BSENTIAL|ESSONS 
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W.E. BALDWIN M. 0. 
AUTHORIZED EDITION THE WERNER EDUCATIONAL SERIES 
(Authorized Edition) 
ESSENTIAL LESSONS 
IN 
HUMAN PHYSIOLOGY 
AND HYGIENE 
FOR SCHOOLS 
WINFRED E. BALDWIN. M.D, 
BY 
CHICAGO 
NEW YORK 
Werner School Book Company INDORSEMENT 
We, the undersigned, have examined the book entitled 
Essential Lessons in Physiology, by W. E. Baldwin, M.D. 
We find its teachings on the nature of alcoholic drinks and 
other narcotics and their effects upon the human system in 
connection with each division of the subject of physiology and 
hygiene, to be in harmony with the findings of modern science; 
we therefore are glad to commend the book for use for inter- 
mediate or lower grammar grade pupils, for which class of 
scholars its selection of matter, and language in the presenta- 
tion of that matter, is well adapted. 
Mary H. Hunt, 
World’s and National Superintendent of Scientific 
Temperance Instruction for the Woman’s Christian 
Temperance Union. 
Text-Book Committee: 
A. H. Plumb, D.D. 
David Dorchester, D.D. 
William A. Mowry, Ph D. 
William E. Sheldon, A.M. 
L. D. Mason, M.D. 
T. D. Crothers, M.D. 
Copyright, 1896 and 1898, 1 \ WEHrflj?MhoOL BOOK COMPANY PREFACE. 
In the preparation of the following chapters on hu- 
man physiology and hygiene, the author has attempted 
to present only such facts as are essential to the most 
practical knowledge of the subject—that is, such facts 
as people in the common walks of life most need to 
know, and such facts as all can remember and make 
use of whenever occasion demands. The plan of the 
work is such as adapts it to the needs, not only of in- 
termediate classes in graded schools, but of the large 
number of pupils in the country schools where the time 
which can be devoted to the study of this subject is 
necessarily limited. As a general rule, an effort has 
been made to speak briefly and to the point, without 
unnecessary verbiage ; and, wherever such could be 
done without sacrificing accuracy or clearness of state- 
ment, rigid condensation has been practiced. It is 
believed, however, that this will not detract from the 
interest of the narrative or from the practical worth 
of the lessons. Many interesting facts, especially in 
anatomy, have been ruled out as not being knowledge 
of value to those for.whom the book is intended. As 
the purpose and end of all such studies is the inculca- 
tion of rules and principles for the preservation of 
health, anatomy and are throughout made 
subservient to hygiene andi hygienic precepts. 
Technical terms have-been avoided as far as possi- 
ble. Instead of confronting the learner with a pre- 
3 4 
PREFACE. 
liminary chapter of definitions—such as is often found 
in text-books of this kind—and thus obliging him at the. 
outset to master a number of disconnected and, to him, 
meaningless statements, the more common terms and 
expressions peculiar to anatomy or physiology are ex- 
plained in alphabetical order at the end of the book. 
By this plan, the greater number of formal definitions 
are omitted from the regular lessons, and all are placed 
where they are most convenient for ready reference 
whenever required. 
Especial attention is given to the injurious effects of 
alcoholic drinks, tobacco, and other narcotics upon the 
human system, thus adapting the work to the require- 
ments of the law in several of the states. The supple- 
mentary chapters on emergencies and the care of the 
sick-room contain brief and simple directions, such as 
every boy or girl should learn when young and remem- 
ber all through life. The growing demand for school 
instruction regarding the prevention of contagious and 
communicable diseases—a demand which has found 
formal expression in the laws of at least one of the 
states of the Union—has induced the author to add a 
third supplementary chapter on that subject. Here, as 
in the other portions of the book, he has endeavored 
to state his message briefly, and to give that kind of 
information which every person can utilize and apply to 
the benefit of himself and those around him. It is 
knowledge of this kind, succinctly given, that imparts 
to the following chapters their distinctive character as 
essential lessons in human physiology and hygiene. 
New York, 1896. CONTENTS. 
CHAPTER 
PAGE 
1. Bone—Its Composition and Uses .... 9 
11. The Skeleton 15 
111. The Joints 24 
IV. The Muscles 27 
V. Care and Development of the Muscles . 35 
VI. The Blood 47 
VII. The Organs of Circulation 53 
VIII. The Circulation of the Blood 62 
IX. The Organs of Respiration 69 
X. Respiration 77 
XI. Food and Drink 86 
XII. Chewing and Swallowing 105 
XIII. Digestion in the Stomach m 
XIV. Digestion in the Intestines 117 
XV. The Skin 126 
XVI, Care of the Skin—Clothing 131 
XVII, The Nervous System 134 
5 6 
CONTENTS. 
CHAPTER 
PAGE 
XVIII, Seeing 151 
XIX. Hearing 160 
XX. Smelling—Tasting—Feeling .163 
Care of the Sick Room 166 
What to do in Emergencies 168 
Contagious and Communicable Diseases . 173 
Questions for Reviews and Examinations . 178 
Definitions 188 INTRODUCTION. 
PHYSIOLOGY is the science which treats of and 
describes the action and functions of the various parts 
and organs of the body. In its most general meaning 
it has to do with all forms of life, both animal and 
vegetable. That division of the science which re- 
lates to the human body alone is called human phy- 
siology. 
Anatomy is the science which treats of and describes 
the situation and the appearance of the component parts 
of the body. A general knowledge of the more com- 
mon facts of anatomy is essential to a clear under- 
standing of physiology, just as a knowledge of the 
structure and appearance of any object helps us to ac- 
quire a clearer comprehension of the nature and uses of 
that object. 
Hygiene is the study which relates to the laws of 
health. It tells us how to take care of our bodies in 
such a way as to promote the health and strength of 
the organs composing them, and warns us against prac- 
tices and habits which would be injurious to our phy- 
sical well-being, or would prevent the full and harmo- 
nious development of all the parts and organs. 
These three studies, physiology, anatomy, and hy- 
giene, are very closely related, each really depending 
upon or supplementing the others. They teach the 
most important facts that can be learned about our 
physical nature; how our bodies are made, and how 
7 8 
INTRODUCTION. 
to preserve them from injury or disease. Many lives 
are lost or destroyed every day through ignorance of 
these facts. 
A correct knowledge of the laws of health and of 
the structure of the human body warns us against 
breathing foul air and eating injurious foods; against 
using a sprained limb before it is able to perform its 
usual duties; against abusing the eyes through care- 
lessness or by overwork; against neglecting what ap- 
pears to be slight affections of various organs; and 
above all against the use of those insidious and power- 
ful enemies to good health and human happiness, alcohol 
and tobacco, the effects of which are such that they 
invariably tend to weaken the body and render it sub- 
ject to disease. Such knowledge also enables one to 
determine what to do, and do quickly, in cases of acci- 
dents or other emergencies; it gives plain, sensible 
directions for the care of the sick; and it shows how 
diseases, especially contagious or communicable dis- 
eases, may be avoided. 
A general diffusion of such knowledge among the 
people, and especially among those who are still in the 
vigor of youth and untrammeled by health-destroying 
habits, will doubtless produce untold benefits. If a 
judicious and practical application is made of the pre- 
cepts derived from such knowledge, it will certainly re- 
sult not only in saving many lives from disease and 
death, but in promoting the health, strength, and hap- 
piness of all who are brought within the radius of its 
influence. The importance, therefore, of the study of 
the essential facts of physiology, anatomy, and hygiene 
cannot well be overestimated. HUMAN PHYSIOLOGY 
CHAPTER I. 
BONE—ITS COMPOSITION AND USES. 
1. Properties of Bone.—Bone, as we usually see it, is 
dead bone and is of a uniformly white color. In the 
living body, however, it is quite different, being of a 
pinkish-white color on the outside and deep red within. 
It is one of the hardest substances in the human body. 
Besides being hard, it is somewhat elastic, and is cap- 
able of standing a very great strain without being 
broken. It is exceedingly strong, and can bear greater 
pressure than the toughest oak wood. 
2. Structure of Bone.—lf a section of bone be exam- 
ined, it will be seen that it is made up of two parts, 
or tissues.* One part is dense and compact, and 
looks very much like ivory. This is called the com- 
pact tissue. The other part is light and spongy, con- 
sisting of numerous fibers curiously interwoven to- 
gether. This is called the cancellous or spongy tissue. 
The outer surface of all the bones is of compact tissue, 
which forms a dense shell of varying thickness around 
the- cancellous tissue within. Where it is necessary 
* See Definitions, p. 190. 
9 HUMAN PHYSIOLOGY. 
that the bone should be very strong, it is largely made 
up of compact tissue. This is the case with the bones 
of the arms and the legs. Where lightness as well as 
strength is desirable, the bone is composed mostly of 
spongy or cancellous tissue, as in the small bones of 
Fig. 1.—A section of bone showing the compact tissue at 
the borders and the spongy tissue within. 
the hands and the feet, and in the enlarged ends of 
some other bones. 
3. Composition of Bone.—It has already been said that 
bone is both hard and elastic; these properties are 
given to it by two widely different substances, of which 
it is chiefly composed. 
One of these substances is earthy or inorganic, the 
other is animal or organic. The earthy or inorganic 
part of bone comprises about two-thirds of its weight, 
and is the part which gives to it its hardness. The 
animal or organic part of bone comprises about one- 
third of its weight, and is the part which gives to it its 
elasticity and toughness. 
Experiment.—Put a bone into a hot fire and let it stay 
there a few minutes, and then carefully remove it. * It 
is still of the same shape as before, but it is much BONE—ITS COMPOSITION AND USES. 
11 
lighter. The reason of this is that the animal or or- 
ganic part has been burned out of it, leaving only the 
earthy or inorganic part. It is now white and very 
brittle, and is easily broken or crushed. It is but little 
different from common lime. 
Now take another bone—a long, slender bone is the 
best—and immerse it for some time in any dilute min- 
eral acid, as dilute muriatic acid. The acid eats out the 
earthy part, but does not affect the animal part. The 
bone has still its original shape, but it is lighter in 
weight, and is soft and so pliable that it may easily be 
twisted or even tied in a knot. 
4. Bone in the Young and in the Aged—The composi- 
tion of bone, as regards the relative amount of earthy 
and animal matter, varies at different pe- 
riods of life. 
In the bones of very young persons 
there is a greater proportion of animal 
matter, and this causes them to be soft 
and very elastic. Consequently, these 
bones will bend, but they are very diffi- 
cult to break. In the aged the bones are 
very largely made up of lime, or earthy 
matter, and are, therefore, hard and brit- 
tle. These bones do not bend, but they 
are easily broken. 
Fig. 2.—Bone 
tied in a knot 
after its earthy 
matter has been 
removed. 
have a heavy fall, without any serious injury; but if an 
old person should have the same fall, he would suffer 
with one or more broken bones. 
Thus it often happens that a child may 
5. Growth and Development of Bone.—In infancy the 
skeleton or framework of the body consists almost al- 12 
HUMAN PHYSIOLOGY. 
together of cartilage, the white, glistening substance of- 
ten called gristle. As the body becomes older, earthy 
matter is deposited in the cartilage, and bone is grad- 
ually developed, becoming harder, and growing propor- 
tionately to the other parts of the body. It is supplied 
with nourishment in the same manner as the other parts 
of the body. One’s bones do not reach their full de- 
velopment until one is about twenty-five years old. 
6. Uses of Bone.—If it were not for the bones, the 
body would be merely a soft, shapeless mass; hence 
one very important use of the bones is to give to the 
body firmness and a definite form. Some of the 
bones afford protection to the delicate organs * which 
they partially enclose. Some act as levers and, with 
the muscles which are attached to them, give to the 
body its power of movement. 
7. The Periosteum.—Surrounding each bone, and close- 
ly covering it, is a tough fibrous membrane,* called 
the periosteum. In this periosteum there are a number 
of small blood-vessels which penetrate into the substance 
of the bone, and carry nourishment to it. The periosteum 
is of the greatest importance to the preservation and 
development of the bones. If it is bruised, or removed 
from any part of a bone, or if it becomes diseased, 
the bone ceases to be properly nourished, and soon 
dies. 
The periosteum is necessary to the formation of 
new bone. It is a well-known fact that a portion 
of bone may be removed from the body, and if the 
periosteum is not also removed, or seriously injured, 
new bone will soon be formed to replace that which has 
* See Definitions. BONE—ITS COMPOSITION AND USES. 
13 
been taken away. If, however, the periosteum be re- 
moved, no new bone will be formed. 
Some of the bones—especially the long, round ones— 
are hollow. The hollow space is filled with a fatty sub- 
stance called marrow. 
8. Diseases and Injuries of the Bones—The bones are 
liable to many diseases which hinder their proper growth 
and development. Rickets is a disease in which the 
bones lack a proper amount of earthy matter, and are 
so soft as to be readily bent out of shape, thus causing 
many deformities of the body. 
Children should not be allowed to stand upon their 
feet at too early an age, for the bones are then soft, 
and bend easily, and the deformity known as bow-legs 
is almost sure to result. 
Bones are frequently injured, sometimes by being se- 
verely bruised, and sometimes by being broken. A 
bruised bone is often a most serious affair, especially so 
if the periosteum be severely injured. In such a 
case partial or complete death of the bone sometimes 
follows. 
Accidents very often happen by which bones are 
broken. If a broken bone is properly set, that is, if 
the broken ends are rightly and skilfully placed to- 
gether and kept there, it soon grows whole again, and 
becomes as strong and as useful as it was before the in- 
jury, Carelessness or ignorance in the setting of broken 
bones is quite sure to produce deformity. Only a skil- 
ful physician, or surgeon, therefore, should be entrusted 
with this duty. 
9. Effects of Alcohol and Tobacco on the Bones.—When 
we speak of alcohol we mean alcoholic drinks—that is, 14 
HUMAN PHYSIOLOGY. 
all drinks which contain alcohol in any quantity, whether 
small or great. Hard cider, beer, ale, wine, whisky, 
brandy, and rum, are drinks of this class. 
Any kind of alcoholic drink, when taken internally, 
is likely to produce harmful consequences to the per- 
son who indulges in its use. The bones receive their 
nourishment from the blood, and if this blood is changed 
in any way, so as to have less nourishing power, then 
the growth and development of the bones is hindered, 
or sometimes stopped altogether. Now, alcohol does 
this very thing; that is, it weakens the nourishing 
power of the blood, and its injurious effects on the bones 
are well known. These effects are especially marked 
in young and growing persons, where every part of the 
body needs the best nourishment possible. 
It requires a much longer time for broken bones to heal 
in a person who is given to the use of alcoholic drinks 
than in one who is not. The same is true of other in- 
juries to the bones ; for here, too, the best of nourish- 
ment and plenty of pure blood are needed to promote 
recovery, and neither is supplied in persons who in- 
dulge in alcoholic drinks. 
Tobacco also has a deleterious effect upon the nour- 
ishment and development of the bones. Its habitual use 
by young and growing persons is especially injurious. 
While interfering with the general nutrition of the body, 
it interferes also with the nutrition of the bones ; and 
proper nourishment not being given, the growth of the 
bones is stunted, and their proper development is him 
dered. Boys who use tobacco in any form cannot ex- 
pect to become as vigorous men as they might if they 
had never touched it. THE SKELETON. 
15 
CHAPTER 11. 
THE SKELETON. 
10, The Skeleton.—The bones of the human body are 
so arranged and joined together as to form a framework 
upon which the other parts of the body are built and sup- 
ported. This framework of bones is called the skeleton. 
There are about two hundred bones in the human skele- 
ton, and these are joined to one another by means of 
ligaments and cartilages. The ligaments and cartilages, 
although they are not bone, are necessary to the con- 
struction of the skeleton, for they serve to hold the 
various bones together, and keep them in their proper 
places. The ligaments are strong bands of fibrous tis- 
sue ; the cartilages are soft, glistening substances, form- 
ing what is commonly called gristle. The framework of 
the living human body, therefore, is formed of three 
different structures—bones, ligaments, and cartilages. 
11. Classification of Bones.—The bones of the skeleton 
are divided into four classes : 
(1) Long bones ; 
(2) Short bones; 
(3) Flat bones; 
(4) Irregular bones. 
The long bones, besides having other uses, act as 
levers, aiding in the movement of the different parts 
of the body. They are found in the legs and the arms, 
the fingers and toes. 16 
HUMAN PHYSIOLOGY. 
The short bones are composed mostly of cancellous or 
spongy tissue, and are found in the hands and the feet, 
where lightness is necessary. 
The flat bones are chiefly used for the protection of 
softer parts of the body. Such are the principal bones 
of the skull, which serve to encase and protect the brain. 
The irregular bones have not only various shapes but 
various uses. The bones of the face and those of the 
backbone are examples. 
12. Groups of Bones.—For convenience of study, the 
bones of the skeleton are divided into three groups:— 
(i) The bones of the head ; 
(2) The bones of the trunk; 
(3) The bones of the extremities, 
13. The Bones of the Head.—The bones of the head 
form what is 
known as the 
skull. The skull 
comprises the 
face, and a hol- 
low, bony case 
for holding the 
brain. This lat- 
ter portion of 
the skull is 
called the cra- 
nium, and con- 
sists of eight 
bones. Its walls 
are composed of 
flat bones,which 
are very strong. 
Fig. 3.—Bonks op the Head. THE SKELETON. 
17 
These bones are joined together by tooth-like edges, 
those of each bone locking into those of another just 
as pieces of carpenter-work are dovetailed together. 
The point where two or more bones are thus fastened 
together is called a suture. 
The bones of the face are fourteen in number; they 
are irregular in shape and are united by sutures. The 
only movable bone in the face is the lower jaw. The 
bones of the face are so arranged as to give position and 
shape to the mouth, the nose, the prominence of the 
cheeks, and the eye sockets. 
14. Bones of the Trunk—The trunk comprises all the 
body except the head and the upper and lower ex- 
tremities. 
The backbone, or spinal column, is the chief support 
of the trunk. It is composed of twenty-four small 
irregular bones, piled one 
upon another, forming a 
strong pillar upon which 
is supported the head. 
These small bones are 
called vertebrce. The ver- 
tebrae are of such a shape 
that when they are all 
placed one upon another, a 
canal, or circular passage, is 
formed extending through 
almost the whole length 
of the backbone, or spinal 
column. Through this canal 
Fig. 4.—A Vertebra. 
A. —The body of the Vertebra. 
B. —Transverse Process. 
C. Spinous Process for the attach- 
ment of muscles. 
there passes a substance called the spinal cord, about 
which we shall learn more at a future time. HUMAN PHYSIOLOGY. 
The vertebrae are attached to one another by strong 
and very elastic ligaments, and between each pair of 
Spines, 
or spinal V 
processes, j 
them is a soft cushion of 
cartilage. This cartilage 
is of much importance. 
It acts as a cushion and 
Vertebrae of 
the neck. 
breaks the force of any 
sudden jar or shock, which 
otherwise might injure the 
brain or the spinal column 
Vertebra of 
the back. 
itself. The spinal column 
. 
is capable of movement to 
a limited extent. When 
you lean forward, the front 
parts of the cartilages, 
being soft and elastic, are 
pressed out and made thin- 
ner; and when you again 
take an upright position, 
Vertebrae of 
the loins. 
they regain their original 
shape. If, when sitting, you 
should allow your back to 
incline forward continually, 
these cartilages would after 
awhile lose their elasticity 
and be unable to regain 
their proper shape. It is 
in this way that the deform- 
ity of round shoulders is 
often caused. The spinal 
Fig. s.—The Spinal Column. 
column serves as a support for the whole body. It pro- 
tects the spinal cord, and to it, at different places, are THE SKELETON. 
19 
fastened a great many strong muscles which help to keep 
the body erect, or aid in 
its various movements. 
In the trunk there are 
two cavities, called re- 
spectively the thorax, or 
chest, and the abdomen. 
The chest occupies 
the upper half of the 
trunk and contains the 
heart and the lungs. 
The abdomen occupies 
the lower half of the 
trunk and contains the 
stomach and several 
other organs. The bones 
that enclose the chest 
are the sternum or 
Fig. 6.—The Chest. 
breastbone in front, and twelve ribs on each side. The 
S. S.—The spinal column. 
ribs are all joined to the back- 
bone, and most of them to 
the sternum in front, as shown 
in Fig. 6. The bones of the 
chest form a kind of cage for 
the protection of the import- 
ant organs that are within it. 
The pelvis is a cup-shaped 
basin at the lower part of the 
abdomen. It is composed 
chiefly of two large irregular 
bones called the hip-bones. 
It serves to contain and sup- 
Fig. 7.—The Pelvis and Thigh Bones, 20 
HUMAN PHYSIOLOGY. 
port the organs of the abdomen. The pelvis is con- 
nected with the backbone, and serves for the attach- 
ment of the thigh bones. 
15. The Bones of the Extremities.—The upper extrem- 
ities comprise the shoulders, arms, and hands. In 
each shoulder there are two bones: the 
clavicle or collar-bone in front, and the scap- 
ula or shoulder-blade behind. 
The arm from the shoulder to 
the elbow consists of one bone 
called the humerus. The 
part of the arm between the 
elbow and the wrist is called 
the forearm and consists of 
two bones, the radius and the 
ulna. The wrist is composed 
of eight small short bones 
called the carpal or wrist 
bones. From the wrist to the 
fingers are five bones called 
the metacarpal bones; and in 
the fingers are fourteen bones 
called the phalanges, two in 
the thumb and three in each 
finger. 
The lower extremities com- 
prise the legs and feet. 
The large bone extending • 
from the hip to the knee is 
Fig. B.—Bones of 
the Shoulder, 
Arm, and Hand. 
Sc.—Scapula. 
Cl.—Clavicle. 
U.—Ulna. 
R.—Radius. 
C.—Carpal Bones. 
Me.—Metacarpal 
Bones. 
Fig. 9.—Bonks of 
the Leg and Foot, 
F— Femur. 
P.—Patella. 
Tb.—Tibia. 
Fb.-—Fibula. 
Tr.—Tarsal Bones. 
Mt.—Metatarsal 
Bones. 
H.—Phalanges. 
called the femur, or thigh bone. It is 
the longest and strongest bone of the 
body. Extending from the knee to the THE SKELETON. 
21 
ankle are two bones, a large one called the tibia and a 
smaller one called the fibula. Resting against and in 
front of the knee-joint, is a small bone, flat and nearly 
round, known as the patella, or knee-cap. The use of 
the knee-cap is to protect the joint from injury in case 
of a blow or a fall. The ankle and heel are made up 
of seven small bones called tarsal bones. The arched 
shape of the foot gives elasticity to the step, and pre- 
vents the jar to the body which would otherwise oc- 
cur in walking, running, or leaping. The instep and 
arch of the foot contain five bones called metatarsal 
bones, and the toes are formed of fourteen bones called 
phalanges. 
The long bones of the extremities have their ends 
enlarged. (See figs. 8 and 9.) This is to form the joints 
and to give more room for the attachment of mus- 
cles. These enlarged ends of the bones are composed 
mostly of cancellous or spongy tissue. This is to 
give lightness, for if these ends were composed of com- 
pact tissue they would be so heavy as to make motion 
difficult and awkward. The part of the bone between 
the enlarged portions is called the shaft, and is hol- 
low. It is composed of compact tissue and the hollow 
space is filled with marrow. 
Rides for the Care of the Bones:— 
(l) Avoid straining them beyond their strength. 
(2) Avoid the habit of stooping or leaning forward. 
(3) Avoid tight clothing, which, by compressing the 
ribs, may cause deformity of the chest. Do not wear ill- 
fitting shoes, for they will be likely to disfigure the feet. 
(4) Beware of the use of tobacco, and shun all alco- 
holic drinks. Skull.- 
Collar-bone. 
Shoulder-blade.' 
Breast-bone.— 
Ribs. - 
-Humerus. 
False ribs.. 
Spinal 
column. 
-Radius. 
Sacrum. 
Pelvis. - 
End of 
spine. ~ 
-Ulna. 
Bones of 
wrist and 
hand. 
-Femur or thigh-bone. 
-Patella or knee-cap. 
-Tibia. 
Fibula. 
Fig, 10. 
Bonos of 
auklo 
and foot. THE SKELETON. 
23 
REVIEW—BONES OF THE SKELETON. 
1 Occipital bone. (Back of head.) 
2 Parietal bones. (Sides of head.) 
2 Temporal bones. (Sides of head.) 
1 Frontal bone. (Forehead.) 
Cranium, 
1 Sphenoid bone. 
1 Ethmoid bone. 
(Base of skull.) 
THE 
SKULL. 
2 Malar bones. (Cheek bones.) 
2 Lachrymal bones. (In orbit of the 
eye.) 
2 Nasal bones. (Nose.) 
2 Inferior turbinated bones. 
Face. 
1 Vomer. (Part of partition of nose.) 
2 Superior maxillary bones. (Upper 
jaw.) 
1 Inferior maxillary bone. (Lower 
jaw.) 
2 Palate bones. 
1 Hyoid bone. (At the base of the 
tongue.) 
THE 
TRUNK, 
Spinal 
Column. 
24 Vertebrae. 
x Sacrum. 
1 Coccyx. 
(At the lower end of the 
spinal column.) 
24 Ribs. 
1 Sternum. (Breastbone.) 
2 Os Innominatae. (Hip-bones.) 
Chest. 
2 Clavicles. (Collar-bones.) 
2 Scapulae. (Shoulder-blades.) 
2 Humeri. (Upper arms.) 
UPPER EXTREMITIES. 
2 Radii, i 
2 Ulnae. 
16 Carpal bones. (Wrists.) 
10 Metacarpal bones. (Hands.) 
28 Phalanges. (Fingers.) 
2 Femurs. (Thigh-bones.) 
(Forearms. 
2 Tibiae. 
2 Fibulae. 
(Legs.) 
LOWER EXTREMITIES. 
2 Patellae. (Knee-caps.) 
14 Tarsal bones. (Ankles.) 
10 Metatarsal bones. (Feet.) 
28 Phalanges. (Toes.) 
In the skull 22 bones. 
In the trunk 54 bones. 
In the extremities 124 bones. 
Note: The teeth are not bones. 
Total, 200 24 
HUMAN PHYSIOLOGY. 
CHAPTER 111. 
THE JOINTS, 
16. Definition.—As has already been stated, the bones 
of the living skeleton are joined one to another. This 
is accomplished in most cases by the aid of ligaments 
and cartilages. Any connection of two or more bones 
forms what is called a joint. 
17. Immovable and Movable Joints.—Some joints are 
incapable of motion, and are called immovable joints. 
The sutures of the cranium and of the face-bones are ex- 
amples of this class of joints. All joints that are capable 
of motion are called movable joints. This class includes 
nearly all the joints of the body. In 
such joints the bones are fastened to- 
gether by ligaments, and the connecting 
parts are protected by cartilages. 
Around each movable joint there is 
a delicate membraneous sac, which se- 
cretes an extremely viscid substance 
having much the appearance of the 
white of an egg. This substance flows, 
as it is needed, directly into the joint 
and serves to lubricate it, just as oil 
lubricates the parts of a machine. This 
prevents any friction between the bones 
when they move upon each other at 
Fig. 11.—The Elbow- 
Joint. 
Section showing it as 
a hinge joint. 
the joint. If it were not for this lubricating fluid, the 
free motion of the joints would be greatly hindered. THE JOINTS. 
25 
18. Kinds of Joints.—Movable joints are classified ac- 
cording to the kind of motion of which they are cap- 
able. In a ball and socket joint the ball-like extremity 
of one bone is set 
into a cup-shaped 
cavity in another. 
This kind of joint is 
capable of motion 
in all directions. 
The hip-joint and 
the shoulder-joint 
are both ball-and- 
socket joints. 
The hinge-joint 
is one which has a 
hinge-like motion; 
that is, it is capa- 
ble of motion in 
only two direc- 
tions, backward 
and forward. Ex- 
amples of hinge- 
joints are the el- 
bow, the knee, and 
the ankle. 
Fig. 12.—The Hip-Joint. A Typical Ball and 
Socket Joint. 
19. Diseases and Injuries of the Joints.—Rheumatism 
is a disease in which there is inflammation in and 
around the joints. Exposure to cold and the sud- 
den chilling of the body, are among the exciting 
causes of this disease, and hence should be avoided 
whenever possible. Severe inflammation of the joints 
occurs from various causes, and should always receive 26 
HUMAN PHYSIOLOGY. 
careful attention and proper treatment by a phy- 
sician. 
A sprained joint is of common occurrence. It is 
sometimes a very serious injury, particularly when it 
happens that the ligaments around the joint are torn 
or injured. Perfect rest is always necessary to the 
recovery of a sprained joint. The joint should have 
the best of care, and it should be remembered that an 
injury of this kind is often as difficult to heal as a 
broken bone. 
When the end of one of the bones forming a joint 
is forced out of its proper place by any cause, a dis- 
location is produced, or as we commonly say, “the 
bone is out of joint.” When this happens to a joint, 
all motion in it is impossible until the dislocation has 
been reduced, that is until the bone has been placed in 
its natural position again. 
In injuries of the joints, as well as in injuries of the 
bones, recovery takes place much sooner in persons 
who do not indulge in alcoholic drinks than it does in 
those who are so addicted. It is a well proved fact 
that alcohol drinkers are slow to recover from any 
injuries or diseases. 
Rules for the Care of the foints:— 
(i) Persons who are predisposed to rheumatism 
should be doubly careful to guard against colds, or any 
sudden chilling of the body. 
(2) When a joint has been sprained no attempt should 
be made to use it until it has fully recovered. 
(3) When a bone is dislocated, or out of joint, a phy- 
sician or surgeon should always be called to replace it 
in its natural position. THE MUSCLES. 
27 
CHAPTER IV. 
THE MUSCLES. 
20. Tissues.—The elements or structures which enter 
into and go to make up any organ are called tissues. 
There are many kinds of tissues in the body. 
Fibrous tissue consists of long, thread-like substances 
called fibers, which are very strong and tough. This 
kind of tissue is found in all parts of the body, binding 
the various parts and structures together, and serving 
for both support and protection. 
Adipose or fatty tissue consists mainly of fat. It is 
found in many parts of the body. 
Osseous or bony tissue comprises the greater part of 
the substance of the bones. As has already been stated, 
it is a very dense, hard tissue, and is either compact 
or cancellous. (See § 3.) 
Cartilaginous tissue is the substance composing the 
cartilages. 
Nerve tissue consists of a thread-like substance called 
nerve-fiber, united with a peculiar substance made of 
numerous small bodies known as nerve-cells. This 
tissue forms the brain, the spinal cord, and the nerves. 
21. Muscular Tissue—The muscles are made up of 
what is called muscular tissue. This tissue consists of 
bundles of fibers, called muscular fibers, bound together 
by fibrous tissue. These fibers are elastic and have a 
very peculiar and wonderful property called contractil- 
ity ; that is they are capable under certain conditions of 28 
HUMAN PHYSIOLOGY. 
becoming shorter. In every part of the muscles there 
are numerous blood-vessels and nerves. 
22. Kinds of Muscles.—The muscles of the body are of 
two classes: voluntary muscles and involuntary muscles. 
The voluntary muscles are those that are 
capable of being put into motion by the will. 
They are composed of reddish fibers, and 
each muscle is intended to aid in some move- 
ment of the body. All the muscles lying on the 
outside of the skeleton are voluntary muscles. 
The involuntary muscles are 
not capable of being put into ac- 
tion by the will. They are com- 
posed of fibers that are paler in 
color and of a different shape 
from those which compose volun- 
tary muscles. 
Involuntary muscular tissue en- 
ters into the formation of the in- 
Fig. 13.—Bun- 
dle of V oluntary 
Muscular 
Fibers. 
ternal organs, as the stomach and the intes- 
tines. The heart is an involuntary muscle, 
but the muscular fibers of which it is com- 
posed are similar in appearance and structure 
to those of the voluntary type, 
23. Attachment of Muscles.—Voluntary mus- 
cles are generally attached at each end to 
some part of the body, one end being fas- 
Fig. 14. Fi- 
bers of Invol- 
untary Mus- 
cular Tissue. 
A. —A bundle 
of fibers. 
B. —An isolat- 
ed muscular 
fiber, very 
highly mag- 
nified. 
tened to a fixed point, the other to a movable point. 
Some muscles are attached directly to a bone, but many 
are attached to it by means of cords of fibrous tissue 
called tendons. One end of the tendon is continuous with 
the substance of the muscle, the other end blends with THE MUSCLES. 
29 
the bone and periosteum. This is illustrated in Fig. 
15, below. 
24. How Muscles Act.—We have said that muscu- 
lar tissue possesses the power of contractility. Now 
when a muscle contracts it becomes shorter and thicker, 
and its two ends are drawn closer together. This action 
of a muscle is nicely 
shown when you bend 
the elbow. Youcansee 
and feel the muscle on 
the front of the upper 
arm (the biceps mus- 
cle) become thicker 
and shorter as it con- 
tracts, thus drawing 
its two ends 
closer to each 
other; and as one 
end is fixed at 
the shoulder, the 
other end which 
is attached to the 
forearm, draws the 
forearm nearer to the 
shoulder. This contrac 
tion of muscular tissue takes 
place whenever it is subjected 
Fig. 15.—Bending the Elbow. 
