1932] Poliak: Afferent Fiber Systems, Primate Cerebral Cortex 63 



the praecuneus in the human brain, is entered by a small number of 

 scattered afferent fibers which, however, reach the posterior extremity 

 of the cingnlar sulcus (partly by way of the cingulum). 



It is also noteworthy that, at least in so far as the ' ' focal zone ' ' of 

 the somato-sensory region is concerned, the supply of the cortex with 

 thalamic fibers is continuous. There are no visible g'aps or small 

 regions without afferent fibers which would alternate with cortical 

 islets receiving such fibers, as supposed by some investigators. (Com- 

 pare similar observations on the supply of the visual cortex: Visual 

 System, in the present work.) 



It can also be noticed that the shape of the areas, showing in the 

 present experiments a richer or a poorer supply of thalamic fibers, 

 closely resembles the shape of the cytoarchit«ctural areas. Thus in 

 Experiment II (fig. 2), the area in front of the central sulcus abun- 

 dantly supplied with somato-sensory fibers, has the form of a narrow 

 triangle stretching more or less parallel along the central sulcus with 

 a sharp point turned toward the Sylvian fissure. That area resembles 

 closely Brodmann's area praecentralis gigantopyramidalis or the 

 so-called motor area (area 4 in fig. 7). In front of it lies the area 

 receiving rare thalamic fibers and corresponding, on the whole, with 

 the precentral agranular area 6 of Brodmann, although, however, it is 

 somewhat smaller. Caudad to the central sulcus the well supplied 

 area in Experiment II corresponds almost exactly to Brodmann's 

 postcentral granular areas 1, 2, and 3 embracing, however, all three 

 mentioned areas (the postcentral region of Brodmann) where area 3 

 stands apart, as said before. This correspondence applies also to the 

 medial face of the hemisphere. Less abundantly supplied caudal 

 areas in Experiment II, however, do not completely cover Brodmann's 

 parietal areas 5 and 7. In Experiment I (fig. 1) areas in front of the 

 central sulcus are smaller and only both of these taken together would 

 correspond with Brodmann's area containing giant cells, while caudad 

 to the central sulcus the abundantly supplied area in that experiment 

 might well correspond with Brodmann's areas 1, 2, and 3 taken 

 together, and the less well supplied area with Brodmann's areas 5 

 and 7 (partly). In Experiment III (fig. 3), the region receiving 

 afferent somato-sensory fibers is, in so far as it receives numerous 

 fibers, a little larger than the postcentral region* of Brodmann. The 

 less well supplied region in this experiment corresponds with the 

 anterior portions of Brodmann's parietal areas 5 and 7. (Compare 

 also Experiment V-a, fig. 4.) 



