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Bones in the hand and wrist.
(From an X ray photograph.)

APPLIED PHYSIOLOGY

INCLUDING

THE EFFECTS OF ALCOHOL
AND NARCOTICS

BY

FRANK pVERTON, A.M., M.D.

SANITARY SUPERVISOR
NEW YORK STATE DEPARTMENT OF HEALTH

ADVANCED GRADE

NEW YORK • : • CINCINNATI • : . CHICAGO

AMERICAN BOOK COMPANY

COPYRIGHT, 1897, 1008, 1910, BY
AMERICAN EOOK COMPANY

uv. PHYSIOL, (ADV,)
Q- B- 64

PREFACE

THIS text-book of Applied Physiology was suggested by
a series of popular lectures in which the author presented
the essential principles of physiology about which a physi-
cian is consulted daily. His explanations of many common
facts were entirely novel to the auditors, and on investiga-
tion it was found that the school text-books were silent
upon many of these points, especially in regard to the cells,
where the essential vital functions of the body are carried
on. Throughout this book the fact that the cells are the
units in which life exists and acts is emphasized.

The author has endeavored to include all the useful
points of the older text-books, and to add such new matter
as the recent progress of physiological and hygienic
science demands. He has avoided technical terms, and
has sought to express the truths' in simple language such
as he would use in instructing a mother as to the nature
of the sickness of her child.

The subject of alcohol is discussed in all its aspects.
Its evil effects are not exaggerated ; but the alleged
good from the use of strong drink is contrasted with its
dangers in a judicial manner, which appeals to men far
more effectively than dogmatic abuse. The relation of
alcoholic indulgence to other forms of intemperance, as
excessive sugar eating, is also explained.

The essential act of respiration is oxidation within the
cells. The relation of oxidation to the disappearance of

5

4 t » « * /f> <-^

6 PREFACE

food, to the production of waste matters, and to the
development of heat and force, is dwelt upon throughout
the book.

Many of the demonstrations at the ends of chapters are
new. All can be performed without the purchase of a
single article of apparatus, except a microscope. The
prepared microscopic specimens can be borrowed from a
physician.

Most of the cuts are entirely new, and have been
sketched by the author from actual specimens. The
microscopic appearances of the tissues are especially illus-
trated. In each cut the illustration of a point, rather than
artistic effect, has been the end in view.

The chapter on Repair of Injuries is an entirely new
feature in a school text-book. How the body restores
its natural functions after injury is as practical and simple
a subject as how it sustains itself in health.

The author wishes to express his gratitude to his friend
and instructor, Professor William H. Porter, of the New
York Post Graduate Medical School, who has given his
valuable counsel and encouragement throughout the entire
preparation of the work; to Dr. W. E. Gordon, Principal
of the Patchogue High School, for his suggestions in
adapting the work to the practical needs of the pupils ;
and to Dr. Thomas E. Satterthwaite, ex-vice president of
the New York Post Graduate Medical School, and Dr.
William Pepper, M.D., LL.D., ex-provost of the Univer-
sity of Pennsylvania, for their kind criticisms of the proof
sheets. Thanks are also due Professor J. O. Lansing
for valuable pedagogical suggestions, and to Mr. Robert
Cruger for suggestions and aid in the illustrations.

PATCHOGUE, N.Y.

CONTENTS

CHAPTER PAGE

I. LIVING BODIES AND CELLS 9

II. ELEMENTS OF THE BODY 22:

III. OXIDATION 33.

IV. FERMENTATION AND ALCOHOL 41

V. DIGESTION OF FOOD IN THE MOUTH . . . -51

VI. STOMACH DIGESTION 66-

VII. ABNORMAL ACTION OF THE STOMACH ... 74

VIII. INTESTINAL DIGESTION . . . . . -79

IX. ABSORPTION AND ASSIMILATION 89

X. ALCOHOL AND DIGESTION 98

XL DIGESTION IN LOWER ANIMALS 104

XII. ANIMAL FOOD 107

XIII. VEGETABLE FOOD 120

XIV. QUANTITY OF FOOD REQUIRED 131

XV. DRINKING WATER 135

XVI. NARCOTICS 140

XVII. DRUGS AND POISONS I4&

XVIII. THE BLOOD 156

XIX. THE HEART 162

XX. THE FLOW OF BLOOD IN THE BODY . . . .172

XXL REGULATION OF THE FLOW OF BLOOD . . .185

7

8 CONTENTS

CHAPTER PAGB

XXII. THE LUNGS ........ 192

XXIII. RESPIRATION OF THE TISSUES .... 206

XXIV. THE AIR AND VENTILATION 220

XXV. HEAT AND CLOTHING 233

XXVI. EXCRETION AND SEWAGE 248

XXVII. THE SKIN AND BATHING 256

XXVIII. NERVES 266

XXIX. THE SPINAL CORD . . . . . . . 276

XXX. THE SYMPATHETIC NERVOUS SYSTEM . , .284

XXXI. THE BRAIN 289

XXXII. INFLUENCES WHICH AFFECT THE MIND . . -305

XXXIII. EFFECTS OF NARCOTICS UPON THE MIND . -315

XXXIV. TASTE, SMELL, AND HEARING . . . -323
XXXV. THE EYE . ' . , 333

XXXVI. THE VOICE . • 349

XXXVII. BONES 357

XXXVIII. JOINTS 364

XXXIX. MUSCLES 371

XL. BACTERIA AND DISEASE 382

XLI. REPAIR OF INJURIES 397

XLII. PUBLIC HYGIENE AND SANITATION . .405

XLIII. INFECTIOUS DISEASES . . 416

GLOSSARY

433

INDEX • . » ' . V * '« . 457

APPLIED PHYSIOLOGY

CHAPTER I
LIVING BODIES AND CELLS

1. What physiology is. — The world is composed of
living bodies and lifeless matter. In living bodies there
is a constant change, in which particles become lifeless
and are thrown off, while, at the same time, a process of
creation is going on by which lifeless matter is given life.
This constant destruction and renewal of the particles of
the body constitutes life.

The science which tells of the structure of living bodies
is Anatomy ; that which tells of their working is Physi-
ology ; and that which tells how to keep living bodies in
good working order is Hygiene. The term physiology
often includes anatomy and hygiene.

Some processes in man's physiology were discovered
only by studying the lower animals ; and others, by
observing plants. In fact, it is by studying the work-
ings of lower forms of life that most of our knowledge
of the working of man's organism has been gained. The
physiological processes in plants and animals throw light
on the physiology of man because man embodies in his
complex system, the same general processes as the lower

9

10 APPLIED PHYSIOLOGY

forms of life. Only man presents the most perfect combi-
nation of these processes.

2. The ameba. — One of the simplest animals lives in
stagnant water and is called the ameba. It is only a lump
of jelly about yoVo °f an ^nc^ *n diameter, yet it is a com-
plete animal, for it moves, and eats, and grows, and pro-
duces other amebas. It has no arms, or legs, or head, but
all parts of its body seem very nearly alike. It puts out
little fingers from its body and then rolls its whole body
into the fingers. In this way it is continually rolling about.
When it finds a particle of food it wraps itself around it
just as a baker rolls a mass of bread dough around a

An ameba, sketched at intervals of ten seconds ( x 400) .

raisin. That part of the body which is in contact with
the food digests as much as is needed, and then unwraps
itself away from the waste. It has no choice as to what
part of its body it shall use for any given purpose. But
man uses each part of his body for only definite purposes.
He has arms which get food, a mouth which eats it, and a
stomach which digests it. The arms cannot eat food,
neither can the mouth digest it, but each part does only
its own kind of work.

3. Man like an ameba. — Each part of a man's body is
made of multitudes of living beings, each of which eats
and grows like an ameba. Each tiny being is called a
cell. One collection of cells forms the skin, another the
muscles of the arm, and another the stomach, and so on

LIVING BODIES AND CELLS

II

through the body. Each collection does its own work,
without interfering with the others. The cells work
together like a well-trained army, so
that we do not feel the workings of
each separate cell. If a collection is
out of order, the person is sick.

4. Cells. — Cells are of various
shapes, according to the work they

have to do. They are from ^ to Plants and animalsound
T^0 of an inch in length. Each cell in stagnant water, each con-
. .., i • i • n 1-1 i sistingofasinglecell(X20o).

is like thick jelly and is almost color-
less. Near its center a small mass of slightly different
composition may usually be distinguished. This central

mass is called the nucleus.
The substance composing
the cell is like the white of
an egg and is called proto-
plasm. Although proto-
plasm is
transpar-
ent and
jellylike,
yet under
a micro-
scope
there ap-
pears an interlacing series of beads and
lines which suggest a structure as com-
plex as that of the body itself.

5. Connective tissue. — The cells are

kept in place by a fine network of strong fibers called con-
nective tissiie. In some parts of the body, as on the outside
of the muscles, it is thick and skinlike, but around each

Cells from the human body (X 200).

a A colored cell from the eye.

b A white blood cell.

c A connective tissue cell.

d A cell from the lining of the mouth.

e Liver cells.

/ A muscle cell from the intestine.

Diagram of the parts
of a cell.

a Nucleus.

b Cell-body or proto-
plasm.

c Covering, generally
absent in animal
cells.

12 APPLIED PHYSIOLOGY

separate cell there are only enough fibers to keep the cell
in place. Even these connective tissue fibers are the
threadlike arms of very small cells set apart for the
menial work of supporting other cells.

6. Three tests of life. — We know that each cell is alive ;
for it moves, it takes in food, and it multiplies.

(1) Motion. — Although each cell is held in place by the
connective tissue, the tiny particles of its body are in con-
stant motion, just as a boy's eyes and mouth and hands
and feet may move, even if he sits still in a chair. Besides
this continual motion of the particles within the cell, some
cells show a greater motion, in which the cell as a whole
takes part. Thus, a muscle cell becomes thicker and
shorter when the muscle bends a joint. A white blood
cell can force its way through the wall of the blood tube,
and can wander about among the cells of the body.

(2) Nutrition and Grozvth. — The blood bathes the cells
with food which does not resemble their protoplasm. Each
cell takes in the food through any portion of its body, and,
endowing it with life, makes it a part of itself. Thus each
cell increases in size.

(3) Reproduction. — During the period of growth of the
body, there is a constant production of the cells ; for the
man is composed of more cells than the child. Even in a
full-grown man certain cells, as those of the skin, are con-
stantly being shed and new ones formed. When a cell
reaches mature life, the nucleus first divides into two parts,
which separate from each other ; then the body of the cell
divides between the two nuclei. Thus each cell becomes
two cells, and each of the two exactly resembles the origi-
nal cell, except that it is smaller at first ; but it soon grows
to be as large as the original cell. All the peculiarities of
the life of the first cell go on in each of the two cells into

LIVING BODIES AND CELLS 13

which it divides ; and so we say that the new cell inherits
the peculiarities of the parent. This process may be
carried on very rapidly ; and a new cell may be produced,
and itself become divided, in a few hours.

Anything that moves, and eats, and reproduces itself by
means of its own power, is alive ; and so the cells of the
body are alive in the fullest sense of the term.

Diagram of the division ot a cell.

7. Other distinctions between the living and the dead. —

Many living bodies will show some spontaneous movement in response
to a prick or a blow, or other irritation. Certain causes, as a low tem-
perature, may suspend the ability to respond to an irritation, but it will
return when warmth is applied. A lifeless thing never puts forth effort,
no matter how much it is irritated.

Decay never occurs in cells while they live ; but after death disinte-
gration soon begins, even if no outside power acts upon the cells. On
the other hand, a body which has never been alive usually changes very
slowly or not at all, unless acted upon by an outside power.

8. Relation of cells. — In the body formed by the cells
there exists a controlling spirit of life, which dominates the
whole. When all the cells are obedient to its influence
the body as a whole is alive ; but if the cells are not
obedient, the body as a whole is dead, although each
separate cell may remain alive. For example, a blow
upon the head may disturb this controlling influence so
that it cannot tell the cells how to act. Then they instantly
stop work, and the body drops dead. Yet each cell may
remain alive for minutes or hours, just as each soldier may
remain alive after an army has been disbanded.

14 APPLIED PHYSIOLOGY

9. Tissues. — While each cell eats, grows, and pro-
duces other cells more or less independently of the rest,
yet, like the members of a large family, each works for
the benefit of all the others, and, in turn, is dependent
upon them for things which it cannot do so well as they.
Cells doing special kinds of work are collected in orderly
groups called tissues. Six kinds of tissues are well
marked, —

(1) Muscular Tissue. — Groups of ribbonlike cells which
have the power of^ moving the adjacent parts are found
everywhere in the body, and form muscular tissue. This
tissue is usually as abundant as all the rest of the tissues
taken together.

(2) Epithelial Tissue. — Covering all the surface of the
body, and lining every cavity and tube which connects
with the surface of the body, is a layer of firm cells which
form epithelial tissue. It protects the underlying parts
and manufactures all the various fluids of the body.
From it, also, the hair and nails are produced. Epithelial
tissue is abundant and important.

(3) Nervous Tissue. — There are cells which control all
the others. By means of their long, threadlike prolonga-
tions they convey orders to every cell in the body. They
and their prolongations form nervous tissue.

(4) Connective Tissue. — Surrounding each cell, and
holding it in place, are the extremely fine arms of small
cells called connective tissue (szt p. 11). Its amount varies
greatly in different parts of the body and in different per-
sons, but its total amount is always very large. In some
parts of the body, as in the skin and lungs, there is a
special kind of connective tissue which is very elastic, and
gives to the parts their stretching properties. This tissue
is called "yellow elastic tissue" from its color.

CALIFORNIA COLLEfii

^ CELLS 1 5

(5) Osseous Tissue. — A special form of connective
tissue, in which enough lime is mixed to make it stiff, is
called bony or osseous tissue. This tissue is rigid and
strong so as to form a framework for the rest of the cells
of the body. A somewhat similar tissue, containing little
or no lime, is called cartilaginous tissue. It surrounds the
jointed ends of bones and often becomes bone late in life.

(6) Adipose Tissue. — Some connective tissue cells are
arranged in microscopic pockets filled with oil or fat.
This forms fatty or adipose tissue. Most of the fat in
the body is stored in this way (see p. 25).

10. The blood as a tissue. — Blood contains two kinds of
cells, each of which has a special work to do. Therefore
the blood may be called a tissue, even though its cells are
floating free in a liquid. The lymph, which is mainly
diluted blood, may also be considered a tissue.

11. Other fluids in the body. — There are other fluids in
the body which, while they contain a few cells, do not
depend upon them for their properties or actions and so
are not tissues. Into the digestive tube there are poured
five fluids concerned in digestion, viz. : the saliva, the
gastric juice, the pancreatic juice, the bile, and the intes-
tinal juice. In order to carry off the waste products of
the body two fluids, the perspiration and the urine, are
continually being formed, while water is given off in
gaseous form by the breath. Three fluids are found in
connection with the eye. Two, .called the aqueous and
the vitreous humors, distend the eyeball, and another,
called tears, runs over its surface to wash away dirt. In-
side the cavity of each joint is a thick fluid, called synovia,
which lubricates the surface of the bones within the mov-
able joints. Lastly, milk is sometimes produced for the
nourishment of the young.

16 APPLIED PHYSIOLOGY

12. Organs. — In order to work to the best advantage,
several kinds of tissues are usually associated together.
Thus, the stomach, which digests food, is composed of
muscular tissue which moves the food about, and epithelial
tissue which pours out digestive fluids, and nervous tissue
which presides over the process, while connective tissue
binds the whole together. A collection of different tis-
sues always arranged in a definite, compact shape for a
special purpose, is called an organ. The stomach, intestine,
pancreas, and the liver are the four principal organs of
digestion. The lungs are organs of respiration, the heart
is an organ for the propulsion of blood. The kidneys and
skin are organs which get rid of waste matter, and the
brain is the organ of thought. The term organ is also
applied to many other parts of the body, but these are
the principal ones.

13. Systems. — Sometimes a definite series of tissues
and organs are not arranged in compact form, but are
scattered through the whole body. This forms a system.
Thus the system of tubes formed of muscular and con-
nective tissue in which the blood moves is called the
circulatory system, while the heart is an organ in the cir-
culatory system. In the same way the brain is an organ
in the nervous system. The five main systems are the
digestive, circulatory, respiratory, nervous, and excretory
systems. In Physiology the action of the cells of each
tissue, organ, and system is studied separately. The
structure and arrangement of the cells of each tissue
are studied by means of a microscope.

14. The microscope. — In order to show even the largest
cell, a compound microscope magnifying at least twenty
times is needed ; while for ordinary use, one magnifying
at least two hundred times is necessary.

LIVING BODIES AND CELLS 17

A compound microscope consists of two lenses set in a
movable tube. The lower lens is called the objective, and
does the main part of the magnifying. It can easily be
removed from the tube or swung aside, and another
objective of different magnifying power substituted for it

EYEPIECE

COARSE ADJUSTMENT

FINE

MIRROR

FOR LIOHTIN9

SPECIMEN-

Compound microscope.

The upper lens is called the eyepiece. It can be re-
moved from the tube, and another substituted. Usually
two or three objectives and two eyepieces of different
magnifying powers are furnished with each microscope.
A microscope is said to magnify as many diameters as
the number of times it enlarges the breadth or diameter

OV. PHYSIOL. — 2

1 8 APPLIED PHYSIOLOGY

of an object. Thus a microscope making a cell appear
100 times as broad as it really is, is said to magnify 100
diameters. But the length and thickness are also magni-
fied. So the surface of the cell is made 100 x 100 or
10,000 times as large, while its bulk is 100 x 100 x 100
or 1,000,000 times as large. A table accompanying each
instrument tells the power of each combination of lenses.

15. Arrangement of the light. — A small mirror placed at the
lower part of the microscope throws light through the object, for other-
wise there would not be sufficient light to spread over its magnified
surface. The mirror can be tilted so as to catch the light from any
direction. Objects usually show best when they are lighted only suf-
ficiently to show their outlines. A stronger light may pass through
extremely small objects so that they do not show at all. Each micro-
scope usually has a device for varying the size of the aperture in the
plate upon which the specimen rests, thus again regulating the amount
of light. It is usually not best to use an amount of light which makes
the field of view brilliant.

16. Focusing. — The tube carrying the lenses can be moved up
and down by means of a small wheel. Arranging the distance of the
lens from the specimen is called focusing. An objective of high mag-
nifying power must be much nearer to the specimen than one of low
power. Thus an objective magnifying 500 diameters must be about
Y1^ of an inch from the specimen, while one magnifying 50 diameters
would be over half an inch distant. For high magnifying powers
the focusing must be very exact. So a second wheel is provided
which moves the tube very slowly. This wheel is called the fine ad-
justment in distinction from the other wheel or coarse adjustment.
The finger of the observer should always be upon the fine adjustment,
turning it back and forth so as to observe now the top and now the
deeper portions of the specimen, for it is magnified in depth as well as
in breadth.

It is often very difficult to find a very small specimen with a high
power lens, for the space in which it lies is magnified to several feet in
diameter. A good plan is to use a low power lens for finding the speci-
men, and then after bringing it to the center of the field, to substitute
the high power lens.

LIVING BODIES AND CELLS 19

Every movement of the specimen is magnified as much as the speci-
men itself. So great gentleness is needed in moving it under the ob-
jective or else it will be moved out of view altogether. The microscope
appears to reverse the sides of the specimen, so in order to move the
image in any direction the specimen must be moved in the opposite
direction. Care should be taken not to press the lens upon the speci-
men. If the lens becomes dirty or moist it should be gently wiped
with a soft, clean handkerchief. A little alcohol rubbed on will aid in
removing the dirt.

17. Preparation of specimens. — Specimens are examined
upon glass plates, called slides. The regulation size is
three inches long and one inch broad. Specimens must
be very thin, so as to show only a single layer of cells or
fibers. A liquid specimen should be a small drop; a powder
should be only a tiny speck. A solid specimen is prepared
in either of two ways. Its cells and fibers may be picked
apart by means of two needles ; but this destroys the
natural arrangement of the parts. So the method of
slicing off extremely thin layers with a sharp razor is
more often used. This requires special training. Nearly
all specimens should be examined in a liquid. Water will
do for nearly all. Glycerine may be used if the specimen
is to be kept, for it does not evaporate. A drop is placed
over the specimen on the slide. Over the drop of liquid
it is well to place a thin piece of glass, called a cover glass,
for the purpose of protecting the objective from the
liquid, and the specimen from currents of air. Air bub-
bles under the cover glass interfere with the view. They
can be forced out by gently pressing upon the cover glass ;
but with care the cover glass can be applied so as to avoid
them. A supply of slides and cover glasses is a necessary
part of every microscopic outfit.

A few fibers scraped off from a handkerchief or a few
scales from the back of the hand are good specimens for

2O APPLIED PHYSIOLOGY

practice. A tiny bit should be placed upon a slide and a
drop of water placed upon it, and the whole covered with
a cover glass. Begin to examine it with the lowest powers
of the microscope, and so gradually learn to use the higher
powers.

SUMMARY

1. Physiology tells how living beings eat and grow and act.

2. The ameba is a tiny lump of living jelly, which eats,

and moves, and produces young amebas.

3. The body of a man is made of tiny cells like an army

of amebas.

4. Each cell is a lump of thick jelly, in which a small

mass called the nucleus may usually be distin-
guished. The cells are held in place by strings
called connective tissue.

5. Each cell moves, eats, and grows, and produces other

cells like the first.

6. The mind lives in the body formed by the cells.

7. The cells obey the mind. When the mind loses con-

trol of them the body is dead.

8. Each cell does some special kind of work for the

benefit of the rest.

9. A collection of cells doing a special kind of work is

called a tissue.

10. A collection of different tissues always arranged in a

definite and compact shape is called an organ.

11. A definite series of tissues and organs scattered

through the body for a definite purpose forms a
system.

DEMONSTRATIONS

i. Scrape the inside of the cheek with a sharp knife and examine
a drop under the microscope, with a power of at least 100 diameters.

LIVING BODIES AND CELLS 21

Notice the flat scales of irregular shape. Each scale is a separate
living cell. It is nearly transparent, but its nucleus appears as a
slightly darker spot. Make a drawing of the cells.

Examine cells scraped from the skin upon the back of the hand;
and cells scraped from the pulp of a leaf. Examine a bit of the green
scum, called pond alga, which forms upon stones in fresh-water ponds.
Notice the long cells joined end to end and containing green matter.

2. Take a drop of stagnant slimy water from a rain barrel or from a
kitchen drain or from a stagnant pool. Examine it with a power of at
least 100 diameters. A specimen of the ameba is likely to be found
rolling about. Notice its nucleus, and also dark spots in its body which
are probably food which it has swallowed. Make a sketch of an ameba.

REVIEW TOPICS

1. Define Anatomy.

2. Define Physiology.

3. Define Hygiene.

4. Describe an ameba.

5. Describe a cell.

6. Describe connective tissue.

7. Give the three tests by which a cell or other body is

known to be alive.

8. Give other distinctions between living and lifeless

bodies.

9. Give the relation of the mind to the cells of the body.

10. Define a t is site and name the different tissues of the

body.

1 1 . Show that the blood is a tissue.

12. Give the different J?#fc& in the body.

13. Define an organ.

14. Define a system.

15. Describe the instrument by means of which the dif-

ferent cells and tissues of the body are studied.

CHAPTER II
ELEMENTS OF THE BODY

18. Proximate principles. — The cells of all animals con-
tain the same substances, differing in amount and arrange-
ment, yet alike in composition. The simple substances of
which the cells are composed are called proximate principles.
The most important proximate principles are water, albu-
min, fat? sugar, salt, lime, soda, and potash.

19. Water and solution. — Water forms nearly three
fourths of the weight of the body and is present in every
part. It reaches each minute part of the body through
the firm walls of the organs. Water has the power of
dissolving solid substances, so that they retain all their
properties unchanged. Sugar in water is sugar still; in
fact, we can appreciate what sugar is only when it is dis-
solved. When a substance is dissolved in a liquid, so that
each remains unchanged in its essential properties, the
result is a solution. Most solutions will go anywhere
water itself will go. In the stomach the food becomes
dissolved, and is taken into the blood tubes. The blood
contains a solution of food which penetrates into the spaces
around each cell, carrying nourishment to the cell and
washing away its waste matters. Water makes the tissues
limber and slippery, so that they bend and move easily.
By means of the perspiration which carries off surplus heat,
water regulates the heat of the body. About three quarts.
of water are taken into the body each day.

ELEMENTS OF THE BODY 23

Water is composed of two gases, hydrogen and oxygen,
very firmly united.

20. Albumin. — The protoplasm of the living cells of the
body is almost entirely composed of a substance like the
white of an egg. Because it turns white when heated, it
is called albumin (from the Latin albus, white). Pure
albumin is hard and brittle as the white of an egg is when
it is dry. In the body it is dissolved in from five to twenty
times its own weight of water. This solution in water is
what is meant by the albumin of the body. In the blood
it is liquid, in the flesh it is somewhat jellylike, and in
the skin it is strong and tough. It is a very complex
body which only plants can form. Animals must get it
from vegetables and change it into their own bodies.
When once formed it may become part of the bodies
of several successive animals, as one makes food of
another.

Albumin forms the principal part of the protoplasm of
all living cells. Some is used in performing the work of
the body and does not reach the cells. About four and
one half ounces "of pure albumin must be eaten each day
to supply the needs of the body.

21. Forms of albumin. — There are many forms of albumin, all
having essentially the same properties. The white of eggs is almost
pure albumin. Lean meat is composed mostly of another form ; cheese,
gelatine, and glue are composed mainly of still other forms.

22. Coagulation. — Most forms of albumin may be hard-
ened either by heat or acids, and once hardened they can-
not be dissolved again to their original state. A boiled
egg illustrates this hardening. Changing a liquid to a
jellylike or solid form so that it cannot be changed back
to its original form is coagulation. Coagulation of its
albumin destroys the life of a cell.

APPLIED PHYSIOLOGY

23. Putrefaction. —When albumin is kept moist and exposed to
the warm air it decays or putrefies, becoming soft and finally completely
dissolving, and at the same time giving off offensive odors. If the
albumin is kept dry it shrivels up and finally becomes a gluelike sub-
stance. Pure sugar or fat will not putrefy, although both may become
sour, but both often contain a slight amount of albumin, and this may
putrefy, giving them a slight taste and odor.

24. Diffusion. — When salt and water are placed in a
bag of thin skin and suspended in a dish of water, some

of the salt and water will pass through
the walls of the bag and will mingle
with the water in the dish, and, on the
other hand, some water will pass into
the bag. This will go on until the
water in the dish is of the same salt-
ness as the water in the bag. The act
of passing through a membrane appar-
Diffusion at the begin- entry impervious is a form of diffiision.
ring of the process. Without pressure albumin will not dif-
fuse except in the form, called peptone,
which is produced from the others by
digestion. Peptone readily diffuses
through the thin sides of the blood
tubes in the walls of the intestine, and
so reaches the blood.

Diffusion at the end
of the process.

25. Iron-bearing albumin. — The nu-
cleus of vegetable cells is composed of a form of
albumin called nucleo-albumin, which contains
iron. There are from thirty to sixty grains of
iron in the human body, all of which is united with the albumin, so
that the metallic properties of the iron are completely absent. A
small amount of this iron-bearing albumin is found in the nucleus of
every cell, both vegetable and animal, and seems to be essential to the
growth and division of the cell. In an animal this substance gives
origin to the substance called hemoglobin, which forms the coloring

ELEMENTS OF THE BODY 25

matter of the red blood cells. The iron gives it the power to carry
oxygen from the lungs to all parts of the body. Only one or two
grains of iron are required each day to supply the loss of the iron in
the body, and several times that amount is eaten daily in our food.

26. Fats and oils. — Fats are a series of smooth, slip-
pery substances found in all animals, and in most vege-
tables. About five per cent of the human body is fat. It
is scattered between the cells of all parts of the body, but
in places, as in the walls of the abdomen, it forms thick
layers. All fats become
liquid when heated, but
those that are liquid at
ordinary temperatures are
called oils. In the living
body fat is always in a
liquid state, stored in
thin-walled pockets made
of connective tissue. By
boiling, the pockets are Fat tissue (x 100).

Softened and the fat runs Connective tissue cells form pockets in which

the liquid fat is stored.

out upon the water. Each

pocket is from -^-j--^ to -%^-§ of an inch in diameter. The fat
is produced from the albumin of the cells by a breaking-
down process. Fat is a simple substance compared with
the complex albumin. Probably all the fat which is stored
in the body is made out of albumin.

27. Emulsion of fat. — However much fat may be shaken with
water it will remain in tiny particles which soon rise to the surface. If
a little white of egg is added, the fat will divide into finer particles and
will remain in the water much longer. A mixture of fat and water is an
emulsion. No emulsion is permanent, but the fat will rise to the surface
in time. Milk is the most perfect emulsion, but even in milk the cream,
or fat, rises in a few hours.

26

APPLIED PHYSIOLOGY

28. Saponification of fats. — When fat is boiled with soda or
potash it is broken up into a small amount of glycerine and a large
amount of a substance called a fatty acid. The fatty acid unites with
the soda or potash to form soap. When by any means fat is broken
up with soda or potash, forming soap, the process is called saponifica-
tion. Both soaps and emulsions are continually being formed during
the digestion of fat.

29. Use of fat. — The, fat of the body is a living garment,
retaining heat and protecting the body from the cold, and
rounding out the rugged outlines of the bones and muscles.
It is a cushion, protecting the internal organs from injury.
It is also a store of food to be used in sickness when food
cannot be eaten. The fat which is eaten is used up in
warming the body. Thus fat acts as a food, as armor for
the body, and as useful and ornamental clothing. About
three ounces of fat must be eaten each day.

30. Starch and sugar. — Starch is produced almost en-
tirely by plants and is stored in the form of little grains

which will not dis-
solve in cold water.
Grains of potato starch
appear like oyster
shells and show dis-
tinct markings as
though they were built
up in layers. It is
supposed that starch
grains grow by deposits
of successive layers of starch between which are layers of
a waterproof substance called cellulose or plant connective
tissue. When the grains are boiled, they swell and burst
and then dissolve, forming a paste. As a plant grows, it
uses the starch in building up sugar, wood, cotton, cellu-
lose, and other plant substances. Starch, sugar, wood, cot-

starch Grains (X40o).
a, of potato. b, of corn.

ELEMENTS OF THE BODY

ton, and cellulose are similar in chemical composition, but
differ widely in character.

Wood is of no use to
the body, but starch and
sugar are common foods.
Starch is changed to
sugar before it becomes
a part of the body of
man. Only a little sugar
is found in the body at
one time, for almost as
fast as it enters it is
used up to produce
warmth. About five

A thin slice of potato (x 200).

a Albuminous and fibrous pockets.
Ounces Of Starch Or SUgar b starch grains in the pockets.

must be eaten each day.

Minerals. — The minerals salt, lime, soda, and potash,
are always found in the body.

31. Salt. — Common salt is found in the bodies of all
animals, and a less amount in vegetables also. There are
about six or seven ounces of salt in the human body. In
animal food there is enough salt to supply the needs of
the body, but some must be added to vegetable food. So
flesh-eating animals, like dogs and cats, will not eat salt,
while vegetable-feeding animals, as horses, like it.

Salt gives an agreeable taste to food, and this causes the " mouth to
water," and all the other digestive fluids to flow freely, so that the salted
food is quickly and easily digested.

Some kinds of albumin in the body will dissolve in water only when
salt is present, and if it is diminished in amount, or is absent, these
albumins cannot do their work.

Salt diffuses very readily, and also aids in the- diffusion of all kinds
of food. So salt has very important uses in the body, and when it is not
used there is great suffering. The proper amount of salt is present in

28 APPLIED PHYSIOLOGY

the food when food tastes just agreeably salt. About one half an ounce
needs to be eaten each day.

32. Lime. — A small amount of lime is found every-
where in the body, but bone is over one half lime. In all,
there are between ten and twelve pounds of lime in the
body, but only six grains need be eaten each day. Much
more than this amount is found in all common food. The
main use of lime is to give stiffness to the bones. It is
mixed with the cells and fibers of the bone, just as starch
is mixed with the fibers of linen to make it stiff.

33. The alkalies — soda and potash. — Some substances
are sour and burning to the taste, and can corrode or eat
away flesh and metals. When soda or potash is mixed
with such a substance, both ingredients in the mixture are
changed and a new substance unlike either is formed.
For instance, strong vinegar is such a sour, corrosive sub-
stance. When soda is added to it the mixture bubbles for
a time, and then the liquid is no longer sour or irritating,
but has a flat, bitter taste, and both the soda and vinegar
have become changed. A substance which is sour to the
taste and corrodes metals and flesh, and unites with soda
or potash with a bubbling, is called an acid. Soda and
potash are called alkalies. They also can corrode certain
substances, but they always unite with acids at the first
opportunity, and by their union each is changed to a
less harmful form. So alkalies destroy or neutralize
acids, and acids neutralize alkalies.

34. Chemical action. — When two substances are mixed
together so that each becomes changed and substances
unlike either are produced, the process is called chemical
action. Sugar will dissolve in vinegar, but it still remains
sugar, and so the mixture is called a solution (see p. 22).
In contrast with it, when soda is dissolved in vinegar it is

ELEMENTS OF THE BODY 29

completely changed, and so forms an example of chemical
action. Some substances are very prone to mix to form
solutions. Thus, impure salt has such an attraction for
water that it takes it from the air and becomes damp. So
salt is said to have an affinity for water. In the same
way some substances are very prone to mix so as to be-
come changed by chemical action. Thus, there is always
chemical action between soda and vinegar when they are
brought together, so soda is said to have a chemical
affinity for vinegar. In the same way, air has a great
" chemical affinity " for wood in a fire. The chief value of
gold comes from the fact that it has no chemical affinity at
all except for one or two uncommon substances. So it
will remain unaltered in the midst of substances which
would destroy other metals.

35. Use of alkalies. — If a fluid contains an acid, it is
said to be acid'm reaction ; if an alkali it is alkaline ; and if
it contains neither it is neutral in reaction. Now, the blood
is always alkaline from the presence of a small amount of
soda and potash. Acid products are being formed in the
body continually, and the duty of the alkalies is to unite
with them at once and change them to harmless sub-
stances, which may be handled by the blood in safety.
The alkalies are found in nearly all foods.

36. Chemical actions in the body. — Everything which makes
up the cells and fluids of the body is composed of some or all the sub-
stances— water, albumin, fat, sugar, or starch, with the minerals —
salt, lime, and soda and potash. These must be eaten to sustain life,
and so they are foods. Other kinds of substances are harmful or
poisonous. All food substances are eaten three times a day, and yet
only water and the minerals leave the body in anything like the form
in which they entered. The rest are entirely changed by chemical
actions and leave the body as gases or liquids or as solids dissolved in
water. The digestion of food from the time it is taken into the mouth

3<D APPLIED PHYSIOLOGY

is a chemical action, as is also its becoming a part of the living cells.
Breathing and the production of the waste matters of the body are
also chemical processes.

These chemical processes can be followed and even imitated in a
laboratory. The living principle in the body directs the work, but
uses few processes which are not also used outside of the body. It has
been a great triumph for science to liberate men from the superstition
that the chemical and physical laws of our bodies were governed by the
arbitrary feelings of indwelling spirits, and so were different from the
laws governing lifeless creatures.

SUMMARY

1. The cells of the body are composed of five substances,

viz., water, albumin, fat, sugar, and minerals.

2. Water is three fourths of the body. It carries food to

the cells and washes away their waste matters.

3. Albumin is like the white of eggs. It forms the pro-

toplasm of all cells. It warms the body, and gives
it strength and weight.

4. Fat is in pockets between the cells. It protects and

heats the body.

5. Starch and sugar are similar substances. They warm

the body.

6. The minerals in the body are salt, lime, soda, and

potash. They are found in all food. In addition
some salt must be eaten.

7. Salt aids in the preparation and distribution of food to

the cells of the body.

8. Lime stiffens the bones.

9. Soda and potash destroy irritating acids within the

body.

10. Water, albumin, sugar or starch, fat and minerals, are

foods and must be eaten to sustain life.

11. Most of the vital actions of the body can be imitated

in a chemical laboratory.

ELEMENTS OF THE BODY 31

DEMONSTRATIONS

3. Illustrate the properties of albumin by the white of an egg.
Notice its sticky character. Dry some upon a piece of paper over a
fire and notice its brittle, gluelike character, and that it will again dis-
solve in water. Boil some and notice that it becomes hard and will
not redissolve. Set some aside and notice that it decays.

4. Inclose a lump of wet flour in a muslin bag and wash it until the
water is clear. This removes the starch grains and leaves the grain
albumin or gluten pure. Notice its tough and sticky character.

5. Show samples of olive oil, lard, and tallow. Show that lard
melts at about the temperature of the body, and so is fluid in the body.

6. Shake together some oil and water. Notice that the oil at once
floats upon the surface. Now shake the oil with some lime water, and
notice that it no longer floats, but that the mixture looks milky, while a
few very small oil drops can be seen floating in the liquid. Explain
that this is an emulsion.

7. Stir together some castor oil and caustic soda, gently heating the
mixture, and notice that it forms soap.

8'. Scrape a potato into a basin of water. Wash it about and notice
that the shreds of potato will float, while a white substance will settle
to the bottom of the basin. Explain that this substance is starch, and
that our great-grandmothers used this method to make starch for
laundering.

9. Place a small drop of the wet potato starch upon a glass slide
and examine it with a power of at least 50 diameters. Notice that the
starch grains appear like oyster shells. Examine also some corn starch
and notice that each grain looks like an irregular cube with a star-shaped
center. Sketch the starch grains.

10. Boil some starch and notice that it swells and forms a jellylike
paste.

Iodine turns starch blue. Apply a drop of the tincture of iodine to
the starch and notice the blue color. Apply it to bread, cake, flour,
etc. Notice the blue color, showing that they all contain starch.
Notice that meat does not respond to the test.

n. Show specimens of sugar. Brown sugar is the impure form,
while granulated sugar is the pure crystallized form. Show some sugar
scraped from the outside of raisins and explain that this is glucose or
grape sugar, and that all sugar and starch must be changed into this
form before it can be used by the body.

32 APPLIED PHYSIOLOGY

12. Burn some bread or meat and save the ashes. The ashes
represent the mineral part of food, and consist mainly of lime, salt,
soda, potash, and iron.

13. Show diffusion by tying a piece of parchment over the end of a
large glass tube. Fill the tube with salt and water and immerse it in
ajar of fresh water. In a little while the liquid will rise in the tube,,
while the water in the jar will begin to taste salt. The process will
continue until the water in the tube and in the jar are of equal saltness.
If the water in the jar were renewed, all the salt could be extracted
from the tube.

14. Show the affinity between acids and alkalies by dropping soda
in vinegar. Notice that the mixture boils and foams, and both sub-
stances become changed. Drop some soda in water and it simply
dissolves and forms a solution.

15. Drop a pinch of baking soda in a small cup of water. Then
stir in some dilute hydrochloric acid, drop by drop, until the mixture
ceases to bubble. Taste the mixture and notice that it is salt. Ex-
plain that the hydrochloric acid and the soda have formed a chemical
combination and each has neutralized the other. The new substa'nce
formed is chloride of sodium or common salt.

REVIEW TOPICS

1. Define and name the proximate principles.

2. Describe water and define a solution.

3. Describe albumin.

4. Describe diffusion.

5. Describe putrefaction.

6. Describe nucleo-albumin, and its relation to iron.

7. Describe fats and oils.

8. Describe an emulsion.

9. Describe saponification.

10. Describe starch, sugar, and wood.

11. Describe salt.

12. Describe lime.

13. Describe the alkalies.

14. Define chemical action and chemical affinity*

15. Name some chemical actions in the body.

CHAPTER III

If

OXIDATION

37. The nature of burning or oxidation. — In addition to
the substances taken in as food, the body is continually
taking in oxygen by the breath. The air which is
breathed is four fifths nitrogen gas and one fifth
oxygen gas. When air is fed to fuel in the hot

fire box of a boiler, burning takes place. Burn-
ing is a chemical process. Oxygen unites with
the carbon and the hydro-
gen of the wood, so that
both the wood and the
oxygen disappear. The
carbon and part of the
oxygen form carbonic acid
gas. The hydrogen and
the rest of the oxygen
form water. Both sub-
stances pass off in the smoke. What is left as ashes is
the mineral part of the wood.

By the burning, heat and a flame are produced. The
heat can be used to make steam which will drive an
engine and do work. Burning is called oxidation.

38. Oxidation within the body. — The body also is an
engine, — self-regulating and self-sustaining. The oxygen
which is breathed into the body slowly burns food and
the cells, just as it oxidizes the wood under the boiler of an

ov. PHYSIOL. — 3 33

f_

Diagram of burning or oxidation in a
stove.

34 APPLIED PHYSIOLOGY

engine. The process goes on so slowly that no flame
is produced, but the same amount of heat is produced as
though the same substances were burned in a furnace.
Some of this heat is used to warm the body, and some
is changed to power which enables the body to do work,
either of motion, or of manufacturing the various products
of the body or of thought. Oxidation is an essential
process of life; when it ceases for an instant life ends.
When the air is cut off from the body for only a minute,
a great feeling of suffocation comes on, and within two
or three minutes the body dies.

Oxidation goes on in each cell, but especially in the
cells of the lungs and liver. It is a process of life, and
in a living cell it can be hastened or retarded according
to the needs of the body.

By the oxidation within the cells of the body, carbonic
acid gas, water, and ashes are formed, as in a furnace.

39. Oxidation of albumin. — An ounce of albumin is
completely oxidized by an ounce and a half of oxygen.
The ashes which are produced are partly the sulphur of
the albumin and partly the nitrogen, which holds some
of the carbon, hydrogen and oxygen, combined in a
solid called urea. Urea must be given off by the kid-
neys and skin as fast as it is formed. When there is
not enough oxygen to burn the albumin entirely, other
substances resembling urea are formed, just as a stove
smokes instead of burning brightly when the draft is
closed. Some of these substances are very poisonous.
The albumin of the living cells is probably oxidized and
replaced continually. Much of the albumin of the food
is oxidized before it reaches the cells.

40. Oxidation of fat — An ounce of fat is completely
oxidized by three ounces of oxygen. So it will produce

OXIDATION

35

twice as much heat as the same amount of albumin, and
is thus a good food for cold weather. It leaves no ashes
behind, for it contains no mineral matter.

41. Oxidation of sugar. — An ounce of sugar is com-
pletely oxidized by one and one fifth ounces of oxygen.
So it produces only about half as much heat as fat. It
is much more easily oxidized than fat or albumin. When
the three substances are mixed together as they are in the
body, the oxygen will go to the sugar in preference to
the fat or albumin, and the latter two substances being
unburned will accumulate in the body. Thus sugar is
said to be fattening. The water and the minerals of the
body cannot be oxidized, but enter

and leave the body unchanged.

42. Reconstruction of living mate-
rial by plants. — In every animal the
living cells are continually uniting
with the oxygen of the air and giving
out carbonic acid gas, water, and min-
eral matters. From these waste mat-
ters plants reconstruct the substances
which were oxidized in the body.
The first substance produced seems
to be starch, and from it as a basis all
other parts of the plant and of ani-
mals are built up.

The plant cells which contain
green coloring matter called chloro- ^

phyll, are set apart for the special a Chlorophyll arranged in
work of reconstructing starch from a spiral.
oxidized material. To them the sap * The^arb^yoftheceU.
brings water from the soil, and carbonic acid gas from
the air. In the chlorophyll these substances are recon-

APPLIED PHYSIOLOGY

structed into starch. Using starch as a basis, plants
construct fat and albumin and all other substances found

in the plant.

43. The sun's work
in reconstructing living
material. — When oxygen
unites with the carbon and
hydrogen of the burning sub-
stances, heat and energy are
given out. Just as much
heat and force must be used
in tearing away the oxygen
as was ^iven out during the
oxidation. The sun furnishes
this heat and force. The
chlorophyll acting as the ma-
chine and using the sun's rays
for power, frees most of the
oxygen from the carbonic
acid gas and water, and gives
it back to the air. At the
same time it unites the re-
maining oxygen with the car-
bon and hydrogen to form living starch. Thus the real work of con-
struction is done by the sun. When the starch is oxidized, oxygen goes
back to the hydrogen and carbon, and the same
amount of heat is given off as was taken from
the sun when starch was formed.

The heat of oxidation can be traced back to the
sun's heat stored up by living beings or beings
once alive. All the carbon of a tree is the car-
bonic acid gas of the air with its oxygen taken^
away by the sun's force acting through chloro-
phyll. Coal is the carbon of trees changed in
form during ages of burial.

Diagram of the restoration of oxygen to
the air after oxidation, and of the rebuilding
of burned material into living forms.

Diagram of the stream
of material flowing through

44. Conservation of energy. — The
energy of the suns heat expended upon the plants in

OXIDATION 37

bygone ages was conserved in the coal, and now can be
made to appear again as force in a steam engine. This
force may run an electric dynamo, and the electricity can
be transported silently over miles of wire, to appear as light
rivaling its original source, the sun. Through all its
changes the original energy is preserved.

Observation of the three facts, (i) the heat of the sun
acting through plants to tear the oxygen from the carbon
and hydrogen, (2) the reunion of the substances in oxi-
dation with the development of the original heat of the
sun, and (3) the various forms of power into which the
energy can be changed, has given rise to the principle that
any form of energy can be changed into another form without
loss. This principle is called the conservation of energy.

This principle is exemplified in the human body. The
energy for the work done by the body is the heat derived
from the oxidation of its food.

45. Relation of plants to animals. — The oxygen of the
air would all be used up in a few years if it were not continually torn
away by plants from its combinations in carbonic acid gas and water.
The carbon and hydrogen would also disappear; but the sun and
chlorophyll continually renew the supply both of food and of oxygen.
Thus there is a stream of material flowing from lifeless soil and air. It
becomes alive in the plant and again in the animal, and then is suddenly
oxidized to a lifeless form, and given back to the soil and air, only to
repeat the round of life. Plants build up living material which animals
use as food and then oxidize back to the form in which it existed before
the plant touched it. Plants give off oxygen which supports animal
life. Each lives upon what the other discards.

46. Organic substances. — Substances which are built
up by living beings are called organic. Thus the plant
takes carbon from the carbonic acid gas in the air, and
builds it up into an organic substance, which forms part of
the plant.

38 APPLIED PHYSIOLOGY

47. Difference between plants and animals. — (i) The

ability to live upon the ordinary waste products of animal life, or, in other
words, to reconstruct organic matter out of crude minerals and gases, is
a distinguishing mark of a plant. On the other hand an animal always
requires organic food, and cannot live upon the soil and air. Yet the
lowest animals very closely resemble plants, and owing to the difficulty
of ascertaining the true source of their food the position of some living
bodies is still a matter of dispute.

(2) In animals the cells are bound together by strings of connective
tissue, which is an albuminous substance of soft consistency. In plants
the substance between the cells has the composition of starch (see
p. 27). It is a hard and firm substance, and gives the rigid strength to
the plant or tree. The outsides of the plant cells often have a thick
coating of the same substance. When it is deposited in so great an
amount as almost to replace the cells the substance forms wood. Yet
in some plants it is entirely absent, so that the distinction applies only
to higher forms of life, where other distinctions between plants and
animals are more obvious.

(3) Most animals have the power of voluntary motion, while most
plants 2xe fixed to one spot. Yet some animals, as the coral, have no
more motion than a flower which opens and closes during the day. On
the other hand some water plants are continually moving about by
means of vibrating hairs projecting from their bodies.

Some plants also move if irritated. The plant called Venus's flytrap
fias stiff, toothed leaves, hinged together in twos so as to open and shut
like a rat trap. When a fly alights upon the open leaf it suddenly closes
upon the insect, crushing it to death. This plant exhibits more move-
ment responsive to a slight irritation and directed to a distinct purpose
than many true animals.

(4) Most animals have a digestive tube, while plants have no organs
of digestion, unless the leaves can be called such. Yet in some animals,
as the ameba, the body looks nearly the same throughout.

(5) Most plants are green in color, from the presence of chlorophyll.
Yet many plants, as toadstools, are destitute of chlorophyll.

48. Source of life. — In the oxidation and reconstruction
of animals and plants no new life is created. Lifeless
material is endowed with life by material already living,
and in its turn the new material imparts life. The same

OXIDATION 39

life continues through all the changes of the body,
although not a single particle of the original body may
remain. The body is but the house in which life resides.
The original source of life itself has never been found.
The Bible gives the only known origin of life :

"And God said, Let the earth bring forth grass, the
herb yielding seed, and the fruit tree yielding fruit after
his kind, whose seed is in itself, upon the earth : and it
was so.

" And the earth brought forth grass, and herb yielding
seed after his kind, and the tree yielding fruit, whose
seed was in itself, after his kind : and God saw that it was
good." — Gen. 1:11-12.

SUMMARY

1. Oxygen unites with carbon and hydrogen, and pro-

duces heat. The process is called burning or oxida-
tion. A steam engine transforms heat into work.

2. Oxygen from the air is continually entering the body.

3. Within the body it is continually uniting with the

albumin, fat, and sugar, and producing heat, some of
which is transformed into work. This is the essential
process of life.

4. By oxidation, the albumin, fat, and sugar become car-

bonic acid gas, water, and urea, and are given off
from the body.

5. The green coloring matter of plants forms the machine,

by means of which the sun's heat tears the oxygen
away from the carbonic acid gas and water and
forms organic substances again.

6. Plants prepare food for animals, and animals prepare

food for plants.

40 APPLIED PHYSIOLOGY

7. All through the oxidation and reconstruction of the

body life remains the same, and no new life is
created.

8. The Bible gives the only known explanation of the

origin of life.

DEMONSTRATIONS

1 6. Lower a lighted candle into a wide-mouthed bottle". When it
goes out pour in a little lime water, then stop the mouth of the bottle
and shake it. The water becomes milky, showing that carbonic acid
gas has been produced. By means of a straw or glass tube blow a
little air through a cup of lime water and notice that again the water
becomes milky. This shows the carbonic acid of the breath.

17. Hold a lighted match under a cold tumbler. In a few seconds
drops of moisture will condense upon the inside of the glass. Explain
that the water is formed by the union of the hydrogen of the match
stick with the oxygen of the air.

REVIEW TOPICS

1. Describe oxidation and its products.

2. Show how oxidation takes place in the body.

3. Describe the oxidation of each proximate principle.

4. Describe the series of changes by which the oxidized

materials of the body are again built up into living
bodies.

5. Define and illustrate conservation of energy y and apply

it to man's body.

6. Define organic bodies.

7. Give points of difference between plants and animals.

8. Give the only known source of life.

CHAPTER IV

FERMENTATION AND ALCOHOL

49. Production of alcohol and vinegar. — Unless great
care is taken to preserve it, a weak solution of sugar soon
turns to vinegar ; a stronger solution
turns to alcohol, while a thick, sirupy
solution remains unchanged. Every-
where there are scattered minute living
germs which, falling into a moderately
strong solution of sugar in water, grow
and produce oval plants each about
f$-Q-Q inch in length. A collection of
these plants is called yeast. By their
growth and multiplication they change
sugar to alcohol and carbonic acid gas.
The gas bubbles up through the
liquid and makes a froth upon the top,
while the alcohol remains in the water.
If only a small quantity of sugar is present another kind
of germ from the air enters and grows, becoming tiny
rodlike plants, each about y0o00 inch in length. By
their growth and multiplication they change the alcohol
to vinegar. They collect in a mass called the mother of
vinegar.

Boiling destroys both the yeast and vinegar germs. If
the sugar and water are boiled and at once sealed tightly,
so that new germs cannot enter, the solution will keep

41

Yeast plant cells (X 500).

42 APPLIED PHYSIOLOGY

for an indefinite time. Fruit when boiled and at once
sealed in air-tight cans will keep unchanged for a long
time. If there is a great deal of sugar present no germs
at all will grow, and the solution will keep indefinitely.
This is why fruit can be preserved in open jars if a great
deal of sugar is used.

50. Fermentation. — Changing sugar to alcohol or vine-
gar is an example of fermentation. A substance which
can change the composition of other bodies without losing
its own identity or characteristics is a ferment. A very
small amount of a ferment can change a very large amount
of another substance.

A very small amount of yeast will cause an indefinite
amount of sugar to become changed to alcohol or vinegar.
At the same time the yeast may not grow weaker, but
on the contrary may become stronger than at first. In the
same way a small amount of " mother " will change a
large amount of weak alcohol to vinegar, and itself will
greatly increase in amount.

51. Kinds of ferments. • — Nature uses many ferments in her
actions. Some are living beings and some are lifeless substances. The
chief part of the digestion of food is done by lifeless ferments. Fer-
mentation is commonly spoken of as a process of decay, but the
common process of decay or rot is in itself only a special kind of fer-
mentation. Ordinary decay is caused by a living being like the
vinegar germ. By its growth and multiplication it softens and liquefies
the albumin of animal and vegetable matter. This process is called
putrefaction (see p. 24). Some of the matter passes off as foul smell-
ing gases, while the liquid part soaks into the soil. Putrefaction is
nature's way of giving dead bodies back to the soil and air so that
plants can build them into useful forms again.

Yeast germs are found everywhere, but they are often grown in wet
meal or flour. The mass is then dried in cakes and sold as yeast.
When a small piece is added to sugar and water it starts alcoholic fer-
mentation at once. Alcoholic fermentation only is usually meant when

FERMENTATION AND ALCOHOL 43

the term fermentation is used alone. An adjective signifying the
special form of fermentation is used to indicate any other form than
the alcoholic. Thus there is acetous or vinegar fermentation, and
putrefactive fermentation.

52. Bread making. — By the growth of yeast plants in
bread dough some of the sugar in the flour is changed
to carbonic acid gas and alcohol. The gas bubbles up
through the dough, making it porous and light. When
the bread is baked, alcohol is driven off and the yeast
germs are killed by the heat. They are eaten with the
bread, for they are perfectly wholesome. When germs
of vinegar or other acid fermentations enter the bread
and grow, the bread sours. These germs grow more
slowly than yeast, and usually do not have time to de-
velop. But if the bread is a long time in rising, they
may grow and make the bread sour.

53. Fermented drinks. — Man uses the same process to
produce drinks, which are erroneously supposed by many to
act as a beneficial food, quenching thirst and giving strength
to the body and power and joy to the mind. There are
three classes of such drinks, all containing alcohol as an
essential part.

54. Malt liquors. — The commonest form is what is
known as malt liquors. Barley and other grain are mois-
tened and permitted to sprout until the new stalk is about
one half inch in length. This changes much of the starch
of the grain to sugar. The sugar is dissolved out by boil-
ing the grain along with hops and various other flavoring
substances. Then yeast is added and alcoholic fermen-
tation occurs. The result is beer. It contains from one
to ten per cent of alcohol. Much of the flavoring which
is often added to it is not only injurious, but actually
poisonous.

44 APPLIED PHYSIOLOGY

55. Wines. — The second class of alcoholic liquors is
wine. The juice is squeezed from grapes, blackberries, or
some other fruit rich in sugar. Germs of alcoholic fer-
mentation from their skins and the air set up fermentation
in the juice and produce wine. Certain localities and cellars
contain special kinds of germs which produce a peculiar
flavor in the wine fermenting in that locality. In this way
different kinds of wine are produced. Wine contains from
five to fourteen per cent of alcohol. Fourteen per cent of
alcohol in the juice kills the germs and stops the fermenta-
tion. So wine cannot contain more than that amount of
alcohol unless more is added.

56. Distilled liquors or spirits. — The third class of
alcoholic drinks is spirits, or distilled liquors. Alcohol
boils at a temperature of 170° F., while water boils at
212° F. Thus when a wine, or beer, or any other alco-
holic solution is heated its alcohol will be changed to
steam very rapidly, while the water will evaporate slowly.
Therefore the steam will contain a larger proportion of
alcohol than the original liquor. This fact is put to use in
separating alcohol from the solution in which it was pro-
duced. The steam is conducted through a coil of pipe
kept cool by running water. Its temperature is lowered
and it is changed back to a liquid form. This new liquid
is whisky, or brandy, or other spirituous liquor, according
to the substance used in its manufacture. The process
of its manufacture is called distillation. Spirituous liquors
are about one half alcohol.

57. Description of alcohol. — If the process of distillation
is repeated the alcohol which passes over is still freer from
water, until after three or four distillations it is almost
pure. It is then a clear, colorless liquid like water. It has
a sharp, sweetish taste and a peculiar odor. It causes a

FERMENTATION AND ALCOHOL 45

severe smarting sensation when applied to a raw sore or to
the eye or mouth. It is a valuable and useful article when
rightly used in the manufactures and arts. But men have
formed the bad habit of liking its taste and the feelings
which it produces. They drink strong drink solely for
the sake of the alcohol which it contains. The alcohol
has an injurious effect upon every part of the body.
These effects will be described in detail as each organ is
studied.

58. Kinds of alcohol. — Alcohol is the name for a series of sub-
stances formed out of the same elements, but varying in composition,
yet alike in essential properties. The simplest form is called methyl
alcohol, or wood spirits, and is formed by distilling wood. It has an
unpleasant odor and taste, but nearly the same properties as common
alcohol. It is much used in manufacturing and in the arts, as a substi-
tute for common alcohol, on account of its cheapness.

The next form, called ethyl alcohol, is the common alcohol made
from wine, beer, etc.

The fifth in the series is called amyl alcohol or fusel oil, from the
German fitsel, bad liquor. It has a bad odor and nauseous taste, and
is far more poisonous than common alcohol. It is formed in con-
siderable quantities when potatoes are fermented. But if the whisky
stands for some years, the fusel oil becomes changed to ordinary
alcohol.

59. What becomes of alcohol in the body. — When taken
into the stomach, alcohol passes into the blood with great
rapidity. The body has the power of rapidly disposing of
it either by giving it off, or, more probably, by oxidizing it
to carbonic acid and water, and thus destroying it. At
any rate, little or no alcohol can be found in any part
of the body or in its waste, no matter how much is taken.
But its oxidation takes place in an irregular way which is
injurious to the body.

46 APPLIED PHYSIOLOGY

60. Effects of alcohol. — (i) Prevents fermentation and
decay. — While alcohol is the product of fermentation, it
has the power to prevent fermentation. The germs pro-
ducing alcohol will not grow when alcohol is present in the
proportion of 14 per cent. Germs of decay will grow in a
much larger percentage of alcohol, but no germs will grow
in a solution of one half alcohol. This fact is put to use
in preserving specimens of animals and vegetables in
museums, by placing them in spirits or alcohol. Since
decay is dependent upon germs, the alcohol, by preventing
their growth, prevents decay. It can also prevent the
digestive ferments from acting upon food.

(2) Extracts water from tissues. — Water and alcohol
mix very readily. An uncorked bottle of alcohol takes up
water from the air, and so becomes weakened. When
alcohol is in contact with a wet substance, it appropriates
some of its water, and the substance then shrivels and
becomes firmer. Strong whisky can produce the same
result in the body to a limited extent.

(3) Hardens tissues. — Alcohol also hardens many ani-
mal and vegetable substances by extracting their water and
by coagulating their albumin. In museums this fact is put
to use in hardening soft and delicate specimens of animals
and vegetables, so they may be preserved and examined
safely. It is not probable that this action occurs in the
body, for nature pours out an abundance of water to dilute
the irritating alcohol.

Within the body the effect of extracting water from the
tissues and of hardening albumin is to produce a smarting
sensation which shows that the organs are being injured.
There would be no limit to this action and death would
soon take place if nature did not provide means for a
partial protection against the substance. When any part

FERMENTATION AND ALCOHOL 47

of the body is harmed, nature pours an abundance of
water over the injured spot, so as to dilute and wash away
the irritating substance, just as she pours out tears to wash
a speck of dirt away from the eye. Alcohol attracts water
to itself, and thus its power to do harm is greatly lessened.
But this protection is only partial. If only a small amount
of strong drink is used steadily for some time, nature
becomes exhausted in her efforts of defense. Thus, while
some exceptionally strong men seem able to use a large
amount of strong drink with little harm, most men are
greatly harmed by the smallest amounts.

61. Cause of thirst for alcohol. — The property of taking
away water from substances which it touches, accounts in part for the
failure of alcoholic drinks to satisfy thirst. A dry state of the surface
of the lining of the mouth gives rise to thirst. If this lining is deprived
of water by an alcoholic drink, the sense of thirst still remains, although
the rest of the body is supplied with water. Moreover, this lining is
somewhat injured by the alcohol of every drink, and to soothe the irri-
tation another drink is needed. So the thirst goes on, growing stronger
with every drink.

When he begins, no drunkard expects to use strong drink, or to
drink more than a glass or two at a time, but his thirst always deceives
him, and the momentary relief which drink gives him is only a deceitful
addition to his thirst.

62. Adulteration of alcoholic drinks. — The manufacture of
pure alcoholic liquors is a slow and expensive process. So cheap imi-
tations are made which closely resemble the real article in taste and
appearance. Beer is often made from cheap rye or corn and quassia,
instead of barley and hops. Its fermentation is often hastened by an
excess of yeast, and then the product is preserved by adding salicylic
acid or other substances which destroy the yeast.

Whisky and brandy are also much adulterated. All kinds are alike
in having a large amount of alcohol. In fact, the cheaper kinds of
whisky and brandy contain the most alcohol.

Often, instead of good grain or fruit, rotten fruit, peelings, and refuse
of all kinds are used in making liquors. When distilled and treated

48 APPLIED PHYSIOLOGY

with flavorings, a drink is produced which an expert chemist can
scarcely distinguish from genuine liquor, and yet its evil effects are
notoriously greater.

63. Temperance drinks. — Strictly speaking, water is
the only temperance drink, for all kinds of flavored and
fermented drinks are designed only to please the taste and
not to fill a want of the body. The use of any except water-
is a form of intemperance, but those which contain alcohol
are especially harmful.

Cider, root beer, and ginger ale, and other " homemade "
drinks which are "worked" or fermented, all contain
alcohol, and should be classed as strong drink. These
drinks are particularly bad, for their use may lead one to
indulge in stronger drinks.

SUMMARY

1. A sirupy solution of sugar will not become sour, but

will " preserve " fruit from spoiling.

2. Sugar in a weak solution becomes alcohol.

3. The change is produced by the growth of microscopic

plants called yeast.

4. Sugar in weaker solution becomes vinegar.

5. The change is produced by a collection of microscopic

rodlike plants which form the "mother" of vinegar.

6. Changing sugar to alcohol or vinegar is fermentation.

7. Wine is made by fermenting fruit juice, and beer is

made by fermenting a solution of sprouting grain.

8. Distilled liquors are made by boiling fermented liquors

and collecting the vapor.

9. Alcohol prevents decay by killing the germs which

produce rotting.

IO. Alcohol takes water away from other substances and
then hardens and shrivels them.

FERMENTATION AND ALCOHOL 49

\

ir. Alcohol disappears very rapidly after being taken

into the body.
12. Alcohol takes water from the lining of the mouth

and produces thirst.

DEMONSTRATIONS

18. Show fermentation by setting aside a bottle containing a little
molasses in water. In a few days bubbles will rise, showing that fer-
mentation has begun. Add a little yeast to another bottleful, and
notice that fermentation begins within a few hours. Boil another
bottleful and at once cork it tightly, and notice that it does not change.
Explain that the first bottleful started with few germs and so fermenta-
tion at first was slow. The second had many and fermentation began
at once. In the third the yeast germs were destroyed and so no fer-
mentation took place.

19. Set aside a bottle of weak molasses and water for a week or two.
Notice that fermentation goes on but that the liquid now tastes sour,
for it has become vinegar.

20. Soak a yeast cake in water for a few hours and examine a tiny
drop under the microscope with a power of at least 200 diameters.
Notice the small oval cells, from the edges of which tiny cells seem to
be budding. These are yeast cells. In the same specimen starch
grains will appear as much larger irregular bodies of a shape depending
upon the kind of grain used in making the yeast.

21. Procure some alcohol. Notice its sharp odor and taste. Show
that it will dissolve and remove grease from the hands. Explain that
in the arts, it is used to dissolve oils, resins, and such substances as
water will not dissolve. Procure some wood spirits and contrast its
odor and taste with that of common alcohol. Show that it, too,
dissolves grease.

22. Pour some alcohol upon the white of an egg. Notice that the
alcohol coagulates it and turns it white.

23. Place a small piece of tender meat in a bottle of alcohol for
a. day or two. Notice that it turns whitish in color and becomes
shriveled, hard, and dry. Explain that the alcohol takes away the
coloring matter of the meat, and 'also coagulates the albumin much in
the same way as hemlock bark tans leather. Explain how alcohol pre-
serves substances in this way.

ov. PHYSIOL. — 4

50 APPLIED PHYSIOLOGY

/

24. Dip a small piece of paper in alcohol and touch it with a match.
It bursts into a flame at once, and develops great heat but no smoke.
Notice that the paper does not burn until the alcohol is nearly used up.
Explain that in the body alcohol seems to be easily oxidized, and uses
oxygen which should go to the proper food of the body.

25. Hold a cold stone in the mouth of a teakettle or in the steam of
a pan of water. Notice that the vapor condenses in drops upon the
stone. This will illustrate distillation as well as a complicated appa-
ratus of coils and running water. Explain that dew upon the grass is
a distillation of water.

REVIEW TOPICS

1. Describe how alcohol and vinegar are commonly

formed.

2. Describe the yeast plant.

3. Describe mother of vinegar.

4. Describe fermentation.

5. Tell how fermentation is applied to bread making.

6. Describe malt liquors.

7. Describe wine.

8. Describe spirits and the process by which they are

made.

9. Describe alcohol.

10. Give the three main properties and effects of alcohol.

11. Tell what becomes of alcohol when taken into the

body.

12. Tell why alcohol does not satisfy thirst.

CHAPTER V
DIGESTION OF FOOD IN THE MOUTH

64. Food and digestion. — Albumin, fat, and sugar are
continually being oxidized in the body, and the products
of oxidation, together with mineral matter and water, are
being thrown off. In order to keep up the strength and
form of the body a constant stream of new material must
be supplied.

Anything which, taken inside of the body, supplies it with
weight, heat, or energy is food (see pp. 64 and 89).

In preparation for the use of the body, food is reduced to a form which
can be dissolved in water, and drawn through the walls of the blood
tubes. The blood distributes it to all parts of the body. The process
of producing a chemical change in food so that it can be taken up by
the blood is digestion.

Man uses as food a combination of albumin, fat, sugar or starch,
mineral matters, and water, which are identical with the proximate prin-
ciples of the body. Of these water and mineral matters can enter the
blood without being changed, while the albumin, fat, sugar, and starch
require digestion. Albumin is changed to a form called peptone, which
can easily diffuse through the walls of the blood tubes, and so become
a part of the blood.

Sugar and starch are both changed to glucose, a form of sugar found
in the grape. Fat is saponified and emulsified.

65. Cooking. — Digestion is begun by applying heat to
food, either with or without water. Preparing food by
heat is cooking. The heat of cooking coagulates the
albumin. It also softens and dissolves the connective

52 APPLIED PHYSIOLOGY

tissue which binds together the cells of the food material,
and thus makes meat and vegetables tender. It devel-
ops an agreeable flavor which stimulates the desire for
food and promotes digestion. Cooking has no effect upon
fat itself, but the tiny pockets of albumin in which it is
stored in meat and vegetables are softened or dissolved
away, and the fat is set free. In vegetables and flour,
starch is in tiny grains, each of which seems to be
made up of layers of starch separated by thin layers of
a waterproof substance. Hot water causes the starch to
swell and burst these envelopes, and the starch itself is
then dissolved, thickening the water to a jelly like mass.
Cooking has no effect upon the sugar and mineral matters
of the food, except to mingle them thoroughly with the food.
Thorough cooking also destroys many poisons, and all
the disease germs in tainted food. Yet cooking does not
render tainted food fit for use.

66. Ways of COOking. — Some foods are best cooked by being
boiled or stewed. Other foods are best when roasted or broiled. The
exact method is not so important as the skill of the one who does the
cooking.

In all forms of cooking the principles are the same. If the solid food
alone is to be eaten, as much of the juices as possible should be retained
in the food by coagulating the albumin upon the outside at once so as to
imprison the juices. This can be done by having the water boil before
the food is placed in the kettle, or by placing the food in a hot oven.
The film which forms upon the outside of the food effectually seals the
juices within. If both the solid food and the liquid in which it is
cooked are to be eaten, the flavors are better developed if the juices are
diffused through the liquid. In this case the food should be placed in
cold water or a cool oven, and heat applied gradually so as to avoid
coagulating the exterior sooner than the interior. In most cases the
food will be of better quality and taste if the cooking is done slowly.
When the heat is continued after the food is thoroughly softened, its
fibers are apt to become hard and dry.

DIGESTION OF FOOD IN THE MOUTH 53

As a general rule it is best to cook each kind of food separately.
Each substance can then be cooked in its own peculiar manner. In
roasting and broiling, the fat drips away. The outside of the meat,
subjected to a high degree of heat, becomes hard, imprisoning the
juices within. The inner part of the meat is protected from the heat
and is cooked at a lower temperature
than the outside. So its juices remain
in a more natural state.

When food made from vegetables or
grain is baked, a crust forms upon the
outside. This consists of hardened albu-
min mixed with starch, which is partly
changed by the heat to a kind of sugar.
If the crust is not too much cooked and
dried it is palatable and easily digested.

67. The alimentary canal. —
Food is taken into the body and
digested by means of a tube lead-
ing through the body. Beginning
at the upper end, the parts of this
tube, which is called the alimen-
tary canal, are the mouth, phar-
ynx, esophagus, stomach, and
intestine.

68. The mouth. — The food is
held in the mouth for a few sec-
onds while it is mixed with the
watery fluid called the saliva, and
ground fine by the teeth. This

grinding is mastication, and the mixture with saliva is in-
salivation. In these two processes, the teeth, tongue,
cheeks, lips, and salivary organs all take part. The
roof of the mouth is formed by the bony palate in front,
and the soft movable palate behind. It is bounded on
the sides and in front by the teeth, cheeks, and lips.

54

APPLIED PHYSIOLOGY

The floor is formed by the tongue and the lower
jaw.

69. The jaws. — The lower jaw is a semicircular bone,
whose hinder extremities are curved upwards. Each tip
forms a hinge which turns in a socket just in front of the
ear. It carries a semicircle of teeth, which exactly fit
against a similar semicircle upon the upper jaw. The
lower jaw is moved by powerful muscles in three direc-
tions : first, up and down ; second, sidewise ; third, back-
ward and forward.

The upper jaw is a strong bone of irregular shape, firmly
fixed to the rest of the skull. Its interior is hollowed out
to form a cavity called the antrum, which has a small
opening into the nose. The upper ends of the teeth some-
times project so far upward as to make slight elevations
upon its floor. Sometimes an inflammation or abscess of

a tooth may extend to the
antrum, so that it becomes
filled with pus, producing a
very serious trouble.

70. Teeth. — The teeth are
hard, bony pegs set deeply
into the lower jawbone and in
the edge of the hard palate.
There are sixteen on each
jaw. Counting from the mid-

The teeth at the age of six and
one half years. /, the incisors;
O, the canine ; M, the molars ; the

last molar is the first of the permanent die of the front of each jaw, the

side

like

bicuspids; JV, of the second molar; chisels, SO as to bite Or gnaw
the sac of the third molar is empty. — re ^i r j j 11 j 4.1.

MARSHALL °ff tne f °°d, and are called the

incisors. In a squirrel, they

are long and sharp, so as to gnaw through wood. The
third tooth is the canine. It is a round, firmly set tooth,

DIGESTION OF FOOD IN THE MOUTH 55

which in animals is the tusk. The next two are larger,
with flat surfaces ; they are called bicuspids. The next
three, the grinders •, or molars, have large, flat surfaces,
well adapted to grinding the food.

In a young child the two bicuspid teeth resemble the molar teeth in
the adult, and the three molars are absent. At about the age of six, a
whole new set of teeth begins to grow beneath the first teeth, and to
press against their roots, cutting off their food supply. The blood
takes away the substance of the old teeth as the new ones advance
against them, until their projecting parts alone are left attached only by
the gum. They finally drop out, while the new ones
advance to take their places. The first teeth, like
the permanent set, may decay and cause toothache,
and should have as good care in filling and cleaning
as is given to permanent teeth.

Sometimes when a baby's gums are being cut
through by the growing first teeth, they are tender

and swollen, making the child fretful. Yet teething

Section of a tooth,
seldom causes sickness in a healthy child.

a enamel.

71. Composition of teeth. — The teeth b dentine.

c pulp cavity con-
are composed of a very hard kind of bone taming blood

called dentine, which in some large animals tubes and

nerves.

is called ivory. It is nourished by blood d cement,
tubes and nerves, which enter at the tip
within the jaw and form a pulplike mass in a small cavity
in the center of each tooth. The root of the tooth is set
into a socket in the jawbone, and a kind of soft bone,
called the cement, fixes it in place. The projecting part of
each tooth, called the crown, is covered with a hard shell
called the enamel.

72. Care of teeth. — When the enamel is too thin, or is worn or
broken off, the dentine beneath it may decay. Then the tooth rapidly
goes to pieces, often with much pain. Picking the teeth with pins and
cracking nuts often break the enamel. Dirt and particles of food be-
tween the teeth are great promoters of decay. The saliva deposits a

56 APPLIED PHYSIOLOGY

brown substance called tartar, which may press the gum back from the
root of the tooth, until a part of the tooth below the enamel is reached.
Then the tooth may decay and break off at the gum, or the gum and
bone may be forced back from the crown until the tooth becomes loose
and drops out. Thoroughly brushing the teeth twice a day with a
tooth brush and water is necessary for preserving the teeth. Particles

The tongue.

of food between the teeth should be removed, either by a soft wooden
toothpick or else by passing a strong thread between the teeth. Still,
with the best of care, some decayed cavities may develop, and these
should be filled at once. With this care, almost any set of teeth should
last a lifetime.

The cheeks and lips are thin layers of skin and muscles,
which can be moved freely in all directions.

DIGESTION OF FOOD IN THE MOUTH 57

The tongue is a long, flat muscle, attached at its back
end only, while its front part is capable of varied and pre-
cise movements in every direction.

73. Mucous membrane. — The cavity of the mouth is
everywhere lined with a thin membrane, directly continu-
ous with the outside skin. It consists of a loose network
of cells carrying blood tubes and nerves. It is covered
with a layer of flat cells, called epithelium. Into the loose
tissue beneath the epithelium, there project pockets or
tubes lined with cells directly continuous with the epi-
thelial cells of the sur-
face of the mouth. In
health, the cells of each
of the tubes and of the
surface of the mouth pro-
duce just enough of a

thin, clear liquid, called

Mucous membrane (X 200).

mucus, to moisten and a cells and loosely woyen fibers forming the

lubricate the Surface Of main part of the membrane.

the mouth. This mem-

brane is called a mucous

membrane. It is continued into the stomach and intestine,

and into the windpipe and lungs.

Mucous membrane is modified skin turned in from the surface of the
body to line the interior of all the cavities which communicate directly
with the air. Every such surface is covered by an unbroken layer of
epithelial cells. Wherever the epithelial cells are absent, the spot is
raw and sore. The epithelial cells of the surface of the mucous mem-
brane are designed mainly for protection ; but those which reach into
the tubes are set apart for the special work of producing mucus from
material supplied by the blood.

74. Gland and secretion. — A collection of pockets or
tubes lined with epithelium which forms a substance out

APPLIED PHYSIOLOGY

of the blood is a gland. The substance formed is called a
secretion. The epithelium of the gland does all the work
of secreting. All the mucous membranes of the body con-
tain glands which secrete
a

mucus, and in addition
many contain glands
which secrete other sub-
stances.

75. Sore mouth. —
Babies sometimes suffer
with a form of sore mouth
in which white specks, like
curdled milk, appear upon
its mucous membrane.
The spots are due to a
kind of mold which
grows in milk. Gently
washing the mouth with
clean, warm water several
times a day will destroy
the mold and remove
the sores.

76. Salivary glands. —
The mouth contains a

d

Diagram of glands.
a epithelium upon the surface of a mucous

cominued

a Simp,e

tube. enters it from three tubes

c the epithelium continued into a simple fa {^ £ach sali_

pocket.
d the epithelium continued into a series of vary tube, after it has 6X-

tended into the flesh on
the face for an inch or

so, abruptly divides again and again like the branches
and twigs of a tree. At the end of the smallest divi-
sions, there are minute pouches -^ of an inch in

DIGESTION OF FOOD IN THE MOUTH

59

diameter. All these tubes and pouches are rolled into
a small mass with blood tubes and nerves. The whole
collection is called a salivary gland. Each tube and
pouch is lined with epithelial cells which make the saliva
out of the fluid parts of the blood in which they are
always bathed. The saliva flows out of the tubes into
the mouth as fast
as it is secreted.
There is a sali-
vary gland in
front of each ear,
called the parotid
gland ; one along
each side of the
lower jaw, called
the submaxillary
gland, and one
just under each
side of the front
end of the tongue,
called the sub-
lingual gland.

77. Saliva. —
The saliva is a
thin, colorless,
alkaline mixture, which often contains air bubbles. About
ToVo Part °f t^ie san'va is a white substance called ptyalin,
which has the power to change starch to glucose while
remaining unchanged itself. Hence, ptyalin is a ferment.
It can act only in an alkaline fluid, and its action stops when
the food is acted on by the stomach. It digests only a
small amount of starch, and its value is due mainly to the
water it contains.

The salivary glands.

6o

APPLIED PHYSIOLOGY

78. Use of the water in saliva. — The water of the saliva has
very important uses. The nerves of taste are covered by the epithelium
of the mucous membrane, and some of the food must be carried through
this epithelium to the nerves in order that it may be tasted. The water
of the saliva dissolves the food and soaks through the epithelium,
carrying a tiny amount of food to the nerves, and thus makes the sense
of taste possible.

During digestion, food must be reduced to a fluid condition as thin
as milk. The saliva begins the process. Enough saliva is mixed with

food to form a pasty mass which the
thin walled stomach can handle with
ease.

79. Production of saliva. —

Saliva enters the mouth continu-
ally, but between meals only
about an ounce an hour is pro-
duced, while during a meal the
food increases in weight about
one half by the addition of saliva.
From one to three pints are pro-
duced daily. The flow of saliva
is excited by the act of chew-
ing, and by anything held in
the mouth, especially if it be of an agreeable taste and
odor. Hunger, or the sight or thought of agreeable food,
"makes the mouth water." The longer food is chewed
the more saliva is produced. This mixing and dissolving
action of the saliva is greatly aided by the movements of
the various parts of the mouth.

80. Mastication. — A morsel of food is pushed between the
molar teeth, which crush and grind it by the three movements of the
lower jaw. Between each movement of the jaw, the tongue and cheeks
roll the morsel into a firm mass so that the teeth can act upon it to
better advantage. The tongue has a delicate sensibility for the proper
condition and position of the food, and its varied and precise move-

A salivary gland ( X 200) .

0 tube of epithelium forming the
gland, cut lengthwise.

b tubes cut crosswise.

C connective tissue binding the
tubes in place.

DIGESTION OF FOOD IN THE MOUTH

61

ments, aided by the movements of the lips and cheeks, keep the food
in the best position for the action of the teeth. In a few seconds, even
hard and dry food becomes a thin and pasty mass. The tongue col-
le'cts the mass into a ball in the back part of the mouth in preparation
for its passage to the stomach. The process of sending food from the
mouth to the stomach is swal-
lowing w deglutition.

81. The pharynx. —
Back of the tongue is a
muscular bag about four
and a half inches in
length, lying against the
spinal column and called
the pharynx. It is lined
with mucous membrane,
which secretes far more
mucus than that of the
mouth. When the secre-
tion of mucus is excessive
it is called catarrh, but it
is usually a harmless
affection. The pharynx
has seven openings; one
into the esophagus or
muscular tube leading to
the stomach ; one into
the ^beginning of the
windpipe ; one into the mouth ; two into the nose, and two
into the middle ear. The openings to the nose and ears
can be closed by raising the soft palate against the spinal
column. The windpipe can be closed in three ways :
first, by the root of the tongue arching itself backward
over the windpipe; second, by a cover to the windpipe,
called the epiglottis ; third, by the vocal cords sliding

Diagram of the beginning of swallowing.

a top of tongue.

b pharynx.

c morsel of food.

d sliding door of the front of the pharynx.

e soft palate.

/ epiglottis.

62

APPLIED PHYSIOLOGY

together in the middle. The opening to the mouth can
be closed by two upright muscles which hang between the
back part of the soft palate and the base of the tongue.

These two muscles come
together in the middle
like sliding doors.

82. Swallowing. — By
a conscious effort, the
tongue quickly pushes the
morsel of food backward
towards the pharynx. The
two upright muscles of
the pharynx, gliding to-
gether over the surface of
the tongue between it and
the food, cut the food off
from the mouth. During
this movement the phar-

ynx closes all its other
„; t the Qne

to the esophagus. The
food fe now beyond the

•*
Control of the WllL The

Diagram of second part of swallowing.

a top of tongue arched backward and up-
ward.

b pharynx.

c morsel of food pushed into the pharynx by
the back of the tongue.

d sliding doors of .^e pharynx which have muscles of the pharynx

come together in the middle. f J

e soft palate lifted upward to shut off the nose, itself now Contract, for-

f ^ilrynx. ^^ downward to close the cing the food into the

esophagus, the opening
of which is the only one not closed.

83. The esophagus. — The esophagus is a muscular
tube connecting the pharynx with the stomach. It is
about nine inches in length. It is lined with mucous
membrane and secretes only enough mucus to moisten its
surface. When food reaches it, a ring of the muscular

DIGESTION OF FOOD IN THE MOUTH 63

tube contracts just above the morsel. This contraction
runs down to the stomach, forcing the food before it as
though a tight iron ring were slipped down over the esopha-
gus. A contraction of a tube within the body in a regular
manner, producing an onward movement of its contents,
is called peristalsis. While a horse is drinking, the peri-
stalsis of the esophagus may be plainly seen along its
neck.

SUMMARY

1. Anything which taken inside the body supplies it with

weight or heat or energy is food.

2. All foods are composed of one or more of the five sub-

stances : water, albumin, fat, starch or sugar, and
mineral matter.

3. Food must become liquid in form and enter the blood

tubes before it can reach the cells of the body.

4. Cooking softens the food and develops its flavors. It

also destroys many poisons in food.

5. In the mouth food is ground fine between the teeth

and mixed with the saliva so as to form a thin paste.

6. Saliva contains a ferment which changes some of the

starch of the food to sugar.

7. The tongue pushes the chewed food backward into

the pharynx. The pharynx then closes all its
openings except the one into the esophagus. The
pharynx then squeezes the food into the esophagus,
and the esophagus forces it into the stomach.

8. All cavities of the body which have an opening leading

to the air are lined with a kind of soft skin called
tmicous membrane.

9. Mucous membrane is a network of cells and fibers

covered with flat cells called epithelium.

64 APPLIED PHYSIOLOGY

10. Mucous membranes contain little pockets of epithelial

cells, which produce a slippery fluid called mucus.

11. A collection of pockets or tubes, lined with epithelium,

which separates a substance from the blood, is a
gland.

12. The saliva is formed in three glands upon each side

of the face.

DEMONSTRATIONS

26. Notice the various movements of the teeth and tongue, lips and
cheeks, in chewing. Have one of the pupils open his mouth wide.
Show how the soft palate which forms the roof of the mouth can be
raised and lowered. Show the sliding doors of the pharynx, which
reach up to the soft palate and with it form an arch over the back part
of the tongue. Notice the small projection which points downwards
from the summit of the arch. This is called the uvula.

