1932] Poliak: Afferent Fiber Systems, Primate Cerebral Cortex 139 



7, second row from the left). All three last mentioned small degen- 

 erated zones are well delimited and mutually separated by zones con- 

 taining normal cells. Only in the most caudal sections the zones (&) 

 and (c) merge into one zone (b -\- c in 8, second row from the left) 

 which is probably due to the fibers being interrupted beneath the lesion 

 (c). A more detailed analysis of the position, size, and so forth, of the 

 three small zones reveals that the zone (b), the smallest in this experi- 

 ment, in accord with the smallest lesion {b, fig. 17) occupies a position 

 closest to the internal brim of the lateral geniculate body (right con- 

 tours in fig. 18). This zone is closest to the internal segment of the 

 body from which fibers arise for the upper lip of the calcarine fissure — 

 a fact that is in good accord with the position of the lesion, the latter 

 also being closest to the upper lip. The next small zone (c in fig. 18) 

 has already a more lateral position, while still more lateral is the 

 third small zone (d) which is close to the lateral segment of the 

 lateral geniculate body. The position of the latter zone agrees with 

 the position of the lesion {d in fig. 17) which is also closest to the 

 lower lip of the calcarine fissure. Thus the position and the arrange- 

 ment of all of the three small degenerated zones within the interme- 

 diate segment of the lateral geniculate body indicates a regular, 

 orderly projection of small sectors of that particular segment of the 

 body upon equally regularly arranged small sectors of the macular 

 cortex. The large zone (a), due to the fact that its lesion is also in a 

 more ''anterior" position (imagining the striate area of a monkey 

 stretched into the sagittal plane to conform to conditions in the 

 human brain), is also in the anterior portion of the lateral geniculate 

 body. This zone although placed in the intermediate segment of the 

 body probably does not correspond entirely to the macula lutea proper 

 which we must imagine to occupy the most ' ' posterior ' ' position in the 

 striate area (in monkey close to the simian sulcus, in man around the 

 pole of the occipital lobe), but to its immediate neighborhood. Also, 

 this zone enters into the ventral cell layers around the hilus of the lat- 

 eral geniculate body, which according to all probability, is the conse- 

 quence of fibers being interrupted by the lesion (o) bringing impulses 

 from the more "peripheral," that is perimacular regions of the 

 retinae and, in the monkey, entering the posterior portion of the cal- 

 carine fissure. Common t)o all of the four degenerated zones is their 

 location in the intermediate or macular segment of the lateral genicu- 

 late body. The zones leave intact both the external and internal 

 "peripheral" segments of that body, which fact is in a good accord 



