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ENTARY

PHYSIOLOGY AND HYGIENE

COLT ON

THE LIBRARY

OF

THE UNIVERSITY
OF CALIFORNIA

GIFT OF

Will C. Wood

ELEMENTARY PHYSIOLOGY
AND HYGIENE

BY

BUEL P. COLTON, A.M.

AUTHOR OF

PHYSIOLOGY : EXPERIMENTAL AND DESCRIPTIVE

"PHYSIOLOGY, ILLUSTRATED BY EXPERIMENT"

" PRACTICAL ZOOLOGY "

AND
PROFESSOR OF NATURAL SCIENCE

IN

ILLINOIS STATE NORMAL UNIVERSITY
NORMAL, ILLINOIS

BOSTON, U.S.A.

D. C. HEATH & CO., PUBLISHERS
1904

COLTON'S PHYSIOLOGIES.

PHYSIOLOGY: Experimental and Descriptive . . . $1.12
For High Schools, Normal Schools, and Colleges. 440 |

pages. Illustrated in colors.

PHYSIOLOGY: Briefer Course • . .90

For High Schools. 399 pages. Illustrated in colors.

ELEMENTARY PHYSIOLOGY AND HYGIENE . . .60

For Elementary Schools. 320 pages. Illustrated.

D. C. HEATH & CO., Publishers, Boston, New York, Chicago.

COPYRIGHT, 1902,
BY BUEL P. COLTON.

EDUC.-
PSYCH.
LIBRARY

GIFT

2=J.

PREFACE.

IN preparing this work for younger students especial
pains have been taken to make it clear and simple. Sen-
tences, paragraphs, and chapters have been made short,
and a concise summary follows each chapter. So far as
possible technical terms have been avoided and English
words preferred to Latin, for instance, post-caval vein
instead of vena cava inferior, spinal bulb instead of medulla
oblongata, etc. The Latin form of the plural puzzles the
student who has not had Latin ; hence the English form
of the plural is used, as pleuras, ganglions, ciliums, vil-
luses, papillas, etc.

The illustrations are made clear and distinct, and are
labeled directly ; that is, the detail labels are on, or very
close to, the part labeled, so that time and effort are
not needed to associate the thing and the name. A large
number of the illustrations are original.

A few simple experiments are given ; for although much
less can be done than with older students, yet considerable
must be done if the subject is to be made clear.

The subject of hygiene has received careful attention ;
for it must not be forgotten that the main object of this
study is that each pupil may learn how to take better care
of his own body. The author has tried not to give mere
arbitrary rules of health, to be blindly and implicitly fol-
lowed, but to base all precepts of hygiene on the general
principles of physiology, so that the pupil may understand

iii

076

iv Preface.

the why and the how so far as possible. His obedience
will be more ready and more complete when based on
intelligence than when it is simply a submission to a
peremptory command. In many cases, too, the general
principle will serve as a guide where no rule has been laid
down ; no treatise can cover all possible contingencies.

The subject of alcohol has been treated very thoroughly
and in full compliance with the laws of the various states.
Throughout the book the effects of alcohol and other nar-
cotics have been discussed in close connection with the
accounts of the functions of the organs of the body. A
number of authoritative quotations have been made, so
that the pupil may know that the statements made are
supported by the most eminent authorities of the world on
these subjects.

The author's larger work, " Physiology, Experimental
and Descriptive," was criticised and corrected by a large
number of eminent authorities, a list of whom is given in
the preface of that book. This book is a condensation,
though largely rewritten, of that work, and therefore
derives the full benefit of their criticism.

At the end of the book is a glossary (page 300) in which
all technical terms are pronounced and explained.

CONTENTS.

CHAPTER

I. Introduction

II. The Bones

III. Muscles and Motion

IV. The Muscles and the Bones

V. The Nervous System — Sensation and Motion

VI. Circulation of the Blood .......

VII. Control of Circulation

VIII. The Blood and the Lymph

IX. External Respiration

X. Internal Respiration ........

XI. Ventilation and Heating

XII. Dust and Bacteria

XIII. Excretion

XIV. Foods and Cooking

XV. The Digestive System — Digestion in the Mouth .

XVI. Digestion in the Stomach

XVII. Digestion in the Intestine .......

XVIII. Absorption

XIX. Hygiene of Digestion — Nutrition

XX. Alcohol

XXI. Exercise and Bathing

XXII. The Brain

XXIII. Effects of Alcohol on the Brain . . . .

XXIV. The Senses — The General Senses — Touch and Temperature

Sense

XXV. The Sense of Sight

XXVI. Taste, Smell, Hearing, and the Voice

XXVII. The Effects of Alcohol on the Senses

XXVIII. Tobacco

XXIX. Other Narcotics

XXX. Accidents — What to do till the Doctor comes

5

16
28
37
49
70

78

88

103

112
1 2O
129
I4I

154
164

174
I83
193
205
2 2O
226

245
252
263
270
277
285
290

GLOSSARY 300

INDEX 312

TO THE TEACHER.

IT is not the fault of the teacher that the human body is very com-
plex in structure and that many of the functions are obscure. Never-
theless the teacher is responsible for making the subject as clear as is
possible. To do this it is absolutely essential to perform some experi-
ments and to show some of the internal organs of such an animal as
the rabbit, or materials obtained from the butcher. This involves
work, and sometimes work that is not altogether pleasant. But no
earnest teacher will shrink from work simply because it is not agreeable.
In the author's " Physiology, 'Experimental and Descriptive" (D. C.
Heath & Co.) are given in detail directions for many experiments and
dissections, some of which can be profitably used in classes in the
grammar grades. Each teacher should be provided with that book,
for in it are given lists of books helpful to the teacher, as well as of
books suitable for pupils to read in addition to their regular lessons.

Every school should have a microscope, by means of which to show
the corpuscles of the blood, cells from various tissues, the circulation
of blood, in a frog's web, or in the gills of a tadpole. A good micro-
scope can be bought for from twenty to thirty dollars, and Clark's
"Practical Methods in Microscopy" (D. C. Heath & Co., $1.60) will
enable a beginner to make fair use of it. From various dealers in
school supplies there can be purchased mounted slides illustrating most
o'f the kinds of cells and tissues of the body. These can be success-
fully used by teachers who have not had the advantages of a thorough
training in histology.

When studying the bones the teacher can usually borrow some
human bones from the nearest physician. Also get a femur of a horse
or cow and saw it in two lengthwise. It will show the structure as
well as a human femur. It is easy to test the composition of bone by
burning and by acid. Corned beef shows well the structure of muscle.
A sheep shank from the butcher may be used to show the joints,
synovia, cartilage, ligaments, etc. By following the directions in the
author's "Experimental Physiology" the brain and spinal cord of a
rabbit can be shown. Most pupils will be ready to help dissect a heart
and will be delighted to see the action of the valves.

By means of a common bulb syringe and a little glass and rubber
tubing the action of the arteries and the nature of the pulse and capil-

vii

viii To the Teacher.

lary flow may be illustrated The circulation of blood in the web of ai
frog's foot is such an interesting and instructive sight that the teacher i
should show it to the class without fail. Even if the school has no
microscope and the teacher without experience, it is often possible to
get a near-by physician to show it to the class, (jhe coagulation of the
blood is readily shown) The experiments illustrating the action of the
diaphragm are very helpful, and any teacher possessing a modicum of
ingenuity and willingness to work can prepare them. In addition to
the experiments given in illustration of the chemistry of respiration, it
is desirable to show nitrogen and the composition of the air. This can
readily be accomplished by following the directions in the larger book
or in any chemistry.

(jo learn the temperature of the body borrow a clinical thermometer
from a physician^ Have the children make little paper windmills to
show the air currents in rooms, over stoves, registers, radiators, etc.
The children should test the currents of air at all gratings and registers
in the schoolroom by holding a handkerchief up close to them. The
teacher should place a board under a window (as directed in this book)
to show how to ventilate a room without unpleasant drafts. (Each
pupil should prepare a section of tooth as directed in this book. When
studying the subject of absorption, the teacher should get from the
butcher about a foot of the small intestine of a calf. He will wash it
clean for a small consideration. Cut this into pieces an inch long.
Turn them inside out and place them in shallow dishes of water. The
villuses will readily be seen. A piece of the gullet will show the mus-
cular and mucous coats. Have the pupils make a careful study of
Fig. 87 and also of Figs. 85 and 86. which are designed to lead up to
Fig. 87. If the teacher is willing to practice, he can soon learn to
demonstrate muscle action by means of frog's muscle and to show
reflex action of the spinal cord with a frog.

Many interesting experiments on the senses can be made with chil-
dren, such as the test of touch with compass points, keenness of sight,
hearing, accuracy of the muscular sense, etc. The internal structure
of the eye never fails to awake enthusiasm, and the teacher should
show this, and perhaps some of the pupils can also succeed in doing
the same. If the teacher can obtain a book on nursing, or, better still,
persuade a physician or trained nurse to come before the class, they
can learn how to prepare and apply bandages, to dress wounds, to treat
for drowning, etc.

ELEMENTARY PHYSIOLOGY.

CHAPTER I.
INTRODUCTION.

The Care of a Machine. — In order to take good care of
a machine one must know about its different parts, what
each part is to do, and the relation of the parts to one
another. He must keep the machine clean and well oiled,
and must not overwork it. Otherwise it will neither do
good work nor last long. This is true not only of machines
like typewriters and sewing-machines, but of bicycles, and
even of such simple tools as knives and scissors. We
would not trust the management of any valuable machine
to one who did not know enough to take good care of it.

The Care of the Body. — The care of the body is of vastly
greater importance. We can get new parts to replace
those worn out in a machine. While we can get artificial
limbs, we cannot replace such organs as an eye, the heart,
or the lungs. If we do not take good care of our bodies,
we cannot keep well, live long, or do good work. So we
need to know about the different parts of our bodies, the
work that each is to do, and the relation of the parts to
each other.

This knowledge is desirable for everybody ; but espe-
cially necessary for those who live a quiet, indoor life. In-
door people do not get as much exercise or as much fresh

i

2 Physiology.

air as those who live outdoors. An indoor life is always
more or less artificial, and we need to take especial care
that our bodies do not suffer. It is believed that one
seventh of the deaths among civilized races are due to lung
troubles. Those who live outdoors have little trouble of
such kind. We need to learn about the air and breathing,
about exercise and bathing, about food and digestion, about
blood and its circulation, about the nervous system, etc.

Hygiene. — Hygiene is the art of preserving the health.
This is the main object of our study of this subject.

Physiology. — Physiology is the science of the action of
the body and its various parts. We must know the natural
action of the parts of the body to be able to keep them in
good working order.

Organ. — An organ is any part of the body that has a
special work to do, as the hand, eye, or heart.

Function. — The work or action of an organ is its
function.

Anatomy. — Anatomy is the science of structure. We
need to know something of the structure of our bodies.
For this purpose we may study the internal structure of
the sheep, pig, calf, and rabbit — which is very similar to
our own. . We can take the hearts, lungs, brains, eyes, arid
muscles of such animals to learn the structure of these
organs in our own bodies ; if we are not willing to do this,
we can never get a clear understanding of the subject.

Tissues. — Every organ is made up of several different
kinds of material. For instance, in a slice across a ham
we see skin on the outside, then fat meat, lean meat, and
bone. These " primary building materials " of the body

Introduction. 3

are called tissues. A tissue is a collection of similar cells
devoted to the same work ; or, in other words, a tissue
is a set of cells having the same structure and the same
function. Thus we have, muscular tissue, nervous tissue,
bony tissue, etc.

Cells. — The whole body is made up of small parts, called
cells, which are to be compared to the bricks in a house.
These cells are of various shapes in the different tissues.
The living material of the body is called protoplasm. It is
a jelly-like substance resembling the
white of an egg, though often pre-
senting a dotted appearance. A cell,
in its simplest form, is merely a dis-
tinct particle of protoplasm. Each Nucleus
cell usually has, however, a more Fig. i. Epithelial ceils from

the Inside of the Cheek.

dense central part, called the nucleus.

The great majority of cells have a distinct covering or
cell-wall. A grape or cherry serves very well to illustrate
a cell. The skin represents the cell-wall, the pulp corre-
sponds to the protoplasm, and the seed to the nucleus.
(See Fig. 39, Cells of the Epidermis.)

Division of Labor in a Community. — We are all aware
of the advantages of division of labor in a community. If
each person learns to do one thing well, all can work
together economically for the common good, time is saved,
and cheaper and better goods are produced.

Division of Labor in the Body. — In the body there is a
division of labor similar to that in a community. In the
first place each organ has its special work, and the various
organs act helpfully together, each working for all the rest
and worked for by them.

4 Physiology.

The general structure of all the cells is about the same,
yet they differ enough for us to tell them apart. They
differ more in their work than in their appearance. Each
has some one kind of work that it can do well, and to
which it devotes itself. The nerve cells receive impressions
from the outer world, carry nerve currents, and control the
various actions of the body. The muscle cells have as
their work the production of motion.

The Life of Cells. — Each cell must take food for itself
and grow. Each has a birth, life, and death, as each indi-
vidual in a community of men; and as the community
continues, while the individual members are constantly
changing, so, in the body, while the form remains about
the same from year to year (in the adult), the cells are
continually changing, some dying, and others taking their
places. Thus it is seen that though the cells are packed
closely together and though they work in groups, each cell
leads, in one sense, an independent life. Like the indi-
vidual in the community, each lives for itself, yet all work
together for the common good.

CHAPTER II.
THE BONES.

The Two Parts of a Skeleton. — The skeleton consists of
two portions, (i) the central axis,} or spinal column, to
which the head belongs ; and (2) the limbs and the bones
belonging to them.

The Uses of the Bones. — i. The skeleton gives the form
to 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 chest, 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.

2. On the dorsal side of this is the neural arch, forming with the
body the neural ring, through which the spinal cord passes.

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 : —

(a) The body is flattened where it fits against the vertebras above
and below it ;

(b} The holes in the vertebras form a passage for the spinal cord ;

(c) The middle projection is the spinous process, and the series of
spinous processes form the ridge of the backbone ;

62?) The two side projections are the transverse processes.

5

Physiology.

Fit together two vertebras in their proper order and observe that : —
(f) The openings at the sides, through which the spinal nerves pass,
are formed by notches, or grooves, in the two vertebras.

Neural Arch

Body

Transverse Process

....Spinous Process

Neural Ring
Fig. 2. Upper View of Thoracic Vertebra.

Demi-facet for Head of Rib

Body...

Anterior Articular
Process

Facet for Tubercle of
Rib

^Transverse Process

Spinous Process

Fig. 3. Left Side View of Thoracic Vertebra.

(/) The two projections extending upward from the ring of one
vertebra fit against two projections extending downward from the other
vertebra. These are the anterior and posterior articular processes.

The Spinal Column. — The central part of the skeleton
is the backbone, or spinal column. As a whole it is a

The Bones. 7

column, widening toward the base, composed of a series of
separate bones called vertebras.

Each vertebra has seven projections, four for joining
other vertebras (two upper and two lower), two side, and
one spinous.

Hole for Blood Tubes ^^li'J^^I?^ Anterior Articular Facet

Neural Arch

Spinous Process
Neural Ring

Fig. 4. Upper View of Cervical Vertebra.

Body-

Spinous Process
Fig. 5. Left Side View of Cervical Vertebra.

How the Vertebras Fit Together. — The smooth places
where the projections join are called facets. Observe on
each side of the body of the vertebra a facet where the
head of the rib joined it. There is also a facet on the side
process where the side of the rib joined it.

The Cervical Vertebras. — The seven rgrvical (neck)
vertebras have holes through their side projections for the
passage of blood tubes.

8

Physiology.

Temporal

Phalanges
i Carpus

Metacarpus Ulna Stern

Parietal

Occipital

Cervical Vertebras

..... Scapula
y Thoracic Vertebras

Lumbar Vertebras

Fibula

Metatarsus
Fig. 6. Side View of the Human Skeleton.

The Bones.

TABLE OF THE BONES.

HEAD (28)

Skull (8)

Face (14)

Ears (6)
CERVICAL REGION (8)
THORAX (37

UPPER EXTREMITIES (64)

LUMBAR REGION (5)
PELVIS (4)

LOWER EXTREMITIES (60)

f Frontal (forehead).

2 Temporal (temples).
J 2 Parietal (side).
1 Occipital (posterior base).

Sphenoid (base).
[ Ethmoid (base of nose and between eyes).

f 2 Superior Maxillas (upper jaw).

2 Nasal (bridge of nose).

2 Malar (cheek).

2 Lachrymal (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).

J 7 Cervical Vertebras (neck).
1 Hyoid Bone (base of tongue).

{14 True, 6 False, 4 Floating Ribs.
12 Thoracic Vertebras (back).
Sternum.

Cr ,,
Shoulder

Arm.

Hand.

/Clavicle (collar-bone).
| Scapuk £shoulder.blade).
Humerus (arm).

8 Carpal (wrist).

5 Metacarpal (palm).

14 Phalanges (ringers).

5 Lumbar Vertebras (loins).

( 2 Innominates.
•I Sacrum.
I Coccyx.

Thigh. Femur.

f Patella (knee-pan).
Leg. \ Tibia (large bone).

I Fibula (outer bone).

{7 Tarsal (instep, heel).
5 Metatarsal (arch).
14 Phalanges (toes).

i o Physiology.

Atlas and Axis. — The first vertebra, the atlas, has no
body. The second vertebra is the axis. It has a peg
which runs up into the atlas. In shaking the head, the
atlas, with the head, turns on this peg of the axis. In
nodding the head, the head simply rocks back and forth
on the atlas.

The Thoracic Vertebras. — The twelve rib-supporting
vertebras are the thoracic vertebras.

The Lumbar Vertebras. — The next five are the lumbar.

The Sacrum and Coccyx. — The sacrum is composed of
five vertebras grown together, and the remaining four are
combined in the coccyx.

Review of the Spinal Column. — Let the eye slowly re-
view the whole spinal column, noting in what points the
vertebras are all alike. Note also their differences.

Flexibility of the Spinal Column. — In well-prepared
skeletons there are pads of felt which take the place of the
layers of cartilage that were between the vertebras. These
cartilages are tough and elastic, and firmly attached to the
vertebras above and below. They serve both to keep the
vertebras apart and to hold them together. When we bend
the shoulders to the right, the right edges of these carti-
lages are compressed, and the left edges are stretched, as
a piece of india rubber would be if it were glued be-
tween the ends of two spools, and the whole were slightly
bent. The cartilages also, by their elasticity, protect
the brain from the shock it would receive in jumping,
walking, etc.

Curves of the Spinal Column. — Vie*w the spinal column
from the side. Draw a line representing all its curves.

The Bones.

1 1

The Cavities of the Skeleton. — Examine the cavity of 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.

Neural Arch

Transverse Process

Neural Ring
Fig. 7. Upper View of Lumbar Vertebra.

Body

Spinous
Process

Posterior Articular Process
Fig. 8. Side View of Lumbar Vertebra.

Observe the conical shape of the chest. 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 jointed with the body only where the inner
ends of the collar bones join the breastbone.

1 2 Physiology.

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. This knowledge will aid in understanding the brain and
spinal cord.

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 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 rings around the
canals, somewhat like the rings seen on the end of a log.

Between the rings are circles of elongated dark dots. These are
cavities in which were the live bone-corpuscles which built up the bone.
The bone was at first cartilage. Later, mineral matter was deposited,
forming true bone.

3. Examine with a High Power. — Now examine the section under a
one-fifth-inch objective. From the dark cavities there run out, in every
direction, little crevices, appearing as fine black lines. Through the

fyjaversian canals, lacunas, and crevices} the nourishing materials of the
blood reach all parts of the bone.

The Chemical Composition of Bone. — i . Take a tall, narrow jar, or
a lamp chimney corked at one end, and nearly fill with 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 thor-
oughly, and examine it. The acid will probably have dissolved out the
mineral matter and left the animal matter so soft that it may be tied
into a knot.

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 Bones. 1 3

Composition of Bone. — Bone is composed of two thirds
mineral matter and one third animal matter ; in childhood
the animal matter is in larger proportion, while in old age
the mineral matter is in excess. The mineral matter is
chiefly phosphate of lime, while the animal matter is
largely gelatin.

Lamellas

Lacunas

Canaliculi Haversian Canal

Fig. 9. Cross-section of Bone. (Highly Magnified.)

Classification of Joints. — i. Immovable, such as the
joints between the bones of the skull;

2. Mixed, such as the joints between the vertebras ;

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;

1 4 Physiology.

(d) Gliding, as between the short bones of the wrist
and of the ankle.

Study of Joints. — Examine these joints in the prepared skeleton,
and so far as possible, in sheep shanks, or in fresh specimens of, rabbits.
Compare the ball and socket joints of the hip and shoulder. Also com-
pare the hinge joints of the knee and elbow.

Hygiene of the Bones. — Sometimes the bones of chil-
dren are lacking in mineral matter, and are too soft and
flexible. This is true in a disease called rickets. Even if
the bones are natural, 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. Unnatural positions or
over-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 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 aids circulation and prevents discoloration. But
if there is inflammation, cold water should be applied.
Bandages may be needed for support.

Broken Bones. — When a bone is broken, of course a
physician should be sent for. Care must be taken that the
limb be kept straight. If this is not done, the sharp ends
of the bone (see Fig. 22) may cut or tear the surrounding
tissues, or even cut blood tubes. So, if the person must
be carried, it is well to tie a piece of board along the limb
to keep from bending it. A cane, umbrella, or any light
rigid bar will serve for this purpose.

The Bones. 1 5

Effect of Alcohol on the Bones. — " The effect of alcohol
in stunting the growth of the body is a well-known fact."
— Bevan Lewis in "Text Book of Mental Diseases."

"The injurious effect of alcohol on the entire develop-
ment of the child is evident from the fact that children
who drink spirituous liquors are noticeably stunted in
growth." - —Professor Adolph Frick of Zurich.

Summary. — i. The skeleton consists of the central axis and the
limbs.

2. Each vertebra consists of a body, ring (around spinal cord), and
processes.

3. Pads of cartilage connect the vertebras.

4. Throughout the bone there are 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 III.
MUSCLES AND MOTION.

Motion and Life. — Motion is one of the surest signs 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.
We often move to avoid injury. Motion is necessary for
speech and in the use of the sense organs. 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 the changes that are felt in the biceps muscle.

Fig. 10. The Shortening and Thickening of the Biceps Muscle in raising the Forearm.

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.

16

Muscles and Motion. 17

3. 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.

4. Clasp the back of the upper right 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.

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

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

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

8. Stand erect with the heels close to each other, but not quite
touching ; let the arms hang freely by the sides ; rise on tiptoes, with-
out moving otherwise ; repeat ten times.

9. Place the tips of the fingers on the angles of the lower jaw ; shut
the teeth firmly, and note the bulging of the masseter muscle.

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

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

The Action of Muscle. — The action of muscle is always
a " pull." The muscle shortens, at the same time thicken-
ing and hardening. It must be kept clearly in mind that
the work of the muscle is done by its shortening and not
by either the hardening or thickening. But the hardening
and thickening are often more noticeable than the shorten-
ing, and by means of them we may locate the muscle that
is producing any motion.

Action of Frog's Muscle. — The action of muscle may be seen much
more clearly in a frog\s calf muscle, as shown in Fig. 11. When the
nerve is stimulated at u A " a nerve impulse runs along the nerve to the
muscle and makes it shorten and widen, raising the weight as shown in
the right half of the figure.

i8

Physiology.

••• Origin

SHORTENED

ELONGATED

Fig. 1 1 . Action of the Calf Muscle of the Frog, showing the Relations of the
Sciatic Nerve.

Structure of Muscle. — Chipped beef shows well the
structure of muscle. The white network is connective

tissue. Its work is to hold
the parts of the muscle to-
of Muscle Fibers gether and to support the
muscle as a whole. In the
meshes of the white network
is the red muscle tissue. The
partitions which run all
through the muscle are con-
tinuous with the muscle
sheath, and both are con-
tinuous with the tendons at
the ends of the muscle. In
fresh muscle the sheath and
the partitions are transpar-
ent, and are not very easily

noticed. When meat is cooked or sal.ted the connective
tissue becomes white and opaque.

f Muscle Fibers

Muscle Sheath \

CROSS SECTION

Tendon

• Insertion
LONGITUDINAL SECTION

Fie. 12. The Structure of Muscle.

Muscles and Motion.

i£- 13- Two Striated Muscle

Fibers showing the termina-

tions of the Nerves

Microscopic Structure of Muscle. — If a tiny shred of
muscle, such as you may remove from the teeth with a
toothpick, be put in a drop of slightly
salted water and examined under a
good microscope, the fibers may be
seen. These are small thread-like
bodies, with cross markings, from
which they are called (striated or
striped muscle fibers^ From the fact
that they are under the control of the
will they are called voluntary muscle
fibers.

Plain Muscle Fibers. — In the walls
of the arteries, of the gullet, stomach, intestines, and
elsewhere, there are muscle fibers of a different kind
from those of the skeleton. These fibers are spindle-
shaped cells, as shown in Fig. 14, with a nucleus near

the center, and do not have the
cross-markings. Hence they are
called //tfz>/, smooth, or |m-striated^
... isolated Fibers muscle fibers. Owing to the fact
that they are not under the control

Fibers Joined Q£ ^ wjU they ^Q c^Qd im,0lun.

tary muscle fibers.

Heart Muscle. — The fibers which
make up heart muscle are different
Plain mnstriated) Muscle in appearance from either the stri-
ated or the smooth muscle fibers.

They are more or less branched, as shown in Fig. 15. No
sheath has been found on these fibers.

The Three Kinds of Muscular Fibers Compared. — The

striated fibers are called voluntary, and the plain fibers

Fig. 14.

20

Physiology.

involuntary. The heart muscle fibers are intermediate,
being striated, but involuntary in their action. A striated

muscle fiber may be ij inches
long and -^^ of an inch wide,
though usually less. The heart
muscle fiber is narrower than
the striated fiber, and the plain
fiber very much smaller than
either. (The figures do not
attempt to give exact propor-
tions.)

A Muscle Fiber is a Cell. -

It is easily seen that each plain
muscle fiber is a single cell, hav-
ing its distinct nucleus. The

Fig. 15. Muscle Fibers from the Heart, Same is true of the heart milSCle

^S:da^]S^rCrOSSStriae' ^ers, though they are not so

The nuclei and cell-junctions are shown simple, being more OF leSS

only on the right hand side of the

figure. branched.

Effect of Cooking Muscle. — In well-cooked corned beef
the connective tissue is thoroughly softened, and the mus-
cle fibers are easily separated. Thorough cooking, espe-
cially stewing, will soften the connective tissue, and may
make tender meat that, cooked otherwise, would be very
tough on account of the large amount of connective tissue.

Imitation of Structure of Muscle. — Take a number of pieces of red
cord to represent the muscle fibers. Wrap each in white tissue paper;
this represents a single fiber sheath. Lay a number of these side 'by
side, and wrap them all in a common sheath. Let the tissue paper pro-
ject beyond the ends of the threads, and here compress it into a com-
pact cylinder ; this last represents the tendon.

Connective Tissue the Skeleton of Muscle. — If all the

muscle fibers were removed from a muscle, the sheaths

Muscles and Motion. 21

and partitions would remain, and show the form of the
muscle just as the partitions remain in a squeezed orange
or lemon. 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. Con-
nective tissue may be called, therefore, the skeleton of the
soft tissues. Muscle consists, then, of soft transparent
tubes, filled with a semi-fluid muscle substance. By scrap-
ing the surface of a steak 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 muscles make up nearly
half the weight of the body. This fact of itself should
lead us to conclude that the muscles are of great impor-
tance. Muscles are used in nearly every action of the
body, not only in locomotion, but in respiration, circulation,
digestion, speech, etc. It is very necessary that at the
beginning we understand their action.

Duration of Muscle Shortening. — A muscle cannot be
kept shortened for any great length of time. If one holds
the arm out horizontally as long as he can, he soon feels
fatigue, later pain, and he is likely to feel a soreness in the
muscle for several days afterward. 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 while the other works.

Alternate Action of Flexors and Extensors. — When the
biceps muscle shortens and bends the arm, the triceps
lengthens (see Fig. 16). When the triceps shortens, as in
straightening the arm, the biceps lengthens. If the biceps
and triceps both shorten at the same time, and with equal

22

Physiology.

Deltoid

Serratus Magnus

Rectus Femoris

Tibialis Anticu

Extensors of the Hand
lexers of the Hand

Pectoralis Major

Rectus Abdominalis

... Sartorius

Vastus Externus

Extensors of the Toes

Fig. 16. Front View of the Superficial Muscles.

Muscles and Motion.

23

Extensors of the Hand

Triceps

Latissimus Dors

Gluteus Maximus

Vastus Externus

Flexors of the Foot

Trap

-• Deltoid

... Flexors of the Hand

Biceps Cruris

Gastrocnemius

Tendo Achillis

Fig. 17- Back View of the Superficial Muscles.

24 Physiology.

force, no motion will be produced. Sometimes this is done
on purpose, as when, in wrestling " square-hold," one holds
the arm rigidly bent at a right angle, to keep his opponent
from either pushing or pulling him. In the body are many
flexors and extensors " paired off"; they act alternately,
like the biceps and triceps in the arm.

Symmetrical Development of the Muscles. — The muscles
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 one-sided.
Most persons step harder on one foot than on the other, as
shown by the sound of the footstep, or by the constant
wearing of one shoe sole or heel faster than the other. In
many persons one shoulder is carried higher than the
other.

To Overcome One-sidedness. — 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 ad-
vantages in being able to use either hand. In carving, in
shaving, in bandaging, in giving medicine, it may be neces-
sary 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 depends
; on our muscles. It is a fine thing to have strong, well-

Muscles and Motion. 25

developed muscles, not only because they give beauty 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

The Number of Muscles. — There are over five hundred
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 naturally 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 an outer 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
fusiform. Some muscles are flat, some have their fibers
arranged like the barbs of a feather, and are hence called
penniform. 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. Muscles which close open-
ings are circular, and are called sphincter muscles.

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,

26 Physiology.

especially in forced expiration, as after violent exercise and
in coughing. The abdominal wall consists of several layers
of muscle.

Muscles of Expression. — The facial expression is due
to the action of the muscles of the face, which in turn are
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 makes a corresponding elevation.

Convulsions. — These spasmodic actions are due to dis-
ordered action of the muscles, and to a disturbed action
of the nervous system that controls the muscles. Various
disturbances, such as indigestion, may by reflex action
bring on convulsions.

Alcohol and Muscular Energy. — Alcohol does not in-
crease the energy of the body for muscular work. Re-
peated experiments have been made which show that
power to do muscular work is diminished as the result
of taking alcohol. The person may, and often does, feel
stronger, but the feelings are neither a sure test nor a
safe guide. As one writer says, the drunken man thinks
he is strong enough to hold two men, whereas he needs
two men to support him in his weakness. Test of ability
to do work shows the weakening effect of alcohol. It was
formerly supposed that when men were called upon to
perform unusually hard work they needed the sustaining

Muscles and Motion. 27

power of alcoholic liquor, and such drink was furnished
to men engaged in harvesting, etc. This belief has been
thoroughly disproved.

The apparent liveliness of the tipsy person, and his more
or less violent movements are no sign of added strength.
We all know that restlessness and nervous activity are often
a sign of weakness and not of strength.

Alcohol and Training. — It is a significant fact that men
who are training for athletic contests (no matter what their
ordinary habits or principles are) let alcoholic drinks alone.
One of the famous pugilists said, "I'm no teetotaler, but
when J have business on hand there's nothing like water
and dumb-bells." The schoolboy or college student who
hopes to gain a place on any athletic team, will be very
unlikely to do so if he indulges in alcoholic drink.

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

2. The action of muscle is a shortening, accompanied by a thicken-
ing 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 can remain shortened only a little while.

7. The muscles should be developed symmetrically.

8. There are about five hundred muscles in the body.

9. The muscles of the two sides are alike.

10. The muscles of the limbs are spindle-shaped.

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,11 does he usually call attention' to the muscle used in
striking?

4. Why are the sides of the body often sore after walking on icy
uavements?

CHAPTER IV.
THE MUSCLES AND THE BONES.

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, making the motion strong, quick,
and accurate. 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 \wxspassive strength.

Relation of the Muscles and the Bones. — Examine Figs.
10, 1 6, and 17. For this work you should have the bones of
an arm. Locate the biceps muscle in its relations to these
bones as shown in the figures. 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. Most of the skeletal muscles are attached to
bones. There are some exceptions, such as the circular
muscle which closes the mouth when the lips are pursed up.

X-Rays and their Use. — By means of X-ray apparatus

28

The Muscles and the Bones.

29

Fig. 18. X-Ray Photograph of Hand showing Shot carried for Twenty Years.
(From Recreation, by permission of G. O. Shields.)

the physician can photograph through the body and show
the location of the bones. This process is useful in show-
ing injuries to the bones. It is also especially useful in

3°

Physiology.

locating a bullet or other solid body, which probing often
fails to discover.

Levers. — The main facts to be learned about a lever are
that it is a rigid bar ; the point about which the lever turns
is called the fulcrum ; the place where the power is ap-
plied is called the power ; and the part to be moved is
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. — There are three kinds of levers. In
the first class the fulcrum is between the power and the
weight, as in prying over a block with a crowbar. In
the second class the weight is between the power and
the fulcrum, as in a wheelbarrow. In the third class the

(I) Tapping on Floor.

(2) Rising on Toe.

(3) Lifting Weight.

Fig. 19. Three Kinds of Levers as shown by the Foot.
P — Power. W— Weight. F — Fulcrum.

power is between the fulcrum and the weight, as in rais-
ing the forearm (see upper part of Fig. 19). We may
find many examples of levers in the body if we look for
them.

Kinds of Levers shown by the Foot. — The different

The Muscles and the Bones.

3

Ball

Articular Extremity

classes of levers may be 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. (See Fig. 19.)

Advantages of Levers in the Body. — - II Medullary Cavity

If the arm consisted merely of the biceps
muscle, 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 farther. It
could not swing the weight outward, or
push it upward. But from the way in
which the biceps is attached to the fore-
arm (see Fig. 10), when the muscle
shortens an inch it may move the hand Fig. 20
a foot. Of course the hand moves much
faster, and we have a great gain in speed by reason of this lever arrange-
ment. But we cannot lift so heavy a weight at this faster rate, as we
could at the elbow.

Hard Bone

- Spongy Bone
Articular Extremity

Longitudinal Section of
Femur.

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

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

32

Physiology.

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

3. Along the sides, especially near the ends, are ridges and projec-
tions, 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 : —

(a) 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. Sup-
pose 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
number of spools on end ; the column is more
lightened than it is weakened by the hollow-
ing out of the sides of each spool. And the
central hollow of the spool does not greatly
weaken it.

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 to-
gether by tough bands and cords of ligament,
a form of connective tissue very much like ten-
don. 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.

Fig. 2 1 . Action of the Mus-
cles in Standing.

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
of the muscles act in keeping the body upright. Our

The Muscles and the Bones. 33

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 balance, 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
bent 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 force exerted 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. Our effort in moving forward is 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 comoine Lightness and Strength. — The muscles,
then, make use of the bones as levers. We carry these
levers with us all the time. Hence the desirability of hav
ing them light as well as strong. A hollow pillar or hoi-

34

Physiology.

low tube has 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.

Muscles always Stretched. — 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 ten-
sion 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. Muscles
act better when slightly
stretched, and probably need a
slight resistant action of the
opposing muscle.

Fig. 22. Fracture of the Humerus.

Effect of Alcohol on the Mus-
cles.— "A paralytic symptom,
which is erroneously regarded as one of stimulation, is also
found in the deadening of the sense of fatigue. There is
a strong belief that alcohol gives new strength and energy
after fatigue has set in. The sensation of fatigue is one
of the safety valves of our machine. To stifle the feeling
of fatigue in order to be able to work on, is like forcibly
closing the safety valve so that the boiler may be over-
heated.

The Muscles and the Bones. 35

" The belief that alcohol gives strength to the weary is
particularly dangerous for the class of people which con-
tains the most numerous members. The poor people,
whose income is already insufficient to procure a suitable
subsistence, are misled by this prejudice into spending a
very considerable part of their earnings on alcoholic drinks
instead of purchasing good and palatable food, which alone
can give them strength for their hard work." — G. von
Bunge, Professor of Physiological Chemistry in the Uni-
versity of Basle.

Beer and Alcohol not Strengthening. — "The popular idea
that beer and other alcoholic drinks are strengthening is a
mistake, a delusion, a mere superstition, which receives no
support from science."- — A. Mullen, M.D.

Alcohol lessens Endurance. — "Unconscious experiments
on a large scale in many ways have shown that alcohol in-
creases muscular fatigue and lessens power of endurance ;
in the same way experience has proved that no work re-
quiring accuracy and steadiness, or brain or nerve force,
can be done well under the use of alcohol." — T. D.
Crothers, M.D.

What makes the Muscles act in Harmony ? — Have you
ever seen two persons, one using the right hand and the
other the left, 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
and left hands of two persons cannot work so well together
as the right and left hands of one person ? What connec-
tion is there between the two, that one knows just what
the other is doing and when it does it ? Why can two

36 Physiology,

individuals never, with any amount of practice, work so
in unity as the parts of the individual ?

