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 streaks are simply the juice rendered more aqueous, owing to the contact of the acid having deprived it of the albumen. At the same time, the centre of the pellicles becomes opaque, and of the colour of the yolk of an egg; they enlarge as if by the prolongation of divergent fibres. The whole liquid assumes at first the appearance of an agate with milky clouds; and it seems as if organic membranes were forming under the eye of the observer. When the coagulum extends to the whole mass, the yellow spots again disappear. By agitation it becomes granulous like soft cheese.* (* The substance which falls down in grumous and filamentous clots is not pure caoutchouc, but perhaps a mixture of this substance with caseum and albumen. Acids precipitate the caoutchouc from the milky juice of the euphorbiums, fig-trees, and hevea; they precipitate the caseum from the milk of animals. A white coagulum was formed in phials closely stopped, containing the milk of the hevea, and preserved among our collections, during our journey to the Orinoco. It is perhaps the development of a vegetable acid which then furnishes oxygen to the albumen. The formation of the coagulum of the hevea, or of real caoutchouc, is nevertheless much more rapid in contact with the air.

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