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How We Learn About The World Outside

( Originally Published 1920 )

Spying Out the Enemy.—In war, men are sent up in airplanes as observers, to find out what is going on behind the lines of the enemy. These airplanes have been called the eyes of the army and the navy. They are compared to our eyes, because it is largely by means of the eyes that we find out what is happening in the world about us.

A great many of our actions are the direct result of something that is going on outside the body. You move toward the fire because the room is cold. You run out to the kitchen because there is a delicious smell of gingerbread or cookies there. You hurry to school because the bell is ringing for the last time.

How do you find out that the room is cold or that there is a good smell in the air or that the bell is sounding?. Why, you feel the cold and smell the gingerbread and hear the bell, of course, you say. It is not quite a matter of course, however; it is one of the most remark-able things about the human body—this power of finding out what is going on in the world about us. Try to think how many different ways you have of finding out what is happening, and what the different objects in the room are really like.

The Story of Helen Keller.—We can understand better the importance of this power of learning what is going on about us by thinking of the true story of a little girl—now a grown woman—named Helen Keller. When Helen was less than two years old, she had a terrible illness which left her without the power of seeing or hearing or speaking. She could smell the flowers in the garden, but she did not know what they looked like. She could feel the jar of the shutting of a door and the shaking of the floor made by footsteps, but she could not hear a voice. She clung to her mother's dress as her mother went about her work, and learned many things by the sense of feeling. She found that a shake of the head meant "No" and a nod "Yes"; that a pull meant "Come" and a push "Go." She learned that other people did not communicate in this way, but did something with their lips, for her fingers could feel the movements of her mother's lips, But she tried in vain to make some sound by moving her own lips. She learned to do little things about the house, and at five she could fold and put away the clean clothes when they came home from the laundry and pick out her own clothes from the rest. As she grew older, how-ever, the, sense of being unable to express anything except by the simplest signs became almost unbearable. She felt as if she were shut up in a prison.

When Helen was seven years old, her parents found for her a teacher from a school for the deaf and dumb in Boston. The deaf and dumb have a language by which they talk to one another by signs made with the fingers. This teacher, Miss Sullivan, after playing with Helen's doll for a little while, spelled out into her hand the letters d-o-1-1 in this sign language. Helen quickly learned to make these movements, though she had no idea at first that they meant anything at all. She learned to spell out other words; and at last one day when she felt the water from the pump running over her hand, and Miss Sullivan spelled the word w-a-t-e-r, she grasped the idea that everything had a name and that she could express the name by her fingers. By these movements of the fingers she could at last break down the wall between herself and all the world outside.

After this, Helen made rapid progress. She was soon able not only to talk by the finger language but to read books. There are' books especially prepared for the blind, in which the letters are raised so that it is possible to feel their shapes. After some years Helen learned to speak. She did this by feeling the movements of the tongue and lips of a person who was making the sound of a particular letter, and imitating the movements with her own lips and tongue. At last this girl The Sense Organs.—The power of learning about. things in the world around us depends on special organs at the ends of the nerves which are called the sense organs.

The most complicated of these sense organs are the eyes with which we see and the ears with which we hear. There are also special sense organs of taste in. the tongue and of smell in the upper part of the nose. Organs of touch, and organs by which we feel heat: and cold, are scattered all through the skin.

The Eyes and How We See with Them.—The eye itself is a sort of hollow ball set in the head, with a bundle of nerves running from it into the brain.

At the front of the eyeball is a window, through which the light enters the eye. This window is the dark round opening in the middle of the eye, which is called the pupil. Around this window is a circular curtain, the iris, which is the colored ring you can see in a person's eye between the pupil and the white part outside.

If you will look at the eyes of a person who has been in a dark room, you will find the iris is only a narrow band and the pupil is quite large. On the other hand, if one has been out in the bright sun, the iris will be wide and the pupil small. We need all the light in a dark place, so the iris curtain draws back to let in as much as possible. But in bright light the curtain closes around the pupil, so that the eye will not be injured by too much glare.

