344 



THE SENSORIAL FUNCTIONS. 



as corresponding to the cornea: each separate division of 

 which has heen termed a Corneicle, heing composed of a 

 horn}^ and perfectly transparent material. Each corneule 



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(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- 



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 



