286 



ANATOMY OF THE CENTRAL NERVOUS SYSTEM. 



series. The portion of the opticus arising from the anterior corpus quadrigeminum, 

 still very large in the rabbit, is considerably atrophied in man. On the other hand, 

 the principal part of the optic nerve arises in man from the corpus geniculatum 

 laterale. 



It may be expressed as follows: Vertebrates which are dependent entirely, or 

 almost entirely, for vision upon the primary centers, or terminals, have a. prepon- 

 derating development of the quadrigeminal branch of the optic nerve. As soon a» 

 cortical vision becomes more developed, however, the centers standing in more inti- 



Fig. 183. — Thalamus and corpora quadrigemina seen from the side. The 

 forebrain removed at the point where its coronal fibers pass into the capsula 

 interna. The relations of the optic radiation to the posterior part of the capsula 

 interna and to the point of origin of the opticus are shown diagrammatically. 

 Bindearm, Peduncle. Fuss, Pes, or crusta. Hint. Arm., Posterior brachium. 

 Stabkrane eu den Optic Centr., Coronal fibers to the optic centers. T". Arm., 

 Anterior brachium. 



mate relation with the cortex — the pulvinar, the corpus geniculatum laterale — 

 become more important, and the quadrigeminal portion of the opticus diminishes 

 relatively. 



So much for the origin of the optic nerve as represented by a preparation of 



