206 University of California Puhlications in Anatomy [Vob.2 



of the retina there corresponds a definite, fixed, small segment in the 

 visual cortex (in each hemisphere for homonymous units of both 

 hemiretinae in so far as the binocular portions of the retinae are 

 concerned). But the individual segments of the cortical bi-retina or 

 the quadrants of the visual fields when projected upon the cortex 

 appear somewhat displaced in their mutual relations. The same is 

 observable in the visual radiation and in the external geniculate body 

 though this displacement may in large part be more apparent than 

 real. That which appeare to be strictly preserved in the entire visual 

 system from the retina up to the striate area, is the matter of the finer 

 mutual relations of tlie individual neurons and neuronic groups. 



Such a conception of the visual system, deduced from the present 

 investigation, yields further implications of consequence to physiology, 

 psychology, and pathologJ^ The striate area is the only "gateway" 

 for visual impulses to the cerebral cortex ; therefore all these impulses 

 regardless of their special form or quality must first reach the striate 

 cortex, whence they are distributed to other cortical areas. The view 

 that extensive regions of the hemisphere or even the entire cerebral 

 cortex might in some way or other be concerned with vision, perhaps 

 even with the more primitive, receptive component of that function, 

 has no anatomical foundation. 



The further course of visual impulses from the striate area to the 

 surrounding areas also shows a certain regularity and cannot be 

 described as ' ' diffuse. ' ' As demonstrated by one of the present experi- 

 ments (fig. 25, 86-94), involving small injuries strictly limited to the 

 striate cortex, the very numerous and delicate association fibers arising 

 here disperse themselves only in part in a " diffuse ' ' way to the neigh- 

 boring portions of the striate cortex itself, the majority entering a 

 definite segment of the area peri-parastriata of Elliot Smith or fields 

 18 and 19 of Brodmann and not reaching other areas of the hem- 

 isphere. This points unmistakably toward the existence of a certain 

 localization even in the further spreading of the visual impulses in 

 the hemispheres as supposed by Henschen, and corroborates the sup- 

 position of Flechsig that after entering the cortex of the hemisphere 

 the visual impulses do not spread immediately over a great region but 

 first go to the area periparastriata surrounding the area striata, thence 

 diffusing over other more distant areas (see also my papers, 1926, 

 1927). This leads to the following preliminary conclusions regarding 

 the principles dominating the various connections of the visual pro- 

 jection cortex. The first of these is the strict localistic principle 