Showing the action of a muscle in 
raising the forearm. 
to a certain kind of irritation ; 
in life the nerves supply the 
stimulus or irritation necessary to bring about this 
contraction. All the voluntary muscles act on the same 
principle. 30 
HUMAN PHYSIOLOGY. 
25. Form and Size of Muscles.—There are about five 
hundred muscles in the human body. They vary in 
shape and size according to the 
uses to which they are put. 
In the extremities the muscles 
are long and spindle-shaped. 
In the trunk they are large and 
broad, flat, and some of them 
fan - shaped. These muscles 
serve for protection as well as 
for motion. Some of the mus- 
cles are large and strong, and 
others are very small. 
Muscles have three very impor- 
tant properties : 
26. Properties of Muscles. 
Fig. 16.—Tendons of the 
Hand. 
(i) They are elastic. If they 
be stretched and made longer, 
they will, when free to act, return to their natural shape 
(2) They have the power of contracting; that is, of be- 
coming shorter. This property has already been no- 
ticed in § 24. 
(3) They have a peculiar sensibility, which enables 
us to appreciate weight and to tell whether a body is 
movable or immovable. 
27. Principal Muscles of the Body.—(1) Muscles of the 
head and neck. These are all small muscles. The mus- 
cles of the face have two objects to fulfill—one is to give 
expression to the face, the other is to aid in carrying 
on the act of chewing, or mastication. The muscles 
of expression are so placed and attached, that by the 
contraction of one or more of them, different emo- THE MUSCLES. 
31 
tions are manifested in the face. Thus some muscles 
produce a frown, others a smile; some close the 
eyelids, others open them ; some express laughter 
and joy, others 
weeping and sor- 
row. The muscles 
of mastication act 
by moving the 
lower jaw, raising 
and lowering it, 
and giving it its 
grinding motion. 
The principal mus- 
cle of mastication 
is called the mas- 
seter muscle. This 
is the muscle which 
elevates the lower 
jaw with such tre- 
mendous force. 
The muscles of the 
neck are arranged 
in layers and are of 
various shapes and 
sizes. They give 
Fig. 17.—Muscles of the Head and Neck. 
to the head its many different movements, and act as a 
protection to the large nerves and blood-vessels that 
are situated in the neck. 
(2) Muscles of the trunk. The muscles of the trunk 
are most of them large, broad, and flat. Those of the 
back are arranged in five layers, forming a thick mass 
°f muscles. They are attached to the backbone, and 32 
HUMAN PHYSIOLOGY. 
it is by their action that we are enabled to assume and 
maintain an upright position. These muscles hold the 
head in its proper position and give to it some of its 
movements. 
The muscles of the chest are broad, flat, and fan- 
shaped. They are so attached that by their contraction 
they aid in the act of breathing. The principal muscle 
of respiration is called the diaphragm. It is a large, 
flat muscle, separating the two cavities of the trunk. 
Above it is the chest, below it the abdomen. The walls 
of the abdominal cavity are formed of broad, flat mus- 
cles, which serve to protect its contents. 
(3) Muscles of the extremities. These muscles are, 
as a rule, long and spindle-shaped. By their action we 
are enabled to walk, and to use our hands and arms. 
They are all very strong, and are so situated and at- 
tached that they aid in the performance of a great va- 
riety of complex and important movements. Numer- 
ous small muscles give to the fingers their various 
delicate movements. 
28. Effects of Alcohol on the Muscles.—Muscular tissue 
constitutes the principal part of the flesh of the body. 
It is a delicate living structure. Alcohol has a tendency 
to destroy all living structures with which it comes in 
contact, and therefore does only harm to the muscu- 
lar tissue. In reality it acts as a poison to all forms of 
life. When alcohol, by which we mean beer, wine, 
ale, whisky, or any other alcoholic drink, is taken into 
the system, it mixes with the blood and is carried 
throughout the body. Alcohol thus comes in direct 
contact with the delicate muscular tissue, irritating it, and 
sometimes partially paralyzing it. It interferes with the THE MUSCLES. 
33 
contracting power of the muscles and prevents their 
proper development and growth. The continued use 
of alcohol causes the muscles to become flaccid, weak, 
and pale, and after a time changes the character of 
the muscular tissue itself. This change which takes 
place in the muscular tissue is called fatty degenera- 
tion, and consists in the depositing of particles of fat 
between the muscular fibers. After a while so much 
fat may be deposited that many of the muscular fibers 
are crowded out and destroyed, and partially or wholly 
replaced by fatty tissue. The result of this is that the 
muscles become weak and crippled, and are totally un- 
able to perform the work that they should. 
Many men who drink beer and other alcoholic liquors 
have large bodies, but this is due to fat and is no sign 
of health. They appear to be very strong, but this is 
not the case, for there is no strength in fat. Alcohol never 
increases muscular power. It blunts a man’s sen- 
sibilities and prevents him from realizing how tired he is. 
It also deceives his judgment, making him think he is 
stronger than before and able to do more work. But ex- 
periments show that he has grown weaker and that he can- 
not accomplish so much as if he had left alcohol alone. 
Many trades and occupations are such that they require 
accuracy and steadiness of muscular action. Persons 
engaged in such occupations do not dare to indulge in 
alcoholic drinks. In proportion to the amount taken, 
alcohol acts upon the muscles in such a way as to im- 
pair both their accuracy and steadiness. The muscles 
°f the drinker become weak and tremulous. They 
sometimes even reach such an advanced stage of degen- 
eration that they lose their power of concerted motion. 34 
HUMAN PHYSIOLOGY. 
If you would see for yourselves this dreadful action of 
alcohol on the muscular system, notice the tottering 
walk and the trembling, twitching hands and arms of 
some habitual drunkard. 
To give strength to the muscles we must have food 
of the right kind and in proper quantities. Alcohol is 
not a food in any sense of the word, it does not give 
nourishment or strength to any part of the body, but it 
does interfere with the nutrition of the body, and there- 
by takes away its strength. 
29. Effects of Tobacco on the Muscles—lt has already 
been stated that muscular tissue requires for its proper 
development, good nourishment. The use of tobacco 
tends to interfere with proper digestion, and therefore 
with the supplying of proper nourishment to the vari- 
ous tissues. The muscular system is thus made to suf- 
fer, and its development is retarded. 
The use of tobacco by young and growing persons 
tends to dwarf the whole body, and consequently the 
muscular system. Tobacco lessens the muscular power 
and, like alcohol, prevents accuracy and steadiness of 
muscular action. Persons whose occupation demands 
steady muscles, rarely indulge in it, for it unfits them more 
or less for their work. Its injurious effects upon boys have 
become so generally recognized, that in some countries 
laws have been passed to restrict its use. The use of to- 
bacco is strictly forbidden in the naval and military schools 
of the United States. The tobacco habit is almost always 
acquired in youth. The boy who abstains strictly from 
its use will not want to indulge in it when he becomes a 
man. But tobacco is harmful not only to young persons; 
it has its bad effects also on full-grown people. CARE AND DEVELOPMENT OF THE MUSCLES. 
35 
CHAPTER V. 
CARE AND DEVELOPMENT OF THE MUSCLES. 
30. Exercise.—To develop the muscles properly, and 
to promote their growth and health, they must be used. 
If a muscle is allowed to remain entirely idle, it finally 
loses its power to make use of the nourishment that is 
provided, becomes soft and flaccid, and gradually grows 
smaller and weaker, until at length nearly all of the mus- 
cular tissue disappears. Exercise increases the flow of 
blood to the muscles, and thus promotes their nourish- 
ment and stimulates their growth. The effects of exer- 
cise are seen in the large, hard, and strong muscles of 
men who do manual labor, when contrasted with the 
thin and flabby muscles of professional men who are 
not accustomed to much exercise. Exercise is essen- 
tial to the health of the whole body ; it increases the 
circulation and the power of breathing, and stimulates 
every part of the body to a good healthy growth. Out- 
door exercise is the most conducive to health, though 
indoor exercise has also many good effects. To obtain 
the greatest advantage from exercise, it should be reg- 
ular and systematic, and should be taken in proper 
amounts; then the muscles grow healthy and strong, 
the joints become flexible, the circulation of the blood 
is quickened, and the power of endurance is increased. 
31. Excessive Exercise.—A proper amount of exer- 
cise is beneficial, but too much of it is harmful. At 
every contraction a muscle loses some of its substance; 36 
HUMAN PHYSIOLOGY. 
that is, a part of its tissue becomes worn out and is 
destroyed. This tissue however is constantly being 
renewed by the nourishment supplied to the muscle 
from the blood. If a muscle be too severely exercised, 
this wearing out of its tissue takes place faster than 
new material can be formed, and hence the muscle 
becomes fatigued and is unable to do its regular amount 
of work. When a muscle becomes fatigued it takes 
quite a time for it to regain its normal condition. 
Exercise should never be continued until it produces 
excessive fatigue. 
32. Indoor Exercises.—The use of gymnastic exer- 
cises, especially by students and others who are con- 
fined much of the time indoors, is a valuable means of 
promoting the development of the muscles and the 
growth and strength of the body. These exercises 
may be so conducted as to bring into action all the mus- 
cles of the body. Many of them may be taken in the 
schoolroom or at home with most beneficial results. 
A certain time each day should be devoted to them, 
and if they are practiced faithfully and systematically, 
the result will be stronger, healthier, and better devel- 
oped bodies. 
The following is a series of indoor exercises which 
may be easily practiced either in the home or in the 
schoolroom. They should be conducted in such a 
manner that each group of muscles shall receive its 
proper share of attention and the whole body be de- 
veloped symmetrically. In most of these exercises 
dumb-bells are supposed to be used. One-pound bells 
are heavy enough to begin with. If dumb-bells are not 
available, practice with the hands tightly closed. CARE AND DEVELOPMENT OF THE MUSCLES. 
33. Exercises for the Muscles of the Back— Exercise I. 
■Stand up straight with the chest expanded and the 
arms out in front of you. Have 
a dumb-bell in each hand. Now 
draw first one elbow and then 
the other quickly back, returning 
them alternately to their first posi- 
tion. This brings into play the mus- 
cles on and between the shoulders. 
Exercise ll.—Stand erect with the 
arms hanging down 
at the sides, and a 
dumb-bell in each 
Fig. 18.—Exercise I. 
hand. Keeping the backs of the 
hands turned upward, raise them 
behind you as far as you can. 
Repeat this exercise eight or 
ten times. This will strengthen 
the muscles on the back of the 
shoulders. 
Exercise lll.—Stand erect 
with a dumb-bell in each hand 
and the arms stretched out in 
Fig. 19.—Exercise 11. 
front of you on a 
level with your 
shoulders. Now 
bring your hands 
around back of you 
as far as you can, 
keeping the arms 
Fig. 20.—Exercise 111. 38 
HUMAN PHYSIOLOGY. 
straight all the while and on a level with the shoulders ; 
then bring them forward again, and so on six to ten 
times each day. This exercise 
puts the muscles of the shoulder 
into action, and will in- 
crease their strength 
Exercise IV.—Stand up 
straight with your hands 
clasped on the back of 
your neck. Now lean 
forward as far as you 
can. Hold the body 
in this position till 
you count ten, then 
slowly rise until you 
are again in an erect 
position. Do this a 
It is good exercise for the muscles of the lower part of 
the back. These are the muscles that we use a good 
Fig. 21.—Exercise IV. 
dozen times each day. 
deal in lifting. 
34. Chest Exercises.—Exercise V.—Stand as erect as 
possible. Hold 
the chin well up, 
and be careful to 
have the chest ex- 
panded. Raise 
your hands high 
above your head. 
Now without bend- 
Fig. 22.—Exercise V. 
ing the elbows, lower the hands far out sideways until 
they are on a level with the shoulders, then slowly raise CARE AND DEVELOPMENT OF THE MUSCLES. 
39 
them again, drawing in the breath as you do so. Do 
this six or eight times each day. 
Exercise VI.—Stand erect with the arms straight 
out at the sides on a level with 
the shoulders. Holding the arms 
straight, bring the dumb-bells to- 
gether in front of you, keeping 
them all the time on a level with 
the shoulders. Do this a dozen 
times each day. 
Exercise VII.—Stand in the aisle 
between two desks or tables, with 
a hand on each. Step back a little, 
then bend the elbows and lean for- 
ward till your chest is on a level 
with your hands, then slowly rise 
again. Try this exercise ten 
times each day. These chest ex- 
ercises will not only develop the 
muscles of the chest, but will ex- 
pand it and increase the breathing 
Fio. 23.—Exercise VI. 
capacity. 
35. Arm Exer- 
cises. Exercise 
VIII. Hold the 
arms full length in 
front of you with 
the hands opened 
wide. Now close 
the hands tightly, 
then open them, 
then close them 
Fig. 24.—Exercise VII. 40 
HUMAN PHYSIOLOGY. 
again, and keep on doing this twenty or thirty times 
each day. In this way you will put into action the mus- 
cles of the forearm that are used 
in the act of grasping. 
Exercise IX.—Stand erect and 
hold the arms straight out in front 
of you, having in one hand a 
long, round stick. Now twirl 
the stick as far as you can, first 
one way, then the other. Do this 
several times, and then practice in 
the same way with the other hand. 
In this manner you will promote 
the development of the muscles of 
the forearm that are used in twist- 
ing the hand and wrist. 
Exercise X.—Take a stick about 
two feet long, and grasp it with the 
hands, one at each end. Twist it 
from you with one hand, at the 
Fig. 35.—Exercise IX. 
same time try to twist it from you with 
the other. This puts into action the 
same muscles as in 
the previous exercise. 
Try this say eight 
times each day. 
Exercise XT.— 
Stand up straight, 
holding your arms 
down at your sides. 
Draw in your breath, 
Fig. 26.—Exercise X. 
expand your chest, and keeping the elbows close to the 
Fig. 27.—Exercise XI. CARE AND DEVELOPMENT OF THE MUSCLES. 
41 
body, bend the elbows, first one and then the other, 
raising the hands to the shoulders, dropping them again 
to the sides, and so on, say a dozen times each day. This 
is a good exercise for bringing into action the muscles of 
the upper arm that are used in bending the elbow. The 
principal one of these muscles is 
called the biceps muscle. Find it 
in the arm above the elbow. 
Exercise XII.—Stand up straight 
and hold your right arm down at 
your side, having the elbow bent a 
little. Place your left hand upon 
your right, and as you raise your 
right hand press down upon it with 
your left. Do the same with the 
other arm. Practice this simple 
exercise nine or ten times daily. 
Fig. 28.—Exercise XII. 
It also will bring into action the biceps muscle and 
give it greater strength. 
Exercise XIII.—Stand up straight, while you hold 
both hands high above your 
head. Bend the elbows, letting 
the hands slowly fall to the 
shoulders, then slowly raise them 
again. Do this nine or ten times 
a day. Do it also first with one 
hand, then with the other. This 
exercise will strengthen the mus- 
cles on the back of the upper 
arm. These are the muscles which 
you call into action when straight- 
Fig. 29.—Exer- 
cise XIII. 
ening the elbow. 42 
HUMAN PHYSIOLOGY. 
36. Shoulder Exercises.— Exercise XIV. Stand up 
straight, with your arms stretched out in front of you, 
the hands on a level with the waist. Now keep the el- 
bows straight, and raise the hands 
until they are level with the shoul- 
ders. Hold them there a little 
while, and then let them fall slowly 
to their original position. Practice 
this exercise nine or ten times 
each day. 
ExerciseXV.—Stand up straight, 
with the arms hanging down at 
your sides. Now, keeping the 
Fig. 30.—Exercise XIV. 
arms straight and the chin well up, slowly raise the hands 
out sideways until they are on a level with the shoulders. 
(See illustration with Exercise V.) Hold them there a 
little while, and then let them slowly drop to the sides 
again. Do this nine or ten times each day. 
Exercise XVl.—Stand up straight, with the elbows 
bent and the hands against 
the front part of the shoul- 
ders. Strike out forcibly, first 
with the right hand, then the 
left. Practice this nine or 
ten times each day. 
Exercise XVll.—Take the 
same position as before, but 
instead of striking out in front 
of you, strike upward above 
Fig. 31. —Exercise XVI. 
the head. Try this exercise as often as the preceding. 
37. Exercises to Strengthen the Legs.—ExerciseXVlll. 
—Stand up as straight as you can; then slowly bend the CARE AND DEVELOPMENT OF THE MUSCLES. 
43 
knees until your body falls about six inches; now 
straighten them again. Try this exercise nine or ten 
times. It will bring into action the muscles on the 
front of the thigh. 
Exercise XlX.—Stand up straight, with the heels and 
toes both touching the floor. Now slowly lift the heels 
and stand on your tip-toes, then slowly let your heels 
drop again. Practice this exercise asoftenasthe others. It 
will strengthen the muscles which form the calf of the leg. 
These few indoor exercises, if rightly practiced, will 
do much toward promoting the development of the mus- 
cles, increasing the strength, and promoting the health 
of the body. 
38. Outdoor Exercise.—Outdoor exercise of every kind 
is of the greatest importance to health, and must not 
be neglected. The various games and sports which 
bring into action the muscles of every part of the body 
should always be encouraged. Walking, running, and 
bicycling are among the most healthful of recreations. 
If you would be strong and well and happy do not al- 
low anything to prevent you from taking plenty of good 
outdoor exercise. 
39. Effects of Alcohol on Muscular Development.—You 
have already learned that alcohol is exceedingly harm- 
ful to the muscular tissue, that it weakens it, and 
causes an unhealthy depositing of fat in it. The mus- 
cles are capable of much training and development, 
but to train and develop them properly they must 
always be kept in a healthy condition. The muscles 
of alcohol drinkers are not healthy, and cannot be prop- 
erly developed. Athletes who are in training for the 
performance of feats requiring great physical strength 44 
HUMAN PHYSIOLOGY. 
or skill realize this fact, and are total abstainers. If 
they were not careful in this regard they would be 
unable to train their muscles properly. 
Very many persons imagine that beer makes them 
strong; and not a few have ruined their health, and 
brought sorrow and poverty into their homes because 
of this mistaken idea. They began by drinking beer or 
cider, which they said would not intoxicate but would 
“tone up the system.’’ But the habit of drinking being 
once formed, there was soon a craving for stronger 
liquors which would not be satisfied. Beer does not 
give strength, it does not act as a healthful tonic to the 
system. The use of it can lead to no good result : it 
may lead to infinite harm. 
Alcohol, as has already been said, makes the muscles 
weak. This has often been demonstrated in the follow- 
ing way: A man who is not addicted to the use of alco- 
holic drinks, is requested to test the strength of his mus- 
cles; after he has done so, a small quantity of alcohol is 
given him, and he tries his strength again; then more 
alcohol is given, and so on. In all cases it has been 
shown that after the man has taken the alcohol, his 
strength has been diminished. He may think that he is 
stronger, and such isthe effect of alcohol that when one be- 
comes addicted to its use he does not seem able to realize 
that his whole system is constantly being weakened by it. 
Alcohol lessens the power of endurance. Soldiers 
who do not use alcoholic drinks are able to march far- 
ther, and endure more hardships, while at the same time 
they suffer less fatigue, than those who are drinkers. 
In the recent war in Afghanistan, the British soldiers 
found that there was no comfort to be derived from CARE AND DEVELOPMENT OF THE MUSCLES. 
45 
beer or ale, but rather weakness and discomfort. They 
could withstand the heat of the deserts better wdien they 
drank nothing but water, and so they carried no alco- 
holic liquors with them on their marches. 
Explorers have frequently related similar experi- 
ences; and it has always been found that in difficult 
journeys, where many hardships are encountered, those 
persons who use alcoholic drinks are the first to give 
up to fatigue or to disease. Several years ago an ex- 
pedition was fitted out to search for Sir John Franklin 
who, with a company of adventurous explorers, had 
been lost somewhere in the Arctic seas. The ship was 
loaded with everything necessary for the comfort of 
the searching party, and besides food there was a plen- 
tiful supply of beer, whisky, and other strong drinks. 
It was thought that these liquors would help the men 
to resist the cold. At last the region of snow and ice 
was reached, and the experiment of fighting the cold 
with alcohol was begun. But it was soon found that 
alcohol was only a deceiver, and that the men who did 
not partake of it were much better able to withstand 
the rigors of the climate than were those who depended 
upon its help to “ keep the cold out.” And, indeed, it 
has invariably proved true that the drinker of alcohol is 
the first to succumb to any great extreme of tempera- 
ture, be it cold or heat. 
Persons who use alcoholic drinks are much more liable 
to disease and much less likely to recover than those 
who do not. Alcohol has the power to put the whole 
system in just such a condition that it is impossible for 
it to resist disease. Many muscular diseases may be 
traced directly to indulgence in alcoholic drinks. 46 
HUMAN PHYSIOLOGY. 
There are two kinds of muscles, voluntary and in 
voluntary. Voluntary muscles act as the will directs; 
involuntary muscles act independently of the will. 
REVIEW—THE MUSCLES. 
There are about five hundred muscles in the body. 
Muscles are elastic ; they have the power of contract- 
ing ; they have a peculiar sensibility. 
They are of different shapes—round, flat, spindle- 
shaped, fan-shaped, etc. They are the organs of motion. 
Exercise, when properly conducted, develops and 
strengthens the muscles. Excessive exercise should 
be avoided. By systematic indoor exercise one may 
gain much strength and promote the symmetrical 
growth of all parts of the body. Almost all kinds of 
outdoor exercise are beneficial. 
Alcohol has a paralyzing effect upon the muscular 
tissue. Its continued use causes fatty degeneration of 
the muscles. 
It never increases muscular power. It tends to make 
muscular movements both unsteady and inaccurate. 
Alcohol is not a food. It cannot, therefore, increase 
one’s strength. On the contrary, it makes the muscles 
weak. 
It makes the body unable to endure extremes of heat 
and cold. It makes the system unable to resist disease. 
Tobacco also lessens muscular power. 
It is especially injurious to young people, hindering 
the healthy development of their bodies. 
Persons who indulge in the use of alcoholic drinks, or 
who have acquired the habit of using tobacco, are not 
likely to excel in feats of strength, skill, or endurance. MUSCLES THE BLOOD. 
47 
CHAPTER VI. 
THE BLOOD. 
40. Nutrition of the Body.—We have already observed 
that the muscles by action become worn out, and 
must be built up again. This same wearing-out and 
building-up process is going on all the time, in every 
organ and tissue of the body. It matters not whether 
we are asleep or awake, working or resting, the pro- 
cess of destruction and repair is going on, and will con- 
tinue as long as we live. To repair the tissues that 
are thus worn out, proper nourishment must be supplied 
to every part of the body. This nourishment is distrib- 
uted by the blood, which, by means of its circulation, 
is carried to every organ, and permeates nearly every 
tissue. 
41. The Blood.—The blood is the nutritive fluid of 
the body. Its office is to carry nutrition to every tis- 
sue in the body. It is the most abundant fluid in 
the body, comprising about one-twelfth of its entire 
weight. Thus, a man of the average size has twelve or 
thirteen pounds of blood. The blood is carried to the 
different parts of the body through the blood-vessels, 
and is kept all the time in motion by the organs of cir- 
culation. It enters into and flows through every tissue 
of the body, except the teeth, the hair, and the nails. 
These obtain their nourishment by a process which we 
call absorption. 48 
HUMAN PHYSIOLOGY. 
42. Composition of the Blood.—If you should place a 
drop of blood under a microscope, and examine 
it, you would find it to be composed of a clear fluid 
holding in suspension a vast number of small, round, 
disc-shaped bodies. The clear fluid is called th & plasma, 
and the disc-shaped bodies are called blood corpuscles. 
43. The Plasma.—The plasma is the fluid part of the 
blood. It is a clear, nearly colorless liquid, and con- 
tains in solution the elements required for the nutrition 
of every tissue in the body. The plasma also serves to 
dissolve and carry the waste matter from the worn-out 
tissues to those organs whose work it is to remove such 
waste from the body. The 
plasma contains a peculiar 
element, which, on exposure 
to the air, causes the blood 
to become a jelly-like mass. 
This property will be further 
explained as we proceed. 
44. Blood Corpuscles.—The 
blood corpuscles consti- 
tute about one-half of the en- 
tire bulk of the blood. There 
Fig. 82.—Red Blood Corpuscles. 
Highly magnified. 
are two kinds of blood corpuscles; 
these are called the red and the 
white corpuscles. 
The red blood corpuscles are by 
far the most numerous, there being 
several hundred of them to one of 
the white corpuscles. They are the 
shape of flattened discs, and each 
measures about xsanr °f an inch in 
Fig. 33.—White Blood 
Corpuscles. 
As they appear when 
magnified. THE BLOOD. 
49 
diameter, and about of an inch in thickness. The 
white corpuscles are larger than the red ones, and in- 
stead of being disc-shaped, are globular in form. 
45. Uses of the Blood.—Since, with every beat of the 
heart, every action of the organs, and every motion that 
is made, some part of the body is worn out, or decom- 
posed—and, since this process goes on constantly—the 
whole body would soon be destroyed, if it were not 
that a process of repair and re-formation of tissue is 
going on at the same time. It is by means of the blood 
that this repairing process is performed. The blood 
not only carries to every tissue of the body that form 
of nourishment which is necessary to the repair of that 
tissue, but it at the same time absorbs and carries away 
the worn-out waste matter from the tissues, and deposits 
it in the proper organs, whence it is removed from the 
body. The principal organs concerned in this process 
of removal are the lungs, the kidneys, and the skin. 
Oxygen is one of the elements of the air, and is indis- 
pensable to all life actions. The red blood corpuscles 
convey this life-giving oxygen to the various tissues 
where it fulfills its proper office, stimulating the parts to 
action and producing a kind of combustion by which the 
worn-out tissues are decomposed. One of the results of 
such combustion is the formation of a waste matter called 
carbonic acid. This carbonic acid is very poisonous, and 
must be removed from the body. These same red blood 
corpuscles absorb it and carry it to the lungs, where 
it is separated from the blood and removed from the 
body during the acts of breathing. 
The white corpuscles of the blood are supposed to be 
concerned in the repair of diseased tissues, and especi- HUMAN PHYSIOLOGY. 
ally to have the power of destroying noxious germs 
which may have entered the blood, thus rendering the 
system less liable to disease. 
46. Coagulation of the Blood.—When blood is exposed 
to the air, its liquid form soon changes, and it be- 
comes a soft jelly-like mass called a clot. This pro- 
cess is called coagulation, and a clot is coagulated 
blood. It is caused by a hardening and contraction of 
the fibrin of the blood. The fibrin is one of the ele- 
ments of the plasma. As the fibrin contracts, it entan- 
gles in its net-like meshes the blood corpuscles. This 
power of the blood to coagulate is of the utmost 
importance to the human body, preventing great loss 
of blood from injuries, by plugging up the bleeding 
vessels. 
47. Effects of Alcohol on the Blood.—When alcohol is 
taken into the stomach it passes directly into the 
blood, mixes with it, and is carried to all parts of the 
body. Take a little blood, mix it with alcohol and ex- 
amine it through a microscope, and you will see that 
the red blood corpuscles have become smaller and are 
shrunken. We have just said that one of the great 
uses of the red blood corpuscles is to carry oxygen to 
the tissues. When the corpuscles become shrunken by 
mixing alcohol with the blood, their oxygen-carrying 
power is lessened, and all the tissues of the body suffer 
from an insufficient supply of oxygen. 
The red blood corpuscles are also concerned in the 
removal of waste matter from the tissues. When they 
are shrunken, this power is diminished, and some 
of the poisonous matter which ought to be removed 
remains in the system, and the system consequently THE BLOOD. 
51 
suffers more or less because of its retention. Especially 
is this true in regard to carbonic acid. 
Alcohol in the blood has also a direct effect upon the 
nutritive elements of the blood, and interferes with the 
nourishment of the various tissues. In persons addicted 
to the use of alcoholic drinks, all the tissues and organs 
of the body suffer from the want of good and proper 
nourishment. The consequence is that the proper de- 
velopment of the body is hindered. Alcohol, as we have 
already said, does not aid in the nutrition of the body in 
any way, but instead, by shrinking the blood corpuscles, 
it causes a temporary retention of waste matters which 
ought to be carried off by the blood. The appetite may 
be diminished, thereby leading to the delusion that the 
alcohol acts as a food. But this insufficient nourish- 
ment results in increasing in the drinker a desire for 
more alcohol. “Two tablespoonfuls of oatmeal,” says 
Dr. B. W. Richardson, “with one of pease meal, made 
into a liquid with milk and boiling water, and flavored 
according to taste with salt or with sugar, forms a 
drink worth any number of glasses of ale or other alco- 
holic fluid.” 
Recent experiments have gone far towards proving 
that alcohol has such an effect upon the blood as to ren- 
der it powerless to destroy disease germs. Careful ob- 
servations have also shown that alcohol has a peculiar 
influence upon the fibrin of the blood, affecting it 
variously according to its action upon the water which 
holds the fibrin in solution. In some instances it com- 
bines the water and fibrin in such a way as to destroy 
the power of coagulation. This explains why drinkers 
are more liable than others to bleed to death in case of 52 
HUMAN PHYSIOLOGY. 
accident; it explains also why surgical operations upon 
such persons are so frequently unsuccessful. In other 
cases, alcohol seems to have exactly the opposite effect 
upon the fibrin, extracting the water from it and causing 
coagulation while it is still in the blood-vessels. 
48. Effects of Tobacco on the Blood.—Tobacco contains 
a deadly poison called nicotine. So deadly is this 
poison that one or two drops of it is sufficient to kill a 
dog or any other small animal. By the use of tobacco, 
some of this poison is absorbed into the blood, and is 
carried to the various organs, exercising its poisonous 
effects on all the tissues. Sometimes severe cases of 
poisoning have resulted from tobacco juice or powdered 
tobacco coming in contact with some portion of the 
body from which the skin had been removed. This 
poisoning was caused by the deadly nicotine. 
Tobacco interferes with the nourishing qualities of 
the blood, and thus serves to prevent the proper growth 
and development of the body. Cigarettes are more in- 
jurious than any other form of tobacco. They tempt 
their users to a more extensive indulgence in the habit 
of smoking, and the practice of inhaling their smoke in- 
troduces larger quantities of the nicotine poison into the 
system. Young men who wish to have strong, healthy 
bodies should beware of acquiring the cigarette habit— 
a habit which is fraught with danger, and which at the 
best can add nothing to their physical strength. 
Experiments have shown that the habitual use of to- 
bacco causes the blood corpuscles to become less round, 
and to lose their power of adherence. The blood be- 
comes thinner, and the general health of the system is 
impaired. THE ORGANS OF CIRCULATION. 
53 
CHAPTER VII. 
THE ORGANS OF CIRCULATION. 
49. The Organs of Circulation.—The blood in the body 
is constantly in motion. This movement of the blood 
is called the circulation, and is produced and carried 
on by certain organs called the organs of circula- 
tion. These organs are the heart and the blood-vessels. 
There are three 
kinds of blood-ves- 
sels in the body, 
called respectively, 
arteries, capillaries, 
and veins. 
The heart is a hol- 
low, pear-shaped, 
50. The Heart. 
muscular organ, 
about the size of 
one’s fist. It is sit- 
uated in the chest 
cavity, slightly to 
the left side, be- 
tween the two 
lungs. It is held 
in position by 
large blood-vessels, 
which are attached 
to its base and to 
the back part of the 
Fig. 34.—The Heart. 
1. Right Ventricle. 
2. Left Ventricle. 
3. —Right Auricle. 
4. Left Auricle. 
5. —Aorta. 
6.—Pulmonary Artery. 
7, 8, 9.—Large Arteries. 
10.—Superior Vena Cava. 
11.—Pulmonary Veins. 54 
HUMAN PHYSIOLOGY. 
chest. The base of the heart is immovable, but not so 
the point, or apex. 
The heart is surrounded by and loosely enclosed in a 
strong membrane called the pericardium. Between 
this membrane and the heart there is a small quantity 
of clear fluid which acts as a lubricator, allowing the 
heart to move freely without producing any friction. 
The heart itself is composed entirely of muscu- 
lar tissue. It is an exceedingly strong organ, and 
is capable of contracting with great force. It is also 
hollow, its interior consisting of four distinct cavities. 
51. Cavities of the Heart.—The interior of the heart 
is divided by 
a muscular parti- 
tion into two parts, 
called the right and 
the left sides of the 
heart. The right 
side of the heart is 
the part which re- 
ceives the impure 
blood from the tis- 
sues, and sends it 
to the lungs to be 
purified. The left 
side of the heart 
receives the puri- 
fied blood from the 
lungs, and sends it 
to the various tis- 
sues. Each side of 
the heart is divided 
Fig. 35.—Cavities op the Heart. 
b.—Right Auricle, 
i.—Left Auricle. 
a, d, e, h.—Blood-vessels. 
c.—Right Ventricle. 
g.—Left Ventricle. THE ORGANS OF CIRCULATION, 
into two cavities, an upper and a lower, thus form- 
ing four distinct cavities, two upper ones and two 
lower ones. The upper cavities are called auricles, 
and the lower ones ventricles. There are then, a right 
and a left auricle, and a right and a left ventricle. The 
walls of the ventricles are thick and strong, those of the 
auricles are rather thin and not so strong. 
