HU 
m APPLIED PHYSIOLOGY 
INCLUDING 
THE EFFECTS OF ALCOHOL 
AND NARCOTICS 
BY 
FRANK OVERTON, A.M., M.D. 
LATE HOUSE SURGEON TO THE CITY HOSPITAL, NEW YORK 
PRIMARY GRADE 
NEWYORK-; - CINCINNATI CHICAGO 
AMERICAN BOOK COMPANY Copyright, 1898, by 
FRANK OVERTON 
OV. PHYSIOL. (PRIM.) 
E. P. 10 PREFACE 
This primary text-book of applied physiology fol- 
lows a natural order of treatment. In each subject 
elementary anatomical facts are presented in a man- 
ner which impresses function rather than form, and 
from the form described derives the function. The 
facts and principles are then applied to everyday 
life. Anatomy and pure physiology make clear and 
fix hygienic points, while applied physiology lends 
interest to the otherwise dry facts of physiology and 
anatomy. From the great range of the science 
there are included only those subjects which are 
directly concerned in the growth and development 
of children. 
The value of a primary book depends largely 
upon the language used. In bringing the truths 
within the comprehension of children, the author 
has made sparing use of the complex sentence. He 
has made the sentences short and simple in form, 
and logical in arrangement. 
3 4 
PREFACE 
A child grasps new ideas mainly as they appeal 
directly to the senses. For this reason, physiologi- 
cal demonstrations are indispensable. Subjects for 
demonstrations are not given, because they cannot 
be performed by the children; but the teacher 
should make free use of the series given in the 
author’s advanced physiology. 
Cuts and diagrams are inserted where they are 
needed to explain the text. They are taken from 
the author’s Applied Physiology, Intermediate Grade. 
Each was chosen, not for artistic effect, but because 
of its fitness to illustrate a point. Most of the cuts 
are adapted for reproduction on the blackboard. 
The effects of alcohol and other narcotics are 
treated with special fulness. The subject is given 
a fair and judicial discussion, and those conclusions 
are presented which are universally accepted by the 
medical profession. But while this most important 
form of intemperance is singled out, it should be 
remembered that the breaking of any of nature’s 
laws is also a form of intemperance, and that the 
whole study of applied physiology is to encourage 
a more healthy and a more noble and self-denying- 
mode of life. CONTENTS 
CHAPTER 
I. Cells 7 
II. Of what Cells are made . . . . .10 
III. Digestion of Food in the Mouth . . . 13 
IV. Digestion of Food in the Stomach . . .17 
V. Foods 23 
VI. Tobacco 31 
VII. Fermentation . . . . . . -37 
VIII. Kinds of Strong Drink ..... 42 
IX. The Blood 49 
X. Breathing, Heat, and Clothing . . . -59 
XL The Skin and Kidneys . . . . -75 
XII. The Nerves, Spinal Cord, and Brain . . .84 
XIII. The Senses . . . . . . . .100 
XIV. Bones and Joints . . . . . . .109 
XV. Muscles 115 
Index . . . .123 
PAGE 
5 APPLIED PHYSIOLOGY 
CHAPTER I 
CELLS 
1. The ameba. Our body is made of many parts. 
Its head thinks. Its legs carry it, and its arms and 
hands take hold of things. The leg cannot do the 
work of the arm, nor the head do the work of the 
hand; but each part does only its own work. 
The bodies of some animals have parts like a 
man’s; but these parts are fewer. No animal has 
arms or hands like a man. A fish has little fins 
in place of legs and arms, while a worm has not 
even a head, but only a body, and yet it moves. 
An oyster has only a body and cannot move. The 
simplest of all animals is very small. A thousand 
of them would not reach an inch. Yet each is a 
complete animal. It is called the ameba. It is only 
a lump of jelly. It can put out any part of its body 
like an arm and take a lump of food. This same 
arm can eat the food, too. It can also put out any 
7 8 
APPLIED PHYSIOLOGY 
part of its body like a leg and move by rolling the 
rest of its body into the leg. It can do some things 
Different forms of an ameba (x 400). 
better than a man can do them, for any part of its 
body can do all kinds of work. So the ameba 
grows and moves and does as it likes. 
2. Cells. A man’s finger moves and grows 
something like a separate animal, but it must 
keep with the rest of 
the body. A little piece 
of a finger moves and 
grows, too. If you 
should look at a finger, 
or any other part of 
your body, through a 
microscope, you would 
see little lumps of jelly, 
and each little lump 
would look like an 
Cells from the human body (X 200) 
a A colored cell from the eye. 
b A white blood cell. 
c A connective tissue cell. 
d A cell from the lining of the mouth 
e Liver cells. 
f A muscle cell from the intestine. 
ameba. We call each lump a cell. The cells 
make up the finger. 
3. What cells do. Each cell does just as an 
ameba does. It gets food and air from the blood CELLS 
9 
and takes them in through any part of its body. 
It also grows and moves. But the cells are not 
free to do as they wish, for they are all tied 
together in armies by very fine strings. We call 
these strings connective tissue. One army of cells 
makes the skin, and other armies make the bones 
and flesh. Some armies make the fingers, and some 
the legs. Every part of our body is made up of 
armies of separate cells. 
4. The mind. The body is a home for the 
mind. The cells obey the mind. The mind pays 
the cells by feeding them and taking good care 
of them. When an army of cells is hurt, the body 
feels sick, and then the mind tells the whole body 
to rest until the cells are well again. When we 
study about a man’s body, we learn about the sepa 
rate cells in his body. 
WHAT WE HAVE LEARNED 
1. Our body is made up of many small parts. 
2. The smallest parts are each like a little animal. 
and are called cells. 
3. Each cell eats and grows. 
4. One army of cells makes a finger and another a 
leg, and so on through the body. 
5. The mind lives in the body. 
6. The mind takes care of the cells. CHAPTER II 
OF WHAT CELLS ARE MADE 
The cells of our body are made of five common 
things. You would know all these things if you 
should see them. 
5. Water. The first thing in the cells is water. 
Water is everywhere in the body. Even the teeth 
Sugar, \ lb. 
Ashes, 12 lb. 
Water, 12 gallons. 
Albumin or gelatine, 20 lb. 
Fat, 10 lb. 
The body is made of these five things 
have water. Most of our flesh is water. Without 
water we should soon shrink up. Our flesh would 
be stiff like bone and no one could live. 
6. Albumin. Second, next to water, something 
like the white of an egg makes the most of the 
body. The white of an egg is albumin. When 
10 OF WHAT CELLS ARE MADE 
dried it is like gelatine or glue. Albumin makes 
the most of the solid part of each cell. Lean meat 
and cheese are nearly all albumin. When it is 
heated it becomes 
harder and turns 
white. The word 
albumin means white. 
Dry albumin is hard 
and tough, but in 
the living cells it is 
dissolved in water 
and is soft like meat. 
It is the only living 
The liquid fat is stored in living pockets. 
Fat tissue (x 100). 
substance in the body, and it alone gives it strength 
7. Fat. Third, next to albumin, the most of 
the body is fat. Fat does not grow inside the cells 
of the body, but it fills little pockets between the 
cells. Fat does not give strength. It makes the 
body round and handsome. It also makes the cells 
warm and keeps them from getting hurt. 
8. Sugar. Fourth, sugar also is found in the 
body. Sugar is made out of starch. When we 
eat starch it changes to sugar. Starch and sugar 
are much alike. We eat a great deal of starch and 
sugar, but they are soon used in warming the body. 
Only a little is in the body at once. 
9. Minerals. Fifth, there are also some min- 12 
APPLIED PPIYSIOLOGY 
erals in the body. When flesh is burned they are 
left as ashes. Salt, lime, iron, soda, and potash are 
all found in the body. 
Everything in the body is either water, albumin, 
fat, sugar, or min- 
erals. These things 
are also our food. 
We eat them mixed 
together in bread, 
meat, eggs, milk, 
Starch grains (X 400). and other foods. 
a, of potato. b, of corn. 
10. Life. Our 
food is not alive, but after we eat it the body 
makes it alive. We do not know how it does it. 
When the body dies we cannot put life into it 
again. There is life in each cell. 
WHAT WE HAVE LEARNED 
1. The body is made of five things : water, albumin, 
fat, sugar, and minerals. 
2. Water is mixed with all parts of the body. 
3. Albumin makes the living part of each cell. 
4. Fat is in pockets between the cells. It warms 
the cells and keeps them from being hurt. 
5. Sugar is made from starch. It warms the body. 
6. The minerals in the body are salt, lime, iron, 
soda, and potash. CHAPTER 111 
DIGESTION OF FOOD IN THE MOUTH 
11. Food of the cells. All the cells of the body 
work and wear out. They must eat and keep grow- 
ing. The food of the cells is the blood. Water, 
albumin, fat, sugar, and minerals are in the blood. 
The cells eat these things and grow. All food 
must be one or more of these five things. Before 
they reach the blood, they must all be changed 
to a liquid. A few cells of the body are set aside 
to do this work of changing them. Changing food 
into blood is digestion. 
12. Cooking. Cooking begins digestion. It 
softens and dissolves food. It makes food taste 
better. Most food is unfit for use until it is 
cooked. Poor cooking often makes food still worse 
for use. Food should always be soft and taste 
good after cooking. Softening food by cooking 
saves the mouth and stomach a great deal of work. 
The good taste of the food makes it pleasant for 
them to digest it. We must cut our food into 
small pieces before we eat it. If we eat only a 
13 14 
APPLIED PHYSIOLOGY 
small piece at a time we shall not eat too fast. 
If we cut our food fine we can find any bones and 
other hard things, and can keep them from getting 
inside the body. 
13. Chewing,— Digestion goes on in the mouth. 
The mouth does three things to food. First, it 
mixes and grinds it between the teeth. 
Second, it pours water over the food through 
fine tubes. The water of the mouth is called the 
saliva. The saliva makes the food a thin paste. 
Third, the saliva changes some of the starch to 
sugar. Starch must be all changed to sugar before 
it can feed the cells. 
14. Too fast eating. Some boys fill their mouths 
with food. Then they cannot chew their food and 
cannot mix saliva with it. They swallow their food 
whole, and then their stomachs have to grind it. 
The saliva cannot mix with the food and so it is 
too dry in the stomach. Then their stomachs ache, 
and they are sick. Eating too fast and too much 
makes children sick oftener than anything else. 
Birds swallow their food whole, for they have no 
teeth. Instead, a strong gizzard inside grinds the 
food. We have no gizzards, and so we must grind 
our food with our teeth. 
15. Teeth.— We have two kinds of teeth. The 
front teeth are sharp and cut the food; the back DIGESTION OF FOOD IN THE MOUTH 
15 
teeth are flat and rough and grind it. If you bite 
nuts or other hard things you may break off a little 
piece of a tooth. Then the tooth may decay and 
ache. 
After you eat, some food will sometimes stick 
to the teeth. Then it may decay and make your 
breath smell bad. After each meal always pick the 
teeth with a wooden toothpick. Your teeth will 
also get dirty and become 
stained unless you clean 
them. Always brush your 
teeth with water every 
morning. This will also 
keep them from decaying. 
16. Swallowing. When 
food has been chewed and 
mixed with saliva until it 
is a paste, it is ready to be 
swallowed. The tongue 
pushes the food into a bag 
just back of the mouth. We 
call the bag the pharynx. 
Digestive organs of a bird. 
a esophagus or swallowing tube. 
b crop or bag for carrying food. 
c stomach. 
d intestine. 
e gizzard or food grinder. 
Then the pharynx squeezes it down a long tube 
and into the stomach. The nose and windpipe 
also open into this bag, but both are closed by 
little doors while we swallow. We cannot breathe 
while we swallow. If the doors are not shut APPLIED PHYSIOLOGY 
tightly, some food gets into the windpipe and 
chokes us. 
1. We eat to feed the cells of the body. 
2. All food must be made into blood. 
3. Changing food to blood is digestion. 
4. Cooking softens food and makes it taste good. 
5. Food is ground fine in the mouth, and mixed 
with saliva to form a paste. Some of its 
starch is changed to sugar. 
6. If food is only half chewed the stomach has to 
grind it. 
7. When we swallow, the tongue pushes the food 
into a bag back of the mouth and the bag 
squeezes it down a long tube to the stomach. 
WHAT WE HAVE LEARNED CHAPTER IV 
DIGESTION IN THE STOMACH 
17. The stomach. When food is swallowed it 
goes to the stomach. The stomach is a thin bag. 
In a man it holds about three pints. Like the 
mouth, it does three things to the food. 
First, the stomach gently 
stirs and mixes the food. 
Second, it pours a fluid 
over the food. This fluid 
is called the gastric juice. 
The gastric juice is sour 
and bitter. 
Third.' the gastric juice 
changes some of the albu- 
min of food to a liquid form. 
If the mouth has done 
its work well, the stomach 
does its work easily and 
Gastric glands in the stomach 
(X 200). 
The cells a and b, form the juice. 
The fibers c, bind the tubes in place. 
we do not know it. But if the mouth has eaten 
food too fast and has not chewed it well, then the 
stomach must do the work of the mouth too. In 
that case it gets tired and aches. 
OV. PHYSIOL. (PRIM.)—2 17 APPLIED PHYSIOLOGY 
18. The intestine.—The food stays in the stom- 
ach only a little while. All the time a little keeps 
trickling into a long coil of tube. This tube is 
called the intestine or the bowels. Three or four 
hours after a hearty meal the stomach is empty. 
Some of the food has been changed to a liquid, 
but most of it has only been ground to smaller 
pieces, and mixed with a great deal of water. 
Now it all must be changed to a liquid. 
19. What the intestine does. Like the mouth 
and stomach, the intestine does three things. 
First, it mixes the food and makes it pass down 
the tube. 
Second, two sets of cells behind the stomach 
make two liquids and pour them into the intes- 
tine. One set of cells is the sweetbread, or pan- 
creas, and its liquid is the pancreatic juice. The 
other is the liver and its fluid is the bile. 
Third, the pancreatic juice makes three changes 
in food. First, like the mouth, it changes starch 
to sugar. Second, like the stomach, it makes albu- 
min a liquid. Third, it divides fat into fine drops. 
These drops then mix with water and do not float 
on its top. 
20. Bile. The bile is yellow and bitter. It 
helps the pancreatic juice do its work. It also 
helps to keep the inside of the intestine clean. DIGESTION IN THE STOMACH 
21. Digestion of water and minerals. Water and 
the mineral parts of food do not need to be 
changed at all, but can become part of the blood 
just as they are. Seeds and husks and tough 
strings of flesh all pass the length of the intestine 
and are not changed. 
22. How food gets into the blood. —By the time 
food is half way down the intestine it is mostly 
liquid and ready to become part of the blood. 
This liquid soaks through the sides of the intes- 
tine and into the blood tubes. At last the food 
reaches the end of the intestine. Most of its liquid 
has then soaked into the blood tubes and only 
some solid waste is left. 
23. Work of the liver. The food is now in the 
blood, but has not become a part of it. It is 
carried to the liver. There the liver changes the 
food to good blood, and then the blood hurries 
on and feeds the cells of the body. Sometimes 
poisons are swallowed and get into the blood with 
the food. The liver takes out the poisons and 
sends them back with the bile. The liver 
keeps us from getting poisoned. 
