First Book in Physiology and Hygiene

CHAPTER XX

1. The Muscles.—Where do people obtain the beefsteak and the mutton-chops which they eat for breakfast? From the butcher, you will say; and the butcher gets them from the sheep and cattle which he kills. If you will clasp your arm you will notice that the bones are covered by a soft substance, the flesh. When the skin of an animal has been taken off, we can see that some of the flesh is white or yellow and some of it is red. The white or yellow flesh is fat. The red flesh is lean meat, and it is composed of muscles.

2. The Number of Muscles.—We have about five hundred different muscles in the body. They are arranged in such a way as to cover the bones and make the body round and beautiful. They are of different forms and sizes.

3. With a very few exceptions the muscles are arranged in pairs; that is, we have two alike of each form and size, one for each side of the body.

4. How a Muscle is Formed.—If you will examine a piece of corned or salted beef which has been well boiled, you will notice that it seems to be made up of bundles of small fibres or threads of flesh. With a little care you can pick one of the small fibres into fine threads. Now, if you look at one of these under a microscope you find that it is made of still finer fibres, which are much smaller than the threads of a spider's web. One of these smallest threads is called a muscular fibre. Many thousands of muscular fibres are required to make a muscle.

MUSCULAR FIBRES.

5. Most of the muscles are made fast to the bones. Generally, one end is attached to one bone, and the other to another bone. Sometimes one end is made fast to a bone and the other to the skin or to other muscles.

6. The Tendons.—Many of the muscles are not joined to the bones directly, but are made fast to them by means of firm cords called tendons. If you will place the thumb of your left hand upon the wrist of the right hand, and then work the fingers of the right hand, you may feel these cords moving underneath the skin.

7. What the Muscles Do.—With the left hand grasp the right arm just in front of the elbow. Now shut the right hand tightly. Now open it. Repeat several times. The left hand feels something moving in the flesh. The motion is caused by the working of the muscles, which shorten and harden when they act.

8. All the movements of the body are made by means of muscles. When we move our hands, even when we close the mouth or the eyes, or make a wry face, we use the muscles. We could not speak, laugh, sing, or breathe without muscles.

9. Self-acting Muscles.—Did you ever have a fit of sneezing or hiccoughing? If you ever did, very likely you tried hard to stop but could not. Do you know why one cannot always stop sneezing or hiccoughing when he desires to do so? It is because there are certain muscles in the body which do not act simply when we wish them to act, but when it is necessary that they should. The muscles which act when we sneeze or hiccough are of this kind. The arm and the hand do not act unless we wish them to do so. Suppose it were the same with the heart. We should have to stay awake all the while to keep it going, because it would not act when we were asleep. The same is true of our breathing. We breathe when we are asleep as well as when we are awake, because the breathing muscles work even when we do not think about them.

10. The stomach, the intestines, the blood-vessels, and many other organs within the body have this kind of muscles. The work of these self-acting muscles is very wonderful indeed. Without it we could not live a moment. This knowledge should lead us to consider how dependent we are, each moment of our lives, upon the delicate machinery by which the most important work of our bodies is performed, and how particular we should be to keep it in good order by taking proper care of ourselves.

1. The flesh, or lean meat, is composed of muscles.

2. There are five hundred muscles in the body.

3. Muscles are composed of many small threads called muscular fibres.

4. Many of the muscles are joined to the bones by strong white cords called tendons.

5. Muscular fibres can contract so as to lessen their length. It is in this way that the muscles perform their work.

6. All bodily motions are due to the action of the muscles.

7. Most of the muscles act only when we wish them to do so. Some muscles, however, act when it is necessary for them to do so, whether we will that they should act or not, and when we are asleep as well as when we are awake.

CHAPTER XXI

1. How to Make the Muscles Strong.—With which hand can you lift the more? with the right hand or with the left? Why do you think you can lift more with the right hand than with the left? A blacksmith swings a heavy hammer with his right arm, and that arm becomes very large and strong. If we wish our muscles to grow large and strong, so that our bodies will be healthy and vigorous, we must take plenty of exercise.

