Elementary Biology. 



FIG. I80.-VKRTICAL SECTION OF KET.NA. 



zone, also continuous with the choroid, known as the ciliary 



is continuous with a 

 ligamentous zone 

 which supports the 

 crystalline lens. 

 The lens thus occu- 

 pies the space im- 

 mediately behind the 

 pupil, and assists in 

 separating the an- 

 terior from the pos- 

 terior chamber of the 

 eye. Lining the 

 choroid is a very 

 delicate membrane, 

 composed partly of 

 nerve fibres, partly of 

 nerve-cells, arranged 

 in a series of definite 

 layers, supported by 

 very delicate con- 

 nective tissue. These 

 nervous elements are 

 the terminations of 

 the optic nerve, which 

 enters, as has already 

 been stated, at the 

 back of the optic 

 capsule. The greatly 

 modified epithelial 



The layer of rods and cones is shown abutting Cells, which form the 

 against the pigment layer of the choroid. Nume- u -, j 



rous granular layers follow, bounded by a layer of true peripheral end- 



nerve-cells and fibres. The layer next the bottom : ncr c n f fV.p nPTVP lie 



of the page is that which is nearest the centre of 1IJ fo b U1 luc 



the e y e - between this nervous 



layer and the innermost pigmented layer of the choroid, and 



