Telephone System Of The Body
( Originally Published 1920 )
How Messages Travel in the Body. Reach out your finger and touch something on your desk or on the table near you; then think a little about what must have been going on in your body to make that simple movement possible. You will say you moved your own finger; but how did you do it?
You have learned that the actual movement of the finger was the result of the action of muscles in the finger itself and of others in the hand and arm. If you studied Chapter II carefully, you will remember, too, that the muscles contracted because a message was sent out through a slender thread called a nerve. The nerve carries such messages very much as a telephone wire carries messages from one place to another. The nerves are to be found running all through the different organs of the body. They give the signal that sets one part or another in action.
There is another sort of message which must be carried in the body, the message which tells you what is going on in various parts of it. If, for instance, you prick your finger, you feel the pain. Perhaps you may think it would be better if there were no nerves in the body to bring in this particular kind of message. Think about it a little, however, and see if it is not a good thing that, when any part of the body is hurt, you feel a pain at once.
How the Parts of the Body Work Together.—Most of the movements we make, require the action not of a single muscle alone but of a number of different groups of muscles, which must all work together in just the right way. When you walk, a great many slight movements must be made to keep the body balanced. If you have ever watched a baby learning to walk, you will realize how difficult a task this really is. When you run fast, you will notice that your breathing be-comes deeper and that your heart beats faster. You will learn later why this is necessary. All such activities, which take place in perfect balance without your thinking of them at all, are brought about by messages going back and forth in the body along the nerves.
In old times when a general was fighting a battle, the only way in which he knew what was going on in different parts of the field was by watching from a hill-side. He received news of more distant places from messengers who would come galloping up, their horses dripping 'with foam. Often a battle was lost because news of some sudden attack of the enemy came too late to send reënforcements to the spot. Today every part of the battle line is connected with the general's Headquarters by field telephones, so that the whole army can work together as a unit to advance here or give way there, as the progress of the battle demands.
The nerves serve the body much as this telephone system serves the army, making it possible for all its parts to work together for the common good.
The Brain and the Spinal Cord.—All the messages from the army field telephone system we have been thinking about, come in at last to Headquarters, where the commanding officer sits and directs the whole battle.
The Headquarters for the human body is the brain, and it is from the brain that the messages go out when you make up your mind to do something and then do it. This important organ is a mass of living matter which fills the skull. Large bundles of nerves come into it from the eyes, the nose, and the ears. It is connected with the organs in the lower part of the body by means of the spinal cord, a thick cord of substance much like that in the brain itself. The spinal cord extends down through the center of the backbone (which is also called the spinal column). The backbone, you remember, is made up of bones shaped like rings, and it is through the centers of these rings that the spinal cord passes. All along its course, bundles of nerves enter it from the various organs of the body.
Reflex Actions.—In order to understand a little better how the nervous machinery of the body works, let us consider what happens in one particular case. Sup-pose a hot dish just out of the oven is placed on the table and you reach out to take hold of it. As soon as you touch the plate, you feel it is hot; but before you have time to think about it at all, you draw your hand quickly away. How was this action brought about?
In the first place, a message came over a nerve from the tip of the finger that touched the hot dish, bringing in the news that something was wrong. In the spinal cord the news was passed along until it reached the nerve going out to the muscles of your arm. This nerve sent out word to these muscles to contract and pull your arm away. There are always two parts to such an action, which is called a reflex action. First, a message comes in, telling of something that has happened outside. Second, another message goes out and starts an action that will save some part of the body from harm or discomfort.
The particular reflex we have been speaking about does not have to be learned. Any child will draw its hand away from something that is hot. There are many other reflex actions which must be learned by practice, but which, once they are mastered, become natural and easy. You have perhaps learned to skate on roller skates or ice skates, or to ride a bicycle. You remember that at first it was very difficult to do these things. You could not skate, for instance, more than a few steps without falling down or holding some one's hand. Gradually it became easier and easier, and now perhaps you can skate off without thinking about it at all. It is just as easy as walking.
Learning to skate is really learning to balance your-self. When you bend or lean too far forward or side-ways, you save yourself by an unconscious movement the other way. Every movement of this kind is a re-flex action. You train the nerves by practice so that when a message comes in that the body is bending too far, the order will go out, quick as a flash, to the right group of muscles. These muscles will act so as to swing out the arm or leg, or to bend the body forward or backward just enough to get in balance again.
There is one other kind of nervous action that you ought to understand, and one other long word that you must learn, the word inhibition. Reflex actions are not always useful; sometimes they must be checked or controlled. Suppose the hot plate we have been thinking about was not too hot for you to pick it up, but was hot enough to be quite uncomfortable after you had carried it halfway across the room. As the heat got into the fingers, some children by a simple reflex action would drop the plate on the floor and break it. I hope you would not drop it, however. You would check the reflex if you could, and stand the pain till you had put the plate down in some safe place. In such a case, the nerve message telling the muscles to drop the plate would be overruled by another message from your central nervous system saying, "Stop! Don't do it. We can hold on a little longer." Such an order to stop is an inhibition.
Inhibitions are usually hard at first, but they can be learned by practice. Some children, for instance have the habit of picking at their lips or their fingers or any place that has been cut or bruised. If they try, however, they can soon learn not to do this unsightly and dangerous thing. They can form an inhibition which, after a time, will keep their fingers away from such places, as naturally and unconsciously as if they had never had the bad habit at all.
