710 



MANUAL OP PHYSIOLOGY. 



The rudimentary lens is a spherical body, hollow in the centre, 

 made up of an anterior and posterior wall, each of which is formed 

 of columnar cells. The posterior wall of the lens increases 

 greatly in thickness, and approaching the anterior wall obliter- 

 ates the original cavity of the lens. 



The cells forming this wall become very much elongated, and 



FIG. 295. 



A further stage of the development of the lens. (Cadiat.) a. Elongating epithelial 

 cells forming lens ; b. Capsule, c. Cutaneous tissue becoming conjunctiva ; d, e. Two 

 layers of optic cup forming retina ; /. Cell of mucous tissue of the vitreous humor ; g. 

 Intercellular substance ; h. Developing optic nerve. 



form long, fibre-like, columnar cells. The cells of the anterior 

 wall, from being a columnar epithelium, are modified to a flat- 

 tened epithelium, and finally become the layer of epithelium 

 lining the anterior surface of the capsule of the lens. The cap- 

 sule of the lens has been variously considered as arising from the 



