NATURE OF THE HUMOURS OF THE EYE. 23 



When expofed to the air, at a moderate temperature. It 

 evaporates flowly, and becomes (lightly putrid. 



When made to boil, a coagulum is formed, but fo fmall as 

 hardly to be perceptible. Evaporated to drynefs, a refiduum 

 remains, weighing not more than 8 per cent, of the original 

 liquor. 



Tannin caufes a precipitate in the frefli aqueous humour, 

 both before and after it has been boiled, and confequently fiiows 

 the prefence of gelatine. 



Nitrate of filver caufes a precipitate, which is muriate of 

 filver. No metallic falts, except thofe of filver, alter the 

 aqueous humour. 



From thefe and other experiments it appears, that theaqueous 

 humour is compofed of water, albumen, gelatine, and a muriate, 

 the bafis of which I found to be foda. 



I have omitted fpeaking of the adlion of the acids, of the 

 alkalis, of alcohol, and of other re-agents, upon this humour. 

 It is fuch as may be expeded in a folution of albumen, of 

 gelatine, and of muriate of foda. 



CryflalUne Humour. 



To follow the order of their fituation, the next of the humours Cryftalllac 

 is the cryftalline. humour. Much 



This differs very materially from the others. of albumen and 



Its fpecific gravity is 1 1000. gelatine. 



When frefli, it is neither acid nor alkaline. It putrifies very 

 rapidly. It is nearly all foluble in cold water, but is partly 

 coagulated by heat. Tannin gives a very abundant precipitate ,• 

 but I could not perceive any traces of muriatic acid, when i had 

 obtained the cryflalline quite free from the other humours. It 

 is compofed, therefore, of a fmaller proportion of water than 

 the others, but of a much larger proportion of albumen and 

 gelatine. 



Vitreous Humour. 



I prefied the vitreous humour through a rag, in order to free Vitreous 



it from its capfules ; and, in that ftate, by all the experiments J?"'™*"""- The 

 T !Ji -T 11 . ,-r^ '3"^^ 3s the 



1 could make upon if, 1 could not perceive any difference aqueous. 



between it and (heaqueoushumour, either in its fpecific gravity, 



(which I have found to be 10090, like that of the other), or 



in its chemical nature, 



M. Fourcroy 



