14 STUDIES ON THE CENTRAL NERVOUS SYSTEM 



in rabbits. We can definitely say that these fibres do not 

 terminate there, but proceed to the anterior colHculus. We 

 have checked this conclusion by cutting a series of sections 

 horizontally after extirpating the left eye. In monkeys 

 these degenerated fibres go along the medial border of the 

 pulvinar but do not terminate there. They avoid the 

 external geniculate body, bend caudally through the 

 bracchium anterius and terminate in the corpus quadrige- 

 minum anticimi. Furthermore, the arguments that the 

 pulvinar in man takes up primary optic fibres, are weak. 



Hence we believe it is better not to regard the pulvinar 

 as a primary optic centre. This does not mean, however, 

 that this region of the brain has nothing to do with vision. 

 The connection of the pulvinar with the gyrus angularis 

 makes it possible that it has something to do with the 

 movements of the eye muscles and with the higher visual 

 functions (stereoscopic vision, the recognition of the relative 

 and absolute distance). 



When the left eye of the monkey is totally extirpated, 

 we see an extensive degeneration in both external genicu- 

 late bodies. But this is not the same on both sides. In the 

 crossed ganglion the degeneration is more intensive than in 

 the non-crossed. It is very clearly seen, that in a part of 

 the periphery of the crossed geniculate body the degenera- 

 tion is more intensive than at the other side. At the 

 ventral border of the uncrossed corpus geniculatum externum 

 a small layer is seen which is lighter and less degenerated in 

 our sections than on the other side. 



What is the significance of this fact? The idea was forced 

 upon us that it is in this layer that the monocular part of the 

 field of vision is to be localized. When we compare the 

 relations between the monocular field of vision and the 

 binocular in rabbits, cats and monkeys, we are led to con- 

 clude as follows. In rabbits the binocular field of vision 

 is small because the eyes stand so far lateral in the head. 

 Hence the part of the external geniculate body reserved for 