24. Bad food. Sometimes the stomach and in- 
testine cannot digest the food. They cannot digest 
green apples, but they try hard to do so. They 
stir the apples faster and faster until there is 20 
APPLIED PHYSIOLOGY 
a great pain. Sometimes they throw up the food 
and then the boy feels well again. Poor and 
spoiled food makes us sick in the same way. 
25. Too fast eating. When the food stays too 
long in the stomach or intestine it sours, or decays, 
just as it does outside of the body. This makes 
us very sick. When we eat too much, or when 
we do not chew the food to small pieces, the 
stomach may be a long time in digesting the 
food. Then it may become sour and make us 
sick. 
26. Biliousness. When the food is poor or be- 
comes sour, it is poorly digested. Then the liver 
has more work to do, and does not change the 
food to blood as it should. It also lets some of the 
sour poisons pass by it. These poison the whole 
body and make the head ache. We call this bil- 
iousness. The tongue is then covered with a white 
or yellow coat and the mouth tastes bad. These 
are signs of sickness. The stomach and liver are 
out of order. 
27. Rules for eating. —lf we eat as we should, 
our stomach will digest its food. We must follow 
three rules. 
First, we must chew the food in the mouth 
until all the lumps are fine. Then the food will 
be ready for the stomach. DIGESTION IN THE STOMACH 
21 
Second, we must eat slowly. If we eat fast we 
cannot chew the food well. The stomach cannot 
take care of food if it comes too fast. We must 
swallow all of one mouthful before we put another 
into the mouth. 
Third, we must eat only at meal times. The 
stomach needs a rest. Even a little candy, or 
apples, or nuts will keep the stomach at work, 
and tire it out. A child needs to eat more often 
than his father. So, besides his meals, he should 
have something to eat in the middle of the morning 
and some more in the afternoon. But he should 
not be eating at all hours. He ought not to eat 
little bits just before dinner, for that spoils his 
meal. 
1. The stomach and intestine stir and rub the 
food, and mix it with juices. 
2. The juices change albumin to a liquid, and 
starch to sugar. They also change fat to 
the form of tiny drops. 
3. The digested food soaks through the sides of 
the intestine into the blood tubes. 
4. The blood carries the food to the liver. 
5. The liver changes food to blood. 
6. Blood goes to all parts of the body and feeds 
the cells. 
WHAT WE HAVE LEARNED 22 
APPLIED PHYSIOLOGY 
7. The liver keeps poisons from getting into the 
blood. 
8. Water and minerals become a part of the blood 
without being digested. 
9. When food is not well digested, the liver can- 
not make it into good blood. This makes us 
bilious. 
10. If food is not soon digested it sours and decays. 
This makes us sick. 
11. We can make food digest quickly by chewing 
it well and eating slowly. CHAPTER V 
FOODS 
28. Kinds of food. The cells of the body need 
water, albumin, fat, sugar, and minerals for food. 
We sometimes eat sugar alone, and we drink pure 
water. But most of our food is a mixture of all 
five kinds of food. Food comes from animals and 
plants. 
29. Milk. Milk is the best food known. It 
contains just enough water, albumin, fat, sugar, and 
minerals. Babies and young mammals live on milk 
alone, A man can live upon four quarts of milk a 
day. In sickness, milk is the very best food for 
men, as well as for babies. 
The albumin of milk becomes hard when the 
milk sours. This makes cheese. The fat of milk 
rises to the top. We call it cream. When cream 
is churned, the pure fat comes together in a lump. 
Pure fat of milk is called butter. Cheese and but- 
ter are both good foods. 
30. Eggs. Eggs are also good food. The white 
of an egg is almost pure albumin. The yolk is 
albumin and fat. Eggs have no starch or sugar. 
23 24 
APPLIED PHYSIOLOGY 
They are not a perfect food, for some sugar must 
be eaten. But they can be quickly digested and 
they produce a great deal of strength. 
31. Meat. Meat contains albumin and fat, but 
no sugar. Fish, oysters, and clams are like meat. 
They all make good food. Boys and girls should 
eat milk, eggs, and meat. These foods are the best 
to give strength to the body. Nearly all food from 
animals is more quickly digested and gives more 
strength than food from plants. 
32. Bread. White bread is a food made from 
wheat. The wheat is ground to flour. Flour is 
mixed with water, and yeast is added. The yeast 
makes a gas, and the gas puffs up the wet flour 
and makes it full of holes. The holes make the 
bread light. Then bread is baked. Rye or corn 
meal makes good bread. Cake, biscuit, and pan- 
cakes are much like bread. Sometimes in place of 
yeast, baking powder is used to make the bread or 
cake light. 
33. Meal. Oatmeal, corn meal, and cracked 
wheat and rice are sometimes boiled, and eaten 
with milk. Bread, biscuit, oatmeal, and corn meal 
are made from grain. All are very much alike. 
The cooking makes them look and taste different, 
but yet they are nearly the same. 
34. Why we need grain food. All kinds of grain FOODS 
25 
have much albumin, but only a little fat. But all 
have a great deal of starch. By digestion the starch 
becomes sugar. Grain is a good food because it 
has starch or sugar. Animal foods have no sugar, 
so we eat grain food with them. The two together 
1 lb. of meat. 
I lb. of butter. 
2 eggs. 
5 lb. of bread. 
A healthy man needs as much food as this every day. 
3 pints of water. 
13 pints of milk. 
make the most nourishing food. Potatoes have a 
great deal of starch and only a little albumin. 
They also are good food with meat. 
A person cannot live well upon plant food alone, 
for it has too much starch and sugar, and too little 
albumin and fat. We need nearly equal parts of 
albumin, fat, and sugar. A mixture of bread, meat, 
eggs, and milk makes the best food. 
35. Fruit. Fruit, like apples, peaches, and plums 
all have sugar. They taste good, and give us an 26 
APPLIED PHYSIOLOGY 
appetite for other kinds of food. They have little 
albumin or fat. 
36. Salt. There is enough mineral matter in all 
food, and we do not have to eat iron or lime or soda. 
People are made sick by drinking water from such a well. 
But we do need some more salt. Even animals 
need salt. Salt makes food taste good, and helps 
its digestion. 
37. Water. Water is also a food, for it forms 
the most of our bodies. All food has water. Even 
dry crackers contain it. FOODS 
27 
38. Pure water. Water in a well runs through 
the dirty earth, and yet is clear and pure. This is 
because sand holds back the dirt. But sometimes 
slops from the house, and water from the barn yard, 
soak through the soil until the sand is full. Then 
the well water will be dirty and poisonous. People 
are often made sick by drinking such water. In 
cities the dirt fills all the soil and spoils the water. 
So the water must be brought from the country in 
large pipes. 
Water in lead pipes takes up some of the lead. 
Lead is a poison. You should let the water run off 
from a pipe a little while before you use it. Good 
water is clear and has no smell or taste. Dirty or 
yellow water, or water with a taste or smell, is not 
fit for use. 
39. T?a and coffee, Tea and coffee are steeped in 
water and used as a drink. The drink is the water. 
The tea* and coffee are neither food nor drink. 
They cause the cells of the body to do more work, 
and at the same time they take away the feeling 
of being tired. They do not give strength to the 
body, but are like a whip and make the body work 
harder. 
40. The appetite. When we have so many kinds 
of food, what kind is best for us ? The taste of 
food tells us the kind of food to eat. Bread and APPLIED PHYSIOLOGY 
meat, and such plain foods, always taste good, and 
we never get tired of them. Sugar tastes good 
until we get enough. Any more makes us sick. 
More than enough sugar or starch is found in 
bread and potatoes. 
One kind of intemperance. 
If we can eat food day after day, without get- 
ting tired of it, the food is good for us. If we get 
tired of its taste, either the food is not good for 
us or we are eating too much. Bad tasting or 
bad smelling food is always dangerous. FOODS 
29 
We can tell how much food to eat by our hunger 
or appetite. We can always feel when we have 
enough. Then is the time to stop. 
41. False appetites. Sometimes we eat plain 
bread and meat until we have enough, and then 
sweet cake or pie is brought in. Then we have a 
false appetite for sweet things. If the sweet things 
had not made a false hunger, we should have had 
enough to eat. But the false appetite makes us 
want more, and so we eat too much, and sometimes 
get sick from it. 
42. Intemperance. Eating for the sake of a false 
appetite is intemperance. Drinking strong drink 
for the sake of its taste is a common form of intem- 
perance. But eating too much preserves, pie, and 
candy is intemperance too, and can do a great deal 
of harm. A little pie, or pudding, or candy, is good, 
because we can eat our sugar as well that way as in 
bread. But we should eat only a little. 
WHAT WE HAVE LEARNED 
1. Food is a mixture of water, albumin, fat, starch 
or sugar, and minerals. 
2. Animal foods, like milk, eggs, and meat, have 
albumin and fat in the best form. 
3. Plant food has albumin and fat, but it has 
very much starch or sugar. So, taken to- 30 
APPLIED PHYSIOLOGY 
gether with animal food, it makes a complete 
food. 
4. Lime, iron, soda, and salt are found in all foods, 
but we must add a little more salt to food. 
5. Water is found in all food, but we must drink 
some besides. 
6. Dirty water, or water with a taste or smell, is 
not fit for use. 
7. Taste tells us what kind of food to use. 
8. Hunger, or the appetite, tells us how much food 
to use. 
9. There can be a false hunger for sweet things. 
This may lead us to eat too much. 
10. Eating too much of sweet things is one form 
of intemperance. CHAPTER VI 
TOBACCO 
43. Harmful eating. Men often eat for the fun 
of eating, and sometimes they eat harmful things. 
They chew tobacco and drink strong drinks, be- 
cause they like their taste, just as a child eats 
candy. 
44. Tobacco. Men have always drunk strong 
drink. Within the last four hundred years, men 
have learned another way to please a wrong taste. 
When Columbus discovered America, the Indians 
were using tobacco. They taught the Spaniards 
how to smoke it, and since then almost the whole 
world has used it. 
Tobacco is the leaf of a tall plant. It needs a 
better soil than any other crop. It takes the rich- 
ness from the ground, and spoils it for other crops. 
45. Nicotine. About of each tobacco leaf is 
a strong poison. This poison is called nicotine. 
A drop or two of it, or as much of it as is in a 
strong cigar, will kill a man. It gives the tobacco 
its smell and taste. Men use tobacco for the sake 
of a poison. 32 
APPLIED PHYSIOLOGY 
46, Why men use tobacco. Men give queer rea- 
sons for using tobacco. One smokes for its com- 
pany, another because he is with company. One 
smokes to make his brain think better, and another 
to keep himself from thinking. Some use tobacco 
to help digest their food, and others use it to keep 
themselves from eating so much. Boys smoke to 
make themselves look like men. The real reason 
for using tobacco is that men learn to like its taste, 
and do not care if it harms them. 
47. Spitting. Tobacco in any form makes the 
saliva flow. Men do not dare swallow it, for it 
makes them sick. So they spit it out. No one 
likes to see this. It is a dirty and filthy habit. 
Besides, the saliva is lost, and cannot help digest 
food. 
Tobacco stains the teeth brown. You can always 
tell a tobacco chewer by his teeth. His breath will 
smell of tobacco, and even his clothes are offensive 
to the nose. 
48. Tobacco lessens strength.— Tobacco always 
makes a person sick at the stomach, at first. After 
a while, he becomes used to it, and an ordinary 
chew or smoke does not make him sick. But a 
large chew or smoke will always make him sick 
again. When a person is sick from tobacco he 
is very weak. Even if he is not sick, the tobacco TOBACCO 
33 
poisons his muscles and makes his strength less. 
When a man trains for a hard race he never uses 
tobacco. 
49. Tobacco hinders digestion. Tobacco and its 
smoke both have a burning taste. This makes the 
throat sore, and causes a cough. Tobacco does 
not help the stomach to digest food. Smokers and 
chewers often have headaches and coated tongues. 
These are signs of a poor digestion. 
50. Effect upon the young. Tobacco is more 
harmful to boys than to men. If boys smoke they 
cannot run fast or long. They cannot work hard 
with their brains or hands. They do not grow 
fast, and are liable to have weak hearts. 
51. Tobacco harms others. Many persons do not 
like the smell of tobacco, and no one likes the spit. 
No one should use it in the presence of others. 
The tobacco user’s pleasure should not spoil the 
comfort and happiness of others. 
52. Snuff. Powdered tobacco is called snuff. 
Snuff causes sneezing. No one should harm the 
nose and the whole body for the pleasure of a 
sneeze. Years ago snuff was used much more than 
it is now. 
53. Chewing. Chewing tobacco is the most 
poisonous way of using it, for it keeps most of 
the nicotine in the mouth. Chewing will make 34 
APPLIED PHYSIOLOGY 
any one very sick, unless he spits out all the 
saliva. 
54. Smoking. Men smoke pipes, cigars, and 
cigarettes. The smoke has nicotine, and is poi- 
sonous. Pipe stems get dirty and full of nicotine. 
After a while they smell bad and are very poison- 
ous. An old smoker’s pipe will make a young 
smoker sick. 
55. Cigarettes. Cigars are not so poisonous as 
a pipe, for more of the nicotine is burned up. 
Cigarettes are made of weak tobacco. A cigarette 
is not so poisonous as a cigar. But a cigarette 
does not cost much. It can be smoked in a hurry. 
It does not make a boy so sick as cigars do. Boys 
and men use a great many cigarettes where they 
would not touch a cigar. This makes the use of 
cigarettes the most dangerous form of smoking. 
Selling cigarettes to young boys is forbidden by 
law. 
56. Habit. When men have used tobacco for 
some time, they like it and feel bad without it. 
So they get into the habit of using it, and find it 
hard to stop. The tobacco seems to help them, 
but it does not do so. It cheats men, and they 
do not know it. 
67. Chewing gum. Chewing gum is made from 
pitch or paraffin, for these substances will not dis- TOBACCO 
35 
solve in the mouth. The gum is flavored with 
sugar and spices. The gum and its flavors are 
not harmful in themselves, and yet chewing them 
is harmful. Chewing makes a great deal of saliva 
flow. All this saliva is wasted, and when we eat 
our meals we may have too little. Then our food 
will not digest well, but we shall have dyspepsia 
and headaches. 
By pulling and handling the gum while chew- 
ing it, you may get some poisonous dirt into your 
mouth, and make yourself very sick. 
Even if your gum should not harm you, there is 
a good reason for letting it alone. When you are 
chewing gum, you look as if you were chewing 
tobacco. No one likes to see a boy or girl even 
appearing to chew tobacco. If you form a habit 
of chewing gum you will be more likely to chew 
tobacco when you are grown. 
1. Men use tobacco for the sake of its nicotine. 
Nicotine is a very strong poison. 
2. Tobacco causes a man to waste his saliva. 
3. Tobacco makes the mouth dry. 
4. Tobacco hinders digestion. 
5. Tobacco stains the teeth, and makes the breath 
smell bad. 
WHAT WE HAVE LEARNED 36 
APPLIED PHYSIOLOGY 
6. Tobacco makes a person sick at the stomach. 
7. Tobacco weakens the muscles. 
8. Tobacco is more harmful to the young than to 
grown persons. 
9. Chewing is the worst form of using tobacco. 
10. Smoking; cigarettes is the worst form of smoking. 
OO £> CHAPTER VII 
FERMENTATION 
58. Souring of fruit. When a little fruit is set 
away in a warm place for a day or two it sours or 
ferments. Anything sweet will do the same thing. 
Little bubbles rise up through the juice and a foam 
comes on top. Then the juice 
has a sharp taste or is sour. 