27. Have the pupils swallow slowly. Notice -that the tongue, begin-
ning at the tip, is applied to the roof of the mouth until its whole length
touches the palate. Notice that when the back part of the throat begins
to swallow, the food is beyond the control of the will. Notice that
breathing is stopped, for both the nose and windpipe are closed.

28. Get a tooth and have it sawed in two lengthwise, so as to show
the cavity in its interior. Get another, partly decayed, to show how the
nerves of the interior are laid bare and exposed to injury.

29. Procure the lower jaw of a sheep or pig. With a hammer and
chisel split open a part of the bone to show how the teeth are set into
the bone.

30. Point out the difference between the skin and the mucous mem-
brane of the lips. Notice that the two are directly continuous. Explain
that the mucous membrane is really a modified skin, and that anything
in the mouth and stomach is really outside the body proper just as it
would be if it were held in the closed hand. •

31. Examine a specimen of mucous membrane under the micro-
scope, using a power of at least 200 diameters. Notice the layer
of epithelial scales covering its outside. Notice the network of fine
connective tissue which makes up the main part of the membrane.
Notice the glands. They are tubes, but are cut across in the specimen

DIGESTION OF FOOD IN THE MOUTH 6$

and appear as circles lined with large cells. Explain that the cells
of the glands produce the mucus.

32. Have a boy open his mouth and raise his tongue upward and
backward. With a handkerchief wipe dry the space between the tongue
and teeth. In a moment a drop of water will collect between the small
projections near the tongue. Move the tongue slightly, and notice
that the liquid flows in a tiny stream. Explain that this is the saliva
flowing from the sublingual gland.

33. Chew a piece of white bread. After a little, notice that it has a
sweetish taste. Explain that the sweetness is due to the action of the
ptyalin of the saliva in changing the starch to sugar.

34. While a horse or a cow is drinking, notice the peristalsis of the
esophagus along its neck as it swallows each mouthful.

REVIEW TOPICS

1. Define food and name the five classes.

2. Tell what change each must undergo in order to enter

the body.

3. Tell what effect cooking has upon each class of food.

4. Discuss the different ways of cooking.

5. Give the parts of the alimentary canal.

6. Describe the mouth.

7. Describe the jaws and teeth.

8. Tell how the teeth are commonly injured, and how to

preserve them.

9. Describe the cheeks •, lips, and tongue.

10. Describe a mucous membrane.

1 1 . Define a gland.

12. Describe a salivary gland.

13. Describe the use and appearance of saliva.

14. Describe mastication.

15. Describe the pharynx.

1 6. Describe swallowing.

1 7. Describe peristalsis.

OV. PHYSIOL. — 5

CHAPTER VI
\

STOMACH DIGESTION

84. Cavities of the body. — A muscular partition, curved
sharply upward, divides the inside of the body into two

cavities, — an upper one,

b

called the chest or thorax,
which contains the heart,
lungs, and the esophagus,
and a lower one, called
the abdomen, which con-
tains the stomach, intes-
tine, liver, spleen, and
g kidneys. This muscular

* partition is called the
. diaphragm.

85. The abdomen and

* peritoneum. — The abdo-
men is a closed cavity,
bounded above by the
diaphragm, on the sides
partly by the ribs, and
behind partly by the
spinal column. The bones
of the pelvis form its floor.
The rest of its walls are
formed by thick sheets of

muscles. It is lined with a very smooth membrane called
the peritoneum.

66

Organs of the chest and abdomen.

a larynx.

b trachea.

c clavicle, or collar bone.

d sternum, or breastbone.

e lung.

/ heart.

g liver.

h stomach.

i large intestine.

j small intestine.

STOMACH DIGESTION 67

The peritoneum also covers the outside of all the abdominal organs.
Such a membrane, lining a cavity which is not in open communication
with the air, is a serous membrane. The peritoneum is the largest and
most important serous membrane. It is a thin, closely-woven network
of interlacing cells covered by a single layer of flat cells, which give it
a shiny appearance. It is moistened by a small quantity of watery fluid,
which is not produced by glands, but is a part of the lymphatic circu-
lation. Its smoothness per-
mits easy movements among
the organs of the abdomen.

86. The stomach. — The

stomach is the first organ
into which the food passes
when it leaves the esoph-
agus. It lies mostly on the
left side of the abdomen

. ir , . . . Organs in the upper part of the abdomen.

half covered by the lower

* a liver, raised up.

ribs. It is a COnical en- b gall bladder upon the under surface of the

largement of the alimen- c splg™r'

tary canal, and is situated d stomach.

between the esophagus ' ~

and the small intestine. the gaii bladder.

It is about twelve inches ff ^enum.

in length and five inches

in diameter. It is composed of a layer of muscle covered

with peritoneum and lined with mucous membrane. Its

walls are from ^ to -| inch in thickness. It is hung in

place by a short curtain of peritoneum, which is attached

above to the under-surface of the liver and diaphragm.

The esophagus opens into the stomach at its upper left

side, called the cardiac extremity. The opening into the

intestine is at the right and narrowest part, and is called

the pylorus. The pylorus can be closed by a thick ring of

muscle.

68

APPLIED PHYSIOLOGY

87. Glands of the stomach. — The mucous membrane of
the stomach contains numerous glands which secrete a
special digestive fluid called the gastric juice. The glands
are short tubes each about ^J^ of an inch in diameter,
and -fa of an inch in length. The tubes are set closely
together and resemble pinpricks in the mucous mem-
brane. Each tube is lined with
a single layer of epithelial cells
which produce the gastric juice
from material supplied by the
blood. Besides these glands
there are many others which
secrete only mucus.

88. Gastric juice. — The gas-
tric juice is a yellowish fluid,
and consists of water holding
in solution hydrochloric acid
and two ferments. These are
the essential agents in stomach
digestion. Hydrochloric acid is
produced by the epithelium of
the gastric tubes from the salt
contained in the blood, and

forms from -^Vir to mhr of the
gastric juice. The ferments
are white, albuminous substances produced from the blood
by the epithelium of the glands, and form about -^-$ of
the gastric juice. The flow of gastric juice is promoted
by a slow, steady in-taking of food at about the tempera-
ture of the body. The saliva, which is slightly alkaline,
an agreeable taste of the food, and a pleasant frame of
mind also aid its flow. About three quarts enter the
stomach each day.

Gastric glands in the stomach

(X200).

a epithelium of the surface of the

stomach.
b epithelium lining the tubes of the

glands.
c connective tissue between the

tubes.

STOMACH DIGESTION 69

89. Peristalsis of the stomach. — Anything taken into
the stomach causes a continuous and regular movement
of the organ, due to the alternate contraction and relax-
ation of its muscular fibers. This is an example of slow
peristalsis. The food is thus caused to flow in a steady
stream from the esophagus to the left, and then down to
the right and back again, completing the circuit of the
stomach in about three minutes. By this movement it is
thoroughly mixed with the gastric juice.

90. Ferments of the gastric juice. — One of the ferments
of the gastric juice, rennin, acts by coagulating milk. In
the child this action is very important.

The other ferment, pepsin, softens the albumin of food
and changes its character so that it will dissolve in water
and diffuse through the walls of the blood tubes to become
a part of the blood. This form of albumin is called peptone.

A quarter of a grain of pepsin can render a whole white of an egg
soluble. It acts best at the temperature of the body, and there must
be an acid present. The surface of the food particles are acted upon
first, and the products of its action are rubbed off by the peristalsis of
the stomach, and the next layer is acted upon in the same manner.
Some of the gastric juice penetrates between the particles of food, and
slowly eats its way into the food mass, thus dissolving apart the sepa-
rate cells which compose the food. Its action is confined solely to the
albumin. In fat meat the albuminous pockets are eaten away, and the
fat is set free. Starch is not acted upon, except to be freed from its
albuminous envelopes.

The result of stomach digestion is a fluid called chyme.
Peptone imparts to it a bitter taste, while small particles
of fat give it a milky appearance. Food then appears as
it would if it had been boiled for a long time.

fc

91. Use of the acid. — Pepsin can act only in the presence of
acid, in an amount at least sufficient to neutralize the alkali always

7O APPLIED PHYSIOLOGY

present in the food. The gastric juice is more often deficient in acid
than in pepsin.

Besides assisting the pepsin the acid alone can perform the first
stages of changing albumin to peptone. Living germs of fermentation
and disease are sometimes swallowed. The acid destroys them if it is
present in the gastric juice in its full amount. This is a provision of
nature to prevent fermentation from taking place in the stomach, which
might otherwise become sour at every meal. This explains why
diseases are more easily caught when the stomach is deranged. In
a healthy person the germs meet the destroying acid almost at the
entrance to the body.

92. Amount of stomach digestion. — The stomach digests
only albumin. The main uses of the stomach are, to act
as a storehouse for food, to mix it with the watery gastric
juice, and to reduce it to a form still more liquid than
when it left the mouth. The acid prevents the food from
spoiling, and, with the pepsin, begins the digestion of the
albumin. The stomach is not absolutely necessary for
digestion, but because of its capacity it enables us to carry
a store of food so that we do not need to eat every few
minutes.

93. Passage of food into the intestine. — Every minute
or two the pylorus opens, permitting a little of the chyme
to escape into the intestine, where the main work of diges-
tion is performed.

Some food begins to pass out of the stomach within a
few moments after eating. The time required for the
stomach to empty itself completely is from two to five
hours, depending upon the amount of food and the ease
with which it is broken up. Thus we commonly say that
it takes from two to five hours for food to digest.

When the stomach has been empty for some time, there
is a sense of hunger. Yet the intestine may still contain
enough undigested food to supply the body for hours.

STOMACH DIGESTION 71

SUMMARY

1. The diaphragm divides the inside of the body into an

upper cavity called the thorax and a lower one called,
the abdomen.

2. In the abdomen are the organs of digestion.

3. The lining of the abdomen and the covering of its

organs is a smooth membrane called peritoneum.

4. The stomach is a muscular bag lined with mucous

membrane and covered with peritoneum. In its
mucous membrane are glands which produce the
gastric juice.

5. The gastric juice is water containing hydrochloric acid,

and two ferments. It changes albumin to peptone.

6. The actions of the stomach may be summed up in three

things : (i) It is a storehouse in which food is held
while being passed on to the intestine in a slow and
steady stream. (2) Its peristaltic movements break
up the food and mix it with the gastric juice. (3) It
digests some albumin by means of the acid and
pepsin of the gastric juice.

7. Every minute or two some of the liquefied food passes

through the pylorus into the intestine.

8. In from two to five hours after a full meal the stomach

is usually empty.

9. The stomach has no action upon starch or fat, and

digests only a part of the albumin.

DEMONSTRATIONS

35. Show the internal organs of an animal. A frog or a mouse will
do ; but a rat, a rabbit, or a cat will be better.

Always prepare the specimen in private, and leave it before the class
only while it is actually being shown. Cover all the parts except those
to be shown, and wash away all traces of blood. Any small animal may

72 APPLIED PHYSIOLOGY

be killed quickly and painlessly by placing it in a tight box or covered
paH and pouring in half an ounce of chloroform. Demonstrations of
the internal organs had better be made only before those members
of classes who wish to see them.

36. It is well to preserve permanent specimens of the different
organs. One part of formalin to 30 parts of water is most excellent.
It is neither expensive nor poisonous, while it preserves specimens in
their natural form and color. The following inexpensive mixture,
known as Mullens fluid, is also good.

Sodium sulphate (Glauber's salt), i part,
Potassium bichromate, 2 parts,

Water, 100 parts.

This forms a yellow fluid and stains the specimens yellow. It is
only slightly poisonous, even if taken into the mouth, while soap and
water will remove it from the hands.

Put the specimen in a large covered earthen or glass jar, with an
amount of the fluid equal to at least five times the bulk of the speci-
men. Remove it from the jar to a platter when showing it to the
class. The fluid will harden the tissues so that even soft organs may
be handled with safety.

Special training is required in preparing microscopic specimens
showing the tissues in their proper position. The difficulty consists in
cutting a slice thin enough ; for the microscope magnifies in thickness
as well as in length and breadth.

37. Open the abdomen of a dead animal by a cut from the ribs to
the end of the body. Notice that the organs and walls of the abdomen
are shiny from their covering of peritoneum. Notice that the perito-
neum is thin and strong, that its appearance differs from that of a
mucous membrane, and that it can be peeled from the abdominal
walls. (See demonstration 35.)

38. Notice the shape and position of the stomach. Open it to show
the folds in the mucous membrane. With a specimen of mucous mem-
brane under the microscope show the short, straight gastric glands stand-
ing side by side. Sketch them. (See demonstration 35.)

39. Notice the dome of muscle extending completely across the body
above the stomach. Explain that this is the diaphragm, and that it
divides the body into two cavities. Open the chest and show its cavity
and the top of the diaphragm, which separates it from the abdominal
cavity. (See demonstration 35.)

STOMACH DIGESTION 73

40. Illustrate stomach action by placing small slices of hard-boiled

egg in —

Hydrochloric acid, 40 drops,

Pepsin, i grain,

Water, £ pint.

Keep the mixture in a warm place, shaking it occasionally. In a few
days the egg will completely dissolve. Show some powdered pepsin
and some dilute hydrochloric acid.

41. Boil some potatoes and meat for several hours, to illustrate the
appearance of chyme as it leaves the stomach.

REVIEW TOPICS

1. Describe the two main cavities of the body.

2. Describe the lining of the abdomen.

3. Describe a serous membrane.

4. Describe the stomach.

5. Describe the gastric juice and the glands in which it

is formed.

6. Tell the name and the action of the acid of the gastric

juice.

7. Tell the names and the actions of the two ferments.

8. Tell how each class of food is affected by the stomach,

and how much.

9. Describe the peristaltic movements of the stomach.

10. Tell how the food passes from the stomach into the

intestine.

11. Tell how important the work of the stomach is in

comparison with the work done in the intestine.

CHAPTER VII
ABNORMAL ACTION OF THE STOMACH

94. The appetite. — Eating is designed to furnish the
body with proper nourishment, but many "live to eat,"
and pay for their meals with a host of bad feelings. The
amount and kind of food, and the time of eating, must be
suited to the needs of the body. A wild animal eats and
thrives without thought of what .it eats, for nature has
given it certain signs which it follows blindly and yet
securely. Man possesses the same signs, and if they
were followed, indigestion would be rare. The sign of
the need of food is the feeling of hunger and thirst, or the
appetite. The kind of food required is indicated by the
sense of tastey and the proper amount of food is known by
the absence of hunger and by the sense of taste begin-
ning to fail.

95. Natural taste of food. — The simplest kind of food
tastes the best to a hungry person. He eats it with keen
enjoyment until his hunger is satisfied. If he leaves the
table now and goes about his work, his meal will digest
without producing unpleasant feelings.

Food flavored only with salt has a natural taste of which
we never tire, and which gives reliable signs as to the
quantity needed, and the time of eating. If only this
kind of food is placed upon the table, the sense of taste
and the satisfied feeling at the end of the meal are reli-
able guides as to the amount and kind of food needed.

74

ABNORMAL ACTION OF THE STOMACH 75

96. Perverted appetite. — After hunger has been satisfied with
all the food needed, a food with an artificial taste is often brought on,
and a new appetite arises. The taste soon learns to prefer the arti-
ficially prepared food, and the education of " living to eat " is begun.
Pie, cake, sweets of all kinds, spices, and seasonings are eaten mainly
to please an acquired appetite.

Sweets and highly seasoned food do not satisfy a hungry man as
plain food does, but on the contrary their taste becomes sickening to
the stomach, before they begin to satisfy his hunger. Moreover, the
appetite for artificial things may persist after the stomach is filled.

97. Intemperate eating. — In the hurry of business or pleasure
men gulp down their dinners in huge mouthfuls, and overload their
stomachs before the surprised organs can take account of the kind or
quantity of food eaten. Some eat too much in prolonging the pleas-
ures of taste. Nearly everybody indulges an appetite for sweets and
highly seasoned food. Satisfying an appetite which is not the expression
of actual need of the body is as much intemperance as drinking strong
drink, and leads to the same kind of serious results.

98. Insufficient mastication. — A whole train of evils follows
intemperate eating. When food is swallowed in large lumps instead
of being masticated to a thin gruel, too little saliva is mixed with it. It
reaches the stomach too dry, and so a larger amount of gastric juice is
needed. But the saliva is the natural stimulant to the flow of juice,
and if it is small in amount, the gastric, juice does not flow in sufficient
quantity and food is not well digested.

99. Too much food. — An excessive amount of food stretches
and weakens the stomach, and peristalsis cannot take place so vigorously
as it should. The lumps of food are neither penetrated by the gastric
juice nor ground to pieces by the peristalsis, but only their outer sur-
faces are slowly dissolved. The food thus remains too long a time
in the stomach, and some may stay there until the next meal.

100. Eating between meals. — Eating at irregular hours or
between meals also disturbs the stomach. Two or three hours after a
meal the work of the stomach should be done, and it should be per-
mitted to rest. If more food of any kind is eaten, the stomach must
either be overworked or the food not be digested.

Food which the gastric juice softens with difficulty behaves like
large lumps of food, and finally either is vomited, or is passed on to the
intestine to create more trouble there.

76 APPLIED PHYSIOLOGY

. 101. Fermentation in the stomach. — The stomach cannot be
abused in any way without suffering in all its actions. It gives expres-
sion to its suffering by pain, headache, heart beating, and a host of other
bad feelings. It makes the whole body weak and sick. Its imperfect
action also permits fermentation to go on, which makes the food sour.
Living germs like those producing alcohol and vinegar are continually
being eaten. In health, the acid of the gastric juice destroys them,
but when anything weakens the acid or prevents it from reaching the
germs, they grow and produce vinegar and other acids, and also gases.
The result is a sour stomach and " wind on the stomach," which comes
up and out of the mouth as though it were vomited. This is a sign
of indigestion.

The gas distends the stomach and presses it against the heart, so that
the beats are felt ; and then the heart and not the stomach receives the
blame. A sour stomach is at first the result of improper action, not the
cause ; but, once developed, it may cause a greater disturbance, and
then there is only a step to actual stomach disease.

102. Drinking while eating. — A great part of the work
of digestion consists in mixing food with water. When
dry food is eaten, the gastric juice must be produced in
large amount before digestion can begin. A glass or two
of water, either alone or with tea or coffee, aids the action
of the gastric juice. If the water is not used in place of
saliva in moistening the food, or is not employed to hasten
the act of swallowing food, drinking during meals will be
beneficial. Many drink too little liquid.

103. Hot or cold food. — Food either too hot or too cold
hinders the production and action of the gastric juice and
disturbs peristalsis, so that the movements of the stomach
may not resume their natural course until a long time after
the temperature of the food becomes that of the body.
A glass of ice water may remain perceptibly cold to the
stomach for from one quarter to half an hour, and its
effects upon the movements of digestion may last much
longer.

ABNORMAL ACTION OF THE STOMACH 77

104. Rest and eating. — When the body is very tired,
the stomach has not the proper energy for digesting food!
If food is eaten just as a person comes home fatigued by
a hard day's work, there is apt to be a night of pain and
indigestion. If, before eating, a glass of warm water or
coffee or milk is taken, followed by a short nap, so as to
rest the body, the meal will be enjoyed, and digestion will
go on unaccompanied by bad feelings.

After a meal the stomach requires an extra amount of
blood and energy. A rest of fifteen minutes after each
meal would be a great health saver.

105. Rules for eating. — Chew each mouthful to a paste
and swallow it before taking another.

Stop as soon as the taste of plain food begins to pall.

Allow four or five hours to elapse before eating again.

SUMMARY

r. Hunger indicates the need of food, and taste indicates
the kind.

2. When only plain food is eaten, these two signs are cor-

rect guides in eating.

3. An appetite for sweet and highly seasoned food may per-

sist after hunger has been satisfied with plain food.

4. Sweet and seasoned foods soon disgust the sense of

taste, thus showing that they are not needed.

5. Eating food for mere pleasure is intemperance.

6. Eating too much, too rapidly, or too often is intem-

perance.
7- As a result of intemperate eating, acid fermentation

often occurs in the stomach, producing discomfort

and sickness.
8. A person should eat only plain food, slowly, and at

intervals of not less than four or five hours.

/8 APPLIED PHYSIOLOGY

DEMONSTRATION

42. Nearly every one has felt the effects of intemperate eating.
When " stomach sick," a sharp-tasting gas and very sour food often
come up to the mouth, showing that acid fermentation is going on.
Notice how plainly a person feels his own heart beats after a large meal,
owing to the pressure of the distended stomach upon the heart.

REVIEW TOPICS

1. Tell how a person knows when and how much to eat

or drink.

2. Define an appetite and tell how it can be satisfied

naturally.

3. Illustrate an artificial appetite and tell how it can be

distinguished from a natural appetite.

4. Tell some of the ways in which men abuse their stom-

achs by indulging their artificial appetites.

5. Tell some of the effects of too rapid eating ; of imper-

fect mastication ; of overeating ; of eating between
meals.

6. Tell how food sours within the stomach.

7. Tell how drinking at meal times is beneficial, and in

what way it can be harmful.

8. Tell how hot or cold food affects the stomach.

9. Give some simple rules for eating.

CHAPTER VIII

INTESTINAL DIGESTION

106. The intestine. — The part of the alimentary canal
below the stomach is called the intestine. The intestine is
a tube of varying size,

whose different parts
have different names.
Next to the stomach
is the small intestine,
which is about one
inch in diameter and
about twenty feet in
length. It opens into
the large intestine,
which is about two
inches in diameter and
five feet in length.

107. The small in-
testine. — The small

intestine is very movable, and is coiled in the abdomen in
no definite order. It is held in place by a fanlike fold of
peritoneum, called the mesentery. The mesentery is about
four inches in length along its back edge, which is fastened
to the spinal column, and twenty feet at its outer edge, to
which the intestine is attached. Its breadth from the spinal
column to the intestine is about four inches.

79

j\

Diagram representing a cross section of th&
small intestine, showing the three layers, and
the way in which the blood tubes pass be-
tween the two folds of serous membrane (the
peritoneum) which forms the mesentery.

80 APPLIED PHYSIOLOGY

In front of the intestine, and partly enwrapping its folds, is a thin
apron of peritoneum, called the omentum. It contains much fat, and
acts as a cushion and as protection against cold. The small intestine
for about ten inches from the stomach is called the duodenum. Then
for about eight feet it is called the jejunum, and the remaining eleven
feet is called the ileum. There is no very marked difference between
any two sections of these divisions.

The intestine ends at about the level of the hip bone,
and opens into the side of the large intestine by a slitlike
valve, which permits matter to pass into the large intes-
tine, but to a great extent prevents its backward movement.

108. The large intestine, or colon. — The whole large

intestine is called the
colon. Its beginning
is a small pouch called
the ccecum, which is
situated on the right
side of the abdomen
at the level of the hip

A piece of intestine showing the folds of the ,
valvulae conniventes upon its inner surface.

From the caecum

there extends a small tube one quarter of an inch in
diameter and two inches long, closed at its outer end.
This tube is called the vermiform appendix. It sometimes
becomes inflamed, forming an abscess, and produces the
disease called appendicitis.

The colon extends upward to the ribs, then crosses the
abdomen to the left side, and then extends downward.
These parts are called the ascending, transverse^ and de-
scending colon. The colon is held in place by a narrow
fold of peritoneum. It is not an even tube, but looks as
though strings were tied about it at intervals of a few inches.

109. Structure of the intestine. — The whole intestine
consists of a tube of muscular tissue, whose walls are

INTESTINAL DIGESTION

8l

from -^g to I of an inch in thickness. It is covered with
peritoneum and lined with mucous membrane. Its muscle
fibers extend both lengthwise and circularly. In the mucous
membrane of the small intestine are folds, each of which

Villi (X2oo).

a epithelium upon the surface of the villi.

b connective tissue fibers which support the blood tubes and lacteals.
c connective tissue cells.
d glands which form the intestinal juice.
e intestinal gland cut across.

extends from one half to three fourths the way around the
intestine. The folds are called valvulce conniventes. Upon
the surface of each fold are finger-like projections called
villi, which are from -^ to \ of an inch in length, and
from 2-^-3- to y\j- of an inch in diameter. Between the bases
of the villi minute tubes, ^o" °^ an ^nc^ *n length and

OV. PHYSIOL. — 6

82

APPLIED PHYSIOLOGY

is b

of an inch in diameter, extend into the mucous membrane.

Each tube is lined with a layer of epithelial cells, which

secrete a fluid called the intestinal juice.

110. Villi. — Each villus consists of an outer covering

of epithelial cells, inclos-
ing a loose meshwork of
fine blood tubes, and also
of tubes called lacteals,
both of which take up
the food as it is di-
gested. Neither villi nor
valvulae conniventes are
found in the large intes-
tine.

111. The pancreas. —
From the duodenum there
extends a very short tube,
about the size of a small
quill. This divides into
two tubes, one of which
goes to the liver and the
other to the pancreas.

Diagram of the essential parts of a villus. The pancreas IS a gland

a epithelium which takes up food and trans- about an inch in diameter

-.I—, and six inches long, lying
behind the stomach. In
lower animals it is called the sweetbread. Its structure
resembles that of a salivary gland. It secretes a thin,
watery liquid called the pancreatic juice, which is poured
into the intestine at the rate of one and a half pints a
day.

112. The liver. — The liver is a firm, dark-red, wedge-
shaped organ, lying under the lowest ribs upon the right

INTESTINAL DIGESTION

side. It is covered with peritoneum and hung closely to
the diaphragm and the spinal column.

The tube leading from the intestine to the liver divides
again and again into branches called bile ducts, the small-

^-ms*wi!qi^w^^^^

A thin slice of liver (x 200).

a veins bringing blood to the liver. c liver cells.

b capillaries between the liver cells. d vein to carry blood away from the liver
e tubes to carry away bile.

est of which are exceedingly minute, and barely recog-
nizable with a microscope. The walls of the smallest of
these ducts are composed of large cells of irregular shape,
which crowd one another so that the bile tubes are almost
closed. These cells make up the greater part of the liver.
Among these tubes there run many fine blood tubes, in
such a manner that the cells seem to be arranged around

$4 APPLIED PHYSIOLOGY

the capillaries instead of around the bile tubes. Each cell
makes bile from the blood and pours it into its bile tube,
down which it runs, uniting with streams from other tubes.
All the tubes finally unite their streams in the single bile
tube which leads to the intestine. A side tube leads from
the large bile tube to a bladder on the under side of the
liver, called the gall bladder, which stores the bile when it
is not needed in the intestine.

113. Bile. — Bile is a thick, golden-colored liquid of a
very bitter taste. It consists of waste albuminous matter,
coloring substances, and mineral matters dissolved in water.
Although it is a waste product, it has very important uses
in digestion. About a quart is produced daily.

114. Intestinal fluids. — As the food enters the intestine
it finds three new substances ready to act upon it. These
substances are the intestinal juice, the pancreatic juice, and
the bile. All these liquids are alkaline, and tend to neu-
tralize the acid in the food as fast as it comes from the
stomach.

115. Intestinal juice. — The intestinal juice is small in
amount, arid contains ferments which change starch to
glucose, and albumin to peptone ; but its action is slight,
and the amount digested by it is small.

116. Pancreatic juice. — The pancreatic juice is a liquid
of which five per cent is made of three ferments which
perform the main part of digestion. As the chyme comes
from the stomach, it contains albumin, some already di-
gested, but much only softened and broken up. It also
contains fat and starch unchanged.

One of the ferments of the pancreatic juice, trypsin,
acts upon the undigested albumin, changing it to pep-
tone.

Another ferment, amylopsin, changes the starch and

INTESTINAL DIGESTION 85

sugar to glucose. It does practically all the work of
digesting starch and sugar.

The third ferment, steapsin, saponifies some of the fat
with the soda and potash of the chyme. About one half
an ounce of soap is thus formed daily. It acts as a lubri-
cating and cleansing agent. The ferment also emulsifies
the remainder of the fat.

117. Action of the bile. — About a quart of bile is poured
into the intestine each day. It has a slight power in emul-
sifying fat, and in converting starch into glucose, but while
its direct action is small, it does a great amount of work in
helping and stimulating all the processes in the intestine.
It almost doubles the power of the pancreatic juice. It
acts as a lubricant to enable the food to slip down the
intestine easily. It stimulates the peristalsis of the intes-
tine, and prevents the growth of germs of fermentation.
It also enables digested food to pass more readily from
the intestine into the blood tubes. When bile is of poor
quality, or too little in quantity, digestion is less perfectly
performed, and headaches, mental dullness, and all the
symptoms called biliousness result.

118. Peristalsis. — The intestine shows peristaltic move-
ments like those in the esophagus. A half an inch or so
of muscle fiber, running lengthwise of the intestine, con-
tracts, pulling the next lower part of the intestine up over
a lump of food. Then the circular fibers contract, squeez-
ing the food down the tube, while the fibers next below
repeat the process, as the first ring of contraction relaxes.
So the contraction runs down the tube, forcing the intestinal
contents before it.

This peristalsis is a slow, gentle movement. By it the intestinal
contents are mixed with its juices, and slowly propelled toward the
large intestine, where it is propelled still more slowly.

86 APPLIED PHYSIOLOGY

119. Result of intestinal digestion. — By the action of
the three digestive fluids, the food is dissolved and reduced
to a thin, milky form, called chyle. As all food contains
many substances wholly indigestible, some solid particles
will still remain in the chyle. Digestive action goes on
during the whole time that food remains in the intes-
tine, but most of the work is done in the small intestine.
As it slowly passes down the tube, the liquid parts are
taken up until, when it reaches the large intestine, it has
become semi-solid again. The expulsion of the solid
waste which finally remains is the last act of digestion.
It takes about twelve hours for food to pass the length of
the small intestine, and thirty-six hours to traverse the
large intestine.

120. What becomes of the ferments. — After the ferments of
the gastric, pancreatic, and intestinal juices have done their work of
digestion, they are probably digested by the new ferments poured out
at the next meal, for they are albumin. Bile is a waste product, yet
some of its parts are taken up by the blood and carried to the liver, and
again poured into the intestine. Thus nature is as economical as
possible with the resources of the body.

121. Perfection of the digestive organs. — The mouth is
perfectly adapted to masticating just such food as the
stomach can readily digest, while it cannot grind such
food as corn or hay. The stomach seems a weak, flabby
organ, but nature made it of just the right size and strength
to do its own proper work.

The bile is a waste product of the body and yet it is
one of the most important agents in digestion. In brief,
each part of the digestive system is perfectly adapted to
its own work. In lower animals the digestive organs are
somewhat modified so as to adapt them to different foods
and different modes of eating

INTESTINAL DIGESTION 8/

SUMMARY

1. From the stomach the food passes into a long, coiled

tube called the intestine.

2. In the intestine the food is acted upon by ferments in

three fluids: the intestinal juice, the pancreatic juice,
and the bile.

3. The intestinal juice has a slight action in changing

starch to sugar, and albumin to peptone.

4. The pancreatic juice does the main part in changing

starch to sugar and albumin to peptone, and of
emulsifying and saponifying fats.

5. The bile greatly increases the power of the pancreatic

juice. It also lubricates the intestine, prevents fer-
mentation, and aids the passage of digested food
into the blood tubes.

6. The muscles of the intestine slowly force the food

down the tube so that it takes about twelve hours
for food to traverse the small intestine, and thirty-six
to traverse the large intestine.

DEMONSTRATIONS

43. Open the abdomen of a dead animal. Notice the thin, gauze-
like omentum containing lumps of fat, and enveloping the intestine.
Lift it up, and notice that the upper part of the large intestine seems to
be inserted through it as though it were split into two leaves. Notice
the difference between the small and large intestine in position, shape,
and movability. Notice the beginning of the large intestine and the
caecum. The vermiform appendix can usually be found also. Notice
the position, size, and feeling of the liver, and the gall bladder beneath
it. By careful search the pancreas can be found behind the stomach,
lying crosswise of the body, flattened out upon the backbone. It is
covered with peritoneum and fat, and so is obscured, but can be recog-
nized by its nodular appearance. A pig's sweetbread has much the
same appearance as a man's pancreas. (See demonstration 35.)

88 APPLIED PHYSIOLOGY

Notice the thin fanlike mesentery, holding the coil of intestine in
place. Notice the blood tubes running across it. Open the intestine
for a few inches to show the folds of the valvulae conniventes.

44. The villi are too soft and too small to be seen without a specially
prepared specimen. A magnifying power of 50 will show them.

Examine also a specimen of the liver, using at first a power of 100
diameters. Notice the capillaries converging toward central veins.
The bile ducts are too fine to be seen.

Next use a power of 400 diameters, and examine the cells carefully.
Notice their large size, and that they sometimes have more than one
nucleus. Make a sketch of a villus and of the liver cells.

45. Pour some oil into a bottle of water. Shake well, and notice
that the two cannot be made to mix. Now add a small pinch of pancrea-
tine. Shake once more, and notice that the oil now forms an emulsion
with the water.

Explain that the pancreatine contains the ferment of the pancreatic
juice, and that it has the same action outside the body that it does
inside.

46. Make a little starch paste. While it is warm stir in a small
pinch of pancreatine. In a few minutes the paste becomes fluid from
the conversion of starch to sugar.

47. Procure some bile. That from a chicken's gall bladder will do.
Pour some into a bottle with oil and water, and notice that it forms an
emulsion.

REVIEW TOPICS

1. Describe the intestine and its various divisions — the

small and the large intestine, the caecum, the vermi-
form appendix, the colon, the mesentery, and the
omentum.

2. Describe the pancreas.

3. Describe the liver.

4. Describe the bile and its uses.

5. Describe the pancreatic juice and its three ferments,

and their uses.

6. Describe the intestinal juice and its use.

7. Describe the peristalsis of the intestine.

CHAPTER IX
ABSORPTION AND ASSIMILATION

122. Absorption of food. — Digested foods which be-
come part of the body are peptone, glucose, and emulsified
fat. While they remain in the intestine, they are still
outside of the body proper. In order to nourish the body,
they must diffuse through the wall of the intestine and
become part of the blood. The process of taking any sub-
stance into the blood is absorption.

The bodies of most cells are semi-fluid and jellylike.
The peptone and glucose, dissolved in water, will soak into
the soft epithelial cells lining the intestine, while the
original albumin and starch or sugar will not. Blood tubes
run so near the inner surface of the wall of the intestine,
that only a layer of epithelium and the capillary wall,
both together thinner than the thinnest paper, separate
the blood from the food in the intestine. The food soaks
through the epithelial cells and the walls of the blood tube,
and is washed away by the blood stream. So there is a
steady flow of digested food through the epithelial cells
toward the blood tube ; while the undigested food remains
behind. The cells are alive, however, and to a degree
select what they transmit. Common salt is necessary in
the process, and bile greatly aids it. Peptone and glucose
are thus absorbed from the intestine by every point of its
mucous membrane. The millions of villi projecting into
the intestine greatly increase the surface for absorption,

89

APPLIED PHYSIOLOGY

while their thin walls are especially designed for the easy
passage of fluid.

Diagram of the course 01 food in its absorption and assimilation.

123. Absorption of fat. — Fat also diffuses in the alka-
line solution contained in the intestine. Under the micro-
scope, particles of emulsified fat may be seen inside the
epithelial cells of the villus. Only a small part enters the

ABSORPTION AND ASSIMILATION 91

blood tube of the villus, while its greater part enters
the lacteal tube. These lacteals unite to form larger and
larger tubes, which run across the mesentery, and finally
open into a single tube, the thoracic duct, running up the
spinal column. This is a tube as large as a goose quill,
and opens into a large vein at the root of the neck, where
emulsified fat from the intestine first reaches the blood.

124. Completion of digestion. — Reckoning the amount of
saliva as two pints a day, of gastric juice as eight pints, of pancreatic
juice one and a half pints, and bile as two pints, and of food three pints,
the liquid introduced into the intestine daily amounts to two gallons at
least, and nearly the same amount is absorbed. More and more of this
liquid is absorbed as the food passes down the intestine, until, about
twelve hours after eating, what is left of the food and digestive fluids
reaches the large intestine in a semi-solid state. In the large intestine
absorption and peristalsis are so very much slower, that from twenty-
four to thirty-six hours are required for the remains of food to traverse
it. Its water and digested food and some of the bile are absorbed,
while the rest of the bile and its other waste products and undigested
matter are left behind. In health the intestine expels the waste matter
regularly at least once a day.

125. Assimilation of fat. — Changing the digested food
into the various fluids and tissues of the body is assimila-
tion. The thoracic duct pours the digested fat into a large
vein on the left side of the neck, whence it is carried with
the venous blood to the lungs. Little or no fat can be
found in the blood leaving the lungs unless it has been
eaten in excessive quantities. It is probably oxidized at
once to carbonic acid and water, an ounce requiring three
ounces of oxygen. It is unlikely that any fat from the
food is stored up, but the fat in the body is probably
derived from the albumin of the cells. The oxidation of
fat produces heat, and the heat may be changed to power,
or be used simply to warm the body.

92 APPLIED PHYSIOLOGY

126. Assimilation of glucose. — Glucose enters the blood
in the villi, and is carried from there to the liver by means
of a large vein called the portal vein. As the blood
emerges from the liver, it contains almost uniformly -^fa§
part of glucose, no matter what amount of sugar is in the
portal vein. The liver contains a sugarlike substance
called glycogen, which increases in amount after digestion,
and almost disappears a few hours after eating. So it is
thought that glucose is stored in the liver as glycogen, and
given up to the blood in a steady stream.

In the blood the glucose is all oxidized to carbonic acid
gas and water, giving out heat and energy. One ounce of
glucose requires about one and one fifth ounces of oxygen
to oxidize it completely.

127. Assimilation of peptone. — Peptone is a poison to
the body and must be changed immediately after entering
the circulation. It is carried directly to the liver by the
portal vein, and there all becomes changed back to forms
of albumin which will not diffuse through a blood tube,
except under pressure. The liver further makes the albu-
min a living part of the blood. Some albumin is oxidized
in the liver, but a large part is carried to the cells of the
body. Each cell in the body is thus bathed in albuminous
food brought to it by the blood.

Like an ameba, each cell chooses as much of the albu-
min as it needs for food, and, taking it in by any part of
the surface of its body, makes it a living part of itself.
Finally, even the living albumin of the cell is oxidized, an
ounce requiring one and one half ounces of oxygen.

128. Absorbed poisons thrown out by the liver. — Fermen-
tation in the intestine produces injurious substances, and
the bile brings in waste matter. Decayed food, too, con-
tains poisons. All these substances may be absorbed and

ABSORPTION AND ASSIMILATION 93

carried to the liver, which either destroys the poisons or
sends them back to the intestine along with the bile. In
this way the liver is a continual protection to the body.

129. Summary of the work of the liver. — The liver serves
as the regulator of the body. The bile which it produces is to the
intestine what the acid is to the stomach. It aids the action of the
digestive ferments and hinders other forms of fermentation. It smooths
the passage of food down the intestine, and aids diffusion into the blood
tubes. The liver changes digested albumin and sugar and fits them for
use in the blood, and intercepts poisons which may be circulating in the
blood. It's work goes on constantly, and upon its perfect action depends
the well-being of the body.

130. Biliousness. — If the liver acts imperfectly, a part
of the peptone remains unchanged; other poisons, too,
brought from the intestine by the blood are not destroyed ;
and the glucose is not properly assimilated and oxidized.
A coated tongue, headache, loss of appetite, and an uncon-
querable feeling of dullness follow, and are symptoms of
what is known as biliousness.

In fevers there is a poisoning of the body by the cause
of the disease. As the liver is one of the principal organs
which remove poisons from the blood, it may soon be able
to get rid of them, and thus cure the fever. But often the
task is too great for it, and then all the symptoms of a
severe bilious attack are added.

131. Liver medicines. — Certain drugs, like mercury or podo-
phyllin, have the power to increase the action of the liver. In proper
doses they cause a great outpouring of bile which carries with it the
poisons of the body. The drugs also cause the liver cells to assimilate
the food more perfectly. Thus nature is assisted by the drugs and the
biliousness is soon overcome.

132. Intestinal indigestion. — When the stomach is over-
worked and acts imperfectly, its work is thrown upon the
intestine. Digestion there is imperfectly accomplished, and

94 APPLIED PHYSIOLOGY

fermentation takes place, with the development of poisons.
The gas from the fermentation causes the abdomen to swell
or bloat. The liver is imperfectly nourished, and is over-
worked in throwing out the poisons; so it fails to make
the proper changes in food. Then the whole body, in-
cluding the stomach, is weakened, and biliousness is pro-
duced. At last nature brings on severe sickness, and
compels the overworked organs to rest.

133. Prevention of biliousness. — Man has it in his power to
prevent almost entirely the evils of indigestion. He should eat only
plain food, in moderate quantities, and at regular intervals. He should
be careful not to eat when he is tired, or heated, or just before or
after hard work. His digestive organs would then furnish a continual
supply of perfectly digested food, sufficient for all the cells of the body ;
the influences producing disease would be resisted by well-nourished
cells, and sickness would be rare.

134. Regularity of the bowels. — The last act of digestion,
or the expulsion of waste matters from the intestine, is as
important as eating, and should be performed with the
same regularity. The mouth and stomach are endowed
with feelings which make known their needs, but the
intestine has only slight sensibility, and we are unaware
of the digestion which is continually going on in it. Only
when some irritating food, or a large collection of gas,
greatly increases its peristalsis are we aware of its action.
At a regular time every day a healthy person feels that
the completing act of digestion should be performed, but
the sensation will pass away if it is neglected, and in
course of time the sensation will be repeated only once
in two, three, or even more days. The retention of waste
matter all that time cannot fail to do harm. Even if
nature does not give the sensation indicating the need of
expelling waste matter, the matters need to be expelled,

ABSORPTION AND ASSIMILATION 95

and the opportunity should be given daily at a regular
time. Even if little food is eaten, the waste matters are
still formed, and need expulsion. It should be remem-
bered that it requires two days for food to pass the length
of the intestine, so refraining from food only a single day
does not make the intestine empty.

When the intestine expels its contents too freely, there
is usually some irritating food which it is trying to expel.
So a dose of medicine, which will aid in its expulsion, is
required rather than something which will restrain the
action.

135. Proper food. — The stomach may be able to begin digesting
an improper meal, while the intestine is unable to finish the work.
Owing to the slowness with which the intestine acts, several meals
may be eaten before its failure becomes noticeable. Then the last
meal is blamed, instead of the offending meal. So persons may gain
wrong ideas about the digestibility of various articles of food.

136. Headaches. — A headache is generally due to disturbances
in digestion. Usually when the liver is stimulated by a proper medi-
cine, the headache ceases. Even if the headache is due to overwork,
probably it would not have come on if the digestive organs had been
performing their work properly.

SUMMARY

1. The peptone and glucose are taken up by the epithelial

cells of the villi, and passed on to the blood in the
capillaries inside the villi.

2. Emulsified fat is taken up by the epithelial cells of the

villi, and passed on to the lacteals within the villi.
From there it goes to the thoracic duct, and finally
is poured into the large vein at the root of the
neck.

3. About two gallons of fluid enter and leave the alimen-

tary canal each day.

96 APPLIED PHYSIOLOGY

4. The fat is carried to the lungs, and is there oxidized

to carbonic acid gas and water, each ounce of fat
using nearly three ounces of oxygen.

5. The gluc6se is carried to the liver, and from there is

given out in a steady stream and oxidized to car-
bonic acid gas and water, each ounce using a little
more than an ounce of oxygen.

6. The peptone is carried to the liver, and there is

changed back to the form of albumin adapted to
the blood and tissues of the body.

7. In the liver some albumin is oxidized, and the rest is

sent out as a part of the blood to feed the cells.

8. Poisons are often absorbed with the food, and are

carried to the liver. But the liver cells separate
out the poisons, and either destroy them or expel
them with the bile.

9. By intemperate eating the stomach is disordered.

Then more work is put upon the intestine, until
it fails in its duties. Then the liver has imper-
fectly digested food and more poisons to take care
of. Then a poor quality of bile is poured out.
Then the intestine fails still more in its work. So
the circle of cause and effect goes on, all depending
at first upon intemperate eating.

10. The last act of digestion, or the expulsion of waste
matters, should be attended to regularly every day.

DEMONSTRATIONS

48. Show the absorption of food in a young kitten or puppy
which had been fed with cream about two hours before being killed.
Place the animal in a tight box along with a sponge containing half
an ounce of chloroform. In a few moments the animal will be dead.
At once open its abdomen and spread out its intestine. Across its
fanlike mesentery will be seen white lines. These are lacteals, which

ABSORPTION AND ASSIMILATION 97

are carrying the emulsified fat from the intestine. The fluid looks
like milk, and so the name lacteals, or milk tubes, was given to the
tubes. (See demonstration 35.)

49. Probably some boy in the schoolroom who is suffering with a
bilious attack will be willing to show his tongue to the class. Notice
that it is covered with a thick white or yellow fur. Explain that the
tongue is a part of the alimentary canal, and that the stomach and
intestine are in a like condition. Explain that, when the rest of the
alimentary canal is acting well, the tongue is clean and the breath
sweet.

REVIEW TOPICS

1. Describe the diffusion of digested food into the blood.

2. Trace a particle of digested fat from the intestine to

the blood, and tell what finally becomes of it.

3. Describe how the liver uses digested sugar.

4. Describe how digested albumin becomes a part of the

blood, and tell of what use it is to the body.

5. Tell how the liver removes poisons from the absorbed

food.

6. Tell how a disturbance of digestion, in either the stom-

ach, intestine, or liver, disturbs each of the other
organs.

7. Show that each organ of digestion is perfectly adapted

to its own work.

OV. PHYSIOL. — 7

CHAPTER X
ALCOHOL AND DIGESTION

0

137. Summary of the action of alcohol. — The action of
Strong alcohol outside of the body is threefold. First, it
takes away water from substances which it touches ; sec-
ond, it hardens and coagulates albumin ; third, as a result
of the first and second actions, it impairs or destroys the
life of cells and of ferments with which it comes in con-
tact. Alcohol harms the body in these ways and also has
special effects upon parts which it does not touch.

138. Effects upon food. — Alcohol produces changes in
food in direct proportion to its strength and amount. If
the alcohol be strong, and large enough in amount to satu-
rate the food, then it may harden the albumin and render
it more difficult of digestion. It may also prevent the
pepsin of the stomach from acting. The habitual drunk-
ard may take strong drink in sufficient amount and strength
to produce this change in his food.

139. Effects upon the mouth. — In the mouth alcohol
may take water from the epithelial cells, and give rise to
a sense of thirst. Although the alcohol may be mixed
with enough water to satisfy natural thirst, yet it causes
a false thirst to arise, which demands another drink.

140. Effects upon the gastric juice. — When it reaches
the stomach, a very strong alcoholic drink has a marked
effect upon the gastric juice. The essential digestive
agent in the gastric juice is pepsin, which is a lifeless
albuminous ferment. The alcohol in any common form

98

ALCOHOL AND DIGESTION 99

of strong drink is in sufficient quantity to hinder or to
stop the digestive action of the pepsin. But when the
alcohol is absorbed or diluted, the pepsin can act as well
as ever.

141. Effects upon the mucous membrane. — Alcohol irri-
tates the mucous membrane of the stomach. Then more
gastric juice is produced in order to dilute the' irritating
alcohol. Thus the effect of the alcohol may be somewhat
overcome by the increased quantity of the digestive fluid.
But the alcohol may cause an increased flow of mucus
also, just as a cold causes the pharynx to produce more
mucus. The mucus may coat the particles of food, and
prevent the gastric juice from acting on them. This is
especially apt to happen when strong drink is taken con-
tinuously in small amounts, and for long periods. In such
conditions both the quality and quantity of the gastric
juice may be impaired.

A drink, such as even a moderate drinker often takes,
may produce redness, swelling, and inflammation of the
stomach. The effect is far greater when the drink is
swallowed upon an empty stomach, for then there is no
food to protect the mucous membrane from the direct
action of the strong drink.

142. Effects upon peristalsis. — The irritation of the
alcohol at first causes an increased action of the stomach
walls, so as to force the harmful substance away. Con-
tinuous use of strong drink is likely to weaken the muscles
and to make peristalsis much less. Then the food is less
perfectly mixed with the gastric juice and is not ground to
pieces, but remains too long in the stomach undigested.
The water and mucus poured out diminish the strength of
the alcohol, and this, together with the poor quality of the
gastric juice and the long stay of food in the stomach,

IOO APPLIED PHYSIOLOGY

permits fermentation to take place. Thus alcohol disturbs
every action of the stomach, and often produces the worst
forms of indigestion.

It is true that a little weak alcoholic drink will not produce all these
evil effects at once. Herein lies the danger. Alcohol is a deceitful
thing. Though the stomach gives notice that it is abused by the
drink, yet the mysterious thirst demands still more alcohol, and bribes
its victim with the memory of its pleasant sensation. So the poor
stomach suffers time after time, and before long becomes permanently
crippled.

143. Protection against alcohol. — When an alcoholic drink is
taken into the mouth, it irritates the mucous membrane. This causes
the saliva to flow and dilute the alcohol, so that at any one time it can
do very little direct harm. In the stomach it causes the gastric juice
to flow in the same way, and thus it soon becomes dilute and has little
direct effect. Even if the pepsin should separate from the gastric juice,
in a little while the ferment will dissolve in the increased quantity of
juice and perform its work well again. Nature may thus protect the
body for some time, but it cannot remove the danger.

144. Effects of alcohol upon the intestine. — By the time
alcohol reaches the intestine, it is usually too dilute to
produce much direct harm. But if it has deranged stom-
ach digestion, the work of digesting the food falls upon
the intestine. Thus intestinal digestion may be imperfect.
Alcohol itself is probably not changed by digestion. In its
diluted form it is quickly absorbed. Even when a large
amount is absorbed, little or none can be found in any of
the tissues or blood tubes. The only probable way of its
disappearance is by oxidation before it can pass beyond
the liver.

145. Effects of alcohol upon the liver. — Alcohol affects
the liver in three ways. In the first place strong drink is
apt to induce stomach and intestinal indigestion. Then
the liver must do an extra amount of work in completing the
imperfect digestion. Thus biliousness is often produced.

ALCOHOL AND DIGESTION IOI

If drinking is continued, the liver trouble is likely t0
persist.

In the second place the destruction or oxidation of
alcohol uses a large amount of oxygen which the liver
should use in assimilating food. Thus food is imperfectly
oxidized. While no products in the body can be traced
directly to oxidized alcohol, yet when alcohol is used poi-
sonous products of imperfectly oxidized albumin are always
abundant. These products circulate through the whole
body and produce far more harm than the original alcohol.
(Seep. 152.)

In the third place the liver cells are directly affected by
these abnormal actions. Long-continued drinking often
results in an incurable wasting away and hardening of the
liver tissues.

146. Unintentional forms of drinking. — There is a form of
alcohol which is used by many innocently and unintentionally. Many
a well-meaning person habitually uses " Strengthening bitters " after
meals, ignorant of the fact that they are only bitter herbs dissolved in
alcohol and water. Each dose is equivalent to a large drink of whisky.

Essence of Jamaica ginger is only ginger dissolved in alcohol, and
its effects are due mainly to the alcohol, and not to the ginger.

147. Intemperance in eating. — There is a common intem-
perance of eating too much starch and sugar. These sub-
stances can never be digested, absorbed, and oxidized with
sufficient rapidity to produce the intoxicating effects of
alcohol, but their excessive use deranges the liver in the
same manner as alcohol. In the first place, starch and
sugar are likely to ferment and produce a sour stomach
and intestinal indigestion ; this is probably the most com-
mon cause of biliousness.

In the second place, when too much sugar or other
food is oxidized too little oxygen is left for the albumin

IO2 APPLIED PHYSIOLOGY

of the food, then the products of incomplete oxidation
resemble those produced by alcohol ; but they usually pro-
duce no more than a sick headache or an attack of bilious-
ness, although under aggravated and repeated conditions
they may endanger life. (See p. 34.)

In the third place, the effect of a continual excess of
food is to injure the liver cells permanently. Even the
wasting away and hardening called "gin drinker's liver"
may be caused by intemperate eating. Intemperance in
eating differs from the intemperance of strong drink in
the quantity of effects produced rather than in their kind.

SUMMARY

1. Alcoholic drinks take water from the mucous mem-

' brane of the mouth and so increase the thirst, even
if the body contains sufficient water.

2. In any considerable amount alcohol hardens the pepsin

in the stomach, and so prevents its acting upon the
food.

3. Alcohol irritates the mucous membrane of the stomach

so that it becomes inflamed and unable to produce
the gastric juice. Then the intestine is overworked
in digesting what the stomach should have digested.

4. Alcohol is quickly absorbed by the intestine. It is

quickly destroyed, probably by oxidation, before it
passes the liver.

5. Because oxygen is used in the destruction of alcohol,

incomplete and poisonous products of the oxidation
of albumin are formed. These go through the whole
body and greatly increase the harm done by alcohol.

6. Bitters, and essence of ginger contain much alcohol.

7. When starch and sugar are eaten in large amounts,

they use oxygen which should oxidize the albumin.

ALCOHOL AND DIGESTION 1 03

So they can produce slowly the same kind of effects
as alcohol.

DEMONSTRATIONS

50. Hold some common salt in the mouth, and at once saliva flows
to dilute it. In a moment it can be held with comfort. Explain that
this is a provision of nature to protect the body from any irritating sub-
stance. The stomach may pour out an excess of gastric juice in the
same manner so as to protect the body against alcohol and other irri-
tating substances. Call attention to other similar ways in which nature
protects the body, as in the flow of tears to wash away a speck of dirt
from the eyes.

5 1 . Prepare two bottles to show artificial digestion (see demonstra-
tion No. 40). In the second one replace a quarter of the water with
alcohol and notice that no digestion takes place in this bottle. Explain
that this experiment may be misleading, for in the stomach more gastric
juice will flow to dilute the alcohol until the pepsin can act as well as
before. Explain that alcohol does not destroy the pepsin, but when the
alcohol is diluted, the pepsin is as good as ever.

REVIEW TOPICS

1. Give the three characteristic actions of alcohol outside

the body.

2. Give the action of alcoholic drinks upon the mouth.

3. Give the action of alcoholic drinks upon the mucous

membrane of the stomach ; upon its secretions ; and
upon the peristalsis of the stomach.

4. Tell why alcoholic drinks have but little direct action

upon the intestine and upon the villi.

5. Give the action of alcoholic drinks upon the liver.

6. Explain why bitters and essence of Jamaica ginger are

both harmful.

7. Explain the effects of intemperate eating.

CHAPTER XI
DIGESTION IN LOWER ANIMALS

148. Digestion in dogs. — All four-footed animals have
essentially the same digestive organs, secreting the
same juices as man. Their food, also, is absorbed and
assimilated in the same way, but there are slight modifica-
tions according to the kind of food eaten. A dog's stom-
ach and intestine have thicker walls, and their juices have
far more digestive power ; so dogs can digest even bones,
which form one of their regular articles of diet.

149. Digestive organs in cattle. — A horse lives upon
hay, which man cannot digest at all. Cattle have an
arrangement which enables them to gather a large amount
of food at once, and then to chew it at leisure. As grass
is eaten, it is swallowed almost whole. It goes first
to a small intermediate stomach, and then to a large
pouch called the paunch or rtimen, which in an ox holds
about two bushels. When this is full, the animal lies
down and proceeds to chew the food. It forces the food
back into the mouth in small masses, called the cud, which
it chews and swallows again. But this time the food is
guided on to a third stomach, whence it soon passes into
the fourth. The fourth stomach corresponds in size and
shape to man's, and is the true digestive stomach, while
the others are only storehouses and passageways for the
food.

104

DIGESTION IN LOWER ANIMALS

105

150. Digestive organs in birds. — Birds swallow their
food whole, for they have no teeth or strong jaws for
chewing. It first enters a pouch

called the crop, where it is soaked
in a fluid secreted there. It
slowly passes on to the stomach,
where it is mixed with the gastric
juice. Then it passes into a
muscular bag called the gizzard.
The walls of the gizzard are from
one fourth to one half an inch
in thickness, and its lining is a
thick, tough membrane. It con-
tains small stones which have
been swallowed. Its thick walls
roll the food about with the
stones, so as to grind it to pieces
and mix it with the gastric juice.
Then it passes into the intestine, where its digestion is
completed, as in man.

151. Digestive organs in insects and worms. — Insects
possess a stomach and intestine which secrete digestive
juices. They also have organs like the liver and pancreas.
Some insects masticate food, and others possess a gizzard,
which grinds the food after it is swallowed.

Worms generally possess a digestive tube which extends
straight through the body. Shellfish, as oysters and clams,
possess a stomach and a coil of intestine, which passes
through the heart. The large, dark-colored, rounded mass
at the back end of the oyster and clam is the liver.

152. Energy required in digestion. — Man's food requires
but little energy in its digestion, hence most of his energy can be
applied to physical and mental effort. To digest dog's food requires

Digestive organs of a bird.

a esophagus.
b craw, or crop.
c stomach.
d small intestine.
e gizzard.

106 APPLIED PHYSIOLOGY

more energy; to digest the food of cattle requires still more. The
lower the form of life, the more time and energy is spent in digestion,
and the less is the action of other parts, until the lowest forms of
animals simply live to eat, and remain at rest except when eating food.
A comparison of man's digestion with that of the lower animals is mis-
leading. Man's alimentary canal is designed to deal with food upon
which but little energy need be expended. More energy is thus avail-
able for his voluntary use. Because of his perfect food man can per-
form more labor and undergo more fatigue and exposure in proportion
to his size than any other animal.

SUMMARY

1. The digestive organs of all animals are similar to

man's, but modified according to the needs of the
animal.

2. Cattle swallow grass whole, and then chew it at leisure.

They have four stomachs.

3. Birds swallow food whole. It passes first into the crop,

and later is ground in the gizzard.

4. Insects, worms, and shellfish each possess a simple

stomach and intestine.

5. Man uses food which is more easily digested than the

food of any lower animal. Thus he devotes less
time to mere eating and digesting food.

REVIEW TOPICS

1. Show in what way and for what purpose a dog's diges-

tive organs differ from those in man.

2. Show the use of four stomachs in cattle.

3. Show how birds digest their food.

4. Point out how the digestive organs are modified in

worms ; in insects ; and in shellfish.

5. Show what advantage man's food gives him over the

lower animals.

CHAPTER XII
ANIMAL FOOD

153. Food elements. — Anything which, taken inside of
the body, supplies it with weight, heat, or energy is food.
Man's food consists of a great variety of substances de-
rived from the animal, vegetable, and mineral kingdoms.
Yet all food consists of the proximate principles : water,
mineral matter, albumin, fat, and starch or sugar. Neither
alone makes a perfect food, but all must be present in
proper proportions or else the body will suffer.

154. Water. — Water requires no digestion, but is con-
tinually entering and leaving the body unchanged in form.
All solid food contains some water, and enough more is
added in liquid food and in drink to supply the full needs
of the body. Twelve or fifteen pints of fluid are used
daily in the work of digestion, but it is absorbed back
again to the blood and so little is lost. Within reasonable
limits, water taken at meal times aids digestion. In order
to digest food and wash away waste matter properly, two
or three quarts must be swallowed daily. If the thirst is
satisfied with pure water, there will be little danger of
taking too much, and the indications of thirst will be the
most reliable guide as to the times of drinking and of the
quantity required.

155. Mineral matters. — Mineral matters are not changed
during digestion, and they leave the body in the same form
in which they enter. More than enough are found in all

107

108 APPLIED PHYSIOLOGY

ordinary food to supply the needs of the body. Only salt
needs to be added to food, but man often adds far more
than is necessary. Since water and mineral matters re-
quire no digestion, it makes little difference in what kind
of food they are eaten. But albumin, fat, and starch or
sugar require digestion, and some forms are more easily
digested than others, so a discussion of their forms in dif-
ferent foods becomes necessary.

/* 156. Digestibility of food. — In judging of the value of
food four things must be considered :

First. The time and energy required. — Some forms of
food require little or no energy in their digestion, while
others cannot be digested at all. Grass contains all kinds
of food substances, but man cannot digest it. The com-
bination of meat, fruit, and flour which we call mince pie
requires far more time and energy in its digestion than
the same substances in the form of roast meat, bread,
and fresh fruit, or in the form of a light pudding.

Second. The amotmt of indigestible matter. — All kinds
of food contain some matter which is wholly indigestible.
Only a little of fruit is digested. Careful experiments
show that ordinarily at least one fifth of the albumin of
vegetable food passes through the intestine undigested,
while only one thirtieth of meat is thus wasted. Animal
oil is easily emulsified and saponified, while vegetable oil
can scarcely be changed at all, but if eaten in any quantity
is a source of intestinal disturbance. Some wholly indi-
gestible matter in food is valuable, for it affords something
upon which the intestine can contract so as to force its
contents down the tube.

Third. The amount of energy developed by the food. —
Fat requires a large amount of oxygen in its oxidation,
and yields a large amount of heat and energy. Sugar

ANIMAL FOOD

requires only one third as much oxygen and develops less
heat and energy. So food rich in fat yields more heat
and energy than a food rich in sugar or starch.

Fourth. Liability to ferment. — A food requiring a long
time in digestion is more liable to ferment than one which
is digested in a short time. Sugar and starch ferment
easily, while fat ferments only with difficulty.

157. Milk. — Among all the different kinds of food milk
seems to be most perfectly adapted for man and for many
animals. The average cow's milk consists of

Water 86 per cent.

Albumin 4

Fat 4j "

Sugar 5

Mineral matter -|- "

Milk thus contains all the five different kinds of food
substances, which, moreover, are in about the proper pro-
portions to support life best.

The albumin, fat, and sugar of milk each re-
quires little time and energy in its digestion, and
leaves but little undigested residue. Milk is more J?
liable to undergo fermentation than some other o
kinds of food, but the quickness of its digestion
overcomes this objection. It develops heat and
energy in amounts best suited to support life. Fat globules in milk
Milk is thus an ideal food, and can be digested (X 300).

when all other kinds of food are rejected.

158. Caseine. — The albumin of milk is called caseine.
In its digestion the rennin ferment in the stomach coagu-
lates it in fine flakes, which the acid and pepsin dissolve to
peptone. When much acid is present in the stomach, as
after a meal, or when fermentation has occurred, the
caseine is apt to be coagulated in hard lumps which dis-

110 APPLIED PHYSIOLOGY

turb digestion, producing a bilious attack. The rennin
ferment is produced the more rapidly when milk is hot,
while the heat hinders the production of the acid of the
gastric juice. So if the milk is taken hot, it will be coagu-
lated in finer flakes, which the gastric juice can digest more
easily. If milk is taken slowly in any form, it is coagulated
in small amounts as fast as it enters the stomach, and so
no large lumps can form. If taken before meals, hot and
slowly, there are but few persons with whom milk will
disagree.

159. Fermentation of milk. — Many kinds of living germs are
continually falling into milk and growing, if the temperature is warm.
Some are germs which produce acid fermentation and turn the milk
sour. The acid coagulates the caseine, forming clabber. Germs of
disease also will grow in milk, especially germs of typhoid fever and oi
tuberculosis. Children are very easily affected by sour milk. Often
the germs of fermentation grow in their stomachs, souring the food
and producing summer complaint. Heating the milk steaming hot
destroys most of the germs, but not the poisons which have already
been produced. All cow's milk given to babies should be heated
almost to the boiling point in order to destroy the germs.

160. Cheese. — Rennet is often added to milk in order to
coagulate its caseine, which, when squeezed into a firm
mass, is cheese. The cheese holds the fat of the milk,
while the sugar remains in the whey. Cheese is about
one third albumin. It contains no sugar or starch. The
amount of fat which it contains depends upon how much
cream was left in the milk of which it was made. It is a
valuable article of food because of the large amount of
albumin always present. It is easily digested by healthy
persons. In some kinds germs are permitted to grow and
develop various acids and flavors which make the cheese
strong. These are somewhat harmful, but mild cheese fur-
nishes a cheap supply of good albumin.

ANIMAL FOOD III

161. Butter. — When milk remains quiet for some hours,
the fat rises to the surface in the form of cream. After
this is removed, milk is called skim milk. Cream is made
up of fine particles of fat, each surrounded by a thin
envelope of caseine. When cream is shaken until the
covering of the caseine is worn off, the fat collects in a
form called butter. The liquid part remaining is called
buttermilk, and does not differ much from milk, except
that the fat is mostly removed. Butter is the most valu-
able form of fat eaten.

162. Value of milk. In sickness milk is almost the
only food which the stomach can digest at all. Only about
one twentieth of the solid part of milk fails to be digested.
When only milk is taken, there is but little residue upon
which the intestine contracts, and so waste matters pass
down the tube more slowly than when solid food is eaten.
Those who eat much milk find it profitable to eat heartily
of substances which, like oatmeal, leave a large undigested
residue to sweep out the waste matters of the intestine.

163. Adulteration of milk. — It is difficult to set a standard
for perfect milk, for no two cows give it of exactly the same composi-
tion. Milk which has a good quality of cream usually contains a good
quantity of albumin and sugar and so is said to be rich. Such milk is
yellow, in distinction from the bluish color of poor or skim milk. The
richness of milk may be measured by observing how thick a layer of
cream will rise in a deep glass tube full of milk. Another way is to
determine how much solid matter the milk contains by means of a
lactometer. This is a closed tube weighted so that it will float upright.
As more solid matter is dissolved in the milk, it becomes heavier and
will more easily sustain a body floating upon it. The richer the milk,
the less the bulb and tube will sink. This instrument is called a
lactometer. By means of it milk brought into large cities is tested by
government inspectors, and all milk which falls below a certain standard
is thrown away. The lactometer really records the specific gravity of
the milk. If it falls below 1.029, ** *s considered to be either watered

112 APPLIED PHYSIOLOGY

or of too poor quality to be sold as good milk. While such milk may
not be injurious, yet it is a fraud to sell it at the price of good milk.
Skim milk is bluish in color from the loss of its cream. To make it
the color of new milk, burnt sugar is often added, and it is then some-
times sold as new milk. It is very apt to become sour from its being
kept for some days.

164. Condensed milk. — Large quantities of milk are boiled
until its water is evaporated and the milk is like thin jelly. This is
condensed milk. In order to keep it, sugar is added. Condensed milk
contains all the nourishment of new milk, with some sugar added. It
can safely be used in place of new milk for all cooking purposes. It is
too sweet to be used as a drink, but babies take it readily. Still it is
undesirable as a baby food, for it contains too much sugar.

165. Imitation cheese and butter. — Cheese made from skim
milk contains but little fat. It easily ferments and becomes dry, so
that it is very indigestible. There is an imitation of butter made from
beef fat, called oleomargarine. It scarcely can be distinguished from
real butter. Butterine is another imitation of butter made from beef
fat and butter. The manufacture and sale of both kinds of imitation
butter are permitted so long as the products are sold under their right
names.

166. Eggs. — Hens' eggs consist of

Water 70 per cent

Albumin 15 "

Fat 14

Mineral matter i "

Since they contain no starch or sugar, they are not a
complete food for man, although a perfect chicken may be
formed out of the egg, as the hen furnishes heat. The
white of egg is almost pure albumin dissolved in water.
The yolk is a mixture of albumin, fat, and water. Both
the albumin and fat of eggs are digested with little expend-
iture of time and energy, and develop a large amount of
heat and energy in their oxidation. They do not easily
ferment in the stomach and intestine, and only about one

ANIMAL FOOD 1 13

thirtieth is left over in their digestion. They are thus a
valuable food, but yet do not rank so high as milk.

167. Digestion of egg albumin. — When boiled for a minute
or two, the albumin of eggs is partly coagulated to a soft, jelly like mass.
Boiling for three minutes coagulates all the albumin to an elastic,
slippery mass ; while after boiling for ten minutes the albumin becomes
brittle, and is easily crushed to fine particles.

A lump of albumin of a raw egg is digested with less expense of
time and energy than the same sized lump of coagulated albumin, and
the longer an egg is boiled the more energy is required to digest it
back to a liquid form. But the raw egg has a tendency to collect
in masses which the gastric juice cannot penetrate.

An egg boiled for less than five minutes is usually masticated only
to medium-sized particles, which, however, owing to their smaller size,
may be digested sooner than the large masses of raw egg. But the egg
boiled for ten minutes is easily chewed fine, and, owing to the still
smaller size of its particles, is digested much sooner than small lumps
of soft-boiled eggs or the masses of raw eggs. Thus an egg boiled
for at least ten minutes is ordinarily the most available for digestion.
When mixed with a considerable quantity of milk, the raw egg is pre-
vented from forming a lump, and in this form it may digest more easily
than a cooked egg.

168. Quality of eggs. — Fresh eggs vary but little in composi-
tion. In time they lose a little water by evaporation through the shell,
which is porous. A fresh egg appears clear and pink when held in
front of a strong light, while an old egg appears dark-colored, even if it
has not begun to decay. It will first show a dark spot where the yolk
settles to the side of the shell, and later will be dark all through. This
test is reliable and is often applied in markets. The shell of a fresh
egg is bright in color and slightly rough like common newspaper, but
an old egg becomes duller in color and shiny in appearance like writing
paper. Ducks' eggs are nearly like hens1 eggs, except that sometimes
they acquire a peculiar taste from the ducks' food. Nearly all kinds of
birds' eggs, as well as the eggs of turtles, are used as food. They
differ but little from hens' eggs.

169. Meat. — The flesh of oxen, sheep, and hogs is the
common form of meat. All kinds of game, fowl, fish, and

ov. PHYSIOL. — 8

114 APPLIED PHYSIOLOGY

shellfish are of the same nature. The muscles form the
lean part of meat, but nearly every part of the animal is
sometimes used as food. Average meat consists of

Water 65 per cent.

Albumin 17 '

Fat 14

Mineral matter 4 "

Albumin is the principal part of meat. Beef has high
food value; mutton, fowl, and game rank next, in the
order named.

r>< 170. Digestibility of meat. — Meat varies greatly in
composition and digestibility. While man cannot digest
stringy connective tissue and tough skin at all, yet good
meat ranks next to milk and eggs, and exceeds all forms
of vegetable food in all the four points of digestibility. It
requires a small outlay of time and energy in its digestion,
and its oxidation develops a large amount of heat and
energy. It does not easily ferment, and only about one
thirtieth remains undigested.

Meat is often salted or smoked or dried, or prepared in
other ways so that germs of fermentation or decay will not
grow in it, and thus it can be kept for a long time. When
thus prepared, its fibers are partly coagulated and har-
dened, so that the gastric juice cannot penetrate them
readily. The digestibility of such meat is greatly impaired.
The toughness of meat is due to strings of connective tis-
sue, which are digested with difficulty and yield little heat
and energy to the body. Tender meat consists almost
wholly of muscular fibers, which are the main nutritive
parts of most meat. Since meat contains no starch or sugar,
some must be added in order to make it a perfect food ;
and, very properly, bread is generally used.

ANIMAL FOOD 115,

171. Soup and beef tea. — The water in which meat is cooked
is often eaten as soup. Soup contains some gelatine and fat, but only
a small amount of albumin, for most of the albumin is coagulated by the
heat, and thus prevented from dissolving. The water also dissolves the
mineral and waste matters of the meat.

Beef juice is made by heating the meat and pressing out the juice.
The best meat juice contains albumin and fat in about the same pro-
portions as milk.

Beef tea is a kind of concentrated soup. Mineral and waste matters
give it flavor. It is very poor in albumin and fat, and is of little value
as a food, while its waste matters may render it harmful. There are no
facts to warrant the assertion that beef tea contains some nutritious
essence of the meat which is of special value as food. Its value must
be judged solely by the amount of albumin and fat which it contains.
Extracts of meat are sold, a teaspoonful of which added to a cup of
water is said to contain the nourishment of a pound of beef. They
consist of mineral and waste matters dissolved in water, and so are of
no value as food. Their taste may be pleasant, and this may assist in
the digestion of other food.

172. Fresh meat. — As a rule any meat is most whole-
some if it is eaten soon after being killed. In the markets
beef is usually hung in a room whose temperature is nearly
freezing. There it remains fresh for weeks, or even months,
and at the same time it becomes more tender and improves
in flavor. When taken out and exposed for sale, it spoils
much sooner than newly killed beef. If there is the slight-
est musty or decayed odor about meat, it is undesirable as
food.

Game animals are often hung just as they are killed,
until they are distinctly decayed, so as to develop peculiar
flavors. Fowl and game are liable to be unwholesome if they
are kept for many days without being opened and cleaned.

173. Points of good meat. — (i) Tender meat usually comes
from well-fed animals, and such animals are always fat. A layer of fat
from one fourth to one half inch in thickness, covering the outside of
the meat just under the skin, usually denotes a well-fed animal. The

Il6 APPLIED PHYSIOLOGY

•fat will also extend in fine white streaks irregularly in every direction
through the meat and can be clearly seen upon its cut surface.

(2) The fat is deposited in the connective tissue which inclose?
separate bundles of muscles. If these bundles are from one eighth to
one fourth inch in diameter, and preserve their shape when the finger
is passed over them, they contain much connective tissue, and the meat
is tough, as in meat from the neck. When a slice of such meat is
gently pulled apart, the bundles separate from each other, and are con-
nected together by strong, veil-like meshes qf connective tissue.

On the other hand, if the bundles of muscle are small and not well
marked, the connective tissue is small in amount. When a slice of such
meat is pulled apart, its bundles do not separate, but the whole piece
•stretches.

(3) The cut edge of good beef soon becomes bright red in color.
When the connective tissue is abundant between the bundles, it im-
parts a paler tint to the meat, and sometimes a bluish tinge. Good
pork and veal are pale or almost white in color, but in other points
resemble beef (see p. 218).

Good meat has an agreeable odor and is clean. Excepting as
it is marked by connective tissue and fat, it should be of a uniform
tint.

174. Fish. — Fish contains albumin about sixteen per
cent, fat about six per cent. It is digested with rather less
•ease than meat, but it can take the place of meat as food. It
used to be thought that it contained more nourishment for
the brain than other kinds of food, but the brain is nour-
ished by the same substances as the rest of the body, and
fish is hardly so good for it as beefsteak.

Fish should always be eaten while fresh, for it is espe-
cially liable to decay.

175. Shellfish. — Shellfish, as oysters and clams, contain
about sixteen per cent of albumin and three per cent of fat.
The large dark mass in their bodies is the liver, which con-
tains some sugar. When eaten raw, their own digestive
fluids and their livers aid in the digestion of their bodies.
When cooked, they require more time and energy for their

ANIMAL FOOD

digestion. Because of their ease of digestion, fresh raw
oysters are a valuable food in sickness. Crabs and
lobsters also are good food if well cooked.

176. Blood. — Blood is digested with difficulty. It contains little
albumin and fat and no sugar. It adds nothing to the value of meat,
and is very liable to decay. It should always be removed, as is usually
done in killing the animal. By the law of Moses the Jews were forbid-
den to eat the meat of animals which had not been bled to death.

177. Inferior meat. — Meat cannot be adulterated, but inferior
meat is sometimes sold as good meat. Old meat is sold for fresh meat,,
and tough meat for tender. Very young animals are dangerous as food,,
and yet they are often sold. Meat from sick animals is always unfit for
use. In France, horseflesh is sold for food under its own name, and in
this country it is sometimes substituted for beef in cheap shops.

178. Diseased meat. — Meat sometimes contains living germsr
which may produce disease in those who eat it. The most common
disease to be feared is tuberculosis, or consumption. Beef cattle are
especially liable to have the disease, which may be located in their
muscles as well as in any other part of their bodies, and is difficult of
detection.

A tapeworm passes one stage of its existence in the muscles of an
animal. Its eggs are accidentally eaten by an animal, and develop into
minute worms, which pass through the walls of the stomach into the
muscles and there form white cavities about the size of a pin head,
in which they lie quietly. When flesh containing such a worm is
eaten and digested by man, the worm is set free from its cavity, and,
fastening itself to the inside of the intestine, grows to many feet in
length. It lays eggs which will grow only when eaten by a lower
animal.

In pork there are sometimes found microscopic worms called trichina.
In the muscles of man they may grow and multiply enormously. The
disease which they cause is both painful and deadly. It is extremely
rare, at least in this country.

179. Prevention of disease. — A sure preventive against any
of these diseases is thorough cooking, for heat destroys all living germs.
It has not been proved that salting and smoking meat kills the germs
in it. There is no way of making musty or spoiled meat fit for food.
Such meat never should be used.

Il8 APPLIED PHYSIOLOGY

SUMMARY

1. Milk is the most easily digested and most perfect of

foods.

2. Hens' eggs contain an abundance of albumin and fat,

but no starch or sugar. They are next to milk in
ease of digestion.

3. Next in order come meats, including fish and shellfish.

4. Of meats, beef has high food value ; mutton, fowl, pork,

game, fish, and shellfish rank next, in the order named.

5. Animal food in general is easily and quickly digested

and only about one twentieth remains undigested.

6. Meat should be fresh and from a healthy animal.

DEMONSTRATIONS

52. Show samples of fresh milk and skim milk. Curdling of milk
can be shown by adding vinegar to milk and gently stirring it until the
curd collects in a lump. Show that this is cheese. By setting some
milk aside in a deep bottle, the amount of cream which rises can be
shown. Butter can be made from some cream, but the process is
uncertain, especially in winter.

53. Test some milk with a lactometer or a specific gravity bulb. In
good milk it should sink to i .030.

54. By cutting a hole in a piece of pasteboard and holding eggs in it
in front of a lamp in a darkened room, contrast the bright pink of a
fresh egg with the dull color of a stale egg, as is done in testing eggs
in the market.

55. Show some fresh meat and some that is stale. Show some very
tender and some very tough meat. Show that the toughness of meat
is due to white strings of connective tissue.

REVIEW TOPICS

1. Give a definition of food and tell what five substances

are used for food.

2. Show why an abundance of water is needed in food.

ANIMAL FOOD

3. Show why salt is the only mineral which man adds to

his food.

4. Give the four points which determine the digestibility

and value of a food.

5. Show that milk is a perfect food and how it may be

used to the best advantage, and how to avoid dis-
eases which it may contain.

6. Show how to distinguish good milk from poor, and

describe two methods for testing it.

7. Describe cheese.

8. Describe butter and its imitations.

9. Show how eggs are valuable as food and how they are

deficient and how they had best be eaten.

10. Show how a good egg can be told from a spoiled one.

1 1 . Show how meat is valuable as food and how it is de-

ficient.

12. Compare beef tea with meat.

13. Compare fresh meat with meat which has been kept

and with decayed meat.

14. Describe what diseases may be transmitted by meat,

and how to avoid them.

15. Show how to select good meat in the market.

1 6. Show how fish and shellfish resemble meat.

CHAPTER XIII
VEGETABLE FOOD

180. Grain. — Food prepared from grain contains

Albumin .... 8 per cent to 1 5 per cent.

Starch or sugar . . 50 " to 75 "

Fat I " to 10 "

Mineral matter . . I " to 3 "

Some forms of its starch or sugar are digested with a
considerable expense of time and energy, and there is
always a considerable portion left over. From grain
nearly all the starch and sugar of food is obtained.

181. Gluten. — The albumin of most grains is called
gluten. It is easily dissolved in water and gives the
sticky character to a mixture of flour and water. Its
digestion requires an expenditure of more time and energy
than the digestion of most forms of animal albumin, but
its oxidation yields the same amount of energy. About
one fifth is left undigested, whereas only one thirtieth of
animal albumin is left.

The husks of the kernels of grain and the cellulose frameworks
within are wholly indigestible. When milk is digested, there is little
waste matter upon which the intestine can contract. A food like grain,
which leaves much waste matter, furnishes something upon which the
intestine can contract, and thus sweep the waste matters on and out of
the body. For this reason vegetable food is of use aside from its
nutritive value.

VEGETABLE FOOD 121

182. Fermentation of grain in the alimentary canal. —

Owing to its large amount of starch and sugar, and to its comparatively
slow digestion, grain foods are liable to ferment. Fermentation will be
the least apt to occur with a mixture of about equal parts of animal and
vegetable food.

183. Bread. — Bread is the most common form of food
made from grain. Usually some means are employed to
make the bread porous and soft. Yeast is commonly
added. Its germs grow and change the sugar of the flour
to carbonic acid gas and alcohol. The gas, bubbling
through the wet and sticky flour, puffs it up and fills it
with small cavities, whose form the stiff and sticky gluten
preserves. Corn meal has but little gluten to make it
sticky, and so it will not preserve enough porous character
to form a loaf of bread.

Instead of yeast, baking powder is often used to make
bread or biscuit light. The powder develops carbonic acid
gas, which bubbles through the dough. Nearly all baking
powders are minerals, and their use in large quantity is
undesirable.

Bread made from wheat flour requires less energy in its
digestion than any other kind of vegetable food. Since
some starch must be eaten, bread, in combination with
milk, eggs, and meat, forms the best diet for everyday
use. Rye flour makes nearly as good bread as wheat flour.

184. Other forms of grain food. — Biscuit is bread with a
little fat added and baked in small lumps.

Cake is a mixture of flour, eggs, fat, and sugar. A large amount of
fat or shortening tends to make it indigestible.

Pancakes are made of flour, corn meal, or buckwheat flour. If they
are light and well cooked, they are of as much value as bread.

Cracked wheat and other preparations of wheat are often boiled in
water, forming a mush or pudding. This has the composition and
digestibility of bread.

122 APPLIED PHYSIOLOGY

Corn meal boiled, or made into pancakes or corn bread, is almost as
easily digested as wheat flour. It contains a larger amount of fat than
any other grain.

Oatmeal when boiled to a mush is a very popular article of diet. It
requires more time and energy in its digestion than any other common
grain food. It leaves a large amount of undigested residue, which
sweeps out other waste matters as it is forced down the intestine.

Rice is poorer in albumin and richer in starch than any other grain.
But when animal food is used in connection with it, there is no better
combination of food, for it is the equal of flour in digestibility.

Barley is but little used as food by man. It contains little albumin
but a large amount of starch.

185. Ways of preparing grain. — The finest grades of flour
make bread which is digested with less cost of energy and with less
residue than flour from the' whole grain, while there is but little differ-
ence in the amount of albumin and starch which they contain. Hot
bread is injurious only when it is moist and sticky so that it cannot be
chewed to fine morsels. Old bread is more easily digested than new
because it is harder and drier, and so can be chewed fine.

186. Beans and peas. — Beans and peas contain

Albumin about 25 per cent.

Starch "60

Fat " 2

Their albumin has much the same composition as the
caseine of milk, and is called legumin. It requires a large
expenditure of time and energy in its digestion. Both
legumin and the starch are very liable to ferment in the
intestine and produce gases. At least one fifth remains
undigested. Beans and peas are good foods for an out-
door laborer who has a great deal of spare energy.

187. Potatoes. — Potatoes contain

Albumin 3 per cent.

Starch or sugar 22

Water 75

VEGETABLE FOOD 123

They are very poor in albumin, but rich in starch, so they
go well with meat and eggs. Potatoes require a greater
amount of time and energy in their digestion than bread
and yield less heat and energy, and leave more undigested
residue, and are more liable to ferment.

188. Difference between animal and vegetable food. —

Animal and vegetable foods differ in several particulars :

First. Animal food requires less energy in its digestion. Animal,
rather than vegetable, food is light diet.

Second. Because of its longer time of digestion, and of the larger
amount remaining undigested, vegetable food is more liable to ferment
in the stomach and intestine, so that in severe sickness vegetable food
is usually entirely withheld.

Third. Vegetable food alone contains too much starch and sugar
for the needs of the body. Fermentation is thus promoted. When
absorbed, sugar is more readily oxidized than fat or albumin, and an
excess of sugar takes oxygen from other parts of the body.

189. Special use of vegetable food. — While animal albu-
mins and fats are more easily digested, and furnish a greater
supply of heat and energy than the same kind of food of
vegetable origin, it by no means follows that man should
use them to the exclusion of vegetables. Their very ease
and completeness of digestion may lead one to eat too
much. Man's mouth and stomach combine the character-
istics of herbivorous and carnivorous animals, and he will
enjoy the best health when both classes of food are used.
He must use some vegetable food for the sake of its starch
or sugar.

