Nourishment of, 61.

Position of, 40.

Size of, 41.

Sounds of, 49.

Structure of, 41.

Valves of, 41.

Ventricles of, 41, 46.

Work and rest of, 48.
Heat and alcohol, 209.

Conduction of, 137.

Convection of, 137.

Distribution of, 138.

And exercise, 137.

From oxidation, 109.

Heat, production of, 106.

Radiation of, 137.

Ways of giving off, 137.
Heating, direct, 118; indirect, 118.
Hemispheres of brain, 235, 240.
Hemoglobin, 74, 104.
Hemorrhage of lungs, 315.

Of stomach, 315.

Hepatic arteries, 177 ; veins, 177, 186.
Hibernation, 201.
Hiccuping, 95.
Hinge joint, 339.
Hoarseness, 313.
Hog cholera, bacillus of, 123.
Hope in illness, 325.
Hot drink, 191.
Humerus, 332, 333.
Humor, aqueous, 288, 289.

Vitreous, 288, 289.
Hump, camel's, 201.
Hunger, 276.
Hyaloid membrane, 289.
Hygiene of bones, 339.

Of breathing, 97.

Defined, 3.

Of digestion, 190.
Hyoid bone, 333.
Hypoglossal nerve, 240.

Ice water, 152.

Ignoring nerve currents, 266.
Iliac arteries, 44 ; veins, 44.
Image, inversion of, 290.
Immovable joints, 339.
Importance of retina, 293.
Impulse, nerve, 28, 36.

Transmission of, 36.
Impurities in water, 151.
Incisor, 164.
Incus, 333.
Indestructibility of force, 204.

Of matter, 203.
Indirect heating, 118.
Induction current, 266.
Inebriety, Clum, 260; Crothers, 260.

A disease, 253.

Palmer, 260.
Inhibition, 67.
Innominate bones, 333.
Insertion of muscle, 10, 15.

INDEX.

379

Inspiration, 91 ; and expiration, 92.

Forces of, 94.

Resistances to, 94.

Intelligence, 243; and convolutions, 240.
Interference with reflex action, 35.
I ntervertebral cartilages, 335.
Intestine, 176, 177.

Large, 186, 188 ; small, 160, 176, 186.
Intestinal glands, 176, 179.
Inversion of image, 290.
Invertin, 179.
Iris, 288.

Iron, in blood, 74.
Irritant poisons, 323.
Irritation of eye, 298.
Ivy poisoning, 324.

Jacketed stoves, 117.
Joints, 19, 339.
Judgment, 266.
Jugular vein, 44.
Juice, gastric, 173.

Intestinal, 179.

Lime, 150.

Pancreatic, 177.

Kaspar Hauser, 271.
Katabolism, 203.
Kidneys, 139.

Diseased, 197.

And skin, 141, 142.
Kinds of teeth, 164.

Labor, physiological division of, 4.
Lacrymal bone, 333 ; gland, 286.
Lacteals, 181, 184, 186.
Lacunoe of bone, 337.
Lamellae, of bone, 337.
Lamps, in sickroom, 328.
Larynx, from above, 311.

Structure of, 310.
Lateral process, 331.
Laughing, 95.
Laxative foods, 189.
Leather, 132.
Ledger of body, 195.
Legumin, 145.
Lens capsule, 289.

Crystalline. 288, 289.

Levers, 16, 17.

Life, artificial, i ; natural, I.

Processes, 203.
Ligament, suspensory, 288.
Ligaments, 19.
Light, electric, 296.

In sickroom, 325.

Strength of, 297.
Lingering of sensations, 267.
Live dust, 121.
Liver, 177, 160.

As food, 189.

Position, 85.

Starch, 178.
Lobes, olfactory, 237.
Local sign, 281.

Location of brain functions, 244.
Locomotion, 19; by reaction, 20.
Loss and gain of body, 195.
Loudness of voice, 311.
Lumbar vertebrae, 332, 333, 335.
Lung diseases, 126.
Lungs, 87.
. Parts of, 84.

Capacity of, 97.

Dorsal view of, 43.

Hemorrhage of, 315.
Lymph, 79.

Cavities, 80.

Flow of, 77.

Importance of, 80.

Renewal of, 200.

Spaces, 75.

Tubes, 76.

