EPITHELIUM OF THE CORNEA. 425 



the corneal epithelium of the Ox by means of the bichromate of 

 potash, and which he has depicted. 



The deepest cell layer resting directly on the corneal tissue 

 is composed of cells that are vertically elongated. They are 

 isolated, but rough in consequence of their detachment from the 

 interdentations of the adjoining ones, and are seated with their 

 broad bases upon the corneal tissue. They do not send off' 

 any processes into this. When seen in profile, the base of the 

 cells appears as a highly refractile line (basal hem or border). 

 The round nucleus of these cells is somewhat nearer their 

 outer than their inner extremity. It may be particularly 

 well seen in sections stained with hsematoxylin, and rapidly 

 hardened in alcohol, of the cornea of those animals that possess 

 remarkably long cells, as for example in the Ox and Pig. 

 Krause* states he has observed peculiar ellipsoidal cells to be 

 sparingly distributed amongst the cells of these layers. 



In the Frog, the epithelium as seen in optical section, where 

 the fresh cornea has fallen into folds, presents the appearances 

 presented in fig. 378. 



I have convinced myself that here also maceration in a ten 

 per cent, solution of common salt until the epithelium sepa- 

 rates in shreds,f constitutes an excellent means of isolation. 



The cells of the outermost layers form a kind of mosaic, the 

 areas of which are circumscribed by highly refractile branching- 

 lines (cell contours with cement that blackens with nitrate of 

 silver), and every polygonal cell contains a beautiful sharply 

 defined granular nucleus (fig. 389, a). 



Rib and prickle cells occur sparingly in the middle cell 

 layers of the Frog. The cells there appear either polyhedric 

 with smooth borders and surfaces, or, as may frequently be ob- 

 served, they give off a limited number of longer or shorter 

 pointed, and often very peculiarly formed, processes (fig. 389, 6). 



The innermost cell layer is here also composed of elongated 

 cells, which, however, vary in length. Thus between shorter 



* Ueber das vordere Epithet der Cornea, (On the anterior epithelium of 

 the cornea,) Gottinger gelehrte Nachrichten, 1870, No. 8 ; Reichert and 

 Dubois-Reymond's Archiv, 1870, p. 232. 



t Schweigger-Seidel, loc. cit., p. 353. 



