answer, "The more wrinkles, the more wits," for that states the case concisely. "But what good do the creases do?" you ask again. "Give more surface for the gray stuff to be spread over," comes back the answer quick and positive. And that answer leads the doctor up to the point of his greatest enthusiasm -the gray and white substance of the brain.

Gray is all you have seen thus far, for it bends in and out with every fold and crease as if the whole substance of the brain were solid gray. "But look here," exclaims the doctor, as he presses open a deep cut which he has made with his knife through the gray cap; "see how little gray there really is; only an outside layer about an eighth of an inch thick, and thinner than that in spots. But every thought you have, every pain you feel, every plan you make, every hope that thrills you, every purpose and ambition of your life belongs nowhere else than in this thin gray layer that covers the white substance below it."

While you are thinking this over in amazement, he will probably go on to say that the injury or disease of any part of that gray layer of the brain may rob you of one sense or another, or even destroy your brain power in the very direction where you thought you were strongest. You will then recall the captain and his interrupted command, and you will understand at once that he happened to be injured in just that

+

part of the brain which had charge of his power to give commands.

"If this particular brain had been injured here," the doctor will say, pointing to a certain spot on the gray surface, "its owner would not have been able to recognize anything that the eye looked at. And this is the worst sort of blindness, for when the seeing part of the cerebrum is gone a man cannot so much as remember what seeing was like."

Accidents to the brain have taught some of these facts, diseases of the brain have taught others; while the study of the brains of animals has let in a flood of light on the whole subject. So that at the present time scientists know that each separate sensation and the power to move each separate part of the body has its own definite locality in a definite region of the gray layer.

This layer is called the cortex, and cortex means bark. It is clear then that the gray bark that covers both cerebrum and cerebellum is the most precious part of the human body. For this reason it needs a stout protection, and it gets it in the firmly knit, sturdy skull which surrounds it.

Instead of being a snug fit in its case, there is a little space filled with liquid, which separates the brain from the skull.

The explanation of the white and gray substance of the brain is given at the close of the tenth chapter.

CHAPTER III

BERTINO'S BRAIN

The work which Dr. Beaumont did in getting an inside view of the stomach of Alexis St. Martin was wonderful enough, surely, but Dr. Mosso1 did something even more wonderful. He followed the working of the brain itself through a hole in the skull.

His first chance to do this was with a poor woman named Margherita. She had a disease which destroyed certain bones of her body. Finally it attacked the bones of the forehead just above the nose and left a round hole through which any scientist was glad to look. This was the chance of a lifetime, for the woman was in a hospital, and Dr. Mosso could follow her case from day to day. Looking through that hole he saw the uncovered brain and noticed that it throbbed and pulsed like the living thing it really was. To test it carefully he invented a delicate instrument which he could slip through the hole in such a way that it rested on the membranes that cover the brain. The machine was also able to keep its own record of the activity of the brain, for a

1 Professor of Physiology in the University of Turin, Italy.

pencil was connected with it which drew longer or shorter marks on a sheet of paper, according as the brain was active or quiet.

One day as Dr. Mosso sat near the woman, watching the machine which he had slipped into place, he noticed. a sudden change in the record. Quite abruptly it began. to draw lines that showed a stronger pulse, while at the same time the brain grew larger.

This seemed strange, for there had been no change in anything in the room, and the woman said she felt as well as usual. Dr. Mosso then asked her what she had just been thinking about, and this brought the explanation. She said that as she had been looking at the hospital bookcase in an absent-minded way, she suddenly saw a human skull between the books, and that this frightened her because it reminded her of her own troubles. "Fright, then," thought Dr. Mosso, "drives the blood to the brain."

Soon after this a scab grew over the exposed brain surface so that tests became impossible.

Two years later, however, Dr. Mosso had an opportunity to experiment with another brain; this one belonged to the head of a vigorous mountaineer. In July, 1877, the man was at work on a church, when a brick was accidently dropped by another man on the roof. It hit Bertino on the head and left him unconscious for an hour.

When he came to himself there was a hole "as big as a shilling in the middle of his forehead," but his mind

TESTING BERTINO'S BRAIN

was as clear as ever. By

careful work the frag

ments of broken bone were picked away one by one, and through the opening the doctors saw the brain steadily throbbing. This was possible because of the open space between the brain itself and the skull which protects it.

In the course of time the machine and the doctor began their records and their observations. Sometimes the pulse lines were low and broad; sometimes they were higher and sharper; almost never were there any two precisely alike.

When the man went to sleep with the