1932] Poliak: Afferent Fiber Systems, Primate Cerebral Cortex 141 



with the finding that all four lesions of the left hemisphere are Cion- 

 fined to the occipital operculum, and none of the fibers destined for 

 the upper and for the lower lip of the calcarine fissure proper were 

 interrupted. (Compare Experiment V-b.) 



The right occipital lobe studied in sections stained according to 

 the method of Nissl revealed two separate and well-delimited lesions 

 in the occipital operculum. The ventral — and larger — lesion occu- 

 pies approximately the lower half of the operculum in its entire longi- 

 tudinal extent (shaded area marked with an asterisk in 3 and 4, 

 figure 17). Beginning with its anterior end close to the extremity 

 of the simian sulcus it extends as a broad slightly curved stripe along 

 the lower limit of the opercular striate cortex and along the collateral 

 sulcus toward the external calcarine sulcus as far back as the tip of 

 the occipital lobe. This extensive lesion at about the middle of its 

 longitudinal extent penetrates deep into the subcortical white sub- 

 stance and even reaches the sagittal strata where it interrupts approx- 

 imately the lower half of the perpendicular or vertical macular 

 branch of the visual radiation (identified as such in Experiment I-IV, 

 and especially in Experiment V-a; compare M in figure 13). One 

 has, therefore, to assume that the effect of both the cortical and sub- 

 cortical lesion is here approximately the same : the destruction of the 

 lower half of the macular radiation and of the lower half of the macu- 

 lar cortex. The upper and the smaller lesion occupies a portion of the 

 upper half of the opercular macular cortex close to its dorsal limit 

 (marked with a double cross in 3 and 4, fig. 17). This lesion remains 

 mostly cortical and penetrates only slightly into the subcortical 

 white substance. Its effect must be purely local, since the afferent 

 visual fibers damaged by it are here already far distant from the sagit- 

 tal strata. The rest of the striate area, above all the entire calcarine 

 fissure, as well as both the upper and the lower horizontal branches 

 of the visual radiation which terminate there, remain perfectly nor- 

 mal in their entire extent. Even in sections where the lower larger 

 lesion reaches the sagittal strata, the fiber layer Qovering the calcar 

 avis (that is, the main horizontal portion of the calcarine fissure which 

 represents "peripheral" retina), because it is situated inward from 

 the posterior horn of the lateral ventricle, remains absolutely intact. 

 (For explanation see Chapter XVI.) 



The right external geniculate body studied in sections of a con- 

 tinuous series stained according to Van Gieson's method (right eight 

 figures in fig. 18), disclosed two distinctive zones where the cells 