Preserved fruit of any kind be- 
comes sour soon after the jar 
is opened, and cider soon turns 
to vinegar. All fruit juice does 
this even in cold weather. But 
in cold weather it keeps for a 
longer time. 
Fermentation in a jar of 
cherries. 
59. Preserving fruit. —lf your 
mother wishes to keep fruit all winter she boils it 
and at once puts it into tight jars. This shuts 
out the air and then the fruit keeps good all winter. 
Boiling kills all living things, and no more can get 
in through the tight jars. Does a living thing 
37 38 
APPLIED PHYSIOLOGY 
have anything to do with making the fruit juice 
turn sour? 
60. Yeast. Yeast will make all sweet things fer- 
ment. Bakers make yeast grow in bread sponge. 
Yeast is alive. It is made of mil- 
lions of tiny round cells. New 
cells sprout out from the side 
of the old cells like young lilies 
on an old lily bulb. Soon each 
new cell breaks off and lives all 
by itself. In a single night 
enough new cells will form to fill 
the whole loaf of bread. 
61. How yeast makes alcohol.— 
Yeast will grow only where sugar 
_ . J ° 
is. When it has grown for some 
Yeast plant cells (X 500). 
time there is no more sugar, and instead of a sweet 
taste there is a sharp or sour taste. The yeast has 
changed the sugar to alcohol. All alcohol is made 
from sugar by yeast. 
The seeds of the yeast plant are everywhere in 
the air. Some are on the skins of fruit and so are 
found in the juice when it is squeezed out. There 
they begin to grow at once and soon change the 
sugar to alcohol. They do this by taking a gas 
away from the sugar. The gas rises in little bub- 
bles, and makes a froth upon the top of the juice. FERMENTATION 
39 
Boiling kills the yeast plant. If the juice is at 
once put into tight jars no new yeast plants can 
get in, and so the juice keeps. 
62. Vinegar. Sometimes fruit juice turns sour. 
The sourness is due to vinegar. Besides yeast, 
other little living plants fall into the juice and turn 
the sugar to vinegar. But if there is much alcohol 
in the juice, the vinegar plants will not grow. 
63. Yeast in bread. Growing yeast plants always 
make alcohol. They change some of the sugar of 
bread dough to alcohol and a gas. The gas bubbles 
through the bread and makes it light. When bread 
is baked, the heat of the oven drives off the alcohol, 
and so we do not eat any in bread. 
64. Alcohol. Alcohol is a clear liquid and looks 
like water. It has a sharp taste and smell. It 
burns very easily and makes a very hot flame. Its 
smoke cannot be seen, and its flame will not make 
anything black, as a match flame will do. 
65. Use of alcohol. Alcohol will dissolve more 
things than water will dissolve. It is used to dis- 
solve drugs, varnishes, perfumery, and many other 
things. It will dissolve even oil and fat. Tailors 
clean grease spots from clothes with it. It takes 
water away from flesh and makes it dry, hard, and 
tough. It will keep anything from rotting. In 
museums we pour alcohol over pieces of flesh or APPLIED PHYSIOLOGY 
40 
plants in glass jars. Then they will keep and we 
can look at them at any time. Thus alcohol is a 
very useful thing, and we could hardly do without it. 
66. Strong drink.— Some men use alcohol in a 
wrong way. They swallow it as a drink. But 
men cannot drink pure alcohol, for it would burn 
their mouths. They always drink it mixed with 
some water. Alcohol in water is called strong 
drink. 
67. Why men use strong drink. Some men take 
strong drink to make themselves warm, and some 
to make themselves cool. Some drink to keep 
themselves awake, and some to make themselves 
sleep. Some drink to keep themselves still, and 
some to make themselves stir around faster. Men 
use strong drink really because it seems to make 
them feel strong for a while. It does not make 
them stronger, but it harms the body and the mind. 
Its alcohol does the harm. 
WHAT WE HAVE LEARNED 
1. Sugar in fruit or in water turns to alcohol or 
vinegar, and a gas. 
2. The change to alcohol is caused by the cells of 
the yeast plant. 
3. The change to vinegar is caused by another 
small plant. FERMENTATION 
41 
4- Boiling fruit juice kills the yeast plants and then 
the juice will keep without change. 
5. Alcohol looks like water. It has a sharp and 
burning taste. 
6. Alcohol takes water from flesh and hardens it. 
7. Alcohol burns with a great heat and no smoke. 
8. Alcohol is used to dissolve things, and to keep 
things from spoiling. 
9. Alcohol in water forms strong drink. CHAPTER VIII 
KINDS OF STRONG DRINK 
68. Wine. All strong drink is alcohol and 
water. There may be other things to give it taste, 
but alcohol and water are always in it. No strong 
drink is over one half alcohol. 
In olden times wine was the only strong drink. 
Men used to crush out the juice of grapes and let 
it ferment. This made wine. But 
very often they used the juice before it 
fermented. Then it had no alcohol and 
could do no harm, but was a good food. 
We read of wine in the Bible. Some 
of it was fresh fruit juice. 
In wine, the sugar is changed to 
alcohol. The rest of the juice stays 
A glass of wine 
contains so 
much alco- 
hol. 
the same. All wine is made by the yeast plant 
growing in fruit juice. No yeast is put in, for 
there is always enough on the outside of the fruit. 
Wine is about one tenth alcohol. 
69. Homemade wine. Cider is a kind of wine. 
It is made from apple juice. It has alcohol a day 
or two after it is made. All homemade wines have 
42 KINDS OF STRONG DRINK 
43 
alcohol. Any of them can make a person drunk. 
Using weak homemade wine and cider often makes 
an appetite for stronger drinks. The alcohol in any 
of them is enough to harm the body. 
70. Beer. After man had made wine for a long 
time, some one found out how to cultivate yeast. 
Then men could make sugar and water 
ferment whenever they wanted to. So 
men boiled grain to take out its sugar. 
Then they poured off the liquor and 
added yeast and let it ferment. This 
made beer and ale. Now millions of 
bushels of grain are used every year 
in making beer. Men call beer a light 
A glass of beer 
contains so 
much alco- 
hol. 
drink. But it has alcohol and is a strong drink, 
and can make men drunk. 
71. Root beer. Some persons boil roots and 
herbs, and add molasses and yeast. Then the 
liquid ferments and becomes root beer. They say 
“it has no alcohol, for we made it.” But it does 
have alcohol, for yeast always makes alcohol. Some 
ginger ale is made by putting yeast in sweetened 
ginger water. It has alcohol, too. 
72. Distillation. Boiling water turns to vapor 
or steam and goes off in the air. When the vapor 
is cooled, you can see the water again. It often 
cools on the window and makes little streams of APPLIED PHYSIOLOGY 
44 
water. You can catch the steam in a tube. If 
you keep the tube cool, the steam will turn to water 
in the tube. This process is called distillation. 
Boiling alcohol also passes off into the air as 
vapor. When the vapor is cooled, it becomes liquid 
again. Alcohol boils with less heat 
than water. When alcohol in water 
is heated, the alcohol boils first. So 
the vapor has more alcohol than the 
water. When the vapor is cooled, the 
liquid has more alcohol than it had at 
first. .When the liquid is distilled again 
it has more alcohol yet. Pure alcohol 
can be made in this way. 
A glass of 
whisky cen- 
tal n s so 
much alco- 
hol. 
73. Whisky. Distilling wine or strong beer 
makes whisky and brandy. Whisky is one half 
alcohol. It is more harmful than wine or beer. 
74. Habit. Some strong drinks have only a 
little alcohol and some have a great deal. No one 
begins to drink the strong liquors. He begins with 
wine or beer. When he has once learned, he has 
a hard time to stop drinking. It is dangerous to 
drink even weak drinks. 
75. Strong drink and thirst. When a man is 
thirsty, water will satisfy him but strong drink will 
not. Sometimes the mouth is dry and dirty and 
then a man feels thirsty. Rinsing the mouth KINDS OF STRONG DRINK 
45 
with water, and rubbing the tongue and teeth 
clean will help the dryness and stop the thirst. 
At any rate, strong drink will only make the 
mouth dryer. 
Some men drink only when they are tired. Then 
a cup of strong and hot tea or coffee will make 
them feel much better than a glass of strong drink, 
and will not harm them so much. 
When strong drink is swallowed, its alcohol takes 
water from the mouth. When your mouth is dry, 
you feel thirsty. Strong drink makes the mouth 
dry, and so a drink makes a man more thirsty. 
The alcohol also makes the mouth smart. Men 
need another drink to cool the mouth after the first 
one. So one drink leads to another. All the while 
a person drinks water with the alcohol until he has 
too much water. But his mouth is dry and he feels 
as thirsty as ever. 
76. Effect of alcohol upon the stomach. When 
strong drink is swallowed it makes the stomach 
smart just as it does the mouth. So the stomach 
feels warm, but it is really no warmer. This harms 
the stomach and keeps it from working well. 
Alcohol also keeps the gastric juice from chang- 
ing albumin to a liquid. Alcohol keeps flesh from 
decaying in a museum. In the same way it may 
hinder the digestion of food in the stomach. 46 
APPLIED PHYSIOLOGY 
When alcohol is used for only a short time, the 
stomach can get well; but if it is used for months 
and years, the stomach will stay weak. Then the 
drinker can hardly eat at all. 
77. What becomes of alcohol. —ln the stomach 
a great deal of gastric juice is mixed with the 
alcohol. So it is very weak when it reaches the 
intestine. Alcohol needs only a little digesting. 
It soon soaks into the blood from the intestine 
along with the other food. The blood flows fast 
and washes the alcohol away as soon as it leaves 
the intestine. Too little gets into the blood at once 
to harm it much. 
Alcohol goes to the liver, and is there destroyed; 
but it still does great harm. The liver has to 
attend to the alcohol, and so it does not change 
the food to good blood, and it does not take all the 
poisons out of the blood. Then the whole body 
becomes weak and sick. Alcohol hurts the liver 
first, and more than other parts of the body. On 
this account, every drinker has bilious attacks and 
stomach troubles. 
78. Bitters. Many medicines are made by dis- 
solving drugs in alcohol. In taking a strong medi- 
cine, we use only a few drops, and so do not get 
much alcohol. Some kinds of medicines must be 
taken in large doses. Bitters are weak medicines, KINDS OF STRONG DRINK 
47 
and must be taken by the tablespoonful. A table- 
spoonful of the medicine has more alcohol than a 
large drink of whisky. The bitters seem to make 
a person feel well, but it is because he is taking 
a large amount of strong drink. 
Jamaica Ginger is only common ginger dissolved 
in alcohol. It, too, is a form of strong drink. 
79. Strong drink as medicine. People sometimes 
keep whisky or brandy in the house to give for 
colds or other slight forms of sickness. A drink of 
hot coffee does more good than the strong drink, 
and has none of its dangers. 
By using whisky or brandy for medicine, chil- 
dren learn to believe in strong drink, and so they 
will be likely to use it when they grow up. This 
reason alone ought to keep any one from giving it 
to a child. 
80. Alcohol in cooking. —ln making bread, alcohol 
is formed in the dough by the yeast. When the 
bread is baked, all the alcohol is driven off by 
the heat, and so we do not eat any. 
Sometimes brandy or wine is put into desserts. 
If it is put in after the dessert is cooked, we shall 
get as much alcohol as if we had drunk it. If the 
liquor is put in before cooking, the heat will drive 
off the alcohol but the flavor of the liquor will 
remain. The flavor will do no harm in itself, but 48 
APPLIED PHYSIOLOGY 
people will learn its taste, and from it may learn to 
like the strong drink itself. The alcohol in bread 
has no special flavor and does not leave any taste 
behind. So we cannot learn to like strong drink 
by eating bread. 
WHAT WE HAVE LEARNED 
1. Fruit juice makes wine or cider. 
2. All kinds of wine contain alcohol. 
3. When the liquid from boiled grain has fer- 
mented, it becomes beer, or ale. 
4. By boiling wine or beer, and cooling the vapor, 
distilled drinks like whisky are made. They 
are one half alcohol. 
5. Water will satisfy a real thirst. Strong drink 
will not. 
6. Alcohol keeps the stomach from digesting food. 
7. Alcohol soaks into the blood tubes and goes to 
the liver. 
8. The liver destroys the alcohol, but is hurt in 
doing it. CHAPTER IX 
THE BLOOD 
81. Blood. After food becomes blood, it goes 
to every part of the body to feed the cells. Even 
a pin prick anywhere in the body draws blood. 
The blood makes the skin pink. 
There are five or six quarts of blood 
. . 
in a man’s body. This is about W 
of his body. ' 
j i i -pi j t • i 
Blood looks like a red liquid. 
Blood corpuscles 
(X 400). 
But if you look at it through a 
strong microscope, it looks like 
water, and millions of little red cells. 
These cells carry air through the 
body. They make the blood look red. 
« a pile of red blood 
cells. 
b red blood cells seen 
c red blood ceils seen 
d whteS Xod ceils, 
There are also a smaller number of white cells. 
Blood is made of red cells, white cells, and a liquid. 
82. The liquid in blood. The liquid part of the 
blood is albumin, and water, with a little fat, sugar, 
and minerals. It is food and drink for the cells of 
the body. When blood is drawn from the body 
it soon becomes like jelly. We call the jelly a 
clot. When you. cut your finger, a clot forms in 50 
APPLIED PHYSIOLOGY 
the cut and plugs up the bleeding place. If it 
did not, the blood would all run out of the body 
and we should die. 
83. The heart. The blood is held in tubes. A 
pump inside the body keeps it always moving. 
This pump is called the heart. The heart is 
a bag of muscle with 
thick sides. It is about 
as large as your fist. 
When it is full, it has 
the power to make it- 
self smaller, and so it 
squeezes the blood out 
through a tube. We 
can feel each squeeze 
as a heart-beat. You 
can find the heart-beat 
just to the left of the 
middle of the body 
about two hand- 
breadths below the 
neck. 
Diagram of the heart while it is beating. 
a vein entering the auricle. 
b auricle. 
c closed valve to keep blood from flowing 
back into the auricle. 
d ventricle. 
e artery. 
f valve to keep blood from returning to the 
ventricle. 
84. The heart-beat. A man’s heart beats about 
seventy times each minute. Boys’ and girls’ hearts 
beat much faster. Running or hard work of any 
kind makes the heart beat faster yet. Your heart 
will keep on beating until you die. It does not THE BLOOD 
51 
seem to rest at all, yet it works only while you 
feel it beat. Between each beat it rests while the 
blood is filling it again. So it really rests one half 
of the time. 
85. Arteries. The heart pumps the blood 
through a single tube. This tube opens into 
smaller tubes. These open into still smaller ones. 
You must use a strong microscope to see the 
finest blood tubes. The tubes reach every part 
of the body, and carry blood to its cells. They 
are called arteries. At each heart-beat a wave 
of blood can be felt 
in an artery. This 
wave is the pulse. It 
can be felt in the 
wrist, temples, and 
other places. By the 
pulse we can tell how 
often and how strong- 
ly the heart is beating. 
Arrangement of capillaries, 
a smallest artery. 
b smallest vein. 
c network of capillaries. 
The smallest arteries 
divide into a fine net- 
-86. Capillaries. 
work of small tubes. These tubes are the capil- 
laries. They lie around every cell of the body. 
