37 



the eye close for a season, and the wound will heal, 

 and the humour recruit. 



Indeed an eminent Italian affirms, that he has slit 

 the pupil of divers animals, and squeezed out all the 

 humours, and has afterwards restored them perfectly 

 to sight : nay, that the eyes of many, instead of being 

 damaged thereby, seemed more lively and vigorous 

 than before. 



The second humour, termed (improperly enough ) 

 the chrystalline, consists of many thousand filaments 

 tending from the circumference to the centre, and 

 closely woven together. Jt is a little convex before, 

 and more behind. It serves to refract the rays of light 

 so that they may meet and form an image,on the bottom 

 of the eye. It is set in the forepart of the vitreous 

 humour, like a diamond in its collet, .and is retained 

 there by a membrane that surrounds it, thence called 

 its capsula. It is toward the outside like a jelly ; 

 but toward the centre as hard as salt. The figure of 

 the outer part is varied by a ligament annexed, which 

 can make it either more or less convex, or move it to 

 or from the retina. And this is absolutely necessary, 

 in order to distinct vision, for as the rays of distant 

 objects diverge less than those of near objects, the 

 dirystalline must either be made less convex, or be 

 set farther from the retina. 



When dried, it appears to consist of a vast number 

 of thin, round scales, one upon another, 2000 of whicli 

 have been counted in one chrystalline. Each of these 

 consists of a single fibre, wound this way and that, iu 

 a stupendous manner, so as to run several courses,aud 

 meet in as many centres, and yet not interfere or cross 

 in any place. 



The third, which is termed the vitreous humour, is 

 not unlike melted glass. It is covered with an ex- 

 ceeding thin coat. The forepart is concave, as re- 

 ceiving the chrystalline ; the other side is convex. 



The whole apparatus of the eye tends to this, that 

 there be produced in the bottom of it, a distinct col- 

 k-ction of all the rays, which proceeding from any 



