1932] Poliak: Afferent Fiber Systems, Primate Cerebral Cortex 155 



is especially 4-c layer of Brodmann, Ramon y Cajal's fifth layer, which 

 contains a great number though of only fine and very fine blackened 

 fibers and granules (while in the lower layers the fibers and dots are 

 coarser). In these layers, according to Ramon y Cajal, afferent visual 

 fibers disperse into terminal ramifications, contributing partly to the 

 formation of the external stripe of Baillarger or the stria Gennari or 

 Vicq d'Azyr. It is the fifth layer of Ramon y Cajal where the densest 

 plexus of the exogenous fiber terminations is found (in Ramon y 

 Cajal's fig. 391 marked with B) . This layer corresponds, on the whole, 

 with Brodmann 's lamina granularis interna profunda (i-c) contain- 

 ing numberless small cells or granules, situated immediately beneath 

 the layer of the large asteriform cells. Yet the latter layer, fourth 

 layer of Ramon y Cajal (in his fig. 391 marked with A), Brodmann 's 

 4-& layer, also receives, according to Ramon y Cajal, numerous terminal 

 branches of afferent visual fibers, although the fiber plexus is here less 

 dense than in Ramon y Cajal's fifth layer, Brodmann 's 4-c layer. 



In my preparations the zone of Gennari 's stripe, 4-6 layer of Vogt, 

 Brodmann 's 4-6 layer, contains accordingly only a few and only fine 

 blackened granules, the latter increasing in number and in size toward 

 the ventral layers ( Brodmann 's 4-c, fifth and sixth layers). The 

 slight discrepancy between Ramon y Cajal's findings and mine can 

 easily be explained by the loss or at least the considerable reduction of 

 myelin sheaths of the ultimate rami of the afferent visual fibers after 

 they enter the zone of the stripe of Gennari or Vicq d 'Azyr. It is, how- 

 ever, remarkable that in our preparations the 4-c layer of Brodmann, 

 Ramon y Cajal's fifth layer, is the place of termination of numerous 

 fine myelinated fibers, exactly the layer which, according to Ramon y 

 Cajal, contains the densest meshwork of ultimate branches, although 

 fine degenerated fibers also ascend unquestionably in a moderate 

 number into the stria Gennari-Vicq d'Azyr. 



Ramon y Cajal also found the upper strata above the fourth layer, 

 layers 1, 2, 3, and 4-a of Brodmann, to be reached only by rare delicate 

 branches ascending from the dense meshwork below. He therefore 

 regards the upper strata (his first, second and third layers) as hardly 

 being in direct relation with the bulk of the afferent visual fibers. The 

 lower strata, the sixth, seventh, eighth, and ninth layers of Ramon y 

 Cajal, the fifth and the sixth layers of Brodmann, on the contrary 

 receive a certain although also a small number of fine branches, while 

 the coarse fibers here are the ones that merely pass toward the fourth 

 layer of Brodmann, fourth and fifth layers of Ramon y Cajal 

 (according to Ramon y Cajal). 



