24 NATURE OF THE HUMOUJes OF THK EYE. 



Kf) phofphatc in M. Fourcroy mentions a phbfphate, as contained in thefe 



thefe humours, j^y^iours ; but I could not perceive any precipitation by muriate 



or nitrate of lime; nor did the alkalis denote tlie prefence of 



any earth, notwithftanding M. Fourcroy 's aflertion of that 



ha. 



HUMAN EYE. 



Human eye; I could not procure a fufficient quantity of thefe, frcfti enough 



dlfte^rent from ^^ multiply my experiments upon them. However, by the 

 other eyes. affiftance of Mr. Carpue, Surgeon to his Majefty's Forces, I 

 fully convinced myfelf, that the humours of the human eye, 

 chemically confidered, did not contain any thing different from 

 the refpefitive humours of the eyes I had examined. The 

 aqueous and vitreous humours contained water, albumen, gela- 

 tine, and muriate of foda ; and the cryftalline humour contained 

 only water, albumen, and gelatine. The fpecific gravity of 

 the aqueous and vitreous humours, I found to be 10053 ; while 

 that of the cryftalline was 10790. 



EYES OF OXEN. 



Sollkewife the J found the eyes of oxen to contain the fame fiibftances as 



•' ' the refpeclive humours of other eyes. The fpecific gravity of 



the aqueous and vitreous humours is I00S8 ; and that of the 



cryftalline 10765. 



Probable law; What is particularly worthy of notice is, that the difference 



the eve^thT more ^^^^'^ appears to exift between the fpecific gravity of the 



does the denfity aqueous or vitreous humour and that of the cryftalline, is much 



diff-r from th'T g''^^'^^'" '" ^^^ human eye than in that of theep, and lefs in the 



of the other eye of the ox. Hence it would appear, that the difference 



humours. between the denfity of the aqueous and vitreous humour and 



that of the cryftalline, is in the inverfe ratio of the diameter 



of the eye, taken from the cornea to the optic nerve. Should 



further experiments fliow this to be a univerfal law in nature^ 



it will not be poffible to deny that it is in fome degree defigned 



for the purpofe of promoting diftindl vifion. 



The cryftalline jj^ taking the fpecific "ravitv of the aqueous and vitreous 

 is confiderably , ° .,.•'. ^ , ., 



more denfe in numours, no particular precaution is neceflary, except that they 



appioacbing the ought to be as frefn as poffible. But the cryftalline humour is 



*^^" ^' not of an uniform denfity throughout ; it is therefore effential, 



that attention be given to preferve that humour entire for this 



operation, I found the '.veight of 3 very frefti cryftalline of an 



ox 