Their sides are very thin. As the blood flows 
through them, some of it soaks through the sides 52 
APPLIED PHYSIOLOGY 
of the tubes. Blood contains all kinds of food 
for the cells. Each cell is always wet with food 
and can eat it at any time. The cells are like 
the tiny animal, the ameba, and can take in the 
food by any part of their bodies. The cells are 
better off than the ameba, for their food is brought 
to them. They pay the body for their food by 
working for it. 
87. Veins. The capillaries come together again 
to form large tubes. These tubes are called veins. 
Only a little of the blood goes through the sides of 
a capillary. The rest flows on into the veins. The 
veins unite to form two large tubes. These two 
tubes open into the heart. 
88. How the blood flows. The blood is pumped 
out of the heart, through the arteries to the capil- 
laries. There some goes out to the cells. The rest 
flows into the veins and goes back to the heart. 
All the blood in the body passes through the heart 
every two minutes. It takes only twenty seconds 
for a drop of blood to go from the heart to the toes 
and back again. The arteries are deep in the flesh, 
but some of the large veins can be seen upon the 
back of the hands. 
89. Bleeding. lf a large artery or vein is cut 
there is a great deal of bleeding. You can always 
stop a cut from bleeding by holding it fast between THE BLOOD 
53 
the hands. Do not be afraid of the blood when 
you see any one bleeding, but hold the sides of the 
cut tightly with both of your hands. This will stop 
any bleeding until help comes. You may keep a 
person from bleeding to death by doing this when 
other persons are afraid of the blood. 
90. Healing cuts. When your flesh is cut it 
soon grows together again. The work of the little 
white cells in the blood is to help heal cuts and 
wounds and bruises. These cells are like little 
amebas in the blood. They keep moving around 
with the blood, and now and then burrow outside 
the capillaries to see if all is well. If they find a 
cut, hundreds and thousands rush to the spot at 
once. Some eat up any specks of dirt on the cut. 
Others fit themselves into the sides of the cut and 
grow long and slender, like strings, and so bind the 
two edges of the cut together. In this way all cuts 
are healed. 
91. The white blood cells kill disease germs. 
There are tiny living beings everywhere in the air, 
and soil, and water. They are the smallest living 
things known. Some of these can grow inside a 
man and make him sick. One kind gives a man 
typhoid fever, and another diphtheria. Another 
kind grows on cuts, and sometimes makes them 
very sore. The white cells of the blood are always 54 
APPLIED PHYSIOLOGY 
watching for these tiny enemies, like a cat hunting 
mice, and when they find them they at once try to 
kill them. But some- 
times the white blood 
cells get killed. Then 
they look like cream 
in the cut. We call 
this matter ox pus, and 
say “We have caught 
cold in the cut.” In 
most pricks and cuts 
the white cells of the 
blood can kill all these 
enemies and heal the 
cut at the same time. 
Bacteria growing in a kidney and producing 
an abscess (X 300). 
a kidney tube. 
b white blood cell attacking bacteria. 
c bacteria. 
d blood vessel of the kidney. 
92. Catching cold. Sometimes the cold air blows 
on our head and hurts the cells of the nose. Then 
we get a “ cold in the head.” The white blood cells 
at once gather around the spot while the capillaries 
pour out more food for the cells. Some of the 
water and the white blood cells run out and we 
have to blow our noses. So the white cells of 
the blood are the best servants of the body and 
are always ready even to die for our good, or to 
grow and form flesh and fill a cut. 
93. The red blood cells. The red blood cells are 
tiny flat plates. When we look at blood we see THE BLOOD 
55 
nothing but the red cells, for there are a great 
many of them. They do not feed the cells of the 
body, but they carry them little loads of air from 
the lungs. The cells of the body have both food 
and air brought to them by the blood. 
94. Why the heart beats hard when we run. 
When we work hard, the cells of our bodies need 
a great deal of food. So the heart beats much 
harder, and sends them much more blood. We can 
feel our heart beat when we run hard. 
When the cells work they get more blood in 
another way. The arteries become larger and hold 
more blood. Then the part looks red and feels 
warm. Thus your face gets red when you run 
hard. This is because your heart and arteries 
bring more blood to feed the working cells. 
95. Need of a strong heart. The heart must 
keep sending blood to feed the cells. If it should 
stop for only a little while, the cells would starve to 
death and we should die. We need strong hearts. 
When we work very hard for a long time, the heart 
gets tired. Then the cells do not get enough food 
and we feel weak all over. Boys ought not to run 
and lift till they are tired out, for this hurts their 
hearts. 
96. What alcohol does to the blood. Alcohol 
hinders the digestion of food. Then too little food 56 
APPLIED PHYSIOLOGY 
will reach the blood, and so the cells of the body 
will get too little. Alcohol does not add strength 
to the body, but it takes it away. It seems to 
make men stronger, for it takes away their tired 
feelings. But it makes them really weaker, for it 
harms the blood. 
97. How alcohol affects the heart. Alcohol at 
first makes the heart beat more strongly and 
quickly, but it tires it out and makes it weaker. 
Then the heart pumps too little blood to the rest 
of the body, and a man is weaker all over. 
If a drinker tries to run or work hard, his heart 
may not pump enough food to the working cells 
of his arms and legs. Strong drink takes away a 
man’s strength and makes him less able to endure 
a long strain. 
98. How alcohol harms the arteries. Alcohol 
causes the arteries to become larger and to carry 
more blood. Then the face will be red and the 
skin will become warm. This makes a person feel 
well, and he seems to be helped. His blood seems 
to be flowing faster because his face is red. But 
really it is flowing slower. 
When the arteries have been made large very 
often, they stay large all the time. A drinker’s 
nose is always red. 
Alcohol sometimes causes the arteries to become THE BLOOD 
57 
hard, and even to change to a kind of bone. Then 
they cannot change their size to carry just so much 
blood as each part needs. 
99. How tobacco affects the heart. Tobacco weak- 
ens all the body, but it harms the heart more than 
the rest. It often makes the heart beat slowly at 
one time and fast at another. It weakens the heart 
and keeps it from working harder when the work- 
ing cells need more food. A smoker gets out of 
breath quickly. He cannot run far or work very 
hard. Chewing is a still more harmful form of 
using tobacco. When men train for a game or a 
race they never use tobacco. 
Boys are not so strong as men, and so tobacco is 
more hurtful to them. Boys are harmed by tobacco 
far more than men. Cigarette smoke harms their 
stomachs and keeps food from their blood. If boys 
smoke, they become pale and weak. The poison- 
ous smoke weakens the heart, and they cannot run 
or work so hard as they should. Even if a father 
uses tobacco, he should not allow his boys to use it. 
WHAT WE HAVE LEARNED 
1. Blood is a liquid. It contains many round red 
cells and a few white cells. 
2. Blood contains all kinds of food for the cells 
of the body. 58 
APPLIED PHYSIOLOGY 
3. The blood is kept moving by the heart. 
4. The heart pumps or beats about seventy times 
a minute. 
5. The blood flows through arteries to all parts 
of the body. 
6. The arteries open into the capillaries. Capil- 
laries make a network around each cell of 
the body. 
7. Some of the liquid parts of the blood go out 
through the sides of the capillaries and 
become food for the cells of the body. 
8. From the capillaries the blood flows into the 
veins and back to the heart. 
9. Bleeding can be stopped by holding the cut 
tightly between the hands. 
10. The white blood cells grow into the sides of 
cuts, and so heal them. They also guard 
the body against the seeds of many diseases. 
11. The red blood cells carry air to the cells of the 
body. 
12. Alcohol weakens the heart and arteries. 
13. Tobacco harms the heart. CHAPTER X 
BREATHING, HEAT, AND CLOTHING 
100. The lungs. Our food becomes blood and 
feeds the cells of our body, but we grow only a 
little heavier. What 
becomes of the 
food ? 
Besides food, air 
is always getting into 
our bodies. In 
breathing, air passes 
through the nose 
into a tube in the 
neck. This tube is 
called the windpipe. 
You can feel it as a 
pile of hard rings in 
the front part of the 
neck. The windpipe 
divides into many 
branches. At the 
end of its smallest 
branches are little 
The air tubes and lung. 
a larynx or voice box. 
b trachea or windpipe. 
d air sacs, each like a tiny frog’s lung. 
59 APPLIED PHYSIOLOGY 
bags or sacs. The branches and the sacs make 
the two lungs. So a lung is a soft and spongy 
piece of flesh, and can be blown 
up like a rubber bag. A frog’s 
lung is a single, thin bag, about 
half an inch across it. Each little 
sac of a man’s lung is like a tiny 
frog’s lung. 
101. The diaphragm. The lungs 
fill the upper part of the body just 
below the neck. They are cov- 
ered by the bony ribs, and rest 
upon a broad muscle. This muscle 
is called the diaphragm. It divides 
a frog’s lung (x 4). 
the inside of the body into 
two parts. The upper part 
is the chest, and holds the 
heart and lungs. The lower 
part is the abdomen, and 
holds the stomach, intestine, 
and liver, and a few other 
parts. 
102. Breathing. When 
the diaphragm lowers itself, 
or the ribs are raised, the 
chest is made larger. Then 
the air rushes through the 
The parts inside the body. 
a lungs. 
b heart. 
c diaphragm. 
d stomach. 
e liver. 
/ intestine. BREATHING, HEAT, AND CLOTHING 
nose and swells out the lungs to the size of the chest. 
This is taking a breath. Then the chest becomes 
smaller again, and blows the air out. A man 
breathes about eighteen times a minute. He does 
not seem to rest in breathing, but as he works only 
when he takes in breath, he rests one half of the 
time. 
103. How air gets into the blood. After the 
blood has been around the body through the ar- 
teries and capillaries and veins, the heart sends 
every drop to the lungs before it sends it out to 
feed the cells again. The blood flows through 
little capillaries upon the sides of the air sacs. 
There the red blood cells take up some of the 
air, and carry it with them. When they have a 
load of air, they become of a brighter red color. 
The blood in the arteries on its way to the cells 
is bright red. 
104. How the cells get air. When the blood 
reaches the capillaries around the cells of the body, 
the red blood cells give up some of the air to the 
cells. Thus each cell of the body gets some air, 
and so it breathes. The cells cannot reach the 
air themselves, and so the red blood cells bring it 
to them. We breathe so as to supply the cells 
with air. 
105. What burning is. When meat is put into a 62 
APPLIED PHYSIOLOGY 
hot stove it quickly burns, and passes off in smoke, 
and leaves only a little ashes. The ashes are the 
mineral parts of the meat. If the fire is very hot, 
you cannot see the smoke. The burning of the 
meat makes heat. Heat in a steam engine makes 
the machine do work. 
Every fire must have plenty of air. If air is shut 
off, the fire goes out. When meat burns, the air 
unites with the meat and makes smoke, and ashes, 
and gives out heat. Air unites with something in 
every fire. 
106. Burning inside the body. —ln every part of 
a man’s body a very slow fire is always burning. 
The blood brings to the cells food from the intes- 
tine, and air from the lungs. The food and air 
join in a burning. The smoke goes back to the 
blood and is carried to the lungs, and breathed out 
with the breath. The ashes, also, go back to the 
blood, and are carried away by the skin and kid- 
neys. The burning makes no flame or light for it 
goes on very slowly. You cannot see the smoke, 
but you can feel the warmth of the burning. Some 
of the heat is turned to power, and gives the body 
strength to do work. The body is like a steam 
engine. It burns up all its food. 
107. How the body is warmed. The body is 
warmed by the slow burning in the cells. This BREATHING, HEAT, AND CLOTHING 
63 
burning keeps the body always at the same warmth. 
On a hot summer’s day you feel warmer than on a 
cold snowy morning. But your body is no warmer. 
Only your skin is warmer. 
If the skin is warm, the whole body feels warm, 
but if the skin is cold, the whole body feels cold. 
On a hot summer’s day the heat is kept in the skin, 
and we feel warm. On a cold winter’s day a great 
deal of heat passes off from the skin, and we feel 
cold. Yet our bodies have the same warmth in 
winter as in summer. 
108. How the sweat keeps us cool. When your 
hands or feet are wet, they are cold. On a hot 
summer’s day, your body becomes wet with sweat. 
This cools the body as if water were poured over it. 
So sweating keeps you from getting too warm, and 
from being sunstruck. 
We are sweating all the time, but the sweat 
usually dries as fast as it forms. When we are 
too warm it comes out faster than it dries. On a 
winter’s day we sweat only a little, and so we save 
the heat. But more heat passes off from the skin 
into the cold air, and we do not grow warmer. 
109. Clothes. —We wear clothes to keep the heat 
in the body. They do not make heat, but they 
keep it from going off. Wool and flannel clothes 
keep the heat in better than cotton. We wear 64 
APPLIED PHYSIOLOGY 
woolen in the winter, and cotton in the sum- 
mer. 
Fur keeps in heat the best of all. In very cold 
lands only fur is worn. 
Linen lets heat out easily. It makes good sum- 
mer clothes. 
110. Where to wear the most clothes. The face 
and hands are kept warm by the blood and we do 
not cover them except in the coldest weather. Our 
feet are more tender and need to be covered enough 
to keep them warm. We ought to wear thick-soled 
shoes or rubbers in damp weather so as to keep 
the feet dry and warm. We ought to dry the stock- 
ings every night, for they will get wet with sweat. 
The trunk of the body needs the most clothes. 
The legs ought to be kept warm, too. If the dress 
reaches only to the knee, thick underclothing is 
needed for the lower part of the leg. 
Do not keep one part of the body warm while 
another part remains cold. It is wrong to bundle 
the neck or wear too much clothing over any part 
of the body. It is also wrong to wear too little and 
be cold. 
When you have worked until you are very warm, 
it is wrong to stop to cool off. When you stop, 
you ought to put on a thick coat or else go into the 
house. If you do not, you may take cold. BREATHING, HEAT, AND CLOTHING 
65 
111. Heating houses. —ln winter our bodies can- 
not make heat fast enough to keep us warm unless 
we put on a great deal of clothing. So we warm 
our houses. Our grandfathers used fireplaces, but 
these did not give out much heat. People now 
use stoves, but some use a furnace in the cellar, 
or heat the rooms by steam. Some use kerosene 
stoves, but they are not so good, for they make the 
air bad. 
If a room is too warm, we may catch cold when 
we go out into the cool air. If the room is too 
cold, we may catch cold in it. The room is of 
the right warmth when we do not notice either 
heat or cold. 
112. Change of air. After air has been breathed 
it is no longer fit for use. In an hour or two you 
would breathe all the air of a small room once if it 
were not changed. When the air is partly used, 
you feel dull and short of breath, and your head 
aches. As soon as you get out of doors, you feel 
better. It is necessary to change the air of all 
rooms often. You can do this by opening a door 
or window. You should take a run out of doors 
every hour or two so as to get fresh air. It is 
a good plan to sleep with your bedroom window 
open, so as to get good air all night. 
Air passes in and out of every crack in the win- 66 
APPLIED PHYSIOLOGY 
dows and doors. If only one person is in a room, 
this will make enough change of air. If many per- 
sons are in a room, you will need to change the air 
Diagram of the natural ventilation of a room. 
The arrows show the direction of the air currents. 
in other ways. You can do this by opening a door 
or window a little way. Do not open it so that the 
cold air will blow upon any one, for it may make 
him catch cold. 
In a sickroom, the air needs to be changed often, 
for it may contain disease germs. BREATHING, HEAT, AND CLOTHING 
You need fresh air at night as much as in the 
daytime. You need not be afraid of the night air, 
for it is good and pure like the day air. You 
ought to sleep with your window open a little. 