190. Effect of cooking. — The distinctions between food
just given were based upon experiments made upon healthy
men, who ate slowly, and masticated food properly cooked.
All vegetable food should be cooked so that it is a dry and
crumbly mass which the digestive juices can easily pene-

124 APPLIED PHYSIOLOGY

trate. Thorough cooking renders all kinds of food more
digestible. Raw starch is indigestible.

191. Green vegetables. — There are many kinds of vege-
table food which supply little weight, heat, or energy to
the body, yet are often eaten because of their agreeable
taste. Beets, turnips, carrots, parsnips, pumpkins, and
melons are poor in albumin. They contain some starch
and sugar and much fibrous substance wholly indigestible.
Their agreeable taste may increase the flow of the diges-
tive fluids, and their bulk may excite the peristalsis of the
intestine.

Tomatoes, cabbage, cauliflower, onions, asparagus, and
all other green vegetables are still poorer in food mate-
rial, and are especially liable to ferment in the intestine.

Green vegetables, such as cucumbers, which are eaten
in an unripe state, are wholly indigestible. Thus they
may pass through the intestine almost unchanged, or they
may ferment and produce pain.

192. Iron in vegetables. — Green vegetables contain a
considerable quantity of iron-bearing albumin or nucleo-
albumin, while grain and animal food contain only a small
quantity. This form of albumin is easily destroyed in the
intestine if fermentation of food takes place. Under these
circumstances green vegetables, by furnishing an abun-
dance of this material, are a real food. Those should
be chosen which do not readily ferment. Of them all,
probably celery and spinach are best.

193. Fruit. — Fruits, such as apples, pears, plums,
peaches, and berries, have little albumin which man can
digest, but often have a large amount of sugar. Their
chief use is to fill the intestine when a food is eaten
which, like milk, leaves but little undigested matter to sweep
along with the bile and other waste matters. But all fruits

VEGETABLE FOOD

are liable to ferment in the intestine. Grapes contain
more albumin than almost any other fruit, while their
sugar is the form produced by digestion. For these
reasons they arft^asily digested, and are a real food.
Bananas also contain much albumin and sugar. Green
fruit is digested .with difficulty and is very liable to injure
the stomach. Over-ripe and decayed fruits often contain
poisons which produce violent sickness. Only a small
quantity of any fruit should be eaten at once.

194. Tart fruits. — Oranges, lemons, «rhubarb, and such tart or
sour articles of food are often said to be "cooling" to the blood. When
the appetite fails, and the mouth is dry with a false thirst, their sourness
excites the flow of the alkaline saliva, and so the mouth and tongue
become moist, and the false thirst is relieved. In long voyages and
expeditions, when fresh food cannot be obtained, they are of value in
warding off scurvy. When eaten at meal times, the acid of sour fruits
hinders the production of the gastric juice, and thus retards rather than
aids digestion. In the stomach the acids unite with the mineral matters
of the food, and then are absorbed into the blood. Their presence in
the blood seems to have some effect on the nutrition and action of the
cells, and on this account they are sometimes given as medicine. They
seldom take part in building up the body, but are quickly thrown off
by the kidneys. The popular idea of their cooling effect is derived
mainly from the fact that they excite the flow of saliva, and thus render
the mouth moist.

195. Nuts. — Nuts contain oil, but it is doubtful if much
of it is emulsified and absorbed. They contain an abun-,
dance of albumin and starch, but their digestion usually
requires more time and energy than the stomach of man
is designed to furnish.

196. Canned food. — When food is heated so as to destroy its
living germs, and then is at once sealed air-tight, it will neither decay
nor sour, and when opened a long time afterwards it will be found to be
as fresh and wholesome as when it was put into the can. Thus it is
possible to carry fresh meat and vegetables on long voyages or to remote

126 APPLIED PHYSIOLOGY

and cold countries. When carefully prepared, canned food is as whole-
some as food recently cooked. When opened it soon spoils.

197. Scurvy. — When men have been living for months
upon bread and salt meat, without fresh food, there some-
times comes a disease called scurvy. Th6 gums become
sore, and the legs ache and turn "black and blue" as
though they were bruised. Then fruit or green vegeta-
bles are of the highest value, probably because they fur-
nish a good supply of nucleo-albumin, in which old bread
and salt meat are apt to be deficient.

198. Seasonings. — Pepper, mustard, nutmegs, cloves, and all such
sharp-tasting things are added to food simply for their taste. They are
probably neither digested nor oxidized, and yield neither weight, nor
heat, nor energy. They irritate and burn the stomach just as they do
the mouth. Yet their pleasant taste may be of value in promoting the
flow of the digestive juices.

199. Tea and coffee. — Tea and coffee are often sup-
posed to supply food to the body. They belong to the
class of substances which, acting through the nervous
system, spur on the work of the cells of the body, espe-
cially of the brain. They supply no heat or energy for
the extra exertion. Substances which excite the cells to
action, without giving them material out of which to
develop heat and energy, are stimulants. The active
principle of tea and coffee is a stimulating substance
called caffeine which spurs the cells of the body to do
more work. They enable a person to do a larger amount
of work in an emergency, and when the body is tired they
rouse the digestive and assimilative organs to renewed
activity, so that these quickly prepare a new supply of
food. When they are used continually the body learns to
rely upon their stimulation. Thus a habit of drinking them
is formed which is not easily broken.

VEGETABLE FOOD I2/

200. Tannin. — Coffee and tea also contain some tan-
nin, which is a substance used in the manufacture of
leather. It puckers and contracts albumin with which
it comes in contact, and is liable to hinder digestion.
Much of the bad effect of strong tea is due to its tannin.

201. Volatile oils. — Both tea and coffee also contain a
considerable quantity of an oil, which gives the drinks their
peculiar odors and flavors, but which evaporates quickly.
It is mainly this oil which produces headache and sleep-
lessness and other troubles, when large quantities of tea or
coffee are taken. Yet both drinks agree with the stomach
better when the oil is retained in the drink.

202. Preparation of tea and coffee. — Both the caffeine and
the oil of tea and coffee are easily dissolved by, boiling water, but by
long boiling the volatile oil is driven off in the vapor, and a large
amount of tannin is extracted. Both these results are undesirable, and
can be avoided by pouring boiling water over the tea and coffee, a^id
then steeping it slowly for only a few minutes.

Coffee will be digested more easily if the milk which is added is
boiled with the coffee. Better still would be to add no milk at all.

203. Adulteration of tea and coffee. — It is easy to add the
leaves of other plants to tea leaves. Green teas are often colored with
copper.

Coffee is adulterated with all kinds of roasted roots. A root called
chicory is cultivated especially for this purpose.

204. Cocoa. — Cocoa contains a small quantity of a sub-
stance which stimulates like caffeine. It also contains a
considerable quantity of albumin and fat, both of which
will dissolve in water. Thus it is more of a food than tea
or coffee, and its use is less likely to cause indigestion.
Chocolate is a preparation of cocoa.

205. Use of tea and coffee. — Tea and coffee are not
necessities, and men would be just as healthy without
their use. They have a reputation of retarding waste

128 APPLIED PHYSIOLOGY

of the body, but this view is not founded upon definite
experiments. The nervous system of children is easily
impressed by tea and coffee, and their bodies cannot stand
the stimulation and extra work which these substances
induce. When long and fatiguing work must be done or
great exposure endured, then tea and coffee are valuable
stimulants.

206. Adaptation of man's stomach to certain foods. -
Green vegetables, fruit, and grass contain the proper
quantities of food elements to support man's life, but
man cannot digest them readily. Lower animals eat the
food and expend their digestive energies on it ; finally,
when man eats it in the form of milk, eggs, or meat, it
needs but little further digestion.

SUMMARY

1. Grain is the main source of vegetable food.

2. Grain albumin, or gluten, is digested at more expense

of time and energy than the albumin of animal food.

3. Grain food contains much starch, and must be eaten

to supply this element.

4. Grain food is more liable to ferment than animal food.

5. Bread is the form of grain most available for digestion.

6. Boiled preparations of grain contain the same food

elements as bread.

7. The most valuable of the grains which are usually

eaten boiled are rice, cracked wheat, corn meal, and
oatmeal.

8. Cake and biscuit may be considered as forms of bread.

9. Beans and peas are rich in albumin and starch, but

require a great deal of energy in their digestion.
IO. Potatoes are poor in albumin but rich in starch. Their
digestion requires much energy.

VEGETABLE FOOD I2Q

11. Animal food in general fulfills the points of digestibil-

ity better than vegetable food.

12. Green vegetables and fruit are of value because their

taste may excite the flow of digestive fluids ; the
large residue left after their digestion may sweep
waste matters down the intestine; and they may
form a supply of nucleo-albumin when the supply
in ordinary food is deficient.

13. Green vegetables and fruit should be eaten a little at

a time, because of their great liability to undergo
fermentation.

14. Tea, coffee, and cocoa spur the cells on to renewed

activity when the body is tired or weakened.

DEMONSTRATIONS

56. Grain albumin, or gluten, can be separated by mixing a small
mass of dough of wheat flour and gently washing out the starch by
kneading it under water. The gluten will be left as a stringy, sticky
mass. The starch in grain can be shown by the iodine test (page 31).

57. Show samples of bread, both light and heavy, sweet and sour,
well-baked and under-done, new and stale, and hot and cold. Show
that the difference between the last three pairs depends upon the one
kind forming a pasty mass when wet or chewed, while the other kind
may be broken into fine particles.

58. Show samples of properly cooked and of improperly cooked
rice, oatmeal, etc.

REVIEW TOPICS

1 . Give the composition of grain.

2. Describe the albumin of grain.

3. Describe bread and the process of its manufacture.

4. Describe foods which are like bread.

5. Describe the various kinds of grain which are eaten

when boiled to a mush.

OV. PHYSIOL. — 9

I3O APPLIED PHYSIOLOGY

6. Give the difference of digestibility between bread

made from unbolted and fine flour; between hot
and cold bread ; between new and old bread.

7, Give a reason why grain food should not be sweetened.

8, Describe beans and fleas.

9. Describe potatoes.

10. State why the method of cooking and the manner of

eating make a great difference in the value of
vegetable foods.

11. Give the main points of difference between animal

and vegetable foods.

12. Name the food elements in green vegetables and in

fruits.

13. Give the important uses of green vegetables and fruits.

14. Tell how green vegetables and fruits should be eaten.

15. Show that man's stomach is adapted to certain kinds

of food only, and tell how all kinds of food may
ultimately become adapted to his use.

16. Give the active principles of tea, coffee, and cocoa,

and the effects of each upon the body.

17. Name the food elements in milk; in eggs; in meat;

in grain ; in potatoes ; in beans.

1 8. Give the organ in which each of the following foods

are acted upon, the digestive fluids which act upon
it, and the chemical change produced by each fluid :
milk, eggs, meat, bread, butter, grain food, potatoes,
beans.

CHAPTER XIV
QUANTITY OF FOOD REQUIRED

207. Amount of food elements required. — Although
oxidation is continually going on in each cell of the bodyj
only a small part of the albumin eaten is required in their
reconstruction; the remainder and all the sugar and fat
are oxidized without ever becoming a part of the living
cells of the body. The amount of heat produced is meas-
ured in Calories, one Calorie being the amount of heat re-
quired to raise the temperature of I kilogram of water i° C.

In order to repair the waste caused by the oxidation of
the cells, and to supply the requisite amount of heat and
energy, the average man must assimilate daily about 13^
ounces of food, with a heat value of about 2250 Calories, as
follows : —

CALORIES
PER Oz.

TOTAL
CALORIES.

Albumin
Fat
Sugar (or sta

I32

285
110

554
1140

55°

4 "

rch) S "

208. Amount of oxygen required. — The amount of oxy-
gen needed to oxidize this food is found from pages 34, 35,
to be about twenty-four ounces. The average amount of
oxygen taken in daily by the lungs is twenty-four ounces.
When more food is eaten than this amount of oxygen can
oxidize, some of the albumin is changed to fat, which
increases the weight of the body.

Anything which causes the lungs to take in more oxygen

132

APPLIED PHYSIOLOGY

will enable the body to oxidize more food. So the laborer
breathing deeply of fresh air is less troubled with the bad
effects of over-eating than a clerk in an office.

209. Oxidation of an excess of sugar. — Sugar is more
rapidly oxidized than other food, and when too large a
proportion of starch or sugar is eaten the other food is
incompletely oxidized, and sickness is the result. A
greater proportion of starch is required when more heat
and energy are needed, as in physical labor.

210. Selection of diet. — To supply the proper elements,
a variety of food may be selected, of which the following
diet for twenty-four hours is a typical example.

OZ. OF

ALBUMIN.

OZ. OF

FAT.

OZ. OF

SUGAR.

7

ounces of bread contains . . .

0.7

0

4.2

3

5 " eggs (2) « . . .

0.5

0.5

O

M

« meat « ...

2.5

2

0

24

« milk(iipt)" . . .

0.9

I

1.2

i

5 « butter « ...

O

i-5

0

Total

4.6

5

5-4

Allowing for the amount usually left undigested, there
would remain about the proper amount of each kind of
food element. This food contains more than enough min-
eral matter to supply all the needs of the body.

211. Choice of food. — The price of food has little to do
with its nourishing qualities. Fine taste, good appearance,
and rarity are usually what make foods costly. The
cheaper kinds are quite as nourishing as the more fashion-
able, and will taste as good if they are well cooked. About
three fourths of a laborer's wages are spent for food.
Cheaper meats and fish, with less sugar and desserts, will

QUANTITY OF FOOD REQUIRED 133

furnish him a better diet, and at less cost. It is as bad
economy for a poor man to buy the best of food as it is for
him to buy silk and broadcloth clothing. Scraps and food
left over from the table are as good quality as ever, and
should be saved for the next meal.

212. Amount at a meal. — Rules prescribing the amount
of food to be eaten at once cannot be given, any more'
than fixed rules regulating the amount of wood to be
added to the fire in a cooking stove. Hunger and taste
are reliable guides when plain food is eaten slowly.

213. Too much food. — In some persons the stomach cannot
digest and absorb food so fast as the lungs can furnish oxygen for its
oxidation. While these persons eat -heartily they generally remain
thin, for, instead of accumulating food, they use it up in developing
energy for active work. They are apt to overwork their stomachs and to
suffer from indigestion. They need nutritious and easily digested food.
Other persons can digest food faster than the lungs can supply oxygen
for its oxidation. These persons eat little, but, since the slow oxidation
allows food to accumulate, they are apt to be fat and lazy and to suffer
from lung troubles. By allowing their strong stomachs to act upon the
less easily digested foods their appetites will probably be satisfied, and
still not enough food will be digested and absorbed to overtax their lungs.

214. Starvation. — When man is deprived of all food, life
is supported by the oxidation of his own flesh as long as it
lasts. In from six to ten days a man will lose two fifths
of his original weight, and then death occurs. When water '
is given, life will last for a much longer time.

215. Brain food. — Brain workers require the same kind of food
as the laborer. In its action the brain uses heat and energy, the same
as any other part of the body. Fish is no more a brain food than beef-
steak. Phosphates, which are popularly supposed to nourish the brain,
are arrested at the liver ; but they stimulate the liver to greater activity^
so that food is more perfectly assimilated, and thus greater strength is
given to the brain cells, as well as to the rest of the body. Phosphorus
is found in most foods in greater quantities than the body needs.

134 APPLIED PHYSIOLOGY

SUMMARY

1. About four ounces of each of the food elements —

albumin, fat, and sugar — must be eaten daily.

2. To oxidize this amount of food requires about twenty-

four ounces of oxygen, which is about the amount
breathed in.

3. A diet of bread, eggs, meat, milk, and butter will fur-

nish the best food elements.

4. If too much sugar or starch is eaten, the albumin and

fat are not fully oxidized.

5. If too much food is eaten, all the oxygen is used up,

and there is none left for an extra exertion.

6. If little or no food is eaten, not enough heat and energy

are produced to keep the body alive.

DEMONSTRATIONS

59. Weigh out the different amounts of bread, eggs, meat, milk, and
butter which are required daily. Also measure out a quart of water.
This will show the class the amounts of food required daily.

60. Weigh out the required quantities of albumin, fat, and sugar.
Albumin may be represented by gelatine or glue.

REVIEW TOPICS

1. Give the amount of albumin, fat, and sugar required

daily.

2. Give the amount of oxygen required to oxidize the food.

3. Give the results of oxidizing an excess of sugar.

4. Give the amounts of bread, meat, etc., required daily to

furnish the body with the proper amount of albumin,
fat, and sugar.

5. Give the best times for eating.

6. Give the effects of eating too much food ; of too little.

CHAPTER XV
DRINKING WATER

216. Pure water. — Water is the only food which man
habitually takes without its previous preparation. Water
is the same from whatever source, but substances dissolved
in the water change its appearance. Carbonic acid gas,
oxygen, and air are dissolved in all ordinary water, and in
it float particles of dust and often a few harmless living
germs. Such water is clear and colorless. It has a slight
taste, due to the dissolved air. When the air is expelled
by boiling, the water is insipid and almost tasteless.

217. Hard and soft water. — Water also contains a vari-
able amount of mineral matter, especially lime, soda, and
potash. Water containing lime makes the fingers feel
slightly rough and puckered. The lime combines with
soap, forming a scum which will not dissolve. Water con-
taining lime is said to be hard, while water with little or no
lime is soft. Although some gases and minerals are dis-
solved in all water, they are harmless and do not make it
impure, but rather they give it a more pleasant taste.
When very hard water is boiled, some of the lime is
deposited on the sides of the kettle, and the water is
improved but not made soft.

218. Mineral waters. — When much mineral matter is present
the water is called mineral water. The principal minerals thus found
in water are salt, lime, soda, potash, iron, and sulphur. These waters
form springs in various parts of the country, and have borne a great

135

136 APPLIED PHYSIOLOGY

reputation as healing agents even among the Indians. Enormous
quantities are sold for drinking and medicinal purposes. Some contain
one or two ounces of mineral substance to each gallon of water. Some
springs contain almost pure salt, and furnish the greater part of the
table salt in common use.

Water in city houses often contains iron rust from the pipes through
which it passes, but the rust is not harmful to health. The water may
dissolve some poisonous lead if it stands in lead pipes, but if it is allowed
to run for a moment, the lead will be washed out.

219. Impure water. — When water becomes impure, the
water itself does not change its nature or become poison-
ous. Its impurities are substances which either float in
the water or are dissolved in it. They consist largely of
harmless clay and mud which are carried by running water,
but soon settle to the bottom in quiet water. Other impuri-
ties are vegetable matters, such as the remains of leaves and
wood, but these too are usually harmless. Streams and
ponds which usually furnish wholesome water are often
cloudy and muddy after a rain, but become clear and whole-
some again after the water becomes quiet.

220. Decayed matters and disease germs. — The princi-
pal substances which make water dangerous to health are
disease germs. If water contains no disease germs, it will
seldom cause sickness, even though it be muddy and dis-
colored and have a bad taste and odor. The germs are not
produced by the water, or the soil, or the air, but come only
from diseased men or animals. In desert and uninhabited
places all the water is usually wholesome, for no sick per-
sons are there to produce disease germs ; but wherever waste
matters are given off from the bodies of sick men or animals,
there germs of disease are almost sure to be found. For
this reason water which contains even a trace of decaying
animal substances is dangerous to health, for it is likely to
contain disease germs. The germs may remain alive after

DRINKING WATER 137

the substances themselves have become so far decayed that
they dissolve like salt and leave the water clear, and odor-
less, and tasteless.

221. Source of impurities. — The usual way in which
disease germs reach drinking water is by means of sew-
age, and slops, and barnyard drainage. There is hardly
a house in which, during a year's time, some sick per-
son does not give off disease germs. The germs are
found in all the waste matters which come from the sick
person's body and in the dish water and bath slops from
the house. The germs may live and grow in the slops
after they have been emptied, and may find their way into
a well, and thus may reach any one who drinks the water.
They may be washed into a river and cause sickness
among those who use its water or ice. This is the usual
way in which typhoid fever is spread. The number of
typhoid fever cases in a town is often taken as an indica-
tion of the purity of the water supply. By keeping the
water supply pure this disease may be almost suppressed.
It might be entirely suppressed by disposing of all sewage
in a harmless way (see pp. 251-253).

222. Purification by oxidation in the soil. — The ground has
the power of oxidizing decayed vegetable and animal matter so that
only the mineral parts remain. Slops from the house are thus oxidized,
if the ground is not soaked through with them. But when the quantity
is great, some may work their way through the ground for a considerable
distance and finally enter a well.

223. Purification by filtration. — Clean sand has the power to
screen out particles carried by the water. Screening out substances
from water by passing it through a powdered substance is called filtra-
tion. As the slops slowly soak through the soil, their solid parts are
filtered out in the first few inches of the top soil, and if the quantity is
not too great, are soon oxidized. Soils differ in their ability to filter.
Clean sand is the best ; clay is the poorest. It is almost impossible to

138 APPLIED PHYSIOLOGY

saturate sandy soil about a single house so that decaying matter can
reach the wells ; but in villages and cities the soil is so completely
soaked with sewage that the well water of these places is impure, and
should not be used.

224. Purification by running water. — The third way in which
water is purified is by the action of the air and sun upon running water.
Sewage from the towns is often conducted into rivers, and the sunlight
and agitation of the waters cause the waste matters and germs to be
oxidized. Yet many of the germs may be carried far down the stream.
Thus few rivers are safe sources of drinking water, unless the water is
first purified (p. 409).

225. Purification by boiling. — It is dangerous to use
impure water for washing, for germs may remain upon
the things washed. Typhoid fever has been spread by
milk cans which were washed in water from a polluted
well. A ready safeguard against the greater dangers of im-
pure water is boiling, which destroys the germs of disease.

SUMMARY

r. Water containing lime is hard, but without lime it is
soft. Lime seldom injures water for drinking pur-
poses.

2. When other minerals, such as sulphur, iron, soda, or

potash, are present, water is called mineral water.
Such water is used as medicine.

3. Air dissolved in water gives it a pleasant taste.

4. Water containing decaying matter is unfit for use.

5. The greatest danger from impure water lies in the

germs of disease which it may contain.
6'. Boiling the water is an easy safeguard against impure

water.
7. The soil purifies water by oxidizing and filtering the

impurities. Running water is generally pure.

DRINKING WATER 139

DEMONSTRATIONS

61. Show that all water contains mineral matter by evaporating a
few drops of pure spring water upon a piece of clean glass. A little
white spot will be left by each drop. Boil some water and notice the
absence of taste. Cool it and shake it in a can, and notice its natural
taste again. Set aside some pure water containing a few bread crumbs
or a shred of meat, and notice the unpleasant odor of decay developed
in a few days.

62. A rough test for the purity of water is to stir in a little pure
sugar and set it aside. If it contains any organic matter, it will turn
yellowish in a few days, but otherwise it will remain colorless. Collect
some rain water from a dirty building, or mud-puddle water, or water
from a barnyard well, and note the color and the odor. After keeping
it a few days, note the deepened color and worse odors, showing decay
within the water.

63. Doubtless the class will ask to be shown " animalculae" in water.
Water has to be almost turpid and putrid before living beings are pres-
ent in sufficient numbers to be easily detected with a microscope. If a
drop of very stagnant water is examined under the microscope with a
power of 100 to 400 diameters, many strange beings will be seen moving
about. Place a little hay in a bottle of water and examine a drop of the
water every day, and notice the changing forms of the living beings as
one kind dies and another is produced.

REVIEW TOPICS

1. Describe the appearance and taste of pure water.

2. State what substances are found in all water ; what in

mineral water ; and the difference between hard and
soft water.

3. State the most dangerous impurity in water.

4. Give three ways in which nature purifies water.

5. Show how to avoid pollution of a well.

6. Show how to render impure water safe for use.

CHAPTER XVI
NARCOTICS

226. What man eats besides food. — Besides eating food
and harmless things which please the taste, man also eats
a variety of dangerous substances, both for pleasure and
to overcome some real or fancied weakness of the body.
The physician prescribes them to overcome diseases of
the cells, but thoughtless and ignorant people use them on
their own responsibility, and suffer great harm thereby.
They may be divided into narcotics, drugs, and poisons.

227. Narcotics. — There is a class of drugs which be-
numb the sense of pain and fatigue and lessen the action
and strength of the cells of the body. These drugs are
called narcotics. They all are powerful poisons. They
lessen the sense of effort and of fatigue, and are often
supposed to be stimulants. A peculiarity common to all
is, that when their benumbing effects have passed off, the
real weakness of the body becomes doubly apparent, and
there is an overwhelming desire for more of the drug to
benumb the increased weakness caused by the first dose.
Thus enslaving habits are formed.

228. Alcohol as a narcotic. — Alcohol should be classed as
a narcotic drug. It really belongs to the class of stimulants as well.
A small amount acts as a stimulant ; but a large amount overwhelms
the body and produces an insensibility to pain and fatigue, a dullness of
mind, and a deep sleep. The use of alcohol tends to become a fixed
habit, as is the case with other narcotics.

140

NARCOTICS 141

229. Alcoholic poisoning. — Besides slow poisoning, alco-
hol can produce severe poisonous effects at once. A man
" dead drunk" is poisoned by alcohol, and is in danger of
his life. In treating him, vomiting should be induced as
soon as possible. He should be rubbed to keep up the
circulation, and stimulated with hot coffee. Keep his
body, and especially his feet, warm.

230. Tobacco and nicotine. — The essential part of tobacco
is a strong narcotic poison called nicotine. Pure nicotine
is a clear and colorless liquid. It can be turned to vapor,
and is found in the smoke when the tobacco is burned. It
is a powerful poison, producing stomach sickness and great
weakness of all the cells of the body, especially of the
heart. Two or three drops will kill a man.

231. Effects of its continuous use. — When used continu-
ously, the body becomes somewhat accustomed to nicotine,
so that it does not produce so great a feeling of sickness.
Then instead of producing a feeling of weakness, it acts
more to benumb the cells and to quiet the body. This is
really the first stage of poisoning, although it seems like a
stimulation. If a little more tobacco than usual is used,
the benumbed and pleasant feeling changes to one of sick-
ness, as though it were being used for the first time. It
always continues to have bad effects upon the muscles,
heart, lungs, eyes, and brain. Tobacco is especially inju-
rious to young persons, hindering their growth and lessen-
ing their strength.

232. How tobacco is used. — Tobacco is used in smoking,
in chewing, and in snuffing it up the nose.

233. Smoking. — Tobacco is smoked in a pipe or by
lighting the end of a roll called a cigar. Some of the
nicotine is turned to vapor and enters the mouth, where
it may be absorbed. Some of the nicotine is half burned,

142 APPLIED PHYSIOLOGY

and forms a substance called pyridine, which is even more
poisonous than nicotine. In a cigar the burning is more
complete, and less pyridine is formed. Cigarettes are small
cigars made of shredded tobacco. They are cheap and
may be quickly smoked, and are less liable to produce imme-
diate sickness than a cigar. So the young are especially
apt to use them. But they are commonly used to excess,
and so make up in quantity of poison what they lack in
quality.

234. Chewing. — Chewing tobacco is the most harmful
form of its use, for all the nicotine is taken into the mouth.
Few people can chew tobacco without spitting out the
saliva which contains the nicotine. The continuous spit-
ting which is necessary to get rid of the saliva makes this
form of using tobacco offensive to everybody near the
chewer. This reason alone should deter any one from the
practice of chewing tobacco.

235. Snuff. — Snuff is powdered tobacco. A hundred
years ago it was fashionable for women, as well as men,
to use snuff. Now a snuffbox is a rare curiosity.

236. Adulteration of tobacco. — The nicotine from stalks and
remnants is extracted by boiling, and the liquor is used to saturate poor
tobacco and the leaves of other plants.

Chewing tobacco owes much of its taste to rum, molasses, licorice,
and other things with which it is flavored.

Most cigarettes are flavored with drugs which color the fingers of
the smokers. Cigarettes are harmful enough at best, but the harm is
far greater when they contain opium. Probably a great part of the
craving which cigarettes induce is caused by the opium.

237. Tobacco habit. — Like all other narcotics, when it
is used for a short time tobacco produces a persistent crav-
ing. Men laugh at the idea of being slaves to such a
small thing as smoking or chewing, and yet when the habit

NARCOTICS 143

is interrupted, there follows a peculiar unsatisfied and
nervous feeling which few men are able to overcome.

Alcohol and tobacco often go hand in hand. Tobacco produces a
dry state of the mouth which demands drink, while alcohol causes a
nervous excitement which the benumbing tobacco tends to overcome.
Most users of alcohol smoke. The only way to break off the habit of
using tobacco is to do so by resolute efforts of the will. So-called cures
of the habit are of no value, for they cannot give a man a strong will.
On the other hand, they may induce sickness.

238. Tobacco poisoning. — Severe tobacco poisoning is
rare ; for when swallowed or inhaled, it produces vomiting,
which expels the poison. When applied to the skin in the
form of a poultice, as is sometimes done, enough may be
absorbed to produce great weakness, for then the stomach
cannot expel it. The principal sign of poisoning is extreme
weakness of the muscles and heart.

To treat it, strong coffee should be given, and the patient
should be kept perfectly at rest.

239. Opium. — Opium is a narcotic drug which is used
to benumb the feelings of fatigue and care. A little of the
drug acts partly as a real stimulant, causing the cells to
act more vigorously and clearly. At the same time its
benumbing action is beginning, and only a little more is
needed to produce a drowsy feeling or a deep sleep. Just
as it causes the brain cells to cease acting in sleep, so also
it lessens the action of all the other cells, and especially
of those of the alimentary canal. The disturbance in the
action of the intestine sets up digestive trouble, which
extends rapidly to the liver. Then the nutrition of the
whole body is lowered. No habit is more enslaving or
more harmful in its effects.

240. Cure of the opium habit. — The only cure for the
opium habit, and yet a safe and sure one, is to keep the

144 APPLIED PHYSIOLOGY

patient entirely away from the drug for a few weeks, con-
fining him if necessary. After a short time the craving
disappears and the patient recovers his health.

241. Opium poisoning. — A lump of opium the size of a
small pea, and weighing about two grains, is enough to put
a man into a deep sleep. Twice that amount may cause
death. When a person takes an overdose he falls into a
deep sleep, from which he can be awakened only with
difficulty. He breathes very slowly, and distends the
lungs very slightly. The pupils of his eyes contract to
small points. These three signs nearly always mean
opium poisoning. They should be remembered, for this
is the most common form of poisoning.

242. Treatment of opium poisoning. — First. Keep the
patient awake by such vigorous measures as slapping his
face, shaking his body, and compelling him to walk.

Second. Induce vomiting. A tablespoonful of mustard
in water should be given at once if the person can swallow.
Tickling the throat with the finger or a feather will gener-
ally cause vomiting.

Third. Stimulate the patient with strong, hot coffee.
Carry out these measures slowly and deliberately.

243. Forms of Opium. — Opium is the dried juice of a kind of
poppy plant growing in Southern Asia. Laudanum is opium dissolved
in ten parts of alcohol. Paregoric is a more dilute solution of opium.
A teaspoonful of it contains one quarter of a grain of opium. About
one tenth of opium is a white substance called morphine. One quarter
of a grain of morphine will cause a deep sleep and contracted pupils
like a large dose of opium.

244. Use of opium. — Opium is used to quiet pain, pro-
duce sleep, and to quiet the intestine.

Paregoric is sometimes used to quiet babies when they
cry. It produces indigestion and leaves the child worse

NARCOTICS 145

than before. " Soothing sirups " are nearly always some
preparation of opium.

245. Chloral. — Chloral is a colorless solid, having a
peppery odor and taste. About twenty grains will produce
sleep, but an overdose may produce death. It injures the
digestive organs and weakens the whole body. It is a
narcotic and a poison.

246. Chloral poisoning. — In treating a case of chloral
poisoning the patient should be kept awake by walking
him about, or even by slapping him. Give a tablespoon-
ful of mustard in water to make him vomit. Then give
strong coffee to stimulate him.

247. Cocaine. — Cocaine is a drug which, when injected
under the skin or applied to a mucous membrane, takes
away the sense of feeling of the part. A grain of it will
render a large area so completely insensitive for half an
hour that large operations can be performed without sense
of pain. It may cause excitement like the beginning of
a state of drunkenness ; sometimes it produces great weak-
ness of the heart and death.

The excitement caused by the drug is pleasant, and per-
sons can acquire a slavish habit of its use. It rapidly dis-
turbs digestion and nutrition, and soon causes death. It
is one of the most rapid and terrible forms of habitual drug-
taking.

248. Hasheesh. — Hasheesh is the juice of the Indian
hemp plant, and is sold as a medicine under the name of
cannabis indica. In Southern Asia it is extensively used
as a narcotic. It produces a happy delirium, in which
a person sees most beautiful persons and figures. The
state is really a temporary insanity, in which one is liable
to injure others. The word "assassin" means one under
the influence of hasheesh.

OV. PHYSIOL. — IO

146 APPLIED PHYSIOLOGY

249. Chloroform. — Chloroform is a sweet-smelling liquid
which, when breathed into the lungs, causes a deep sleep.
It is used to produce insensibility during surgical opera-
tions. Its use requires extreme care, for it can easily
result in death. No one should even smell a bottle con-
taining it, for two or three breaths of it may render a per-
son insensible.

SUMMARY

1. Narcotics lessen the sense of fatigue and pain and

produce sleep, but weaken the body and may cause
death. Their use may become an uncontrollable
habit.

2. Alcohol is a kind of narcotic.

3. Tobacco contains the narcotic nicotine. A little nico-

tine quiets the cells, while more causes weakness,
and stomach sickness which may result in death.

4. Tobacco used in any form produces poisonous effects.

5. The tobacco habit tends to the use of strong drink.

6. Opium quiets the cells of the body, lessens the sense

of pain, and produces sleep. A little causes a feeling
of exhilaration, while a few grains may cause death.

7. The opium habit deranges digestion and finally causes

death.

8. In poisoning by opium there are a deep sleep and

contracted pupils and slow breathing.

9. The poisoned person should be kept awake, made to

vomit, and stimulated by coffee.

10. Laudanum, paregoric, and soothing sirups are all

forms of opium.

11. Chloral produces sleep. A large dose may cause

death. Treat its poisoning like opium poisoning.
.12, Chloroform, when inhaled, produces insensibility.

NARCOTICS 147

REVIEW TOPICS

1. Define and describe narcotics and show how their use

may become a habit.

2. Show that alcohol is a narcotic, and give the signs

and treatment of its poisonous effects.

3. Describe the poison of tobacco and its effects.

4. Describe the harm resulting from the use of the several

forms of tobacco.

5. Show the fraud and harm of adulterating tobacco.

6. Show that the use of tobacco and alcohol naturally go

together.

7. Describe the effects of opium and the opium habit.

8. Describe the signs and treatment of opium poisoning.

9. Name some common forms of opium and give their

uses.
10. Describe chloral, and give the signs and treatment of

poisoning by it.
n. Describe cocaine, its use in surgery, and its poisonous

effects.

12. Describe hasheesh.

13. Describe chloroform and the danger of its use.

CHAPTER XVII
DRUGS AND POISONS

250. Nature of disease. — Disease is due to some de-
rangement of the action of the cells of the body. The
derangement is almost always produced by overwork of
some kind, for the cells are able to protect the body
against all ordinary causes of disease. Few people who
are exposed to epidemic diseases take them, because the
cells are able to destroy the germs as fast as they enter
the body. If men would eat, breathe, and in all things
live as physiology and hygiene show that nature intended
them to live, the cells would be strong enough to resist
almost any disease. The diseases caused by germs are
discussed on pages 382-432 ; only those produced by drugs
and poisons are discussed in this chapter.

251. Action of drugs. — Each drug has a special influ-
ence upon certain cells of the body, and is able either to
stimulate or to restrain their action. Under the influence
of the proper drug, each deranged cell takes in nourishment
and performs its duties more perfectly, and soon overcomes
the sickness. Thus the cells themselves, and not the drug,
cure the disease.

252. Action of a few common drugs. — When the liver is

deranged, calomel or podophyllin will usually stimulate it to action. In
stomach indigestion muriatic acid and pepsin supply the missing diges-
tive agents. When the heart is weak, digitalis or strychnine cause it
to act more strongly, while if it is excited, aconite will quiet it. A fever
is often lowered by aconite or phenacetine. When there is pain, opium
will generally relieve it. When the brain is excited and the person is

148

DRUGS AND POISONS 149

nervous or delirious, chloral or bromide of potash will quiet the cells.
These are a few examples of the actions of drugs which physicians
prescribe.

253. Quack medicines. — Drugs should never be given except
by a physician. The country is flooded with medicines advertised to
cure various diseases. People who take them generally get well, but
they forget that the cells of the body themselves tend to overcome all
diseases, and that in all probability they had no disease at all, but were
only feeling bad because of improper eating, or of overwork.

254. Poisons. — All narcotics and drugs are poisons and
cause sickness or death when taken in overdoses. The
signs of poisoning are much alike in all cases. A person
previously well suddenly feels very sick and weak, or be-
comes unconscious. Vomiting often occurs, and pain is
often present.

255. Treatment of poisoning. — The first thing to do
whenever a poison is swallowed is to empty 'the stomach
as quickly as possible. Almost anybody can be made to
vomit by tickling the throat with a finger, or with a feather
passed through the nose if the mouth cannot be opened.
A tablespoonful of mustard in a cup of warm water will
generally cause vomiting and is always safe. A teaspoon-
f ul of alum in water will act in the same way. Water or
soft food of any kind should then be swallowed and vomit-
ing continued, so as to remove all traces of the poison.

The second thing is to give castor oil or salts, so as to
remove any poison which may have entered the intestine.

The third thing is to give something, called an antidote,
which will destroy the poison in the body.

The fourth thing is to give a stimulant, for the person
will be very weak. Strong coffee should be given by the
cupful, without sugar or milk.

256. Poisoning by acids or alkalies. — If the lips and
mouth are covered with a white film or are raw, some

150 APPLIED PHYSIOLOGY

acid or alkali has probably been swallowed. If it is an
alkali, a drink of weak vinegar should be given at once as
an antidote. If it is an acid, soda, soapsuds, or lime water
should be given as an antidote.

Also give water, or flour and water, or the white of an
egg, or milk, so as to dilute the substance as soon as
possible.

257. Carbolic acid. — When swallowed, pure carbolic
acid produces great weakness and rapid death. In small
doses, or even applied to the skin in surgical dressings, it
may produce headache and weakness, which may result in
death.

In treating its poisonous effects, a stomach pump will
generally have to be used to remove the poison, because
the stomach will be paralyzed by the burning to which it
is subjected. The antidote is Epsom salts.

258. Narcotic poisoning. — If the person poisoned is
sleepy, it shows that a narcotic like opium or chloral has
been taken. Care should be taken not to mistake a faint-
ing spell for the drowsiness of poisoning. In faintness,
the face is of a deathly pale color, and no pulse can be
felt, and breathing ceases, while in drowsiness the face is
of a natural or even deeper red color, the pulse can be
felt, and breathing will continue.

259. Strychnine poisoning. — Strychnine produces vio-
Jent convulsions, like lockjaw, within half an hour after it
has been taken. Vomiting should be induced at once.
Chloral and bromide of potash are its antidotes, and
should be given as soon as possible, to quiet the convul-
sions. In an emergency tobacco may be used.

260. Arsenic and other metals. — Rat poison and Paris
green contain arsenic. Arsenic is a metal, and its poison-
ing is much like poisoning by mercury, lead, copper, silver,

CALIFORNIA COLLGQI

151

or antimony. Sugar of lead and white lead paint are the
common forms of lead which poison the body. Copper
is seldom dangerous. Some forms of silver are very
poisonous.

Antimony is poisonous in the form of tartar emetic and
wine of antimony -, both of which are used in treating colds.

All forms of metallic poisoning are much alike. Vomit-i
ing usually comes on within half an hour, followed by1*
great weakness, cramps in the abdomen, and burning thirst.
If vomiting has not freely occurred, it should be induced
by tickling the throat or by giving mustard in water.

Afterwards the white of eggs, flour paste, or milk should be given as
an antidote. The albumin of these substances forms a chemical union
with the metal, producing a harmless compound which should be
vomited and more of the antidote given.

The special antidote for arsenic is oxide of iron. The settlings which
form in a mixture of tincture of iron and baking soda may be used in an
emergency. The special antidote for lead is Epsom salts; for silver,
common salt ; and for antimony, tannin, which is found in a strong tea
made of almost any bark.

261. Phosphorus. — Phosphorus poisoning may occur
from sucking the ends of matches. It produces vomiting
and violent cramps in the abdomen for two or three days,
and then jaundice appears, with delirium and death. It
resembles a slow poisoning by a metal.

Phosphorus poisoning is treated by giving something to cause vomit-
ing and to expel the poison from the intestine. Always avoid castor
oil or other fat, for phosphorus is dissolved by fat. A small pinch of
sulphate of copper (blue vitriol) given every few minutes will destroy
the poison and also cause vomiting.

262. Aconite. — Aconite produces extreme weakness of
the whole body. A tingling in the throat is the only dis-
tinguishing sign of the poison.

152 APPLIED PHYSIOLOGY

A poisoned person should be kept absolutely quiet, and
strong coffee should be given as a stimulant.

263. Belladonna. — Belladonna, or its active principle,
atropine, is used to enlarge the pupil in examinations of
the eye. In overdoses it produces redness of the face,
dryness of the throat, enlargement of the pupil of the eye,
delirium, and great weakness. The enlarged pupil is its
distinguishing sign. Its treatment consists in giving an
emetic, stimulating by coffee, and giving tannin or strong
bark tea.

264. Mushroom poisoning. — Poisonous mushrooms pro-
duce violent cramps in the abdomen, with vomiting and
great weakness. One form produces symptoms within an
hour or two, and is seldom fatal, for the poison is thrown
off. The other, and by far the more dangerous, form of
poisoning does not come on for ten or twelve hours, or
until the poison has entered the intestine. In poisoning
by mushrooms, vomiting should be induced, and castor oil
given to remove the poison from the intestine. Strong
coffee should be given as a stimulant.

265. Decayed food. — All forms of decayed food, espe-
cially fish, eels, and crabs, may produce vomiting, cramps,
and weakness, like mushroom poisoning. The symptoms
usually come on within six hours after eating, and are seldom
fatal. The treatment is to empty the stomach and intestine.

266. Alkaloids. — The active principles of many vege-
table drugs can be separated from the crude drugs. They
are called alkaloids. Nicotine, morphine, strychnine, atro-
pine, and quinine are alkaloids. Over one hundred in all
are known. A single grain of almost any alkaloid except
quinine can produce violent poisoning.

267. Leucomaines. — As a result of the imperfect oxida-
tion of albumin within the body, compounds resembling

DRUGS AND POISONS 153

alkaloids are formed. They are called leucomaines. They
circulate in the blood and produce headaches, drowsiness,
and other mild forms of poisoning which may become
severe and produce death when, as in Bright's disease,
the kidneys and skin do not remove the poisons. At least
sixteen leucomaines are known.

268. Ptomaines. — As a result of decay and other changes
after death, another set of poisons like alkaloids and leuco°
maines are produced. They are called ptomaines. They
cause most of the symptoms produced by eating decayed
meat. A special kind of the poison, called tyrotoxicon,
sometimes forms in milk and ice cream which has been
kept for some time. Ptomaines and leucomaines can
always be found in the bodies of dead persons.

269. Hypodermic injections. — When injected beneath the
skin by means of a hypodermic needle, drugs and poisons reach the
blood at once and produce much more powerful and rapid results than
when absorbed from the stomach. Alkaloids are well fitted for this use.

270. Snake bites. — In the upper jaw of a poisonous
snake is a sharp, hollow tooth, which is the outlet for
a bag of poison. When the snake bites, the pressure of
the flesh against the bag forces some poison through
the tooth, which thus acts as a hypodermic needle. The
poison is a kind of leucomaine. It produces pain and
swelling at the point of injection, great weakness of the
whole body, and sometimes death.

The treatment of snake bites must be prompt. A
handkerchief should be tied very tightly round the limb,
above the wound, so as to prevent the poison from reach-
ing the whole body. Then the wound should be sucked
for some time, so as to remove as much as possible of the
poison. No harm can come to the person who sucks the
wound if the blood is spit out at once. If bleeding does

154 APPLIED PHYSIOLOGY

not take place freely, the wound should be cut open.
Active stimulation with such substances as strong coffee
or ammonia is also necessary.

271. Insect stings and bites. — Bees, wasps, and hornets pos-
sess a hollow sting through which the insect injects poison into the flesh.
This poison produces swelling and pain, and if there are a great num-
ber of stings, there will also be a considerable weakness of the whole.
body. Usually the swelling begins to decrease within an hour. To
allay the smarting, a lump of cold mud is an effective remedy. Carbolic
acid in water sopped on with a cloth is also good. If the insect has
left its sting in the flesh, it should be removed by pressing over the
sting with the open end of a watch key, or by picking it out with the
point of a sharp knife.

The bites of mosquitoes and of flies produce swelling and pain or
itching in some people. Ammonia water or carbolic acid in water
usually gives relief.

SUMMARY

1. Disease is a derangement in the action of some of the

cells of the body. Drugs either stimulate or retard
the action of the cells.

2. All narcotics and drugs are poisons.

3. In every case of poisoning the stomach and intestine

should be emptied at once, and a stimulant with
an antidote to destroy the poison should be given.

4. Spoiled or poisonous food produces stomach and intes-

tinal disturbance. It should be expelled from the
body as soon as possible.

5. The active principles of many vegetable drugs are

called alkaloids.

6. Leucomaines and ptomaines are substances resembling

alkaloids, but are produced in the bodies of animals.

7. The poisons of snakes and insects are substances

like leucomaines, and are injected into the flesh by
means of a hollow tooth or sting.

DRUGS AND POISONS 155

REVIEW TOPICS

1 . Describe the nature of disease and how drugs tend to

restore health.

2. Describe the general signs and treatment of poisoning.

3. Describe the treatment of poisoning by acids, and by

alkalies.

4. Describe carbolic acid poisoning and its treatment.

5. Distinguish between the drowsiness due to narcotic

poisoning and a fainting spell.

6. Describe strychnine poisoning and its treatment.

7. Describe poisoning by arsenic and give its treatment.

8. Give the signs and treatment of poisoning by metals

in general.

9. Describe phosphorus poisoning and give its treat-

ment.

10. Describe poisoning by aconite ; by belladonna.

11. Describe poisoning by mushrooms, and by decayed

food.

12. Describe alkaloids, leucomaines, ptomaines, and their

poisonous effects.

13. Describe hypodermic injections.

14. Describe snake and insect bites and give the treatment.

CHAPTER XVIII

THE BLOOD

272. The circulatory system. — Nature has provided an
intricate arrangement of tubes to conduct food to each cell
of the body, and to wash away its waste matter. These
two objects are accomplished by the blood. The* conduct-
ing tubes and the blood which they contain make the
circulatory system.

273. The blood. — About one thirteenth of the body is a
red liquid called blood. It consists of a multitude of cir-
cular flat red plates, called the red blood corpuscles or cells,
floating in a colorless liquid, which also contains a few

round colorless cells, called white blood
corpuscles or cells.

274. Red blood corpuscles. — The red
corpuscles of the blood form about 45 per
cent of its weight. Each one is a circular
flat plate, with rounded edges, and with
a depression in the center of each face.
Each cell is about -^Vo °f an ^nc^ *n
j- of an inch in thick-
ness. Each one is of a reddish yellow
color, but when great numbers are piled
together they appear bright red. Each corpuscle is com-
posed of a jellylike albuminous substance, four fifths of
which is a reddish substance called hemoglobin. Hemo-

156

Blood corpuscles
(x 400).

a a pile of red blood
cells.

b red blood cells,

seen flatwise. ..

c red blood cells, diameter and T
seen edgewise.

d white blood cells.

THE BLOOD 157

globin is the essential part of the red corpuscle. It con-
tains a small amount of iron, which gives to it the prop-
erty of carrying oxygen without itself being oxidized. By
means of the hemoglobin the red corpuscles are able to
carry oxygen from the lungs to all parts of the body.
When the hemoglobin contains a large amount of oxy-
gen the blood is of a bright red color, but as the oxygen
is used up it becomes darker, or almost purple. Bright
red blood, called arterial blood, is continually flowing
toward the cells of the body; while that returning from
the cells, called venous blood, is purple in color, from the
lack of oxygen.

275. White corpuscles. — White corpuscles are each
about ^0^0 of an inch in diameter, and are about -- as
numerous as the red corpuscles.
They are round and colorless, and
each contains a nucleus. They
have the power of changing their
shape, and of adhering to the
sides of a blood tube, and of
passing through its wall, and of
moving about between the cells

£ .. i j , , , i A white blood cell of a frog,

of the body as though endowed sketched at intervals of two
with a will of their own. They <>r three minutes, showing its

changes in form (X 300).

have important duties to perform

in destroying disease germs and other foreign substances,
and in the healing of wounds. (See p. 398.)
^ 276. Plasma. — The liquid part of the blood is called
the plasma. It is composed of ninetyparts of water,
holding in solution about eight parts of aTrJumin and two
parts of mineral matter. The mineral matter is mostly soda
and potash. This alkaline property of the blood plasma
aids it in dissolving carbonic acid gas, and in carrying it to

158

APPLIED PHYSIOLOGY

the lungs, where it is breathed out from the body.
Some of the mineral matter of the blood enters into the
composition of the cells of the body, especially of bone
cells.

The albumin is the substance out of which all of the
cells of the body are mainly built. It is formed by
the liver out of the peptone which was absorbed from the
intestine. A little pressure causes the solution of albumin
and minerals to flow through the sides of the capillaries ;
and thus it reaches the separate cells of the body. Waste
matters are continually being poured into the plasma, but
they are removed as fast as they enter, so that carbonic
acid is the only one to be found except by the most deli-
cate tests.

277. Clotting. — When blood is drawn from the body it
soon becomes a jelly like mass, called a clot. After a longer
time the clot becomes firmer and smaller, squeezing out a
clear, straw-colored liquid, called serum. The process of
changing blood from a liquid to a jelly like form is coagu-
lation, or clotting: In the process a part of the albumin
becomes solidified in small interlacing strings, called
fibrin, which entangles the rest of the blood into its
meshes. The network soon contracts, squeezing out the
serum, and retaining the corpuscles. The serum is com-
posed of all the materials of the plasma, excepting the
fibrin. The process may be represented thus :
' albumin ) f f albumin

Plasma or

mineral matter

I water
Corpuscles . . .

Serum, or

Clot, or

mineral matter

+

water
( fibrin

+
[ corpuscles

THE BLOOD 159

While the blood is in motion within a healthy blood
tube, no clotting occurs, but as soon as blood is drawn,
it clots, or if a blood vessel is wounded, a clot forms at
the wounded spot. The use of clotting is to stop bleeding.
Sometimes no clot will form, but a wound will keep on
bleeding until it is healed. This is a disease called hemo-
philia, and may cause death.

278. Anemia. — Sometimes there are too few red cor-
puscles in the blood. Then the skin appears pale and
there is shortness of breath, because too little oxygen is
carried by the diminished number of red blood cells. The
disease is called anemia, meaning lack of blood. It is
mainly a lack of red corpuscles.

279. Good and bad blood. — The terms good and bad blood
are remnants of the old idea that disease was caused by watery sub-
stances, called humors, in the blood. From their supposed influence
on the mind the terms good and bad humored are derived.

For many years attempts have been made to inject healthy blood
into the veins of sick persons. Injecting a liquid into the veins of a
living person is transfusion. In bleeding, the loss of water is one of
the greatest dangers, and to replace it water is sometimes injected into
the veins. It answers better than blood itself.

260. The blood in lower animals. — All living beings
possess some form of fluid circulating in their interior.
In higher animals, birds, reptiles, and fishes, the fluid is
red, and contains both red and white corpuscles. In
insects the blood is usually white or colorless. In worms
the blood is sometimes colorless and sometimes red or
green. In shellfish the blood is colorless, and contains no
corpuscles. In animals which are made up of a single
microscopic speck of matter, there seems to be a continual
motion of fluid within their bodies, although they are so
extremely small that nothing definite can be seen.

I6O APPLIED PHYSIOLOGY

281. The spleen. — The spleen or milt is a soft red
organ, shaped like a tongue, lying just to the left of the
stomach. It is composed of small cells and fibers, among
which the blood circulates as through a sponge, without
being held within firm walled tubes. The spleen is sup-
posed to form the red blood cells, but they are also formed
in the marrow of bones. The spleen can be removed with
but little harm to the body. The pain in the side caused
by running is often due to an excess of blood in the spleen.

SUMMARY

1. Blood is composed of a liquid called plasma, in which

float great numbers of extremely small red cells, and
fewer white cells.

2. The red cells carry oxygen from the lungs to the cells

of the body.

3. The white cells repair injuries to the body.

4. The plasma contains albumin and mineral matters,

both of which are food for the cells of the body.

5. The soda of the plasma carries carbonic acid gas to the

lungs. The gas is there given off in the breath.

6. After standing outside of the body for a few minutes,

some of the albumin hardens to a stringy mass and
entangles the cells, forming a clot.

7. All animals possess a fluid somewhat like man's blood.

8. The spleen is a soft organ in which red blood cells are

formed.

DEMONSTRATIONS

64. Set aside a spoonful of chicken's blood to clot. In a few hours the
serum will begin to separate. Breathe on a slide and place a tiny drop
of fresh chicken's blood upon it, cover it with a cover glass and exam-
ine it with a microscope magnifying at least 200 diameters to see the
red blood cells. Notice their oblong shape and their nuclei.

THE BLOOD l6l

65. Human blood may be obtained without pain by tying a string
snugly around the finger. After a moment make a quick prick with
a clean needle upon the back of the finger just behind the nail. Remove
the string, and a drop of blood will flow which can be examined under
the microscope. Notice the circular shape of the red cells and the
absence of nuclei. Notice that they tend to arrange themselves in rows
like piles of coins.

66. Place a drop of salt water on the slide by one edge of the cover
glass, and notice that the cells become shrunken.

67. White blood cells are too few in number to be readily found
within a specimen of blood, but they form most of the white matter of
a pimple or boil. Prepare and examine a specimen, and notice the
dark specks scattered through the cells, and the nuclei which may be
three in number in each cell. Add a drop of vinegar and notice that
each cell becomes transparent, only the nuclei remaining visible.

68. With a little care the movement of the white cells may be shown
in frog's blood. Prepare a fresh specimen of frog's blood upon a slide
slightly warmed. After a little search an irregularly shaped white blood
cell can usually be found. Watch it carefully, and it will be seen slowly
changing its shape exactly as an ameba changes, only more slowly. A
magnifying power of at least 200 diameters will be necessary.

69. Prepare a specimen of blood for the microscope. (See demon-
stration No. 65.) At the edge of the cover glass drop a tiny bit of
alcohol. Notice how the red blood cells shrivel and become irregular
in form, because the alcohol takes away their water.

REVIEW TOPICS

1. Describe the blood.

2. Describe the red blood cells.

3. Describe the white blood cells.

4. Describe the blood plasma.

5. Describe the clotting of blood.

6. Show what was meant in olden times by the terms good

and bad blood and good and bad humored.

7. Describe the blood in some of the lower forms of living

beings.

8. Describe the spleen and its use.

OV. PHYSIOL. — II

/•>f

CHAPTER XIX

THE HEART

282. The heart. — The blood is kept flowing through all
parts of the body by the heart. The heart is essentially a

hollow shell of muscles, which
has the power of squeezing its
sides tightly together, so as to
force out the blood. It is coni-
cal in shape. Its side lies upon
the diaphragm, with its tip
cb pointing downward, forward,
^ and to the left. Its small end
touches the chest wall about
two and a half inches to the
left of the lower end of the
sternum or breastbone, and its
large end extends along the
right side of the breastbone,
from its lower end upward as
high as the third rib. It is
almost covered by the lung,
and is inclosed in a bag of
serous membrane called the
pericardium. The pericar-
dium is very smooth, so as to permit free movements of
the heart within it. (See cut, p. 66.)

162

The heart.
a, right ventricle.
b left ventricle.
c artery between the two ventricles,

nourishing the heart's muscles.
d pulmonary artery.

left auricle.

aorta.

artery to left side of head.

artery to left arm.

artery to right side of head.

artery to right arm.

descending vena cava.

right auricle.
m ascending vena cava.

THE HEART

163

283. Cavities of the heart. — The heart is designed to
pump two separate streams of blood at once. Its left side
pumps blood through the
whole body, while its right
side pumps it only through
the lungs. The cavity on
each side is partly divided
into an upper chamber called
an auricle, and a lower one
called a ventricle. Each
auricle has thin, flabby walls,
and does little of the work of
pumping blood.

The ventricles have thick
and strong walls, which form
nearly all the bulk of the
heart. The left ventricle has
walls three times as thick as Valves of the heart-

the right Ventricle, for it must a artery with its lower end split open.

pump blood through a much
greater part of the body.
From each ventricle a tube,
called an artery, conducts the
blood away.

\ 284. Valves of the heart.
— Blood enters each auricle
through tubes called veins,
and streams through the
opening into the ventricle,
but is prevented from flow-

vein leading into the heart.
c auricle with the front cut away.
d cut edge of the auricle, showing its

thinness.
e semilunar valves; their upper edges

are free and movable.
/ mitral valve spread open.
g strings from the edge of the curtain

of the valve to steady it.
h muscular projection upon the inside

of the ventricle to which the strings

are attached.
i indentations upon the inner surface of

the ventricle.

/ wall of the ventricle, showing its thick-
ness as compared with that of the

auricle, d.

ing back by thin, strong cur-
tains which are attached to the edge of the opening and
hang suspended in the ventricle. From the edges of each

1 64

APPLIED PHYSIOLOGY

curtain fine threads extend to projections upon the muscu-
lar walls of the ventricle, to keep the curtains smooth and
straight. Blood flowing from the auricle into the ventricle
readily separates the curtains, but blood pressing upon
them from the ventricle forces them tightly together, so

that not a drop can pass
through. Thus they form
a valve in each opening.
The valve upon the left
side is composed of two
curtains, and is called the
mitral valve. The one
on the right side is com-
posed of three curtains
and is called the trictispid
valve. From their situa-
tion, these valves are
often called the auriculo-
ventricular valves.

285. Semilunar valve.
— At the beginning of
each artery leading from
the ventricles are three
thin, silklike flaps, shaped
like half-moons. They

are arranged so that blood flowing from the ventricle pushes
each flap against the side of the artery ; but between the
beats of the heart, the blood in the artery presses backward,
forcing the flaps away from the side of the artery, so that
they all meet tightly in the middle. They form a valve
called the semilunar valve, from the shape of each flap.

286. Action of the heart. — The heart is a pump with
valves permitting blood to flow through an auricle into a

Systole of the heart.

vein entering the auricle.

b auricle.

c closed valve to keep blood from flowing

back into the auricle.
d ventricle.
e artery.

THE HEART

I65

a

ventricle and out into an artery, while preventing any flow
in the opposite direction.

As blood enters the heart it passes through the auricles
into the ventricles. Just before the ventricles are full the
auricles suddenly contract and drive the blood into the
ventricles, which are
thus filled full and im-
mediately begin to con-
tract, while the auricles
relax. The pressure
closes the mitral and
tricuspid valves and
opens the semilunar
valves. The blood is
thus prevented from
flowing back to the auri-
cles, but flows through
the open entrance to the
arteries. During the
contraction of the ven-

Diastole of the heart.

a blood entering auricle.

tncles, the auricles re- b auricle.

open valve to permit blood to flow into the
ventricle.

the blood returning to d ventricle.

e artery.

/ closed semilunar valve.

main relaxed and receive

the heart.

When all the blood is
expelled from the ventricle it relaxes, and the blood falls
back upon the semilunar valves, closing them so that none
returns. At the same time the blood in the auricles presses
open the mitral and tricuspid valves, and again fills the
ventricles.

287. Rate and time of the heart's action. — The contrac-
tion of the heart is called its systole, and its relaxation its
diastole. At each systole from two to four ounces of

1 66 APPLIED PHYSIOLOGY

blood are expelled. It occurs about seventy-two times
each minute. While the heart beats occur regularly
without apparent pause, yet it rests in diastole about
one half the time.

288. Sounds of the heart. — Two sounds are produced by each
beat, which may be heard by listening with the ear close to the heart.
The first sound is the longer and softer, and is caused by the vibration
of the contracting muscles. The second sound is shorter and sharper,
and is caused by the sudden closing of the semilunar valves. At each
systole the portion of the heart touching the wall of the chest may be
felt to become suddenly harder, as though it beat against the chest
wall. Its movements are transmitted through the chest walls so that
they may be plainly seen and felt. Ordinarily a person is not aware of
his own heart beats, but when they are very forcible they are plainly
felt, and are called palpitation.

289. Nerves of the heart. — A nervous mechanism within
the heart itself causes it to contract even after it is sepa-
rated from the body. A fish's or turtle's heart will con-
tract regularly for hours after being removed from the
body. Man's heart is easily affected by outside influ-
ences, but, because of its own nervous mechanism, it is
not so sensitive as has been supposed. Wounds com-
pletely penetrating the ventricle have been sewed up, and
recovery has taken place. The action of the heart is regu-
lated and adapted to the varying needs of the body through
two sets of nerves, one set from the brain and the other
set from the spinal cord. In physical exertion the spinal
nerves cause it to beat faster and more forcibly. This
adaptation is so delicate that rising from a sitting to a stand-
ing position perceptibly increases the number of heart beats.
Joy, or anger, or excitement of any kind hastens its action,
while grief usually retards and weakens it.

290. Effect of violent exercise. — In prolonged and vio-
lent physical exercise the heart performs more work than

THE HEART l6/

is natural, and grows larger to accommodate itself to the
strain. Repeated calls to extra exertion may cause it to
respond more quickly and with more vigor than occasion
demands, so that a slight excitement or exertion causes
palpitation. Those who engage in races are especially
liable to overwork their hearts.

291. Palpitation of the heart. — The response of the heart
to influences from the outside may be excessive, so that it beats too
quickly and more forcibly than occasion demands. Sudden noises,
and excitement of any kind, cause the heart to beat violently or palpi-
tate in some persons. But palpitation of the heart is an annoyance
rather than a disease. While the will has no control over the heart,
yet it can control the emotions which cause the palpitations. Persons
of calm temperament, who exercise self-control over their emotions, are
rarely troubled with palpitation. Our words ending in "hearted," as
" warm-hearted," are records of the old belief that the heart governed
the feelings instead of the feelings affecting the heart.

292. Fatty heart. — The heart may become diseased,
but heart disease is by no means so dangerous as is com-
monly supposed. In fact, those having diseased hearts
are usually unaware of it for years, while, on the other
hand, those who think their hearts are diseased are almost
always mistaken.

There is a common change of the heart's muscle, in which little
particles of the muscle cells are changed to fat. The cells are thus weak
ened, and made unable to respond to a sudden extra demand. A per
son with excessive development of fat elsewhere, is liable to have a
fatty heart. Avoidance of things which tend to cause excitement and
overwork will enable such a heart to work on without noticeable change
in its actions.

293. Disease of the valves of the heart. — The other
common form of heart trouble is a thickening and puck-
ering of the valves, causing a leakage so that some blood
flows backward. But the heart grows larger and stronger,

1 68 APPLIED PHYSIOLOGY

so that it can pump enough blood to supply the body in
spite of the constant leakage backward. The heart may
thus become twice its natural size, but there is a limit to
its enlargement, and finally it grows weak. If exertion
is avoided, such a heart may work perfectly for years.

The nervous system contained in the heart's muscle makes it the
most resistant of all the organs of the body, and the one whose disease
is least to be feared. It is the first organ formed in the child, and is
the last to die. When it begins to fail, the blood accumulates in the
lowest parts of the body, and produces swelling of the feet, which is
one of the first signs of heart disease.

294. Fainting. — When the heart is suddenly checked
and made weak in its action to such an extent that little
blood is driven to the brain, unconsciousness and complete
loss of muscular power result, so that the person falls to
the ground. The face appears pale, because there is but
little blood in it. This paleness and loss of consciousness
is called fainting. When a person faints he should be laid
upon his back with his head as low as his body, so that the
blood may flow to the brain more easily. Cold water should
be thrown upon the face so that the sudden shock may
stimulate the spinal nerves which hasten the heart's action.
In a few seconds the heart beats become stronger, and con-
sciousness is regained. Remember not to raise the head
of a fainting person.

295. Effects of alcohol upon the heart. — The first effect
of alcohol is to increase the force and frequency of the
heart beats. This sends more blood through all the body,
and there is a feeling of greater strength, which is called
stimulation. Men take strong drink for this effect. This
feeling comes on within a few minutes after drinking
and passes off in the course of an hour, Then the

THE HEART 169

drinker feels a desire for more alcohol and so forms a
habit of its use. While a little alcohol may make a man
feel better, yet the strength and endurance of his heart
is really diminished. Alcohol is like a whip which makes
the heart beat harder for a- time but leaves it less able
to do its work in the future. Its blow is pleasant at the
time it is given, but it is all the more harmful because
it is enjoyed.

296. Effects of continuous drinking". — The derangement
of digestion and assimilation resulting from long-continued
drinking impairs the nutrition of the whole body, includ-
ing the heart. Drinkers confound the absence of fatigue
with strength itself.

297. Effects x>f tobacco upon the heart — Tobacco used
in any form is a direct poison to the heart's muscle and
causes it to beat with less strength. When a large amount
is used, it poisons the nerves of the heart and hinders their
harmonious action. Then the heart will beat irregularly,
and there will be palpitation on slight exertion, so that
hard physical exercise becomes an impossibility. The
trouble may be only an inconvenience, so that the person
cannot engage in violent exercise ; but in its severe forms
it may be the cause of death.

SUMMARY

1. The blood is kept in constant motion by a double

muscular pump, called the heart.

2. The heart contains two pairs of cavities, each con-

sisting of an auricle and ventricle.

3. Between each auricle and ventricle there is a valve

which permits blood to flow into the ventricle, but
keeps it from flowing back.

APPLIED PHYSIOLOGY

4. Each ventricle contracts upon the blood about seventy-

two times a minute, forcing it out through a tube
called an artery.

5. Blood is kept from running back into the heart by a

valve at the beginning of the artery.

6. The heart contains a nervous mechanism which

makes it partially independent of the rest of the
body.

7. The heart has great power of resistance against

disease, and of accommodating itself to increased
work, so that heart disease is less to be feared
than disease of almost any other part of the
body.

8. Alcohol at first causes the heart to beat faster and

more strongly than the body needs, thus causing
it to tire itself out.

9. Alcohol soon weakens the heart by impairing its nutri-

tion.

10. Tobacco makes the heart beat irregularly and with
less power.

DEMONSTRATIONS

70. The left side of a chicken's heart closely resembles a man's
left auricle and ventricle, and can be used to show the cavities and
valves. In removing it, be careful to preserve its covering of peri-
cardium. A pig's, or sheep's, or bullock's heart is more like a human
heart. The butcher should be instructed not to cut off the auricles.
(See demonstration 35.)

71. The heart of a frog or fish which has just been killed should be
removed to show its persistence in beating. (See demonstration 35.)

72. Have the students listen to each other's hearts so as to get
a clear idea of the two sounds. Feel the heart beats upon the chest,
and notice how they increase in force and frequency when a person
rises after lying down, and more yet when he walks and runs.

THE HEART I /I

REVIEW TOPICS

1. Describe the heart: its situation, pericardium, cavi-

ties, and valves.

2. Describe the action of the heart and the flow of blood

through it.

3. Describe what may be heard, seen, and felt by examin-

ing the body over the heart.

4. Describe the nervous mechanism of the heart.

5. Give the effect of violent exercise upon the heart.

6. Discuss palpitation of the heart.

7. Describe a fatty heart.

8. Describe how the valves of the heart may be diseased.

9. Describe fainting and its treatment.

10. Give the effects of alcohol upon the heart.

11. Give the effects of tobacco upon the heart.

CHAPTER XX

THE FLOW OF BLOOD IN THE BODY

298. Arteries. — The tubes which conduct the blood
away from the heart are called arteries. From the left

ventricle there goes a single
tube called the aorta. It
gives off branches, which
subdivide again and again,
until they are of micro-
scopic size and penetrate
to every part of the body.
From the right ventricle
there extends another tube,
called the pulmonary artery,
which conducts blood only
to the lungs, where it is
purified.

299. Structure and action
of arteries. — An artery is a
muscular tube covered with
a tough layer of connective tissue and lined with a layer
of very smooth, platelike cells. Its muscle can diminish
the size of the tube. The arteries are elastic, and are
always so full of blood that they are somewhat distended.
At each systole of the heart, from two to four ounces of
additional blood are suddenly forced into the already full
aorta. During the heart's diastole, the elasticity of the

172

An artery cut across (X 200).

a smooth inner coat.

b middle or muscular coat.

c outer or connective tissue coat.

d small artery to nourish the large one.

THE FLOW OF BLOOD IN THE BODY

173

artery causes it to contract, forcing the blood onward in
a steady stream. But the artery can exert no more power
in contracting upon its blood than the heart exerted in
distending the artery, and so it is really the heart's force
which propels the blood.

300. The pulse. — The extra distention of the aorta by
each systole of the heart produces a wave in the blood
which runs along the arterial tubes. Wherever an artery
runs near the surface, as in the wrist, the wave may be
felt, and is called the pulse. The pulse is not a sudden
current of blood shot through the artery, but is a wave
in the steady stre'am. By means of the pulse the fre-
quency and regularity of the heart beats may

be determined. When an artery is cut, a
continuous jet of blood spurts out to a con-
siderable distance, which momentarily in-
creases in size with each wave beat.

301. Capillaries. — The smallest arteries
suddenly divide into an extremely fine net-
work of tubes, called capillaries. Each capil-
lary tube is from ^Ao" to soW of an inch in
diameter, and from y0W to -^j- of an inch in
length. It is composed of the same kind of
smooth and flat cells as those which line the
arteries ; in fact, the capillaries are the pro-
longation of the linings of the arteries. They

* ing the platelike
penetrate the spaces between the cells of the ceils of which it

body in such a close network that several is comP°sed (x

500).
capillaries may be in contact with each cell,

and the point of a fine needle cannot be thrust into the
body without wounding some. The blood in the capillaries
gives the pink tinge to the skin, which disappears when
the blood is pressed out. The total capacity of the capil-

Diagram of a

174

APPLIED PHYSIOLOGY

Arrangement of capillaries.

a smallest artery.

b smallest vein.

c network of capillaries.

laries is about three hundred times that of the arteries,
and hence the blood pressure is much less than in them ;

yet the pressure is always
sufficient to keep the blood
in steady motion.

302. Action of the white
blood cells in the capil-
laries. — Often a white blood
cell will adhere to the wall of
the capillary and partially block
the blood stream for a moment.
It may work its way through
the wall of a capillary, and yet
leave no hole behind it. Many
are thus found in the spaces
outside the capillaries, and are
finally returned to the heart by
means of another set of tubes

called lymphatics. When a capillary is injured, many of the white

cells adhere to the injured spot and furnish food for its repair. They

may even grow and change

to connective tissue for its

further repair.

303. Diffusion of blood
plasma in the capillaries.

— The slight pressure to
which the plasma is sub-
jected is just sufficient to
cause it with its albumin
to diffuse through the ex-
ceedingly thin wall of the
capillary. It fills the

spaces between the capillary network and bathes each cell
of the body with an abundant supply of nourishment.

Diagram showing how food reaches the
cells from the capillaries.

175

304. Exchange of oxygen and carbonic acid in the capil-
laries. — The blood in a capillary is separated from a living
cell of the body by a wall so thin that it is no hindrance
to the passage of oxygen from the red blood cells. In
return for the oxygen received from the blood, the body
cells give out carbonic acid gas, which passes through the
capillary walls into the blood as readily as the oxygen
passes in the opposite direction. A given particle of
blood remains in a capillary only a second at most, and
in that time there occurs an exchange of oxygen and
nutritive matter between the blood and the body cells.
Arteries are simply tubes which conduct blood to the
capillaries, where all the actual work of nourishing the
cells is performed.

305. Veins. — The network of capillaries at the end of
each artery unites to form a single tube, called a vein.
Each vein unites with others again and again, to form
larger tubes which run alongside of each artery, and finally
all unite to form two main veins. One vein, called the
descending vena cava, returns blood from the head and
arms ; the other, called the ascending vena cava, returns
blood from the lower extremities and trunk. Each opens
into the right auricle. The veins have about three times
the capacity of the arteries. Their walls are composed of
the same material, but are very much thinner, for they do
not have to stand much pressure of blood. The blood
current is correspondingly slow. The veins have valves
at intervals which permit of a free flow toward the heart,
but oppose its passage backward, so that when a vein is
pressed the blood is forced only towards the heart. The
contraction of the muscles pressing upon the veins is
thus a great aid to the flow of blood. The flow of blood
is also aided by the movements of the chest in breathing,

176

APPLIED PHYSIOLOGY

which suck venous blood toward the heart just as it sucks
air into the lungs.

306. Pulmonary circulation. — As the blood enters the
veins from the capillaries, it has lost some oxygen and

gained carbonic
acid gas and other
waste matter. This
makes it much
darker in color.
Before it is used
again it is purified
and given a new
supply of oxygen.
For this purpose
it is sent to the
lungs as soon as it
reaches the heart.
From the veins
the blood flows in-
to the right side
of the heart, and
then to the lungs
through the pul-
monary artery.
The pulmonary
artery divides
again and again
into small twigs,
and these divide
into a close net-
Diagram of the course of the blood in the circulation. work of capiHaries

within the lungs, where the blood is separated from the air
by only the thin walls of the capillaries. Through these

THE FLOW OF BLOOD IN THE BODY 177

thin walls the oxygen of the air readily penetrates to the
red blood cells; and the carbonic acid gas just as readily
passes from the blood to the air. As a result of this
change, the blood becomes of a bright red color, and is
called arterial blood. From the capillaries of the lung the
arterial blood is collected into the pulmonary veins and
carried to the left auricle, and then to the left ventricle,
where it is ready to make another circuit of the body.

307. Summary of the circulation of the blood. — In making
a complete circuit of the body the blood passes through the left auricle,
and through the mitral valve to the left ventricle ; then past the left
sem f lunar valve to the aorta, and then through the arteries to all parts
of the body ; then through the capillaries into the veins, and back to
the heart ; next through the right auricle, then the right ventricle,
then through the pulmonary artery to the capillaries of the lung', then
through the pulmonary veins to the left auricle once more. Thus in
making the complete circuit of the body, a drop of blood passes through
the heart twice, and through two different sets of capillaries. The
circuit of the body in general is called the systemic circulation, and that
through the lungs is the pulmonary circulation.

308. The portal system of circulation. — The blood from
the capillaries of the stomach and intestine is collected
into a single vein, called the portal vein, which goes to the
liver and there divides into capillaries. The liver capil-
laries can be considered as millions of small tubes which
are substituted for a few inches of the portal vein. Just
outside of the liver they empty into three veins which
open into the ascending vena cava. The circulation
through the liver is sometimes called the portal circulation.

309. Time required in the complete circulation. — It re-
quires about twenty seconds for a drop of blood to go the round of the
circulation from the left ventricle back to its starting point. All the
blood passes through the heart about once every two or three minutes.
All the arteries, except the pulmonary artery, carry bright red arterial

ov. PHYSIOL. — 12

APPLIED PHYSIOLOGY

blood, while all the veins, excepting the pulmonary veins, carry dark
red or venous blood.

310. The lymph. — In order to nourish the body, the
plasma of the blood is continually being diffused through
the capillaries into the spaces between the living cells.
Each cell is thus bathed in a plentiful supply of plasma,
from which it absorbs its nutriment. The spaces also
contain many white cells, which have left the capillaries.
The blood plasma and blood cells filling the spaces be-
tween the cells are called the lymph, and the spaces are
called lymph spaces.

The lymph is a thin, colorless fluid. In fact, it is blood
without the red corpuscles, but with many waste matters
from the cells of the body added. The lacteals of the

intestine are also
lymphatics which
carry the digested
fats, and hence
their lymph is of a
milky-white color.
311. Lymphatics.
— Lymph is con-
tinually collecting,
and its removal is
provided for by
means of a set of
tubes, called the
lymphatics. The
smallest lymphatic
tubes are much
smaller than a capillary, and their walls are so thin that
they can scarcely be seen with a microscope. Each begins
in the open space between a capillary and a cell of the

Lymphatics of the head and neck.
B thoracic duct.

THE FLOW OF BLOOD IN THE BODY

1/9

body. They unite again and again to form about twenty
main trunks for each limb. Each trunk extends upward,
and most of them finally unite to form a tube of the size
of a goose quill, called the thoracic duct.

The thoracic duct lies upon the spinal column, and
extends upward into the neck, where it opens into a large
vein. The lymphatics have numerous valves, all opening
toward the heart. They prevent the backward flow of lymph.

312. Lymph nodes. — At irregular intervals the lym-
phatics open into small, baglike bodies composed of a
spongy network of fibers filled with

cells, some of which become white
blood cells. Each body is called a
lymph gland or node. The lymph
flows through these nodes as water
flows through a filter. They strain
out matters which are injurious to
the system, while their cells en-
velop and destroy poisons and dis-
ease germs, and so they protect the
rest of the body.

The lymph nodes may be felt in
the neck and groins and armpits, as
small kernels about the size of a
grain of wheat or corn. When the
lymph carries certain kinds of poi-
sons, they swell up and produce the
disease called scrofula. In boils,
erysipelas, and other inflamma-

Lymph node and vessels

tions, they swell and become very (xio).

tender and sometimes break down and form abscesses.

313. Flow of the lymph. — A little pressure transmitted
from the blood in the capillaries is exerted upon the lymph,

180 APPLIED PHYSIOLOGY

but not enough to force it along the lymphatics. Its flow
is aided by the pressure of muscles upon the spaces and
the tubes. Its current is slow and unsteady. It is finally
poured through the thoracic duct into a vein at the root of
the neck, where it mingles with the blood. About two
quarts of lymph pass through the thoracic duct daily. If
a hollow needle is thrust into the skin, and through it
water containing medicine is forced, the medicated water
spreads through the lymph spaces between the living
cells. Some is taken up by the capillaries, and some passes
into the circulation by means of the lymph, and produces
the same effect as though it entered the blood through the
stomach.

Sometimes the lymph cannot be removed by the lym-
phatics so fast as it is poured out by the capillaries. It
then distends the lymph spaces, producing uniform
swellings called dropsy. Dropsy can. be recognized by a
small pit remaining when the finger is pressed into the
skin.

314. The circulation in lower animals. — Land animals
and birds possess a heart and blood tubes like man's, and
their circulation follows the same order. The heart of rep-
tiles and toads consists of two auricles and one ventricle,
and the ventricle always contains both arterial and venous
blood.

Fishes possess only one auricle and one ventricle. The
ventricle forces the blood through two sets of capillaries,
and the circulation is made correspondingly sluggish.

Insects possess a row of eight or nine sacks connected
by a tube, with valves opening toward the head. The
contraction of the sacks forces the blood toward the head,
where it escapes into the lymph spaces between the cells.
There are no arteries or veins, and so the blood is slowly

THE FLOW OF BLOOD IN THE BODY l8l

forced toward the back part of the body through the
lymph spaces until it again reaches the tube. Their cir-
culation is thus like the circulation of lymph in man.

Shellfish usually possess a heart and arteries and veins.
In the very lowest animals, like the ameba, there seems to-
be a flow of fluid within the body, but no part of the body
is set aside for the purpose.

315. History of the knowledge of the circulation. — The

ancients thought the heart was the seat of life, because the heart was
seen to be the first organ formed in an egg which was being hatched.
The idea was confirmed to them by the heart's constant action, which
they thought was caused by the boiling of the animal spirits. The
spirits then flowed away in a sluggish stream through the veins, and
were not supposed to return to the heart.

They concluded that the arteries carried only air, because they always
found them empty after death. They knew nothing whatever of the
capillaries. They thought that food was carried to the liver and was
there partly cooked, and was then sent on to the heart where it was
cooked still further in the heart's vital flame, until it was turned to
blood. Then it was sent out by way of the veins to irrigate the body.
The valves of the veins were supposed to oppose its flow and to render
it sluggish. The boiling in the heart was supposed to heave the chest
up and down, and cause air to rush in and prevent too great a degree
of heat. The brain also was supposed to cool the blood. Because of
its more violent action during physical exertion or emotion, they con-
cluded that the heart, instead of the brain, was the seat of the mind
and feelings. We still use the word heart with this meaning in such
expressions as kind-hear ted2c&& free-hearted.

Incredibly few discoveries were made for thousands of years, for
until within two hundred years the law forbade any one to dissect a
human body. In 1628 a true explanation of the heart and the course
of the blood was first published by Harvey, an English physician.
The only point which he omitted was the explanation of how the blood
gets from the arteries to the veins. Three years after his death micro-
scopes were made powerful enough to reveal the capillaries for the
first time, and thus the truth of our present ideas concerning the cir-
culation was fully established.

1 82 APPLIED PHYSIOLOGY

SUMMARY

1. The tubes carrying blood away from the heart are

called arteries. They are thick-walled and elastic,
and in them the blood is under considerable pressure.
Each heart beat causes a perceptible wave in the
artery, which is called the pulse.

2. The arteries divide and finally break up into fine

tubes called capillaries, which touch each cell of the
body.

3. In the capillaries some of the plasma passes outside the

tubes and bathes the cells in nourishment. Some of
the oxygen leaves the red blood corpuscles to go to
the cells of the body. Some carbonic acid gas also
leaves the cells of the body and combines with the
plasma within the capillary.

4. The capillaries join together to form thin-walled vessels

called veins, which return the blood to the heart.

5. The plasma which has left the capillaries is called

lymph. It is returned to the blood by means of a
set of fine tubes called lymphatics.

6. The lymphatics unite to form a tube called the thoracic

duct, which runs up the backbone and opens into a
vein at the root of the neck.

7. The right side of the heart sends the venous blood to

the lungs, where it passes through the capillaries
and is freed from its impurities, and then returned to
the left side of the heart as arterial blood ready for
another circuit of the body. This is called the pul-
monary circulation.

9. The venous blood from the stomach and intestine passes
through a second set of capillaries in the liver. This
is called the portal circulation.

THE FLOW OF BLOOD IN THE BODY 183

DEMONSTRATIONS

73. The flow of blood in the veins and the action of the valves of
the vein can be shown by placing a finger upon a vein in the skin upon
the back of the hand. Then press out the blood by running another
finger a few inches up the vein. When the second finger is removed,
notice that the blood does not return in the vein, for the valves stop
the backward flow ; but if the first finger is removed, the vein at once
fills up. This is one of the proofs which Harvey used to prove the
circulation of the blood.

74. The position of the main arteries upon the limbs should be
shown upon the body. Remember that they are usually over the middle
of a joint upon the side toward which it can be bent. Explain that
wherever a beating can be felt there is a pulse and an artery.

75 . Examine an artery and vein prepared for the microscope. Notice
its smooth and thin inner layer puckered because of the contraction of
its outer coats. Next is the muscular layer, each cell wrapped around
the tube. The next and outermost layer is composed of connective
tissue. Notice that the main difference between the artery and the
vein is that the artery is thicker.

76. Tie a string or a rubber band rather tightly around the finger.
Notice that in a few minutes the finger becomes purple, cold, swollen,
and painful. Explain that the string does not exert enough pressure
to close the thick arteries which are under high pressure, but that it
readily closes the veins.