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

Reading. — " How to Get Strong and How to Stay So," Blaikie-,
" Sound Bodies for Our Boys and Girls," Blaikie.

Summary. — i . In the limbs the muscles are spindle-shaped and have
their greatest diameter opposite the central, or narrower, portions of the
bones, concealing the fact that the bones are largest at the ends, as is
so evident in the skeleton.

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

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

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

5. Locomotion is brought about by reaction.

Questions. — i . Find other examples of levers in the body.

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

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

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

5. Analyze and explain jumping, hopping, etc.

CHAPTER V.

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 shortening
they act on the bones as levers to produce our varied mo-
tions. 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, both voluntary
and involuntary, depend upon the nervous system.

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

The Brain. — There are two main parts of the brain, the
cerebrum, which fills all the upper part of the cranium,
and the cerebellum, very much smaller, in the lower back
part of the cranium. The cerebrum is divided into right
and left hemispheres by a lengthwise groove. The sur-
face of the cerebrum is covered with ridges called convo-
lutions. The outside of the brain is of gray matter,
consisting of cells, while the inside is white, consisting of
nerve fibers.

37

Physiology.

Fig. 23. The Cerebro-spinal Nervous System.

Two Functions of the Brain. — Only two functions of the
brain are to be noticed now. One is sensation, the other
motion, or rather the control of motion. Nerve currents
that come to the brain, produce all our sensations. Sen-

Nervous System. 39

sation is in the gray matter on the outside of the brain.
When we wish to move any part of the body, the first
thing is to will to do it. This action is also in the gray
matter on the outside of the brain, but in a different part
from that which has sensation. The act of willing to do
anything sends nerve currents, or inipulses, along nerve
fibers to the part that is to be set to work. The white
fibers of the inside of the brain connect the cells of the
gray matter with the various parts of the body through the
base of the brain, the spinal cord, and the spinal nerves.

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 cervical enlarge-
ment, where the large nerves are given off to the arms.
In the region of the loins is the lumbar enlargement, where
the nerves are given off to supply the legs. The outside
of the cord is white, but the central portion consists of
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. They pass out through notches
between the successive vertebras, so there is no danger of
their being crushed, or even pinched, when the backbone
bends. 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

40 Physiology.

root, the other nearer the ventral surface, the ventral root.
These two roots soon unite to form one spinal nerve.

Structure of Nerves. — If we trace a nerve outward, we
find that it is continually subdividing. This division con-
tinues 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 separation of the fibers in
floss silk.

Nerve Fiber Sheath

I Axis Cylinder

Medullary Sheath
Fig. 24. Structure of a Nerve Fiber.

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 ma-
terial around the axis cylinder.

3. The nerve fiber sheath is a thin, transparent outer
sheath of connective tissue.

Function of Nerve Fibers. — The only 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.

Nervous System. 41

Afferent and Efferent Nerve Fibers. — Nerve fibers that
carry impulses toward tr^e spinal cord or brain are called
afferent nerve fibers. Fibers that convey impulses from
the brain or spinal cord are efferent nerve fibers.

Cross-section of the Spinal Cord. — If a thin slice of
the spinal cord be made as shown in Fig. 25, 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.

Dorsal Septum

Dorsal or Sensor
Root

Ventral Fissure
Ventral or Motor Root

Fig. 25. Cross-section of Spinal Cord.

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. 26. 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.

Physiology.

Branched Processes

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

i. Its conducting power, by means of the white fibers
which make up the outer part of the cord. These fibers

may be regarded as connect-
ing 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.

Ganglions. — Masses of
nerve cells make up nerve
centers, or ganglions, 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. The gray matter
of the spinal cord is considered a collection of ganglions.

Reflex Action in a Sleeping Child. — If the sole of the foot of a sleep-
ing child is gently tickled, the foot will be drawn up. The child has no
sensation. The brain has nothing to do with it. It is purely reflex
action. A nerve impulse has gone to the spinal cord, and another
impulse has been sent out to make the needed movement. But some-
times the child may be half awake and the foot might be drawn up by
voluntary action. Let us take another case, with which nearly every
one is familiar, to show that the brain has nothing to do with reflex
action.

A Hen with its Head cut off. — Nearly everybody knows that after a
hen's head is cut off, it "flops" around for some time, and that fre-
quently when one takes hold of its feet to pick it up, it begins to struggle.
Now this also is reflex action of the spinal cord. And there can be no
doubt that the brain has nothing whatever to do with it.

Fig. 26. A Large Nerve Cell from the
Gray Matter of the Spinal Cord.

Nervous System. 43

r The Gray Matter of the Cord the Center of Reflex
Action. — In reflex action the current runs up the nerve
to the spinal cord. The gray matter of the central part of

Afferent Dorsal Root

Sensor Fiber

Skin

\

Motor Fiber \
Efferent *

Ventral Root

Fig. 27- Diagram of Reflex Action of the Spinal Cord.
(After Landois and Stirling.)

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 irritation.

The Parts Essential to Reflex Action of the Spinal
Cord: — i. 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.

Steps in Reflex Action. — In the above examples the
steps in order are : —

i. Stimulation of the nerve endings in the skin of the
foot. 2. Passage of nerve impulses up the afferent fibers
to the spinal cord. 3. Reception of the impulse by cells
of the gray matter in the cord. 4. Sending back nerve
impulses 5. Along efferent fibers to 6. Muscles which
shorten and move the foot.

44 Physiology.

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
such motions as winking when anything comes quickly

Nerve Cells Connected by Interlacing Nerve Network.

Afferent Nerve Fiber " « Efferent Nerve Flber

_ Muscle

Sensory

Epitheliur

(Skin)

Fig. 28. Parts used in Reflex Action.

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

Destination of Nerve Fibers. — The sciatic nerve (the
large nerve of the thigh, see Fig. 23) is composed of many
fibers. If this nerve is traced outward, it is found to be
continually subdividing and sending smaller 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.

Nervous System. 45

These fibers from the skin carry nerve impulses inward,
as those going to the muscles carry impulses outward.

Nerve Roots and their Functions. — Observations made
on animals, and accidents in the case of man, show that
all the fibers of the nerves that carry currents to the mus-
cles 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 sensation,
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 an electric shock, two effects
are produced : first, motion in the parts whose muscles are
supplied by the nerve ; second, sensation, which is referred
to the parts of the skin supplied by the branches of the
nerve. This double effect is because both sets of fibers in
the nerve have been stimulated, one set carrying currents
inward, the other outward.

Cramp. — Cramp is a spasmodic shortening of the mus-
cles, 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

46 Physiology.

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 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, there-
fore, are in the left half of the brain, and the right half of
the brain controls the left hand.

Nervous System compared to a Telegraph System. -

It is convenient to compare the nervous system to a tele-
graph system. Nerve impulses pass along the nerve fibers
as electric currents travel along the wires. The ganglions,
which receive and send impulses, are similar to the offices
which receive and send out electric currents. But there is
one important difference : in telegraphing, the same wire
is used, both for sending and receiving messages ; while
in the nervous system there are two sets of fibers, one for
incoming impulses and another for outgoing impulses.

Harmony in Muscle Action. — In throwing a stone a
number of muscles are used. 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
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
harmony. What the player is to the instrument, the brain
is to the body.

Effect of Alcohol on the Nerves. — Alcohol may, and
often does, cause inflammation of the nerves. This dis-
ease may be brought on by the so-called " moderate "

Nervous System. 47

drinking, as well as by drinking large quantities of alco-
holic liquor. The presence of such inflammation is indi- .
cated by pain or by paralysis. While inflammation of the
nerves may be due to other causes, it is said that alcohol
produces it as frequently as all other causes combined.

Alcohol retards Nerve Action. — Experiment shows that
alcohol diminishes the transmitting power of the nerves ;
that is, a nerve impulse does not travel as fast along a
nerve fiber after taking alcohol as before. " Alcohol makes
all the nervous processes slower, although they seem to
the person himself to be quicker than usual."- - BRUNTON.

Beer injures the Nerves. — " That the alcohol in half a
pint of beer, or a single glass of whiskey, lessens the
rapidity of nerve transmission, mental perception, acute-
ness of the special senses, and muscular strength, has
been abundantly demonstrated by the application of in-
struments of precision. That the same amount of alcohol
deludes man with the impression that he is stronger and
more active when he is actually doing less is a fact familiar
to all who have given attention to the subject. The only
rational conclusion, then, is that the degenerating influence
of alcohol upon man, physical and mental, commences
with the beginning of its use, and increases in proportion
to the quantity used and the length of time it is con-
tinued." • —Journal of Inebriety.

Temporary Loss of Muscular Power. — It may have hap-
pened 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.

48 Physiology.

The brain starts the nerve currents, and they run along
the nerve as far as the compressed part ; here they stop.
On account of external pressure the nerve has temporarily
lost its power of conducting nerve currents. 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.

Dependence of Nerves and Muscles. — But what beside
the nerve has been compressed ? 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
keeping up their activity ?

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

CHAPTER VI.
CIRCULATION OF THE BLOOD.

The Blood and its Work. — 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 know that loss of blood causes weakness, and may
soon cause death.

What kind of a substance is blood ? 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 children it beats faster.
The rate is increased by exercise, by heat, by food, and by
mental excitement.

The Heart Beat and the Pulse. — i. The heart beat may be felt at the
left of the breastbone. \

2. The pulse may be felt-at tbe wrist, in the neck beside the wind-
pipe, and in 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.

3. Let one or two pupils 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.

4. Let all count the pulse while sitting. Get the average of the
class.

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

6. Compare the pulse before and after meals.

49

Physiology.

The Shape of the Heart. — The heart is cone-shaped.
But the point or apex is down, and the big end, or base,
is up, so when we speak of the base of the heart we mean
the upper part, not the lower.

The Position of the Heart. — The base of the heart is
in the center of the chest, just back of the breastbone,
but the apex points downward and to the left (see Figs.
32 and 53).

To Head and Arms

Pre-caval Vein

Right Auricle

Pulmonary Artery
Left Auricle

Left Ventricl*

Apex

Fig. 29. The Heart, from the front.

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

The Covering of the Heart. — The heart is inclosed in a
loose-fitting bag, the pericardium. Within the pericardium
and around the heart is a small quantity of liquid, called
the pericardia I fluid.

The External Features of the Heart. — The larger part
of the heart is made up of 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.

Circulation of the Blood.

The line of division between the two ventricles is marked
by a groove, which runs obliquely along the front surface.
In this groove are blood tubes and usually some fat. (See
Figs. 29 and 30.)

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

Pre caval Vein

Right Pulmonary Artery

Right Pulmonary Veins

Post-caval Vein

Right Auricle

Fig. 30. The Heart, from behind.

The Valves of the Heart. — Between the auricles and the
ventricles are curtain-like valves (see Fig. 33), whose
upper edges are attached to the inner surface of the walls
at the upper margin of the ventricle. These flaps are
somewhat triangular, 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, make up the mitral valve. In the resting heart

52 Physiology.

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.

The Aur-vent Valves. — Since these valves are between
the auricles and the ventricles they are often called the
auriculo-ventricular valves. Nearly every one knows of the
town named Pen Mar on the line dividing Pennsylvania
from Maryland. The meaning of the name is clear. And
any one can tell where Texarkana must be. So for con-
venience we shorten auriculo-ventriculaj* to aur-vent, and
when speaking of the aur-vent valves we know, without
having to stop and think, that they are between the auricles
and ventricles.

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. As they are between the ventricles and
the arteries they are sometimes called the ventriculo-arterial
valves. And this may be shortened to vent-art valves.
(See Fig. 33-)

Dissection of the Heart. — No description (or even pictures) 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

Circulation of the Blood.

53

54 Physiology.

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 arises from the left ventricle. The
pulmonary artery springs from the right ventricle and
sends blood to the lungs. The pre-caval and the post-caval
veins enter the right auricle. The pulmonary veins, two
from each lung, enter the left auricle. (See Figs. 31 and 32.)

The Aorta. — The aorta is the largest artery in the body.
It arises from the base of the left ventricle and runs a
short distance toward the head, then it arches over and
runs toward the lower part of the body. The bend, above
the heart, is called the arch of the aorta. At the arch
branches are given off which supply the right and left
arms, and the right and left sides of the head. Beyond
the arch the aorta passes behind the heart and runs along
the backbone and passes through the diaphragm. Just
beyond the diaphragm it gives off branches to the liver,
stomach, intestine, pancreas, and spleen. ', It gives a
branch to each kidney, and finally divides into two large
branches to the lower limbs. Numerous small branches
are sent to other organs; in short, the "aorta supplies
blood to every organ of the body except the lungs. (See
Figs. 29, 30, and 32.)

The Caval Veins. — There are two caval veins, the pre-
caval and the post-caval. The pre-caval brings the dark
blood from the head and arms. It has four main branches,
one from each side of the neck, the jugular veins ; and
one from each arm, the subclavian veins. These four

Circulation of the Blood.

55

Vein

Vein

Fig. 32. Distribution of Arteries and Vein*.

56 Physiology.

unite to form the pre-caval vein, which runs downward and
enters the right auricle. The post-caval vein begins in the
lower part of the abdomen, by the union of the two large
veins from the lower limbs. As it runs upward, it receives
branches from the kidneys and from the liver; it passes
through the diaphragm and enters the right auricle. (See
Figs. 29, 30, and 32.)

The Distribution of the Arteries and Veins. — The organs
of the body receive a supply of blood in proportion to
their size and activity. The artery supplying the blood to
any organ and the vein which returns it usually lie side
by side (see Fig. 32). The larger arteries are usually
deep-seated and in protected places.

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 heart contracts 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 aur-vent are open, and their flaps hang
loosely beside the walls of the ventricles. The blood,
therefore, instead of stopping in the auricles, passes on
into the ventricles. As the ventricle fills, the aur-vent
valves float up, as seen in the experiment of pouring water
into the ventricle. (See right-hand part of Fig. 33.)

The Contraction of the Auricle. — When the ventricle is
full, but not stretched, and the auricle partly full, the auricle

Circulation of the Blood.

57

suddenly contracts, thus forcing more blood into the ven-
tricle, and distending it. At the same time the aur-vent
valves, whicli 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 muscles to which
the cords are attached.

Fig- 33. Diagram of the Heart, showing the Action of the Valves.

The Contraction of the Ventricle. — Next comes the con-
traction of the ventricle, slower, but more powerful than
that of the auricle. As the walls of fhe ventricle are
drawn together, they press upon the blood. It cannot go
back into the auricles, for the more- it presses against the
aur-vent valves, the more tightly they are closed. The
vent-art (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 vent-art
valves are forced open, and 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

58 Physiology.

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 is 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 makes a slight suction,
so the blood is in part drawn into the ventricle. During
the remainder of the pause the blood accumulates in the
ventricle and auricle till the auricle again contracts and
the action is repeated. This is true of both halves of the
heart, which work at the same time, the two auricles con-
tracting together, and then the two ventricles. The rjght
heart pumps dark blood while the left heart pumps bright
blood. The left ventricle is thicker walled and stronger
than the right.

Work and Rest of the Heart — Immediately after the
contraction of the auricle comes the contraction of the
ventricle. The pause is as long as the contractions of
the auricle and ventricle put • together. In other words,
the heart is resting half the time. It is often said that the
heart never rests. Its periods of work and rest are so short
and follow each other in such rapid succession that it is
hard for us to realize that there is a resting time between
each two beats, and that this resting time is as long as the
working time.

Overworking the Heart. — During violent exercise the
heart is likely to be overworked trying to pump blood
enough to supply the overworked muscles. One very
important part of training an athlete is to strengthen the

Circulation of the Blood. 59

heart by regular exercise so it will not tire out in pumping
the blood to the muscles during an athletic contest, such as
a foot race or boat race.

The Work of the Auricle. — The auricle has three func-
tions: (i) to complete the filling of the ventricle; (2) to
complete the closing of the aur-vent valves ; (3) to act as a
reservoir for the blood entering the auricle while the ven-
tricle is contracting, that is, while the aur-vent valves are
closed.

s The Work of the Ventricle. — The contraction of each
ventricle forces the blood around to the ventricle of the
other side of the heart.

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

1. A short, sharp sound made by the closing of the
semilunar 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 aur-vent valves.

Action of the Large Arteries. — The arteries have elastic
tissue in their walls. When the blood is forced into them,
they are stretched. As soon as the ventricle ceases to con-
tract, 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 into the ventricles, for it
fills the pockets of the semilunar valves, and closes them
with a click. The blood therefore flows along the arteries,
through the pulmonary artery to the lungs, and through

60 Physiology.

the aorta and its branches to all the other parts of the
body.

The elastic reaction of the arteries thus helps to make
steady the flow of blood, which is jerky as it leaves the
heart.

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, demands much
more blood than does such an inactive organ as a bone.
Further, the working tissues, such as the brain and mus-
cles, need a great deal more blood while they are at work
than when they are resting. An organ needing a large
supply of blood all the time 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 leading

to the parts. In the walls of these

Nucleus . , . i rn

arteries are plain muscle fibers.
They are arranged circularly in the

isolated Fibers walls of the arteries (see Fig. 36).
These fibers have, like all muscle

Fibers joined 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 it. When the muscle

Fig. 34. Plain Muscle Fibers. _. .,

fibers relax, the artery widens, and
allows more blood to pass through it.

Illustration of the Action of Muscles in Arterial Walls. — To illus-
trate the action of the muscles in the walls of an artery, let the water

Circulation of the Blood.

61

run through a hose or large rubber tube. Now, if a row of persons take
hold of this tube, the grip of their hands is like that of the muscles.

Connective Tissue

Endothelium

Muscle Fiber

Fig. 35. Plain Muscle Fiber. Separate and in Wall of Artery.

Endothelium —

When the hands tighten their grip, the size of the hole in the tube is
made smaller, and less water is allowed to flow through it. When 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 intern^ Elastic
small, thin-walled rubber tube and
wind a red thread around it. Now, if Circular Mus_
the thread could shorten, it would cle Fibers
make the tube smaller.

The Action of Plain and Striated
Muscles Fibers compared. — These
plain muscle 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. 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 blood goes to the muscles of the legs when we walk, more to

The Outer
Coat

Fig. 36. Coats of a Small Artery.

62

Physiology.

the brain when we are studying, to the digestive organs after eating, etc.
The plain muscle fibers shorten at a much slower rate than the striated

fibers. They are also slower in relaxing.

Circulation of Blood in the Web of a
Frog's Foot. — This is a beautiful sight.
Here you may see, under the microscope,
the active streams of blood. Small ar-
teries divide to form capillaries, and capil-
laries unite again to form the small veins.
In the narrow capillaries the corpuscles
may be seen moving along in single file,
with barely width enough to pass through
the slender tube. If you see this in the
frog's foot, you can understand how the
blood flows through all the active tissues
of your body. (See Figs. 37 and 39.)

the Capillaries. — The arteries

Fig. 37. "Capillary Blood Tubes in
the Web of a Frog's Foot, under
a Low Power of a Microscope."
From Hall's " Physiology."

The Blood Flow in

divide and subdivide, and surface view

become capillaries, which
have connecting branches,
forming a close network
of tiny thin-walled tubes.
These penetrate nearly
every tissue 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 Fig. 38.
work of the heart and ar-
teries is to keep a slow and steady flow of blood through
the capillaries, that the tissues may be constantly supplied.

The Veins. — The capillaries, after penetrating the tis-
sues, unite again to form small veins, which in turn unite
to form larger ones, till finally two great veins, the pre-

Longitudinal Section

Capillaries, composed of a Single
Layer of Cells.

Circulation of the Blood. 63

caval from the upper and post-caval from the lower part of
the body, return the blood to the heart. The veins, like

Walls of Capillaries

Fig. 39. Part of Frog's Web (highly magnified).

the arteries, are smooth inside and elastic (though less
elastic than the arteries). They are thinner-walled than
the arteries (see Fig. 40) and collapse when empty,

Physiology.

vein

Artery

Fig. 40

whereas the larger arteries stand open, after they are
emptied of blood. There are many cross-branches unit-

ing veins, so that if the flow
is stopped in one vein, the
blood can take a " cross-
road" into another large

. „, .

vein. Inis cross-branching
may usually be seen on the
back of the hand.

The Valves in the Veins.
— The only valves in the
arteries are those at the be-
Small Artery ginning of the aorta and pul-
monary artery. Many of the

veins have similar pocket-like valves though less strong
than those of the arteries. They are usually in pairs, but
sometimes single or in threes. They all have the mouths
of the pockets toward the heart, so that the blood flows
freely toward the heart, but is kept from flowing the other
way on account of the filling
of the valves by the back
pressure of the blood. When
the blood is flowing through
the veins toward the heart,
the valves lie against the walls
of the veins (see Fig. 41).

Illustration of Valves in the Veins.
— Make a cloth tube (or take the Open Shut

lining of a boy's coat sleeve) and Fig. 41. Vaives of the Veins.

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. This shows how the valves fill
and block the passage when there is back pressure of the blood.

Circulation of the Blood. 65

Evidences of Valves in Our Veins. — i. 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.

2. Stroke a vein toward the body, and the blood is pushed a/ong
without resistance.

3. 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.

Effect of Pressure on the Veins. — Since the valves in
the veins open toward the heart, any alternating pressure
on the veins helps to push the blood on toward the heart.
The valves are most numerous in the veins near the sur-
face and in the veins of the muscles. The pressure of the
muscles during their action (thickening while shortening)
produces pressure on the veins ; and as the muscles act
for a short time only, and then relax, this alternate com-
pression and release aids very much in moving the blood
on toward the heart.

How the Muscles help the Heart. — This effect is greater
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

66 Physiology.

amount of work to do, as when one is using a large num-
ber 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 and Capillaries. — The
blood flows rapidly in the arteries, slowly 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. Hence as the blood flows on it is continu-
ally entering a wider and wider channel ; for if all the cap-
illaries fed by the aorta were united they would make a
tube several hundred times as large as the aorta.

The Flow of the Blood compared with the Current of a
Stream. — If we walk along a stream, we see that the
channel keeps changing 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
comparatively narrow artery is swift. In the capillaries,
although any single 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 num-
ber of channels running past many islands.

The Flow of Blood in the Veins. — When two veins unite,
the one vein they form is not quite equal to the sum of the
two ; so when the blood gathers in the veins it is really en-
tering a narrower channel, and it flows faster. And it
keeps gaining in speed till it reaches the heart.

Flow in Arteries and Veins compared. — Although the
blood keeps flowing fast as it gets nearer the heart in the

Circulation of the Blood.

caval veins, it does not go as fast as when it left the heart
in the aorta, for there are two caval veins each about as
large as the aorta.

Pulmonary Vein —

Left Auricle

Left Ventricle

Aorta

Digestive Tube

Pulmonary Artery

Lymph Vein

Right Auricle

•• Right Ventricle
Caval Vein

r-y&f-tt Liver

Fig. 42. Plan of Circulation. (Back View.)

Rate of Flow in Arteries, Capillaries, and Veins. — The

blood flows rapidly in the arteries, slower in the veins, and
slowest in the capillaries.

Effects of Alcohol on the Circulation. — The continued
use of alcoholic liquors frequently causes what is known
as "fatty degeneration" of the heart. The muscle cells
are more or less replaced by fatty tissue, thus greatly

68 Physiology.

weakening the heart. Experiments show that the first
effect of alcohol on the heart is to weaken the force of
the beat, though the rate is usually quickened. This indi-
cates a deadening effect, such as is often seen in disease.
Frequently the approach of death is indicated by a quick-
ened but enfeebled heart-beat.

Alcohol Overworks the Heart. — " Even what is called
moderate drinking has a greater share than is generally
supposed in not only increasing heart diseases, in cases
where they already exist, but also in inducing their develop-
ment in those constitutionally and hereditarily predisposed
to become affected by them." — Dr. George Harley, Lon-
don Lancet, 1888.

Alcohol Exhausts the Heart. — " The action of spirits
on the heart in a number of experiments yielded startling
results. The number of beats was increased, usually run-
ning up eight or ten a minute, but always dropping down
below the normal level. If at eighty in health, the alco-
holic impulse would send it up to ninety in the first hour,
but the next hour it would drop to seventy, usually going
below the health level as far as it went above." — T. D.
Crothers, M.D.

Alcohol Injures the Structure of the Heart. — " The
heart from continued over-action becomes dilated, and its
valves relaxed. The membranous structures which en-
velop the organ are thickened, rendered cartilaginous, and
occasionally calcareous. The valves, which consist of folds
of membrane, lose their suppleness, and valvular disease
has come to stay. These derangements are likely to cause
death from sudden failure of the heart itself. There is
always danger of the heart failing to do its work, for alco-
hol has made it inefficient." — H. H. McMichael, M.D.

Circulation of the Blood. 69

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 separate streams are flowing through it.

5. Valves allow the blood to flow through the heart in one direc-
tion, but prevent its return.

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

7. The heart works about 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 jerky, in the capillaries
slow and steady.

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 alternating 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 aid circulation ?

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

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

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

6. Trace a drop of blood from the tip of a finger around the circuit
to the same point again.

7. Does the pulse at the wrist occur at exactly the same time as at
the temple ? Or at the same time as the heart-beat ?

CHAPTER VII.
CONTROL OF CIRCULATION.

Circulation controlled by the Nervous System. — We
know that fear often causes the face to turn pale and that
shame makes it red. Certain emotions also
quicken or retard the action of the heart.
Great grief or joy has caused sudden 9eath
by stopping the action of the heart.

Nervous Control Involuntary.

— But this control is not volun-
tary. The will has nothing di-
rectly to do with it. We often wish to keep
from getting red in the face when embar-
rassed, but cannot prevent it. Neither can
we keep from turning pale through fright
or pain. We cannot keep the heart from
beating faster when we are excited. Instead
of being controlled by the brain, circulation
is chiefly under the control of a special part
of the nervous system, known as the Sym-
pathetic Nervous System.

The Sympathetic Nervous System. — The
sympathetic nervous system consists of two
rows of ganglions in the body cavity, one p.g 43 Ront Vje^
along each side of the spinal column, re- of spinal cord with

. . , -'" .. Sympathetic Gang-

ceivmg branches from the spinal nerves, nons of one side.

70

Carotid Plexus

Superior Cervical Ganglio

Middle Cervical Ganglion

Pharyngeal Brrnches

Cardiac Branches

Deep Cardiac Plexus,

Superficial Cardiac Plexys

Solar Plexus

Aortic Plexus

Lumbar Ganglion

Fig. 44. Vertical Section of Body, showing Sympathetic Nerves and Ganglions of Right
Side and their Connection with the Cerebro-spinal Nerves.

72 Physiology.

and sending branches to the heart and lungs in the chest,
and to the liver, stomach, and other organs in the abdomen.
In many places these nerves form a thick network called
a plexus. One very large plexus on the dorsal surface of
the stomach is called the solar plexus. (See Fig. 44.)

Regulation of the Size of the Arteries. — In the last chap-
ter we learned that in the walls of the arteries are muscle

fibers having a ring-like

Spinal Cord

arrangement. When these

muscle fibers shorten they

i ^i

make the artery narrower,
and less blood can flow
through it. When the
muscle fibers relax, they

Fig. 45. ideal Cross-section of the Nervous lengthen : the artery be-

System. (After Landois and Stirling.) •'

comes wider, and more

blood flows through it. Now these muscle fibers are .under
the control of the sympathetic nerves. The sympathetic
nerves, therefore, regulate the amount of blood that goes
to every organ.

Blushing. — The sudden reddening of the face means
that more blood is flowing through the skin of .the face.
The arteries by which blood reaches the face have quickly
widened, and this is because the muscle fibers in the walls
of the arteries have suddenly relaxed. To go still further
back in the explanation, some emotion has started nerve
currents which travel along the fibers of the sympathetic
nerves and caused the arteries to widen.

Sudden Pallor. — On the other hand, if the muscle fibers
in the walls of the arteries suddenly shorten, the face will
turn pale, because less blood flows in the skin of the face.
Such a change, as before, is due to the nerve currents

Control of Circulation.

73

brought by the sympathetic nerves. Of course the face
may turn pale as the result of the stopping, or checking,
of the action of the heart, as in ordinary fainting.

Ordinary Changes in Blood Flow. — Without going to the
extreme of pallor and blushing, the color of the face varies,
under the control of the sympathetic nerves. All the or-
gans of the body receive now more, now less, blood, accord-
ing as they need it. And all this variation in blood supply
is regulated by the sympathetic nervous system.

Effect of Exercise on" the Size of the Arteries. — When
the muscles work, of course they need more blood. To
give them more blood the
arteries widen. When one
exercising actively, the

Symoathetic Nerve Chains
GRAY \

IATTEP

IS

muscles take so much blood
that we should not

Dorsal Root

expect the brain or spmai Nerve — _
the digestive organs Ventral Root
to do much work, for there
is only a certain amount of
blood in the body. Hence if
one organ, or set of organs,

£etS more blood, the Other Fig. 46. Relation of Spinal Cord and

Sympathetic Nervous System.

organs must, for the time,

receive less. Therefore we see why we should rest after

eating, both from muscular as well as from mental work.

How the Heart is made to Beat Faster. — When many
large muscles are at work, it is not enough merely to widen
the arteries. This would allow more blood to go to them,
but would not send them as much as they need. The
heart must beat faster, or with more force, or both. And
the heart is made to beat faster and stronger by the nerve

74

Physiology.

currents that it receives through the sympathetic nerves.
When we exercise actively, the fact that the muscles need
more blood is telegraphed both to
the heart and to the arteries leading
to the muscles of the arteries, and
they are regulated accordingly.

How the Heart is made to Beat
Slower. — The slowing of the beat of
the heart is due to other nerves, not
belonging to the sympathetic system.
The vagus nerves are a pair
of cranial nerves. They arise
from the sides of the spinal
bulb, at the base of the brain,
and, passing downward, give
branches to the gullet, stomach,
lungs, and . heart. The distri-
bution of the vagus nerves is
shown in Fig. 47. Nerve cur-
rents reaching the heart through the
vagus nerves make it beat slower,
and if the current is strong enough,
as in case of a severe blow over the
stomach, may, by reflex action, stop Flgf- 47'
the heart.

Lungs

Heart

Liver

Stomach

of vagus

Influence of Gravity on Circulation. — Although the heart
pumps the blood around through the body independent of
the force of gravity, yet the circulation is influenced by this
force. For instance, a person who has fainted should ,be
laid flat on his back, that the heart may more easily drive
blood to the brain. A sore hand feels less pain if held up,
as in a sling, than when hanging by the side, and a sprained

Control .of Circulation. 75

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
the pupils 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 projection of the veins.

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

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

Clothing and Circulation. — No part of the clothing
should be tight enough to interfere with the circulation.
Such interference is perhaps most frequent in our foot
wear. In cold weather tight shoes keep the feet cold
and may result in their freezing, while the same thickness
of covering, if loose, would be comfortable. Men often
wear hats too tight ; this probably leads to baldness. Tight
garters sometimes hinder circulation and cause cold feet.

Congestion. — Congestion is an unnatural collection of
blood in any part or organ. This may be merely for a
short time, and no serious harm results from it. But if it
is long continued, it may do great harm.

Inflammation. — If the congestion becomes permanent,
we call it inflammation. That is, it is a permanent over-
supply of blood, which may bring many bad results.
There is usually redness, pain, and often swelling. We
have all seen such a condition around a boil or a wound.

Use of Mustard Plaster. — Mustard applied to the skin
causes irritation. It makes the skin red. This means that
more blood is drawn into the skin through the action of

76 Physiology.

the sympathetic nerves on the muscles in the walls of the
arteries. If there is more blood in the skin, there must be
less somewhere else at the same time. Now this is what
makes a mustard plaster useful. When there is congestion
or inflammation in some internal organ, a mustard plaster
applied to the outside draws away some of the blood and
thus affords relief to the congested part.

The Hot Foot Bath. — When one has a cold, a hot foot
bath relaxes the arteries of the feet. This is a good means
of drawing the blood away from internal organs, and often
saves the person from serious or even fatal results from
a bad cold.

Effect of Alcohol on Circulation in the Skin. — The warm
and flushed condition of the skin which follows the drink-
ing of alcoholic fluids is due to interference with the nerve
center that has control of the muscles in the walls of the
arteries leading to the skin : 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 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 becomes permanent. The circulation in
the whites of the eyes may be affected, making them
"bloodshot."

General Effect of Alcohol on Circulation. — The general
effect of alcohol on the circulation is well illustrated by
the effect on the skin. The muscles in the walls of the
arteries relax because of the paralyzing effect of alcohol
on the nerve centers controlling these muscles. Every-
where in the body alcohol tends to cause a flushed con-
dition. To tell all about this would be to take up digestion,

Control of Circulation. 77

respiration, muscle action, brain action, etc. Hence the
effects on each of these processes will be taken up in the
separate chapters.

Effect of Alcohol on the Heart. — The effect of alcohol
on the heart is through the nervous system, which controls
the heart. The heart is held in check all the time by the
action of the vagus nerves. Alcohol more or less paralyzes
these nerves, so they can no longer restrain the heart.
Hence it at once begins to beat too rapidly. The heart is
like a horse that always wants to run away. Just as soon
as the brake is taken off it jumps into a run. A team of
vicious horses may be held in so long as the driver retains
his seat and his strength. But if the driver falls from his
seat, they immediately plunge into a wild gallop. Alcohol
paralyzes the restraining driver of the heart and arteries,
and they at once run wild.

Summary. — i. Circulation is controlled by the nervous system.

2. This control is involuntary.

3. The sympathetic nervous system consists of two rows of ganglions
in the body cavity along each side of the spinal cord.

4. The sympathetic system regulates the size of the arteries, and by
this means regulates the amount of blood going to any organ.

5. The heart may be made to beat faster through the sympathetic
nervous system. This may come through reflex action and be caused
by emotions.

6. The heart may be made to beat slower through the vagus nerves.

7. Alcohol may cause the arteries of the face to dilate and thus make
the face become red.

8. Alcohol often makes the heart beat faster; but soon it beats more
slowly than before alcohol was taken.

Questions. — i . Why do the feet easily get cold while studying ?

2. What makes the hands grow red and puff up after snowballing ?

3. Why does light exercise before retiring make one sleep better ?

4. How does the application of ice, or cold water, relieve headache ?

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

CHAPTER VIII.
THE BLOOD AND THE LYMPH.

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 drop of blood. Put a very 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. Although in the mass they give the blood
a red appearance, when seen singly they are faint yellow-
ish red. In shape they are seen to be circular disks,
hollowed on each side like a sunken biscuit. These cor-
puscles tend to gather side by side, in rolls, like coins.
Each colored corpuscle is a cell without a nucleus.

The Colorless Corpuscles. — In the open spaces between
the rolls of colored corpuscles may occasionally be found
some spherical corpuscles. They are often called the
white corpuscles. The colorless corpuscles are very numer-

•78

The Blood and the Lymph.

79

ous around a wound. They seem to help in repairing
tissues.

White Corpuscles

HIGHLY MAGNIFIED

White Corpuscle ...:.:

Red Corpuscles
in Rolls

MODERATELY MAGNIFIED
Fig. 48. Red and White Corpuscles of the Blood.

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 tis-
sues on their way out of the body.

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

8o Physiology.

color, but a thin layer of the same jelly, as when one takes
a spoonful on a plate, has a pale color, more yellowish.
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. The hemoglobin in the corpuscles is
the chief agent in picking up the oxygen from the air in
the lungs and carrying 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. The liquid
that afterward separates from the clot is the serum, and
differs from the plasma only in the absence of the fibrin,
which is exceedingly*' small in quantity, though of great
importance in its action. Coagulation often serves to stop
the flow of blood from wounds.

Fibrin. — If freshly drawn blood be stirred rapidly with
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.

Watching Coagulation. — If you have a slight cut on the
hand, it will pay to watch the changes in the blood. First
it is a red liquid. Then it becomes jelly-like. Then a
clear or yellowish liquid comes out ; this is serum. The
serum evaporates and the dried clot forms a scab.

The Blood and the Lymph. 81

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

[Plasma . . . j Serum ; 1

Liquid Blood | ( Fibrin | I Coagulated Blood.

Corpuscles

\

" Black-and-blue " Spots. — A bruise often breaks some
of the capillaries without breaking the skin. Blood escapes
into the spaces in the skin or under it. This blood clots,
and the dark color shows through the skin. This clotted
blood is gradually absorbed and the color disappears.

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.

Quantity of Blood in Different Organs. — 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
crevices in the connective tissue of the different parts of
the body.

The Lymph Tubes. — Opening out of the lymph spaces
are irregular passage-ways called lymph capillaries, and

82 Physiology.

these lymph capillaries are continuous with larger but
still thin-walled lymph tubes, called lymph veins. But,
unlike the blood veins, the lymph veins do not gradually
increase in size by uniting. They suddenly form a large
tube, the receptacle of the chyle, beginning in the upper
part of the abdomen. (See Figs. 50 and 81.)

The Main Lymph Duct. — 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." (See Figs. 50 and 81.)

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.

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.
They may be felt in the armpits, in the groins, and some-
times in the neck. Lymph contains corpuscles which are
considered the same as the colorless blood corpuscles. It

The Blood and the Lymph.

is thought that these corpuscles are formed in the lymphatic
glands. In a disease called scrofula the lymphatic glands
become swollen. (See Figs. 49 and 81.)