2. Effects of Idleness.—If a boy should carry one hand in his pocket all the time, and use only the other hand and arm, the idle arm would become small and weak, while the other would grow large and strong. Any part of the body which is not used will after a time become weak. Little boys and girls who do not take plenty of exercise are likely to be pale and puny. It is important that we should take the proper amount of exercise every day, just as we take our food and drink every day.

3. Healthful Exercise.—Some kinds of play, and almost all kinds of work which children have to do, are good ways of taking exercise. A very good kind of exercise for little boys and girls is that found in running errands or doing chores about the house.

4. Food and Strength.—A great part of our food goes to nourish the muscles. Some foods make us strong, while others do not. Plain foods, such as bread, meat, potatoes, and milk, are good for the muscles; but cakes and pies, and things which are not food, such as mustard, pepper, and spices, do not give us strength, and are likely to do us harm.

5. Over-Exertion.—We ought not to exert ourselves too much in lifting heavy weights, or trying to do things which are too hard for us. Sometimes the muscles are permanently injured in this way.

6. The Clothing.—We ought not to wear our clothing so tight as to press hard upon any part of the body. If we do, it will cause the muscles of that part to become weak. If the clothing is worn tight about the waist, great mischief is often done. The lungs cannot expand properly, the stomach and liver are pressed out of shape, and the internal organs are crowded out of their proper places.

7. Tight Shoes.—People are often made very lame from wearing tight shoes. Their muscles cannot act properly, and their feet grow out of shape.

FOOT OF CHINESE WOMAN.

8. In China, it is fashionable for rich ladies to have small feet, and they tie them up in cloths so that they cannot grow. The foot is squeezed out of shape. Here is a picture of a foot which has been treated in this way. It does not look much like a human foot, does it? A woman who has such feet finds it so difficult to walk that she has to be carried about much of the time. Do you not think it is very wrong and foolish to treat the feet so badly? You will say, "Yes;" but the Chinese woman thinks it is a great deal worse to lace the clothing tight about the body so as to make the waist small.

9. Effects of Alcohol upon the Muscles.—When an intemperate man takes a glass of strong drink, it makes him feel strong; but when he tries to lift, or to do any kind of hard work, he cannot lift so much nor work so hard as he could have done without the liquor. This is because alcohol poisons the muscles and makes them weak.

10. Effects of Drunkenness.—When a man has become addicted to strong drink, his muscles become partly paralyzed, so that he cannot walk as steadily or speak as readily or as clearly as before. His fingers are clumsy, and his movements uncertain. If he is an artist or a jeweller, he cannot do as fine work as when he is sober. When a man gets very drunk, he is for a time completely paralyzed, so that he cannot walk or move, and seems almost like a dead man.

11. If you had a good horse that had carried you a long way in a carriage, and you wanted to travel farther, what would you do if the horse were so tired that he kept stopping in the road? Would you let him rest and give him some water to drink and some nice hay and oats to eat, or would you strike him hard with a whip to make him go faster? If you should whip him he would act as though he were not tired at all, but do you think the whip would make him strong, as rest and hay and oats would?

12. When a tired man takes alcohol, it acts like a whip; it makes every part of the body work faster and harder than it ought to work, and thus wastes the man's strength and makes him weaker, although for a little while his nerves are made stupid, so that he does not know that he is tired and ought to rest.

13. When you grow up to be men and women you will want to have strong muscles. So you must be careful not to give alcohol a chance to injure them. If you never taste it in any form you will be sure to suffer no harm from it.

14. Effects of Tobacco on the Muscles.—Boys who smoke cigars or cigarettes, or who chew tobacco, are not likely to grow up to be strong and healthy men. They do not have plump and rosy cheeks and strong muscles like other boys.