77. Show the capillary circulation in a frog's foot. Place the frog
in a covered glass of water to which a teaspoonful of ether has been
added. When it ceases to move, spread its web over a hole cut in card-
board. A ring of dried mucilage will hold it in place. Examine it
under a microscope with a magnifying power of about 200 diameters.
Oval cells will be seen shooting through a network of capillaries. The
tail of a small fish also will show the circulation.

REVIEW TOPICS

i. Describe the tubes which conduct blood to the cells
of the body, their structure, situation, arrangement,
action, and pulse.

184 APPLIED PHYSIOLOGY

2. Describe the capillaries, their structure, and action in

regard to nutrition and respiration.

3. Describe the veins, their structure and action.

4. Describe the pulmonary circulation and the portal cir-

culation.

5. Give the time required for a drop of blood to make the

complete round of the circulation.

6. Describe the lymph, the lymphatics, the flow of lymph,

and the use of lymph.

7. Describe lymph nodes and give their use.

8. Describe the circulation in reptiles and toads, in fishes,

in insects, in shellfish, in the ameba.

9. Give an outline of ancient ideas concerning the circula-

tion of the blood, and tell when and by whom the
true circulation was discovered.

CHAPTER XXI

REGULATION OF THE FLOW OF BLOOD

316. Vaso-motor nerves. — The muscles in the walls of
the smaller arteries regulate the amount of blood passing
through them. A special set of nerves, called vaso-motor
nerves, causes the arteries to contract. When these nerves
are paralyzed, the muscles relax, and the artery becomes
fully distended by the pressure of the blood. When any
part of the body is working, its arteries dilate in order
to supply a greater amount of blood to the part.

The vaso-motor nerves are affected by influences from
the brain. Embarrassment and bashfulness paralyze those
of the head, so that more blood goes to the face and it
becomes redder, or blushes. On the other hand, fear and
grief stimulate the nerves and cause a contraction of the
arteries, which drives the blood from the face so that pale-
ness results. Heat applied to the skin causes the arteries
to dilate, and thus to contain more blood.

317. Congestion. — More than the natural quantity of blood re-
maining in a part for some time is called congestion. It is liable to
injure the cells. Cold causes the arteries of the skin to contract so
that 'less blood passes through them, and consequently an extra amount
of blood flows through the deeper arteries. So congestion of the deeper
parts often results, and the injured cells become unable to resist the
growth of disease germs. In this way we often take cold.

318. Secondary effects of heat and cold. — When heat has
acted upon the skin for some time it causes a contraction of the blood
tubes. When first put into a tub a washerwoman's hands become

185

186

APPLIED PHYSIOLOGY

red, but in a few moments they become white and shriveled from the
contraction of the arteries.

When cold has acted upon the arteries for some time it paralyzes
them so that they dilate. When a boy begins to snowball, his hands
are cold, but after a while his hands glow with redness and warmth
because the paralyzed tubes admit more warm blood.

319. Effects of injury upon the arteries. — When injured
in any way, the injured part becomes red and warmer.
This is because the same cause which produces the injuries
also partly paralyzes the smaller arteries, so that they dilate
and bring an extra quantity of blood for the repair of the
wounded part. Here, as elsewhere, nature wonderfully
adapts the body to its surroundings.

320. Nature's arrest of hemorrhage. — Cut capillaries
cause only an oozing of blood which collects like drops of

dew over the whole cut
a surface. Blood does not
spurt from a cut vein, but
wells out in a slow stream.
When an artery is cut, the
blood flows in a strong jet.
Bleeding from either of the
vessels usually stops in a
few moments. The mus-
cles of the blood tube
contract and lessen the
size of the tube, or even
entirely shut it up ; the blood also clots in the cut, and a
small plug of clot extends into the end of the blood tube.
In these two ways bleeding from small cuts is soon stopped
naturally. But in a large artery the blood pressure is so
great that it forces away the clot as fast as it is formed,
so that bleeding may continue until death occurs.

Diagram of a bleeding cut.

a upper edge of a cut.
b a cut blood tube.

REGULATION OF THE FLOW OF BLOOD l8/

321. How to stop a bleeding. — It should be remembered
that sufficient pressure will instantly stop any bleeding.
If a hand is placed on each

side of the cut, so as to
hold its edges firmly to-
gether, no bleeding can *>
occur. A second way of
stopping bleeding is by
pressing a handkerchief,
or a finger, or even the
whole hand, into the Natural stoppage of bleeding.

wound. A third way in ? w^ edf of.a cut-

b blood tube, showing its contracted cut

which bleeding may be end filled with a clot,
stopped is by cutting off e bloodclot-

the supply of blood to the part. This may be done by
tying a handkerchief very tightly around the limb be-
tween the wound and the heart. The knot in the hand-
kerchief should lie over the artery, and, if necessary, a
stick may be inserted under the band and twisted tightly.
Of these three ways of stopping bleeding, that of compres-
sion by the hands is the best to use at first.

322. Position of arteries. — Main arteries run in a general
direction down the middle of each limb, upon the side on which the
limb can be bent. Thus in the upper part of the arm, the artery run?
across the center of the armpit, and then down the inner side of the
upper arm. At the elbow it lies in the center of the front side of the
arm. An artery lies upon the thumb side, and another upon the little
finger side of the front of the wrist.

In the leg the main artery lies in the middle of its upper part, and
reappears at the surface in the middle of the bend of the knee. At the
ankle it is divided into two, one of which is just behind the inner ankle
bone, and the other runs down the middle of the front of the foot.

There is a large artery and a large vein in the middle of each side
of the neck. These positions should be remembered, for they are the
principal places in which a large blood tube is likely to be wounded,

188

APPLIED PHYSIOLOGY

and they mark the course of the tubes in case they should need to be
compressed to stop bleeding.

323. Repair of wounded tubes. — When a vein is cut
in two, its ends may grow together again, but when an
artery is cut, each end of the tube remains permanently

The left upper arm.

The dotted line indicates the
course of the main artery (the
brachial).

The right thigh.

The dotted line indicates the
course of the main artery (the
femoral) .

closed, and thus the supply of blood to the part is at least
partly cut off. Branches from an artery communicate
with other branches which begin a few inches further
down the same artery. When the artery is cut, these
communicating branches enlarge, and thus permit the
natural amount of blood to flow around the wound and

REGULATION OF THE FLOW OF BLOOD 189

so reach the artery below the cut. When capillaries are
cut, a new set is produced to take their place.

324. Effect of tight bands. — A tight band will obstruct the
flow of blood in the veins, while, unless it is very tight, it scarcely
affects the arteries. So the blood freely enters a part through the
arteries, but is held back in the veins below the band, until the part is
distended with blood, and the proper amount of new arterial blood is
prevented 'from entering. As a result the nutrition of the part suffers
and slight injuries do not heal readily. The veins swell from the extra
amount of blood they contain, and finally enlarge in places, forming
what are called varicose veins. Tight garters are common offenders in
this respect.

325. Alcohol and arteries. — When a cup of hot coffee
is swallowed, the temperature of the stomach and of the
blood in its walls is raised. Then nature at once causes
the arteries of the skin to become enlarged so that more
blood may come in contact with the cool air, and thus give
off the surplus heat. Probably in the same manner the heat
produced by the destruction of alcohol causes the arteries of
the skin to dilate so that they contain an excess of blood.
A red face and nose are well-known signs of drinking.
This dilation of the arteries is one of the most marked
and constant effects of drinking.

326. Alcohol and the nutrition of cells. — Naturally,
when a part of the body is at work, its blood tubes
become larger, while those of the resting parts become
smaller. If the blood tubes of distant parts remain large,
there will not be sufficient blood to fill those of the work-
ing part, and thus the part will not be able to put forth its
full strength. If a part is injured, it cannot get enough
extra blood to repair itself quickly. Thus wounds will be
apt to heal slowly, while inflammation will be more likely
to set in.

IQO APPLIED PHYSIOLOGY

If a part is continuously supplied with an excess of
blood by dilated arteries, there is apt to be an overgrowth
of some of its tissues, especially of connective tissue. An
excess of this tissue interferes with the action of the work-
ing cells of the part. This change is apt to occur especially
in the arteries themselves, making them thick and hard.
It naturally comes on during old age, but is often hastened
by the use of strong drink. The affected arteries cannot
change their size, and so the parts which they supply
surfer in nutrition. Although an excess of blood may go
to a part, yet it is not renewed so often as it should be.

SUMMARY

1. The muscles in the arteries give them the power of

becoming smaller or larger in order to regulate the
amount of blood going to any part of the body.

2. The contraction and relaxation of the arteries is con-

trolled by a set of nerves called vaso-motor nerves.

3. Heat, cold, work, and mental influences are a few causes

which excite the action of the arterial muscles.

4. Contraction of arteries near the surface and dilatation

of the deeper ones is the common cause of taking
cold.

5. Alcohol causes a paralysis of the muscles of the arteries

so that they may remain permanently enlarged. The
arteries of the face and stomach are most affected.

6. Small blood tubes, when cut, bleed for a moment until

the ends of the tubes contract and a clot plugs them
up completely.

7. Large blood tubes may bleed until death occurs.

Bleeding can always be stopped by grasping the
part boldly and firmly.

CALIFORNIA COLLE6I

~f PHARMACY

REGULATION OF THE FLOW OF BLOOD IQI

8. Large blood tubes run down the middle of the limb

upon the side toward which the limbs are bent.

9. Tight bands obstruct the flow of blood going from a

limb, but permit blood to enter. Thus the limb
swells and the veins enlarge.

DEMONSTRATIONS

78. The effect of injury upon the arteries can be illustrated by scratch-
ing the arm with the point of a pin. In a few seconds a bright red
mark appears in its track.

79. Hold the hand in a basin of hot water. Notice that at first the
skin is red from the dilatation of the arteries. In course of ten min-
utes the skin becomes white and puckered, because heat has a second
effect of contracting arteries.

80. Show how bleeding can be stopped, by boldly grasping an imag-
inary cut and holding its edges tightly together. Show how a band
can be tied loosely around a limb above a cut, and then by means of a
stick inserted under the band, can be twisted as tightly as one pleases
so as to control bleeding.

REVIEW TOPICS

1. Describe vaso-motor nerves.

2. Show how vaso-motor nerves are affected by influences

from the brain ; by heat and cold ; by injuries.

3. Describe congestion and how it is caused by cold.

4. Give the effects of alcohol upon the contraction and

dilatation of the arteries.

5. Give the difference between arterial, capillary, and

venous bleeding.

6. Describe how bleeding naturally stops.

7. Describe three ways of stopping bleeding.

8. Describe how nature restores the circulation after an

artery is cut in two ; after a vein is cut ; and after
capillaries are cut.

9. Give the effect of tight bands upon the circulation of a

limb.

CHAPTER XXII
THE LUNGS

.327. Oxidation. — Life is a process of oxidation. The
body is an engine. The living cells are the machinery,
and both they and the blood are the fuel. The fires are
lighted at birth, and burn without cessation until death.

328. Respiration. — In every fire a free draft of air must
be supplied and the burned products must be carried off.
So in the body air must enter continually, and the oxidized
products pass out again. The red blood cells are set apart
for the special work of carrying oxygen to the rest of the
cells of the body, while the lungs are arrangements in
which the red blood cells can obtain oxygen from the air.
The passage of air into and out of the lungs is breathing.
Breathing and oxidation together constitute respiration.

329. Respiratory organs. — An air tube leads from the
surface of the body to the lungs. The parts of the tube
from the surface to the lungs are the nose, pharynx, larynx,
trachea, and bronchi. These parts taken together form the
respiratory tract. They, together with the lungs and red
blood cells, form the respiratory system.

330. The nose. — The nose is a double tube lined with
mucous membrane. Each tube has a smooth bottom and
inner wall, but its outer wall is thrown into three curved
folds extending lengthwise so as almost to form partitions
across the tubes. The folds warm the air and strain out
dust as it passes over their surfaces. From each side of

192

THE LUNGS 193

the nose 'a tube extends to the eye to drain away tears, and
another opening extends into the antrum or cavity in the
upper jawbone. In the nose there are special nerves of
the sense of smell. (See p. 324.)

331. The pharynx. — The pharynx is the muscular bag
just back of the mouth, through which both food and air
pass. Air should always enter it from the nose. Just in
front of the pharynx upon each side is a fleshy body, look-
ing like an almond, and called the tonsil. Sometimes the
tonsils become very large in children and close the open-
ing into the nose, making it necessary to breathe through
the mouth.

332. Adenoid vegetations. — In the upper part of the
pharynx, just behind the opening of the nose, there often
grows a collection of soft, grapelike bodies, called ade-
noid vegetations. They close the opening to the nose and
compel a person to breathe through the mouth. They
begin to form during early childhood while the bones are
growing. The unnatural breathing and open mouth de-
form the upper jaw so that it becomes narrow and pointed.
The trouble is a serious one, for it compels mouth breath-
ing; it renders the child very susceptible to taking cold
and other infectious diseases; and it is the most common
cause of deafness, for it stops the Eustachian tube lead-,
ing to the ear. Often adenoids are associated with large
tonsils.

When a child becomes grown, the adenoids often shrink,
and so cure themselves, but the deformed jaw lasts through
life. They can easily be broken down and removed, and
this should be done in every case.

333. Mouth breathing. — The mouth contains no means for
warming the air, or for screening out dust and disease germs, as the
nose has. So a mouth breather is very likely to take cold. When he

ov. PHYSIOL. — 13

194

APPLIED PHYSIOLOGY

makes an extra exertion and becomes short of breath, the air irritates
the throat and brings on a cough.

With many, mouth breathing is a habit which can easily be broken
by attention to the breathing. In others, it' is due to a cold, or to ade-
noid vegetations, or to enlarged tonsils.

334. The larynx. — In the front side of the lower part
of the pharynx is the opening of a box called the larynx,
through which air passes. The larynx is a box of carti-

A slice from the trachea (x 200).

a cartilage. b glands in the mucous membrane.

c lining of epithelial cells.

d cilia upon the surface of the epithelium.

lage. Across its upper end are stretched two thin elastic
bands, the vocal cords, which can be tightened and brought
near together at will. Air passing between them produces
a sound called the voice.

335. The trachea. — From the bottom of the larynx
there extends downward a tube called the windpipe or
trachea. The trachea is about four and one half inches
in length and three quarters of an inch in diameter. It
is composed of a framework of twenty hoops of cartilage,

THE LUNGS

195

bound together with tough connective tissue and lined with
mucous membrane.

336. The bronchi. — Within the chest the trachea divides
into two tubes, the bronchi. Each bronchus divides again
and again, until the finest

divisions are about -fa
inch in diameter. Like
the trachea, each bron-
chus is composed of hoops
of cartilage lined with
mucous membrane.

337. Cilia. — The sur-
face of the epithelium of
the mucous membrane of
most of the nose and
larynx and the whole of
the trachea and bronchi
is covered with micro-
scopic hairs, the cilia.
Each cilium is slightly
curved upward and waves
continually in a rapid up
and down motion which

and Diagram of trachea and bronchi.

the a larynx> ^ trachea. c bronchi.

* d air sacs of the lung.

lungs.

338. The lungs. — The ends of the bronchi are studded
with numerous cup-shaped depressions called air sacs, each
about Yj-g- inch in diameter. Upon the inner surface of
each air sac is a close network of capillary blood tubes.
The collection of bronchi, air sacs, and blood tubes forms
two spongy bodies called lungs. Between the air sacs
is a thin layer of connective tissue. The lungs can be

tends to force dust
mucus away from

APPLIED PHYSIOLOGY

stretched like rubber bags, when air is blown through the
trachea, and will contract to their former size when the air
has been let out.

339. The chest or thorax. — The lungs are covered by
the ribs, which are hinged to the spinal column behind,
and to the breastbone in front, so as to form a bony frame-

Diagram of the air sacs in a man's lung.

a smallest bronchial tube.

b a"collection of air sacs cut lengthwise.

c air sacs cut across.

d connective tissue between the air sacs.

Diagram of a frog's
lung.

work inclosing a cavity called the chest or thorax. The
floor of the thorax is formed by a muscle called the
diaphragm, which is attached to the lower border of the
ribs, and arches upward. It is lined with a smooth and
shining serous membrane like peritoneum, called the
pleura. Each lung is covered with pleura also.

340. Inspiration and expiration. — Muscles connect and
cover the ribs. They raise the ribs and expand the chest.
The diaphragm flattens its arch and makes the chest

THE LUNGS 1 97

deeper. Thus the size of the chest can be increased in
all directions. When the chest expands, air rushes in
to distend the lungs. The entrance of air into the lungs
is called inspiration. At the end of inspiration the
muscles relax. Then the weight of the parts and the
elasticity of the distended lung forces out the air. In
addition, the muscles of the abdomen and arms can be
made to contract so as to expel the air with greater force.
Driving out the air from the lungs is called expiration.

341. Amount of expansion. — In an ordinary inspiration the
chest becomes from one half an inch to one inch larger around. By
taking a very deep breath most people can expand the chest two or
three inches. An expansion of four or five inches is exceptional. By
breathing exercises the expansion can be increased.

342. Amount of air used in each breath. — After the .
fullest possible inspiration, the lungs contain about 330
cubic inches of air. After the fullest possible expiration,
the lungs still contain about 100 cubic inches of air. So it

is possible, by strong effort, to inhale and exhale about
230 cubic inches of air. This is called the vital capacity
of the lungs, and is the breathing power which can be
used in violent exercise. But in quiet breathing only
about 30 cubic inches of air are inhaled. This is called
tidal live. By an effort about 100 cubic inches of air can^
be inhaled in addition to the tidal air. This is called the
complemental air. By a forced expiration, the lungs can
expel about 100 cubic inches of air more than in quiet
breathing. This is called the reserve or supplemental air.
There still will be left 100 cubic inches of air, called
residual air.

343. Action of the cilia. — The motion of the cilia creates
an air current in the smaller bronchi, which mixes the in-
coming fresh air with that already in the lungs, so that

198 APPLIED PHYSIOLOGY

while all the air is not changed with each inspiration, yet
there is a free mingling of the fresh with the impure air.
The cilia also intercept particles of dust which the nose
and pharynx have failed to remove.

344. Rate of breathing. — In health an inspiration occurs
with every four heart beats, or about eighteen times each
minute, but in exercise its rate may be increased to sixty
or seventy times a minute. A baby breathes about forty
times a minute. The rate slowly diminishes until, at
eighteen years of age, it is the same as in a man.

An inspiration takes about five sixths as long as expira-
tion, but the regularity and force of both inspiration and
expiration can be varied indefinitely. Respiration usually
goes on without a person's knowledge or thought, yet it is
somewhat under the control of the will in talking, blow-
ing, and other actions.

345. Modifications Of breathing. — Coughing is a forcible expi-
ration in which the closed vocal cords are suddenly blown open with
force.

Sneezing \s> a sudden expiration in which air is driven mainly through
the nose.

Blowing is a long forcible expiration in which air is forced in a steady
stream through a small opening in the lips.

Laughing and crying are each a succession of short expirations.
They sound so much alike that it is often impossible to tell which a
child is doing.

Sobbing is a succession of short inspirations.

Hiccoughing is a single inspiration caused by a sudden contraction of
the diaphragm.

Snoring is a sound produced during inspiration by air passing over
the soft palate. It is usually due to air passing through both the nose
and the mouth at the same time.

Gaping or yawning is a long and deep inspiration and expiration
through the open mouth, while the muscles of the throat are strongly
contracted.

THE LUNGS

199

Sighing is a deep inspiration followed by a sudden relaxation of the
muscles so that the escaping air makes a sound.

Choking is a sudden stoppage of the larynx or trachea. When a
person is choked, he should lie down upon his face with his head
lowest. Slapping his back will aid in jarring the substance loose,
.f this does not dislodge it, he should be hung head downwards while
his back is pounded vigorously. In that position the substance may
fall out, while if he sits upright, it may fall in deeper unless it is coughed
out.

Suffocation, or smothering, is a cessation of breathing caused by
shutting off the air either partly or wholly.

Sucking is an inspiratory act, done by depressing the floor of the
mouth so as to form an empty space into which anything held between
the lips is forced by the pressure of the air.

Spittings an expiratory act in which the lips are blown open with
an explosive noise.

346. Breathing sounds. — In natural breathing, air rush-
ing in and out of the lungs produces a low, blowing sound,
distinct .from the sound made by the breathing in the nose
and throat. The sound of the voice, when transmitted
through the chest, has a characteristic quality and pro-
duces a vibration of the chest walls. When the chest is
struck with the finger, the sound is modified by the reso-
nant quality of the lungs. All these sounds are changed
in lung diseases, and give a sure indication of the nature
and extent of the disease.

347. Abdominal and thoracic breathing. — When the dia
phragm contracts, it forces the abdominal organs down-
ward, making the abdomen more prominent. Breathing
by the free use of the diaphragm is called abdominal
breathing. When the diaphragm remains comparatively
quiet, the ribs are compelled to move more freely. Breath-
ing mainly by use of the ribs is called thoracic breathing.
In men abdominal breathing is greatest, while in women
thoracic breathing seems more prominent.

2OO

APPLIED PHYSIOLOGY

Distention of the stomach and intestine by a full meal,
or by gas, interferes with the downward movements of
the diaphragm, and compels a greater extent of thoracic
breathing.

Natural form

348. Effect of tight lacing. — A person whose waist is
laced tightly with corsets cannot breathe in the proper
amount of air, but is short of breath and easily fatigued.

Tight corsets also compress the liver and other abdomi-
nal organs. In extreme cases the liver becomes divided
almost into two parts by the pressure.

THE LUNGS

2O I

349. The respiratory center. — The movements of the
chest and diaphragm in breathing are controlled by a
small part of the brain situated just above the spinal cord,
and called the respiratory center. When it is destroyed,

*

Results of unhealthful dress.

respiration ceases at once, and no power can arouse it
again.

Stimulation of the nerves of the body which go to the respiratory
center may cause it to send out orders for the respiratory muscles to
t. Thus, suddenly throwing cold water on the chest will cause a

202

APPLIED PHYSIOLOGY

contraction of the muscles of breathing which lasts for a few seconds,
so that a person cannot catch his breath.

A substance sucked into the trachea irritates the nerves which go to
the respiratory center. The center sends back an order to the respira-
tory muscles to expel the substance by a forcible blast of air. Thus
the substance is coughed or sneezed up.

350. Artificial respiration. — The walls of the chest are
elastic and quickly return to their natural size when they

are relieved of
stress. It is pos-
sible, therefore, to
imitate natural
respiratory move-
ments upon a man
who has stopped
Diagram of artificial respiration, showing inspiration, breathing. This

The arrows show that the arms are moved outward jg called artificial
from the sides of the chest.

respiration.

By pressing hard upon the chest fifteen or twenty times
a minute, a great deal of air will be made to pass in and
out of the chest.
A more effective
method is to lay
the person upon
his back, with the
head lowest if pos-
sible. Standing
at his head, draw
each arm out-
ward and upward,
in a semicircle,

Diagram of artificial respiration, showing expiration.

The arrows show that the arms are carried directly for-
ward until they are pressed hard against the chest.

away from his body, until they are stretched above his head
almost in a line with his body. This raises the chest and

THE LUNGS 2O3

produces an inspiration. Then carry the arms directly
forward and down and press them forcibly against the
side of the chest. This produces an expiration. These
movements should be repeated about fifteen or twenty
times a minute, or at the rate of natural breathing.

If an assistant grasps the tongue and pulls it forward
during each inspiration, it will open the larynx and also
stimulate the nerves going to the respiratory center.

Every person should know how to perform artificial
respiration, for it may be the means of saving a life from
drowning or from an electric shock. No one should
hesitate to attempt artificial respiration in these cases, for
even crude and ignorant attempts will result in the entrance
of some air and may save a life.

SUMMARY

1. The lungs are two organs from which the red blood

cells obtain oxygen for the use of the cells of the
body.

2. Each lung is made of tiny air sacs which communicate

freely with the air through the windpipe and nose.

3. Each lung rests upon a curved muscle called the dia-

phragm, and is covered by curved ribs.

4. When the ribs are lifted or the diaphragm depressed,

air enters the lungs. This is inspiration.

5. When the muscles relax, the weight of the parts and

the elasticity of the lungs drive out some of the air.
This is expiration.

6. Inspiration and expiration occur alternately about

eighteen times a minute.

7. The movements of the ribs and diaphragm in breath-

ing are controlled by a small part of the brain just
above the spinal cord.

7. x:

204 APPLIED PHYSIOLOGY

8. Artificial respiration can be performed by alternately
pulling the arms above the head and compressing
them against the chest about twenty times a minute.

DEMONSTRATIONS

81. Each pupil can notice the different movements of his own
breathing. At will he can change from abdominal breathing to thoracic
breathing, or can use all of the muscles of the chest in taking a very
deep inspiration. A tape measure passed around the body just under
the armpits will show how the chest increases in size with each inspira-
tion and diminishes with expiration.

82. A small animal should be killed and its chest opened so as to
show the lungs and heart in place. Notice the shining pleura, and
that at the back part of the chest it leaves the chest wall and covers
the lungs. Notice the position of the ribs and diaphragm, and the ar-
rangement and direction of their muscle fibers. (See demonstration 35.)

83. In a recently killed cat or dog the diaphragm can be made to
contract by irritation of the nerve called the phrenic nerve, which con-
veys orders for motion from the respiratory center to the diaphragm.
There are two nerves, one of which enters the diaphragm near the
middle of each side of the arch. Remove the lungs carefully. Then
the site of the nerve can be recognized by a slight roughness in the
otherwise smooth pleural covering. Pricking or pinching this point
will cause a contraction of the diaphragm. (See demonstration 35.)

84. Kill a frog by placing it in a tight jar with a few drops of chloro-
form. Open its chest and abdomen. Insert a small pointed glass tube
into its trachea. The slitlike opening can be found upon the back of
the tongue. Blow through the tube to inflate the lungs, and at once tie
a string tightly around their base. Remove the lungs and let them dry.
Notice the partitions like the cells in a honeycomb, extending a little
way into the central cavity. Explain that a man's lung is like a col-
lection of tiny frog's lungs. (See illustration on page 196.)

85. Examine a prepared microscopic specimen of a lung and of
the trachea and bronchi. Notice the ciliated epithelium in the trachea
and bronchi. Notice that the walls of the air sacs form an irregular
network inclosing the large spaces of the air sacs. The specimen
will probably show a small bronchus. Notice its thick walls containing
some muscular tissue and possibly some cartilage.

THE LUNGS 2O5

86. Show the class how to perform artificial respiration. Have a
boy lie upon a desk and go through the movements of carrying his
arms above his head and of pressing them against his side again. Do
not perform the movements too rapidly and do not press the arms too
far backward above the head.

87. The pharynx and palate are puzzling parts to understand, but
are very simple when shown upon a small animal. With a sharp knife
and fine saw, divide the head and neck of a small animal through the
middle of the nose and backbone. Show that the hard palate and the
soft palate divide the nose from the mouth. Show that the pharynx
extends upward behind the nose and downward lower than the tongue.
Show the position of the tonsils and where adenoid vegetations form.

88. Cilia can be shown with cells from a frog's mouth. Gently
scrape its roof, removing a drop of slime with some of the epithelial
cells. Examine it with the high power of the microscope. The cilia
will appear as a fringe in rapid motion. (See demonstration 35.)

REVIEW TOPICS

1. Define respiration and state its object

2. Describe the nose, pharynx, larynx, trachea, bronchi,

cilia, air sacs, lungs, and pleura.

3. Describe adenoid vegetations and their effects.

4. Give the evil effects of mouth breathing.

5. Describe the chest, ribs, and diaphragm.

6. Describe inspiration and expiration.

7. Give the amount of air used in ordinary and in forced

breathing.

8. Give the action of the cilia.

9. Give the rate of breathing, and its variation in laugh-

ing, sobbing, coughing, hiccoughing, sneezing, gap-
ing, sighing, and snoring.

10. Describe the sounds produced by breathing.

n. Describe abdominal and thoracic breathing.

12. Give the effects of tight lacing.

13. Describe the respiratory center and its action.

CHAPTER XXIII
RESPIRATION OF THE TISSUES

351. Changes in respired air. — The air is composed of
about 80 per cent of nitrogen, 20 per cent of oxygen, and
T$1T Per cent °f carbonic acid gas. The nitrogen has no
effect upon the body, but acts simply by diluting the oxy-
gen. Air which is ordinarily breathed out from the lungs
contains 16 per cent of oxygen and 4 per cent of carbonic
acid gas, while the amount of nitrogen remains unchanged.
Thus, in breathing, the air gains as much carbonic acid
gas as it loses oxygen. Expired air is warmer and con-
tains more watery vapor than inspired air, and sometimes
contains a trace of a very poisonous organic gas.

352. Blood changes in the lungs. — Every 100 cubic
inches of venous blood entering the lungs contain 46 cubic
inches of carbonic acid gas, and from 8 to 12 cubic inches
of oxygen gas. As it leaves the lungs the same amount
of blood contains about 40 cubic inches of carbonic acid
gas, and 20 cubic inches of oxygen gas, and it has changed
its shade from the dark red of venous blood to the bright
red tint of arterial blood. It has also lost a small amount
of water and some heat. The essential change which
occurs in the passage of blood through the lungs is the
exchange of carbonic acid for a corresponding amount of
oxygen gas. In health, during quiet breathing, the blood
becomes completely saturated with oxygen.

353. Affinity of blood for oxygen. — Blood exposed to

206

RESPIRATION OF THE TISSUES

207

the air takes up oxygen very readily and becomes of a
bright red color. Thus, blood as it usually flows from
a slight wound, takes up
oxygen gas almost im-
mediately and becomes
the color of arterial blood,
and venous blood is sel-
dom seen. Between the
dark color of the venous
blood in the veins of the
hands, and the brighter
pink hue of the surround-
ing skin due to the capil-

. . Sketch of a thin slice of a lung, showing

lanes, there IS a contrast the arrangement of capillaries upon the

which is a good indica- walls of the air sacs (x 50).

tion Of the USUal differ- a interior of an air sac.

b bottom of an air sac covered with capillaries.
ence between venOUS and c Side of an air sac with capillaries.

arterial blood.

354. Exchange of oxygen and carbonic acid in the lungs.

— The blood in the capil-
laries of the lungs is sepa-
rated from the air in the
air sacs by only the thin
walls of the capillaries.
Oxygen from the air in
the air cells passes
through the capillary
walls into the blood
almost as readily as

though there were no
Capillaries upon the sides of an air sac

(X2oo). walls at all. In the blood

the oxygen combines with
the hemoglobin of the red blood cells, and the blood be-

208

APPLIED PHYSIOLOGY

comes of a brighter red color as it gains oxygen, Car-
bonic acid, which was combined with the alkalies of the
blood plasma, passes through the capillary wall into the
air of the air sac as easily as the oxygen entered the blood.

355. The skin and stomach as respiratory organs. —
Wherever the blood tubes are in contact with the air,
absorption of oxygen will take place. In the stomach and
intestine the blood tubes are very near the surface, and
are in contact with air swallowed with the food. So some
oxygen will be absorbed and some oarbonic acid gas given
off. The skin also absorbs oxygen and gives off carbonic
acid gas. In a frog at least J of the respiration is per-
formed in this Way. In man, about ^^ as much respira-
tion is carried on by the skin, stomach, and intestine as by
the lungs.

356. Respiration of the cells of the body. — After leaving
the lungs, the blood is distributed through the arteries,

and enters the capillaries
of the body. As it enters
the capillaries it contains
the same amount of gases
as when it left the lungs ;
that is, each 100 cubic
inches of blood contains
40 cubic inches of car-
bonic acid gas and 20 of
oxygen. As it leaves the
capillaries, it contains the same amount of the gases as
the venous blood which enters the lungs; that is, each 100
cubic inches contains 46 cubic inches of carbonic acid gas
and 12 of oxygen. The exchange in the capillaries bal-
ances the exchange in the lungs.

When a piece of flesh is put into a dish of blood, oxygen

Diagram of the respiration of cells.

RESPIRATION OF THE TISSUES 2CK)

will leave the red blood cells and combine with the cells
of the flesh. In a similar way oxygen leaves the red blood
cells in the capillaries and, passing through their thin walls,
unites with the cells of the body, producing carbonic acid
gas, water, and urea. The water and urea go back to the
blood and are thrown off by the kidneys. The carbonic
acid gas passes through the capillary wall into the blood
and unites with the alkalies of the plasma. This goes on in
every capillary and cell of the body and constitutes the
real act of respiration. The lungs and red blood cells are
only devices for carrying oxygen to the deep cells of the
body.

357. Oxidation of SUgar and fat. — Neither sugar nor fat
becomes a living part of the cells of the body, but after being absorbed
both are oxidized at once and furnish about three times as much heat
and energy as the albumin, which forms a part of the cells. But oxi-
dation in the body is a living process, and requires the operation of
living tissues. So it is unlikely that it occurs in the blood stream. As
sugar is absorbed, the cells of the liver take it into their own substance,,
and probably oxidize it there. In the same way the fat is probably
taken up by the epithelial cells of the air sacs of the lungs and oxidized.
In each case the heat is distributed through the whole body by the
blood.

358. Respiration a continuous process. — When the
breath is held, the oxygen in the lungs and that carried
by the red blood cells is sufficient to supply the body for
only about half a minute. By the end of that time all the
blood becomes venous and a great shortness of breath is
felt.

Oxygen passes from the lungs through the blood tubes
to the cells of the body with great rapidity, so that by a
few deeper breaths enough extra oxygen is taken up by
the red blood cells to relieve shortness of breath caused
by their lack of oxygen.

OV. PHYSIOL. — 14

2IO APPLIED PHYSIOLOGY

359. Amount of oxygen used daily. — The amount of
oxygen used in the body is constantly varying. During
muscular exertion greater power is required than when the
body is at rest. To keep up the increased power, more
oxygen must leave the blood and unite with the muscle
cells. During sleep less oxygen is needed, but the average
amount used each day is fairly constant.

It is a simple example in arithmetic to calculate how much oxygen
the red blood cells usually carry.
1 8 = no. of respirations per minute.

30 = no. of cubic inches of air in each inspiration.
540 = no. of cubic inches of air inspired each minute.

60
32400 = no. of cubic inches of air inspired each hour.

.04 = per cent of air which enters the red blood cells as oxygen.
1296 = no. of cubic inches of oxygen entering the blood each hour.
1296-:- 1 728 = 0.75= cubic feet of oxygen entering the blood each hour.

0.75

1.2 = ounces weight of a cubic foot of oxygen.

0.9 = ounces of oxygen entering the blood each hour.

24
21.6 = ounces of oxygen entering the blood each day.

Allowing two or three ounces more for extra exertions, about 25
ounces of oxygen enter the body each day. This is about the amount
needed to oxidize the food which a man usually eats.

The amount of carbonic acid given out is about the same as the
amount of oxygen taken in, if it is measured in cubic inches. But since
the carbonic acid is heavier, it amounts to about 30 ounces a day. About
20 ounces of water are also breathed out each day.

360. Effect of exercise upon the amount of oxygen
absorbed. — In quiet breathing each red blood cell is
loaded with oxygen to its full capacity. During muscular
exertion the heart beats more forcibly and faster, driving
the red blood cells more rapidly, and thus, in a given time,
more oxygen will be carried. But when the cells are shot

RESPIRATION OF THE TISSUES 211

through the capillaries too rapidly, there is no time for
either giving or receiving oxygen, and the body may be
actually starved of oxygen. So the average amount of
oxygen which the blood can carry is found to be about
25 ounces daily.

It is possible to educate the respiratory muscles so that
during physical exertion they act more regularly and
strongly. As a result, the lungs are expanded more, and
a greater area of capillaries is exposed to the air. The
heart also may be trained to restrain its violent action, so
that the blood is not shot through the capillaries of the
lungs too rapidly to take up oxygen. An athlete trains
his body so that it can absorb more than 25 ounces of
oxygen daily, and thus he can put forth a greater
amount of exertion. Such a person is said to be long
winded.

361. Causes of shortness of breath. — The sensation of short-
ness of breath is usually due to a deficiency of oxygen in the blood
which circulates through the respiratory center. The blood contains
too. little oxygen when an extra amount of oxygen is used during great
physical exertion. At first, the heart pumps the blood faster so that it
carries more oxygen in a given time, but when the blood is pumped
very rapidly, the red blood cells are shot through the lungs so quickly
that they cannot obtain the necessary oxygen. When, as in heart dis-
ease, the blood is pumped too slowly, only a small amount of oxygen will
be carried through the respiratory center, and there will be continuous
difficulty in breathing. Shortness of breath is often the first sign of
heart failure. After severe hemorrhage there are too few red blood
cells to carry the full amount of oxygen, and so shortness of breath will
be felt. Death by bleeding is due to suffocation and lack of oxygen.
In the disease called anemia there are too few red blood cells to carry
oxygen, and so there is shortness of breath on exertion. When the
larynx or the trachea is compressed or obstructed, as in choking, or
when the smaller bronchi are filled with mucus, as in bronchitis, oxygen
j is prevented from entering the blood, and the respiratory center feels a

iat shortness of breath.

212 APPLIED PHYSIOLOGY

362. Oxygen inhalations. — Since the red blood cells
are loaded with oxygen to their full capacity as they leave
the lungs, they could absorb no more even if it were in-
haled in a pure form. When there is a shortness of breath
during disease, pure oxygen is sometimes inhaled to take
the place of the diluted oxygen of the air. When the lack
of oxygen is due to a diminished number of red blood
cells, or if the blood flows too slowly to carry enough oxy-
gen, inhaling oxygen can do no good, for the blood cells
leaving the lungs are already loaded with it. The poisons
of certain diseases may cause the arteries to contract and
the heart to beat with great force and rapidity. Then the
blood cells may move so quickly that they have no time to
take up oxygen from the lungs. Neither rest nor violent
inspiratory efforts will relieve the resulting shortness of
breath, but more oxygen may reach the blood cells if it
is inhaled in a pure form.

If there is an obstruction to the entrance of air into the
lungs, more oxygen may pass the obstruction if it is inhaled in
an undiluted form. When the larynx or trachea is obstructed
by a membrane in diphtheria, or when the small bronchi are
rilled with mucus, as in bronchitis and pneumonia, then the
inhalation of pure oxygen may be of great benefit.

363. Asphyxia. — When the breath is held, a feeling of
discomfort comes on in about half a minute, which soon
{becomes great distress. If a person is prevented from
taking a breath, he will become unconscious in a few
seconds, but will make great inspiratory efforts for a
minute or more. There will be convulsions, and the face
will turn purple, for all the blood is venous. Death will
take place in less than five minutes. This is called
asphyxia. At any time before death actually takes place
life can be restored by artificial respiration.

RESPIRATION OF THE TISSUES 21$

364. Drowning. — Drowning is a form of death by
asphyxia, but is complicated by the entrance of water into
the lungs.

The treatment of drowning is simply to perform artifi-
cial respiration. In order to do it, it will be necessary to
remove the water from the lungs. This can be done by
turning the person upon his face and forcibly compressing
his back. It will be still better to suspend him head down-
wards for a few seconds, or standing astride him to raise
him up and down about twenty times a minute by grasp-
ing him about the lower part of the chest. This performs
artificial respiration and lets out the water at the same time.

The person's limbs should be rubbed vigorously toward
the heart and kept warm by hot water bottles. No time
should be lost by carrying him to a building, but artificial
respiration should be done on the spot. Even if the per-
son has been in the water half an hour or more, it is
possible to restore life.

365. Electric shock. — A shock of electricity kills by
overwhelming the nervous mechanism which controls the
heart and lungs. A shocked person is unconscious, and
apparently lifeless, and yet life may be restored by artifi-
cial respiration. It should be done at once, and continued
for a long time if life is not quickly restored.

366. Effect of alcohol upon the lungs. — Alcohol partially
paralyzes the arteries of the body so that they dilate and
permit a larger quantity of blood to pass through. Thus,
the capillaries of the lungs may be distended with the rest.
Then they may partly fill the air sacs so that less air can
enter. If the distension continues for some time, the walls
of the capillaries may thicken so that oxygen will pass
through them less readily. The walls of the air sacs
themselves may become thickened, and the exchange of

214 APPLIED PHYSIOLOGY

oxygen and carbonic acid impeded. This effect may be
produced by continuous moderate drinking.

367. Alcohol interferes with the respiration of the cells. —
Alcohol is quickly absorbed from the stomach and intes-
tine and as quickly disappears. After it is taken, little
or no alcohol, or any substance like alcohol, or any sub-
stance containing so little oxygen as alcohol, can be found
in any waste of the body. Hence the inference is that it
must be oxidized, although the exact point and the manner
of its oxidation may not be known. But the evidence for
its oxidation is the same as that for the oxidation of sugar.

Every ounce of alcohol requires nearly two ounces of
oxygen to oxidize it fully. Taking twenty-five ounces of
oxygen gas as the amount used in a day, there will be only
one ounce used in an hour. So to oxidize an ounce of
alcohol takes an amount of oxygen equal to the whole
supply of the body for two hours. Three or four drinks
of whisky contain this ounce of alcohol. • If this amount
is drunk, there will soon be a lessened action and a nar-
cotic effect throughout the body, due mainly to the lack
of oxygen. A noticeable degree of uncertain action is
called intoxication.

Using alcohol in the body is like burning kerosene in
a coal stove. By taking great care a little kerosene can
be made to give out some heat from the stove, but the
operation is dangerous. Some people seem to oxidize
alcohol within the body with but little harm ; but they
run great risks of doing themselves harm, and the result
is not nearly so good as if they had used proper food.

368. Poisons produced by alcohol. — When too little oxy-
gen enters the draft of the stove, the wood is burned imper-
fectly, and there are clouds of smoke and irritating gases.
So, if oxygen goes to the alcohol and too little reaches

RESPIRATION OF THE TISSUES 21 5

the cells, instead of carbonic acid gas, and water, and urea
being formed, there are other products, some of which are
exceedingly poisonous and which the kidneys handle with
difficulty. The poisons retained in the circulation never
fail to produce their poisonous effects, as shown by head-
aches, clouded brain, pain, and weakness of the body.
The word intoxication means, "in a state of poisoning."
These poisons gradually accumulate as the alcohol takes
oxygen from the cells. The worst effects come last, when
the brain is too benumbed to judge fairly of their harm.
It is not true that alcohol in a small amount is beneficial.
A little is too much, if it takes oxygen which would
otherwise be available to oxidize wholesome food.

369. Effects of tobacco. — Tobacco smoke contains the
same kind of poisons as the tobacco, with other irritating
substances added. It is usually sucked into the mouth
and at once blown out again, but cigarette smoke is com-
monly drawn into the lungs and afterwards blown out
through the nose. It is irritating to the throat, causing
a cough and rendering it more liable to inflammation. If
inhaled into the bronchi, it produces still greater irritation,
and the vaporized nicotine is more readily absorbed as the
smoke is inhaled the more deeply. Cigarettes contain the
same poisons as other forms of tobacco, and often contain
other poisons which are added to flavor them.

370. Respiration in birds. — The lungs of all land ani-
mals are like man's lungs, and the process of respiration
is the same. The lungs of birds are fixed in the upper
part of the thorax, and in addition they are provided with
two smooth bags, each somewhat larger than the lung.
Each bag connects with the air sacs of the lung, and also
with the interior of the larger bones. Respiration can
occur in the bags and bones as well as in the lungs.

2l6 APPLIED PHYSIOLOGY

The air bags are expanded with air during flight, and
thus the body is made lighter in proportion to its size,
in order that the bird may fly more easily.

371. Respiration in water animals. — Some water ani-
mals, such as the porpoise and the whale, possess lungs like

land animals, and are compelled
to come to the surface of the
water in order to breathe, but
fish have a special apparatus so
that they can use the oxygen

which is dissolved in water. On

Gills of a fish. each gide of a fish>s head is a slit>

like opening reaching from the interior of the mouth to
the surface of the body. In each opening are four half
circles of limber bone. From the back of each circle a
row of thin fingerlike plumes projects, so that it looks
like a red feather with plumes only on one side. These
half circles are the gills. Each plume contains a blood
tube which is separated from the water by a very thin
wall. The fish forces the water through his mouth and
out between the gills, and the oxygen contained in it
readily passes through the thin wall of the blood vessel
into the red blood cells.

372. Respiration in a frog. — A frog in the tadpole
form is provided with gills which project into the water
from its neck, but when it becomes a perfect frog the
gills disappear and lungs are formed. But the frog's skin
is able to absorb oxygen and to give off carbonic acid
gas about one eighth as rapidly as the lungs.

373. Respiration in insects. — In insects from three to
nine tubes extend into ea.ch side of the abdomen and
divide into small branches, but do not communicate with
any cavity. The fluid which answers for the insect's

RESPIRATION OF THE TISSUES

blood comes in contact with the surface of the tubes and
absorbs oxygen from the air in them. As they possess no
hemoglobin or red blood cells, oxygen is simply dissolved
in the blood ; but owing to the small size of their bodies,
this is sufficient for their use.

374. Respiration in shellfish. — Shellfish, such as oysters
and clams, have gills like fringes along their front edges.
The gills are covered with cilia which cause currents of
water bearing food and air to flow through the shell.

375. Respiration in plants. — A plant also breathes.
While it uses heat from the sun in the manufacture of
starch from the carbonic acid gas and water, yet for its
own movements it requires a production of heat within
itself. In order to climb a pole and unfold its flowers, a
vine requires power which is furnished by the oxidation of
its own substance. At the height of the flowering season
the temperature of the plant is raised slightly above that
of the surrounding atmosphere, and carbonic acid gas is
given off. In every case the heat and power is furnished
by oxidation of some of the plant's own substance, but the
amount of carbonic acid gas given off is insignificant in
comparison with the amount of carbonic acid gas which
the plant uses as food. A little oxygen is absorbed by
the leaves, but it is small in amount compared with what
is given off by the plant.

SUMMARY

1. As blood passes through the capillaries of the lungs it

gives carbonic acid gas to the air and takes about
the same amount of oxygen from the air.

2. As blood passes through the capillaries of the body it

gives up oxygen to the cells and takes carbonic acid
gas from the cells.

APPLIED PHYSIOLOGY

3. The exchange in the two sets of capillaries balances.

4. Within the living cells the oxygen unites with the

albumin, fat, and sugar, producing carbonic acid
gas, water, and urea.

5. About twenty-five ounces of oxygen are used daily in

oxidizing the body.

6. When not enough oxygen is present within the body,

there is a shortness of breath.

7. Alcohol often causes distension and thickening of the

capillaries and of the walls of the air sacs, so that
oxygen passes through them less readily.

8. The alcohol of three or four strong drinks of liquor

uses as much oxygen as would supply the whole
body for two hours.

9. As a result of taking oxygen from the cells of the

body, the cells act in an uncertain manner, which is
called intoxication.

10. Tobacco smoke irritates the air passages. It contains

nicotine, which can enter and poison the body.

11. All kinds of animals and plants breathe in oxygen

and give off carbonic acid gas.

DEMONSTRATIONS

89. With a glass tube, blow air through some limewater, and notice
that it grows milky, showing the presence of carbonic acid gas. Breathe
upon a cold glass and notice that moisture collects from the breath.
Call attention to the fact that bad odors in the breath are due to de-
cayed teeth, a coated tongue, or foul stomach, or possibly to a dirty nose.

90. The change in color from venous to arterial blood can be illus-
trated by cutting into a thick slice of beef. At first the cut surface is
dark and purplish, and of the color of venous blood. But in a few sec-
onds the blood in the meat absorbs oxygen from the air and becomes
bright red in color like arterial blood.

91. With two needles tease apart a bit of gill from a shellfish and
examine it with the microscope for the waving cilia.

RESPIRATION OF THE TISSUES 2 19

92. Show a fish's gills and if possible a tadpole's also. Wigglers,
the young of mosquitoes, can be found in rain barrels, and are very
interesting. Each wiggler has a breathing tube near the hinder part
of its body. The insects wiggle about in the water and at intervals
come to the surface and thrust their breathing tubes above the surface
to get oxygen directly from -the air.

REVIEW TOPICS

1. Give the changes occurring in the air within the lungs.

2. Give the changes which occur in the blood within the

lungs.

3. Show that the blood carries oxygen.

4. Show that the skin and stomach are respiratory organs.

5. Show that the cells of the body take oxygen and give

off carbonic acid gas.

6. Show that the blood carries carbonic acid gas.

7. Show that respiration is a rapid and continuous

process.

8. Calculate how much oxygen is used daily and how

much carbonic acid gas is given off.

9. Show why a person becomes long winded by training.
10. Give some causes of shortness of breath.

n. Tell when and why inhalations of pure oxygen are of
benefit.

12. Give the effects of alcohol upon the walls of the air

sacs.

13. Show how alcohol affects the respiration of the cells.

14. Show how alcohol causes poisons to develop within the

body.

15. Give the effects of tobacco upon the air passages.

16. Show how respiration is modified in birds, in fish, in

frogs, in insects, and in shellfish.

17. Explain the respiration of plants.

CHAPTER XXIV

THE AIR AND VENTILATION

376. Composition of air. — Every 100 parts of air are
composed of about 20 parts of oxygen and 80 parts of
nitrogen : T^ per cent of the air is carbonic acid gas.
Air contains water in varying amount. Some dust par-
ticles are always floating about, and also a few living
germs of plants like those producing mold and yeast.
These substances are found in all air, and none are
harmful.

377. Ozone in the air. — There is a form of oxygen called
ozone which is much more active than common oxygen. It
can be made by passing a strong current of electricity
through a tube of oxygen. During thunderstorms some is
formed, which imparts a peculiar odor and exhilarating
property to the air. Some is formed in pine forests, and
to it the beneficial effects of the forests upon consumptives
may be due. It is never found in any great amount in
the air.

378. Argon. — It was discovered in 1894 that the part
of the air supposed to be pure nitrogen contains a gas
hitherto unknown, to which the name argon has been given.
One per cent of the air is argon. Like nitrogen, it cannot
be made to unite with any substance directly from the air,
and so both act simply to dilute the oxygen. But, unlike
nitrogen, it does not form a chemical combination with
anything at all, but is always found simply mixed with the

220

THE AIR AND VENTILATION 221

air, or with a few other substances. Its discovery has not
modified our ideas of the physiological effects of the air.

379. Dust in the lungs. — If the dust in the air is small in
amount, it adheres to the moist surface of the nose and pharynx, and
does not enter the trachea. If some enters the trachea, it becomes
entangled in the cilia of the epithelial cells and is forced back towards
the mouth and then coughed out. If the air is very dusty, some dust
will enter the air sacs. Then the dust particles will be carried by the
lymphatics to the nearest lymph nodes, where they will be deposited
and remain harmless. But the greatest danger from dust is that many
of the particles may consist of disease germs (p. 418).

380. Occupation diseases. — Even though the lymph nodes
take care of inhaled dust, after a while the continuous irritation of the
hard particles injures the delicate lining of the bronchi and air sacs,
and causes bronchitis or asthma or pneumonia. Tool grinders are
especially liable to the trouble, for the fine particles of stone and steel
which fly off in their work and are inhaled, cannot be taken up by the
lymphatics. Potters, miners, flax workers, and pearl button makers
are all subject to lung troubles to a greater degree than workers in a
dustless atmosphere. Those who work with quicksilver or phosphorus
are liable to inhale the fumes and be severely poisoned.

381. Amount of oxygen needed to support life. — When
inspired air contains less than 20 per cent of oxygen, a
shortness of breath comes on, which is in proportion
to the lack of oxygen. A candle will not burn in air
containing less than 17 per cent of oxygen, while air
containing only 15 per cent of oxygen will support life,
but there will be great shortness of breath. In old wells
and cellars oxygen is often replaced by carbonic acid gas,
and men have been suffocated in them. A simple test of
the safety of entering them is to lower a lighted candle
into the suspected place. If it burns, there is surely
enough oxygen to support respiration. When the amount
of oxygen is diminished to ten per cent, animals die in a
few moments with all the symptoms of suffocation.

222 APPLIED PHYSIOLOGY

382. Rarefied air. — Every square inch of surface, in-
cluding that of the body, sustains a weight of fifteen
pounds of air, but it is balanced by an equal pressure of
air inside the body, in the lungs and stomach and other
cavities, and so it is not felt. At high elevations there is less
atmosphere pressing from above, and so the air expands
and becomes lighter. Then a lung full of air will contain
less oxygen. At a height of three and a half miles the air
is only one half as dense as at the surface of the earth,
and at the height of five miles it is almost impossible to
breathe enough oxygen to sustain life. The lessened
pressure upon the body disturbs the flow of blood, espe-
cially in the brain, and produces dizziness and fainting.

In mountainous regions the air is lighter and holds less
moisture than in lower regions. It is also purer, for it is
removed from the contamination of cities which crowd the
lower waterways. So those regions are favorable for those
suffering with lung diseases such as consumption. Proba-
bly a still greater benefit is derived from the respiratory
exercises and the full expansion of the lungs which are
necessary in order to obtain sufficient oxygen.

383. Effect of increased pressure of air. — In working
under water in laying deep foundations for buildings, a
large box called a caisson is sunk to the bottom, and into it
air is forced so as to keep out the water. Men work within
the caisson subjected to double or triple the natural pres-
sure of air. Although more air is inspired with each breath,
the blood does not seem to take up more oxygen than usual ;
but the increased pressure of air upon the arteries and veins
produces great disturbances of the circulation. It is impos-
sible to remain in the caisson longer than an hour or two
at a time. In leaving the caisson, the air pressure must
be diminished as slowly as on entering, so as to permit

THE AIR AND VENTILATION 223

the liberated gases to expand slowly. The ear drums
could be easily ruptured by a quick change in pressure.
Sometimes the pressure causes a severe injury of the
spinal cord.

384. Effects of carbonic acid gas. — Carbonic acid gas
itself has very little harmful effect upon the body. When
air containing one fourth its bulk of carbonic acid gas is
inhaled, the air sacs soon contain more of the gas than
is found in the blood. Then carbonic acid gas is no longer
given off, but remains in the blood and air sacs, and pre-
vents the entrance of oxygen. Shortness of breath, uncon-
sciousness, and death soon occur, caused mainly by the
displacement of the oxygen. Carbonic acid has been used
to produce insensibility during surgical operations but its
effects cannot be controlled, and its use is unsafe.

When many persons are confined in a small room, the
oxygen is speedily used up, and carbonic acid gas takes its
place. When the amount of oxygen is diminished to ten
per cent, death will occur, caused rather by the lack of
oxygen than by the presence of the carbonic acid gas or
other substances in the expired air. But discomfort will
be felt long before the oxygen is diminished to an appre-
ciable degree.

385. Foul air. — Besides the carbonic acid gas, the ex-
pired air contains a greater or less quantity of water and
of foul-smelling vapors. Odors are constantly given off
also by the skin of the most cleanly persons. In the air
of a closed room in which several people have been for
some time, there is a characteristic odor which belongs to
man, just as certain odors are peculiar to different lower
animals. These odors are very oppressive. They cause
sickness in sensitive persons mainly because of their
unpleasantness. This effect passes off when pure air is

224 APPLIED PHYSIOLOGY

breathed. The heat of a closed room greatly intensifies
the effect of the foul air.

386. Cause of bad effects of foul air. — No one thing can
be found in stuffy air to account for all the bad feelings which it pro-
duces. The diminution of oxygen is too slight to produce noticeable
effects, but the combination of heat and foul odors is very oppressive
to persons not accustomed to them, while the carbonic acid gas tends
to cause drowsiness and dullness of mind. Those who live in a foul
atmosphere continually are usually too poor to buy nourishing food,
and too busy to take exercise in the open air, and, moreover, are
greatly overworked. These causes produce even more ill health than
the foul air.

387. Bad odors. — Decaying matter gives off bad odors. Many
animals and vegetables have an offensive smell, and in many manu-
factures foul odors are continually poured into the air. These odors
in the air are seldom harmful, yet the s*ource of the odors is usually
dangerous to health, and the odors are given off as a warning. It
is nearly always true, that harmful things have an offensive smell and
taste. So a bad odor reveals a decaying body which might poison a
well, or a disease which might be communicated to others.

Since odors are only signs, the danger is not past if only the odor
is destroyed. Ammonia, carbolic acid, or perfumery may mask the
odor, but they only obscure the source of danger.

388. Sewer gas. — Sewer gas is exceptionally offensive
and penetrating. The odor is not especially harmful, but
disease germs which are emptied into the sewer from sick
rooms are easily carried with the gas. Usually the strong
odor betrays the leak in the pipes before the germs have
gained an entrance.

389. Cellar air. — Cellars are apt to be closed, so that little
fresh air and light can enter. Decaying vegetables and other sub-
stances may accumulate in the corners. This makes a breeding place
for disease germs, which may be carried up through the floors into
living rooms above. A cellar should be kept dry, clean, and well
aired.

THE AIR AND VENTILATION 22 5

390. Malaria. — Malaria, chills and fever, fever and
ague, or intermittent fever, as the disease is variously
called, is caused by germs that grow within the bodies
of certain kinds of mosquitoes, and are left beneath the
skin when the insects bite a person. In order to rid a
place of malaria, the malarial mosquito must be extermi-
nated. All mosquitoes spend the first part of their lives
in stagnant water as wigglers, and may be destroyed by
draining the marshes and stocking the pools with fish
which eat the wigglers.

391. Night air. — There is a popular belief that during the night
the air contains some harmful substance which disappear^ during the
day. But the air of the early evening, which is supposed to be the
worst air of the day, has been purified by hours of sunshine, while
the air of early morning, which is supposed to be the best of the day,
has been exposed to hours of the noxious influences of darkness. So
the belief is a contradiction in itself.

392. Contamination of air by fire and light. — In addi-
tion to the impurities produced by breathing, the air of
inhabited rooms is further rendered impure by fires and
lamps. A tallow candle will consume half as much oxy-
gen in a given time as a man. A lamp burning a pint of
oil in an evening uses as much oxygen, and gives off as
much carbonic acid, as a man gives off during a whole
day. A stove uses an immense amount of oxygen, but the
gases pass up the chimney. Candles and lamps often
pour bad-smelling gases into the air.

393. Coal gas. — When coal is heated, it gives off a gas called
carbonic oxide. Carbonic oxide is the main part of illuminating gas,
and in a stove, burns with a blue flame. It is extremely poisonous
when breathed. It unites with the hemoglobin of the red blood cells
and destroys their power of carrying oxygen. Gas from a smoking

ov. PHYSIOL. — 15

226 APPLIED PHYSIOLOGY

coal stove or a leaking gas pipe may smother a whole family while they
are asleep.

In treating a case of poisoning by gas, an abundance of fresh air
should be admitted, and artificial respiration should be performed.

394. Germs of disease in foul air. — Disease germs may
be breathed into the air. If the air of a room smells
stuffy, it is a hint that the germs as well as the stuffy
ddors may be accumulating. Lung diseases are especially
frequent among those who work in close rooms. The
germs of " colds," scarlet fever, and all other " catching "
diseases, are also likely to accumulate in a close room.
Sick persons often breathe out the germs of disease, which
may reenter the body and continue the disease. More-
over, every discomfort retards recovery, so in sick rooms
and hospitals a continuous supply of fresh air is especially
necessary, while in every room the air should be changed
often enough to prevent the stuffy odor from developing.

395. Consumption. — Tuberculosis of the lungs, or consumption,
is an infectious disease, caused by the growth of living germs within
the lungs. A person suffering with consumption is continually giving
off the germs in the secretions from his air passages. His handker-
chief contains millions of them. While moist they remain on the
handkerchief or clothes, but when dry they may float through the air,
and when inhaled may produce the disease. A consumptive is always
a menace to other occupants of a room, especially if he does not exercise
great care with the secretions from his nose and mouth (p. 392).

396. Ventilation. — Continually replacing the impure air
of a room with fresh air is ventilation. Nowadays, with
air-tight rooms and closed stoves, openings need to be pro-
vided for the exchange of air. When, by breathing, the
quantity of carbonic acid gas in the air is increased by one
half its natural amount, other substances have also en-
tered the air, so that it begins to be stuffy. When the

THE AIR AND VENTILATION 227

quantity of carbonic acid gas is doubled, the air is mark-
edly oppressive. If the carbonic acid gas is increased to
three times its natural amount, the air is too oppressive for
comfort, and may contain enough germs of disease to be
dangerous to health.

397. Computation of amount of fresh air. — About ^ per
cent of fresh air is carbonic acid gas. When T^7 per cent more of
carbonic acid gas has been added to the air, the air begins to be stuffy
and unfit for use. Suppose there is an air-tight room twenty feet square,
and ten feet in height, and in it one man is living ; the room will con-
tain 4000 cubic feet, yf^ per cent of 4000 cubic feet is T8^ of a cubic
foot, which is nearly the average amount of carbonic acid gas breathed
out by the man each hour. Thus in an hour a man renders 4000 cubic
feet of fresh air stuffy. In reckoning the amount of fresh air to be
admitted to rooms, 4000 cubic feet per hour is the smallest amount
which can be safely allowed. Therefore, if only one person breathes
the air of a room twenty feet square, and ten feet high, the air needs
to be wholly renewed each hour, and yet it contains enough oxygen to
last a week. Fresh air is needed when the air of a room smells stuffy
to a person coming from pure air.

398. Natural ventilation. — When air is heated it ex-
pands so as to fill more space. While a cubic foot of air
at a temperature of 32° F. weighs about 1.2 ounces, at
80° F. it weighs about i.i ounces. So heated air, being
lighter, tends to rise. The air is slightly warmed in
breathing, and so tends to rise to the ceiling, while the
cool air which enters the room remains near the floor.
So the floor is usually cooler than the ceiling. If an
opening is made near the ceiling, and another near the
floor, the warm air of the breath will naturally pass out at
the upper opening, and the cool fresh air will enter the
lower opening. If only a few persons are in a room,
the openings about windows and doors may be sufficient
without special ventilation. If many persons are together

228

APPLIED PHYSIOLOGY

in a room, the natural cracks and openings are not suffi-
cient, but other openings must be made.

399. Methods of ventilation. -<— In ventilation a per-
ceptible current of air must be avoided, for many people
easily take cold when a single part of the body is cooled

Diagram of the natural ventilation of a room.

The arrows indicate the direction of the air currents.

as by a draft. The air of a room can be changed only
three times an hour without producing noticeable drafts
throughout the room.

Many devices have been used to secure an even distribution of the
incoming fresh air. The simplest is to lower the upper window sash.
Warm air will pass out above the upper sash, while the cooler fresh air
will enter between the two sashes, and will be given an upward direc-

THE AIR AND VENTILATION 22Q

lion toward the warmer air of the ceiling. There it will become warm,
and finally will spread through the room like a gentle shower, instead
of in a rushing stream.

A modification of the same idea is to raise the lower sash a few inches
and insert a narrow board in the lower opening, so that a space is left
between the sashes for the entrance of fresh air. The opening for fresh
air may be through the floor under the stove, and thus the air will be
heated as it enters the room. An open fireplace produces an upward
current of air. An opening into the chimney flue near the ceiling will
:arry off much of the foul air.

In many churches a small part of the window is hinged so that its
top can incline inward. If the window is placed about two thirds of
the way between the floor and ceiling, the warm air will pass out above
the window, while the cool, fresh air will enter below it. The inclina-
tion of the window will cause the air to flow toward the ceiling at first,
where it will be warmed and scattered so tnat it cannot produce drafts
upon the heads of the listeners. The addition of an opening in the
center of the ceiling for the escape of the warm air forms an efficient
mode of ventilation.

Hot air registers both heat and ventilate a room, if care is taken to
admit fresh air to the pipes. The hot air passes up from the furnace
because it is lighter than cold air. An opening in the window or into
the chimney is needed to allow the air of the room to escape, so that
the warm fresh air can enter.

Since on a cold day the air inside a room is much warmer than the
air outside, a current of air will rush through every crack, so that
good ventilation will be secured by a very small opening. Since on a
warm summer's day the air inside and outside is nearly of the same
temperature, large openings are necessary to effect the change of air.

400. Forced ventilation. — In large buildings, such as factories
and theaters, warm fresh air is forced into the rooms by rotary fans, and
the impure air escapes through openings in the ceiling. Thus the
amount of heat and air admitted can be exactly regulated.

Another way of ventilating large houses is to suck out the impure
air by rotary fans, while fresh warm air is admitted through small open-
ings near the floor, thus preventing drafts. This method is being
adopted in large buildings to the exclusion of other methods.

401. Filtration of air. — In forced ventilation the air is con-
ducted through a large box, which has partitions arranged so as to

230 APPLIED PHYSIOLOGY

break the air current and allow the dust to settle. In some, the air is
passed through a layer of cotton. Cold air contains less moisture than
warm air, and unless the air is given more moisture before it is sent to
the rooms, it will be very dry. So a pan of water should always be
kept inside the air box of a furnace.

402. Schoolroom ventilation. — Children are especially
susceptible to unhealthful surroundings, and the air of
a schoolroom, in which they spend the greater part of the
day, should be kept pure. Pure air means clearer brains
and better lessons, and may determine whether or not a
child shall gain a sufficient knowledge to assure his suc-
cess in life. In every half day of school it is well to allow
a short recess in which windows and doors can be thrown
wide open and the pupils sent out to get deep breaths of
oxygen during play.

The upper sashes of all the windows on the side of the
schoolroom away from the wind can be kept open a space
so as to produce a gentle outward current of foul air.

If the upper sashes cannot be lowered, the lower one
can be raised and a board inserted under it so that the
only opening left is between the two sashes.

If registers or special means of ventilation are provided,
they should be watched and regulated according to the
needs of the air.

403. Purification of the atmosphere. — Although it is con-
tinually receiving impurities, the atmosphere as a whole never becomes
foul, for the process of purification never ceases. First, the wind scat-
ters the impurities to a height miles above our heads and over the seas
to arctic and uninhabited regions, and thus dilutes the impurities.
Second, rain washes out dust and germs and soot, and foul gases, and
carries them into the earth. Third, sunlight destroys living germs
floating in the air, and dries up stagnant sources of impurities. Fourth,
plants, both on land and in the sea, absorb carbonic acid gas and
restore the oxygen to the air. By these means the composition of the
air is kept always the same.

THE AIR AND VENTILATION 23!

SUMMARY

1. Air is essentially oxygen diluted with four times its

volume of nitrogen.

2. When the amount of oxygen is diminished there is

shortness of breath.

3. Exhaled carbonic acid gas is not poisonous in itself,

but if present in great amounts it may keep oxygen
out of the lungs.

4. Foul-smelling vapors, carbonic acid gas, moisture, and

the contamination by fire and lights make the air of
crowded rooms oppressive.

5. Coal gas inhaled may unite with the hemoglobin in the

red blood cells so that they will not carry oxygen.

6. The main thing to be feared in close air of crowded

rooms is the disease germs which may be breathed
into it.

7. The air of a room should be changed often enough to

allow 4000 cubic feet of fresh air to each person
each hour.

8. Breathed air is warm, and tends to rise and pass out of

cracks and openings in the upper part of the rooms,
while cold, fresh air enters by lower openings.

9. In large buildings the foul air is either forced or

drawn out by rotary fans, and fresh warmed air
enters to take its place.

IO. The atmosphere is purified by winds, rain, sunlight,
and plants.

DEMONSTRATIONS

93. The harmlessness of carbonic acid gas can be illustrated by
soda water, which is water in which a large amount of the gas is held
under pressure. Open a bottle and inhale the liberated gas. Notice
its pungent odor and taste.

232 APPLIED PHYSIOLOGY

• i"*-" : ' ' •

94. Hold a candle or lighted match near each crack of the room and

notice that usually the flame is blown towards the inside from cracks
near the floor, while it is blown outward in cracks higher up.

95. Clap two blackboard erasers together to make a small cloud of
dust, and watch the movements of the particles in a ray of sunlight, so
as to detect the direction of the air currents in the room.

96. Show methods of ventilation by lowering the upper sash ; by
raising the lower and inserting a board in the opening. Show and
explain the methods of ventilation adopted in the school.

REVIEW TOPICS

I. Give the composition of the air.

' 2. Describe ozone ; argon ; nature's method of removing
dust from inspired air ; and the dangers of inhaling
dust in certain trades.

3. Tell how much oxygen is needed in the air to sustain

life, and give a simple test to determine whether
sufficient is present.

4. Give the effects of rarefied air, and air under increased

pressure.

5. Give the effects of carbonic acid gas.

6. Describe foul air and its effects.

7. Discuss the meaning and the effects of bad odors ; of

sewer gas ; of night air ; and of cellar air.

8. Describe 'malaria.

9. Show how fire and lights contaminate the air.

10. Describe coal gas poisoning.

11. Show that foul air may contain disease germs.

12. Calculate how much fresh air should be admitted into

a given room for a given number of persons.

13. Describe how ventilation naturally goes on, and tell

some ways of assisting nature in ventilation.

14. Tell how a schoolroom may be ventilated.

15. Tell how the atmosphere is purified.

CALIFORNIA COLLEil
of PHARMACY

CHAPTER XXV
HEAT AND CLOTHING

404. Temperature of the body. — During health a man's
body has a temperature of 98^° F., which does not change
either upon the warmest day in summer or the coldest day
in winter. The body is warmed by the oxidation of its
own cells and of digested food.

405. Change of heat to energy. — The power which the
body puts forth in performing work is derived from the
heat of oxidation. The work of the heart requires the
use of yxg- of all the heat produced in the body ; the respi-
ration requires g^ ; digestion and absorption require a
smaller amount. An ordinary day's work requires T3^ of
the total amount of heat. So nearly three fourths of all
the heat produced is used simply to heat the body.

406. Uniformity of temperature. — In some parts of the body
oxidation is many times more active than in others. Probably most
of the sugar is oxidized in the liver, and most of the fat in the lungs.
As fast as heat is developed it is carried all over the body by the blood?
so that there is scarcely half a degree's difference between the tem-
perature in any two parts. Only the surface of the skin is cooler
because it comes in contact with cooler air.

407. Fever. — When the temperature of the body is
raised only a degree there is a feeling of warmth and dis-
comfort, which is called a fever. The discomfort is worse
as the temperature is higher. A temperature of 104 de-
grees is a sign of severe sickness.

234 APPLIED PHYSIOLOGY

408. Sensation of heat and cold. — If the temperature is
lowered only a degree, there is a feeling of coldness called
a chill. A chill is a recognized sign of beginning illness.
The ordinary feeling of heat or cold is due to the state of
the nerves of the skin, whose special duty is to conduct
sensations of temperature. These nerves are so abundant
in the skin that their sensations overpower the sensations
of the rest of the nerves of the body. If the skin is warm,
the whole body feels warm ; while if the skin is cold, the
whole body feels cold.

409. Chills during a fever. — It often happens during a fever
ehat the blood goes to deeper parts, leaving the skin pale and without
its usual supply of heat, and so the whole body feels cold, and the per-
son has a chill, although the temperature of the body may be raised
several degrees.

In severe sickness the heart is sometimes too weak to pump the
blood to the skin, and so it feels cold, although the temperature of the
inside of the body may be raised several degrees. This condition is
often called inward fever. On the other hand, the body may be cold,
and yet if the blood is brought to the surface, the person will feel warm.

410. Regulation of the heat produced. — The amount of
heat produced in the same body varies widely at different
times, and some persons always produce many times as
much as do others. So in order to keep the temperature
constant, heat must be given off at one time and saved at
another. Nature regulates the temperature of the body
by varying both the amount produced and the amount
given off. The production of heat depends partly upon
the amount of food. In summer man naturally eats less
than in winter. Inhabitants of arctic regions eat large
quantities of fat, the oxidation of which produces a large
amount of heat, while the inhabitants of hot climates
naturally avoid fat.

HEAT AND CLOTHING 235

The production of heat also depends upon the amount
of oxygen taken into the body. In work, deeper inspira-
tions are taken, and more oxygen reaches the cells, and
thus exercise warms the body.

411 . Regulation of the heat given off. — Nature also
regulates the amount of heat given off. The body loses
some heat through the breath, and more by contact with
the cool air. When the temperature of the inside of the
body is raised, the blood tubes of the skin dilate, so that
more blood comes in contact with the air. If the tempera-
ture falls slightly below the natural point, the blood tubes
of the skin contract, so that less blood comes to the sur-
face, and more heat is retained until the temperature rises
to the natural point again. A change of temperature too
small to be felt will produce these changes in the blood
tubes of the skin.

412. Effects of tight bands. — When the circulation is hindered
so that less blood enters any part of the body, its temperature falls. A
finger whose veins are compressed by a tight string becomes percepti-
bly cooler in less than a minute. Garters often cause cold feet in the
same way. Compression of the waist may cause the whole body to feel
cold.

413. Effects of perspiration. — Sometimes men work in
air which is hotter than their bodies. Then instead of
giving, they receive heat. In order to keep them cool
under these circumstances, nature has provided a self-
acting bath by means of the sweat, ox perspiration. When
the temperature of the body is raised from any cause, the
perspiration is poured out in greater quantity, which in-
creases as the quantity of heat increases.

The heat of the body is used in changing the water of the perspira-
tion to steam, which then passes off from the body. The process is

236 APPLIED PHYSIOLOGY

like the boiling of water in a teakettle, where the heat passes off in the
steam, so that the temperature of the water does not rise beyond the
boiling point. Some perspiration is given off even if the body is cold,
but with an overproduction of heat more perspiration is often pro-
duced than can be turned into vapor. A person is usually said to per-
spire only when it is produced in so great a quantity that it collects in
drops upon the skin.

414. Moisture in the air. — When there is a great amount of
moisture in the air on a hot summer's day, the perspiration does not
evaporate from the skin, and so heat is retained within the body, and
the air seems " heavy " and oppressive. On such days the humidity of
the air is said to be great. Dry air at a temperature of 90 or 95 degrees
seems cooler than moist, humid air at a temperature of 80.

415. Sunstroke. — Men and animals, while working, pro-
duce a large amount of heat. On excessively hot and humid
days the extra heat may not pass off so fast as it is formed,
but may accumulate until the temperature rises several
degrees. The increased heat overwhelms the body, and
produces a sudden attack of faintness called sunstroke.
The unconsciousness lasts for a long time, and is followed
by great weakness, and sometimes by death. When a
person is sunstruck he should be laid in a cool place, with
his head lowest. Cold water should be dashed upon his
head and chest. His limbs should be rubbed to help the
circulation.

416. Damp days in winter. — While moisture in the air makes
the body warmer in summer, in the winter it makes the air seem colder.
Dry air is a poor conductor of heat, but a little moisture makes it a
much better conductor. So a damp wind rapidly extracts the heat
from the body, and seems to penetrate even thick clothing. Moist air
at a temperature of 20 degrees seems colder than dry air at zero.

417. Heating living rooms. — In addition to the means
provided by nature, man is often compelled to add devices
of his own for regulating the heat of his body. Man lives

HEAT AND CLOTHING 237

with the greatest comfort while the temperature of the
air is about 70 degrees, which is but little more than half-
way between the temperature of freezing and the heat of
the blood. A temperature of 80 degrees feels too warm,
while 90 degrees is hot, and 98 J, or the temperature of the
body, is oppressive.

In winter a temperature of 70 degrees in a living room
feels neither warm nor cold, and the change between it
and the outside cold air is less noticeable than at any other
temperature. A temperature of 75 or 80 degrees feels too
warm, and when the person goes out of doors the cold air
produces a sudden contraction of the arteries and a chill,
which often results in taking cold. A sleeping room should
be at a lower temperature than a living room.

418. Clothing. — Man protects his body against the loss
of heat by covering it with clothes. Some kinds of sub-
stances readily permit heat to pass through them, and are
called good Jieat conductors, while others carry heat poorly
and are called poor conductors. Linen is a good conductor
of heat. It is a poor protection against cold, for it lets
out the heat of the body, but it makes good summer cloth-
ing. When the linen clothing is adjusted to one tempera-
ture, a change to cooler air is quickly and suddenly felt.
Thus it is an undesirable clothing material in changeable
climates or in cold weather.

Cotton also conducts heat readily, but if it is loosely
woven, the air in its meshes makes it a poor conductor of
heat. Then it makes warm clothing.

Wool is a poor conductor of heat. When the tempera-
ture is suddenly lowered, it permits the heat of the body
to pass off but slowly, and thus gives the skin time to ad-
just itself to the change. In summer it retains too much
heat, and does not make so good summer clothing as cot-

APPLIED PHYSIOLOGY

ton or linen, but when the temperature of the air is higher
than that of the body, it prevents the heat from entering,
and thus is cooler than linen or cotton. So men who tend
hot furnaces are cooler if they wear thick flannel than if
they wear linen or cotton.

Silk is also a poor conductor of heat. While more ex-
pensive than wool, it is lighter in weight and feels softer
to the skin, and so makes the best kind of clothing.

Fur is the poorest conductor of all, and is the best pro-
tector against cold. Nature has given a thick coat of fur
to animals that live in cold regions. In winter their fur
is long and thick, but it drops out during spring, and a
new fur grows during the summer, becoming thick and
long again by the following winter.

Air itself is a poor conductor of heat, and when a considerable quan-
tity is imprisoned in the meshes of cloth, the garment offers a greater
resistance to the passage of heat. So loosely woven cloth is much
warmer than cloth made up of tightly twisted thread. Fur is warm
largely because of the amount of air which it imprisons. For the same
reason loose clothing is warmer than tight-fitting clothes.

419. Color and heat. — When exposed to the sun, black objects
take up twice as much heat as white objects. This difference of tem-
perature is noticeable in clothing. Light-colored or white clothing is
best for summer, and dark-colored or black for winter.

420. Distribution of clothing. — The different parts of the
body vary in their ability to resist cold. The face and hands usually
need no covering. The feet need less than the body, while the back,
chest, and abdomen need the most. Nature has distributed fur upon
the animal's body in the same way, leaving the head and feet poorly
covered. The sense of warmth is the best guide as to the amount of
clothing to be worn on any part. A person should wear enough to
keep each part of the body comfortably warm, while no part, especially
one which is usually left uncovered, should be covered so as to be
uncomfortably warm.

Dampness produces cold by the evaporation of water. If all the

HEAT AND CLOTHING 239

clothing is wet, heat is taken from the whole body equally, and there is
equal contraction of the arteries with no congestion or inflammation.
But if a single part is wet, it feels cold, while the rest of the body is
warm; so wet feet often produce inflammation of different parts of
the body.

Cold feet. — When the feet perspire a great deal, the stockings
and soles of the shoes become saturated with moisture and make the
feet feel as cold as if they were wet. Thicker stockings make the
feet perspire still more, and so do not add to their warmth. Tight
shoes allow of no ventilation, and so the moisture is retained, and the
feet are wet and cold.

Drying the shoes and stockings every night before the fire will pre-
vent their becoming saturated with moisture. A new inside sole cut
out of thick paper put in the shoe each morning will absorb moisture
and help keep the feet warm. Rubber boots and shoes do not permit
the moisture of insensible perspiration to pass off, and so they seem-
ingly cause the feet to perspire.

Bathing the feet each morning in cold water and drying them by
brisk rubbing improves the circulation, so that they will be more likely
to stay warm all day.

421. Paper as a protection against cold. — Paper is a poor
conductor of heat. A newspaper wrapped around the body under the
coat is as good as an overcoat for warmth. A few newspapers spread
between the quilts of a bed will make up for a lack of bed clothing upon
a cold night. One need not suffer from insufficient clothing, day or
night, if a few newspapers are at hand.

422. Sufficient clothing. — The amount of clothing which
one needs depends largely upon a person's occupation and
previous habits. A day laborer seldom needs an overcoat,
but works in his shirt sleeves, while a clerk would be
'chilled were he to step outdoors without extra wraps. It
is a mistake to think that by exposure to the cold one
can always become hardened to it. It is true only when a
person takes active exercise and lives out of doors continu-
ously. The body cannot adapt itself to the sudden changes
from hours spent in a warm room to an hour or two in the
cold air. Enough clothing should be worn so that the body

240 APPLIED PHYSIOLOGY

does not feel chilled on entering the cold air. When by
exercise the body feels warm, the overcoat may be unbut-
toned or removed, but while one is resting it should be put
on at once before the body feels chilly. Cold air blowing
on our body while it is heated may cause us to have pains

in our muscles and joints.

>

423. Airing clothes at night. — At night it is usually best to
remove all clothing worn during the day. Woolens have the power of
absorbing a great deal of moisture without feeling damp. But the
moisture and the waste matters from the skin should be removed each
night by thoroughly airing the underclothes. If it is not done, the
woolen may become so saturated with moisture that it affords no more
protection than cotton, and so may render a person liable to take cold.

424. Beds. — Feather beds and thick quilts enable a
person to get warm when he goes to bed on a cold night,
but after he falls asleep he becomes too warm and per-
spires too freely. Then he throws off the coverings, and
soon the evaporation of the perspiration makes him cold.
We should use as thin bed covers as possible so as to avoid
overheating. If we sleep in a very cold room, we can keep
ourselves comfortably warm with light covers if we use
woolen blankets for sheets instead of sheets made of linen
or cotton. As a rule a plain mattress is more comfortable
and gives a more even heat than a feather bed; but in
beds, as in clothing, a person's sensation forms the best
guide as to the kind to be used.

425. Effect of lowering the temperature of the body. —
In extremely cold weather heat may be lost from the body
faster than it can be produced, and thus the temperature
falls. Then the body and mind cannot act, but become
numb and sluggish, just as the hands become numb and
powerless when cold. If the temperature continues to fall,
the respiration becomes less, and as the cells cease to act

HEAT AND CLOTHING 24!

an agreeable feeling of drowsiness steals over the mind,
until the actions of life cease. After the drowsy feelings
begin, life can be restored only by applying heat to the
body and performing artificial respiration so as to start the
process of oxidation again.

426. Frost bites. When a part becomes very cold the
cells may be seriously injured long before they are frozen.
A toe or an ear which has been on the verge of freezing
will begin to prick and tingle when warmed. For a long
time afterward, sensations varying from an itching to severe
pricking and smarting will cause great annoyance. In
severe forms, short of actual freezing, the part swells and
becomes red and inflamed, while the sensations are ex-
tremely annoying. A part which is actually frozen is
likely to die. The part turns black soon after being
thawed, and has no feeling. After a few days the dead
part comes off, leaving a raw sore. Fingers, toes, and
ears are very liable to become frozen, but the eyelids are
almost the last thing to freeze.

427. Frozen limbs. — When a solution of a substance in water
freezes, the first ice formed is composed of crystals of pure water, while
that frozen last contains most of the dissolved substance imprisoned in
the meshes of the crystals. The cells of the body are made of water
in which albumin and mineral substances are dissolved. When freez-
ing occurs, the first ice is composed of needles of pure water which has
been taken from the cells. If the freezing takes place rapidly, the
water produces swift currents which break down the delicate framework
of the cells and cause their death. If freezing occurs very slowly, the
water may leave the cells so slowly that no damage is done by the tiny
flood. If thawing occurs just as slowly, the water may reenter the
cells so that they may be preserved alive. When a hand or a foot is
frozen, it should be rubbed gently either with snow or else while im-
mersed in ice water, and the raising of the temperature of the water
should be done very slowly, taking, at least, two or three hours for the
thawing process. The preservation of the frozen part depends upon

ov. PHYSIOL. — 1 6

242 APPLIED PHYSIOLOGY

its very slow thawing. Never apply warmth of any kind to a frozen
part, and avoid sitting near a warm stove afterwards.

428. Effects of raising the temperature of the body. —

When a living body is exposed to a higher temperature
than is natural, the respiration and circulation are much
increased by the extra heat and there is much mental
excitement. In fevers there are usually excitement and
delirium. A continuous temperature of 105 degrees is
usually fatal.

It is possible to work in an atmosphere which has a temperature
of 150 degrees or more, and men have remained in hot ovens for many
minutes without harm. Their perspiration flows very freely, and its
evaporation carries off the extra heat, so that the temperature of the
body does not rise. If the perspiration should cease, the temperature
of the body would rise at once, and death would soon take place.

