510 THE SOLIDS. 



of the cornea : this is of such delicacy and tenuity as to be 

 readily overlooked ; it consists of angular cells which form a 

 tesselated epithelium, and rests upon the posterior surface of 

 the elastic lamina above described. (See Plate L XVIII. 

 Jig. 11.) This epithelium is doubtless concerned in the 

 secretion of the aqueous humour, but it does not appear to 

 extend beyond the limits of the elastic lamina. 



The fifth layer, to which reference has already been made, 

 is the anterior elastic lamina, which is described in the third 

 part of " Physiological Anatomy " as follows : " This is a 

 transparent homogeneous lamina co-extensive with the front 

 of the cornea, and forming the anterior boundary of the 

 cornea proper. It is a peculiar tissue, the office of which 

 seems to be that of maintaining the exact curvature of the 

 front of the cornea ; for there pass from all parts of its pos- 

 terior surface, and in particular from its edge into the sub- 

 stance of the cornea proper, and schlerotic, a multitude of 

 filamentous cords, which take hold, in a very beautiful arti- 

 ficial manner, of the fibres and membranes of those parts, and 

 serve to brace them and hold them in their right configura- 

 tion. These cords, like the elastic lamina of which they are 

 productions, appear to be allied to the yellow element of the 

 areolar tissue. They are unaffected by the acids. The an- 

 terior elastic lamina sustains the conjunctival epithelium 

 which covers the cornea, and is very probably a representa- 

 tive of the basement membrane of the mucous system, as it 

 occupies the corresponding position in regard to the epithe- 

 lium." 



The writer has made diligent and repeated search for 

 this lamina, or for any structure resembling it, without 

 success however ; and he has no hesitation in asserting 

 his disbelief in the existence of any membrane in the 

 slightest degree analogous to the posterior elastic lamina in 

 the situation indicated : he is not prepared, however, to deny 

 the presence of an exceedingly thin layer of structureless 

 basement membrane, although of this even he has not yet 

 discovered any evidence, but conceives it possible that it 

 may exist. Its detection has been attempted in several ways ; 



