146 University of Calif ornia Puhlications in Anatomy [^^^h. 2 



From the above description it seems fairly certain that the visual 

 disturbance in this experiment was that of a hemianopsia on the right 

 side although the same was probably incomplete, due to the incomplete 

 destruction of the left-sided striate area. 



Both external geniculate bodies including the entire betweenbrain 

 and the adjacent portion of the midbrain were cut in a continuous 

 series and stained with thionine blue acoording to Nissl's method. 



A careful examination of the entire well-stained series revealed : 

 (a) a complete degeneration of all the nerve cells of the external 

 geniculate body ipsilateral with the damaged left hemisphere in the 

 central, the anterior, and the dorsal portion of that nucleus with the 

 cells of the two most posterior (caudal) layerH and those of the ven- 

 tral layers remaining normal; (&) a complete absence of any undoubt- 

 edly degenerated nerve cells in the opposite external geniculate body ; 

 and (c) a complete absence of any degenerated nerv^e cells in the mid- 

 brain, especially in the superior colliculi. 



In particular the left external geniculate body appeared in toto 

 somewhat reduced in size in comparison with the right normal body. 

 Of the left body the medioventral or internal and a portion of the 

 lateroventral or external segment remained normal ; of the most pas- 

 terior (caudal) segment a portion also remained normal — at least the 

 cells exhibit here less advanced degenerative changes than those of 

 the undoubtedly degenerated segments. Roughly, the degenerated 

 portions of the left external geniculate body comprised the interme- 

 diate or the macular segment and the greater portion of the lateral 

 segment as far as the dorsal end of the nucleus (consider the segments 

 as they usually appear on the frontal sections through the geniculate 

 body, e.g., fig. 16) . The boundary lines or lines of demarcation between 

 the normal and degenerated segments of the cell layers are in the 

 greater part remarkably sharp, in only few instances did the normal 

 and the degenerated cells mingle for a short distance. It is note- 

 worthy that the degenerated zones did not respect the cell layers but 

 passed through two or more of the layers at the identical levels. 

 Further the emphasis has to be put upon the fact that in the portions 

 of the geniculate body which degenerated the process of degeneration 

 was complete : no nerve cells — large, medium-sized, or small — could be 

 found which could be regarded as normal or even less advanced in the 

 degenerative process. On the contrary, in the normal segments none 

 of the nerve cells showed definite signs of degeneration, or at any 

 rate, they showed only slight changes. 



