62 ANALYSTS OF VEGETABLE MILK 



I have endeavoured by these comparisons to bring into 

 consideration, under a more general point of view, the milky 

 juices that circulate in 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 

 foetid 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 abun- 

 dant, 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,* 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 ileshy 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 phe- 

 nomenon 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 



" The same viscosity is also remarked in the fresh milk of the 

 palo de vaca. It is no doubt occasioned by the caoutchouc, which ii 

 not yet separated, and which forms one mass with the albumen and the 

 caseum, as the butter and the caseum in amimal milk. The juice of a 

 enphorbiaceous plant (Sapium aucuparium), which also yields caoutchouc 

 U so glutinous that it is used to catch parrots. 



