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 experiments
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, dissolves 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 degrees. The
jelly condenses in proportion as more water is poured upon it. It
preserves a long time its whiteness, only growing yellow by the
contact of a few drops of nitric acid. Guided by the experiments of
Fourcroy and Vauquelin on the juice of the hevea, I mixed a solution
of carbonate 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
alkaline solution. The membranes appear only when, by adding an acid,
the soda is neutralized, and the acid is in excess. I made the
coagulum formed by nitric acid, the juice of lemons, or hot water,
likewise disappear by mixing it with carbonate of soda. The sap again
becomes milky and liquid, as in its primitive state; but this
experiment succeeds only when the coagulum has been recently formed.

On comparing the milky juices of the papaw, the cow-tree, and the
hevea, there appears a striking analogy between the juices which
abound in caseous matter, and those in which caoutchouc prevails. All
the white and newly prepared caoutchouc, as well as the waterproof
cloaks, manufactured in Spanish America by placing a layer of milk of
hevea between two pieces of cloth, exhale an animal and nauseating
smell. This seems to indicate that the caoutchouc, in coagulating,