24 BRAINS OF RATS AND MEN 



whole. Looked at anatomically, there is no organ 

 of the human body whose structure is more distinc- 

 tive and whose recognition is more easy. Neverthe- 

 less, there is real confusion about the exact boundaries 

 of the cortex in the human brain and the criteria by 

 which these boundaries are fixed. And there is much 

 uncertainty and great difference of opinion about 

 its physiological action and the way in which its 

 functions are related with those of the remainder of 

 the nervous system. 



Turning to an examination of the cerebral cortex 

 of infrahuman species, as we pass down the animal 

 scale we are impressed by the rapid diminution of the 

 mass of the cortex and by the progressive simplifica- 

 tion of the histological pattern of its texture, until 

 in lower vertebrates we reach a point where cortex 

 can be recognized with difficulty or not at all. In 

 view of these facts, the question. What is the cerebral 

 cortex? is by no means easily answered, and, in fact, 

 the most diverse views have been expressed. 



As the name implies, cortex in general is superficial 

 gray matter, but it does not necessarily appear on the 

 surface of the brain; for we have a cortex of some 

 buried structures, as the cortex of the inferior olive. 

 The two most important superficial cortical sheets are 

 the cortex of the cerebrum and the cortex of the 

 cerebellum. 



"Pallium," or brain mantle, is a morphological 

 term applied to the massive dorsal convexity of the 