- 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 our bodies the

flow of lymph is largely aided by any

pressure 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 muscles 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 very much slower than that in

the blood veins.

Relations of Blood Flow and Lymph
Flow. — While the blood leaves the left
ventricle by one tube, the aorta, it re-
turns to the right auricle, not merely
by the two caval veins, but a part of
the blood (i.e. of the liquid part of it)
does not return by blood veins, but hav-
ing left the blood system proper through
the thin walls of the capillaries, is
brought back by the lymph veins, which,
however, join the blood veins just before
they empty into the heart. There is
only one set of distributing tubes, but
there are two sets of collecting or re-
turning tubes.

Fig. 49. Lymphatic
Tubes of the Surface
of the Arm. Lymph
Glands at a, b, c, and d

84

Physiology.

The Lymph. — Lymph is a clear liquid. It is more
watery than the blood plasma, but contains a share of all

Left Jugular Vei

Mouth of
Lymph Vein —
Left Subcla- _
vian Vein

^\- Right Lymph Vein

..Right Subclavian
Vein

....Pre-caval Vein

Post-caval Vein

Main Lymph Vein
(Thoracic Duct)

Lymph Capillaries

— Blood Capillaries

Fig. 50. Diagram of the Circulation of Blood and Lymph (Back View).

its nourishing substances. Lymph may be defined as
" diluted blood minus red corpuscles" The blood proper
never reaches the tissues.

The Blood and the Lymph.

Lymph

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
there is connective tissue in
all the organs of the body), capillary
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.

Oxygen

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.

Food

Muscle
' Fiber

Carbon
Dioxid

— Water

Other
Wastes

Fig. 51. Relation of Blood and Muscle.
(Lymph being Middleman.)

Lymph Cavities or Serous Cavities. — We have noticed
the pericardial liquid (page 50). There is also a small
quantity of similar liquid around the lungs in the pleural
cavities, and in the abdominal 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.

86 Physiology.

Hypodermic Injections. — When it is desirable that a
medicine act on the body very quickly, it is sometimes
introduced under the skin. This is done by means of a
hypodermic syringe, which is a syringe with a slender,
needle-shaped nozzle. By means of this the medicine is
injected into the tissues under the skin. Here it is taken
up by the lymph and is quickly carried through the system
and acts on the cells of the body. If the same medicine
were taken into the stomach, it would require some time
for it to be absorbed and carried into the tissues. Hence
time is gained. We can see how much advantage there is
in this way of giving medicine when the physician wishes
to stop severe pain.

The Spleen. — The spleen is a flattish red body at the
left end of the stomach. There is an active circulation of
blood in it, and it is supposed to form the colored blood
corpuscles. It is often called a blood gland.

Effect of Alcohol on the Blood. — Experimenters have
reported finding various changes in the blood as a result
of the action of alcohol. Some have found that alcohol
diminishes the hemoglobin of the blood ; others have found
that it diminishes the alkalinity of the blood. The effect
of reducing the hemoglobin would render the blood less
capable of taking up oxygen. The effect of making the
blood less alkaline would be to make it less able to feed
the tissues and remove waste. In this state there is an
increase in the amount of uric acid found circulating in
the blood. It is thought that the oxygen used in oxidizing
the alcohol leaves not enough for the necessary oxidations
by which harmful waste substances like uric acid are
changed to others less harmful before they are thrown
out.

The Blood and the Lymph. 87

Alcohol a Poison. — " The introduction of alcohol into
healthy blood can do nothing but mischief. No one who
is familiar with the action of poisons upon the living ani-
mal body has the smallest hesitation in saying that alcohol
is a poison." — W. B. Carpenter.

A poison is any substance whose nature it is when ab-
sorbed into the blood to injure health or destroy life.*

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

2. The color of blood is given by a substance, called hemoglobin, in
the colored corpuscles.

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

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

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

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

Questions. — i. What is blood poisoning ?

2. Which is heavier, blood or water ?

3. Does it help a sick person to bleed him ?

4. What is meant by good blood ? Bad blood ?

5. What is meant by good humored ? Bad humored ?

6. Does the blood remain the same from day to day ? Or even from
hour to hour ?

* See Taylor's "Treatise on Poisons," page 18, footnote.

CHAPTER IX.
EXTERNAL RESPIRATION.

The Close Relation between Circulation and Respiration.
— Is it not a very striking fact that we breathe once for
every four heart beats ? And that whatever quickens the
breathing also quickens the heart so that the two always

keep in almost the
same ratio? Let us
try to learn why this
is so.

The Organs of Res-
piration. — i. The

lungs and air tubes.
2. The organs which
increase and dimin-
ish the size of the
chest, chief among
which are the dia-
phragm and the mus-
cles acting on the
ribs.

Fig. 52.

The Trachea and Bronchial Tubes, showing
Two Clusters of Air Sacs.

External Features
of the Lungs. — The lungs are of a pinkish color; they are
very elastic, soft, smooth, and moist.

The Air Tubes. — The windpipe, or trachea, has in its
walls rings of gristle or cartilage, which keep the tube
always open. These rings of cartilage are not complete

External Respiration,

89

3. Left Auriculo-Ventricular Orifice

4. Right Auriculo-Ventricular Orifice

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

1. Pulmonary Orifice

2. Aortic Orifice

Fig. 53. Front View of the Thorax. The Ribs and Breastbone are represented in
Relation to the Lungs, Heart, and other Internal Organs

9°

Physiology.

rings, but are C-shaped. As the windpipe branches (bron-
chi) into the two lungs, the cartilages continue in the
smaller branches which extend into every part of the lungs.

The Internal Structure of the Lungs. — The lungs are
full of small cavities, like a loaf of light bread. The small
cavities are called air sacs or air vesicles, and each air sac
communicates with the end of one of the branches of an
air tube, through which air comes into and goes out of
every air sac. The air sacs are very thin walled, and
around the sacs are networks of the fine blood tubes called
capillaries.

Elastic Tissue in the Lungs. — The air sacs and air tubes
and their surrounding blood tubes are bound together by
elastic tissue, which fills up most of the space between them.

The Mucous Membrane. — The lining of the trachea is
a mucous membrane. It pours out on its surface a sub-
stance somewhat
like white of egg,
called mucus. This
keeps the air moist,
and catches parti-
cles of dust that are
in the inspired air.

Fig. 54. Ciliated Cells lining the Air Tubes (x 300). -pi • ,

slow current of mucus toward the throat, whence it is, from
time to time, hawked up.

Ciiiums. — This current of mucus is caused by the ciii-
ums projecting from the lining cells of the trachea. They
are little hairlike projections, in countless numbers, like a
field of grass, each cilium having the power of bending
back and forth, making a quick stroke toward the throat,
then a slower recover stroke. Thus the united wavelike

External Respiration. 9 1

action of the myriads of lashing ciliums paddles the mucus
headward.

The Pleura. — The outside of each lung is covered by a
thin membrane, the pleura, which completely surrounds it,
except at the root of the lung, where the bronchus and
blood tubes enter. Here the pleura turns toward and
becomes attached to the inner wall of the chest, forming
its lining (still called the pleura), and below passes over

Trachea

Pleural Space
(Exaggerated)

Chest Wall

Pleura

Fig. 55. Diagram of the Lungs and Pleuras.

the upper surface of the diaphragm. The lung is thus
free, except at its root, where the air and blood tubes
enter. A very small quantity of liquid moistens the sur-
faces of the pleuras 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 dis-
tended enough to fill the chest cavity, these two surfaces
are always in contact.

Pleurisy. — Pleurisy is an inflammation of the pleura.
In breathing there is pain from friction or adhesion of the
pleuras of the lungs and chest wall.

92

Physiology.

Pneumonia. — Pneumonia is inflammation of the lungs.
It was formerly called "lung fever." It is due to bacteria.

The Diaphragm. — The diaphragm is a thin muscle mak-
ing a complete partition between the abdominal cavity and
the chest cavity. It is convex above and concave below
where it fits over the liver and stomach. Its front edge is
attached to the inside of the chest wall about opposite the
lower end of the breastbone. Its general position is shown
in Figs. 53, 55, and 58.

Triangularis Sterni
Internal Mammary Vessels \

Left Phrenic
Nerve

Pleura
Pulmonalis

Pleura Costal!

Mediastinum

( Sympathetic Nerve

Vena Azygos Major )

Posterior

I Thoracic Duct Pneumogastric Nerves)

Fig. 56. A Cross-section of the Chest, showing the Heart, Lungs, and Blood Tubes.

To show the Action of the Diaphragm and Lungs. — MATERIAL. —
Bell jar with stopper, sheet of rubber (such as used by dentists) large

External Respiration.

93

enough to cover the mouth of the jar, toy rubber balloon, cork (rubber
preferred), glass tube, cotton string, collar button.

PREPARATION. — Lay the collar button on the center of the sheet of
rubber, double the rubber over it, stretching the rubber strongly over
the head of the button, and tie the head firmly in its place. Stretch
the sheet of rubber over the base of the jar with the base of the
button on the outside, and fasten with string. Bore a hole in the cork,
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*

CILIA

.BRONCHIAL TUBE.

Fig. 57. Minute Structure of the Lungs, showing Air Sacs and Capillaries.

EXPERIMENT i. — Insert the balloon and tube into the jar, inflate
the balloon, and while it is inflated tightly cork the jar. If all the parts
fit well, the balloon should now remain inflated, and the rubber which
represents the diaphragm will be arched upward.

EXPERIMENT 2. — Pull the diaphragm down, using the base of the
collar button 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 diaphragm. On releasing the diaphragm, it springs
upward, and the balloon becomes smaller, 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 is 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

94

Physiology.

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
bottom 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.

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

. . . . Increased Air
Space

Inspiration Expiration

Fig. 58. Sections of the Body in 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 raise the ribs.

Work of the Diaphragm in Inspiration. — The diaphragm
is a muscle, and when its fibers shorten, the diaphragm is
pulled down. In moving down it presses on the abdomi-
nal organs, and makes the abdomen protrude forward and
sideways. This lowering of the diaphragm increases the

External Respiration. 95

space in the chest. Air, from the outside, enters through
the trachea, presses on the inside of the elastic lungs, and
makes their bases extend, following the diaphragm in its
descent. The bases of the lungs remain in contact with
the upper surface of the diaphragm all the time.

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

Effort required in Depressing the Diaphragm. — Inspira-
tion requires considerable effort, because the diaphragm
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 sooa 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 front ends of the
bony parts of the ribs with the breastbone (see Fig. 6) are
slightly bent. When the muscles relax, the elasticity of
the rib cartilages makes the ribs spring back to their
former position, thus reducing the chest to its former
width.

Expiration Easy. — Thus we see why expiration- jjs« easy ;
in fact, "does itself" (in ordinary respiration) by elastic
reactions. But inspiration is harder than it would be if it

96 Physiology.

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 rib 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 use
more force 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 ^tored energy
shuts the door while we pass on. We can better afford to
expend 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.

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

External Respiration. 97

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.

Abdominal and Thoracic Respiration. — The main part of
respiration is performed by the diaphragm, and is there-
fore called diaphragmatic or abdominal breathing. Breath-
ing by means of the chest walls is called thoracic, or costal
breathing.

The Rate of Respiration. — Adults breathe about seven-
teen or eighteen times a minute, or about one breath to
four heart beats. The rate is increased by exercise, tem-
perature, digestion, excitement, age, etc.

Special Forms of Breathing. — Coughing is a forcible
expiration, usually directed through the mouth, and for the
purpose of getting rid of some irritating substance. In
sneezing there is first a deep inspiration, and then the air
is forced out, chiefly through the nose. Sneezing may be
prevented by pressing firmly on the upper lip. Hiccuping
is sudden inspiration, produced by a jerky action of the
diaphragm, accompanied by a sudden closing of the en-
trance to the windpipe. In case of choking it is well to
hold the head well forward, and perhaps downward. A
smart slap between the shoulders sometimes helps dislodge

98 Physiology.

anything stuck in the throat, and it may be necessary to
hold a child with the head downward. There are various

-

COMPLEMENT AL 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.
AIR THAT CAN BE BUT IS SELDOM DRIVEN OUT.

RESIDUAL AIR.

100 CUBIC INCHES.
AIR THAT CANNOT BE DRIVEN OUT.

Fig. 59. Diagram of Lung Capacity.

*•§

\- CL ^i

qj C\j

1

"^

other peculiar forms of respiration, such as yawning, sniff-
ing, laughing, etc., which you can explain after watching
and thinking about them.

External Respiration. 99

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 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 consid-
erably increase his vital capacity.

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

Hygiene of Breathing. — Those persons who take con-
stant exercise in the open air are not likely to surfer much
from deficient respiration. But persons who lead an indoor

ioo Physiology.

life, especially those who are sitting much of the time, need
to pay especial attention to the matter.

The Nasal Passages. — 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 abundant 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 passage-way.

Breathing through the Mouth. — If we breathe through
the mouth (especially out of doors in cold weather), the
air may not be sufficiently warmed before entering the
lungs. In breathing through the mouth much more dust
is 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 ciliums, which
extend from most of the cells lining the air passages, 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.

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
engaged in office work or studying should form this habit,
especially if he does not give an hour daily to exercise.

Control of Respiration. — Breathing is an involuntary
action. It is under the control of the nervous system, and,
without attention on our part, it goes on, varying in rate
according to the needs of the body. About every fifth

External Respiration. 101

breath is a little deeper than the others, and if we are sit-
ting in a cramped position, or are depressed, this occasional
deeper breath is still more marked and is called a sigh.
If the tissues are not well supplied with oxygen, they make
it known to nerve centers through the nerves, and, by
reflex action, breathing is quickened.

Effect of Alcohol on the Lungs. — Just as alcohol pro-
duces reddening of the face by the enlargement of the
arteries, so it causes congestion in the lungs. The pas-
sage of oxygen from the air sacs into the blood, and of
carbon dioxid and other waste matters from the blood into
the air sac, is hindered. The lung capacity of drinkers is
diminished. Both respiration and circulation are interfered
with, and, as a result, the drinker is less vigorous and has
less endurance than the abstainer.

Alcohol and Lung Disease. — "Habitual moderate drinkers
of alcoholic liquor give a much higher ratio of mortality
when attacked with cholera, continued fever, pneumonia,
influenza, or almost any acute disease, than the total
abstainers." — N. S. Davis, M.D?, F.S.S.

"The lungs, from the congested state of their vessels
produced by alcohol, are more subject to the influence of
cold, the result being frequent attacks of bronchitis."

— Martin.

Nearly all physicians agree that the continued use of
alcohol weakens the vitality of the body, and that this is
the reason why drinkers are so much more likely to die
when attacked by severe disease such as pneumonia. When
pneumonia is prevalent, it gets a very much larger number
of victims from the drinking class.

Alcohol and Consumption. — At one time it was widely
believed that alcohol was a cure for consumption. So far

IO2 Physiology.

is this now known to be from the real facts of the case
that it is well established that the use of alcoholic drinks
makes the body less able to resist the germs of consump-
tion. Under the former mistaken view many consump-
tives used alcoholic liquors to their own injury. But time
and experience have taught that they only increase the
trouble.

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 being
between them.

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

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

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

5. Inspiration requires extra effort; but ordinary expiration is with-
out effort because of the elastic reactions.

6. Forced expiration, as coughing, requires active muscular effort.

7. The vital capacity may be increased by practice and by exercise.

8. We should breathe through the nose, not through the mouth.

9. Respiration is under the control of the nervous system.

Questions. — I. Is it well to see how long one can hold his breath ?

2. Should the head be covered by bedclothes ?

3. How is respiration affected by a stooping posture ?

4. What are the "lights" of an animal ?

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

6. From the statements in this chapter of the amount of air taken in
at each breath and of the rate of breathing, find out how much air is
breathed in an hour. How much in twenty-four hours ?

CHAPTER X.
INTERNAL RESPIRATION.

Composition of the Air. — Air has about 20 per cent oxy-
gen and 80 per cent nitrogen, or one fifth oxygen and four
fifths nitrogen. There is a very small amount of carbon
dioxid, and usually there are traces of other gases.

Experiments illustrating Internal Respiration. — MATERIAL NECES-
SARY. — A piece of candle an inch or two long, two tumblers, a tube
eight inches long (a straw will serve), a nail, and lime water. The lime
water should be prepared the day before by putting a piece of fresh
quicklime as big as a hen's egg in a quart of water. The next morning
carefully pour off the clear water for use in experiment.

EXPERIMENT i. — Light the candle and hold a cold tumbler inverted
a little above it. The moisture that dims the inside of the tumbler is
water that has been produced by the burning of the candle. The oxy-
gen of the air unites with something in the candle and forms water.

EXPERIMENT 2. — Breathe into a cold tumbler. The tumbler is
dimmed by the water in the air we breathe out.

EXPERIMENT 3. — Lower a tumbler over the burning candle till the
tumbler rests on the table. Observe that the flame is soon put out.
Carefully lift the tumbler and slip one hand under it so that the palm
tightly covers the mouth of the tumbler. Invert the tumbler. Lift one
edge of the hand and pour in about two tablespoonfuls of lime water.
Thoroughly shake the tumbler, keeping it tightly closed. The lime
water is turned milky by the carbon dioxid produced by the burning
candle. There is carbon in the material of the candle, and the union of
oxygen with this carbon produces carbon dioxid.

EXPERIMENT 4. — Pour about two tablespoonfuls of lime water into
a tumbler and breathe through it by means of a tube. The lime water
is turned milky by the carbon dioxid in the breath. There is carbon in

103

1 04 Physiology.

the tissues of the body. Oxygen unites with this carbon, forming car-
bon dioxid. We know that there is carbon in beef, for when it is over-
baked we see 'the black carbon where it is charred. There is carbon in
our muscles and in all the other tissues.

EXPERIMENT 5. — Place a nail, or any piece of iron, in a tumbler of
water. It will soon rust. Rusting is caused by the union of oxygen
with the iron. When anything unites with oxygen it is said to oxidize.
When the union is rapid, as with the burning candle, it is called com-
bustion.

EXPERIMENT 6. — Hold a thermometer at arm's length. It shows
the temperature of the air, — of the air you are breathing in. Breathe
for a few minutes upon the bulb of the thermometer and you have proof
that the air we breathe out is warmer than the air we breathe in.

How the Body is like a Candle. — The burning candle
and the body both produce heat. To do this each must
have oxygen. The oxygen unites with carbon and other
elements in each, and produces carbon dioxid, water, and
other substances. And just as a candle flame is soon put
out in a closed tumbler, so life would be destroyed by suf-
focation if an animal were shut in an air-tight room.

Exchanges between the Air and the Blood in the Lungs. —
Whatever the air coming from the lungs contains 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 blood in the
pulmonary capillaries only by the thin wall of the air vesicle
and the thin capillary wall.

What the Air gets from the Blood. — 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 through the bronchial tubes and windpipe. The
air also gets heat from the blood (see Fig. 60).

Internal Respiration.

105

What the Blood gets from the Air. — Oxygen from the air
in the vesicle passes through these layers into the plasma,
and most of it is quickly picked up by the colored corpus-
cles. The colored corpuscles are the carriers of oxygen.

BRONCHIAL TUBE
FROM PULMONARY ARTERY ^_ -f TO PULMONARY VEIN

Fig. 60. Exchanges between the Air and the Blood in the Lungs.

Hemoglobin and Oxy-hemoglobin. — The hemoglobin in
the colored corpuscles is eager to unite with- 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 oxy-hemoglobin, which is of a
bright red color. Hence the change in the color of the blood

io6

Physiology.

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.

?u,

^

c^^/e^ _^
ofcfeF^r "^

Fig. 6 1 . Circulation in the Capillaries of the Lungs and in the Capillaries of the Body.

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. The rise in tempera-
ture has been repeatedly proved by experiment. We know
that the blood is flowing more rapidly through the muscle

Internal Respiration. 107

when it is at work. The more rapid stream brings the
muscle more oxygen. This it needs, for it is by the oxida-
tion of the muscle (or substance in it) that the muscle
produces heat and motion. The oxidation in our tissues is
a slow oxidation, more like the rusting of iron than the
burning of a candle. Oxidation in our bodies never pro-
duces a high degree of heat and never produces light.

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 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 mes-
sage to the blood tubes, making them widen, and the heart
also may be made to beat faster.

Increased Respiration from Exorcise. — But would it do
any good to have the blood flow through the muscles faster,
if it could not bring more oxygen, 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
muscles will not work faster unless they are ordered to do
so. A message must be sent to them telling of the need.
Thus, by a series of reflex actions, all these processes are
kept in close relation to each other. It must be borne in
mind that increased blood flow is the result, 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-

io8 Physiology.

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 com-
pared to a stove. Into one we put fuel and produce heat.
In the other we get heat from food. Both take in oxygen.
Both produce carbon dioxid, water, and other waste matter.

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 material stored in the
tissues. It is as though we were to build a stove 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 sub-
stance. This is the case with the body.

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

The muscles make up nearly half of the weight of the
body. They are more active than most of the tissues.
We would naturally infer, as 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
in vigorous action they oxidize very much more rapidly.

Production of Heat in the Liver. — 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 wiU be better
to compare the body to a locomotive, as we produce not
only heat, but motion: — I. Both are warm; 2. Both
move ; 3. Both use fuel (food or coal) ; 4. Both take in

Internal Respiration. 109

air. 5. Both give off gases, consisting mainly of carbon
dioxid and water vapor.

How the Body differs from a Locomotive : — i . The body
does not get hot enough to burn ; i.e. the oxidation is
relatively slow, and is not combustion. 2. The oxidation
of the body never produces light. 3. The oxidation in the
body 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
expired air may reach 7 or 8 per cent. During violent
exercise the amount of carbon dioxid given off may be
more than twice as much as when we are at rest. In
ordinary respiration there is one hundred times as much
carbon dioxid in the air we breathe out as there was when
it was taken in. Oxygen is carried chiefly in the cor-
puscles, but the carbon dioxid is carried in both plasma
and corpuscles.

Effect of Re-breathing Air. — Every one knows how
unpleasant it is to breathe the air of a close room where
many people are present. In many persons such air
causes headache and drowsiness. This effect is not due
to the reduced amount of oxygen, nor is it due to the
increase of carbon dioxid. It is believed to be due to
the " organic impurities" which are thrown out in the
expired breath. It is this matter that gives the offensive
odor to a room which is kept close and warm after a crowd
has been in it. If in a crowded lecture room you divide
the space by the number of people present, you find that
each one has really very little room. In such rooms
special attention to ventilation is necessary, or great injury
will be done. When we learn how many cases of lung

I 10

Physiology.

diseases are found wherever people are crowded into ill-
ventilated rooms, we can realize the force of the statement,
" Man's own breath is his worst enemy."

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
motion) 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 and the exchanges
between the air and the blood in the lungs may be called
"external, or mechanical respiration." The action of the
oxygen of the blood in the tissues is the " real, or internal
respiration."

Effect of Alcohol on Internal Respiration. — Alcohol is
easily oxidized. This is shown in the readiness with which
alcohol burns and the amount of heat it produces in burn-
ing. Alcohol, to a certain extent, may be oxidized in the
body. But it is not useful on this account. For, while it
produces some heat, it causes much more heat to be lost
by the greater flow of blood in the skin. When alcohol
is oxidized in the body, so much oxygen is taken that the
blood has not enough left for the needed oxidation in the
tissues where work is to be done. The consequent lack of
oxygen through the body weakens it everywhere. Not only
is there a shortage in the supply of oxygen, but there is an
over-amount of carbon dioxid. Much of the carbon dioxid
which should have left the blood in the lungs remains, and
does great harm. For blood with a surplus of carbon dioxid
injures the tissues, and they all suffer. This condition of
the blood — too much carbon dioxid and too little oxygen

Internal Respiration. i 1 1

— shows most plainly in the face of the habitual drunkard,
purple, not merely from the over-amount of blood, but from
the lack of oxygen in the blood. While this abnormal
color does not show in the moderate drinker, the same
condition is nevertheless present, though in a lesser
degree.

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

2. 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.

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

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

5. When we exercise more, the muscles need more oxygen, so the
heart must beat faster and we must breathe faster.

6. The body is like a locomotive in producing heat and motion by
oxidation.-

7. Air, once breathed, has one hundred times as much carbon
dioxid as before.

Questions. — I. In what part of the lungs is the best air? Where
the worst?

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

3. How is the air of a room affected by having many lamps or gas
jets burning.

4. How is air affected by gasolene or kerosene stoves?

5. Could a locomotive be run by feeding it with bread and meat?

CHAPTER XI.
VENTILATION AND HEATING.

Need of Proper Ventilation. — When one is actively
exercising he may keep warm outdoors even on a cold
winter day. 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 best appliances, defective appa-
ratus is often put in. Any system that does not provide for
a constant renewal of the air is defective.

The General Principles of Ventilation. — Of the forces
that renew the air of rooms two are natural, (i) diffusion
and (2) the wind ; and two are artificial, (3) warm air shafts
and (4) fan systems.

Diffusion. — Gases tend to mix. We know that if a
bottle containing an odorous substance is opened in a
room where there are no air currents the odor tends to

112

Ventilation and Heating. 113

spread equally through the room. If a person is in one
corner of a large room, where there are no inlets or out-
lets, and no currents, as he uses the oxygen immediately
around him, the oxygen farther away will diffuse toward
him so that he will continue to get oxygen as long as there
is any in the room. So, 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 be renewed by diffusion.

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 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 below, and push the lighter,
warmer air out above.

Grates as Heaters. — Grates are the simplest and prob-
ably the earliest form of heater. The fire throws out heat
in straight lines, or as we say, radiates heat into the room.
So much of the heat goes directly up the chimney that a
grate is very wasteful of fuel.

Grates as Ventilators. — But a grate is an excellent ven-
tilator. There is always a decided draft toward a grate
fire. This means a constant renewal of air. The air

1 1 4 Physiology.

pushing toward the grate may be cold, and this has disad-
vantages that are hard to overcome in cold weather if there
is no other way of supplying heat. But it is a serious
question whether, with all our modern improvements in
heating, we have better air in our houses, or take cold less
often than our grandfathers, even if they did "roast on
one side while they froze on the other."

Stoves as Heaters. — A stove is a very much more effec-
tive heater than a grate. In the first place the stove gives
off heat on all sides. In the second place a good deal of
heat is given off by the stovepipe ; while in the grate
almost no heat is saved from the flame and smoke.
Again, the fire can be better regulated in the stove.

Air Currents produced by Stoves. — There is always a
current of heated air rising above a hot stove. Children
make whirligigs and other toys to place in these up-currents.
When this heated air reaches the ceiling it passes along
the ceiling, and comes down along the walls in the colder
parts of the room. At the same time colder air is flowing
along the floor toward the stove. This, in turn, is heated
and rises, making a constant circuit, along the floor to the
stove, up from the stove to the ceiling, along the ceiling
to the walls, and down the walls to its starting-point, again
to repeat the round.

Stoves as Ventilators. — If there is an opening at the
top of the room, heated air will escape through it. Often
the heat is used to warm upstairs rooms in this way. If
a window is open at the top, some heat is lost. To make
up for the losses above named, and also for the air that
enters the stove and goes up the chimney, more air is
drawn in usually around doors and windows. It is espe-
cially noticeable where there are openings near the floor.

Ventilation and Heating. . 115

For the cold air is heavier than the warm air and continu-
ally pushes the warm air up and out of the room wherever
it can. But the stove does not send as much air up the
chimney as the grate does, and so does not draw in as
much fresh air. It is therefore not a good ventilator.
But the stove gets much more heat from a given amount
of fuel.

A Stove and Jacket. — In some cases a jacket is placed
around a stove, and a duct from the outer air connects

Fig. 62. The Unjacketed Stove.

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.

n 6 Physiology.

The Furnace. — A furnace is practically a jacket stove
(almost always placed in a basement). Furnaces have this
good feature, that they are all the time sending fresh air
into a room. The main trouble is, the air is usually too
dry. There should be in the furnace a pan of water to
furnish moisture to the air.

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
near the center of the building, and a small stove placed
in it to create a sufficient up-current. In many public
buildings the currents created by heat are not strong
enough to renew the air properly. Revolving fans are
used, which force the air, properly heated, into the room.

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. It
gives direct heat, and produces air currents within the
room. In itself it has no provision for renewing the air.

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. — It is a
good plan to combine direct and indirect heating. Where

Ventilation and Heating. 1 1 7

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 from the furnace, 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
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 through the glass. The air
next to the window, 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 ceil-
ing, and so on around again. There may thus be currents
without any 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

1 1 8 Physiology.

vestibules at entrances, and build special ducts by which
fresh air may enter, and heat it properly on its way in.

To Air a Room without Draft. — To introduce fresh air
into a room without having a draft, a good plan is to get a
board four inches wide and as long as the width of the
window sash. Raise the window, place the board under
it and shut the window down upon the board. This will
allow air to enter between the upper and lower sash, and
it will be directed toward the ceiling. This is of double
advantage; in the first place, it does not strike any one
directly ; in the second place, it mingles with the warm air
of the upper part of the room before it reaches us.

Wearing Slippers. — In rooms heated by stoves or grates
there is always more or less cold air moving along the
floor. Wearing slippers in such a room causes many per-
sons to take cold. The ankles have been warmly dressed
through the day and while the person was more active.
Especially if one is studying there is a tendency to draw
the blood away from the feet and make them cold. It is
restful, in the evening, to take off the shoes that have been
worn during the day ; but, for most persons, it would be
better to put on a pair of loose shoes so the ankles will be
protected. The floor is usually the coolest place in a room.
In sitting in a room heated by a grate, or stove, the head
usually gets the most heat, and the feet the most cold, just
the reverse of what it should be. If much heat escapes
from a furnace, the floor may be warm. Those who use
stove heat in loosely built houses, learn to keep the feet up
on a stool when sitting in a room in cold weather.

Ventilation of Cellars. — The cellar is the source of con-
tamination of the air of many houses. Of course a cellar

Ventilation and Heating. 119

ought to be dry, well lighted, and well ventilated. But
since many of them are dark and ill ventilated, especial
care should be taken to keep them dry. Fruit and vege-
tables should not be allowed to decay in the cellar. On
entering many houses one can at once detect the smell
of decaying potatoes and other vegetables. Such material
should be promptly removed. The best time to ventilate
a cellar is at night, for if the cellar windows are opened
in the day time, the entering air will deposit moisture,
making the cellar more damp instead of dryer.

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

2. Air in rooms needs constant renewal.

3. Grates are good ventilators, but not economical heaters.

4. Stoves are economical heaters, but poor ventilators. Both grates
and stoves heat very unevenly.

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 indirectly
(placed in flues). It is best to combine direct and indirect heating.

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 ?1 ?

6. Compare stove and furnace heating.

7. Compare heating by steam and by hot water.

8. Read about the " Black Hole of Calcutta.11

CHAPTER XII.
DUST AND BACTERIA.

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 most of the various impure gases
that are in the air. The raindrops and snowflakes also
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 that the
water has an inky tinge, 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. Crush it in your hand before dropping it, and
much of it floats in the air for some time. Any substance
that is easily dried and reduced to powder 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. Indoors we are

120

Dust and Bacteria. 121

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 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. — This dust 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. Exam-
ination shows that the lungs have many black specks from
particles of carbon, etc., that have become lodged, and are
of no benefit, to say the least.

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
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 oft
a cloud of dust when they are crushed. So, too, from a
patch of mold, when brushed, we often see a little cloud of
dust. This dust is composed of live spores that will grow
in suitable places and conditions.

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

122 Physiology.

a kind of living germ or spore that has gotten into it from
the dust on the fruit before it was crushed, or from dust
in the room. Boil the cider to kill the spores already in
it, and cork it securely so that air cannot get at it, and it
will not ferment. These are a few instances of kinds of
living dust that do not affect human beings any more
than so much dead matter.

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
of some of these spores in our bodies. Our bodies are a
good soil for certain germs. The germs that cause con-
sumption, typhoid fever, Asiatic cholera, erysipelas, diph-
theria, lockjaw, and the grippe, 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 small-
pox, yellow fever, measles, mumps, whooping-cough, 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 think
about, is too terribly true to allow of being called an imag-
ined case.

The Danger from Consumption. — A consumptive spits
on the pavement. In this sputum are probably hundreds,
if not thousands, of germs known as bacilli (Bacillus tuber-

Dust and Bacteria.

123

culosis\ 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 mat-
ter any day, for there are persons afflicted with this dreaded

Bacillus of Diphtheria (x 1000)

Bacillus of Typhoid Fever

Bacillus of Tuberculosis (x 1000)

Bacillus of Typhoid Fever (x 1200)
showing flagellums

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

Fig. 63. Different Kinds of Bacilli.

disease in every community. Our bodies furnish the very
best soil for the germs. We do not need to go into the
street to be exposed. These germs may be brought into
the most cleanly houses upon one's clothing, or by the wind.

How to avoid the Danger. — Of course, all such material
known to be dangerous should be destroyed. If those
suffering from such diseases were careful to burn all such
matter, in time we might stamp out the diseases. But so

1 24 Physiology.

long as people spit 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.* Many of the railroad and street
car companies now forbid spitting on the floors of cars
and stations, not merely because it is uncleanly, but be-
cause 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 called Bacteria.

How to avoid Dust. — We need to learn a good deal
more about avoiding and destroying dust, and the things
that make it. Towns and cities need more sprinkling to
keep the dust down. Much more of the refuse and street
sweepings and 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

Dust and Bacteria. 125

air of the room. Compare this with the condition 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 so-called dusting.
But do we get rid of the dust ? For those who cannot have
hard wood floors a most excellent substitute is oilcloth or
linoleum.

Sweeping the Sick Room. — The improved carpet
sweepers are not only convenient, but sanitary. 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 on
the floor is of much less significance than dust in the air
we breathe. No one likes dust 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 others. Probably anything that lowers the general
vitality makes the system more ready to yield to any of
these contagious diseases. We have all noticed what a
difference there is among individuals in the readiness with
which they " catch" contagious diseases.

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

1 26 Physiology.

liness, plenty of direct sunshine, care in diet, and the keep-
ing of the body in good tone, reduce the chances of
"taking" contagious diseases. An open-air life, abundant
nutritious food, and freedom from anxiety are probably the
best cures for the first stages of consumption.

Destruction of Germs by Colorless Corpuscles. — The

colorless blood corpuscles may take these germs of disease
into their substance, 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.

Germs killed by Plasma. — Sometimes the blood con-
tains a substance that kills or prevents the action of dis-
ease germs. Such a substance is called anti-toxin, which
means a counteracting poison. But the blood of most
persons does not naturally contain anti-toxin, and so, if the
disease germs gain entrance, the disease follows.

Vaccination. — Vaccination is the introduction of an anti-
toxin. That it is a " poison against poison" is shown in the
fact that one is likely to feel some bad effects after vaccina-
tion. If the anti-toxin is successfully introduced into the
blood, the person is usually safe from the disease. A per-
son seldom has the smallpox more than once. This is
because when he has the disease the germs in their growth
produce an anti-toxin, which remains in the blood, and
keeps these germs from growing in that blood again. The
material used in vaccination is called vaccine lymph, and is
obtained from cows, in whose lymph it is produced.
Physicians now vaccinate or inoculate against a number
of diseases by introducing the proper anti-toxin.

Danger of getting Germs into Wounds. — There is danger
of introducing germs of disease in so simple an act as pick-

Dust and Bacteria. 1 27

ing out a sliver with a pin. If such germs happen to be
on the point of the pin, the mischief is easily done. Great
care should be taken in any such operation to use a
thoroughly clean needle or lancet. Formerly any surgical
operation that required opening the body cavity, either
the chest or the abdomen, usually resulted in death. Now-
adays such operations are commonly successful, because
surgeons sterilize their instruments, hands, and 'everything
used about the work. They kill any germs that might
be introduced. In a word, they Jiave learned to be
clean.

In caring for a patient ill of any germ disease, one should
wash the hands in some disinfectant, such as chlorid of
lime, and should not touch the fingers to the lips; .igno-
rance of these simple rules has caused many deaths.

Malaria. — This is due to an animal germ (not a bac-
terium) that gets into the blood. It is introduced by mos-
quitoes that have bitten persons whose blood contains these
germs.

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 and moisture for their
growth just as higher plants do.

128 Physiology.

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., pre-
serve 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. If milk is heated to
1 60° or 170° F., any germs of tuberculosis present will be
killed. Boiled milk is less readily digested, and it is not
necessary to boil it to kill most kinds of germs that it may
contain.

Summary. — I . Dust as mere dry, dead matter is irritating.

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

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

4. Burning is the surest method of destroying germs.

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

6. Putrefaction is caused by bacteria.

7. Preservation of food depends on destroying, excluding, or retard-
ing the growth of the bacteria of putrefaction.

Questions. — I. Is the air in the mountains or on the seashore better
than elsewhere ?

2. What regions are recommended for consumptives? Why?

3. How is milk sterilized?

4. Why do people seldom take cold while " camping out "?

5. Why are the "steel grinders," in factories, short-lived?

6. What occupations should be avoided by one who is predisposed
to consumption ?

7. What are some of the occupations suitable to those predisposed
to consumption?

CHAPTER XIII.
EXCRETION.

The Formation of Waste Matter in the Body. — All the

force, or energy, of the body is produced by oxidation in
the tissues; thought by oxidation in the brain; motion by
oxidation in the muscles; and heat wherever oxidation
goes on. This oxidation produces waste matter in our
bodies just as we have seen that oxidation in a stove
produces waste matter.