You ought to open the windows wide every morn- 
ing and air your bed well. At night you ought to 
take off all your clothes and put on a night-dress. 
Then hang your clothes up to air and dry. 
113. When to air a room. When you first enter 
a room full of bad air it smells musty and un- 
pleasant. But after you have been in the room 
a while, you get used to it. If, however, you go 
out of doors a minute and then come back, you 
will smell the bad air again. If the air smells bad, 
open a door or window until it is sweet again. 
114. How to breathe. When you run hard, the 
cells of your body use up all the air, and then you 
feel short of breath. While you run, burning goes 
on faster, and you feel warmer. You can work 
harder and longer if you can breathe in a great 
deal of air. You will also feel better and stronger 
for it. Then if you are sick, you will be able to 
get well more quickly. You ought to know how 
to breathe right. 
First, you ought to breathe through your nose. 
Even when you run, you ought to keep your mouth 
closed. 68 
APPLIED PHYSIOLOGY 
Second., you should try to breathe deeply. You 
should take a very deep breath often, and hold it as 
long as you can. By practice you can learn to hold 
it a full minute. 
Third' you ought to run, or do some hard work, 
every day. When you get short of breath, you will 
have to breathe more deeply. After a while you 
may be able to run a half mile, or even a mile, with- 
out getting out of breath. But do not get tired out 
in your run, for this will harm you. 
Fourth, you must sit and stand with your shoul- 
ders back, and your chest thrown forward. A 
round-shouldered boy cannot have large lungs or 
be long-winded. 
By breathing right, you can make your lungs 
very much larger and stronger. 
115. The voice. —We talk by means of the breath. 
At the upper part of the windpipe is a small box. 
Its front corner can be felt in the neck, just under 
the chin, and is called the Adams apple. Two 
thin, strong covers slide across the top of the box, 
and can be made to meet in the middle. The 
covers have sharp edges. When they are near 
together, and air is breathed out between them, a 
sound is made. This sound is the voice. The 
tongue and lips change it to form words. 
116. Care of the voice. The voice shows our BREATHING, HEAT, AND CLOTHING 
69 
feelings, even if we do not tell them in words. We 
can form a habit of speaking in a loud and harsh 
tone, as if we were always angry, or we can speak 
gently and kindly. We shall be more pleasant 
company to others if we are careful always to speak 
in gentle but distinct tones 
Top view of the larynx, with the 
vocal cords closed, as in speaking. 
Top view of the larynx, with the 
vocal cords open, as in breathing. 
a epiglottis. 
b vocal cords. 
a epiglottis. 
b vocal cords. 
Shouting strains the voice and spoils its tone for 
singing. Reading until the throat is tired makes 
the voice weak. Singing or shouting in a cold or 
damp air is also bad for the voice. Breathing 
through the mouth is the worst of all for the 
voice. 
117. What becomes of alcohol in the body. When 
alcohol is taken up by the blood, it is carried to the 
liver. The liver tries to get rid of it by taking 
some air from the blood and burning it up, just as 
it burns the real food of the body. But this takes 
some air from the cells of the body. Then they do 
not burn as they should. 70 
APPLIED PHYSIOLOGY 
When a stove gets too little air through its draft, 
it makes an unpleasant smoke, and cools off. Just 
so, when the cells of the body do not burn as they 
should, they produce the wrong kind of smoke and 
ashes. This poisons the body and makes men sick. 
The most of the poisoning of alcohol is due to 
these new poisons. 
When alcohol takes air from the cells of the 
body, they do not get enough air. Then they are 
like a short-winded boy, and do not do their work 
well. In this way alcohol makes the body weak. 
Alcohol does not cease to be harmful because it 
is burned up in the body. It is harmful just because 
it burns so quickly. Using alcohol in the body is 
like trying to burn kerosene in a coal stove. The 
body is not made to burn alcohol any more than a 
coal stove is made to burn kerosene. You can 
burn a little kerosene in a coal stove if you are 
very careful. Just so, men can burn alcohol in 
their bodies. But kerosene will always smoke and 
clog up the stove, and may explode and kill some 
one. So alcohol in the body burns quickly and 
forms poisons. It always harms the body and 
may destroy life at once. 
118. Alcohol and the lungs. —lf you run ,a long 
race, your lungs will need a great deal of air. If 
you take strong drink, the alcohol will use up BREATHING, HEAT, AND CLOTHING 
71 
much of the air, and you will not have enough 
to use on your run. So you will feel short of 
breath, and will surely lose the race. You cannot 
drink and be long-winded. 
Two drinks of whisky will use up as much air 
as the body uses in an hour. It would be easy to 
smother a person with strong drink. Drunken 
persons are really smothered; they often die be- 
cause of the failure of their breathing, even while 
their heart is able to beat well. 
Alcohol often causes the lungs to become thick- 
ened. Then air cannot easily pass through their 
sides, and a person suffers from shortness of breath. 
Sometimes these persons cannot lie down at all, 
but must sit up to catch their breath. 
119. Drinking and taking cold.— A strong, healthy 
man can stand a great deal of cold and wet. If he 
breathes deeply in his work, all the cells of his body 
get plenty of air, and if he eats good food, the cells 
get plenty to eat. Then it will take a great deal to 
harm them. But alcohol hinders the digestion of 
their food, and also takes away their air. So the 
cells are both starved and smothered, and are easily 
hurt. Then a little cold and wet will do great 
harm to his body, and cause him to take cold in his 
lungs or other parts. 
Men often drink to keep themselves from taking 72 
APPLIED PHYSIOLOGY 
cold. The alcohol really makes them more liable 
to take cold. It causes the blood to flow near the 
surface of the skin; there it is easily cooled, and 
the drinker soon becomes chilled; then he feels 
colder than ever. The cold harms the cells of his 
body and makes him sick. In this way he easily 
takes cold in his throat or on his lungs. Drunk- 
ards are very liable to have pneumonia, and to die 
from it. 
120. Alcohol lessens the warmth of the body.— 
Alcohol causes the blood tubes in the skin to be- 
come larger. Then more blood will touch the cool 
air, and the body will become cooler. But because 
more warm blood flows through the skin, a man 
feels warmer. But he is really colder. Alcohol 
makes men less able to stand the cold. Travelers 
in cold lands know this and do not use it. 
121. How tobacco affects breathing. —We would 
not live in a room with a smoking stove. But 
tobacco smoke is more harmful than smoke from 
a stove, for it has nicotine in it. Tobacco smoke 
in a room may make a child sick. 
Cigarette smoking is very harmful to the lungs, 
for the smoke is drawn deeply into them, and more 
of the poison is likely to stay in the body. The 
smoke of tobacco burns the throat and causes a 
cough. This harms the voice. BREATHING, HEAT, AND CLOTHING 
73 
WHAT WE HAVE LEARNED 
1. Air is always being breathed into little sacs 
inside the body. The sacs form the lungs. 
2. The red blood cells pass through the lungs, 
and take little loads of air. They then 
carry the air through the arteries to the 
capillaries. 
3. In the capillaries the air leaves the red blood 
cells, and goes to the cells of the body. 
4. The air unites with the cells, and slowly burns 
them to smoke and ashes. 
5. The smoke goes back to the blood, and is 
carried to the lungs and given off by the 
breath. The ashes go back to the blood 
and pass off through the skin and the kid- 
neys. 
6. The burning in the cells makes heat. 
7. Some of the heat is changed to power, as it 
is in a steam engine. 
8. The heat also warms the body. It keeps it 
at the same warmth on a cold day as on 
a hot day. 
9. We wear clothes to keep the heat in, and so 
to keep us warm, 
10. The air of a room needs to be changed often 
It is made stuffy by our breath. APPLIED PHYSIOLOGY 
74 
11. The voice is made by the breath in a box in 
the neck. 
12. Alcohol uses air belonging to the cells of the 
body. 
13. Tobacco smoke has the same poisons as to- 
bacco. It can poison the whole body through 
the lungs. CHAPTER XI 
THE SKIN AND KIDNEYS 
122. Waste matters. The food is burned in the 
cells. As this burning goes on, the smoke goes off 
by the lungs and the 
unburned substances, 
the ashes, go off by 
the skin and kid- 
neys. The ashes are 
mostly the minerals 
of the cells, but there 
are also some from 
the burned albumin. 
All these go back to 
the blood and are 
carried to the skin 
and kidneys. 
The skin (X 100). 
123. The skin. 
The skin covers the 
whole body. It is 
a, b, and c epidermis. 
d and g tough and thick part of skin, 
e sweat gland. 
/blood tubes. 
h fat pockets. 
strong and keeps the body from being hurt. 
124. The epithelium. The skin is covered with 
a thin layer of cells like fine scales. These scales 
75 APPLIED PHYSIOLOGY 
are called epithelium, or epidermis. They have no 
blood tubes or nerves and so have no feeling. 
You can run a pin under them without feeling 
pain. They are always growing on their under 
side and wearing off on their upper side. They 
keep the nerves and blood tubes of the skin from 
being hurt. 
125. The nails. The top scales of epithelium 
at the ends of the fingers become matted together 
to make the nails. The nails keep the ends of 
the fingers from being hurt. They can also be 
used to hold or cut small things. The new parts 
of the nails form under the skin and push down 
the older parts. So the nail grows farther than 
the end of the finger and needs to be cut off. 
Biting the nails leaves their ends rough. Then 
they may catch in the clothes and tear into the 
tender flesh. We ought to keep the nails cut 
even with the ends of the fingers. 
The nails are not poisonous, but the dirt under 
them may be. We ought to keep them clean. 
Clean nails are one mark of a careful boy or girl. 
126. Hair. Some of the scales of epithelium 
over some parts of the body dip into tiny holes 
in the skin. In each hole they become matted 
together to form a hair. Fine short hair grows 
on almost every part of the body. On the top THE SKIN AND KIDNEYS 
77 
of the head it grows long and thick. When boys 
become men, it also grows long upon their faces. 
The skin pours out a kind of oil to keep the hair 
soft and glossy. 
127. Care of 
the hair. The 
hair may be- 
come dirty like 
any other part 
of the body. 
Brushing it 
takes out a 
great deal of 
dirt, but you 
should also 
wash it once a 
week. 
A hair (X 200). 
The oil in 
the skin ought 
to be enough 
for the hair. 
a the surface of the skin. 
b a hair. 
c an oil gland. 
d a muscle to make the hair stand on end. 
e and g, the growing cells of the hair. 
f fat in the skin. 
Hair oils do not do the hair any good. If you 
wet the hair too often, you may make it stiff 
and take away its gloss. It is best to comb the 
hair dry. Brush it so as to spread the oil of 
the skin. Hair dyes are poisonous, and ought not 
to be used. 78 
APPLIED PHYSIOLOGY 
128. The sweat or perspiration. The scales of 
epithelium dip into the skin and there line tiny 
tubes. The tubes form the sweat, or perspiration, 
out of the blood. The tubes are too fine to be 
seen, but they are upon almost every part of the 
body. They take the ashes or other waste matter 
or poisons from the blood and wash them out of 
the tubes with the perspiration. So the perspira- 
tion has two uses. First, it takes heat away from 
the body (see § 108). Second, it gets rid of the 
waste matters or ashes of the body. It has very 
little of these at any one time, but in a day it gets 
rid of a great deal. 
129. The kidneys. —The kidneys are close to the 
backbone, below the heart. They are made of 
tiny tubes much like the sweat tubes in the skin. 
The tubes take the waste matter from the blood. 
They also take away a great deal of water to wash 
away the waste matter. 
The kidneys act all the time. The skin also 
acts all the time, but on cold days only a little 
water passes off. On hot days, however, more 
passes off, and makes our skin wet. The kidneys 
take away most of the ashes and waste, but the 
skin helps a great deal. 
130. Need of bathing. When the perspiration 
dries from the skin, it leaves the waste and poisons THE SKIN AND KIDNEYS 
79 
behind. The skin may look clean, and yet be 
covered with poisons. So it needs to be washed 
often. The whole body needs to be washed with 
soap and water once a week in winter, and more 
often in summer. You should wash the skin often 
enough to keep it from having an unpleasant smell. 
131. Bathing. —We bathe to get rid of the waste 
and dirt of the body. After we have bathed, we 
feel better. Sometimes we bathe when we are 
clean, so as to get refreshed. If we bathe in warm 
water, we feel better for a time, and then we are 
apt to feel sleepy. The best time to take a warm 
bath is at night. If you cannot sleep, a hot bath 
may make you sleepy. 
If we bathe in cold water, we feel cold at first. 
In a little while, we feel warm again. Then we 
feel stronger, and refreshed for work. If we stay 
in the bath too long, we become cold again. Then 
we feel weak, and are a long time in getting back 
our strength. When boys go in swimming, they 
ought to come out before they begin to feel cold. 
It is a good plan to take a cold bath every morn- 
ing when you get up. You can wet yourself with 
your hands, and dry the body with a towel. This 
will take only a few minutes, but it will keep you 
clean. It will also wake you up, and make you feel 
more like doing your day’s work. APPLIED PHYSIOLOGY 
132. A fair skin. —We must wash often, to make 
the skin fair and smooth. Use enough good soap 
to keep the skin clean. 
If you eat as you should, and digest the food 
well, your skin will have the least amount of waste 
to give off. Then it will look well. A bad looking 
skin is due to bad food and to bad digestion. If 
you do not digest your food well, you cannot have 
a fair skin. 
Face paint and powder make the skin look worse, 
for they hinder perspiration. Nothing of that sort 
will do the skin any good. You must eat as you 
should, and you must keep clean. Then your skin 
will be clear. 
133. Washing clothes. Our clothes rub off a 
great deal of the perspiration and waste. They 
become soiled. A great deal of dirt also gets upon 
the sheets of our beds. Our clothes need to be 
washed as well as our bodies when they are soiled. 
Air and the sun as well as water destroy the waste 
of the body. Our clothes need to be aired at night, 
and the bed and bedroom should be aired through 
the day. 
134. Slops. After water has been used to wash 
our body or our clothes it is dirty and is not fit to 
be used again. It must not be thrown where it can 
run into a well. If a person has typhoid fever or THE SKIN AND KIDNEYS 
cholera or other catching disease, the water may 
carry the disease to the well and so other persons 
may get it. Slops from the house should not be 
poured out at the back door, but they should be 
carried away from the house. In cities the slops 
are poured into large pipes and tunnels under- 
ground. These pipes are called sewers. They 
empty outside the city. 
135. Alcohol and the skin. Alcohol interferes 
with digestion and causes biliousness. This makes 
the skin rough and pimply. A drinker seldom has 
a clear skin. 
Alcohol causes the arteries of the face to become 
enlarged. Then the face is red. A red nose is one 
of the signs of drinking. When a person uses 
strong drink he is often uncleanly. He does not 
care for the bad looks of his clothes and skin, and 
so he lets them stay dirty. This harms the skin 
and makes it look bad. The dirt also poisons the 
skin and may itself be a cause of sickness. 
Because alcohol poisons the whole body and 
often produces kidney diseases, the drinker is apt 
to catch other diseases. Drinkers are the first to 
catch such diseases as smallpox and yellow fever. 
Where there are great numbers of cases, the 
drinkers are the first and often the only persons 
to die. This is because their skin and kidneys 82 
APPLIED PHYSIOLOGY 
have been harmed by the alcohol and cannot throw 
off the poisons of the disease. Any kind of sick- 
ness will be worse in a drinker. Surgeons do not 
like to operate on drinkers, for their wounds do not 
heal so quickly as in other people. 
