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 w r ith 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 my Experiments on the Irritable and Nervous Fibre, 

 (in German,) rol. \, p, 177. 