The Need of Removal of Waste. — When we waken 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 maga-
zine (though usually some 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 as neces-
sary as the addition of a fresh supply of fuel. In this case
more necessary, for no amount of fuel will do any good so
long as the ashes shut off the draft. In our bodies the
removal of waste is still more important, because waste
matter not only clogs the system, but, if present in any
great amount, acts as a poison to the tissues.

The Skin throws off Waste Matter. — The skin is
constantly throwing off waste matter called sweat, or
•perspiration.

129

3o

Physiology.

HAIR

Experiment to show insensible Perspiration. — Thrust the hand into
a cold glass jar. Note the moisture that soon gathers on the inside of
the jar from the insensible 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.

The Structure of the Skin. — The skin has two layers,
the inner, or dermis, and the outer, or epidermis. The

epidermis is thick

sweat Pore over the palms and

soles; elsewhere it
is thin. The skin is
much thicker than
we would naturally
suppose, and makes
one fifteenth of the
weight of the body.

The Epidermis. —

The epidermis con-
Cells sists of many layers
of cells packed
closely together.
The deepest cells
may be compared to
grapes with their cell
walls plumply filled out with the liquids of the cell. Sup-
pose for the inner' layer, grapes set on end, and so closely
packed together as to press each other more or less flat on
the sides. Above these are cells less closely pressed, more
nearly spherical ; then 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 grape skins. These flat cell walls come off

Hai

Blood
Tube

Fig. 64. Vertical Section of the Skin.

Excretion.

in flakes (those from the scalp are called dandruff) from
all the surface of the skin, and new cells are continually
formed in the deeper layers.

Mouth of Sweat Duct

Horny Epider-
mis

Soft Layer -

Papilla

•Dermis

Vein Artery

Fig. 65. Section of Epidermis, showing Papilla. (Highly magnified.)

The Color of the Skin. — The coloring matter, or pig-
ment, of the skin lies in the deeper layer of the epidermis.
In albinos the pigment is wanting. In persons with fair
skin it is small in amount, in dark skins more abundant.
Where the pigment is scattered irregularly 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 at B, in Fig. 64. Serum, or
blood, fills the space between the separated layers.

132 Physiology.

The Dennis. — 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.

Papillas. — The outer surface of the dermis has many
conical elevations, each of which is called a papilla. Over
most of the skin they do not show on the outer surface, as
the epidermis fills in the spaces between them, but is, itself,
smooth on the outside. On the palms and soles the papillas
are in rows, and these rows are indicated by the ridges.

Hairs. — Hairs are outgrowths of the epidermis, but are
deeply embedded in the dermis. They are supplied with
blood at the tip of the root, where the growth takes place.
The exposed part of the hair does not contain blood and is
not sensitive. (See Fig. 64.)

Hair-muscles. — There are small muscles connected with
the roots- of the hairs, by which the hair may be slightly
moved. In the lower animals this power is much more
used, as when the hair is made to stand erect on the back
or tail of an angry cat or dog. The action of these muscles
when frightened is what gives a peculiar feeling in the
scalp, and to express strong fright we say, " It made his
hair stand on end."

Oil Glands. — The oil glands of the skin are distributed
over all the surface except the palms and soles. The oily
matter is usually poured out around the hairs as they
emerge from the skin ; but some of the ducts open on the
skin away from a hair. The oil serves to soften the skin
and hair and keep them from becoming too dry. (See
Fig. 64.)

Excretion. 133

. — The nails, like the hair, are outgrowths of the
epidermis. At the base the nail is supplied with blood, and
here it grows. It is alive, hence this part is called the
quick ; but at the outer surface and the tip it is dead.

Examination of the Skin with a Lens. — Place a linen tester, or other
hand magnifier, over the palm, and note the sweat pores or openings of
the ducts of the sweat glands. 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.

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 pur-
sues a corkscrew-like course through the epidermis, then
becomes straighter, and is coiled up in a ball in the deeper
layer of the dermis, or, more often, in the connective tissue
just beneath the skin. (See Fig. 64.) The cells forming
the walls of the coiled part are different from those of the
duct, or straighter part of the tube. As the blood flows
through the capillaries of the skin it gives off lymph. In
this lymph are waste matters brought from the muscles
and other tissues that have been at work. The sweat
glands absorb this waste matter, with considerable water,
and pass it out to the surface.

Composition of Sweat. — Sweat is mostly water. About
one per cent is solid matter, including salt and certain
matter which like the organic waste matter from the lungs,
easily putrefies. Sweat varies greatly in its wateriness and
hence in the relative amount of solid matter contained.
Ordinarily the sweat is evaporated as fast as it is poured
out. In distinction from this insensible perspiration, there
is the sensible perspiration — when it accumulates enough
to be seen. These are not two kinds of sweat, but it is con-
venient to distinguish between the visible and the invisible.

1 34 Physiology.

The Amount of Perspiration. — There is about one quart
in twenty-four hours. It varies with (i) The temperature
and dryness of the air. (2) The condition of the blood,
e.g. if watery from drinking much water. (3) Muscular
exercise.

Gland Action and 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 supply of blood, and at the same time the glands
are more active, for during exercise and for some time
afterward there is more waste matter to be thrown out.

Control of the Sweat Glands. — But the activity of the
gland is not a mere filtering process ; it is not always in
proportion to the amount of liquid present. There may
be a cold sweat, i.e. when the skin is pale. This usually
is due to excitement or emotion, which shows that the
action of glands is under the control of the nervous system.

Sweat Glands are Excretory. — The sweat glands rid the
body of certain waste matters, and are therefore called
excretory glands. A sweat gland is a simple gland.

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 and soles.
In the armpits the glands are also large.

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

Excretion. 135

The Body gives off Heat. — In considering the regulation
of the temperature of the body, we must bear in mind that
the body is surrounded by air that is almost always con-
siderably 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. they keep us from losing too much heat. Indoor
air in winter 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 sweat is the most
important factor in regulating the heat of the body. Any
liquid in evaporating absorbs heat. The cooling effect of
alcohol, ether, or cologne on the skin is due to the fact
that heat is taken from the skin in converting the liquid
into a gas.

Experiment in Evaporation. — With a medicine dropper put a drop
of cologne on the back of the hand. Note two facts : (i) it produces a
cooling effect ; (2) the liquid quickly disappears.

Practical Applications of this Principle. — We sponge a
feverish patient to reduce his temperature. The cooling
effect is due not so much to the coolness of the water itself
as to the absorption of heat from the skin in evaporating
the water. We sprinkle the floor in hot weather and thus
cool the air of the room.

136 Physiology.

Heat and Exercise. — When we exercise we produce more
heat ; we sweat more ; more heat is taken from the body
to evaporate this sweat. If we are not exercising and are
in cooler air, we sweat less, and less heat is given off.
When we exercise there is more blood in the skin, and
more heat is given off by radiation, convection, and con-
duction. When we exercise less, the skin, especially in
cool air, is paler, i.e. has less blood in it, and heat is econo-
mized. Thus the temperature of the body is kept uniform.

Distribution of Heat in the Body. — If more heat is pro-
duced in one part of the body than in others, the circula-
tion of the blood tends to equalize the temperatures of the
different parts. So, too, if one part is cooled, i.e. is losing
heat faster than others, the blood brings heat from other
organs to that part. If the hands and feet are exposed to
cold, it may do little good to have the rest of the body well
covered. A pair of wristers and a pair of leggings may
often add more to one's comfort than a heavy overcoat.

Regulation of Temperature by Clothing. — In cold weather
we put on more clothing and select non-conductors of
heat, as woolen, leather, and fur. Many authorities recom-
mend light woolen for summer wear, since with it we do
not cool off so rapidly.

Regulation of Temperature by Food. — In cold weather
we eat more. We also eat more fat and other heat-
producing foods.

Effect of Wet Clothing. — In getting the clothing wet the
cooling effect is not so much from the temperature of the
water as from 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

Excretion. 137

possible. It is dangerous to sit down in wet clothing, even
on a warm day. Children seldom take cold from wading,
even in cold water, if barefooted ; but with wet shoes and
stockings they are likely to take cold.

Mechanical Protection by the Skin. — This is the most
evident function of the skin. The skin is tough, strong,
and elastic, hence well fitted to cover the body and yield
with every motion, yet protect the softer and more delicate
tissues beneath it from injury.

Absorption by the Skin. — The skin has slight power of
absorption ; hence there is some danger in handling cer-
tain poisonous substances. The chief danger, however, is
when there are cracks or sores on the hands. If one must
handle suspicious material, it is well to rub the hands with
vaseline. To use rubber gloves is safer still.

Review of the Functions of the Skin. — (The skin as a
sense organ will be considered later.) i. Sensory. 2.
Heat-regulating. 3. Absorptive. 4. Protective. 5. Ex-
cretory. It will be easy to remember these five functions
if it is noted that their initials spell the word s-h-a-p-e.

Skin-grafting. — Sometimes after extensive burns, or
other injury of the skin, bits of skin are taken from an-
other part of the body, or from another person, and trans-
planted to the injured part, where they grow.

External Features of the Kidneys. — The kidneys are a
pair of bean-shaped bodies attached to the dorsal wall of
the abdomen. (See Fig. 32.) The spot corresponding to
the stem-scar of the bean is called the hilum. At this point
are three tubes, the artery by which blood enters the kid-
ney, the vein by which the blood leaves, and the ureter, by
which the urine is conveyed to the bladder,

138 Physiology.

The Blood-supply of the Kidneys. — On entering the
kidney the renal artery divides and subdivides, forming a
very complicated set of capillaries. Through the thin walls
of the capillaries certain waste matters pass into the cavity
of the kidney, from which they are conveyed by the ureter
to the bladder. (See Fig. 32.)

Urea. — Urea is the nitrogen-containing waste of the
body. There is nitrogen in muscle, brain, and in all the
important organs of the body. When they work, some
urea is formed. If the urea accumulates in the blood, it
acts as a poison to the tissues.

Importance of the Work of the Kidneys. — The kidneys
are the only organs that can remove the urea from the
blood ; hence their great importance. Small as they are,
their removal would soon cause death. Urea is a solid, and
could not very well be carried out of the body unless dis-
solved. So the urine consists mainly of water containing
urea, salt, and various other substances in small amounts.

Relation between the Kidneys and the Skin. — There is a
very close relation between the kidneys and the skin. In
warm weather, and when exercising actively, we sweat more
and the kidneys excrete less water ; on the other hand,
when we exercise less, and especially in a cool place, we
sweat less, and the amount excreted by the kidneys is in-
creased. For instance, when one has a cold he is
more or less feverish ; that is, the action of the skin is inter-
fered with, and there is less perspiration. At such time
the kidneys have more work to do, and nay be so over-
worked as to injure them permanently.

Effects of Alcohol on the Excretion of Waste Matter. -
It has long been known that the use of alcohol diminishes
the amount of urea given off. This was thought to prove

Excretion. 139

that alcohol, if not a food, at least acted in such a way as
to save food, and prevent the oxidation of the tissue?.
Careful investigation shows that the use of alcohol does not
reduce the amount of waste matter produced by the tissues,
but it does interfere with giving off these waste matters.
They are retained in the system and do great harm.

" All forms of irritation of the kidneys and urinary pas-
sages are usually aggravated by the use of alcohol. Even
healthy kidneys are irritated by moderate doses of alcohol."

— Professor Binz of Bonn.

Action of Alcohol on the Skin. — " When an alcoholic
drink is taken, it circulates with the blood and frequently
causes congestion of the s\in, predisposing it to various
forms of skin eruptions, causing much discomfort, itching
and burning of the skin." - W. E. Baldwin, M.D.

Effect of Alcohol on the Kidneys. — " The kidneys are
among the most important organs of the body, as they sep-
arate from the blood the products of disease and worn-out
material. These organs are frequently overworked by the
consumption of alcoholic beverages, thereby losing their
power of separating waste matters from the blood. In
consequence the kidneys become diseased." — Dietetic and
Hygienic Gazette.

" Alcohol produces hypertrophy of the kidneys, thereby
causing an altered amount of secretion of urea and other
normal constituents of the urine, which, in turn, tends to
produce headaches, neuralgia, and loss of appetite."
Milton J. Parke, M.D.

Alcohol causes Half of the Disease of the Kidneys. — Dr.

Bollinger, director of the Anatomico-pathological Institute,
in Munich, asserts that it is very rare to find a sound heart
or sound kidneys in an adult resident of that city. The

140 Physiology.

reason for the kidney disease is the tax put upon these
organs by the drinking of large amounts of beer.

One of the leading German professors of Berlin is quoted
in a medical journal as saying that diseases of the kidneys
are more frequent than in former years. This he attrib-
utes to beer-drinking, which he says is more general than
formerly, especially among the country people.

Summary. — i. When the body works it produces waste matter.

2. Waste matter must be removed or it will poison the body.

3. The skin throws off sweat, — mostly water carrying waste matter.

4. Sweat is taken from the lymph by the sweat glands, which are
coiled tubes, opening on the surface of the skin.

5. The skin consists of two layers, the dermis, and the epidermis.

6. The amount of sweat varies with heat, exercise, food, etc.

7. The body gives off heat by (i) radiation, (2) conduction,
(3) convection, (4) evaporation.

8. The temperature of the body in health stays at about 98.5° F.

9. The temperature is regulated by the evaporation of sweat.

10. Heat is distributed through the body by the blood.

11. In cold weather we eat more fat, and other food, to make heat.

12. The skin has five functions: touch, heat-regulation, absorp-
tion, protection, excretion.

13. The kidneys remove urea from the blood. Urea is the nitrogen-
containing waste of the body.

14. If much urea is in the blood the body is poisoned, and the re-
moval of the kidneys would soon cause death.

15. Alcohol injures the kidneys.

Questions. —

1 . Do dogs, cats, and cows sweat ?

2. Why is thirst relieved by moistening the skin ?

3. Why is it a good sign when the skin of a feverish person be-
comes moist ?

4. Why should clothing worn during the day be removed at night ?

5. Can food, medicine, or poison, be absorbed through the skin ?

CHAPTER XIV.
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 supply of new
material, the heat and energy of the body cannot long be
kept up.

Food Defined. — Foods are substances that build tissues
or produce energy without injuring any organ or function
of the body. Certain substances that -do not become part
of any tissues, nor in themselves produce energy, are use-
ful in aiding the processes going on in the body. These
may be called accessory foods, e.g. condiments, such as
pepper.

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; and in it 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.

141

142 Physiology.

Kinds of Foodstuffs. — i. Proteids (example, casein).

2. Fats. 4. Water.

3. Carbohydrates (starch and sugar). 5. Salts.

The Proteids. — The chief substance m 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 circumstances
more desirable from the fact that it is very easily digested.

Importance of Proteids. — The proteids are of special
importance as foods because the most active tissues —
those of the muscles, nerves, and glands — and the most
important liquids of the body, e.g. blood and lymph, con-
tain proteid. Proteid food, therefore, must be taken to
make good the losses of these tissues during their oxida-
tions. Proteid is the only foodstuff containing nitrogen.

Proteid-containing Foods. — The principal proteid-contain-
ing 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 proteid,
the rest being chiefly water. Beef and mutton are more
easily digested than veal and pork. Pork sometimes con-
tains a parasitic worm called trichina, which causes illness,
or even death, if eaten. Pork should be thoroughly cooked.

Fish. — Fish, when fresh, is a good food. Although, as
a rule, salted meats are less easily digested than fresh,

Foods and Cooking. 143

salted codfish is a nourishing and economical food. Fish
is not an especially valuable brain food, as commonly
believed.

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 surrounded by a thin envelope of albumen,
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 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 hard to digest, we do not use
it much 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).

1 44 Physiology.

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. They are composed of carbon, hydrogen,
and oxygen, but not in the same proportions as in fats.
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 carbo-
hydrate-containing foods are the grains, vegetables, and
fruits. The most important grains are wheat, corn, rice,
oats, rye, and barley.

Wheat — Wheat furnishes the principal breadstuff among
the more civilized nations. It is especially adapted to the
temperate zones. Taking into consideration its composi-
tion, digestibility, and other characteristics, it is the most
desirable of all the grains.

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 tried to live
on common white bread alone. It is almost entirely 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

Foods and Cooking. 145

take more proteid from other sources than if we used the
entire wheat flour. This is not economy. It is claimed
that the entire wheat bread is more wholesome as well as
more nutritious. The part thrown away has in it phos-
phates as well as the nitrogenous material. This flour is
ground fine so that it has not the coarse particles which are
in Graham flour, and which are, in some persons, a source
of irritation to the mucous coat of the digestive tube.

Corn. — Corn is one of the most nutritious of the grains.
Although somewhat less readily digested than similar
preparations of wheat, and, consequently, less desirable
for indoor workers, it is a fact that, for a given amount of
money, more nutriment can be obtained in corn meal than
in any other food known.

Rice. — Rice forms a larger part of human food than the
product of any other plant, being often an almost exclusive
diet in India, China, and the Malayan islands. Rice has a
larger proportion of starch, and less of fats and proteids,
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 prevalent 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 digest-
ible than the corresponding preparations of wheat.

Barley. — This grain has wide range of cultivation, and,
while inferior to wheat, is considerably used where other
grains cannot be raised.

146 Physiology.

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, 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 cook-
ing. The fibrous matter, cellulose, while indigestible, is of
value in adding bulk to the mass of food to be digested.

Scurvy. — Formerly sailors were subject to scurvy; this
is now attributed to a diet of fat and salt meat, to the
exclusion of fresh vegetables, etc. The disease is avoided
by a greater use of vegetables, lime juice, etc.

Fruits. — Ma.ny of the fruits, such as bananas and
apples, have considerable starch and sugar. But the
fruits are 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 dissolves and carries 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

Foods and Cooking. 147

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
filters down until stopped by some layer, such as clay,
through which it cannot soak. This water is the supply
of our wells and springs. It always has more or less
earthy matter, especially lime, 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.

Impurities in Water. — The great source of danger is
from what are called "organic" impurities. Bacteria do
not thrive in pure water. They must have something on
which to feed and grow. But in water containing 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 bacteria in
it, but is very likely to harbor such foes.

Contamination from Cesspools. — The ordinary cesspool
is a grave source of danger. Because the well may be on
higher ground than the cesspool does not give assurance
that the water may not be polluted. Often when the sur-
face of the ground slopes in one direction, the strata
underneath may slope in 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.

148 Physiology.

Abolish the Cesspool. — 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 usually caused by
drinking-water. The excretions 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 proved. Of
course the excretions 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 frozen in water, as
was formerly supposed. Further, ice, in forming, does
not throw out all the impurities, as was formerly believed.
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, the melted
product will be essentially unchanged so far as the com-
position is concerned. Water may be cooled by placing
any ice around it, and we may have the desired tempera-
ture without danger.

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

Foods and Cooking. 149

better to heat the water twice nearly to the boiling point
than to boil once only. The first heating may start the
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. — 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 bene-
ficial. When overheated, avoid drinking much cold water.
Repeatedly 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 dur-
ing digestion and in other processes. We cannot live
without salt. Lime in the form of calcium phosphate and
calcium carbonate is essential, especially in the bones and
teeth.

Necessity of a Mixed Diet. — Our experience, together
with the results of experiments on animals, teaches that
we could not live long if fed on any one class of food-
stuffs 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

150 Physiology.

and fowl, macaroni and cheese ; they " go well together "
chiefly because each contains what the other lacks.

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
nitrogen as is needed would be taken ; to get rid of this
extra nitrogen would severely tax the kidneys and liver.

Effect of Cold on Appetite for Fats. — In cold climates
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." 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 carnivora ; (2) the intestine in
carnivora is very short, that of the herbivora very long,

Foods and Cooking. 151

but in man intermediate. Nevertheless, 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.
Strong tea is likely to produce nervousness and dyspepsia.
Boiling the tea leaves also brings out the tannic acid that
they contain, and produces bad effects.

Coffee. — Coffee owes its stimulating effect to a sub-
stance called caffein, which is considered the same as thein.
Coffee is used in the army and in penitentiaries, not as a
luxury, but as a matter of economy in food supply. Coffee
used to excess, frequently causes palpitation of the heart.
Its stimulating action makes it unsuitable for the young
and growing, and exact observations of its effects would
probably show that every one would be in better health
without it.

Cocoa and Chocolate. — Cocoa contains a stimulant called
theobromin. But unlike tea and coffee, cocoa and the prep-
aration from cocoa known as chocolate are true foods by
virtue of the fat and proteid contained. With some people,
however, they cause digestive disturbances.

Beef Tea. — Beef tea and various beef extracts are very
helpful. There is not enough nourishment in them to
maintain strength without other food. But many of the
soups and drinks made from these preparations are bene-
ficial. 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 sys-
tem, such as follows the use of alcohol.

152 Physiology.

Cooking. — Cooking is designed to make food more pala-
table and more digestible. Some foods, such as eggs, are
as digestible before they are cooked as after. 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. — 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 coagulate
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 sort of crust through which the nutritious
juices cannot escape. In these modes of cooking it is very
desirable to reduce the heat applied after the first few
minutes, so that the interior may be cooked enough with-
out over-cooking the outside; this is 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 fre-
quently soaked with fat and rendered very indigestible.
But true frying, that is, by immersion in boiling fat, is a
good mode of cooking. This coagulates the albuminous

Foods and Cooking. 153

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.

Summary. — i . Food is to build tissue or produce energy.

2. Foodstuffs are the simpler materials in foods.

3. The foodstuffs are proteids, fats, carbohydrates, water, salts.

4. The proteids are albumen, casein, gluten, legumin, fibrin, myosin,
gelatin.

5. They are found in meat, egg, milk, peas, beans, and a little in
grains.

6. The carbohydrates include starch and sugar.

7. Starch is obtained from potatoes and the grains.

8. The most important grains are wheat, oats, corn, rice, rye. and
barley.

9. Wheat is considered the best grain, though more nourishment
can be obtained from corn meal, for a given amount of money, than
from any other food.

10. Vegetables contain some starch, but are of value from giving
bulk to the food.

1 1 . Water containing decaying organic matter is dangerous to drink,
because it is likely to contain bacteria, which poison us or cause disease.

12. Boiling water usually kills the bacteria in it.

13. Drinking ice water is injurious.

14. We take a mixed diet, as no one food contains all we need.

15. Tea and coffee are stimulants. Cocoa is a food.

1 6. Beef tea is stimulating, but less nourishing than commonly
supposed.

17. Cooking is to render food more palatable and digestible.
Questions. — i. Is the appetite always a safe guide in eating?

2. Which kind of foodstuff is most expensive? Why?

3. Why is bread the " staff of life " ?

4. Make a list of the common foods, naming the foodstuffs in them.

5. How do flour and potatoes compare in cheapness.

6. Why are foreigners prejudiced against corn?

7. Why is broiling better than frying?

8. Why do Englishmen in India suffer from "liver complaint"?

CHAPTER XV.
THE DIGESTIVE SYSTEM.

DIGESTION IN THE MOUTH.

The Object of Food. — The tissues are worn out by their
oxidation. They are built up again by the blood, and the
blood is renewed by the food.

The Digestive Tube. — All food must be reduced to the
liquid condition, if it is not already liquid. The chief organ
in this work of liquefying the food is the digestive ttibe, or
"alimentary canal." As the food passes through the
digestive tube it is ground and liquids are poured upon it.
Thus it is reduced to a liquid that can be absorbed and
taken 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 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. The beefsteak, as such,
must be thoroughly destroyed ; in the liquid produced by
the digestion of the beef there is no trace whatever of the
structure of the beef. But the blood, taking this material,
builds muscle which can hardly be distinguished from the
original beef.

154

The Digestive System. 155

If the food taken is a liquid and ready to build tissue, as
a thin syrup, it will not need to go through these changes.

The Organs of Digestion. — The organs of digestion are
the digestive tube, with the masticating organs, and the
glands in and along 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, and the large intestine.

The Mouth and Gullet. — 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 back side of the windpipe, and
close to the spinal column. It extends the length of the
chest, and then passes through the diaphragm and widens
into the stomach, at the upper left end of the latter.

The Stomach. — The stomach is somewhat 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 duqdejnim. (See Figs. 53, 72, and 74.)

The Liver and Pancreas. ... 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 pinkish 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. — The first part of the intestine is the
small intestine. At the lower right part of the abdomen

156

Physiology.

INTESTINE

ABDOMINAL CAVITY

this enters the larger intestine. The intestine is held
in place by the mesentery, a thin fold of transparent

membrane folded closely
around it, and supported
from the back 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.

Fig. 66. Cross-section of Abdomen.

The Mouth. — The

pupil should carefully examine his own mouth by means
of a mirror. 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
disappears when the mouth is closed. If one notes the
sensations from the mouth when it is closed, he will per-
ceive that the tongue almost entirely fills the space, touch-
ing the roof of the mouth, and the teeth in front and at
the sides.

The Tongue. — The tongue consists chiefly of muscles,
running in different directions, thus giving it 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, and so is useful in detecting and removing any
food particles that may remain on the teeth after eating.
During mastication the tongue, with the lips and cheeks,

The Digestive System.

157

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 supply of teeth from
the dentist for the asking. These should be cleaned before using them
in the class. Use pearline or any washing soda. Let each pupil make
a drawing of one of each of the four kinds of teeth ; draw both a front
(outer surface) and a side view (surface adjacent to another tooth) of
all but a molar.

Longitudinal Section

Side View

Face View

Enamel

Crown

Neck

Root

for Blood Tubes and Nerves ,

Fig. 67. 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, dividing the crown from the root.

4. A hole at the tip of the root.

To make a Section of a Tooth. — Let each pupil prepare a longitudi-
nal section of a tooth as follows : Embed 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. 67. Make a drawing of the surface thus exposed, naming the

158 Physiology.

parts. If human teeth cannot be obtained, almost any kind will serve.
Let each pupil keep his preparation.

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 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 Arrangement of the Teeth. — Beginning at the middle
of the front of the mouth, there are (in the normal adult)
eight teeth in each half jaw : two incisors, one canine, two
bicuspids (or premolars), and three molars (see Fig. 68).

Dental Formula. — The kinds and arrangement of teeth
are expressed by a dental formula, in which the nume-
rators indicate the upper jaw and the denominators the
lower, thus : I|, C^, PMf, M| (for one side of the head).

The Kinds of Teeth. — 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
in the crown. The canine tooth has a conical crown, and
a longer root than the incisor. The bicuspid has two
points. The molar has a cube-shaped 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
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

The Digestive System.

'59

gone the first of the permanent set appear. The first of
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.

KINDS OF TEETH
Incisors

Canine

Molars

TIME OF APPEARANCE
7th Month
9th "
18th "

Incisors
Canine .. .-.
Bicuspids ...

Molars

TEMPORARY SET
Upper

Lower
PERMANENT SET

Fig. 68. TEETH : Kinds, Arrangement, and Times of Appearance.

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-

160 Physiology.

mended by a reliable dentist, is not used, a good white
castile soap will serve well. It is better to use tepid water.
Toothpicks are useful in removing the larger particles.
Quill toothpicks are best; metal should never be used.
The teeth should be examined twice a year by a dentist,
and .any cavities promptly filled.

Cause of Decay of Teeth. — If the teeth are not thoroughly
cleaned 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. When the teeth are
neglected, a limy substance, called tartar, forms on them
and encourages decay.

The Salivary Glands. — The salivary glands make the
saliva and pour it into the mouth. There are three pairs
of salivary glands — the parotid, just back of the angle of
the jaw, under the ear ; its duct 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 under the tongue (see Fig. 74).

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.

The Digestive System.

161

Action of the Salivary Glands. — The salivary glands
pour into the mouth a liquid which they make 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
the saliva. From each of these cavities the liquid passes
into its duct, represented by the stem of a single grape ;
many of these unite to form the main duct, which corre-
sponds to the main stem. A thick network of capillaries

Mucous Membrane

Duct of Gland

Secreting Cells

Fig. 69. Diagram of a Salivary Gland. (After Landois and Stirling.)

surrounds the gland ; 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.

Nerve Control of Salivary Glands. — The glands are
doubly dependent on nerve control: —

1. Through the nerve control of the muscles in the
walls of the arteries 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,"

1 62 Physiology.

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 ( I ) to keep the mouth moist.
The water of the saliva soaks the food during mastica-
tion and (2) helps the process of grinding; it (3) enables
us to taste by dissolving any food that is soluble ; it
further (4) enables us to swallow what would otherwise
be a dry powder. The special element of the saliva,
ptyalin, has the power (5) 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 is needed.

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 clear sub-
stance called mucus, resembling white-of-egg. It is mucus
in saliva that makes it "stringy."

Mumps. — In the mumps the salivary glands are in-
flamed and painful. This is most noticeable in the
parotid gland, which feels the pressure of the lower jaw
in the attempt to chew.

Effect of Alcohol on the Throat. — M. Lanceraux, a
French authority, says that the use of alcoholic drinks
produces a softening of the salivary glands, together with

The Digestive System. 163

other changes in the tissue composing them. This causes
alterations in the saliva itself and accounts for the dryness
of the mouth so common among persons addicted to the
use of alcohol.

Tobacco and the Salivary Glands. — " The excessive
secretion of saliva induced by the use of tobacco is fol-
lowed by dryness of the mouth and throat, a natural result
of the overwork forced upon the salivary glands. This
dryness leads, in many persons, to the drinking of alcoholic
beverages."- — Roger S. Tracy, M.D.

Summary. — i. The chief work of digestion is to make the food into
a liquid, ready 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.

3. The parts of the digestive tube are the mouth, gullet, stomach,
and intestines.

4. Along this tube are several large - glands, such as the salivary
glands, pancreas, and liver, which make liquids to pour upon the food.

5. The tongue is composed of muscles, is very movable, and
(i) tastes the food; (2) keeps the food between the teeth during
chewing; (3) aids in swallowing.

6. A tooth has crown, neck, and root.

7. The tooth consists of dentine, containing a pulp cavity. The
crown is covered with enamel, and the root is covered with cement.

8. There are thirty-two teeth in a full set, eight in each half jaw,
beginning at the front, two incisors, one canine, two bicuspids, and
three molars. The first set of twenty teeth are called " milk teeth."

9. The teeth must be kept clean by brush and tooth powder.

10. There are three pairs of salivary glands, parotid, submaxillary,
and sublingual. Their action is controlled by nerves.

1 1 . The chief use of saliva is to change starch to sugar.

Questions. — i. Why should we not crack nuts with the teeth ?

2. Why does the physician examine the tongue of his patient?

3. Is it well to eat much soaked food ? Why not?

4. How many teeth have you, and of what kinds?
5 Why is gum-chewing injurious ?

CHAPTER XVI,

DIGESTION IN THE STOMACH.

The Pharynx. — The cavity back of the mouth, beyond
the soft palate, is the pharynx. The pharynx is a funnel-
shaped cavity, connecting above with the passages from
the nostrils; in front it opens into the mouth; below it

Eustachian Tube
H-d Palate ^\ | Soft Pa|ate, Down

Pharynx
Epiglottis, Raised

Gullet, Closed
. Glottis, Open

Fig. 70. Positions of the Organs of the Mouth and Throat during Breathing.

connects with the windpipe, through the glottis, and with
the gullet, which lies just back of the windpipe (see Figs.
70 and 71).

Position of Organs during Respiration. — In quiet respira-
tion 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 epiglottis pro-
jecting upward from below. The glottis is open and the

164

Digestion in the Stomach. 165

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.

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 epiglottis is pulled down

-Eustachian Tube
-Soft Palate, Raised
Food

Epiglottis, Down
Gullet, Open

Glottis, Closed

Fig. 71. Positions of the Organs of the Mouth and Throat during Swallowing.

over the glottis, or opening of the windpipe ; and the base
of the tongue extends back over the epiglottis; thus the
,air passages, above and below, are shut off, and the food
passes over the epiglottis into the gullet. The muscles of
the pharynx 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.

1 66 Physiology.

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
effort, temporarily arranged 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
close the air passage and hold open the food passage until
the food has passed.

Structure and Action of the Gullet. — The gullet has
an outer muscular coat and an inner mucous coat (see
Fig. 72). The muscular coat has two layers, an inner
with circularly arranged fibers, and an outer layer with
fibers running lengthwise. When the food enters the gul-
let 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 mouthful has entered the gullet the action is
involuntary. The mucous lining of the gullet has many
mucous glands which make the passageway smooth 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 persons
hold a large rubber tube with their hands in contact. Put an egg-shape,^
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 digestive
tube widens suddenly, forming the stomach ; the stomach

Digestion in the Stomach. 167

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 greatly 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 arrange-

GULLET

Fig. 72. Longitudinal Section of Stomach, showing Gastric Glands in Position.
(Back View. Mucous Coat unduly Thickened.)

ment 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 submucous coat between them, and when the stomach col-
lapses, the mucous coat is thrown into folds, usually running lengthwise.

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 be either a simple tube (see Fig. 73) or to divide
into branches, usually two or three.

1 68

Physiology.

Mouth of Giand

Epithelium

The Gastric Juice. — The liquid secreted by these glands
is called the gastric juice. The gastric juice is chiefly
water, containing a substance called pepsin, and a small
amount of acid. The amount of gastric juice secreted
daily has been estimated at four or five quarts. Of course,
we must bear in mind that nearly all of this is again
absorbed from the digestive tube, and is not a loss to the
body.

Blood Supply of the Stomach. — The mucous membrane
is well supplied with blood-tubes, but while it is resting the

blood flow is dimin-
ished, and it is pale.
But as soon as food
is introduced into the
stomach the blood flow
is greatly increased,
principal and the mucous mem-
brane becomes red.
This blood supply gives
the glands the materi-
als with which they
manufacture the gastric
juice. At the same
time the cells of the

glands are stimulated to action, and the secretion is poured
out rapidly. The saliva also aids in stimulating the secre-
tion of the gastric juice.

The Work of the Gastric Juice. — The special work of the
gastric juice is accomplished by the pepsin, aided by the
acid ; these change proteids into a soluble substance, called
peptone, which can be absorbed through the walls of the
digestive tube into the blood.

Celts

Connective Tissue
Fig. 73. Three Glands of the Stomach.

Digestion in the Stomach. 169

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 curdled. This curdling, or coagulation, is caused
by a substance in the gastric juice called rennin.

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. This muscular
action of the stomach is called the peristaltic action. The
food is thus gradually reduced to a pulpy mass called
chyme. During the first part of digestion in the stomach
the thick ring of circular fibers, called the pylorus (gate-
keeper), around the opening from the stomach into the
intestine, keeps the passage nearly closed, leaving a small
hole for liquids only. But £s~the food is reduced to the
proper condition the muscles relax and allow the chyme to
pass into the intestine. And at last any indigestible sub-
stances are usually allowed to pass.

Sphincter Muscles. — Such rings of muscular fibers as
the pylorus, guarding openings, are called sphincter
muscles.

Time of Stomach Digestion. — The time required for the
stomach digestion of a meal is from three to four hours,
though this may be much longer if very indigestible sub-
stances have been eaten, or if the condition of the body
or mind is such as to retard the process of digestion.

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
undigested materials. Some of the starch has been changed

1 70 Physiology.

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 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 m.elting 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 indigestible
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.

Heart-burn. — Heart-burn is a burning feeling in the
stomach and lower part of the chest caused by indigestion.
There is a fermentation in the stomach, usually producing
an acid or sour stomach.

Effects of Alcohol on the Stomach. — Since foods go
immediately to the stomach, and are detained there some
time, they exert their first decided influence there. This
is especially true of alcohol. The stomach receives the
full force of the blow, so to speak. The first effect of a
small amount of alcohol is to produce congestion of the
stomach. If alcohol is habitually taken, there is likely
to be a permanent congestion, or inflammation, of the
stomach. And this, in time, may result in an ulcerated
condition from which it is difficult for the stomach to
recover.

Alcohol retards Digestion. — For generations it has been
generally believed that alcoholic drinks, especially wines,

Digestion in the Stomach. 171

aid digestion. Let us look at the results of some careful
experiments on this point. Drs. Chittenden and Mendel
of Yale University have carried out a series of experi-
ments in which the digestive liquids were allowed to
act upon various food substances of the proteid class.
It was found that when so small a quantity as two per
cent of alcohol was present the digestive activity was
always diminished, and it was uniformly decreased in
direct ratio to the quantity of alcohol used. The experi-
ments with brandy, gin, and rum all showed decreased
digestive action. Three per cent claret showed decreased
activity in every case. Lager beer, in so small a quantity
as three teaspoonfuls at a meal, was found to retard di-
gestion to a very marked degree. One tablespoonful of
whisky reduced digestive activity more than seventy-five
per cent. This was the result in experiments carried on
outside of the living body, and in which only the chemical
side of digestion was studied. In the living body the irri-
tating effects of alcohol upon the stomach, together with
its effect upon the nerves, cause the glands to send out so
much more gastric juice that the delay is not so great.
But yet, these experimenters found that in the stomach
digestion with alcohol took from fifteen to twenty minutes
longer than digestion when no alcohol was given. Thus
when put to the test alcohol does not appear to act as an
aid to digestion.

Alcohol and Dyspepsia. — Instead of aiding digestion,
the use of alcohol tends to produce dyspepsia. "The
effect of alcohol is to produce a state of excitement and
irritation in the stomach, the result of which, when fre-
quently repeated, is permanent congestion and numerous
forms of dyspepsia." — J. H. Kellogg, M.D.

