22 Mature of the humours on the eye. 



which produce the efFe6ls, cannot fail to be a ufeful appendage 

 to a knowledge of the mechanical ftrudure of the organ. 

 Humours of the The chemical hiftory of the humours of the eye, is not of 

 *P ''."'^,''"°^" much extent. The aqueous humour had been examined by 



chemically, _ .... 



Aqueous Bertrandi ; who faid, that its fpecific gravity was 975, and 



humour, therefore lefs than that of diftilled water. Fourcroy, in his 



Syfthne des Connoissances chimiques, tells us, that it has a failifh 

 tafte ; that it evaporates without leaving a refiduum ; but chat 

 -it contains fome animal matter, with fome alkaline phofphate 

 and muriate. Thefe contradidions only prove, that we have 

 no accurate knowledge upon the fubjeft. 

 Vitreous The vitreous humour is not better known. Wintringham 



humour. j^^^ given its fpecific gravity (taking water at 10000) as equal 



to 10024-; but I am not acquainted with any experiments to 

 inveftigate its chemical nature. 

 Cryfttllinc lens. We are told by Chrouet, that the cryftalline lens affords, 

 by deftru6live diftillation, fetid oil, carbonate of ammonia, and 

 water, leaving fome carbon in the retort. But, deftruftivedif- 

 tillation, although it has given us much knowledge as to animal 

 matter in general, is too vague a method for inveftigating par- 

 ticular animal fubftances. 



I fliall now proceed to mention the experiments I have made 

 upon all the humours. I fhall firft relate thofe which were made 

 upon the eyes of flieep, (they being the moft eafily procured,) 

 and fliall afterwards fpeak of thofe of the human body, and 

 other eyes. I think it right to obferve, that all thefe eyes were 

 as frelh as they could be obtained. 



SHEEPS* EYES. 



Aqueous Humour. 



Offlieeps'eyes: The aqueous humour is a clear tranfparent liquid, of the 



The aqueous fpecific gravity of 10090 *, at 60^ of Fahrenheit. When freflj, 



humour. Water, . , ,. , r ,, ,. i\ 



albumen, gela- ^t has very httle fmell, or tafte. 



tine and muriate It caufes very little change in the vegetable reactive colours ; 



©f foda. and this little would not, I believe, be produced immediately 



after death. I imagine it to be owing to a generation of am- 

 monia, fome traces of which I difcovered. 



* All thefe fpecific gravities are mean proportionals of feveral 

 experiments. The eyes of the fame fpecies of animal, do not differ 

 much in the fpecific gravity of their humours. 



When 



