378 



THE PERIPHERAL NERVOUS SYSTEM 



lens, and that on its distal surface, give rise to the vascular capsule of the lens 

 (Fig. 358). On the distal surface of the lens this is supplied by branches of the 

 anterior ciliary arteries and is known as the pupillary membrane. The vessels in 

 this disappear and it degenerates just before birth. The artery of the lens also 

 degenerates, its wall persisting as the transparent hyaloid canal. Fibrillar ex- 

 tending in the vitreous humor from the pars ciliata of the retinal layer to the cap- 

 sule of the lens persist as the zonula ciliata or suspensory ligament of the lens. 



Raphe between 



Anterior epithelium 

 of cornea 



Posterior epithelium 

 of cornea 







Y&At£VhM«B*\ 





N. 



Xt».ar-,«Hm. 



Fig. 360. — Section through the distal half of the eyeball and through the eyelids of a 65 mm. embryo. 



X35- 



Differentiation of the Optic Cup. — We have seen that of the two layers of the 

 optic cup the outer becomes the pigment layer of the retina. Pigment granules 

 appear in its cells in embryos of 7 to 9 mm. and the pigmentation of this layer is 

 marked in 12 mm. embryos (Fig. 358). 



The inner layer of the optic cup is the retinal layer and is subdivided into a 

 distal zone, the pars cceca, which is non-nervous, and into the pars optica, or the 