172 Physiology.

How Alcohol deceives. — The alcohol dyspeptic has an
uncomfortable or painful sensation in the stomach. He
takes a drink of liquor and the pain disappears; so he
thinks the alcohol has benefited him. He realty knows
that the trouble will soon return, and worse than before.
The fact is, that the last dose of alcohol has, by its narcotic
effect, deadened sensation in the stomach. The following
authoritative quotations prove this. " The deceptive feel-
ings of ease, warmth, and comfort which cause the unwise,
excessive eater to think that alcohol has aided the diges-
tion of the mass within, are mainly deceptive feelings, due
to the benumbing influence of the anaesthetic poison
in deadening the uneasiness and pain of indigestion."

— Norman Kerr, M.D.

"The invariable effect of alcohol when taken into the
stomach is that of paralysis of the nerves of sensation, the
amount of this paralysis depending upon the quantity of
the poison administered. This explains why it is that per-
sons feel better after having partaken of the liquid. They
have less feeling, and what they do have is less reliable."

— C. H. Shepard, M.D.

Alcohol and Peristaltic Action. — Alcohol at first quick-
ens the peristaltic action of the stomach. But after a time,
like the rate of heart-beat, it becomes slower than it was
before alcohol was taken. And the result of the continued
use of alcohol is sluggishness in this necessary part of
digestion and, of course, serious hindrance of digestion.

Summary. — i. The pharynx opens into the mouth, nostrils, wind-
pipe, and gullet.

2. In breathing, air passes through the nostrils and the pharynx,
and enters the windpipe ; the soft palate is down and the epiglottis is
up.

3. In swallowing, food passes from the mouth, through the pharynx,

Digestion in the Stomach. 173

into the gullet ; the soft palate is raised and the epiglottis is pressed
down, covering the opening into the windpipe.

4. Food is pushed along the gullet by the shortening of the ring-
like muscles.

5. The stomach is pear-shaped, with the large end to the left.

6. The stomach has four coats, — serous, muscular, submucous, and
mucous.

7. The gastric glands are tube-like pits in the mucous coat of the
stomach. They make gastric juice.

8. The mucous coat of the stomach contains more blood during
digestion, and is more red, than when resting.

9. Pepsin in the gastric juice changes proteids to peptones.

10. The muscles of the stomach wall give a churning motion.

1 1 . The food is reduced to a thick liquid called chyme.

12. The stomach requires three or four hours to digest a meal.

Questions. — i. Why is one more likely to choke if he thinks about
the process of swallowing?

2. What are the peculiarities of a cow's stomach?

3. What is the " rice ordeal " ? What can we learn from it?

4. Why do athletes eat sparingly before a game?

5. How does indigestion sometimes make one short-winded?

6. Why is it uncomfortable to hold the organs in the " swallowing
position"?

7. Why is it hard to swallow a pill? Why take water with it ?

8. Try swallowing repeatedly. Why is it difficult?

9. How is the structure of the windpipe favorable to swallowing?
10. Why is indigestion more noticeable in the stomach than later?

CHAPTER XVII.
DIGESTION IN THE INTESTINE.

The Parts of the Intestine. — The intestine consists of two
parts : first, the long and narrow small intestine ; second,
the short and wide large intestine. (See Fig. 76.)

The Small Intestine. — The small intestine has essentially
the same structure as the parts of the digestive tube already
studied; namely, a muscular coat and a mucous lining. The
muscular coat has two layers, one of circular and the other1
of longitudinal fibers. The muscular coat mixes the juices
with the food and moves it along. The muscular action
of the intestines is a slow writhing motion, called peristaltic
action. The mucous coat supplies mucus, which keeps
the surface soft and smooth.

The Liver. — The liver is just under the diaphragm. It
is convex above, where it fits the hollow under surface of
the diaphragm, and hollow below, where it fits over the
upper surface of the stomach. The greater part of it is
on the right, as the greater part of the stomach is on the
left, side of the body. The liver is dark colored and of
very delicate structure, chiefly because it has very little
connective tissue. It is the largest gland in the body,
weighing nearly four pounds.

Bile. — Bile is a bitter, golden red, or sometimes greenish
yellow, liquid made by the liver from the blood. About
two and a half pints of bile are made daily.

Digestion in the Intestine. 175

The Bile Sac. — This is a sac of about the size and shape
of a pear, and is attached to the under surface of the liver.
It has a duct, the bile duct, which empties into the small
intestine a few inches beyond the stomach. Part of the

Sublingual
I i vary Gland

Submaxillary
—-Salivary Gland

Mesenteric —
Vein

•••• Mesentery

Fig. 74.

Intestine
The Organs which change Food into Blood.

bile is at once poured out into the intestine, but part,
especially when we are not digesting, is stored in the bile
sac, to be poured out during digestion.

Functions of Bile. — i. It aids in emulsifying the fats.
2. It aids in the absorption of fat.

1 76 Physiology.

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 retards this putrefaction.

The Pancreas. — Just back of the stomach is another im-
portant gland, the pancreas. It is a pink organ, weighing
three or four ounces and having the shape of a dog's
tongue. It has a duct which empties into the small intes-
tine at the same point where the bile enters, but it has no
sac in which to store the liquid which it secretes. It takes
from the blood certain materials and makes a liquid called
pancreatic juice.

Pancreatic Juice. — • This is a clear, sticky liquid, very
much like saliva in appearance. Although the pancreas is
a small organ, its work is very important. It gets a large
blood supply and makes a large amount of pancreatic juice.
The pancreas is often eaten, being known by the name
" sweetbread."

The Work of the Pancreatic Juice. — The pancreatic juice
acts on all the principal classes of foodstuffs : —

1. A substance in it called am^lopsin acts on starches,
changing them to sugar even more actively than the ptyalin_
of the saliva.

2. Another substance in pancreatic juice is trypsin ; like
the pepsin of gastric juice, it changes proteids to peptones.

3. The pancreatic juice also emulsifies the fats. The
fat is divided into exceedingly fine drops, each covered
with a coating of albumen. An emulsion can be made
artificially by shaking together water, oil, and white-of-egg,

Digestion in the Intestine. 177

The shaking breaks the oil into fine drops, which would
soon gather again if no other substance were present ; but
the albumen forms a thin coating around each droplet,
enabling it to remain distinct in the liquid.

The Intestinal Glands. — The mucous membrane of the
small intestine has an immense number of tube-like glands.
(See Fig. 78.) Their structure is
much like that of the gastric glands
shown in Fig. 73. Fig. 75 shows
them as seen when cut across.
These glands make a liquid called
intestinal juice, which completes the
work of the other digestive liquids.

Review of Digestive Liquids. -

Saliva acts only on starch, gastric
juice on proteids, bile on fats; but
pancreatic juice acts on all three. the intestine, showing intestinal

Glands in Transverse Section.
T A r^, . (Highly magnified.)

The Large Intestine. — This con-
sists mainly of the colon, the final portion being called the
rectum.

The Colon. — The small intestine joins the colon near the
lower right side of the abdomen. Where the small intes-
tine enters the colon there is a valve which keeps the
material from coming back into the small intestine. The
colon runs upward on the right side (ascending colon),
crosses over to the left side (transverse colon), and descends
on the left side (descending colon), and, after curving some-
what like a letter S, becomes straight again, this part being
called 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. (Fig. 76.)

78

Physiology.

Gullet

Stomach
Duodenum

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 mem-
brane. The muscular coat
pushes the contents along
and mixes them with liq-
uids ; 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
| make the surface slippery,
o 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 ducts; these com-
pound glands are the sali-
vary glands, the pancreas,

Fig. 76. The Stomach and Intestines. and the liver.

Length of the Intestine. — The length of the small in-
testine is about twenty-five feet, and of the large intestine
five or six feet. The large intestine is not a direct contin-
uation 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 (see
Fig. 76). In some animals this is large and has consider-
able length, but in man it is very short. There is a closed

Vermiform
Appendix

Rectum

Digestion in the Intestine. 179

prolongation of the cecum, the vermiform appendix. This
appendix is frequently the seat of serious or fatal inflam-
mation, called appendicitis. This disease is not usually
caused by the lodging of seeds in the cecum, as most
people suppose ; still it is better not to swallow such things.

A Simple Gland. — A gland is a structure which takes
liquid from the blood and pours it out on some surface.
In its simplest form a gland is a mere pit, or hole, such as
the gastric glands, shown in Fig. 73. The blood capilla-
ries give off lymph around the gland, and from this lymph
the cells of the gland take their material. A sweat gland
needs more length than a gastric gland, and the extra
length is coiled up in a ball at the inner end. Many
small glands are forked at their inner ends, thus increas-
ing their surface.

Kinds of Glands. — Fig. 77 shows different forms of
glands, from the simplest to the most complex. In the
compound glands the lining of the duct, which is merely
a passageway, is different from the rest of the gland.
Glands that take waste matter from the blood are called
excretory glands, such as sweat glands ; they do not usu-
ally make much change in the material. Such glands as
the gastric glands change the material that they pour out;
the gastric juice is different from anything found in the
blood. Such glands are called secretory glands. Sweat is
an excretion ; gastric juice is a secretion. Still, all glands
are said to secrete, that is, to separate something from the
blood. And gland action in general is called secretion.
In structure, then, glands may be simple or compound.
In function they may be excretory or secretory.

Control of Glands. — All glands are under the control
of nerves. But this control is involuntary, and under the

i8o

Physiology.

management of the sympathetic nervous system. The
mouth may "water" for some attractive food, or become
dry through fear or anxiety. Hence we can see why a
restful, contented condition of mind and body will be
likely to favor the action of the many glands along the
digestive tube; and, on the other hand, why anxiety or
fretfulness are likely to hinder their action.

Epithelium or Epidermis.
i

Compound Glands
Fig. 77. Simple and Compound Glands.

Effect of Alcohol on the Small Intestine. -- The effect
of alcohol on the small intestine is not so noticeable
as on the stomach, for two reasons. First, part of the
alcohol is absorbed in the stomach, and so does not reach
the intestine. Second, the alcohol that does pass on into
the intestine is diluted by the gastric juice.

Nature's Efforts for Protection. — Wherever alcohol
comes in contact with any of the tissues of the body it

Digestion in the Intestine. 181

produces irritation. So, in the mouth, gullet, stomach,
or intestine, the irritating effect of alcohol causes an
increased secretion by the glands. That is, more saliva
is poured out, more gastric juice, etc., and more mucus is
secreted and poured out all along the digestive tube. All
this is an effort of self-protection; and the diluting of the
alcohol thus brought about diminishes, though it cannot
stop, the poisonous effects of the alcohol.

Effect of Cider on the Small Intestine. — The continued
use of hard cider is likely to have a very injurious effect
on the small intestine. Cases have been known in which
it has caused death, with extensive ulceration of the walls
of the small intestine.

Summary. — i . The intestine has two coats, an outer, muscular, and
an inner, mucous, coat.

2. The intestine consists of two parts, the small intestine and the
large.

3. The liver is the largest gland in the body. It secretes bile, which
is stored in the bile sac.

4. Bile aids in emulsifying and absorbing fats, and retards putre-
faction. Bile is partly waste matter.

5. The pancreas is a small tongue-shaped organ back of the
stomach. It secretes the pancreatic juice.

6. Pancreatic juice acts on proteids, fats, and starch.

7. In the walls of the intestine are many small intestinal glands.
Their secretion helps complete the process of digestion.

8. The main part of the large intestine is the colon. It has three
parts, ascending, transverse, and descending. The last part of the
intestine is the rectum.

9. The small intestine is twenty-five feet long, the large, five or six.

10. A gland is a hollow structure that secretes a liquid from the
blood.

1 1 . Glands are simple, like an intestinal gland, or complex, like the
pancreas.

12. Glands are excretory,, such as the sweat glands, or secretory,
such as the gastric glands.

182 Physiology.

Questions. — I. Why is there such a difference in the lengths of
intestine in the cat and the cow?

2. What is biliousness?

3. Why is the pancreas sometimes called the "abdominal salivary
gland"?

4. Why does digestion proceed more slowly in the intestine than
in the stomach?

5. In what direction should the abdomen be rubbed to assist a
movement of the bowels?

CHAPTER XVIII.
ABSORPTION.

Absorption a Living Process. — The layer of cells which
forms the inner surface of the mucous membrane is called
epithelium. These cells are moist, soft, and thin-walled.
They take up the digested foods, now in liquid form, and
pass them on to the lymph and so into the blood capillaries
that are thickly distributed just beneath the surface.

Absorption from the Mouth. — Sugar, and some other
substances, may be absorbed by the mouth as soon as it is
dissolved. But very little material is thus absorbed.

Absorption from the Stomach. — Some parts of the food
that are already digested, or such matters as are soluble,
e.g. water containing sugar, peptone, salts, etc., may be
absorbed immediately through the walls of the stomach
into the blood capillaries. Recent experiments show, how-
ever, 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."

Absorption from the Small Intestine. — Most of the
digested food is absorbed in the small intestine.

Increased Surface for Absorption. — The mucous mem-
brane of the small intestine is thrown into ridges, but,
unlike those of the stomach, they run crosswise. Again,

183

1 84

Physiology.

while the folds in the lining of the stomach are temporary,
these are permanent. They increase the surface of the
lining and retard the passage of the food material, and so
aid the process of digestion and of absorption.

Villuses. — To increase, still further, the surface for
absorption, the mucous membrane of the small intestine is

thickly covered with
little cylindrical pro-
jections, like the
"pile" on velvet.
Each of these pro-
jections is a villus.

Villuses

Intestinal Glands —

Structure of a Vil-

Fig. 78. Mucous Membrane of Small Intestine, showing lug A

Intestinal Glands and Villuses.

IS

about a thirtieth of
an inch long. It is made up of four parts : (i) on the out-
side a layer of soft, moist, thin-walled cells; (2) plain
muscle fibers, running lengthwise; (3) a network of blood

Lacteal with Valves

Capillaries Muscles

Fig. 79. Four Parts of a Villus.

Epithelium

capillaries; and (4), near the center, lymph capillaries,
called lacteals. Fig. 79 shows these four parts separate,
while Fig. 80 shows them combined, as they are in the
complete villus.

Absorption. 185

Absorption by the Villuses. — The digested food is in
liquid form and surrounds the villuses. The three main
substances to be absorbed are peptones, sugar, and fat.
The outer cells of each villus absorb these and pass them
inward. The peptones and sugars are taken into the blood
capillaries, while the fats enter the lacteals.

Muscular Action of the Villuses. — 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-
srl." cular Fibers
Capillary Network

Fig. 80. A Complete 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. This action also helps the flow in the blood
capillaries.

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 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 circu-
lation. During most of the time the thoracic duct and

i86

Physiology.

the lymphatics of the intestines would hardly be noticed
because they are filled with the clear lymph. But after

Right Lymph Vein

Junction of Thoracic
...- Duct with Left Sub-
clavian Vein

Mam Lymph Vein
(Thoracic Duct)

Intestine

Lymphatic Glands

Fig. 81. Lymph Veins (Lymphatics).

absorption of fatty matter they are filled with a white
liquid, called chyle, and are easily seen. (See Fig. 81.)

The Portal Circulation. — All the veins coming from the
stomach and intestines unite to form a large vein that goes
to the liver ; this is the portal vein. When the portal vein
enters the liver it does what veins do not do elsewhere in
the body, — it divides into smaller branches. This division

Absorption.

i87

and subdivision goes on till the portal vein forms capil-
laries branching all through the liver.

The blood from these capillaries collects again in veins,
which unite in one vein, the hepatic vein, which carries
the blood into the postcaval vein just under the diaphragm.

Fig. 82. Diagram of Portal Circulation.

Going back again to the beginnings of the portal vein,
it is clear that it starts from the capillaries of the stomach
and intestines. And these capillaries, as we have just seen,
absorb the peptones and sugars. The sugars and peptones,
therefore, go directly to the liver after being absorbed.

Double Blood Supply to the Liver. — The liver also re-
ceives blood from the hepatic artery, a branch of the aorta.

i88

Physiology.

Thus the liver gets blood from two sources, the portal vein
and the hepatic artery, but is drained by one vein, the
hepatic vein.

Work of the Liver. — We have seen that the liver makes
bile. The liver also makes another substance out of the
blood that passes through it. This is glycogen, or "animal
starch." It is also called " liver sugar," as it gives to liver

Mesenteric
Lymph Veins •<
(Fats)

Fig. 83. Plan of Absorption.

a sweetish taste. Glycogen is given back to the blood and
carried away by the hepatic vein to the body, where it
serves as food to the tissues.

Routes of Different Foods after Absorption. — There are,
then, two routes taken by the food after absorption. The
peptones and sugars go to the liver through the portal

Absorption.

189

vein, while the fats are carried by the main lymph duct, or
thoracic duct. These two streams unite before reaching
the heart. The fats pass around the liver, instead of
through it as do the peptones and sugars.

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. '}
Salts. |
Sugars.
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 Fats I Emulsified.
L ' Decomposed.

Water. ]
Salts.
Sugar. f
Peptone. )
Fats.

Blood

Capillaries.

Lacteals.

LARGE
INTESTINE.

Food
Forced on.

Mucous.

Mucus.

Water.

Fig. 84. Outline of Digestion and Absorption.

Amount of Liquid Absorbed. — It is estimated that there
is poured into the digestive tube daily one quart of saliva,
four or five quarts of gastric juice, one quart of bile, and
about a quart of pancreatic juice. If the food and drink
amounts to two quarts, there must be more than two gal-
lons of liquid absorbed from the digestive tube each day.

1 90 Physiology.

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 is 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
stove, 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 pro-
duced by the oxidation of the tissues, and are mostly thrown
off by the lungs, kidneys, and skin.

Effect of Alcohol on the Liver. — Alcohol is absorbed by
the blood capillaries of the mucous membrane of the stom-
ach and intestine, and so goes directly to the liver through
the portal vein. Alcohol is capable of seriously injuring
both the structure and the functions of the liver.

Alcohol and the Structure of the Liver. — We have
already learned that the main reason why the liver is so
tender and delicate in structure is because it has in it so
little connective tissue. Alcohol causes an increased de-
velopment of connective tissue in the liver, so that the
continued use of alcoholic liquors makes the liver hard and
tough. This over-growth of the connective tissue presses
upon and squeezes out the soft tissue of the liver cells, so
that the surface is covered with little roughened elevations

Absorption. 191

resembling the heads of hob-nails. A liver of this kind
is called a " hob-nailed liver," or sometimes "gin-drinker's
liver."

Alcohol and the Work of the Liver. — The liver is a very
important organ for working over the newly absorbed food.
All the sugars and digested proteids go directly to the liver
through the portal vein. The alcohol is absorbed by the
capillaries in the stomach and intestine, and goes with the
sugars and proteids. In the first place alcohol acts on
the proteid material, coagulating albumen, for instance.
The liver is, in part, an organ of excretion ; that is, it
throws out waste matter. The use of alcohol injures the
liver so that it does not do its work perfectly. Hence we
can see why the liver is almost sure to show the effects
of drinking alcoholic liquors. Not only is the liver itself
injured, but the whole body suffers because of the failure
of the liver to do its part of the work of getting rid of
waste matter.

Alcohol and the Vital Organs. — "Alcohol exerts its
essential and most significant influence on the vital organs
by being taken up in the circulation, and thus brought into
contact with the cellular tissue of the vital organs. Cirrho-
sis of the liver, diseases of the heart, of the arteries, of the
mucous membrane of the alimentary canal, along with
gout, diabetes, and fatty degeneration, are all ascribed to
it." —Adolf Striimpell, M.D.

Alcohol causes Degeneration. — The habitual use of alco-
hol may result in degeneration of the muscles, heart, brain,
nerves, liver, kidneys, or of other organs ; but of course this
is not the only cause of degeneration. The use of alco-
holic liquors tends to make these other causes active.

192 Physiology.

Summary. — i . The cells lining the digestive tube take up the
digested food, now in liquid form, and pass it into the lymph.

2. There is some absorption, from the stomach, of sugar and
peptone. Most of the absorption is from the small intestine.

3. The hair-like villuses greatly increase the absorbing surface.

4. A villus has four parts, the outer layer of cells, plain muscle
fibers running lengthwise, blood capillaries, and lacteals.

5. The outer cells of the villus take up the liquefied food.

6. Sugar and proteids enter the blood capillaries; fats enter
the lacteal capillaries.

7. The muscles of the villus pump the liquids along and aid
absorption.

8. The lacteals are part of the lymph system of the body. They
absorb and carry fats.

9. The veins from the stomach and intestine join to form the por-
tal vein which enters the liver. Here it breaks up into capillaries.

10. The liver has two supplies of blood, from the portal vein and
the hepatic artery. It is drained by one vein, the hepatic vein.

1 1 . The liver makes bile and glycogen.

12. Sugars and proteids go through the liver; fats pass around the
liver through the main lymph vein, or thoracic vein.

13. There are over two gallons of liquids absorbed daily.

Questions. — i. Why is it best to begin a hearty meal with soup ?

2. Why should the liver receive so much blood ?

3. What is the meaning of " biliousness " ?

4. What is the advantage of a " fruit diet " ?

5. Why does active exercise tend to keep the bowels open ?

CHAPTER XIX.
HYGIENE OF DIGESTION. — NUTRITION.

Digestion and Circulation. — During digestion there must
be a large supply of blood in the digestive organs. It is
needed both to supply the material for the glands to make
the digestive liquids and also to absorb and bring away the
newly digested food. Therefore, during digestion there
must be less blood in other parts of the body.

Digestion and Muscular Work. — If one exercises actively
immediately after eating, the process of digestion will be
interfered with, because the bloo'd will be drawn away
from the digestive organs to the muscles. It is well to
rest for a short time after eating a full meal.

Digestion and Study. — For the same reason it is better
not to begin hard study immediately after a full meal. The
blood needed for the work of digestion will be called to the
brain, and digestion will suffer.

Solid Foods digest Slowly. — If a very hungry person
begins his dinner 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-
cesses of digestion, and be absorbed into the system and
satisfy hunger.

Value of Soup. — But if the meal begins with soup, which
is readily absorbed, the demand of the system will begin to
be met, and there will not be the same tendency to rapid

193

1 94 Physiology.

eating. Further, a warm soup stimulates the blood flow in
the mucous membrane, and thus prepares for more thorough
digestion.

Desserts. — Dessert and sweetmeats, following a meal,
are often helpful by further stimulating the secretion of the
glands. Nuts, which are not very digestible, are beneficial
if eaten sparingly. The agreeable taste stimulates the
salivary glands, and the saliva stimulates the gastric glands
to increased activity. The danger in taking dessert is that
the pleasing taste tempts us to continue eating after we
have had enough. Pie is usually hard to digest.

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 digestive 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. Of course the organs
suffer and break down if this treatment is continued.

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 condition, as
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 dismissed from the mind. For those whose
digestion is not strong, it is desirable to rest after each
meal.

Conversation at Meals. — During a meal there should be
conversation on topics of general interest. Talking at the

Hygiene ot Digestion. 195

table also makes us more deliberate in eating. " Chatted
food is half digested."

Time of Eating. — The American custom of three meals
a day seems well adapted to the needs of our people. The
best time for the chief meal is 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. In
many homes 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 a time. 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 mankind
eat too much.

Intemperance in Eating. — "I have come to the conclu-
sion that more than half of the disease which emoitters 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

196 Physiology.

use of alcoholic drink, considerable as I know that evil to
be." — Thompson.

" Bitters." - Many of the patent medicines sold under
the. name "bitters" contain alcohol, and may do great
injury both on account of the alcohol and of other power-
ful drugs of whose presence the user is unaware. No such
medicines should be used except under the advice of a
physician.

Fat as a Tissue. — As a tissue fat serves as a stored-up
food. A fat person can endure starvation 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 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.

Importance of Renewal of Blood and Lymph. — The

lymph surrounds the individual cells which make up the
tissues of the body. Every cell lives an independent life,
to a certain extent, taking its nourishment directly from
the lymph around it. The importance of an abundant
supply of good lymph is apparent. The supply and renewal
of the lymph depends on the blood.

Effect of Digestion on Blood and Lymph. — If digestion is
not good, or if there is not enough good food, 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 general tone of the body will
soon be lowered; for the health of the body as a whole
depends on the average condition of the cells composing

Hygiene of Digestion.

197

the body, just as the condition of any community depends
on the average condition of the individuals of that com-
munity.

Assimilation. — The formation of tissue from the mate-
rials brought by the blood is assimilation. It is the last
step in building up the tissues.

Capillaries

Vein....

Artery,

Artery

Vein

Capillaries
Fig. 85. Diagram of the Heart and Blood Tubes (Back ViewX

Blood a Mixture of Good and Bad. — In the blood streams
are combined the good and the bad. The newly digested
food is received into a current of impure blood in the post-

198 Physiology.

caval 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 pure, — the same

Lung Capillaries

Pulmonary Vein

Left Auricle
Left Ventricle.

Aorta___

Body Capillaries

Fig. 86. Plan of Circulation, representing the Right and Left Halves of the Heart sepa-
rated, showing that the Blood makes but One Circuit.

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.

Hygiene of Digestion. 199

Action of Diseased Kidneys. — The kidney takes, during
health, only the waste matters, leaving the valuable nour-
ishing material. But, in disease, the kidneys may take out
some of the most valuable nourishing material. 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 diseased kidney may
be said to have become crazy, and in the disease called
"diabetes" throws out sugar, and in " albuminuria " ex-
cretes 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. Figs. 85, 86, and 87 show what the blood stream
gives to each of the organs of the body and what it takes
from them to throw out as waste matter.

How the Body Changes. — The body is continually
changing, new material from the digested food taking the
place of the worn-out tissues. It is a common saying that
the body changes once in seven years. But while the
more active tissues, such as muscle, must change many
times in a year, we know that the teeth do not grow after
they are once formed.

The Body like an Eddy. — The changes in the body have
been compared to an eddy in a stream. The form of the
eddy remains the same, while particles of water are enter-
ing on one side and leaving on the other. In a short time

2OO Physiology.

all the particles are changed. But in the body the more
permanent parts change slowly.

Nutrition. — Nutrition includes all the changes that take
place in the body from the reception of food to the excre-
tion of the waste matter. It includes digestion, absorption,
circulation, assimilation, respiration (oxidation), and excre-
tion. The first four of these processes are stages in build-
ing up the tissues ; the last two are process of tearing doivn.

We cannot destroy Matter. — When a stick of wood is
burned it is no longer wood. But the matter is not de-
stroyed. It could all be obtained again from the smoke
and ashes. So, in the continual wasting away of our
bodies, there is no real loss of matter. Our weight is re-
duced, but the wastes are still part of the earth or the air,
and are of use in the world. We are as unable to destroy
matter as we are to create it.

The Ceaseless Round of Matter. — A particle of carbon
in the carbon dioxid of the expired breath may be taken in
by a blade of grass. A cow eats the grass, and we may
before long take the very same particle of carbon in the
milk or the flesh of the cow. Or the particle of carbon
may become part of a grain of wheat, and be made into
flour and be eaten as bread and be a part of the body
once more. Thus, there is a ceaseless round of matter
into and out of our bodies. No one has a monopoly of
any portion of matter ; it is now ours, now some one else's.

We cannot create Force. — We get our energy from the
food we eat, just as an 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
living, growing, self-directing, and self-maintaining ma-

Hygiene of Digestion. 20 1

LUNG

PULMONARY VEIN
LEFT AURICLE

LEFT VENTRICLE

PULMONARY ARTERY

RIGHT VENTRICLE

RIGHT AURICLE

Fig. 87. The Circulation and the Work of the Blood

202 Physiology.

chines. Still, starvation soon puts an end to our ability
to produce energy of any kind.

How we depend on Plants. — The larger part of our food
is vegetable. And the animal foods, such as meat, milk,
cheese, butter, eggs, etc., were made by the animals from
vegetable matter. We are, therefore, directly or indirectly,
dependent on plants for all our food. On the other hand,
plants use as their food considerable of the waste matter
thrown off by animals.

Effect of Alcohol on Nutrition. — Nutrition includes diges-
tion, absorption, circulation, respiration, assimilation, oxi-
dation, and excretion. Alcohol is capable of interfering
with every one of these processes. In the digestive tube
alcohol, taken in sufficient quantity, coagulates albumen
and retards the action of the gastric and other juices.
Circulation is usually disturbed by the presence of alco-
hol, and its continued use, even in quantities that the user
considers moderate, may permanently injure the organs
of circulation in several ways that have been described.
Respiration may be affected, and the whole system weak-
ened by reducing the lung power. But the effects of
alcohol on nutrition are especially marked in the processes
that are more particularly designated by the word " nutri-
tion." These processes take place in the tissues : growth,
the oxidations in the cells, the production of force, and
the production of waste material in the cells. All these
processes are seriously hindered by the presence of the
poisonous substance, alcohol.

Alcohol and Oxidation. — The imperfect oxidation in the
tissues caused by alcohol is like the imperfect burning of
a lamp or stove, which produces little heat, but much
smoke. The soot of a smoking lamp illustrates the inju-

Hygiene of Digestion. 203

rious waste matter that is produced in our bodies by the
imperfect oxidation when alcohol is present. Finally,
alcohol interferes with the excretion of waste matter;
and this process would go on more slowly than before,
even if there were not more waste matter to be thrown
off. So, from first to last, alcohol is capable of doing
great harm to the process of nutrition. This is true of
nutrition in the bodies of grown persons, and still more
marked in the young, where nutrition should go on more
actively because new tissues should be built.

Summary. — i . During digestion a large supply of blood is required
in the digestive organs.

2. Muscular workj immediately after eating, interferes with digestion
by calling the blood away to the muscles.

3. Hard study, right after a hearty meal, hinders digestion in the
same way.

4. Soup is a good beginning of a hearty meal, as it is more readily
absorbed than solid food.

5. Desserts, in moderate quantity, are useful in stimulating the
glands which supply the digestive liquids.

6. Hot drink at meals aids weak digestion.

7. Imperfect mastication leads to eating too much, and throws too
much work upon the other organs of digestion.

8. A calm condition of the nervous system favors digestion.

9. Conversation on cheerful topics is favorable to digestion.

10. Three meals a day are best for most persons.

1 1 . For persons hurried in the middle of the day it is often better
to take the chief meal at the close of the day's work.

12. Meals should be regular, and one should not eat between meals.

13. There is much intemperance in eating.

14. Fat, as tissue, is stored food.

15. The cells depend on the lymph for their nourishment, and the
lymph is supplied by the digested food.

1 6. The blood is a mixture of good and bad material ; each organ,
in health, selects from the blood what it needs, the tissues taking
nourishment, and the organs of excretion removing the waste
matters.

204 Physiology.

17. Diseased kidneys may remove valuable nourishing materials
from the blood.

1 8. The body keeps changing, taking new matter to replace worn-
out tissue.

19. Nutrition includes digestion, absorption, circulation, respiration,
assimilation, oxidation, and excretion.

20. We cannot destroy matter. Our waste products become part
of earth or air.

21. We cannot create force. We get our energy from food as an
engine gets its energy from fuel.

22. We depend on plants for our food.

23. Alcohol interferes with nutrition at every step.

Questions. — i . Should a person who has studied hard try to do hard
muscular work the same day ?

2. What are the advantages of a " course " dinner?

3. Which is more wholesome, dry toast or soaked toast ? Why?

4. Why do we give a horse exercise and keep fattening stock quiet?

5. Are fat people large eaters ? Are thin people light eaters?

6. Do sweat glands ever excrete valuable material?

7. In Fig. 87 find what the blood gives to each organ and what it
takes from each.

8. Classify the organs represented in Fig. 87.

9. Name the organs that change most rapidly.
10. Name the organs that change most slowly.

n. What is the source from which plants get their energy?
12. Is matter defiled in passing from one body to another?

CHAPTER XX.
ALCOHOL.

Fermentation. — The juice of the apple as it is found in
the fruit is healthful. If the juice is pressed out of the
fruit and set in a warm place, it will soon be observed that
bubbles of gas are given off. From this we may know
that a sharp, pungent liquid is forming in the juice. The
gas is carbon dioxid, and the new liquid is alcohol.
Pressed-out fruit juices undergoing this change usually
become frothy, or "work," as we say, and at the same
time acquire a sharp taste. This change is due to a
process called fermentation.

Any substance in which alcohol is produced in this way
is found to contain a microscopic, one-celled plant, oval or
elliptical in outline, which acts as a ferment. These fer-
ments are found on the skins and stems of fruit as it is
ripening, and there they do no harm ; but when the fruit
is crushed and the juice pressed out, these ferments are
washed into the juice, and as has been clearly proved, are
the causes of the changes in the fruit juice described above.
In the liquid they begin to grow and multiply, and as they
grow they break up or decompose the sugar of the juice,
and form at least two substances, carbon dioxid and alcohol.
This change is called alcoholic fermentation.

A small number of ferments can change a large amount
of the sugar of a fruit juice into carbon dioxid and alcohol.
The juice of sweet apples contains much sugar, and thus

205

206 Physiology.

will produce more alcohol than that of sour fruit. Then,
too, we must remember that the growth of the ferments is
so rapid that a small number of ferments soon becomes a
large number.

Cider. — Ripe apples are a healthful fruit. There is no
alcohol in a sound apple. But the juice of the apple while
it is in the fruit, and that same juice after it is pressed out
and changed by the ferments, are very different in char-
acter. In the latter the ferments have changed the sugar
to alcohol. Under ordinary circumstances, alcohol is
formed so rapidly after the juice is pressed out of the
crushed fruit, that what is often called sweet cider contains
2 per cent or more of alcohol, and is, therefore, by no
means a safe beverage. The amount of alcohol in a barrel
of cider when it is put in the cellar in the fall may be
small, but as the ferments keep on with their work, the
quantity of alcohol increases until it may reach as much as
10 per cent of the whole. Besides the ordinary cider
obtained from apples, a cider made from pears and called
perry is used.

Cider is not only intoxicating, but experience has proved
that some of the worst forms of disease result from the
habitual drinking of cider. It also leads to the desire for
stronger drinks.

Fermented Drinks. — All the alcoholic liquors are the
result of alcoholic fermentation of various substances.
Such liquors may be classed in three groups, — wines,
malt liquors, and distilled liquors.

Wines. — The wines are the result of fermentation in
the juice that has been pressed out of grapes or other
fruit which is rich in sugar. This fermentation was, in all
probability, discovered very early by the human race, for

Alcohol. 207

we find it in use among nearly all races of men, and ac-
counts of it in the early records of history. But it was
not until the microscope was invented that the ferment
which is its cause was known. When alcohol accumulates
in the fermenting liquid to the amount of 14 per cent, it
kills the ferment germs ; consequently no natural wine
can contain more than this amount. Wines are classed
as light wines and heavy wines. The light wines contain
from 5 to 12 per cent alcohol. The heavy wines include
all wines with more than this amount, and have had
brandy, or other spirit, added to them, having from 16
to 25 per cent, or even more, alcohol.

The Danger in Wine-drinking. — Because some of the
wines contain a relatively small per cent of alcohol, there
is a common delusion that there is not much harm in
drinking them. Let us consider three points regarding
this, (i) We do not argue or act in the same way in re-
gard to other substances that are known to be poisonous.
We do not venture to take small doses of arsenic or phos-
phorus, saying, " Oh ! a little will not hurt me." The
poison is there just the same and will have its effect.
(2) In small quantities the alcohol in the wine has the
power to fix the alcohol habit, which is cumulative, and
leads to a desire for more, which is almost impossible to
resist. (3) Because of the very fact that the percentage
of alcohol in wines is low, enough more of the liquid is
taken to introduce into the system actually more alcohol
than is taken by those who drink stronger liquors.

Wine-drinking cannot be too strongly condemned, either
on the ground of the effects it directly produces or the fact
that it leads to the use of stronger liquors.

Vinegar. — After sweet cider has fermented — or become

208 Physiology.

" hard," as we call it — it usually passes on to become vine-
gar. This change is another form of fermentation, due
to another kind of ferment. This formation of vinegar is
likely to take place in any weak solution of alcohol-fer-
mented liquor. In this fermentation acetic acid is pro-
duced, hence it is called the acetous fermentation. It is
interesting to note that the word " vinegar " comes from
the French vin (wine) and aigre (sharp or sour), as vinegar
was formerly made by this secondary fermentation of the
lighter wines.

"Temperance Drinks." — Many well-meaning persons
use the various preparations called "root beer," perhaps
without realizing that most, if not all, of them are made
with yeast and in their preparation undergo fermentation,
thereby producing alcohol, though not ordinarily in large
amounts. By giving such drinks (often called "temper-
ance drinks ") to children, an appetite for alcohol may be
cultivated and the beginning of a terrible habit made. It
may be well here to call attention to the real meaning of
the word " habit," that which holds us.

Ferments. — There are many other ferments which, when
introduced into liquids, cause various changes, i.e. there
are many sorts of fermentation. For instance, putrefac-
tion is a kind of fermentation of substances containing
nitrogen, during which process offensive gases are given
off. Most of the ferments belong to a group of very
simple, one-celled plants called Bacteria. (The alcoholic
ferment is an exception, not belonging to the Bacteria.)