-52. Valves of the Heart.—The blood must flow only 
in one direction in the heart, and this is brought 
about by an arrangement of valves at the open- 
ings into and from the 
cavities of the heart. 
Between each auricle 
and ventricle is an 
orifice supplied with 
valves which open 
only downward into 
the ventricle. These 
allow the blood to 
flow from the auricle 
into the ventricle, but 
they close in such a 
way that the blood 
cannot flow from the 
ventricle into the au- 
Fig. 36.—Valves of One Side of the Heart, 
The blood flowing from the auricle. 
ricle. Passing out from each ventricle is a large blood- 
vessel. At the opening of each of these blood-vessels 
there are valves, which allow the blood to flow from 
the ventricles into the vessels, but not from the vessels 
into the ventricles. Several large blood-vessels open 
into the auricles, but these have no valves, as the mild 
force of the auricles renders valves unnecessary. It may 56 
HUMAN PHYSIOLSGY. 
thus be seen that the heart has four sets of valves, one set 
between each auricle 
and ventricle, and one 
set at the opening of 
the blood-vessel lead- 
ing from each ventri- 
cle. These valves are 
composed of a deli- 
cate but strong mem- 
brane. Their shape is 
such that when they 
are closed no blood 
can pass through 
them. Their action 
will be more fully 
described later on. 
Fig. 37.—Valves of One Side of the Heart. 
The blood flowing from the ventricle. 
53. Blood-Vessels Opening into and from the Heart.—lnto 
the right auricle open two large veins, one called the 
superior vena cava, the 
other the inferior vena 
cava. These pour into the 
right auricle the blood 
which has been brought 
from the tissues. From the 
right ventricle opens a 
large blood-vessel called 
the pulmonary artery. Into 
the left auricle open four 
blood-vessels called the 
pulmonary veins ; and from 
FIG- 38-— Blood-Vessels Opening into 
the Heart. 
the left ventricle opens the 
largest blood-vessel in the body, called the aorta. THE ORGANS OF CIRCULATION. 
57 
54. The Action of the Heart.—The heart may be called 
the force-pump which keeps the blood in motion. It 
has two movements, contraction and relaxation. When 
the heart contracts, its cavities become smaller, and 
the blood is forced from them into the blood-ves- 
sels. When it relaxes, or regains its proper size, the 
cavities are again filled with blood, only to be sent out 
into the blood-vessels again by another contraction. 
The heart contracts and relaxes, on an average, about 
seventy-two times a minute. 
55. The Sounds of the Heart.—lf you should place 
your ear on the chest of a person, over his heart, 
you might hear what is called “the heart-beat.” That 
is, with each action of the heart you could hear a sound. 
There are two different sounds occurring alternately 
with each movement of the heart. The first sound, or 
that which occurs when the heart contracts, is caused 
principally by the closing of the valves between the au- 
ricles and ventricles. The second sound, or that which 
occurs when the heart begins to relax, is caused by the 
closing of the valves at the openings of the blood-ves- 
sels into the ventricles. These sounds have certain char- 
acteristics by which the physician is able to determine 
the condition of the valves of the heart, and to tell 
whether one or more of them be diseased or incapa- 
ble of performing its proper work. 
56. Nerves of the Heart—The heart is supplied with 
two sets of nerves. One set of nerves causes the 
heart to beat rapidly, the other set restrains it, making 
it act slowly, and serving as a check to the first set. 
Whenever this latter set of nerves loses its power from 
any reason, the first set is no longer held in check by it? 58 
HUMAN PHYSIOLOGY. 
and the heart beats very rapidly, or as we might say, it 
runs away. 
57. The Pulse.—With each contraction of the heart, 
blood is forced through the arteries. If you place your 
finger on an artery you can feel it expand every time the 
blood is forced through it. This is called the pulse. 
The best place to feel the pulse is in the wrist just back 
of the ball of the thumb. 
The average frequency of the pulse is seventy-two to 
seventy-six times in a minute. It varies in frequency, 
however, in different persons and under different con- 
ditions. Sudden emotions, such as fright, joy, or grief, 
cause it to beat more rapidly. It beats more rapidly 
when one is working than when resting; and its fre- 
quency is also increased during digestion. Most dis- 
eases of the system cause the pulse to become more rapid. 
58. Capacity of the Heart—Each ventricle, at each 
contraction of the heart, forces into the blood-ves- 
sels about six ounces of blood. At this rate all the 
blood in the body passes through the heart in less 
than one minute. The aggregate force exerted by 
the heart in one day’s action is immense. It is esti- 
mated that the entire amount of blood forced from 
it, or rather through it, in the course of twenty-four 
hours is equal to more than 300 barrels. 
59. The Arteries.—The arteries are the vessels which 
convey the blood from the heart to the different 
parts of the body. They are cylindrical, having firm, elas- 
tic walls, formed of muscular and fibrous tissue. The 
main artery in the body is the aorta. It starts 
from the left ventricle of the heart, and divides and 
sub-divides into innumerable branches; as the arteries THE ORGANS OF CIRCULATION. 
59 
divide they become smaller and smaller, until finally 
they are so small as to be invisible to the naked eye. 
-6- The Capillaries.—The smallest arteries finally ter- 
minate in a sort of net-work of exceedingly small and 
delicate blood-vessels called cap- 
illaries. These capillaries exist 
in every part of the tissues of 
the body, and so closely do they 
lie together, that it is impossible 
to prick the skin with a needle, 
without injuring some of them. 
It is in the capillaries that the 
blood carries on its work of 
nourishing and rebuilding the 
body. It is also in the capillaries 
that it begins the process of re- 
Vein 
Artery 
Fiq. 39.—Capillary Blood- 
Vessels (Magnified.) 
moving the waste matter from the worn-out 
portions of the tissues. 
61. The Veins, The vessels which carry 
the blood from the tissues back towards the 
heart are called veins. The veins begin where 
the capillaries end, and at their beginning 
they are exceedingly small. They join one 
another, growing larger and larger, until 
finally all the veins of the upper part of the 
body unite to form one large vein, and 
those of the lower part of the body unite 
to form another. These two veins are the 
vena cavce (see § 5 3), and the blood from them, 
as has already been stated, is poured into 
Fig. 40. 
VALVES OF 
the Veins. 
the right auricle of the heart. The walls of the veins 
are thinner and contain less muscular tissue than the HUMAN PHYSIOLOGY. 
walls of the arteries. In the veins there are numerous 
valves, which are so arranged that the blood is allowed 
to flow through them only in the direction of the heart. 
When the veins are empty their walls collapse; but 
when the arteries are empty their walls retain their 
original shape. 
62. Effects of Alcohol on the Organs of Circulation.—When 
alcohol is taken into the body, the effect upon the 
heart is almost instant. The frequency of the heart’s 
action is increased, because the alcohol has a ten- 
dency to paralyze to a certain extent that set of 
nerves whose function it is to hold the heart’s action in 
check. This allows the other set of nerves to have free 
play, and consequently the heart is inclined to “ run 
away ” with itself. This increased action puts more 
work on the heart; and if it is kept up for some time, 
the heart becomes weakened on account of being so 
much over-worked. When the heart works naturally it 
rests nearly half of the time, but under the paralyzing 
effect of alcohol its period of rest is shortened, causing 
it, sooner or later, to become exhausted, and its action 
to become feeble and irregular. 
It has already been explained that alcohol interferes 
with the nutritive powers of the blood. The heart de- 
pends on the blood for its nourishment, and consequently 
when its nourishment is interfered with, it suffers just 
as other parts of the body would suffer from the same 
cause. Continued use of alcoholic drinks causes a deposit 
of fat in many of the tissues. This fatty degeneration 
has a special tendency to attack the heart. Particles of 
fat are deposited in the heart substance, crowding out and 
replacing the muscular fibres, and thus weakening the THE ORGANS OF CIRCULATION. 
action of the heart-muscle. This condition is most se- 
rious. The valves of the heart also often become dis- 
eased as a result of the continual use of alcoholic drinks. 
Alcohol has also a decidedly harmful effect on the 
blood-vessels. The walls of the blood-vessels are all sup- 
plied with nerves which regulate their size, thus control- 
ling the quantity of blood sent to each part of the body. 
Alcohol paralyzes these nerves, allowing the blood- 
vessels to become dilated and enlarged, so that their 
capacity is increased and too much blood is sent to 
certain parts. This action of alcohol on the blood- 
vessels is seen in the flushed face and the red nose of 
the habitual drinker. The enlargement of the blood-ves- 
sels causes their walls to become thinner and weaker, and 
it occasionally happens that they become so thin and 
weak as to be unable to withstand the pressure of the 
blood in them, and they burst. Fatty degeneration of 
the walls of the blood-vessels often occurs in habitual 
alcohol drinkers, weakening the walls and interfering 
with the proper circulation of blood. 
63. Effects of Tobacco on the Heart.— The use of to- 
bacco sometimes produces injurious effects upon the 
organs of circulation. It sometimes acts upon the nerves 
of the heart in such a way as to modify its action. 
A peculiar condition of this organ, known as “ tobac- 
co heart,” is common with persons who are habitual 
users of this narcotic poison. In such persons the 
heart’s action becomes irregular and weak; very slight 
influences cause it to beat rapidly, and moderate ex- 
ercise causes its action to be so forcible as to become 
troublesomely apparent to them. This results in the 
disease called palpitation of the heart. 62 
HUMAN PHYSIOLOGY. 
CHAPTER VIII. 
THE CIRCULATION OF THE BLOOD. 
64. Course of the Circulation. —ln the circulation, 
the blood goes from the heart through the system 
and then returns again to the heart. Let us trace a 
portion of blood through its circulation, beginning 
with the left ventricle. The 
blood in the left ventricle is 
forced through the aorta and its 
branches to all parts of the body. 
From the arteries the blood pass- 
es through the capillaries, then 
into the veins, and through the 
venae cavse it is emptied into the 
right auricle of the heart. From 
the right auricle it passes into 
the right ventricle, and is then 
sent through the pulmonary ar- 
fig. 41 .-Course OF the Ciecu- 
LATION THROUGH THE HEART. 
tery to the lungs. From the 
j 
the pulmonary veins back to the left auricle, then 
into the left ventricle, the place from which it origi- 
nally started. 
lungs the blood passes through 
65. Color of the Blood.—When the blood starts from 
the left ventricle it is of a bright red color, and so re- 
mains while it is in the arteries. After it circulates in 
the capillaries it becomes blue in color, and so re- 63 
THE CIRCULATION OF THE BLOOD. 
mains until it is purified in the lungs. Hence it is gen- 
erally said that arterial blood is bright red, and venous 
blood is bluish in color. 
The arterial blood is pure and contains much oxygen ; 
the venous blood is impure, containing much carbonic 
acid and other waste matter from the tissues. As this 
dark, impure blood passes through the lungs it loses its 
carbonic acid and takes up oxygen in its place, becom- 
ing again bright red in color as it returns to the left 
side of the heart. 
66. Proper Exercise and the Circulation.—The heart 
is a muscle, and is the organ most concerned in carry- 
ing on the circulation. Proper exercise of the body 
strengthens the heart’s action, as it does that of 
other muscles, and improves the circulation of the blood. 
It consequently tends to keep the whole body in good 
condition by aiding in its proper nutrition. If a person 
takes but little exercise, his heart soon becomes weak- 
ened and unable to endure exertion. Such a person 
suffers from shortness of breath, and, if obliged to per- 
form any unusual exercise, he is likely to be troubled 
with palpitation of the heart. Proper exercise is really 
necessary to the proper circulation of the blood. 
67. Disorders of the Circulation.— Diseased conditions 
of different parts of the body modify the proper 
circulation of the blood. Any disease of the heart 
always has this effect. The valves of the heart are 
often so diseased that they cannot perform their proper 
office, and the circulation is, as a consequence, weak- 
ened. Shortness of breath, dropsy, and general exhaus- 
tion often result from this obstruction of the circulation. 
Heat and cold have a decided influence on the circula- 64 
HUMAN PHYSIOLOGY. 
tion. Heat stimulates the heart’s action, and quickens 
the circulation. Extreme cold lowers the heart’s action, 
and enfeebles the circulation. This explains why in hot 
weather parts of the body are flushed, and in cold 
weather are pale and blue. It is best to avoid expos- 
ing the body to extreme heat or extreme cold, and to 
keep it so clothed as to adapt it to any state of the 
weather. Sudden emotions of joy or grief modify the 
heart’s action and the circulation. 
68. Hemorrhage. By hemorrhage is meant a loss 
of blood from the body. Nature has its own way of 
checking bleeding from 
a wounded blood-vessel. 
When an artery is cut 
its walls instantly con- 
tract, rendering the ves- 
sel smaller and causing 
the blood to escape more 
slowly, thus allowing it 
to coagulate. By coagu- 
lating, the blood clot 
serves to plug up the 
divided blood-vessels, 
and thus checks the 
bleeding from them. 
Very often, however, na- 
ture is unable of itself 
to check a severe hemor- 
rhage, and must be as- 
sisted. The best way of 
checking hemorrhage is 
by applying firm pres- 
Fiq. 42,—Injure!) Blood-Vessels. THE CIRCULATION OF THE BLOOD. 
65 
sure on the bleeding vessels. This pressure is to be ap- 
plied between the bleeding point and the heart, if the 
hemorrhage be from an artery; but if it be from a vein, 
the pressure is to be applied on the other side of the 
bleeding point. Thus in Fig. 42, A represents a bleed- 
ing artery and B the point where the pressure should 
be applied in such a case. C represents a bleeding vein 
and D the point where pressure should be applied. If 
the wound be small, apply pressure directly on it. The 
application of cold water or ice to a wound will often 
check quite profuse bleeding. 
By the application of certain substances called styp- 
tics we may produce excessive coagulation of the blood, 
tnus checking the bleeding. The principal styptics 
are the persulphate of iron, alum, tincture of iron, and 
tannic acid. The styptics should be used only when 
it is not possible to apply pressure to the bleeding 
vessels. 
69. Fainting.—When the circulation becomes so weak 
that the amount of blood sent to the head is not suf- 
ficient, a person faints, or becomes unconscious for a 
greater or less time. The face becomes pale, and the 
pulse is weak. To revive a person who is in a faint, lay 
him flat on his back, with the head lower than the feet 
if possible. This gives the blood a better chance to 
flow to the head. Now dash a little cold water into his 
face, or apply it to his head. This is usually all that is 
necessary to be done. A sufficient quantity of blood 
soon flows to the head, and the person recovers. 
70. Effects of Alcohol on the Circulation.—The harmful 
effects of alcohol upon the heart and the blood-ves- 
sels, modifying the heart’s action and the condition of 66 
HUMAN PHYSIOLOGY. 
the vessels, have already been alluded to. It is easy to un- 
derstand, therefore, that when it does this, it also neces- 
sarily interferes with and hinders the proper circulation 
of the blood. Too much blood is sent to some of the 
organs and not enough to others. An excess of blood 
is sent to the lungs, liver, stomach, and brain, causing 
congestion of these organs, and interfering with their 
proper work. The circulation in the skin becomes slug- 
gish, and the skin does not receive sufficient nutrition. 
This effect of alcohol on the circulation is easily seen 
in the face of an habitual drunkard. His nose and 
cheeks are purplish red in color, and are often cov- 
ered with unsightly pimples and blotches ; his eyes are 
blood-shot and watery; and his whole face is swollen, 
giving him the characteristic appearance of an alcohol 
user. 
The arteries of a person addicted to the use of alco- 
holic liquors become so changed that their walls are 
extremely weak. When this happens in the arteries of 
the brain they sometimes burst. In such case death is 
the immediate result, and the person is said to have 
died from apoplexy. Sometimes persons who do not 
use alcohol have apoplexy, but it is much more common 
with drinkers than with total abstainers. 
How to Promote the Healthy Action of the Circulatory 
Organs:— 
Eat wholesome food in proper quantities and at the 
right time. Take plenty of exercise. Avoid exposing 
the body to extreme heat or extreme cold. Have a 
care to adapt the clothing to the state of the weather. 
Avoid the use of any drink or other substance 
which may affect the heart’s natural action. CIRCULATION OF THE BLOOD, THE CIRCULATION OF THE BLOOD. 
67 
REVIEW—THE BLOOD AND THE CIRCULATION. 
The blood is the nutritive fluid of the body. It is 
composed of a clear fluid called plasma, and of two 
kinds of corpuscles, red and white. 
The blood in the body is all the time in circulation. 
The organs of circulation are the heart and the blood- 
vessels. 
The blood-vessels comprise the arteries, veins, and 
capillaries. 
In general, the arteries carry pure blood, the veins 
carry impure blood. The pulmonary artery, however, 
carries impure blood, and the pulmonary veins carry 
pure blood. 
The blood is purified in the lungs. Pure blood con- 
tains much life-giving oxygen ; impure blood contains 
much carbonic acid gas and other waste products. 
The blood carries to every tissue that form of nour- 
ishment which is necessary to its repair or growth. It 
also carries away the worn out portions of the tissue 
that are no longer of any use. 
The red blood corpuscles carry oxygen to the tissues. 
The white blood corpuscles aid in destroying noxious 
germs and in repairing diseased tissues. 
When blood is exposed to the air it coagulates. 
Hemorrhage may be checked by applying strong pres- 
sure upon the wounded blood-vessel and elevating the 
wounded part. 
Proper exercise strengthens the heart’s action and 
improves the circulation of the blood. 
Violent emotions have a tendency to increase the 68 
HUMAN PHYSIOLOGY. 
rapidity of the circulation. Heat also increases it; cold 
retards it. Hence the clothing should be adapted to 
the temperature of the weather. 
Alcohol has a harmful effect upon the red blood cor- 
puscles, and is supposed also to interfere with the white 
blood corpuscles in the performance of their necessary 
functions. 
Alcohol, by disturbing the nutritive elements of the 
blood, prevents the proper nourishment of all the tis- 
sues, It produces fatty degeneration of the different 
organs. 
Drinkers of alcoholic liquors are less able to survive 
surgical operations than those who abstain from their 
use. Alcohol interferes with the coagulation of the 
blood, and sometimes drinkers bleed to death from 
what in other persons would be only slight wounds. 
Alcohol sometimes causes palpitation of the heart. 
It causes a distention of the blood-vessels, and makes 
the walls of the veins and arteries thinner and weaker. 
Its use sometimes induces a predisposition to apoplexy. 
The effects of alcohol on the circulation are easily 
seen in the flushed face of the habitual drunkard. 
To have pure blood and a strong, healthy body, one 
must never indulge in the use of any kind of alcoholic 
liquor. 
Tobacco contains a poison called nicotine. This 
poison interferes with the blood’s action and hinders 
the proper development of the body. 
The smoking of cigarettes is especially harmful, not 
only to boys, but to men, and the practice of inhaling 
the smoke is likely, sooner or later, to produce serious 
results. THE ORGANS OF RESPIRATION, 
69 
CHAPTER IX. 
THE ORGANS OF RESPIRATION, 
71. Organs of Respiration.—The organs of respiration 
consist of : 
(1) The respiratory tract, or air passages ; 
(2) The lungs; 
(3) Certain muscles which assist in the act of 
breathing. 
The respiratory tract consists of the passages of the 
nose and mouth, the pharynx, the larynx, and the 
trachea or windpipe. 
72. The Mouth and Nose. The air passages begin 
with the mouth and nose. The proper passages for 
the air to enter in the act of breathing are those 
through the nose. These passages are lined with a 
smooth, soft membrane, called mucous membrane, the 
surface of which is increased by the projection into the 
nasal cavity of peculiarly shaped bones. This mucous 
membrane is constantly kept moist, thus catching par- 
ticles of dust from the air as it passes through the nose, 
and serving also to render the air moist to a certain ex- 
tent. As the air passes through the nasal passages it 
becomes slightly warmed. 
It is always better to breathe through the nose than 
through the mouth ; for if one breathes through the 
mouth, the mucous membrane there is unable properly HUMAN PHYSIOLOGY. 
to purify the air, moisten it, or warm it before it enters 
the lungs. 
1, 2.—Back of Nasal Passage. 
3, 4.—Back of Mouth. 
5. Tonsil. 
6. —Pharynx. 
7. Epiglottis. 
Fig. 43.—Sectional View op the Upper Air Passages. 
8. Cartilage of Larynx. 
9. —Esophagus. 
10. Trachea. 
11. Nose. 
13, 13.—Mouth. 
14—Tongue. 
15. Hyoid Bone. 
16. Larynx. 
17. 18.—Cartilages. THE ORGANS OF RESPIRATION. 
71 
73. The Pharynx.— From the nose and mouth, the 
air enters the pharynx, or as it is commonly called, the 
throat. The pharynx has two openings at its lower 
part. One of these is the opening into the esophagus, 
the tube which leads to the stomach, and through which 
the food passes when it is swallowed ; the other opening 
leads to the larynx, through which the air passes on its 
way to the lungs. 
74. The Larynx,—The larynx is a box-shaped cavity 
the walls of which are composed of cartilage. It is con- 
nected with the pharynx above, and with the trachea or 
windpipe below. It is lined with mucous membrane. 
Across its upper opening are stretched two fibrous bands 
or cords, called the vocal cords. These cords are con- 
cerned in the production of the voice. Small muscles 
separate these cords as the air enters on its way to- 
ward the lungs, thus making a pas- 
sage for the air between them. The 
opening thus formed is called the 
glottis. Just above this opening 
there is a leaf-like portion of car- 
tilage called the epiglottis. Dur- 
ing the act of breathing the epi- 
glottis lies in such a position that 
the passage into the larynx is 
unobstructed, but when food or 
drink is being swallowed, the epi- 
glottis shuts down, closing the 
Fig. 44.—The Glottis. 
b b.—Vocal Cords. 
A.—Epiglottis. 
glottis and preventing the entrance of any foreign sub- 
stances into the windpipe. 
It is by the action of the vocal cords stretched on 
each side of the larynx that the various tones of the 72 
HUMAN PHYSIOLOGY. 
voice are produced. When the vocal cords have been 
tightened and drawn closer to each other by the small 
muscles attached to them, the air, upon being expelled 
from the lungs, strikes against their edges and causes 
them to vibrate, thus producing sound. If the cords 
are stretched tight, the sound will be high ; if they hang 
loose and far apart, a bass tone is produced. The many 
differences in the quality of the human voice result from 
differences in the structure of the larynx and in the size 
and position of the vocal cords. The vocal sound is 
further modified by the tongue, teeth, 
lips, and palate, and thus shaped into 
articulate words. 
75. The Trachea.—Beginning at the 
lower part of the larynx and extending 
down into the chest is a hollow tube or 
pipe called the trachea, or windpipe. It 
is about four inches long and about one 
inch in diameter. It is lined 
with mucous membrane and is 
surrounded by from sixteen to 
twenty rings of cartilage. The 
walls of the trachea are com- 
posed mostly of fibrous tissue. 
The rings of cartilage which 
surround it keep the walls rigid, 
thus preventing their collapse 
Fig. 45.—Larynx, Trachea, and 
Bronchial Tubes. 
during the act of breathing. 
After entering the chest the 
trachea divides into two branches which are called bron- 
chial tubes. One of these tubes goes to the right lung, 
the other to the left. THE ORGANS OF RESPIRATION. 
73 
The trachea and the bronchial tubes are lined with 
a smooth mucous membrane which is constantly kept 
moist by a secretion of mucus. This membrane extends 
with the vessels into all parts of the lungs. Cartilagi- 
nous rings also surround the bronchial tubes, and are 
found even around the small branches of these tubes. 
76. The Lungs.—The lungs are two cone-shaped organs 
situated within the cavity of the chest, one on each side. 
Fig. 46.—The Position of the Lungs and Heart in the Chest. 
A, B, C, D.—Heart. 
E, F.—Lungs. 
G.—Diaphragm. 
I.—Pulmonary Vein. 
2. —Pulmonary Artery. 
3. Aorta. 
4. —Superior Vena Cava. 
5. Carotid Artery. 
6. —Jugular Vein. 
7. Windpipe. 
8. —Larynx. 
9. —Coronary Artery. 
Between the two lungs is the heart. Each lung is cov- 
ered with a smooth membrane, called the pleura, which 
is reflected or turned back upon itself so as to line the 74 
HUMAN PHYSIOLOGY. 
chest walls. This membrane secretes a thin fluid, the 
object of which is to prevent friction between the sur- 
face of the lungs and the chest walls during the acts of 
breathing. 
The lungs have a peculiar structure. When the tra- 
chea divides into two bronchial tubes, one of these tubes 
goes to the right lung, and the other to the left. Each 
tube, after it enters the lungs, divides and sub-divides 
much like the branches of a tree; the branches become 
smaller and smaller, and pene- 
windpipe, 
trate every part of the lungs. 
The very smallest of these tubes 
terminate in minute cavi- 
ties called lobules. Each of 
these lobules contains nu- 
merous small 
Bronchial 
tube. 
cells or cavities 
called air-cells. 
The walls of the air-cells 
are very thin and deli- 
cate and are formed prin- 
cipally of a net-work of 
capillary blood-vessels. 
All the tubes, lobules, 
and air-cells of the lungs 
are lined with mucous 
Bronchial 
tubes. 
Fig. 47.—Sectional View of the Lungs. 
Showing how the Bronchial Tubes divide 
membrane, the thickness 
wllldl V3.riCS With thlG 
size of the tubes or cells. 
77. Muscles of Respiration.—Certain of the muscles aid 
in the acts of breathing. The most important of these 
is the muscle called the diaphragm (see |2/ [3]). This THE ORGANS OF RESPIRATION. 
is a broad, flat muscle which separates the cavity of 
the chest from that of the abdomen. When at rest, or 
during the act of expiration, this muscle extends up- 
ward into the chest cavity in a vaulted form. When it 
contracts, the vault is diminished and the capacity of 
the chest is increased, thus drawing air into the lungs. 
The muscles of the chest, which elevate or depress 
the ribs, also aid in the act of breathing, and are there- 
fore often spoken of as muscles of respiration. 
78. Effects of Alcohol on the Organs of Respiration.—No 
organ, nor system of organs, is exempt from the harmful 
effects of alcohol when it 
is introduced into the liv- 
ing body. The delicate 
mucous membrane which 
lines the lungs and the 
whole respiratory tract is 
particularly susceptible to 
its destroying influence. 
This membrane is sup- 
plied with blood-vessels 
and nerves, and contains 
many small glands, the ob- 
ject of which is to secrete 
a substance called mucus, 
by which the membrane 
is kept moist. When al- 
cohol is taken into the 
Fig. 48 A Lobule of a Lung. 
1. Small Bronchial Tube. 
2. —Air-Cell. 
3. Lung Tissue. 
system, it circulates with the blood and causes the blood- 
vessels to become distended. As a consequence the 
linings of the air passages are thickened and con- 
gested. When the mucous membrane is in this condi- 76 
HUMAN PHYSIOLOGY. 
tion the glands are unable to perform their proper work, 
and the membrane becomes covered with a thick, viscid 
mucus. This causes a persistent, hacking cough. When 
the membrane is thus continually congested, respira- 
tion is impeded. Colds and lung troubles are easily 
contracted and are cured only with difficulty. 
It is a well recognized fact that persons who are ad- 
dicted to the use of alcoholic drinks are especially liable 
to contract pneumonia, and that it is with extreme diffi- 
culty that such persons survive an attack of it. Bron- 
chitis, catarrh, and throat troubles are of frequent oc- 
currence among alcohol drinkers, and the continued 
congestion of the mucous membrane renders recovery 
very slow. 
79. Effects of Tobacco on the Organs of Respiration—The 
inhalation of tobacco smoke tends to cause irritation 
and congestion of the respiratory organs. Many dis- 
eases of the mouth and throat are induced or aggravat- 
ed by the poisonous nicotine which is absorbed by the 
tissues or brought into direct contact with the delicate 
and sensitive surface of the mucous membrane which 
lines the air passages. The throats of many persons 
are easily irritated by tobacco smoke. This irritation, 
if continued, causes a redness and soreness of the mu- 
cous membrane which lines the larynx and trachea, 
and frequently results in the disease called “ smoker’s 
sore throat.” The only cure for this trouble is to give 
up the use of tobacco altogether. Snuff taking causes 
many diseases of the nose. That very terrible disease 
called cancer of the throat, or cancer of the mouth, 
if not directly caused by the use of tobacco, is certain- 
ly aggravated by it. RESPIRATION. 
77 
CHAPTER X. 
RESPIRATION. 
80. Breathing.—In breathing we draw air into the lungs 
and then expel it. The act of drawing air into the 
lungs is called inspiration; that of expelling the air from 
the lungs is called expiration. 
The chest is really an air-tight box, only communi 
eating with the outer air 
through the air-passages. 
Now when the diaphragm 
and other muscles of respi- 
ration contract, the size of 
the chest cavity is increased 
and the air rushes into the 
lungs to fill up the in- 
creased amount of space. 
When the diaphragm and 
other muscles relax, the 
Fig. 49 —Diagram showing the action 
of the diaphragm when one 
is breathing. 
A. A.—Diaphragm. 
tissues of the lungs being elastic, the air is expelled from 
the lungs, and the chest cavity becomes smaller. It is 
thus that the act of respiration is performed. A healthy 
adult breathes from sixteen to twenty times a minute. 
Exercise and certain diseased conditions increase the 
rapidity of breathing. 
81. Capacity of the Lungs—The extreme capacity of 
the lungs, that is the total amount of air they are cap- 
able of containing, is about three hundred and thirty 78 
HUMAN PHYSIOLOGY. 
cubic inches. Of this amount, one hundred cubic inches 
always remains in the lungs and cannot be driven out; 
another one hundred cubic inches is not expelled during 
ordinary acts of respiration, but can be expelled by for- 
cible expiration ; about twenty cubic inches is taken into 
the lungs with each natural inspiration and expelled with 
each expiration ; and the remaining one hundred and 
ten cubic inches is what it is possible to draw into the 
lungs by forcible inspiration. From this it will be seen 
that about two hundred cubic inches of air is contained 
in the lungs at all times during ordinary respiration, 
and that only about twenty cubic inches of air is drawn 
into the lungs and expelled with each breath. 
82. Modified Respiration.—Coughing and sneezing are 
involuntary acts caused by irritation in the air passages 
of the nose. In both of these acts there is first a deep 
inspiration, then a violent, spasmodic expiration. 
Hiccoughing is a sudden spasmodic action accompany- 
ing the act of inspiration. It is produced by a quick 
involuntary contraction of the diaphragm, and with this 
contraction there is also a closing of the space between 
the vocal cords. Hiccoughing is usually the result of 
some disturbance of the stomach or digestive system. 
Laughing and sobbing are modifications of the respi- 
ratory act. Snoring is a peculiar sound sometimes 
accompanying the acts of respiration during sleep. It 
is caused by sleeping with the mouth open and breath- 
ing through the nose and mouth at the same time. 
83. The Air.—The air which we breathe is a mix- 
ture of two gases. One of these, called oxygen, con- 
stitutes about one-fifth of the air; the other, called 
nitrogen, constitutes about four-fifths of it. The oxy- RESPIRATION. 
79 
gen as you have learned, is absolutely essential to all 
life and to all life actions. The nitrogen does not sup- 
port life, but serves to dilute the oxygen, thus regulat- 
ing its supply. 
The air also contains a very small quantity of car- 
bonic acid gas. This gas, when pure or nearly so, is 
very dangerous if taken into the lungs. It is clear and 
colorless, and is heavier than the air. It is this gas 
which accumulates in deep wells, old cellars, and mines. 
It will not support combustion, and hence its presence 
is easily detected by lowering into any place where it is 
supposed to exist, a lighted candle or torch. If any 
considerable quantity of carbonic acid is present the 
light will be extinguished. This test should always be 
used before entering a deep well, mine, or any sus- 
pected place. Many lives have been lost through fail- 
ure to take this precaution. 
84. The Object of Respiration.— Respiration performs 
two services in the body, both of which are essen- 
tial to life. It is the act by which the life-giving oxy- 
gen is supplied to the system, while at the same time 
the poisonous and life-destroying carbonic acid to- 
gether with various other waste matters, is removed 
from it. 
85. Change in the Blood During Respiration.—When 
the blood leaves the capillaries and enters the veins it 
is impure and of a bluish color. It contains much car- 
bonic acid and but little, if any, oxygen. This impure 
blood goes to the right side of the heart, and from there 
it is sent to the lungs. In the lungs it circulates through 
the net-work of capillaries which surrounds the air- 
cells. Here it comes in close contact with the air that HUMAN PHYSIOLOGY, 
is breathed, and it undergoes a wonderful change. It 
parts with its carbonic acid and in its place takes up 
oxygen. It becomes bright red in color and again 
pure and life-giving, and is therefore ready to be again 
sent to the tissues. 
