We think only on the left side of our heads—that is easy to say if we are normal right-handed persons. If for any reason we have got to thinking on the right side, that will, as I have explained, usually result in making us left-handed.

Yet we do not use the whole of even one side of the brain. So far as is known, we do not think at all with the front part of the head. All our speaking and most of our thinking are done from a spot hardly larger than a cart-wheel dollar, which lies on the side of the head just above the left ear. At any rate, an injury to this particular part of our brain puts a sudden stop to our ability to think and speak.

When you put your left elbow on the table and lean your head on your hand, your hand just about covers the only portion of the brain with which you ever do any thinking at all; while only with the part that lies directly under the middle of the palm, and is as I have said, about the size of a silver dollar, do you ordinarily think very much or hard. This thinking part of the brain lies on the outside, and is just about as thick thru as the hand is.

But even this small thinking place in the brain is not all alike. Directly over the ear, a place that you can almost cover with your thumb, lies the most important part of all, the place where we remember and handle words. At the bottom of this word spot, we remember how words sound. An inch farther up and toward the back, we remember how words look in print. A little farther up and forward lies the “speech center,” from which, when we want to talk, we direct the tongue and lips what to say. Thus we get our word-hearing, our word-seeing, and our word-speaking centers close together, so that when we speak we have close by and handy our memory of what we have heard in words, and of what we have read.

Just below the place where we remember words, and a little forward of it, lies the place where we remember other sounds which are not words, such as the noises of bells and whistles, barking of dogs, mewing of cats, all buzzings and creakings and gratings and crashings, all laughing and crying. Every kind of sound which isn’t either words or music is recognized and remembered here. Beyond this spot, still farther forward and down, and just above the rear end of the cheek-bone, is the place where we remember music. If we don’t know anything about music, and can’t tell Yankee Doodle from Old Hundred, then we don’t use this part of our brains at all. But if we do know one tune from another, and know a good many to recognize them when we hear them, here is where we do the knowing.

Back of the word-seeing part of the thinking spot, and reaching pretty well round to the back of the head, lies the place where we remember everything we see, except words written or in print. Above the word-speaking part of the brain, or speech center, from which we control the mouth, throat, lips, and tongue, which we use in speaking, lie the various points from which we manage other parts of the body. As you might expect, next the speech center lies the center for the rest of the face and for the head and eyes. Above that comes the center for the hand and arm. Still higher up, right on the top of the head, comes the center for the legs. So whenever we do anything with any part of the body, we have to signal the proper muscles from the part of the brain that lies between the tip of the ear and the top of the head. Close behind this region is the spot where we feel everything that touches the skin; so that we can make the movement and feel the results most handily.

So as you see, the surface of the brain is a sort of map or chart of the entire body. Every muscle, every point on the skin, the eyes, the ears, the nose, the tongue, every several organ which we possess, has its own special spot on the surface of the brain, somewhere above or behind the ear. Each half of the body is charted on one side of the brain, a spot in one for each spot in the other. But we who have to use these brains to think and remember with, as well as to see and hear and feel with, and to control our muscles, have chosen to do this thinking and remembering with the spot on the left side of the head which corresponds to the muscles of the lips and mouth and tongue, and to the eyes and ears and the right hand. Thus we have everything convenient, all in one small spot on one side of our heads, where we can get at everything with the least trouble. But what the front part of the brain is for, is something that nobody knows much about.

Certain very strange results follow from this practice of ours of using only one side of the brain to think, remember, and speak with; and using different parts of that for thinking and remembering about different sorts of things. Once upon a time there was a workman who was hit hard enough to break his skull, on the left side of his head, pretty well round toward the back, and just over the spot where, as I have explained, are stored up all the memories of things seen. He seemed not seriously hurt; but when his wife came to see him at the hospital, he did not know her. Neither did he know his children nor his friends. In fact, he didn’t even know that they were human beings. He had absolutely lost the memory of everything that he had ever seen.

But the minute his wife spoke he knew her at once. Or if he could feel of any familiar thing he knew what it was. All the while, he could see perfectly well. His eyesight remained as good as ever, he simply couldn’t remember that he had ever seen things before. The plain seeing, he could do with either side of his head; and the left side being hurt, he did it with the other. But the remembering that he had seen the same thing before, he did with the left side only; and when he could no more do it with that, he could not do it at all. Yet his memory for sounds and the feeling of things was just as good as ever; because the places where he did these sorts of remembering were not under the place where he got hit. And the moment the doctors lifted out the splinter of bone that was pressing on his seeing-things spot, then he remembered wife, children, friends, everything as before.

Here is another case, much like the first, and yet curiously different: An educated woman, somewhat well along in years, went to bed at night in ordinary health. During the night, however, a small blood-vessel burst and formed a tiny blood blister on the left side of her brain, about an inch in front of the spot where, as I have been telling, the workman was hit who couldn’t remember his wife when he saw her. She had, in short, a sort of internal black eye, just on the spot that she had been using for sixty years and more to remember written and printed words.

She woke up in the morning, therefore, totally unable to read a single word. She could see as well as ever, understand perfectly every word said to her, speak and write without the least difficulty—but she simply could not read. Give her a printed book, she could count the letters in every word, draw them on paper, tell which were tall, short, round, or square, see them in fact just as well as before—but she no longer knew what they meant. It was exactly as if she had never learned to read at all; and being much too old to learn again, she never read another word as long as she lived.