429. Burns. — A temperature of 1 10 degrees feels very warm, 115
degrees is hot, while 120 degrees is all that a person can commonly
stand. A temperature higher than this injures the cells so that a blister
will be raised in a few minutes. A temperature of 170 degrees coagu-
lates albumin at once and so destroys the life of cells which it touches.
A temperature of 212 degrees, or boiling point, at once produces a deep
scald, while higher temperatures burn the skin to a crisp.

Cold water applied at once to a burn prevents its extension and
soothes the smarting, but it should be applied only for a short time
lest it should injure the cells. Common baking soda is one of the
most soothing applications. A mixture of linseed oil and lime water
is a good application for continuous use. After a deep burn has healed,
a puckered scar will be left, but the scar will be less noticeable if healing
is hastened by skin grafting.

430. Burning clothing. — When the clothing on a person takes
fire, a great danger is that the flames may be inhaled. It will take
some time for the flames to penetrate to the flesh, but they may quickly
spread upward. So a person should always lie down at once. Then
let him roll over and over so as to crush out the fire. Even if the fire
is not extinguished, the flames cannot reach the face, while the clothes
can be removed as well lying down as while standing. In helping a

HEAT AND CLOTHING 24$

person whose clothes are burning, at once throw the person to the floor.
Many have lost their lives by persisting in standing up while attempt-
ing to remove the burning clothes.

If it is necessary to enter a burning building, or to carry a person,
whose clothes are burning, the best protection will be to wrap a thick
coat or blanket around the body. A thick coat wrapped around burning
clothes or thrown over the body after a person lies down will quickly
smother the flames.

431. Alcohol and heat. — The amount of heat in the
body depends upon the balance between its production
and its loss. The rapid destruction of alcohol, in all
probability, yields heat too rapidly to be utilized by the
body. The most constant effect of taking alcohol is to
dilate the arteries of the skin, so that an extra amount of
heat is lost. More heat is always lost than is produced.
Alcohol lessens the power of the body to endure cold. On
a cold day when the arteries of the skin are contracted so
that there is but little blood to warm its nerves, alcohol
may send the blood to these nerves and produce an agree-
able sense of warmth, but in reality this feeling of warmth
is due only to the heat which is passing off from the inte-
rior of the body.

432. Regulation of temperature in the dog. — The temper-
ature of many animals is slightly above man's temperature,
but is regulated in the same way. Some, like dogs, sweat but
little, but the animal takes short and rapid breaths through
his open mouth, thus creating a strong current of air over its
moist surface. The evaporation of the saliva cools the blood.

433. Hibernation of animals. — When winter comes on,
some animals, like the woodchuck, retire into their holes
and go to sleep. Their temperature falls to 50 degrees,
or even lower, while respiration occurs only three or four
times a minute. Only enough oxidation of their own
bodies occurs to keep life from completely dying out

244 APPLIED PHYSIOLOGY

When warm weather comes again, their respiration and
temperature rise to the natural point, and the animal re-
sumes its former condition, but is thin from the oxidation
of its fat and albumin during his long sleep. The dormant
state during the winter is called hibernation.

434. Cold-blooded animals. — In frogs and snakes, oxi-
dation is not sufficient to raise their temperatures much
above that of the surrounding air. So they feel cold to
the touch, and are called cold-blooded. On warm days
they do not lose heat so rapidly, and more heat is retained
within their bodies, and thus they become more active.
When cold weather comes on, they cannot produce enough
heat to enable them to move, but they lie unconscious
until warm weather comes again.

Insects cannot produce enough heat during winter to
enable them to fly about, so they remain apparently life-
less until the warm weather comes again.

SUMMARY

1. The heat developed by oxidation is distributed through

the body by the blood so that everywhere it has a
temperature of 98.5 degrees.

2. The sensations of heat and cold are caused by the

blood circulating in the skin. If little circulates,
we feel cold; while if much circulates, we feel
warm.

3. An increased quantity of food, oxygen, or exercise

increases the amount of heat produced in the body.

4. Heat is given off by contact of the skin with the cold

air and by means of the perspiration.

5. A temperature of about 70 degrees in a room is the

most comfortable.

HEAT AND CLOTHING 245.

6. Moisture in the air prevents the evaporation of per-

spiration, and increases the feeling of warmth.

7. Fur, silk, woolen, cotton, and linen protect the body

from cold in the order given.

8. Raising the temperature of the body causes excite-

ment and delirium.

9. Alcohol dilates the arteries of the skin and permits'

an increased loss of heat, in spite of the feeling of
warmth.

IO. In animals while hibernating, and in all cold-blooded
animals, oxidation is feeble, the temperature is low,
and their movements are sluggish.

DEMONSTRATIONS

97. To show that more blood goes to a part, and that it becomes
warmer while acting, let a boy roll up his sleeve and hang his arm by
his side. Notice that the veins slowly fill, because the flow of blood is
slowed by running up hill. Now have him open and shut his hand
rapidly, and notice that at once the veins become filled full of blood.
After a moment the hand feels warmer than the other, especially if
they were a little cold at first.

98. Take some ice water, some water at the temperature of the air,
and some hot water. Notice that the water at the medium temperature
feels warm when the hands have just been taken from the ice water,
but cold when they have just been in the hot water.

99. Feel of a piece of iron and of a stone after exposing both to the
cool outside air. Notice that the iron feels colder, for it takes heat
from the hand faster.

100. To show that obstructing the flow of blood makes a part
cold, tie a string rather tightly around the finger. In a moment it
becomes filled with venous blood, and feels cold, for the blood is
not renewed.

101. That the sensation of heat and cold depends partly upon the
amount of blood in the skin can be shown by holding a piece of ice in
the hands for several minutes. At first, the hands feel cold, for the
arteries are contracted. In a little while the blood circulates freely

246 APPLIED PHYSIOLOGY

again, and there is a feeling of warmth, although the ice still continues
to cool the hand.

102. Take some cotton and some woolen cloth of equal thickness.
Wet them and notice how much more quickly the cotton will dry than
the wool. Wrap them around the hand and notice that the woolen
feels warmer, because evaporation from it does not carry heat away
from it so fast as from the cotton. Then blow upon them and notice
how much colder the cotton feels.

103. Place two pieces of ice of equal size in the sun and cover one
with a black cloth and the other with a white piece of the same kind,
and notice that the piece under the black cloth melts faster.

104. Needles of water crystals can be shown by setting aside a cup
of water out of doors until it just begins to freeze, if it is a cold day, or,
if it is a warm day, by putting a large piece of ice in the sun and break-
ing it when it is half melted. Each needle is pure water.

105. A wasp or a fly will illustrate the hibernation of animals. In
winter a few wasps can usually be found in a sunny garret window.
When the air is quite warm, the wasps will be lively, and as it becomes
colder they become more sluggish, until at night they are apparently
lifeless.

REVIEW TOPICS

1. Give the temperature of the body and tell how the

heat is distributed.

2. State what causes sensations of heat and cold, and

how the body may feel warm while it is cold, and
cold while it is warm.

3. State how the production of heat is regulated.

4. State how the amount of blood in the skin regulates

the amount of heat given off.

5. State how the perspiration regulates the amount of

heat given off.

6. State how tight bands about a limb cause cold feet or

hands.

7. Give the best temperature of living rooms and of bed

rooms.

HEAT AND CLOTHING 247

8. Give the effect which moisture in the air has upon the

heat of the body during summer and during winter.

9. Give the value of linen as a protection against heat

and cold ; of cotton ; of wool ; of fur ; and of air.

10. State how color affects temperature.

11. State how much clothing should be worn, and how it

should be distributed over the body.

12. Discuss feather beds and thick bed coverings.

13. Give the effects of lowering the temperature of the

whole body; of frost bites; of frozen limbs; and
their treatment.

14. Give the effects of raising the temperature of the

body, as in fever and in sunstroke.

15. Give the effects of alcohol upon the temperature of

the body.

1 6. State how a dog's temperature is regulated.

17. Describe the hibernation of animals.

1 8. Describe oxidation in cold-blooded animals, and in

insects.

CHAPTER XXVI
EXCRETION AND SEWAGE

435. Getting rid of oxidized and waste substances is
excretion. All oxidations in the body produce carbonic
acid gas and water. In addition, the oxidation of albu-
min produces a substance called urea, which ' contains
the nitrogen of the albumin. These substances together
with the minerals or ashes left from the burned cells
niast continuously be excreted by the lungs, liver, intes-
tine, skin, and kidneys. These organs also excrete poisons
which are produced by disease germs.

436. Difference between a secretion and an excretion. —
In a general way, anything separated from the blood by
glands is a secretion. But the term strictly is applied only
to those substances which, like saliva and gastric juice,
are of use to the body. Substances which, like carbonic
acid gas and urea, are only waste and harmful products,
are true excretions.

437. Sweat glands. — Numerous coiled tubes lined with
epithelium project into the skin over nearly its whole sur-
face. Each tube is a sweat gland, whose epithelium is
continually secreting the sweat, or perspiration. They are
very numerous on the forehead, chest, palms of the hands,
and soles of the feet. Only a few are found in the upper
part of the back.

438. The perspiration. — The perspiration is over 99 per
cent water. It contains a small amount of urea and min-
eral substances. Ordinarily it evaporates so fast that its

248

EXCRETION AND SEWAGE

249

presence is not noticed. Nearly a quart of water a day
thus passes off from the surface of the body in insensible
perspiration. In hot weather and during exercise so much
is produced that it accumulates in drops upon the skin.

439. The kidneys. — The main work of excretion is
performed by the kidneys, There are twe kidneys, one on
each side of the backbone, half

covered by the two lower ribs. Each
kidney is bean-shaped, about four
inches in length, by two in breadth,
and one in thickness. It is com-
posed of millions of fine tubes made
up of epithelial cells; they unite, and
finally open into a pocket on the side
of the kidney.

440. How the kidneys excrete. —
The epithelial cells of the tubes have
the power to draw urea and mineral
substances from the blood. They
also extract a large amount of water

in order to wash away the excreted matter. The excre-
tion runs down a tube called the ureter to the bladder.
About a quart and a half of a fluid called urine is thus
excreted daily.

441. Kidney disease. — Kidney disease usually takes the form
of an aggravated bilious attack. There are headaches, loss of appetite,
coated tongue, and great weakness. Usually the urine is diminished,
and contains some albumin derived from the blood.

Urea itself is as harmless as carbonic acid gas and is as easily
excreted, but when oxidation is incomplete, substances are produced
which are as much more harmful than urea as a smoking lamp is more
unpleasant than one burning perfectly. When more food is eaten than
can be oxidized, poisons are developed from the imperfectly oxidized
albumin. Some are leucomaines or substances like them. The kid-

Kidney cut across.

25O APPLIED PHYSIOLOGY

neys try to excrete the poisons, but they become overworked, producing
what is called Bright"1 s disease. Then the sweat glands excrete more waste
matters, and in the emergency often do enough to relieve the kidneys.

442. Relation of the skin and kidneys. — The skin excretes
but little urea compared with the kidneys, yet its capacity for excreting
water is unlimited. When much water is excreted by the sweat glands,
only a little is excreted by the kidneys, and when little perspiration is
formed, the kidneys excrete more water. The amount of urea remains
nearly the same from day to day, and so the urine will be more colored
at one time than another.

The amount of perspiration is governed principally by the tempera-
ture, and remains nearly the same whether much or little water is taken.
The amount of urine is increased by the water swallowed. A large
amount of water tends to wash away the urea more perfectly. Often
when one thinks that he has kidney trouble, an increased amount of
water swallowed will pass through the kidneys and bring their secre-
tion to a natural appearance.

443. Excretion of poisons swallowed. — When poisons have
been swallowed, those which pass by the liver are seized by the kid-
neys and excreted. Carbolic acid and turpentine are thus excreted by
the kidney. In passing through the kidneys these drugs may irritate
their cells and set up inflammation. Most drugs, whether they are
vegetable or mineral, pass out by the kidneys.

444. Excretion by the liver. — The liver is constantly
destroying all kinds of poisons, which it receives not only
from the blood of the intestine, but also from the rest of
the body. Two bile substances, glycocholic and taurocholic
acids, are probably formed directly from albumin; and
while they are excretory products, yet they are elements
essential to digestion. Another substance, bilirubin, con-
tains most of the waste coloring matter of the blood.
When the liver fails to excrete these substances, as in
jaundice, they pass out by the kidneys and color their
secretion yellow.

445. Excretion by the intestine. — Although the intes-
tine absorbs food, yet it also pours out some waste matters.

EXCRETION AND SEWAGE 25 1

When the intestine does not expel its contents, symptoms
like liver and kidney diseases arise. So the intestine
excretes some waste matter. Under certain conditions
even the stomach may become an excretory organ, and
vomiting may be a life-saving act, just as it often is when
poisons are swallowed.

446. Intemperance and kidney disease. — Alcohol, by
disturbing oxidation and the liver, is especially liable to
cause the production of poisons whose excretion severely
taxes the kidneys. It alone causes over one half of kidney
diseases. Candies, pie, cake, and preserves are all eaten
simply for their taste, and usually after a sufficient amount
of proper food has been taken. So, in oxidizing this
increased amount of food, some must be imperfectly oxi-
dized. Thus poisons are developed and the kidneys are
overworked.

Intemperance in sugar eating is extremely common. It
produces imperfect oxidation in the same way as alcohol,
only its effects are much slower and less noticeable.

447. Sewage. — The excretions of man and animals,
together with the dirty water used in washing, is sewage.
Sewage is composed of substances which are often very
poisonous, and often contain disease germs (p. 136).

448. Purification of sewage. — Nature is very efficient in
changing sewage so that it is no longer harmful. In the upper layers
of the soil it is fully oxidized to carbonic acid gas and water and min-
eral substances. The soil can dispose of a great quantity of sewage and
prevent it from polluting the surrounding wells.

In the second place, plants feed upon sewage. They aid in its oxi-
dation and use it as food. Thus plants may form again the substances
which were oxidized in man's body so that he may eat the very prod-
ucts which he once excreted.

In the third place, running water washes away sewage, and by means
of the oxygen which it always contains it fully oxidizes the excretions.

252

APPLIED PHYSIOLOGY

449. Danger from sewage. — Sewage often is a poison
itself, and when much is collected it often develops poisons
by its decay. The foul smell of sewage is due to gas

called sewer gas. While
the gas itself is but slightly
harmful, yet it is a sign
of decay and of lurking
sources of danger. But
sewage is dangerous mainly
because it may contain
germs of typhoid fever
and other diseases which
come from the excretions
of sick persons.

450. Disposal of sewage.
• — In thinly settled country
places small quantities of
slops and sewage may
safely be emptied in the
back yard, for the soil de-
stroys and removes all of-
fensive matters and disease
germs, so that only pure

water from being sucked out of the

trap. water reaches the deeper

d waste pipe, down which the slops pass ]ayers of the ground. If

into the sewer.

e pipe from the gutter on the roof. a house has a bath TOOm,

/ waste pipe passing under the street. there win be SQ much waste

g ventilation pipe.

water that some device will

be needed for its disposal. The simplest contrivance is to
conduct the sewage into a hole called a cesspool, from
which it slowly soaks into the ground. A cesspool should
always be so located that the underground flow of water
from it will be away from any wells (p. 1 36).

Diagram of the plumbing of a house.
a sink or washstand.

b trap, which remains full of water and pre-
vents the entrance of sewer gas.
C air pipe for ventilation and to prevent the germs

EXCRETION AND SEWAGE 2 53

451. Sewers. — In cities the houses are too near together
to permit the use of cesspools, and so underground tubes
or tunnels, called sewers, are built at public expense in
order to conduct the sewage outside the town. There it
should be treated in a sewage disposal plant, although it
is often emptied into the nearest body of water (p. 407).

452. Plumbing. — In houses pipes are arranged to carry
off the sewage as fast as it is formed in the sinks, wash
bowls, and closets. Since they open into a common sewer
of the town, sewer gas can readily enter the houses. To
keep it out, each pipe is bent into a loop which remains
full of liquid and prevents the entrance of gas.

453. Cleanliness. — No matter how good the natural or artificial
drainage may be, if decaying matter is left in cellars, it may poison the
air. Sinks may become clogged and poison the air, while slops and
dirty dishes may be carriers of disease. So cleanliness is of great im-
portance, aside from its mere looks.

454. Choice of a house Site. — In choosing a site for a dwell-
ing house we should consider the natural drainage of the ground. If
the soil is low and marshy, or if the subsoil consists of clay or rock, the
sewage may not soak away readily. Mosquitoes breeding in marshy
ground may cause malaria (p. 225). The site for a house should be
such that the barnyard and outhouses can be put so they will drain
away from the house and well. Attention to these details of drainage
is of far more importance than the natural beauty of a site.

SUMMARY

1. Excretions are waste and poisonous substances ex«

pelled from the body. The principal ones are car-
bonic acid gas, water, urea, and mineral matters.

2. Sweat, or perspiration, is formed in tubes in the skin.

It contains some urea and mineral matters.

3. The kidneys are collections of minute tubes which sepa-

rate urea, mineral matter, and water from the blood.

254 APPLIED PHYSIOLOGY

4. When, in Bright's disease, or from any other cause,

the kidneys cease acting, death by poisoning soon
takes place.

5. The skin can aid the kidneys, but cannot take their

place.

6. Alcohol causes poisons to develop whose excretion

overworks the kidneys.

7. The liver and intestine each excrete a great amount

of waste and poisonous substances.

8. The excretions from man remain poisonous until

destroyed by the soil, by plants, or by running
water.

9. In thickly settled districts it is necessary to carry off

the excretions by means of a sewer.

DEMONSTRATIONS

106. Carefully weigh several boys early on a warm day. Have
them run about and take violent exercise, eating and drinking nothing,
or only known amounts. In a few hours weigh them again. A loss of
half a pound or more may be noted.

107. Insensible perspiration may be shown by touching a cold glass
to the skin, when moisture will at once condense upon the glass.

108. Secure a specimen of kidney mounted for the microscope.
With a power of about 200 diameters show the class how capillaries
form a bunch in a pocket at the beginning of each tube, and then pass
out to surround the tubes, and finally unite to form the veins. Show
them the large size of the cells of the tube.

109. Cut open a pig's or sheep's kidney lengthwise and notice the
pocket in its side and the radiating lines of the kidney reaching almost
to the surface and marking the course of the tubes.

no. A pot of growing flowers will illustrate nature's method of dis-
posing of sewage. Although manure and dirty water are poured upon
the earth, yet they give out no odor, but become fresh and clean and
nourish the plant.

III. Show the pupils the traps for sewer gas under the sinks.

EXCRETION AND SEWAGE 255

REVIEW TOPICS

1. Explain the difference between a secretion and an

excretion.

2. Name the principal excretions and tell how they leave

the body.

3. Describe sweat glands and the perspiration as an

excretion.

4. Describe the kidneys and their excretion.

5. Discuss how imperfect oxidation may overwork the

kidneys.

6. Show how the skin aids the action of the kidneys and

how the one acts less when the other is more active.

7. Show how alcohol produces kidney diseases and how

sugar acts in the same way.

8. Describe three ways in which nature destroys the

excretions of man.

9. Discuss the dangers which may arise from sewage.

10. Tell how sewage is disposed of in cities.

11. Describe how sewer gas is prevented from entering

houses through waste pipes.

CHAPTER XXVII

THE SKIN AND BATHING

455. The derma. — The skin
which covers the entire body.

The skin (X 100).

a dead layer of epidermis.

b growing layer of epidermis.

c layer of cells containing the coloring

matter of the skin.

d papilla.

e sweat gland.

f small blood tube.

g fibers of the derma.

A fat cells in the derma.

256

is the tough, loose sack
It is designed to protect
the body and to give
off perspiration and
heat. (See pp. 235, 248.)
The main part of the
skin is a tough, elastic
network of fibers, called
the derma or cutis, which
forms a layer from -^ to
\ of an inch in thickness.
The derma of animals,
when tanned, forms
leather. The skin is
connected with the body
by a loose network of
fibers called the siibcu-
taneous tissue, which per-
mits the skin to move
freely over the deeper
parts. Over some parts
of the body, as upon the
abdomen, the subcutane-
ous tissue contains a
thick layer of fat.

THE SKIN AND BATHING

257

456. The epidermis. — The derma is covered with a layer
of epithelial cells, called the epidermis or cuticle. New
cells are continually being produced in the deeper layers
of the epidermis, while the older cells become matted in a
firm mass which is continually being worn away. These
cells are directly continuous with the epithelial cells of the
mucous membrane and are of the same nature. The epi-
dermis has no nerves and no blood tubes.

A corn.

457. Upon the palms of the hands and soles of the feet the epi-
dermis forms a very thick layer for the better protection of these much-
used parts. When hard labor is performed with the hands, nature
causes the protecting epidermis in the exposed parts to form a thick
and horny spot called a callus. Sometimes pressure and rubbing cause
a small area to become thickened so that a point of hardened cells is
formed which presses into the deeper parts of the skin. This is a corn.

When the skin is vigorously rubbed, or certain drugs are applied,
the deeper layers of the epidermis are killed, and water accumulating
between them and the outer layers raises a blister.

458. Color of the skin. — The deeper layers of the epidermis
contain colored granules which give the peculiar color to different races
of men. Exposure to the sun's rays produces a darker coloring matter.
In some people the coloring matter is deposited in small spots called
freckles.

ov. PHYSIOL. — 17

APPLIED PHYSIOLOGY

459. Skin grafting. — A spot of skin deprived of epithe-
lium is tender and sore. New flesh forms over its surface,
while the epithelial cells at its edge produce new ones
which spread over the whole surface and complete the
healing. If they do not grow, the new flesh sprouts above

the skin, forming
proud flesh.

The deeper cells
of the epidermis
may remain alive
for some hours
after being cut off
from the body.
ft When placed upon
a clean ulcer, they
6 may grow and
e produce a new epi-
g thelium. This is
skin grafting.
^x-460. Papillae.
— From the sur-
face of the derma
small projections
about ^0- of an
inch in length,
called papillcs, ex-
tend a short dis-
tance into the epidermis. They contain nerves of feeling.
The papillae over a small area sometimes become over-
grown, so that they project above the skin, forming a
wart. Rows of papillae form the fine curved lines upon
the balls of the fingers and the palms of the hands. They
are most numerous where the sensation of touch is greatest.

A hair (X 200).

a epidermis of the skin.

b hair shaft.

c sebaceous gland.

d muscle which makes the hair erect.

e epidermis of the hair root.

/ fat cells in the derma.

g papilla from which the hair grows.

THE SKIN AND BATHING

259

461. Hair. — Extending obliquely nearly through the
derma are numerous minute tubes lined with epithelium.
Their cells become joined together in a tough string, called
a hair, which projects out of the tube. When the hair is
pulled out, the epithelium covering the projection in the
tube soon produces another hair. A small muscle is
attached to the bottom of each hair root. Cold causes
the muscles to contract and to pull the hair tubes to an
upright position imparting to the skin a roughness called
goose flesh. Hair covers almost the entire body.

462. Sebaceous glands. — Near each hair is a gland called
a sebaceous gland. It secretes a kind of oil, which softens
the skin and keeps the hair glossy. The glands are espe-
cially numerous down the center of the face. When their
mouths are stopped by — - — -r-^ — : — _-_•*- **
dirt they often become " T — i_~"~— "T-'-^ ~ r &
distended and form small,

black spots called black-
heads, which are often
mistaken for small worms.

463. Nails.— The epi-
dermis upon the backs of
the last joint of each finger
and toe is hardened into a
nail. The nail is formed
at its back part and is
pushed onward in its

A nail (X 200).
a surface of the nail.

b body of the nail.

c epithelial cells just before they are welded
into a nail.

growth. An epithelial cell d papillae.

- , . ., e growing epithelium.

remains a part of the nail

about three months before it is pushed from its root to its

end.

464. The complexion. — In health the skin has a velvety appear-
ance, and a rosy color, and is free from spots or scales. Its moisture is

260 APPLIED PHYSIOLOGY

of the proper degree to cause it to feel soft and pliable. Its appearance
is changed by ill health. If the stomach and intestine are not in good
order, it is almost impossible for the skin to be beautiful. Plain food,
fresh air, and exercise make a beautiful skin, and no skin can be beauti-
ful without them. Cold dry air or exposure to the sun's rays often
cause it to become red or to blister. These effects are much greater
upon those who are unaccustomed to the exposure.

465. Care of the complexion. — Washing the skin with soft
water and soap as often as it becomes dirty, and following it by a
thorough drying with a soft towel, are the only effective means of
beautifying the skin. Paint, powder, and perfumery cannot cause the

'skin to grow more beautiful. They simply coat its outside, and at the
same time stop its sebaceous and sweat glands, so that when, it is
removed the skin looks worse than before. They act like any other
dirt. Many of these preparations contain poisonous minerals such as
lead.

Drugs taken internally to beautify the skin act mainly through the
arsenic which they contain. Arsenic destroys the blood cells, and so
gives a peculiar paleness to the skin. Paleness is only a sign of poison-
ing which is working harm to the health.

466. Absorbent power of the skin. — Since the outer part
of the epidermis is dry and dead and contains no blood
tubes or lymphatics, substances rubbed upon the skin
will not be absorbed. So man can handle virulent poisons
and disease germs without danger. On the other hand,
when the epithelium is removed, the exposed blood tubes
and lymphatics take up drugs and poisons very readily.
Drugs may be absorbed from surgical dressings, and germs
of disease may enter through even a minute scratch.

467. Care of the hair. — The hair of man, like that of animals,
is soft and glossy in health, but often dry and rough during disease.
Daily brushing to remove the dirt, and to distribute the oily secretion
of the sebaceous glands, will keep the hair in the best condition. All
that is necessary beyond this is frequent washing with soft water. The
secretion of the sebaceous glands is sufficient to oil the hair and scalp.
There is no substance which will cause hair to grow, neither will any

THE SKIN AND BATHING 26 1

stop its growth. When hair is shaved off, it soon regains its former
length and then ceases to grow. Shaving seems to have some effect
in causing the hair to grow coarser, but it does not add to the number
of separate hairs.

468. The beard. — At about the age of sixteen the hair upon a
boy's face begins to grow larger and coarser, and if let alone becomes
a full beard in the course of two or three years. . A shaved beard is not
so silky as one that has never been cut.

A beard gives to a young man an appearance of age and experience
and is popularly taken for a sign of mental and physical strength. As
a matter of fact the presence or absence of a beard has nothing to do
with a person's experience or knowledge.

469. Care Of the nails. — Biting the nails makes their edges
ragged, besides making the ends of the fingers sore. The nails them-
selves are not poisonous, but underneath their projecting ends germs
of disease may be mixed with the dirt which gathers there. Naturally
the nail adheres to the finger nearly down to its end, but is often kept
raised and sore by too persistent cleaning. The edge of the semicircle
of flesh surrounding the root of the nail is naturally soft and slightly
raised so that it looks like a fine silken braid. Sometimes it becomes
hard and cracks, especially upon cold, dry days. Cutting away the
hard edge down to its soft margin in the flesh prevents the extension
of the cracks. A tiny sliver of the edge of flesh around the nail torn
back into the flesh forms a hangnail. The hangnail should be cut off
close to the flesh. It is best prevented by gently pushing the skin
back from the nail. Tight shoes bind the toes together, curving the
great toe nail into the flesh, causing an ingrowing toe nail. Broad
shoes are the best preventive of the trouble.

470. Bathing. — A noticeable odor of perspiration about
any part of the body is a sign of uncleanliness, and is the
best indication of the need of a bath. Even in cold weather
a bath is needed at least once a week, while in the summer
it may be necessary to bathe daily. Soap and hot water
soften the epithelium, and if the skin is then rubbed vigor-
ously, a large amount may be rolled into small balls, which
are often supposed to be dirt. When much epithelium is
removed in this way, the body is more sensitive to the cold,

262 APPLIED PHYSIOLOGY

the perspiration passes off with greater ease, and the skin
is made tender.

471. Hot baths. — The heat of a bath in which the body
is kept warm from the time it enters the water until it is
dry dilates the blood tubes of the skin, so that the blood
accumulates upon the surface. Thus the internal organs
contain less than their natural supply of blood, and the
body is apt to feel weak and drowsy. After mental labor
a hot bath may cause the blood to leave the brain and so
bring about sleep. When a cold is coming on, a, hot
bath may increase the excretion of poisons from the
skin. Then the body may be able to overcome the germs
of the sickness, and thus the cold may be prevented.
The proper time for a hot bath is at night, just before
retiring, so that the circulation may become natural before
morning. A hot bath requires the use of a warm room,
and of a tub sufficiently large to admit most of the body
at once, for evaporation of the warm water causes a cold
feeling on coming out of the bath.

472. Cold baths. — When a cold bath is taken, the blood
tubes of the skin at first contract and give a cold feeling ;
but they soon dilate. With the dilatation there comes an in-
creased flow of blood throughout the whole body, so that
there is a feeling of warmth and vigor in marked contrast
with the drowsiness of the hot bath. The invigorating
effects of a bath are called its reaction. If a cold bath
is long continued, there comes on a second contraction of
the arteries, so that the blood is forced within the body,
producing a feeling of coldness and weakness from which
the body is a long time in recovering. This second con-
traction of the blood vessels is called the secondary reaction.
The bath should be stopped at the first appearance of a
chill.

THE SKIN AND BATHING 263

473. An easy way of bathing. — A cold bath requires nothing
more than some water and a towel. A simple wetting of the body with
the hands, followed by rubbing with a soft towel, produces all the effects
of an elaborate bath tub. Such a bath can be taken in two minutes
upon rising and is very invigorating and refreshing.

474. Turkish baths. — A Turkish bath is a combination of hot
and cold baths in which the body at first is made to perspire in a hot
bath while being rubbed. The body is then suddenly deluged with
cold water and rubbed dry. At night the bath is refreshing, but the
removal of epithelium and the excessive perspiration make the bather
liable to take cold.

475. Sea bathing. — Running water carries off the heat of the
body, and thus produces a greater effect than still water. The motion
of the waves makes sea bathing exhilarating, and the salt in the water
seems to have some stimulating effect.

476. Bathing in fevers. — A cold bath always lowers the ten>
perature of a feverish person, and if properly given, greatly adds to his
comfort. It also stimulates the skin to greater activity so that it aids
the kidneys in their work of excretion. A good way of bathing a
feverish person is to uncover only an arm, and wet it with lukewarm
water. Then gently rub it with the bare hands until it is dry. The
evaporation rapidly produces an agreeable coldness, while the rub-
bing keeps up the circulation and prevents taking cold. Then cover
it and go over the other arm, and then the legs, and the body in
the same way. Finish by washing the face and brushing the teeth.
It is proper to give such baths several times a day if the fever is
high.

SUMMARY

1. The skin consists of a thick network of connective

tissue, called the derma, covered with several layers
of epithelium, called the epidermis.

2. A hair is formed by the welding together of epithelium

in a minute tube in the skin.

3. Sebaceous glands pour an oily substance upon the hair

roots to soften the skin and hair.

264 APPLIED PHYSIOLOGY

4. At the backs of the ends of the fingers and toes the

epithelium is thickened and hardened to form the
nails.

5. Digestive disturbances are the principal causes of a

poor complexion.

6. Paints and powders irritate the skin and have the

same effect as dirt.

7. Daily brushing the hair and frequently washing it

with soap and water are the best means of keep-
ing it soft and glossy.

8. Nails should be smoothly trimmed, and gently cleaned.

9. The skin should be washed often enough to prevent

an odor of perspiration.
10. The heat of hot baths dilates the arteries of the skin

so that blood leaves the internal organs and brain

and produces a feeling of rest and drowsiness.
n.f A cold bath contracts the arteries of the skin. But

they soon dilate and produce a feeling of warmth

and exhilaration, called the reaction.
12. If a cold bath is continued, the arteries again contract,

producing chilliness and a feeling of exhaustion.

DEMONSTRATIONS

112. Examine a specimen of skin with a microscope. Notice the
network of connective tissue in the derma, and the numerous arteries
and veins. Notice its projections of papillae and their covering of
epithelium. Notice that the epithelial cells in the deepest layers are
large and round, and the outermost layers are flat and shriveled and can
scarcely be recognized. Notice a faint line of colored granules in the
third or fourth layer of cells. In a negro the colored layer is very dis-
tinct. The specimen will also probably show one or two winding sweat
glands.

113. The skin specimen will probably show a few hairs, but one
specially prepared will be better. Notice the deep tubelike depression

THE SKIN AND BATHING 265

in which the hair rests, and the little knob embraced by the hair at its
bottom. Notice the whitish cells of the sebaceous glands reaching off
from the side toward which the hair points. Underneath the gland will
likely be seen the faint outlines of the small muscle which causes the
hair to stand on end.

114. A specimen of nail under the microscope will appear almost
transparent, but the papillae of the skin and the young epithelial cells
beneath it will show well.

115. Wash a boy's arm. Then apply a cloth wet in hot water for
a few minutes and show how the softened epithelium can be rubbed
off. Explain that it is not dirt, but the protection of the arm.

REVIEW TOPICS

1. Describe the skin, its derma, epidermis, subcutaneous

tissue, and coloring matter.

2. Describe the modifications of epidermis in a callous

spot and a corn.

3. Describe freckles ; a blister ; an ulcer.

4. Describe the papillae.

5. Describe a hair, sebaceous glands, and blackheads.

6. Describe the nails.

7. Give the causes and treatment of a bad complexion,

and the effects of paints and powders and drugs.

8. Give simple directions for the care of the hair.

9. Give simple directions for the care of the nails.

10. Give a general rule when to bathe for cleanliness.

11. State the effects of a hot bath, and when to take it.

12. State the effects of a cold bath, and give a simple and

easy way of taking one.

13. Describe a Turkish bath, and give reasons for not soak-

ing and rubbing the skin to an excessive degree.

14. Give an easy way of bathing a feverish person.

CHAPTER XXVIII

NERVES

477. Uniformity of cell action. — Certain cells forming
the nervous system are set apart for purpose of command-
ing the rest to work in the proper time and manner. The
commanding cells, called nerve cells, form the essential
part of the brain and spinal cord. From them as a center,
fine threads called nerves run to the cells of the body.
The outer end of each nerve thread touches a company of
cells and carries to them the orders from the central nerve
cells. Although each cell in the body lives and acts inde-
pendently of the rest, yet the central nerve cells cause all
to act in harmony.

478. Nerves. — Each nerve thread is composed of a
central fiber surrounded by a protective layer of a kind

of fat. The whole
thread is only about
A * n inch in diam-

A nerve thread (X 400). ' .

eter. Those which

a central conducting fiber. b covering of fat.

go to each part of

the body, as a hand or leg, run together in a bundle, which
divides into its separate threads upon reaching its destined
part. Each bundle of nerve threads is usually called a
nerve. The main nerves of the arms are about the size
of knitting needles, while the great sciatic nerve of the
leg is as large as the end of the little finger.

266

NERVES

267

As a general rule, a large nerve accompanies an artery down the
inside of each limb and across the center of joints upon the side toward
which the limb is bent. Thus they are in protected positions. One
nerve cord is situated on the inside of the back of the elbow joint
and is called the funny bone. Owing to its unusual position, it is some-
times hit, producing a pain in its ending on the inside of the hand.

479. Nerve action. — When one of the main nerves of
the arm is irritated, as by a pinch or prick, or shock of
electricity, an impulse is started along the nerve in each
direction. It goes to the brain
and produces- a sensation either
of pain or pleasure. It also
goes to the muscle cells of the
arm, causing them to contract
and move the arm. If a nerve
is cut and the end nearest the
brain is irritated, a sensation
will be felt, but there will be
no motion. If the other cut
end is irritated, the muscles a nerve thread.

Will move the arm, but no feel- b connective tissue binding the

threads into a cord.

mg whatever will be produced.

Whether the nerve be irritated at its outer endings
at the cells or anywhere in its course, an influence will
travel to the central nerve cells carrying the news, and
also in the opposite direction to the cells of the body,
causing them to act. The cells of the body can originate
influences which travel up the nerve to the central nerve
cells ; and, on the other hand, the nerve cells can origi-
nate influences which travel to the cells of the body and
cause them to act. Transmitting impulses is the essential
duty of nerves. They may be compared to telephone
wires which transmit any kind of electrical influences over

268 APPLIED PHYSIOLOGY

their whole length without affecting anything in their
course.

480. Kinds of nerves. — Each thread of a nerve trans-
mits influences in only one direction. Some threads carry
influences only from the cells of the body to the central
nerve cells. Because they often produce sensation they
are called sensory nerves. Other threads carry orders for
action from the nerve cells to the cells of the body and
are called motor nerves. Most nerves are made up of
both sensory and motor threads, but some are wholly sen-
sory and others wholly motor. There is no difference in
their appearance.

481. Distribution of sensory nerves. — Nearly every cell in
the body, except in the epidermis and blood, is probably in connection
with a sensory nerve, and, through it, is in touch with the central nerve
cells. The endings of the nerves are so abundant in the skin just
beneath the epithelium, that the point of a fine needle cannot be thrust
in without producing pain. In the ends of the fingers they are more
numerous than in any other part of the body. The muscles and internal
organs have fewer sensory nerves than the skin, so that a cut may be
continued into the deeper parts with but little pain.

482. Kinds of sensations. — The cells are continually
sending impulses to the central nerve cells telling of
their needs, as of food or rest. These impulses often give
rise to feelings which may seem to pervade the whole body.
Then they are called common sensations. Some are pleas-
ant and some are disagreeable. The natural unreasoning
inclinations to gratify desires aroused by the needs of the
body are instincts.

When something outside the body is acting upon the
nerves it produces a feeling or impression of which a per-
son is usually aware. By means of these sensations the
mind forms definite ideas of the surroundings of the body,

NERVES 269

and so the feelings are called special sensations. Unlike
common sensations, the meaning of the sensations must
be learned.

483. Common sensations. — Hunger, thirst, and fatigue
are the usual common sensations felt by the mind.
Hunger seems to be located in the stomach. If a sub-
stance swallowed is not nutritious, hunger soon returns,
even if the organ is filled full. On the other hand, if
nutritious food is introduced into the body through the
intestine, the feeling of hunger will pass away, even
though the stomach remains empty. Some persons suffer-
ing from indigestion are always hungry, though they eat
enormously. But the food is not digested, and does not
reach the cells, and there is always a feeling of hunger.

Thirst seems to be located in the mouth. Moistening
the mouth allays it but for a moment only, while if water
is introduced into the intestine or veins, the thirst disap-
pears, even though the mouth receives no water.

The amount of common sensations is small compared
with similar impulses which we do not feel. Every cell
is continually sending tiny messages of its needs, and the
central nerve cells promptly respond.

484. Special sensations. — Knowledge of the outside
world is gained by means of the touch, sight, hearing,
smell, and taste. Of these, touch is located in all parts
of the body, while special organs are needed to enable the
nerves to catch the delicate impressions of sight, sound,
smell, and taste.

485. Sensations of touch. — When an object touches
the epithelium of the skin, it causes an impulse to travel
to the central nerve cells as a sensation either of touch,
temperature, pain, or weight. All these sensations are
included under the general term of touch. Touch proper

2/0 APPLIED PHYSIOLOGY

is a slight sensation caused by contact of the skin with an
object. By means of it such ideas as those of shape,
smoothness, size, and dampness are gained.

Different parts of the body vary greatly in the ability of their nerves
to detect slight differences between two sensations. Thus the ends of
the fingers distinctly feel two points T\ inch apart as separate points,
while if two points are applied to the back, they seem as one point
until they are separated two inches. So we naturally use the ends
of the fingers to feel with.

486. Sensations of temperature. — In the skin special
nerves seem to end in minute points which are situated
from ^g to J- of an inch apart. When these are touched, a
sensation of heat or cold is felt, while the skin between
feels only a touch or pain. Some spots give a sensation
of cold only, and others of heat only.

Sensations of extreme heat or of extreme cold cease to be feelings of
temperature, but are felt only as pain. The skin is so sensitive that it can
detect a difference of £ of a degree of temperature between two objects.

487. Painful sensations. — A sensation of touch or of
temperature, if greatly increased or often repeated, be-
comes unpleasant and is called a pain. The same sensa-
tion may be felt at one time as a pleasant touch and at
another as a pain. When an influence is becoming great
enough to endanger the body, it arouses the nerves of
pain and produces a strong and unpleasant feeling which
overpowers the simple sensation of touch and compels us
to withdraw from the danger. Pain is a protection for the
body and not altogether an evil or a punishment. When
the nerves of pain in an arm or leg are diseased, the
limb may be burned beyond recovery without a person's
knowledge. In many diseases pain is a prominent symp-
tom, and the physician is besought to give it relief. Yet he

NERVES 2/1

hesitates before giving morphine, knowing that to relieve
the pain is to mask the danger signals so that he cannot
judge of the real cause of the trouble.

Tickling is a sensation between touch and pain. It is produced in
parts which are poorly supplied with nerves of touch, as on the back or
the neck. At first, tickling is a pleasant sensation, but if continued,
it becomes extreme suffering. Some persons and animals who are able
to endure great pain are unable to control themselves when tickled.

Itching is a sensation which is overcome by producing a greater
sensation in the part, as by scratching. Although itching is usually
only an annoyance, in a greater degree it is a torment even worse than
pain, and may lead a person to injure the skin seriously by deep
scratching.

488. The muscular sense. — Sensations of weight or of
resistance are judged partly by the amount of muscular
effort needed to move the body, and so depend in large
part upon the motor nerves. But the feelings of pressure
upon the body and of muscular effort aid in producing the
sensation. An object lifted seems distinctly heavier if its
weight is increased only ^y, while if it is placed upon
the skin, its weight must be increased \ before it feels
heavier.

489. Necessity of epithelium. — The covering of epithelium
not only protects the nerves from injury, but also modifies an impulse
which produces a sensation, so that it is spread over a larger area of
nerves and is made a gentle instead of a painful sensation.

490. Motor nerves. — Besides touching a sensory nerve,
each cell probably communicates with a motor nerve also.
Motor nerves begin at the central nerve cells and end at
the cells of the body. Over them the central nerve cells
send orders based upon information brought by the sen-
sory nerves. Many orders are sent by willful efforts of a
person, but by far the most are sent without our knowledge.

2?2 APPLIED PHYSIOLOGY

Motor impulses are of three kinds, — for motion, for
secretion, and for growth.

491. Impulses producing motion. — The action of every
muscle cell depends upon an impulse brought from the
central nerve cells by its motor nerve. When these influ-
ences are cut off, there is paralysis of the part, so that no
amount of willful effort can cause the muscles to move the
limb. The peristalsis of the intestine and the beating of
the heart are caused by influences brought to their muscle
cells by motor nerves. Orders for movements of which
we know nothing are far greater in amount than those
sent to voluntary muscles.

492. Impulses producing secretion. — Secretion is also
dependent upon orders brought to the glands by motor
nerves. For example, when food is taken into the mouth,
the sensory nerves carry the news to the nerve cells, which
at once send out an order along the motor nerves to the
salivary glands to produce more saliva. If the nerves are
cut, only a little saliva will be produced, while if the end
in connection with the gland is irritated, the gland will
respond with a greater quantity of saliva. In the same
way the secretion of all glands is controlled.

493. Influences producing growth. — When the motor
nerve to a part is cut, the cells will be inactive, and, as it
were, too lazy even to eat. So, unless continually under
the influence of motor nerves, the cells become weak and
waste away. When the cells of a part are much used,
impulses are sent causing them to take in more nourish-
ment, so that they increase in size and strength. Thus a
muscle becomes larger and stronger by use. During the
action of a muscle its motor nerves also bring orders for'
the arteries to dilate and carry more blood to feed the
working part.

NERVES 273

494. Rate of transmission of nerve impulses. — Ordinary
sensations travel about 100 feet per second. This is about the rate of
the fastest express trains, but our arms are so short that pain seems to
follow an injury instantly. In some diseases the rate is very much
retarded, so that if the hand should happen to rest upon a hot stove
it would be badly burned before the sensation would travel to the brain
and give warning of the danger.

495. A sensation traveling over a nerve seems to come from its
beginning. When the funny bone, or nerve that winds around the
back of the elbow, is pinched, the little finger side of the hand, where
the nerve ends, feels as if pricked by needles. When an arm or a leg
is cut off, and the nerves in the stump are irritated, a pain is felt which
seems to be in the lost limb. When a nerve is pressed upon, it may
be partly paralyzed for a while. Then the part which it supplies
becomes less sensitive and is moved with difficulty. At the same
time an impulse caused by the irritation of the pressure produces a
sensation which seems to the brain to come from the end of the nerve.
Thus when sitting crosslegged the foot often seems asleep and full of
needles, while it is itself insensitive when touched.

A cut nerve will become whole again, but it takes some weeks. In
the meantime the parts supplied by the nerve cannot feel or move.

496. Diseases of the nerves. — Nerves may become inflamed,
producing the disease called neuritis. Then there will be great pain and
tenderness over the entire course of the nerve. In severe cases there will
be paralysis and loss of feeling. The disease is very slow in its course.

Sciatica is a mild but painful form of inflammation in the main nerve
of the leg. Inflammation of the nerves may be caused by rheumatism or
malaria, but, above all, by alcohol.

497. Effect of alcohol upon nerves. — A little alcohol
seems to hasten the rate of transmission of nervous im-
pulses by increasing the circulation of the blood, but a
few drinks retard their action. A great danger of using
alcohol is that it may cause neuritis or inflammation of the
nerves. Slow, steady drinking may produce it as well as
occasional sprees. It comes without warning, but remains
a long while, producing pain and paralysis. Alcohol pro-
duces the disease as often as all other causes combined.

OV. PHYSIOL. — 1 8

274 APPLIED PHYSIOLOGY

SUMMARY

1. The cells of the body are made to act harmoniously by

means of orders sent from a few cells in a central
nervous system.

2. A nerve is a bundle of microscopic threads, each run-

ning from a central nerve cell to the cells of the
body.

3. Nerves transmit impulses caused by irritation from out-

side the body, and also impulses originated in either
the cells of the body or the central nerve cells.

4. Sensory nerves carry from the cells news concerning

a substance which is touching the body, and they
inform the central nerve cells when the cells are tired
or are in need of food.

5. Motor nerves carry orders to the cells to move, to

secrete, to eat, and to grow.

6. Impulses in nerves travel about 100 feet per second.

7. Nerves may become inflamed and produce pain and

paralysis.

8. Alcohol often produces severe inflammation of the

nerves.

DEMONSTRATIONS

1 1 6. Skin the leg of a small animal or frog, and push apart the
muscles upon the inside of its upper part. White nerve cords will be
•seen to lie alongside the main artery and vein, and can be traced up-
ward to the spinal cord and downward until they become lost in the
skin or muscles. Notice that those which branch off to the skin are as
large and numerous as those which supply all the rest of the leg.
Notice how much force is needed to break one of the nerves. In
ancient times it was supposed that tendons and nerves were the same.
Compare a nerve with a tendon to see their points of resemblance.

117. To show the effect of irritating a nerve in its course, pinch a
boy's funny bone. He will wonder how the sensation travels to the

NERVES 275

brain when he feels it go down to his little finger. Explain that it
only seems to come from the finger, but does not go there.

1 1 8. With a power of at least 200 diameters, show specimens of a
nerve mounted for the microscope. In a specimen of nerve cut length-
wise, notice the slender conducting fiber running down the middle of
each thread and its thicker, clear covering of fat. In a specimen cut
across the nerve, notice that the conducting fiber of each nerve thread
appears as a central dot within a circle of the protecting fat. Notice
the fine connective tissue between the threads. Sketch the specimen.

119. Show the difference in sensibility of different parts of the skin
by touching it with the points of a pair of compasses. Upon the balls
of the fingers the points will seem separate even if near together, while
upon the back they will seem one when separated two inches.

120. Show that some parts of the skin feel sensations of temperature
more than the others by drawing the point of a lead pencil slowly
across the cheek. At intervals there will be felt a cold sensation, show-
ing that a special nerve of temperature has been touched.

121. Cut a nerve in a recently killed frog and separate it from the
flesh for a short distance. After a moment, pinch the nerve, and
the muscles will contract.

REVIEW TOPICS

1. Describe the essential parts of the nervous system.

2. Describe a nerve.

3. Explain the two results of irritating a nerve.

4. Define and name the kinds of sensory impulses.

5. Describe the sensations of touch, pain, temperature,

and weight.

6. Tell how the cells make known their wants.

7. Show how epithelium aids the sense of touch.

8. Name and describe the three kinds of motor impulses.

9. Give the rate of transmission of impulses along nerves.

10. Describe the effects of pressure upon a nerve; of

cutting a nerve ; and of disease of a nerve.

11. Tell how alcohol affects a nerve.

CHAPTER XXIX
THE SPINAL CORD

498. The first collection of central nerve cells is in the
spinal cord. The spinal cord is a soft white cylinder of
nervous tissue, about half an inch in diameter. It is
securely hung in the upper two thirds of the tube formed
by the bony rings of the backbone. It extends from the
bottom of the skull to about the level of the lowest rib, a
length of about eighteen inches. It is only about two
thirds as large as its tube, and so is not likely to be injured
by bending the backbone.

499. The gray matter. — When the cord is cut across,
the central part of its end shows the grayish outline of a

butterfly surrounded by a
thick layer of a whiter
substance. The gray mat-
ter is a collection of nerve
cells, which give off nu-
merous nerve fibers like
the central fibers of ordi-
nary nerve threads. The

A thin slice from the spinal cord with the 11 ahrmt * of an

cells and nerves magnified 200 diameters. * TOITO O

inch in diameter. Some

a cells in the gray matter.

b fibers in the gray matter. of the nerve fibers COm-

c nerve threads in the white matter. municate with Other cells

of the cord, and some take coverings and become ordinary
nerve threads. The whole is bound together by delicate
connective tissue.

276

THE SPINAL CORD

277

The spinal cells receive a part of every impulse from the
sensory nerves, and take part in sending out motor impulses
to the various parts of the body.

500. The white matter. — The white matter is made up
of nerve fibers which still retain their coverings. In fact,
the white matter is simply a huge nerve. The nerve
threads of the white matter adjoining the right and left
sides of the gray matter are motor threads carrying im-

FRONT SIDE

Diagram of the action of each part of the spinal cord.

pulses from the brain to the cells of the gray matter. The
nerve threads outside of these and the threads behind the
gray matter are prolongations of the sensory nerves of the
body, some of which finally go to the brain, and others
connect with the cells of the gray matter of the cord.

501. Spinal nerves. — The spinal cord gives off thirty-
one pairs of nerves through openings between the rings
of the backbone. Each nerve is made of a sensory
and of a motor part which soon unite into a single
bundle in which the two kinds of nerves cannot be dis-

APPLIED PHYSIOLOGY

Diagram of the origin of nerves in
the spinal cord.

tinguished. These spinal nerves supply the whole body

below the neck.

502. Action of nerve cells in voluntary motion. — The

spinal cells do/ not originate impulses or act of their own

accord, but they act only when
ordered to do so by the brain
or when the cells of the body
express a need of protection,
nutrition, or rest. When a

a motor nerve root from the front part person wishes to lift his hand,

of the nerve. -L • v • i i

b sensory nerve root from the back hlS bram SGnds an Order to

part of the cord. these nerve cells, and they in

c gray matter of the cord. j ., -,

d white matter. turn send the order over the

nerves to the muscles which

move the hand. In this way the mind sends all orders
for voluntary motion. For each muscle there is a sepa-
rate group of spinal cells. If these cells are injured or
destroyed, a person cannot move his muscles voluntarily.

a tack pricking the hand.

d motor nerve.

Diagram of reflex action.

b sensory nerve. c nerve cell in the spinal cord.

e muscle moving the hand.

503. Reflex action. — The spinal _c£lie- * also send out
orders in response to impulses brought by sensory nerves.
Motor impulses sent in response to influences brought by

THE SPINAL CORD 279

sensory nerves are reflex acts. Reflex action is designed
to protect the body from injury and to supply its needs.
Most acts of the cord are reflex. When the finger touches
a hot object, the sensory nerves carry the sensation to the
cells of the spinal cord and to the brain. Before the sen-
sation reaches the brain, the spinal cord sends out an order
for the muscles to move the finger away from the heat.
The brain becomes conscious of the burn and of the move-
ment of the finger at about the same time. In this way
the spinal cord protects the body against all kinds of
injuries.

504. Reflex action in relation to nutrition. — Digestion
is mainly a reflex act. Motor impulses for glands to pro^
duce the digestive juices are sent out from the spinal cord
when the sensory nerves bring word that food is present
in the stomach or intestine. Peristalsis is also a reflex act
dependent upon the presence of food. The sensory nerves
also carry to the spinal cells news of the temperature of
a part and of its need of more or of less blood, and, in
response, the cells send out motor impulses for the arteries
to change their size. The heart is also somewhat affected
in a reflex way. The sensations of exertion and fatigue
are carried to the spinal cells, which send out orders for
more rapid heart beats. Fear, joy, anger, and sorrow all
affect the heart in a reflex way.

The growth of each separate cell is controlled by the same set
of spinal cells that produce motion in a part. Muscle cells, especially,
need the constant stimulus of the spinal cells to keep them growing, for
otherwise they slowly waste away and become weak. The spinal cord
is continually overseeing the nutrition and growth of cells, and if it
were to cease its oversight, their death would soon take place.

505. Reflex action in habitual movements. — The reflex
action of the cord aids in performing simple movements of

28O APPLIED PHYSIOLOGY

the body. The peculiar sensations which tell a man that
he is beginning to fall pass to the cells of the cord, and
they in a reflex way send out the proper orders for the
muscles to put the body in an upright position again.

506. Reflex action in education. — The reflex action of
the spinal cord can be educated. Even a simple reflex
action like standing must be learned. When a baby first
tries to walk, his brain cells give the proper orders to the
cells of the spinal cord, and they in turn give them to the
muscles. Thus he slowly directs each detail of the move-
ments with his brain. Soon the spinal cord learns to send
the next order as soon as it feels the sensation of the
previous movement, and finally all the movements needed
become reflex, and the child runs about with but little
effort on the part of his brain.

In learning to play a piano, the brain is occupied both in reading
the notes and directing the movements of the fingers in playing.
But, at last, the brain has only to read the notes to the cord and it
instantly sends the proper orders that they be played.

Education and skill in any art consist in the ability of the cord to
execute proper movements while the brain is wholly occupied with the
design. In this ability to acquire new uses, the cells of the nervous
system differ from all other cells of the body. When the hand is
educated, it is really the spinal cells which are educated.

507. Excessive reflex action. — Reflex acts are some-
times not beneficial. A slight noise gives some people a
fright, and in lockjaw the slightest sensation causes the
spinal cells to send out orders for the muscles of the body
to contract violently. Self-control is largely the power
which the brain has of restraining the spinal cells from
sending out orders even when strong and sudden sensa-
tions are received. Thus, when something tickles the
throat, it is possible for the brain to restrain the spinal

THE SPINAL CORD 28 1

cells from sending the order to cough. In the same way
men sometimes endure great pain without shrinking.

508. Broken back. — Injuries to the backbone may
injure the spinal cord so that it cannot conduct nervous
influences past the injured point. Then parts of the body
below the point of injury can neither send nor receive
messages from the brain, but are paralyzed both in sensa-
tion and motion. Yet the reflex action of the part may
persist, for the part of the cord below the injury still
retains its vitality.

509. Disease of the spinal cord. — There are diseases
which may destroy the action of any single part of the
cord or of the whole cord below the seat of the disease.
Then there will oe loss of sensation or of motion or
impairment of nutrition, usually in the lower part of the
body. The diseases are generally slow in their course and
incurable.

510. The action of the cord is unconscious. — The cord
always acts wholly without a person's knowledge. Like a faithful
nurse, it stands guard over the cells of the body and controls them in
their nutrition, growth, and work. The brain restrains its excessive
action and directs it in ordering the voluntary movements, but leaves
to it almost the entire care of individual cells.

SUMMARY

1. The spinal cord is made up of a central mass of gray

matter surrounded by white matter.

2. The gray matter is made up of cells from which nerve

fibers extend both to the brain and to the cells of the
body.

3. The white matter is composed of nerve threads which

connect the cells of the cord with the brain and with
the nerves of the body.

282 APPLIED PHYSIOLOGY

4. Thirty-one pairs of nerves connect the cord with all

parts of the body.

5. The use of the cells is to send orders over the motor

nerves when told to do so by the brain, and also
to send orders in response to information brought
to them by sensory nerves.

6. Orders sent in response to sensations are reflex acts.

7. Reflex acts are for protection, nutrition, and to relieve

the brain from the drudgery of sending orders for
every detail of bodily movements.

8. The reflex action in an educated spinal cord enables a

person to work with skill.

9. Restraint of excessive reflex acts constitutes self-control.

•

DEMONSTRATIONS

122. Procure a spinal cord at the butcher's. Notice the nerves
going off from the cord. Notice how the cord is enveloped by a thick,
fibrous sheath and is held in place by the nerves and fibrous bands.
Remove the cord from the bone and. slit open its sheath. Notice the
soft consistency of the cord and its shape like two cords pressed
together. On its clean-cut edge notice the grayish butterfly-shaped
center and the pure white outer part.

123. Examine a thin cross section of the cord under the microscope
with at least 200 diameters. In the outer parts of the specimen notice
the round circles of cut nerve threads. Explain that this is the white
matter of the cord.

Examine the central part, noticing the large nerve cells and nerve
fibers which run in all directions. Notice the fine and wavy connective
tissue fibers binding the whole together.

124. The pure reflex action of the cord can be shown with a decapi-
tated frog. Place a small piece of blotting paper, wet with a strong
acid, upon its back, and it at once kicks it off with its hind leg. Prick
its back, and it makes one leap. Suspend it with its hind legs hanging
down, and let a toe touch a dish of acid, and it at once draws up the
leg. (See demonstration 35.)

Explain that the frog has no feeling or sense, but performs the move-

THE SPINAL CORD 283

ments in a reflex way to escape danger in the same way that a boy
suddenly jumps when he touches a sharp pin.

125. To show reflex action, have a boy sit with one knee crossed
over the other and hanging perfectly limp. Now strike the front of
the knee just below the patella. The thigh muscles will contract and
cause the leg to kick. This will succeed best if the boy is not looking
when you strike.

REVIEW TOPICS

1. Describe the spinal cord ; its appearance and situation ;

its gray matter, its white matter, and the origin of
the nerves which arise from it.

2. Describe how the cells of the gray matter act in caus-

ing voluntary movements, and in causing reflex
movements.

3. Explain how reflex action is a protection to the body ;

how it controls all processes of the growth and secre-
tion of the cells; and how it enables a person to
acquire skill in movements.

4. Explain how reflex acts may be harmful; how self-

control may overcome the harm.

5. Describe the effects of injury to the spinal cord.

6. Describe the effect of diseases of the spinal cord.

CHAPTER XXX

THE SYMPATHETIC NERVOUS SYSTEM

511. Of what the system consists. — The spinal cord con-
trols the contraction of the arteries, the peristalsis of the
intestine, and the growth of cells. Yet the impulses which
it sends out for these purposes pass through another set
of nerve cells and nerves called the sympathetic nervous
system.

The sympathetic nervous system consists of small bodies
like grains of corn or smaller, called ganglia, from which
nerves go out in all directions. There are four main jjairs
of ganglia, in the head, and twenty-three in a row down
the front of the backbone all connected by nerves. Each
ganglion is a collection of nerve cells and nerve fibers
bound together by connective tissue. Nerve threads con-
nect its cells with the cells of the spinal cord and also with
the muscle cells of the arteries and intestine. Through
the arteries they probably affect all the cells in the
body. The nerve threads are smaller than those of ordi-
nary nerves, and seldom form bundles large enough to be
seen. They usually consist of a fiber like the central fiber
of an ordinary nerve thread .without its fatty covering.
They are thus not easily found even with the aid of a
microscope.

The nerves from the ganglia run mainly along the
course of the large arteries. Upon the aorta and its

284

THE SYMPATHETIC NERVOUS SYSTEM 285

main branches in the chest and abdomen, nerves and small
ganglia form intricate networks, each called a plexus.

Just back of the stomach there is a large and important
plexus called the solar plexus, whose nerves supply the
muscles of the organs of the abdomen. A plexus within
the heart controls the action of the heart.

512. Sensory sympathetic nerves. — The sympathetic
nerves carry both sensory and motor impulses, but only
faint impulses of pain and touch. Thus the circulation
of the blood and digestion of food go on almost without
our knowledge, but a very strong irritation may give rise
to an abdominal pain, as in colic.

Sensory impulses telling of the wants of the cells and of
the need of secretion or movements of the arteries or digest-
ive organs are continually being received by the ganglia.
These impulses travel slowly and require some time to
produce an impression. Most of them travel only to the
cells in the ganglia, and few get farther than to the cells
in the spinal cord. Only very strong impressions, whose
cause may injure the body, reach the brain and produce a
feeling of pain, hunger, thirst, or fatigue.

513. Motor sympathetic nerves. — The ganglia send
orders to the epithelial cells of the glands to produce
their secretions, and to the muscles of the intestine and
arteries either to contract or to dilate. They do this in
response to information furnished by the sensory nerves.
They also send out orders for the growth and nutrition
of the cells of the body on receipt of news of their needs.
Most orders from the ganglia are reflex.

514. Mode of action of the ganglia. — If cut off from connec-
tion with the cord, the ganglia send few impulses. The cord seems
to furnish them with a supply of nervous energy. They seem to take
a small amount of its active impulses and transform it into a large

286 APPLIED PHYSIOLOGY

amount of gentle impulses for the arteries and intestine. When poisons
or spoiled food irritate the intestine to a dangerous degree, the sensa-
tion goes beyond the ganglia and excites the spinal cells to action. In
response they send out direct orders which cause energetic and painful
peristalsis to remove the food, in marked contrast with the gentle action
caused by the ganglia alone.

515. Influence of the brain. — The brain has some power over
the ganglia. Excitement or fear may influence the spinal cord so that
it in turn modifies the impulses going through the ganglia. Sorrow
seems to depress the ganglia so that the processes of digestion and
assimilation are not so well performed, and the nutrition and growth of
the cells of the body are diminished. But nature has arranged that after
leaving the brain, mental influences shall act through two sets of nerve
cells before they can directly affect the nutrition of the body. Thus
man's body is protected against injury from his ever-changing moods.

516. Connection of organs with each other. — By means of
the sympathetic system, a nervous influence in one organ is spread over
all the rest. Because other organs seem to share in the sickness when
one is deranged, the nerves controlling them are called sympathetic
nerves. Thus, when one organ is deranged, the others act less strongly
and impose less work upon the disabled part.

517. Injury to sympathetic nerves. — The sympathetic
nerves are less influenced by outside impressions than any
other nerves in the body, and great violence is needed to
impair their action seriously. Poisons which are swallowed
or produced during disease may injure them so that the
ganglia almost cease to send out their orders. Then life is
endangered, and strong nerve stimulants like strychnine
are needed.

Aside from poisons, almost the only grave danger which
may threaten the sympathetic system is a blow upon the
abdomen or neck. A hard blow or great pressure just
below the ribs may paralyze the solar plexus. The arteries
then enlarge and hold so much blood that too little goes
to the head and brain. So there is danger of sickness and
of death. A blow upon the side of the neck may injure

THE SYMPATHETIC NERVOUS SYSTEM 287

the large ganglia which are situated there, as well as
the large nerves near by, and make such a profound
impression upon the heart that death may take place
at once. Blows upon the neck or abdomen are always
dangerous.

SUMMARY

1. The sympathetic nervous system consists of collec-

tions of nerve cells called ganglia, and of both
sensory and motor nerves which follow the course
of the arteries.

2. The cells of the spinal cord send impulses to the

ganglia, and they in turn distribute them to the
arteries and glands and to the organs of the chest
and abdomen.

3. The ganglia send orders only in a reflex way accord-

ing to impressions received from their sensory
nerves.

4. The ganglia control the contraction and dilatation of

the arteries, the peristalsis of the intestine, the secre-
tion of glands, and the growth of the cells of the
body.

5. The ordinary sensory impulses conducted by the sym-

pathetic nerves produce no feeling.

6. The heart is controlled mainly by a set of small ganglia

within its own walls.

7. The sympathetic system produces slow and gentle

movements in contrast with the quick and active
movements made by the spinal cord.

8. The brain has no direct control over the ganglia.

9. Blows upon the neck or abdomen may injure the sym-

pathetic nerves so as to cause death.

288 APPLIED PHYSIOLOGY

REVIEW TOPICS

1. Describe the sympathetic nervous system: its ganglia,

nerves, plexus, and its connection with the spinal
cord.

2. Describe the sensory impulses of the sympathetic

nerves.

3. Describe its motor impulses and their relation to the

arteries ; to secretion of glands ; to peristalsis ; to
the growth of cells, and to the heart.

4. Describe how the ganglia send out their impulses.

5. Describe how the spinal cord has influence over the

ganglia, and how they work independently of the
cord.

6. Describe how the brain can affect the ganglia.

7. Describe how the action of the ganglia may be seriously

impaired by injuries.

CHAPTER XXXI
THE BRAIN

518. General structure. — The brain is the part of the
central nervous system which can originate orders in dis-
tinction from the spinal cord, which acts only in response

Brain of a frog ; top view (X 10).
a cerebrum.
b optic tubercles.
c cerebellum.
d medulla.
e upper end of spinal cord.

Brain of a hen ; side view (X
a cerebrum.
b optic nerve.
c optic tubercle.
d medulla.
e cerebellum.
/ spinal cord.

to impulses brought to it. In reptiles, toads, and frogs, it
is very simple in structure, but yet contains parts corre-
sponding to all the parts of the brain of man. In them the
spinal cord swells out to form a cone-shaped body called
the medulla oblongata. Above it there is a small flat

OV. PHYSIOL. — 19 289

2QO APPLIED PHYSIOLOGY

swelling called the cerebellum, the next two smaller bodies
called the optic tubercles, and at the top two larger bodies
which together are called the cerebrum. They follow
each other in a straight line. In man the parts are bent
upon each other, while the cerebrum is so large that it
covers all the other parts.

519. Coverings. — The brain of man is a very soft body
weighing about fifty ounces. It is contained in the top of
fche skull. It is covered with a delicate network of fibers
called the pia mater, which carries the numerous blood
tubes of the brain. Outside of the pia mater is a
thick, tough membrane called the dura mater. The dura
mater is the periosteum of the inside of the skull.

520. The medulla. — The upper end of the spinal cord
becomes enlarged into a wedge-shaped body called the
medulla oblongata, or simply the medulla. The medulla
is about one inch and a quarter in length and three quarters
inch in breadth at its upper end. Its center is gray matter
covered with white matter, both of which are direct con-
tinuations of the same matter in the cord.

521. Nerves of the medulla. — From the medulla there
go out seven pairs of nerves to supply the head and face.
They, together with five other pairs which the brain gives
off, are called cranial nerves, in distinction from the spinal
nerves. The cranial nerves which arise in the medulla
are sensory and motor, and supply the head and face just
as the spinal nerves do the rest of the body. They con-
nect with cells in the medulla which act only in a reflex
way. In this sense, the medulla is a part of the spinal
cord, and not of the brain. One of these seven cranial
nerves is partly a nerve of the special sense of taste.
Impressions of hearing, sight, and smell are carried by
three cranial nerves arising higher up in the brain.

THE BRAIN 2QI

522. The vagus nerve. — One of the pairs of cranial nerves is
called the vagus, or pneumogastric, nerve. It supplies a small sensory
branch to the ear, and motor branches to the larynx and pharynx ;
then it passes into the thorax and gives off branches to the heart,
which restrain its action. It gives sensory branches to the esophagus
and lungs, and finally reaches the stomach and liver. The main nerve
supply of these organs is from the spinal cord, or from the sympathetic
system, but the vagus nerve is an additional means for better regulating
their action to suit the needs of the body.

523. Centers originating impulses. — In the medulla, a
collection of nerve cells, called the respiratory center,
sends out a regular succession of orders for respiratory
movements. While the orders may be hastened or re-
tarded by other nerve centers to suit the needs of the
body, yet the medulla compels the respiratory muscles to
act so as to keep the body supplied with sufficient oxy-
gen. Thus it is a real part of the brain. When the
respiratory center is destroyed, respiration and life cease
instantly.

There is another part of the medulla, called the vaso-
motor center, which controls the contraction of arteries,
and another which regulates the peristalsis of the esoph-
agus in swallowing. While these are partly reflex acts,
yet their perfect action requires original impulses to be
sent from the medulla.

524. Effects of reflex influences. — The respiration, circula-
tion of the blood, and taking of food are essential vital processes of
life which the medulla controls without our being aware of it. Strong
influences from the nerves of the body may act in a reflex way to
modify the impulses of the medulla. Great fear may cause the vaso-
motor center to send out impulses for the contraction of the arteries so
as to produce great paleness. Instances have occurred in which the
disturbance of circulation from this cause has produced death.

525. Effects of injury. — An injury to the respiratory and vaso-
motor centers causes death at once. A broken neck, if high up, may

292

APPLIED PHYSIOLOGY

involve the medulla and cause instant death. But the medulla is
so situated that only the greatest violence can harm it.

526. The cerebellum. — Just above and overhanging the
medulla is a rounded mass called the cerebellum. It forms
less than one fifth of the brain. It consists of an interior

white mass of nerve
threads, covered with
a layer of gray matter
about -j1^- of an inch in
thickness. On the sur-
face are deep fissures
into which the gray
matter dips, so that its
amount is greatly in-
creased. In the gray
matter are nerve cells
which are connected
with the rest of the nervous system through the nerves
of its white matter. These nerve cells are the essential
part of the cerebellum. They have no connection with
any vital process of life, and do not take part in thought.
A man with a diseased cerebellum can perform a single
muscular act like raising his hand, but he cannot direct
changing and complicated movements, such as are required
in writing, walking, or balancing his body. Thus the cere-
(bellum acts like a balance wheel, so that orders for com-
plicated movements may be sent with regularity and pre-
cision.

527. The Optic tubercles. — The optic tubercles are two small
collections of gray matter situated upon the main nerve tracts which
connect the cerebrum and medulla. They seem to be connected with
the reflex movements of the eye. Other collections of gray matter near
them seem also to be connected with the eye.

Diagram of a human brain.
a cerebrum. b cerebellum. c medulla.

THE BRAIN

295

528. The cerebrum. — The main nerve tract, after pass-
ing through the spinal cord, medulla, and optic tubercles,
spreads out to form a mass called the

cerebrum. While in frogs and fishes it
is no larger than the medulla or optic
tubercles, in man it forms more than
four fifths of the whole brain and over-
hangs all the other parts.

It consists of a central mass of nerve Cellg from the gray
threads covered with a layer of gray matter of the cerebrum,
matter one eighth of an inch in thick-
ness, containing numerous large cells. Each cell gives off
numerous fine fibers. Most of these fibers form an intri-
cate network among the cells, but one from each cell takes
a covering and becomes a nerve thread of the white mat-
ter, and finally reaches other cells of the brain or even of
the spinal cord.

529. Fissures of the brain. — The cerebrum is divided
nearly into two parts, called hemispheres, by a deep furrow

running forward and
backward upon the mid-
dle of its upper surface.
Another furrow, called
the Sylvian fissure, starts
near the bottom of the
fore part of the side of
the cerebrum and runs
backward and upward.
Many other furrows and
fissures from one quarter
to one half inch in

depth, run in waving lines between its main furrows, throw-
ing its surface into folds called convolutions. The convo-

294

APPLIED PHYSIOLOGY

lutions increase the surface of the cerebrum, so that in all
it measures about four square feet. This greatly increases
the area over which the nerve cells in the gray matter may
be spread. The interior of the cerebrum is a small irregu-
lar cavity, called the ventricle, which is filled with a clear
liquid.

Regions of the head and action of the different parts
of the brain.

530. Regions of the cerebrum. — The fissures and con-
volutions are nearly the same in all men, and mark out
definite regions upon the surface of the brain. First, is
the region just behind the forehead, called the frontal
region. Second, is the region lying under the upper part
of each side of the skull, and called the parietal region.
Third, is the region about the ear, called the temporal
region. It lies just above and in front of the ear. Fourth,

THE BRAIN 295

that part of the brain lying under the back of the skull
is called the occipital region. Each region of the brain
does a special work.

531. Action of the cerebrum. — The nerve centers may
act reflexively in response to sensory impulses, as the spinal
cord usually does; or automatically by originating their
own impulses, like the respiratory center in the medulla
and the nerve cells in the heart. The spinal cord, sym-.
pathetic system, medulla, and cerebellum all act in one or
the other of these ways, and without our being conscious
of their action. The cerebrum is the seat of the thinking
mind. It acts in an automatic way, but we may be con-
scious of any of its actions. It acts first by feeling sensa-
tions; second by sending orders for voluntary muscular
movements ; third, by thought. It does each kind of work
in a particular region of its surface.

532. Sensory regions. — Sensory impressions of which
we are conscious are sensations. Sensations of hearing,
smell, and taste are felt by the temporal region ; of sight
by the occipital region ; and of touch by the parietal region.
If either region is destroyed, the impressions going to that
area are no longer received, and the person is devoid of the
corresponding sense. Unless each impression reaches its
own region of the surface of the brain, it produces no sensa-
tion, although it may still reach reflex centers in the optic
tubercles, medulla, or cord, and give rise to reflex action.

533. Memory. — Impressions may be retained in the cells
and be recalled. These constitute memories. Our memo-
ries are complex stores of impressions in widely separated
parts of the brain. The sum of our different memories
constitutes a great part of our knowledge.

Different regions of the brain are connected by nerve
fibers. So when one region recalls a memory, another

296

APPLIED PHYSIOLOGY

region recalls another memory of the same object. Thus,
when the temporal region recalls the memory of a sound

of a bell, the occipital
region recalls its appear-
ance.

534. Motor regions. -
Orders for voluntary mo-
tion are sent by the cells
lying just in front of a
zone connecting the two
ears. Each muscle of
the body is controlled
by a special set of nerve

cells called
center.

its motor

A motor impulse passes
down through the white mat-
ter of the cerebrum, medulla,
and spinal cord to the spinal
nerve cells, and then out along
a motor nerve to a muscle. In
y or disease in the top

an

the motor region may be in-
volved, giving paralysis of cer-

Diagram of the course of nerve influences
in voluntary motions.

a object to be picked up.

b sensory nerve.

c the part of the influence which goes to the

cells of the cord, and tends to produce of the skull some of the cells of

reflex action.
d cell of spinal cord.
e motor nerve from spinal cord.
/ continuation of the sensory nerve b up the tam "^scles. By tl

cord to the brain. affected one can often judge

g cell of the brain which perceives touch. of the exact location
h motor cell. , , ,

i thought cell. trouble and rem°V

j motor nerve fiber running to the cells of the operation.

cord, and carrying an influence which 535. Relation

continues along the motor nerve e.
k muscle which moves the hand.

of the
it by an

of the

sensory to the motor re-
gions. — The motor and sen-
sory regions are in close connection by nerve fibers in the white matter.
The motor region regulates its impulses according to information brought

THE BRAIN

to sensory regions by sensory nerves. A carpenter regulates the force
with which he pushes his plane according to the feeling of muscular
resistance.

536. Memory of movements. — Acts of motor cells are
stored in memory and constitute a part of knowledge.
All motions must be learned at first. When the brain
centers have learned a movement thoroughly they teach
the spinal centers so that finally their work is almost en-
tirely relieved, and they can be occupied in other thoughts.
Awkwardness is usually the result of the brain's attempt-
ing to send out orders for motion while it is occupied with
other thoughts. Ease and grace of motion come when the
spinal centers have learned to relieve the brain center.

537. Thought regions. — The cells of the frontal regions
take note of memories stored in other regions, and by their
comparison form new ideas. Thus, a pause between two
sensations or mental acts gives rise to an idea of time;
and the sight of two objects removed from each other gives
the idea of space and of number. Neither time nor space
nor number in itself can make an impression upon the
senses, and yet they are realities in the mind. Comparison
of memories and the formation of new ideas is thinking.
Thoughts themselves are stored in memory and can be
recalled and compared.

538. Speech. — Thought is expressed by speech. Bv
means of speech new sensory and motor ideas and new
thoughts are gained and stored in the memory without the
cells of the different regions experiencing the particular
sensations. Herem is the main difference between a man
and an animal. An animal gains new ideas only by
memory of its sensations and acts which it itself experi-
ences, but a man can acquire them second hand by being
told. Thus a man may be profited by the experience of

298 APPLIED PHYSIOLOGY

others. Knowledge gained only by long and patient
research of wise men is imparted to children in a few
moments, while an animal can impart knowledge only in
a limited degree.

539. Speech in animals. — All animals have a variety of natural
cries. Monkeys have a dozen separate cries which are similar in all
species. A hen has at least five different cries to express as many
different ideas. Parrots and crows have been taught to speak a few
words, but they do it just as the mocking bird or brown thrush imitates
any sound which it hears. Speech belongs to man alone.

540. Of what speech consists. — Speech is one of the
highest and most complicated of mental processes. It is
not a natural gift, but must always be learned at first.
A child first hears a word spoken. He records it in the
temporal regions of the brain, and learns to recall certain
sensory and motor memories when he hears the word.
By the time he is a year and a half old his motor region
begins to form the word when he thinks of the memory.
At the age of six or eight he begins to recognize the printed
word with his sight region, and finally he learns to write
the word with his motor region. Thus nearly every region
in the brain takes part in some form of speech.

541. Center for spoken words. — The muscles of the
mouth can be moved by the cells of the face center in the
motor region, but their movements in speech are so precise
and complicated that a center is especially provided to pro-
duce their movements in talking. It is situated just below
and in front of the motor area, but is usually upon only
one side. When this center is disturbed, a person cannot
talk, although he understands spoken and written speech,
and has control of his lips and tongue in doing other things.

542. Disturbance of the speech centers. — There are cases
in which the word-seeing center is disturbed so that a person can

THE BRAIN 299

speak and write correct answers to questions, but cannot read and un-
derstand what he has just written. Sometimes a person cannot speak
his thoughts, but can read aloud what he has written. Careful observa-
tion of the speech is of great value in locating brain diseases, for the
speech centers involve nearly every region of the brain.

543. The Intellect. — The cerebral cells act in as definite
and uniform ways as the cells of the intestine or heart, and
men studied the laws of their minds long before the struc-
ture or even the existence of cells was known. The actions
of the mind are divided into three great divisions. First,
is the intellect, or the pure knowledge-gaining faculty. This
includes the work of all the sensory regions of the brain
and such a part of the frontal regions as is concerned in
receiving knowledge through speech. It is the basis of the
other mental acts.

544. The sensibilities. — The second division of mind
study comprises the sensibilities, or the feelings. Much
of knowledge does not concern us in the least. All feeling
is based on knowledge, and all knowledge leads up to
feeling as we come to know a thing intimately. We love
it or hate it, and are sorry for its loss.

545. The will. — The third and highest act of the mind
is to will to do. It is the control which the frontal region
has of the motor region. In order to do a thing we must
first have knowledge, and, second, we must feel some degree
of emotion or desire to do it. Only a small part of knowl-
edge causes feeling or emotion, and only a small part of
even our strong feelings are expressed in action.

Of all the actions of the mind the will is the most difficult to arouse
and control. Since it depends upon feeling, this faculty must first be
aroused. Men readily act their feelings of anger and fear. To form a
new will, active and brave, which is capable of controlling the natural
and acquired appetites and passions, is the highest and noblest work
of man.

300

APPLIED PHYSIOLOGY

546. Brains of animals. — The medulla is much the same in
all animals from the frog up to man. This is because breathing and the
flow of blood are much the same in all. The cerebellum in a frog or
snake or fish is very small, for they need but a small regulating and
balancing part. A bird or a hen must make precise movements in
balancing itself in fly ing or roosting, and so it has a large cerebellum.

Brain of an ox.
a outline of brain in the skull. b the brain removed from the skull.

The optic tubercles of frogs and birds are well developed, for their eyes
are perfect. The cerebrum of frogs and snakes and fishes is very small.
Its hinder parts are the largest, for in them the impressions of sight,
hearing, and smell are located. Its fore parts are mere points, as would
be expected from the low intelligence of the animals. A bird has a
larger cerebrum, corresponding to a greater mind. An animal's cere-
brum is much larger and is somewhat folded to give room for more
nerve cells, but the frontal or thought region is small. An animal's

THE BRAIN 30 1

senses are as acute as a man's, and so the back parts of its brain are
well developed.

547. Animal intelligence. — An animal is capable of storing
sensory and motor impressions in memory, and of sending out motor
impulses according to sensory impressions. In some respects he is
capable of doing this to a far greater extent than man. For instance,
a dog can find his master by the sense of smell alone. He can also
use his frontal region in thought and judgment, but to an extent which
corresponds to the small size of this region.

548. The essential difference between man and animals. —
The possession of speech seems to be the key to man's progress and
noble ambitions. By means of it the Creator has revealed to him a
knowledge ot things before the foundation of the world, and of things
to come. Animals are incapable of receiving instruction except through
the senses and so they make no progress. Man rises in thought above
time and space itself.

549. The nervous system in lower animals. — All four-
footed animals, birds, fish, and reptiles possess nerves, a spinal cord,
and a brain. Their nerves, sympathetic system, spinal cord, and
medulla are developed nearly as much as in man, for the creatures eat,
feel, move, and breathe, often to a greater extent than man. The
cerebrum is developed according to the intelligence of the animal, and
the cerebellum according to the complication of its movements.

Insects and worms and shellfish have no brain or spinal cord, but
a row of ganglia like those in the sympathetic system extends through
the body. Each ganglion gives off nerves to the cells of the body
These creatures do little else than eat and digest food, and hence the
highest nervous system is not needed.

In the lowest form of life there is no nervous system at all. When
the animal consists of a few cells or of only a single cell, no nervous
system is needed.

SUMMARY

1. The brain is the part of the central nervous system

which originates impulses.

2. The brain is continuous with the spinal cord, and

consists of the medulla, cerebellum, optic tubercles.

3O2 APPLIED PHYSIOLOGY

and cerebrum. Each consists of gray matter con-
taining nerve cells, and of white matter made of
nerve threads.

3. The medulla is like the spinal cord in that it gives off

sensory and motor nerves.

4. The medulla also originates impulses controlling res-

piration and the contraction of arteries.

5. The cerebellum adjusts the voluntary motor impulses

of the brain, so that movements like balancing of
the body are done with precision.

6. The optic tubercles are reflex centers for the eyes.

7. The cerebrum forms four fifths of the brain, and con-

sists of a puckered covering of gray matter over a
central mass of white nerve fibers.

8. The cells of each part of the brain have a definite

work to do. They receive sensory impressions,
send motor impulses, and think.

9. The impressions of each cell remain as permanent

memories which can be recalled at will.

10. By means of speech, thought, sensory and motor

impressions are conveyed to other persons and there
become memories as though they had actually been
experienced.

11. In speech the centers for motion, sound, and sight

all take part.

12. There is a special center for producing the movements

of the mouth in speech.

13. The first stage of mind action is knowledge ; the next,

emotion ; and the third, willing and acting.

DEMONSTRATIONS

126. Show as types the brains of a frog or fish ; of a hen ; and of a
fourfooted animal. A frog's, fish's, or chicken's brain can easily be

THE BRAIN 303

removed by cutting away the skull. After opening the top of the skull,
place it with the brain in Muller's fluid or formalin for a few days, when
the brain will be hard and can be removed with little injury.

127. In the frog, note the medulla, then the thin cerebellum, look-
ing like a disk of paper with its edge inserted just above the medulla.
Note the swelling optic tubercles, and then the long, pointed halves of
the cerebrum.

Next compare the same parts on a bird's brain. Note the similar
medulla and optic tubercles. Note the large cerebellum forming a half
moon above the optic tubercles, and marked with cross fissures upon
its back part. Note the cerebrum in front, shaped like a chestnut and
as large as the rest of the brain.