86. Change in the Air During Respiration.—When the 
air enters the lungs it is about one-fifth oxygen. When 
it is expelled from the lungs it has lost much of its oxy- 
gen, and has gained much carbonic acid, watery vapor, 
and other waste matter which it has taken from the 
blood. It is now loaded with impurities. It is poisonous, 
and unfit to be again taken into the lungs. The ill effects 
of this impure air upon the system, when it is again 
breathed, are especially apparent to persons who remain 
in close, ill-ventilated rooms or buildings. Such per- 
sons suffer with drowsiness and headache, and some- 
times with attacks of fainting. 
87. Ventilation.—Fresh, pure air at all times is es- 
sential to bodily comfort and good health. Air may 
become impure from many causes. Poisonous gases 
may be mixed with it; sewer gas is especially to be 
guarded against; coal gas, which is used for illuminat- 
ing purposes is very poisonous and dangerous if inhaled ; 
the air rising from decaying substances, foul cellars, or 
stagnant pools, is impure and unhealthful, and breeds 
diseases; the foul and poisonous air which has been 
expelled from the lungs, if breathed again, will cause 
many distressing symptoms. Ventilation has for its 
object the removal of impure air, and the supply- 
ing of fresh, wholesome air in its place. Proper ven- 
tilation should be secured in all rooms and buildings, 
and its importance cannot be overestimated. RESPIRATION. 
In the summer time, and in climates which permit of 
it with comfort, ventilation may be secured by having 
the doors and windows open, thus allowing the fresh air 
to circulate freely through the house. In stormy and 
cold weather, however, some other means of venti- 
lation must be supplied. If open fires or grates are 
used for heating purposes, good ventilation exists, for 
under such circumstances, the foul and impure air is 
drawn out of the rooms through the chimneys, and the 
fresh air enters through the cracks of the doors and 
windows. 
Where open fireplaces are not used, several plans of 
ventilation may be used, as they all operate on the 
same principle. Two openings should be in the room— 
one of them near the floor, through which the fresh air 
may enter, the other higher up, and connected with a 
shaft or chimney, which producing a draft, may serve to 
free the room from the impure air. The size of these open- 
ings is to be regulated according to the size of the room. 
This method of ventilation is sometimes used in school- 
rooms and public buildings. It would be well for 
any one who has charge of an assembly-room of any 
kind, or of a dwelling house, or who contemplates 
building, to study carefully the different methods of 
ventilation. In a book of this kind there is not suffi- 
cient space to explain the subject in all its details. 
88. Asphyxia.—Asphyxia, or suffocation, results when, 
from any cause, the necessary supply of oxygen is shut 
off from the blood. When this happens, carbonic acid 
accumulates in the blood, bringing it into such a condi- 
tion that it cannot properly circulate in the body. 
Asphyxia from drowning, strangling, or any other cause, 82 
HUMAN PHYSIOLOGY. 
may be recovered from if the heart still beats, provided 
that the person be speedily supplied with fresh air from 
which the blood may obtain the needed oxygen. 
89. Artificial Respiration.—The object of artificial res- 
piration is to force fresh air into the lungs, and thus to 
supply oxygen to the blood. It is, as nearly as pos- 
sible, an imitation of the natural act of breathing. 
Artificial respiration may be performed in the follow- 
ing manner: Lay the person flat on his back with the 
head a little lower than the shoulders. Then, taking 
Fig. 50.—Method of Performing Artificial Respiration. 
hold of the arms above the elbows, bring them above 
the head as far as possible; hold them there two or 
three seconds, then bring them down to the sides press- 
ing them firmly against the ribs. 
Repeat this operation twelve to sixteen times a min- 
ute, and keep it up until the person shows signs of life 
and can breathe without assistance. When the arms 
are drawn upwards, the ribs are elevated and the size 
of the chest cavity is increased, thus tending to form a 
vacuum. To prevent this vacuum the air rushes in and 
expands the lungs. When the arms are lowered the chest RESPIRATION. 
83 
contracts, and the air in the lungs is driven out, as in 
natural breathing. Thus both inspiration and expira- 
tion are accomplished. 
Artificial respiration is always to be used in the 
resuscitation of asphyxiated persons, and it should be 
persisted in until it is successful or until all hopes of 
life are abandoned. 
90. Effects of Alcohol on Respiration.—Alcohol modi- 
fies the acts of respiration; this modification is due 
to the effects which it has upon the respiratory 
organs and about which you have already learned. 
It lessens the power of removing carbonic acid from 
the system, and interferes with the absorption of oxy- 
gen by the blood. To overcome this, the acts of 
breathing are increased in frequency. 
Alcohol was at one time thought to be beneficial to 
persons suffering with consumption, but it is now a well 
recognized fact that its use tends to hasten the progress 
of that disease. The same may be said to be true with 
respect to its effects upon other diseases of the lungs. 
The breath of a person who has taken alcoholic liquor 
into his stomach is sure to betray him. This shows 
that the alcohol has entered into the circulation and 
that the blood has been freed of a portion of it in the 
lungs. The air which is breathed out from the drink- 
er’s lungs is therefore over-laden with impurities, and 
should on no account be breathed by another person. 
The harmful effects of alcohol upon the heart’s action 
have already been explained. Any injury to the heart of 
course interferes with the act of breathing, and prevents 
to a still greater extent the proper purification of the 
blood in the lungs. 84 
HUMAN PHYSIOLOGY. 
REVIEW—RESPIRATION. 
The chief organs of respiration are the nose, the 
pharynx, the larynx, the trachea, the bronchial tubes, 
and the lungs. 
The larynx is the upper part of the trachea or wind- 
pipe, It is also the organ of voice. 
The trachea is a hollow tube or pipe for the passage 
of the air to and from the lungs. 
The bronchial tubes are divisions of the trachea, one 
for each lung. They divide and subdivide into numer- 
ous branches in the lungs. They terminate in numer- 
ous very small cells or cavities. 
The lungs are two cone-shaped organs within the 
cavity of the chest. 
The pleura is the covering membrane of the lungs, 
and also the lining membrane of the chest. 
Inspiration is the act of drawing the air into the lungs; 
expiration is the act of expelling the air from the lungs; 
respiration is the act of breathing, and is both inspira- 
tion and expiration. 
The object of respiration is (i) to supply the system 
with life-giving oxygen, (2) to remove from the system 
the life-destroying carbonic acid and other waste mat- 
ters that accumulate in the blood. 
The action of the diaphragm and of the muscles which 
elevate the ribs aids in the process of breathing, or res- 
piration. 
Coughing, sneezing, hiccoughing, laughing, and sob- 
bing are various modifications of the act of breathing. 
Fresh, pure air is always necessary to bodily comfort 
and good health. RESPIRATION. 
To promote the action of the respiratory organs and 
consequently the health of the entire system, one should 
have a care that the clothing about the chest does not 
impede the free movement of the ribs and diaphragm 
in respiration; should habitually sit or stand erect and 
in such a way as to allow the chest freely to expand 
in the act of inspiration; should take plenty of good 
exercise in the open air; should not expose the air 
passages and throat to extremes of cold or heat; 
should breathe through the nose and not through the 
mouth. 
Alcohol causes the mucous membrane of the air pas- 
sages to become thickened and congested. By irritat- 
ing the throat and lungs, it often produces a trouble- 
some hacking cough. 
Alcohol interferes with the acts of respiration and 
lessens the power of the lungs to remove impurities 
from the .blood. The use of alcohol aggravates and 
hastens the progress of lung diseases. 
Persons addicted to the use of strong drinks are 
especially liable to pneumonia, bronchitis, and throat 
troubles. 
The breath of a person addicted to drinking alcoholic 
liquors is over-laden with poisonous impurities. 
Alcohol tends to injure the health of the entire sys 
tern, because it prevents the proper purification of the 
blood in the lungs, and hence interferes with the nour- 
ishment of all the organs. 
Tobacco, especially tobacco smoke, irritates and in- 
jures the respiratory organs. It causes many diseases 
of the throat. The continued use of tobacco in any 
form may finally injure the lungs. 86 
HUMAN PHYSIOLOGY. 
CHAPTER XI. 
FOOD AND DRINK. 
91. Bodily Nutrition.—It has already been explained 
that with every movement of the body, and every 
action of its organs, certain tissues are worn out 
and decomposed. These worn-out tissues must be re- 
placed by new tissues, in order that the health and 
strength of the body may be preserved. Hence, every 
tissue must be constantly supplied with nourishment, in 
order that its worn-out parts may be again renewed. 
This nourishment is supplied to the tissues by the blood, 
and through the blood bodily nutrition is carried on. 
Each tissue has the property of taking from the blood 
only those elements of nutrition which are necessary to 
supply its own needs. This taking of the elements of 
nutrition from the blood is called assimilation. A 
proper balance between the wearing out of tissues and 
their assimilation of nutrition is necessary to health. In 
children the assimilation exceeds the wearing out of tis- 
sues, and thus it is that the body is enabled to grow. In 
middle age the two processes are about equal, and in 
old age the wearing out goes on faster than the assimi- 
lation, and thus the body gradually grows weaker, and 
death results, if not from disease, from “ old age.” 
By the discharges from the body, both solid and 
liquid matter is removed from the system. This loss 
must be constantly renewed, or the body will die. The FOOD AND DRINK. 
87 
loss goes on constantly, whether we are asleep or awake, 
working or resting. To renew these losses from the 
system, and to keep the tissues of the body properly 
nourished, it is necessary to take into our bodies a suffi- 
cient quantity of both food and drink. 
92. Hunger and Thirst.—When the wearing out of the 
tissues has proceeded to such an extent that the 
blood is unable to supply enough nutrition to restore 
its worn-out parts, a peculiar sensation is felt, which we 
call hunger. Hunger is, in reality, a demand on the part 
of the system for food with which to supply nutrition 
to its tissues. The first stage of the feeling of hunger 
may be said to be appetite, and when food is taken into 
the stomach this appetite disappears. 
Thirst is a demand on the part of the system for 
water, and this demand must be satisfied, or great suf- 
fering will ensue, finally ending in death. A person 
can live a much longer time without food than with- 
out water. 
To keep the body in a healthy condition, and enable 
it to perform its proper work, both food and drink 
should be taken in such quantities as to satisfy all the 
needs of the body, supplying it with sufficient nutri- 
tion to rebuild the tissues as fast as they are worn out. 
93. A Variety of Food is Necessary to Life.—Each tis- 
sue of the body requires for its nutrition and develop- 
ment certain food elements. The bones require one 
class of elements, the muscles another, the fatty tis- 
sues still another, and so on with the other tissues. 
It is plain, therefore, that several food elements are 
necessary to supply the tissues of the body; and, since 
different elements exist in different foods, a variety of 88 
HUMAN PHYSIOLOGY. 
food is required in order to supply the body with proper 
and sufficient nourishment. 
94. Classification of Food.—All substances which may 
be used for nourishing the body are called foods. Foods 
are derived from either the inorganic, the vegetable, or 
the animal kingdom, and are classified as follows: 
(i) Inorganic or mineral foods. 
The latter are divided into 
(2) Organic, or animal and vegetable foods. 
{a) Foods which build up the tissues of the body, 
or tissue-making foods. These are sometimes called 
nitrogenized foods. 
{&) Foods which supply the body with heat, or 
heat-producing foods. These are sometimes called non- 
nitrogenized foods. 
95. Inorganic Foods.—All the tissues and fluids of the 
body contain more or less inorganic matter; hence, in- 
organic foods are essential to the proper nutrition and 
development of the body. They are found to a greater 
or less extent in all classes of food, both animal and 
vegetable, in combination with other substances. 
Water is the most important of the inorganic foods. 
It is found in every tissue of the body, without exception, 
and is absolutely necessary to life. All articles of food 
contain water; vegetable foods usually contain it in large 
proportions. Water is the basis of all drinks. In its 
natural condition it is never absolutely pure ; it always 
contains more or less salts and impurities in solution. 
The waters of mineral springs are especially rich in salts. 
Rain-water is more nearly pure than any other. Per- 
fectly pure water may be obtained by distillation. 
Another inorganic food which is of vital importance, is FOOD AND DRINK. 
89 
common salt. Salt occurs in both animal and vegetable 
foods. It improves the flavor of food, assists in diges- 
tion by exciting and stimulating the flow of the diges- 
tive fluids, and meets the demand on the part of the 
system for a certain kind of nourishment. 
Phosphate of lime is an inorganic substance which exists 
in all forms of vegetable food. It serves chiefly to supply 
substance to the bones, developing and hardening them. 
96. Tissue-making1, or Nitrogenized Foods.—These con- 
stitute all kinds of animal and vegetable food, except 
the sugars, fats, and starches. 
The most important of the tissue-making foods is meat, 
or muscular tissue. Of all the different kinds of meat, beef 
is the most nutritious. Other meats—as the flesh of birds, 
fishes, and wild animals, pork, mutton, etc.—are all very 
nutritious ; yet if any one of these be eaten daily, it soon 
becomes extremely distasteful, and the appetite fails, thus 
showing a demand on the part of the system for a change 
of diet. All meat should be cooked, thus rendering it not 
only more palatable to the taste, but more easily digested. 
Next to meat in nutritive value is albumen. Albumen 
occurs as an article of diet principally in the white of 
eggs. It is an important food, but is of itself incapable 
of sustaining life. Animals fed on albumen alone, soon 
die of starvation. 
Casein is a tissue-making food, and is a most important 
article of diet. It is found chiefly in milk. The var- 
ious kinds of cheese that are manufactured from milk 
contain it in great abundance. 
Among the vegetable foods which help to form tissue, 
one of the most important is gluten. This exists in the 
various grains, being especially abundant in wheat. 90 
HUMAN PHYSIOLOGY. 
It is of the greatest nutrfive value to the system, 
and experiments have shown that animals may sub- 
sist on it as an exclusive article of food for an in- 
definite length of time, It seems, indeed, to supply 
all the demands of the body for nutrition. Bread 
made of gluten is highly nutritious. The presence 
of gluten makes it possible for bread to be fight 
and porous. 
Several other substances exist in the vegetable 
foods, the exact properties of which are not yet fully 
understood. 
97. Heat-Producing, or Non-Nitrogenized Foods.—These 
principles comprise the sugars, fats, and starches. They 
are all of great importance and are believed to be es- 
pecially useful in the production and maintenance of 
the heat of the body. 
Sugar occurs in both animal and vegetable foods. 
Honey and sugar of milk are the varieties which are 
obtained from the animal kingdom. From the vegeta- 
ble kingdom two kinds of sugar are obtained. One 
of these is called grape sugar, the other cane sugar. 
Grape sugar comprises all sugars that exist in fruits. 
Apples, pears, grapes, and peaches, all contain sugar. 
The chief source of cane sugar is the sugar-cane. It is 
derived also from the sap of the sugar-maple and var- 
ious other substances. All sugars have a sweet taste, 
and are soluble in water. Cane sugar is the sweetest, 
and also the most soluble. 
Fats include all fatty matter and oils. They too ex- 
ist in both animal and vegetable foods. Fat is found 
in all parts of the body, except in the bones, teeth, and 
fibrous tissue. FOOD AND DRINK. 
91 
Fat exists in the vegetable kingdom in many fruits 
and seeds. Cotton-seed oil is obtained from the seeds 
of the cotton plant; it has now become an important 
article in the preparation -of foods. Olive oil is derived 
from the fruit of the olive, and is much used as an ar- 
ticle of diet. Butter, which is an animal product, is the 
most important fatty article of diet. 
Although fatty foods are of great importance to the 
proper nutrition of the body, they can not by them- 
selves support life. The amount of fat required as a 
food varies much in different climates. For people who 
live in exceedingly cold climates, fats not only form the 
chief article of diet, but are indispensable to the comfort 
and health of the body. People who live in warmer 
countries, and especially in the torrid regions, do not 
require such foods, and hence use them but sparingly, 
if at all. 
Starch is found chiefly in the cereals—wheat, corn, 
rye, and barley—in potatoes, peas, beans, and in many 
roots. It occurs most abundantly in rice. It is a prod- 
uct of the vegetable kingdom only. Starch consists of 
minute granules. It is insoluble in water, but when 
boiled in water the granules swell and become trans- 
parent, the mixture forming, when cool, a transparent, 
jelly-like mass. Starch is not assimilated by the sys- 
tem directly as starch, but, by a curious chemical pro- 
cess, it is always converted into grape sugar before en- 
tering the blood. Starch also, though an important 
food, is incapable by itself of supporting life. 
98. Drinks.—By drinks we mean substances which are 
taken into the body for the purpose of quenching thirst. 
Water is the only substance that will actually quench 92 
HUMAN PHYSIOLOGY. 
thirst, and hence it is the foundation of all drinks. 
Water that is used for drinking purposes should be 
the purest obtainable. Rain-water is generally the 
best; well-water, from deep wells, is usually whole- 
some ; and spring-water, if clean, is fairly pure. All 
water used for drinking purposes should be clear and 
odorless. If it contains organic impurities, is of a dark 
color, or has an unpleasant odor, it is unfit to drink, and 
is likely to give rise to diseases. 
Many diseases, such as typhoid fever and others of 
similar character, have been occasioned by drinking im- 
pure water. If the water used for drinking purposes is 
suspected of being contaminated in any way, it should 
always be filtered and boiled for quite a length of time 
before being used. Many epidemics have risen, and 
many deaths occur every year, on account of neglecting 
to take this precaution. 
The amount of water necessary to the system is from 
four to five pints daily. This includes the water taken 
into the body with the food. The quantity of the liquid 
taken as a drink consequently varies in proportion to 
the amount of water contained in the food that is eaten. 
If much soups and milk are taken, less water is required 
as a drink. For the purpose of quenching thirst, tea, 
coffee, lemonade, and all other drinks of a similar kind 
are, as we may say, merely flavored water. 
99. How Foods are Changed into Poisons.—A food, as 
has been explained, is a substance, either liquid or solid, 
which, when taken into the body, nourishes and sus- 
tains it, by renewing and rebuilding the tissues and thus 
giving strength and vigor to the various organs upon 
whose harmonious action life depends. FOOD AND DRINK. 
93 
A poison is a substance whose nature it is, when ab- 
sorbed into the blood, to injure or destroy the tissues, 
or in some other way to interfere with and derange the 
vital processes. 
Poisons are, therefore, in their nature and effects, the 
exact opposites of foods. Foods sustain life ; poisons 
destroy life. Foods promote health ; poisons produce 
disease. Most of the diseases with which mankind is 
afflicted are directly traceable to the action of some 
kind of poison. 
Although the difference between a food and a poison 
is most marked, strange as it may seem, foods are 
readily and frequently changed into a state in which 
they possess all the dangerous properties of poisons. 
Examples of such change are of every-day occurrence. 
A piece of meat, which, a few hours ago, was fresh and 
palatable and nourishing, has lain exposed to moisture 
and the warm sun, and has become putrid. It is no 
longer fit for food, but, if eaten, will act as a poison, 
causing sickness, and possibly death. A peach, which 
yesterday was hanging in luscious ripeness upon the 
tree, falls to the ground, and decays. No one would 
think of eating it now, for its very nature has been 
changed, and it is loathsome to the taste. So also 
milk, when exposed for some time to the air, becomes 
sour ; butter becomes rancid ; bread becomes mouldy ; 
the best of foods lose their nutritious qualities, and con- 
sequently cease to be foods. 
If we look a little further into the matter, we shall see 
that changes of this kind are universal. There seems to 
be a law of Nature, which requires that all organized 
matter which has ceased to live must be decomposed 94 
HUMAN PHYSIOLOGY. 
into the parts of which it is made up, in order that these 
parts may enter into and help to make up other forms 
of life. Animal matter putrefies, fruits decay, grains 
rot; that which is beautiful, cleanly, healthful, pleasant 
to the taste, becomes repulsive, poisonous, and finally 
disappears in new combinations. If this were not true, 
the earth would long ago have been so filled with dead 
substances as to leave no room for new forms of life ; 
but nothing that has had life is exempt from this law of 
change. It is to prevent these changes that meats are 
salted, that fruits are sealed up in air-tight cans, that 
grain is kept in dry places, and that various perishable 
substances are put away in “ cold storage ” rooms or 
packed in ice. The name fermentation is applied to the 
process by which these destructive changes occur. 
What is Fermentation ?—Scientists, and, indeed, most 
people, have long been acquainted with the appearance 
of fermentation and many of its results, but not until 
very recent years has its true cause been understood. 
It was formerly supposed to be a kind of spontaneous 
chemical process, in which old compounds were broken 
up and new compounds took their places. The inves- 
tigations of M. Pasteur and others have, however, com- 
pletely disproved this theory, and, although chemical 
changes certainly do take place, the causes of fermenta- 
tion have been traced to the presence of minute living 
objects, which are known by the general name of bac- 
teria. These tiny objects are present everywhere, float- 
ing unseen in the air, and ready at all times to begin 
their work. They also exist in other forms, as in the 
well-known yeast plant. They are of many different 
kinds ; each kind has its own particular class of sub- FOOD AND DRINK. 
95 
stances upon which it lives, and it produces its own par- 
ticular form of fermentation. Those which act upon 
meats give rise to what is called putrefactive fermejita- 
tion ; those which act upon fruits, changing their sweet 
juices into carbonic acid and poisonous alcohol, are the 
producers of vinous fermentation; and those which cause 
the alcohol in any fermented liquor to change into 
vinegar bring about what is known as acetous fermenta- 
tion. The tiny objects that change good fruit juices 
and grain infusions into alcoholic drinks are known by 
the common name of ferments. 
Work of the Ferments.—We are now ready to under- 
stand why alcohol is so injurious to anyone who uses it. It 
is the product of vinous fermentation, which has changed 
a food to a poison. How does this change take 
place? If we look closely at the skin of a ripe apple, 
just picked from the tree, or at a bunch of grapes fresh 
from the vine, we find that they are covered with a 
delicate bloom, which is easily rubbed off, and which 
looks something like dust. Under a microscope, this 
bloom is found to contain, among other things, germs 
of tiny plants, which live on oxygen when they are 
growing. These plants, which are much too small to be 
seen with the naked eye, are the ferments that cause 
vinous fermentation. A scholar who has carefully 
studied the ferments (Trouessart) says : “ The ferments 
are seldom or never found upon green fruits, but when 
these begin to ripen the ferments collect upon their 
skins and stems.” 
If the fruit remains on the tree or vine until it dries up 
or begins to decay, the wind finally scatters the ferments, 
and they fall to the ground, and there lie buried during 96 
HUMAN PHYSIOLOGY. 
the winter, ready to return to the same kind of fruit the 
following year. 
These tiny plants or ferments do not harm whole 
fruits, because they cannot penetrate the unbroken 
skins which protect them. When the juices of these 
fruits are pressed out, however, as is the case when wine 
or cider is made, the ferments can do a great deal of 
harm. Some of them are washed from the skins and 
stems of the fruit into the pressed-out juice, and begin 
at once to change its nature. They must do this to live. 
Ferments need oxygen in order to grow, but while in 
the pressed-out juice they cannot get from the air the 
oxygen they need. Where do they get it ? From some- 
thing in the juices themselves. There is oxygen in 
the sugar which exists in ripe fruit juices, and the fer- 
ments take this sugar to pieces to get this oxygen. After 
the oxygen is used by the ferments, substances, which 
are very unlike sugar, are left in its place. One of these 
is a gas, which bubbles up to the top and escapes. This 
is carbonic acid gas. The other substance is a liquid, 
which stays in the fruit juice, and entirely changes its 
nature. Its name is alcohol, and, when taken by itself, 
it is a clear liquid, very burning to the taste, and has a 
peculiar, penetrating odor. It is a poison, and very 
fatal to life. If any living being, whether animal or 
plant, be immersed in alcohol, it dies almost imme- 
diately. Even small quantities of clear alcohol, when 
taken into the stomach, are dangerous to life. In its 
undiluted form this liquid is so deadly that it cannot 
be used as a beverage; it must first be combined 
with other substances, or diluted with milder liquids 
having a more pleasant taste. But, no matter how it FOOD AND DRINK. 
97 
may be diluted, the poisonous qualities of alcohol re- 
main, and its effects, although they may not be so im- 
mediately apparent, are harmful in proportion to the 
quantity present. 
All alcoholic drinks are either fermented or distilled, 
according to the way in which they are made. 
Cider is not a Food.—The most common of the fer- 
mented drinks are cider, wine, and beer. Cider is made 
by the fermentation of apple juice. The apples are 
crushed, and their juice is pressed out. The ferments, 
which have been washed into the juice from the surface 
of the fruit, begin almost at once to take the sugar to 
pieces to get the oxygen which it contains, and thus 
alcohol is formed. 
When first made this liquid is called sweet cider, but, 
as some alcohol may be found in it about six hours 
after it has been pressed out, and possibly sooner, it is 
much better and safer to get one’s apple juice by 
eating the apples. 
As soon as bubbles of gas can be seen rising to the 
surface of pressed-out apple juice, it may be considered 
a sign that alcohol has begun to be formed in it, and that 
it is no longer a safe drink. If cider is left standing, 
more and more of the sugar which it contains turns to 
alcohol, until in every one hundred glasses of cider there 
may be as many as fourteen glasses of alcohol. This is 
enough to kill the ferments themselves. Ferments of 
another kind now begin to work, and these, if left to 
themselves, will change the alcohol into acetous acid— 
the acid of vinegar. There is no alcohol in vinegar. It 
is used to flavor some kinds of food. 
One danger in cider drinking lies in the fact that it is 98 
HUMAN PHYSIOLOGY. 
very likely to make a person cross, disagreeable, and 
bad-tempered. Another danger is that the alcohol con- 
tained in cider has the power to make the drinker want 
other liquors which contain more alcohol. In some 
sections of the world cider has led more people to 
drunkenness than any other alcoholic liquor. 
Wine is not a Food.—Wine, like cider, is a product of 
vinous fermentation. It is made from grapes in much 
the same way that cider is made. The difference in taste 
is due to the different flavors of the fruits, but the same 
poison, alcohol, is found in both. The housewife some- 
times says : “ There is no alcohol in my home-made 
wine ; for I made it myself, and didn’t put in even a 
drop.” Is it true that there is no alcohol in such wine? 
Scientists have found that it is not necessary to put 
alcohol into grape juice, because the ferments which 
are always to be found on the skins and stems of ripe 
grapes have the power themselves to form alcohol in 
pressed-out grape juice. If the grapes are very sweet, 
more alcohol will be formed, and hence a stronger and 
more poisonous wine will be produced. The juices of 
ripe currants, blackberries, gooseberries, elderberries 
and other kinds of fruits are sometimes used to make 
wine ; but all of these liquors are harmful, because al- 
cohol, in larger or smaller quantities, is to be found in 
each. The fresh fruits themselves, and the jellies and 
preserves which are made from them, as well as raisins 
and other forms of dried fruit, are wholesome and nutri- 
tious foods, but the presence of even a little alcohol in 
pressed-out fruit juices so changes the nature of these 
juices as to make them entirely unfit to be drunk. 
People who drink wine not only learn to like its FOOD AND DRINK. 
99 
taste and to crave it more and more, but are likely soon 
to want stronger liquors. 
Lord Bacon once told the English people that wine 
was the most powerful of all things for exciting and in- 
flaming the passions, and this is just as true for Ameri- 
cans and people of other nationalities as it is in the case 
of the English. 
Beer is not a Food.—Of all alcoholic beverages, beer 
is perhaps the most generally used. Many people claim 
that it is altogether a harmless drink, and that it is even 
beneficial to the health and strength of the body. But 
the facts point directly the other way. Because it lacks 
in itself the most important elements of nutrition, beer 
does not furnish what is needed for the nourishment of 
the tissues. Because it contains alcohol, it maybe taken 
in sufficient quantities to produce drunkenness. Even 
when used moderately, it induces a craving for more 
alcohol, a craving which, at first, may be satisfied by 
more and more beer, but which is very likely soon to 
lead to indulgence in stronger drinks. There is the 
same danger even in home-made beer and so-called root 
beers, for all are produced by fermentation and contain 
alcohol. The manufacture of beer and of all other malt 
liquors depends upon that principle in Nature which has 
already been explained—the going to pieces of organic 
matter which has ceased to live. But in beer-making 
the brewer has learned to hasten or retard, or otherwise 
change this process of decomposition in such a way as 
to produce the results which he desires. 
The grain (barley, rye, wheat, or corn) of which most 
malt liquors are made, contains, in its natural state, a 
great deal of starch and but little sugar. Now, in order HUMAN PHYSIOLOGY, 
that vinous fermentation may take place in any sub- 
stance, there must be moisture, a moderate degree of 
warmth, and the presence of sugar. Besides these, we 
must have present something else, of which we have 
already spoken—the ferments. These plants are not 
found upon grains as they are upon the outside of 
fruits ; so the brewer himself adds them in the form 
of yeast. 
More work is necessary to make beer than to produce 
wine or cider, because grain contains starch instead of 
sugar and not enough moisture; but men have found a 
way to make sugar out of this starch. In the first place, 
the barley, or other grain, is put into a vat or cistern of 
stone or brick, where it is covered with water. Here it 
is allowed to soak for forty hours or more, until the 
grains become soft and begin to swell. Then it is 
shovelled out, and piled in level heaps upon the floor 
of a warm room. The seed germs in the grain grow 
rapidly, just as would have happened if the grains had 
been planted in the warm ground. As these tiny germs 
grow, the starch, which formed a large part of each 
grain, and which could not be dissolved in water, is 
changed into a kind of sugar, which is soluble, and 
which serves as food for the growing sprout. If left 
alone, the little plant would soon take up the sugar and 
make it a part of itself. But here the brewer steps in. 
He has allowed the sugar to be produced for his own 
purposes, and he does not intend that the infant plant 
shall make use of it. He, therefore, places the sprout- 
ing grain in a hot chamber, where the sprouts shrivel up 
and die. The young plant is killed, but the sugar re- 
mains unhurt by the heat. The grain is now called FOOD AND DRINK. 
malt. It is next crushed between metal rollers, and 
again put into a huge vat, with much water, where the 
sugar is dissolved out of it. This sweet liquid is called 
wort. It is finally drawn off, and boiled with hops, to 
give it a flavor and prevent the growth of undesirable 
germs. The wort is then cooled and drawn off into 
large tanks, where the yeast is added and the process 
of fermentation takes place. 
If yeast had not been added to the wort, fermenta- 
tion might have been caused in time by different kinds 
of germs from the air falling into it. But the yeast 
hastens the operation, and prevents the formation of 
moulds. The yeast changes the sugar in the wort into 
carbonic acid gas, which escapes in bubbles from the 
surface, and into alcohol, which remains in the liquid. 
When the fermentation has gone far enough to produce 
a liquor of the desired alcoholic strength, the product 
is poured into strong casks, which are then closed, air- 
tight, and kept in a cool place until used. If it is beer 
that has been thus produced, it contains four or five per 
cent, of alcohol; if the fermentation has been allowed 
to go on until it contains eight or ten per cent, of alco- 
hol, the liquor is called ale, porter, or stout. 
Great quantities of beer are drunk with the mistaken 
idea that it is a kind of food. But beer adds nothing 
whatever to the health and vitality of the body. The 
drinking of it frequently changes healthy, muscular tis- 
sues into fat, and thus causes weakness instead of 
strength. Instead of building up the body, Dr. Bunge 
says that “no other intoxicant so readily destroys the 
appetite for normal food and nourishment as does beer.” 
The drunkenness that has resulted from beginning 102 
HUMAN PHYSIOLOGY. 
to drink beer is appalling to think of. The danger of 
beginning to use beer and other liquors that contain 
relatively small amounts of alcohol is so great that 
thirty-five physicians of eminence signed the following 
as a statement that should be taught the children and 
youth in all public and private schools: 
“Accumulative Action of Alcohol:—Alcohol, like other 
substances of a narcotic nature, has the power when taken 
frequently, even in small quantities, to create a diseased 
appetite for more, which may become uncontrollable, and 
its gratification destructive.” 
100. Is There Alcohol in Bread?—lf yeast produces al- 
coholic fermentation, you will perhaps wonder whether 
bread, which is made light and porous by yeast, is a 
good food, or whether it, too, contains alcohol, and thus 
is harmful in its nature. How is bread made? First, 
yeast is added to the warm bread sponge, and fermenta- 
tion is presently set up. A little free sugar is present 
in the flour, and this is changed by the yeast into 
alcohol and carbonic acid. The latter, which we have 
found to be a gas, in its efforts to escape raises the 
bread dough with it, making it light and porous. If 
then put into the oven, all the alcohol, which was but 
little to begin with, is driven off by the heat, and we 
have left a well-baked loaf of bread, which contains 
nothing harmful, but is instead a healthful food. The 
process of fermentation in bread-making and beer-mak- 
ing is something the same, but the results are very dif- 
ferent. There is no alcohol in well-baked bread, because 
it is all driven off by the heat while baking; but all 
the alcohol remains in the beer. Thus in the one case 
we have a food and in the other a poison. FOOD AND DRINK. 
103 
Distilled Liquors.—Fermented liquors usually contain 
but a small amount of alcohol—from two to ten per cent. 