Yeast. — Yeast is used in bread-making for the purpose of producing
gas within the dough, and by this means causing the dough to puff up
and become light. The yeast acts on the free sugar in the flour, and
produces carbon dioxid and alcohol. The alcohol turns to vapor and
passes*out of the bread while it is baking.

Alcohol. 209

Malt Liquors. — These are obtained from the small grains,
especially barley, by soaking the grain and then allowing
it to sprout. During this process most of the starch is
converted into grape sugar. The sugar is extracted by
boiling, and then, by the addition of yeast, which is one
kind of alcoholic ferment, alcohol is produced. The chief
product is beer, which contains from 2 to 5 per cent of
alcohol. Hops and other substances are usually added.
Although the per cent of alcohol in beer is low, the effect
of beer-drinking is marked. As in the case of wine, often
the drinker takes such enormous quantities of the liquor
that the total amount of alcohol introduced into the sys-
tem is large, and the effect correspondingly pronounced.
In the case of many beer drinkers there is apparent a
continual state of heaviness, a sort of perpetual stupefac-
tion, which points significantly to the narcotic effect of
alcohol. More than any other drink, beer seems to prepare
the way for deeds of coarseness and brutality, probably
from its deadening effect upon the sensibilities. It is said
on good authority that in the city of Munich it is rare to
find a sound heart or sound kidneys.

Distilled Liquors. — Distilled liquors, or spirits are ob-
tained from wines and fermented liquors by the process of
distillation. This process depends on the fact that alcohol
boils at 173° F., while water boils at 212° F. The still
consists of a large boiler with a large tube rising from the
top, and this tube is coiled about in and extends through a
reservoir which is kept filled with cold water. On heating
the fermented liquid in the still up to 173° F., the alcohol
is converted into vapor. As this vapor passes along the
coil (known as the worm), the vapor is condensed by the
cold, and thus the alcohol is separated from the water and

2 1 o Physiology.

other liquids, which boil at a higher temperature. By dis-
tilling wine a large part of the water is left behind, and
brandy is the result. Whisky is made by distilling the
fermented grains, especially rye and corn, while rum is
manufactured by the distillation of fermented molasses.
Most of the distilled liquors contain from 40 to 50 per cent
of alcohol. By repeated distillation and rectification pure
alcohol is obtained. Pure alcohol is not largely used, the
ordinary commercial alcohol being about 91 per cent alcohol.

Physical Properties of Alcohol. — Alcohol is a clear liquid
of .79 specific gravity. It boils at I73°F., and does not
freeze, hence it is often used in thermometers. Alcohol
dissolves gums and resins, and many substances which are
insoluble in water.

Chemical Properties of Alcohol. — Alcohol is composed
of carbon, hydrogen, and oxygen. In composition the
alcohols (for there are many kinds of alcohol) resemble
fats. In both there is only a small proportion of oxygen
to the amount of carbon and hydrogen. For this reason
both burn with great readiness and produce great heat.
Alcohol burns with a nearly colorless but very hot flame,
and does not produce soot ; hence the alcohol flame is very
useful in delicate work, such as watch-making, etc.

Physiological Effects of a Moderate Dose of Alcohol.

— A moderate dose of diluted alcohol or ordinary alcoholic
drink usually has about the following effects, especially
upon those not accustomed to its use. First, a dilation of
the blood tubes of the face and of the mucous lining of the
stomach ; nervous excitement shown by restlessness and
talkativeness ; followed by more or less dullness or drowsi-
ness, usually followed by a depressed feeling on the next
day.

Alcohol. 2 1 1

Effects of Larger Doses of Alcohol. — Larger doses of
alcohol, or more than what might be called moderate
drinking, are usually followed by more giddiness, diminished
sensibility of the skin, partial loss of control of the muscles,
as shown in speech and gait ; the eyes cease to work in
harmony, and the person may see double ; nausea is a
common effect ; and after a time stupor comes on. In such
drunken sleep the temperature has been known to fall as
low as 75° F. From this it is very evident how foolish
it is for one who is exposed to severe cold to drink alco-
holic liquor to keep himself warm, and the extreme danger
of such a course. Members of exploring parties in cold
climates have lost their lives by ignorance of, or disobedi-
ence to, this well-known rule. In the unconsciousness of
drunken sleep the full narcotic effects of alcohol are seen.
It is significant that the word by which we designate this
condition — intoxication — means poisoning.

Alcohol formerly regarded as a Stimulant. — Until late
years nearly all authorities considered alcohol a stimulant.
Its effects were apparently such as to rouse the organs of
the body to a higher degree of activity. But recent experi-
ments have shown that this effect, which is of a very short
duration, is not its real characteristic action. In from ten to
twenty minutes this preliminary excitement begins to abate,
and is followed by a period of diminished activity. Its
essential action is that of a narcotic or paralyzing agent.

Alcohol as a Narcotic. — Many of the later writers who
have investigated the subject say that alcohol is not a
stimulant, but always a narcotic. A narcotic is a drug that
deadens sensibility, or pain, such as opium. The effect
on the capillaries is explained as follows : In ordinary
conditions of circulation, when only a moderate amount of

2 1 2 Physiology.

blood is needed in any given organ, the circular muscle
fibers in the walls of the arteries leading to that part are
kept shortened by nervous impulses sent to them from the
nerve centers which control them, hence a moderate supply
of blood. A narcotic has a paralyzing effect on these
nerve centers ; hence the usual impulses which would have
been sent are no longer sent, the muscle fibers relax, the
artery widens, and the part becomes flushed.

How Alcohol affects the Heart. — In regard to the effect on the action
of the heart, it must be remembered that in the first place there are
ganglions embedded in the walls of the heart, and that the heart tends
to beat rhythmically ; second, that there are two sets of nerve fibers
reaching the heart from without, the sympathetic, which bring impulses
which quicken the activity of the heart, and the vagus nerves, which
slow its action. The sympathetic fibers are accelerators, while the
vagus fibers retard', the vagus nerves exert an inhibitory effect, i.e.
they act as a brake on the heart's action. If they were strongly stimu-
lated, the heart would stop. If .impulses are not continually sent to the
heart along these fibers, the heart begins to beat faster, just as a wagon
going down hill begins to go faster when the brake is taken off.

The action of the narcotic is to paralyze the nerve center from which
the restraining impulses normally are sent to control the heart. Hence
the rapid beat. As to the force of its beat there is difference of opinion ;
many maintain that it has less force than before.

Alcohol in the Army. — Colonel Alfred A. Woodhull,

surgeon United States army, says in regard to this matter,
" I do not think any of our medical officers would seriously
advocate the issue of alcohol as a measure of health."

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."

Dr. Frank H. Hamilton said: "It is earnestly desired
that no such experiment ever be repeated in the armies

Alcohol. 213

of the United States. In our own mind the conviction is
established by the experience and observation of a lifetime,
that the regular routine employment of alcoholic liquors
by men in health is never, under any circumstances, useful.
We make no exceptions in favor of cold, or heat, or rain."
General Kitchener prohibited all drinks containing
alcohol in the Soudan campaign, and of the result a war
correspondent said : "Of one thing I am sure — that the
mortality from fever and other diseases during the Atbara
campaign and the final Omdurman campaign would have
been infinitely greater than it was if alcoholic liquors had
been allowed as a beverage, or even as an occasional
ration."

Alcohol and Mountain-climbing. — Statistics have been
collected from mountain-climbers, and a large majority
testify that alcoholic drinks are injurious, or at least not
helpful. This testimony is all the stronger from the fact
that it comes largely from Englishmen and Germans,
many of whom have the habit of moderate drinking
when at home. Mountain-climbing calls for a greater
expenditure of energy than is probably realized by any
who have not tried it. Aside from the natural exhaustion
of such severe exertion, there is likely to be giddiness or
nausea as a result of the rarefied air. The keeper of the
house on the summit of Pike's Peak says that such symp-
toms are almost invariably aggravated, instead of being
relieved, by taking alcoholic drink.

Testimony of a Naturalist. — W. T. Hornaday, author
of Two Years in the Jungle, who has had years of experi-
ence as collector in many lands, has the following to say
as to the use of alcoholic drink : " Above all things, how-
ever, which go farthest toward preserving the life of the

214 Physiology.

traveler against diseases and death by accident, and which
every naturalist especially should take with him wherever
he goes, are habits 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 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 jungle is not
worth his salt, and as a companion in a serious under-
taking, is not even to be regarded as a possible candidate."

Is Alcohol a Food ? — It is not justifiable to call a sub-
stance a food because it possesses one characteristic of a
food, when in all other respects it has the opposite char-
acteristics of a poison. Alcohol certainly cannot build up
muscle or brain or nerve, because these tissues must have
nitrogen as a constituent element, and alcohol contains no
nitrogen.

Undoubtedly the best test of a food is its ability to
maintain working power. Does alcohol do this?

In the above paragraphs are given the results of much
experiment and observation. Alcohol has been tried in

Alcohol. 215

the army and navy, on the march and in camp, in hot and
cold climates, in mountain-climbing, in training for boxing,
boating, and other athletic contests, and as a result the
uniform testimony is that it fails to sustain energy, that is,
as a food it is a failure. 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 deprivations in all
climates. Neither in hot nor in cold climates is alcohol
necessary to health, and even its moderate use does more
harm than good.

This testimony as to the uselessness of alcohol is all the
stronger on account of the chemical nature of alcohol and
the claims made for it. Alcohol contains but little oxygen
and burns readily and yields a large amount of energy in
the form of heat. It seems very natural, therefore, to
jump to the conclusion that it will oxidize in the body
and produce heat and, perhaps, other useful energy. It
does oxidize in the body, but, as already shown, it tends
to lower the temperature of the body, and when it does so
it causes the body to lose more heat than it furnishes.
The work accomplished during the period of its influence
is less than that accomplished without it.

The fact of the oxidation of alcohol in the body does
not necessarily prove that it is a valuable source of energy
that can be utilized by the body. Other substances, every-
where recognized as poisons, such as morphine and car-
bolic acid, are also oxidized in the body. Alcohol makes
the body less able to carry on its daily work than when no
alcohol is taken.

On the other hand, we can see how the readiness with
which alcohol is oxidized in the body is plainly injurious.

2 1 6 Physiology.

It is well known that most persons eat more than is
needed ; in fact, some of the best authorities state that the
larger part of the ills of the body, especially in later life,
come from overeating. Now when, in addition to a sur-
plus of food, alcohol is also taken, the ready oxidation of
the latter prevents the complete oxidation of food, and
favors the accumulation of incompletely oxidized waste
products, which are very harmful in the system. They
clog the excretory organs, especially tending to over-
work, and consequently to break down, the liver and the
kidneys.

The Danger of Moderate Use of Alcohol. — Thus far we
have mainly considered the question whether alcohol is or
is not useful in supporting the energies of the body. It
is time to ask another question, What effect does the con-
tinued use of alcohol have upon the body ?

No one denies that the use of alcohol may, and often
does, create an appetite for more, and that this appetite
frequently becomes uncontrollable. If one eats a sufficient
amount of bread to-day, he does not, in consequence,
crave a larger amount to-morrow. But the appetite for
alcohol grows. The law of its use is the law of increase,
until the terrible alcohol habit is formed. History is full
of accounts of men who thought they could stop it when
they chose. The man who says that he can take it or let
it alone usually takes it. The grip of the alcohol habit is
well nigh as relentless as the grip of death.

There is one safe rule : Touch not, taste not> handle not.

Alcohol as a Poisonous Drug. — Alcohol should be
classed with the poisonous drugs (e.g. opium, arsenic, chlo-
roform, belladonna, strychnine, etc.). We know that they
are very dangerous substances.

Alcohol. 2 1 7

Diseases produced by Alcohol. — The organs most directly
affected and altered in structure by alcohol are the stomach,
heart, liver, kidneys, lungs, and nervous system. Even
moderate drinking may affect any of these organs. Tremor
of the muscles, especially noticeable in the hands, is often
observed. This tremor reaches its extreme in the terrible
disease known as delirium tremens. The heart often un-
dergoes fatty degeneration, fat replacing part of the mus-
cle. The arteries may undergo the same change. The
kidneys are disordered, and one form of resulting disease
is known as Bright's disease. This is often caused by
moderate drinking. The lungs are more liable to be
attacked by consumption. But the most positive, and
the most serious, effect of 'alcoholic drinks is on the
nervous system, of which more will be said later.

Predisposition to Disease caused by Alcohol. — In many
cases where the use of alcoholic drink has not actually
shown a diseased condition, there is marked weakness and
inability to resist or throw off disease. Drinkers are much
more subject to sunstroke and to many* of the infectious
diseases. Yellow fever is almost surely fatal to the intem-
perate. Some forms of pneumonia are more likely to
attack the intemperate. The insidious nature of alcohol
and the evil effects of moderate drinking appear when the
body is attacked by disease. The body is found to be
undermined and sapped of its strength at the very time
when a reserve fund of vitality is needed to ward off the
approach of disease.

Inheritance of the Effects of Alcohol Drinking. — The

evil is great enough when seen only in the individual who
indulges in the drink habit. But the inherited results are
often worse. The child of drinking parents may develop

2 1 8 Physiology.

a craving for liquor which may take a mild form, and a
person of good will power may resist it. But sometimes
this inherited craving takes the form called dipsomania,
in which at intervals the craving is so strong that the
person seems unable to resist it, while there may intervene
considerable periods when there is no desire whatever for
strong drink. Then, too, idiocy, imbecility, and epilepsy
are common in the children of intemperate parents.

Alcohol and Poverty. — No one needs to be told that a
large share of the poverty, everywhere so common, is due
to the drinking of alcoholic liquors. Much of the earnings
are frequently spent for liquor ; the man's working capac-
ity is diminished, his work Becomes irregular, and so unre-
liable that the drinker often fails to obtain employment
when he is sober.

Alcohol and Crime. — Every one knows from observation
and newspaper reports that much of our daily crime is due
to alcohol. Withoflt quoting figures it may be stated that
carefully collected statistics show that a large per cent
of the inmates of our jails, reformatories, and penitentia-
ries are brought to such places through the influence of
alcohol.

The Business Man's View. — Many firms and corpora-
tions now refuse to hire any one who is known to indulge
in alcoholic liquors or to frequent saloons. Drinking
makes men unreliable, and the wise business man will not
intrust matters of importance — and all business is impor-
tant— to those on whom he cannot rely. No boy or
young man can afford to risk his position and his reputa-
tion by taking a single drink of liquor.

Alcohol and Character. — Serious as are the effects of
alcohol on bodily health, and prejudicial as it is to all busi-

Alcohol. 219

ness prospects and what we usually call success, still more
fearful are the effects, through the nervous system, on the
mind and character.

Summary. — i . Alcohol is produced in sugary liquids by fermen-
tation.

2. Alcoholic fermentation is produced by a ferment called yeast.

3. There are many kinds of ferments, each producing its own kind
of fermentation.

4. Alcoholic liquors are classed as wines, malt liquors, and dis-
tilled liquors.

5. Cider, when fermented, contains from 2 to 10 per cent of
alcohol.

6. The so-called 4i root beers" contain alcohol.

7. Beer is a malt liquor, obtained from the fermentation of barley.

8. Wine is the fermented juice of the grape or other fruit.

9. Alcohol was formerly regarded as a stimulant.

10. Alcohol is now recognized as a narcotic.

11. The use of alcohol in the army and navy has been abandoned.
It was found that men could do more work and endure more without it.

12. Alcohol is not a food, but a poison.

13. Alcohol causes many diseases, and renders the user more likely
to have many diseases.

14. The evil effects of the use of alcohol may be inherited.

15. Alcohol leads to poverty, crime, and degradation of character.

Questions. — i. Why do some persons say that alcoholic drinks
give warmth ? ^

2. What do statistics show as to the "expectation of life" among
abstainers and users of alcohol ?

CHAPTER XXI.
EXERCISE AND BATHING.

How Exercise is Beneficial. — Exercise stimulates the
cells to activity and renews the lymph around the cells
both by quickening the blood flow and by pressure on the
lymph tubes. 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. It is not so much strength as
health that we neecl. The ability to do our daily work, to
do it with comfort and without any feeling of strained
effort, is what we need.

Exercise prolongs Life. — Many men would live longer,
feel better, and do greater good in the world, if they took
regular and systematic exercise. It is a shortsighted
policy to say, "I cannot afford the time." Not to take
time for exercise is to mortgage one's future. "He who
does not take time for exercise will have to take time for
illness." The latter half of every person's life Bought in
many respects to be by far the most productive of good.
But many cut off this half, or render it less useful through
breaking down in health as a result of violating the laws
of health.

Exercise and Bathing. 221

Nature's Rewards and Punishments. — Nature never
fails to punish every violation of her laws. Her reward
for obedience is health and the delight that accompanies it.

Useful Exercise. — The man, woman, boy, or girl who
has regular work that calls for muscular activity is to be
congratulated. Duty obliges them to take regular exer-
cise. The boy who has " chores " to do is to be envied
rather than pitied.

Choice of Exercise. — But many persons are so situated
that they have no work to do. They must choose some
exercise that is not for a directly useful purpose. In se-
lecting exercise one should choose (i) that which is enjoy-
able, for exhilarating exercise is much more beneficial than
that which is taken as a necessity ; (2) exercise should be
in the open air whenever possible.

Forms of Exercise. — There is a great variety of forms
of exercise from which each person can select according
to his age, strength, etc. For active youths there are run-
ning, jumping, wrestling, boxing, fencing, hare and hounds,
putting the shot, putting the hammer, vaulting, baseball,
and football. In their season come boating and swim-
ming, skating and coasting. Suitable for both boys and
girls are archery, basket ball, bicycling, croquet, golf,
horseback riding, tennis, and last, but not least, walking.
The main trouble with walking is that it is likely to be
taken from a sense of duty and becomes mechanical.
The good feature of most games is that there is active
competition, which makes them so enjoyable that one en-
tirely forgets his work for the time. He is, therefore, in
better condition to return to his work.

Exercise in One's Room. — In one's room he can use
dumb-bells or Indian clubs to good advantage. There are

222 Physiology.

also various forms of " home exercisers," such as pulley
weights, rubber bands, etc., which are valuable. After
exercise should come a sponge bath.

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. Two can make up a game, and a little time can be better used
than with the games requiring more players. The exercise, too, is more
evenly distributed. There is no long waiting, as in some games, but a
constant interchange of play, active but not severe, with almost no danger
of injury.

Baseball and Football. — For those who can pursue the more vigor-
ous games of baseball and football they are admirable. 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. 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.
Boxing brings 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 exercise. It develops a degree of self-
reliance that is worth much. Like tennis, boxing calls for little appa-

Exercise and Bathing. 223

ratus, 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 over-
taxing the heart. The handle bar should be adjusted to allow a fairly
upright position. The saddle should be such as to sustain the weight
properly.

" 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 likely to take cold.
The application of cold to the skin causes the arteries
(through reflex action) to become smaller. Thus when rest-
ing in a cool place the skin becomes pale and cold. Dur-
ing a " cold " there is fever. The regulation of the heat by
the skin is interfered with. Waste matter is not given off
by the skin as it should be. At the same time it is often
noticeable that the urine is more abundant than usual. A
cold is often associated with constipation and inactivity of
the liver, indicating a clogged condition of the system. As
a cold may lead to fatal lung disease, so it may be the
beginning of disease of the kidneys that may, in the end,
bring fatal results.

Bathing. — One purpose of bathing is to cleanse the
skin. For this purpose warm water is best, and it is desir-
able to use soap, especially on those parts which are espe-
cially exposed to contamination, such as the hands, the
feet, the armpits, and groins. The feet should be bathed
every night.

224 Physiology.

Cold Baths. — Another important function of bathing is
to strengthen the system. For this purpose cold bathing
is better, but this should not be too long continued, and
must be followed by a 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, or bath mits made of Turkish toweling,
and the body thoroughly rubbed with a coarse towel. The
whole process should be completed very quickly, especially
if the room is not warm. At the beginning of a bath, cold
water should be applied to the head and face.

Time for Bathing. — For those who do not take a great
deal of vigorous exercise, which keeps the skin active,
bathing is especially valuable. The use of warm water
for cleansing seems best adapted 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 weakening, 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.

Exercise and Bathing. 225

and we can understand how the system can be trained to
adjust itself to cold, and enabled to avoid "taking cold."

Habit of Cold Bathing acquired Gradually. — There are
undoubtedly many persons who do not profit by cold bath-
ing, but probably many of these would soon adapt them-
selves to it by beginning with tepid water and gradually
using cooler. To bath slowly in a cold room is not safe.
The great secret of the benefit that may be expected from
a cold bath is to be very brisk, the whole process occupying
only a few minutes. Many are opposed to cold sponge
bathing, and condemn it without giving it a fair trial.

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 should be taken 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 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 XXII.
THE BRAIN.

The Coverings of the Brain. — There are two coats of
the brain, the dura mater, a tough membrane, adhering 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 parts of the brain are the
cerebrum, the cerebellum, and the spinal bulb.

The Cerebrum. — The cerebrum consists of two lateral
hemispheres, separated by a deep groove in the middle
line. The surface of the cerebrum is in irregular ridges,
the convolutions. The outside of the brain consists of
gray matter. The inner part of the brain is white, and
the two halves are connected by a broad band which con-
sists of many white fibers.

The Cerebellum. — Back of, and below the cerebrum is
the cerebellum. It 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 Spinal Bulb. — The enlarged beginning of the
spinal cord is the spinal bulb. It is white, like the rest of
the cord.

226

The Brain.

227

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.

- I, Olfactory
(Smell)

Hypoglossal
12 (Tongue
Motor)

II, Spinal
Accessory

Fig. 88. The Base of the Brain, showing the Origin of the Cranial Nerves.

2. The optic nerves, or nerves of sight, join each other
before reaching the brain.

3. The third pair of cranial nerves controls the muscles of the eye-
balls.

4. The fourth pair also controls eye muscled.

5. Back of these is the larger fifth pair, the trigcminal.
This pair supplies part of the face, and sends branches to

228 Physiology.

the teeth. It is the nerve affected in neuralgia of the face.
It is the nerve of sensation for most of the head and face.

6. The sixth pair controls eye muscles.

7. 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 expression.

Cerebrum

Spinal Bulb

Fig. 89. Vertical Section of Brain.

8. The eighth, or auditory nerves, are the nerves of
hearing.

9/ The ninth pair arise on the sides of the spinal bulb.
They supply the back of the tongue and the pharynx, and
are called the glosso-pharyngeal nerves. They give the
sense of taste from the base of the tongue.

10. The tenth pair, or vagus nerves, pass down out of
the brain cavity, g^ive off branches to the pharynx and

The Brain.

229

larynx, and are distributed to the heart, lungs, and
stomach.

11. The eleventh pair arise in part from the spinal cord outside of
the cranial cavity, enter the skull, and pass out again to supply certain
muscles of the neck and shoulders.

12. The last pair of cranial nerves, the twelfth, supplies the muscles
of the tongue, and are called the hypoglossal nerves.

Gray and White Matter of the Brain.
— The gray matter of the brain is com-
posed of cells 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 of the nerves.

Ganglions of the Brain. — There are several masses of
gray matter in the interior of the brain. These are the

ganglions Of the _^^^A .- Gray Matter

brain. The white
fibers inside the
brain connect the
gray matter of
the convolutions
and these gang-
lions with all parts
of the body

through the Spinal Fig. 91. Diagram of the Brain, showing the Spinal Cord,
P/-VJ- A Ganglions, and Course of the Fibers.

Functions of the Cerebrum. — The gray matter of the
outside of the brain is the central organ of intelligent sen-
sation and motion. The functions of volition, or willing,
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.

Ganglions

Cerebrur

Cerebellum

230

Physiology.

The Center of Sensations itself Insensible. — All sensation
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 cere-

sight

-Spinal Cord
- 1st Spinal Nerve
2d Spinal Nerve

Fig. 92. The Cranial Nerves and Sense Organs.

brum they rouse the cells here to an activity that gives us
what we call sensation. It is never a sensation 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
body, it also, in part, has control of its own side. Paralysis

The Brain.

231

of one side is due to injury of the opposite hemisphere of
the cerebrum.

Location of Brain Functions. — Much has been learned in
late years as to the location of special functions in the brain.

CENTRAL FISSURE

MOTOR AREA

FISSURE OF SILVIUS

Fig. 93. Location of Brain Functions.

Some of the motor and sensory centers are shown in
Fig. 93.

Connection of Brain Centers. — These different brain
centers are connected by nerve fibers, and through these
connecting fibers we produce various actions as a result of
sensations. For instance (see Fig. 94), nerve impulses come
through the nerve of hearing to the auditory center, and we
have hearing ; this center is connected with the speech
center ; and, as a result, we send out nerve currents to the

232

Physiology.

organs of speech, and thus we speak in response to what
we hear. Currents from the eye reaching the visual center
may connect with the writing center, and we send out cur-
rents by which we write in response to what we have read.

Writing

Speech

Fig. 94. Connection of Brain Centers. (After Landois and Stirling.)

Left Hemisphere Better Developed. — The " speech cen-
ter " 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.

The Function of the Cerebellum. — The cerebellum is the
center for regulating the actions of the skeletal muscles.

The Brain. 233

When we walk or run, or even stand still, a number of
muscles must act, and act in concert. The nerve impulses
originate in the cerebrum, but the cerebellum is the center
for harmonizing the action of these various muscles. When
the cerebellum is injured, an animal staggers instead of
walking steadily.

Functions of the Spinal Bulb. — The spinal bulb is the
enlarged part of the spinal cord which is within the cra-
nium. From it arise all the cranial nerves except the first
five pairs. The spinal bulb is also the center for the con-
trol of respiration, of circulation, of swallowing, 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 par-
tial activity ; that is, incomplete rest. 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 dwindles away,
and may entirely lose its power.

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 subject
to this sort of trouble as any one class of men. Keeping
the blood continually in the brain is likely to lead to a per-
manent congestion, or inflammation, that may cause seri-
ous, 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

234 Physiology.

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
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 per-
ceptible change in nerve fibers as a result of fatigue.

Blood Supply of the Brain. — Blood is supplied to the
brain through four arteries : the right and left internal
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.

Cause of Fainting. — If the supply of blood to the brain
is shut off, unconsciousness quickly follows. In the ordi-
nary faint the blood supply to the brain has been reduced.
It is due to checking the action 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.

Apoplexy. — Apoplexy is caused by rupture of a blood
tube and1 the formation of a clot that presses on the brain.

Meningitis. — Meningitis is an inflammation of the mem-
branes immediately surrounding the brain or spinal cord
or both.

The Brain. 235

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 the senses of sight, smell, taste, and
hearing.

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 center "
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 XXIII.
EFFECTS OF ALCOHOL ON THE BRAIN.

" Oh, that man should put an enemy into his
mouth to steal away his brains ! "

The Effects of Alcohol on Nervous Tissue. — The physi-
ological effects of alcohol which have been considered in
connection with the muscles, circulation, digestion, etc., are
quite secondary to its effects on the central nervous system.
It is difficult to understand the extreme delicacy of organ-
ization of the nervous system. We can readily see how
thoroughly nature has guarded this tissue by placing it in
the most protected places in the body. But even after we
have considered this point, we are not yet ready to com-
prehend the fine texture and sensitiveness of this tissue
above all others. It is this high degree of susceptibility
of the nervous system that renders it peculiarly subject to
the effects of alcohol.

Delicacy of Brain Structure. — The injury done to the
brain by alcohol may not be readily discovered ; but as it
is so delicate we cannot expect to trace the changes in
structure as we might in some of the coarser organs of the
body. For instance, the rupture of a small blood-tube in
most of the tissues of the body results in a small clot,
which ordinarily is a matter of no special consequence ; it
forms a " black-and-blue-spot," which is hardly more than
a temporary inconvenience, for it does not ordinarily inter-
fere with the function of the organ. It is soon absorbed,

236

Effects of Alcohol on the Brain. 237

and all traces of it pass away. Not so with the brain : a
clot produces pressure on the delicate nervous tissue, which
results in paralysis — more or less complete — or death.

Brain most affected by Alcohol. — " The brain is more
unfavorably affected by alcohol than any other organ, and
that in a variety of ways."- —M. S. WJiitcstonc, M.D.

" Science has established that alcohol destroys first and
most those parts which are the most delicate. These are
those wonderfully delicate brain cells upon whose proper
formation the difference between men and beasts chiefly
depends." - — Franz Schb'nenberger, M.D.

" All indications point to the conclusion that it is the
nervous tissue which is especially exposed to the cumula-
tive action of the alcoholic poison. The alcohol sets up a
chemical action in the nervous tissue, which at first inaugu-
rates only imperceptible change ; but once inaugurated,
the process goes on until the tissue passes into a perma-
nently diseased condition."- — Dr. A. Striimpell.

Effect on the Brain quickly shown. — The effects of
alcohol on other organs may not be revealed for some
time. But the effect of alcohol on the brain is very
quickly apparent. The brain controls most of the actions,
so the action, or even the inaction, of the body promptly
reveals the indulgence in alcoholic drink.

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,

238 Physiology.

and the functions of this organ so far transcend the func-
tions of all the others, that I might say, there is no com-
parison."

Dr. Crothers, in common with many physicians, regards
inebriety as a disease.

Effects of Small Doses of Alcohol on Mental Opera-
tions. — The common, but erroneous, idea is that alcohol
stimulates the brain to a higher degree of activity. There
does appear to be an exhilaration for a short time, but this
is undoubtedly due to the increased flow of blood to the
brain; for the liquor has paralyzed the smaller blood-
tubes, thus allowing the brain to be flushed with blood.
But careful experiments show that any temporary increase
in mental activity, following small doses of alcohol, is
always at the expense of accuracy and power, and that its
effects cannot truly be called stimulating. And this period
of exhilaration is extremely short-lived.

Testimony of German Professors. — In describing his
methods of work, Helmholtz said that slight indulgence in
alcohol instantly dispelled his best ideas. Professor Gaule
states that once during the strain of an examination he
suddenly stopped his wine and beer, and was surprised to
find how much better he could work. An eminent pro-
fessor in Leipsic once said that the German students could
do twice as much work if they would let their beer alone.
Dr. August Smith has found that moderate, non-intoxicant
doses of alcohol lowered tu's ability to memorize as much
as 70 per cent.

Permanent Effects of the Continued Use of Alcohol. —

" The long-continued use of quantities not immediately so
disastrous, produces various structural changes, which are
often markedly perceptible ; and in chronic alcoholic dis-

Effects of Alcohol on the Brain. 239

ease, hardening of the brain structure, increase of the con-
nective tissue, with diminution of the proper brain cells,
thickening of the membranes, and effusions of serous fluid
into the ventricles or cavities, are among the appearances
often found. All these changes are usually accompanied
with inflammatory and other degenerative processes, with
a lowering and perversion of function, and with premature
decay of all the mental and physical powers." - — Palmer.

How Alcohol affects the Brain. — " Alcohol in the body
acts as a paralyzant on certain portions of the brain, de-
stroying the more delicate degrees of attention, judgment,
and reflective thought." - Graham Lusk, M.D.

" The rapidity of thought, the clearness of memory, the
capacity to reason, the power of control of the will, are
measurable by instruments, and are all found to be lowered
and palsied by alcohol." - —Journal of Inebriety.

Loss of Control through Alcohol Under the influence

of alcohol the person says and does foolish things ; he en-
gages in rash undertakings ; his higher nerve centers in
the brain are more or less paralyzed; his judgment is
weakened ; in short, he has lost self-control.

" That a man is in a different mental state when intoxi-
cated and when sober no one will deny. He says, feels,
thinks, and does things which in a sober condition he
would not have felt, thought, or done. The cause of these
changes, however, lies neither in the muscles nor in the
skin, nor in any other part of the body, but simply and
solely in the brain. It is a disturbance of the mental
life." — August Forel, M.D.

Alcohol impairs Mental and Moral Faculties " Many

of the worst forms of nervous disease, including epilepsy
and paralysis, are results of alcoholic indulgence. All

240 Physiology.

authorities are agreed that a large proportion of cases of
insanity are produced by alcohol. But even when taken
in much smaller quantities than will excite the above dis-
eases, alcohol is still potent to impair the intellectual
and moral faculties. Perception is blurred, the intellect
clouded, sensation dulled, the disposition perverted, will
power enfeebled, and the moral sense blunted." — Medical
Pioneer.

Alcohol and Sunstroke. — It is a well-known fact that
drinkers are much more subject to sunstroke, also called
heat-stroke, than those who do not use alcohol. Even
very moderate drinkers are unable to bear the heat of
summer, and especially the trying climate of the tropics,
as well as abstainers.

Alcohol and Self-control. — When under the influence
of alcohol the higher functions of the brain are checked.
Hence the lower instincts gain the upper hand. The
man has become a brute, and may give way to his brut-
ish instincts, so that he is a terror in a community. No
one can foresee what he will do. He may remain quiet
and peaceable, or he may become quarrelsome, bestial, or
murderous.

Delirium Tremens. — This terrible disease is usually seen
in those who have long used alcohol immoderately, but may
occur in persons who have always regarded themselves as
moderate drinkers, and have seldom or never been intoxi-
cated. The nervous system has been almost shattered as
a result of the continued effect of alcohol. The word " de-
lirium " indicates the loss of mental control, while the word
" tremens " signifies the trembling, which is often fearful to
behold. This disease takes various forms, sometimes being

Effects of Alcohol on the Brain. 241

marked by frantic action and shrieks of fear, at other
times comparatively quiet, the victim cowering in abject
terror, making but little noise. The mind is filled
with the most horrible visions, frequently of snakes
or other dreaded forms, causing loathing, fright, and
horror. Repeated attacks of delirium tremens usually
end in death.

Alcohol and Insanity. — In a drunken fit the person
may be said to be temporarily insane. In the more or
less complete loss of self-control he shows the symptoms
of insanity. This temporary insanity may, and too often
does, lead to permanent insanity. Statistics show that
many of the insane have become so through the influ-
ence of alcohol.

Inheritance of the Effects of Alcohol. — The evil effects
of alcohol are shown not only on the individual who in-
dulges in alcoholic drink, but often on his children or
even grandchildren. First there is a tendency to inherit
an impaired nervous system with weakened will power. It
becomes very difficult for one with such an inheritance to
resist the temptation to drink, while the craving for drink
is more quickly acquired. Many children are weak-minded,
even idiotic, or have various defects as a direct result of
the effect of alcohol on the parent. If the evils multiply
and increase from generation to generation, the line of
descent soon becomes extinct.

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,

242 Physiology.

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,
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."

Effects of Alcohol on the Brain. 24.3

Moral Deterioration produced by Alcohol. — " One result
of a single dose of alcohol is that the control 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 over-
excitement of the emotional nature, and enfeeblement of
the will; the man's highly emotional state exposes him
to special temptations, to 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, truth-
fulness 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 passion 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 momentary 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. — Professor H. Newell Martin.

Summary. — i . The nervous system is especially affected by alco-
hol.

2. The effects df alcohol on the brain show very quickly.

244 Physiology.

3. Small doses of alcohol affect mental processes, interfering with
study.

4. Continued use of alcohol alters the structure of the nervous
system.

5. Alcohol destroys self-control.

6. Alcohol weakens the moral faculties.

7. Alcohol produces various diseases, such as delirium tremens.

8. Alcohol sometimes causes insanity.

9. Users of alcohol are much more likely to have sunstroke than
abstainers.

10. The evil effects of alcohol are hereditary.

CHAPTER XXIV.
THE SENSES.

THE GENERAL SENSES. — TOUCH AND TEMPERATURE

SENSE.

Afferent and Efferent Nerve Currents. — Up to this point
we have been studying efferent, or out-going, nerve cur-
rents, such as control muscles and glands. Now let us
turn to the in-coming, or afferent, currents ; for it is by
means of the afferent currents to the brain that we get all
our sensations. In other words, it is through these cur-
rents that we get all our knowledge.

Two Classes of Sensations. — There are two classes of
sensations, the special and the general. The special senses
include sight, hearing, taste, smell, touch, and temperature
sense. Among the general sensations are hunger, thirst,
fatigue, nausea, satiety, faintness, pain, muscular sense, etc.

Special Sensation due to External Force. — Sensations
from the organs of special sense are due to the action of
an external force. For instance, sound waves entering the
ear affect the nerves of hearing, and we have a sensation
of hearing. Light acting on the optic nerve gives sight.

General Sensations due to Conditions within the Body.

— There are nerves of general sensibility in all parts of
the body. The endings of these nerves are acted on by the
blood and lymph. Currents are all the time coming through

245

246 Physiology.

these nerves to the brain. But ordinarily we are not con-
scious of them. If the body is in need of food, the mes-
sages are stronger and we have a sensation of hunger. If
the poisonous waste matters are not removed by the organs
of excretion, their presence in the lymph is reported to the
brain, and we have a feeling, perhaps of fatigue, or of
decided discomfort, or even of pain.

The Muscular Sense. — In judging the weight of a body
by holding it in the hand, our estimate is the result of sen-
sations aroused by nerve impulses from the organs used.
There are afferent nerve fibers with endings in (i) the skin,
(2) the muscles and tendons, and (3) the joints. In hold-
ing out the arm and in moving it up and down, all three
of these sets of nerve endings are stimulated, and impulses
are conveyed to the brain producing the muscular sense.