There is another accident which is so little uncommon that probably every one who reads this book will some time in his life see an example of it. This is a case where a blood vessel bursts on the left side of the brain and wrecks the speech center. The person to whom this happens, immediately forgets how to talk. If the blood clot is small, so it presses upon the speech center and nothing else, the victim of this sort of accident can read and write as before, and understand all that is said to him. Oddly enough, too, he can make any sound that he ever could, and repeat parrot-like any words that he hears. But he cannot remember the meaning of words. He is precisely like a man suddenly transported to a foreign country where they speak a language which he never heard. His own language has become to him like Chinese.

Strange indeed are the freaks of these accidents to the left side of the head above the left ear. One man, a musician, finds that while he can hear music as before, he hears it only as noise, and no longer recognizes it as tunes. He has been hit low down on the side over the spot where he keeps his music memory. Another, hurt a little higher up, can hear noises as before, but cannot tell a factory whistle from a church bell. Not that they sound alike; but he has forgotten which is which. Occasionally, a watch-maker, engraver, or other skilled artisan, will get an injury well up on the side of his head at the place from which he manages his right hand. Then he loses all his special skill of hand. He can still use his right hand for ordinary acts, dressing, eating, shoveling coal; but the power of doing thinking-things is gone. He has become like a day laborer who has never learned a skilled trade.

There is a strange case of a business man who got a blood clot just over his word-thinking spot, but toward the upper side so that while it ruined his speech center and the place where he kept his memory for the look of printed words, his memory for the sound of words escaped. He could neither read nor write, nor speak a word; but he could understand what was said to him. Curiously enough, he could handle figures as well as ever, for the figure-remembering spot and the figure-writing spot had escaped. So for seven years this man kept on with his business. Every letter had to be read to him; and all he could do in answer was to write down figures and point to them. Meanwhile, he took lessons most diligently, trying to learn to write and speak with the other side of his brain. But it was no use.

There was also a learned man, who in addition to his native language, which was English, knew Greek, Latin, and French, and could besides read music. After his accident, he could read his native English only with the greatest difficulty, about like a child of six or eight who can make out easy words, slowly; while writing, he could scarcely read at all. French, he could read much better; as well, say, as a high school graduate. Latin he could handle pretty well; about like a boy just out of college. But Greek and music he could read and write exactly as well as he ever could. The accident, which had pretty well spoiled the place where he remembered his native language, had only damaged the spot where he remembered his French, had hardly touched the place where he remembered his Latin, and had missed entirely the place where he kept his memory of music and Greek.

You understand, of course, that when one of these very same accidents occurs to a left-handed person, no matter how much it damages his head on the left side, it does not destroy his speech or memory. Or if the same thing happens to a right-handed person, on the right side of the head, his speech and memory do not suffer. The hurt has to be on the thinking side in order to affect the thinking.

When little children are hurt in these ways, at first they suffer loss of speech or memory just as men and women do. But little children, as I have already explained, are not hard and set like grown up people. They can start over again, and learn to think, speak, and remember with the other halves of their brains. But as soon as any one gets too old and stiff to learn anything new, then he is too old to learn an old thing over again on the other side.

Do you see now why you have to go to school five hours a day, and sit on a hard seat studying still harder lessons, when you would much rather sneak off and go in swimming? It is so that you may build up these thinking spots in your brains. We are born with brains like the animals, alike on both sides. Only slowly, painfully, with much hard and disagreeable work, that we had a great deal rather not do, do we manufacture a one-sided human brain. We begin young, while the brain is still growing. With years and years of work and study, we slowly form the thinking spots over our left ears, which we are to use the rest of our days. When we are grown up, we can no more form new thinking places on one side of our heads, than we can form new thinking places on the other side, after the old ones have been destroyed. The business man who lost his ability to read, never learned to read again, tho he worked at it six years, harder than any child ever studied. If he had put off learning to read till his old age, he could never have learned at all.

It does seem a long time that we sit on a piano stool doing our daily practicing, and mighty little fun. Let us then remember that all the while, we are making a time, tune, and harmony remembering place just back of the left temple, and tying it up with the spot farther up on the side of head from which we manage our hands and fingers. It is slow work; but when once we get the job done, we shall be able to enjoy and remember music with it for the rest of our lives—forty, fifty, sixty years. Surely, this is cheap enough at the price of a little daily practicing.

It really is a good deal as if we were born like a dog or a horse, with head, body, and legs, but no hands, and had to make our hands for ourselves. How we should work in such a case, building our fingers, shaping our thumbs, and in every way getting the best possible sort of hands to use thereafter. And what should we think of any careless child who left off a finger or two, or was too lazy to put on a proper thumb, and so had to be deformed and crippled all the rest of his life.

But the thing which makes us different from dogs and horses, isn’t half so much our hands, as it is the spot of brain substance which we build for ourselves over our left ears. This spot looks like the corresponding spot on the other side. But somehow or other, nobody knows just how, our work and study and trying hard make that particular patch more important for us than anything else in our whole bodies. If we fail to build good thinking spots while we are young, we shall be deformed and crippled for the rest of our lives.