10 STUDIES ON THE CENTRAL NERVOUS SYSTEM 



can look with both its eyes together, may be seen pro- 

 jected. Here binocular vision is made possible. The 

 figure 1 shows this projection of the crossed and uncrossed 

 fibres through the whole external geniculate body. They 

 are made by Dr. Overbosch, who will shortly give a full 

 description of the material. Regarding the uncrossed part, 

 one point must still be mentioned. This part does not 

 occupy the whole external geniculate body but leaves the 

 oral part free. 



In rabbits there is also a very fine projection of the 

 retina on the corpus quadrigeminum anticum. The lower 

 quadrants are lying oral and medial, the upper quadrants 

 caudal and lateral. This ganglion is in rabbits of much 

 higher significance for sight than in higher mammals and 

 does not merely serve for lower reflex movements. 



Recapitulating we conclude that the principle of localiza- 

 tion in rabbits distinctly comes to the foreground. The 

 position of the different quadrants of the retina is, however, 

 unexpected. 



In cats an exact localization in the external geniculate 

 body is also found. Cats differ from rabbits. This is not 

 surprising, seeing that the eyes in the former stand more 

 frontal in the head, and that the form of the external 

 geniculate body is not the same. Hence the number of 

 non-crossing fibres is much greater than in rabbits and the 

 binocular part of the external geniculate body has become 

 bigger. Here also it is situated medially, as Minkowski 

 was the first to show. We have further found that the 

 upper quadrants of the retina lie a little more frontal than 

 the lower. It has not been possible to determine the 

 localization of various parts of the retina in the midbrain of 

 cats. The secondary degenerations to this part of the brain 

 after partial lesions of the retina were not sufficiently in- 

 tense to enable us to come to a definite conclusion. Fig- 

 ure 2 shows Dr. Overbosch's and our results about the pro- 

 jection of the retina in cats. 



