34 



INNERVATION. 



[CHAP. xvii. 



already described. It only remains to add, that the anterior wall of 

 the capsule is nearly four times thicker than the posterior ; greater 

 strength being required in front, where the surface is free in the 

 aqueous humor, than behind, where it is adherent to the tissue of 

 the vitreous body. The diminution in thickness does not occur 

 abruptly at the rim of the lens, but commences gradually on the 

 anterior surface near the rim, at a line corresponding to the attach- 

 ment of the anterior wall of the canal of Petit. The capsule is 

 perfectly closed, and cannot allow of the passage of either vessel or 

 nerve to its interior. 



The body of the lens is constructed in a manner calculated to ex- 

 cite admiration. Its superficies, by which it comes into contact with 



the capsule, consists of a 

 layer of extremely trans- 

 parent nucleated cells 

 represented in fig. 122, 

 a. These cells form 

 an organized connecting 

 medium between the 

 body and capsule of the 

 lens, and there is no in- 

 terspace not occupied by 

 them. After death, they 



arkrm V, Anr YYif> 

 SOOn bCCOme 



Fig. 122. 



a. Cells connecting the body of the lens to its capsule (hu- 

 man). 6. Fibres of the lens, with slightly sinuous edges 

 (human), c. Ditto from the Ox, with finely serrated edges, d. -JA. WQ f v /' Q 

 Ditto from the Cod; the teeth much coarser. Magnified 320 WltH water (a 



probably by the capsule 



from the aqueous humor), which is the aqua Morgagni, that some 

 have supposed to exist naturally between the capsule and body of 

 the lens near its border. 



The body of the lens is composed of fibres superimposed on one 

 another, and united side to side in laminae, of which many hundreds 

 must exist. The mode of arrangement of the fibres is, however, 

 more artificial than this. In the mammalia, in general, there are 

 visible on the front surface, when the lens has slightly lost its 

 transparency, three lines, extending from the centre two-thirds to 

 the border, and dividing it into three equal parts : and on the 

 opposite surface three similar lines exist, having an intermediate 

 position. From and to these lines the fibres pass from surface to 

 surface. Thus, a fibre proceeds from the centre in front, advances 

 midway between two of the lines over the border, and comes on the 

 opposite surface to the extremity of one of the lines. Others pass 

 from the extremities of the lines in front, and are lost in the centre 



