1932] PoUak: Afferent Fiber Systems, Primate Cerebral Cortex 5 



lem demands above all anatomical investigation of the association, 

 eallosal, efferent, and other fiber systems of each of the known cyto- 

 architectural areas or at least regions. Not before this has been 

 settled and the main paths for diffusion of the nervous impulses dis- 

 closed, can the finer problems of the cortex be studied successfully; 

 this is particularly true of the question of the functional significance 

 of the minute cortical structures and elements as revealed by Golgi's 

 and similar methods. 



Thus, only by foUoioing the course of special impulses from the 

 peripheral receptors along their speciM paths to their special cortical 

 "gateways" and from these latter to other cortical areas and regions, 

 in connection with physiological and pathological investigations, can 

 an adequate conception of the fundamental processes of the cerebral 

 cortex be achieved. 



Scarcely more than the main facts concerning the central portions 

 of the afferent paths, their cortical terminations, and their internal 

 organization is now possessed by us. It is true that the majority of 

 modem neurologists maintain that the main questions of the organiza- 

 tion and working' of the brain are, on the whole, satisfactorily solved. 

 For example, we know, approximately at least, the position of the 

 somatic sensory, the auditory, and the visual paths and their respec- 

 tive cortical terminal regions. There is likewise fair agreement as to 

 the boundaries of the cortical "primary" or projection areas. What 

 still remains to be settled consists, in their opinion, merely of minor 

 problems or of the details of finer organization. 



But a contrary opinion claims consideration. In the formulation 

 of some modern views the interpretation of the data has certainly not 

 always been sufficiently objective. It could be shown that important 

 facts which did not confirm certain favored conceptions either have 

 not received adequate consideration or have been entirely disregarded. 

 For this reason, some ideas must still be regarded as insufficiently 

 founded, needing further study ; and others, as the present study will 

 show, must be abandoned and replaced. 



A few examples may be given. I mention first the extent of the 

 somatic sensory cortex and its relationship to the motor cortex. 

 (Compare also Bechterew, Monakow, 1914, p. 271; Bergmark, 

 Economo-Koskinas, pp. 503, 532, 538.) As is well known, the dispute 

 between the unitarian and the dualistic conception regarding the rela- 

 tion of the cortical ' ' sensorium ' ' and * ' motorium ' ' which arose imme- 

 diately after the discovery by Fritsch and Hitzig of the electrically 



