506 THE SOLIDS. 



Cornea. 



The cornea, although in a state of health as clear as 

 crystal, yet possesses a complicated and beautiful organis- 

 ation, plainly demonstrable with the aid of the microscope. 



Notwithstanding also the definite line of demarcation by 

 which the limits of the cornea and schlerotic are marked out, 

 these two parts are yet inseparably united to each other ; 

 this indissoluble union depending upon the circumstance of 

 the existence of a structural connection between them, the 

 nature of which will shortly be rendered evident. 



The cornea is clearly divisible into four, and, according to 

 some observers, even five laminae ; these are, reckoning from 

 before backwards, conjunctival epithelium, cornea proper, 

 posterior elastic lamina, and the epithelium of the aqueous 

 humour ; the fifth layer has been described in the " Physio- 

 logical Anatomy " under the title of the " anterior elastic 

 lamina." These several layers will be separately noticed, and 

 in the order mentioned. (See Plate LXVII. Jig. 1.) 



The conjunctival epithelium forms a distinct membrane of 

 appreciable thickness and capable of separation as such shortly 

 after death. It consists of several layers of superimposed 

 cells, which partake of many of the characters of ordinary 

 epidermic scales or cells. 



Those cells which constitute the outer or more superficial 

 layers are large, flat, and membranous ; whilst those nearest 

 to the cornea proper, and which appear to rest directly upon 

 it, are baton-shaped, and disposed vertically to the surface of 

 the cornea. (See Plate LXVIII./^. 3. 5., and Plate LXVII. 

 fig. 1.) 



After death this epithelium becomes whitish and opaque, 

 and it then forms the film of the eye. 



The second lamina, according to the observations of the 

 author, is the cornea proper ; and it is this which constitutes 

 the principal bulk of that structure. 



Externally, the cornea proper is firm and dense in texture, 

 but becomes more lax and soft gradually as we approach the 



