1932] Poliak: Afferent Fiber Systems, Primate Cerebral Cortex 185 



cortex will also he damag'ed in such a case. Yet it is improbable that 

 the macular cortex will be destroyed on one side and be unimpaired 

 on the other. The result will almost surely be an incomplete or com- 

 plete hemianopsia of the opposite side with perhaps hemianoptic 

 scotomata of the same side ; 



(3) if only the occipital pole is destroyed this will produce a 

 "central" homonymous hemianopsia of the opposite side. A partial 

 injury of the occipital pole will produce, if the lower half of the 

 occipital pole is destroyed, superior quadrantic macular hemianopsia; 

 if the upper half is destroyed, an inferior quadrantic macular hemia- 

 nopsia. Small injuries to the macular cortex will produce small 

 congruent homonymous scotomata of the corresponding macular 

 quadrants, usually of an irregular shape ; 



(4) partial destructions of the striate cortex in the anterior por- 

 tion of the fissura calcarina will result in congi-uent homonymous 

 scotomata of various forms in the perimacular or the "peripheral" 

 portions of visual fields, except when the most oral or also the most 

 "peripheral" zones of the striate cortex along the upper and the lower 

 lip are destroyed ; in which case portions of the temporal crescent will 

 be added ; 



(5) if the fringes of both lips of one fissura calcarina and the 

 bottom of that fissure in its anterior portion are damaged (for example 

 by superficial cortico-malacic and similar processes) there will be an 

 isolated loss of the opposite "temporal crescent." If the bottom of 

 that fissure, besides the fringes of both lips, is also involved in the 

 destruction, including portions closer to the occipital pole, a temporal 

 crescent-hemianopsia will be accompanied by an ordinary hemianop- 

 sia of the extramacular quadrants of both visual fields. It is also easy 

 to understand why loss of vision in the temporal crescent alone is 

 a rare symptom. It is seldom that the anterior portion of the fissura 

 calcarina and its fringes suffer an isolated destruction without 

 impairment of either the visual radiation (at least both horizontal 

 branches), or other more "centrally" located portions of the striate 

 cortex nearer the occipital pole. On the other hand the nearness to 

 the falx cerebri of the anterior portion of the striate area and of the 

 bundles of the visual radiation supplying it (both most dorso-antero- 

 medial and ventro-antero-medial bundles of the horizontal branches 

 first entering into the fissure) can explain the impairment of the 

 temporal crescent as an initial symptom of pathological processes near 

 the splenium of the corpus callosum or even of tumors in distant 



