Chapter 8 SEEING AND READING

You can learn a great deal through your ears, but think how much more you can learn through your eyes. Just count over all the things that you have had to get your eyes to tell you to-day, and then shut your eyes for a minute and think what it would mean never to be able to see. Don't you think you ought to take very good care of your eyes? You are going to keep them very busy all your life, and they deserve the very best care you can give them.

THE LIGHT ON THE PAGE, NOT IN THE EYES

Just as soon as lessons begin, you get out your books; and a good share of the day in school you have a book before you, reading it or studying it or copying from it. It makes a great difference to your eyes how you hold the book and how the light falls. In reading, you should always hold your book so that the light falls upon the page from behind you, or from over one of your shoulders. In this way, the brightest light that comes into your eyes is not from the window, but from the page of your book.

If the light comes from a window in front of you, or if you sit in the evening with your face toward the lamp when you read, the light coming straight from the lamp or the window, as well as the light coming up from the pages of the book, pours into your eyes; and this dazzles and confuses your eyes, so that you can't see plainly and comfortably and are very likely after a while to find that your head aches. At home, of course, you can seat yourself with your back to the light when you read; and usually at school your seats are so arranged that the light falls from behind you or from one side. If not, by turning a little in your seat, you can get the light from over your shoulder.

Notice how the light falls upon the blackboard. When the light comes from the windows behind you, or from one side, you can see what is written there quite plainly. But if the blackboard happens to be between two windows, and especially if this is the lightest side of the room, you will find that the light dazzles you so that you cannot see the writing clearly.

You must have noticed, too, that if, after you have been reading from the blackboard you look down again suddenly to the page of your book, for an instant you will not see the letters plainly. Then, almost before you have time to notice it, you feel a little change take place inside your eyes, and the print upon the page of your book becomes quite plain. This is because your eye has to change the shape of one of the parts inside it, called the lens, before you can see clearly the things that are near you. This change, which is called accommodation, is made by a little muscle of the eye; and if you keep your eyes working at close work, like reading or writing or fancy-work, too long at a time, or if your eyes need glasses to make them see clearly, and you haven't them on, this little muscle becomes tired. Then the print of your book, or your writing, or the stitches you have taken begin to blur before your eyes. Your eyes begin to feel tired, and your head begins to ache. This is what we call eye strain.

Sometimes this eye strain upsets your appetite or your digestion and makes you sleepless and worried. The trouble may be caused by your own carelessness: you may have been reading too long, or in a poor light, or with the light shining right in your face instead of coming over your shoulder. But sometimes it is caused by the fact that your eyes are not just the right shape; and then the only way to relieve it is to have proper glasses, or spectacles, fitted, which will make up for this too flat or too round shape, or too large or too small size, of your eyes.

If you cannot see clearly what is written on the blackboard when the light falls upon it from behind you, or above; or if, in a good light, you cannot read the words in your book quite easily, without straining at all, when you hold the book either at arm's length or a foot from your face; or if your head aches or your eyes begin to feel tired or uncomfortable, or the letters begin to blur, after you have read steadily-say, for half an hour,-it is a pretty sure sign that there is some trouble with your eyes. Then you had better have them examined at once by your family doctor or by the school doctor. In many schools now there are doctors to test the children's eyes, and ears, too, so that each child may have a chance to see and hear everything that the other children can see and hear.

Not very many years ago people thought that glasses were only for old people, but now we know that many children's eyes need glasses, too. I knew a little girl whose sight was so poor that when she was standing and looked down at the grass, she couldn't see the green blades. She thought that the grass looked like a green blur to everyone, just as it did to her; and so she never said anything about it. She was twelve or thirteen years old before she found out that she couldn't see clearly. Of course, trying hard to see things gave her a headache and made her tired and cross. So some one took her to a doctor, and he saw at once what was the matter and fitted her with glasses. Soon she was quite well and strong; and how glad she was to see the leaves and a hundred other things she had not seen before!

THE EYEBALL IN ITS SOCKET

The muscle from M to M, which helps to turn the eyeball, has been cut away to show the optic nerve.

Here we have a picture of the eyeball, as we call it. The little bands fastened to it are the bands of muscle; and as soon as I say muscle you know what they are for-to move the eyeball about, up and down and from side to side. There are muscles outside the eye as well as inside. Coming out from the back of the eyeball is a pearly white cord quite different from the muscle bands. This is what we call a nerve. This nerve in your eye carries to your brain, or thinking machine, picture-messages of whatever you look at.

The nerve in your eye gets messages of light much as the nerve deep in your ear gets its messages of sound-from tiny waves in the air. The light waves are smaller and faster even than the sound waves, and the eye nerve is the only nerve that can get pictures of them. You know that, for wireless messages, the receiving machines are not all alike and cannot all take the same messages, if the messages are sent with different sorts of electric waves; and neither can our receiving machines. Some get messages of sight, and some of sound, and some of touch, or taste, or smell.

Now shut your eyes as quickly as you can. How long did it take you? A minute? No, not a quarter of a second. It is about the quickest thing you can think of-"the twinkling of an eye." You shut your eyes "quick as a wink" whenever anything seems likely to fly or splash into them, and this is what the eyelids are for. If anything gets into the eye before the lids can shut, the eye "waters," and tears pour out of it. These are made by a gland-sponge up under the upper lid, so as to wash any dust or sand or other harmful speck out of the eye before it can hurt the sensitive eyeball.

Now look at some one's eyeball. It is like the picture, isn't it?-bright white around the edge and then a ring of color, brown or blue or gray; and inside the color-ring, or iris, a little round black hole that we call the pupil. Watch the little hole change as you turn the face toward the window. It becomes ever so much smaller. Now turn the face away from the window, back again into the shadow. How did the pupil change this time?

EYES PROTECT THEMSELVES AGAINST THE LIGHT

The iris, or color-ring, acts like a curtain, like the ring-shutter of a camera, and closes up the hole, or pupil, when the light is too bright and would dazzle or burn the inside of the eye; but when the light is dim, the iris opens again, so as to let in light enough with which to see. Look at the little window in your kitten's eyes. It is not the same shape as yours; but when you carry her to the light, you see how the iris closes in and leaves just a little black slit or line.

You remember the blind children? Isn't it wonderful how they can play games and study, too, even though they are blind! They have to make their senses of touch and hearing tell them many things that you learn through your sense of sight. Many of these children need not have been blind, if the nurse who first took care of them when they were born had known enough to wash their eyes properly, not with soap and water, of course, but with just one or two drops of a kind of medicine-an antiseptic, as we call it-that makes the eye perfectly clean.

But you children who have good eyes that can see, do you really see things when you look at them? You can train your eyes just as you can train your ears. You can teach them to read quickly down a page, and to find things in pictures, and, better still, to see things out of doors, in the garden and the woods and on the seashore. We hear a great deal about "sharp eyes," but most of us see very little of all we might see. Our eyes are on the lookout, too, to protect us from dangers that may come; with our skin and nose and ears, they are constantly on the watch; so the better we see the safer we are.

Even if your eyes are perfect now, you will need to take good care of them to keep them strong. Don't let any story, no matter how interesting it is, tempt you to read in a dim light or a light that is too strong. And if you can't see the blackboard easily, or can't read big print, like the school calendar, across the room, tell your mother or your teacher, so that she can ask the doctor to find out what the matter is.