Applied Physiology, Including the Effects of Alcohol and Narcotics

CHAPTER I. Cells

CELLS

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.

=1. The simplest animal.=--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 part of its body like a leg and move by rolling the rest of its body into the leg. It can do some things 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.

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.]

=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 that it is composed of little lumps of jelly. Each little lump looks like an ameba. We call each lump a cell. The cells make up the finger.

=3. What cells do.=--Each cell acts much as an ameba does. From the blood it gets food and air 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 separate 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

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 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 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 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 minerals in the body. When flesh is burned they are left as ashes. Salt, lime, iron, soda, and potash are all found in the body.

a, of potato. b, of corn.]

Everything in the body is either water, albumin, fat, sugar, or minerals. These things are also our food. We eat them mixed together in bread, meat, eggs, milk, and other foods.

=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 III. Digestion of Food in the Mouth

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 growing. 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 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 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.

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