—but people who have indulged in the use of the milder 
drinks soon crave those which are stronger, and distilled 
liquors are sought to gratify their abnormal appetite. 
Distilled liquors are made by heating fermented 
liquors to a little below the boiling point. The alcohol 
which becomes vapor at a lower temperature than water 
passes off through cold tubes into a receiver called a 
still. By being thus cooled, this vapor is again changed 
into a liquid which contains less water and more alcohol 
than before. By repeating the process several times, 
very strong alcoholic liquors are produced. 
The most common drinks made by distillation are 
whisky, rum, gin, and brandy. These usually contain 
from forty to sixty per cent, of alcohol. Not only 
whisky and brandy but almost all other alcoholic 
liquors commonly sold are adulterated by admixtures 
with various cheap and often poisonous substances. 
They contain not only the poison alcohol, but other 
liquids and drugs, which are also unwholesome and 
dangerous. We sometimes hear it said that if pure 
wines, pure whiskies, and other like drinks unmixed 
with foreign substances were the only ones used, there 
would be little or no drunkenness. This is not true. 
There is no such thing as a pure alcoholic drink, if by 
this term is meant that which is harmless in its nature 
and effects. The alcohol, which is always present in 
wine or any other fermented or distilled drink, is under 
all circumstances a powerful narcotic poison. 
101. The Alcoholic Appetite.—All alcoholic drinks, of 
whatever kind, when taken into the stomach, have the 104 
HUMAN PHYSIOLOGY. 
power to cause what is known as the alcoholic appetite 
—that is, they create an unnatural craving for more 
alcohol. It is this craving which leads so many men to 
become habitual drunkards. The only safe rule with 
respect to fermented or distilled liquors of any kind is 
“Never take the first drink." 
Summary.—We have learned how substances which 
might be used as wholesome and nutritious foods are 
changed into insidious poisons. By being subjected 
to fermentation they are converted into liquors con- 
taining in various proportions a poisonous substance 
called alcohol. These liquors are known by various 
names. They are directly injurious in proportion to 
the amount of alcohol which they contain. But the 
weaker kinds are much more harmful than they seem, 
because they are able to produce an unnatural craving 
for more and more alcohol, and thus lead to destruc- 
tive indulgence in the stronger drinks. Alcohol when 
taken frequently, even in small quantities, has the power 
to create an uncontrollable appetite for more. It is to 
satisfy this strange appetite that immense quantities of 
grain and fruit are every year made into fermented or 
distilled liquors. These liquors are not foods, for they 
are deficient in those elements necessary to supply the 
tissues with nourishment. It may be stated as a fact 
of general importance that fermentation always changes 
the character of the substance it works upon. CHEWING AND SWALLOWING. 
105 
CHAPTER XII. 
CHEWING AND SWALLOWING. 
102. The Digestive Canal.—All food, before it is in a 
condition to afford nourishment to the tissues, must 
.. Esophagus. 
-Pancreas. 
'■Stomach. 
. Liver. 
..Pylorus. 
Gall-bladder 
Spleen. 
Colon. 
Large intestine 
Small intesdne. 
Colon. 
Caecum 
Vermiform 
appendix. 
Fig. 51.—The Digestive Canal and other Organs of Digestion. 
Small intestine. 
Rectum. 
undergo a certain process in the body, called digestion. 
The passage in which the digestion of the food is per- 106 
HUMAN PHYSIOLOGY. 
formed is the digestive or alimentary canal. This canal 
includes the mouth, the esophagus, the stomach, and the 
intestines. The food first enters the mouth, then passes 
back into the pharynx, from there through the esoph- 
agus into the stomach, and then into the small intestine. 
Lastly what indigestible matter remains is forced into the 
large intestine, whence it is expelled from the body. 
103. Mastication, or Chewing.—In order that the food 
may be properly digested it is necessary that, before being 
swallowed, it should be in a finely divided state and 
mixed with the secretions of the mouth, so that it can 
be easily acted upon by the juices of the stomach. This 
process of dividing the food and mixing it with the se- 
cretions of the mouth is called mastication. Improper 
or insufficient mastication is often the cause of a trouble- 
some disease called dyspepsia. 
104. The Organs of Mastication.—The organs concerned 
in the act of mastication are the upper and the lower 
jaw, the muscles which move the lower 
jaw, and the tongue, the lips, and the 
cheeks. 
105. Teeth.— Each jaw contains six- 
teen teeth, making thirty-two in all. 
Each tooth consists of a crown, a neck, 
and a root. The crown is that part 
which is not covered by the gums. It is 
covered by a white, glistening substance 
A TooTH2'~A.-Cr°ownP 
b.—Neck. c.-Root. 
called enamel. This enamel is the hard- 
est substance in the human body. It is 
thickest on the top of the tooth. Its hardness varies in 
different persons; in some it is so soft that the teeth 
soon wear away. The greater part of a tooth is com- CHEWING AND SWALLOWING. 
posed of ivory, and is covered over with a bone-like 
structure. The neck of a tooth is the part covered by 
the edge of the gum. The root is that part of the tooth 
-Vein. 
Artery 
■Nerve. 
Opening for passage of nerves and bloodvessels. 
Fig. 53.—The Jaws and Teeth. 
below the neck, and is surrounded by the bony struc- 
ture of the jaw. 
There are four classes of teeth:—(l) The incisors; 
(2) the canines; (3) the bicuspids; (4) the molars. HUMAN PHYSIOLOGY. 
Most people have eight incisors, four canines, eight 
bicuspids, and twelve molars. The incisors are the 
sharp front teeth, and are used in cutting the food. 
The canines are the pointed teeth at the corners of the 
mouth, and are used for tearing the food. The bicus- 
pids and molars are large, broad teeth, and are used in 
crushing and grinding the food. 
It is very important that the teeth should be kept 
clean, for injurious substances are likely to collect be- 
tween or around them and cause them to decay. If 
the enamel of a tooth is once broken or destroyed, it 
will not be renewed. One should, therefore, avoid bit- 
ing very hard substances, or cracking nuts with the 
teeth. The teeth should be carefully washed every 
morning and night with water and a soft brush, and 
particles of food which lodge between them should be 
carefully removed. 
106. The Jaws.—The lower jaw being alone movable, 
the muscles attached to it act in such a way as to ele- 
vate it against the upper one, and at the same time give 
it a side to side grinding motion. 
The tongue, lips, and cheeks all assist in the act of 
mastication, by moving and keeping the mass of food 
between the teeth. 
107. The Saliva.—The fluid which is mixed with the 
food during the act of mastication, and which keeps the 
interior of the mouth moistened, is called the saliva. It is 
in reality the digestive fluid of the mouth. It is formed 
and secreted by three pairs of glands called salivary 
glands. The largest of these glands is called the parotid 
gland, and is situated in front of the lower part of the 
ear. The next in size is called the submaxillary gland, CHEWING AND SWALLOWING. 
and is situated below the lower jaw. The smallest is the 
sublingual gland, situated beneath the tongue. Albthese 
glands open into the mouth by ducts, and are stimu- 
lated to action by the presence of food in the mouth and 
by the operation of chewing. 
108. Object of the Saliva.—The saliva is of the greatest 
importance in the 
proper digestion of 
food. It moistens and 
softens the food, so 
that when it enters 
the stomach the di- 
gestive juices there 
can easily act upon it. 
It keeps the lining of 
the mouth moist and 
pliable. You have 
learned that before 
starch can be of use 
to the system it must 
be converted into 
grape sugar. Now 
the saliva acts upon 
the starch in the food 
and changes much of 
° 
it into sugar, thus put- 
1 p JHES™GT'n, „ 
I.—Parotid Gland. 2.—Submaxillary Gland, 
3 —Sublingual Gland. 
ting it in such a condition that it can easily be assimi- 
lated by the system. 
109. Swallowing.—At the back of the mouth is the 
pharynx, and from the pharynx to the stomach extends 
a muscular tube or passage, about nine inches in length, 
called the esophagus. The walls of this tube are com- HUMAN PHYSIOLOGY. 
posed mostly of muscular tissue, and are lined with soft 
mucous membrane. In the act of swallowing, the food is 
forced into the pharynx, then through the esophagus into 
the stomach. The trachea, or windpipe, also opens into 
the pharynx, but in swallowing, the little leaf-like carti- 
lage, called the epiglottis, about which you have already 
learned, closes this opening so that no particles of food 
or drink can enter the air passages. 
110. Effects of Alcohol on Mastication.—Alcohol, when 
taken into the system, interferes with the action of many 
of the glands. By interfering with the salivary glands, 
it prevents the formation and secretion of a proper 
amount of saliva. It also changes its quality, and makes 
it less fit to perform that for which it is intended. As a 
consequence, many troublesome forms of dyspepsia and 
indigestion are induced and aggravated. Alcohol also 
has a parching effect upon the mouth and throat, pro- 
ducing an unnatural thirst. If sufficient liquid of any 
kind is drunk to allay this thirst, the digestion of the food 
is impaired and the whole body suffers in consequence. 
111. Effects of Tobacco on Mastication.—Tobacco over 
stimulates the action of the salivary glands, causing the 
saliva to flow oftener and in greater quantities than is 
natural. This constant over stimulation weakens these 
glands, and after a while they are unable to secrete 
a sufficient quantity of saliva for the proper mastica- 
tion of food. The result is dyspepsia and indigestion. 
Dryness of the mouth and throat often exists in per- 
sons who smoke tobacco. This condition is not only 
troublesome and uncomfortable, but it interferes with 
proper mastication and swallowing, and in the end is 
pretty sure to induce disease. DIGESTION IN THE STOMACH. 
CHAPTER XIII. 
DIGESTION IN THE STOMACH. 
112. The Stomach.—When food is swallowed, it enters 
the stomach. This organ is a dilated portion of the di- 
gestive canal. In an adult it is about thirteen inches 
long and five inches wide. Its capacity varies in different 
Fig. 55.—The Stomach. 
Outside view, showing the directions of the muscular fibers. 
persons, but on an average it will contain from three to 
five pints of fluid. It has two openings ; one from the 
esophagus, called the cardiac orifice, the other, called 
the pylorus, at the opposite end, where the food passes 
into the small intestine. The wall of the stomach is 
composed principally of muscular fibers of the involun- 112 
HUMAN PHYSIOLOGY. 
tary type. These muscular fibers are arranged in three 
layers, those of the first running lengthwise of the 
stomach, those of the second running round it, and 
those of the third crossing it obliquely. 
113. Digestion in the Stomach—The interior of the stom- 
ach is lined with a soft, velvety, mucous membrane. On 
the surface of this membrane there are vast numbers 
of very small orifices. These are openings of the ducts 
Fig 56 —Section of the Stomach. 
E.—Esophagus. C.—Cardiac Orifice. P,—Pylorus. I.—Small Intestine, 
from small glands called peptic glands. The peptic 
glands secrete the gastric juice, the digestive fluid of the 
stomach. It is a clear, straw-colored liquid and contains 
pepsin and hydrochloric acid. Its digestive power is 
dependent on the presence of these two substances, and 
if they be removed from it, it becomes useless as a diges- 
tive fluid. In the stomach of an adult almost fourteen DIGESTION IN THE STOMACH. 
pints of gastric juice is secreted in the course of each 
twenty-four hours. 
Not all kinds of food are digested in the stomach. 
The stomach digests chiefly the tissue-making substances. 
The fats and starches pass on to the small intestine and 
are there digested. 
Fluids are absorbed into the circulation directly from 
the stomach. 
114. Action of the Stomach.—When the stomach is at 
rest, its lining membrane is of a pinkish color. When, 
however, food enters the stomach, this membrane be- 
comes bright-red in color, owing to the increased flow 
of blood to its blood-vessels, and then the secretion of 
the gastric juice begins. At the same time the muscu- 
lar fibers in the walls of the stomach begin slowly to 
contract and relax, giving the stomach a sort of a mo- 
tion which causes its contents to roll about its interior. 
In this way the gastric juice becomes thoroughly mixed 
with the food. Those portions of the food which be- 
come digested are absorbed into the circulation, and 
when the stomach has digested as much as it can, all 
that remains is forced into the small intestine where 
the process of digestion is completed. 
115. Time Required for Stomach Digestion.—Different 
kinds of food, and differently cooked foods, require dif- 
erent lengths of time for their digestion in the stomach. 
The time varies from one to four hours. The time re- 
quired for the stomach digestion of an average meal is 
from two and a half to three hours. Moderate exer- 
cise, taken before a meal, aids in facilitating digestion. 
116. Care in Eating and Drinking. —We should eat 
enough, but not too much ; and we should eat and HUMAN PHYSIOLOGY. 
drink that which is most conducive to the easy and 
proper action of the stomach. If the stomach is over- 
loaded the gastric juice is required to do more work 
than it is able to perform ; then, as a result, part of the 
food is not properly digested and we suffer with indiges- 
tion. In this troublesome ailment gas is formed in the 
stomach, causing colic, diarrhoea, and other disagree- 
able symptoms. 
The temperature within the stomach is about ioo°, 
and at this temperature the gastric juice acts to the best 
advantage. Now, if ice-water or frozen foods be par- 
taken of, the temperature in the stomach will be re- 
duced and the process of digestion retarded. Digestion 
is also retarded if extremely hot food or drink is indulged 
in. Care should consequently be taken to avoid very 
hot or very cold foods and drinks. 
Regular eating is necessary to good digestion. The 
stomach, like other organs of the body, requires a certain 
length of time to rest. When one eats too often, that 
is, between meals and at all hours of the day, the stom- 
ach is kept busy all the time, till at last it gives out and 
is unable to perform its proper functions. It is in this 
way that various aggravating and painful diseases of the 
digestive organs are frequently produced. 
117. Effects of Alcohol on the Stomach.—When alcohol 
is taken into the stomach, it acts as an irritant to the 
mucous lining of that organ, causing it to become con- 
gested, and producing an unhealthy secretion of mucus 
which, being thick and viscid, covers over the mucous 
membrane, preventing the proper secretion of gastric 
juice and consequently interfering with digestion. 
The gastric juice, as we have already stated, contains DIGESTION IN THE STOMACH. 
a very important element called pepsin. Without this 
element it would be of but little use in the process of 
digestion. Now, if you add alcohol to a solution con- 
taining pepsin, it acts upon this solution in such a way 
as to render the pepsin inert. It acts in a similar way on 
the gastric juice when mixed with it in the stomach. It 
thus interferes with digestion, and if the quantity of alco- 
hol taken into the stomach be considerable, the process 
of digestion is stopped until it has been removed. Very 
often the presence of alcohol in the stomach becomes so 
offensive that nature removes it from the system by in- 
ducing vomiting. 
Persons addicted to the use of alcoholic drinks usually 
have an offensive breath and a coated tongue. They 
suffer from loss of appetite, and are tormented with un- 
natural thirst. These symptoms all denote a disordered 
digestive system. 
Various diseases of the stomach are caused by the 
continued use of alcoholic drinks. When the lining 
membrane of the stomach is constantly irritated, it be- 
comes permanently congested, and causes sour stomach, 
heartburn, nausea, and vomiting. Continued interfer- 
ence with the secretion of gastric juice and with the 
proper action of the stomach, after awhile results in in- 
curable dyspepsia. 
118. Effects of Tobacco on the Stomach.—The use of to- 
bacco very commonly causes indigestion. All tobacco 
users, especially chewers, are great spitters, and in this 
way they waste much saliva. Now if food enters the 
stomach unmixed with a sufficient quantity of saliva, it 
cannot be easily digested. 
Tobacco users have usually a coated tongue, foul 116 
HUMAN PHYSIOLOGY. 
breath, and dry mouth and throat. These are all 
signs of a more or less disordered state of the diges- 
tive organs. 
119. Diseases of the Stomach, and Diseases Caused by 
Unwholesome Food.—Dyspepsia is a common disease. 
In this disease the food is not properly digested, and, 
as a consequence, the whole system suffers. This dis- 
ease is usually accompanied by pain, discomfort, and 
loss of appetite. The principal causes of dyspepsia are: 
the use of alcohol or tobacco, irregular eating, over- 
eating, and indulgence in rich articles of food or food 
too highly seasoned. 
Cancer of the stomach is an incurable disease, result- 
ing in a short time in death. This disease, though often 
existing in persons who do not use alcohol, is especially 
likely to occur in those who are hard drinkers. 
Very many diseases are the direct result of eating 
unwholesome food. Pork is often infested with minute 
parasites called trichina, which, when taken into the 
stomach, increase rapidly in numbers and penetrate to 
various parts of the body, causing severe illness and 
death. Pork chops, ham, and bacon should, therefore, 
always be thoroughly cooked before being eaten. 
Decayed fruits, mouldy bread, sour milk, meat that 
has begun to decompose, all these, if eaten, are liable 
to produce disease. The milk of unhealthy cows fre- 
quently contains germs which communicate the most 
dangerous diseases to those who partake of it. Any 
noxious germs contained in milk may be destroyed 
by boiling it. If this precaution were oftener taken, 
much of the sickness prevalent among children might 
be avoided. DIGESTION IN THE INTESTINES. 
CHAPTER XIV. 
DIGESTION IN THE INTESTINES 
120. Intestinal Digestion.—When the food enters the 
stomach, some of it, as you have learned, is there di- 
gested, and the remainder is forced into the small intes- 
tine. Before leaving the stomach, however, the food is 
reduced to a grayish, semi-liquid mass called chyme. 
When this chyme enters the small intestine it is there 
thoroughly mixed with the pancreatic jiiice, the bile, and 
the intestinal juice—all of which are digestive fluids. 
There the process of 
digestion is completed. 
There the sugars, fats, 
and starches are all 
changed and prepared 
for absorption into the 
circulation. 
Villi 
Glands. 
—The small intestine is 
that portion of the diges- 
tive canal between the 
stomach and the large 
intestine. It is a tube 
about twenty feet in 
length. Its walls are 
121. The Small Intestine, 
Areolar tis- 
sue. 
Circular mus- 
cular fibres. 
Longitudinal 
muscular 
fibres. 
Fig. 57.—Section of Small 
Intestine. (Magnified.) 
formed of muscular tissue, like that of the stomach, 
and it is lined with mucous membrane. This mem- 
brane contains many glands which secrete the intestinal 118 
HUMAN PHYSIOLOGY. 
juice. On the surface of the membrane are numerous 
hair-like projections called villi, the function of which is 
Fig. 58.—Relative Position op the Internal Organs. 
to absorb or suck up the digested food, and transfer it 
to the circulatory system. DIGESTION OF THE INTESTINES. 
122. The Duodenum.—As the small intestine extends 
from the stomach, the first eight or ten inches of 
it is called the duodenum. Into this portion of the in- 
testine open two ducts or tubes, one from the pancreas, 
the other from the gall-bladder. Through these canals 
the bile and the pancreatic juice are poured into the 
intestine where they are mixed with the food. With 
the aid of the intestinal juice they complete the process 
of digestion. 
123. The Liver.—The liver is the largest gland in 
the body. It is situated in the right side of the body, 
! CALL 
BLADDER 
RIGHT LOBE 
LEFT LOBE 
just below the diaphragm. Its weight in an adult is 
about four pounds. Connected with it is a small sac, 
called the gall-bladder, from which a duct or tube pro- 
ceeds into the duodenum. The liver secretes bile, 
which is stored up in the gall-bladder and then emptied 
into the small intestine. 
Fig. 59.—The Liver. 
124. The Bile.—The bile is a viscid, golden-brown 
liquid, which is discharged from the gall-bladder into 120 
HUMAN PHYSIOLOGY. 
the duodenum. It is a digestive fluid. When it enters 
the small intestine it mixes with the chyme, or undigested 
food, and aids in its digestion. Its chief use is prob- 
ably to help digest the fats. If the supply of bile be 
shut off from the intestine, as sometimes occurs in cer- 
tain diseased conditions of the liver, the constituents of 
the bile enter the blood, and cause jaundice. In such a 
case the proper nutrition of the body is impeded, and 
the general health is impaired. 
125. The Pancreas.— The pancreas is a gland about 
six inches in length, situated behind the stomach. It 
Fig. 60,—The Pancreas. 
1, 2.—Duct of Pancreas. 3.—Duodenum. 
communicates by a duct with the duodenum. It secretes 
a digestive fluid called the pancreatic juice. This fluid 
is of great importance in the digestion of food in the 
small intestine. 
The chyme which passes undigested from the stom- 
ach contains, as we have already observed, the starches, 
sugars, and fats which were not acted upon by the gas- 
tric juice. These substances now come in contact with 
the bile and the pancreatic juice. The pancreatic juice DIGESTION IN THE INTESTINES. 
121 
acts upon the starch, changing it to grape-sugar. It also 
changes cane-sugar to grape-sugar ; and it acts upon the 
fats, breaking up the fat globules, and forming a creamy 
mass, which is capable of being absorbed into the sys- 
tem through the proper channels. 
126. Effects of Alcohol on the Liver.—When alcohol is 
taken internally, it interferes with the action of the di- 
gestive fluids, not only in the stomach, but in the small 
intestine. On the liver especially, alcohol has an injur- 
ious and very decided effect, often producing fatty de- 
generation and other ailments and derangements in 
this, the largest gland in the body. When this hap- 
pens, the proper functions of the liver are disturbed, 
and the secretion of bile is lessened. 
One of the most common diseases of the liver, in 
persons addicted to the use of alcohol, results from 
the deposit of fibrous tissue in that organ. The 
fibrous tissue replaces the liver substance, causing the 
liver to become small and shrunken, hardened, and 
covered with small elevations, which have given it the 
name of “hob-nailed liver.” This disease of the liver 
is most serious, often interfering with its functions to 
‘such an extent as to cause death. 
127. Absorption.—By absorption is meant the process 
by which digested matters are taken into the blood. 
During the process of digestion, as has already been ex- 
plained, certain portions of the food become liquefied, 
while the fats are converted into a creamy mass, or 
emulsion. In this way the absorption of the food into 
the circulatory system is made possible. Two kinds of 
vessels are concerned in the process of absorption, 
namely, blood-vessels and lacteals. The liquefied foods 122 
HUMAN PHYSIOLOGY. 
are absorbed principally by the blood-vessels, and the 
emulsified foods by the lacteals. 
128. Absorption by Blood-Vessels.—A considerable por- 
tion of the food is absorbed through the capillaries and 
the small veins that are distributed through the lining 
membranes of the stomach and intestine. Carefully 
■3 
S . 
I* 2•§ 
g° 
conducted experiments have demon- 
strated that soluble and liquid sub- 
stances pass through the delicate walls 
of the small blood-vessels, and mix 
directly with the blood. This is the 
way in which absorption in the stom- 
| 
•§. 
£ 
ach takes place. Substances which are 
liquefied and in condition to mix with 
the blood are taken into 
the minute capillaries and 
veins, and by them soon 
■*>ClvisseisUS 
conveyed into 
the general cir- 
culation. 
•Intestines. 
by Lacteals. The lacteals 
or chyliferous vessels are 
small vessels which have 
their origin in the mucous 
129. Absorption 
03 
5 
0 
+-> 
o 
a 
Fig. 61. —Vessels 
concerned m the 
Process of Ab- 
sorption. 
membrane lining the small 
intestine. It is through 
them that the greater part of the digested food is absorbed 
from the small intestine and transferred to the circula- 
tory system. This absorption is carried on as follows: pro- 
jecting from the lining membrane of the small intestine 
are vast numbers of delicate, hair-like projections, about DIGESTION IN THE INTESTINES. 
123 
one-third of an inch in length, which are called villi. In 
each of these villi are numerous small blood-vessels and 
lacteals. The villi dip into the digested and liquefied 
food substance, which is thus taken up into the lacteals, 
and by them finally transferred into the circulatory sys- 
tem. The blood-vessels in the villi also directly absorb 
a portion of the food, just as is done in the stomach. 
The liquefied food which is found in the 
lacteals during the period of digestion 
is a milky white fluid and is called chyle. 
130. The Lymphatics.—The lymphat- 
ics are very small vessels which exist 
beneath the skin and in all the mucous 
membranes of the body. These ves- 
sels are similar in appearance to the 
lacteals, and they carry a transparent, 
colorless liquid called lymph. They 
exist in large numbers, and as they pro- 
ceed in their course they pass through 
certain glands called lymphatic glands, 
where numerous corpuscles resembling 
Fig 63.—Section of 
a Villus (highly 
magnified). 
a, a.—Covering of 
Villus. 
b, b.—Capillaries. 
c, —Lacteal. 
the white corpuscles of the blood are formed. These 
corpuscles are carried away from the glands by the 
stream of lymph which flows through them. Finally, 
the lymphatics unite with some of the lacteals at the 
back of the abdomen and form a vessel called the thoracic 
duct. This thoracic duct, passing up the body in front 
of the spinal column, opens directly into one of the large 
veins of the body, and the nourishing fluid which is car- 
ried by the lacteals, together with the lymph and lymph 
corpuscles, is thus mixed with the venous blood, and 
emptied immediately into the right auricle of the heart. 124 
HUMAN PHYSIOLOGY. 
REVIEW—FOOD AND DIGESTION. 
Food is necessary in order to supply materials for the 
repair of the worn-out tissues of the body. 
The process by which the food is prepared to be taken 
into the blood is called digestion. 
The process by which the digested food is taken from 
the digestive organs and transferred to the circulatory 
system is called absorption. 
The process by which the elements of nutrition are 
taken from the blood and become changed into living 
tissues is called assimilation. 
Foods are of three classes: inorganic, organic tissue- 
making, or nitrogenous, and organic heat-producing, or 
non-nitrogenous. The most important inorganic foods 
are water, salt, phosphate of lime ; the tissue-making 
foods are meats, albumen, casein, gluten, etc. The 
heat-producing foods are sugars, fats, and starches. 
Water is the only substance that will quench thirst. 
Milk, tea, coffee, chocolate, and other substances are 
healthful drinks, but it is only the water which they 
contain that quenches thirst. 
The organs of mastication are the teeth, the tongue, 
the lips, and the cheeks. The saliva assists in mastica- 
tion and also in digestion. 
The teeth may be preserved from decay if properly 
cared for. 
In the process of swallowing, the food passes from 
the mouth into the pharynx, from the pharynx into the 
esophagus, and thence into the stomach. 
The nitrogenized foods are digested in the stomach, 
by the action of the gastric juice. DIGESTION IN THE INTESTINES. 
125 
The fats, starches, and sugars are digested in the small 
intestine. Three fluids assist in this intestinal digestion. 
The liver and the pancreas are important organs and 
secrete fluids which aid in digestion. 
Absorption takes place from the stomach and from 
the small intestine. Fluids and nitrogenized food prin- 
ciples are absorbed directly by the blood-vessels. The 
emulsified fats and other substances are absorbed by 
the lacteals. 
The principal alcoholic drinks are beer, cider, wine, 
whisky, brandy, rum, etc. 
Alcoholic drinks are produced by fermentation or 
distillation. They do not quench thirst, but create an 
unnatural thirst. 
Beer pf whatever kind contains alcohol. Alcohol, 
taken even in very small quantities, has the peculiar 
power of exciting a desire for more. The drinking of 
beer or cider is almost certain to awaken an appetite 
for stronger drinks. The only safe rule is to abstain 
entirely from the use of anything that contains alcohol. 
Whiskies, brandies, and wines are seldom free from 
adulterations. There is no such thing as a pure alco- 
holic drink. ' 
Alcohol interferes with digestion. It causes diseases 
of the stomach, heartburn, nausea, vomiting, incurable 
dyspepsia. It causes fatty degeneration of the liver, 
hob-nailed liver, and interferes with the secretion of 
the bile. It hinders the proper nutrition of the sys- 
tem, and prepares the way for disease. 
Tobacco is of no possible value, either as a food or 
as a drink. It interferes with the mastication of the 
food. It hinders digestion. 126 
HUMAN PHYSIOLOGY. 
CHAPTER XV. 
THE SKIN. 
131. The Skin.—The skin is a tough, elastic structure 
which covers the entire surface of the body. It is 
estimated that the skin surface in an adult is equal to 
about sixteen square feet. The skin varies in thickness 
in different parts of its surface. Where it is exposed to 
friction and pressure it is quite thick, as on the soles 
of the feet and palms of the hands. At the edges of 
the openings into the body it merges into, and is con- 
tinuous with, the mucous membrane. 
132. Uses of the Skin.—The skin is one of the most 
important structures of the body, and it performs many 
functions, among which are the following:— 
(i) It forms a protective covering for the surface of 
the body; 
(2) It aids in equalizing the temperature of the body; 
(3) It acts as an organ of excretion, removing certain 
waste matters from the body. 
133. Structure of the Skin.—The skin consists of two 
layers—an inner one, called the tmie skin, or derma, 
and an outer one, called the cuticle, or epidermis, or 
scarfskin. 
The true skin merges with the fatty tissues beneath 
it. In this layer of the skin is found blood-vessels, 
nerves, and glands, 
The cuticle, or epidermis, which is the outer layer of THE SKIN. 
127 
the skin, contains neither blood-vessels nor nerves. It 
is composed entirely of cells, and contains a peculiar 
matter called pigment- 
ary matter, which gives 
to the skin its color or 
complexion. This mat- 
ter varies in color; in the 
negro it is almost black. 
The outer cells of the 
cuticle are flat, hard, and 
horny-like. The cuticle 
serves as a protection to 
the delicate structures 
of the true skin, and 
varies in thickness as the 
parts are more or less 
exposed to friction. 
134. The Hair and the 
Nails.—These are both 
appendages of the skin. 
Hairs exist on nearly 
the whole surface of the 
Fig. 63.—Section op Skin (magnified). 
body, and vary in size 
and length. The roots 
1. Epidermis. 4.—Coloring matter. 
2. —Derma or true skin. 5.—Nerve termination 
3. Hair follicle. o.—Sweat gland. 
of the hairs are imbedded in small openings in the 
skin, called hair follicles. These follicles are from 
to of an inch in depth. The shaft of the hair is 
that part outside the skin ; it consists of hard, flat cells, 
covering a fibrous center. This center contains pig- 
mentary matter, upon which the color of the hair de- 
pends. Hair is not supplied with blood-vessels, but 
obtains its nourishment by absorption from the true skin. 128 
HUMAN PHYSIOLOGY. 
The nails begin near the tips of the fingers and the 
toes ; they consist of two parts, a root and a body. The 
body of the nail is that part which is exposed to sight; the 
root is about one-fourth the length of the body, and is 
closely adherent to the true skin underneath. The nails 
are really modifications of the cuticle, or scarfskin, 
and have the same general structure. 
135. Uses of the Hair and the Nails.—The hairs have 
several important uses. They serve to protect cer- 
tain parts and organs of the body. The 
hair on the head and face protects these 
parts from cold, and in extremely hot 
weather shields them from the burning 
rays of the sun. The eyebrows prevent 
perspiration from running down upon the 
eyelids, and the eyelashes protect the eye 
Fof 
fief/)ly maen1’ 
A. The follicle. 
B. root. 
from the entrance of dust and other for- 
eign substances. 
... . 
Ihe nails serve as protection to the 
ends of the fingers and toes, and aid the fingers in tak- 
ing hold of, and picking up small articles. 
136. Perspiration.—lt has already been explained how 
carbonic acid and other poisonous matters produced by 
the decomposition of tissues are removed from the sys- 
tem through the lungs. The skin also serves to elimi- 
nate certain waste materials from the body; this pro- 
cess of elimination is produced by the perspiration, or 
sweat. This function of the skin is very important. If the 
skin were to be covered with an impervious coating, such 
as varnish, so as to prevent perspiration or sweating, 
death would soon ensue. The quantity of perspiration 
varies according to the conditions of the weather, the THE SKIN. 
129 
amount of exercise taken, and the character and quantity 
of food and drink introduced into the body. The average 
amount of sweat secreted by the skin is about two pints 
daily. There is constantly more or less sweat being se- 
creted, and it is the evaporation of this which does so 
much toward equalizing the heat of the body. 
137. Glands of the Skin.—There are two kinds of glands 
found in the skin. One of these is called sebaceous glands, 
the other sudoriparous or sweat-glands. 
The sebaceous glands are small glands which open 
by a duct into the hair 
follicles. They secrete 
an oily substance which 
serves to keep the hair 
and skin soft and pliable. 
The sweat-glands are the 
most numerous and most 
important, and every por- 
tion of the skin is sup- 
plied with them. They 
consist merely of a small 
tube, opening on the out- 
side of the skin and coiled 
1.1.1.1. —Openings of the sweat-glands. 
2.2.2.2. —Grooves between the papillae. 
Fig. 65.—Surface of the Skin. 
up just below the true skin. These are the glands which 
secrete perspiration. 
138. Other Uses of the Skin.—Besides serving as a pro- 
tection to the surface of the body, helping to equalize 
the temperature, and assisting in the elimination of use- 
less waste matters, the skin has other important func- 
tions. It serves as an organ of sensation, for in it are 
situated the nerves which convey the sense of touch, 
pain, and temperature. It assists in the respiratory 130 
HUMAN PHYSIOLOGY. 
process, for it absorbs oxygen to a slight extent and ex- 
hales carbonic acid gas. It has also an absorptive power 
by which certain substances may be transferred from its 
outer surface into the capillaries and veins, and thus 
into the system. 