Variations in, 80.
Lymphatic glands, 77, 183.
Lymphatics, 183, 184.

Malar bone, 333.

Malleus, 333.

Malted milk, 155.

Massage, 81.

Masseter muscle, 8.

Mastication, imperfect, 192.

Matter, animal, in bone, 338, 339.

Indestructibility of, 203.

Mineral in bone, 338, 339.
Maxilla, inferior, 333.

Superior, 333.
Meals, conversation at, 192.

INDEX.

Meat, 146; baking, 1^6; boiling, 156;
broiling, 156 ; roasting, 156 ; salted,
189 ; smoked, 189.
Mechanism, of body, 2.
Media, refracting of eye, 289.
Medullary sheath, 27.
Membrane, hyaloid, 289.
Memory, 267.
Meningitis, 248.
Mesentery, 161, 186.
Mesenteric artery, 177 ; vein, 186.
Metabolism, 203.
Metacarpus, 333, 334.
Metatarsal bones, 333.
Metatarsus, 332, 333.
Middle ear, 305.
Milk, 144, 146.

Boiled, 189; Malted, 155.

Souring of, 127.

Teeth, 164.
Mind, control of, 247.
Mineral matter in bone, 338, 339.
Mitral valve, 41.
Mixed diet, 153.

Joints, 339.

Modification of respiration, 95.
Molars, 164.
Molds, 121.
Morphia, 255.
Morphine, 255.
Motion, experiments with, 7.

Involuntary, 24.

And locomotion, 19.

Production of, 106.

Voluntary, 24.

Mouth, 162 ; breathing through, 98.
Movable joints, 339.
Movements of eye, 287.

Of respiration, 91.

Mucous glands, 169; Membrane, 86, 87.
Mucus, 169.
Muscle, action of, 9.

Capillaries of, 54.

Explosion in, no.

Insertion of, 10, 15.

Normal condition of, 13.

Origin of, 10, 15.

Shortening, 13, 24.

Structure of, 10, n.
Muscle-action, harmony in, 36.

Muscle-action, laws of, 12.
Muscle-cells, 5, 345; of heart, 344.
Muscle-fiber, a cell, 345.
Muscle-fibers compared, 344.

Plain, in artery, 50.

Plain and striated, 52, 344.

In lymph tubes, 77.
Muscle-plasma, coagulation of, 346.
Muscles, arrangement of, 341.

Arterial, exercise of, 233.

Biceps, 8.

Ciliary, 290, 291.

Of expression, 345.

Of eyeball, 286, 288.

And fat, 346.

Forms of, 341.

Importance of, 12.

Names of, 344.

Number of, 341.

Papillary, 46.

Relation to bone, 15.

Size of, 341.

Skeletal, 15.

Sphincter, 175.

Superficial, 342, 343.

Symmetrical development of, 14.

Temporal, 9.

Triceps, 8.
Muscular exertion and urea, 202.

Power, loss of, 37.

Sense, 272.

Sense and sight, 274.
Myosin, 145.

Nails, 133.

Rusty, wounds from, 323.
Names of muscles, 344.
Narcosis, 254.
Narcotics, 254, 257.
Nasal bones, 333.
Nature, punishments, i, 227.

Of sensation, 264.
Nausea, 272.
Near sight, 291, 292.
Neck, bleeding from, 314.

Of tooth, 163, 164.
Negative after-images, 295.
Nerve cells, 5, 28.

Centers, 29.

Currents afferent and efferent, 268, 269.

INDEX.

Nerve, currents ignoring, 266.

Endings, in skin, 278.

Fibers, crossing of, 35, 243.

Fibers, destination of, 33.

Fibers, function of, 28.

Fibers, gray, 28.

Fibers, sheath of, 28.

Fibers, similarity of, 262.

Fibers, structure of, 27, 28.

Impulse, 28, 36.

Roots, functions of, 33.

Stimuli, 261.

Supply of heart, 66.

Supply of tongue, 302.
Nerves, Auditory, 239, 305.

Cranial, 237, 242.

Of diaphragm, 100.

Effect of pressure, 37.

Facial, 238.

Glossopharyngeal, 239.

Of hearing, 242, 305.

Of heart, 66.

Hypoglossal, 240.

Olfactory, 238, 303.

Optic, 237, 238, 288.

