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The cryftalline humour in tliis eye, was fo clofely joined to the tu- 

 nica cornea, as to force it out into a kind of globular extuberance or 

 rihng, which appearance I'eemed very flrange to me, having never 

 obferved the like, in any fifh or animal. 



I took ofFa piece of the tunica cornea, rather more than an incli in 

 diameter, and, after leaving it a while to dry, I cut it by an oblique 

 incifion into flices, in order to count, with greater facility, the num- 

 ber of thin membranes of which it was compofed, and I found, that 

 it confifted of, at leaft fixteen or eighteen of thofe thin membranes, 

 laid one on another. 



This tunica cornea, was lined on its infide, with a black membrane, 

 every where entirely impervious to the light, excepting an oval aper- 

 ture immediately in front of the cryftalline humour, through which 

 the liglu was tranfmitted ; this alfo was to me an unufual appear- 

 ance. This oval aperture was in length half an inch, and in breadth 

 fomewhat lefs than a quarter of an inch. 



From this laft obfervation, a thought occurred to me, whether the 

 whale has not a power of enlarging and contra6ling this aperture at 

 j)leafure, fo as to alter the manner of its vifion, as occafion may re- 

 quire. The fame power of dilating and contracting the pupil, I re- 

 member to have obferved in the eyes of a cat. 



I then employed myfelf, to extra<51; the membrane which covers 

 the back part o^ the eye, and to examine the optic nerve ; this I 

 found to be no larger than the optic nerve in the eye of an ox, but 

 I noted this fingular circumftance attending it, tliat inniany places, 

 and I eafily counted as far as twenty five of them, I law adhering to 

 the membrane, arteries and nerves, which ifllied from the part 

 through which the optic nerve palles. Some of thefe, were about 

 the fize of a common pin, others much larger. 



Thefe are the matters, which appeared to me worthy of note on tliis 

 occafion, though, if it were pofliblc to obtain the eye of a \Miale when 