139. Effects of Alcohol on the Skin.—If you should place 
pure alcohol upon the skin, and then cover it with a 
piece of rubber, so that it cannot evaporate, the alcohol 
would act in the same manner as a mustard plaster—ir- 
ritating the skin and perhaps blistering it. When an 
alcoholic drink is taken, it circulates with the blood 
and frequently causes congestion of the skin, pre- 
disposing it to various forms of skin eruptions, causing 
much discomfort and itching and burning of the skin. 
This effect of alcohol upon the skin is frequently seen 
in persons who are hard drinkers, their faces being red- 
dened and blotched and otherwise disfigured. 
140. Injuries and Diseases of the Skin—Probably the 
most common injury to the skin is that caused by burning 
or scalding. If the skin be burned throughout its entire 
thickness, a scar always results. The pain accompanying 
a burn is very severe ; it may be relieved by protecting 
the injured part from the air. Moistened baking soda, 
sweet oil, and linseed oil are valuable for this purpose. If 
none of these are at hand, flour slightly moistened will 
answer the purpose. The burned surface should be cov- 
ered completely with one of these substances. Erup- 
tions of the skin are often caused by indigestion. The 
skin is frequently injured and permanently disfigured by 
the use of cosmetics designed to improve the complex- 
ion. Corns are a thickening of the scarfskin, and are 
usually caused by the wearing of ill-fitting shoes. CARE OF THE SKIN—CLOTHING. 
131 
CHAPTER XVI. 
CARE OF THE SKIN—CLOTHING. 
141. Cleanliness of the Skin.—In order that the skin 
may be in a condition to perform its several important 
functions, it is very necessary that it should be kept 
clean. The perspiration contains much waste matter, 
which, by its evaporation, soon accumulates upon the 
surface of the skin. The sebaceous glands constantly 
secrete an oily matter, which also tends to accumulate. 
The outer layer of the skin, the cuticle, is constantly 
wearing out, forming bran-like scales, which, together 
with dust and dirt, are caught in the drying perspira- 
tion, and remain on the surface of the skin. All these 
things, by their accumulation, fill and choke up the 
openings of the glands, interfering with the discharge 
of their secretions, and with the comfort and health of 
the body. 
To maintain a proper and healthy condition of the 
skin and consequently of the entire system, all these 
accumulations of waste matter and dirt should be re- 
moved, and, so far as possible, prevented. The only 
way in which this can properly be done is by bathing. 
142. Bathing.—Baths are of great importance to the 
general system, keeping the skin clean and healthy, 
quickening the circulation, and adding to one’s per- 
sonal enjoyment and bodily vigor. Bathing should be 
indulged in often, A cold bath may be taken every day, 132 
HUMAN PHYSIOLOGY. 
if no chill follows. Every one should take a warm bath at 
least once a week, thoroughly washing the whole body. 
The cold bath is the most stimulating and strength- 
ening, and if followed by a good rubbing with a coarse 
towel, will rarely produce any chilly or uncomfortable 
sensations. The cold bath causes the skin to become 
rosy, the heart to beat more vigorously, and the whole 
system to feel a sense of comfort and well-being. The 
warm bath, though very useful in removing the dirt 
from the skin, and though feeling more pleasant to the 
bather, is nearly always followed by a sense of languor 
and exhaustion. The skin is left in a relaxed condi- 
tion, which makes it very easy for the person to con- 
tract colds. After taking a warm bath quite a time 
should elapse before going into the open air. 
Do not take a bath soon after a meal, and while 
digestion is going on. Wait until two or three hours 
after you have eaten. When bathing, do not stay in 
the water too long. Three to five minutes is long 
enough for a cold bath, and ten to fifteen minutes for 
a warm one. 
Strong soap should never be used on the skin. Such 
soap contains much alkali, and this tends to remove the 
oily matter from the skin, rendering it harsh and rough. 
It removes more of the cuticle than is advisable. In 
bathing use only as much soap as is necessary for cleanli- 
ness, thereby keeping the skin smooth, soft, and pliable. 
The hair and scalp should be kept clean, the same as 
the rest of the body. Give the scalp a thorough wash- 
ing and rubbing at least once a week. It is very im- 
portant also that the teeth and nails should be kept 
clean. CARE OF THE SKIN—CLOTHING. 
133 
143. Clothing . One of the main objects of cloth- 
ing is to keep the body at a comfortable temperature. 
The clothing should consequently vary in kind and 
quantity, according to the climate, and according to 
the needs of the body. In cold weather it is well to 
wear, next to the skin, clothing made of such material 
as will not readily conduct the heat from the body. 
Woolen goods, flannels, and furs, are materials of this 
class. In hot weather, linen, cotton, and silk are worn, 
as these materials conduct the heat from the body, 
thus reducing its temperature and producing comfort. 
Light colors are cooler than dark ones in the summer 
time. 
Clothing should vary in amount according to the con- 
dition of the weather. The outside clothing should be 
such as can be changed to meet the different require- 
ments. Over-clothes of different weights should be 
used according as the weather is cold or warm. 
The feet should always be well covered, and care 
should be taken to keep them dry. The neck and face 
should not be bundled up closely, even in very cold 
weather, for, by so doing, colds and soreness of the 
throat are more likely to be contracted. 
144. Effects of Alcohol on the Skin.—Alcohol is respon- 
sible for many diseases of the skin. A clear skin and a 
healthy complexion are unknown in persons addicted to 
the alcohol habit; they may have what we call a florid 
complexion, but it is neither natural nor healthy. Persons 
who would have natural, healthy complexions should let 
alcohol in all its forms absolutely alone. The same may 
be said with reference to the inveterate use of tobacco, 
which frequently produces a tawny color in the skin. 134 
HUMAN PHYSIOLOGY. 
CHAPTER XVII. 
THE NERVOUS SYSTEM. 
145. What is the Nervous System ?—The nervous sys- 
tem, although in a certain sense distinct from all the 
other systems, unites the various parts and organs into 
one complete organic whole. It is the medium through 
which all impressions upon the mind are received and 
appreciated. It regulates the movements of the body 
and all the processes of life. It comprises:— 
(1) The cerebrospinal system ; 
(2) The sympathetic system. 
146. Nervous Tissue.—Nervous 
tissue is either white or gray in 
color, and consists of two struc- 
tures, nerve-cells and nerve-fibers. 
The nerve-cells are the parts that 
are capable of creating nerve force. 
The nerve-fibers do not create nerve force, but act as 
conductors of this force 
after it has been gen- 
erated by the nerve- 
cells. The nerve-cells 
form the gray matter 
and the nerve - fibers 
the white matter of 
nervous tissue. Every 
nerve-fiber is connect- 
ed with a nerve-cell. 
Fig. 66.—Nerve-Fibers 
(Highly magnified.) 
Fig. 67.—Nerve-Cells. (Highly magnified.) THE NERVOUS SYSTEM. 
135 
147. The Nerves.—A group or collection of nerve-cells 
forms a nerve center ; from each nerve center pass great 
numbers of nerve-fibers, arranged in bundles, into differ- 
ent parts of the body, the bun- 
dles dividing and sub-dividing 
as they proceed. The bundles 
of nerve-fibers form white, glis- 
tening cords, called nerves. 
These nerves penetrate every 
part of the body. 
148. Motor and Sensory Nerves. 
—Nerves contain two kinds 
of nerve-fibers; one of these 
conducts to the nerve cen- 
ters, the other conducts from 
the nerve centers to the mus- 
cles or organs. Nerves of the 
first kind are called sensory 
nerves; the others are called 
motor nerves. 
Fig. 68.—A Nerve and its 
Branches. 
We may illustrate the action of these two kinds of 
nerves as follows ; If one should place a finger on a 
hot stove, the sensation of pain would travel to the 
nerve center through the sensory nerves; in the nerve 
center there is then generated a peculiar force, which, 
being conducted from it to the muscle through the 
motor nerves, causes the muscle to contract and thus 
to remove the finger from its uncomfortable position. 
149. Nerve Current.—This passing of sensation to a 
nerve center and of force back to the muscle from the 
nerve center constitutes what is called the nerve cur- 
rent. It is estimated that the rapidity of this current is 136 
HUMAN PHYSIOLOGY. 
about 110 feet in a second, much slower than an electric 
current. It requires one-twentieth of a second for a 
Fig. 69.—The Sympathetic Nerve System. 
sensation to travel from the foot to the brain, and an 
equal time for the force generated to travel back. THE NERVOUS SYSTEM. 
150. Varieties of Motor and Sensory Nerves.— By the 
nerves we are enabled to appreciate many different sen- 
sations. We accordingly have many nerves of sensation. 
Hearing, seeing, feeling, tasting, and smelling are all dif- 
ferent kinds of sensation, and there are special nerve cen- 
ters which preside over each. Of the motor nerves also 
there are several varieties, some coming from centers 
which preside over muscles, others from those which 
preside over the heart and stomach, and so on. 
Certain motor nerves, called the vaso-motor nerves, 
are distributed to the walls of the blood-vessels, and 
control the circulation by regulating the size of the 
blood-vessels, causing them to dilate or to contract in 
proportion to the amount of blood that is required. 
151. The Sympathetic System.—The sympathetic sys- 
tem consists of nerves and nerve centers. The nerves 
are composed of nerve-fibers; and the nerve centers, or 
ganglions, as they are called, are composed of nerve-cells. 
There are two chains of ganglions, one on each side of 
the spinal column, within the body, running its whole 
length (see Fig. 69). There are thirty pairs of these gang- 
lions. The sympathetic system of nerves supplies the 
involuntary muscular tissue, governs all acts of secretion, 
equalizes the circulation, and governs the nutrition of the 
body. The nerves from the ganglions are distributed to 
the mucous membranes and to the organs concerned 
in nutrition, namely the stomach, liver, intestines, etc. 
The vaso-motor nerves belong to this system of nerves. 
152. The Cerebro-Spinal System.—This system of nerves 
consists of the brain and spinal cord, and the nerves 
which come from them. This is the system of 
nerves that supplies the greater part of the body. It 138 
HUMAN PHYSIOLOGY. 
Fig. TO.—The Cerkbro-Spinal System. THE NERVOUS SYSTEM. 
139 
presides over sensation, the special senses, voluntary 
motion, intellect, and all the movements which charac- 
terize different individuals. 
153. The Brain.—The brain is a mass of nervous tis- 
sue contained within the cranium. It is composed of a 
number of ganglions, 
or nerve centers, 
which are connected 
with one another and 
with the motor and 
the sensory nerves of 
the system. It con- 
sists of both white 
and gray matter. Its 
average weight is 
about three pounds 
in men, and four or 
Fig. 71.—Side View of the Brain. 
five ounces less than this in women. The brain con- 
sists of three portions, called the cerebrum, the cerebel- 
lum, and the medulla oblongata. 
154. The Cerebrum.—The cerebrum comprises the 
greater portion of the brain, forming almost its entire 
mass. It is divided into two halves, called hemispheres, 
by a deep fissure, running from the front backward. It 
is composed of both white and gray matter—the white 
matter forming the interior, while the gray matter lies 
on the surface. The surface of the cerebrum is not 
smooth, but is arranged in large wrinkles called convolu- 
tions. This arrangement on the surface gives room for 
more gray matter than would be possible if the surface 
were smooth. The whole mass of the cerebrum is cov- 
ered with membrane, and is contained within the cranium. 140 
HUMAN PHYSIOLOGY. 
155. Functions of the Cerebrum.—-The cerebrum is the 
organ of intelligence. It is in man that it reaches its 
highest development. Usually, but not always, the 
degree of intelligence varies with the size of the brain. 
In animals the brain, 
when compared with 
that of man, is very 
small in proportion 
to the size of the 
body. The brain of 
an idiot is usually 
small and imperfect- 
ly developed. 
All operations .of 
thought and intellect 
take place in the 
cerebrum. If this 
part of the brain of 
any animal is re- 
moved or destroyed, 
the animal at once 
becomes stupid and 
utterly indifferent to 
its surroundings. It still possesses power of motion 
and sensation, and can still see and hear, but it con- 
nects no idea with anything heard or seen, and is 
totally indifferent to everything. It may feel hungry 
or thirsty, but it has no idea of relieving its hunger or 
thirst by eating or drinking. 
Fig. 72.—View of the Top of the Brain. 
1.1. —Convolutions. 
2.2. Division between the hemispheres. 
156. Injuries and Diseases of the Cerebrum.—Different 
portions of the cerebrum perform different func- 
tions. If it be injured or become diseased, then the THE NERVOUS SYSTEM. 
141 
function of a portion of it may be changed or de- 
stroyed. Thus there may be diseased conditions which 
cause paralysis of particular muscles or of one whole 
side of the body. Certain diseases of the cerebrum 
may cause a person to be deprived of the power of 
speaking, or of writing, or of both. In all diseased 
conditions of the cerebrum, the mind is affected in one 
way or another. 
157. The Cerebellum.—This portion of the brain weighs 
about five ounces. It is situated beneath the back 
Cerebrum. 
Cerebellum, 
Medulla oblongata. 
Fig. 73.—Sectional View of the Brain. 
part of the cerebrum, and is connected with it. .It 
is composed of white matter within and gray matter 
without. Its surface is rough, being arranged in thin 
layers, or folds. It consists of two halves or hemi- 
spheres, and is much more fully developed in man than 
in any other animal. 142 
HUMAN PHYSIOLOGY. 
158. Functions of the Cerebellum.—There are differences 
of opinion as to the exact functions of this part of the 
brain, and we may say that all 
of its functions have not as 
yet been satisfactorily ascer- 
tained. Its principal busi- 
ness, however, is undoubt- 
edly to preside over co-ordi- 
nate muscular movements, 
especially those used in walk- 
ing (see Definitions, p. 182). 
If this part of the brain be 
injured or diseased, the power 
of locomotion is greatly hin- 
dered, the muscles not acting 
together as they should. 
Cere- 
brum 
Cere- 
bellum." 
Spinal 
cord.' 
159. The Medulla Oblongata. 
—This portion of the brain 
connects the spinal cord with 
the various ganglions of the 
brain. It is about an inch 
and a quarter in length and an 
inch wide. It is composed of 
a mass of white matter, within 
which is imbedded a collec- 
tion of gray matter or nerve- 
cells. The medulla oblong- 
ata, by connecting the spinal 
cord with the brain, serves 
to conduct the sensation and 
motor stimulus to and from 
the brain. Its most import- 
Spinal_ 
corci. 
Fig, 74.—The Brain and Spinal Cord. THE NERVOUS SYSTEM. 
143 
ant function however, is in connection with respiration. 
The small mass of gray matter within the medulla ob- 
longata has entire control over the acts of respiration, 
and if it be injured or destroyed, breathing ceases and 
death is the result. This mass of gray matter has aptly 
been called the “ vital point.” 
160. The Spinal Cord.—The spinal cord is that part 
of the nervous system which extends through the 
spinal canal from the brain to almost the lower end of 
the spinal column. It is composed of gray matter in- 
ternally and white matter externally. From it are given 
off thirty-one pairs of nerves which, leaving it at differ- 
ent points, divide and sub-divide and go to all parts of 
the trunk and limbs. 
161. Functions of the Spinal Cord and Spinal Nerves.— 
The spinal nerves rise from the spinal cord by two 
roots. The one in front is called the anterior 
root, the other the pos- 
terior root. Both sen- 
sation and motion are 
conducted by these 
nerves; the sensation 
is conveyed from the 
parts to the spinal cord 
through the posterior roots, and the motor power is 
conveyed from the spinal cord to the parts through 
the anterior roots. On the posterior root of each nerve 
there is a small ganglion, or knot of nervous matter. 
If the anterior root of a spinal nerve be cut or divided, 
sensation in that nerve is not affected, but the motor 
power is lost; if the posterior root be divided, the 
power of motion is not impaired, but sensation is lost. 
Fig. 75.—Section of Spinal Cord. 
(Showing Roots of Spinal Nerves.) 144 
HUMAN PHYSIOLOGY. 
This shows that the anterior root contains motor nerves ; 
the posterior root, sensory ones. The spinal cord acts as a 
conductor between the nerves 
and the brain. It also acts as a 
nerve center, generating nerve 
force. This force is generated 
independently of the brain and 
produces certain actions known 
as reflex actions. If the foot 
of a sleeping person be tickled 
gently with a straw, it will be 
drawn up out of danger. This 
is a reflex act and the force gen- 
erating it is independent of the 
brain and thought. 
162. Diseases of the Spinal Cord. 
—Diseases and injuries of the 
spinal cord always affect motion 
and sensation below the diseased 
portion. Sometimes injury or 
disease so affects the cord as to 
destroy its communication with 
the brain. In such cases there is 
paralysis of the lower part of 
the body, and although volun- 
tary motion is no longer possi- 
ble, reflex action still exists. 
Fig. 76.—How the Spinal Nerves 
ARE GIVEN OFF FROM THE 
Spinal Cord. 
A, A, A.—Anterior roots. 
P, P, P.—Posterior roots, 
c, d.—Filaments passing be- 
tween the posterior roots, 
g, g, g.—Ganglions of posterior 
roots. 
M, M.—Nerves formed by union 
of two roots. 
(The size of the roots is not so 
large in nature as here repre- 
sented.) 
163, Effects of Alcohol on the 
Brain.—Alcohol is a deadly 
enemy to the brain and spinal 
cord. Its effects are felt by the entire nervous system. 
It acts directly upon the nervous tissues. The nerves in THE NERVOUS SYSTEM. 
145 
the walls of the blood-vessels, called the vaso-motor 
nerves, are paralyzed by it. This allows these small blood- 
vessels to expand, and an undue amount of blood is 
pumped into them by the heart. The heart’s action is 
quickened on account of the paralyzing effect of the 
alcohol on the nerves governing its action. Alcohol 
causes a sense of exhilaration and well-being for a short 
time after it is taken, because of its power to deaden 
the nerves of feeling, but when the alcohol effect has worn 
off, the whole system is left in a more exhausted state. 
To renew this feeling of exhilaration alcoholic drinks are 
often again resorted to, resulting after a while in the 
formation of the most dangerous and injurious of all 
habits, that of drinking alcoholic liquors. 
Intoxication.—The immediate effects of alcohol vary 
with the quantity taken. With considerable quantities 
there is first excitement and exhilaration, the person 
easily giving way to his emotions. He laughs or cries, 
is happy or morose. Then he begins to lose control of 
his muscles ; his under lip falls and his tongue becomes 
paralyzed, so that he is unable to talk plainly. His in- 
tellect becomes so muddled that he cannot talk or act 
with any intelligence, and his whole moral nature seems 
to be changed. At the same time his muscles refuse to 
act in their natural way; they become weak and tremu- 
lous, and he staggers along, scarcely able to stand. If 
a large quantity of alcohol has been taken he soon be- 
comes insensible, falling down and lying as though 
dead, with all the muscles relaxed. This is the usual 
course of intoxication. 
After the person recovers from his intoxication, he 
suffers with general depression, headache, dizziness, and 146 
HUMAN PHYSIOLOGY. 
great nervousness for quite a while ; showing that the 
system has been under the influence of a most powerful 
poison. 
Alcohol users are generally troubled with sleepless- 
ness, and what little sleep they are able to obtain is dis- 
turbed by distressing dreams. 
Delirium Tremens.—This is one of the most frightful 
nervous diseases known. It is caused by the continued 
use of alcoholic drinks. A person who is addicted to 
the use of alcohol sometimes goes on a prolonged 
debauch, drinking day and night, and scarcely eat- 
ing any food. Pretty soon the whole nervous sys- 
tem is exhausted and the mind becomes deranged. 
He cannot sleep and everything around appears to him 
to be some living object. His face becomes haggard, 
his eyes bloodshot, and his gait unsteady. He is in 
mortal terror of everything, and in his disordered mind 
he imagines that he sees insects, snakes, devils, and other 
horrible objects around him, mocking him and ready 
to pounce upon him and do him injury. He cannot 
eat and cannot sleep, and if relief is not soon afforded 
him, death occurs. If he recovers, he is a mental and 
physical wreck for a long time afterwards. 
Chronic Alcoholism.—A person who persists in the 
use of alcoholic drinks sooner or later becomes a chronic 
alcohol drinker. Our poorhouses and penitentiaries 
are filled with just this class of men. A man may be 
of good moral character, ambitious and successful, but 
when he becomes a confirmed drinker all this is changed. 
He becomes immoral, he loses his self-respect, and his 
ambition; he cares no longer for success in life, and 
sooner or later he goes to the poorhouse, the peniten- THE NERVOUS SYSTEM. 
tiary, or the drunkard’s grave. Many men who were 
once good men, have been brought to poverty and deg- 
radation by this giant evil, alcohol drinking. Chronic 
drinkers are often subject to serious nervous diseases. 
Alcohol acts directly upon the nervous tissue causing 
it to become diseased. Paralysis of different organs 
and parts of the body often occurs. Neuralgias are of 
common occurrence, and sometimes the mind itself be- 
comes affected. 
164. Effects of Tobacco on the Nervous System—A very 
frequent cause of nervousness is undoubtedly the use of 
tobacco. The poisonous element called nicotine, which 
is contained in all tobacco, when absorbed into the sys- 
tem, affects the whole nervous organism. For this reason, 
persons engaged in work which requires great care and 
accuracy, necessarily abstain from the use of tobacco. 
For this reason, tobacco is especially injurious to the 
young, making them weak mentally as well as physically. 
It is the influence of this poison on the nerves of the 
heart which frequently changes its action and pro- 
duces in many persons a diseased condition called the 
“ tobacco heart.” 
By causing a constant nervous irritability, tobacco, as 
we have already noticed, retards the nutrition. Often 
the inveterate tobacco user becomes pale, nervous, and 
thin, but when he gives up his tobacco he again be- 
comes hale and hearty. 
Cigarette Smoki7ig.—“ Scarcely less injurious, in a sub- 
tle and generally unrecognized way, than the habit of 
taking ‘ nips ’ of alcohol between meals, is the growing 
practice of smoking cigarettes incessantly,” says a writer 
in that famous medical journal, the London La7icet. “It 148 
HUMAN PHYSIOLOGY. 
is against the habit of smoking cigarettes in large quan- 
tities, with the belief that these miniature doses of nico- 
tine are innocuous, we desire to enter a protest. The 
truth is that, perhaps owing to the way the tobacco leaf 
is shredded, coupled with the fact that it is brought into 
more direct relation with the mouth and air passages 
than when it is smoked in a pipe or cigar, the effects 
produced on the nervous system by a free consumption 
of cigarettes are more marked and characteristic than 
those recognizable after recourse to other modes of 
smoking. A pulse-tracing, made after the subject has 
smoked a dozen cigarettes, will, as a rule, be flatter and 
more indicative of depression than one taken after the 
smoking of cigars. It is no uncommon practice for 
young men who smoke cigarettes habitually to consume 
from eight to twelve in an hour, and to keep this up 
for four or five hours daily. The total quantity of to- 
bacco used may not seem large, but, beyond question, 
the volume of smoke to which the breath organs of the 
smoker are exposed, and the characteristics of that smoke 
as regards the proportion of nicotine introduced into 
the system, combine to place the organism very fully 
under the influence of the tobacco. A considerable 
number of cases have been brought under our notice 
during the last few months, in which youths and young 
men who have not yet completed the full term of phy. 
sical development have had their health seriously im- 
paired by the practice of almost incessantly smoking 
cigarettes. It is well that the facts should be known, 
as the impression evidently prevails that any number of 
these little ‘whiffs’ must needs be perfectly innocuous, 
whereas they often do infinite harm.” THE NERVOUS SYSTEM. 
149 
is a narcotic poison which is obtained from the juice of 
the poppy. It has, perhaps, the most decided effect of 
all drugs upon the nervous system. It should never be 
taken in any form into the body, except by the direction 
of a reliable physician. The habit of using it is easy to 
acquire, but it is one of the most difficult to overcome. 
165. Effects of Opium upon the Nervous System.—Opium 
An opium eater or smoker is to be pitied, for as the 
habit grows on him his mental and moral faculties are 
ruined. He loses all honor and ‘self-respect. He will 
lie, steal, or commit any crime to gratify his habit. He 
soon becomes a complete wreck ; he cannot cure himself 
of the habit, for as soon as his opium is given up he 
suffers the most acute mental and physical anguish, and 
is forced to its use again in order to obtain relief. Thus 
he exists until death comes to his relief, taking him off 
many years earlier than it would had he not acquired 
this deplorable habit. 
The most common preparations of opium are mor- 
phine, laudanum, and paregoric. Many patent medi- 
cines, especially soothing syrups for babies, contain 
opium in some form. All these should be avoided, for 
they are all more or less dangerous. 
166. Other Narcotics.—Chloral and cocaine are two 
drugs which are most injurious in their effects upon 
the nervous system. Chloral acts by numbing the nerve 
centers, thus producing deep sleep—not a natural but 
an artificial sleep. If this drug be used habitually, the 
nervous system is soon wrecked and the physical ener- 
gies are exhausted. 
Cocaine produces much the same effects as opium. It 
is the most subtle drug known, and the habit of using HUMAN PHYSIOLOGY. 
it is the most injurious and fatal to life. The nerves are 
shattered, the physical health is ruined, the intellect is 
weakened, and death comes early as the result of its 
continued, use. 
Tea and coffee, although mild in their action, are 
classified among narcotics. They both have a decided 
influence upon the nervous system, and if they are 
used to excess their effects are very likely to be in- 
jurious to the whole system. Especially are the in- 
jurious effects of these drinks noticeable in young and 
growing persons, and in persons of a highly nervous 
temperament. Children who indulge in tea and coffee 
become nervous and often irritable, and their ner- 
vous system is apparently under a sort of stimulation 
which renders its proper and healthy development im- 
possible. The best drinks for any one are water and 
milk, and, generally speaking, the less tea and coffee 
taken the better it is for one’s nervous system. The 
drinking of tea and coffee, with many people, sometimes 
produces headache and dizziness, and generally a tired 
and languid feeling, but sometimes the opposite effect, 
restlessness and sleeplessness. SEEING. 
151 
CHAPTER XVIII. 
SEEING. 
167. The Special Senses.—The senses which enable us 
to appreciate the properties of external objects are 
called special senses. They are- seeing, hearing, smell- 
ing, tasting, and feeling or touch. 
168. The Eye. The eye is the organ of seeing. 
The eyeball is a ball-shaped body, about one inch 
in diameter. The wall 
or shell of the eyeball 
is composed of three 
layers, or membranes. 
The outer one of these 
layers is the toughest 
and hardest, and is 
called the sclerotic coat. 
It forms what is usually 
known as the white of 
the eye. It surrounds 
the whole eyeball except 
a small portion in front, 
which is covered with a transparent membrane called 
the cornea. 
a. Nasal duct for passage of tears into 
the nose. 
b. Iris. 
c. —Position of tear gland. 
d. —Pupil. 
e. —Sclerotic coat of the eye. 
Fig. 77.—The Eye. 
The middle layer, or membrane, lies just within the 
sclerotic coat; it contains numerous blood-vessels, and 
is of a dark color. This layer is called the choroid coat 
of the eyeball. Within this is the third layer, or mem- 152 
HUMAN PHYSIOLOGY. 
brane, called the retina. This is a very delicate struc- 
ture containing a complicated arrangement of nervous 
tissue. The sensation of sight is received from the 
retina. 
Fig. 78.—Vertical Section of the Eyeball. 
1. —Cornea. 
2. —Aqueous humor. 
3. —Pupil. 
4. —lris. 
5. Crystalline lens. 
6.—Ciliary processes. 
7.—Canal around the lens. 
B.—Sclerotic coat. 
9.—Choroid coat. 
10.—Retina. 
11.—Vitreous humor. 
12.—Optic nerve. 
13, 14, 15.—Muscles of the 
eyeball and eyelid. 
The interior of the eyeball is filled with a clear, trans- 
parent, jelly-like substance, called the vitreous humor. 
Just in front of the vitreous humor and behind the 
cornea is a small transparent body, called the crystal- 
line leiis, and in front of this lens is a sort of curtain 
with a circular opening in its center. This curtain 
is called the iris, and the opening in it forms the pupil 
of the eye. Between the crystalline lens and the cornea 
is a small space filled with a clear fluid called the aque- 
ous humor. SEEING. 
153 
169. Movements of the Eyeball.—The eyeball is cap- 
able of being turned about in all directions. Fas- 
tened to the sclerotic coat are six small muscles, 
which produce these movements by their contractions. 
Sometimes certain of 
these muscles lose their 
power of contraction or 
become weak. When 
this happens it causes 
cross - eyes or strabis- 
mus. 
170. The Optic Nerve.^ 
The optic nerve, or 
nerve of sight, enters 
each eyeball from be- 
hind, and divides into 
many small branches in 
the retina. The fibers 
of the optic nerves min- 
gle in such a way that 
often an injury to one 
eye also affects the sight 
of the other. 
Fig. 79.—Section of the Eye. 
}, 3, 3, 4, s.—Muscles of the eyeball. 
(..—Lacrymal gland, with its ducts, 7, 8, 9. 
,171. The Eyelids .—The eyelids are folds of skin lined 
with a delicate mucous membrane, which may be drawn 
over the front of the eyeball. In each eyelid are 
numerous small glands, that secrete an oily substance. 
This substance, covering the edge of the lids, prevents 
the overflow of tears upon the cheek. The eyelids 
protect the front of the eyeball from the entrance of 
foreign bodies. They also protect the eye from too 
strong light. 154 
HUMAN PHYSIOLOGY. 
172. The Tear Gland.—At the outer side of the eye- 
ball and within the socket is a small gland, the 
lacrymal gland, whose object it is to secrete tears. 
The tears secreted flow through a duct and then are 
spread out upon the eyeball. 
A certain amount of this se- 
cretion is being constantly 
formed. It serves to keep 
the eyeball moist, and pre- 
vents friction between it and 
the eyelids ; if dust or any 
foreign substance enters the 
eye, the tears are poured out in abundance, and help 
to wash this matter from the eye. 
Fig. 80.—Position of the Tear 
Gland. 
At the inner angle of the eyelids is a small opening. 
This is the opening of the nasal duct, a duct extending 
from the eye into the nose. Through this duct the tears 
are constantly drained from the eye; if, however, they 
are too abundant to pass 
through the duct, they 
overflow, and run down 
upon the cheeks. 
- 173. How we See.— If a 
double convex lens is held 
a certain distance from a 
screen of ground glass, an 
image of the objects in 
front of the lens is formed 
upon the screen (see Defi- 
nitions, page 186). This 
image is small, and certain 
objects which are near or 
Sc.—Sclerotic coat. Co.—Cornea. 
Ch.—Choroid coat. I.—lris. 
R.—Retina. V.—Vitreous humor. 
X-—Crystalline lens. Aq.—Aqueous humor, 
Fig. 81.—Section of Eyeball. SEEING. 
155 
far from the lens do not appear distinct. If we wish 
these objects to be more distinct, we must use a thin- 
ner lens for near objects, and a thicker one for more 
distant ones, or change the position of the lens to 
conform with the distance of each object. In the eye, 
the rays of light from an object pass through the crys- 
talline lens, which is a double convex lens (see definition), 
and an image is formed upon the retina. The crystal- 
line lens is supplied with a small muscle, which makes 
it thicker or thinner 
as is necessary, thus 
adjusting the eye to 
far or to near objects. 
When the image is 
formed upon the ret- 
ina an impression is 
produced which is 
transmitted to the brain by the optic nerve. This con- 
stitutes the act of seeing. The power which the lens 
possesses of becoming thicker or thinner, thus adjusting 
the eye to far or near objects, is called accommodation. 
Any interference with this accommodation hinders cor- 
rect sight. 
A. —Lens adjusted for near objects. 
B. —Lens adjusted for far objects. 
Fig. 83.—Accommodation. 
-174. Near-sightedness and Far-sightedness—To form a 
distinct image on a screen you must have the screen at 
the proper distance from the lens; if it be either too far 
from it or too near it the image will appear indistinct. 
In the well-formed natural eye, the retina, which is the 
screen, is just the right distance from the crystalline 
lens, and all images are distinct. In some people, how- 
ever, the eyeball is longer from the front backward than 
it should be, and therefore the retina lies too far from 156 
HUMAN PHYSIOLOGY. 
the lens (see Fig. 83). In this case distant objects can- 
not be distinctly seen, and the person has what is called 
near-sightedness. If, as sometimes happens, a person’s 
eyeballs are shorter than they should be, the retina is 
drawn too close to the lens. In such cases far objects 
are distinctly seen, but near objects are indistinct. This 
is what is called far-sightedness. In old age the crystal- 
A.—Normal Eye. 
X.—Correct place for 
image or focus. 
B.—Near Sight. 
X.—Where image is 
formed. 
C.—Far Sight. 
X.—Where image is 
formed. 
Fig. 83.—Diagram to Illustrate Near- 
sightedness and Far-sightedness. 
line lens becomes more or less hardened, and loses its 
power of accommodation, and the eyesight is thus made 
imperfect. 