When there is too little air, a fire burns slower, 
and makes a blacker smoke and more ashes. Alco- 
hol takes some air from the cells of the body. So 
they burn with smoke and ashes of the wrong kind. 
The skin has to work harder to get rid of these, 
and sometimes it cannot do it well. Then the body 
is poisoned. The alcohol is burned and cannot 
poison the body any more. But it causes the body 
to make poisons, and so it is to blame. The poisons 
do great harm to the skin and kidneys. Alcohol 
causes more kidney disease than all other things 
put together. 
WHAT WE HAVE LEARNED 
1. Little tubes in the skin are always giving off 
ashes and waste matters in the perspiration. 
2. Perspiration dries on the skin. So the skin 
must be washed often. 
3. The kidneys get rid of more water and waste 
matter than the skin does. 
4. Perspiration also gets upon the clothes and bed 
sheets. These must be washed too. THE SKIN AND KIDNEYS 
83 
5. Dirty water from washing should be thrown out 
where it cannot run into a well. 
6. The skin is thick and strong and keeps the body 
from being hurt. 
7. The skin is covered with a layer of scales. The 
scales have no feeling. 
8. The scales form the nails on the ends of the 
fingers. 
9. The scales also form the hair. CHAPTER XII 
THE NERVES, SPINAL CORD, AND BRAIN 
136. Need of nerves. The cells of the mouth, 
stomach, and intestine digest food; the cells of 
the liver change the food to blood; the cells of the 
heart pump the blood to feed all the cells of the 
A nerve thread (x 400). 
a central conducting fiber. 
b covering of fat. 
body; the red blood cells carry air for the cells to 
breathe; and the cells of the skin and kidneys 
carry away the waste of the rest of the cells. Each 
set of cells works for all the rest. If the cells of the 
body were only tied together, each one would do as 
it pleased, and no two would work together. But 
something tells each cell of the body to work with 
the others. The cells all obey the mind. A tiny 
thread goes to each cell of the body. Each thread 
is a nerve. The mind and the cells signal to each 
other over the nerves. By means of the nerves the 
mind makes the cells work together. 
84 THE NERVES, SPINAL CORD, AND BRAIN 
85 
137. Nerve messages. The nerve threads run in 
bundles and form nerves large enough to be seen. 
The mind uses the nerves to tell the cells to do 
work. It tells the muscles 
to move the arms and legs. 
It tells the heart to beat 
and stomach to pour out 
gastric juice; and it tells 
each of the cells to eat. 
The cells also send word 
over the nerves to the mind. 
They tell the mind when 
they are touching anything, 
and whether it is hard, or 
A thin slice from the end of a cut 
nerve (X 200). 
a nerve thread. 
b connective tissue binding the 
threads into a cord. 
smooth, or hot, and many other things about it. 
The cells also tell the mind if they need more 
food, or are tired. 
The nerves are always carrying messages to and 
from the cells. The cells depend upon these mes- 
sages to tell them when and how to work. If the 
nerve of any part of the body is hurt or cut, we 
cannot feel with the part or move it, and its cells 
do not act in the right way. We do not feel the 
nerves while they are carrying the messages. We 
wish the cells of the arm to work, and they work, 
but we do not feel the message as it goes from the 
mind to the cells of the arm. 86 
APPLIED PHYSIOLOGY 
138. The spinal cord. The nerves start inside the 
backbone. The backbone is hollow. It has a soft, 
white cord inside, as 
thick as the little finger. 
Part of the mind lives 
in this cord. The cord 
iscalled the spinal cord. 
Some of the nerves 
start from cells of the 
spinal cord. These 
cells send word to the 
muscles to move and 
A thin slice from the spinal cord with the 
cells and nerves magnified 200 diameters. 
a cells in the gray matter. 
b fibers in the gray matter. 
c nerve threads in the white matter. 
to all the cells of the body to eat and grow. They 
also send word to the arteries to carry the right 
amount of blood to the cells. 
From the nerves the spinal cord gets word when 
something hurts any part of the body. You may 
put your finger on a sharp pin. The spinal cord 
feels the prick, and quickly sends word to snatch 
the finger away. So the finger is taken away 
before you really feel the prick. When some one 
sticks a pin into you, you cannot help jumping. 
This is because the spinal cord sends word for you 
to jump away from the pin before it can harm you 
much. Thus the spinal cord keeps the body from 
being hurt. It acts while we are asleep as well as 
when we are awake. THE NERVES, SPINAL CORD, AND BRAIN 
139. Need of a spinal cord. —We do not feel the 
spinal cord acting, and we cannot keep it from act- 
ing. It tells the cells when to eat and grow, and it 
tells the heart and arteries how much blood to send 
to each cell. If we had to think about feeding an 
Regions of the head and action of the different parts 
of the brain. 
arm or a leg, we should sometimes forget it, but the 
spinal cord keeps doing it without our thinking of 
it. We put food into the body, and the spinal cord 
tells the cells to use it. If it stops acting for an 
instant, the cells stop work and we die. We cannot 
change its action by any amount of thinking. 88 
APPLIED PHYSIOLOGY 
140. The brain. The nerves of the body go to 
the brain as well as to the spinal cord. The brain 
lies in the top of the head. A hard cover of bone 
keeps it from getting hurt. It is a soft white mass, 
and weighs about three pounds. Its outside is made 
of cells, while its inside is the very beginning of the 
nerves of the body. 
141. The mind. The mind is the real man. It 
is the thinking part of himself. It lives in the body 
and works by means of the cells of the brain. If 
these cells are hurt or killed, the body seems to 
have no mind, but yet it may keep on living. If all 
the mind leaves the body, the body is dead. 
By means of the mind we feel, and know, and 
think. The mind uses each part of the brain for 
only one kind of work. 
142. The senses. The cells of the body send 
word to the brain over the nerves. The eye tells 
of sight, the ear of sounds, the nose of odors, the 
mouth of tastes, and the skin of feelings. All these 
messages go to the back part of the brain. They 
tell the mind of the news outside of the body. We 
get all our knowledge in this way. The cells also 
tell of their need of food and drink by means of 
the feelings of hunger and thirst. 
143. Motion. The mind in the cells of the top 
part of the head sends the orders for moving the 89 
THE NERVES, SPINAL CORD, AND BRAIN 
different parts of the body. When we wish to 
run, the mind in the top of our head sends an 
order over our nerves to our legs, and they carry 
the body where we wish. If the top part of your 
brain is hurt, as by a blow, it cannot send orders 
to move, but you will lie stunned. 
144. Memory. The mind lays away all its mes- 
sages, and often looks them over again. These old 
messages are called memories. They always stay 
with the brain, and the mind can call them up at 
any time. Our memories make our knowledge. 
Every act of the mind leaves some mark on the 
memory. We may not be able to bring it back 
when we want to, but it will come back some time. 
Every bad word and evil deed will tend to come 
back and make us bad again. Every good work 
and word will leave its memory and make us 
better. We ought to fill our minds with good 
memories. 
145. Thinking. The brain also thinks. Think- 
ing is different from feeling and from moving, but 
we can think about our feelings and about our 
movements. The brain just back of the forehead 
does all our thinking. A dog has only a little 
forehead, and cannot think much. But the rest 
of its brain is large, for it can see and hear and 
run as well as a man. A baby can see and hear APPLIED PHYSIOLOGY 
90 
and move, but it cannot think until it is taught 
how. Boys and girls go to school to learn to think. 
Thinking is work, just as truly as running is work. 
At school, no one can learn to think without work- 
ing. Looking at things and hearing some one 
talk about them will not make you a strong-minded 
man, but thinking about these things will. Boys 
and girls should study and think, as well as look 
around and listen. 
146. How thought rules the body. —We are 
always feeling and moving. We often do these 
things without trying, but we must make ourselves 
think. We can make our bodies move, or keep 
still, and we can keep from too much feeling. Our 
thoughts direct our natural desires to move and 
feel. In an animal, the feelings and movements 
direct the thoughts. When men let their feelings 
rule their thoughts, they are like animals. When 
the thoughts control the feelings and acts, we are 
men. If you get angry and cry, when you hurt 
your finger, then you are like an animal; but if 
you think about it and control your feelings, you 
are behaving like a strong and noble man. The 
thought part of the brain ought to rule all the 
rest. 
147. Sleep. Most of the brain does its work 
without our knowing it, but we know when we THE NERVES, SPINAL CORD, AND BRAIN 
91 
think. The thinking part of the brain gets tired, 
like any other part of the body. When it stops 
work, we are asleep. 
We must give the brain a rest in sleep, just as 
we must rest an arm or a leg. We ought to give 
it regular rest. Every night we ought to go to 
bed early. Then we shall be ready to get up early 
and shall feel like working. Boys and girls need 
nine or ten hours’ sleep each day. When they 
are grown, they need seven or eight hours’ sleep 
each day. 
The spinal cord and some parts of the brain 
must always stay awake to make the cells of the 
body eat and grow. When we are asleep, they 
must be wide awake, and must repair the worn-out 
parts. They do not seem to rest at all. If they 
rested for any length of time, then the lungs, heart, 
stomach and all other parts of the body would stop 
work, and we should die. But they really rest a part 
of the time. Like the heart, they act for a second, 
and then stop for a second. They seem to act all 
the time, but in all they rest half the time. 
148. Worry. The mind can do a great deal of 
work, if it gets good sleep. If a person gets 
enough sleep and rest, he cannot harm his mind 
by hard work. Sometimes the mind is troubled 
and worried over a danger or a loss. Then 92 
APPLIED PHYSIOLOGY 
it cannot rest, but soon wears itself out. Worry is 
far more tiresome than hard work. By an effort, 
we can keep from worrying. It never does us 
good to worry, and we ought to keep from it. 
149. Nervousness. The thoughts are able to 
rule all the rest of the mind. They can keep us 
from feeling ill-tempered when we cannot have our 
own way. Sometimes a little unpleasant feeling 
makes us very unhappy, and keeps us from think- 
ing about our work. A little noise or pain keeps 
some children from study, while others can bear 
a great deal without being disturbed by it. Some 
persons jump at a little noise, and are afraid of 
a tiny bug or mouse. This is because their feel- 
ings rule their thoughts. Such persons are called 
nervous. 
A nervous person is very uncomfortable and 
makes others so too. Yet any one can get over the 
habit of being nervous, if he will try. You ought 
not to laugh at a nervous person if he is afraid 
of some little thing while you are not. You should 
help him to get over his nervousness and to become 
brave. 
150. Fear. Some persons are always brave. In 
danger they calmly stop to think, and then know 
how to save themselves. A timid person does not 
think, but rushes where his feelings lead. When THE NERVES, SPINAL CORD, AND BRAIN 
93 
a crowd is in danger, all will rush to do one thing. 
All will run for a door, and perhaps tread on one 
another. Then some one will surely be hurt. At 
a fire, or in any other danger, you should always 
stop to think how to act. If you rush with the 
crowd, you may be hurt. You will be more likely 
to be safe, if you stay away from them. Then, if 
help comes, you will be able to receive it. Besides, 
if you are cool and brave, you will help others 
around you to be brave too. 
151. Fire drill. —ln schools the children are 
taught how to go out of the building when there is 
a fire. A bell is struck when the children do not 
expect it. Then every child must leave his seat at 
once and march out of the building. The bell is 
struck every few days. Then, when the bell really 
sounds for a fire, the children know how to march 
out quickly, and so they learn to be brave. 
By training we can learn to be brave at all times. 
We fear many harmless things, and in many cases 
do not fear real dangers. We are liable to be hurt 
at any time. We are more liable to be hurt by a 
horse when we are out driving than we are by the 
dark. Yet we do not fear the horse, while some do 
fear the dark. We ought to learn to think, so as to 
control our fear. 
Some are afraid of the dark, some are frightened 94 
APPLIED PHYSIOLOGY 
by ghost stories, and others expect to see a wild 
animal jump from behind every bush. No one 
fears these things unless he has been told about 
them. We ought to be careful not to tell children 
of these things. We ought to teach them to con- 
trol their fear. 
152. Habit. After we have thought about a 
thing a few times, its hold on our memory becomes 
strong, and leads us to think about it often. When 
we have done a thing a few times, we are likely to 
do it again without knowing it. We call this doing 
things over again habit. When we once form a 
habit, we find it very hard to break. We can form 
habits of doing right or of doing wrong. We can 
get into the habit of swearing or of drinking by 
doing these things a few times. Then we shall do 
these things when we do not want to. When a 
drinker begins, he does not expect to keep on 
drinking. But his habit makes him drink, and he 
cannot help it. We should be careful not to do 
bad things, for we easily form the habit of doing 
them. 
153. Good habits. —We can form habits of doing 
right. We can speak kindly and be generous. 
Then we shall do these things as easily as others 
get cross. After a person has tried to do good a 
few times, he will find it much easier to do good. THE NERVES, SPINAL CORD, AND BRAIN 
95 
Then he will speak kindly and give generously just 
as easily as others get angry and keep their good 
things to themselves. 
154. Alcohol takes away thought. Alcohol affects 
and weakens the cells of the brain sooner than it 
does those of any other part of the body. It first 
makes the thought cells weak. Then a person does 
not think how he acts. He lights his pipe in the 
barn and throws the match in the hay. He drives 
his horse on a run through a crowded street. He 
swears and uses bad language. He gets angry at 
little things and wants to fight. He seems to think 
of himself, and of no one else. He is happy, for 
he does not think of the bad effects of the drink. 
He has a good time, and does not care for its 
cost. He likes to drink, because it makes him feel 
happy. 
155. Alcohol spoils motion. Some cells of the 
brain cause the arms and legs, and all other parts 
of the body, to move. Alcohol next makes these 
weak. Then a person cannot move his legs right, 
but he staggers when he walks. He cannot carry 
a full cup to his lips. His hands tremble, and he 
cannot take care of himself. He is now really 
drunk. 
156. Alcohol takes away feeling. After a man is 
drunk, he loses the sense of feeling. He does not 96 
APPLIED PHYSIOLOGY 
feel cuts and blows. Because he does not feel tired, 
he feels very strong. He often sees two things for 
one, and hears strange noises. The whole brain at 
last gets weak, and cannot act. Then the drinker 
lies down in a drunken sleep, and cannot be waked 
up. Some die in this state. 
157. Insanity. When the brain is misused by 
alcohol for some time, it cannot get over it. Then 
the person becomes insane. Drink sends more per- 
sons to the insane asylum than all other causes put 
together. 
158. Delirium tremens. —lf a drinker gets hurt, 
or becomes sick, he sometimes has terrible dreams. 
In them he sees dirty and savage animals coming 
to harm him. These dreams seem very real to 
him, and he cries out in his fright. This is called 
delirium tremens. A person is liable to die from it. 
159. Alcohol harms a drinker’s children. The 
children of drinkers are apt to be weak in body and 
mind. A drinker hurts his children even more 
than he hurts himself. They are liable to catch 
diseases, and are often cross and nervous, or weak- 
minded. It is a terrible thing for a man to make 
his children weak and nervous. 
160. Other bad things about drink. There are 
many other terrible things about drink, besides the 
harm it does a man’s body. Many a man has THE NERVES, SPINAL CORD, AND BRAIN 
97 
made himself drunk so as to steal or kill. No man 
can drink long without becoming a worse man for 
it. Men will not trust him, and he loses the respect 
of his friends. 