15. The evil effect of tobacco upon boys is now so well known that in many countries and in some states of this country laws have been made which do not allow alcohol or tobacco to be sold or given to boys. In Switzerland, if a boy is found smoking upon the streets, he is arrested just as though he had been caught stealing. And is not this really what a boy does when he smokes? He robs his constitution of its vigor, and allows tobacco to steal away from him the strength he will need when he becomes a man.

16. Tea and Coffee.—Strong tea and coffee, while by no means so bad as alcohol and tobacco, may make us weak and sick. A person who drinks strong tea or coffee feels less tired while at work than if he had not taken it, but he is more tired afterwards. So you see that tea and coffee are also whips, small whips we might call them, and yet they really act in the same way as do other narcotics and stimulants. They make a person feel stronger than he really is, and thus he is led to use more strength than he can afford to do.

1. We must use the muscles to make them grow large and strong.

2. Exercise should be taken regularly.

3. Exercise makes the muscles strong, the body beautiful, the lungs active, the heart vigorous, and the whole body healthy.

4. Things we ought not to do: To run or play hard just before or after eating; to strain our muscles by lifting too heavy weights; to exercise so violently as to get out of breath; to lie, sit, stand, or walk in a cramped position, or awkward manner; to wear the clothing so tight as to press hard upon the muscles.

5. Good food is necessary to make the muscles strong and healthy.

6. Alcohol makes the muscles weak, although at first it makes us feel stronger.

7. A boy who uses tobacco will not grow as strong and well as one who does not.

8. The use of strong tea and coffee may injure the muscles.

CHAPTER XXII

1. How we Think.—With what part of the body do we think? You will at once say that we think with the head; but we do not think with the whole head. Some parts of the head we use for other purposes, as the mouth to eat and speak with, and the nose to smell and breathe with. The part we think with is inside of the skull, safely placed in a little room at the top and back part of the head. Do you remember the name of this organ which fills the hollow place inside of the skull? We learned some time ago that it is called the brain. It is with the brain that we study and remember and reason. So the brain is one of the most important organs in our body, and we must try to learn all we can about it.

2. The Brain.—You cannot see and examine your own brain because it is shut up in the skull; but perhaps you can find the brain of a sheep or a calf at the meat market. The brain of one of these animals looks very nearly like your own.

THE BRAIN.

3. The Large Brain and the Small Brain.—In examining a brain we should notice first of all that there are really two brains, a large brain and a small brain. The large brain is in the top and front of the skull, and the small one lies beneath the back part of the larger one, If we look again we shall see that each brain is divided in the middle into a right and a left half. Each half is, in fact, a complete brain, so that we really have two pairs of brains.

4. Brain Cells.—The brain is a curious organ of a grayish color outside and white inside. It is soft, almost like jelly, and this is why it is placed so carefully in a strong, bony box. If we should put a little piece of the brain under a microscope, we should find that it is made up of a great number of very small objects called nerve or brain cells. In the illustration you can see some of these brain cells.

BRAIN CELLS.

5. The Nerves.—Each cell has one or more branches. Some of the branches are joined to the branches of other cells so as to unite the cells together, just as children take hold of one another's hands. Other branches are drawn out very long.

6. The long branches are such slender threads that a great number of them together would not be as large as a fine silk thread. A great many of these fine nerve threads are bound up in little bundles which look like white cords. These are called nerves.

7. The nerves branch out from the brain through openings in the skull, and go to every part of the body. Every little muscle fibre, the heart, the stomach, the lungs, the liver, even the bones—all have nerves coming to them from the brain. So you see that the brain is not wholly shut up in the skull, because its cells have slender branches running into all parts of the body; and thus the brain itself is really in every part of the body, though we usually speak of it as being entirely in the skull.

8. The Spinal Cord.—There are a number of small holes in the skull through which the nerves pass out, but most of the nerves are bound up in one large bundle and pass out through an opening at the back part of the skull and runs downward through a long canal in the backbone. This bundle of nerves forms the spinal cord. The spinal cord contains cells also, like those of the brain. It is really a continuation of the brain down through the backbone.

