1932] Poliak: Afferent Fiber Stjstems, Primate Cerehral Cortex 187 



for the "decentralistic" attempts at explanation (see Monakow, 1914, 

 pp. 406, 407). 



Lastly, without going into further details of possible combinations 

 of injuries of the central visual apparatus and the various symptoms 

 produced in these ways, it should be mentioned that unilateral sjrtnp- 

 toms can be combined with bilateral symptoms if the opposite hem- 

 isphere is at the same time injured. Since the position of the visual 

 radiation and of the striate areas in the two hemispheres is symmet- 

 rical, the injuries, e.g., gunshots which course horizontally and with 

 their direction more or less perpendicular to the long axis of the 

 hemispheres or, what is almost the same thing, to the longitudinal axis 

 of the visual radiation, will produce symptoms, on the whole, of a 

 symmetrical character. If on the contrary, the direction of the injury 

 varies from the horizontal plane, different portions of the visual 

 mechanisms will inevitably be damag^ed on each side and asj^mmetric 

 symptoms be produced. An almost symmetrical damage to the upper 

 horizontal branches of the visual radiation on both sides owing to a 

 malacic softening can also occur with the resulting incomplete inferior 

 bilateral quadrantic hemianopsia (blindness of the lower halves of 

 both visual fields with the escaping of the macular vision), as one of 

 my unpublished cases demonstrates. 



From what has been said in the preceding pages on the projection 

 of various extramacular and macular quadrants upon certain segments 

 of the striate area, it can easily be understood that the cortical projec- 

 tion of the retina is not in every respect a faithful copy or replica of 

 the retina. Although, in the main, the relative positions of small 

 cortical segments remain the same as in the retina, the positions of 

 quadrants appear, however, slightly or even considerablj^ displaced 

 with respect to each other. Their shape also is considerably changed. 

 What appears presented from the original "spatial" relations of the 

 retina is preponderantly the relative or the mutual relation of small 

 structural units, fiber bundles, and cell groups. The units which were 

 contiguous in the retina remain neighboring in the central visual path 

 and in the visual cortex. Thus, for instance, the macular fibers of the 

 visual radiation, although almost entirely separated from the remain- 

 ing fibers conducting impulses from the extramacular portions of the 

 retinae, preserve among themselves their original mutual relationships. 

 Only on two points does the macular perpendicular branch of the 

 external sagittal layer touch the extramacular portions, viz., where it 

 is continuous with the upper and lower horizontal branches. The 



