1932] Poliak: Afferent Fiber Systems, Primate Cerebral Cortex 133 



(marked with an asterisk) was found to pass through all cell layei*s of 

 this particular seg-ment down to the most ventral layers containing 

 large nerve cells. Both degenerated zones have no stable position 

 within the nucleus inasmuch as they both gradually descend from 

 caudal sections where they appear {3 and 9 in fig. 16) to the ventral 

 edge of the nucleus in the oral direction {12 in fig. 16). Thus, the 

 large degenerated zone is closer to the apex of the nucleus (to its dor- 

 sal tip ) on oral sections, being confined on caudal sections to the ventral 

 tip of its lateral segment. Also on oral sections this zone does not pene- 

 trate through all cell layers {3, 4, 5, in fig. 16) reaching the ventral 

 layers containing large cells on subsequent and more caudal sections 

 {6-12 in fig. 16). It is remarkable that in both zones the boundary' 

 lines between the normal and degenerated portions of the cell layers 

 are quite sharp and that the boundaries pass through several cell 

 layers in the same direction, as the accompanying fig. 16 well demon- 

 strates. (Compare E. Vries and Heuven). The nerve cells in both 

 degenerated zones appear reduced in number, are pale and shrunken, 

 and show signs of phagocytosis, while the nuclei of glia cells are 

 increased in number. Also no normal nerve cells were found in the 

 degenerated zones, the degeneration here being complete. 



The present experiment showed that: (a) After a small lesion of 

 the striate area on the inner face of the hemisphere just in front of 

 the ascending branch of the calcarine fissure (in fig. 14 marked with a 

 double cross and shaded with continuous perj^endicular lines; also 

 fig. 15), a small portion of the ipsilateral external geniculate body, 

 which occupies a part of the inner segment of that body where accord- 

 ing to Brouwer and Zeeman optic fibers from the upper extramacular 

 homonymous quadrants of both retinae terminate, degenerated ; and 

 that {!)) after the damage to the lower horizontal branch of the visual 

 radiation (shaded area in fig. 14 marked with an asterisk which, how- 

 ever, shows only the hidden striate area projected upon the surface) 

 a comparatively large portion, almost the entire lateral segment of the 

 external geniculate body where, according to Brouwer and Zeeman, 

 optic fibers from the lower extramacular homonymous quadrants of 

 both retinae terminate, degenerated. It is, however, probable that in 

 our case a small number of macular fibers — those entering the striate 

 area close to the posterior end of the calcarine fissure — were also 

 interrupted, and the degenerated zones in the external geniculate body 

 to a small extent spread over into the macular segment of that body. 



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