1932] Poliak: Afferent Fiber Systems, Pnniate Cerebral Cortex 59 



portion of the figures.) Some of the finer fibers were seen traversing 

 long stretches in the lower strata along the inner contour of the cortex ; 

 yet the same kind of fibers was also observed in a few instances in the 

 inner stripe of Baillarger itself. In the precentral and the postcentral 

 cortex corresponding with the convexities of both central convolutions, 

 in contradistinction to the bottom of the central sulcus, no degenerated 

 fibers were found in the upper strata above the outer stripe of 

 Baillarger. 



A little further back caudally on the convexity of the postcentral 

 convolution close to the intraparietal or postcentral sulcus correspond- 

 ing approximately with Brodmann's area 2, there exist hardly any 

 appreciable differences as to the number, course, and so forth of the 

 intracortical somato-sensory fibers when compared with the oral half 

 of the convexity of the same convolution corresponding with area 1 

 of Brodmann. Yet a decrease of the exogenous intracortical fibers is 

 noticeable in that portion of the somato-sensory cortex which coats the 

 postcentral sulcus, and on the inner face of the hemisphere. 



In the precentral convolution, that is, in Brodmann's areas 4 and 6 

 the behavior of the afferent somato-sensory fibers is less complicated 

 especially when compared wnth the inextricable meshwork around the 

 bottom of the sulcus centralis, as described above. (Compare figs. 61, 

 62, with figs. 58-60.) While particularly in the latter area the 

 degenerated afferent fibers form a dense plexus of more or less irregu- 

 larly arranged fibers (figs. 9, 60), their courses in the subcortical white 

 matter and within the voluminous precentral cortex are straighter, 

 being for comparatively long distances in the same direction (figs. 

 61, 62). According'ly, there are only a few more or less "horizontal" 

 fibers below the precentral cortex and in that cortex itself, at any rate, 

 less than found in the postcentral cortex. Although the majority of 

 the afferent somato-sensory fibers of the precentral cortex approach 

 more the course of the ' ' radiated bundles, ' ' they, too, must mostly be 

 kept apart from the actual "radiated fibers." They for the most part 

 cross the "radiated bundles" at a sharp angle. As to the number of 

 the somato-sensory fibers in the precentral cortex, this is hardly below 

 that found in the cortex covering the convexity of the postcentral 

 convolution. Considering, however, the wider extent of the precentral 

 region, the total number of the afferent intracortical fibers probably 

 exceeds such fibers entering the postcentral-parietal areas, with the 

 exclusion of area 3 of Brodmann. 



