ANATOMY IN A NUTSHELL 



367 



of the diaphragma sella. Above it is the lamina cinerea, behind it is the 

 tuber cinereum. On either side is the anterior perforated space. The optic 

 tracts extend outward and backward from the chiasma to (1) the external gen- 

 iculate body. (2) The posterior or inferior quadiigeminal body. (3) The 



PLATE CLXXXVII. 





DESCUSSATION OF PYRAMIDS. 



Showing Superficial Origin of the Cranial Nerves. 



internal geniculate body. (4) Under part of the pulvinar of the optic thala- 

 mus. From these four parts the optic radiations extend to the center of sight. 

 Those fibers which do not decussate at the OPTIC COMMISSURE have already 

 decussated in the corpora quadrigemina. This is the reason that a lesion of 

 one center of sight will cause blindness in the opposite eye and vice versa, for 

 both sets of decussating fibers are destroyed. A lesion through the middle of 