Pneumogastric (see vagus).

Sciatic of frog, 9.

Of smell, 303.

Spinal, 26.

Structure of, 27.

Of taste, 302, 301.

Trigeminal, 237.

Trophic, 251.

Vagus, 66, 239.

Vaso-constrictor, 67.

Vaso-dilator, 67.

Vaso-motor, 68.

Nervous impulse, nature of, 28, 36.
Nervous system and alcohol, 250.

Cerebro-spinal, 24.

Sympathetic, 65, 66.

And telegraph, 268.
Nervous tissue and starvation, 247.
Neural arch, 330; ring, 330.
Neuralgia and cold baths, 233.
Neuroglia, 241.
Nicotine, 258.
Nitrogen in air, 100.
Nose, bleeding from, 315.
Nourishment of heart, 61.

Nucleus, 4; of ciliated cell, 86; of epi-
dermic cell, 53.
Nurse, qualities of, 325.
Nursing, 325 ; books on, 328.
Nutrition, 202.
Nuts, 191.

Oats, 149.

Occipital bone, 332. 333.

Oculist, consultation of, 299.

Odontoid process, 335.

Oil gland, 130.

Olfactory bulb, 303, 238, 242.

Lobes, 237, 242.

Nerves, 303, 242, 238.
Onions, 189.
Opium, 255.

Optic nerves, 237, 242, 288, 297.
Organ, defined, 3.
Organs of digestion, 160.

Ledger account of, 195.
Origin, of muscle, 10, 15.
Osmosis, 182.
Outline of digestion, 187.
Oxidation, source of heat, 109.

Of tissues, 107.
Oxygen in the air, 100.

Amount used, 104.

In blood, 104.

Storage in tissues, no.
Oxy-hemoglogin, 104.
Oysters, 189.

Pain, 274; extent of, 275.

In eyes, 294.

A general sense, 276.
Palate bone, 333.

Hard, 170, 171.

Sense of taste in, 302.

Soft, 160, 170, 171.
Pancreas, 160, 177, 186.
Pancreatic duct, 186.

Juice, 177, 178.
Panting, 96.
Papillae, circumvallate, 303.

Filiform, 301.

Fungiform, 301.

Of skin, 130, 131, 279.

Of tongue, 301.
Papillary muscles, 46.

382

INDEX.

Parietal bone, 332, 333.

Parotid salivary gland, 186.

Pastry, 189.

Patella, 332, 333.

Peaches, 189.

Peas, green, 189.

Pepper, 189.

Pepsin, 173.

Peptone, 176.

Periosteum, 19.

Peritoneum, 161.

Perspiration, 130; amount of, 136.

Insensible, 135; sensible, 135.
Phalanges, 333, 334.
Pharynx, 160, 169.
Physician's directions, 326.
Physiology defined, 3.
Pia mater, 235.
Pie, 191.

Pigeon without cerebrum, 241.
Pigment cells, 52, 53.

Of eye, 288.

Of human skin, 132.
Pitch of voice, 312.
Pivot joint, 339.

Plain muscle fibers, 49, 50, 344.
Plants, relation to animals, 205.
Plasma, 73.
Pleura, 87.
Plexus, solar, 66.
Plums, 189.
Poison ivy, 324.
Poisons, 322, 347.

Irritant, 323; neutralizing, 323.
Pollen, 121.
Pores, sweat, 130.
Portal circulation, 177; Vein, 177.
Positive after-images, 295.
Postcaval vein, 42, 44, 177, 186.
Potatoes, 149, 189.
Potential energy, in respiration, 93.
Poultry, 189.
Power, of levers, 16.
Precaval vein, 42, 44, 186.
Premolars, 164.
Preservation of food, 127.
Pressure sense, 280.

Effect on nerves, 37 ; on veins, 58.
Prevention of sneezing, 328.
Process, articulating, 331 ; lateral, 331.

Process, odontoid, 335.

Spinous, 331.

Processes, of vertebra, 330.
Production of heat, 106; of sound, 306.
1'ronation, 337.
Protection of eye, 285.
Proteid food, 146.
Proteids, 145; importance of, 145.

Vegetable, 147.

Protoplasm, 4; animal, 202; vegetal, 202.
Ptyalin, 168, 176.
Puff-balls, 121.
Pulmonary arterv, 42 ; veins, 42, 43.

