194 University of California Puhlications in Anatomy [^'ol. 2 



a similar composition of small, equally organized, though less per- 

 fect, units must be assumed here, too. 



Besides the light stimuli which serve as the material for the higher, 

 "psychic" processes in vision, and which preponderantly use the 

 macular portion of the visual system and enter the macular cortex, 

 other stimuli from the "peripheral" extramacular retina, ser\dng 

 primarily for reflex acts, reach the striate cortex. Since the "peri- 

 pheral" segments of the retinae are in connection by their own cetri- 

 petal fibers with the extramacular portion of the striate area, it is the 

 latter which preponderantly serve for the reflex acts of the visuo- 

 motor apparatus. 



As regards the relation of fibers of the visual path which conduct 

 crossed and non-crossed impulses, the present experiments lead to the 

 acceptance of a most intimate interrelation of both of these fibers 

 within the visual radiation. It is most probable that fiber bundles 

 emerging from small sectors of the cell layers of the external genicu- 

 late body corresponding with homonymous points of both retinae soon 

 mingle with one another, forming a single iso- or homodynamic fiber 

 bundle terminating in a single segment of the \dsual projection 

 cortex. This, of course, is to be accepted only for those portions used 

 together in the binocular act of vision. 



As is apparent from the above statements, the conclusions derived 

 from the present experimental study are decidedly "localistic" both 

 in the main lines, and in all details. With a few exceptions my views 

 are identical with those of the modern "localists" who formed their 

 conceptions mainly upon pathological experience. 



With confirmation of the existence of a strictly "spatial" organ- 

 ization of the entire visual system from the retina to the visual cortex 

 our task may be considered as fulfilled. Yet it would be unfair by 

 silence to admit the imputation that all problems of the finer organ- 

 ization and function of the visual apparatus have been solved here- 

 with. To undertake further steps in the explanation of the physiology 

 and psychology of the vision by structures would, however, mean in 

 the present state of our knowledge a departure from the firm ground 

 of positive facts and an ascension into the uncertain sphere of uncon- 

 trollable hypothesis and speculation. It is for this reason that I would 

 ask the reader to regard the following statements as mere suggestions. 



The fundamental enlightenment derived from the works. of Wil- 

 brand, Henschen, Minkowski, Brouwer-Zeeman, Oberbosch, Heuven, 

 and from the present investigations is that the organization of the 

 afferent visual system renders possible an isolated reception, conduc- 



