1932] Poliak: Afferent Fiber Systems, Primate Cerebral Cortex 151 



From the above description it is fairly certain that in this experi- 

 ment a complete homonymous hemianopsia to the rig:ht was produced 

 by the complete destruction of the striate area of the left side. 



A careful study of an uninterrupted series through both geniculate 

 bodies, the thalamus, and the anterior portion of the midbrain, well 

 stained with thionine blue aecording to Nissl's method revealed: (a) 

 a complete degeneration of all nerv^e cells of the entire external genic- 

 ulate body ipsilateral with the destroyed striate area (left), (b) a 

 complete preservation of all nerA^e cells of the entire external genic- 

 ulate body opposite to the side of the destroyed striate area (right), 

 and (c) a complete absence of any changes of the cells of the midbrain, 

 especially of the superior colliculi. 



In particular, the left external geniculate body appeared reduced 

 in size about one-fourth in comparison with the normal body of the 

 right side. The individual fiber and cell layers of the left-sided 

 body appeared also considerably reduced in thickness, their outlines 

 blurred and indistinct, their nerve cells, not excluding the large ele- 

 ments of the ventral layers, exhibiting extensive degenerative changes 

 notably the reduction in size and the poor staining. Not even indi- 

 vidual cells remained normal, not to mention a. complete absence of 

 normal segments of cell layers. Only a few scattered cells were found 

 to be stained somewhat better, but even these show marks of degenera- 

 tion. The emphasis has to be put upon the fact that all the large cells 

 of the ventral layers, which in the preceding experiment remained 

 normal, degenerated completely in the present experiment. On the 

 contrar}^ the corpus (grise'um) praegeniculatum of the left side, as 

 well as the internal geniculate body of the same side preserved its 

 normal appearance. 



The external geniculate body of the side opposite the injured 

 striate area (right) remained perfectly normal in all its parts includ- 

 ing its intermediate macular segment. There are neither degenerated 

 zones in it nor individual scattered degenerated nerve cells. 



Likewise no degenerated nerve cells were found in the midbrain, 

 particularly in the superior colliculi, though a portion of the pulvinar 

 degenerated (due to the damage of the parieto-occipital cortex). 



The present experiment demonstrated that : (a) the external genic- 

 ulate body degenerated completely when the striate area of the 

 same side was destroyed completely, (b) the external body remained 

 fully preserved although its opposite striate area was completely 

 destroyed, (c) no cells in the external geniculate body remained 



