Page:Popular Science Monthly Volume 35.djvu/757

Rh removed the dog will lose the power of movement," and this reasoning was found in fact to be correct; for when this part, which they named "the motor area," was taken away, the animal was found to be paralyzed, while removal of other parts had no such effect. These experiments, since that time repeated in every laboratory of Europe and America, and tried upon various animals, have established the fact that there is in the brain a certain part which directs voluntary movements.

The second step toward the new phrenology was taken in England in 1873 by David Ferrier. Reasoning from the fact that our movements are usually the result of some preceding sensation, he concluded that sensation as well as motion must be governed by the brain. If motion is governed by one part, sensation may be received in another part. This reasoning led him to undertake a series of experiments to settle the question. He soon succeeded in showing that sensations, which are received by the various sense organs of our bodies—by the eye, ear, nose, mouth, or by the skin—are all sent inward to the brain, and that each of these organs sends its impressions to a distinct region of the brain; sensations of light going in one direction, those of sound in another, and so forth.

The work of Munk, of Berlin, in 1881, confirmed and added to the discoveries of Ferrier, and finally established the conclusion that sensations as well as motion can be located. So that to-day it is possible to lay out a sort of map on the brain of animals, and to say that each of the regions put down on the map has a particular sense with which it is related. On such a map there are here and there empty spaces, such as there are on our geographical maps of Africa—for no one knows what is there. But that, of course, does not invalidate our knowledge of regions which are known, and only shows that further discovery is possible. When we come to see the practical results of these discoveries, the arguments of those who oppose vivisection will cease to interest or move us.

These physiological experiments, however, are only of importance to us in our study of our own mental action, provided they have a bearing upon the working of the brain in man. And this is a question which has only been settled within the past fifteen years. It was admitted, indeed, that in the structure and appearance of his brain man resembled quite closely the higher types of gorilla and ape, and yet the apparently impassable barrier between men and animals as regards mental activity prevented any hasty conclusion that these facts could be applied to men. The question whether sensation and motion could be assigned to parts of the brain in the human race was still (ten years ago) an open one. Of course, it is impossible to experiment upon the human brain. But on a little consideration it soon became evident that Nature