Next compare the same parts in a mammal's brain. Note the similar
medulla, but the larger cerebellum. The optic tubercles are obscured
by the cerebrum. Note the cerebrum, large enough to cover almost
all the rest of the brain. Note the convolutions.

Now compare these brains with a model or a picture of the brain
of man. Note the large frontal regions in man and the larger and
more numerous fissures and convolutions, and that the cerebrum com-
pletely covers all the other parts of the brain.

128. When the skull of an animal is opened, note the lining of tough
and thick dura mater, which may be peeled off with little difficulty.
Note that it extends in between the two hemispheres of the brain and
between the cerebrum and cerebellum. Underneath it, note the deli-
cate meshes of the pia mater, containing numerous blood tubes. Note
that it dips into all the fissures and contains a small amount of a thin,
clear fluid.

129. Examine a specimen of the gray matter of the cerebrum or
cerebellum with a microscope magnifying 400 diameters. Note its nerve
cells with fine branches. The white matter will appear like a collection
of ordinary nerve fibers. Sketch the specimen.

REVIEW TOPICS

1. Name the different parts of a frog's brain in order,

and tell how they differ from the same parts in a
man's brain.

2. Describe the two coverings of the brain.

304 APPLIED PHYSIOLOGY

3. Describe the fd.e3iill.a, its nerves and reflex action;

its respiratory center; its vasomotor center; and
the effects of its injury.

4. Describe the cerebellum and give its action.

5. Describe the optic tubercles and give their action.

6. Describe the cerebrum ; its hemispheres, fissures, con-

volutions, gray and white matter, and regions.

7. Locate the region in which impressions of sight are

received ; of touch ; of hearing ; of smell ; and of
taste.

8. Describe the region from which motor impulses for

voluntary motion are sent out.

9. Describe the memory, and show why recalling one

thought brings to mind another thought of the
same object.

10. Locate the thought region of the brain, and describe

the process of thought.

1 1. Show that by speech man gains ideas which an animal

can get only by actual experience.

12. Locate and describe the mode of action of the center

for spoken words; for written speech; and of the
speech-hearing and speech-seeing centers.

13. Describe the three main divisions of the acts of the

mind.

14. Compare the corresponding parts of the brains of

different animals with each other and with the same
parts of the brain of man.

15. Describe the nervous system in insects, worms, shell-

fish, and in the lowest forms of animals.

CALIFORNIA COLLEGE
of PHARMACY

CHAPTER XXXII

INFLUENCES WHICH AFFECT THE MIND

550. Stimulation to action. — The thought cells of the
brain are given power over voluntary actions of the body,
with no higher power to cause them to act, except the will,
which is the result of their own action. Were a child left
entirely to itself, it would probably exercise its mind no
more than an animal, But the sight of objects and ambi-
tions not yet attained spurs the thought cells to action,
just as sensations cause the spinal cord and motor region
to act. Without constant stimulus of the senses and feel-
ings the thought cells languish and almost cease to act.
As the body is compelled to grow by the cells of the spinal
cord, so must the mind be compelled to grow by an effort
of the will. Few men possess a will strong enough to act
without the stimulus of other minds, but association with
trained minds arouses the will to exercise one's own mind.

551. Concentration of the mind. • — In order to become
educated, the mind must be exercised persistently and for
hours at a time. The mind does not grow unless its whole
energies are often directed towards a single object. It is
not study to read a page and then to converse about sports
for a moment and then to study another moment, for each
impression sweeps away the preceding one. True study
is to sit down in a quiet room, and to fix the mind upon the
book continuously for an hour or more. Then the mind
will be occupied so that it takes no note of time or outside

OV. PHYSIOL. — 20 70 C

306 APPLIED PHYSIOLOGY

impressions. Any one will find study interesting if he will
concentrate his mind upon a subject so that he gains
knowledge. Then when playtime comes he will enter
into the sport with zest and satisfaction. No one who has
not been working can truly enjoy play.

552. Persistence of mental impressions. — Brain work re-
quires heat and energy like muscular work. The cells of the cerebrum
retain an impression of each thought, which is deep and permanent in
proportion to the power expended upon it. A lesson learned in a
minute makes some impression upon the cells, but it is gone in another
moment. A dull boy hammers away at a lesson by the hour, but at the
end of a year he will have retained far more than the brilliant boy who
loses his impressions as fast as he gains them.

It is extremely difficult to efface impressions once really made upon
the cerebral cells. Apparently, knowledge may be forgotten, but some
day something will cause the cells to recall the impressions. Thus it
is very important to avoid all thoughts which we should be ashamed to
recall.

553. Habit. — Memories of thoughts often repeated may
arise in spite of the will to restrain them, and may compel
the motor region to do acts which the will utterly abhors.
At first a man's will has to direct the thoughts to speak
profane words. Soon the words become so imprinted in
thought that they arise even without his knowledge.
Habits grow faster and stronger than the will to overcome
them. On the other hand, one can form a habit of study
and of mind cultivation so that mental work is a pleasure.
The more one works with his mind, the more he enjoys
his work. The mind is constantly forming habits of
thought. Even if it thinks nothing bad, yet it may soon
acquire a lazy habit of not thinking at all.

554. Heredity. — Impressions of any kind may become
so permanent that one's children have a tendency to

INFLUENCES WHICH AFFECT THE MIND 307

acquire them. The son of a criminal has a natural
tendency to become a criminal, and even if he is well
brought up in an upright family he will be far more likely
to yield to temptation than a well-born child. Children of
educated parents take naturally to study. Children of
excitable and nervous parents will also inherit their
disposition. By education, natural tendencies of mind and
character can be overcome. If a wrong tendency is known
and is not .corrected, the blame for future action of the
child will lie with his educators rather than with the man.

555. Unconscious mind action. — When the mind is intensely
occupied it may not take note of severe sensory impressions. Thus
soldiers in battle often fight on, unconscious of severe wounds. You
may try in vain to recall a name. Later, when you are thinking of
something else, the name may flash into your mind. You may strive
to direct the mind to a lesson, but thoughts of a sick friend may persist
in arising, and may shut out all thoughts connected with the study. In
acquiring any new thought the mind must reason by conscious efforts,
step by step, until the idea is clearly in view. Ever afterward the mind
may reason out the steps unconsciously and almost instantly, so that we
may lose sight of the complexity of the mental processes involved in
forming the idea. Learning to perform any mental process is essen-
tially becoming able to do it with little or no conscious effort. Then
the mind, relieved of the conscious direction of thoughts already
learned, is free to acquire new ones. Man is probably unconscious
of most of the steps in his mental processes.

556. Sleep. — It is as impossible for the mind to put
forth conscious effort continually as it is for the mus-
cles. A rest from conscious effort is called sleep. As a
rule, a man needs about seven or eight hours of good
sleep ; a boy of sixteen needs nine or ten hours, while one
of six needs twelve. Sleep should be regular, so that the
brain may not become excessively tired between times.
As a general rule, an early hour both for going to bed and

308 APPLIED PHYSIOLOGY

for rising is desirable. If a student would go to bed when
he feels sleepy, and would sleep an hour or two longer
each night, he would feel able to do more and better work
during his working hours.

557. Sleeplessness. — Like other organs while resting, the brain
contains but a small quantity of blood during sleep. If a large amount
of blood continues to flow through it, sleep will be impossible. Often
when a person cannot sleep he can feel the pulse in his temples throb
and hear it as his head lies upon the pillow.

A common cause of sleeplessness is an empty stomach. A light
lunch will often cause the arteries of the abdomen to dilate and take up
the blood which circulates in the brain and so relieve the cause of sleep-
lessness.

Lack of work during the day may be a cause of sleeplessness. Many
a man finds himself suddenly unable to sleep when he retires from active
business. It seems to be a law of nature that he who does not work
cannot sleep, for he is not tired enough to need a rest. Occupation for
the mind and body will give such persons a good night's sleep.

Worry will also cause sleeplessness, for it keeps the cells of the brain
in action just sufficiently to attract the blood to the head. The brain
can endure extremely hard work if it only gets fest between times.

Narcotics, like opium and chloral, will always produce sleep if taken
in sufficient doses. But they injure the cells to a greater degree than
they do good. In times of anxiety the temptation to resort to them is
great, but their use at such times invariably leads to a habit of using
them, with all its accompanying evils and dangers.

558. Dreams. — Sometimes during sleep the sensory and
motor regions recall their memories with the vividness of
real life. This is a dream. The thought regions rarely
take part in a dream. Disordered memories of the sensory
and motor regions seem to be realities, but in the absence of
judgment they seem harmonious and natural, and we recog-
nize their fantastic nature only when reason returns with
the waking hours. Formerly dreams were supposed to be
heralds of events to come; but now it is known that they
are but the shadows of previous experiences.

INFLUENCES WHICH AFFECT THE MIND 309

559. Change of occupation. — When one set of brain cells
has become tired, it is well to direct the thoughts to another
subject and let the first set of cells rest. It is a relief to
study a history lesson after working hard at arithmetic
problems. A change of occupation is the best kind of
rest. It is well to alternate pure brain work with work
which, like gardening and carpentering, requires muscular
effort

560. Healthy bodies. — The brain depends upon the blood and
digestive organs for the power with which to work. When any of the
organs are acting improperly the brain is the first to suffer. The strong-
est brains are contained in the healthiest bodies. No kind of food is
brain food more than another, but fish and phosphates are hardly so
valuable as beefsteak and salt.

561. Exercise and brain work. — Muscular exercise is needed
to keep the body in the best physical condition. Thus it makes the
brain stronger. It also takes some blood which otherwise would con-
tinue to circulate in the Drain, and thus it rests the mind after work.

If exercise is continued until the body is tired, no energy is left for
the brain, but sleep comes on as soon as the body composes itself for
brain work. Exercise for the benefit of the brain should be brisk in
order to produce the best effect upon the circulation of the blood, but
it should never be carried to the point of fatigue.

562. Nervousness. — When the brain is exhausted from
overwork or from worry, it has not enough energy to con-
trol itself or the reflex actions of the spinal cord. Slight
and strong sensations are equally unpleasant, and the
effort to control the feelings seems to increase the suffer-
ing. Thus there arises a condition called nervousness.

Nervousness is a lack of self-control. The judicious ex-
pression of sympathy by a strong-willed person is the best
means of overcoming it. On the other hand, sarcasm and
scolding only do injury and increase the nervousness.

563. Hysteria. — An extreme lack of self-control is called

3IO APPLIED PHYSIOLOGY

hysteria. The person laughs or cries at trivial things. The
motor and sensory regions often seem paralyzed. Persons
may even wound themselves to inspire sympathy. Yet
there may be most violent convulsive movements. A well-
marked case closely resembles the actions of a spoiled child
when his will is crossed.

The treatment of hysteria is to arouse the will power. Expressions
of sympathy only make the condition far worse. A firm and stern
nurse can usually command obedience. Any sudden fright will gener-
ally break up an attack.

564. Insanity, — A persistent lack of control of the
brain in one or more directions is called insanity. Ner-
vousness often repeated and yielded to may become insan-
ity. Worry and overwork are extremely common causes,
while alcohol causes half the cases in asylums. Often the
weakness of the brain cells is inherited.

A person about to become insane is changed in dispo-
sition and character. There is a lack of self-control and
of judgment. Prompt rest and care of the body may over-
come the attack, but a strong-willed friend will be needed
to guide the treatment, for the patient thinks that every-
body except himself is wrong.

565. Forms of insanity. — In insanity there are no new mental
traits or possessions by demons, as used to be supposed, but only an in-
crease of some mental acts and a decrease of others. The expression
.an unbalanced mind well describes the condition. There are three
main forms of its disturbance, giving rise to three forms of insanity.

An increase or hastening of one or all mental acts sometimes takes
place. The thoughts flow faster than words can express them, and so
the talk is a meaningless gibberish. The senses are uncommonly alert,
and one may think he hears and sees things which do not exist. He
cannot understand why others are so slow and dull, and so is apt to
show violent outbursts of temper. Yet although he may harm others,

INFLUENCES WHICH AFFECT THE MIND 311

he will seldom hurt himself intentionally. This condition is called
mania, and constitutes the popular idea of a crazy person.

In a second form of insanity the thoughts flow slowly. Questions
are answered in a hesitating way of which the person is conscious, so
that he feels that he is incapable of doing business or even associating
with men. He becomes gloomy, and imagines he has committed an
unpardonable sin which he endeavors to discover. He reads his Bible,
but imagines that all its curses apply to him personally. He finally
tries to destroy himself so that he may no longer be a burden to his
friends. This condition is called melancholia.

A 'weakening of the whole brain is the third form of insanity. De-
generation of the brain cells often occurs in old people, and is commonly
called softening of 'the brain. It may occur in middle age. Alcoholic
drink is a common cause of the condition.

566. Treatment of insanity. — Insane persons can usually talk
and exercise some reasoning powers. A sympathetic nurse should win
their confidence and control them by reason and persuasion. Special
training is required to carry out proper treatment, and so it is usually
best to remove them to an asylum. Most cases of insanity improve in
from three to six months, and many permanently recover.

567. Delirium of fever. — In poisoning, either by drugs or by
the poisons of sickness, the mind is apt to be somewhat disturbed.
Anything which diminishes the fever will quiet the mental disturbance,
and with the end of the fever the mind regains its right state. In rare
cases, the delirium persists, and is then a real insanity.

568. Injuries to the brain. — The effects of a blow or
other injury to the brain depend upon its situation. Any
injury may cause unconsciousness. Injuries to the top of
the brain impair the faculties situated in the injured regions,
but seldom cause death. Injuries to the base of the brain
are usually fatal by involving the medulla. After the ef-
fects of the blow have passed off, a blood clot remaining
may still cause paralysis of the cells of a particular part so
that the person may lose certain mental powers.

569. Apoplexy. — The arteries of old persons sometimes
become hard and brittle so that one is liable to burst in the

312 APPLIED PHYSIOLOGY

brain, especially in its motor region. Then the pressure
of the escaped blood injures or destroys some of the brain
cells. This constitutes apoplexy, or a stroke of paralysis.
There is usually unconsciousness for a time, followed by
paralysis of some limb and of speech. Recovery is usually
slow and imperfect. If the medulla is affected, death
quickly results. Confusion of speech, dizziness, and tin-
gling in a limb usually precede an attack for some days.
When a person is taken with a stroke of apoplexy, he
should be kept very quiet, with his head raised, so that the
blood will flow through the brain as gently as possible.

570. Fits. — If the cells of the motor region of the brain are irri-
tated, as by a sliver of bone or a blood clot, they may send impulses at
intervals to produce violent movements of the muscles. This is called
a convulsion or a^£/. An operation for the removal of the substance
which presses upon the cells will relieve the fits.

In young children, irritation of indigestible food in the intestine or
of the poisons of fevers may cause the spinal cord or motor region to
send out reflex orders and so produce a convulsion or fit. Convulsions
in a child can be stopped by immersing it in a tub of very warm water.
Then something to clear out its intestine should be given so as to re-^
move the cause of the convulsions. In all forms of convulsions there
is little suffering, for the person is wholly unconscious.

Convulsions may come without warning and produce entire uncon-
sciousness for a minute or two, when they cease, and the person is ap-
parently none the worse for it. This trouble is called epilepsy or Jits.

During the fit there is no danger except that a person may bite his
tongue. So the only thing to be done is to stuff a handkerchief into
his mouth so as to crowd the tongue away from the teeth. Excitement
is liable to bring on fits in a person subject to them.

571. Panics. — In times of bodily or financial danger, where many
are assembled, a single person may infect the whole audience with an
insane fear. Then each person thinks only of his own safety, and
many are sure to be trampled upon and injured. In such a time a
single cool head will do much to calm the excitement. Fire drills in
school teach the pupils to be orderly in the face of danger.

INFLUENCES WHICH AFFECT THE MIND 313

SUMMARY

1. Constant effort of the will is needed to keep the thought

cells of the brain acting.

2. A few repetitions of either good or bad acts produce

habits of doing them.

3. Many mental acts are done without consciousness.

4. In sleep the thought cells rest from work and there is

complete unconsciousness. Lack of mental occupa-
tion during the day, worry, and an empty stomach
are common causes of sleeplessness.

5. A change of occupation is rest for the mind.

6. Active exercise, short of fatigue, improves the mind

as well as the body.

7. A lack of self-control when irritated by slight sensa-

tions is nervousness. An extreme lack of will power
is hysteria.

8. A persistent lack of control of the thoughts is

insanity. The thoughts may either be hastened, or
hindered, or suppressed, giving rise to three forms
of the trouble.

9. In fevers there is often a temporary delirium which

resembles insanity.

10. In old people, an artery of the brain sometimes bursts,

and the clot, pressing upon the nerve cells, stops
their action and produces a shock of apoplexy.

11. Irritation of the motor region may cause the cells to

send orders for violent muscular movements, pro-
ducing a fit or convulsion.

REVIEW TOPICS

I. State how the cells of the cerebrum differ from the
other cells of the body in regard to being controlled
and made to act.

314 APPLIED PHYSIOLOGY

2. Tell how best to study.

3. Discuss persistence of impressions ; habit ; heredity.

4. Show how the mind acts without our knowledge.

5. Tell the nature of sleep ; its use ; how much is

required ; and when to sleep.

6. Tell how sleeplessness is produced by an empty

stomach ; by worry ; and by lack of work.

7. Tell the nature of dreams and of what ideas they

usually consist.

8. Show how a change of occupation rests the brain.

9. Show that good health is needed for good brain work,

and tell how exercise affects the brain.

10. Show the nature of nervousness, and of hysteria, and

tell how to overcome them.

11. Give the causes of insanity, its three forms, and its

treatment.

12. Give the result of blows upon the brain.

13. Give the nature of a stroke of apoplexy, and show

how it produces paralysis.

14. Discuss fits ; their causes, forms, and treatment.

15. Discuss panics.

CHAPTER XXXIII
EFFECTS OF NARCOTICS UPON THE MIND

572. Stages of action. — A perfect engine acts smoothly,
and with an ease of motion which suggests a delight in its
work. The body is an engine at the service of the will.
A derangement of any part disturbs the action of the
brain according to the extent of the disorder. While little
or no alcohol can ever be found in the brain, yet the leu-
comaines and other poisons produced by the action of
alcohol reach the whole body, and produce a profound
effect upon the brain sooner than upon any other part.
Three stages of the effects of alcohol are well marked : —

First, there is a stage of stimulation ; second, the cells
act in an uncertain manner. This is the stage of disturbed
action; third, the cells act slowly or even cease to act.
This is the stage of paralysis. All three stages are often
seen in drunken men upon the streets.

573. Stage of stimulation. — A small amount of alcohol
causes the blood to circulate more rapidly. More food
reaches the brain cells, and so they show more activity.
It produces a happy state of mind in which men over-
estimate their abilities. Men drink mainly for this effect
of the alcohol.

Some gifted men with weak wills exert themselves only when under
the influence of strong drink, and from this fact many reason that
alcohol increases the brain power. These gifted men hang about the
saloons, eating little and drinking much. In this condition their brains
receive no strength or energy to devote to any object. A drink fur-

3l6 APPLIED PHYSIOLOGY

nishes a quick stimulation which at once excites the brain to great
activity. Thus it is enabled to do brilliant work while the effects of
the alcohol last. In half an hour the poisonous effects assert them-
selves, and the man's condition is worse than ever. Good food and a
regular life would give such a man a continuous store of energy with
which he could perform brilliant work day after day. Alcohol is such a
poor substitute for the food that it enables him to work only for a few
moments at a time.

574. Stage of disturbed action. — The stimulation of a
drink of alcohol is uncertain, and, at best, lasts only for a
few minutes. Alcohol uses oxygen which would otherwise
be available for the brain cells as well as for the other
cells of the body. An ounce and a half of alcohol a day
will begin to interfere with oxidation and to disturb the
brain, and far less will do so if it all is taken at once.

575. Moral effect — Alcohol weakens and disturbs the
action of the brain cells, beginning with those most
highly developed. These are thoughts of our relation to
other men. So a person beginning to be under the influ-
ence of drink will be selfish and inconsiderate of others.
He will insult his friends and get angry without cause.

576. Effect upon his judgment. — The judgment or
reasoning concerning the effect of one's acts upon himself
is the next to be disturbed. He becomes daring and
careless. He proposes impossible plans in business. If
he has a tendency to commit a crime, he will do it now.
Many a thief or murderer has gotten himself into this
state of drunkenness to enable him to commit his crime
recklessly. If a man has a tendency to swear or to be
unkind, he will show it, for the restraint of judgment is
gone. The blunted judgment takes no note of coming
danger or of business failure. Many a man drinks to
drown trouble.

EFFECTS OF NARCOTICS UPON THE MIND 317

577. Effect upon the motor regions. — Shortly after the
judgment is clouded the motor regions begin to fail. Then
the hand will be unsteady, and the legs will totter as they
support the body. The person is now visibly -drunk, and
his judgment is so far gone that he could not decide where
to go even if his legs could carry him. The cerebellum is
also affected, so that he is still more uncertain in his
movements.

578. Effect upon the sensory regions. — Next after the
motor regions, the sensory regions begin to fail. Sensa-
tions of touch are first affected, so that the drinker cannot
feel the glass at his lips. In former days it used to be
the custom to make a person drunk and insensitive before
he underwent a surgical operation. After the sensations
of touch are benumbed the sight begins to fail. A
drunken man sees double, or the buildings and trees seem
to sway and dance before his eyes. Hearing, smell, and
taste are also lessened, so that he does not heed loathsome
surroundings, but will lie contented in a filthy gutter.

579. Stage of paralysis. — When the thought, motor,
and sensory regions of a man's brain are all weakened or
stopped in their action, the mind is dull and drowsy, and
soon he is in a condition resembling a deep sleep, from
which he can be roused only with difficulty. The medulla
and spinal cord still carry on the processes of life, but
they too begin to be overpowered. By the time the
cerebrum is almost overcome, the spinal cord is also much
decreased in action so that there is no response to pricks
or blows. Then the medulla is all that remains of the
central nervous system. It continues to send out impulses
for respiration. The respiration and circulation are the
only remaining signs of life, but even they are weak,
and may become almost imperceptible. Since little oxy-

318 APPLIED PHYSIOLOGY

gen enters the body, little heat is produced. If the night
is at all cold, the drunken man is in great danger of
freezing to death. It is only a step to the total cessation
of the action of the medulla and failure of respiration.

In cities men often are found in the streets in the last
stage of drunkenness. They closely resemble cases in
which the action of the brain is destroyed by a severe
blow upon the head which leaves no external mark.

580. Effects of long-continued drinking. — Either heavy
or moderate drinking* may cause in the brain and mind
a slow change which resembles an excessively slowly
developed drunken state. As in drunkenness, the first
change is a disregard for the comfort of others. Then
the thoughts wander, and the mind cannot grasp a situa-
tion as it once could. Later the motor region is affected so
that the hand trembles and the gait is unsteady. All these
changes are like those which naturally occur in old persons.
Drink makes a person old too soon. In many drinkers the
judgment entirely disappears, and the drinker is insane.
He is in a continual state resembling drunkenness. Alco-
hol produces more insanity than all other causes combined.

581. Effects of bad company. — The low companionship which
a drunkard keeps, itself tends to dwarf the mind and to make one care-
less in morals and judgment. Men also lead each other into tempta-
tion. If a man were alone, one drink might satisfy him, but meeting
others, he lingers to talk, and so drinks again to keep company with
the rest.

582. Delirium tremens. — After a prolonged drunken state, or
after severe injury, a heavy drinker is liable to violent disturbance of
the mind, called delirium tremens. In it his sensory regions form
exaggerated memories of fantastic and hideous views, in which demons
and foul reptiles seem present on purpose to torment him. In his fear
he will cry out and will use violence in his endeavors to escape. The
trouble may last continually for several days, and may permit the suf-
ferer to take neither food nor sleep.

EFFECTS OF NARCOTICS UPON THE MIND 319

583. Alcoholic inheritance. — The weak body and mind of a
confirmed drunkard are almost surely transmitted to his children, but any
one who drinks at all may transmit some undesirable traits. The appe-
tite for liquor also may be transmitted to the children. If they are kept
from temptation, they will lead temperate lives, but they will be very apt
to yield to the desire for drink if the temptation is thrown in their way,

584. Treatment of the alcoholic habit. — By a few repeti-
tions of drink the memory of its sensations becomes so
strong that it overrules the thoughts and will, and compels
its own gratification in more drink. At first, a man can
resist the appeals of his appetite, but after the cells of the
sensory region have gained gratification a few times, they,
instead of the will, direct the motor region to secure the
drink. Many a drunkard can no more control his appetite
than he can control the memory of the drink. What was
once a pleasant memory of the subordinate sensory region,
becomes the giant demon, enslaving the kingly thought
regions.

A drinker should not be laughed at or scorned, but he
should be encouraged to use his will in overcoming the
desire for drink. To this end everything ennobling should
be placed in his way. Good books, good companionship,
and, above all, the encouragement of sincerely Christian
people are almost absolute necessities in his reformation.

Drugs have almost no effect upon the habit, for they
cannot abolish memory nor increase the will power. Total
abstinence, not only from the drink, but also from buildings
where it is sold and from the association of those who
have been drinkers, is necessary for a cure.

585. Tobacco. — By smoking, a greater amount of blood
is drawn into the head, and the increased flow of blood
seems to make the brain more active. Sucking air through
a small quill produces the same effect upon the brain as

320 APPLIED PHYSIOLOGY

sucking smoke through a pipe. In fact, smokers often
cannot tell by the taste alone, whether the pipe or cigar is
alight or not; but they unconsciously judge mainly by see-
ing the smoke. Since tobacco weakens the heart, less
blood will flow through the body when tobacco in any
form is used, and this fact will tend to make the mind act
less strongly than before. The nicotine is also a direct
nerve poison.

586. Drug habits. — Opium, cocaine, and other narcotic
drugs whose use may become a habit, affect the mind in
the same way as alcohol. Every one who habitually uses
any of these drugs will surely become a mental as well as
a physical wreck. Opium, especially, seems to have a
fiendish effect in destroying the morality of its users.
They begin by lying and cheating in order to obtain the
drug without the knowledge of their friends, and they
finally end by becoming dishonest in all things. But the
drug produces a weak mind and body which soon end in
death. Most of these drugs are far more dangerous than
tobacco or alcohol.

587. Ether and chloroform anaesthesia. — Ether and chloro-
form are both substances manufactured from alcohol. When they are
breathed into the lungs they produce effects which resemble a rapid
state of drunkenness carried to its last stage. For a brief time, the
brain is excited and then its faculties disappear one after another. In
from five to fifteen minutes the brain and spinal cord are completely
overcome, and only the medulla continues in action to carry on respira-
tion and the circulation of blood. A person may be safely kept in this
condition for two or three hours. Upon stopping the inhalation the
effects pass off in reverse order, until in from ten minutes to an hour
one has the full use of his brain again. The thought regions are over-
come long before the motor regions, and so a person taking ether may
struggle and cry out in apparent agony long after he has become com-
pletely unconscious. The struggling is reflex and takes place while a
person is insensible to suffering.

EFFECTS OF NARCOTICS UPON THE MIND 32!

SUMMARY

1. Because a small quantity of alcohol stimulates the

heart and increases the flow of blood in the brain,
it stimulates the mind to greater action. This lasts
for a short time only.

2. A little more alcohol is a narcotic to the brain cells

and weakens them so that they act in an uncertain
manner.

3. The first action to be disturbed is one's thoughts of

the welfare of others, and the second is the judg-
ment of one's own affairs. At this stage the actions
are wild and foolish.

4. Next the motor region is disturbed, and a man is now

noticeably drunk.

5. Next his sensory regions are disturbed so that he can-

not see and hear and feel so well as he should. He
is now dull and sleepy, or dead drunk.

6. Next the medulla is affected so that the respiration

and action of the heart are disturbed. Then death
is near at hand.

7. Continued drinking slowly overcomes the faculties of

the mind in the same order that they are overcome
in drunkenness. When the cells are seriously
affected, the person is insane.

8. The habit of taking alcohol may become so deeply

set in the brain cells that it is a disease overcoming
the will.

9. Sucking in tobacco smoke causes more blood to flow

to the brain, and so slightly increases its power, but
the tobacco itself weakens the brain.

10. Opium, cocaine, and all other drugs, when habitually
used, always weaken and destroy the mind.

OV. PHYSIOL. — 21

322 APPLIED PHYSIOLOGY

* REVIEW TOPICS

1. Tell why alcohol affects the brain and give the three

stages of its effects.

2. Describe the stage of stimulation.

3. Trace the career of a man as he becomes more and

more under the influence of drink, giving the effects
of alcohol upon the moral feelings ; upon the judg-
ment ; upon the motor region and cerebellum ; upon
the sensory region ; and upon the medulla.

4. Describe the permanent effects which long-continued

drinking produces in the brain.

5. Show how the bad company kept by drinkers affects

their minds.

6. Describe delirium tremens.

7. Show that the taste for alcohol and the effects of its

use may be transmitted to children.

8. Show that the alcohol habit is a disease, and give its

treatment.

9. Tell how tobacco affects the brain.

10. Tell how drug habits, as opium using, affect the

brain.

11. Tell how ether and chloroform produce insensibility,

and how the state resembles drunkenness.

CHAPTER XXXIV
TASTE, SMELL, AND HEARING

588. Touch. — Touch is a special sense. Its sensations
are aroused without the need of any special organ. So
the discussion of sensory nerves is really a discussion of
the special sense of touch. (See p. 269.)

589. Taste. — Taste is a special sense which is located
in the tongue, palate, and pharynx. All these parts are
endowed with a delicate sense of touch, but in addition
two pairs of cranial nerves carry special sensations of taste.
The impulses are aroused by the direct action of sub-
stances upon the nerves. The motions of chewing and a
good flow of saliva aid the sense of taste by bringing food
in contact with the nerves, while a dry substance, or one
which will not dissolve in water, can have no taste. All
tastes are some combination of sweet, sour, bitter, and salt
tastes. Sweetness and sourness are recognized mainly by
the front part of the tongue, and bitterness and saltness
by the back parts and pharynx.

Taste is greatly influenced by the sense of smell. The
real taste of coffee is greatly changed by the odor which
reaches the back part of the nose as it is swallowed.

590. Use of taste. — Taste enables a man to detect
spoiled or unwholesome food. The sense is capable of
great education. The prices of different grades of tea are
determined by expert tea tasters, who devote their whole
time to tasting different samples. Alcohol and tobacco

323

324

APPLIED PHYSIOLOGY

irritate the nerves in the mouth and so blunt the taste for
good food. For this reason a drinker does not enjoy plain
food, but requires spices to excite his taste.

591. The nose. — Impressions of smell originate within
the nose. Each nostril leads to a wedge-shaped cavity,

The outer wall of the nose.

a the nerve of smell at the base of the

brain.

b air spaces in the skull bones.
c branches of the nerve of smell.

d curved curtains of bone.

e opening of the Eustachian tube.

/ soft palate.

g upper jawbone.

which opens into the pharynx. The inner wall of each
cavity is smooth, and is formed by the thin bone that
separates the two nostrils. Each outer wall is formed by
three very thin bones which hang down like narrow cur-
tains. They nearly cover cavities, called sinuses, which
are situated in the neighboring bones. One sinus occupies
the interior of the upper jawbone, and is called the antrum.
The part of the skull behind the eyebrows is honeycombed
with small cavities, called the frontal sinuses.

TASTE, SMELL, AND HEARING 325

592. Olfactory nerves. — From the under surface of the
brain, about twenty nerves extend through perforations in
the upper part of the nose and spread out over the upper
one third of the surface of the nasal cavities. An odorous
gas entering the nose comes in contact with the ends of
these nerves and excites the sense of smell. An odor is
found only in substances which can be turned to a vapor.

The olfactory nerves are so delicate that they can perceive the
presence of gases which cannot be detected in any other way. Some
substances excite the sense of smell when they are in such small quan-
tities that they are given off for years without causing a perceptible
lessening of the weight of the substance.

When too much mucus covers the nerve endings, or when the sur-
face of epithelium is dry, no gas can reach the nerves, and then the
sense of smell is diminished. A cold in the head can produce either
condition.

593. Use of smell. — Smell is a warning against foul air
and decaying matter. The gases themselves are in too
small quantities to do harm, yet they are a sign that
other substances are present which can harm the body.
Air which has no odor is almost surely fit to be breathed.
Meat which has a pleasant odor is almost certainly fresh.

Tobacco smoke and snuff are irritating to the delicate
nerves of smell, and partly deprive its users of nature's
most useful protection against foul air.

594. The inner ear. — Sound is produced by certain air
waves which are received by nerves in the ear. There
they excite impulses which the brain interprets as sound.
In the hard bone, which rises from the bottom of the
skull by each ear, is a tortuous cavity, called the laby-
rinth or internal ear. The center of the labyrinth is about
one eighth of an inch in diameter, and is called the ves-
tibule. From the vestibule there extends a small spiral

326

APPLIED PHYSIOLOGY

tunnel, called the cochlea, which is like the inside of a
snail's shell, and also three other tunnels called the semi-
circular canals, from their shape.

The labyrinth is filled with a clear liquid, and is lined
with epithelial cells, among which the nerves of hearing
end. Upon the surface of the epithelium are cilia, among
which are fine hard particles called the ear sand. The air
waves produce waves in the liquid which beat against the

a outer air passage.
b membrana tympani.
c malleus or hammer bone.
d incus or anvil bone.

Diagram of the ear.

/ semicircular canals.
g vestibule of inner ear.
h cochlea.
i Eustachian tube.

e stapes or stirrup bone. j tympanum or middle ear.

cilia and produce the sense of sound. Waves in the fluid
surrounding the nerves must occur at least sixteen times a
second in order to produce a sound. When they occur
more than thirty-eight thousand times a second, they are
too rapid for the nerves to take account of their motion,
and so no sound at all will be heard.

The semicircular canals do not seem to be essential to hearing, but
when they are diseased a person is unable to balance himself so as to
walk or even to stand. The movements of the fluid in the canal seem
to produce nervous impressions which, in the cerebellum, excite such
reflex actions as are necessary to balance the body in an upright position.

TASTE, SMELL, AND HEARING 327

595. The middle ear. — To make hearing distinct, a
special mechanism is provided for transmitting the air
vibrations to the inner ear through two outer cavities.

A small aperture connects the inner ear with a middle
cavity called the middle ear, or tympanum. The middle
ear is half an inch long and a quarter of an inch broad.
It is lined with mucous membrane and is filled with air. Its
outer end is closed like a drum, by a thin leaf called the
drum membrane or membrana tympani, while a similar mem-
brane closes the aperture to the inner ear. The cavity of
the middle ear is greatly increased by its extending back-
ward into a bony projection called the mastoid process,
which can be felt just behind the outer ear. It connects
with the pharynx by means of a tube which is about the
size of a knitting needle and is called the Eustachian
tube. The act of swallowing opens the tube.

596. Bones of the middle ear. — The essential part of the
middle ear is a chain of small bones called the malleus,
incus, and stapes, which extend across its cavity from one
membrane to the other.

Air waves, striking the ear drum, throw it into vibra-
tions, which the chain of bones transmits to the inner ear.
The tympanum and its extension into the mastoid cells
act like the sounding box of a violin to increase the
vibrations.

597. Deafness. — The Eustachian tube permits air to pass in and
out of the middle ear so as to keep the air pressure within the same as
it is outside. When it is closed, the air pressure outside may change,
and thus the drum membrane will be pressed upon and prevented from
vibrating freely. This results in partial deafness. Enlarged tonsils
and adenoid vegetations are liable to cause a stoppage of the tube and
to produce deafness, and for this reason they should always be removed.
When the tube is stopped, there is a feeling of fullness in the ear, and
roaring or singing noises will be heard.

328 APPLIED PHYSIOLOGY

Deafness due to a stoppage of the Eustachian tube is the most com-
mon form. It often can be relieved by opening the tube by swallow-
ing. By blowing the nose hard with the nose and mouth closed and at
the same time puffing out the cheeks and swallowing, one can almost
always force air through the tube into the ear and thus relieve the deaf-
ness. This should be done several times a day.

Sometimes an inflammation extends from the pharynx up the Eusta-
chian tube and sets up an inflammation in the middle ear like that in
the throat. Mucus and matter then collect in the middle ear and
press upon the ear drum, causing a severe earache. If the tube does
not open, the membrane may burst and allow the matter to run out of
the ear.

598. A running ear should be kept clean by cleansing it with warm
boiled water as often as the matter collects. Sometimes in running ears,
the disease eats away the bones and produces inflammation of the brain.
For this reason running ears are always dangerous.

Some drugs may produce a ringing in the ears and partial deafness.
Quinine, which is taken for malaria, and salicylic acid, which is taken for
rheumatism, may cause it, but the effects pass off within a few hours.

Boxing the ears suddenly compresses air against the drum mem-
brane, producing pain and sometimes even bursting the membrane.
Loud reports, as of cannon, cause such extensive and painful vibra-
tions of the membrane that deafness may result.

599. Early in life a child may become deaf, and yet no
one may be aware of the trouble. Then the child is appar-
ently inattentive and does not answer when spoken to.
At school the teacher may ascribe his lack of attention to
carelessness or ill temper. In consequence, the child re-
ceives unjust punishment. The hearing of every dull and
inattentive child should be examined.

600. The outer ear. — Outside of the drum membrane
is a passage to the air about an inch in length and one
quarter of an inch in diameter, formed partly of bone and
partly of flesh. Around its opening is a shell-shaped fold
of flesh which, together with the passage, is called the
outer ear. Connected with it are rudimentary muscles

TASTE, SMELL, AND HEARING 329

which are so well developed in some persons that they can
move their ears as a horse does.

601. Ear wax. — The epithelium of the outer half of the
passage secretes a kind of bitter and sticky wax which
keeps insects and dust from reaching the drum mem-
brane. The epithelium grows outward towards the surface
like the nails, and carries the wax with it, thus preventing
its accumulation. Often in picking the ears the wax is
pushed against the drum membrane so that it cannot
vibrate. Next to throat trouble this is the most common
cause of deafness. The accumulated wax can be softened
and removed by gently syringing with warm water. Wax
can best be removed with the loop of the smallest-sized
hair pin, taking care not to insert it far enough to touch
the drum membrane.

602. Illusions of hearing. — Too dense or too rare air in
the middle ear, too much blood circulating in the inner ear,
the use of certain drugs, as quinine, blows upon the head
or wax in the ear, are all causes which may excite the
nerves of hearing. Then the impression goes to the
brain as though a real sound had excited the nerves.

The cells of the brain itself may interpret a sensation
wrongly ; thus an insane person may think that the sound
of his own pulse beating in his ears is the echo of the
blows of demons within his head.

Sometimes persons recall memories of sounds so vividly
that they seem to be real. This occurs naturally in dreams,
but it may occur in an insane person at any time.

603. The ear in lower animals. — In four-footed animals
and in birds the ear is the same as in man. In turtles and
frogs there is no outer ear, but the drumhead lies just
under the skin, forming a visible circle behind the eyes,
while the middle ear contains a single bone. In the snake

330 APPLIED PHYSIOLOGY

there is no external or middle ear, although a bone extends
from the inner ear to a kind of drum membrane just under
the skin. In the fish there is no external or middle ear,
and the labyrinth has no cochlea, but the vibrations are
transmitted only through the skull. In the lobster there is
a small cavity filled with liquid, in which are the endings
of the nerves of hearing. The vibrations producing sound
are transmitted to the bag through the sides of its head.
Thus all animals which have ears at all, possess what in
man is the internal ear.

SUMMARY

1. The sense of taste is excited by substances which

become dissolved in the saliva and excite special
nerves in the tongue and pharynx.

2. The sense of taste enables one to distinguish good

food from bad.

3. The sense of smell is excited by minute amounts of

gas, which excite special nerves in the upper part
of the nose.

4. Smell guards us against foul air and decayed sub-

stances.

5. Sound is produced by vibrations of the air.

6. The inner ear consists of winding canals filled with

liquid into which special nerves project. Vibra-
tions of the air excite the nerves and produce the
sense of sound.

7. The middle ear consists of a bony cavity across which

three small bones convey the vibrations of the air
to the inner ear.

8. Deafness is often caused by the Eustachian tube being

stopped.

TASTE, SMELL, AND HEARING 331

9. Inflammation of the throat may extend into the middle
ear and produce an earache.

10. Enlarged tonsils and adenoid vegetations are the two

principal causes of earache and deafness.

1 1. Running ears should be kept clean.

12. In all animals having a hearing apparatus, the essen-

tial and often the only part is the inner ear.

DEMONSTRATIONS

130. Examine the tongue of one of the pupils. Notice that its sur-
face contains three kinds of projections. There is a V-shaped row of
large, flat, and smooth projections upon its back part. There are red
pinhead-sized projections scattered over the whole front surface. There
are also fine projections like velvet spread over the whole surface. In
all these projections the nerves of taste seem to end. Examine also a
cat's tongue, and note the stiff hairs upon its surface.

131. Test the power of taste in different parts of the tongue. Place
a bit of a sweet or of a sour substance in the back of the mouth, and notice
the slight taste, while it is easily tasted in the front part. Now place
some salt or bitter substance upon the front of the tongue. Notice that
it has little taste until it spreads to the back part.

132. Saw lengthwise through a calfs head so as to open the nose.
Notice the smooth inner surfaces of the nostrils, and their furrowed
outer surfaces produced by the folded bones. Notice that the nostrils
open into the pharynx. (See demonstration 35.)

133. Have a butcher remove the bone containing the middle and
internal ear from a calf's skull. Carefully cut away the shell of bone
over the middle ear. One can judge of its position by measuring down
the outer air passage. Notice the size and shape of the middle ear.
Notice the ear drum, and the three little bones which stretch from it
entirely across the cavity. Notice also that the last bone fits into the
small opening leading into the inner ear.

134. The inner ear will be more difficult to show, for it is small and
complicated, and is situated deep in a very hard bone. Cut away the
bone a little farther in, when the cochlea may be opened, and possibly
a semicircular canal will be recognized. The spiral tube of fhe cochlea
is barely £ of an inch in diameter, while the semicircular canals are as
small as a sewing needle, but yet form loops about f of an inch across.

332 APPLIED PHYSIOLOGY

REVIEW TOPICS

1. Describe the process of tasting, and tell how smell

influences the sense of taste.

2. Give the use of the sense of taste.

3. Describe the endings of the nerves of smell in the

nose, and tell how the sensation of smell is pro-
duced.

4. Give the use of the sense of smell.

5. Describe the inner ear : its cochlea, semicircular

canals, and nerves of hearing, and tell how they act.

6. Describe the middle ear : its bones, the two mem-

branes which close it, and its Eustachian tube.

7. Show how a stoppage of the Eustachian tube may

lead to deafness ; to running ears.

8. Show how throat trouble may cause ear disease.

9. Tell how to care for running ears.

10. Show why boxing the ears is dangerous.

11. Describe the outer ear : its air passage and wax.

12. Show how the ears may seem to hear sounds which

do not exist.

13. Describe the ear in a frog; in a snake ; in a fish ; in a

lobster.

CHAPTER XXXV

THE EYE

604. Light. — Straight lines of light called rays pass off
from objects in all directions. Each ray is supposed to be
a vibrating line in a thin
substance called ether,
which fills all space.

The vibrations of ether take
place many millions of times
each second. In sound the air
vibrates only a few hundred
times. Light travels nearly
185,000 miles each second, while
sound travels about 1000 feet in
the same time. Light waves are
from ^fony to TOfcny inch in
length, but each sound wave
reaches several feet. The length
of a wave of light determines its
color. Red waves are about
twice as long as violet waves.
A mixture of all colors produces

Diagram of light passing from an object.

It passes in every direction, and, falling
upon a screen, produces a confused multi-

white light, while black is due !U(?e of images' which form only a mass of

light, but no one clear image,
to the absence of light. Colors

which, like red and green, form white light, are called complementary
colors. *

In passing through glass or other clear substances, rays of light may
be bent from their courses. By a properly shaped glass called a lens,
rays may be spread apart or may be brought together in a point called

333

334

APPLIED PHYSIOLOGY

Diagram of the formation of an image with a

lens.

a an object sending off light.

b a lens which brings all the rays from any point
in the object together again into a single
point.
c image of the object a.

a focus. If the focus falls upon a screen, an image of the object giving

the light will appear. By changing the kind and the position of the

lens the image may be
made either larger or
smaller than the real
object.

Light has the power to
produce a chemical change
in substances. Photog-
raphy and bleaching
clothes are examples of
the action of light. In
photography a prepared
plate is inclosed in a tight
black box, into which light
from an object is admitted
through a small lens.

The lens brings the light to a focus and forms an image upon the

plate.

605. The eye. — The eye is an apparatus like a photog-
rapher's camera, but is more perfect. It consists of a
round, hollow shell about \ of an inch in diameter, formed
of a very tough membrane about -^ of an inch in thick-
ness, called the sclerotic coat. The sclerotic coat is lined
with a thin black membrane called the choroid coat, which
carries the blood tubes, and is colored black so as to
prevent reflection of the rays of light. Inside of the
choroid coat is a very thin and transparent membrane
called the retina. The cavity of the eyeball is filled
in front with a thin, clear liquid called the aqueous humor,
while its back part contains a thick, jellylike fluid called
the vitreous humor. The two humors keep the eyeball
distended and in shape.

The nerve of sight, called the optic nerve, enters the
back part of the eye and separates into fine threads which
end in microscopic rods set closely together on their ends

THE EYE

335

in the retina. The retina corresponds to the photographic
plate of a camera. A bulging transparent tissue, called
the cornea, forms a round window through the front part
of the eyeball, and admits light to the retina. Behind the
cornea is hung a curtain called the iris, in whose center is
a hole called the pupil. The iris is colored to a shade

a bone of the orbit.

b muscle which moves

the eyeball.
c sclerotic coat.
d choroid coat.

The human eye.

e retina.
/ eyelid.
g iris.
h lens.

* cornea.
j muscle which changes

the shape of the

lens.
k optic nerve.

varying from blue to dark brown, and it is this which gives
the color to the eye.

The iris is composed of muscle fibers which can contract so as to
make the pupil smaller. A strong light acts in a reflex way to cause
the iris to contract and make the opening of the pupil smaller, but in a
dim light the pupil is large, so as to admit all the light possible. Thus
the iris regulates the amount of light admitted to the retina.

606. Sight — Behind the pupil is a lens whose shape
can be changed at will by the action of muscles. The

336 APPLIED PHYSIOLOGY

lens brings the light to a focus so as to form an image of
an object upon the retina. In the cells of the retina are
particles of brown coloring matter in which light produces
an instant change. This excites in the optic nerve an
impulse which the brain interprets as sight.

607. Coverings of the eye. — The eyeball is loosely situ-
ated in a deep depression of the skull, called the orbit.
The space between it and the bone is padded with fat and
crossed by numerous muscles, nerves, and blood tubes.
Thus it is thoroughly protected from injury. It can be
freely turned at will in all directions by six slender mus-
cles which rise from the back part of the orbit. It is pro-
tected in front by two thin but strong lids, which can be
moved up and down at will. From the edges of the lids
there project two or three rows of stiff curved hairs, which
still further protect the eye. The lids can be closed by a
flat circular muscle which completely surrounds them.
The insides of the lids and the front side of the eyeball,
except the cornea, are covered with a soft mucous mem-
brane, called the conjunctiva.

608. Tears. — The conjunctiva and cornea are mois-
tened by a saltish fluid called tears. Tears are secreted by
a gland called the lachrymal gland, which is situated just
above and to the outer side of the eyeball. At the inner
end of the edge of each lid is the opening of a small tube
which unites with the tube from the other lid and forms a
single tube called the nasal duct, leading to the nose.
Ordinarily the nasal duct drains away the tears as fast
as they are formed, and sometimes, as in crying, their
salt taste can be noticed in the mouth. Often they are
produced so fast that some run over the lids and fall down
the face. The uses of tears are to wash away particles of
dust which fall upon the eyeball, and to moisten its surface.

THE EYE 337

Field of view. — A person can clearly recognize
objects in only a small part of the field of view just in
front of the eyes, while the rest seems to be only indistinct
shadows. To be distinct, the image must fall upon the
part of the retina less than -^ of an inch across, which is
situated directly behind the cornea. In reading a book,
the eye can distinctly see two or three words at once, but
by rapid and unconscious movements of the eyes sidewise,
we cover a larger field of view.

610. Duration of sensations. — The sensation of sight is
produced almost instantly when the eyes are directed
towards an object, but the image persists for ^ of a
second. If a succession of pictures of a moving object
are thrown upon a screen at that rate, the object will seem
to go through its motions without interruption. Birds
flying and waves dashing upon the beach may be thus
shown absolutely true to life. A point of light swung
about a circle seems to be a shining ring. If two colors
are revolved at that rate, the eye no longer sees either one,
but a mixture of the two. Thus a blue and a yellow spot
side by side, when revolved before the eye, seem a single
green spot.

611. Color blindness. — Sometimes the nerves of the
retina are unable to recognize certain colors. In the
most usual form of color blindness red is supposed to
be green or gray. In locomotive engineers and sailors
color blindness may be a serious defect, for they are
guided by different colored signals, especially those con-
taining red.

612. Exhaustion of the retina. — When the eyes look
steadily at objects for a long time the vision becomes
blurred. If one gazes steadily at a bright colored object,
the retina is fatigued by that color. A white object looked

OV. PHYSIOL. — 22

33$ APPLIED PHYSIOLOGY

at now will show a colored spot shaped like the first object,
for a part of the retina is no longer able to recognize all
the colors which make white light. Its color will always
be complementary to the color of the object first looked at.
Thus when a red object is used first, a green image ap-
pears. The eye is really made color blind for a brief
period.

Ordinary lamps and gas jets give a yellowish light, while the sunlight
is white. So by lamp light, the colors of objects seem to be changed.
In incandescent electric lamps the light is given off from a white-hot
filament. Owing to its steadiness, its color and the absence of heat
and foul gases, it is the most agreeable light in common use.

613. Care Of the eyes. — No light should be strong enough to
dazzle the eyes. When, as in public halls, bright lights are in front of
the eyes, there is a natural tendency to gaze directly at them, thereby
tiring the retina. It would be better to look at the darkest objects in
the room.

It is best to have the light come from behind the eye. In working
with a lamp in front of the eyes, a shade should cover either the light
or the eyes. When the sun shines brightly upon the snow the excess
of light exhausts the retina. Then the eyes become painful, and blind-
ness may result.

614. Contraction of the pupil. — A strong light excites
the reflex center in the optic tubercles to send out an
order for the contraction of the muscles of the iris so as
to make the pupil smaller. On the other hand, in the
dark the pupil is large, so as to admit all the light possi-
ble. When a light is very strong, the reflex centers send
orders to the muscles both of the upper and lower lids,
and of the eyebrows to pucker themselves over the eyes,
so as to leave only a narrow slit for the entrance of light.
In this way the eyes are well protected against too strong
lights, but the contracted muscles may become tired and
painful.

THE EYE 339

615. Accommodation. — Rays of light coming from a dis-
tant object are less diverging than when coming from one
near by ; then the lens does not need to bend them so much
as in seeing objects near by. Adjusting the lens of the
eye to near or far vision is called accommodation. When
the eye muscles are at perfect rest, the eye is accommo-
dated to see clearly at all distances over twenty feet. So
distant vision requires no effort. When one wishes to see
an object less than twenty feet away from the eye, the
muscles must cause the lens to become more curved.
Thus the eye can see clearly up to about five inches from
the eye. Vision is best when the object is about ten
inches from the eye.

Diagram of the eye in far sight.

The lens b does not bring the rays from a point of light a together soon enough.
So the rays fall over the whole surface of the retina from d to e, making a confused
image instead of a clear point. When the rays spread less apart, as when the light
is moved farther away, to/ the lens brings them together sooner. Then the rays
fall upon a single point of the retina at^, and thus form a clear image.

616. Far sight — At the age of about forty-five, the muscles of
the lens lose some of their power of contraction and are unable to
make the lens so curved as in youth. Then the eye cannot be adjusted
for near vision, while for far vision the sight is as good as ever. So an
old man holds his newspaper at arms' length. He also aids the action
of his lens by placing before his eye a spectacle lens which corrects
the deficiency in the lens of his eye.

617. Near sight. — In young people the lens often brings the
rays together too soon. The rays must be made more diverging by

340 APPLIED PHYSIOLOGY

bringing the object very near the eye. Such persons cannot see dis-
tinctly at a distance greater than a few inches, but walk about as in
a perpetual fog.

Diagram of the eye in near sight.

The lens b brings the rays from a point of light a together at c too soon. So
the rays cross and fall over the whole surface of the retina from d to e, making a
confused image instead of a clear point. When the rays are spread apart by
bringing the light near the eye, as at / they come together farther away upon the
other side of the lens, as at g. Thus they fall upon a single point of the retina
and produce a clear image.

Near sight can be remedied by placing in front of the eye a lens
which will make the rays more diverging. So the spectacles have the
glasses hollowed out instead of bulging.

618. Astigmatism and headaches. — Sometimes the lens or
cornea is more curved in one direction than in another. Then a part
of the object will seem distinct, and another part blurred, and the eye
muscles will constantly change the focus in the attempt to obtain a full
and clear image. This is very tiresome to the eyes, and often causes
severe headaches. The remedy is to use a glass which is curved in one
direction only, so as to correct only the defective part of the lens.

619. Cataract. — Sometimes the lens becomes hard and white.
Then no light can pass through, and there is total blindness. This is
called a cataract. By a simple and safe operation the lens can be
removed, when the light will fall upon the retina as before. Spectacles
to take the place of the lens enable the person to see.

620. Judgment of position. — In perfect vision each eye
is turned toward the same point, so that the images fall
upon corresponding points of the retina. But the two eyes
view an object from different positions, and so the images

THE EYE 341

are not exactly alike. The blending of the images will
give the idea of solidity or of position in distinction from
the impression that everything is a flat surface. This per-
ception is not natural, but must be learned. Distant objects
always seem flat.

621. Movements of the eyes. — If the images of an object do
not fall upon corresponding parts of the retinas of the two eyes, two
images will be seen. Sometimes a muscle will draw one eye aside so
that it does not look in the same direction as the other eye. A person
with this defect is said to be cross-eyed.

Young babies have no control of their eye muscles, and so have no
distinct vision, except as they catch accidental glimpses. A bright
cloth gives them a sensation of color at whatever distance it is held,
and so amuses them. At about the age of three months they begin to
gain control of their muscles, so that they can focus the eyes and turn
them to any object at will. It takes them several months more to
acquire a knowledge of solidity and position.

Anything touching the eye causes the lids to close in a reflex man-
ner for protection. Tears flowing over the eye cause the lids to wink
and distribute the moisture over the whole surface.

In reading in the cars, the constant jarring of the paper compels- the
muscles of the eyes to be in constant action to adjust the eye to the
ever-varying positions and distances. So they soon become tired and
ache. In reading while lying down, the eyes must look toward the
feet. The constant strain of turning the eyes down tires the muscles,
so that the vision becomes blurred.

622. Diseases of the eye. — An ulcer or scar upon the cornea,
closure of the pupil, cataract, and wasting of the optic nerve are com-
mon causes of blindness. If your eyes are sore, or red, or painful,
you should consult a doctor at once; for blindness may result from
what seems to be a mild trouble.

A particle of sand or other substance between the eyeball and the
lids causes great pain. Rubbing the eyelid forces the particle into the
delicate flesh and increases the pain and danger. If the lid is gently
held away from the eyeball for a moment, the tears may wash out the
particle.

The eye is wel! protected from injury, for the sclerotic coat is the
strongest tissue ic the body.

342 APPLIED PHYSIOLOGY

Eyes may become sore and run matter ; or pimples may come on
the edges of the lids. The soreness is usually caused by disease germs
which enter the eye with dust and dirt. Some eye diseases are caused
by using towels or handkerchiefs on which other persons have wiped
their sore eyes, or by rubbing the eyes with dirty fingers which have
touched the matter from the sore eyes of another person. Babies often
have sore eyes because their eyes are not kept clean, or because flies
are allowed to crawl over them. We should wash our eyes with clean
water as often as we wash our faces, and should remove all scales and
dried matter from the edges of the lids. If the eyes are red and tender,
they should be washed with boiled water to which borax has been added,
so as to kill the germs. In granulated lids the conjunctiva becomes
red and roughened. A dangerous form of granulated lids, called
trachoma, is catching, and often spreads among school children. Every
person who has trachoma should be required to take treatment so as to
prevent the spread of the disease.

623. Illusions of sight. — Irritating the optic nerve ex-
cites the sensation of light. A blow upon the head causes
a sensation of seeing bright stars. Pressure upon the
eyeball causes a sensation of a ring of light.

In dreams, sight memories return to consciousness with
all the vividness with which they were first made. A
crazy man may imagine the face of the clock to be a man's
face mocking him, and so he may attack and destroy it.
To insane persons of a religious turn of mind, a cloud
may seem to be an angel urging them on to some inspired
mission.

624. Effects of alcohol and tobacco. — Alcohol weakens
the optic nerves, and tends to cause dimness of vision
while the eyes may appear healthy. Tobacco has a still
greater effect upon the optic nerve.

625. X rays. — In December, 1895, a kind of light pro-
duced by electricity was discovered which can penetrate
wood, flesh, and other substances. By means of it photo-
graphs can be taken. Although it makes no impression

THE EYE

343

upon the retina, yet by passing it through certain sub-
stances the rays become visible to the eye. Bone is pene-
trated by the rays with greater difficulty than flesh, and
so they can be photographed and seen within the body.
These rays cannot be bent from their course, and so can-
not be brought to a focus to produce a real image;
but images of objects are formed in shadows, due to the
varying degrees of light which passes through different
objects.

The rays are sometimes called Rontgen rays from their
discoverer, and sometimes simply X rays because of their
unknown nature. Practical use of the rays is made in
looking within the body so as to determine by sight the
condition of the bones and the location of substances im-
bedded in the flesh.

A foot in a shoe.
(From an X ray photograph.)

344 APPLIED PHYSIOLOGY

626. The eye in lower animals. — In all fourfooted animals,
and in birds, reptiles, and fishes, the eyes are essentially the same as in
man.

Most insects possess large immovable eyes shaped like a dome. Each
eye is made up of many smaller eyes like a honeycomb. Each little
eye contains a lens which forms an image
upon the nerve at the bottom of the cavity.
In some lower forms of animals, like the
leech, there is a spot of dark coloring matter
under the skin in which the nerves of sight
end. Such eyes cannot form an image, on
account of the absence of the lens, but a
bright light or a shadow of a large object
can affect the nerve and give the leech
The eye of a house fly. some idea of its surrOundings. Some still
a eye, made of many small lower forms of animais seem to be able to
eyes. b mouth. . ,. , ^ /• , f , , ,

recognize light, for they fold themselves up

when darkness comes, and yet they have nothing which at all re-
sembles an eye.

Some plants, like the morning glory, are affected by light, for their
flowers fold themselves at night and open again when the sun
rises.

SUMMARY

1. Light is the name given to the vibrations of a very

rare gas which fills all space.

2. The eye is like a photographer's camera.

3. The eye is set deep in a bony socket, called the orbit,

and is protected in front by the lids, and moistened
by tears.

4. The eye can see distinctly only a small space directly

in front, but can distinguish the presence of objects
in a full half circle.

5. A sensation of sight is produced instantly, but persists

for one tenth of a second after the light disappears.

6. Some eyes cannot see some colors, especially red.

CALIFORNIA COLLEGE
of PmWftlACY 345

7. If the lens cannot bring the rays of light together, a

person is far-sighted^ but if it brings the rays to-
gether too soon, he is near-sighted. If it brings
some of the rays together sooner than others, the
condition is called astigmatism.

8. If the lens does not permit light to pass through, the

condition is called a cataract.

9. By means of the two eyes viewing an object from

slightly different positions, we form an idea of

position and solidity.
10. If one of the muscles of the eye pulls the eyeball

to one side, the person is cross-eyed and sees two

objects instead of one.
12. Irritation of the optic nerve causes a sensation of sight

as though light had caused the impression. Mem-

ories of sight may be recalled so vividly as to seem

real, as in a dream.

DEMONSTRATIONS

135. Examine the eyeball of a calf in its socket. Carefully sepa-
rate the eyeball and its muscles and nerves from the fat. Notice the
cushion of fat surrounding the whole eyeball. Notice the slender mus-
cles which arise from the back part of the orbit and are attached to the
outer edge of the eyeball. Notice the optic nerve entering the middle of
the back side of the eye. Notice other nerves and the numerous blood
tubes which cross the space. Preserve the specimen in Miiller's fluid.

136. Procure several eyes removed from their sockets, and place
some in Miiller's fluid for a week or two, and examine others fresh.

Notice the bulging and clear cornea, and the tough white sclerotic
coat. Holding the eye with its cornea toward you, cut it completely
into halves. Notice the aqueous and the jellylike vitreous humors.
Notice the curtain of the iris and its pupil. Behind the iris notice the
lens. Remove the lens and note its shape and its firm consistency.
Notice the black choroid coat lining the eyeball next to the sclerotic.
Notice the thin retina, which readily separates from the choroid.

346 APPLIED PHYSIOLOGY

137. With a common magnifying glass show how a convex lens
brings rays of sunlight to a focus. Show also a photographer's camera.
Show the image which appears upon the ground glass. Then compare
the camera with the eye specimen, pointing out the resemblances.

138. Have the students look steadily at a line of print and tell how
much they can read without moving their eyes. An inch and a half
will be all they can see at once.

Next have them look steadily at an object, and notice how they can
see dimly all objects in a semicircle about them.

139. Illustrate the duration of impressions by spinning a square top.
It will appear circular.

140. Illustrate the exhaustion of the retina by having the students'
gaze at a square of black cloth upon a white paper. After a moment
let the students look steadily at the wall, when a square spot of light
will appear, for the part of the retina upon which the image of the
cloth fell is less exhausted than the rest, and so it sees the light from
the wall more clearly.

141. Illustrate color blindness by taking a sheet of light pink paper.
Have the students first look steadily at a bright red object in a strong
light. Then gaze at the pink paper ; a green image of the first object
will appear, showing that a part of the retina has become exhausted for
the red rays, but can still see other colors.

142. Notice the pupil of the eye and its varying size in different
lights. Shade another person's eyes with the hands, and, quickly
removing them, notice that the pupils grow smaller. Have a person
look steadily at your finger held a few feet in front of the eyes, and
then quickly bring the finger near the eye and notice that the pupil
contracts while looking at it near by.

143. Illustrate a near-sighted eye by holding a magnifying glass in
front of the eye, which is the same as increasing the power of the lens.
Notice that the object must be brought nearer the eye.

Show a double concave lens and explain that it scatters rays and so
is used in glasses for near sight.

144. Illustrate far vision by looking through two magnifying glasses
of different strengths. Notice that the weaker glass must be held
farther away from the object.

145. Place a book edgewise before the eyes and notice that one eye
sees one side and the other eye the other side.

Now examine a stereopticon photograph of a statue, and notice that

THE EYE 347

the two pictures are not exactly alike. When the views are blended
into one by the stereopticon; the image seems to stand out like a real
statue. Explain that in this way the two eyes gain a knowledge of
position and solidity.

146. Illustrate double vision by pressing one eyeball aside while
looking at an object.

147. Have a person gaze at your finger held at a distance from his
eye. Now bring the finger near the eye, and notice that the eyes each
turn towards the nose so as to keep directed toward the object. This is
the only manner in which we can move the eyes in opposite directions.

148. Press hard upon the closed eyelids. Notice the ring of light
which appears. Explain that this is due to the irritation of the optic
nerve.

149. Test the individual members of the class for color blindness
by showing them shades of red, green, and yellow, telling them to
match the shades and arrange them in order. Also test the power of
vision of the individual members of the class by placing before them
printing with letters of various sizes. Have each pupil read as far as
he can, all standing at the same distance.

REVIEW TOPICS

1. Describe light; color; focus; and the effects of light

in a photographer's camera.

2. Show that the eyeball is like a photographer's camera,

describing its outer coverings ; its retina ; nerve ;
cornea ; iris, pupil, and lens.

3. Describe the orbit ; eyelids ; the lachrymal gland ;

tears, and the tear ducts.

4. Show that a person can see more clearly directly in

front of his eyes than upon either side.

5. Show that the duration of a sight sensation changes

the appearance of moving objects.

6. Describe color blindness.

7. Show that the retina may become unable to act from

overwork, as by gazing at bright objects; at colored

348 APPLIED PHYSIOLOGY

objects; and by a light in front of the unshaded
eyes.

8. Show that the iris protects the retina against too

strong light.

9. Show that the lens must change its shape to accom-

modate itself to near vision and to far vision.

10. Tell the condition of the lens and the remedy in far

sight ; in near sight ; and in astigmatism.

11. Describe a cataract and its remedy.

12. Show how two eyes aid in the judgment of form and

position.

13. Describe the condition of the eye muscles in a cross-

eyed person, and tell how vision is affected.

14. Show how reading upon a moving railway train and

reading while lying down overwork the eye mus-
cles.

15. Tell how to care for an eye which runs matter, and

how to remove a speck of dirt from under the lid.

1 6. Show that rubbing a sore eye is always liable to do

harm.

17. Show that irritation of the eye may produce false

sensations of sight; and that sight memories may
seem to be real again.

1 8. Describe the X rays.

19. Describe the effects of alcohol and tobacco on the

eye.

20. Describe the eye in lower animals ; in insects ; and in

a leech.

CHAPTER XXXVI
THE VOICE

627. The larynx. — The basis of the voice is a sound
made in the larynx during expiration. The larynx is a
triangular box about three quarters
of an inch across, made of cartilages.
It connects the trachea and pharynx.
Its two sides are formed of a flat
cartilage, bent sharply backward,
and called the thyroid cartilage.
The upper end of the fold projects
slightly from under the chin and is
called the Adams apple. Under-
neath the thyroid cartilage is a cir-

J i_ i Back view °* the terynx.

cular cartilage whose back part pro-

a thyroid cartilage.

jects upward so as partly to fill in b vocal cords.

space between the back edges of c movable cartilage for the

attachment of the vocal

the thyroid cartilage. In form and cords.
size it resembles a large finger ring, d cricoid cartilage.

' e epiglottis.

and is called the cricoid cartilage.

On top of the back part of the cricoid cartilage are two
small cartilages, shaped like triangular pyramids, and so
arranged that they can turn sidewise. One lower corner
of each projects forward. From it a flat band extends
across the larynx, and, with its fellow from the opposite
side, attaches itself to the lower part of the thyroid carti-
lage. Muscles can tighten them and bring them close

349

350

APPLIED PHYSIOLOGY

together. Expiring air between these bands, while they
are tight and close together, causes them to vibrate and
produce a sound which is called the voice. Hence the

Top view of the larynx, with the

vocal cords closed, as in speaking.

a epiglottis. b vocal cords.

Top view of the larynx, with the
vocal cords open, as in breathing.

a epiglottis. b vocal cords.

bands are called the vocal cords. The whole larynx, ex-
cept the edges of the vocal cords, is covered with loose
mucous membrane.

628. Pitch of the voice. — All sound has the four char-
acteristics of pitch, intensity, quality, and duration. The
same characteristics apply to the voice.

Pitch depends upon the number of vibrations which
occur each second. In order that the vibrations of the
air shall blend into a musical note they must occur at the
rate of sixteen times a second, but until they reach a rate
of fifty the sound is more like a buzz than music. Upper
C of the bass voice which corresponds to lower C of a
soprano, is produced by 256 vibrations per second. The
shorter or tighter the vocal cords are, the higher will be
the pitch. In men the cords are longer than in women,
making a man's voice an octave lower in pitch. The
larynx and voice of a boy resemble those of a girl. At
about the age of fifteen the voice of a boy becomes like
a man's, while in a girl it remains unchanged.

629. The intensity of the voice depends upon the force
with which air is expelled through the larynx. In making

THE VOICE 351

a very loud sound, the great force of the air current causes
the vibrations of the vocal cords to be painful.

630. The muscles of the larynx will grow strong by judicious prac-
tice, so that a person can be heard across a hall in which he formerly
could not be heard a few feet away. If the voice becomes husky, or
causes a cough, or if the throat begins to feel painful, the vocal cords
are being overworked and should be rested.

631. Quality of the voice. — A string stretched between
the hands produces a faint unpleasant sound ; but if it is
stretched over a hollow box, like the body of a violin, the
whole box will vibrate and greatly magnify the sound and
also will make it full and pleasant.

The vibrations of the vocal cords alone produce a faint
and almost squeaking sound very unlike that of the voice ;
but below the larynx are the hollow trachea and lungs.
Above it are the hollow mouth, nose, and frontal sinuses.
All these vibrate with the vocal cords, and so the quality
of the voice is modified. Each person's voice has a peculiar
quality of its own which is at once recognized.

When a person sings with the nose stopped, we say
that he sings through the nose. In reality, a nasal voice
is due to the absence of vibrations in the nose.

632. Ventriloquism. — The quality of sound is modified by
distance, so that one can judge accurately whence it comes. It is
possible to imitate the quality of distant sounds, so that there seems to
be another person talking in a remote part of the room or inside of the
real talker. This is called ventriloquism.

633. Speech. — Speaking consists mainly in rapid changes
in the quality and duration of vocal sounds. In singing or
crying out, single sounds are more or less prolonged, but
in forming spoken words, the sounds are cut off by the
tongue and lips several times a second. It is not even
necessary to form a sound with the larynx. In whispering,

352 APPLIED PHYSIOLOGY

air is simply breathed through the mouth, while the tongue
and lips cut it off at intervals as though a sound were
being made.

634. A simple sound continuously uttered is a vowel
sound. If the mouth is simply opened without effort, the
sound 'formed will be that of a as in father. When the
mouth is closed the most, it forms the sound oo as in room.'
A consonant sound is a vowel sound suddenly modified in
either its beginning or ending. For instance, when the
tip of the tongue is held against the palate just back of the
teeth, and a vowel sound is begun by forcibly blowing it
away, the sound will be either t, d} or th.

635. Rate of talking. — A public speaker will ordinarily utter
125 words a minute. On an average each word will be composed of,
at least, four different sounds. Thus the vocal organs must make 600
separate adjustments each minute, or 10 each second.

636. Relation of sound and speech. — Words spoken must
first be heard. So no matter what the race of a child, it will speak
exactly the speech which it hears. If a child is brought up in com-
pany with an ignorant nurse girl, its speech will be her brogue. On
the other hand, if the child is brought up among educated and refined
persons, it will speak an elegant tongue.

A deaf person has great difficulty in learning to speak at all, for he
can have no idea of the sound which he should make. Without special
instruction deaf persons would never learn to speak at all, but by letting
them see or feel the position of the lips and tongue in forming words,
they learn to place their own parts in the same position and so finally
learn to talk.

637. Necessity of the tongue in speech. — The tongue is
usually considered to be so necessary in speech that the language itself
is called a tongue. As man's mouth is constructed the tongue does do
the most important part of forming words, but if the organ is removed
as far back as possible, th.e stump can still form intelligible words.
Sometimes the front part of the tongue is bound down or " tied " so
that it cannot move so freely as it should. This is supposed to hinder
a child in talking, but in reality it does not.

THE VOICE 353

638. Benefits of vocal exercise. — -In singing and lec-
turing, the breathing must be regular and deep. The
abdominal muscles must act, and often a sound must be
prolonged until the air in the lungs is exhausted. The
respiratory muscles must act continuously and strongly
and for long periods of time. Thus an increased amount
of oxygen will be taken into the body. Voice training is
one of the best modes of exercise, especially for a weak
person who cannot endure long walks or gymnastic exer-
cises. It is all the more valuable because a person does
not think of the exercise, but directs the mind to an inter-
esting and useful occupation.

639. Diseases of the larynx. — In a cold in the throat
the mucous membrane becomes tender and swollen. Then
the movements of the vocal cords are impeded and painful,
so that only a hoarse sound, or no sound at all, can be
produced. By repeatedly overworking the vocal cords,
they and the muscles of the larynx become flabby and
tender so that their vibrations are painful or impossible.
Then the voice is reduced to a whisper. Sometimes the
nerves of the larynx are paralyzed so that no motor orders
can reach the muscles. Then no sound can be formed.

640. In mouth breathing, the air is drawn directly into the larynx
without being purified, warmed, and moistened in the nose. This irri-
tates the larynx and vocal cords so that the voice is made weaker and
harsher. A mouth breather can seldom become a good singer or
speaker.

641. Tobacco. — Tobacco smoke may produce such an
irritation that there is a constant hacking cough. Cigar-
ettes are especially bad for the voice, for the smoke is
deeply inhaled. Alcohol interferes with the voice by
inducing indigestion and weakness of the muscles.

ov. PHYSIOL. — 23

354 APPLIED PHYSIOLOGY

SUMMARY

1. The larynx is a box of cartilage across which two

strong bands called vocal cords are stretched.

2. When the vocal cords are tightened and air is expelled

between them, a sound called the voice is made.
'3. The pitch of the voice will depend upon the tightness
and length of the cords.

4. The intensity of the voice depends upon the force

with which the air is expired.

5. The quality of the voice is imparted to it by vibrations

of the air in the lungs, mouth, and nose.

6. In speech sounds are modified mainly by the lips and

tongue.

7. A man must first hear the sound of speech, and then

learn to imitate it. Special means must be employed
to teach a deaf person to talk.

8. If the vocal apparatus is overworked or becomes

inflamed, the voice is injured.

DEMONSTRATIONS

150. Procure a larynx from a butcher's shop. Notice the large flat
thyroid cartilage, and under it the ring-shaped cricoid cartilage. Notice
the white vocal cords passing forward to the lower part of the thyroid.
Notice the loose mucous membrane above the vocal cords. Grasp the
thyroid cartilage so as to move the cricoid forward and backward, and
note how the movements tighten and relax the vocal cords. Notice
the muscles which move the larynx. Test the pyramidal cartilages to
which the vocal cords are attached.

151. If possible, get a physician to show the vocal cords in action
upon a living person. He will do it by means of a small mirror held
in the back part of the mouth.

152. Have the pupils feel each other's chests while counting one,
two, three, and note the marked vibrations. In the same way feel of

THE VOICE 355

the larynx and of the nose and teeth. Explain that these vibrations
also produce sound and give quality to the sound in the larynx. Then
compress the nose and note the nasal quality of the voice.

1 53. Show how the different vowel sounds are formed. Make a con-
tinuous sound as of e in need. Without changing the pitch or intensity
change the mouth to a position to utter in succession the sounds a as
in made, a as in mat, ah as in father, o as in note, and oo as in room.
Note how the sounds glide into each other.

154. Note the positions of the tongue and lips in uttering the
different consonant sounds. Note that p, b, and f are formed much
alike ; and also k, ch, and^; and /, d, and th.

155. Show how some lower animals and insects produce sounds.
Have the pupils notice how a canary bird swells his throat in singing,
and explain that this is because it has two or three pairs of vocal cords.

Upon the backs of a katydid's wings show the drumheads, which,
when rubbed together, produce its sound. Show that a fly's buzz is
due to the exceedingly rapid motion of its wings.

REVIEW TOPICS

1. Describe the larynx.

2. Show how the vocal cords produce sound.

3. Show how \hzpitch of the voice can be changed.

4. Show how the intensity of the vocal sounds can be

changed.

5. Show how the quality of the voice is modified.

6. Describe ventriloquism.

7. Show that speech depends upon modifications in the

duration and mode of production of vocal sounds.

8. Show the relation between speech and hearing.

9. Show that the tongue is not absolutely necessary in

speech.

10. Show how vocal exercise benefits the whole body.

11. Show how inflammation of the larynx and taking

certain things into the mouth injure the voice.

Bones of the

Head and Face.

Clavicle, or Collar Bone.

Sternum, or Breastbone.

• Bones of Vertebral Column.

-Scapula, or Shoulder Bone.

Ribs.-

--Humerus.

.---Ulna.

Pelvis, including (51.) Sacrum and
(C*.) Coccyx.

Radius.

-Carpus, or Wrist. — Eight

small bones.
. Hand. — Nineteen bones.

Patella.

Tibia, or Large Bone of Fore Leg.

Tarsus, or Ankle and Heel Bones (7).
Bones of foot. — Nineteen bones.

Femur.

Fibula, or small Splint Bone of Leg.

The human skeleton, showing position of bones.
356

CHAPTER XXXVII
BONES.

642. Use of bone. — Bones give shape and support to
the body and impart to it strength and stiffness. Like
beams of the strongest oak, they extend the length of
every limb, and form arches for the protection of the
organs in the head, chest, and abdomen. They are of va-
rious sizes and shapes, as are suited to the different parts.
In the whole body, about two hundred are jointed together
to form its framework, called the skeleton.

643. The skeleton. — Eight rounded plates of bone form
the top of the head, and fourteen of irregular shape form
the face. Together, they form the skull.

Twenty-six irregular rings of bone piled one upon the
other form a support for the trunk of the body. It is
called the backbone or spinal column, or simply the spine.
The lowest bone is called the coccyx, and the one next
above it, the sacrum. Each ring of bone is called a verte-
bra. The spine is made of a series of small bones so that
it can bend without breaking. It is gently curved so as to
lessen the jarring in running and other violent movements
of the body.

From the vertebrae, beginning at the eighth, twelve pairs
of bones called ribs curve around the body. In front they
join a flat bone called the sternum or breastbone. They
inclose and protect the heart and lungs.

Each shoulder is formed in front by a slender bone

357

358

APPLIED PHYSIOLOGY

called the collar bone or clavicle, and behind by a flat bone
called the shoulder blade or scapula. Their outer ends
meet and form a support for the arm.

The upper arm has one long bone
called the humerus. The forearm has a
long bone on its thumb side called the
radius, and another on its little finger side
called the ulna. The wrist has eight
rounded bones called carpal bones. The
palm of the hand has five long bones

The pelvis.

called metacarpal bones. The fingers have
fourteen slender bones called phalanges.

Two irregular and massive rings of
bone form the hip bones. With the sa-
crum they form a ring called the pelvis.
The body sits upon the lower part of
each hip bone. The pelvis forms the
bottom of the abdomen.
The bones of the leg have nearly the same plan and
arrangement as those of the arm. The thigh has one long
bone called the femur. In front of the knee is a flat bone

The spinal
column.

BONES 359

called the patella. The shin is formed by one long bone
called the tibia, upon the outside of which is a very slender
bone called the fibula. The lower end of the fibula forms-
the outer ankle bone, while a projection from the tibia
forms the inner ankle bone.

Seven rounded bones, called tarsal bones, form the instep
of the foot. Five slender bones beyond them, called meta-
tarsal bones, form the ball of the foot. The tarsal and meta-
tarsal bones are bound together so as to form an arch
which bears upon the ground only at the heel and ball of
the foot. The arch is somewhat elastic and prevents jar-
ring of the body in walking. It sometimes becomes flat-
tened, producing the painful deformity called flat foot.
Fourteen slender bones, called phalanges, form the
toes.

644. Structure of bones. — Bones are dense and brittle
upon the outside. All are covered with a very tough mem-
brane, called \ht periosteum. In flat or rounded bones the
hard outside surfaces are scarcely thicker than paper, and
the two surfaces are connected together by a network of
bone which looks like a honeycomb, and is called cancel-
lous bone.

In long bones, the central shaft is composed of a thick
shell of hard bone surrounding a cavity filled with fat;
their ends consist of a thick shell of hard bone covering a
large mass of cancellous bone.

A bone is about twice as strong as a piece of oak of the same size.
It is elastic and can bend considerably without breaking. Any given
weight of a substance is stronger when made into a hollow shaft, like
a bicycle frame, than when formed into a solid rod of the same length.
So the strength of a bone is still further increased by its being either
hollow, as in the shaft of a long bone, or else braced with cancellous
bone, as in a flat bone and the ends of a long bone.

360 APPLIED PHYSIOLOGY

645. Microscopic appearance. — Bone is composed of
branching connective tissue cells and fibers, which are
arranged in circles around minute tunnels called Haversian
canals. Each Haversian canal contains arteries, veins,
and nerves. Lime is mixed with the cells and canals like
starch among the fibers of linen, and imparts to them their

a

Thin slice of bone (x 200).
a bone cells. b Haversian canal, containing blood tubes and nerves.

hardness and rigidity. Lime forms about two thirds of
the bone by weight.

646. The periosteum carries arteries and nerves which
enter minute openings in the bone. During childhood, or
when a bone is diseased, the cells of its inner layer are
very active in reproducing themselves and in forming new
bone. Bone stripped of its periosteum is apt to die,
but when the bone dies the periosteum usually remains
alive and soon reproduces new bone. The periosteum
also affords an attachment for muscles.

647. Cartilage. — The bones of very young animals
contain little or no lime, but are soft and pliable. In this

BONES 361

condition they are called cartilage. As age advances,
lime is deposited among the cells, and they become hard
and brittle, forming true bone. A layer of cartilage re-
mains to cover the ends of most bones. Late in life it
may take up lime and so become like bone.

648. Rickets. — Sometimes a child's bones contain too little lime ;
then under the influence of continual pressure of standing, the bones of
the leg may gradually grow into a bowed shape. This disease is called
rickets, and is due to too little nourishment. When fed on a sufficient
amount of proper food, the bones soon grow rigid again, and as the
child's legs grow longer, their curves become less noticeable.

649. Broken bones. — Bones are often broken. Then
the cells are injured, and blood tubes and nerves are torn
across. So there will be great pain and tenderness. When
a bone is broken, its cells reproduce themselves and fill in
the space with new connective tissue. In course of a
few weeks, lime is deposited in the new tissue, and the
union is complete. When a bone is broken, the surgeon
pulls its ends in place and binds them to stiff splints until
healing is complete.

If a bone is broken, the limb should be at once bound to a board or
stick with handkerchiefs or strips of cloth. Take care not to tie the
bands tightly enough to stop the flow of blood.

As a person grows older, more lime is deposited in his bones, and
they become harder and more brittle. Then they are more likely to be
broken and are less able to grow together again. Often a child's bone
will bend until it breaks, but its ends still hold together like a broken
green stick. In older people it snaps like a dry twig.

650. Diseases of bones. — Bruises or consumption or other
causes of disease may produce inflammation and abscesses of the bone
as in any other part of the body. Then the bone is very painful and
tender and may die. Then the periosteum will form a new bone. If
a large piece of bone dies, it wastes away more slowly than new bone
is formed. All fourfooted animals have nearly the same bones arranged

362 APPLIED PHYSIOLOGY

in the same way as man. A bird's wing is bone for bone almost like a
man's arm and hand. A turtle's shell is its ribs, while- the bones of its
limbs are like those of man.

SUMMARY

1. About 200 bones give the body form and strength.

2. The outside of all bone is a hard plate, while the inside

is either a fine network of bone or else is hollow.
3.- The hollow form of bone combines strength with light-
ness.

4. Bone is composed of living cells and fibers nourished

by arteries and endowed with sensibility by nerves.
Lime is mixed with the cells like starch with linen.

5. Bone is covered with a tough membrane called theferi-

osteum, which carries the blood tubes and nerves to
the bone, and forms new bone during the period of
growth or when the bone is diseased.

6. Cells and fibers resembling those in bone, but contain-

ing no lime, form cartilage.

DEMONSTRATIONS

156. Show a complete skeleton of at least a small animal. Point
out the different shapes of the bones and how they are adapted to their
positions and work. Point out in the living body where the different
bones can be felt.

157. Procure a fresh beef bone, and another similar one dried. Note
the bright pink color of the fresh bone, and the white or brown color
of the dried specimen. Notice that the periosteum can be stripped
from the bone. Notice the soft cartilage which covers the ends of the
bone.

