STRUCTURAL ARRANGEMENTS OF CEREBRUM 



431 



or ascending frontal convolution, we find below the granular layer the well- 

 marked pyramidal cells or Betz cells, which are larger than any other element 

 in the cerebrum. The layer of pyramidal cells is also very thick, while 



A. 



INTERMEDIATE 

 POSTCENTRAL 



XX 



NTERMEDIATE PRECENTRAl 



Fi. 224. 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.) 



the granular layer is but slightly developed. In this area the actual average 

 thickness of the different layers is as follows : 



Molecular or outer fibre lamina . . . .0-34 mm. 



Pyramidal or outer cell lamina . . . .0-90 mm. 



Granular or middle cell lamina . . . .0-22 mm. 



Betz or inner fibre lamina . . . . .0-22 mm. 



Polymorphous layer or inner cell lamina . . .0-31 mm. 



