1932] Poliak: Afferent Fiber Systems, Primate Cerebral Cortex 129 



folded in, diTe to the more rapid expansion of the non-receptive areas 

 of the parieto-occipital lobes (Elliot Smith, Brodmann 1909, Ariens 

 Kappers 1921, Kuhlenbeck ; for somewhat different explanation see 

 Economo 1930). In higher primates, in anthropoids, and in man, that 

 portion lines approximately the posterior one-third or two-fifths of the 

 calearine fissure and covers the tip of the occipital lobe. If one can 

 accept essentially the same arrangement of the visual radiation in 

 anthropoids and in man, as found here to be valid for the lower pri- 

 mates — and no plausible argument against this can be produced — one 

 must conclude that also in higher primates the macular portion of the 

 visual radiation has a course directly to the occipital pole and to the 

 posterior portion of the calearine fissure, running along the lateral 

 face of the posterior horn of the lateral ventricle, touching dorsally 

 those fibers which gradually enter the upper lip of the calearine 

 fissure, and ventrally those destined for the lower lip. There is, how- 

 ever, in anthropoids and in man this difference in comparison with 

 lower monkeys: in the former the macular fibers eventually turn 

 medially around the posterior end of the lateral ventricle to reach the 

 posterior portion of the calearine fissure ; while in the lower primates, 

 where the greater portion of the macular cortex is on the lateral face 

 of the occipital lobe, the majority of the macular fibers turn laterally. 

 (On the visual radiation in general and on the macular pathway in 

 particular compare Chapter XVI.) 



Experiment V-b 



In this experiment the intent was to perform an isolated injury 

 to the lower lip of the calearine fissure, and in such a way to produce 

 the retrograde changes in the lateral geniculate body according to 

 Nissl's method of the "primary irritation of cells" or of the ''retro- 

 grade degeneration. " In a young Java monl^ey the left occipital lobe 

 was luxated and the lower lip of the fissure damaged by means of a 

 lancet (lower figure in fig. 14). 



Twenty-two days later the animal was killed. A careful macro- 

 scopic and microscopic examination of an interrupted series through 

 the left occipital and parietal lobes, well stained with thionine blue 

 according to Nissl, revealed two injuries: a small superficial one 

 close to the ascending' branch of the calearine fissure strictly limited 

 to the cortex lining the inner face of the hemisphere and hardly 

 reaching the subcortical white matter (marked with a double cross, 