All these troubles in the sight can be remedied to a 
great extent by the" use of glasses, the shape of which 
should vary, according to the trouble which they are in- 
tended to remedy. SEEING. 
157 
175. The Iris.—The iris is a delicate curtain with a 
circular opening in its center. It is of different colors 
in different individuals, and hence we say of one per- 
son that he has blue eyes, of another that he has gray 
eyes, etc. The circular opening in the iris is called the 
pupil. It is placed immediately in front of the center 
of the crystalline lens, and thus by admitting the rays 
of light only at that point, prevents the image, which 
falls upon the retina, from being blurred, as would other- 
wise be the case. 
Another important use of the iris is to regulate the 
amount of light admitted into the eye. All the light 
that enters the eye enters through the pupil. Too 
much light irritates the retina; hence, to prevent the 
entrance of too much or too strong light the iris con- 
tracts, and the pupil becomes smaller. If there is too 
little light the iris relaxes, and the pupil grows larger, 
thus allowing the entrance of more light. The peculiar 
action of the iris may be clearly illustrated by observing 
the eye of a cat. 
176. Color-Blindness.—The perfect or normal eye is so 
constituted that its possessor is able readily to distin- 
guish between different colors. Sometimes a person’s 
eyes are in such a condition that they do not give the 
power of distinguishing colors, especially the difference 
between red and green. This condition is called color- 
blindness. Occasionally, color-blindness is such as to 
prevent the appreciation of any color, all colors appear- 
ing simply as shades. 
177. Why we see an Object Single.—It would seem that 
as we have two eyes everything we look at would ap- 
pear double. The reason that this is not the case is HUMAN PHYSIOLOGY. 
that the eyes are kept in such a position by the muscles 
of the eyeball as to cause the image to fall upon exactly 
the same place on both retinas. If the eyes are not so 
arranged, the image falls at different points on the two 
retinas, and we see double. This is what is called double 
vision. 
178. Directions for the Care of the Eyes. —The eye is 
the most delicate and complicated organ of the body, 
and, therefore, requires the greatest care. It is 
liable to many diseases, and for any of these the 
advice of a trustworthy physician ought always to 
be sought. 
Should any object enter the eye by accident, it 
should be at once removed, for if allowed to remain it 
may cause serious inflammation. Try to wash it out 
with water, and if this is found to be impossible, con- 
sult a physician. If lime or alkali should enter the 
eyes, wash them out quickly with a weak solution of 
vinegar, and bathe them freely with water. 
If the eyes become painful and irritated from exposure 
to cold or from overwork, rest and frequent bathing 
with tepid or hot water will often afford complete relief. 
Proper care of the eyes is most important to good 
eyesight. Avoid looking too long at distant or small 
objects. Never read or write by a feeble or unsteady 
light. 
Do not read by a light which shines directly into 
the eyes, but turn your back to the light, allowing it to 
shine over the shoulder upon the paper or book. Read- 
ing while riding on the cars is hurtful to the eyesight. 
If the eyes become tired easily, or ache frequently, an 
eye specialist should be consulted. SEEING. 
159 
Avoid using eye-washes or salves unless advised to do 
so by your physician. Such things often cause serious 
irritation and inflammation of the eyes. 
179. Effects of Tobacco on the Eyes.—Tobacco has very 
injurious effects upon the eyes. It is a frequent cause 
of color-blindness. The irritating action of tobacco 
smoke causes haziness, and sometimes produces a total 
loss of the sight. Tobacco sometimes produces a wast- 
ing away of the optic nerve, and this leads, sooner or 
later, to partial or total blindness. This disease of the 
eye is called tobacco-amaurosis, and the peculiar symp- 
toms which accompany it very clearly indicate tobacco 
as its principal cause. 
180. Effects of Alcohol on the Sense of Sight.—The use 
of alcohol is responsible for many painful and serious 
diseases of the eyes. The blood-shot, inflamed condi- 
tion of the eyeballs in confirmed alcohol drinkers shows 
that the eyes are very easily affected by this poison. 
Nearly all such persons are troubled, sooner or later, 
with disordered eyesight. 
Drinkers of alcohol find it difficult to recover from 
diseases of the eye, especially if these diseases be of an 
inflammatory nature. The constant congestion which 
alcohol produces acts as a prevention to recovery, often 
hastening and rendering serious what might otherwise 
have been a slight and temporary disease. 
Acute eyesight is absent in persons who indulge in 
alcohol, and the eyes of these persons easily tire with 
moderate work. Color-blindness and haziness of vision 
are of common occurrence among them, and indeed it is 
rarely that this class of people have normal, healthy 
eyes and eyesight. HUMAN PHYSIOLOGY. 
CHAPTER XIX, 
HEARING. 
181. Sound.—Every movement of matter causes vi- 
brations, or waves, in the air surrounding it. This 
being appreciated by the mind, produces the sensation 
of sound ; and the appreciation of this sensation consti- 
tutes what is called hearing. 
182. The Ear.—The ear is the organ by which we are 
enabled to hear. It consists of three parts:— 
(1) The external ear ; 
(2) The middle ear ; 
(3) The internal ear, or laby- 
rinth. 
183. The External Ear.— The 
appearance of the external 
ear is too well known to 
need any minute description. 
It is composed of cartilage, 
covered with skin. Attached 
to it are three small muscles, 
which are so slightly developed 
in man as to be useless, but 
in many animals they are fully 
developed, causing the ear to be freely movable. From 
the external ear a canal or opening extends inward for 
about one and a quarter inches, being closed at its inner 
extremity by a thin membrane, called the drum of the 
ear, or the membrane of the tympanum. 
Fig. 84.—The External Ear. HEARING. 
161 
In this canal there are several small glands, which se- 
crete a waxy substance called the cerumen, or ear-wax; 
and from the walls of the canal grow short, stiff hairs, 
the object of which is to prevent the entrance of insects 
and foreign bodies into the inner ear. 
184. The Middle Ear.—Just within the drum of the 
ear is a small, irregularly-shaped cavity, called the 
tympanum, or middle ear. Opening into the middle ear 
is a small tube, called the eustachian tube, which leads 
to the upper part of the throat. 
This tube allows the air to pass in and out of the mid- 
dle ear. Within this tympanum, or middle ear, there 
is a chain of very small bones, three in number. One 
of them is attached to the drum of the ear, another to a 
membrane of the internal ear, and the third lies be- 
tween these two. 
The middle ear 
is separated from 
the internal ear 
by means of a 
thin, delicate 
membrane. 
185. The Inter- 
nal Ear.—The in- 
ternal ear is a 
cavity, very ir- 
regular in shape 
and very compli- 
cated in struc- 
ture. It is, in 
large part, made 
up of spiral tubes 
n. —Auditory canal. 
o. Drum of the ear. 
p. —Tympanum or mid- 
die ear. 
Fig. 85.—Section op the Ear. 
1, 2, 3.—Bones of the ear. 
4, 5, 6, 7.—lnternal ear. 
B.—Auditory nerve. 
b.—Eustachian tube. 162 
HUMAN PHYSIOLOGY. 
which open into a sort of a cavity called the vestibule. 
The internal ear is filled with a watery fluid, and in its 
walls branches of the nerve of hearing are distributed. 
The nerve of hearing is called the aziditory nerve. 
186. The Act of Hearing.—The way we hear is as fol- 
lows: The vibrations of the air, or the sound-waves 
strike upon the external ear, are collected by it, and 
sent through the canal to the drum of the ear. The 
sound-waves striking upon this drum cause it to vi- 
brate. This vibration is carried to the chain of bones 
in the tympanum, and thence to the liquid in the in- 
ternal ear, finally producing certain impressions upon 
the fine nerves of hearing. These impressions are 
conveyed to the brain, and are there appreciated as 
sound. 
187. Diseases and Injuries of the Ear.—Catarrh often 
causes deafness by the inflammation spreading from the 
throat to the ear through the eustachian tube. The 
drum of the ear sometimes becomes broken by violence, 
and deafness results. The hearing may often be af- 
fected by sudden loud noises, or by the introduction 
of foreign objects into the ear. Cold in the head is 
a very common cause of partial deafness. 
188. Effects of Alcohol and Tobacco on the Hearing.—The 
habitual use of alcohol often causes a congestion of 
the throat, which, extending through the eustachian 
tube, affects the hearing. 
The use of tobacco, especially the smoking of it, 
often leads to congestion of the internal ear. Snuff- 
taking is very harmful, and should never be indulged 
in. Persons who are habitual users of tobacco, very 
rarely have an acute sense of hearing. SMELLING—TASTING—FEELING. 
163 
CHAPTER XX 
SMELLING—TASTING—FEELING. 
189. The Sense of Smell.—The organ of the sense of 
smell is the nose. The mucous membrane which lines 
the nasal passages, is supplied with filaments, or branches 
of the olfactory nerve, which is the nerve of smell. 
These filaments enter the nose through a sieve-like 
bone in the roof of the 
nasal cavity. The most 
common theoryconcern- 
ing this subject is that 
every object which has 
odorous properties gives 
off invisible particles, 
and these particles, com- 
ing in contact with the 
nerve filaments in the 
nose, produce a peculiar 
sensation. This sensa- 
tion, when appreciated 
by the brain, is called 
smell. 
(Showing the Branches of the Olfactory 
Nerve.) 
Fig. 86.—Section op the Nose. 
If one would properly enjoy the sense of smell, the 
lining membrane of the nose must always be kept in a 
healthy condition. Colds in the head should not be 
neglected, and irritating substances ought never to be 
inhaled. The object of the sense of smell is to enable 164 
HUMAN PHYSIOLOGY. 
us to distinguish fit articles of food, and to warn us of 
poisonous or impure air. 
190. The Sense of Taste.—The sense of taste lies in 
the tongue and the upper part of the throat. A sub- 
stance to have taste 
must be soluble, so that 
it may be partially ab- 
sorbed by the mucous 
membrane which lines 
these parts, and thus 
come into contact with 
the nerves of taste, 
which are distributed 
there. 
The tongue is cov- 
ered with small eleva- 
tions, called papilla, 
and it is in these pa- 
pillae that most of the 
nerves of taste are sit- 
uated. Different parts 
of the tongue perceive 
and convey the sensa- 
tion of different tastes 
—as bitter, sweet, sour, 
salty, etc. Both the 
sense of taste and that 
of smell are exercised 
when eating or drink- 
ing such substances as have an aroma. This explains 
why the taste of many articles resembles their odor. 
The nerves of taste are in close sympathy with the 
(Showing also the back part of the mouth.) 
a. —The palate. 
b. Tonsil. 
Fig. 87.—The Human Tongue. 
c.—Epiglottis. 
d, e, f.— Papilhe. SMELLING—TASTING—FEELING. 
165 
stomach, and often tell us that the stomach will rebel 
against certain articles of food. Taste enables us to 
distinguish between wholesome and unwholesome foods. 
By taste, flavors are appreciated, and these when pleas- 
ant, stimulate the flow of the saliva and gastric juice, 
and thus aid in the digestion of the various foods. 
191. The Sense of Touch.—The sense of touch is located 
in the skin, and in some of the mucous membranes. 
The skin is covered with minute elevations, or pa- 
pillae, and in these the nerves of touch are distrib- 
uted. The sense of touch enables us to appreciate 
pain, heat, cold, roughness, hardness, and other qualities 
of different substances. The sense of touch in the tip of 
the tongue and the tips of the fingers is very acute. The 
sense of touch is relied upon in all acts and movements 
of the body. It acts as the safeguard of the body. 
192. Effects of Alcohol and Tobacco on these Senses.—The 
use of alcohol and tobacco tends to blunt all the 
senses, and to weaken the action of all the nerves of 
sensation. It especially interferes with the sense of 
smell, often completely destroying it. Alcohol causes 
congestion and thickening of the mucous membrane 
of the nose, thus paralyzing, to a certain extent, the 
nerves of smell. The sense of taste is blunted by the 
use of alcohol or tobacco. The persistent smoking of 
tobacco often renders a person almost totally incap- 
able of distinguishing flavors. Alcohol and tobacco 
both benumb the nervous system. The sense of feel- 
ing, as well as the delicacy of touch, is frequently blunt- 
ed. If alcohol is taken in large quantities, it causes 
unconsciousness and complete insensibility to pain or 
touch. 166 
HUMAN PHYSIOLOGY. 
FIRST SUPPLEMENTARY CHAPTER. 
CARE OF THE SICK ROOM. 
If you have a sick friend or relative, and would have 
him recover his health in the least possible time, you 
should see that proper care is taken of his sick room. 
193. Air.—Fresh air and sunlight are direct enemies 
to disease, so see to it that the patient has both. His 
room should be on the sunny side of the house, where 
the cheerful sunlight can be allowed to pour into it. 
Sunlight kills disease germs, but darkness breeds them. 
A light and cheerful room will hasten recovery, but a 
dark and cheerless one will retard it. 
Plenty of fresh air is of the utmost importance. Have 
an open fire-place in the room if possible. If not, then 
see that the windows and doors are opened enough to 
supply an abundance of fresh air. If the patient be 
protected from a draught by the use of extra blankets, 
the room may frequently be aired out. 
194. Furniture in the Room.—The less furniture the 
better. Have the floor bare, with rugs or strips of 
carpet placed upon it to deaden the sound when walk- 
ing. Have hard-bottomed chairs; upholstered ones are 
not suitable for a sick room. 
195. Noise.—Have a care not to wear squeaky shoes 
when entering the room; and see that the hinges of 
the doors do not creak. 
Do not allow any unnecessary noise in or near the CARE OF THE SICK-ROOM. 
167 
room, for sick persons are easily disturbed and annoyed. 
Do not allow visitors to enter the room except in cases 
of necessity. 
Never converse in whispers in the presence of the 
patient, but carry on all your conversation in the natural 
tone of voice. Do not converse with the sick person so 
much as to tire him, nor allow others to do so. 
196. Medicines.—Keep the medicines out of sight, 
and do not allow drinking-water to stand in the room, 
but always supply fresh water when it is required. Have 
all the medicines properly labeled, so that no mistake 
will be made in giving them. Be very careful to give 
them punctually at the time designated by the physician. 
197. Cleanliness. Keep the bed fresh and clean, 
and the room likewise. All soiled clothing should be 
removed from the room at once and placed in boiling 
water. Never neglect cleanliness. 
198. Temperature.—Keep the temperature of the room 
as nearly uniform as possible ; usually a temperature 
of 70° or 750 is advisable. Avoid the admission of 
sudden draughts of cold air; and, with equal care, avoid 
making the room so warm as to induce lahguor. 
199. The Physician.—Above all things, obey the or- 
ders of the attending physician and never give to the 
patient this, that, or the other thing which kind neigh 
bors may recommend as being useful, or as having cured 
some one else of the same disease. 
By giving heed to the above suggestions you will add 
greatly to the comfort of your friend or relative, and as- 
sist in promoting his speedy recovery. Always remem- 
ber that these five things are necessary in the sick room ; 
light, cleanliness, fresh air, quiet, and cheerfulness. HUMAN PHYSIOLOGY. 
SECOND SUPPLEMENTARY CHAPTER. 
WHAT TO DO IN EMERGENCIES. 
The following hints are intended to give you an idea 
of what to do in certain cases, “ until the doctor comes.” 
Never attempt to treat a severe injury, or an acute 
disease yourself. Always send for a physician, and un- 
til he arrives, follow any hints you may derive from 
the following suggestions: 
200. Accidents.—In all cases of accident, the first thing 
to do is to see that a crowd does not gather closely 
about the victim. A space should be left clear about 
him of at least eight or ten feet on every side. Send 
immediately for a physician. If the victim be uncon- 
scious, or in a faint, lay him flat on his back, with his 
arms and hands extended. This gives his heart a chance 
to act without interference. At the same time loosen 
his clothing about his neck and chest, and remove any- 
thing which may interfere with the flow of blood tow- 
ard the head. If the person be but slightly injured, he 
will probably begin to recover soon after you have given 
him a sip of water, and have bathed his face and fore- 
head with water, and, perhaps, have held a little am- 
monia near his nostrils. 
By the time you have done all this, a physician will 
likely have arrived, and all further examination and 
treatment should be left to him. 169 
WHAT TO DO IN EMERGENCIES. 
201. Drowning.—Drowning is a form of asphyxia. Af- 
ter the body of a drowned person is recovered from 
the water, the face should be turned downwards, and 
the tongue pressed down, so that any water or mucus 
which may be in the throat may be removed. Then 
persistently perform artificial respiration, as explained 
on page 82, at the same time rubbing the extremities 
with the dry hands, and applying hot flannels to the 
body. After the patient has begun to recover, keep 
him warm and quiet for quite a while. In asphyxia 
from strangling, suffocation by gases, etc., carry out the 
same plan of treatment. 
202. Sunstroke.—ln cases of sunstroke, place the per- 
son attacked in a cool, airy place. Do not allow a crowd 
to collect closely about him. Remove his clothing, and 
lay him flat on his back. Dash him all over with cold 
water—ice-water, if it can be obtained—and rub the en- 
tire body with pieces of ice. This treatment is used to 
reduce the heat of the body, for in all cases of sun- 
stroke the temperature of the body is greatly increased. 
When the body has become cooler, wipe it dry, and 
remove the person to a dry locality. If respiration 
ceases, or becomes exceedingly slow, practice artificial 
respiration, as on page 82. After the patient has ap- 
parently recovered, he should be kept quiet in bed for 
some time. 
203. Burns and Scalds.—If the clothing of a person 
catches fire, throw him on the ground, and instantly 
wrap his body up in a carpet, rug, overcoat, or anything 
that will serve to smother the flames and keep them 
from the face. If a burn is very slight, a constant ap- 
plication of cold water is sufficient treatment. After HUMAN PHYSIOLOGY. 
the pain has disappeared, apply lard or vaseline to the 
parts. Very useful applications to a burned surface 
are: linseed oil and lime-water, olive oil, flour, white of 
an egg, and a lather of soapsuds. If a burn be severe, 
leave all further treatment to a reliable physician. 
204. Bruises.—In bruises of a moderate kind, the best 
treatment is to elevate the part affected, and then to 
apply to it ice, or cold, wet cloths. If the person be- 
come chilled, discontinue the cold applications, and 
keep the injured part perfectly clean and dry. Keep 
the part perfectly quiet until the soreness and swelling 
have disappeared. 
205. Cuts.—In cuts, if the bleeding be profuse, check 
it by the methods given on page 65, for checking hem- 
orrhage. Then draw the edges of the wound together 
and secure them there by a bandage, or by strips of ad- 
hesive plaster. Do not change the dressings on a cut 
too often, but when you do change them, see that the 
cut is washed perfectly clean before renewing them. 
206. Frost-bite.—Frost-bite is caused by exposure to 
intense cold. It usually attacks the nose, ears, fingers, 
or toes. When a part of the body becomes frost-bitten, 
do not enter a warm room, or make warm applications. 
Briskly rub the part with snow, or apply ice-water to it 
until the circulation of blood is started in it. Do not 
even then hold a frost-bitten part of the body near the 
fire. If the itching and burning is severe, bathe the 
part in cold water, or apply some simple ointment to it. 
If the frost-bite is severe, always consult your physician 
in regard to it. 
207. Choking.—Choking occurs from the lodging of a 
foreign body in the throat. Quite often a sharp blow WHAT TO DO IN EMERGENCIES. 
with the hand between the shoulders will serve to dis- 
lodge it. If not, then have the person open the mouth 
widely, and by pressing the tongue down, you may be 
able to see the foreign substance, and to remove it. If 
this cannot be done, have the choking person drink 
water, and swallow mashed potatoes, or something of 
that kind, so that, if possible, the substance may be 
forced down into the stomach. If none of these bring 
relief, then produce vomiting by giving to the per- 
son copious draughts of warm salt-water, or warm water 
in which mustard has been mixed. 
208. Croup.—Croup usually begins somewhat sudden- 
ly, and if severe, a physician should at once be sent for. 
In the meanwhile, try to induce vomiting by tickling 
the throat, or with a teaspoonful of syrup of ipecac 
repeated every ten or fifteen minutes. Then keep the 
throat well wrapped in hot, wet cloths, and allow the 
person affected to breathe steam. 
209. Sore Throat.— There are many kinds of sore 
throat, and some of them are very serious; hence, it is 
always advisable that a physician should be consulted. 
A gargle of salt and water, or of a solution of chlorate of 
potash, or of salt-petre is useful in relieving a sore throat. 
External applications of salt pork, lard, or vaseline on a 
rough piece of flannel, will also aid in its recovery. ■ 
210. Foreign Bodies in the Eye.—Nature’s method of 
removing foreign bodies from the eye, is to wash 
them out by an increased secretion of tears. Sometimes 
washing the eye freely with warm water will answer the 
purpose. A very useful way of removing bodies from 
the inside of the upper eyelid is as follows : Separate the 
eyelid from the eyeball by pulling upon the eyelashes, HUMAN PHYSIOLOGY. 
then draw the upper lid down over the lower one, 
and allow it to move back to its natural place. The 
lashes of the lower lid thus act as a brush on the inner 
surface of the upper lid. If the foreign body can be 
seen, it can generally be removed by brushing it with 
the corner of a handkerchief. If these means fail con- 
sult a physician. 
211. Poisons.—A person may be poisoned by acids, 
alkalis, arsenic, opium, aconite, strychnine, etc. 
The first thing to do in all cases of poisoning is to 
empty the stomach. This may be done by giving to 
the person a warm and strong solution of salt, or a tea- 
cupful of warm water into which a teaspoonful of 
ground mustard has been stirred. Tickling the throat 
with the finger or a feather will often produce vomit- 
ing. After vomiting has been induced, give to the pa- 
tient a quantity of milk and white of egg, mixed with 
water, to drink. If the poison is such as to injure and 
inflame the stomach, give barley-water, olive oil, etc. 
By this time a physician will have arrived, and can carry 
out any further treatment required. 
212. Poisonous Bites and Stings.—If a person has been 
bitten by an animal supposed to be mad, or by a snake, 
tie a bandage about the limb directly above the wound. 
Apply suction to the wound until the blood flows freely ; 
then wash it out and paint it with tincture of iodine or 
nitrate of silver, or burn it with the red-hot end of some 
pointed instrument, as a knitting needle. In case of a 
sting by a bee or other insect, pull the sting from the 
wound, if it has been left there, and rub the part with 
a strong solution of soda, or of salt; or, if these are not 
at hand, a coating of mud will help allay the pain. CONTAGIOUS DISEASES. 
THIRD SUPPLEMENTARY CHAPTER. 
CONTAGIOUS OR COMMUNICABLE DISEASES—-HOW 
SPREAD AND HOW PREVENTED. 
213. The Germ Theory of Disease.—By contagious dis- 
eases we understand those diseases which are commu- 
nicated from one person to another, either by direct 
contact or by breathing air rendered impure by such 
persons. All contagious diseases are caused by certain 
specific microscopic bodies or organisms called “ germs.” 
Each disease has its own peculiar germ, and if such 
germ finds its way into the body of a person, under 
certain conditions, it will produce in that person the 
disease of which it is the peculiar germ. These germs 
may be carried from one person to another in several 
different ways. They are exceedingly small. Some float 
with minute particles of dust in the air, and may thus 
be breathed into the lungs, or may find lodgment in 
some part of the body where the skin or mucous mem- 
brane is broken; some find their way into the body 
by being in the water which is drunk, or the food which 
is eaten. If such a thing could be possible as to kill all 
these germs, then contagious diseases would cease to 
exist; but as such is not possible, it is our duty to do all 
in our power to prevent the spreading of the germs and 
consequently the increase of the diseases which they 
produce. Vast numbers of deaths occur every year from 
contagious diseases, and certainly with due precautions 
and care this death rate could be greatly reduced. 174 
HUMAN PHYSIOLOGY. 
The principal diseases which we may class as contagious 
or communicable diseases are consumption, diphtheria, 
typhoid fever, scarlet fever, smallpox, measles, whoop- 
ing cough, and, perhaps, pneumonia. Let us, so far as 
our space will permit, endeavor to learn how these dis- 
eases are spread and what measures should be taken to 
prevent their increase. 
214. Consumption.—Phthisis or consumption is a dis- 
ease of the lungs, and a most dreaded disease. More 
persons die of consumption than of any other disease, 
hence the importance of its prevention cannot be 
over-estimated. The germs which cause consumption 
are called bacilli (see Definition, p. 181). They exist 
in great numbers in the sputum (see Definition, p, 189) 
of consumptive persons. When this sputum becomes dry 
it is easily converted into dust, and thus floats in the air, 
carrying the germs with it, to be breathed by other per- 
sons. The only way, therefore, of preventing the spread 
of these germs is by the immediate and total destruction 
of the sputum of consumptive persons. Such persons 
should never expectorate upon the streets and side- 
walks, or upon the floors of street cars or other con- 
veyances, for the sputum becoming dry and mixing with 
the dust is carried and spread by the air. The best 
precaution that all who have a cough can take is to 
carry pieces of cloth to receive the sputum, which cloths 
should be at once put into a paper or a rubber bag, and 
then the whole be burned at the first opportunity. A 
consumptive person should always sleep alone, and the 
utmost care should be taken to keep his room well aired 
and scrupulously clean. Consumption is now known to 
be a contagious and communicable disease. CONTAGIOUS DISEASES. 
175 
215, Diphtheria.—This dreaded disease is communi- 
cated by the saliva and excretions from the throat. By 
the drying of the excretions, a fine dust is formed which 
floats in the air and is breathed by other persons. Poor 
drainage and sewerage, no doubt, cause many cases of 
diphtheria. It should be remembered, that the diph- 
theria germs often remain in the throat many days after 
the patient has apparently recovered. To prevent the 
spread of this disease every one who is suffering from it 
should be at once isolated, and all clothing and articles 
of furniture used by him should be thoroughly disin- 
fected before coming in contact with any other person. 
For several days after the patient has apparently re- 
covered, he should remain isolated, and not be per- 
mitted to mingle with others until all possible danger 
of infection is removed. 
216. Typhoid Fever.—This disease is rarely contracted 
immediately from the patient by being in his company, 
but is contracted from the germs arising from the dis- 
charges of the person. It is frequently caused by germs 
contained in the water which one drinks. If there is 
the least doubt as to the purity of water, such water 
should be well boiled before being used for drinking 
purposes, as boiling kills the typhoid germs. Drainage 
and sewerage should be well looked after, and all 
clothing and discharges of a typhoid patient should 
be destroyed or thoroughly disinfected. 
217. Scarlet Fever.—This disease is very easily con- 
tracted, and is very contagious. The scarlet fever germ 
is present in the discharges of the nose and throat, and 
especially in the small scales which occur on the surface 
of the skin during the progress of the disease. To pre- 176 
HUMAN PHYSIOLOGY. 
vent the spread of this disease the patient should be 
isolated, and all clothing, etc., be thoroughly disin- 
fected. This same rule applies to cases of smallpox, 
measles, and whooping cough. 
218. General Precautions.—No person who has been ex- 
posed to any contagious disease should be allowed 
to mingle with other persons, especially children, un- 
til it is certain as to whether such person is infected 
with the disease. No one should go from a sick room 
to children, or other persons, until he has changed his 
clothing, and thoroughly washed his face, head, and 
hands. The clothing of a diseased person should never 
be worn by any one else, and none of his bed clothing 
should be used until thoroughly disinfected. It is al- 
ways best not to go near a sick person unless you are 
absolutely needed there, and never should the lips be 
touched to cups, spoons, food, or drink, which have 
been in the sick room or which the sick person has 
handled. After the sick person has recovered, every 
thing that has touched him or was in his room, should 
be burned or thoroughly disinfected. Perfect cleanli- 
ness of houses, food and water is necessary to the 
prevention of the spread of contagious diseases, as is 
also the utmost care in keeping away from sick persons, 
and those who have been exposed to disease. 
219. Effects of Alcohol in Contagious Diseases.—Alcohol 
drinkers, in contagious diseases as well as in other dis- 
eases, can scarcely hope for speedy recovery. Their 
general health has been undermined by this poison, and 
the consequence is that they are not in a proper con- 
dition to combat any disease. The muscular system 
has been weakened, the nervous system is unstrung, CONTAGIOUS DISEASES. 
the circulatory system does not act right, and the 
digestive system is unable to perform its work prop- 
erly. If a person is in this condition, it is easy to 
understand why he is not only very liable to con- 
tract disease, and especially one of the contagious dis- 
eases, but also why he cannot expect to recover 
as soon as persons who do not indulge in alcoholic 
drinks. The generally exhausted condition of the alco- 
hol drinker explains all this. Many a man has died of 
disease, who, if he had not been an alcohol drinker, would 
probably have recovered and lived many years. Disease 
seems especially likely to attack persons who are drinkers 
of alcohol, and disease germs seem to find in such per- 
sons a congenial soil for their growth and development. 
With these facts before us, why should we not say that 
one very important precaution to be taken, in order to 
prevent the spread of contagious diseases, is always to 
let alcoholic drinks absolutely alone ? 
220. Alcohol in Hereditary Diseases.—Children of pa- 
rents addicted to the alcohol habit have often an un- 
controllable appetite for strong drinks. This appetite 
must be considered as nothing more nor less than a dis- 
ease, the result of inheritance. This, however, is not 
the only disease which drunken parents transmit to their 
offspring. Statistics show conclusively that a large pro- 
portion of persons afflicted with insanity are the de- 
scendants of alcohol drinkers; they show also that the 
children of intemperate persons are frequently predis- 
posed to epilepsy, or fits; and that in very many cases 
of idiocy, one or both of the parents were addicted to 
drink, and the deprivation of intellect was directly 
traceable to the alcohol habit. HUMAN PHYSIOLOGY. 
Questions for Reviews and Examinations. 
Introduction. 
Define physiology. What other studies are closely 
allied to it ? Define anatomy. What is hygiene ? What 
important facts do physiology, anatomy, and hygiene 
teach us? Why is it important that we understand 
these studies ? 
Chapter I. 
What is the color of bone ? What are the properties 
of bone? What are the uses of bone ? How many tis- 
sues exist in bone ? What are these tissues called ? 
What are their uses ? Of what is bone composed ? 
Which part gives bone its hardness ? Which gives it 
its elasticity ? By what experiments are the parts com- 
posing bone separated ? What is the difference in the 
bones of the young and of the old ? What is the char- 
acter of bone in very young infants? When do one’s 
bones reach their full development ? What is the peri- 
osteum ? What are its uses ? What diseases and in- 
juries of bones are common? What are the effects of 
alcohol and tobacco on the bones ? 
Chapter 11. 
What is the skeleton? How many bones are there 
in the human skeleton ? How are they united to one 
another? What are ligaments ? What structures form 
the human skeleton? How are the bones classified? REVIEWS AND EXAMINATIONS. 
179 
What are the uses of these classes? How many groups 
of bones are there ? What is the skull ? What is the 
cranium ? How are the bones of the skull united ? 
What is a suture? How many bones are in the face? 
How many of these are movable ? What is the trunk? 
What is the spinal column ? Of what is it composed ? 
Describe a vertebra. How are the vertebrae attached 
to each other ? What is the use of the backbone ? 
What is the chest ? What is the abdomen ? What are 
the bones of the chest ? What is the pelvis ? Describe 
the bones of the upper extremities. Describe the bones 
of the lower extremities. What is the appearance of the 
ends of the long bones? 
Chapter 111. 
What is a joint? How many kinds of joints are 
there? What are movable joints? How is a joint lu- 
bricated ? Name the principal kinds of movable joints. 
Give examples. What diseases and injuries of joints 
are common ? 
Chapter IV. 
What are tissues? What is fibrous tissue? Fatty 
tissue ? Bony tissue ? Describe the formation of mus- 
cular tissue. How many classes of muscles are there ? 
Describe each. How are muscles attached ? How do 
they act ? How many muscles are there in the human 
body? How do they vary in size and shape? What 
important properties do muscles possess ? What are 
the muscles of expression ? What are those of masti- 
cation ? Describe the muscles of the trunk ; of the 
upper extremities; of the lower extremities. What 
are the effects of alcohol on the muscles ? Of tobacco ? HUMAN PHYSIOLOGY. 
Chapter V. 
How may muscles be developed ? What change 
takes place in a muscle which is not used ? How should 
exercise be taken ? What are the results of excessive 
exercise? Of what uses are indoor exercises? How 
should they be practiced ? What are the effects of alco- 
hol upon muscular development ? 
Chapter VI. 
How is bodily nutrition carried on? What is the 
blood ? About how much blood exists in the human 
body? How is the blood carried to different parts 
of the body? What is the composition of blood? 
What is the plasma? Of what use is it ? How much 
of the blood is made up of blood corpuscles? How 
many kinds of blood corpuscles are there ? Which is 
the most abundant ? What are the uses of the blood ? 
What is oxygen ? What is carbonic acid ? What has 
the blood to do with these two substances ? What are 
the uses of the white blood corpuscles ? What is co- 
agulation ? What is a clot ? What are the effects of 
alcohol on the blood ? What effect does tobacco have 
on the blood ? 
Chapter VII. 
What is meant by the circulation of the blood ? 
What are the organs of circulation ? What is the heart ? 
