( 239 ) 



compofing it, in order to reduce tlie fize fmaller, it altered its figure 

 to an oblong and flat fliape, as fliewn ^t Jig. 9, where E is the fame 

 part which, m fg. 8, was fhewn at D , being the point where the 

 filaments are united, or, in other words, where they lo clofely ap- 

 proach, and are fo exceedingly flender, as to become invrllble : hence 

 we may conclude, that the filaments which lie neareft to the central 

 point, being very thin, do thereby produce the oblong round Ihape, 

 and, where the crylialline humour is larger, the filaments in the 

 middle are tliicker, and thus caufe the Ihape to be flattened, which I 

 myfelf have feen ; for the filaments in the eye of a turkey, where 

 they were thickeft, were, fingly, larger than thofe in the eye of an 

 ox, hog, or Iheep. 



I have often, while looking in a mirror, taken notice of that liquid 

 fubftance or moifture, with which the exterior membrane or coat of 

 the eye is covered, and, in which liquid, there are always fome few 

 very minute globules intermixed ; which moifture, aiid tlie globules 

 in it, as often as we fliut our eye-lids are tliereby made to change 

 their places: feeing this, I gathered the reafon, why it is necefiiiry 

 for terreftrial animals to be furniflied with eye-lids (for fiflies, and 

 other inhabitants of the waters do not need them) and, tliat if it were 

 not for the eye-lids, we fliould become blind ; becaufe if the eye-lids did 

 not continually, when we clofe them, moiften the external membi-ane 

 or coat of the e3'e, its furface would grow dry, and contra61; in 

 wrinkles, efpecially in ftrong funfliine, or when we approach a large 

 fire. And I think it very probable, that there is continually, fome 

 kind of humour or moifture, protruded from the inner part of the 

 eye through the tunica cornea, which, by the eye-lids, is fpread 

 over the eye : for, in feveral eyes of hogs, whofe bodies had been 

 immerfed in hot water, to facilitate the fcraping off the hair, I almoft 

 always law a tliia membrane, lying on the outer furface of the tunica 



