262 



NERVOUS SYSTEM OF VERTEBRATES. 



it. In birds on account of the large size and importance of the 

 eyes both the tectum opticum and optic thalami are well developed. 

 In mammals and man the number of uncrossed fibers in the 

 optic tract increases greatly. The corpus geniculatum laterale 

 (Fig. 131) becomes the most important center for optic impulses 



Fig. 131. Lower part of the corpus geniculatum laterale of the newborn cat. 

 From Cajal (Beitrage u.s.w.). A, B, C, D, endings of opticus fibers. 



and some fibers end in the center of similar structure situated in 

 the pulvinar of the thalamus. The relations in mammals show 

 that with the increasing size of the corpus geniculatum there has 

 gone hand in hand a process of differentiation of function between 



