CHAPTER Vn. 

 THE CORXEA. 



Cornea is elliptical in shape, is perfectly trans- 

 parent, which is clue to the arrangement as well as the 

 transparency of its individual parts. It closes the 

 anterior opening of the sclerotic and forms one-fifth of 

 the external envelope which it completes. It fits into 

 the sclerotic like the crystal of a watch into its case, 

 the cornea being beveled on its outer edge. The 

 cornea is composed offivelayers: (1) The anterior epithe- 

 lial layer is, as its name indicates, composed of epithelia 

 disposed in layers and continuous with that of the 

 conjunctiva. (2) Boicman^s membrane. A very elastic 

 tissue which possesses a tendency to curl up. Neither 

 acids or boiling renders this layer opaque as it does 

 the other layers. This layer has no lacunae nor lymph 

 canals, but contains fibrillse and faciculi. Has no 

 fixed cells or movable corpuscles. Is intimately ad- 

 herent to the parenchyma. Cannot be separated as a 

 distinct layer. (3) The parenchyma is composed of fine 

 fibrillae united into fasciculi, bound together by a 

 cement matter. Has a system of canals which are a 



continuation of lymphatic spaces. These lymphatic 

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