158. Saw a long bone in two crosswise and then saw one half in two
lengthwise. Notice the hollow cavity in the shaft of the bone and the
fat or marrow which fills it. Notice the honeycombed appearance of
the inside of the ends of the bone.

159. Procure a specimen of bone mounted for the microscope.
Using a power of at least fifty diameters., notice the circles of bone cells

BONES 363

and the numerous fine branches of the cells. Notice the Haversian
canal in the center of each circle. Examine also a specimen of
cartilage.

1 60. Procure two slender bones which are exactly alike. Place one
in a hot fire for a few hours. This will burn out the cells and fibers
and leave only the lime. The bone is now very brittle and easily crum-
bles to pieces. Place the other in a bottle containing one part of
muriatic acid and ten of water. After a week this acid will have
removed the lime, leaving only the cells and fibers. The bone can now
be twisted and bent like a piece of flesh.

161. Boil a leg bone of a half-grown animal until the flesh is re-
moved. Notice that a disk of cartilage extends nearly through the
shaft very near the ends. Possibly the end beyond it will come off.
Explain that the cartilage forms new bone which increases the length
of the shaft as long as the bone continues to grow.

REVIEW TOPICS

1. Show why bones are needed in the body.

2. Describe the bones of the skull; of the spine; of the

ribs ; of the arms ; of the pelvis ; and of the legs.

3. Describe the appearance of a bone when sawed in two

both lengthwise and crosswise.

4. Show the advantage of having some of the bones

hollow.

5. Describe the microscopic appearance of bone.

6. Give the uses of periosteum.

7. Describe cartilage.

8. Describe the changes which occur in bones with ad

vancing age.

9. Describe rickets.

10. Describe the condition of a bone when broken, and

tell how it is repaired, and how to care for a broken
limb.

11. Show how a bone can become inflamed ; and how dead

bone is replaced.

CHAPTER XXXVIII

JOINTS

651. Kinds of joints. — The union of two bones is called
a joint. Some bones grow together and form a single
rigid bone, while others are joined together only by loose
fibrous tissue which permits the joints to bend freely.
Between these two extremes, joints possess all gradations
of movement.

652. Inflexible joints. — Some bones of the skull are
joined together by cartilage during childhood. Later in

life, when growth ceases, the cartilage
becomes bone and unites the two bones
into a single one.

Other bones of the skull are dove-
tailed with each other, so that while
they can move slightly, they cannot be
separated. The thick bones of the top
of the skull are united in this way.

Between the separate bones of the
pelvis and between the vertebrae there
are large pads of fibrous tissue, almost
like cartilage. These pads permit slight
movements between the bones and so
prevent jarring during violent move-
They are usually stronger than bone
itself, so that, by pulling or bending, the bones will be
torn apart rather than the pads.

364

Hinge joint of the elbow.

z humerus. 2 ulna.

ments of the body.

JOINTS 365

Between the ends of the ribs and the sternum there are
cartilages of the shape of the ribs. In old age they often
take up lime and become real bone.

653. Flexible joints. — The joints of the head and trunk
of the body are mostly inflexible, while those in the limbs
permit very free movements of the bones. In flexible
joints the bones are held together by a strong fibrous
membrane called a ligament. The ends of the bone are
smooth and rounded so as to move freely upon each other.

In some joints the movements are simply forward and
backward like a hinge. The fingers, toes, elbows, knees,
and ankles are hinge joints.

In some joints the movements can be made forward and
backward and sideways like a ball in a socket. The
thumbs, great toes, shoulders, and hips have this kind of
a joint. In each the end of one bone is spherical and fits
into a hollow socket in the other.

In other joints one bone can only rotate about another
as a pivot. In its union with the spine, the skull turns
about a fingerlike projection upon the top of the second
vertebra. At the elbow, the upper end of the radius
turns in a socket upon the side of the ulna through half
a circle of revolution.

654. Structure of joints. — In all flexible joints the liga-
ments pass from bone to bone, like a collar upon the out-
side of the bone, enveloping a cavity which is lined with
a thin and smooth membrane, called synovial membrane.
The synovial membrane secretes a fluid like the white of
an egg, called the synovial fluid. The fluid moistens and
lubricates the joint so that it turns smoothly and easily.
If it is absent the joint creaks when moved.

655. Loose joints. — The two bone surfaces of each joint fit
together accurately. There is a considerable difference in the depths

366 APPLIED PHYSIOLOGY

of the joint sockets and in the lengths of the ligaments in different per-
sons. In some persons the sockets are shallow and the ligaments long>
so that the joints can be bent to a far greater degree than usual. These
persons are able to twist and contort themselves into strange posi-
tions and shapes, and thus they make good circus actors.

656. Action of muscles as ligaments. — Nearly every
joint is crossed by muscles. By their pressure the mus-
cles aid in keeping the bones in place. In addition, when
one muscle acts, those upon the opposite side of the joint
also contract enough to prevent the head of the bone from
being drawn out of its socket.

If all the muscles and cords about a joint are cut, the
ligaments stretch and the joint becomes loose and flabby.
If the ligaments are cut while the muscles and cords are
left, the joint remains snug and firm.

657. Effects of pressure. — After being kept in an un-
natural position for some time, joints tend to retain the
deformity. In wearing tight shoes, the great toes are
bent outward, while the little toes are bent inward. If
the joints are kept in this position day after day for years,
they remain permanently fixed in the deformed position.
The great toe joint may be tender, forming a bunion.

658. Curvature of the Spine. — The spine is naturally straight
from side to side. Strong muscles aid in keeping the head erect and
the shoulders thrown well back. By weakness of the muscles or by
carelessness the shoulders fall forward, increasing the natural curve of
the spine so that a person becomes round shouldered.

If a child habitually sits sidewise at the desk, leaning continually
upon one arm, the growing bones and the ligaments of the spine will
gradually become fixed in the deformed position, which persists all
through life. Any person who, in his occupation, always assumes the
same attitude, may finally be unable to remove the curvature from his
spine. On the other hand, if one acquires a habit of sitting and walk-
ing and working in an erect position, the spine will grow in a natural
curve.

JOINTS 367

659. Sprains. — When a joint is bent to a greater ex-
tent than is natural, the ligaments and muscles are
stretched and often torn. Then there will be great
swelling and pain. When this accident happens, the
joint should at once be put in water as hot as can be
borne, while more hot water is added from time to time to
keep up the temperature of the water. The joint should
have rest for some time after the injury. Recovery is
apt to be slow.

660. Dislocations. — When the bones of a joint are
forced apart, the joint is dislocated, or out of joint.

In a dislocation, the ligaments are always torn. Then
bleeding will take place, and there will be great pain and
swelling, while only slight movements of the limb will be
possible.

In a dislocation, the muscles around the joint are irri-
tated, and so contract and hold the bone away from its
socket. Often it is necessary to make a person insensible
with ether before the muscles will relax enough to get the
joint in place.

When a joint is dislocated, the limb should be kept as
quiet as possible by binding a splint above and below the
joint, as in a broken bone.

661. Inflammation of joints. — Sometimes the synovial mem-
brane becomes inflamed and pours out a quantity of thin fluid which
distends the joint and produces great pain. In rheumatism this often
occurs. Sometimes a blow or a wrench may cause it.

Sometimes waste matter of the body is deposited in the synovial
membrane and cartilage. This produces great pain and tenderness
and constitutes an attack of gout. The great toe joint is especially
liable to this disease.

Sometimes the cartilage and ends of the bone become distorted and
rough, or form hard swellings. Then the limbs cannot be bent without
producing pain and a creaking sensation. This change naturally occurs

368 APPLIED PHYSIOLOGY

in old persons, and is due partly to deposits of lime in the cartilage and
partly to a dry state of the synovial membrane.

Sometimes a joint slowly swells and discharges yellow matter for a
long time, while the sufferer gradually loses flesh and strength. The
disease is commonly known as a white swelling, but is really tuber-
culosis, or consumption of the joint. When it affects the hip joint, it
is called hip joint disease. A form of the disease without the discharge
of matter may affect the spine and produce the deformity called a
hunchback.

SUMMARY

1. The union of two bones is called a joint.

2. In joints in which the bones do not move, the bones

are united either by bone or strong pads of fibrous
tissue, or by cartilage, or by being dovetailed into
each other.

3. In flexible joints, bones are joined together by a collar

of fibrous tissue and by the action of muscles.

4. Flexible joints are lined with synovial membrane, which

secretes a fluid like the white of an egg to lubricate
the joint.

5. By assuming one position day after day the joints

become fixed in that position.

6. In sprains and dislocations the ligaments are stretched

or torn, and require long rest in recovery.

7. The synovial membrane may become inflamed and

swollen.

"8. A joint may become affected with tuberculosis, forming
a white swelling or hip joint disease. In it the joint
forms an abscess and often discharges matter.

DEMONSTRATIONS

162. A fowl dressed for the table will illustrate the different kinds of
joints. Notice that in some places the muscles unite with the ligament
and in others simply cross it, usually as a white cord or tendon. Cut

JOINTS 369

the ligaments half in two to show the cavity of the joint. Notice the
smooth and shining appearance of the synovia! membrane which lines
the joint and its slight amount of synovial fluid. Bend the joint back
and forth to show how the surfaces of the bone fit into each other.
Sketch a joint.

163. Notice some of the inflexible joints. In an animal's skull notice
that the joints are dovetailed together with but little cartilage between.
Notice the tough pads between the vertebrae, and how they permit the
spine to bend slightly. Notice that the ribs are united to the sternum
by flexible cartilage.

164. To show that muscles and cords act as ligaments, clench the
fist tightly. Notice that the cords upon the back of the hands tighten,
as well as those which shut the hand.

REVIEW TOPICS

1. Describe and locate the inflexible joints with bony

union ; with union by cartilage ; with union by pads
of fibrous tissue; and with union by being dove-
tailed together.

2. Describe and locate hinge joints ; the ball and socket

joints ; and the pivot joints.

3. Describe the structure of joints, their ligaments, syno-

vial membrane, and fluid.

4. Show how muscles aid the action of the ligaments.

5. Show how long-continued pressure affects the joints,

as in the great toe.

6. Show how the position of the body may produce curva-

ture of the spine.

7. Describe the nature and treatment of a sprain, and of

a dislocation.

8. Show how joints may become inflamed.

9. Describe a white swelling.
10. Describe a bunion.

OV. PHYSIOL. — 24

The muscular system.

370

CHAPTER XXXIX
MUSCLES

662. Movements within the body. — Every action of the
body has motion for its basis, and every cell possesses
motion of some form. But certain cells of the body are
set apart to produce motion in the various liquids of the
body and to move different parts of the body itself. Cells
whose work is to produce motion are called muscle cells.

663. Involuntary muscles. — Some movements of the
body go on wholly without our knowledge and are not
affected by the will. Such are the movements of the
blood, and of the peristalsis of the intestine. These invol-
untary movements are produced by muscle cells which are
governed by the sympathetic nervous system. Each mus-
cle cell resembles a string with pointed ends. They are
wrapped around the arteries, intestine, bronchi,

and other hollow organs. They are inter-
woven with the other tissues of the organ and
cannot be recognized without a microscope.

664. Voluntary muscles. — The muscles which
enable the body to move are under control of
the will. They are situated mostly upon the
outside of the bones, and altogether form over

one half of the weight of the body. They A muscle cell
round out the figure and impart to it strength (x 4°o)<
and beauty. The other organs of the body of man exist in
order that the brain and muscles may subsist and work
out the plans of man's higher nature.

37*

372

APPLIED PHYSIOLOGY

Muscle cells cut across

(x 200).
a muscle cell.
b connective tissue binding the

cells together.

The lean part of meat, is muscle. Each muscle can be

split lengthwise into bundles again and again until each

muscle cell is separated from the rest. Connective tissue

binds the whole together.

A muscle cell is a cordlike body about -^ of an
inch in thickness. Extending
crosswise upon its surface are
alternate dark and light bands
which serve to distinguish a
muscle cell from all other cells of
the body. Each cell is surrounded
but not penetrated by a network
of capillaries and is held in place
by delicate fibers of connective
tissue, which are always small in
quantity compared with the cells.
665. Attachment of muscles. — One end of a muscular

bundle is usually attached to the

periosteum of a bone, while the

other end is joined to a string of

connective tissue called a tendon.

A tendon is a white pliable cord

and is exceedingly strong. It

runs in a groove lined with

synovial membrane, and its end

is usually attached to a bone.

A muscle usually forms a

rounded projection above a

joint to be moved, while its

tendons extend across the joint

and are attached to the perios-
teum of the next lower bone. This arrangement keeps the

weight of the limbs near their upper extremities.

a

A thin slice of a voluntary mus-
cle cut lengthwise (X 100).

a muscle cell.

b capillaries surrounding the cells.
c connective tissue binding
cells together.

the

MUSCLES

373

666. Contraction of muscles. — When a muscle cell is
cut or pinched or irritated in any way, it becomes shorter
and thicker. This is called a contraction, and is the essen-
tial peculiarity of muscles. An end of a motor nerve
thread touches every muscle cell and conveys to it orders
from the cells of the spinal cord and brain. Each order
causes a contraction.

A muscle cell requires about fa of a second to contract and another
fa of a second to become relaxed. So it is impossible to move a limb
more than ten times a second. The brain sends about ten orders per
second. Thus before the muscle relaxes it receives another order and
so remains in a tremulous state of contraction which becomes apparent
during excitement or when a great effort is being made. Each con-
traction is a change in the shape and not in the size of the muscle.

I. II. III.

The three classes of levers, and also the foot as a lever.

667. Bones as levers. — A rigid bar turning about a
fixed point or fulcrum is called a lever. When the weight
is at one end of the bar and the power at the other end
while the fulcrum is between the two, the bar is called a
lever of the first class.

When the weight is between the power and the fulcrum,
the bar is called a lever of the second class.

When the weight is at one end, the fulcrum at the other,
and the power between, the bar is called a lever of the
third class.

374

APPLIED PHYSIOLOGY

Tendon

If the power is farther away from the fulcrum than the
weight, it will move a weight greater than itself, but if it
is a less distance away, it can move only
a weight less than itself.

A bone is a rigid bar. The joint is
thfe fulcrum upon which it turns. The
power is the contraction of the muscles
which are attached to it. The weight
is the weight of the body or limb to-
gether with anything which may be

Muscle, gasped.

668. Levers of the first class are not
numerous in the body. The foot when
pressing down with the toes, and the
head when it is raised, are two examples.

669. Levers of the second class are
also few. The best example is the foot
when standing on the toes. The power
is attached to the heels and is furnished
by the muscles upon the back side of
the leg below the knee. They end in a
very strong tendon called the tendon of
Achilles, which can be felt under the
skin above the heel. It is the largest
tendon in the body.

670. Levers of the third class are
the most numerous. The foot in rais-
ing a weight upon the toes is an example. In nearly
all joints of the arms and legs the power is furnished
by the muscle attached to a bone near the fulcrum
.or joint, while the weight is farther away or near the
outer extremity of the bone. Most of these muscles are
so attached to their bones that they must exert a force

Right forearm.

MUSCLES 37$

greater than the weight which they move. But the outef
end of a lever moves over a greater distance in a given
time than the part near the fulcrum. So if a muscle
loses power by its attachment to a bone, it gains in rapidity
of motion. The muscles of the body are strong enough to
combine strength with quickness of motion.

The joints of the arms and legs are mostly so arranged that the limb
can form a straight line, but can be bent in only one direction. The
muscles which bend a limb are called the flexors, while those which
straighten it are called extensors. Flexor and extensor muscles are"
usually arranged in opposing pairs, with the flexors upon the front and
the extensors upon the back side of the limb. The flexor of the elbow
reaches from the elbow to the shoulder upon the front of the arm and
is called the biceps. The extensor of the elbow extends in the same
way upon the back of the arm and is called the triceps. Both the flexors
and extensors of the wrist and fingers are situated between the elbow
and the wrist. Only a few small ones are in the hand.

The muscles which flex the knee end in strong tendons which can
be felt as the hamstrings upon the back of the joint. The muscles
which extend the knee end in a single large tendon inside of which is
the patella. The patella acts as a pulley to protect the joint from the
action of the tendon.

The muscles of the ankles and toes are arranged much like those of
the wrist and fingers. By practice while young, it is possible to learn
to use the toes in the same way as the fingers.

671. Back muscles. — The backbone is held upright and
bent backward by large mustles which form ridges upon
each side of the spine. They stretch the whole length of
the spine so that the weight and power are at the same
place while the fulcrum is the point of bending. Thus the
spine is equivalent to a lever of the second or third class
which uses most of the power of the muscle. So the back
possesses great power with slow motion.

672. Standing is done by the contraction of the opposing flexof
and extensor muscles of the lower part of the body, so that the

3/6 APPLIED PHYSIOLOGY

spine and legs are held rigid. If one set overacts, it pulls the body to
one side and tends to upset it. Then the opposing set contracts and
rights the body. In standing, the two sets continually act in this way.
Walking is due to a regular action of the flexor and extensor muscles
of the leg, in such a way that there is always one foot upon the ground.
In running, the whole body is completely removed from the ground
at every step.

673. Face muscles. — The expression of the face is due
to flat muscles which are attached to the skin. A circular
muscle surrounds the mouth and each eye, while other
muscles radiate from their edges. The contractions of

Illustration of the change of expression produced by the muscles
of the mouth.

these muscles cause the mouth and eyes to assume a great
variety of positions. Even the nose may be moved by
muscles, and in rare cases the ears also. The different
shapes of the mouth and eyes which these muscles produce
are reliable indications of the feelings of the mind.

674. Muscular power. — The power which the muscles
use is derived from the oxidation both of food and of their
own substance. In their work they use about one fourth
of the total heat produced in the body.

A horse can drag about two thirds of its own weight, while an ant
can drag 40 times its own weight, and a grasshopper can leap 300 times
its own length. In proportion to their size, all insects seem to be far
stronger than man. The strength of a muscle depends upon its thick-

MUSCLES 377

ness and not upon its length, yet in animals the muscle must be made
many times longer than in insects as well as thicker. Thus the muscles
of animals have more weight to lift and do a greater amount of work in
proportion to their size. A man's muscle fiber is really the strongest
known. An insect made as large as a man would probably be unable
to move a limb .

675. Precision of movement. — By means of the muscular
sense it is possible to regulate the action of a muscle with
great precision. But as the effort put forth is greater, the
ability to regulate it is less. So while slow and delicate
movements can be made with precision, rapid and power-
ful motions are less under control. After a muscle has
exerted itself to its full capacity, it is unable to perform
delicate movements with precision for some time.

676. Alcohol and muscle. — Strong drink in any form dimin-
ishes both the strength and the endurance of muscles. Soldiers and
athletes are not allowed to use it during periods of great exertion. It
also interferes with the precision of movements. Drinkers are not
allowed to work at railroading, where quickness and precision of move-
ments are always required. Tobacco also weakens the muscles and
lessens their precision of movement.

677. Physical effects of exercise. — When used, most
cells of the body take in more nourishment, and increase
in size and strength. Muscles, especially, grow larger and
stronger by use. Then the digestion, circulation, and
respiration all show increased vigor to supply them with
extra energy. Thus the whole body grows stronger.

Round shoulders are most often due, not to weakness of the spine,
but to weakness and inaction of the muscles of the back. The remedy
is not to apply braces, for that only permits the muscles to rest and be-
come weaker, but to make constant efforts to throw the shoulders back
and so to increase the strength of the muscles. Military drill makes
soldiers erect for this reason.

678. Overwork. — If the muscles turn too much heat
of the body to motion and work, there is too little left

3/8 APPLIED PHYSIOLOGY

to carry on the actions of the internal organs. Then
there will be less food prepared for the repair of the cells,
and to replenish the fuel for oxidation. So the whole
body, including the brain, will remain fatigued. Besides
the energy expended by the muscles, the brain also does a
large amount of work in sending orders for their work.
Probably the nervous system always becomes fatigued
before the muscles.

679. Kinds of exercise. — It is a problem for students
and clerks to determine how much exercise will rest and
stimulate the brain to the greatest degree, and yet take
no energy from it. The kind which a person enjoys best
is the best exercise for that person. If possible, the exer-
cise should be of a form which will turn one's thoughts
completely from the day's work and from the exercise
itself. So a useful occupation or some absorbing game is
especially valuable as exercise. Dumb bells, chest weights,
and all kinds of gymnastic exercises are excellent for
developing the muscles. Their only disadvantage is that
their use becomes monotonous, and a person must force
himself to use them. They have the advantage that they
can be exactly regulated to develop any defective part of
the body. When done in classes and under an instructor
they are especially valuable.

680. Amount of exercise. — A few moments of brisk
running or romping will set the blood flowing faster and
produce a clearer brain than an hour of slow walking. A
person's own feelings should warn him when to stop,
Boys and girls need plenty of exercise toward the. end of
their time of growth. A body well developed by exercise
carries its strength through life.

In a school, a position upon either the baseball or football or athletic
team often uses the surplus energy which in former years was expended

MUSCLES 379

in midnight hazings, and also develops the traits of bravery, manliness,
and self-reliance. There is a special danger of overexertion in com-
petitive sports, but with intelligent oversight of the teachers they are a
great benefit to all.

SUMMARY

1. Cells whose use is to produce motion are called

muscle cells.

2. In the arteries and in most of the organs of the chest

and abdomen are spindle-shaped muscle cells, which
are not affected by the will, but are controlled by
the sympathetic system.

3. Muscles covering the bones and moving the body

under the control of the will form one half of the
body.

4. Voluntary muscles are made of ribbonlike cells which

are marked crosswise.

5. Impulses from motor nerves cause a muscle to be-

.come thicker and shorter, so that it moves any-
thing attached to its end.

6. A muscle ends in a stringlike tendon which crosses a

joint, and is attached to the lower of the two bones
which form the joint.

7. Muscles are arranged in pairs. Those upon the back

side of a limb usually straighten the joint, while
those upon the front side bend it.

8. Owing to the manner of their attachment, most muscles

must put forth far greater force than the weight
which they can lift.

9. A piece of a man's muscle is stronger than any other

muscle of the same size.

IO. The power for contraction of a muscle is derived from
the heat of oxidation within the body. About one
fourth of the heat is thus used.

380 APPLIED PHYSIOLOGY

11. By exercise of the muscles, the nutrition of the whole

body is improved.

12. Too much exercise uses the power which should go

to the brain and other organs and so harms the
body.

13. That form of exercise is usually best which most

interests a person.

DEMONSTRATIONS

165. Skin a chicken's leg and separate each muscle. Show their
broad upper attachments and the small tendons into which the lower
ends taper. Cut off the skin from the lower parts of the legs and toes
and show how the tendons are attached to the toes. Notice that bend-
ing the leg tightens the tendons and flexes the toes. Explain how this
compels the toes to grasp the perch while the fowl is roosting. Pick a
muscle apart to show the separate fibers. Sketch a muscle.

1 66. Point out the main groups of muscles upon a boy. Have him
perform such motions as raising his arm and clenching his fist, and feel
what muscles are in action. Notice that when one set of muscles is in
action the opposing set also acts so as to steady the limb. Point out
the tendons, especially in the wrist and knee.

167. With two needles tear apart a small shred of muscle from a
piece of cooked meat and examine it under the microscope with a power
of at least 200 diameters. Sketch the ribbonlike muscle cells and their
fine cross markings. Notice the small amount of wavy connective
tissue between the cells. Examine a prepared specimen to show the
cells cut across and the capillaries surrounding the cells.

168. Show involuntary 'muscle cells by preparing a shred from a
fowl's gizzard, as in demonstration 167. Sketch the specimen.

169. Hold a pencil firmly with the elbow flexed. Contract all the
muscles of the arm strongly. Notice that the whole arm trembles.
Now let the pencil tap the table by means of this trembling motion, and
notice that the taps are about ten a second. Explain that the taps are
due to successive motor impulses from the brain. Now tap the table
rapidly with the ordinary motion of the hand. Notice that it can be
done only about five or six times a second. Explain that in this case the
mind must cause two separate sets of muscles to contract alternately.

MUSCLES 381

REVIEW TOPICS

1. Show that motion is essential to the process of life.

2. Describe involuntary muscles and tell their use.

3. Describe how voluntary muscles appear to the naked

eye and under the microscope.

4. Describe tendons; how they cross the joints; and

their attachment to bones.

5. Describe the contraction of a muscle.

6. Describe the three kinds of levers ; show how bones

and muscles form levers ; and give examples of each
kind.

7. Describe the arrangement of muscles in opposing sets.

8. Describe the action of muscles at the elbow ; at the

wrist ; at the fingers ; at the hip ; at the knee ; at
the ankle ; at the toes ; in the back ; over the abdo-
men ; and upon the face.

9. Show how standing is performed ; how walking ; and

how running.

10. Give the source and amount of muscular power.

11. Show that great exertion impairs the precision of

movements.

12. Show that muscle training is really mind training.

13. Show that physical exercise benefits the whole body;

and that overwork fatigues the -brain.

14. Show what kind of exercise is the best.

15. Show how to regulate the amount of exercise.

1 6. Give an estimate of the value of competitive sports in

schools.

CHAPTER XL

BACTERIA AND DISEASE

881. Dangers to life. — Man's health is often assailed
by his inward appetites and desires. He is also exposed
to accidents and dangers from without. Formerly men
were in constant danger from wild animals, but now man —
the noblest and most powerful living being — is constantly
assailed and often conquered by the smallest and simplest
of living creatures. In the midst of his work he may be
stricken with a deadly disease because millions of tiny
creatures are poisoning the cells of his body.

The microscope has revealed a world of tiny creatures of
an infinite variety of form and manner of life. Three of
the simplest forms are yeast, mold, and bacteria. All of
them are of importance to man.

682. Yeast is a plant which consists of a single cell
scarcely larger than a red blood cell. The cells live upon
sugar, and begin a series of changes to return it to the air
and water for use 'as plant food. Were it not for this
provision, much plant food might encumber the earth in
the form of sugar and starch, and both man and animals
might starve. After the sugar upon which yeast cells feed
is used up, they remain in a dormant state, and some be-
come dried and pass off as dust. Some are always float-
ing about in the air ready to grow in anything containing
sugar. Yeast must have warmth and moisture for its
growth. So cold or dried fruit does not sour. Yeast is

382

BACTERIA AND DISEASE

383

used in bread making and in the manufacture of alcohol
(see Chapter IV).

683. Molds form a class of plants which may grow in
nearly all kinds of moist substances, and there induce a
kind of decay. They may usually be recognized by their
furry growth on the surface of the affected substance.

Diagram of mold (X 200).

a ball of spores above the surface.
b threads beneath the surface.
c spores beneath the surface.

The plants themselves are usually a series of threads which
burrow beneath the surface. At intervals they send up
slender shoots which bear germ cells or spores. These
shoots constitute the fur which is usually called mold, but
many kinds form their spores beneath the surface. The
spores are microscopic in size, and can float in the air and
grow into mold plants when they fall upon a suitable soil.
Most forms grow only on dead material, but a few can
grow on living matter. The smut and rust on grain and
fruit are plants similar to molds. Ringworm is due to a

384 APPLIED PHYSIOLOGY

mold which grows in the human skin. Mildew and toad-
stools belong to the same family as molds. In nature
molds disintegrate, and return to the soil and air all kinds
of dead plant and animal substances, especially hard and
resisting tissues like bones, tree trunks, and skins, so that
they can again become available as plant food. In warm,
humid weather molds grow readily and are often destruc-
tive to food and clothing.

684. Bacteria. — The smallest and simplest, as well as
the most numerous of living creatures, are round or rod-
shaped bodies from 2TTro Q" to Tiroinr °^ an ^nc^ m breadth,
and seldom more than ysV^ of an inch in length. They
are sometimes called microbes, but more common names
are bacteria or germs. They are all plants whose mode of
growth somewhat resembles the yeasts and molds. Like
yeast and mold they, or their spores, are scattered every-
where in the air. When they fall upon moist albumin they
grow. A single one can produce over 10,000,000 in the
course of twenty-four hours. They often resist influences
which would destroy most other forms of life. Even boiling
for five minutes fails to destroy the spores of some.

685. Effects of bacteria. — Bacteria destroy the substances
in which they grow. Most forms of decay are due to the
action of certain varieties of bacteria. They cause dead
matter to become soft and melt away, usually with the
production of foul-smelling gases and a variety of poison-
ous ptomaines. In the soil there are forms of bacteria
which oxidize all kinds of animal and vegetable albumin
as thoroughly as though it were burned. Thus bacteria
destroy the dead and waste matter of vegetables and ani-
mals and prepare it for vegetable food again. Yeast, mold,
and bacteria are indispensable friends of all living beings ;
and decay is a step in the preparation of our food.

BACTERIA AND DISEASE

385

686. Effects of bacteria upon living bodies. — Wherever
there is a moist cavity containing albumin, bacteria may
grow. The mouth is
usually swarming with
them, and may be offen-
sive from the decay
which they cause. They
also grow abundantly in
the intestine. A few
forms can grow in the
lymph spaces within a
living body. There
they form poisons called
toxins, which circulate
with the blood and pro-
duce various diseases,

Bacteria growing in the mouth (x 400).

The specimen was obtained by scraping a

healthy mouth.

a nucleus of an epithelial cell.
b different forms of bacteria.
c outline of an epithelial cell.

such as erysipelas, diphtheria, typhoid fever, consumption,
cholera, lockjaw, and the grippe. Because these diseases are
always caused by germs which are planted in the body they

are said to be infectious.
All diseases caused by
germs are infectious.

Measles, scarlet fever,
mumps, whooping cough,
and smallpox also are due
to some influence from
without the body. This

Bacteria growing in a kidney and producing

an abscess (X 300).
a kidney tube.

b white blood cell attacking bacteria.
c bacteria.
d blood tube of the kidney.

room with a sick person, and so are said to be contagious.

OV. PHYSIOL. — 25

influence
proceed
of germ
diseases can
by being

is supposed to
from a kind

also. These
be caught

in the same

386 APPLIED PHYSIOLOGY

687. How bacteria enter the body. — Germs of an infec-
tious disease may remain alive outside the body in anything
containing animal or vegetable matter. They may grow
in damp clothing, or in sinks or wells, or in the soil, and
may cause disease in whoever happens to fake them into
the body. Dirt and filth make good soil for the growth of
the germs, and are well-known causes of disease. The
germs may become dry and remain in a dormant state for
years, and finally produce the disease again.

Bacteria may enter the body wherever the epithelium is gone, and
the lymph spaces are bare. Even a scratch or a pin prick may admit
thousands at one time. They can also enter through the mucous mem-
brane of the nose or throat, or they may be swallowed in drinking
water or licked off from a knife or spoon which another person has used.

688. How the body destroys bacteria. — Germs of disease
constantly surround us, and the skin is constantly being
scratched and pricked, affording them entrance. Yet only
in rare instances do they grow and produce sickness, for
the body has three very efficient weapons of defense.

First. The white blood cells have a special power of
seeking out bacteria and the toxins which they produce,
and of enveloping and destroying them (p. 397).

Second. The plasma of the blood and lymph, by some
chemical power, is able to destroy germs of disease.

Third. The serum of the blood often contains a sub-
stance called an antitoxin, which destroys the toxins of the
germs and so stops their action. When a disease has pro-
gressed for a few days or weeks, the antitoxin is formed in
sufficient amount to overcome the germs, and so the dis-
ease comes to an end.

If the toxins of diphtheria germs grown outside the body are injected
into a horse, the plasma of its blood will contain the antitoxin of the
disease. If its blood is drawn and allowed to clot, the clear serum will

BACTERIA AND DISEASE 387

contain the antitoxin, and if injected into a man suffering with diphthe-
ria, will tend to overcome the germs and to cure the disease.

Cows sometimes have a disease which seems to be a modified form
of smallpox. By vaccination, the same disease can be transmitted to a
man in whom it causes but slight inconvenience, but yet protects him
against smallpox almost as thoroughly as an attack of the disease it-
self. Universal vaccination has destroyed the terrors of smallpox, so
that from being one of the most common and deadly of diseases it is
now one of the rarest.

689. Destruction of germs outside the body. — The sun is

one of the most efficient agents in destroying bacteria of disease. It
acts partly by drying the food upon which they live and partly by
means of its own chemical power. An abundance of sunshine in a
place renders it almost surely free from disease. In some hot and dry
climates decay is almost unknown, for bodies become dried before
the germs can grow. On the other hand, darkness, decay, and disease
go together.

The wind drives away the germs. In the open air it is almost im-
possible to transmit disease. In closed rooms, germs which are given
off from a diseased body may collect in great numbers, and in sick
rooms may reenter the sick person and so prolong his sickness. Good
ventilation is one of the best means of preventing diseases.

The soil destroys germs of disease. In it are special germs whose
work is to oxidize all organic matter, including other kinds of germs.
It also filters out the germs from dirty water which soaks into it. Burial
will destroy the disease germs on all kinds of substances and dead bodies.

690. Antiseptics. — Man uses three principal means to
destroy disease germs which may threaten him. In the
first place, he may wash them away with soap and water.
He can thus get rid of most germs.

Secondly. A boiling heat applied for fifteen minutes
will kill all kinds of germs. A substance freed from germs
is said to be sterilized or disinfected. Clothes and utensils
used in a sick room can be made safe for future use by
boiling, Before a surgical operation, the instruments and
dressings are thoroughly sterilized by boiling.

388 APPLIED PHYSIOLOGY

Thirdly. A variety of chemical substances called anti-
septics are poisonous to bacteria and destroy them almost
at once. Carbolic acid added to from twenty to one hun-
dred times its weight of water is very efficient in destroy-
ing germs which it can touch. Bichloride of mercury
added to from one thousand to five thousand times as
much water, is also very good, but it destroys iron or tin
vessels. Chloride of lime is also much used.

Substances must come into intimate contact with germs in order to
kill them. A little carbolic acid or other antiseptic may impart an
odor to a room or overcome a smell, but to destroy the germs it must
be applied in quantity directly to the germ.

Before a surgical operation the surgeon washes and sterilizes his
hands, and covers his clothes with a sterilized gown. He carefully
avoids touching any object which has not been sterilized either by heat
or by chemicals. Before he operates he scrubs and sterilizes the field
of operation just as he did his hands, and then surrounds it with steril-
ized towels. At the end of the operation he covers the wound with a
dressing which has been sterilized by heat or chemicals. Then no
germs can enter, and the largest wounds heal in a few days without
pain or discharge. The safety of operations now as compared with
those of forty years ago lies in the discovery of how to exclude germs
of disease.

691. Care of a sick room. — When a person is sick, every
effort should be made to exclude germs of sickness. Fresh air and
sunshine are always of the utmost importance in a sick room. It will
always be better to run the risk of having the room a little cold than to
have its air close.

In contagious and infectious diseases, air and sunlight are the chief
means of destroying the germs.

Cleanliness should always be enforced in a sick room. The night
clothes and bed linen should be changed as often as they are soiled.
The whole body should be bathed daily, and the teeth and mouth
cleansed.

Talking above all things disturbs a patient. Especially avoid all
references to doleful cases of suffering like the patient's. Do not ask

BACTERIA AND DISEASE 389

him if he will have this thing or that, but bring it to him without
annoying him with the necessity of deciding for you. Anything which
disturbs or annoys him uses up some of the strength which he needs in
overcoming the germs of disease.

In a contagious disease all visitors should be excluded from the room,
and all furniture not absolutely necessary should be removed.

When the disease is at an end, the sick room should be thoroughly
scrubbed with an antiseptic. It should be opened to the sunlight and
air for several weeks before being used again. Everything possible in
the room should be boiled or scrubbed. The patient should receive a
thorough bath before leaving the sick room.

692. Blood poisoning. — Disease germs may grow upon
any open wound, making it tender and causing it to run
matter. In severe forms they cause a swelling of the sur-
rounding parts, producing erysipelas or blood poisoning.
All this can be prevented or overcome by applying clean
or antiseptic dressings.

Milk, in summer time, forms a good soil in which germs
from the air grow and form acids and other poisons.
They produce stomach and intestinal disease in bottle-fed
babies. Boiling the milk and bottles destroys the bacteria
and prevents the disease.

693. Tuberculosis. — Almost the first disease of which
bacteria were proved to be the cause was tuberculosis of the
lungs, or consumption. The discovery was made by Rob-
ert Koch, a German physician, in 1881. He found that
the germs which are always present in the tissues of a con-
sumptive can be grown in a bottle of blood serum, and will
multiply to an unlimited extent when small amounts from
one bottle are planted in another. He also found that
artificially grown bacteria will produce tuberculosis when
they are injected into a healthy animal.

Though the cause of consumption was determined before that of
most other infectious diseases, yet consumption is among the last of these

390 APPLIED PHYSIOLOGY

diseases to be actively combated. It still causes one tenth of all deaths,
and kills more persons than all other infectious diseases combined.
Thus in New York State during 1907 there were 147,442 deaths, of
which 14,406 were directly due to tuberculosis of the lungs, while all
other infectious diseases, including the grippe, caused 10,306 deaths.
Either inexcusable ignorance or wilful neglect is responsible for the
greater number of these deaths by tuberculosis, for the disease is pre-
ventable and in its early stages is usually curable.

694. Nature of tuberculosis. — It is not probable that any
person or animal is born with tuberculosis. The disease is
caught from tubercle bacteria. Men usually catch it by in-
haling bacteria which a consumptive has expectorated on
the floor or ground, and which have been dried and blown
about as dust ; sometimes, however, tuberculosis is caught
through milk or meat from an infected animal. The germs
may multiply in almost any tissue in which they find lodg-
ment. They cause the growth of white nodules, or tubercles,
like pin heads, and do harm in three ways: first, the tu-
bercles destroy the tissues of the infected part; second,
the tubercles may break down and form abscesses; and
third, the bacteria form poisons which circulate in the blood
and poison the whole body. The most common seat of
the trouble is the lungs, for the bacteria usually enter the
body with the air that is breathed. The bones and joints
also are often affected, especially in children.

Usually the first sign given by developing tuberculosis is loss of flesh
and strength. Affected bones and joints become sore and swollen. If
the lungs are affected, there is a cough with the expectoration of mucus,
and there are changes in the breathing sounds. If the temperature of
the body is taken at regular intervals, it will be found that there is a fever
toward night and after exertion. The continued presence of a slight
afternoon fever in a person who has lost strength and weight is sugges-
tive of tuberculosis. While some cases of consumption develop and
produce death within a very few weeks, the usual course of the disease

BACTERIA AND DISEASE 391

is slow. It usually lasts for years rather than months or weeks. It
produces but little pain, and those who suffer with it are usually hopeful
of recovery. They may be expected to recover if they take the trouble
to follow the proper mode of life.

695. Tendency to consumption. — Tubercle bacteria are
very often present in the dust that fills the air in streets
and houses. A closed room acts like a trap for dust, and
the air in it will have more germs per cubic foot than the
air outside. If a person is vigorous and well nourished,
and always has fresh air to breathe, his body is not a favor-
able soil for the growth of tubercle bacteria; but if his
muscles are poorly developed and his breathing is restricted
from any cause whatever, or if he sleeps in a poorly ven-
tilated room, he is very liable to take the disease. When
the breathing is deep and forcible, the bacteria are kept in
constant motion and have little chance to lodge and grow.
Deep breathing of fresh air also promotes a good circula-
tion, and healthy blood has great power to destroy the few
germs that may find lodgment. On the other hand, if the
air in any part of the lungs is not changed thoroughly and
often, bacteria may remain in the air sacs and smaller
bronchi, and multiply there ; and if foul air is breathed over
and over, the blood is not able to destroy the germs.

Thus it happens that such persons as clerks and students,
who sit still a large part of the time and breathe lightly, are
much more likely to take consumption than those who, like
explorers, hunters, pioneer miners, and many farmers, lead
a life of muscular activity in the open air, though they are
constantly exposed to inclement weather. And thus it is
that men who live and labor all day in pure air often con-
tract consumption from close sleeping rooms when their
mode of life otherwise would insure their freedom from
almost all forms of infection.

392 APPLIED PHYSIOLOGY

696. Scrofula. — In some children the lymphatic glands under the
lower jaw and on the side of the neck are swollen. These children are
usually pale and subject to colds and other forms of illness. The swol-
len glands often break down and produce abscesses. In many cases
the children have swollen joints or bones. The trouble is usually called
scrofula. In many cases, though by no means always, scrofula is due
to the presence of tubercle germs. Scrofulous children are likely to take
tuberculosis of the lungs and they should be subjected to the same pre-
ventive and curative treatment as though they actually had tuberculosis.

697. Prevention of consumption. — When all tubercle
germs are destroyed, consumption will be extinct, and no
new cases can arise. The breath of a consumptive does
not contain the germs. The bacteria are spread almost
exclusively by means of the sputum. They are not likely
to escape from the sputum unless it is dried, but the dust
from the streets and other places on which consumptives
have expectorated contains them in a dormant state, ready to
grow when inhaled. Thus the key to the prevention of
tuberculosis consists in collecting and destroying the spu-
tum before it dries.

A consumptive should never expectorate on the floor, or
on the ground, or on any other place where the sputum
may dry. All matter that comes from the nose and mouth
should be deposited in cups or flasks which should be burned,
or on clean handkerchiefs which should be kept in a special
pocket or other place and boiled before they are washed.
Sputum cups may be purchased cheaply at drug stores.

In coughing and sneezing, consumptives should hold a handkerchief
tothemouthto avoid unconsciously expelling mucus. They should keep
the hands and face free from dried sputum. A consumptive man should
not wear a beard on account of its likelihood to be soiled. A consump-
tive's room should face the sun, and the curtains should be drawn
aside and the windows kept open to the air. Any other detail which
would promote the destruction of the bacteria should be observed.

BACTERIA AND DISEASE

393

698. Curing consumption. — In order to recover, con-
sumptives should be specially careful of the disposal of
their sputum, since by that means they avoid reinfecting
themselves with the bacteria. They should breathe pure
air at all times, day and night. The windows of the sleeping
rooms should be kept wide open. It is still better to sleep
in the open air, in
tents or on roofs or
piazzas. By using a
form of window tent
a patient can sleep
with his head in an
open window while
his body remains in
the warm room.

There is a ground-
less fear that cold
air and the wind are
bad for consump-
tives. This is not true. Patients should be warmly clothed
and be protected -from the rain and from direct drafts
which cool the body unequally. Experience proves that
they do not take cold when observing these two precautions.

A consumptive can be cared for as efficiently, as comfortably, and
as cheaply in his own home as in any other place. The air of high
mountains is of value mainly because its rarity compels deep breathing.

Consumptives need an abundance of nourishing food. Meat, eggs,
milk, and fish should form a large part of the diet, because of their high
nutritive value and their ease of digestion. Consumptives should avoid
everything that interferes with their digestion. In all other things
they should lead a simple, quiet life according to well-known rules of
hygiene.

By these means a large proportion of cases may be cured. It is well

Window tent.

394 APPLIED PHYSIOLOGY

for consumptives to go to a sanitarium for a short time, in order to re-
ceive instruction how to eat, sleep, and manage their mode of life.

SUMMARY

1. Yeast is composed of living plants which begin the work

of returning sugar back to its original elements.

2. Mold is composed of tiny rodlike plants which grow

through animal and vegetable tissues and destroy
their albumin.

3. Bacteria are the smallest living beings. They cause

decay and change albumin back to its elements in
the air and soil.

4. Bacteria may produce virulent poisons.

,5. A few kinds of bacteria grow* in the body and there
produce various forms of disease, some of which
can be transmitted to other persons.

6. The body is protected against the bacteria of disease

by the white blood cells, by the plasma, and by sub-
stances produced in the blood.

7. Outside of the body, sunlight, fresh air, running water,

and the soil destroy disease germs.

8. Man destroys disease germs by washing them away,

by boiling objects containing them, and by poison-
ing them with such substances as carbolic acid and
bichloride of mercury.

9. Sunlight, fresh air, and cleanliness are essentials in

every sick room, and especially in infectious diseases.

10. After an infectious disease, the room and all its con-

tents should be scrubbed, and aired for a month.

11. Consumption, or tuberculosis, is an infectious disease,

spread mainly by means of dried sputum.

12. Fresh air day and night, and good food, are essential in

the prevention and cure of consumption.

BACTERIA AND DISEASE 395

DEMONSTRATIONS

170. Place a little yeast upon a microscope slide and examine it
with a power of at least 200 diameters. Notice the oval cells from
which smaller cells are budding.

171. Take a bit of mold from cheese or bread and examine it with a
power of at least 200 diameters. Notice the strings of mold which
appear like very small jointed rods. Notice the collections of round
spores at the tops of the projecting stalks.

172. Place a little hay in a bottle of water and set it in the sun.
After a few days, place a drop of the water upon a glass slide and
examine it with a power of at least 400 diameters. Notice that
numerous bodies of various sizes and shapes are swimming in the
drop. These are the animalcules which older books describe. Notice
also the real bacteria which appear as the finest kinds of dots and short
lines. Most of them are in constant motion. Only a few kinds of
bacteria can be recognized by their appearance.

173. Prepare some gelatine as if for the table, and pour some
while hot into a tightly covered dish which has been boiled. Take off
the cover for a moment before the class, and, replacing it, set the dish
aside for a few days. Then a few specks of mold or of scum will appear
upon the surface, each showing where a germ has fallen from the air
and multiplied to form the spot. Explain that bacteria are studied in
laboratories in much the same way.

174. Have a druggist prepare a solution of carbolic acid i to 100,
and of bichloride of mercury i to 1000. Show the class how they should
be used in washing the hands and clothes. Also show the pure drugs,
and warn the class against using them in this form. Show also chloride
of lime and other common antiseptics.

REVIEW TOPICS

1. Describe yeast and give its uses in nature.

2. Describe mold and give its uses.

3. Describe bacteria and their relation to decay.

4. Give the uses of decay.

5. Show how bacteria can enter the body and how they

produce sickness.

APPLIED PHYSIOLOGY

6. Show how bacteria are destroyed in the body by white

blood cells and by the blood plasma.

7. Describe an antitoxin and tell how it is used in treat-

ing diphtheria.

8. Describe vaccination.

9. Show how bacteria are destroyed by sunlight ; by the

air ; by running water ; and by the soil.

10. Show how man destroys bacteria by cleanliness ; by

heat ; and by antiseptics.

1 1. Show how a surgeon destroys germs before and after

a surgical operation.

12. Give some hints about the care of a sick room; and

about cleansing it after an infectious disease.

13. What is the cause of consumption ?

14. How is consumption usually caught ?

15. What are the signs of a developing case of consump-

tion ?

1 6. What precautions should a consumptive take in order

to avoid infecting other persons ?

17. What should a consumptive do in order to recover?

NOTE. — For a more extended discussion of bacteria and disease, see "The
Story of the Bacteria," by T. Mitchell Prudden, M.D.

CHAPTER XLI
REPAIR OF INJURIES

699. Injuries. — Many causes outside the body operate
upon its cells to injure them. Excessive heat or cold may
impair their vitality or cause their death. A sudden change
from heat to cold is a common cause of injury. Blows and
cuts may kill whole armies of cells. Above all, bacteria
may cause injury and disease. In a few hours, the injured
part shows a change, which is apparently due to an in-
crease of the injury, but which is really caused by nature's
attempt to repair the part.

700. Congestion. — After an injury has been received
the first step in its repair is to dilate the arteries so as
to permit more blood to flow through the part. Then
more plasma will penetrate into the lymph spaces. This
produces redness and some swelling and is called conges-
tion. Congestion is a sign of attempted repair. This
alone may be sufficient to heal the injured part.

701. Inflammation. — If the injury is greater, there is
a change in the behavior of the white blood cells. Ordi-
narily they tend to flow more in the outer part of the
blood stream, but when the arteries enlarge as a result of
injury they adhere to the sides of the smallest blood tubes
and some pass entirely through their walls and lodge in the
lymph spaces. There they envelop and digest the injured
parts and carry them away with the lymph. The lymph
and blood cells have great power of absorbing blood and

397

398

APPLIED PHYSIOLOGY

dead cells, or even such substances as stitches left in the
body by a surgeon. The excess of white blood cells causes
more swelling, and some pain. This is an aggravated form of
congestion, and is called inflammation. Some of the white
^_ ___ blood cells grow in place

Beginning of inflammation (x 400).

a white blood cells adhering to the wall of a
capillary and passing through it.

b white blood cells which have passed outside
of the capillary in order to repair an
injury.

c red blood cells passing through the capil-
lary.

d wall of capillary.

of the removed cells and
so fill in the gap. Each
cell becomes long and
branched and finally de-
velops into a connective
tissue cell. If the new
cells are in great amount,
they have a different ap-
pearance from the origi-
nal cells and are then
called a scar.

702. Repair of cuts.—
When a cut is made in
a tissue, the same proc-

ess takes place, but in addition new blood tubes sprout
from each side of the wound and interlace in the middle.
The white blood cells grow about the new tubes and
become connective tissue and so bind the edges of the
cut together.

When the skin is injured, the white blood cells form
new tissue upon the surface while the epithelium spreads
over it from the edges, stopping the growth and complet-
ing the healing process. Sometimes the new connective
tissue grows faster than the epithelium and forms soft
tufts, which project above the healthy flesh. These tufts
are called proud flesh. If they are scraped off, or cauter-
ized, the epithelium is enabled to cover the wound, and
to complete the healing.

REPAIR OF INJURIES

399

703. Injuries due to bacteria. — If bacteria cause the
injury to the cells or if they enter and grow after the
injury is done, the blood cells must fight them as well as
repair the damage. Sometimes they cannot do both at
once. Then the white blood cells and plasma leave the
blood tubes to a still greater degree and lay siege to the
bacteria until they

J a> « ^ A »

completely fill the
lymph spaces. They
even stop up the
blood tubes, produc-
ing great swelling
and pain. White
blood cells and bac-
teria are now tightly
wedged among the
injured tissues with
no chance for escape
and with no nourish-
ment. Then the
whole injured part
becomes soft and
finally bursts and
runs out as a creamy
matter called pus.
Thus nature sacrifices a part of the body in order to get
rid of the bacteria which threaten to overcome the whole
body. Then the white blood cells grow and repair the
wound as in clean wounds. A mass of pus in the body is
called an abscess. Every abscess or collection of pus is
caused by bacteria.

If bacteria grow upon an open cut, the white blood cells must devote
part of their energies to fighting them, and so healing goes on slowly,

The repair of a wound (X 200).

a new white blood cells upon the surface of a raw

spot.
b growing white blood cells.

e older white blood cells which are becoming
elongated and branched like connective tissue
cells.

f old capillary sending out a new branch.

g old connective tissue.

400

APPLIED PHYSIOLOGY

while the dead cells, or pus and plasma, run off in a continuous stream.
So bacteria hinder the repair of wounds, and prevent their edges from
growing together directly. Then the cut must slowly heal from its
bottom. When a wound begins to be tender and to discharge, it is
said that one has taken cold in it. Taking cold in a wound means
that bacteria are growing in it. Their toxins may poison the whole
body and produce a severe fever, which may cause death. Surgeons
now exclude bacteria from the wounds which they make. The white
blood cells then have nothing to do but repair the cut, and every part
of the wound heals at once. Healing applications do good mainly by
destroying germs which may come near the wound.

704. Treatment of in-
flamed wounds. — A
tender discharging
wound should be
cleaned with boiled
water, and covered with
a a clean antiseptic dress-
ing, to soak up the dis-

The second stage of inflammation (X 200). charges and bacteria.
a white blood cells which have left the capillary. The dressings should

be changed as soon as
they become full of
matter. Inflammation

may be prevented by covering fresh wounds with clean

dressings.

When an abscess is forming, the heat of a poultice dilates the blood
vessels, and so hastens the softening process. Thus it "brings the
abscess to a head " and hastens the discharge of the pus. Since the pus
will form anyhow, it is always better to open the abscess and let out
the matter at once. This can be done without pain by using cocaine.

705. Taking cold upon the lungs. — When a mucous
membrane is injured, as by exposure to cold, there will
be the same changes in its blood tubes as in a wound

b white blood cells which nearly block the

capillary.

c a few red blood cells which still circulate.
d wall of the capillary.

REPAIR OF INJURIES

401

of the flesh. Then the membrane will be red and tender
and possibly swollen. Owing to the thinness of the mem-
brane and of its epithelium, the plasma and white blood
cells will come to the surface. The matter may collect
until it is coughed up and expelled. The nose and throat
are the most often affected, but in severe cases it extends
to the trachea and lungs. When the matter fills the air
sacs of a part of the lung, the disease is called pneumonia.

59

The third stage of inflammation, or the formation of an abscess (X 50).

a epithelium of the skin softened and bursting.

b white blood cells which have packed the tissues full and shut out nourishment

c blood tube stopped by white blood cells.

In order to take cold there must be an injury to the cells, and
bacteria must grow upon the injured spot. It often happens that the
cells are exposed to injury, and no cold is contracted, for germs do
not happen to grow, while on the other hand the exposure may be
slight, and yet may enable germs to produce £ severe cold.

In colds and in an abscess, the pus and discharged substances are
not foul matters which have been circulating in the blood, but consist
of the strong blood cells which have died fighting for the defense of the
body, and of plasma, which is an efficient protection against the germs.
Both being dead and charged with the toxins of the bacteria, they are
no longer of use, but should be expelled from the body.
ov. PHYSIOL. — 26

4O2 APPLIED PHYSIOLOGY

When a cold is first coming on, a hot bath and hot drinks and hot
bed clothing, together with a liver stimulant, may cause the skin and
liver to excrete enough toxins to enable the white blood cells to over-
come the bacteria.

706. A long life. — Although in former times man was
often* conquered by bacteria of disease and even now is
continually assailed, yet now he knows more about his tiny
foes and is able to protect himself. He knows that his
eating, his breathing, his work, his rest, and in fact his
every action will render his cells either more or less able
to combat with disease germs. If all men would live up
to their knowledge, germs of disease would find no lodg-
ment in the body, while there would be no cause of dis-
ease in the body itself. Then man's mind would remain
with his body far beyond the allotted three score and ten
years, and, during all its long stay, would find the body a
willing servant to build the ideal plans of the spirit into
enduring realities.

SUMMARY

1. An injury to the cells of the body causes the arteries to

dilate and bring more blood to the part.

2. Over a sore spot the white blood cells form new con-

nective tissue while the epithelium of the healthy
skin spreads over the new tissue, stopping its growth
and completing the healing process.

3. When bacteria are growing in an injured spot, the white

blood cells attack them, but are often killed them-
selves and pass off as creamy matter called pus.

4. If the white blood cells cannot overcome the bacteria,

they hem them in until they and the tissues starve
and run out as pus.

REPAIR OF INJURIES 403

5. The changes which take place about an injured part

cause it to become red, painful, swollen, and warmer
than usual.

6. If wounds and all other injuries were protected against

bacteria, they would heal at once without discharg-
ing pus or other matter.

7. In injuries to mucous membranes, the white blood cells

and plasma pass through the thin tissues to the sur-
face and are discharged at once.

8. Taking cold means an injury due to bacteria.

9. The matter discharged from an abscess or from a

"cold" is composed of the best cells of the body
which have died in its defense.

DEMONSTRATIONS

175. Scratch the skin upon the lower part of the arm. Notice that a
red line develops in a moment. Explain that the scratch injured the
cells and partly paralyzed the blood vessels, and that the redness is due
to more blood in the part, which has come to repair the damage and to
protect the rest of the body.

176. A pimple upon the face will illustrate the different stages of
inflammation . Explain that a pimple may be caused by a prick too small
to be noticed, but which has introduced some bacteria beneath the skin.
Explain that the redness is due to the blood which has come to repair
the damage. Explain that the white spot upon the top of the pimple is
the softened area through which bacteria and dead cells will finally pass
out, and that the pus is composed of white blood cells which have died
fighting to protect the body against the bacteria.

177. Place a tiny drop of matter pressed from a pimple or a cut or a
scratch upon a microscope slide and examine it with a power of 400
diameters. Notice that it is composed of white blood cells, containing
nuclei. Examine also a drop of mucus from the nose and notice that it
consists largely of the same kind of cells.

178. Obtain a prepared microscopic specimen from a wound in the
process of healing. Show that the newly formed tissue consists of

404 APPLIED PHYSIOLOGY

round blood ceils upon its surface, and that in the deeper layers the
cells grow larger and become branched. Explain that the deeper layers
are the older and that their cells are white blood cells which are grow-
ing to become connective tissue.

REVIEW TOPICS

1. Explain in order what happens in an injured part ot

the body, describing the increased flow of blood,
and the action of the white blood cells.

2. Explain the healing of a cut.

3. Explain how a raw spot of skin becomes healed, and

what part the epithelium takes in the process.

4. Explain how bacteria in an injured part retard healing.

5. Explain how white blood cells overcome the bacteria.

6. Explain the formation of an abscess.

7. Explain taking cold in a wound, and in a mucous

membrane.

8. Give the signs of inflammation and its use.

9. Tell what composes the matter discharged from an

abscess and from the nose and throat during a cold.

10. Show how to treat a wound in which one has taken

cold.

11. Explain how to treat a cold of the air passages.

CHAPTER XLII
PUBLIC HYGIENE AND SANITATION

707. Boards of Health. — In every community a Board
of Health is established to have the oversight and control
of matters in which the property or acts of one person may
affect the health of others. For example, the Board has
jurisdiction over sewage, water supply, contagious diseases,
obnoxious trades, and nuisances. In many cases its duties
are strictly denned by law, but in others, such as serious
epidemics of contagious diseases, its powers are almost
unlimited.

A Health Board consists of a number of persons who are appointed
according to the laws of the several states. Usually each township or
county and each village and city has a local board, and over the local
boards is some central authority. Each local board makes its own rules
in accordance with the general laws of the state. Usually a physician
is appointed by the local board as health officer, and has direct con-
trol over the enforcement of the health regulations. He investigates
complaints about any property or person alleged to be injuring the
health of the neighbors, and causes any unsanitary conditions to be
remedied. The health officer is a teacher who instructs the public in
the elements of modern sanitation and requires his instructions to be
carried out. Owing to the strictness and efficiency of the inspections of
the various boards and to the educational value of their work, contagious
diseases and offensive nuisances are now becoming rare.

708. Garbage. — A subject that often comes before a
health officer is the disposal of household garbage and
slops. In large cities the garbage is collected by the city

405

406 APPLIED PHYSIOLOGY

and sorted, and a large share of the cost of its removal is
met by the sale of useful material which is recovered. In
thinly settled places all household waste is often thrown
on an ash heap behind the most convenient outbuilding,
producing an offensive accumulation which might become
dangerous if material from a case of infectious disease
were mixed with it A garbage pile usually becomes
offensive and a menace to health from one or more of
three causes.

First, water in any form keeps the mass wet and in a
decaying state. Liquid slops and waste containing offen-
sive matter should never be poured upon it. Dry garbage
is seldom unhealthf ul. That which cannot be utilized or de-
stroyed should be kept dry and its combustible parts burned.

Second, bones and other table scraps and kitchen refuse
decay and furnish a soil in which bacteria of disease may
survive and possibly grow. Most of these substances
might be used as food for poultry or as garden fertilizer.

Third, dirty tin cans containing rain water are offensive
and become breeding places for flies and mosquitoes.
Cans which are clean and dry are useful and salable.

709. Sewage disposal. — Ordinary household sewage is
over ninety-nine and one half per cent water, and is in a
state of offensive putrefaction. Its proper disposal is
necessary, for it often contains disease germs. In an ordi-
nary family which has no bath room or running water,
each person uses only a pail or two of water daily. The
resulting sewage is almost entirely kitchen waste and wash
water, and may safely be thrown upon the ground if the soil
soaks it up at once. If there is a bath room and running
water, each person is likely to use at least twenty gallons
of water daily. . The drain pipes should lead the waste
water either into a cesspool or into a sewer (pp. 137, 253).

PUBLIC HYGIENE AND SANITATION 407

710. The cesspool. — A cesspool is a hole in the ground
for receiving sewage and, usually, for allowing it to soak
into the soil. A double cesspool is of advantage, so ar-
ranged that solid matters will remain in the first cesspool,
and only liquids pass into the second. In a properly act-
ing cesspool there are a few inches of sediment in the
bottom and a layer of floating solids, neither of which
increases in quantity, for decay takes place and destroys
and liquefies the solid matter in much the same manner
as though it were buried in the soil.

Chloride of lime and other antiseptics used in the bath room hinder
the process of decay, and cause the cesspool to become stopped up with
solid matter. In a sandy soil a pair of cesspools, each seven feet in
diameter and seven feet deep, should dispose of at least two hundred
gallons of sewage daily, or as much as a large family produces. Cess-
pools work well in sandy soil where there is an abundance of room and
no danger of contaminating the water supply.

711. A sewer system. — In the simplest and oldest sewer
systems the untreated sewage is emptied into the nearest
body of water. In order that sewage may not be detected
by the senses, it must be mixed with an amount of flowing
water at least two hundred times as great as its own
volume. But the river which receives the sewage is made
unfit for use as a source of water or of ice supply, even
when the dilution is far greater. In order that sewage
may not be a menace to public health, it must usually
undergo treatment at a disposal plant.

An old form of sewage disposal is treatment with chem-
icals; but this is costly, and the final disposition of the
solids formed by the chemicals is often difficult.

Another old plan is to maintain a public farm on which
the sewage supplies both irrigation and fertilizer. One
acre of sandy land will soak up the untreated sewage of

408 APPLIED PHYSIOLOGY

one thousand people continuously and in safety without
needing attention except the occasional removal of the
accumulated solid matter. This method is still used with
success by some large European cities.

A modern plan is to provide a water-tight cesspool or
septic tank in which the solid matter rots away, leaving
only liquid to flow out upon the land. Where this method
is used, an acre of land can soak up the sewage of several
thousand people without the accumulation of offensive
solid matter.

A septic tank should be large enough to contain at least as much
sewage as the town produces in a day. In the course of the twenty-four
hours which it takes a given specimen of sewage to pass through the
tank, it undergoes decay by which over half of its solid matter is liquefied ;
the larger particles fall to the bottom or float on the surface, and re-
main in the tank till they are liquefied also. The bacteria which pro-
duce the greater part of the decomposition, especially of the fats, flourish
only in the absence of air ; and this condition is secured by the thick
scum which accumulates in the tank. As the sewage flows out of the
tank, it is made to absorb oxygen in some manner, as by letting it fall in
small jets or thin sheets through the air, or by making it flow over a bed
of broken stone. Then it is usually allowed to soak into the soil of
large sandy beds set aside for the purpose. In the soil the remaining
decaying matters are oxidized to harmless products by bacteria which
flourish in an abundance of oxygen.

This system closely imitates nature's method of returning decompos-
ing substances to the soil, and is one of the simplest and cheapest of
all systems for the disposal of domestic sewage. In a septic tank that
is working properly no solid matter accumulates, but the system does
not work well if the sewage contains much chemical or factory waste,
as such substances prevent the bacteria from flourishing and destroying
the solid matter. Street drainage should not be mixed with the sewage.

712. Water supply. — An open well is not a safe source
of drinking water, for under the best conditions germ-laden
dust and dirt blow into it. In a thickly settled village or
city sewage cannot be prevented from filtering into wells,

PUBLIC HYGIENE AND SANITATION 409

and all wells should be filled up. A driven pipe is much
safer than a large, open well. Its point should be driven
at least twenty feet below the water level, and there should
be no cesspools or barnyards near it.

Usually water for a city is derived from an outside source
and is distributed by means of underground pipes. River
water is often used, but most rivers are infected by sewage
from other towns or from houses or camps along its banks.
The drainage from the excretions of a typhoid fever case,
reaching a river, has caused epidemics of typhoid fever in
other places in which the river was the source of the water
supply.

713. Purification of water. — River water should be
purified before it is used. The simplest method of purifi-
cation is to store the water in a reservoir and allow the
bacteria and other solid particles to settle to the bottom.
This does not remove all the bacteria, though it greatly
improves the water; but reservoir water may be almost
completely freed from bacteria and other solid substances
by means of good filter beds.

The ordinary filters used in houses have little effect except to remove
very large particles of dirt. For efficient filtration water must pass
through the filter slowly and under little pressure. Filter beds for the
purification of city water consist of underground beds of clean sand
about four feet deep. A new bed does not work properly, for the
spaces between the particles of sand allow the bacteria to pass through.
In the course of a few days, however, a kind of vegetable organism re-
sembling mold grows in the upper layer of sand and covers the sand
grains with a gelatinous coating. This coating entangles about ninety-
nine per cent of the solid matters which may be floating in the water,
and allows only clear water to pass through.

A filter bed an acre in extent will purify about three million gallons
of water daily. If a small quantity of alum is added to the reservoir
water, a soft, flaky substance is formed which becomes entangled in the

410 APPLIED PHYSIOLOGY

sand and holds back the impurities just as the vegetable growth does.
By this method one hundred and twenty million gallons of water per
acre can be purified daily.

714. Street cleaning. — In thickly settled places dirt
from the streets is often a menace to health, for it contains
many kinds of bacteria which cause sickness in men and
animals. In wet weather the dirt forms mud which may
be carried into houses on shoes and clothing, while in dry
weather the germ-filled dirt is blown into our houses in the
form of dust. Among the bacteria which are often found
in street cleanings are the germs of tuberculosis, lockjaw,
and grippe. It is necessary that the streets be kept clean
as much on account of the health of the people as for the
sake of good appearances. Each community may properly
spend large sums of money for street cleaning.

715. Quarantine. — The laws of the various states require
physicians to report to the Health Board all cases of infec-
tious or contagious diseases with which they come in contact.
The health officer visits the sick person's house and requires
all persons living there to conform to all necessary require-
ments in order to prevent other persons from catching the
disease. Smallpox, diphtheria, and scarlet fever may be
caught by inhaling the air from the sick room. So in cases
of these diseases only the physician and nurses are allowed
to enter the sick room; all other persons are required either
to leave the premises, or to live in a part of the house re-
mote from the sick person. This enforced isolation is
called quarantine.

Cases of measles, German measles, whooping cough,
chicken pox, and mumps should also be quarantined, but
they usually are not, — mainly because of the popular be-
lief that they are not dangerous diseases. Yet in New
York state during 1907 measles caused nearly as many

PUBLIC HYGIENE AND SANITATION 41 1

deaths as scarlet fever. Every effort should be made to
prevent children from taking any of these diseases.

Influenza, or the grippe, is a contagious disease, and it is
probable that ordinary cases of "cold" and sore throat are
also mildly contagious. Persons with colds should keep
alone as much as possible, and while in the house they
should remain in a well-ventilated room. In cases of
typhoid fever and consumption the sick persons may usually
be allowed to associate with other persons if all discharges
from the sick persons' bodies are destroyed.

716. Fumigation and disinfection. — After every case of con-
tagious or infectious disease all infected rooms and articles should be
freed from bacteria. The best method of getting rid of bacteria is by
scrubbing, washing, and airing, as is done in a thorough housecleaning.
To the wash water that is used in the room some antiseptic should be
added, such as a tablespoonful of formalin to each quart of water. In
addition to the cleaning it is well to fumigate the house with some
antiseptic gas. Fumigating candles of sulphur or formaldehyde may be
bought at drug stores. In order to do any good a large quantity of the
fumigating material should be used while the room is damp, and with
all doors and windows tightly closed. Fumigation which does not kill
the flies in the room is of no value in killing bacteria, no matter how
bad the gas may smell.

717. House flies. — A common carrier of disease is the
/house fly. Alighting on diseased persons and infected ex-
cretions, they carry bacteria on their legs and bodies and
infect persons and food on which they next alight. They

1 may carry diphtheria and typhoid fever to well persons and
may cause babies to have intestinal troubles. In all cases
of infectious disease flies should be kept out of the room and
away from all excretions that come from the sick persons.

House flies hatch from eggs which are laid in decaying substances,
especially in stable manure. The young flies are white and worm-like,
and are called maggots. In about a week they change to brown.

412

APPLIED PHYSIOLOGY

House fly, greatly magnified.
Showing its hairy body and legs, to which filth and bacteria may adhere.

hard-shelled pupas, from which full-grown flies emerge in about another
week. There could be no house flies if there were no manure piles,
garbage heaps, or other collections of decaying substances in which the
young flies could grow. Stables and barnyards should be kept dry and
clean, and no collections of decaying substances of any kind should be
allowed to exist. Then we should be free from flies in summer as well
as in winter.

PUBLIC HYGIENE AND SANITATION 413

718. Mosquitoes. — Mosquitoes are the carriers of malaria
and yellow fever. These diseases are due to germs which
must pass a part of their life in the body of a mosquito and
part in the body of a man, and their prevention depends
upon the extermination of mosquitoes. The extermination
may be effected by drying up all stagnant bodies of water
in which mosquitoes breed. Marshy land should be drained
dry, or its pools should be converted into running streams.
Barrels, pails, and cans of rain water and waste water
should be emptied. A little kerosene or other oil poured
on the water will kill the young mosquitoes. Persons sick
with malaria or with yellow fever should be protected with
screens of mosquito netting so that no mosquitoes may
become infected by them. By such means as these di-
rected against mosquitoes, tropical countries like Panama
have been almost freed from malaria and yellow fever.

719. Pure food laws. — Food that is exposed for sale in open
booths and in front of stores may become infected through dirt and
dust blown upon it, and from unclean persons handling it, and from flies
which alight upon it. Much food is adulterated, often with harmful
substances. Food that is kept too long may become spoiled and unfit
for use, and so antiseptics are often added to prevent decomposition.
Chickens that have been kept on ice for days and weeks without clean-
ing are poisonous and unfit for use. Until calves, lambs, and pigs are
at least a month old they are unfit to be killed for use as food. Milk
that is produced under unclean conditions, or that has not been kept
cool during its transportation, may become filled with bacteria and unfit
for use before it actually tastes sour. In these and other matters per-
taining to the purity or freshness of food offered for public sale, Boards
of Health are given great power of enforcing laws designed to prevent
abuses.

SUMMARY

I. Boards of Health have control over matters affecting
the public health-

414 APPLIED PHYSIOLOGY

2. Garbage should be kept dry and not allowed to ac-

cumulate in heaps.

3. In a cesspool the solid matter in household sewage

liquefies and decays, and its liquid parts soak into
the soil.

4. A septic tank is practically a water-tight cesspool.

5. An effective method for the disposal of city sewage

is to run it through a septic tank, then through an
oxygenating device, and then upon the surface of
plots of ground set aside for the purpose.

6. An efficient method of purifying the water supply

of a city is to have it stand in a reservoir and then
filter it through sand beds.

7. Dust and dirt on a street contain bacteria of many

diseases.

8. Every case of contagious disease should be isolated

from the rest of the community, and after the re-
covery of the sick person the sick room should be
cleaned and fumigated.

9. House flies are disease carriers. Their breeding places

are wet manure piles and garbage heaps.

10. Mosquitoes cause malaria and yellow fever. Their

breeding place is stagnant water.

11. Boards of Health should enforce a high standard of

purity and freshness in food that is offered for
sale.

DEMONSTRATIONS

179. Procure the rules and regulations of the local Board of Health,
and call the attention of the class to their important features. Many of
the state and city Boards of Health issue, for free distribution, circulars
on contagious diseases and disinfection.

1 80. Have the class visit any water works and sewage disposal works
which may be in the vicinity of the school. Notice the cleanliness of

PUBLIC HYGIENE AND SANITATION 415

the streets, and the condition of fruit and vegetables which are exposed
for sale in front of stores, and on the streets of the town.

181. In manure piles and garbage heaps look for maggots and pupa
cases of house flies. Call attention to the ease with which flies might be
exterminated if the whole community would cooperate.

182. Notice the rain barrels about town, and see if they contain
" wigglers," or young mosquitoes. Find out if there is malaria in town,
and if so look for the breeding places of the mosquitoes that cause it and
plan the means for its prevention.

REVIEW TOPICS

1. Name some duties of a Board of Health.

2. Describe a good method for the disposal of garbage.

3. In what manner is garbage detrimental to health ?

4. In a cesspool what becomes of the solid part of sew-

age ? What becomes of the liquid part ?

5. In a septic tank what becomes of the solid part of

sewage ? What becomes of the liquid part ?

6. Describe a form of sewage disposal plant.

7. Why is a driven pipe a safer source of water supply

than an open well ?

8. Describe a method of filtering river water that is to be

used as the water supply of a city.

9. What is meant by quarantine ?

10. In what way are house flies detrimental to health ?

1 1. How may we get rid of house flies ?

12. What diseases do mosquitoes cause? How may we

get rid of mosquitoes ?

13. What powers have Boards of Health regarding the

purity and freshness of foods that are offered for
sale?

CHAPTER XLIII
INFECTIOUS DISEASES

720. Resistance to infectious diseases. — All infectious
and contagious diseases are caused by living germs (p. 385).
Our body always has some power of protecting itself against
disease germs, for the white blood cells and the blood plasma
attack them. If the body is injured in any way, the germs
may succeed in growing. Then the body produces great
numbers of new white blood cells, and also develops anti-
toxins against the poisons of the disease (p. 386). Thus,
as a disease develops, the body usually increases its powers
of resistance, and so most cases of infectious diseases end
in recovery. The white blood cells finally overcome the
disease germs, the liver, skin, and kidneys throw off the
poisons of the disease, and thus the disease ends (p. 248).

Often the power of resisting and overcoming the germs
of a disease lasts for the rest of a lifetime. Thus a person
seldom has smallpox or scarlet fever or measles twice. In
some other diseases, as in diphtheria, the resistance lasts for
only a few weeks or months. If a person's body can pre-
vent the germs of a disease from growing, that person is
said to be immune to that disease.

721. Immunity. — A few persons are born with such a high resist-
ance to diseases that they escape measles, scarlet fever, whooping cough,
and other common diseases, although they may be exposed to them.
Other persons have such a low resistance to diseases that they readily
take diseases to which they may be exposed. Those who have adenoids

416

INFECTIOUS DISEASES 417

or large tonsils are likely to take diseases easily, for disease germs grow
readily in these tissues (p. 193). Our powers of resisting infectious
diseases are lessened by intemperance, overwork, improper food, or by
anything else which weakens the body. Our resistance to diseases can
be increased by good food, fresh air, exercise, and by anything else
which promotes the strength and vigor of the body.

722. Vaccines. — The body can be made immune to many dis-
eases. One way of producing the immunity is by growing the disease
germs outside of the body and then killing the germs and injecting them
into the flesh. The small quantities of toxins that are used do not pro-
duce even a slight sickness, and yet they rouse the body to resist the
disease just as if the person really had it. In vaccination against small-
pox the living germs of cowpox are used. The vaccines against small-
pox, erysipelas, and a few other diseases can be bought at drug stores.
We can also buy the antitoxins against diphtheria, lockjaw, snake poison,
and a few other diseases (p. 386).

723. How disease germs leave the body. — Few disease
germs can penetrate a healthy skin, either to enter or to
leave the body. So the skin has little to do with the
spread of diseases, except those in which the skin itself is
affected.

The most virulent forms of disease germs are given off
from the body in the discharges of the intestine and kid-
neys. In the days when all sewage was simply thrown
out of windows and doors every yard and street contained
great accumulations of filth, from which epidemics and
pestilences were widely- spread. The present rarity of
severe forms of epidemics is due largely to the cleanliness
of our houses and yards, and to proper sewage disposal.
Yet a great deal still remains to be done. Thus, in every
year improper sewage disposal still causes two or three
cases of typhoid fever among every thousand inhabitants
of the United States. The disposal of sewage is one of the
most important branches of government work (pp. 406-
408).

OV. PHYSIOL. — 27

4i8

APPLIED PHYSIOLOGY

The saliva and the mucus from the nose contain the germs in most
infectious diseases. In ordinary breathing we do not expel the germs
from the nose and mouth, but in talking and sneezing and coughing we
often expel tiny drops of liquid which may be full of disease germs.
These drops may dry in a moment, and then the germs may float in the
air as dust. The result is the same as if we had breathed the germs
directly into the air. Thus foul and dusty air usually contains disease
germs. Most infectious diseases are now spread by means of the dis-
charges from the nose and throat, for these two organs are in use during
every moment of our lives, while we can easily control the other means
by which germs leave the body.

724. Means of spreading disease germs. — Disease germs
are likely to be found on anything that has been soiled by
the discharges from the body. Dust and dirt containing

A safe form of public drinking
fountain.

An unsafe drinking place in a
public school.

the germs settle on our floors and carpets. Everything on
which saliva falls may contain the germs. The habit of
spitting spreads millions of germs. Soiled dishes, handker-
chiefs, towels, bedclothing, and underwear are all likely to

INFECTIOUS DISEASES 419

be covered with germs. Dirty water, impure milk, and
soiled food also spread the germs. If we observe the mod-
ern standard of cleanliness which is set by good society,
we shall keep ourselves free from most disease germs.

Many diseases are spread by the habit of putting things into the
mouth unnecessarily. Sucking the ends of the fingers, wetting the
fingers with the lips on turning the leaves of a book, and touching
the point of a pencil to the tongue on writing are often the means of
spreading diseases.

A grave source of danger is a public drinking cup. It is impossible
to take a cup between the lips without leaving saliva on the cup.
Germs of tuberculosis have often been found on cups in railroad
stations and schools. A public drinking fountain should be so arranged
that we may drink directly from a stream of running water without the
need of a cup.

725. The weather and infectious diseases. — When the
germs of an infectious disease grow in any part of the body, we often
say that we have taken cold there, but the expression is an uncertain
and indefinite one which came into use at a time when the weather was
supposed to cause epidemics and pestilences. Infectious diseases are
not caused by cold air, or dampness, or any other condition of the
weather, for disease germs are seldom found in the open air. During
cold, damp weather people often keep their doors and windows closed
tightly, and thus they breathe air which is foul and dusty and full of
disease germs. They are likely to have nose and throat troubles, and
lung diseases which they catch from the bad air of their houses and
not from anything wrong with the outdoor air. We may be as free
from colds and lung troubles in winter as in summer if we keep our
houses and meeting places as clean and well ventilated in cold weather
as in the summer time.

Hot weather is often supposed to cause intestinal diseases. These
forms of sickness are not due to the heat itself, but are usually caused
by spoiled food or by house flies.

726. Suppression of infectious diseases. — There are several
reasons why it is difficult to suppress infectious diseases entirely : —

i. A person who is just coming down with a disease may give its
germs to others before he knows that he has it. Thus measles may be

42O APPLIED PHYSIOLOGY

spread by a sick child before there are any signs to show that the
disease is anything more than a common cold.

2. Some persons may have a disease so mildly that they do not know
that they have it. Diphtheria and scarlet fever are usually spread from
this kind of cases, for bad cases usually receive care.

3. Germs of a disease may sometimes be found in the mucus and
folds of the nose and mouth of healthy persons who are immune, and
may spread from them to some one in whom they will grow. Diphtheria
is sometimes spread in this way.

4. We cannot always tell how soon a person is free from all germs
after he has recovered from a disease. Germs of typhoid fever may re-
main alive in the gall bladder for years, and thus a person who seems
entirely recovered from the disease may be the means of its spread to
others.

727. Fever. — While an infectious disease is coming on,
the body can throw off the toxins as fast as they are pro-
duced. When the germs have multiplied enormously,
some of the poisonous toxins will be retained in the body,
and then the disease suddenly develops. The toxins pro-
duce a headache and a great weakness of the whole body,
and cause the heart beats to become weak and rapid.
But the principal sign of an infectious disease is usually
fever. A fever is seldom caused by anything else than the
poisons of disease germs which are growing in the body.
The poisons, and not the increased heat of the body, are
what make a fever dangerous. We can easily lower the
temperature of a feverish person, but it does little good
^unless we also get rid of some of the poisons which cause
the fever (p. 263).

728. Cause of Colds. — The most common infectious
diseases are what are called colds. Colds are caused by
several kinds of disease germs which grow in the mucous
membrane of the nose and throat. The sickness usually
comes on after some part of the body has been wet or
chilled, but dampness and cold drafts do not make us take

INFECTIOUS DISEASES 421

cold unless we take disease germs into the body. The
germs come from persons who have a cold, and are found
in whatever is given off from the nose or throat. Tiny
drops of saliva and mucus are driven out with every
cough and sneeze, and when they are dried, their germs
float in the air as dust. Millions of the germs are scat-
tered through the air from every spot of dried phlegm
which has been spit upon the floor or pavement, and mil-
lions more may be spread from every handkerchief on which
the nose has been blown. Colds are extremely common,
and thus the germs are widely spread and are likely to be
found wherever the air is close and foul. Great numbers
float in the air of crowded meeting places, but those who
attend the meetings often suppose that they take cold
from drafts of fresh air, when the real cause is the germs
floating in the foul air. Fresh air is the best of all . pre-
ventives of colds.

729. Danger from colds. — A cold is usually a harmless kind of
sickness, but it is not always so. Some mild colds are caused by the
germs of the grippe, or of pneumonia, or of erysipelas, or of whooping
cough, and are the means of spreading the diseases to others in bad forms.
Many mild sore throats are caused by the germs of diphtheria which
may produce the disease in a deadly form in the next person who takes
the germs. Thus we should consider any cold to be serious, and should
do all that we can to prevent the germs from spreading.

730. Prevention and cure of colds. — Colds are spread
chiefly by means of dried sputum, just as tuberculosis is
spread, and may be prevented or cured in the same way
as tuberculosis (p. 392). A person who has a cold should
keep away from other people. He should sleep in a clean
room alone, and with a window open to admit fresh air
day and night. None of the phlegm should be spit upon
the floor or pavement, but it should be caught upon hand-
kerchiefs, and several clean ones should be used each day.

422 APPLIED PHYSIOLOGY

731. Tonsillitis. — The tonsils (p. 193) are often full of deep holes
and pockets, in which disease germs may collect and grow. Then the
holes may become filled with thick matter, so that the tonsils seem to be
spotted with whitish points. These spots are a sign of tonsillitis. Every
case of tonsillitis is infectious, and should be treated like a severe cold.

732. Diphtheria. — Diphtheria is an extremely danger-
ous disease whose . germs usually start to grow in the
tonsils, and there form a whitish patch which looks like
a scab on the skin. Sometimes the disease looks like a
mild tonsillitis, so that it can hardly be recognized. If a
patch covers the tonsils, or if it extends beyond the tonsils,
the disease is almost certainly diphtheria.

The germs of diphtheria produce toxins which are ex-
tremely poisonous to the heart, so that death often results
from the disease. The toxins usually make the throat sore,
but sometimes they paralyze the nerves so that no pain is
felt, and there are no signs that suggest a throat trouble.
Then the disease may not be noticed until it is too late to
be cured. Yet if the disease is severe, any one can easily
see the patches by looking into the throat. The disease
usually occurs in children, but grown people may also
take it.

733. Prevention of diphtheria. — Germs of diphtheria are
long-lived, and are hard to kill. They are found in everything which
comes from the nose and throat of a person who has the disease, and
they may rise as dust from anything on which they have dried. They
are likely to be shaken from bedclothes, handkerchiefs, and clothing,
and to settle on the carpets and furniture. So every person who has
diphtheria should be closely quarantined (p. 410). At the end of the
disease the room and everything which the sick person has used should
be disinfected and made free from the germs in the most thorough man-
ner (pp. 387 and 411). After the sick are entirely well they should not
mingle with other persons for at least two weeks, for a few germs may
still remain alive in the throat. The only way to be sure that no germs

INFECTIOUS DISEASES 423

are left in the throat is to send a specimen of the throat discharge to a
laboratory to see if the germs can be found.

734. Diphtheria antitoxin. — Antitoxin should be given
to every one who has diphtheria and to every person who
lives in a house where the disease is (p. 386). A small dose
of antitoxin will prevent the disease from developing in
any one who has just taken the germs into the body. If the
disease has already started, a larger dose will stop the
growth of the germs, but it will not overcome the damage

A syringe full of antitoxin, as it is sent from the laboratory.

that has already been done by the toxins. When it is used
early, it is an almost sure cure for the disease. Owing to
its extensive use, the number of deaths yearly from diph-
theria in New York State is less than half what it was
before the antitoxin was discovered. Nearly all of those
who now die either did not receive the antitoxin, or else
received it late in the disease. Its value is so great that
many states now furnish it free to those who are unable
to purchase it.