Good and Bad Habits. Most of the things you do, from the time you get up in the morning till you go to bed at night, are done by unconscious habit, by reflexes and inhibitions which have been trained by practice. You do not have to make up your mind to put your clothes on in the morning or to brush your hair (I hope). You just do these things without thinking about them at all. You do not have to wonder how to get to school.
You walk down the familiar streets without a moment's hesitation.
Since habit plays so large a part in our lives--grownups as well as children—it is very important indeed to form good habits and not bad ones. One girl may be always 'cheerful and pleasant, another cross and disagreeable. One boy may be courteous and considerate, another rough and rude. It is all a matter of the kind of reflexes and inhibitions they have practiced. It is just as easy for most people to be cheerful and polite as cross and grouchy; the difference is merely in the habits they have formed. A child who has by practice learned to be punctual and obedient is just that much better off than one who has not; just as a child who has learned to ride a bicycle and skate is better off than one who can only walk and run.
Truthfulness is a habit; courage is a habit; unselfishness is a habit. All through our lives happiness and success for ourselves and those about us depend very largely on whether we have formed in youth the habit of being honest and brave and kind. You know that a soldier cannot be sent into battle until he has been trained; and this training means not only making the muscles strong and fit, but much more. It means learning habits of neatness, punctuality, obedience, courage, and self-sacrifice. Every boy or girl who wants to serve our country can be training himself or herself now by forming the habits which will make a good citizen in the days to come.
The Story of the Boy Who Walked around Mont St. Michel.—In France there is a high and very steep rock with a church on the top of it, called Mont St. Michel. Once upon a time when bitter wars were going on, this rock was captured by the enemy, and the leader of the invading army made his headquarters in the chapel on its top. Here he ordered brought to him the citizens who had been taken prisoners, and among them one of the principal men of the village, M. de Bretteville and his little son, Louis. The cruel captain threatened to have de Bretteville thrown from the wall over the rock to punish him for his loyalty to his own people and to his religion, for this was a war between people of different religious beliefs. De Bretteville would not yield, and neither he nor his brave son showed any fear.
"I have a good mind to throw you after him," said the captain to the boy.
"You would not make me a coward if you did," said Louis, "and I would gladly leap off the wall myself if I could save my father's life by doing it."
One of the other officers whispered something to the captain, and he turned quickly to the boy. "We will see how brave you really are," he said. "There is a narrow ledge of rock outside the wall. If you can walk around the rock on that ledge, I will set both you and your father free."
"No, no," cried de Bretteville, "I will not have R. I would rather a hundred times be killed myself."
"It shall be so, whether you like or not," replied the captain, "or I will have both you and the boy thrown over."
"Will my father be freed if I make the attempt, whether I get round safely or not?" asked Louis. "He will; you have my word on that."
"Then I am ready," said Louis. He took off his shoes and stockings and was lifted over the wall so that he stood on the narrow ledge outside, with hundreds of feet of steep jagged cliffs below. The shelf of rock on which he had to walk was in places only a few inches wide, and he could keep from falling only by clinging to bits of projecting stone or roots and branches of bushes growing between the rocks. Step by step he made his way onward, never looking downward into the terrible chasm, but carefully and skilfully selecting the places to put his feet and to hold on with his hands. Even the soldiers watched every step with eager anxiety, hoping that the brave lad would succeed—and perhaps you can imagine the suffering of his father while the minutes slowly passed.
Louis came at last to a place where there seemed no hope of getting farther, for the ledge be-came narrower and narrower and he could see that ahead it disappeared entirely, leaving nothing but a smooth wall of rock. To turn back was impossible, for he was already on a ledge only a few inches wide.
Slowly and carefully the boy looked downward along the face of the cliff. About three feet below, he saw a jutting point of rock from which another ledge extended on around the corner of the cliff. He measured with his eye the distance down-ward and forward, saw that there was a holly bush growing out from the rock just at a good place to give a handhold,—and then he jumped. He landed safely with his feet on the ledge and the holly branches in his hand. The rest of the way was easier, and at last, after what had seemed like a year, but was really only fifteen minutes, Louis was again clasped in his father's arms. They were both saved, saved by the courage and devotion of a boy.
I always remember Louis de Bretteville and the cliffs of Mont St. Michel when I think of habits. It was the habit of strong muscles and well-trained nerves, and above all the habit of coolness and courage and the habit of loving service, that made it possible for him to do this splendid deed.
Rest and Sleep.—The nerves and the brain require rest, just as any other part of the body does. If you try to concentrate on one thing too long, you soon be-come tired, and your work should be arranged so that this will not happen. Short periods of hard work, with rest or play or some other kind of occupation between, will enable a child to accomplish most in the long run.
The most complete kind of rest we can get is that which we find in sleep. A child of your age should have about ten hours of sleep each night. If you do not get this much on account of late evening work or play, you are pretty sure to suffer from it in the end.
Alcohol and the Nervous System.—Something was said in the last chapter about the effect of alcohol upon muscular work. Those who want to excel at physical games must avoid alcohol, but alcoholic drinks are even more harmful to the nerves than to the muscles. In fact, the reason why alcohol interferes with running or jumping or any other athletic exercise is probably more because it affects the nerves which control the muscles than because it hurts the muscles themselves.
Alcohol interferes particularly with the inhibitions, so that even when it is used in very slight quantities, the reflexes are slower, the body is more clumsy and the mind more cloudy. People who use it in considerable amounts say and do things they would never think of saying or doing if they had not taken alcohol.