Capillaries, 86.
Pulp-cavity, 163, 164.
Pulse, 40.

Punishment, by nature, 227.
Pupil, 288, 289.
Putrefaction, bacteria of, 127.
Pylorus, 175.

Quality of voice, 312.

Quantity of blood in organs, 75.

Rabbit, muscles of leg, 9.

Nerves of leg, 9.
Radiation of heat, 137.
Radius, 332, 333.
Rainwater, 150.
Raspberries, 189.
Rate of blood-flo\v, 59.

Of heart beat, 39.

Of respiration, 95.
Reaction of blood, 75.

Time, 262.

Reading in convalescence, 298 ; heavy
books, 296; mornings, 297; even-
ings, 297 ; outdoors, 296.
Receptacle of chyle, 186.
Rectum, 188.

Reference in sensation, 282.
Reflex action, 30, 32, 263.

Essentials of, 32.

And habit, 267.

Importance of, 32.

Of spinal cord of frog, 30.
Refracting media of eye, 289.
Regulation of blood-flow, 68, 69, 107.

Of hearl beat, 66, 67.

Of lymph-flow, 77.

INDEX.

Regulation of respiration, 99, 108.

Of temperature, 136.
Renal arteries, 44; veins, 44.
Renewal of blood and lymph, 200.
Rennet, 174.
Rennin, 174.

Repose, effeet on digestion, 192.
Reserve air, 97.
Residual air, 97.
Respiration, abdominal, 95.

And candle, 201.

Chemistry of, 100.

Control of, 99.

Forced, 94.

Modifications of, 95.

Movements of, 91.

Organs of, 84.

And oxidation, 201.

Rate of, 95.

Thoracic, 95.

Respiratory center, 99 ; sounds, 99.
Rest of brain, 246, 247.

Of eyes, 297.

Of heart, 48.

Usefulness of, 268.
Restoring breathing, 320.
Resuscitation from carbon dioxid, 322.

From drowning, 317.
Retina, 287, 292, 293.
Rhubarb, 189.

Ribs, 332, 333; in respiration, 92.
Rice, 149, 189.
Rickets, 339.
Rigor mortis, 346.
Ring, neural, 330.
River and blood-flow, 195.
Roasting meat, 156.
Rods and cones, 293, 292.
Roots of spinal nerves, 26, 29, 31.
Running, 20.
Rye, 149.

Sacrum, 333, 334, 335.

Sago, 189.

Salines, 302.

Saliva, amount of, 168; uses of, 168.

Salivary glands, 166, 186.

Salted meat, 189.

Salts, 153.

Satiety, 272.

Scapula, 332, 333.
Sciatic nerve of frog, 9.
Sclerotic coat, 287, 288.
Sculpture and anatomy, 346.
Semicircular canals, 305, 306.
Semilunar valves, 42.
Sensation centers, 243, 245

Defined, 265.

Nature of, 264.

And stimulus, 262.
Sensations and brain, 30.

Of color, 294.

Common, 272.

Cutaneous, 278.

General, 271.

Lingering, 267.

Referred to nerve ends, 282.

Relative, 265.

Subjective, 265.
Sense of equilibrium, 306.

Of hearing, 304.

Muscular, 272.

Of sight, 285.

Of smell, 303.

Of taste, 301.

Temperature, 283.

Of touch, 279.

Senses, classification of, 271.
Serous cavities, 80.
Sewer and water pipes, 199.
Sheath, medullary, 27.

Of muscle fiber, u, 12.

Of nerve fiber, 28.
Sick, care of, 325 ; food for, 327.
Sickroom, 324.

Sweeping, 125, 327.

Temperature of, 325.
Sighing, 95.
Sight, 285.

Sigmoid flexure, 188.
Sign, local, 281.
Skeleton, 330.

Appendicular, 330.

Axial, 330.

Cavities of, 337.
Skeleton, side view of, 332.
Skin, color of, 132.

Functions of, 130, 136.

And kidneys, 141.

Papilla; of, 279.

INDEX.

Skin, structure of, 130.

Skull, 332, 333.

Sleeplessness, 246.

Small intestine, 160.

Smell, 303.

Smoked meat, 189.

Snake bites, 324.

Sneezing, 95 ; prevention of, 328.

