231 



indicated, doing away with the apparent anomaly of an 

 epithelial pavement in direct contact with a fibrous structure. 



In the human eye a thin structureless membrane support- 

 ing the epithelium is traceable all over the face of the cornea, 

 and which, no doubt^ from its very intimate adhesion to the 

 anterior elastic lamina, has hitherto escaped detection. At 

 b, fig. 1, Plate XV, this membrane is shown in vertical section, 

 and at b, fig. 2, it is seen in face, and as it were ripped up 

 from c, the anterior elastic lamina, near the border of the 

 preparation, a portion of the conjunctival epithelium remain- 

 ing at a. Fig. 3, Plate XV, represents a vertical section of the 

 cornea of the pig, showing, faintly, the same membrane at b, 

 with an anterior elastic lamina very similar in appearance to 

 the corneal structure beneath, and very different from e, the 

 posterior elastic lamina, though nearly of the same thickness. 



In the ox and sheep, as above noticed, an anterior elastic 

 lamina caimot be detected, though the tissue of the cornea 

 proper is evidently more condensed and highly refracting 

 immediately beneath the conjunctiva than elsewhere, as 

 seen at c, fig. 4, Plate XV. 



The substance of the cornea in the shark (Plate XVI, fig. 1, 

 h) consists of a superimposed series of unbroken laminte ex- 

 tending over its Avhole area, and seen in face ; these layers 

 exhibit deUcate fibrous markings, taking different courses, 

 though more or less uniform in each. At the border of the 

 cornea they are seen to be directly continuous with the 

 fibrous tissue of the sclerotic, into which the lamellation may 

 be traced for some considerable distance, as shown at c. The 

 alternately light and dark appearance of the plates would 

 seem to be an optical effect due to the different directions 

 taken by the component fibres ; but if this explanation be not 

 correct it is still a problem requiring solution. In my notes 

 I have named the first and last of these plates respectively 

 the anterior and posterior elastic laminse, but I cannot now be 

 sure whether they are quite structureless or not. 



In the human eye the anterior elastic lamina, or Bowman's 

 membrane, is considerably thicker than the posterior, or the 

 membrana Descemetii, which appears to have been first 

 observed in the eye of the horse. This latter membrane, 

 fitting loosely to the cornea proper, is much more easily 

 demonstrated than the former, and is lined posteriorly with a 

 single pavement of transparent cells, which appear to rest 

 upon a fine basement membrane continuous with the invest- 

 ment of the iris and ciliary processes and the lining of the 

 choroid. 



The pillars of the iris (Plate XVI, fig. 5,^), soon after they 



