16 STUDIES ON THE CENTRAL NERVOUS SYSTEM 



binocular vision is relatively small, the fibres of the monocu- 

 lar vision occupying the greatest portion. We have seen 

 that the field of binocular vision must be localized medially 

 in this ganglion (fig. 3). In cats the part for binocular 

 vision becomes greater, and finally in monkeys it occupies 

 by far the larger portion of the external geniculate body 

 (fig. 4). Yet in monkeys, and also in man, there always 

 remains a part of the field of vision where only one eye sees. 

 This lies very laterally. Hence the division of the field of 

 vision into monocular and binocular parts is of great im- 

 portance. As assumed above, the former in monkeys is 

 probably situated in the ventral layer of the crossed ex- 

 ternal geniculate body. Further investigations proved, 

 that this view is correct. When Professor Zeeman extir- 

 pated the most nasal part of the retina, which belongs to 

 this monocular part, in two cases, I saw degeneration only 

 in this peripheral border of the crossed geniculate body. 

 The largest part of this ganglion serves for binocular vision, 

 a much smaller one for monocular vision. 



The significance of the pathology of the monocular field 

 of vision in man has been especially shown by Behr. Lutz 

 has recently reviewed cases from the literature in which 

 defects in the monocular field of vision were present. The 

 anatomical aspect of this problem is, however, still unsolved. 

 But localization of the monocular field of vision in the exter- 

 nal geniculate body in apes may stimulate further studies 

 in this direction. We should not be surprised if a special 

 area is found to be reserved in the calcarine cortex also for 

 this part of the retina. 



All the secondary degenerations seen in our sections end 

 in the corpus geniculatum externum and in the corpus 

 quadrigeminum anticum. Our references to the anterior 

 colliculus may be brief. In monkeys these bundles are 

 very small, especially on the uncrossed side. The course 

 and ending of the degenerated fibres after partial lesions in 

 the retina differed from one another, suggesting that also in 



