1932] Poliak: Afferent Fiber Systems, Primate Cerebral Cortex 203 



of the external geniculate body and in the upper horizontal branch 

 of the visual radiation, and their cortical representation in the upper 

 lip of the fissura calcarina. These correspond with the lower homony- 

 mous quadrants of both visual fields, including the lower half of the 

 monocular crescent but excluding- the macular portions. 



The lower extraniacular quadrants of both homonymous hemire- 

 tinae have their subcortical representation in the external segment of 

 the external geniculate body and in the lower horizontal branch of the 

 visual radiation, and their cortical representation in the lower lip of 

 the fissura calcarina. These correspond with the upper homonymous 

 quadrants of the visual fields, including the upper half of the monocu- 

 lar temporal crescent but excluding the macular portions. 



The homonymous halves of both maculae have their subcortical 

 representation in the large intermediate segment of the external 

 geniculate body and in the intermediate vertical or perpendicular 

 branch of the visual radiation interposed between both extramacular 

 horizontal branches, and have their cortical representation in the pole 

 and (in the monkey) in the operculum of the occipital lobe {Oo in 

 figs. 21 and 24). Here the upper homonymous quadrants of both 

 hemimaculae (lower homonymous quadrants of the macular portions 

 of the visual fields) are localized in the upper half of the vertical 

 branch, closer to the upper horizontal branch, and in the upper half 

 of the occipital pole and operculum. The lower homonymous quad- 

 rants of both hemimaculae (upper homonymous quadrants of the 

 macular portions of the visual fields) are localized in the lower half 

 of the vertical branch, closer to the lower horizontal branch, and in 

 the lower half of the occipital pole and operculum. 



The arrangement of the segments or quadrants of the homonymous 

 hemiretinae as projected into the visual cortex is, therefore, as fol- 

 lows (fig. 23) : 



The monocular portion of the crossed retina, the so-called tem- 

 poral sickle or crescent, has its cortical representation in the anterior 

 portion of the fissura calcarina nearer to the splenium of the corpus 

 callosum. Its shape is that of a crescent with both horns turned 

 occipitalward, one in the upper lip, the other in the lower lip. 



Behind and partly embraced by it, is the projection zone of the 

 binocular extramacular homonymous quadrants, likewise approx- 

 imately crescent shaped. This zone, in the brain of the monkey, covers 

 the inner face of the occipital lobe, immediately behind the ascending 

 and descending branches of the calcarine fissure (lower figure in figs. 

 21 and 24). 



