vegetables; and the milky emulsions that the fruits of the
amygdalaceous plants and palms yield. I may be permitted to add the
result of some experiments which I attempted to make on the juice of
the Carica papaya during my stay in the valleys of Aragua, though I
was then almost destitute of chemical tests. The juice has been since
examined by Vauquelin, and this celebrated chemist has very clearly
recognized the albumen and caseous matter; he compares the milky sap
to a substance strongly animalized--to the blood of animals; but his
researches were confined to a fermented juice and a coagulum of a
fetid smell, formed during the passage from the Mauritius to France.
He has expressed a wish that some traveller would examine the milk of
the papaw-tree just as it flows from the stem or the fruit.

The younger the fruit of the carica, the more milk it yields: it is
even found in the germen scarcely fecundated. In proportion as the
fruit ripens, the milk becomes less abundant, and more aqueous. Less
of that animal matter which is coagulable by acids and by the
absorption of atmospheric oxygen, is found in it. As the whole fruit
is viscous,* (* The same viscosity is also remarked in the fresh milk
of the palo de vaca. It is no doubt occasioned by the caoutchouc,
which is not yet separated, and which forms one mass with the albumen
and the caseum, as the butter and the caseum in animal milk. The juice
of a euphorbiaceous plant (Sapium aucuparium), which also yields
caoutchouc, is so glutinous that it is used to catch parrots.) it
might be supposed that, as it grows larger, the coagulable matter is
deposed in the organs, and forms a part of the pulp, or the fleshy
substance. When nitric acid, diluted with four parts of water, is
added drop by drop to the milk expressed from a very young fruit, a
very extraordinary phenomenon appears. At the centre of each drop a
gelatinous pellicle is formed, divided by greyish streaks. These