CHAPTER IV 

 THE ORIGINS OF THE CEREBRAL CORTEX 



There must be a number of anatomical arrangements 

 which are present in the same form in all vertebrates, ar- 

 rangements which mediate the simplest manifestations of the 

 activities of the central organs. In order that any particular 

 mechanism may be understood, we have only to discover the 

 species of animal or the favorable developmental stage of an 

 animal in which it is present in so simple form as to be fully 

 intelligible. When the relations of such a structure, say a fiber 

 tract or a group of cells, have once been accurately deter- 

 mined anywhere, then it is usually easy to recognize them 

 again, even when new complications have more or less ob- 

 scured the facts. 



— LuDwiG Edinger 



THE cortex of a man is twice as massive as 

 that of an ape of equal body weight. Ana- 

 tomically, the cerebral cortex is by far the 

 most distinctive human characteristic. It is common- 

 ly believed that mankind differs from all brutes even 

 more in the functions of his cerebral cortex than in its 

 obvious structure. But an exact account of just what 

 these functions are and of the mechanisms by which 

 they are performed in either men or brutes is perhaps 

 the biggest biological problem that still awaits solu- 

 tion. 



The approach to this problem by way of introspec- 

 tive analysis of human faculties has usually promptly 



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