26 THE EMBRYOLOGY OF THE EYE. 



The vitreous when shrinking in the process 

 of hardening contracts in the direction of 

 these striations, and, becoming detached, takes 

 with it the layer of retinal vessels. When this 

 occurs, the anterior portion of the retina Is 

 also often detached, ruptured at its origin, 

 and drawn inward. The folds in the retina, 

 which are almost always found in preparations, 

 and which are represented In Figs. 7, 8, 9, 10, 

 are probably all artificial, though many writers 

 have described them as normally existing. 



Some anatomists have described the vitreous 

 as consisting of concentric layers, others have 

 described it as homogeneous. The striations 

 along the vessels certainly divide the vitreous 

 to a certain extent, but I cannot confirm the 

 observations of those who have described the 

 vitreous in the embryo as showing a distinctly 

 lamellar structure. 



In Fig. G we have a diagram showing the ves- 

 sels in a half-grown embryo, A being the hy- 

 aloid artery, B the system of vitreous arteries, 

 and C the arteries and veins of the retina 

 which are detached from the equator forward. 



