THE EMBRYOLOGY OF THE EYE. 37 



The endothelial layer lies on the stroma of 

 the cornea for a time. Later in foetal life a 

 delicate double-contoured membrane appears 

 between them. This membrane gradually 

 thickens until, in the grown animal, it is a 

 thick lamina which may be stripped off cleanly, 

 and which is very resistant to pathological 

 processes and does not stain like the stroma 

 of the cornea. It is to be considered a 

 product of the endothelium. When the en- 

 dothelial layer in the human eye is displaced, 

 it may proceed to the development of a new 

 elastic membrane, altogether similar to the nor- 

 mal membrane of Descemet (Wagenmann). 



In mammals, as we have seen, the stroma 

 cells of the rudimentary cornea lie directly on 

 the posterior surface of the epithelium (Fig. 

 7). The cells become spindle-shaped and 

 fibres are formed, between the bundles of 

 which the cells remain permanently as the 

 fixed corneal corpuscles. When the cells 

 have become long spindle-cells we find that 

 no nuclei lie on the exterjial epithelium, but 



