STRUCTURAL ARRANGEMENTS OF CEREBRUM 489 



the various elements of the cortex. Thus in an animal, such as the 

 rabbit, the polymorphous layer is three times the thickness of the 

 pyramidal layer ; whereas in man, with an infinitely greater range of 



B 



INTERMEDIATE 

 POSTCENTRAL 



NTERMEDIATE PRECENTRAL 



FRONTAL 



FIG. 222. Human brain showing outer (A) and mesial (B) surfaces, and the situation 

 of the chief motor and sensory areas. The different shading represents the extent 

 of each of these areas as determined by a study of the histological structure of 

 the cortex. (CAMPBELL.) 



reaction, it is only one-third of the thickness of this layer. If we may 

 roughly assign a function to each of the types of cells found in the 

 cortex, we may say that the pyramidal cell layer is generally associative 

 in functions. The large pyramidal cells of Betz are motor ; the 



