First Book in Physiology and Hygiene

by John Harvey Kellogg

2. The Brain.—You cannot see and examine your own brain because it is shut up in the skull; but perhaps you can find the brain of a sheep or a calf at the meat market. The brain of one of these animals looks very nearly like your own.

THE BRAIN.

3. The Large Brain and the Small Brain.—In examining a brain we should notice first of all that there are really two brains, a large brain and a small brain. The large brain is in the top and front of the skull, and the small one lies beneath the back part of the larger one, If we look again we shall see that each brain is divided in the middle into a right and a left half. Each half is, in fact, a complete brain, so that we really have two pairs of brains.

4. Brain Cells.—The brain is a curious organ of a grayish color outside and white inside. It is soft, almost like jelly, and this is why it is placed so carefully in a strong, bony box. If we should put a little piece of the brain under a microscope, we should find that it is made up of a great number of very small objects called nerve or brain cells. In the illustration you can see some of these brain cells.

BRAIN CELLS.

5. The Nerves.—Each cell has one or more branches. Some of the branches are joined to the branches of other cells so as to unite the cells together, just as children take hold of one another's hands. Other branches are drawn out very long.

6. The long branches are such slender threads that a great number of them together would not be as large as a fine silk thread. A great many of these fine nerve threads are bound up in little bundles which look like white cords. These are called nerves.

7. The nerves branch out from the brain through openings in the skull, and go to every part of the body. Every little muscle fibre, the heart, the stomach, the lungs, the liver, even the bones—all have nerves coming to them from the brain. So you see that the brain is not wholly shut up in the skull, because its cells have slender branches running into all parts of the body; and thus the brain itself is really in every part of the body, though we usually speak of it as being entirely in the skull.