735. Pneumonia. — Disease germs growing in the lungs produce
the sickness called pneumonia (p. 401). Pneumonia is one of the most
frequent causes of death, and is always a serious disease from which
recovery is slow. Persons who have any kind of serious illness, such as

424 APPLIED PHYSIOLOGY

typhoid fever or the grippe, are also likely to take pneumonia if they
breathe foul or dusty air, or live in a room with any one who has a
bad cold. A common way of taking pneumonia is to breathe the foul
air of a hot, close room after becoming exhausted and chilled in stormy
weather. Pure air is the most essential thing in preventing pneumonia,
A pneumonia which is caused by the germs of tuberculosis is called
consumption (p. 389).

736. Whooping cough. — Whooping cough is due to a
kind of disease germ which is breathed into the nose and
throat. The toxins of the germs cause the sick person to
have short spells of coughing until he is out of breath.
Then he suddenly takes a breath so forcibly as to produce
a whooping noise. The disease is usually considered
harmless, and yet it often produces pneumonia and is the
cause of thousands of deaths each year. One who has
had the disease is usually immune to it for the rest of his
life. It seldom affects grown people, probably because
nearly everybody has it in childhood. It lasts from one to
three months, and may be given during the whole course
of the disease.

Whooping cough may be caught by being in a room
with a person who has the disease, and yet its germs are
not long-lived, and are not likely to be carried on the cloth-
ing, or to remain alive in a room after the disease is at an
end. It may be prevented by keeping the sick away from
those who have not had the disease. Every person who
has it should remain away from school, and church, and
other meeting places.

737. Inflamed wounds. — Germs of disease may enter the
flesh through any wound in the skin. The disease which
they cause is often called a cold in the wound, or an in-
flamed wound, or erysipelas, or blood poisoning. It may
be prevented by covering all wounds with clean, antiseptic

INFECTIOUS DISEASES 425

dressings (p. 400). Soldiers in time of war often die as
the result of inflammation in their wounds, but in the
great war between Japan and Russia few Japanese died
from this cause, for each soldier carried a case of dress-
ings and was taught how to apply the dressing at once
after receiving a wound.

738. Intestinal diseases. — Several kinds of disease germs
may grow in the intestine. The intestine increases its
peristalsis (p. 85) in an attempt to expel the toxins, and
thus the germs are the cause of abdominal pains, and
stomach aches, and dysentery.

Babies often suffer greatly from intestinal diseases, for
in them the toxins of disease germs are absorbed more
readily than in grown persons. The germs of intestinal
diseases usually enter the body with impure water or
spoiled food, or are deposited on the food by house flies
which come into our kitchens from filthy garbage heaps.
Intestinal diseases may be suppressed by attention to the
purity of drinking water and food, and by the extermi-
nation of house flies (p. 411). Owing to increased knowl-
edge in the care of milk, the amount of intestinal diseases
among babies has been greatly lessened (p. 1 10).

739. Typhoid fever. — One of the most serious forms of sick-
ness which is caused by impurities in drinking water and food is typhoid
fever. The disease is like a severe and prolonged dysentery, and is the
cause of thousands of deaths each year.

We take typhoid fever only by swallowing the germs which have
grown in the intestine of a sick person. The germs are given off in
the discharges from the body of any one who has the disease. They
may remain alive in garbage heaps and slops and sewage, and so may
reach our drinking water, or be carried to our food by house flies.
They may also be deposited on dishes or milk cans which have been
washed in impure water.

Typhoid fever may be prevented by proper sewage disposal and the

426 APPLIED PHYSIOLOGY

extermination of house flies. It is not carried by the air or the dust
of the sick room, and so quarantine of the sick room is not necessary.
But it may be carried by soiled bedclothes, or on the hands of the
nurse. It is necessary to be careful in the cleanliness of everything in
the sick room, and to dispose of all slops and sewage in such a way that
the germs in them cannot escape.

Cholera is an intestinal disease which is spread in the same way as
typhoid fever. It is seldom seen in civilized lands, but is common
among people who drink river water which is full of sewage.

740. Mumps. — Mumps is caused by the growth of a
kind of microbe in the salivary glands, producing swellings
around the lower jaw. It seldom causes a severe illness.
Its germs are not long-lived and do not readily spread.
The disease may be suppressed by keeping the sick away
from well persons, and by washing their dishes and towels
and handkerchiefs separately from those used by other
persons.

741. Eruptive diseases. — There are a number of infec-
tious diseases in which spots appear on the skin. For this
reason they are called eruptive diseases. The common
eruptive diseases are measles, scarlet fever, chicken pox,
and smallpox. A person who has had one of these dis-
eases is usually immune to it for the rest of his lifetime.

The eruptive diseases are caused by germs whose exact nature has
not been discovered. The germs may live in clothing, or carpets, or
other things which are laid away in a dark, close room, but they soon
die when they are exposed to the sunlight and fresh air. The dis-
eases are usually spread by well persons living in the same room or
house with the sick, or by using some article which the sick have
handled. They may be suppressed by closely quarantining the sick,
thoroughly cleansing everything in the sick room, and properly dis-
posing of all slops and sewage from the sick. The chief obstacle in
the way of entirely stamping out the diseases is the great difficulty of
recognizing extremely mild cases of the diseases in which few or no
spots are seen.

INFECTIOUS DISEASES 427

742. Measles. — Measles starts like a common cold, and
on about the fourth day of the disease red spots appear
over the whole body. The sickness is so mild that little
attempt is usually made to control its spread. Yet it may
weaken the body so that pneumonia, kidney diseases, and
other severe forms of sickness may follow it, and thus it
is the cause of thousands of deaths each year. Its germs
are not usually long-lived. The disease would soon be
suppressed if every case of measles were kept away from
other persons for two weeks, and if everything about the
sick room were kept clean and well aired.

743. Scarlet fever. — Scarlet fever is one of the most
dangerous of the contagious diseases, and yet it does not
cause more deaths than measles, for most persons fear it
and take pains to suppress it when it appears in a town.
It usually comes on suddenly and produces vomiting and
pains in the head and back. Fine red spots appear on the
skin within a day or two, and there is a sore throat due to
spots in the mouth. After the disease is at an end, coarse
flakes of the outer skin peel off for two or three weeks, in
even the mildest cases. When we are in doubt if a person
has the disease, we should wait to see if the skin peels off.
Scarlet fever may be suppressed by strict quarantine and
cleanliness.

744. Chicken pox. — Chicken pox is a common disease in which
small spots like blisters appear on the skin. It seldom causes a severe
sickness, and yet it is important, for it closely resembles mild smallpox.
It is very rarely seen in grown persons, and so if a grown person seems
to have it, the disease is likely to be smallpox. It may be suppressed
by keeping the sick at home and away from those who have not had it.

745. Smallpox. — Smallpox was once one of the most
common and deadly of all forms of sickness. Before the
year 1800 it had often swept over Europe in waves of

428 APPLIED PHYSIOLOGY

pestilence from which few persons escaped, and had
almost exterminated the native tribes of some parts of
America ; but since that time it has been largely controlled
owing to the wide use of a method of conferring immunity
to the disease.

Smallpox begins as a painful fever, and in about four days the skin
breaks out with raised spots which become filled with a creamy pus, and
leave deep scars at the end of the disease. The disease sometimes
occurs in a mild form which is mistaken for chicken pox, and yet those
who take it from these mild cases may have it in its most severe form.

Smallpox usually spreads directly from the sick to those who come
near them. Clothing and other things which the sick have handled
may also be the means of spreading the disease even months after the
sick are well, for the germs are long-lived if they are kept from the air
and sunlight. Every case of smallpox should be closely quarantined,
and nothing should be taken from the sick room unless the germs on it
are destroyed.

Vaccine.

On bone points, inclosed in glass cases. In liquid form, in a small sealed tube.

746. Vaccination. — There is a mild disease among cows
called cowpox or vaccinia, in which the skin breaks out as
in a mild smallpox in man. If a bit of the matter from one
of the sores is rubbed upon a scratch on a person's arm
the germs produce a sore spot on the skin, and at the same

INFECTIOUS DISEASES 429

time they cause the body to produce substances which will
prevent the growth of smallpox germs in the person. This
method of immunizing the body is called vaccination, from
the name of the disease in cattle. It was discovered by
an English physician named Edward Jenner.

It is doubtful if quarantine and attention to hygiene would be sufficient
to prevent the spread of smallpox, for mild cases sometimes occur which
are not recognized until some one catches the disease in a bad form.
Vaccination is an almost sure protection against these unrecognized
cases, and very few vaccinated persons who are exposed to severe
smallpox take the disease. Every child should be vaccinated before
going to school and again a few years later. Objection is often made
to vaccination because it has sometimes been followed by severe sick-
ness when it has been done with impure vaccine or in a dirty manner.
Pure vaccine can now be bought at most drug stores. If it is used in a
clean manner, and the vaccinated spot is kept clean, there are no bad
results after vaccination.

747. Lockjaw. — Lockjaw ', or tetanus, is caused by a kind
of bacteria which grow in a wound. Their toxins poison
the nerve cells so as to produce convulsions which usually
end in death. The bacteria are often found in the soil of
gardens and roads, and reach our flesh through wounds.
They cannot grow in the presence of much air, and so they
seldom grow in clean, open wounds, but they are likely to
grow where they are thrust deep into the flesh, as by dirty
nails. They are also likely to grow in wounds made by
fireworks on the Fourth of July, for the dead and burned
flesh keeps out the air. Lockjaw can usually be prevented
by covering all wounds with clean antiseptic dressings.
An antitoxin against lockjaw can be bought at drug stores,
and should be given soon after a person receives a wound
in which there is dirt from soil.

748. Rabies. — Rabies, or hydrophobia, is a deadly form of sick-
ness which resembles lockjaw, and is caused by large germs which are

430 APPLIED PHYSIOLOGY

found in the cells of the brain, and in the saliva. It is caught from the
bite of dogs or cats which have the disease. It is spread mostly by
means of homeless animals. Dogs running loose should be muzzled, and
stray ones should be caught by a public dog catcher. If a person is bitten,
the animal should be securely shut up to see if it has the rabies. If it has
the disease it will soon die, but if it remains alive the wound is no more
serious than one made by a needle. The germs in a bite may be killed
by opening the wound and cauterizing it to the very bottom. In those
bitten by a rabid animal the disease may be prevented by injecting an
immunizing substance prepared from rabbits which have been given the
disease. This substance may be had by application to the boards of
health of the greater cities.

749. The plague. — The black plague is a pestilence
which has often appeared in Europe. It killed half the
inhabitants there in the fourteenth century. It still
exists in some parts of the world, and is as deadly as
ever when it is allowed to go unchecked. It is due to-
bacteria which produce swellings and abscesses in the
flesh. It seldom spreads from one person to another, but
the bacteria are carried from rats, which have the disease,
to persons by means of fleas. Its control and suppression
depend principally on the extermination of rats.

750. Hook-worm disease. — A kind of intestinal worm
called the hook worm produces a sickness in which there
is an intense feeling of lifelessness or laziness. The
worms lay eggs which hatch in the ground. The young
bore their way through the skin and finally fasten them-
selves by tiny hooks to the inside of the intestine and be-
come about a half an inch in length. They produce
their bad effects by sucking blood from the mucous mem-
brane. They may be killed by medicines which kill other
intestinal worms. The disease may be prevented by dis-
posing of all sewage so that the eggs and young worms
cannot reach the soil where people work. Cleanliness and

INFECTIOUS DISEASES 431

wearing shoes are also necessary in order to keep the
young worms away from the skin. The disease is widely
spread in the warmer parts of the United States, and is
the cause of much suffering which was once supposed to
be due merely to shiftlessness and laziness.

SUMMARY

1. Infectious diseases are common during cold and damp

weather because then people shut themselves in close
rooms containing disease germs.

2. Disease germs may spread from a mild case of infec-

tious disease as well as from a severe case.

3. Resistance in infectious diseases can be increased by

anything which promotes the vigor of the body.

4. The germs of infectious diseases are found in the dis-

charges from the bodies of the sick.

5. Quarantine and proper sewage disposal are necessary

in suppressing infectious diseases.

6. The toxins of disease germs cause a fever.

7. Colds are caused by disease germs, and are infectious.

8. A person who has diphtheria should be quarantined

and should receive antitoxin.

9. Vaccination is the only safe and sure preventive of

smallpox.

10. Antitoxin is a safe and sure preventive of diphtheria.

1 1. Typhoid fever and other intestinal diseases are spread

by impure water and milk, and by house flies.

12. Rats and stray dogs are a menace to health.

DEMONSTRATIONS

183. Show the class specimen vaccine points and tubes of antitoxin
borrowed at a drug store. Explain the ease-and safety of their use.

184. Show a thermometer which is used in taking the temperature
of the body, and explain how it is used.

432 APPLIED PHYSIOLOGY

185. Trace the origin and cause of the colds of some of the mem-
bers of the class. Determine which were evidently caused by exposure
to dampness and cold air, and which were due to breathing foul air or
contact with other persons who had colds.

REVIEW TOPICS

1. Explain why infectious diseases seem to be largely,

due to the weather.

2. Give some reasons why it is difficult to suppress in-

fectious diseases entirely.

3. What is meant by immunity f How may it be in-

creased ?

4. How may we increase the power of our body to resist

the growth of disease germs ?

5. How do vaccines and antitoxins produce immunity

to a disease ? Discuss their use.

6. Mention some of the means by which disease germs

may be spread from a sick person.

7. What is the cause of fever ?

8. Discuss the cause and prevention of colds.

9. Why should we consider a cold to be a dangerous

form of sickness ?

10. How may we recognize that a person has diphtheria?

How can we prevent the disease ?

1 1. How may we prevent pneumonia ?

12. How may we prevent erysipelas ?

13. Discuss the advisability of quarantining every case of

whooping cough, measles, mumps, and chicken pox.

14. What are some of the usual causes of intestinal

diseases ?

15. What methods should be taken to prevent the spread

of scarlet fever, diphtheria, and smallpox ?

1 6. Discuss the cause and prevention of lockjaw ; of rabies ;

of hook-worm disease.

CALIFORNIA COLLEil
of PHARMACY

GLOSSARY.

Ab-do'men (Lat. abdomen, belly), the cavity of the body which contains
the stomach, intestine, liver, pancreas, and spleen.

Ab'scess (Lat. abs, away, and cedere, to move), a collection of dead
creamy matter in the flesh of a living person.

Ab-sorp'tion (Lat. ab, away, and sorbere, to soak in), taking a substance
into the tissues of the body, without change in its composition.

Ac-com-mo-da'tion (Lat. ad, to, con, with, and modus, measure), adjust-
ing the lens of the eye to the proper shape to cause the image of an
object to fall upon the retina.

A'cid (Lat. acere, to sour), any sour, irritating substance, which will
corrode other substances.

A'con-ite (Gr. akoniton, the plant commonly called monkshood), an
extremely poisonous plant. It is used to lower fevers. In over-
doses it produces extreme weakness of the whole body.

Ad'e-noid vegetations (Gr. aden, gland, and eidos, form), collections of
soft, grape-like bodies growing in the upper part of the pharynx.
They are common in children.

A-dul'ter-ate (Lat. ad, to, and alter, another), to make impure by an
admixture of an inferior substance.

Al-bu'min (Lat. albus, white, because it generally turns white when
heated), a term applied to a class of substances, some form of which
is the essential part of every living cell. It is composed of the
elements carbon, hydrogen, nitrogen, oxygen, and sulphur. The
form of albumin which is found in the white of an egg is spelled
albumen.

ATco-hol (Ar. al-kohl, a powder of antimony used in painting the
eyebrows), on account of its extreme fineness the name came to be
applied to the product formed by repeatedly distilling wine, for this
was supposed to be the real " spirits " of the wine.

ov. PHYSIOL. — 28 433

434 GLOSSARY

Al-i-men'ta-ry (Lat. alere, to feed), having nourishing qualities capable
of being used as a food, or pertaining to food.

Al'ka-li (Ar. al, the, and kali, a plant whose ashes were used in making
glass), a substance whose properties are in contrast with those of
an acid. An alkali forms soap when united with an oil.

ATka-loid (Ar. alkali, and eidos, form), the substance in certain vege-
table drugs which gives the drugs their characteristic qualities. A
small dose of an alkaloid produces the same effect as a large dose
of the drug from which it is derived.

A-me'ba (Gr. amoibe, change), the simplest form of animal life, con-
sisting of a single lump of jelly, capable of changing its shape at will.

Am-y-lop'sin (Gr. amulon, starch), the ferment in the pancreatic
juice which changes starch to glucose.

A-nat'o-my (Gr. ana, up, and temnein, to cut), the science which tells
of the structure of living bodies.

An-e'mia (Gr. a, without, and haima, blood), the state of the blood in
which there are too few red blood cells and too little plasma.

An-es-the'si-a (Gr. an, not, and aisthanesthai, to perceive), a tempo-
rary lack of sensibility produced by drugs.

An'ti-dote (Gr. anti, against, and didonai, to give), a substance which
prevents a poison from acting upon the cells when it is introduced
into the body.

An-ti-sep'tic (Gr. anti, against, and sepein, to rot), a substance which
prevents the growth of bacteria, and hence prevents rotting.

An-ti-tox'in (Gr. anti, against, and toxikon, poison), a substance which
is produced in the body to overcome the poison of a disease. It is
commonly applied to a substance used in the treatment of diphtheria.

An'trum (Gr. antron, a cave), the hollow cavity within the upper jaw
bone.

A-or'ta (Gr. aeirein, to lift up), the large artery which rises from the
left side of the heart, and distributes blood to all parts of the body.

Ap-O-plex'y (Gr. apo, from, and plessein, to strike), a sudden loss of
consciousness, usually due to pressure upon the brain caused by a
burst artery.

Ap-pen-di-ci'tis, inflammation of the vermiform appendix.

Ap'pe-tite (Lat. ad, to, and peter e, to seek or long for), a strong desire
for something. It is used mainly of the desire for eating and drinking.

A'que-ous hu'mor (Lat. aqua, water, and humor, a liquid), the liquid
which fills the eyeball in front of the lens.

GLOSSARY 435

Ar'gon (Gr. a, not, and ergon, work), a gas (discovered in 1894) which
forms about one per cent of the air. It resembles nitrogen.

Ar'sen-ic (Gr. arsenikori), a gray metal whose combinations with oxy-
gen are very poisonous.

Ar'ter-y (Gr. aer, air, and terein, to hold), the tubes which conduct
blood to the cells of the body. After death they are empty, and it
was formerly supposed that in life they contained only air.

As-phyx'i-a (Gr. a, not, and sphuzein, to throb), death by suffocation.

As-sim-i-la'tion (Lat. ad, to, and similis, like), the process of chang-
ing digested food to substances like those which compose the body.

A-stig'ma-tism (Gr. a, not, and stigma, a point), the condition of art
eye in which one part of the rays are brought to a focus sooner than
another part.

Au'ri-cle (Lat. auris, an ear), the upper two cavities of the heart.
They are thin and resemble dog's ears.

Bac-te'ri-um (pi. bacteria) (Gr. bacterion a staff), the simplest and

smallest form of plant life, consisting of a tiny sphere or rod. Some

kinds can grow in the human body and produce disease.
Bel-la-don'na (Ital. bella, beautiful, and donna, lady), an herb which

produces excitement of the brain and great weakness. It enlarges

the pupils of the eyes, and was formerly used by ladies to render

themselves more beautiful.
Bi'ceps (Lat. bis, twice, and caput, head), the muscle upon the front of

the upper arm which bends the elbow. Its upper end has two

branches.
Bi-chlo'ride of mer/cu-ry, a compound of .mercury and chlorine. It

is very poisonous especially to bacteria of disease. When dissolved

in water in the proportions of one part to five thousand, it kills

disease germs.
Bi-cus'pid (Lat. bis, twice, and cuspis, a point), the fourth and fifth

teeth from the middle upon each side of each jaw ; each bicuspid

ends in two points.
Bile (Lat. bills), a yellow, bitter fluid formed by the liver cells and

poured into the intestine. It is a part of the waste of the body,

but while it is being excreted it assists the pancreatic juice and

intestine in performing their work.
Bil-i-ru'bin (Lat. bills, bile, and ruber, red), the coloring matter of

the bile. It consists of broken down hemoglobin.

GLOSSARY

Blad'der, a thin muscular bag in which a fluid is stored in the body.
It is especially applied to the bag in the pelvis containing urine.

Brain, the mass of nerve cells and nerve fibers which is inclosed with-
in the skull. It is the seat of the consciously acting mind.

Bright's disease, almost any disease of the kidneys. Dr. Bright
gave the first true description of kidney diseases. He died in
1858.

Bron'chus (Gr. brogchos, the windpipe), one of the numerous branches
into which the trachea divides. It is applied to the smallest sub-
divisions as well as to the two main branches.

Bun'ion, a swelling of the great toe joint caused by tight shoes.

But'ter-ine, artificial butter made from butter and suet.

Cae'cum (Lat. caecus, blind), the blind or closed end of the large
intestine ; the small intestine opens into the side of large intestine
about an inch from its end.

•Caf-fe-ine (ka-f^in)^ a white, bitter alkaloid obtained from coffee.

Callus (Lat. callus), hard and thickened epidermis. It is caused by
rubbing a part during hard work, and is nature's way of protecting
.the deeper parts from injury.

Can-cel'lous (Lat. cancelli, a lattice), having an open or porous struc-
ture.

'Cap'il-la-ry (Lat. capillus, a hair), a hair-like blood tube. Capillaries
surround each cell of the body. From them plasma and oxygen
go out from the blood to nourish the cells.

-Car-bol'ic acid (Lat. carbo, coal, and oleum, oil), a poisonous sub-
stance obtained from coal tar. It is commonly used to kill dis-
ease germs and to prevent decay.

'Car'bon (Lat. carbo, coal), a substance, of which the diamond is the
pure crystallized form. Coal, charcoal, and lampblack are more
common forms. Combined with other substances it is a part of
the bodies of all animals and plants.

•Car-bon'ic acid gas, a heavy, colorless gas formed when carbon burns.

Car'di-ac (Gr. kardia, heart), pertaining to the heart. It is also
applied to the left end of the stomach, which lies just under the
heart.

•Car'pal bones (Gr. karpos, wrist), the bones of the wrist.

Car'ti-lage (Lat. cartilago), the soft substance commonly called gristle
which covers the ends of bones within joints.

GLOSSARY 437

Casein (ka'se-iri) (Lat. caseus, cheese), the part of the albumin of
milk which forms the curd or clabber. In cow's milk nearly all
the albumin is casein. The remaining albumin coagulates and
forms a scum when the milk is heated.

Cat'a-ract (Gr. kata, down, and rhegnunai, to break), a cloudiness of
the lens of the eye which shuts out the light.

Catarrh (katar1) (Gr. kata, down, and rhein, to flow), an excessive
production of mucus from the nose and throat.

Cells (Lat. cella, a cavity), the smallest particles of the body capable of
fulfilling the tests of life.

Cellu-lose (Lat. cellula, a little cell), a substance which forms most of
the framework of vegetable tissues.

Ce-ment' (Lat. caementum, a builder's stone), the soft bone-like sub-
stance which fixes the teeth in their sockets in the jaws.

Cer-e-bel'lum (Lat. cerebellum, little brain), the rounded part of the
brain situated under the cerebrum and above the medulla. It
assists the brain to direct precise movements, as movements ii>
which the body is balanced.

Cer'e-brum (Lat. cerebrum, brain), the uppermost part of the brain.
In man it covers all the rest. It is the seat of consciousness and
of thought. It receives all sensations, and sends all voluntary im-
pulses to produce motion.

Chem/is-try, the science of the composition of substances. It is
concerned in destroying or decomposing substances, and in form-
ing new substances having different properties from the original
substances.

Chlo'ral (klo'ral), a substance made from chlorine and alcohol and used
to produce sleep.

Chlo'ride (klo'ride), a combination of the gas chlorine with another
substance. Chloride of lime is used to kill disease germs. Chlo-
ride of sodium is common salt.

Chlo'ro-form, a volatile liquid made from chlorine and /0r;//y/. When
its vapor is inhaled for some minutes it produces a deep sleep and
complete insensibility to pain. When its inhalation is stopped,,
consciousness soon returns. It is used in surgical operations.

Chlo'ro-phyll (Gr. chloros, green, and phullon, leaf), the green coloring
matter of leaves. It forms starch out of carbonic acid and water.

Chol'e-ra (Gr. chole, bile), a contagious disease of the intestine in which
there is great pain, and an increased excretion and peristalsis.

438 GLOSSARY

Cho'roid (Gr. chorion, skin, and eidos, form), the middle lining of the
eye. It carries the blood vessels for the nourishment of the inner
parts of the eye.

Chyle (kile) (Gr. chulos, juice), the liquid produced by intestinal di-
gestion.

Chyme (kime) (Gr. chumos, juice), the partly digested contents of
the stomach as they enter the intestine. The word is falling into
disuse.

Cilia (sil'i-a) (Lat. cilia, eyelashes), microscopic hairs upon the surface
of certain cells. They are in constant motion to sweep out secre-
tions and dust. They line the trachea and bronchi.

Clab'ber, or bonny-clabber (Irish baine, milk, and clabar, mud), sour
and curdled milk.

Clav'i-cle (Lat. dams, a key), the slender bone which extends from the
breast bone to the shoulder. The collar bone.

Co-ag-U-la'tion (Lat. con, together, and agere, to force), the process
of changing a liquid to a solid form of a different nature from the
original liquid. Thus in curdled milk coagulation has taken
place.

Cocaine (kdca-iri), a bitter, white substance obtained from coca. It
benumbs pain when applied to the nerves and produces excitement
of the brain.

Coccyx (kok 'six) (Gr. kokkux, a cuckoo), the small bone which forms
the lower end of the backbone. It is shaped somewhat like a
cuckoo's bill.

Cochlea (kok'le-a) (Lat. cochlea, snail shell), the coiled canal of the
inner ear in which the nerves of hearing end.

Cold, an unhealthy state of a part of the body caused by exposure to
coldness and dampness. It is an increased activity of the cells and
an increased blood supply due to nature's attempt to repair the
injury caused by the exposure. The injury is usually due to the
growth of disease germs. fc

Colon (Gr. kolon), the large intestine.

Con-ges'tion (Lat. con, together, and gerere, to bring), overfullness of
the blood tubes of a part of the body. It is the first stage of repair
of wounds and of inflammation, and is nature's way of supplying an
excess of nutrition to repair an injured spot.

Con-junc-ti'va (Lat. conjunctions, joined together), the mucous mem'
brane lining the eyelids and covering the front of the eyeball.

GLOSSARY 439

Connective tissue, the stringlike cells scattered through the whole

body to keep the other cells of the body in place.
Conservation of energy, the law that no force is destroyed, but can be

recovered as heat, electricity, motion, or in other forms.
Contagious disease (kon-ta'jus) (Lat. contagio, a touch), an infectious

disease which can be transmitted through the air.
Con-trac'tion (Lat. con, together, and trahere, to draw), the shortening

and thickening of a muscle to produce movement in a part of the

body.

Cook (Lat. coqiiere), to prepare food by the use of heat.
Cor'ne-a (Lat. corneus, horny), the round, bulging window in the front

of the eyeball through which light enters the eye.
Cor'pus-cle (Lat. corpusculum, a little body), one of the cells which float

in the plasma of the blood.
Cra'ni-al (Gr. kranion, skull), pertaining to the contents of the skull

or brain.
Cricoid cartilage (Ikrfkoid} (Gr. krikos, a ring, and eidos, form), the

ring which forms the lower part of the larynx.
Cud, the food which most cloven-hoofed animals bring up from the

stomach to chew the second time.
Cu'ti-cle (Lat. cuiicula, little skin), the outer and insensitive layer of

skin. The epidermis.
Cu'tis (Lat. cutis, skin). A more common name is the derma.

Deglu-ti'tion (Lat. de, from, andgtutire, to swallow), swallowing.

De-lir'i-um (Lat. delirart, to rave), a state of mind in which judgment
and reason are disordered and illusions of the senses are present.
It is usually caused by fevers.

Delirium tre'mens, a form of delirium which occurs in drunkards. It
causes the sufferer to struggle violently to escape the torments of his
imagination.

Der'ma (Gr. derma, skin), the true skin, or the part beneath its insen-
sitive covering.

Di'a-phragm (Gr. dia, through, and phragnunai, to fence), the muscu-
lar partition extending across the cavity of the body and dividing
the chest from the abdomen. It is the main muscle of breathing.

Diastole (di-as'to-le) (Gr. dia, through, and stellein, to place), the
relaxation of the heart during which it is being filled with blood in
preparation for another beat.

44O GLOSSARY

Diffusion (Lat. diffusio), the act of passing through membranes appar-
ently impervious. Thus, peptone passes by diffusion through the sides
of the blood tubes in the walls of the intestine, and reaches the blood.

Di-ges'tion (Lat. dis, apart, an&gerere, to carry or wear), changing food
into such forms that it can pass through the walls of the blood
tubes and become a part of the blood.

Diph-the'ri-a (Gr. diphthera, leather), an infectious disease in which
there is a skin-like membrane covering the affected part, usually the
throat.

Dis-lo-ca'tion (Lat. dis, apart, and locare, to locate), the separation of
two bones whose union forms a joint.

Dis-til-la'tion (Lat. de, from, and stillare, to drop), the process of sepa-
rating a substance which easily becomes a vapor from one which
forms a vapor less easily. Heat is applied to the substance, and
the vapor is cooled or condensed to a liquid in a coil of tube from
which it runs in drops, and hence the name. As far back as the
year 1200 the process was used by the Arabs in their endeavors to
find an essential spiritual principle which would sustain life and
restore youth.

Drop'sy, a uniform swelling of a part without pain or redness. It is
an accumulation of lymph due to a disturbance in the circulation of
the blood.

Duct (Lat. ducere, to lead), any tube which conducts a secretion away
from a gland.

Du-o-de'num (Lat. duodeni, twelve), the beginning of the small intes-
tine for the length of about twelve finger breadths.

Du'ra ma'ter (Lat. dura, harsh, and mater, mother), the periosteum
lining the skull. It is very thick and sends prolongations into the
main fissures of the brain to hold the brain in place.

Dys-pep'si-a (Gr. dus, ill, and peptein, to cook or digest), imperfect
digestion of the food.

E-mul'sion (Lat. e, out, and mulgere, to milk), a milky-looking liquid

consisting of microscopic drops of oil floating in a liquid.
En-am' el, the hard calcified tissue which covers the exposed parts of

the teeth.
En'er-gy (Gr. en, in, and ergon, work), any force which can be made

to do work. The energy of the body can be traced to oxidation

within the cells.

GLOSSARY 441

Ep'i-der'mis (Gr. epi, upon, and derma, skin), the thin insensitive
layer of cells upon the outside of the skin. It is sometimes called
the cuticle.

Ep-i-glot'tis (Gr. ept, upon, and^&taz, the tongue), the leaf-like lid upon
the back of the tongue which closes the larynx when swallowing.

Ep'i-lep-sy (Gr. epilepsis, a seizure), a disease in which, at intervals
a person suddenly falls to the ground unconscious, while all the
muscles of the body contract strongly.

Ep-i-the'lium (Gr. epi, upon, and thele, nipple), the cells which cover
the skin and mucous membrane and line the tubes of glands. Epi-
thelium is a protection for the body, and does all the work of secre-
tion and absorption.

Er-y-sip'e-las (Gr. erutkros, red, and pella, skin), a disease of the
skin in which there is pain, redness, and swelling. It is caused by
the growth of bacteria of disease in a wound. It varies in severity
from a simple maturated scratch to a severe blood poison.

E-soph'a-gus or ce-soph'a-gus (Gr. otso, I shall carry, and phagein, to
eat), the tube connecting the mouth with the stomach.

E'ther (Gr. aithein, to burn), a colorless liquid which evaporates with
such great rapidity that its vapor may catch fire if near a lamp. It
is used to dissolve gums, and also, like chloroform, to produce in-
sensibility during surgical operations.

E'ther (Lat. aether, the upper pure air where the gods abode, in dis-
tinction from the lower or true air in which man lived), the sub-
stance which is supposed to pervade all space, and whose vibrations
are supposed to form light, heat, and electricity.

Eustachian tube (yu-sta'ki-ari), the tube leading from the middle ear
to the pharynx. It is named after its discoverer, Eustachi, an
Italian physician, who died in 1574.

Ex-cre'tion (Lat. ex, out, and cretus, sifted), a waste substance extracted
from the blood by the epithelium of a gland.

Ex-pi-ra'tion (Lat. ex, out, and spirare, to breathe), breathing out air
from the lungs.

Ex-ten'sor muscles (Lat. ex, out, and tender e, to stretch), the muscles
which straighten limbs.

Fat, a white greasy substance composed of carbon, hydrogen, and

oxygen, but with much less oxygen than is in starch.
Fe'mur (La&. femur), the thigh bone.

442 GLOSSARY

Fer'ment (Lat. fervimentum, boiling), a substance a small amount of

which produces a chemical change in a large amount of another

substance without losing its own identity or characteristics. During

the process the most common ferment — yeast — liberates bubbles

of gas, like a boiling.
Fe'ver (Lat. febris, a fever), increased warmth of the body due to poisons

of disease.
Fi'brin (Lat.y££r#, a thread), the stringy threads of coagulated blood

albumin which permeate the blood and imprison its cells and plasma,

causing it to become jellylike or clotted.
Fib'u-la (Lak. fibula, clasp), the long bone upon the outside of the shin

bone.
Fil-tra'tion (Lat. feltrum, felt), separating a solid from a liquid by

straining it through a porous substance.

Fis'sure (Lat. fissura, a cleft), one of the deep furrows upon the sur-
face of the brain.
Fit, a sudden state of unconsciousness and of contraction of the muscles

lasting only a minute or two. Epilepsy is a kind of fit.
Flex'or muscles (Lat. flectere, to bend), muscles which bend

the limbs.
Fo'cus (Lat. focus, a fireplace), the point where rays of light come

together when passed through a lens.
Food, anything which is assimilated by the body, and gives it weight,

heat, or energy. The term includes water and mineral matter as

well as vegetable and animal substances.
Front'al (Lat. frons, the forehead), pertaining to the region of the skull

or brain behind the forehead.
Furcrum (Lat. word meaning a prop), the fixed support around which

a lever turns.

Gall (gawl}, a name applied to the bile while it is stored in the bag

under the liver.
Gan'gli-on (Gr. gagglion, a knot), a collection of nerve cells in the

sympathetic system. Each looks like a grain kernel.
Gas' trie (Gr. gaster, stomach), pertaining to the stomach.
Gelatine (jel'a-tin) (Lat. gelare, to harden), a kind of albumin which

forms the principal part of connective tissue. It will dissolve in

hot water, and forms a jellylike or solid mass when cold. Glue is

an impure form.

GLOSSARY 443

Germs (Lat. germen, a bud), a name loosely applied to bacteria.

Giz'zard, the muscular organ in a fowl's abdomen which grinds food to
pieces and acts in place of teeth.

Gland (Lat. glans, an acorn), a collection of microscopic tubes which
form a watery substance within the body.

Glu'cose (Gr. glukus, sweet), a form of sugar found in the grape, and
produced artificially by the action of sulphuric acid on starch ; it is
also produced in the body by the action of the digestive fluids upon
starch and sugar.

Glu'ten (Lat. gluten, glue), the albumin of grain.

Gly-co-chol'ic acid (Gr. glukus, sweet, and chole, bile), one of the prin-
cipal waste substances in the bile.

Gly' co-gen (Gr. glukus, sweet, and genein, to generate), a form of
sugar to which digested sugar and starch is turned by the liver.

Gout (gawf) (Lat. gutta, a drop), a swelling of a joint, especially of the
great toe, caused by a disturbance of digestion and oxidation. It
was formerly supposed to be due to a fluid or humor which flowed
down in drops from the upper parts of the body.

Grippe (grip} (Fr. grippe, influenza), a kind of fever which occurs in
epidemics. It is caused by the growth of a germ in the body.

Hash'eesh, the gum of a kind of hemp. It produces an excited and
dreamy state of mind.

Ha-ver'si-an canals, the minute tunnels in bone through which the
arteries run. They were discovered by Havers, an English physi-
cian, who lived in the seventeenth century.

Hem-o-glo'bin (Gk. haima, blood, and Lat. globus, a ball), the coloring
matter of the red blood cells.

Hem-o-phiri-a (Gr. haima, blood, and philein, to love), a state of the
blood in which it will not clot.

Hem'or-rhage (Gr. haima, blood, and rhegnunai, to break), a flow of
blood from a blood tube.

Hi-ber-na'tion (Lat. hibernus, wintry), passing the winter in a torpid
state, as frogs and snakes do.

Hu'mer-us (Lat. humerus), the long bone in the upper part of the arm.

Hu'mors (Lat. humor, moisture), substances which were formerly sup-
posed to circulate in the blood and to cause disease.

Hy-dro-chlor'ic acid, a compound of hydrogen and chlorine, commonly
called muriatic acid. It is a violent poison.

444 GLOSSARY

Hy-dro-gen (hy'dro-jen) (Gr. hudor, water, and genein, to generate), a
light, colorless gas. When ignited it unites with oxygen to form water.

Hygiene (hy'ji-een) (Gr. hugieinos, healthy), the science which tells
how to keep living bodies in good working order.

Hy-po-der'mic injection (Gr. hupo, under, and derma, skin), the intro-
duction of a solution under the skin by means of a hollow needle
and syringe. The solution fills the lymph spaces and is absorbed
into the capillaries or enters the circulation by way of the
lymph.

Hys-te'ri-a, a nervous disease in which there is great lack of self-con-
trol. The sufferer easily gives way to the emotions, and especially
to those of sorrow or mirth.

Il'e-um (Gr. eilein, to twist), the lower half of the small intestine.

In-ci'sor £eeth (Lat. inddere, to cut into), the teeth in front, with which
food is bitten into.

Incus (irikus) (Lat. incus, anvil), the middle bone of the chain in the
ear drum, which transmits waves of sound from the drumhead to
the inner ear.

Jn-fec'tious disease (Lat. in, in, and facere, to make), a disease which
has for its cause some matter which can multiply and grow when
introduced into the body of a healthy man.

In-flam-ma'tion (Lat. in, in, and flamma, a flame), redness, swelling,
pain, and increased heat in a part as a result of injury. It is nature's
attempt to repair the part. Often it goes on to form matter.

In-san'i-ty (Lat. in, not, and sanus, safe), unsoundness of mind per-
sisting for a considerable time.

In-spi-ra'tion (Lat. in, in, and spirare, to breathe), taking a breath
into the lungs.

In-tem'per-ance (Lat. in, not, and temper are, to regulate), gratifica-
tion of a desire which does not denote a real need of the body.

In-tes'tine (Lat. intus, within), the long tube in the abdomen in which
digestion of food is completed after it leaves the stomach.

In-tox-i-ca'tion (Lat. in, in, and toxicum, poison), great mental excite-
ment or lack of control, usually due to alcohol.

I'ris (Gr. iris, rainbow), the colored curtain in the eye behind the cornea.

Jaundice (jahn'&s} (Fr.jaune, yellow), yellowness of the skin due to
a deficient excretion of bile by the liver.

GLOSSARY 445

Je-ju'num (Lat. jejunus, empty), the middle portion of the small

intestine.
Joint (Lat. jungere, to join), the union of two bones.

Kid'ney, the organ which excretes urea.

Lab'y-rinth (Gr. laburinthos}, an intricate arrangement of passages.

The inner ear.
Lach'ry-mal glands (Lat. lacrima, a tear), the glands which produce

the tears. They are situated in the orbit just above the eyeball, upon

its outer side.
Lac'te-al tubes (Lat. lac, milk), the fine lymphatic tubes which take

up fat from the intestine. During digestion they can be seen as

milky lines across the mesentery.
Lac-tom'e-ter (Lat. lac, milk, and metrum, measure), an instrument for

testing the purity of milk.
Larynx (lah' rinks) (Gr. larugx), the box in the upper part of the neck

in which the windpipe begins. It contains the vocal cords.
Lau'da-num, opium dissolved in nine times its weight of alcohol.
Lens (Lat. lens, lentil), a transparent substance having curved surfaces.

It has the power of changing the directions of rays of light.
Leu-co-ma-ine (lew-kef mah-in) (Gr. leukoma, white), a class of sub-
stances resembling alkaloids which are found in the body during

life. They are very poisonous, and much sickness is due to their

presence.
Lev'er (Fr. lever, to raise), a pry ; a rigid bar, one part of which is made

to turn about a fixed point called a fulcrum, while an opposite part

presses against a resisting object which it moves.
Lig'a-ment (Lat. ligare, to bind), the fibrous bands of connective

tissue which bind bones together to form joints.
Liv'er, the large red gland in the upper right side of the abdomen. It

forms bile and changes digested food to blood.

Lymph (Lat. lympha, a spring of water), the plasma and white cor-
puscles which have left the capillaries to nourish the cells of the

body.
Lym-phat'ics, the tubes which convey lymph back to the veins. Lymph

nodes are spongy bodies like grains of wheat which strain out waste

or poisonous substances from the lymph. In the neck and groin

they can be felt, and are usually called kernels.

446 GLOSSARY

Ma-la'ri-a (Ital. malo, bad, and aria, air), a disease caused by the bite

of a certain kind of mosquito.
Mal'le-us (Lat. malleus, hammer), the first bone of the chain of small

bones which conveys sound waves across the tympanum .
Malt, grain, usually barley, soaked in water until it has sprouted about

half an inch, and then dried. The sprouting changes a large part

of the starch to sugar.
Ma'ni-a (Lat. mania, rage), a form of insanity in which the intellect

is so active that the judgment cannot control it.
Mar'row, fat which fills the hollow bones.
Mas-ti-ca'tion (Lat. masticare, to chew), properly, the grinding to

which food is subjected by the teeth, tongue, and lips. Usually the

mixing with the saliva is also included.
Mas'toid process (Gr. mastos, the breast), the rounded projection of

bone situated behind the ear.
Me-dul'la oblongata (Lat. medulla, marrow), the part of the brain just

above the spinal cord. It controls respiration and the contraction

of arteries.
Mel-an-choli-a (Gr. melas, black, and chole, bile), a form of insanity

in which a person's mental actions are excessively retarded. He

feels downcast and thinks every one is avoiding him on account

of his sins. It is the opposite of mania. It was formerly supposed

to be due to black bile circulating in the blood.
Mem'brane (Lat. membrana, skin), any skin-like part of the body.

The membrana tympani is the skin-like tissue which separates the

middle ear from the outer ear.
Mer'cu-ry (Lat. Mercurius, the messenger of the gods), the liquid

metal commonly called quicksilver.
Mes'en-ter-y (Gr. mesos, middle, and enter on, intestine), the thin fold

of peritoneum which holds the intestine in place.
Met-a-car'pal bones (Gr. meta, after, and karpos, the wrist), the five

slender bones just below the wrist which form the palm of the

hand.
Met-a-tar'sal bones (Gr. meta, after, and tarsos, the flat of the foot),

the five long bones in front of the ankle which form the front part

of the foot.
Mi'crobes (Gr. mikros, little, and bios, life), the smallest living being.

Microbes are plants, some of which may grow in the human body

and produce diseases. They are the same as bacteria and germs.

GLOSSARY 447

Mi'cro-scope (Gr. mikros, little, and skopein, to see), an instrument
which makes minute objects appear large.

Milk, the fluid which all female mammals secrete for the nourishment
of their young.

Mi'tral (Gr. mitra, a head covering), the valve between the left auricle
and ventricle ; when closed it resembles a priest's miter or hat.

Molar (Lat. mola, a mill), a tooth having a flat surface for grinding
food. The last three teeth on each side of each jaw are molars.

Mold, a low order of microscopic plants which usually grow in the in-
terior of substances. Common forms send up spore stalks which
form the velvety coating popularly called mold.

Mor-phine' (Gr. morpheus, the god of sleep), the principal alkaloid of
opium.

Mo'tor nerves (Lat. mover e, to move), the nerves which carry orders
from the brain or spinal cord to cause the cells of the body to act.

Mu'cous mem'brane, the soft, skin-like membrane lining cavities which
open upon the surface of the body.

Mu'cus (Lat. mucus), the thin, slimy fluid produced by the epithelium
lining the organs of digestion and respiration.

Mu-ri-at' ic acid (Lat. muria, brine), the common name of hydro-
chloric acid. The acid is very sour and corrosive. It combines
with sodium to form common salt, but many of its combinations
are poisonous.

Mus'cle (Lat. musculus, a little mouse), a collection of cells which can
become thicker and shorter and so produce motion.

Nar-cot'ic (Gr. narkoun, to benumb), a substance which hinders the

action of nerves and nerve cells and produces sleep.
Na'sal duct (Lat. nasa, the nose), the duct which carries tears from

the eyes to the nose.
Nerve (Gr. neuron, nerve), a collection of the threads which conduct

impulses between the cells of the body and the central nervous

system.

Neuritis (new-rftis) (Gr. neuron, nerve), inflammation of a nerve.
Neu'tral-ize (Lat. neuter, neither), to make neither acid nor alkaline.
Nic'o-tine, the active principle in tobacco, named from the Frenchman

Nicot who introduced tobacco into France in 1560.
Nu'cle-o albumin, a form of albumin containing iron and found in the

nucleus of cells. From it hemoglobin is formed.

448 GLOSSARY

Nu'cle-us (Lat. nucleus, kernel), a mass usually distinguishable near the
center of each cell. It seems to be endowed with special vital powers.

Oc-cip'i-tal region (Lat. 06, against, and caput, the head), the region
of the skull or brain which is situated farthest back.

0-le-o-mar'ga-rine, a compound made from beef fat and milk. It has
the properties and nutritive value of butter.

01-fac'to-ry (Lat. olere, to have a smell, and facer e, to make), pertain-
ing to the sense of smell.

0-men'tum (Lat. omentuni), the fatty apron in front of the intes-
tine.

O'pi-um (Gr. opion, poppy juice), the dried juice of a kind of poppy
growing in western Asia. It is a narcotic and is used to produce
sleep and to benumb pain.

Op'tic (Gr. optikos), pertaining to sight. The optic nerves convey
impressions of sight. The optic tubercles are collections of gray
matter in the brain between the medulla and cerebrum. They are
reflex centers for the eye.

Or'bit (Lat. orbis, a circle), the bony cavity which contains the
eyeball.

Or'gan (Gr. organon, a tool), a collection of tissues having a definite
compact form and purpose.

Or-gan'ic (Gr. organon, a tool), a term designating a substance built
up only by the agency of living substances.

Ox-i-da'tion, the union of oxygen with another substance. It is the
essential part of the processes of burning and of breathing.

Oxygen (px'y-jen) (Gr. oxus, sharp or acid, and genein, to generate), a
gas forming one fifth of the air. Its union with the cells of the
body forms the essential part of the process of breathing.

O'zone (Gr. ozon, smelling), a very active form of oxygen formed by
electricity and sometimes found in the air.

Pal'ate (Lat. palatum), the roof of the mouth.

Pal-pi-ta'tion (Lat. palpitare, to throb), violent throbbing of the

heart, so that its beats make themselves felt through the chest wall.
Pan'cre-as (Gr. pan, all, and kreas, flesh), the gland situated behind

the stomach which forms the pancreatic juice. The sweetbread.
Pan-cre-at'ic juice, the liquid secretion of the pancreas which digests

albumin, fat, and sugar in the intestine.

GLOSSARY

449

Panic (Gr. to panikon, from Pan, the god of the woods, and of sudden
fear), a sudden and infectious fear which sometimes seizes upon a
crowd.

Pa-pil'la (Lat. papilla, pimple), a minute projection of the true skin
into the epidermis. It contains the endings of the nerves of
touch .

Pa-ral'y-sis (Gr. para, beside, and luein, to loosen), lack of action of
a part due usually to a failure of the motor nerves to bring the im-
pulses for action.

Par-e-gor'ic (Gr. paregoros, soothing), a sweet-tasting mixture contain-
ing opium and used chiefly in quieting children.

Pa-ri'e-tal bones (Lat. paries, a wall), the top and sides of the
skull.

Pa-ro'tid glands (Gr. para, near, and ous, ear), the salivary glands in
the front of the ear.

Pel'vis (Lat. pelvis, basin), the massive ring of bone which forms the
hips. Its cavity is somewhat larger than a large tea cup and con-
tains some of the intestine.

Pep'sin (Gr. peptein, to cook or digest), a lifeless ferment found in the
stomach of all animals. It digests albumin.

Pep'tone (Gr. peptos, cooked), the form to which albumin is changed
by digestion.

Per-i-car'di-um (Gr. peri, around, and kardia, heart), the thin bag
which surrounds the heart.

Per-i-os'te-um (Gr. peri, around, and osteon, bone), the thin, tough
membrane which covers bone, reproduces its cells, and transmits Us
blood vessels and nerves.

Per-i-stal'sis (Gr. peri, around, and stellein, to arrange), the regular,
worm-like movements of the alimentary canal, which force its con-
tents onward.

Per-i-to-ne'um (Gr. peri, around, and teinein, to stretch), the thin,
shining membrane which lines the interior of the abdomen and
covers its organs.

Per-spi-ra'tion (Lat. per, through, and spirare, to breathe), the watery
secretion of the skin. The sweat.

Pha-lan'ges (Gr. phalagx, a rank of soldiers), the rows of bone which
form the fingers and toes. Its singular is phalanx.

Pharynx (far1 inks} (Gr. pharugx, the throat, from pharein, to cleave),
the cavity back of the nose and mouth.
ov. PHYSIOL. — 29

450 GLOSSARY

Phos'phor-us (Gr. phos, light, and pherein, to bring), a waxy, yellowish
substance which combines with oxygen at ordinary temperatures,
giving off heat and a faint light. The light produced by rubbing
matches is due to the phosphorus.

Phys-i-ol'o-gy (Gr. phusis, nature, and logos, discourse), the science
which tells of the working of living bodies.

Pi-a ma-ter (Lat. pia, pious, and mater, mother), the delicate cover-
ing of the brain which carries its blood vessels, in distinction from
the thick protecting dura mater.

Plas'ma (Gr. plasma, molded), the liquid part of blood in distinction
from the cells which float in it. It is composed chiefly of water,
albumin, and minerals. It is food for the cells of the body and it
washes away their waste matters.

Pleura (plew'ra) (Gr. pleura, rib), the lining of the chest and coating
of the lung.

Plex'us (Lat. plectere, to braid), a network of sympathetic nerve cells
and fibers.

Plumb'ing (Lat. plumbum, lead), the pipes which conduct water and
sewage in a house. Many ar.e made of lead.

Pneumonia (new-mo* ni-a) (Gr. pneumon, a lung), a disease in which
the air sacs of the lung become filled with coagulated matters from
the blood.

Poi'son (Lat. potto, a drink), a substance which destroys or interferes
with the life of the cells, when it is taken into the body.

Por'tal vein (Lat. porta, a gate), the vein formed by the union of the
veins from the digestive organs. This vein divides into the capilla-
ries of the liver. Finally three veins conduct the blood to the ascend-
ing vena cava.

Pro'to-plasm (Gr. protos, first, and plasma, form), the albuminous sub-
stance which forms the body of every living cell.

Proximate principles, the elementary substances existing as such in
the body.

Ptomaine (to'mah-iri) (Gr. ptoma, a dead body), a class of poison-
ous substances resembling alkaloids and leucomaines, which are
found in dead bodies. Their presence makes decayed food
dangerous.

Ptyalin (ti'a-ltn) (Gr. ptuein, to spit), the lifeless ferment in the saliva
which changes starch to sugar.

PuTmo-na-ry (Lat. pulmo, lung), pertaining to the lungs.

GLOSSARY 45 1

Pulse (Lat. pulsus, a blow), the wave which may be felt in an artery

with each heart beat.
Pu'pil (Lat. pupilla}, the opening in the iris through which light enters

the eye. It appears as a round black spot in the center of the col-
ored part of the eye.
Pus (Lat. puteo, to rot), the creamy matter which flows from an abscess.

It is formed mostly of dead white blood cells.
Pu-tre-fac'tion (Lat. putris, rotten, and facere, to make), the process

of decay accompanied by bad odors.
Py-lo'rus (Gr. pule, a gate), the orifice in the right end of the stomach,

through which food passes into the intestine.
Py'ri-dine (Gr. pur, fire), a poisonous substance formed by burning

nicotine.

Ra'di-us (Lat. radius, the spoke of a wheel), the bone upon the thumb

side of the arm, below the elbow.
Re'flex action (Lat. re, back, and flectere, to turn), the action of the

central nerve cells in sending orders for motion in response to

an impulse brought by sensory nerves.
Ren'nin, a lifeless ferment extracted from the lining of the fourth

stomach of a calf, and used to curdle milk in cheese making.

The same ferment is found in the human stomach, especially in

infancy.
Res-pi-ra'tion (Lat. re, again, and spirare, to breathe), the process of

breathing and of the interchange of oxygen and carbonic acid gas

in the cells of the body.
Ret'i-na (Lat. rete, a net), the inner lining of the eye in which the

nerves of sight end.

Rheumatism (ru1 ma-tisni) (Gr. rheum, a flowing or stream), a swell-
ing of the joints in which they are often quickly affected one after

another. Usually it is due to fluid collecting in the bag of the

synovial membrane.
Rick'ets, a disease in which the bones have too little lime and bend too

easily.

Sa'crum (Lat. sacer, sacred, for the bone was offered in sacrifice), the
part of the backbone which completes the pelvis behind.

Sa-li'va (Lat. saliva; Gr. sialon, spittle), the watery fluid in the
mouth.

452 GLOSSARY

Sa-pon-i-fi-ca'tion (Lat. sapo, soap, and facer e, to make), the process
of making soap. Commonly the name soap is applied only to the
combination of soda or potash with the acid part of fat. But lime,
or magnesium, or other metal may take the place of soda or potash,
as it does when hard water and soap are used to wash the hands.
The lime soap which is formed feels sticky and rough, and does not
dissolve in water, but forms a white scum on the surface.

Scap-u-la (Lat. scapulae, the shoulder blades), the flat bone upon the
back behind the shoulder. The shoulder blade.

Sciatica (si-at'i-kd) (Gr. ischiadikos, pertaining to the hip), a painful
inflammation of the main nerve of the leg which begins just behind
the hip joint.

Sclerotic (skler-ot'tc} (Gr. skleros, hard), the tough outer covering of
the eyeball.

Scur'vy, the disease caused by lack of variety of food. It consists of
pain and of bleeding under the skin, especially of the legs and gums.

Sebaceous glands (se-ba1 'skits) (Lat. sebum, fat), the glands in the skin
which secrete oil.

Se-cre'tion (Lat. secretus, separated), a substance which is separated
from the blood by the epithelium of glands and used by the body.

Sem-i-cir'cu-lar canals, the three tunnels in the inner ear in which there
are nerves whose duty is to take note of the position of the body in
balancing itself.

Sem-i-lu'nar valves, three half-moon-shaped valves at the beginning
both of the aorta and of the pulmonary artery. They prevent blood
from flowing back to the heart.

Sen-sa'tion (Lat. sentire, to feel), a conscious impression made upon
the brain by an impulse brought by a sensory nerve.

Sen'so-ry nerves (Lat. sentire, to feel), nerves which carry impulses
from the cells to the central nervous system.

Se'rous membrane, the thin membrane lining the cavities of the body
which do not connect with its surface. It is named from the fluid,
like serum, which forms in it in a quantity just sufficient for lubri-
cation.

Se'rum (Lat. serum, the watery part of curdled milk), the straw-colored
liquid which separates from a blood clot.

Sewer (su'er), an underground tunnel for carrying slops from the houses
of a town.

Si'nus (Lat. sinus, curve), a cavity.

GLOSSARY 453

Skel'e-ton (Gr. skellein, to dry), the bones of the body.
So-lu'tion (Lat. solutus, dissolved), a liquid mixture in which the in-
gredients are not changed in essential properties.
Speech, the expression of thoughts by words.
Spine (Lat. spina, the backbone), the backbone.
Spleen (Gr. spleri), a soft, red organ lying to the left of the stomach.

Its use is probably to form the red blood cells.
Spore (Gr. spora, seed), a reproductive cell of a flowerless plant. Spores

are extremely minute, and some are capable of resisting influences

which are fatal to most other forms of life.
Stapes (Lat. stapes, stirrup), the third bone in the chain of bones which

conducts sound from the membrana tympani to the inner ear.
Starch (Anglo-Saxon, stearc, strong), a food substance composed of

carbon, hydrogen, and oxygen. It is the first recognizable form

through which organic substances pass as they are built up by plants.

In the body it is changed to sugar.
Ste-ap'sin (Gr. stear, suet), the ferment of the pancreatic juice which

digests fat.
Ster'il-ize (Lat. sterilis, without power to produce seed), to destroy

bacteria and their spores as by heat or chemicals. It is usually

applied to the preparation of surgical dressings.
Ster'num (Gr. sternon, the breast), the flat bone which extends down

the front of the breast ; the breast bone.
Stim'u-lant (Lat. stimulus, a whip), a substance which excites a part

to action without increasing its supply of energy.
Stomach (jstum'ak) (Gr. stoma, a mouth or entrance), the muscular

bag into which food enters when swallowed, and which begins the

work of digestion.
Strych'nine (Gr. struchnos, a kind of shrub), a substance obtained from

the seeds of the strychnos shrub. It is used to increase the power of

the nervous system ; in overdoses it produces violent convulsions.
Sub-lin'gual glands (Lat. sub, under, and lingua, tongue), the two

salivary glands under the front part of the tongue.
Sub-max'il-la-ry gland (Lat. sub, under, and maxilla, jaw), the

salivary gland situated under the side of the lower jaw.
Su'gar (Lat. saccharum, sugar), a sweet substance composed of carbon,

hydrogen, and oxygen in nearly the same proportions as in starch.

There are many varieties, but during digestion all are changed to

glucose or grape sugar. It gives heat to the body.

454 GLOSSARY

SyTvi-an fissure, the deep fissure extending backward upon each side

of the brain. It was named after the French physician Sylvius, who

died in 1555.
Sym-pa-thet'ic system, the collection of nerve cells and nerves which

control the preparation of food and its distribution to the cells. It

is subordinate to the spinal cord.

Syn-o'vi-a, the fluid which lubricates the movable joints.
Syn-o'vi-al membrane, the membrane lining the movable joints.
Sys'tem (Gr. sunistanai, to place together), a series of tissues and

organs, working together for a definite purpose.
Sys'to-le (Gr. sun, together, and stellein, to set), the contraction of

the heart forcing blood into the arteries of the body.

Tan'nin (Fr. tan, originally meaning oak), an acid found in the barks
of most trees, and used to toughen and harden skins into leather.

Tape worm, a kind of worm inhabiting the intestine. It resembles a
long piece of white tape.

Tar'sal bones (Gr. tarsos, the sole of the foot), the seven irregularly
shaped bones in the hinder half of the foot.

Tar'tar, a kind of hard, brown substance which often forms upon the teeth.

Tau-ro-chol'ic acid, one of the waste substances in the bile.

Tem'po-ral (Lat. tempora, the temples), pertaining to the regions of
the skull in the neighborhood of the ears.

Ten'don (Lat. tendere, to stretch), a strong white cord, one end of
which is attached to a muscle above a joint, and the other to a bone
or to flesh below a joint.

Thoracic duct, the tube running upward upon the backbone and con-
veying lymph to the veins.

Tho'rax (Gr. thorax, breastplate), the cavity of the body under the
ribs.

Thy'roid (Gr. thureos, a shield, and eidos, form). The large folded
cartilage which forms the principal part of the larynx.

Tib'i-a (Lat. tibia), the shin bone.

Tissue (ti'shu), a group of cells or fibers alike in form and action.

To-bac'co (West Indian tabaco, the name of the pipe used in smoking),
a narcotic plant used for smoking and for chewing.

Ton'sil (Lat. tonsilld), a round body situated one on each side of the
throat in front of the pharynx. They have no special use. Some-
times they become enlarged, and need to be removed.

GLOSSARY 455

Tox'in (Gr. toxikon, arrow poison), a virulent poison formed within a
living body. Most toxins are ptomaines.

Tra'che-a (Gr. trachus, rough), the windpipe ; rings of cartilage make
its outside irregular and rough.

Trans-fu'sion (Lat. trans, across, and /under ~e, to pour out), transferring
blood from the veins of one person into the veins of another.

Tri'ceps (Lat. tri, three, and caput, head), the muscle extending down
the back of the arm from the shoulder to the elbow. It straightens
the elbow. Its upper end has three branches.

Trichinae (trick-i1 nee) (Gr. thrix, a hair), microscopic worms which
live in the muscles of a pig. They sometimes remain alive in par-
tially cooked pork, and if eaten produce a deadly disease.

Tri-cus'pid valve (Lat. tres, three, and cuspis, point), the valve between
the right auricle and ventricle ; it is formed of three leaves.

Tryp-sin (Gr. tribein, to rub), the ferment of the pancreatic juice which
digests albumin.

Tu-ber-cu-lo'sis (Lat. tuberculum, a little lump), a disease in which
small white lumps like pinheads form in the flesh. Later, these
soften and run out as matter. The disease is commonly called con-
sumption.

Tym'pa-num (Lat. tympanum, drum), the middle ear.

Ty'phoid fever (Gr. tuphos, a cloud, and hence a stupor arising from
fever, and eidos, form), a tedious and weakening fever caused by the
growth of a kind of bacteria.

Ty-ro-tox'i-con (Gr. turos, cheese, and toxicon, poison), a virulent
ptomaine poison sometimes found in cheese and other substances
made from milk.

Ul'na (Lat. ulna, the elbow), the bone on the little finger side of the

lower arm.
U're-a (Gr. our on, urine), a very soluble crystalline substance, one of

the three principal waste products of the body. It is the essential

part of urine.
U-re'ter (Gr. our on, urine), the tube leading from the kidney to the

bladder.

Vac-cin-a'tion (Lat. vacca, a cow), the introduction of the germs of
cowpox into the skin for the purpose of causing the disease as a
protection against smallpox.

456 GLOSSARY

Valv'u-lae con-ni-ven'tes (Lat. valvulae, little sliding doors, and conni-
ventes, winking), deep puckers in the mucous membrane of the
small intestine.

Var'i-cose veins (Lat. varix, an enlarged vein), distended and enlarged
veins.

Vas-o-mo'tor nerves (Lat. vasa, a vessel, and motor, pertaining to
motion), nerves which produce either contraction or dilatation of the
arteries.

Vein (vane) (Lat. vena, a vein), a tube which carries blood back to
the heart.

Ven-ti-la'tion (Lat. ventilare, to winnow), changing the air of a room.

Ven'tri-cle (Lat. ventriculus, stomach), one of the large, thick-walled
cavities of the heart.

Ven-triTo-quism (Lat. venter, the abdomen, and loqui, to speak),
speaking so that the voice seems to come from a distance away
from the speaker.

Ver'mi-form ap-pen'dix (Lat. vermis, worm, appendix, something
added), the closed tube, shaped like an earthworm, which projects
from the beginning of the large intestine. In some of the lower
animals, as in the hen, it is as large as the other part of the intes-
tine, but in man is only about two inches in length and one eighth
inch in diameter.

Ver'te-bra (Lat. vertebra), a joint of the backbone.

Vest'i-bule (Lat. vestibulum, a porch or entrance), the cavity of the
internal ear from which the cochlea and semicircular canals extend.

Vil'lus (Lat. villus, a tuft of hair), one of the minute slender projections
upon the inner surface of the intestine.

Vin'e-gar, a sour liquid made from wine or cider by the oxidation of its
alcohol to acetic acid, of which it contains from two to four per cent.

Vit're-ous hu'mor (Lat. vitrum, glass), the jelly-like fluid which fills
the eyeball behind the lens.

X rays, a form of radiant energy discovered by Roentgen in 1895. It
penetrates wood, flesh, and many other substances which are opaque
to sunlight.

Yeast, a collection of single-celled plants, whose growth changes sugar
to alcohol and carbonic acid gas. The ager<l which causes bread to
become light.

INDEX

Abdomen, 66.
Abscess, 399.
Absorption, 89, 260.
Accommodation, 339.
Achilles' tendon, 374.
Acid, 28, 149.
Aconite, 148, 151.
Adam's apple, 349.
Adenoid vegetations, 193, 327.
Adulteration, of alcohol, 47.
of coffee, 127.
of milk, in.
Air, 206, 220.
in lungs, 207.
in clothing, 238.
moisture in, 236.
rarefied, 222.
sacs, 195.

Albumin, 23, 34, 69, 84, 92.
Alcohol, 44, 140.

effects on arteries, 189.

brain, 315.

digestion, 98.

excretion, 251.

habit, 319.

heart, 168.

heat, 243.

heredity, 319.

intestine, 100.

judgment, 316.

kidney, 251.

liver, 100.

lungs, 213.

muscle, 377.

nerves, 273.

paralysis, 317.

peristalsis, 99.

respiration, 214.

sight, 342.

stomach, 99.

voice, 354.

Alimentary canal, 53.
Alkalies, 28, 149.
Alkaloids, 152.
Ameba, 10.
Amylopsin, 84.
Anaesthesia, 146, 223, 320.
Anatomy, 9.
Anemia, 159.
Antidote, 149.
Antimony, 151.
Antiseptics, 387.
Antitoxin, 386, 423.
Antrum, 54, 193, 324,
Aorta, 172.
Apoplexy, 311.
Appendicitis, 80.
Appendix, vermiform, 80.
Appetite, 74.
Aqueous humor, 334.
Argon, 220.
Arsenic, 150.

Arterial blood, 157, 177, 207,
Artery, 163, 172, 187.
Asphyxia, 212.
Assimilation, 91.
Astigmatism, 340.
Auricle, 163.

Bacteria, 384, 410, 411.
Barley, 122.
Bathing, 261.
Beans, 122.
Beard, 261.
Beds, 240.
Beef tea, 115.
Beer, 43.
Belladonna, 152.
Biceps, 375.
Bicuspid tooth, 55.
Bile, 84, 85, 93.
Biliousness, 85, 93.

457

458

INDEX

Bilirubin, 250.
Biscuit, 121.
Bitters, 101.
Blackheads, 259.
Bladder, 84, 249.
Bleeding, 186.
Blister, 257.
Blood, 156, 206.

as food, 117.

in lower animals, 159.

poisoning, 389, 424.
Blowing, 198.

Boards of health, 405, 413.
Bones, 357.

Bowels, regularity of, 94.
Brain, 289.

food, 133, 309.

in lower animals, 300.
Bread, 43, 121, 122.
Breathing, 192, 198.
Bright's disease, 249.
Broken, back, 281.

bones, 361.
Bronchi, 195.
Bunion, 366.
Burns, 242.
Butter, in.
Butterine, 1 12.

Caecum, 80.

Caisson, 222.

Cake, I2i.

Callus, 257.

Cancellous bone, 359.

Canine teeth, 54.

Cannabis indica, 145.

Canned food, 42, 125.

Capillary, 173, 208.

Carbolic acid, 150, 388.

Carbon, 33, 36.

Carbonic acid gas, 33, 206, 208, 223.

Cardiac, 67.

Carpal bones, 358.

Cartilage, 360.

Caseine, 109.

Cataract, 340.

Catarrh, 61.

Cellar air, 224.

Cells, u, 13, 92, 174, 397.

Cellulose, 26.

Cement, 55.

Cerebellum, 292.

Cerebrum, 293.
Cesspool, 252, 407.
Cheeks, 56.
Cheese, no.
Chemical action, 28.
Chicken pox, 427.
Chill, 234.
Chloral, 145.
Chloride of lime, 388.
Chloroform, 146, 320.
Chlorophyll, 35.
Choking, 199.
Cholera, 385, 426.
Choroid coat, 334.
Chyle, 86.
Chyme, 69.
Cigar, 141.
Cigarette, 142.
Cilia, 195, 197, 205, 218.
Circulation, 177.

in lower animals, 180.
Clabber, no.
Clams, 1 1 6.
Clavicle, 358.
Clothing, 237.
Clot, 158.
Coagulation, 23.
Coal gas, 225.
Cocaine, 145.
Coccyx, 357.
Cochlea, 326.
Cocoa, 127.
Coffee, 126.
Cold, sensation of, 234.

feet, 239.

taking, 185, 400, 420.
Colon, 80.
Color, blindness, 337.

and heat, 238.

of skin, 257.
Complexion, 259.
Condensed milk, 112.
Congestion, 185, 397.
Conjunctiva, 336.
Connective tissue, n, 38, 398.
Conservation of energy, 36.
Consonants, 352.
Consumption, see Tuberculosis.
Contagious diseases, 385, 416.
Contraction of muscles, 373.
Convolutions of brain, 293.
Cooking, 51, 123.

INDEX

459

Copper, 150.
Corn meal, 122.
Cornea, 335.
Corns, 257.
Corpuscles, 156.
Cotton, 237.
Coughing, 198.
Crabs, 117.
Cranial nerves, 290.
Cricoid cartilage, 349.
Crown of tooth, 55.
Crying, 198.
Cud, 104.

Curvature of spine, 366.
Cuticle, 257.
Cutis, 256.

Deafness, 327.
Decay, 13, 24, 42, 46, 384.
Decayed food, 152.
Deglutition, 61.
Delirium, 311.

tremens, 318.
Dentine, 55.
Derma, 256.
Diaphragm, 66, 196.
Diastole of heart, 165.
Diet list, 132.
Diffusion, 24.
Digestion, 51, 104, 108.
Diphtheria, 385, 416, 420, 422.
Disease germs, 136, 148, 157, 193, 221,

226, 248, 251,385,410,416.
Disease of bone, 361.

of eye, 341.

of heart, 167.

of hip joint, 368.

of spine, 281.
Disinfection, 387.
Dislocations, 367.
Distillation, 44.
Dreams, 308.
Drinking cup, 419.
Dropsy, 180.
Drowning, 213.
Drugs, 148.
Duodenum, 80.
Dura mater, 290.
Dust, 221, 418.
Dyspepsia, 74, 93.

Ear, 325.
wax, 329.

Ear, in lower animals, 329.
Eating, 76, 132.
Eggs, 112.
Electric shock, 213.
Emergencies —

Alcoholic paralysis, 141, 317.

Apoplexy, 311.

Asphyxia, 212.

Bleeding, 186.

Broken bones, 361.

Burns, 242.

Choking, 199.

Coal gas, 225.

Cold, taking, 185.

Contagious diseases, 385.

Dislocation of bones, 367.

Drowning, 213.

Electric shock, 213.

Fainting, 150, 168.

Fever, 233, 242, 263.

Fits, 312.

Fright, 312.

Frozen limbs, 241.

Hysteria, 309.

Insanity, 310.

Panics, 312.

Poisoning, 144, 149.

Sprains of joints, 367.

Stings, 154.

Sunstroke, 236.
Emulsion, 25.
Enamel, 55.
Energy, conservation of, 36.

source of, 233.
Epidermis, 257.
Epiglottis, 61.
Epilepsy, 312.
Epithelium, 57, 58, 68, 82, 248, 257,

261, 271, 398.
Eruptive diseases, 426.
Erysipelas, 385, 389, 417.
Esophagus, 62.
Ether, 320.

Eustachian tube, 193, 327.
Excretion, 248.
Exercise, 166, 309, 377.
Expansion of lung, 197.
Expiration, 196.
Extensor muscles, 375.
Eye, 334-

in lower animals, 344.
Eyelids, 336.

460

INDEX

Face, 376.

Fainting, 150, 168.

Far sight, 339.

Fat, 25, 34, 91, 209.

Fatty heart, 167.

Femur, 358.

Fermentation, 42, 76, 100, 109.

Fever, 233, 242, 263, 420.

Fibrin, 158.

Fibula, 359.

Field of view, 337.

Filtration, 137, 409; of air, 229.

Fissures of brain, 293.

Fish, 1 1 6.

Fits, 312.

Flat foot, 359.

Flexor muscles, 375.

Flies, 411, 426.

Fluids of body, 15.

Focus, 1 8.

Food, 51, 107, 120, 131,413.

Foul air, 223, 421.

Freckles, 257.

Frontal region, 294.

Frozen limbs, 241.

Fruit, 124.

Fulcrum, 373.

Fur, 238.

Fusel oil, 45.

Gall bladder, 84.

Ganglia, 284.

Gaping, 198.

Gastric juice, 68.

Gelatine, 23.

Germs, see Disease germs.

Gills, 216.

Gizzard, 105.

Gland, 57.

Glucose, 51, 92.

Glue, 23.

Gluten, 120.

Glycocholic acid, 250.

Glycogen, 92.

Goose flesh, 259.

Gout, 367.

Grain, 120.

Gray matter, 276, 290, 292, 293.

Grippe, 385, 421.

Habit, 142, 306.
Hair, 259.
Hangnail, 261.

Hasheesh, 145.

Haversian canals, 360.

Headache, 95, 340.

Heart, 162.

Heat, 34, 233.

Hemoglobin, 24, 156, 207.

Hemophilia, 159.

Hemorrhage, 186.

Heredity, 306.

Hibernation, 243.

Hiccough, 198.

Hip, 358.

Hip joint disease, 368.

Hook-worm disease, 430.

Humerus, 358.

Humors, 159.

Hunchback, 368.

Hunger, 269.

Hydrochloric acid, 68.

Hydrophobia, 429.

Hygiene, 9, 405.

Hypodermic injections, 153, l8o,

Hysteria, 309.

Ileum, 80.

Illusions, 329, 342.

Immunity, 416.

Incisor, 54.

Incus, 326.

Indigestion, 73, 93.

Infectious diseases, 385, 416.

Inflammation, 397, 424.

Ingrowing nail, 261.

Insalivation, 53.

Insanity, 310.

Inspiration, 196.

Instincts, 268.

Intellect, 299.

Intemperance in eating, 75, IOI, 251.

Intensity of voice, 351.

Intestinal juice, 84.

Intestine, 79, 425.

Intoxication, 214, 317.

Iris, 335.

Iron, 24, 124.

Itching, 271.

Ivory, 55.

Jaundice, 250.
Jaws, 54.
Jejunum, 80.
Joints, 364.

INDEX

46l

Kidneys, 249.

Labyrinth, 325.
Lachrymal gland, 336.
Lacing, tight, 200.
Lacteal, 91.
Lactometer, ill.
Larynx, 194, 349.
Laudanum, 144.
Laughing, 198.
Lead, 136, 150.
Lens, 333.
Leucomaines, 152.
Levers, 373.
Life, 9, 12, 38, 402.
Ligaments, 365.
Light, 333.
Lime, 28.
Lips, 56.

Liver, 82, 93, 250.
Living rooms, 236.
Lobsters, 117.
Lockjaw, 417, 429.
Lungs, 192, 400.
Lymph, 178.
Lymphatics, 174, 178.
Lymph nodes, 178.

Malaria, 225, 413.
Malleus, 126.
Malt, 43.
Mania, 310.
Marrow, 160, 359.
Mastication, 60.
Mastoid, 327.
Measles, 416, 419, 427.
Meat, 113.

Medulla oblongata, 290.
Melancholia, 311.
Membrane, 327.
Memory, 295, 297.
Mercury, 150, 388.
Mesentery, 79.
Metacarpal bones, 358.
Metals, 150.
Metatarsal bones, 359.
Microbes, 384.
Microscope, 16.
Milk, 109.

Mind, stimulation of, 305.
Minerals, 27, 33, 51.
Mitral valve, 164.

Molar teeth, 55.

Mold, 383.

Morphine, 144.

Mosquitoes, 225, 413.

Motor, region, 296; center, 278, 296.

nerves, 271.
Mouth, 53.

breathing, 193, 353.
Mucous membrane, 57.
Muller's fluid, 72.
Mumps, 426.
Muriatic acid, 363.
Muscles, 366, 371, 376.
Muscular sense, 271.
Mushroom, 152.

Nails, 259.
Narcotics, 140, 150.
Nasal duct, 336.
Near sight, 339.
Nerve cells, 276.
Nerves, 266.

of heart, 166.

motor, 271.

sensory, 268.

sympathetic, 285.
Nervousness, 309.
Neuritis, 273.
Neutralize, 28.
Nicotine, 141.
Night air, 225.
Nose, 192, 324, 420.
Nucleo-albumin, 24, 126.
Nucleus, II, 12, 24.
Nuts, 125.

Oatmeal, 122.
Occipital region, 295.
Occupation diseases, 221.
Odors, 224.
Oleomargarine, 112.
Olfactory nerves, 325.
Omentum, 80.
Opium, 143, 320.
Optic, nerve, 334.
tubercles, 292.
Orbit, 336.

Organic substances, 37.
Organs, 1 6.

Oxidation, 33, 46, 137, 209, 233, 243.
Oxygen, 33, 131, 207, 212, 221.
Oysters, 116.
Ozone, 220.

462

INDEX

Pain, 270.

Palate, 53.

Palpitation of heart, 166, 167.

Pancakes, 121.

Pancreas, 82.

Pancreatic juice, 84.

Panics, 312.

Paper clothing, 239.

Papilla, 258.

Paralysis, 272.

Paregoric, 144.

Parietal region, 294.

Parotid gland, 59.

Patella, 359, 375.

Paunch, 104.

Peas, 122.

Pelvis, 358.

Pepsin, 69.

Peptone, 24, 69, 92.

Pericardium, 162.

Periosteum, 359, 360.

Peristalsis, 63, 69, 85.

Peritoneum, 66.

Perspiration, 235, 248.

Phalanges, 359.

Pharynx, 6 1, 193.

Phosphorus, 151.

Physiology, 9.

Pia mater, 290.

Pitch of voice, 350.

Plague, 430.

Plants and animals, 37.

Plasma, 157.

Play, 378.

Pleura, 196.

Plexus, 285.

Plumbing, 253.

Pneumogastric nerve, 291.

Pneumonia, 401, 421, 423.

Poisoning, 149.

Portal, circulation, 177.

vein, 92.
Potash, 28.
Potatoes, 122.
Poultice, 400.
Protoplasm, n.
Proud flesh, 258, 398.
Proximate principles, 22.
Ptomaines, 153, 384.
Ptyalin, 59.

Public drinking cup, 419.
Pulmonary circulation, 176.

Pulse, 173.
Pupil, 335.

Purification of air, 230.
Pus, 399.

Putrefaction, see Decay.
Pylorus, 67.
Pyridine, 142.

Quality of voice, 351.
Quarantine, 410, 422, 426.

Rabies, 429.

Radius, 358.

Reaction of bath, 262.

Reconstruction after oxidation, 35,

Red blood cells, 157.

Reflex action, 278.

Regions of brain, 294.

Rennin, 69.

Repair, of injuries, 397.

in blood tubes, 188.

in nerves, 273.
Respiration, 175, 192, 208, 217.

artificial, 202.

in lower animals, 215.
Respiratory center, 201, 211, 291
Retina, 334.

exhaustion of, 337.
Rheumatism, 367.
Ribs, 357.
Rice, 122.
Rickets, 361.
Ringworm, 384.
Root beer, 48.
Round shoulders, 377.
Rumen, 104.

Sacrum, 357.
Saliva, 59.
Salt, 27.
Sanitation, 405.
Saponification, 26, 85.
Scapula, 358.
Scar, 398.

Scarlet fever, 416, 427.
Sciatica, 273.
Sclerotic coat, 334.
Scrofula, 1 79, 392.
Scurvy, 126.
Seasonings, 126.
Sebaceous glands, 259.
Secretion, 58, 272.
Semicircular canals, 326.

INDEX

463

Semilunar valve, 164.

Sensation, 268.

Sensibilities, 299.

Sensory regions, 295.

Serous membrane, 67.

Serum, 158.

Sewage, 251, 406, 417, 426.

Sewer, 252, 407.

Sewer gas, 224, 252.

Shortness of breath, 211.

Sick room, 388.

Sighing, 199.

Sight, 335.

Silk, 238.

Silver, 150.

Sinus, 324.

Site for house, 253.

Skeleton, 357.

Skin, 256.

grafting, 258.
Sleep, 307.

Smallpox, 416, 417, 427.
Smell, 325.
Smoking, 141.
Smothering, 199.
Snake bites, 153.
Sneezing, 198.
Snoring, 198.
Snuff, 142.
Soap, 26.
Sobbing, 198.
Soda, 28.
Solar plexus, 285.
Solution, 22.
Sounds, of heart, 1 66.

of breathing, 198.
Soup, 115.
Specimens, 19, 72.
Speech, 297, 351.
Spinal, column, 357.

cord, 276.

nerves, 277.
Spitting, 199.
Spleen, 160.
Spores, 383.
Sprains, 367.
Standing, 375.
Stapes, 326.
Starch, 26, 35, 84.
Starvation, 133.
Steapsin, 85.
Sterilization, 387.

Sternum, 357.
Stimulants, 126, 168.
Stings, 154.
Stomach, 67.
Strychnine, 150.
Subcutaneous tissue, 256.
Sublingual gland, 59.
Submaxillary gland, 59.
Sucking, 199.
Suffocation, 199.
Sugar, 26, 35, 132, 209.
Summer complaint, no.
Sun in plant growth, 36.
Sunstroke, 236.
Swallowing, 62.
Sylvian fissure, 293.
Sympathetic system, 284.
Synovial membrane, 365.
Systems, 16.
Systole of heart, 165.

Tannin, 127.
Tapeworm, 117.
Tarsal bones, 359.
Tartar, 56.
Taste, 74, 323.
Taurocholic acid, 250.
Tea, 126.
Tears, 336.
Teeth, 54.

Temperance drinks, 48.
Temperature, of body, 233,
in lower animals, 243.
sense, 234, 270,
Temporal region, 294.
Tendon, 372.
Tetanus, 429.
Thirst, 47, 269.
Thoracic duct, 91, 179.
Thorax, 196.
Thought regions, 297.
Thyroid cartilage, 349.
Tibia, 359.
Tickling, 271.
Tissues, 14.
Tobacco, 141.

effects on brain, 319.

heart, 169.

lungs, 215.

sight, 342.

smell, 325.

voice, 353.

464

INDEX

Tongue, 57, 352.

Tonsil, 193, 422.

Touch, 269, 323.

Toxins, 384.

Trachea, 194.

Triceps, 375.

Trichinae, 117.

Tricuspid valve, 164.

Trypsin, 84.

Tuberculosis, 117, 226, 368, 389, 424.

Tusk, 55.

Tympanum, 327.

Typhoid fever, no, 385, 420, 425.

Tyro lexicon, 153.

Ulna, 358.

Unconscious mind action, 307.

Urea, 34, 248.

Ureter, 249.

Urine, 249.

Vaccination, 387, 417, 428.
Vagus nerve, 291.
Valves of heart, 164.
Valvulae conniventes, 81.
Varicose veins, 189.
Vasomotor, center, 291.

nerves, 185.
Vegetables, 124.
Veins, 163, 175.
Venous blood, 157, 177.

Ventilation, 226.
Ventricle, of brain, 294.

of heart, 163.
Ventriloquism, 341.
Vermiform appendix, 80.
Vertebra, 357.
Vestibule, 325
Villi, 81.
Vinegar, 41.
Vitreous humor, 334.
Vocal cords, 350.

exercise, 353.
Voice, 194, 349.
Vowels, 352.

Walking, 376.

Wart, 258.

Water, 22, 33, 135, 408, 425.

White blood cells, 157, 174, 386, 397.

matter, 276, 290, 293.

swelling, 368.
Whooping cough, 424.
Will, 299.
Wine, 44.
Wood, 26, 38.
Wool, 237.

X rays, 342.

Yawning, 198.
Yeast, 41, 382.

4 * • ' '