Making strong drink takes thousands of men 
away from good work. They might work at build- 
ing houses, or raising grain, or teaching school. 
As it is, their work is wasted. 
A great deal of money is wasted on strong drink. 
All the mines of the world cannot produce enough 
gold and silver to pay the drink bill. The people 
of the United States pay more for strong drink 
than for bread. 
The price of two or three drinks a day would 
amount to enough, in ten years, to buy a small 
home. 
The cost of strong drink is made much greater 
it we count the cost of jails and insane asylums. 
Over one half of all crimes and cases of insanity are 
caused by strong drink. 
We must also add the misery and suffering of 
most children of drunken fathers. This loss cannot 
be counted in money. Numbers of children be- 
come truants from school and learn theft and false- 
hoods from lack of a father’s care. When all the 
cost is counted, nothing will be found so expensive 
as strong drink. 98 
APPLIED PHYSIOLOGY 
On the other hand, what do people get for their 
money and suffering? -They get only a little 
pleasure, and then they are ashamed of it. Men 
use strong drink only because they like it more 
than they dislike its bad effects. 
Since drink does a great deal of harm, with no 
good to any one, it is right to make laws to control 
its sale. 
161. How tobacco affects the brain. Some men 
smoke to make themselves think, and some to keep 
themselves from thinking. Now, smoking cannot 
do both things. It really makes the brain less able 
to think, for it weakens the whole body. A school- 
boy’s brain will surely be harmed if he uses tobacco 
at all. 
WHAT WE HAVE LEARNED 
1. The mind makes all the cells of the body work 
together. 
2. Tiny nerve threads carry messages from the 
mind to the cells. 
3. Most of the nerves begin at the spinal cord in 
the backbone. 
4. The mind in the spinal cord tells the cells to 
eat and grow. It tells the arteries how much 
blood to carry to the cells. 
5. The cells tell the spinal cord if they need food, THE NERVES, SPINAL CORD, AND BRAIN 
99 
or if something suddenly hurts them. The 
spinal cord sends word to snatch the part 
from danger. 
6. Nerves carry to the brain news of sight, sound, 
odor, taste, and touch. 
7. The brain sends word to the muscles to move 
the arms, the legs, and the rest of the body. 
8. The brain thinks. 
9. The brain stores up all its messages; these 
make memory and knowledge. 
10. The thought part of the brain can control the 
feelings and the movements of the body. 
11. Alcohol is more harmful to the brain than to 
any other part of the body. CHAPTER XIII 
THE SENSES 
162. A man has five ways of knowing about 
things outside of the body. He can feel, see, hear, 
smell, and taste. 
163. Feeling. Nerves go to nearly every cell in 
the body. They carry news to the brain when 
anything touches them. The news produces a 
feeling. Feelings are of three kinds: 
First, when anything touches the cells with- 
out harming them, we feel a touch. We feel a 
touch by nerves in the skin. Those in the ends of 
the fingers and tongue can feel the best. Those 
upon the back give but little feeling. 
Touch tells whether anything is hard, or rough, or 
round, or square, or has other qualities and shapes. 
Second., when anything touches the bare nerves 
or hurts the cells, we feel a pain. We can feel a 
pain anywhere in the body. Pain tells us if we are 
being harmed. If we had no feeling of pain, we 
might be killed before we could know of our 
danger. Pain warns us away from danger. 
100 THE SENSES 
Third, we can feel heat and cold. Anything 
very hot or very cold, however, makes only a pain 
and gives no feeling either of cold or of heat. 
164. Sight. —We see with our eyes. An eye is a 
hollow ball. In its front is a clear window. Behind 
The human eye. 
a bony case of the eye. 
b muscle to move the eye. 
c and d coverings of the eye. 
e lining or seeing part of the eye. 
f eyelid. g colored curtain or iris. 
h and i clear windows of the eye. 
the window is a round curtain with a round hole in 
its middle. When we speak of the color of the 
eye, we mean the color of this curtain. Light passes 
through the hole in the curtain and falls upon some 
nerves in the back of the eyeballs. There it forms 
a picture like a photograph. The nerves carry this 
picture to the brain, and we see it. 102 
APPLIED PHYSIOLOGY 
165. Movements of the eyes. —We can turn our 
eyes so as to look in any direction. Sometimes 
a person has one eye turned sidewise. Such a 
person is cross-eyed, and sees out of only one eye 
at a time. Glasses may help the eyes, but some- 
times a surgeon has to cut a tiny muscle. 
166. Coverings of the eyes. The eyeballs lie in 
a bony case, upon a soft bed of fat. In front each 
is covered with two lids. We can shut the lids to 
keep out dust and insects. When we are sleepy, 
they come together and cover the eyes. Little hairs 
at their edges help to keep out the dust. 
Sometimes the lids get sore or some dust gets 
under them. Then the eye smarts or itches, and 
we want to rub it; but this may grind the dirt in 
deeper. When you get something in your eye, 
hold your handkerchief lightly over the eye to keep 
it still, but do not rub it. Then get some one else 
to lift your eyelid and pick out the dust with a soft 
handkerchief. If you cannot get help, lift the lid 
by the eyelashes; blow your nose hard, and the 
tears will wash the dust away. 
167. Tears. Clear salt water is always running 
over the eyes and down a tube into the nose. This 
makes the tears. The tears wash away dust and 
dirt. When something is in your eye, they flow 
faster, so as to wash it away sooner. THE SENSES 
103 
When you feel unhappy, the tears flow faster than 
the tube can carry them into the nose. Then some 
run over upon the cheeks. When they do this, 
you are crying. 
168. How to use the eyes. The eyes can become 
tired and painful. Facing a bright light while 
working makes the eyes and head ache, and soon 
one cannot see well. Shade your eyes while you 
study. A cap can be used as a shade if you cannot 
get anything else. Never try to look at the sun or 
a very bright fire. 
You should have the light at one side or behind 
you. The light should be steady. Reading in a 
dim light will harm the eyes. 
169. Near sight. Some persons cannot read 
unless they hold the book very near their eyes. 
Such persons are said to be nearsighted. It is 
very hard for nearsighted persons to see well, 
and they ought to wear glasses all the time. 
170. Far sight. Old persons cannot see so well 
near by as they can far off. They are then said 
to be farsighted. They, too, can be helped by 
glasses. Old people almost always have to wear 
glasses. 
171. Alcohol and the eyes. Alcohol makes the 
eyes red. It weakens the eyes and may produce 
blindness. A drunken person often sees double. 104 
APPLIED PHYSIOLOGY 
172. Tobacco causes dimness of sight and some- 
times produces blindness. 
173. Hearing. —We hear with the ears. Sound 
is made by waves in the air. The part of the 
ear on the outside of the head catches the air 
waves and throws them inside the ear. These 
a outer ear. 
b drum head. 
c d and e bones to carry sound to inner ear. 
Diagram of the ear 
/g and h inner ear. 
i tube to the mouth. 
j middle ear. 
air waves strike against a little drum. Three little 
bones then carry the waves on to nerves farther 
inside the head. Animals can turn their ears and 
catch sound from any direction. 
174. Ear wax. Wax is formed just inside the 
ear. It keeps flies and insects from crawling into 
the ear. Boys in swimming sometimes get cold 
water into their ears. This may make them have 
an earache. THE SENSES 
105 
175. How the throat affects the ear. —An air tube 
runs from the inside of the ear to the mouth. 
Sometimes when you blow your nose, you blow 
air into the ear. This makes you partly deaf and 
you hear a roaring in your ears. 
Sometimes when you have a cold in your throat, 
this little tube is stopped. Then your ear may 
ache and may even discharge matter. This may 
make you somewhat deaf. Earache and deafness 
are most often due to a cold in the throat and a 
stoppage of this tube. 
Many little boys and girls are deaf and do not 
know it. They cannot hear the teacher well, and 
sometimes the teacher thinks they are bad or care- 
less because they do not answer. 
176. Care of the ears. Very loud noises may 
harm the ear and make you deaf. When you 
expect a very loud noise, put your fingers in your 
ears to shut out the sound. 
Boxing the ears may break their tiny drums 
and make you deaf. 
Do not get cold water in your ear. This may 
cause an earache and make you deaf. If you get 
water in your ear while you are in swimming, 
turn your head to one side and shake it. This 
will get the water out. 
Do not put cotton or anything else into your ears. APPLIED PHYSIOLOGY 
177. Smell. —We smell with the nose. Some 
things give out a vapor to the air. When we 
draw the air into the nose, this vapor touches the 
nerves, and we perceive a smell. The nerves are 
high up in the nose. In order to perceive smell 
clearly, we sniff the air far up the nose. 
178. Use of smell. Bad air and spoiled food 
smell bad. A bad smell is the sign of something 
spoiled. The sense of smell tells us when food 
or air is unfit for use. Some people try to hide 
a bad smell with perfumery. To do this only 
makes the danger greater, for then the smell does 
not tell us of the danger of food or air. 
Some animals can smell much better than a 
man. A dog will smell the track of a wild animal 
hours after it is made. Savages can smell much 
better than civilized men. 
179. Taste.—We taste with the tongue. Dry 
food has no taste, but it must first dissolve in 
the mouth. Spoiled food tastes bad. Bad-tasting 
food is not fit to eat. Taste tells us whether food 
is good or bad. 
We can learn to like the taste of harmful things. 
At first no one likes tobacco or strong drink, but 
the liking is formed the more one uses these. 
We ought to be careful not to begin to use 
such things. THE SENSES 
Alcohol and tobacco burn the mouth and harm 
the taste. Food does not taste so good and we 
may eat spoiled food and not know it. 
WHAT WE HAVE LEARNED 
1. We can feel in every part of the body, but 
mostly in the ends of the fingers. 
2. Light makes a picture upon the nerves inside 
of the eye. 
3. If the eyes ache, the light should be softened 
or the position of the book or work changed, 
or else the eyes should be rested. 
4. Sound in the air goes into the ear and strikes 
against a drum. Bones then carry the sound 
to the ear nerves. 
5. Air snuffed up the nose gives the sense of 
smell. Smell tells us if the air or food is 
fit for use. 
6. Taste tells us whether food is fit for use. Men 
can learn to like the taste of wrong things 
like tobacco or alcohol. Bones of the 
Head and Face. 
■Bones of Vertebral Column, 
Clavicle, or Collar Bone. 
■Scapula, or Shoulder Bone, 
Sternum, or Breastbone 
Ribs. 
Humerus. 
Ulna. 
Pelvis, including (S.) Sacrum and 
(Cx.) Coccyx. 
--Radius. 
Carpus, or Wrist. Eight 
small bones. 
Hand. Nineteen bones. 
-Femur. 
Patella. 
Tibia, or Large Bone of Fore Leg. 
Fibula, or small Splint Bone of Leg. 
Tarsus, or Ankle and Heel Bones (7) 
Bones of foot. Nineteen bones. 
The Human Skeleton, showing position of bones. 
108 CHAPTER XIV 
BONES AND JOINTS 
180. Bones make the body stiff and strong, and 
give it shape. Long bones reach through the 
arms and legs, and little bones reach down the fin- 
gers and toes. Rounded plates of bone form the 
head, and a pile of bony rings makes up the back- 
bone. Each bone is built to fit exactly into its 
own place and to do its own work. In all there 
are over two hundred bones in the body. They 
form one seventh of its weight. 
181. Form of bones. A bone is not like a solid 
piece of timber, but is hollow like the frame of a 
bicycle. This makes it strong and light. At its 
ends a bone is like a hard sponge covered with a 
firm shell. This makes it too strong to be easily 
crushed, and keeps it light. 
A bone grows like any other part of the body. 
It is made of living cells like woven threads. Lime 
is mixed among the cells, and makes them stiff like 
starch among the threads of a linen collar. Blood 
tubes go through every part of the bone so as to 
109 110 
APPLIED PHYSIOLOGY 
feed the cells. The living cells form one third of 
the bone, while the lime forms two thirds. 
182. Broken bones. Bones are very hard, and 
yet they can bend a little without breaking. Most 
of them are curved a little, and so they will spring 
instead of breaking when they are pressed hard. 
But sometimes they break. Then a person must 
wear a splint and bandage to keep the bones in 
place until they grow together again. The living 
cells will mend a bone in about a month. 
An old person’s bones are more tender than a 
child’s, and will not spring much without breaking. 
An old man is afraid of falling and breaking his 
bones, while a child falls a dozen times a day with- 
out danger. 
The bones of some children bend too easily. 
When they stand, the bones of their legs bend a 
little. After a while they grow in the crooked 
shape, and the child is bow-legged. 
183. Joints. Some bones are hinged upon each 
other. A bone hinge is a joint. The rings of the 
backbone are held together by very tough pads 
of flesh. Each pad lets the backbone bend only a 
little, but altogether they let us bend our backs in 
any direction. These pads are like rubber springs 
in a wagon, and keep our bodies from being jarred 
too much. BONES AND JOINTS 
111 
The finger and toe joints, the wrists and ankles, 
the elbows and the knees, bend back and forth like 
a hinge. Tough bands of flesh bind the bones 
together. The ends of the bones are rounded 
and smooth. They fit together and make perfect 
hinges. The joints are oiled by 
a fluid like the white of an egg. 
In old people this fluid sometimes 
dries up. Then the joints become 
stiff, and creak like a squeaking 
hinge. 
The shoulders and hips can be 
moved in every direction. The 
upper ends of the arm and leg 
bones are round like half a ball. 
They fit into cups on the shoul- 
der and hip bones. They are 
Hinge joint of the elbow. 
x humerus 
2 ulna 
very smooth, and are oiled like the hinge joints. 
The joints are made to work very smoothly and 
easily. 
184. Bones out of joint. When the ends of bones 
are torn away from each other, the bone is out of 
joint. Then the bone cannot be moved without 
great pain. It should be put back in place at once 
and kept there by splints and bandages. A person 
is less liable to have his joints out of place than he 
is to have his bones broken. APPLIED PHYSIOLOGY 
185. Sprains. Sometimes a joint is turned too 
much. This stretches the flesh around the joint, 
and makes it very tender and painful. This is a 
sprain. When you sprain a joint, you should put it 
in hot water for an hour or two. Then keep it 
still for a few days. 
186. Why bones and joints grow wrong. While 
bones and joints are growing they can be made to 
take any shape we please. They cannot be bent 
all at once, but if we hold them in one way much of 
the time, they will keep that shape. Some boys and 
girls sit with their backs bent forward and lean 
against the desk as if they were too lazy to sit up. 
When they grow up, they will be bent and round- 
shouldered. You should sit and stand straight. 
Then you will grow tall and straight and strong. 
A soldier has square shoulders and walks erect 
because he is drilled until his bones and joints grow 
in the proper shape. As you stand straight with 
your feet together, your two big toes, your two 
ankles, and your two knees should touch each 
other. 
If you wear tight shoes and press the toes out of 
shape, they will soon grow so. Nearly every one’s 
feet are out of shape from wearing short, pointed 
shoes. Your toes should be straight and not 
cramped by the shoe. If you wear pointed shoes, BONES AND JOINTS 
113 
you will harm your feet. It is better to have one’s 
feet useful, even if they are large, than to make 
them small and useless. 
WHAT WE HAVE LEARNED 
1. Bones make the body stiff, and give it form. 
2. Some bones are long, some round, and some flat. 
All are hard and springy. 
3. Some bones are hinged together. The hinge 
is a joint. 