Dependence of Sight on Muscular Sense and Touch. — It is difficult to
realize the importance of the muscular sense. An illustration of the as-
sistance which touch and the muscular sense give to the sense of sight
is furnished in the case of a boy who had been blind from birth, and re-
ceived 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 between
the new sense of sight and the old familiar ones of touch and the mus-
cular sense. On putting the cat down he said, " So, puss, I shall know
you next time."

Pain. — The nerves of general sensibility give informa-
tion of the state of nutrition in the tissues and the condi-
tion of the body as a whole. Ordinarily we are not aware
of these nerve currents. When they become stronger
than usual they give rise to feelings of general discomfort,
such as fatigue, depression, restlessness, etc. When the
currents become stronger still, we have pain.

The Senses. 247

Use of Pain. — Pain is a warning of over-use or injury
The milder nerve impulses that cause slight discomfort
ought to be sufficient to call attention to the condition. But
often these first reports are neglected. Fqr instance, over-
use or abuse of the eyes may cause irritation, that is allowed
to go unheeded. The person may show the effect, by rub-
bing the eye, but, being absorbed in study, may fail to
stop reading and go on until there is actual pain. When
the first warnings are not heeded, pain follows and demands
attention.

Pain in the Skin. — While the internal organs are ordina-
rily without feeling, the skin is especially sensitive. v The
skin senses stand guard at the outposts 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. In amputating a limb
the chief pain is in cutting through the skin. It is a com-
fort to know that the more severe wounds do not cause
pain in proportion to their extent.

Hunger and Thirst. — The cause of these sensations in
a healthy body is plainly the need of food and water
throughout the system. The sensation of thirst seems to
be in the throat, and the longing may be somewhat re-
lieved by merely moistening the throat. So hunger may,
for the time, be appeased by filling the stomach with indi-
gestible material. But the sensation soon returns. The
system has a crying need, and it is not to be put off.
That these sensations are really demands made by the
body as a whole may be 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.

248

Physiology.

Since, however, food and drink naturally enter by the
throat and stomach, the mucous membrane of these
organs has become the spokesman of the body.

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 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 experi-
ments show that several sensations are involved in the
handling of objects, and that the knowledge so gained is
complex.

Cutaneous Sensations. — The sensations from objects
resting on the skin of the hand may all be referred to im-
pressions made on nerve endings in the skin, and are
called cutaneous sensations. They include: (i) the pres-
sure 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 (see Figs. 64 and 65).
In the papillas of the dermis are nerve endings called
touch corpuscles (see Fig. 95).

Nerve

Fig. 95. Papilla of Skin with
Touch Corpuscle.

The Senses. 249

Pressure on the skin affects these nerve endings, and
starts impulses that pass along the sensor fibers, through
the spinal cord, to the brain, and give us sensations of
touch. If a nerve fiber is touched, not at the end, but
somewhere along its course, we get a sensation, not of
touch, but of pain.

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. 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 gener-
ally lack this sense.

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.

Location of Touch Sensations. — Each small spot of skin
has its own nerve endings and each nerve fiber connects
with a particular part of the gray matter of the brain. The
brain can therefore tell where each nerve current came
from, and thus we locate a sensation.

Accuracy in locating Touch Sensations. — The accuracy
varies, and is ordinarily keenest where the nerves are most
numerous. Where the sense of locality seems to be im-
proved by cultivation, this appears to be due to keener per-
ception in the brain cells, and not to changes in the nerves
or nerve endings. This is shown in the fact that if the
fingers of one hand become more skilled in touch by prac-

250 Physiology.

tice, 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
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 sensi-
tiveness : tip of tongue, tips of fingers, lip, tip of nose, eye-
lid, cheek, forehead, knee, neck ; while the middle of the
back seems least sensitive.

Reference of Sensation to the Region of Nerve Endings. —
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 currents
along this nerve rouse sensations that we have learned to
locate at the endings of the nerve fibers. If, then, owing
to injury, the currents start from the elbow, the brain still
refers them to the nerve endings in the hand and wrist.
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.

The Temperature Sense. — Many cases are on record in
which, from accident or disease, the sense of touch was
lost and the temperature sense retained, or vice versa.

The Senses. 251

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.

Summary. — i . The special, senses result from the action of external
forces, such as light, heat, etc.

2. General sensations are referred to our bodies and their condition.

3. The muscular sense depends on impulses from muscles, tendons,
and joints.

4. The muscular sense and touch aid the sense of sight in giving us
correct perceptions of size and form.

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.

7. The cutaneous sensations are touch, temperature sense, and pain.

8. There are touch, corpuscles in the papillas of the dermis.

9. Touch is the most general of the senses.

10. Touch proper, or pressure sense, is tested by perception of pres^
sure.

11. Touch localization is tested by discrimination as to the distance
of two points of contact.

12. Temperature is discerned by a special set of nerve fibers.

13. Sensations are referred to the region of the nerve endings.

Questions. — i . What is the explanation of tickling.

2. Where does the change occur by which we become more skilled
in the sense of touch ?

3. Why does an emotion, such as shame, make one feel hot ?

4. If we had no sense of pain, what might result ?

5. If we pass by a meal time without eating why does the sense of
lunger usually disappear ?

CHAPTER XXV.
THE SENSE OF SIGHT.

Protection of the Eye. — The eye is set well back in its
socket and guarded by three bony projections, — the brow,
cheek bone, and the bridge of the nose. It is further
protected by the eyelids and eyelashes.

The LaJrymal Secretion. — The lacrymal gland, or tear
gland, is just above the outer angle of the eye, and pours
its secretion over the eyeball. The lids serve as curtains
to admit or shut out light, and, by winking, wash the eye.
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 into the nasal cavity as fast as it is made. If
the ducts are stopped, or if the secretion is 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 light 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
very sensitive.

252

The Sense of Sight.

253

Movements of the Eye. — There are six pairs of muscles which move
the eyes to right and left, up and down, and give rotary movements.
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.

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.

Ciliary Muscle

Optic Nerve Choroid

Fig. 96. Horizontal Section of Right Eye.

The Coats of the Eye. — There are three coats, the outer
or sclerotic, the middle or choroid, and the inner or 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.

254 Physiology.

The Choroid Coat. — The middle coat of the eye is the
choroid. It is thinner than the sclerotic and of much more
delicate structure. It is full of blood tubes, and has an
inner lining of dark color to prevent the reflection of light
in the eye, just as most optical instruments are painted
black on the inside.

The Retina. — The retina is an expanded part of the
optic nerve and forms an inner coat that lines all but the
front part of the eye. It is a thin, translucent film, some-
what like the film that forms over the white of an egg when
it is first dropped into hot water. It is very 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
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 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

The Sense of Sight. 255

room. The iris has circular muscle fibers that make the pupil smaller
when there is too much light for the eye, and when the light is feeble
the pupil opens wider.

The Aqueous Humor. — There is a small space between
the cornea and the iris. In this space is the clear, watery
aqueous humor.

The Vitreous Hmour. — All but the front part of the
space within the eye is fille with a clear, jelly-like sub-
stance, the vitreous humor.

Fig. 97. The Formation of an Image on the Retina.

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.

Experiment with Lens to show Inversion of Image. — Take a
double-convex lens or any hand magnifier. Hold this up at the rear
of the room and catch the inverted image of the window on a piece of
paper held back of the lens. This illustrates how the image of an
external object is formed by the crystalline lens upon the retina of
the eye.

Experiments to illustrate the Adjustment for Distance. — (0 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.

Accommodation. — We cannot, at the same time, see
distinctly a near and a distant object. When we look at

256

Physiology.

a near object the lens becomes thicker, and when we look
at a distant object the lens becomes less thick. This ad-
justment is called accommodation.

CILIARY MUSCLE

FAR NEAR CILIARY PROCESS

Fig. 98. Changes of the Lens in Accommodation.

Defects of Eyesight — In old age the lens usually be-
comes less elastic, and cannot adjust for near sight. Since
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-

(2) Far-sighted Eye. (I) Normal Eye.

Fig. 99. Defects in Eyesight.

(3) Near-sighted Eye.

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.

The Sense of Sight.

257

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. 100. The rays of light pass through the 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.

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. 100. Section of the Retina. (Waller.)

Importance of the Retina. — The chief structure in the
eye is the retina. Without this all else is useless. If light
falls on the retina, nerve impulses pass along the fibers of
the optic nerve to the brain, and we have a sensation of
light. 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 be able to tell light from darkness. Light from

258 Physiology.

an object passes through the cornea, aqueous humor, lens,
and vitreous humor, and the rays are so refracted as to
form an inverted image on the retina.

The Blind Spot. — Light falling on the optic nerve itself has no effect
in giving a sensation of light. 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, at the same time noticing, whether the bright
spot can be seen. To succeed in this the eye must not be allowed to
waver. Have the pupils tell when the bright spot disappears, then
read on, and note when the spot reappears.

Another Experiment. — In this experiment shut the right eye, and
be careful not to let the left eye waver.

>fc 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 Ojftic Nerve not Sensitive. — The optic nerve, while capable
of carrying nerve impulses that cause sensations 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 be-
tween the two eyes.

The Sense of Sight. 259

Color Blindness. — It is found that some persons cannot 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.

THE CARE OF THE EYES.

1. 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, or white
wall. White walls are likely to injure the eyes. Choose
a dark cover for a reading table. Sewing with a white
apron on has injured the eyes. Direct sunshine very near
the book oV table is likely to do harm.

2. Position in Reference to Light. — Preferably have the
light from behind and above. Sitting under and a little
forward of a hanging lamp will allow the light to fall on
the book and keep it away from the face. In reading by
daylight avoid cross-lights so far as possible.

3. Electric Light. — The incandescent electric light has
advantages in throwing the light downward and in giving
out little heat ; but owing to its irregular illumination (due
to the shadow cast by the wire or filament), 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 read
while lying in a hammock is bad. Too much light directly
enters the eye, and too little falls upon the printed page.

260 Physiology.

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-
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.
At twice the distance from a lamp 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
fading of the light.

8. Evening Reading. — Do the most difficult reading by
daylight, and save the better print and the books that are
easier to hold for work by artificial light. Writing is usu-
ally much more trying to the eyes than reading. By care-
fully planning his work one may economize eyesight.
Weak eyes, by proper care, may outlast and do more work
than those naturally stronger, but injured by abuse. Read-
ing before breakfast by artificial light is usually bad.

9. Reading during Convalescence. — Many eyes are
ruined during convalescence. At this time the whole sys-
tem is weak — including the eyes. There is a strong
temptation to read, perhaps to while away the time, per-
haps to make up for lost time in school work. This is a
time when a friend may show his friendship.

The Sense of Sight. 261

10. Irritation of the Eyes. — If one finds himself rubbing
his eyes, it is a sign that they are irritated. Stop read-
ing, find the cause, and do not read on unless the irritation
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. 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 convenient and safe instrument with
which to remove the particle.

1 1. 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 intro-
ducing foreign matter that may be very harmful. It is
very desirable that each person have his individual face
towel. By not observing this rule certain contagious
diseases of the eyes often spread rapidly.

12. 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.

Summary. — i. The eye is protected by its bony surroundings, lids,
lashes, tears, sensitiveness of the conjunctiva, etc.

2. The eye has three coats — sclerotic, choroid, and retina.

262 Physiology.

3. The pupil is a hole in the iris, and varies in size to regulate the
amount of light admitted.

4. The cornea, aqueous humor, lens, and vitreous humor form an
inverted image on the retina. The eye is a camera, darkened inside.

5. The lens changes its thickness for seeing at different distances.

6. Suitable lenses overcome many of the defects in eyesight.

7. The retina is an expansion of the optic nerve, and is exceedingly
complicated in its structure.

8. The blind spot is the place where the optic nerve enters the eye.

9. The optic nerve is insensitive to light, but injury to it causes
sensations of light.

10. Most of the fibers of the optic nerve cross to the other half of
the brain, but some do not cross.

11. Defects in eyesight are much more common among civilized
men than with the uncivilized.

12. The care of the eyes must be made a subject of study and care-
ful thought by all reading people.

Questions. — i . What is " cataract " ?

2. What is the cause of " double vision "?

3. Why does the well eye sympathize with the affected one ?

4. Why does looking at a bright light often cause a person to
sneeze ?

5. What is the condition of one who is "cross-eyed"?

6. Compare the pupils of a man, a cat, and a cow.

7. Does the color of the eye have any relation to the strength of
eyesight ?

8. Why is one blinded on entering a bright room from the dark ?

9. Why is one going from a bright room into the dark unable to
see at first, but gradually sees more distinctly ?

10. Why can one not see well when the eye " waters "?

11. 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 ?

12. If each eye has a blind spot, why are there not blank spaces in
the field of vision ?

13. What advantage has a stereoscopic view over a single view ?
How are stereoscopic views made ?

CHAPTER XXVI.
TASTE, SMELL, HEARING, AND THE VOICE.

Uses of the Sense of Taste. — The sense of taste helps
us in judging of the fitness of food. By reflex action the
taste of agreeable substances aids in digestion by stimulat-
ing the glands, especially the salivary glands.

The Papillas. — The surface of the tongue is covered
with papillas. Most of them are slender, and like the

Papillas

Glosso-pharyngeal
Nerve (9th)

Gustatory Branch of Fifth Nerve
Fig. 101. Nerves and Papillas of the Tongue.

papillas of the skin, are organs of touch. Scattered among
these are larger papillas in which are the endings of the

nerves of taste.

•

The Nerve Supply of the Tongue. — The nerves of taste
are the glosso-pharyngeal, distributed to the back part of
the tongue, and the gustatory in the front part. The tip
of the tongue seems to be most sensitive to sweets and
salts, the back part to bitters, and the sides to acids.

263

264

Physiology.

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, a piece of onion
placed on the tongue does not produce what we usually call the taste
of the onion. By holding the nose we may get rid of the disagreeable
part of taking certain medicines. Let the pupil experiment with various
substances as above indicated.

The Sense of Smell. — The nerves of smell, the olfactory
nerves, are distributed in the walls of the nasal passages.
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.
we find the organ

Olfactory Bulb

Olfactory Nerves.

Branches of
Fifth Nerve'

Turbinated

Hence
placed

at the opening of the
respiratory passages, and
close to the organ of
taste.

Fig. 102.

Nerves of the Outer Wall of the
Nasal Cavity.

Why we Sniff. — In cfuiet breathing the air passes along the lower
air passages just above the hard palate. 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 the
upper nasal passages, over the walls of which the olfactory nerves are
spread in the mucous memDrane. In inflammation, as from a cold^
the narrow nasal passages, especially the upper, are often closed.

Taste, Smell, Hearing, and the Voice. 265

The Parts of the Ear. — The parts of the ear are the
external, the middle, and the internal ear.

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

Stirrup Anvil

Semicircular Canals "' -^

PHARYNX.

Fig. 103. Structure of the Ear.

from the cavities beyond by a thin membranous partition,
the tympanic membrane or drum skin. This passageway
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
to the inner surface of the membrane of the tympanum,

266 Physiology.

and the stirrup being fastened by its base to the wall of
the internal ear.

The Eustachian Tube. — The middle ear communicates
with the pharynx 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
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. 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 Care of the Ear. — In cleaning the ear no hard sub-
stance should be used ; even the finger nail is likely to
do harm. A moistened cloth should be used. It is not

Taste, Smell, Hearing, and the Voice. 267

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 inflamma-
tion of the mucous membrane of the pharynx. This in-
flammation may extend along the eustachian tube to the
middle ear and affect the hearing.

Epiglottis
Base of Tongue _

Hyoid Bone

False Vocal Cord

..Ventricle
Vocal Cord

Cartilage

.Trachea

FROM RIGHT TO LEFT MEDIAN

Fig. 104. Longitudinal Sections of the Larynx.

The Ear and the Voice. — The delicate structure of the
ear is fully matched by the fine adjustment and range of
the voice. The voice is produced in the larynx at the upper
end of the windpipe. The projecting angle of the larynx
is called " Adam's apple."

The Vocal Cords. — The vocal cords are not cord-like.
They are mere ridges projecting inward from the sides of
the larynx. They maybe stretched to various degrees and
placed in different positions, according to the sound that
is to be produced.

268 Physiology.

The Position of the Vocal Cords. — While we are quietly
breathing, the vocal cords lie back, like low ridges, against
the sides of the larynx, and offer nearly the whole channel
of the larynx for the free passage of air for breathing pur-
poses. 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. The
vocal cords are attached close to each other in front, but
at the back of the larynx they diverge widely, forming a

— . Epiglottis

_ False Vocal Cords

True Vocal Cords

Glottis Narrowed, High Note Glottis Wider. Quiet Breathing

Fig. 105. The Vocal Cords, seen from Above.

letter V, with the angle of the V just back of Adam's
apple. " When changes in the voice or in breathing are
being made, the white glistening 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 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 squeak-
ing balloon, or "squawker." Here the air is driven out past a band of
rubber stretched across the inner end of the tube. If instead 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 touching at
one end and considerably separated at the other end, we would have a
pretty fair resemblance to the larynx

Taste, Smell, Hearing, and the Voice. 269

Loudness of Voice. — The loudness of the voice depends on the force
with which the air is driven past the cords, and on the size and con-
dition of the cords themselves.

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 modi-
fied by the lips, tongue, teeth, cheeks, etc. We have voice as soon as
born, but we only gradually acquire the power of speech. This dis-
tinguishes man from the animals below him.

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 the sense of equilibrium
and not with hearing.

8. Colds and catarrh often seriously affect hearing.

9. The larynx is very complicated. Various muscles move the car-
tilages and vary the length and tension of the vocal cords, and thus
produce the varying degrees of pitch.

10. The vocal cords are not cords, but are band-like ridges on the
sides of the larynx.

11. The higher animals have voice but not speech.

12. Whispering is speech without voice.

13. The larynx is affected by "colds" and catarrh.

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 ?

7. Why does one become hoarse from hearing others shouting ?

CHAPTER XXVII.
TfiE EFFECTS OF ALCOHOL ON THE SENSES.

Alcohol a Narcotic. — Alcohol is not only an irritant
poison, but is also a narcotic poison. Its narcotic effect
is shown in the general deadening of the senses. In small
doses alcohol seems at first to have a stimulating effect.
But this is also true of opium, which is perhaps the best
example of a narcotic.

Alcohol dulls the Senses. — " Alcohol, after a most care,
ful physiological investigation, has been declared to be not
a stimulant but an anesthetic, a depressing and paralyzing
agent under all circumstances. It lowers the temperature
and the pulse rate, diminishes the senses, lessens the mus-
cular strength, impairs the memory, slows all the brain
functions, and brings them below their normal acuteness.
It diminishes the power of reason and judgment." — /. D.
Mishoff, M.D.

Alcohol and the Sense of Touch. — Alcohol blunts the
sense of touch. It is said that the drunkard sometimes is
unable to tell whether or not the glass is touching his lips.
Under the influence of alcohol no one would be capable of
exercising the fine sense of touch that is necessary in many
kinds of skilled work, such as watch-making. Here, of
course, steadiness of the muscles is necessary. But the
sense of touch must also be delicate or else the workman
cannot tell whether or not he is holding his instruments
properly. Any such expert work as judging of fabrics like
cloth by the sense of feeling, or judging of the quality or

270

The Effects of Alcohol on the Senses. 271

finish of goods by touch, would be impossible for one whose
sense of touch is not keen.

Experiments on the Effects of Alcohol on the Senses. -
During the last few years a number of observers have
experimented on the effects of alcohol on the senses. By
testing the degree of sensibility after giving small doses of
alcohol they have proved that the senses are invariably less
keen than before. It is proved that alcohol exercises
a narcotic, or deadening, effect on the senses. Dr. Kellogg
found that alcohol reduced the sense of touch and the tem-
perature sense more than one hundred per cent, while
muscular strength was diminished thirty per cent. Alcohol
benumbs nerve structures of every sort and does not in-
crease the activity of either the nerves or the brain.

Effects of Alcohol on the Temperature Sense. — The tem-
perature sense is so closely related to the sense of touch
that until late years they were considered to be one and
the same thing. Now they are regarded as separate.
Along with the dulling of the sense of touch, under the
influence of alcohol, comes a deadening of the temperature
sense. The drunken man may take hold of a hot iron and
severely burn the hand without realizing the injury. Thus
the use of pain is lost, for its purpose is to tell us when
any organ is injured, and by the pain compel us to remedy
the trouble. The drunken person exposed to cold does
not feel it. In the first place the increased circulation of
blood in the skin gives him a false sense of heat, at the
very time when he is losing heat faster than usual. But
the main trouble now is that he has lost his sensibility to
cold, as well as to heat. He is likely to freeze without
knowing the danger. Every winter we read of drunkards
who have been thus frozen to death in the streets and

272 Physiology.

alleys of our towns and cities. All Arctic explorers now
know this danger and avoid the use of alcohol.

Alcohol and the Sense of Sight. — It takes very little
alcohol to dull the sense of sight. No hunter or marksman
would think of taking alcohol before attempting accurate
shooting, for alcohol blunts vision as well as makes the
muscles unsteady. Alcohol often causes the person to
"see double," because alcohol interferes with uniting prop-
erly the images formed in the two eyes of the one object.
No one whose work calls for accuracy of sight can take
alcoholic drinks without interfering with his business.

Alcohol and Railroad Men. — Probably in no business is
it more important that the senses should be alert and
keen than in the railroad business. Railroad men must
watch for signals and read orders constantly. And on
the accuracy and care with which they get these signals,
and the faithfulness with which they obey these orders,
depend the lives of all who travel on railway trains.
Especially is this true of the engineer, on whose clear sight
and acute hearing, on whose sound judgment and prompt
action in a crisis, so many lives depend. Everybody
rejoices that the railway companies are each year
becoming more strict in their rules as to the habits of
trainmen.

Alcohol and the Sense of Hearing. — Alcohol blunts the
sense of hearing. Many an intoxicated man, staggering
along a railway track, fails to hear a train that he would
easily have heard when sober, and is run over and killed.
When bystanders call to him, he fails to hear or does not
understand ; so their effort to save him is useless, because
he has, for the time, lost his sense of hearing.

The Effects of Alcohol on the Senses. 273

Alcohol and the Sense of Taste. — Alcohol blunts the
sense of taste. So the drunkard no longer relishes the
taste of plain food, but must have dishes highly seasoned
with peppers and spices. He prefers very strong tea
and coffee and strong-tasting foods, such as highly salted
or smoked meats. And this use of strong seasoning, in
turn, calls for strong drink. His digestion is ruined, and
he goes on from bad to worse.

Alcohol and the Sense of Smell. — The sense of smell,
too, is dulled. The drunkard falls into a gutter and lies in
filth and dirt, failing to notice what would be highly offen-
sive to him when sober.

Alcohol and the General Senses. — The general senses,
as well as the special, are affected by alcohol.

Alcohol and Muscular Sense. — All muscular action is
affected by the use of alcohol. The staggering gait and
unsteady movements of the intoxicated are the best of
proof. But it is especially evident that any form of
delicate muscular work will be interfered with by the use
of alcohol. Take, for instance, the work of the telegrapher.
He must use the muscles with very great accuracy. The
presence of alcohol in the' tissues has a double effect on
such work. In the first place, it interferes with the nerve
control of the muscles. Second, the muscular sense,
which is one of the chief means of regulating these move-
ments, is blunted, so that the operator cannot tell whether
he is doing the work accurately or not. This double effect
is produced wherever there is muscular work, and especially
where the nature of the work calls for delicacy and pre-
cision.

274 Physiology.

Alcohol and Pain. — The nerves of general sensibility in
the skin, and elsewhere, are dulled. Hence pain is not
felt as when sober. Great injury may occur and pass
unheeded, because of this loss of sensibility. The un-
fortunate person may be badly burnt, cut, or bruised, and
hardly be aware of it. If aware of it, he is not likely to be
able to remedy the difficulty. In earlier times, before
anesthetics were in general use, it was the custom to make
a person drunk, and, hence, nearly or quite insensible,
before a surgical operation. Ether or chloroform deaden
sensibility much more surely, and without such serious
reaction afterward.

Alcohol and Fatigue. — The main reason why alcohol
seems to restore a tired person is because it deadens the
sense of fatigue. This is also true of the apparent banish-
ment of the feeling of depression, or any of the other
general sensations.

Loss of Nerve Sensibility. — " It is the diminution of
nerve sensibility that renders the individual, first, light,
airy, and hilarious, giving the popular idea of excitement
or stimulation ; second, dull, hesitating, or incoherent in
thought or speech, and unsteady or swaggering in gait, -
a stage popularly recognized as incipient intoxication ; and,
third, brings on entire unconsciousness and muscular pa-
ralysis, constituting dead-drunkenness, or complete anes-
thesia. These successive stages are developed in direct
ratio to the quantity taken." — N. S. Davis, M.D.

Alcohol not Stimulating. — "People appeal to their feel-
ings, and as they seem more excited, brisker and livelier
after a dose of alcohol, they jump to the conclusion that
the alcohol has had a direct stimulating effect upon them.
Exact measurements have proved that this is an illusion,

The Effects of Alcohol on the Senses. 275

and that from the first measurable effect of alcohol to the
last there is a gradually increasing paralysis of the ner-
vous system." — /./. Ridge, M.D.

The Delusive Nature of the Effects of Alcohol. — Alco-
hol is one of the most delusive substances known to man.
It seems to give warmth to the cold, strength to the weak,
activity to the sluggish ; it seems to refresh the weary, to
quench thirst, and to satisfy hunger ; it seems to rouse the
mental faculties to a higher pitch of activity, bringing
forth a greater degree of wit and wisdom than the indi-
vidual ordinarily displays. It seems to banish fear and
make the timid brave.

Let us glance over these seemings and try to get at the
real facts in the case.

The feeling of increased warmth after taking alcohol is
due to the greater amount of blood in the skin where the
nerve endings are affected, or to the deadened sensibility
to cold, or to both ; test by the thermometer shows that
the body's temperature is lowered.

After taking alcohol a person may feel stronger ; actual
test of strength shows diminished muscular power.

Fatigue seems to have been done away with because
sensibility is blunted ; any form of drowsiness would pro-
duce the same result.

Hunger appears to be satisfied through the action on
the nerves of the stomach ; but the body's need of food
has not been satisfied. Thirst may seem to have been
allayed ; but only soon to return intensified. What usu-
ally passes for wit, under the influence of alcohol, is ordi-
narily the silliness of the tipsy ; under this influence the
person overestimates his wisdom, while others can easily
see that his judgment is warped. He may fear danger

276 Physiology.

less than before, but it should not be called bravery ; he is
less sensible of danger, and he has become rash or even
reckless.

In all these cases sensibility is lowered, and the nerve
centers, especially the higher centers, have become more
or less paralyzed. For a short time the blood and the
brain run riot, the reins of judgment having been thrown
loose. Power has not been gained, but control has
been lost. Alcohol is not the "elixir of life," it is the
"fountain of death."

The Danger of using Alcohol. — The danger is espe-
cially great where there is a latent hereditary tendency to
inebriety or insanity. 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 they know that the reac-
tion will bring them into a worse condition than the one
from which they sought relief. 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 School Physiology Journal.

Summary. — i . Alcohol is both an irritant and a narcotic poison.

2. Alcohol dulls all the senses ; this is especially noticeable in sight,
touch, temperature sense, hearing, muscular sense, and pain.

3. Because of the blunting of the senses alcohol is very delusive.

Questions. — i. What makes the intoxicated person see double?
2. Why does a drinker use so much seasoning on his food ?

CHAPTER XXVIII.
TOBACCO.

Origin of Tobacco. — Tobacco was unknown to civilized
man till after the discovery of America. Here it was
found in use by the natives, having been brought originally
from South America. Its use has unfortunately spread
throughout the world. As an American product, we can-
not point to it with pride, as we can to corn and the potato,
which have proved such blessings to mankind. The
United States produces about half of the world's supply
of tobacco.

The Tobacco Plant. — The tobacco plant is an annual,
growing from three to six feet high, and bearing large
fuzzy leaves, the lower ones sometimes two or three feet
long. It is in these leaves that we find the principal sub-
stance for which tobacco is used, that is, the nicotine.
From two to six per cent of nicotine is found in the leaf.

Nicotine. — Nicotine is a clear, oily liquid. It is a most
violent poison, one drop being enough to kill a rabbit in
less than four minutes.

Effects of Nicotine. — Nicotine is one of the most power-
ful of nerve poisons. In very small quantities it at first
reduces the pulse rate, but afterward quickens it. The
pupils of the eyes are dilated. Larger doses produce con-
vulsions, followed by paralysis and often by death from
failure of respiration.

277

278 Physiology.

First Effects of Tobacco. — When taken for the first time,
tobacco usually produces the following effects : first, giddi-
ness, faintness, with a miserable feeling of great weakness,
shortly followed by nausea and severe and long-continued
vomiting, and relaxation and feebleness of the whole mus-
cular system. The skin becomes moist and pale. The
pulse grows very weak. These effects may be felt for a
day or two after the taking of the poisonous substance.
If a larger amount of the poison is absorbed, all these feel-
ings may be still more intense, and there may be cramps,
violent pains in the abdomen, convulsions, profuse purging,
and heart failure.

No antidote for this poison is known.

Ways of using Tobacco. — The chewing of tobacco is
much more harmful than smoking. The disgusting habit
of taking snuff is fortunately on the decline, so that we
see little of it.

Tobacco and Digestion. — The use of tobacco stimulates
the action of the salivary glands. Being kept in action
too much of the time, the saliva is wasted, and the digestion
of foods containing starch is less perfect. It is also said
to poison the saliva, and this also has a very bad effect. It
is not. natural that the salivary glands should be kept active
so much of the time, even by such a simple substance as
chewing gum ; much more harm is done when the exciting
substance is actually poisonous. It is said that the tongue
of the habitual smoker is always in bad condition. Smok-
ing produces a dryness of the mouth and throat.

The continued use of tobacco, especially when used in
large amounts, leads to a dry, foul condition of the mouth,
to more or less constant thirst, and to loss of appetite,
especially in the morning, and to chronic dyspepsia.

Tobacco. 279

The effect of all narcotics, of which nicotine is one, is
to lessen the secretion of the gastric juice, giving rise to
dyspepsia. By interfering with digestion the nutrition of
the whole body is affected.

Tobacco and Circulation. — Tobacco has a very powerful
effect on the action of the heart. The nerves which con-
trol the action of the heart are affected by the nicotine.
The beat of the heart becomes irregular. It is said that
one in four among tobacco-users shows this effect in the
beat of the heart. So well known is this condition that it
has received the name, as a distinct disease, of "tobacco
heart." The beat may be now feeble, now violent, now
slow, and soon rapid. Of course such a condition unfits
one for any work calling for severe muscular exertion.

Tobacco and Respiration. — Tobacco smoke has a very
decided effect on the mouth, throat, and all the air pas^
sages. In the first place the smoke is hot and would have
an unnatural effect even if there were no injurious vapors
in it. The vapors in the smoke are very irritating to the
mucous membrane of all the respiratory passages. The
mouth is dried and irritated, and frequently shows inflam-
mation. This inflamed condition may extend along the
eustachian tubes and interfere with the sense of hearing.
Very many habitual smokers are troubled with what is
known as " smoker's sore throat." Chronic bronchial
catarrh may be produced, or if already present, made
worse. From the interference with respiration the blood
may not get enough oxygen, and the whole system will
suffer. When a person unused to tobacco enters a room
filled with tobacco smoke, its poisonous effects are quickly
apparent He coughs, often soon gets a headache, and
shows the symptoms of tobacco poisoning. The fact

280 Physiology.

that those accustomed to such irritating smoke do not
show these symptoms is merely another proof of what
the system can learn to endure when it is compelled to
bear what is at first repulsive to nearly every human
being.

Cigarette Smoking. — Bad as other forms of smoking
are, this is still worse. Many cigarette smokers actually
inhale the smoke into the lungs. Here is not only the
irritation on the delicate mucous membrane, but the close
relation of the air and blood gives opportunity for absorp-
tion of the poisonous vapors into the blood. Again, since
the cigarette is small, many of them are used, the smoker
using one after another. The system is saturated with
nicotine, and the effect is usually much worse than from
any other form of smoking.

Just as beer, with its smaller amount of alcohol, often
has a more injurious effect than some of the other alcoholic
drinks containing much more alcohol, so cigarettes, though
small, are much more injurious tthan cigars. Perhaps this
is because, being so small, many of them are used, and so
the total amount of tobacco used is greater. But whatever
the cause, there are many observers who testify to the
fearful effects of the cigarette.

Effects of Cigarettes. — One of the instructors in the
naval academy at Annapolis said he could pick out the
boys who used tobacco because they were not able to draw
a clean, straight line.

" After making a study of several hundred boys, running
through a period of ten years, I found accompanied with
the use of the narcotic were certain disordered physical
functions, such as nervous affections and diseases of the
heart." — H. H. Seerly, Prin. Iowa State Normal School.

Tobacco. 281

" The use of cigarettes affects the nervous system, weak-
ens the will power and destroys the ability of the boy to
resist temptation, and because of this he easily falls a victim
to those habits which not only destroy the body, mind, and
soul, but irresistibly lead him into a violation of the laws."
— Hon. Geo. Torrance, Supt. 111. State Reformatory.

" Youths who before the habit of smoking was contracted
were resolute, manly, and vigorous in mental fiber, become,
after indulgence in tobacco, timid, fearful, hesitating, and
irresolute. The mental stamina is gone, and the quality of
manhood produced is much inferior to that originally
promised." — Journal of Hygiene.

" Boys who use tobacco are easily provoked, cross, un-
pleasant, and unable to work or play with vigor for any
length of time. They more quickly resort to falsehoods
and untruthfulness. Fathers and mothers are awaking to
full knowledge of the mental decay and physical wrecking
which follows the persistent use of this insidious youth
destroyer. If our boys are to be manly men, it will never
be by the cigarette route. • —Edwin E. Ashley, M.D.

Tobacco and Brain Work. — The use of tobacco interferes
with brain work. This is especially true of the young.
The continued use of tobacco unfits for study or any good
brain work. It is the almost universal testimony of teach-
ers and business men who employ boys, that the user of
tobacco, especially the cigarette smoker, becomes lazy and
is not to be relied upon for either mental or bodily work.
Smokers usually fall behind in their studies, even if they
were bright and capable students at the outset. To begin
this habit amounts to saying, " I am willing to give up part
of my mental and physical strength for the sake of this
habit." At least, this is just what the smoker does. No

282 Physiology.

student with an ambition to succeed in life can afford to
handicap himself by such a dead weight as the tobacco-
habit. Tobacco, like all other narcotics, gets a strong hold
on the system that habitually uses it, and we have but to
ask any habitual tobacco-user, to find how almost impossi-
ble it is to give up the habit after it is once formed.

Effect of Tobacco on the Nerves. — Tobacco affects the
nerves which have control of the muscles, so the use of
tobacco often causes loss of muscular power, not unfre-
quently resulting in paralysis. Even if no unsteadiness is
noticeable, there is less strength than before, and the young
man who uses tobacco unfits himself for going on any
athletic contest. Trainers are almost unanimous in for-
bidding the use of tobacco in their crews and teams.

Effect of Tobacco on the Senses. — It is stated on good
authority that there is no poison that has a greater destroy-
ing power upon the sensory nerves than nicotine.

Effect of Tobacco on Sight — JMicotine causes the pupils
to dilate ; this often causes obscurity of vision. In many
cases where the eyesight was affected, there has been
restoration on quitting the use of tobacco.

Effect of Tobacco on Growth. — The bad effects of tobacco
on the body are most plain in the young. It retards growth
and development. The law recognizes this in forbidding
the sale of tobacco to the young. The use of tobacco is
forbidden in our military and naval academies.

" Tobacco retards both physical and mental development
of boys and youth. This effect is so fully proved that all
intelligent writers agree in prohibiting the use of narcotics
until maturity of growth has been attained." • — N. S. Davis,
M.D.

Tobacco. 283

"The habit of cigarette smoking, indulged in by boys
under twenty, results in stunted growth, nervousness, indi-
gestion, and disease of the brain and kidneys." —C. P.
Chesley, M.D.

Tobacco leads to the Use of Alcoholic Drinks. — The con-
tinued use of tobacco, especially smoking, produces a dry-
ness of the mouth and throat that creates thirst. Plain
water does not satisfy this thirst. The tongue and other
parts of the mouth are now accustomed to a strong stimu-
lation, and, consequently, crave strong drink. Thus the
use of tobacco leads to taking alcoholic drink. This does
not always follow, for there are many men who smoke but
do not use alcohol in any form, but the one naturally leads
to the other.

The Extravagance of Using Tobacco. — Tobacco-using is
an expensive habit. With the excellent cheap printing of
to-day, many of the best works ever written may be bought
for the money that is paid for as many cigars. Many a
man spends enough for tobacco to send a boy through
college. Even for those who can afford it the habit seems
very selfish, for it is entirely needless, and there are so
many ways in which the money might do good to some one.

The Selfishness of Tobacco-using. — Most smokers seem
to forget that the air is public property* Even on the
streets there are many occasions when it is not possible for
a man to smoke without having the smoke carried directly
to the nostrils of those to whom it is both offensive and
injurious. The habit of chewing tobacco is almost invaria-
bly offensive to sensitive persons, and the indulgence in
the habit in public is an infringement on the rights of
others.

284 Physiology.

Perhaps Robinson Crusoe might have been excused for
using tobacco, having no one to save money for, no un-
fortunates 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 is so offensive, ought seri-
ously to ask himself whether he is doing right to continue
such a practice.

