£?G8 Ohscrvalions on (he Chr-m'nal Nature 



1802 in lat. 20° north, very near the coast. The latter had 

 also lost three anchors, and had several times struck ; as 

 had been the case with the Lady Nelson, which by these 

 means had broken her slidinir keel. Captain Flinders con- 

 tinued his voyage to the Gulph of Carpentaria. 



XLVII. Obsrivalions on the Chouical Kalure of the Hn- 

 monrsfi/'the Eye. By Richaud Chenkvix, Esq. F.R.S. 

 and M.R.I.J.'^ 



JL UK functions of the eye, so far as they are physical, have 

 been found subject to the connnon laws of optics. It can- 

 not be expected that chemistry should clear upsucli obscure 

 points of phx'siologv as all the operations of vision appear 

 to be ; but some acquaintance with the intimate nature of 

 the substances which produce the ciTects cannot fall to be a 

 useful appendage to a knowledge of the mechanical struc- 

 ture of the organ. 



The chemical history of the humours of the eve is not of 

 much extent. The aqueous iiumour had been examined by 

 Bertrandi ; who said that its speeilie gravity was 975, and 

 therefore less than that of distilled water. Fourcroy, in his 

 Si/sinne cles Connoissances Chlmiqiies, tells xis that it has a 

 saltish taste; that it evaporates wllliout leaving a residuum; 

 but that it contains some animal niatter, with some alkaline 

 phosphate and nuu'iate. These contradictions only prove 

 that we liave no accurate knowledge upon the subject. 



The vitreous humour is not better known. Wintringham 

 has o-iven its specllic gravity (taking water at lOOOO) as 

 equal to 100i34 ; but I am not acquainted with any experi- 

 ments to investigate its chemical nature. 



We are told by Chrouet, that the cryst-lline lens affords, 

 by destructive distillation, ftetid oil, carbonate of ammonia, 

 and water, leaving some carbon in the retort. Jiut destruc- 

 tive distillation, although it has given us much knowledge 

 as to animal matter in general, is too vague a method for 

 investii'-ating particular animal substances. 



I shall now proceed to hiention the experiments I have 

 made upon all the humours. I shall first relate those which 

 were made upon the eyes of sheej) (they being the most 

 easily procured), and shall afterwards speak of those of the 

 human body, iuid other eyes. I think it right to oi)serve, 

 that all these eyes were as fresh as they could be obtained. 



* From the TiwisacUons of the R'jul Soc'iciy for 1802. 



SIIKEP'S 



