1932] Poliak: Afferent Fiber Systems, Primate Cerebral Cortex 153 



Chapter XV 



CORTICAL TERMINATIONS OF THE VISUAL AFFERENT 

 FIBERS (FINDINGS) 



As regards the finer details and the modes of intracortical termina- 

 tions of the afferent visual fibers, as far as such information can be 

 secured by Marchi's method, the following facts deserve to be 

 mentioned. 



In the fissura calcarina, where these details were pai-ticularly 

 studied, the afferent visual fibers occupy, as mentioned before, the 

 zone of the subcortical white substance close beneath the striate cor- 

 tex (fi^. 57, 65, 72, 73, 75, 76). From this zone they gradually 

 penetrate into the cortex mostly in slightly curved arches, sometimes 

 also in sharp turns. Arriving in the cortex (fig 65), they ascend 

 through the lower cortical strata directly or more obliquely upward 

 toward the stripe of Gennari or Vicq d 'Azyr represented in the figure 

 65 by the uppermost of the three horizontal striae (this figure as well 

 as figs. 57, 72, 73, 75, 76, show at the points marked with arrows the 

 abrupt cessation of all the mentioned striae, indicating the boundary 

 of the striate cortex). 



Within the striate cortex the exogenous visual fibers, however, 

 seldom lie parallel to the actual "radiated" bundles and for the most 

 part do not correspond with them. (Compare an identical observation 

 with regard to the thalamo-cortical fibers in the somatic sensory cortex, 

 Chapter VII, and figs. 58-64.) Some of the exog^enous visual fibers 

 reach the stria Gennari or Vicq d'Azyr in a more irregular way. 

 A few traverse, as horizontal or oblique fibers, longer or shorter 

 stretches within the lower cortical strata immediately adjacent to the 

 white subcortical substance. Within the lower cortical strata, the 

 sixth and the fifth layers of Brodmann, the ninth, the eighth, the 

 seventh, and the sixth layers of Ramon y Cajal, the afferent visual 

 fibers are mostly coarse, although less than when still within the white 

 subcortical substance. 



In my preparations degenerated fibers, gradually decreasing in size 

 and number, have been seen to ascend toward the surface of the cortex 

 as far upward as the 4-& cell layer of Brodmann containing the stripe 

 of Gennari-Vicq d'Azyr, the fourth cell layer of Ramon y Cajal, indi- 



