224 



a few hours the yellow colour turns to brown, 

 no doubt because the carbon is set more free 

 progressively as the hydrogen, with which it was 

 combined, is burnt. The coagulum formed by 

 the acid becomes viscous, and acquires that 

 smell of wax, which I have observed in treating 

 muscular flesh and mushrooms (morels) with 

 nitric acid *. According to the fine experi- 

 ments of Mr. Hatchett, the albumen may be 

 supposed to pass partly to the state of gelatine. 

 The coagulum of the papaw-tree, when newly 

 prepared, being thrown into water, softens, dis- 

 solves in part, and gives a yellowish tint to the 

 fluid. The milk, placed in contact with water 

 only, forms also membranes. In an instant a 

 tremulous jelly is precipitated, resembling starch. 

 This phenomenon is particularly striking, if the 

 water employed be heated to 40° or 60°. The 

 jelly condenses in proportion as more water is 

 poured upon it. It preserves a long time it's 

 whiteness, only growing yellow by the contact 

 of a few drops of nitric acid. Guided by the ex- 

 periments of Messrs. Fourcroy and Vauquelin 

 on the juice of the hevea, I mixed a solution of 

 carbonat of soda with the milk of the papaw. 

 No clot is formed, even when pure water is 

 poured on a mixture of the milk with the alka- 



* See raj Experiments on the Irritable and Nervous Fibre, 

 (in German,) vol. i, p. 177. 



