14 University of California Publications in Anatomy [Vol. 2 



problems of the central visual apparatus still remaining unsolved is 

 considerable. To date it is not known precisely where the most 

 important portion of the visual radiation— the macular path— lies, 

 and whether the ''macular bundle" is a small or, on the contrary, a 

 considerable portion of the visual radiation, and how and where it 

 reaches the macular cortex. Another problem has to do with the 

 determination of the shape, size, and position of the individual seg- 

 ments of the visual cortex supplied by individual bundles of the visual 

 radiation and in particular their shape and position in the macular 

 and in the perimacular portion of the cortex. A further question 

 requiring a clear-cut answer is, whether or not a portion of the visual 

 radiation, especially macular fibers, undergoes a second decussation or 

 re-crossing through the corpus callosum ("fasciculus corporis callosi 

 cruciatus" of R. A. Pfeifer). Such or a similar decussation and con- 

 sequently the existence of a double or bilateral cortical representation 

 of each total macula in both hemispheres has been presupposed by 

 some investigators (Heine, Wilbrand, Lenz, R. A. Pfeifer, Foerster) 

 in their attempts to explain the preservation of "central" or macular 

 vision in cases of hemianopsia. And finally, the general architectural 

 principle according to which the entire visual system is organized 

 must be elucidated— certainly a problem of paramount importance 

 for the psychology, physiology, and pathology of vision. We refer 

 to whether the individual small fiber fascicles which form the visual 

 radiation supply small segments of the visual cortex, each bundle 

 supplying only its own segment, without intermingling or over- 

 lapping, as postulated by the strict localistic conception ; or whether, 

 on the contrary, no such strictly regular or "spatial" arrangement 

 with absolute separation and isolation of the individual bundles exists, 

 these probably terminating in "diffuse" way or with mutual over- 

 lapping, as claimed by the opponents of the localistic conception (not 

 to mention the purely "dynamic" concept of the "Gestalt" psy- 

 chologists). If it were possible after injury (isolated or not) of the 

 subcortical visual nucleus or of the visual radiation to show ana- 

 tomically that (ft) all fibers of the visual radiation terminate in the 

 striate area exclusively, and (6) that each definite, individual fascicle 

 of the visual radiation supplies a definite, well delimitable portion of 

 the visual cortex and only that, the dispute between the localists and 

 their opponents could be considered finally settled in favor of the 

 localists. If, on the other hand, the visual apparatus is not organized 

 according to the principle of localization but is in its gross relation 



