38o 



THE PERIPHERAL NERVOUS SYSTEM 



ning centrally. Lens sutures are formed on the proximal and distal faces of the 

 lens when the longer newly formed peripheral fibers overlap the ends of the 

 shorter central fibers. By an intricate but orderly arrangement of fibers these 

 sutures are later transformed into lens-stars of three, and finally of six or nine 

 rays (Fig. 379). The structureless capsule of the lens is probably derived from 

 the lens cells. The lens, at first somewhat triangular in cross section, becomes 

 nearly spherical at three months (Fig. 379). 



, I „/.-,■;„,• ,-h:i,.-i;u,. 



Raphe between 



piilpchya 



Posterior epithelium 



nf rinicii 



Pigment layer 

 of retina 



Lmis fibers 

 Lens capsule 



Vitreous 

 body 



*4>h» cH I 



Fig. 379. — Section through the distal half of the eyeball and through the eyelids of a 65 mm. human 



fetus. X 35. 



The origin of the vitreous body has been in doubt, one view deriving it from 

 the mesenchyma which enters the optic cup through the chorioid fissure and 

 about the edge of lens, another view holding that it arises from cytoplasmic 

 processes of cells in the retinal layer. 



■ It is certain that the vitreous tissue is formed before mesenchyma is present in the cavity 

 of the optic cup. Szily (Anat. Hefte, Bd. 35, 1908) regards this primitive vitreous body as a 



