Page:Popular Science Monthly Volume 42.djvu/22

 12 a serious extent. When we speak of mental weariness we really refer to brain weariness, or more accurately to alterations in the delicate machinery of brain-cells. The brain itself is affected by the condition of the rest of the organism. A man with wearied muscles, or blood starving for oxygen, can not think well.

These illustrations may suffice to explain my general attitude, that to study educational methods scientifically we must betake ourselves to an examination of the human brain. Fortunately, within the last twenty years brain physiology has made great



progress, owing to the investigations of anatomists, physiologists proper, pathologists, and practicing physicians. The chief advance has been in the direction of extension and accuracy of knowledge as to the function of the gray matter on the surface of the brain, the so-called cortex. The functions of nearly every region of this cortex are now known approximately, and as regards some areas with great accuracy; so much so that surgeons have, in consequence of a diagnosis of the site of an irritation or of pressure, been enabled to cut down on the very spot affected and so relieve the patient.

The region which we least know is just that about which the phrenologists have had so much to say, and mapped out to their own satisfaction with great precision. Of this region physiologists can as yet draw conclusions only by a sort of process of exclusion.

We know very definitely the motor area concerned in