4. The ends of bones in joints are rounded and 
smooth, and are oiled with a liquid like the 
white of an egg. 
5. Some bones are bound together by springy pads, 
as in the backbone. 
6. Bones can be broken. They will grow together 
again themselves. 
7. Joints can be put out of place; then we must 
put them back. 
8. If joints or bones are kept in wrong positions 
they will grow into bad shapes. Tight shoes 
deform the feet. The muscular system. 
114 CHAPTER XV 
MUSCLES 
187. Shape of muscles. Bones are covered with 
muscles. Muscles give shape to the body, and 
move it about. One half of the body consists of 
muscles. These are arranged in bundles, and each 
causes a bone to make one motion. There are over 
four hundred separate bundles of muscle in the body. 
One end of a muscle is large and round and is 
fast to a bone. The other end tapers to a strong 
string or tendon. The tendon passes over a joint, 
and becomes fast to another 
bone. You can easily feel 
the tendons in the wrist and 
behind the knee. 
A muscle is made of tiny 
strings. You can pick them 
apart until they are too fine 
to be seen with the eye. Each 
string is a living muscle cell. 
It is the largest kind of cell 
Muscle cells, cut across 
a muscle cell. 
b connective tissue binding the 
cells together. 
(X 200). 
in the body. You can see the fine strings in cooked 
meat. 116 
APPLIED PHYSIOLOGY 
188. How muscles act. A nerve runs from the 
brain, and touches every cell of the muscle. When 
we wish to move, the brain sends an order down 
the nerve. Then each mus- 
cle cell makes itself thicker 
and shorter. This pulls its 
ends together, and bends the 
joint. We can make muscle 
cells move when we wish to, 
but we cannot make any 
other kind of cell move. We 
make all our movements by 
A thin slice of a voluntary mus- 
cle, cut lengthwise (X 100). 
a muscle cell. 
b capillaries surrounding the cells. 
c connective tissue binding the 
cells together. 
means of our muscles. 
muscles. —ln a butcher’s shop you can see lean 
meat. This is the animal’s muscle. White and 
tough flesh divides the tender red meat into 
bundles. Each red bundle is a muscle. You will 
see how the muscle tapers to a string or tendon. 
The butcher often hangs up the meat by the ten- 
dons. You can see the muscles and tendons in a 
chicken’s leg or wing when it is being dressed for 
dinner. 
189. Where you can see 
Roll up your sleeve to see your own muscles. 
Shut your hand tight. You will see little rolls 
under your skin, just below the elbow. Each roll 
is a muscle. You can feel them get hard when MUSCLES 
you shut your hand. You can feel their tendons 
as they cross the wrist. 
Open your hand wide. You can see and feel 
the tendons of the fingers upon the back of the 
hand. These tendons come from muscles on the 
back of the arm. You can feel the bundles of 
these muscles when they open the fingers. There 
are no muscles in the fingers, but all are in the 
hand or arm. You cannot open your hand so 
strongly as you can close it. 
190. Strength, of muscle. —By using a muscle you 
can make it grow larger and stronger. If you do 
not use your muscles they will be small and weak. 
Children ought to use their muscles in some way, 
but if they use them too much, they will be tired 
out. Then they will grow weaker instead of 
stronger. Lifting heavy weights, or running long 
distances, tires out the muscles, and makes them 
weaker. Small boys sometimes try to lift as much 
as the big boys. This may do their muscles great 
harm. 
191. Round shoulders. The muscles hold up the 
back and head, and keep us straight when we sit 
or stand. A lazy boy will not use his muscles to 
hold himself up, but will lean against something. 
He will let his shoulders fall, and will sit down in 
a heap. Sometimes he is made to wear shoulder 118 
APPLIED PHYSIOLOGY 
braces to keep his shoulders back. This gives the 
muscles nothing to do, and so they grow weaker 
than ever. The best thing to do for round shoul- 
ders is to make the boy sit and stand straight, like 
a soldier. Then he will use his muscles until they 
are strong enough to hold his shoulders back. 
192. How exercise makes the body healthy. 
When you use your muscles, you become warmer. 
Your face will be red, for the heart sends, more 
blood to the working muscle cells. You will be 
short of breath, for the cells need more air. You 
will eat more, for your food is used up. Your 
muscles are like an engine. They get their power 
from burning food in their own cells. When they 
work they need to use more food and air. So 
working a muscle makes us eat more and breathe 
deeper. The blood flows faster, and we feel better 
all over. The muscle itself grows much larger and 
stronger. 
If we sit still all day, the fires in our bodies burn 
low and get clogged with ashes. We feel dull and 
sleepy. If we run about for a few minutes, we 
shall breathe deeply. The fires will burn brighter. 
Our brains will be clearer, and we shall feel like 
work again. Boys and girls need to use their 
muscles when they go to school. Games and 
play will make you get your lessons sooner. MUSCLES 
119 
193. How to use the muscles. You should use 
your muscles to make yourself healthy, and not 
for the sake of growing strong. Some very strong 
men are not well, and some men with small mus- 
cles are very healthy. Some boys have strong 
muscles because their fathers had strong muscles 
before them. Strength of muscle does not make 
a man. 
You ought to have healthy muscles. Then your 
whole bodies will be healthy, and you can do a great 
deal of work. You ought to learn how to use your 
muscles rather than how to make them strong. An 
awkward and bashful boy may be very strong, but 
he cannot use his muscles. A boy is graceful 
because he can use them. 
The best way to use your muscles is in doing 
something useful. You can help your mother in 
the house and your father at the barn. You can 
run errands. You can learn to use carpenter’s 
tools or to plant a garden. Then you will get 
exercise and not know it. You will also be learning 
something useful. 
Play is also needed. Work gets tiresome, and 
you will not want to use your muscles. Play is bad 
when it takes you from your work or when you 
hurt yourself trying to beat somebody. 
194. Alcohol and the muscles. Men use alcohol APPLIED PHYSIOLOGY 
120 
to make themselves strong. It dulls their weak 
feelings, and then they think themselves strong. 
They are really weaker. The alcohol hinders diges- 
tion and keeps food from the cells. Then the fires 
in the body burn low, and there is little strength. 
Alcohol sometimes causes muscle cells to change 
to fat. This weakens the muscles. 
Men sometimes have to do hard work in cold 
countries; and at other times they must make long 
marches across hot deserts. Neither the Eskimos 
in the cold north, nor the Arabs in the hot desert, 
use strong drink. Alcohol does not help a man in 
either place. It really weakens the body. The 
government used to give out liquor to its soldiers; 
but soldiers can do more work and have better 
health without liquor and it is no longer given out. 
A few years ago men were ashamed to refuse to 
drink. Even when a new church building was 
raised, rum was bought by the church and given to 
the workmen. Farmers used to give their men a 
jug of rum when they went to work. Farm hands 
would not work without it. 
Now all this has changed. Men do not want 
drinkers to work for them. A railroad company 
will discharge a man at once if he is known to 
drink at all. A man can now refuse to drink any- 
where and men will not think any less of him. MUSCLES 
121 
195. Tobacco poisons the muscle cells and makes 
them weak. At first it makes boys too sick to move. 
It always poisons the cells even if they do not feel 
sick. 
196. A long life. A man’s body is built to last 
eighty years, but only a few live so long. If you are 
careful in your eating and drinking, if you breathe 
pure air, and if you use your muscles, your body 
will be healthy and will last the eighty years and 
more. All through your life you will be strong and 
able to do good work. 
WHAT WE HAVE LEARNED 
1. Muscles cover the bones and move the body. 
2. Muscle is lean meat. It is made of bundles of 
cells like strings. Nerves from the brain 
touch each cell. 
3. Each muscle is fast to a bone. It becomes 
a small string or tendon at the other end. 
The tendon crosses a joint and is fast to 
another bone. 
4. When we wish to move, the brain sends an 
order to the muscle cells to make themselves 
thicker and shorter and so bend the joint. 
5. You can feel the muscles and tendons in the 
arm and wrist. 122 
APPLIED PHYSIOLOGY 
6. Muscle work makes us breathe deeper, and eat 
more food. It makes the blood flow faster. 
So it makes our whole bodies more healthy. 
7. Every one ought to use his muscles some part of 
the day. 
8. Alcohol and tobacco lessen the strength of the 
muscles. INDEX 
Alcohol and heat, 72. 
heredity, 96. 
insanity, 96. 
Jamaica ginger, 4 7 
kidneys, 81. 
liver, 46. 
lungs, 70. 
medicine, 47. 
money waste, 97. 
motion, 95. 
muscles, 119. 
sickness, 82. 
skin, 81. 
stomach, 45. 
strength, 56, 120. 
strong drink, 40. 
suffering, 97. 
taste, 107. 
thirst, 44. 
thought, 95. 
Alcohol, use of, 39. 
Ameba, 7, 52. 
Appetite, 27. 
Abdomen, 60. 
Adam’s apple, 68. 
Air, 59, 65. 
Albumin, 10, 17, 18, 49. 
Alcohol, 38. 
Alcohol and arteries, 56. 
biliousness, 46. 
bitters, 46. 
blood, 55. 
brain, 95. 
breathing, 70. 
burning, 69. 
catching cold, 71. 
character, 97. 
cooking, 47. 
delirium tremens, 
96- 
digestion, 46. 
eyes, 103. 
feeling, 95. 
habit, 44. 
heart, 56. 124 
INDEX 
Arteries, 51, 55. 
Ashes, 12, 62, 78. 
Cells, 8. 
Cells, blood tubes of, 51. 
breathing of, 61. 
burning of, 62. 
composition of, 11, 
food of, 13, 55, 
messages of, 85, 100 
Cells of blood, 49, 
bone, 109. 
brain, 88. 
epithelium, 76, 
muscle, 115. 
skin, 75. 
spinal cord, 86. 
yeast plant, 38. 
Cheese, 23. 
Chest, 60. 
Chewing, 14. 
Chewing gum, 34. 
Chewing tobacco, 33. 
Cider, 42. 
Cigarettes, 34. 
Cigars, 34. 
Clams, 24. 
Clot, 49, 
Clothes, 63. 
Coated tongue, 20. 
Coffee, 27. 
Cold, feelings of, roi. 
Connective tissue, 9, 
Bathing, 78. 
Beer, 43. 
Bile, 18. 
Biliousness, 20. 
Biscuit, 24. 
Bitters, 46. 
Bleeding, 49, 52. 
Blood, 13, 19, 49. 
Bones, 109. 
Bowels, 18. 
Bowlegs, no. 
Brain, 88. 
Brandy, 44. 
Bread, 24, 38, 
Breathing, 59, 60, 67. 
Broken bones, no. 
Burning, 61, 118. 
Butter, 23. 
Cake, 24. 
Candy, 29. 
Canning fruit, 37, 
Capillaries, 51, 61. 
Catching cold, 54, 64, 71 INDEX 
125 
Cooking, 13. 
Cotton, 63. 
Cream, 23. 
Cross-eyes, 102. 
Cuts, 53. 
Far sight, 103. 
Fat, 11, 18, 25, 49, 92. 
Fear, 92. 
Feeling, 100. 
Fermentation, 37. 
Fire drill, 93. 
Fish, 24. 
Flannel, 63. 
Food, 12, 13, 19, 23. 
Fresh air, 67. 
Fruit, 25. 
Fur, 64. 
Deafness, 105. 
Delirium tremens, 96. 
Diaphragm, 60. 
Digestion, 13. 
Diphtheria, 53. 
Dirt in eye, 102. 
Disease germs, 53, 66, 81 
Distillation, 43. 
Gastric juice, 17. 
Gelatine, 11. 
Gizzard, 14. 
Glue, 11. 
Good habits, 94. 
Grain, 24. 
Ear, 104. 
Ear wax, 104. 
Eating, 20. 
Egg, 23. 
Epidermis, 76. 
Epithelium, 75. 
Eustachian tube, 105. 
Exercise, 118. 
Eye, 101, 
Eyeball, 101. 
Eyelids, 102. 
Habit, 94. 
Hair, 76. 
Hair dyes, 77. 
Hair oil, 77. 
Healing, 53. 126 
INDEX 
Hearing, 104. 
Heart, 50. 
Heart beat, 50, 55. 
Heat, 62, 101, 
Heating houses, 65. 
Hunger, 29. 
Matter, 54. 
Meal, 24. 
Meat, 24, 116. 
Memory, 89. 
Microscope, 8, 
Milk, 23. 
Mind, 9, 84, 88. 
Minerals, n, 19, 49 
Motion, 88. 
Motor nerves, 85. 
Mouth, 14. 
Muscles, 115. 
Intemperance, 29. 
Intestine, 18. 
Iron, 12. 
Jamaica ginger, 47. 
Joints, no. 
Nails, 76. 
Near sight, 103. 
Nerve messages, 85 
Nerves, 84, 116. 
Nervousness, 92. 
Nicotine, 31. 
Night air, 67. 
Kidneys, 62, 78. 
Knowledge, 89. 
Lead, 27, 
Life, 12. 
Lime, 12. 
Linen, 64. 
Liver, 18, 19. 
Lungs, 60. 
Oatmeal, 24. 
Oysters, 24. INDEX 
127 
Sleep, 90. 
Slops, 80. 
Smell, 106. 
Smoke, 62. 
Smoking, 34. 
Snuff, 33. 
Soda, 12. 
Spinal cord, 86. 
Spitting, 32. 
Sprains, 112. 
Starch, 11, 14, 18, 25. 
Steam engine, 62. 
Stockings, 64. 
Stomach, 17. 
Strength, 117. 
Strong drink, 40. 
Sugar, 11, 14, 18, 25, 28, 38, 
42, 49. 
Swallowing, 15. 
Sweat, 63, 78. 
Sweetbread, 18. 
Pain, 100. 
Pancakes, 24. 
Pancreatic juice, 18. 
Perspiration, 78. 
Pie, 29. 
Poisons, 19. 
Potash, 12. 
Potatoes, 25. 
Pulse, 51. 
Pus, 54. 
Red blood cells 49, 54, 61. 
Reflex action, 86. 
Root beer, 43. 
Round shoulders, 112, 117. 
Rubbers, 64. 
Saliva, 14. 
Salt, 12, 26. 
Senses, 88, 100. 
Sensory nerves, 85 
Sewers 81. 
Sick room, 66. 
Sight, 101. 
Skin, 63, 75. 
Taste, 28, 106. 
Tea, 27. 
Tears, 102. 
Teeth, 14. 
Tendon, 115. 
Thinking, 89. 128 
INDEX 
Tight shoes, 112. 
Tobacco, 31. 
Tobacco and brain, 98. 
breathing, 72, 
chewing, 33. 
children, 33. 
digestion, 33. 
eyes, 104. 
habit, 34, 
heart, 57. 
muscle, 121. 
strength, 32. 
taste, 107. 
teeth, 32. 
Tongue, 15. 
Toothpick, 15. 
Touch, 100. 
Typhoid fever, 53. 
Ventilation, 65. 
Vinegar, 39. 
Voice, 68. 
Warmth, feeling of, 63. 
Washing clothes, 80. 
Waste of body, 75, 78. 
Water, 10, 19, 26, 49. 
Wells, 26, 81. 
Whisky, 44, 71. 
White blood cells, 49, 53 
Windpipe, 15, 59. 
Wine, 42. 
Wool, 63. 
Words, 68. 
Working of fruit, 37. 
Worry, 91. 
Vegetables, 25, 
Veins, 52. 
Yeast, 24, 38, 42.