1 66 MAN, — THE ANIMAL 



able that in the severe cases of shell shock 

 some one of these ancient centers has been af- 

 fected with the result that recovery must be cor- 

 respondingly slow. For reason controlled men 

 as they faced undreamed of danger on the fields 

 of Flanders and France, and this aspect of mind in 

 man is largely if not entirely confined to his "new 

 brain." But when these old centers once broke 

 away from the control of the "new brain," they 

 literally assumed an ancient right which only 

 patience and time can restore. 



Through this long past history there has been 

 built into the nervous system a definite method of 

 acting. Various attempts have been made to un- 

 ravel the mystery and these explanations have 

 for a time been accepted. One of the most prom- 

 inent is the localization hypothesis which happen- 

 ed to hit upon a portion of the correct interpreta- 

 tion. During the evolution of the vertebrate 

 nervous system groups of cells came to act to- 

 gether. 



Their purpose at all times was to serve the best 

 interests of the living organism. Modern neu- 

 rologists have arranged these groupings into four 

 classes. First, the sensations that come to the 

 brain from all of the receptors located on the ex- 

 ternal surface of the body; secondly, the sensations 

 that come to the brain from the internal receptors 