Sniffing, 95, 304.

Snoring, 95.

Sobbing, 95.

Socket-joint, 339.

Soft palate, 160.

Solar plexus, 66.

Sound, 306.

Sounds of heart, 49.

Respiratory, 99.
Soup, 156; value of, 191.
Special senses, 271, 278.
Specific gravity of blood, 75.
Speech center, 245, 264.

And voice, 312.
Sphenoid bone, 333.
Sphincter muscles, 175.
Spices, 189.
Spinach, 189.
Spinal bulb, 236, 245, 246.
Spinal column, 334; flexibility of, 335.
Spinal cord, 24.

Cross section of, 28.

Figure of, 29.

Functions of, 29.

Reflex action of, 30.
Spinal nerves, 26.

Roots of, 26, 29.

Effect of severing, 34.
Spine, curvature of, 339.
Spinous process, 331.
Spirillum, of Asiatic cholera, 123.
Spitting, 96.
Spleen, 81.
Spot, blind, 293.

Yellow, 288.

Spots, cold, 283 ; warm, 283.
Sprains, 339.
Squash, 189.
Standing, 19.
Stapes, 333.
Starch, 189.
Starvation of cells, 200.

Starvation of nervous system, 247.

Steapsin, 179.

Stereoscopic vision, 295.

Sternum, 332, 333.

Stiffened joints, 340.

Stimulants, 210, 212 ; in resuscitation, 320.

Stimulating nerve roots, 34.

Spinal nerves, 33.
Stimuli of nerves, 261.
Stimulus and sensation, 262.
Stings of bees, 324.
Stirrup bones, 333.
Stomach, 160, 172, 186.

Absorption from, 175.

Blood-supply of, 173.

Coats of, 172.

Churning, 174.

Digestion, time of, 175.

Hemorrhage of, 315.

Position, 85, 160, 172, 186.

Structure of, 172.
Storage of oxygen, no.
Stove, 116; with jacket, 117.
Strength of light, 297.

Source of, 14.
Structure of artery, 51.

Of bone, 18, 337.

Of brain, 238, 239, 241.

Of eye, 288.

Of gullet, 171.

Of heart, 41.

Of kidney, 139, 140.

Of larynx, 310.

Of muscle, 10, n.

Of nerves, 27.

Of retina, 292.

Of skin, 130.
Structure of stomach, 172; of tooth, 163,

164.

Subclavian vein, 44, 186.
Subjective sensations, 265.
Sublingual salivary gland, 166, 186.
Submaxillary salivary gland, 166, 186.
Sucking, 96.

Suffocation in wells, 322.
Sugar, 144 ; cane, 179 ; grape, 179.

In diabetes, 199.
Sunshine, 139.
Sunstroke, 317.
Supination, 337.

INDEX.

Suspensory ligament, 288.

Swallowing, 171 ; and breathing, 170, 171.

Sweat, 130.

Composition of, 135.

Evaporation of, 137.

Glands, 130, 133, 135.

Pores, 130.
Sweeping, 125.

Sickroom, 125, 327.
Sweetmeats, 191.
Sweets, where tasted, 302.
Swimming, 321.

Sympathetic nervous system, 65, 66.
Sympathy between eyes, 294.

In nursing, 325.
Synovia, 19.
Systole, 47.

Table of bones, 333.

Tapioca, 189.

Tarsal bones, 333.

Tarsus, 332, 333.

Taste, 301.

Tasting, conditions of, 302.

Tea, 154, 189, 212 ; beef, 155.

Tears, 286.

Teeth, 162, 163.

Arrangement of, 164.

Care of, 166.

Kinds, 164.

Milk, 164.

Temperance drinks, 211.
Temperature of body, 108.
Temperature, regulation of, 136.

Sense, 283.

Of sickroom, 325.

Effect on taste, 302.
Temporal bone, 332, 333 ; muscle, 9.
Tendinous cords, 41, 46.
Tendon, 7, 10, n, 15.
Tennis, 228.
Tetanus, 35.
Thein, 154.
Theobromin, 155.
Thermometer in sickroom, 325.
Thigh, wounds in, 315.
Thirst, 276, 272.
Thoracic duct, 183.

Respiration, 95.

Vertebra, 331, 335.

Thorax, cross section of, 89.

