196 University of California Piihlications in Anatomy [Vol. 2 



arises, the special and additional structural and functional arrange- 

 ments spring in and complete the images till they achieve complete, 

 definite forms. The question arises as to where these mechanisms 

 are and what they are. And here our positive knowledge is utterly 

 lacking. This state of affairs is only natural. The investigation of 

 the visual system has until recently been one of merely settling com- 

 paratively rough problems. A sufficiently reliable basis for the study 

 of the finer and more minute problems was largely absent. The minute 

 structures of the retina, of the external geniculate body, and of the 

 visual cortex were studied in a few instances but mostly for other 

 reasons. Most striking is the absence of careful and exhaustive 

 studies with the help of Golgi's and similar methods. The human 

 retina, especially the fovea centralis remains still an unexplored 

 region. Almost so is the striate area. Special attention must be given 

 here to the possibilities of a minute experimental investigation of the 

 macular cortex and by means of the silver methods. This might, per- 

 haps yield some clues as to the structures underlying the phenomena 

 observed by the Gestalt-psychology, and perhaps help to reconcile 

 both opposing conceptions of "localists" and "dynamists." No less 

 important is the study of the area peri-parastriata under the same 

 aspect (and of other regions of the cerebral cortex). The results of 

 Experiment XIV (figures 25, 86-94), which, however, consider only 

 a part of the existing cortical "relations," that is, medullary intra- 

 cortical and subcortical association fibers, demonstrate a great wealth 

 of especially subcortical association connections of the macular por- 

 tion of the striate area with the next neighboring segments of the 

 area peri-parastriata. A certain preference of the fiber directions and 

 hence a certain localization of higher, cortical visual processes is 

 elucidated thereby. But many other association relationships and 

 their significance, the stripe of Vicq d'Azyr for example, and 

 other elements remain unexplained. Thus, while the strictest prin- 

 ciple of localization in the afferent portion of the visual system must 

 he accepted as an undeniable fact, intricate intracortical mechanisms 

 of the visual region, in the striate and peri-parastriate areas, might 

 co-exist which have another function, that of integrating the single, 

 individual dynamic ' ' elements ' ' reaching the cortex from the periphery 

 into "whole," "complete" visual images. To disclose the identity 

 of these structures and their minute work remains the task of future 

 investigators.^^ 



16 Gurwitsch correctly postulates besides an analyzing apparatus in the visual 

 system another mechanism, which he calls "continuum," whose main function 



