1932] Poliak: Afferent Fiber Systems, Primate Cerehral Cortex 49 



three experiments the posterior boundaries of the presently delimited 

 somatic sensory region are fairly congruent, the anterior boundaries 

 being somewhat similar only in Experiments I and II : in Experiment 

 III the anterior limit corresponds almost exactly to the sulcus centralis 

 C in fig. 3). The Experiment V-a stands apart from the foregoing 

 three experiments ; its somatic sensory region occupies the intermediate 

 cytoarchitectural areas 1, 3, 4, and 43 in anid around the central sulcus 

 (fig. 4) . This can also easily be explained by the small lesion damaging 

 just the "knee" of the internal capsule and leaving the anterior and 

 posterior "fans" of the thalamo-cortical radiation undamaged (fig. 5). 



On the internal face of the hemisphere the somatic sensory region 

 occupies in Experiment I (fig. 1), Brodmann's areas 1, 2, 3, and a 

 considerable portion of area 4, not quite reaching the cingular sulcus 

 (Fc). In Experiment II (fig. 2), the extent of the somatic sensory 

 region on the internal aspect of the hemisphere is the largest, occupy- 

 ing Brodmann's areas 1, 2, 3, 4, 5, and 7 entirely, and probably also a 

 portion of the areas 6, 23, and 24, In Experiment III (fig. 3), the 

 somato-sensory region occupies on the internal face of the hemisphere 

 Brodmann's areas 1, 2, 3, and the portion of area 5 situated above the 

 cingular sulcus (Fc). In this latter experiment, accordingly, the 

 somato-sensory region on the internal face of the hemisphere cor- 

 responds fairly exactly with the cytoarchitectural postcentral and a 

 part of the parietal region, leaving free the precentral or the oral half 

 of the somatic sensory region corresponding to the anterior half of the 

 paracentral lobule, and also the praecuneus, in the same way as found 

 on the external face of the hemisphere. The reason is that mentioned 

 before ; namely, the fact that only the posterior segments or ' ' fans ' ' 

 of the thalamo-cortical radiation were interrupted in Experiment III. 

 In Experiment V-a the somatic sensory region over the inner face of 

 the hemisphere in agreement with the size and the position of the 

 lesion occupies the intermediate cytoarchitectural areas 1, 3, and 4, 

 and just reaches the cingular sulcus (Sc in fig. 4) . 



Taking all four experiments together the ' ' minimal somatic sensory 

 region" of the macacus' hemisphere (fig. 6) embraces on the external 

 face: Brodmann's areas 1, 2, 3, 5, and a considerable portion of 

 area 7, all of which belong to the postcentral and parietal region 

 (compare fig. 7). In front of the sulcus centralis, area 4 and at least 

 the greater portion of area 6 belong to the "minimal somatic sensory 

 region." Over the internal face of the hemisphere the "minimal 

 somatic sensory region" occupies Brodmann's areas 1, 2, 3, 4, 5, and 7. 



