344 



THE SENSORIAL FUNCTIONS. 



as corresponding to the cornea: each separate division of 

 which has been termed a Corneule, being composed of a 

 horny and perfectly transparent material. Each corneule 



422 



423 



424 







(c) has the form of a truncated pyramid, the length of 

 which (L) is between two and three times the diameter 

 of the base (B.) The outer surface (B) is very convex; 

 but the internal, or truncated end (D) is concave; and 

 the concavity of the latter being smaller than the con- 



425 



42G 



N 



vexity of the former, its optical effect is that of a menis- 

 cus, or concavo-convex lens, with power of converging to 

 a distant focus the rays of light which traverse it. With- 

 in these corneules there is extended a layer of an opaque 