Just behind the iris is a part of the eye called the lens. This is made of a substance like glass, which makes a picture—of whatever you look at—on the extreme back of the eye, the retina. You have probably seen a stereopticon or magic lantern, and you know that the glass lenses inside it throw on a screen a big picture of the slide that has been put behind the lenses. In a similar way, the lens in the eye makes upon the retina a little picture of the part of the room in front of you. From the retina, the nerves carry to the brain messages telling about what you see.

Helping the Eyes to do Their Work Well: The eyes are delicate and complicated organs and very often they do not do their work quite perfectly.

Many children have poor eyesight, without knowing it. They may be able to read a book well, but the writing on the blackboard seems blurred. Such children are called near-sighted; they can see things well that are close to their eyes but not things that are far off. Other children, called far-sighted, can see well across the room, but their eyes hurt when they read or sew. Often children are backward in their studies and are perhaps thought to be stupid, when really the trouble is only with their eyesight.

If the eyes do not see clearly, there is a constant strain on them. The result is often a headache and sometimes indigestion and other troubles that you would never think had anything to do with the eyes at all.

If the writing on the blackboard looks blurred, your eyes must be at fault. If you have to hold a book very close to your eyes when you read, there is something wrong. If your eyes hurt after you have been reading for a while, if your eyes are red and inflamed, or if you have many headaches, there is probably some-thing the matter with your eyes. You should have them examined at once by a physician trained in this work. If he finds anything wrong, he will fit you with eyeglasses, which will make up for the defects of your eyesight and enable you to see clearly.

It is quite wonderful what the effects of eyeglasses are on the children who need them (and at least one child out of every five does need glasses). The books and the blackboard come out clearly; discomfort and headaches vanish. Often a child who was dull in the schoolroom and listless on the playground becomes one of the best pupils and one of the jolliest children in the school.

Keeping the Eyes in Good Condition.—Whether you wear glasses or not, it is very important to take good care of the eyes. Be sure that you do not injure them by using them in an improper way. Many children do serious harm to their eyesight by reading or sewing too long at a time, or by using the eyes in a dim light. In the late afternoon it is easy to go on reading without noticing how fast the light is failing, and the eyes may be seriously strained by this practice. It is harmful, too, to read by a flickering unsteady light or in a railroad train or street car where the print is constantly jiggling about.

Too bright a light may be just as harmful to the eyes as one that is too dim. One should always avoid facing toward a window or a lamp or sitting in such a position that there is a direct glare of sunlight on one's work or the pages of one's book.

The proper position in reading or sewing is to sit with the light coming from above over the left shoulder.

The book or work should be held about twelve inches away from the eyes. Lying down while you read brings an unnatural strain on the eyes.

The Ear and How We Hear.—The outer organ which we ordinarily speak of as the ear is just a sort of trumpet to catch the sound. The most important part of the ear is inside and quite out of sight. The ear that we can see out-side opens into a tube, at the end of which is a thin membrane, some-what like a piece of paper, called the ear drum.

When a person speaks to you, or when some other noise is made the air is set to moving in waves, like the waves that spread over the surface of a pond when you throw a stone into it. These waves strike the ear drum and make it quiver, or vibrate, in a certain way. As the ear drum quivers, it sets up a similar movement in a liquid inside the ear itself. The movement of this liquid in turn affects the ends of nerves in the ear, which carry to the brain the messages that are called sounds.

Guarding against Diseases of the Ear.—From the back of the throat there is a tube that runs up to the inside of the ear behind the ear drum. Sometimes when a person has a cold in the head, germs may work their way up from the throat through this tube into the middle ear, and painful disease and even deafness may result. Any stopped-up feeling or rumbling in the ears, earache, or a discharge from the ears is a sign that something is wrong. The doctor should be consulted at once before the trouble becomes serious.

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