Summary. — i . Tobacco is an American product.

2. The essential thing in tobacco is nicotine, a very violent poison.

3. Nicotine acts powerfully on the nervous system.

4. No antidote for this poison is known.

5. Tobacco interferes with digestion.

6. Tobacco causes palpitation and irregular action of the heart.

7. Tobacco irritates the respiratory organs.

8. Cigarette smoking is especially bad, most of all on the young.

9. Tobacco interferes with brain work, especially in young students.

10. Tobacco makes the nerves unsteady.

1 1 . The use of tobacco dulls the senses, especially sight.

12. The use of tobacco by the young is a frequent cause of stunted
growth .

13. The use of tobacco is likely to lead to the use of alcoholic drinks.

14. Tobacco-using is an extravagant habit.

15. The use of tobacco is selfish, and disregards the rights of others.

1 6. Tobacco-using is a filthy habit.

CHAPTER XXIX.
OTHER NARCOTICS.

Narcotics. — A narcotic is a substance that deadens the
senses and, in large quantities, produces complete insensi-
bility. Narcotics are used to deaden pain or to induce
sleep, or lack of sensibility. When there is complete lack
of sensibility the person will not waken as from sleep.
This condition is known as anesthesia.

The principal narcotics are opium, hashish, belladonna,
stramonium, and henbane.

Alcohol is a narcotic, but is not used for narcotic effects
by physicians.

Ether, chloroform, chloral hydrate, etc., are narcotics,
but as their main use is to produce loss of sensibility for
surgical operations, they are called anesthetics.

Opium. — Opium is the dried and thickened juice of the
head or capsule of a species of poppy. The properties
of opium are due to morphia or morphine, which it con-
tains. One fourth of a grain of morphine equals four
grains of opium.

Use of Opium. — Opium is a stimulant narcotic, the
effects of which deaden the sensations of pain and pro-
duce sleep. Its habitual use is injurious and difficult to
break up. It is classed as a stimulant narcotic, acting
almost exclusively on the central nervous system when
taken internally ; in large quantities it is a powerful nar-

285

286 Physiology.

cotic poison, resulting in a deep sleep characterized by
great contraction of the pupils of the eyes, insensibility,
and death.

Chloroform. — Chloroform is a liquid that readily evapo-
rates. Its vapor, mingled with air, is inhaled to produce
unconsciousness and loss of sensibility. It is one of the
most valuable of modern discoveries for use in surgical
operations. When used repeatedly, to induce sleep, it
becomes a habit hard to break, for, like other narcotics,
it produces such an effect on the system that there is a
craving for it. It should be used only by physicians.

Ether. — The use of ether is about the same as that of
chloroform. Ether is considered safer than chloroform,
as the latter occasionally causes death by paralyzing the
heart. In some cases chloroform is preferred. Both
ether and chloroform produce death if too large an amount
is taken.

Nitrous Oxide. — This gas also produces loss of sensi-
bility, though often not so complete a loss of conscious-
ness. Its effects soon pass away. It is therefore more
suited to very short operations, such as the extraction of
teeth, and is much used by dentists.

Chloral Hydrate. — This drug is frequently, but incor-
rectly, called chloral. It is a powerful sleep-producer and
lowers the action of the brain and spinal nerve centers,
and, to a limited extent, is an anesthetic. It is very useful
in fevers accompanied by brain excitement, and in convul-
sions. Its effects in producing sleep 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.

Other Narcotics. 287

Cocaine. — Cocaine is an extract of a shrub native to the
Andes. Its effects are similar to those of coffee, but are
more intense. Large doses have a narcotic effect. Its
long-continued use is followed by sleeplessness, decay of
moral and intellectual power, emaciation, and death. It
produces loss of sensibility in a limited area of surface to
which it is applied; hence is valuable for minor surgical
operations, such as those performed on the eye.

Soothing Syrups. — Probably all of the soothing syrups
contain some form of opium. The frequent use of such
drugs on children is dangerous. None of them should be
used except under the advice of a physician. They do
stop pain, but they are not likely to cure the trouble that
caused the pain, and are of doubtful benefit, even where
they are not actually harmful. By their continued use
many sickly children are really soothed to death.

Narcotics reduce Strength. — " Such narcotics as opium,
cocaine, and tobacco, by lessening the sensibilities of
the nervous structures, correspondingly lessen muscular
activity, both voluntary and involuntary, and thereby
lessen the depth and frequency of respiration. Conse-
quently, the individual who uses any one of these agents,
even within the limits of so-called moderation, from day to
day, through months and years, inevitably dulls his nervous
energy, uses a less amount of oxygen, and slowly but surely
impairs the vital properties of his tissues and invites early
old age." — N. S. Davis, M.D.

The Use of Narcotics. — The use of anesthetics and
narcotics may all be represented by alcohol. They all act
on the nervous system. They produce at first a pleasing
effect or they bring relief from pain. The use of many of
them is begun during illness, when they are administered

288 Physiology.

to relieve pain, as in neuralgia. The habit, once formed,
is hard to break. Only the confessions of such victims,
and the degrading effects on character, show how power-
ful 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. One
of their first effects is to weaken the will. The history of
their use is ever the same. They enslave. They destroy.

Summary. — i . Narcotics deaden pain or produce insensibility.

2. Opium is the chief narcotic; morphine is extracted from opium.

3. Chloroform, ether, and nitrous oxide are anesthetics, and are used
to produce insensibility during surgical operations.

4. Chloral hydrate is a sleep-producer, or hypnotic.

5. Cocaine is a local anesthetic, useful in minor surgical operations.

6. Soothing syrups usually contain opium or other narcotic, and
their use is dangerous unless under the direction of a physician.

7. Narcotics reduce strength as well as sensibility.

8. Narcotics make the habitual user a slave to their influence, and
are usually ruinous to mind as well as to body.

• I

CHAPTER XXX.
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. Pressure should be applied
between the cut and the heart. To know where to apply the pressure,
study the course of the main arteries. By examining Fig. 32 it will be
seen that the arteries to the .arms pass down the inside of the upper
arm. Here they come near the surface. By putting a thick book or
roll 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 Fig. 32.)

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 may be possible to stop the flow by compressing
the artery lower down the neck.

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.

289

290 Physiology.

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 posi-
tion 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 blow-
ing the nose, as this often starts bleeding again.

Treatment of Burns. — Plunge the burned part into cold water. As
soon as possible apply a solution of cooking soda (a tablespoonful of
bicarbonate of soda to a teacup 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.

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 has lost
presence of mind and starts to run, throw him to the ground, putting a
wrap of some kind around the body at the same time if possible. Roll-
ing 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 remedies do not
soon restore consciousness, send for a physician. A faint is not usually

Accidents.

291

a serious matter. Bad ventilation, disagreeable odors, or even the over-
sweet odors of such flowers as the tuberose, may cause fainting.

Broken Bones. — Keep the patient as quiet as possible till the physi-
cian arrives. If there is inflammation, cold water may be applied.
Cooling applications are desirable in case of severe bruise's. 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 along-
side a leg, and supported by a pillow or a coat. Otherwise 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.

^v^

Fig. 106. Resuscitation from Drowning. (Lincoln, 3 Figures.)
(Position I.)

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 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.
1 06, Position i), and give the body a smart jerk to remove mucus from

292

Physiology.

the throat and water from the windpipe ; hold the body suspended long
enough to count slowly, one, two, three, four, five, repeating the jerk
more gently two or three times.

RULE 2. Place the patient on the ground face downward, and, main-
taining 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 armpits, clasping your thumbs over the points of the shoulders,
and raise the chest as high as you can (Fig. 107, Position 2) without
lifting the head quite off the ground, and hold it long enough to count

Fig. 107.

Resuscitation from Drowning.
(Position 2.)

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. 108, Position 3), over the lower ribs, and press
downward and inward with increasing force long 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 alternate 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.

Accidents.

293

RULE 3. After breathing has commenced, restore the animal heat.
Wrap him in warm blankets, apply bottles of hot water, hot bricks, or
anything to restore heat. Warm the head nearly as fast as the body
lest convulsions come on. Rubbing the body with warm cloths or the
hand, and slapping the .fleshy parts, may assist to restore warmth, and
also the breathing. If the patient can surely swallow, give hot coffee,
tea, milk. Alcoholic liquors are liable to produce depression. Place

108.

Resuscitation from Drowning.
(Position 3.)

the patient in a warm bed, and give him plenty of fresh air ; keep him
quiet.

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
secondary. Do not stop to remove wet clothing. Precious time is
wasted, and the patient may be fatally chilled by the exposure.

First restore Breathing. — Give all your attention and effort to re-
store breathing by forcing air into, and out of, the lungs.' If the breath-
ing 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.

294 Physiology.

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 suffocation ; the second, fatal choking.

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 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.
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 does not try to lift much of his body out of
the water.

Suffocation in Wells. — Persons are sometimes suffocated 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 unconscious, 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

Accidents. 295

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.

1. Mustard a Common Emetic. — The most common emetic is mus-
tard ; 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. Pro-
voke vomiting 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 poison-
ing 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 neutralized 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 poison 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 physician should be sent for imme-
diately, as the after-treatment is of great importance.

296 Physiology.

Wounds from Thorns and Rusty Nails. — Promote bleeding by rub-
bing and pressing the wound and bathing with warm water. Or suck
the wound. This tends to remove any injurious matter. Apply
poultices.

Bites of Cats, Dogs, 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 ap-
plied 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).
Then apply caustics, or a live coal. Wash the wound with vinegar or
strong salt solution. If ammonia water is at hand, add five teaspoon-
fuls to a pint of water and drink this. 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.
To bee stings, apply soda or dilute ammonia.

Poison Ivy. — The itching and discomfort may be relieved by bath-
ing 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 nursing is often " half the battle." The patient
should have a cheerful room, but the bed should be so placed that he
will not face the light. Evidence of illness, such as medicine bottles,
etc., should be kept out of sight so far as possible. 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 greatly improved. Nothing sustains like hope.
Keep the air of the room pure. Remove excreta and everything offen-
sive just as soon as possible. Do not rely on feeling as to temperature,
but keep a thermometer in the room.

Sympathy with the Patient. — One of the necessary characteristics
of a good nurse is the power of imagination. " How would I feel, and

Accidents. 297

what would I like to have done, 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 suffer for want
of a bath.

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 clothing 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 thoroughly
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 yourself 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.

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,
sawdust, etc. Any dusting should be avoided ; furniture may be wiped
with a damp cloth.

Do not Whisper. — Do not whisper, as it disturbs more than talking,
and also has an air of secrecy that rouses suspicion in the patient.

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 or glass 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 poultices, as an ordinary wood or coal fire is likely to die down,

298 Physiology.

making it impossible for the nurse to do this work quickly, as it is often
necessary to take advantage of a favorable time, as when the patient
wakens.

Care of Lamps. — Most lamps, when turned low, give off a disagree-
able gas. It is better to have a very small lamp burning at full height
than a large one turned low ; sperm candles are recommended. Do not
let the light shine into the patient's face.

To Prevent Sneezing. — It is well known that a sneeze may be pre-
vented 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.

Summary. — i . To stop flow of blood from an artery apply pressure
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 checks, nosebleed.

4. In case of a burn apply cooking soda.

5. If the clothing takes fire, lie down and roll, or wrap a rug or shawl
about the body.

6. If a person with clothing on fire loses his presence of mind, seize,
throw down, and wrap rn 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 send for a physician.

8. Before going down into a well, test the air by lowering a lighted
candle.

9. Learn the antidotes of every poison in your house as soon as it is
bought, and keep the antidote at hand.

10. 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 bleed-
ing ?

2. What other methods of resuscitation from drowning are in use ?

3. What are some of the poisonous substances commonly kept in
the house ?

GLOSSAEY.

Albumen (alrbu'-meri). The white of an egg.

Albumin (al-bu' -rain) . 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 the urine,
indicating changes in the blood or in the kidneys.

Amylopsin (am-i-lop'-sin) . 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'-bor m'-ie}. A term applied to the branched appear-
ance of a section of the cerebellum.

Argon (ar'-^on). 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 (bi'-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.

299

300 Glossary.

Bronchus (brQng'-kus"), 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-iri). An alkaloid that occurs in the leaves and beans of
the coffee-tree, in Paraguay tea, etc.

Canaliculus (kan-a-lik'-u-lus}, pi. canaliculi. The crevices extending
from lacunae, through which nutrition is conveyed to all parts of
the bone.

Canine (ka-nln' or kd'-nln~). 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'-sul). A tunic or bag that incloses a part of the body or
an organ.

Carbohydrate (kar-bo-hl'-drat}. 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-laj}. Gristle of various kinds, articular, etc.

Casein (fcd'-se-in). 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 (fco'-roid). The second or vascular coat of the eye, continu-
ous with the iris in front, and lying between the sclerotic and the
retina.

Glossary. 301

Chyle (kli). The milk-white fluid absorbed by the lacteals during di-
gestion.

Chyme (&im). Food that has undergone gastric digestion, and has not
yet been acted upon by the biliary, pancreatic, and intestinal
secretions.

Cilium (siT-i-wm), 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 (siT-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-jungk-tl'-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, diabetes
mellitus, 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-al'-i-sis\ The operation of separating crystalline from
colloid substances by means of a porous diaphragm, the former

302 Glossary.

passing through the diaphragm into the pure water upon which the
dialyzer rests.

Digastric (di-gas'-trik). Having two bellies, as the digastric muscle,
enlarged near each end and with a tendon in the middle.

Duodenum (du-o-de'-num). The first part of the small intestine, begin-
ning with the pylorus.

Emulsion (e-mul'-shun). Water or other liquid in which oil, in minute
subdivision of its particles, is suspended.

Enamel (en-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'-zira). Any chemic or hydrolytic ferment, as distinguished
from organized ferments such as yeast; unorganized ferment.

Epiglottis (ep-i-glot'-is). A thin nbro-cartilaginous valve that aids in
preventing food and drink from passing into the larynx.

Esophagus (e-sof-a-gus}. 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'-ef). A small plane surface. The articulating surface of a
bone.

Femur (/e'-raer). 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 (fil'-i-form}. 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 (gang'-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.

Glossary. 303

Gastric (gasf'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 (glos'-o-fa-riri-je-al}. Pertaining to the tongue and
larynx.

Gluten (glo'-ten). A substance resembling albumin, and with which it
is probably identified ; it occurs abundantly in the seeds of cereals.

Glycogen (gll'-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'-td-to-ri). Pertaining to thfi special sense of taste and
its organs.

Hashish (hash'-esh). 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-d-glo'-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 (/m'-me-rus). The bone of the upper arm.

Humor (/m'-raor). Any liquid, or semi-liquid, part of the body.

Hyoid (lii'-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-glos'-al}. Under the tongue.

Iliac (tf'-i-afc). Pertaining to the ilium, or region of the flanks, as iliac
artery, vein, etc.

Incisor (m-si'-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.

304 Glossary.

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-tin). 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-liir*). 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 (la-mel'-a), pi. lamellae. A thin lamina, scale, or plate ; of
bone, the concentric rings surrounding the haversian canals.

Larynx (lar'-ingks}. The upper part of the air passage between the
trachea and the base of the tongue ; the voice-box.

Legumin (le-gu'-min}. A proteid compound in the seeds of many plants
belonging to the natural order Leguminosae (peas, beans, lentils,
etc.).

Lumbar (lum'-bar\ 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 (mecf-w-Jd-n). 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.

Glossary. 305

Mesentery (mezf-en-ter-i}. A fold of the peritoneum that connects cer-
tain portions of the intestine with the dorsal abdominal wall.

Metabolism (me-tab'-o-lizm}. 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-kiir'-pus'). The bones of the palm of the hand.

Metatarsus (met-a-tar'-sus'). The five bones of the arch of the foot,
situated between the tarsus and the phalanges.

Mitral (ml'-tral}. Resembling a miter; mitral valve, with two flaps,
between the left auricle and the left ventricle.

Molar (mo'-ldr). Mill; the grinding-teeth.

Mucous (mu'-kus*). A term applied to those tissues that secrete mucus.

Mucus (muf-kus'). A viscid liquid secretion of mucous membranes,
composed essentially of mucin, holding in suspension desquamated
epithelial cells, etc.

Myosin (mi'-o-sm). A proteid of the globulin class, — the chief proteid
of muscle. Its coagulation after death causes rigor mortis.

Narcosis (ncir-fco'-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-kot'-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-rao'-sis). That property by which liquids and crystalline
substances in solution pass through porous septa ; endosmosis and
exosmosis.

306 Glossary.

Oxy-hemoglobin (ok-si-hem-o-glo'-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'-kre-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'-kre-a-tin}. 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-uni}. 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 bone,s, except at the points of tendinous and liga-
mentary attachments, and on the articular surfaces where cartilage
is substituted.

Peristaltic (per-l-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-td-ne'-al). Pertaining to the peritoneum.

Peritoneum (per-i-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'-langks). Any one of
the bones of the ringers or toes.

Glossary. 307

Pharynx (far'-ingks*). 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 nascent,
living matter. The fluid part of the blood and lymph.

Pleura (p/o'-rd). 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-mo-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 hilum of an organ,
especially of the liver, as the portal vein.

Postcaval (post-ka'-val). Pertaining to the postcava; the postcaval
vein, formerly called the inferior vena cava, or vena cava ascendens.

Precaval (pre-ka'-vaty. Pertaining to the precava; the anterior caval
vein, formerly called the superior vena cava, or vena cava de-
scendens.

Pronation (pro-nd'-s^wn). 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 (ti'-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 (rd'-di-ws). The outer of the bones of the forearm.

Renal (re'-naV). Pertaining to the kidneys.

Rennin (ren'-in). 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.

308 Glossary.

Sacrum (sd'-fcrwm). 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'-rws). Pertaining to, characterized by, or having the nature

of, serum.
Serum (se'-rwm). The yellowish fluid separating from the blood after

the coagulation of the fibrin.

Solar plexus (so'-lar). Solar, with radiations resembling the sun.
Sphincter (sfingk'-ter^) . A muscle surrounding and closing an orifice.
Splenic (splen'-ik}. Pertaining to the spleen.
Steapsin (step'-siri). A diastasic ferment which causes fats to combine

with an additional molecule of water and then split into glycerine

and their corresponding acids.
Sternum (ster'-num}. The breast-bone.
Subclavian (sub-kla'-vi-an}. Situated under the collar-bone ; subcla-

vian artery and vein.
Sublingual (sub-ling'-gwal). Lying beneath the tongue, as sublingual

gland.
Submaxillary (sub-mak'-si-la-rC). Lying beneath the lower maxilla, as

submaxillary salivary gland.

Supination (su-pi-na'-shun}. The turning of the palm upward.
Synovia (si-no'-vi-a). The lubricating liquid secreted by the synovial

membranes in the joints.

Tarsus (tar'-sus^). The instep, consisting of seven bones.
Temporal (tem'-pd-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.
Them (the'-in). An alkaloid found in tea.

Theobromin (the-d-bro'-min}. A feeble alkaloid obtained from cacao-
butter ; the essential substance found in cocoa and chocolate.

Glossary. 309

Thyroid .(thl'-roi<T). Shield-shaped, as the thyroid cartilage oi the
larynx.

Tibia (tib'-i-a). The larger (inner) of the two bones of the leg, com-
monly called the shinbone.

Trachea (tra-ke'-a or tra'-ke-a}. The windpipe.

Triceps (tri'-seps). Triceps of the arm, the extensor of the arm, lying
along the back of the humerus.

Tricuspid (tri-kus'-pid) . Having three cusps or points, as thetricuspid
valve.

Trypsin (trip'-sin}. The proteolytic ferment of pancreatic juice.

Ulna (wZ'-na). The larger (inner) of the two bones of the forearm.

Ureter (u-re'-ter'}. The tube conveying the urine from the pelvis of the
kidney to the bladder.

Vaso-constrictor (vas'-o-kon-strik'-tor}. Causing a constriction of the
blood-vessels.

Vaso-dilator (vas'-o-di-la'-tor}. Pertaining to the positive dilating mo-
tility of the non-striated muscles of the vascular system.

Vaso-motor (vas-d-mo'-tor). Serving to regulate the tension of the
blood-vessels, as vaso-motor nerves ; including vaso-dilator and
vaso-constrictor mechanisms.

Ventricle (veri-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 (mT-ws), pi. villi. One of the numerous minute vascular projec-
tions from the mucous membrane lining the small intestine, for ab-
sorbing digested food.

Vitreous (vif-re-ws). Glass-like, as the clear, jelly-like, vitreous humor
of the eye.

INDEX.

Absorption, 183-189.
Accidents, 289-298.
Accommodation, 255.
Adam's apple, 267.
Air, composition of, 103.

Effects of rebreathing, 109.

Washed by rain, 120.

Washed by snow, 120.
Albinos, 131.
Albumen, 151.
Albuminuria, 199.
Alcohol, 205-219.

In the army, 212.

And blood corpuscles, 86.

And bones, 15.

And character, 218, 243.

And circulation, 67.

And consumption, 102.

And crime, 218.

And degeneration, 191.

Delusive, 171, 275.

And digestion, 170.

And disease, 217.

And dyspepsia, 171.

And endurance, 35.

And energy, 26.

And excretion, 138.

And fatigue, 274.

And hearing, 272.

And heart, 68, 77, 212.

Inherited effects, 217.

And insanity, 241.

And intestines, 180.

And kidneys, 138, 139.

And liver, 190, 191.

And lungs, 101.

And mountain-climbing, 213.

And muscles, 34.

And muscular sense, 273.

And nerves, 46, 47.

And pain, 274.

And peristaltic action, 172.

A poison, 87.

And poverty, 218.

And railroad men, 272.

And respiration, no.

And the senses, 270.

And sight, 272.

And skin, 76, 139.

And smell, 273.

And stomach, 170.

And strength, 25.

And sunstroke, 240.

And taste, 273.

And temperature sense, 271,

And throat, 162.

And touch, 270.

And training, 27.

And vital organs, 191.
Amylopsin, 176.
Anatomy, defined, 2.
Anesthetics, 285.
Anti-toxin, 126.
Anvil, 265.
Aorta, 54, 187.
Apoplexy, 234.

Appendix, vermiform, 178, 179.
Aqueous humor, 255.
Arteries, action of, 59-61.

Blood flow in, 66, 67.

Structure of, 60, 61, 64.
Artificial respiration, 291-294.
Asiatic cholera, 122.
Assimilation, 197.
Astigmatism, 256.
Atlas, 10.
Auricle, 55, 59.
Axis, 10.

3I2

Index.

Bacilli, kinds of, 123.
Bacteria, 124, 206.
Baking, 152.
Barley, 145.
Baseball, 222.
Bathing, 224, 225.

The sick, 297.
Bee stings, 295.
Beef tea, 151.
Beer, 47, 208, 209.
Belladonna, 285.
Bicycling, 223.
Bile, 174.
Bites of cats and dogs, 296.

Of snakes, 296.
Bitters, 196.

Black-and-blue spots, 81.
Bleeding, from arm, 289.

From arteries, 289.

From lungs, 290.

From neck, 289.

From nose, 290.

From stomach, 290.

From thigh, 289.

From veins, 289.
Blind spot, 258.
Blister, 131.
Blood, 78-80.

Amount of, 81.

-Poisoning, 122.
Blushing, 72.
Boats upsetting, 294.
Body and candle, 103, 104.

And locomotive, 108, 109.

And stove, 108.
Boiling water, 148.
Bones, 5.

Broken, 14, 34, 291.

Composition of, 12, 13.

In ear, 265.

Structure of, 12, 31.
Boxing, 223.
Brain, 37, 226-234.

Blood supply of, 234.

Functions located, 231.

Rest, 233.

Work, 233.
Brandy, 209.
Broiling, 152.
Bronchus, 91.
Burns, 290.

Caffein, 151.

Candle, oxidation of, 103, 104.

Capillaries, blood flow in, 62, 63.

Carbohydrates, 144.

Carbon dioxid, 103, 109.

Carpets, 124.

Carpet sweepers, patent, 125.

Cartilage, 10, 32, 95.

Cecum, 178.

Cellars, ventilation of, 119.

Cells, 3.

Of blood, 78.

Of brain, 229.

Of epidermis, 63.

Of ganglions, 41, 42.

Of glands, 161.

Of lymph, 82.

Of muscle, 19, 20.
Cellulose, 152.
Cerebellum, 226-228.

Function of, 232.

Cerebrospinal nervous system, 37.
Cerebrum, 226.
Cesspools, 147, 148.
Cheese, 143.

Chloral hydrate, 285, 286.
Chloroform, 285, 286.
Chocolate, 151.
Choking, 97.

Choroid coat of eye, 254.
Chyle, 185, 186.

Receptacle of, 82.
Chyme, 169.
Cider, 181, 205.

And small intestine, 192.
Cigarette smoking, 280, 281.
Ciliums, 90.
Circulation and clothing, 75.

Control of, 70.

In frog's web, 62, 63.
Clot, 80, 81.

Coagulation of blood, 80, 81.
Cocaine, 287.
Coccyx, 10.
Cochlea, 265, 266.
Cocoa, 151.
Coffee, 151.
Colds and deafness, 267.

Taking, 223.
Colon, 177, 178.
Color blindness, 258.

Index.

3'3

Color of eyes, 252, 254.
Congestion, 75.
Conjunctiva, 252.
Connective tissue, 20.
Consciousness, 229.
Consumption, 122.
Contagious diseases, 125.
Convolutions of brain, 226.
Convulsions, 26.
Cooking, 151.
Cords, vocal, 267, 268.
Corn, 145.
Cornea, 252, 254.
Corpuscles of blood, 78, 79.

Lymph, 82.
Coughing, 97.
Cramp, 45.
Crazy bone, 250.
Crossing of nerve fibers, 230.
Crystalline lens, 255.
Cutaneous sensations, 248.

Dandruff, 131.

Deafness and colds, 267.

Delirium tremens, 240.

Dermis, 132.

Desserts, 194.

Diabetes, 199.

Diaphragm, 89, 91, 92, 94, 187.

Diet, mixed, necessity of, 149.

Proper, 150.
Diffusion of gases, 112.
Digestion and circulation, 193.

In the intestine, 174.

In the mouth, 154.

And muscular work, 193.

And repose, 194.

In the stomach, 164, 169.

And study, 193.
Digestive tube, 154.
Diphtheria, 122.
Disease germs, 122.
Dislocations, 14.
Distillation, 209.
Distilled liquors, 209.
Dropsy, 85.

Drowning, treatment for, 291-294.
Duodenum, 178.
Dura mater, 226.
Dust, 120-124.
Dyspepsia and alcohol, 171.

Ear, 265, 266.

Eating, intemperance in, 195.

Time of, 195.'
Eddy, body like, 199.
Eggs, 143.
Emulsion, 143, 176.
Energy from food, 200.

Potential, 96.
Entire wheat flour, 144.
Epidermis, 130, 131.
Epiglottis, 164, 165.
Equilibrium sense, 266.
Erysipelas, 122.
Ether, 285, 286.
Eustachian tube, 265, 266.
Excretion, 129, 179.
Exercise and blood flow, 73, 107

Forms of, 221.

For general health, 220.

And respiration, 107.
Extensors and flexors, 21.
Eye, 252-262.
Eyesight, defects of, 256.

Fainting, 234, 290.

Fans, 116.

Far sight, 256.

Fat, as tissue, 196.

Fatigue, 233.

Fats, absorption of, 185, 189.

As food, 144.
Fermentation, 205.
Ferments, 206, 208.
Fibrin, 80.
Fish, 142.
Flavors, 264.

Flexors and extensors, 21.
Food, 141.

Amount needed, 195.

And foodstuffs, 141, 142.

Need of, 141.

Object of, 154.

Preservation of, 128.
Football, 222.
Foot-bath, hot, 76.
Foul-air shafts, 116.
Freckles, 131.
Fruit, 146.
Frying, 152.
Function, defined, 2.
Furnace, 116.

Index.

Ganglions, 71, 229.
Glands, 179, 180.

And blood supply, 134.

Control of, 134, 179.

Gastric, 167, 168.

Intestinal, 177, 184.

Lacrymal, 252.

Lymphatic, 82, 83.

Mucous, 162.

Oil, 130, 132.

Plan of, 161.

Salivary, 160-163, X7S-

Sweat, 130, 133.
Graham flour, 145.
Grates, 113, 117.
Gravity and circulation, 74, 75.
Grippe, 122.
Gullet, 155, 164-166.

Hair, 130, 132.

Hammer, 265.

Hashish, 285.

Heart, 50, 51.

Heart-beat, control of, 73, 74.

Rate of, 49, 73.
Heart-burn, 170.
Heat, conduction of, 135.

Convection of, 135.

Distribution of, 136.

And exercise, 136.

In the liver, 108.

Production of, 106.

Radiation of, 135.
Heating, direct, 116.

By hot water, 116.

Indirect, 116.

By steam, 116.
Hemoglobin, 80, 105.
Hemorrhage, of lungs, 290.

Of stomach, 290.
Henbane, 285.
Hiccuping, 97.
Hops, 208.
Humor, aqueous, 255.

Vitreous, 255.
Hunger, 247.
Hygiene, defined, 2.
Hypodermic injections, 86.

Image, on retina, 255.
Inflammation, 75.

Inoculation, 126.

Intestine, large, 156, 177, 178, 190.

Small, 155, 174, 178.
Iris, 252, 254.

Joints, 13.

Juice, gastric, 167, 168.

Intestinal, 177.

Pancreatic, 176.

Kidneys, 137, 138, 199.

Labor, division of, 3.

Laciymal secretion, 252.

Lacteals, 184, 185, 188.

Larynx, 269.

Lens, crystalline, 255.

Levers, 30.

Liver, 155, 174, 186-188.

Lock-jaw, 45, 122.

Lungs, 88, 90.

Capacity of, 99.

Diseases of, 125.
Lymph, 84-86.

Capillaries, 81.

Cavities, 85.

Spaces, 81.

Tubes, 8 1.

Veins, 186.

Lymphatic glands, 82, 83, 186.
Lymphatics, 82, 185, 186.

Mad dog bite, 297.
Malaria, 127.
Malt liquors, 208.
Mastication, 156, 162, 194.
Measles, 122.
Meat, 142.

Cooking, 152.
Meningitis, 234.
Mesentery, 156.
Milk, 143.

Sterilizing, 128.
Molds, 121.

Morphine (or Morphia), 285.
Motion, 16, 37.

Production of, 106.
Mouth, 155, 156.

Breathing through, 100.
Mucous membrane, 90.
Mucus, 90, 162.
Mumps, 122, 162.

Index.

Muscle fiber, of heart, 19.

Plain, 19, 60, 61.

Striated, 19.
Muscles, 16.

Action of, 17.

And bones, 28.

Skeletal, 28.

Sphincter, 169.

Structure of, 18, 19.
Muscular sense, 246.
Mustard, an emetic, 295.

Plaster, 75.

Nails, 133.
Narcotics, 285.

And strength, 287.
Nasal passages, 100, 164, 165.
Near sight, 256.
Nerve endings in skin, 248.
Nerves, auditory, 228.

Cranial, 227-230.

Facial, 228.

Fibers, 40.

Yunction of, 40.

Glosso-pharyngeal, 228.

Hypo-glossal, 229.

Olfactory, 227.

Optic, 227.

Roots of, 39, 41.

Sciatic, 18, 38, 44.

Spinal, 39.

Structure of, 40.

Sympathetic, 71, 72.

Of taste, 263.

Of tongue, 263.

Trigeminal, 227.

Vagus, 74, 77, 228.
Nicotine, 277.
Nitrogen, 103.
Nitrous oxide, 286.
Nucleus, 3, 63.
Nutrition, 200.

Oats, 145.
Opium, 285, 286.
Organ, defined, 2.
Oxidation in the body, 108.
Oxygen, 103, 104.
Oxy-hemoglobin, 105.

Pain, 246, 247.

Palate, 164, 165.
Pallor, 72.

Pancreas, 155, 175, 176.
Pancreatic juice, 176.
Papillas, of skin, 130-132.

Of tongue, 263.
Paralysis, 230.
Pepsin, 168.

Peptones, 168, 169, 185, 189.
Pericardial fluid, 50.
Pericardium, 50.
Peristaltic action, 169, 172.
Perspiration, 129.
Pharynx, 164.
Physiology defined, 2.
Pia mater, 226.
Pigment, in skin, 131.
Plants, source of food, 202.
Plasma, 78, 79.
Pleura, 91.
Pleurisy, 91.
Pneumonia, 92.
Poison ivy, 296.
Poisons and antidotes, 295.
Pollen, 121.
Portal circulation, 186, 187.

Vein, 175, 186-188.
Potatoes, 146.
Potential energy, 96.
Pressure sense, 249.
Proteids, 142.
Protoplasm, 3.
Ptyalin, 162.
Puff balls, 121.
Pulse, 49.

Pupil of eye, 252, 254.
Putrefaction, 127.
Pylorus, 167, 169.

Rectum, 177.

Reflex action, 42-44.

Rennet, 168.

Rennin, 168.

Respiration, artificial, 291-294.

Control of, 100.

Forced, 97.

Movements of, 94-97.

Organs of, 88.

Rate of, 97.
Retina, 254, 257.
Rice, 145.

3i6

Index.

Rickets, 14.

Roasting, 152.

Root beer, 208.

Roots of nerves, 39, 41.

Rum, 209.

Running, 33.

Rye, 145.

Sacrum, 10.
Saliva, 161-163.
Salt, 149.
Scarlatina, 122.
Sclerotic coat, 252, 253.
Scrofula, 83.
Scurvy, 146.
Secretion, 179.

Lacrymal, 252.
Semicircular canals, 265, 266.
Sensations, cutaneous, 248.

General, 245.

Special, 245.
Sense of equilibrium, 266.

Muscular, 246.

Of pressure, 249.

Of temperature, 250.
Serous cavities, 85.
Serum, 80, 81.
Sick, care of, 297.
Sight, sense of, 252.
Skin, absorption by, 137.

Color of, 131.

-Grafting, 137.

Nerve endings in, 248.

Protection by, 137.

Structure of, 130.
Sleeplessness, 233.
Slippers, 118.
Smallpox, 122.
Smell, 264.
Snake bites, 296.
Sneezing, 97, 298.
Sniffing, 264.
Solar plexus, 71.
Soothing syrups, 287.
Sound, 266.
Soup-making, 152.

Value of, 193.
Spinal bulb, 226, 233.

Cord, 39, 41, 42.

Nerves, 39.
Spleen, 86.

Sprains, 14.
Standing, 32.
Starch, 144.
Sterilizing milk, 128.

Surgical instruments, 127.
Stirrup, 265.

Stomach, 155, 166-170, 175, 178.
Stoves, 114, 115.
Stramonium, 285.
Suffocation in wells, 294.
Sugar, 144, 185.
Sunstroke, 291.
Swallowing, 165, 166.
Sweat, 129.

Amount of, 134.

Composition of, 133.

Evaporation of, 135.
Sweeping, 124, 125.
Swimming, 295.
Sympathetic nervous system, 70, 71.

Tartar, 160.

Taste, 263, 264.

Tea, 151.

Tear gland, 252.

Teeth, 157-160.

Temperance drinks, 208.

Temperature of body, 107.

Regulation of, 134.

Sense, 250.
Tennis, 222.
Tetanus, 45.
Thein, 151.
Theobromin, 151.
Thirst, 247.

Thoracic duct, 82, 186.
Tissues, denned, 2.
Tobacco, 277-284.

And alcoholic drinks, 283.

And brain work, 281.

And circulation, 279.

And digestion, 278.

Expensive, 283.

And growth, 282.

And nerves, 282.

And respiration, 279.

And salivary glands, 163.

Selfish, 283.

And senses, 282.

And sight, 282.
Tongue, 156.

Index.

3'7

Touch, 249, 250.
Trachea, 88.
Trypsin, 176.
Tuberculosis, 123.
Tympanic membrane, 265.
Typhoid fever, 122, 148.

Urea, 138.
Urine, 137, 138.

Vaccination, 126.

Vaccine lymph, 126.

Valves of heart, 51, 52, 57, 59.

In lymph tubes, 82.

In veins, 64, 65.
. In villuses, 184, 185.
Vegetables, 146.
Vegetarians, 150.
Veins, 62-66.

Hepatic, 187, 188.

Iliac, 56.

Jugular, 56, 84.

Portal, 186-188.

Post-caval, 54, 156, 84.

Pre-caval, 54, 56, 84.

Renal, 56.

Sub-clavian, 56, 84, 186.
Ventilation, 112, 118, 119.
Ventricle, 57, 59.

Vertebra, 5-11.
Vesicles of lungs, 90.
Villuses, 184, 185, 188.
Vinegar, 207.
Vitreous humor, 255.
Vocal cords, 267, 268.
Voice, 267-269.
Volition, 229.

Walking, 33.

Waste matter, source of, I2Q.

Water, 146.

Drinking, 149.

Ice, 148.

Impurities in, 147.

Rain, 146.

Well, 146.
Wheat, 145.
Whisky, 181, 210.
Whooping-cough, 122.
Wind, 113.
Windows, 117.
Wines, 206, 207.
Wounds, 289, 296.

X-rays, 29.

Yeast, 121, 208.
Yellow fever, 122.

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