How is it held in position? What is the pericardium? 
How many cavities are in the heart ? What are they 
called? Which have the thickest walls? How many 
valves are in the heart ? What are their uses ? Where 
are they situated ? Of what are they composed ? What REVIEWS AND EXAMINATIONS. 
181 
large blood-vessels open into the heart ? Describe the 
action of the heart. How often does the heart con- 
tract ? What are the sounds of the heart ? What 
causes them? How may it be told if the valves of the 
heart are in good condition or not ? What nerves are 
supplied to the heart ? What effect do they have on the 
heart’s action? What is the pulse? How can you feel 
it ? What will cause it to be more rapid ? What is the 
capacity of the heart ? What are arteries ? What is 
the largest artery of the body ? What are capillaries ? 
What are veins? How do veins differ from arteries? 
What are the effects of alcohol on the organs of circu- 
lation ? 
Chapter VIII. 
Describe the course of the circulation. What is the 
color of the pure blood ? Of the impure ? What ef- 
fect has exercise upon the circulation ? What disorders 
of the circulation often occur ? What are the causes of 
these disorders ? What is hemorrhage ? How may it be 
checked ? What is fainting ? What should be done 
with a fainting person ? What are the effects of alcohol 
on the circulation ? 
Chapter IX. 
What are the organs of respiration ? What is the res- 
piratory tract? Describe the nasal passages. Why 
should you breathe through the nose ? What is the 
pharynx ? What is the larynx ? What is the glottis ? 
What are the vocal cords ? What is the trachea ? How 
is it lined ? What helps it to keep its circular shape dur- 
ing the act of breathing ? What are the bronchial tubes ? 
Describe the lungs. What is the pleura ? What are HUMAN PHYSIOLOGY. 
air-cells ? Of what are their walls principally composed ? 
What are the muscles of respiration ? Which is the 
principal one ? What effects do alcohol and tobacco 
have on the organs of respiration ? 
Chapter X. 
How do we breathe? What is inspiration? What 
is expiration? How often does a person breathe? 
What is the total capacity of the lungs? How much air 
is taken into the lungs in ordinary inspiration ? Give 
some examples of modified respiration. What is the 
air? What is the most important part of the air? 
What is carbonic acid ? Is it poisonous ? What test 
should be used where its presence is suspected ? What 
are the objects of respiration ? What changes take 
place in the blood during respiration ? What change 
occurs in the air? What is the character of air when it 
leaves the lungs? How may the air become impure? 
What is ventilation ? What is the object of ventila- 
tion ? Describe the principles of ventilation. What 
is asphyxia? From what causes may it occur? What 
is necessary to restore an asphyxiated person ? De- 
scribe artificial respiration. How long should artificial 
respiration be practiced on an asphyxiated person ? 
What are the effects of alcohol on respiration ? 
Chapter XL 
Do the tissues of the body ever wear out ? What 
becomes of them ? What is assimilation ? What is 
hunger? How may it be satisfied? What is thirst? 
How may it be satisfied? What kind of food is neces- REVIEWS AND EXAMINATIONS. 
183 
sary to proper nutrition? What is food? How are 
foods classified ? Of what use to the body are these 
principles supposed to be ? What are drinks ? What is 
the basis of all drinks ? What kind of water should be 
used for drinking? If water be suspected of being im- 
pure, what should be done with it? How much water 
does the system require each day ? What is the differ- 
ence between a food and a poison ? What law of na- 
ture affects all matter that has ceased to live ? What 
causes fermentation ? Explain how healthful fruit juices 
and grain solutions are changed to poisonous liquors ? 
Describe alcohol. What is the difference between apple 
juice in the apple and cider? What are the dangers in 
cider-drinking? Why is it better to eat grapes than it is 
to drink wine ? Why is beer made from good grains not 
a good drink ? What is the danger of beginning to use 
beer and other alcholic drinks? and what do physicians 
wish taught in the schools about this? Why is there no 
alcohol in well-baked bread ? What makes all drinks 
that contain alcohol impure ? What causes the alcoholic 
appetite, and what will prevent it ? 
Chapter XII. 
What is the object of digestion ? What is the diges- 
tive canal? Of what does it consist? Describe the 
course the food follows when taken into the body. 
What is the object of chewing the food ? What is mas- 
tication ? What are the organs of mastication? How 
many teeth are there ? Describe the construction of a 
tooth. How are the teeth classified ? What work does 
each class perform ? How many jaws are there? Are 
they movable ? What is the saliva ? From where does 184 
HUMAN PHYSIOLOGY. 
the saliva come ? What is the parotid gland ? Where 
are the salivary glands situated ? What is the object of 
the saliva ? What is the esophagus ? Where does the 
food pass when it is swallowed ? What are the effects 
of alcohol and tobacco on mastication ? 
Chapter XIII. 
Describe the stomach. What is its capacity? What 
openings has it? Of what are its walls chiefly com- 
posed ? With what is it lined ? What are the peptic 
glands? What is the gastric juice? What class of food 
is digested in the stomach ? Describe the action of the 
stomach during digestion. How long does it take food 
to be digested in the stomach ? What care and pre- 
cautions should be taken in eating? Why should our 
meals be at regular intervals ? What are the effects of 
alcohol on the stomach ? What are the effects of 
tobacco on the stomach? What diseases of the stomach 
are common ? 
Chapter XIV. 
What becomes of the food which is not digested in 
the stomach? What is the chyme? With what fluids 
does it come in contact in the small intestine ? What 
is the small intestine? What is the duodenum ? What 
ducts open into it? Describe the liver. What digestive 
fluid is secreted by the liver? What is bile ? What is 
its action in digestion? What is jaundice? Describe 
the pancreas. What digestive fluid does it secrete ? 
What action has this fluid in digestion ? What are the 
effects of alcohol on the liver? What is absorption? 
How is the food absorbed? How does absorption take REVIEWS AND EXAMINATIONS. 
place in the small intestine? What are the lacteals? 
What are the intestinal villi ? What substance is chiefly 
absorbed by the villi ? What are the lymphatics ? De- 
scribe the thoracic duct. 
Chapter XV. 
What is the skin ? What are the uses of the skin ? 
Of how many layers does the skin consist? Describe 
each layer. What gives color to the skin? What are 
the hair and the nails? Describe a hair. Describe a 
nail. What are the uses of the hair and the nails ? 
What is perspiration ? What amount of perspiration is 
secreted by the skin? What is the object of perspira- 
tion ? What glands are found in the skin ? What is 
the object of each? What are the effects of alcohol on 
the skin? Name some common injuries to the skin. 
How would you treat such injuries? 
Chapter XVI. 
Why is cleanliness of the skin necessary? What is 
the proper way to keep the skin clean ? What kind of 
a bath is most strengthening? What precautions should 
be observed when a warm bath is taken ? When should 
a bath be taken? How often? What kind of clothing 
is most comfortable in winter? In summer? 
Chapter XVII. 
What is the nervous system? What are its objects? 
What two great nerve-systems are there ? Of what 
does nerve-tissue consist ? What office do nerve-cells 
perform ? Nerve-fibers ? What is a nerve center ? 186 
HUMAN PHYSIOLOGY. 
What are nerves? What two kind of nerve-fibers form 
the nerves? Give an example of their action. What 
constitutes a nerve current? What is the rapidity of a 
nerve current? Name a few varieties of motor and 
sensory nerves. Of what does the sympathetic nerve 
system consist ? How many ganglions are there ? What 
part of the body does this system supply? Of what 
does the cerebro-spinal system consist ? What part of 
the body does this system supply? What is the brain? 
Of what is it composed? What is its average weight? 
Describe its appearance. Describe the cerebrum. What 
are the functions of the cerebrum ? What occurs if the 
cerebrum be removed from a bird ? What occurs if the 
cerebrum be injured or diseased ? Describe the cere- 
bellum. What are its functions? What is the medulla 
oblongata? Describe it. What are its functions ? 
What is the spinal cord? Describe it. How many 
nerves branch from it? What part of the body do they 
supply? What are the functions of the spinal cord and 
spinal nerves ? What is “ reflex action ” ? What effects 
do diseases or injuries of the spinal cord produce? 
What are the effects of alcohol on the brain ? What are 
the general effects of alcohol on the nervous system ? 
What are the special senses ? What is the eye ? De- 
scribe the eyeball. Of how many layers does its wall 
consist ? What are these layers called ? What is the 
vitreous humor ? What is the iris ? What is the crystal- 
line lens? How is the eyeball moved? Describe the 
optic nerve. What are the eyelids ? What glands are 
in the eyelids ? What secretes the tears? How are the 
Chapter XVIII. REVIEWS AND EXAMINATIONS. 
tears drained from the eye ? What is near-sightedness? 
What is far-sightedness ? How is each remedied ? How 
is the amount of light admitted to the eyes regulated ? 
What is color-blindness ? How is it that we see ob- 
jects single? What injuries to the eyes are common? 
What precautions should we take so as to preserve our 
eyesight ? What are the effects of alcohol and tobacco 
on the eyes ? 
Chapter XIX. 
What is sound ? Of how many parts does the ear 
consist ? Describe the external ear. What is the drum 
of the ear? What is the object of the short hairs in the 
ear ? Describe the middle ear. What is it called ? 
What is the eustachian tube ? Describe the internal 
ear. What is the nerve of hearing ? Describe the way 
in which we hear. What diseases and injuries of the 
ear are common ? What are the effects of alcohol and 
tobacco on the hearing? 
Chapter XX 
What is the organ of smell? How do we smell? 
What precautions are necessary to preserve a normal 
sense of smell ? Where is the sense of taste situated ? 
What are the papillae of the tongue? Of what use is 
the sense of taste to us ? Where is the sense of touch 
located ? How are the nerves of touch distributed ? 
In what part of the body is the sense of touch especially 
acute ? What are the effects of alcohol and tobacco on 
the sense of smell ? On the sense of taste ? On the 
sense of touch ? 188 
DEFINITIONS. 
DEFINITIONS. 
abdo'men. The cavity of the trunk situated below the ribs and 
diaphragm. The name is also applied to the outside front 
portion of the trunk between the chest and the pelvis. See 
§ 14- 
albu'men. One of the most important food principles. See 
§ 96. It is found in its purest natural form in the white of 
an egg. 
al'COhol. A liquid formed by the fermentation of aqueous sugar- 
solutions, or by the destructive distillation of organic bodies. 
Throughout this book the word is used to include all liquors 
containing alcohol in any quantity, whether small or great. 
See §§ 9, 28, 39, 47, 62, 70, 78, 90, 99, 100, no, etc. 
al'coholic liquors. Liquors which contain alcohol in either small 
or large quantities, and are used as beverages. See §9. 
ale. Carefully made beer of a certain strength. See definition 
of beer, below. 
anat'omy. The science which describes the bodily structure of 
animals or plants. Human anatomy is the science which 
describes the appearance and structure of the different parts 
of the human body, Animal anatomy, or comparative an- 
atomy, relates to animals in general. Vegetable anatomy re- 
lates to plants. 
aor'ta. The main artery in the body, from which all the other 
arteries (except the pulmonary) have their origin, either di- 
rectly or indirectly. See § 53. 
append'age. That which is attached to something as a neces- 
sary part of it. Thus the hair and nails are said to be ap- 
pendages of the skin. See § 134. 
a'queous hu'mor. The fluid which fills that portion of the eye 
between the cornea and the crystalline lens. See § 168. 
ar'tery. One of a system of blood-vessels which conveys the 
blood from the heart to all parts of the body. The two DEFINITIONS. 
189 
principal arteries are the aor'ta, which rises from the left 
ventricle of the heart, and the pulmonary artery, which rises 
from the right ventricle. The former, with its branches, 
carries pure blood to all the tissues; the latter, with its 
branches, carries impure blood to the lungs, there to un- 
dergo purification. See § 59. 
artificial respira'tion. Breathing by artificial means. See § 89. 
asphyxia (as fix'ia). A stoppage of the breath, as in choking, 
drowning, or paralysis of the muscles of respiration. See 
§BB. 
assimila'tion. The process by which nutriment is changed into, 
and becomes part of, a living tissue. See § 91. 
au'ditory nerve. The nerve of hearing. See § 185. 
au'ricles. The two upper cavities of the heart into which the 
blood enters as it returns from the other parts of the body. 
See § 51. 
bacilli (ba sill). Microscopical vegetable organisms, having the 
form of very slender, straight filaments. A germ of the 
large class of micro-organisms known as bacteria. See § 213. 
beer. An alcoholic liquor made generally from barley. The 
grain is first induced to sprout, thereby changing its starch 
into sugar. It is then ground, and its fermentable substance 
is extracted by hot water. It is then boiled with an infu- 
sion of hops, after which it is drawn off into vats, and suf- 
fered to ferment. After it has become clear it is put in 
barrels, or kegs, and stored away, or sent to market. The 
quality of the beer depends upon the length of time that it 
has been allowed to ferment. See definition of fermenta- 
tion, below. See § 99. 
biceps. The large muscle on the front part of the arm below 
the shoulder. See § 24. 
bile. A fluid secreted by the liver. See § 124. 
blood. The fluid which circulates in the arteries and veins, car- 
rying nutriment to all parts of the body, and assisting in the 
removal of useless and worn-out matter. See §§ 40-48. 
cap'illaries. The smallest of the blood-vessels, connecting the 
veins and arteries. See § 60, 190 
DEFINITIONS. 
cartilage. Gristle. An elastic animal tissue, similar to bone, 
but softer. See §5. 
casein (ka'se in). A nitrogenous food principle, found abund- 
antly in milk. See § 96. 
catarrh (ka tar'). An inflammation, either acute or chronic, of 
the mucous membrane of some organ, usually of the nose 
or throat. 
cerebellum. The little brain. The smaller and hinder division 
of the brain. See §157. 
cere'bro spi'nal sys'tem. That part of the nervous system which 
has its origin in the brain and spinal cord. See§§ 142-161. 
cer'ebrum. The larger division of the brain. See § 154. 
cerumen (se roo' men). The wax-like substance secreted in the 
passage of the external ear. See § 183. 
chest. The cavity of the body above the diaphragm. See § 14. 
chlo'ral (klo'ral). A narcotic compound, prepared from chlorine 
and alcohol. See § 166. 
cho'roid coat (ko' roid). The middle coat of the eye. See §l6B. 
chyle (klle). The milky fluid found in the lacteals during the pro- 
cess of digestion. See § 129. 
chyme (klme). The food as it passes into the small intestine after 
partial digestion in the stomach. See § 120. 
ci'der. The juice of apples. There is no alcohol in the juice 
of sound apples, but when this juice is pressed out of the 
apples It soon begins to ferment. Hard cider is apple juice 
which, by fermentation, has lost its sweetness, and has be- 
come an alcoholic liquor. If the fermentation is suffered to 
continue the alcohol is changed into acetic acid, and vine- 
gar is produced. See definition of fermentation, below. 
See § 99. 
congest'ed. Containing an unnatural accumulation of blood, 
convolutions. The wave-like projections on the surface of the 
brain. See § 154. 
co-or'dinate move'ments. The consistent and harmonious ac- 
tion of various parts, as of the muscles in walking, etc. 
cor'puscles. Small bodies, usually too minute to be distinguished 
by the naked eye. See § 44. DEFINITIONS. 
circula'tion. The passage of the blood from the heart into all 
parts of the body, and its return to the heart. See §§ 64-70. 
cir'culatory sys'tem. The heart and blood-vessels taken to- 
gether as an assemblage of organs for the performance of a 
particular function. See §§ 49-63. 
coagula'tion. The change of a liquid from the fluid form to a 
curdlike state, not by evaporation, but by some kind of 
chemical reaction. See § 46. 
cor'nea. The transparent portion of the external coat of the eye. 
See § 169. 
crystalline lens. The lens of the eye, situated immediately be- 
hind the pupil. See §§ 168, 175. 
cuticle. The outer layer of the skin. See § 133. 
der'mis. The true skin, or inner layer of the skin. See § 133. 
diaphragm (dva fram). The membraneous muscle which sepa- 
rates the thoracic from the abdominal cavity. See § 80. 
digestion. The process by which the food is prepared for absorp- 
tion into the circulation. See §§ 102-125. 
distillation. The process of obtaining the spirit or essence of a 
substance by evaporating it and then condensing it. 
drum of the ear. The membrane between the external ear and 
the tympanum. See § 183. 
duode'num (duo de' num). The upper part of the small intes- 
tine, in which the bile and pancreatic juice come in contact 
with the food. See § 122. 
elimination. The process of removing or thrusting out. 
enam'el. A dense, smooth, glistening substance which covers 
the crown of a tooth. See § 105. 
epider'mis. The outer layer of the skin. See § 133. 
epiglottis. The valve which prevents the entrance of food and 
drink into the larynx. See § 74. 
esoph'agus. The canal through which food and drink pass into 
the stomach; the gullet. See § 109. 
eustach'ian tube. The tube extending from the middle ear to 
the throat. See § 184. 
excretion. The removal of useless or harmful substances. Also, 
any of these useless or harmful substances so removed. DEFINITIONS. 
fainting*. See § 69. 
fi'ber. A slender, thread-like element, as of any tissue, 
fi'brous tis'sue. The connective tissue of different parts of the 
body, such as that composing the ligaments of joints, the 
tendons of muscles, etc. It is composed chiefly of white in- 
elastic, or of yellow elastic fibers. See § 20. 
fi'brin. A complex nitrogenous substance which appears in fresh 
blood, and is found in the chyle. It is elastic and generally 
of a thread-like structure, which is insoluble in water, but 
softens when exposed to the air, and becomes viscid, brown, 
and semi-transparent. See § 46. 
fil'ament. A separate fiber of a nerve, or other tissue, 
fermenta'tion. The transformation of any organic substance into 
new compounds by the action of minute living organisms, 
or “ ferments.” There are many kinds of fermentation pro- 
duced by different kinds of ferments. 
Alcoholic fermentation, or “vinous fermentation,” is pro- 
duced by the presence of various microscopic plants, or fer- 
ments. Under favorable conditions, in solutions containing 
sugar, they increase very rapidly, and decompose the sugar in 
such solutions into carbonic acid and alcohol. The carbonic 
acid escapes into the atmosphere, and alcohol, which is not 
only totally useless as nutriment, but destructive to all forms 
of life, remains. See § 99. 
Acetous fermentation, is caused by the vinegar-plant, and 
takes place in liquids which have already undergone alco- 
holic fermentation. 
Lactic fermentation, or the souring of milk, is caused by 
minute living organisms, called bacteria. 
Putrefactive fermentation, or putrefaction, occurs in dead 
animal tissues, and in certain plant products, and is pro- 
duced by various forms of bacteria. 
foll'icles. Small glandular tubes. See § 135. 
food. That which when eaten supplies nourishment to the body. 
See §§ 91-101, 
fimo'tion. The particular action, or mode of operation, which is 
proper to any organ. DEFINITIONS. 
193 
g'an'glion. A knot or enlargement on a nerve or lymphatic, 
gas'tric. Pertaining to the stomach. Gastric juice, an impor- 
tant digestive fluid secreted by the peptic glands. See § no. 
germs. Microscopic organisms, especially of injurious kinds. 
See § 213. 
gland. A smooth, rounded part, or organ, which secretes or ex- 
cretes some substance peculiar to itself. The liver is the 
largest gland in the body. Other glands are, the pancreas, 
the salivary glands, the lacrymal glands, etc. 
glot'tis. The opening between the pharynx and the larynx. See 
§ 74- 
glu'ten. The nitrogenous part of various grain foods. See § 95. 
gray matter. The gray, or ash-colored, portion of the nervous 
system. See § 146. 
heart. See §§ 50-64. 
hem'orrhage (hem' or age). Bleeding ; a discharge of blood 
from the blood-vessels. See § 68. 
hy'giene (hi' jien). A system of principles, or rules, for the pres- 
ervation of health. 
inorgan'ic. Not having the organization of parts which charac- 
terizes living bodies; not possessing life. See §6. 
intes'tines. The lower part of the alimentary or digestive canal. 
The small intestine is smooth and tubular, and is twenty to 
twenty-five feet in length. The large intestine is more or 
less sacculated, and is about five feet in length. See §§ 
102, 120-128. 
invol'untary mus'cles. Muscles that are not under the control 
of the will. See § 22. 
i'ris. The colored curtain between the cornea of the eye and the 
crystalline lens. See §§ 169, 175. 
jaun'dice (jan'dis). A disease in which the yellow bile pigments 
are in the blood, thus giving a yellow tinge to the skin and 
the whites of the eyes. See § 124. 
lab'yrinth. The principal portion of the internal ear. See § 185. 
lac'rymal. Of, or pertaining to, tears. See § 162, 
lac'teals. Minute tubes which absorb the chyle from the small 
intestine, and convey it into the circulation. See § 129. 194 
DEFINITIONS. 
lar'ynx. The upper part of the trachea, in which vocal sounds 
are made and modulated. See § 74. 
lens. A transparent substance bounded by two curved surfaces 
(usually spherical), or by a curved surface and a plane sur- 
face. Rays of light passing through it are bent from their 
original direction. Artificial lenses are commonly made of 
glass. The most perfect example of a natural lens is the 
crystalline lens of the eye. All convex lenses are thicker at 
the center and thinner at the circumference. A double 
convex lens is one in which both of the surfaces are spheri- 
cal and curve outward from the center, thus, (). In a 
double convex lens, like the crystalline lens of the eye, the 
rays of light are converged to a point beyond, called the 
focus. See §174. 
lig'ament. A band of tissue, binding one part to another. 
liv'er. The largest gland in the body. See § 120. 
lungs. The chief organs of respiration. See §§ 76-90. 
lymph. An alkaline fluid of a yellowish color. It is very similar, 
in appearance and composition, to the blood deprived of 
its red corpuscles and diluted with water. See § 127. 
lymphatics (lim fat'ics). Small transparent vessels, existing in 
various tissues of the body. Like the veins, they are pro- 
vided with valves, which permit the matter which they 
carry to flow only toward the heart. They convey lymph, 
and those which run from the intestines also take up some 
of the chyle, and are there called lacteals. See § 130. 
lymphatic glands. Small bodies through which the lymphatics 
pass on their way toward the thoracic duct. They vary in 
size, from that of a pin-head to that of an almond. See 
definition of gland above. See § 130. 
mar'row. The soft tissue found in the interior of many of the 
bones. In the long bones of the arms and legs it is of a 
yellowish.color, and consists of about ninety-five per cent, 
of fat. In various other bones it is of a reddish hue, is 
much softer, and contains but a small proportion of fat. 
See §7. The spinal cord is not marrow, but a tissue of an 
entirely different character. See § 160. DEFINITIONS. 
195 
masse'ter mus'cle. The principal muscle which moves the lower 
jaw. See §§ 27, 106. 
mastication. The act of chewing. See § 103. 
medulla oblong'a'ta. That portion of the brain which is con- 
tinuous with the spinal cord. See § 159. 
mid'dle ear. See § 184. 
mem'brane. An expansion of any soft tissue, or part, in the form 
of a thin layer, generally covering or lining some other part. 
miTcous mem'brane. The soft, velvety lining of the alimentary 
canal, and of all the cavities of the body which communi- 
cate with the air. At the openings of the body it blends 
with, and is continuous with, the skin. See § 72. 
mu'cus. The viscid fluid secreted by the mucous membrane. See 
§ 72. 
mus'cles. The flesh, or “lean meat ”of the animal body. See 
§§ 20-29. 
narcotic. A substance which blunts the senses, deadens sensi- 
bility, induces sleep, and, in large quantities, produces com- 
plete insensibility, The most typical of narcotics is opium. 
See § 166. See also, definition of stimulant, below. 
nasal (na'zal). Pertaining to the nose. 
nerve. The name usually applied to a nerve-fiber, or bundle of 
nerve-fibers. See § 147. 
nerve-cell. Any cell composing a part of the nervous system. 
See § 146, 
nerve-cen'ter. A group of nerve-cells closely connected with 
one another, and acting together for the performance of 
some particular function. See § 146. 
nerve-fi'ber. A very minute cord, the function of which is to 
convey impressions to, or from, some central portion of the 
nervous system. See § 146. 
nerve-tis'sue, or nervous tissue. The tissue of which the nerv- 
ous system is composed. It includes the nerve-fibers and 
the nerve-cells. See § 146. 
ni'trogen. A colorless, odorless, tasteless gas, which forms 
about seventy-seven per cent, of the air, by weight. See § 
83. 196 
DEFINITIONS. 
nitro'genlzed foods. Tissue-making, nutritious substances con- 
taining nitrogen. See § 96. 
non-nitro'genized foods. Heat-producing, nutritious substances 
which contain no nitrogen. See § 97. 
nutri'tion. The process of absorbing into the system such food 
as will build up and repair the living tissues. See § 90. 
olfact'ory nerve. The nerve of smell. See § 189. 
O'pium. The juice of the opium-poppy thickened by evapora- 
tion. In small quantities it is a stimulant-narcotic, and is 
largely used in medicines. In larger quantities, or when 
taken frequently into the system, it is a narcotic poison. See 
§165. 
op'tic. Pertaining to the eye, or to the sense of sight. Optic 
nerve. See § 170. 
or'bit. The bony cavity which contains the eye. 
or'gan. A part, or member of the body, by means of which some 
vital process is carried on; as the organs of digestion, of 
circulation, etc. 
organism. An individual belonging to the animal or vegetable 
kingdom, and therefore possessing organs. 
ox'ygen. A colorless, odorless, tasteless gas which forms about 
twenty-three per cent, of the air, by weight. See § 83. 
pan'creas. A large gland near the stomach, the function of 
which Is to secrete pancreatic juice. See § 125. 
pancreat'ic juice. A clear, viscid fluid which aids in intestinal 
digestion, particularly in the digestion of the fats and starch. 
See § 125. 
papilla. A minute, threadlike projection, generally soft in tex- 
ture, and sensitive. See § 190. 
par'asite. An animal that lives in, or on, or at the expense of 
another animal. See § 119. 
parot'id. The largest of the salivary glands. See § 107. 
pep'sin. The organic principle of the gastric juice, and a very 
important ingredient of the digestive fluids. See §ll3. 
perios'teum. The dense, fibrous membrane which surrounds the 
bones in the living body. See §7. 
perspira'tion. The liquid excreted from the skin. See § 136. DEFINITIONS. 
phar'ynx. A muscular membraneous cavity at the back of the 
mouth. It is continuous below with the esophagus, and 
above with the mouth, nasal passages, and eustachian tube, 
while it also opens near its front into the larynx. See § 73. 
physiol'ogy. The science which relates to the functions or uses of 
the different parts and organs of the body. Human physiology 
relates specially to man. Animal physiology is a more gen- 
eral term, and is applied to the study of the physical func- 
tions, not only in man, but in all animals. Vegetable phys- 
iology relates to the functions of the various parts of plants. 
pig'mentary matter. Organic coloring matter. See § 133. 
plas ma. The liquid part of the blood before coagulation. See 
§ 43. See also definition of serum, below. 
pleu'ra. The serous membrane that invests the lungs, and lines 
the walls of the chest. See § 76. 
pul'monary. Pertaining to the lungs. 
pulse. The series of beats, or pulsations, in any blood-vessel, 
caused by the contractions of the heart. See § 57. 
pu'pil. The hole, or opening, in the center of the iris, for the 
passage of light into the eye. See § 168. 
respira'tion. The act of breathing. See §§7l, 79. 
ret'ina. The innermost coat of the eye, consisting of an expan- 
sion and modification of the optic nerve. See § 168. 
sali'va. Spittle; the fluid secreted by the salivary glands. See 
§§lo7, 108. 
sal'ivary glands. See § 105. 
sclerotic coat. The dense white membrane continuous with the 
cornea,the two forming the external coat of the eye. See§ 168. 
seba'ceous glands. Glands of small size, secreting an oily sub- 
stance which lubricates the hair and skin. See § 137. 
secre'tion. The process of preparing and separating substances 
usually necessary for the activity and health of the body. 
Also a substance so prepared and separated. The glands 
are the principal organs of secretion. 
se'rous mem'brane. A thin, delicate, but strong, membrane 
which lines those cavities of the body that do not communi- 
cate with the air. It secretes serous Jiuid. DEFINITIONS. 
se'rum. The pale-yellow liquid which exudes from the clot in 
coagulation of blood. It is not the same as plasma. See 
definition oi plasma, above. 
spi'nal col'umn. The backbone. See § 14. 
spi'nal cord. The nerve substance which extends through the 
canal of the spinal cord. See §§ 160-162. 
spi'nal nerves. The thirty-one pairs of nerves which have their 
origin in the spinal cord, together with all their branches. 
See § 161. 
sprain. A violent straining or wrenching of the parts surround- 
ing a joint, not resulting in a dislocation. See § 19. 
spu'tum. Saliva; spittal; the product of expectoration. See §213. 
stim'ulant. A substance which, taken into the system, tempo- 
rarily produces increased vital action in one or more of the 
tissues. Some stimulants act directly on the tissues, some 
excite the nerves which control their action, others para- 
lyze or restrain the nerves. Alcohol and tobacco are stim- 
ulants, exciting the nerves and tissues to unnatural, and 
therefore, unhealthy and destructive action. See definition 
of narcotic, above. See alcohol. 
stom'ach. See §§ 112-119. 
structure. A term used in physiology to denote some organic 
form, or some special organization of parts or tissues. 
styp'tic. A substance which, by its astringent qualities, acts 
toward the checking of hemorrhage. See § 68. 
subling'ual. Salivary glands under the tongue. See § 107. 
submax'illary. Salivary glands under the jaws. See § 107, 
su'ture. An immovable joint, or line of union, like those be- 
tween the bones of the skull. See § 17. 
sympathetic sys'tem. That portion of the nervous system 
which controls the involuntary functions of the various or- 
gans. See §l5l. 
sys'tem. When used in its widest, or most general sense, this 
word indicates the entire body, regarded as a physiological 
unity. In such case we say the system. 
Used in a more restricted sense, it refers to an assemblage 
of parts or organs concurring in the performance of some DEFINITIONS. 
199 
particular function. The principal systems of the body, in 
this sense are the digestive system, the circulatory system, the 
respiratory system, etc. 
Used in a still more restricted sense, this word refers to 
an assemblage of parts or organs having a similar structure, 
or composed of the same, or similar, tissues. The princi- 
pal systems in this sense are the osseous, including the bones 
and cartilages; the muscular, both voluntary and involun- 
tary; the vascular, including the blood-vessels and the lym- 
phatics; the tegument ary, including the skin and its append- 
ages; the mucous, embracing the mucous membranes; the 
serous, embracing the serous membranes; and the nervous, 
including the sympathetic and the cerebro-spinal sys- 
tems. 
ten'don. A band of dense fibrous tissue, generally continuous at 
one end with the periosteum, or fibrous covering of a bone, 
and at the other with the tissues which invest or compose 
a muscle. See § 23. 
thoracic duct (tho ras'ik). The tube or canal which conveys 
the greater part of the lymph and a portion of the chyle 
into the circulation. Its average length in adults is from 
fifteen to eighteen inches, and its diameter is about equal 
to that of a goose-quill. It lies along the front of the spinal 
column, extending to the root of the neck, where it ends in a 
large vein. It has three coats, and, like the veins, is pro- 
vided with valves. See § 130. 
tho'rax. The chest. See § 14. 
tis'sue. The fabric, or particular substance, composing any or- 
gan. For description of the principal tissues in the human 
body, see §§ 20, 21. 
tra'chea (tra' kea). The windpipe. See § 75. 
trichina (tri ki'na). A minute parasitic worm, sometimes found 
in the flesh of swine, and certain other animals. See § Ix 9. 
tym'panum. The middle ear, including both its cavity, its con- 
tents, and its walls. See §§ 183, 184. 
va'so-mo'tor nerves. The nerves which are supplied to the 
muscular coat of the blood-vessels. See § 150. 200 
DEFINITIONS. 
Vein. One of a set of canals, or tubes, the function of which is 
to convey the blood to the heart. See § 61, 
ve'na ca'va. Either of the two large veins which discharge the 
blood into the right ventricle of the heart. See § 61. 
ventila'tion. The theory and art of supplying buildings, etc., 
with pure air. See § 87. 
ven'tricle. Some small cavity of the body. The ventricles of the 
heart are the two cavities which receive the blood from the 
auricles, and force it into the arteries. See § 51. There 
are also other ventricles, as ventricles of the brain, olfactory 
ventricles, etc., the description of which is not essential to 
an elementary knowledge of physiology. 
ver'tebra. One of the bones of which the spinal column is com- 
posed. See § 14. 
villi. Minute projections on the inner surface of the small in- 
testine. See § 129. 
vit'reous hu'mor. The transparent, jelly-like fluid which fills 
about four-fifths of the eyeball, or the entire space behind 
the crystalline lens. See § 169. 
vo'cal cords. The borders of two folds of mucous membrane 
within the larynx, the vibration of which produces vocal 
sound. See § 74. 
vol'untary mus'cles. The muscles that are controlled by the 
will. See § 22. 
white matter. That portion of the nervous tissue which serves 
to transmit nerve force, but does not originate it. See 
§ 146.