BRAIN AND SPINAL CORD.

9. Nerves from the Spinal Cord.—The spinal cord gives off branches of nerves which go to the arms, the chest, the legs, and other parts. One of the branches which goes to the hand runs along the back side of the arm, passing over the elbow. If we happen to strike the elbow against some sharp object, we sometimes hit this nerve. When we do so, the under side of the arm and the little finger feel very numb and strange. This is why you call this part of the elbow the "funny" or "crazy bone." The cells of the spinal cord also send out branches to the body and to other cells in the brain.

10. How we Feel.—If we cut or burn ourselves we suffer pain. Can you tell why it hurts us to prick the flesh with a pin, or to pinch or burn or bruise it? It is because the flesh contains a great many nerve-branches from the brain. When we hurt the skin or the flesh, in any way, these nerves are injured. There are so many of these little nerves in the flesh and skin that we cannot put the finest needle into the flesh without hurting some of them.

11. The Use of Pain.—It is not pleasant for us to have pain, but if the nerves gave us no pain when we are hurt we might get our limbs burned or frozen and know nothing about it until too late to save them.

12. Nerves of Feeling.—We have different kinds of nerves of feeling. Those we have learned about feel pain. Others feel objects. If you take a marble or a pencil in the hand you know what it is by the feeling of the object. This kind of feeling is called the sense of touch.

13. There are other nerves of feeling by means of which we are able to hear, see, taste, and smell, of which we shall learn in another lesson. Besides these we have nerves which tell us whether objects are cold or hot, and heavy or light. Nerves of feeling also tell us when we are hungry, or thirsty, or tired, and when we need more air to breathe.

14. Nerves of Work.—There are other nerves which are made just like the nerves of feeling, but which do not feel. These nerves have a very different use. They come from cells in the brain which have charge of the different kinds of work done in the body, and they send their branches to the parts which do the work; hence we call them nerves of work.

15. One set of cells sends nerves to the heart, and these make it go fast or slow as is necessary. Another sends nerves to the liver, stomach, and other digestive organs, and causes them to do their part in the digestion of the food. Other cells send branches to the muscles and make them act when we wish them to do so. Thus you see how very useful the brain and nerves are. They keep all the different parts of the body working together in harmony, just like a well-trained army, or a great number of workmen building a block of houses. Without the brain and nerves the body would be just like an army without a commander, or a lot of workmen without an overseer.

16. How we Use the Nerves.—If you happen to touch your hand to a hot stove, what takes place? You will say that your arm pulls the hand away. Do you know why? Let us see. The nerves of feeling in the hand tell the nerve cells in the brain from which they come that the hand is being burned. The cells which feel cannot do anything for the hand, but some of their branches run over to another part of the brain, which sends nerves down to the muscles of the arm. These cells, through their nerve branches, cause the muscles to contract. The cells of feeling ask the cells which have charge of the muscles to make the muscles of the arm pull the hand away, which they do very quickly.

17. So you see the nerves are very much like telegraph or telephone wires. By means of them the brain finds out all about what is happening in the body, and sends out its orders to the various organs, which may be called its servants.

18. An Experiment.—A man once tried an experiment which seemed very cruel. He took a dove and cut open its skull and took out its large brain. What do you think the effect was? The dove did not die at once, as you would expect. It lived for some time, but it did not know anything. It did not know when it was hungry, and would not eat or drink unless the food or water was placed in its mouth. If a man gets a blow on his head, so hard as to break his skull, the large brain is often hurt so badly that its cells cannot work, and so the man is in the same condition as the poor dove. He does not know anything. He cannot think or talk, and lies as though he were asleep.

19. By these and many other facts we know that the large brain is the part with which we remember, think, and reason. It is the seat of the mind. We go to sleep because the large brain is tired and cannot work any longer. We stop thinking when we are sound asleep, but sometimes we do not sleep soundly, and then the large brain works a little and we dream.