Thorns, wounds from, 323.

Thyroid cartilage, 309.

Tibia, 332, 333.

Tidal air, 97.

Time for bathing, 233 ; of eating, 193.

Tissue defined, 3.

Connective, n, 12.

Fatty, 201.

Tissues, oxidation of, 107.
Tobacco, 258.
Tomatoes, 189.
Tongue, 162.

Nerves of, 301.

Papillae of, 301.
Tooth, structure of, 163, 164.
Touch, sense of, 279.

Corpuscles of, 279.
Trachea, 43, 86.
Training and alcohol, 209.
Transfusion of blood, 81.
Transmission of nerve impulse, 36.
Treatment of burns, 316.

Of the drowned, 317.

Of fainting, 316.

In poisoning, 322, 347.
Triceps muscle, 8.
Tricuspid valve, 41.
Trigeminal nerve, 237.
Trophic nerves, 251.
Trypsin, 178.
Tube, digestive, 159.

Eustachian, 305, 306.
Tubes, lymph, 76.
Tuberculosis, bacillus of, 123.
Turbinated bones, 333.
Typhoid fever, 151 ; bacillus of, 123.

Ulna, 332, 333.

Upsetting of boats, 321.

Urea, 139; and muscular exertion, 202.

Uses of bones, 330.

Utilization of energy, 205.

Uvula, 160.

Vagus nerves, 66, 239.

Valve, mitral, 41 ; tricuspid, 41.

Valves of heart, 41.

Of lymph tubes, 76.

Semilunar, 42, 46.

386

INDEX.

Valves of veins, 57.
Variation of blood-supply, 50.
Vaso-constrictor nerves, 67.

-dilator nerves, 67.

-motor nerves, 68.
Vegetable proteid, 147.
Vegetables, 149.
Vegetal protoplasm, 202.
Vegetarians, 154.
Veins, 57.

Bleeding from, 315.

Distribution of, 44.

Flow in, 61.

Hepatic, 177, 186.

Iliac, 44.

Jugular, 44.

Mesenteric, 186.

Portal, 177.

Postcaval, 42, 44, 177, 186.

Precaval, 42, 44, 186.

Effect of pressure on, 58.

Pulmonary, 42, 43.

Renal, 44.

Subclavian, 44, 286.

Valves in, 57.
Ventilating flues, 115.
Ventilation, need of, 114.

Principles of, 115.
Ventricle, contraction of, 46.

Dilation of, 47.

Of heart, 41.

Vermiform appendix, 187.
Vertebra, articulations of, 335.

Parts of, 330.

Processes of, 330.
Vertebrae, cervical, -332, 333, 334.

Lumbar, 335.

Thoracic, 331, 332, 333, 335.
Vesicles, air, 84.
Villi, 179, 181, 184, 185.
Vision, stereoscopic, 295.
Visual center, 264.
Vital capacity, 97.
Vitreous humor, 288, 289.
Vocal cords, 309.
Voice, 309.

Change of, 313.

Culture of, 313.

I^oudness of, 311.

Pitch of, 312.

Voice, quality of, 312.

And speech, 312.
Volition, 242, 243.
Voluntary inhibition. 35.
Vomer, 333.
Yourls and consonants, 312.

\Yalking, 20; in sickroom, 327.
Warm baths, 233.

Spots, 283.

Watching in sickroom, 326.
Water, 150.

Boiling, 152.

Drinking, 152.

Ice, 152.

Impurities in, 151,

Rain, 150.

Well, 150.

Water-cushion of brain, 248.
Water-pipes and bloodstream, 199.

And sewer, 199.
Wearing glasses, 299.
Web of frog's foot, 52, 53.
Weight of bones, 337.

In levers, 16.
Well-water, 150.
Wheat, 148.

Flour, 148.

Whispering, 313 ; in sickroom, 327.
Whistling, 96.
White matter of brain, 241.

Circulation in, 249.

Of spinal cord, 28, 29.
Wild game, 189.
Wind, 116.

Windows, double, 119.
Windpipe, 86.
Work of blood, 39.

Brain, 246.

Of heart, 48.
Worker, outdoor, 2.

Wounds from rusty nails, 323; from
thorns, 323.

In thigh, 315.

Yawning, 95.
Yeast, 121.
Yellow spot, 288.

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