4 University of California Puhlications in Anatomy [Vol. 2 



Chapter II 

 PROBLEMS 



The cerebral cortex may be reg^arded as a resonance chamber of 

 external happenings, as a transformer and place of synthesis of exo- 

 genous impulses, and as an executor of its own decisions (these being 

 evoked by external stimuli or by their internal residua) ; any attempt 

 to disclose the nature of cortical processes — that is, the fate of the 

 incoming impulses from the external icorlcl — must commence hy trac- 

 ing the afferent paths traversed dy these external impulses on their 

 way to the cortex. To explain adequately what happens to various 

 external impulses in the cortex itself or how they are utilized and 

 combined one with another hj the cortical structures before being 

 manifested as various effector actions, we must definitely settle other 

 preliminary problems. For obviously the fate of the impulses reaching 

 the cortex depends primarily on the organization of the afferent paths 

 and on the mode of their relation to the cerebral cortex (compare 

 Henschen 1918, p. 438, and 1919, p. 58). 



The first task is that of disclosing the anatomical identity of func- 

 tionally distinct afferent paths fronv their peripheral receptor organs 

 to their cortical terminations. Are there within the cerebral hemi- 

 spheres anatomically definable fiber systems, distinct for each of the 

 main afferent impulses (somato-sensory, auditory, visual, and so 

 forth) and terminating in definite, well circumscribed, and relatively 

 small cortical areas, delimited by sharp lines or boundaries, or, on the 

 contrary', do some or all of these impulses use diffusely arranged (or 

 perhaps multiple and differently organized) paths terminating in 

 extensive and ill-defined cortical regions, and thus enter the cortex by 

 several rather widely separated ''gateways"? 



The second and no less important prohlem is that of the internal 

 organization of the afferent paths. There are substantial reasons for 

 assuming that the forms or qualities of various impulses reaching the 

 cortex, in addition to other factors, depend largely on the mutual 

 relationship of the neurons composing these afferent paths. 



Only after these proMems find a satisfactory solution can an attack 

 he made on the following question: By what paths and mechanistns 

 are the impidses streaming into the cortex distributed and conibined 

 to form higher, complex forms of cortical activity^ This latter prob- 



