12 THE POPULAR SCIENCE MONTHLY. 



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 



Fig. 2. — Lateral Surface of Brain of Monkey, displaying Motor Areas (after Horsley 



and Schafer). 



progress, owing to the investigations of anatomists, physiologists 

 proper, pathologists, and practicing physicians. The chief ad- 

 vance 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 sur- 

 geons have, in consequence of a diagnosis of the site of an irri- 

 tation 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 physiolo- 

 gists can as yet draw conclusions only by a sort of process of ex- 

 clusion. 



We know very definitely the motor area concerned in volun- 



