SAP. 69 



proper juice or sap is generally obtained by making an incision which 

 penetrates a little below the bark. 



The characters and properties of the elaborated or descending sap^ 

 are extremely various. It may, however, be divided into milky sap, 

 saccharine sap, gummy sap, and resinous sap, according to the na- 

 ture of the juices dissolved or suspended in the liquid. As several 

 of the peculiar juices of vegetables contain principles employed in 

 the arts or in medicine, they have been more carefully studied, and 

 their history is more complete than that of the ascending saps. I do 

 not propose to give a monograph gf these juices ; in this place I 

 shall only mention those which have been examined with some care. 



MILKY SAPS. 



The milky saps, as their name indicates, have the appearance of 

 milk ; they owe this milky appearance to globules of insoluble mat- 

 ter, minutely divided, and suspended in a liquid. 



SAP OF THE PAPAW-TREE, (CARICA PAPAYA.) 



The carica papaya grows in tropical regions. The sap, which is 

 extracted from the fruit by incision, is white, and excessively vis- 

 cous. In a specimen of this sap, which came from the Isle of France, 

 Vauquelin found water in large quantity, and also a matter having 

 the chemical properties of animal albumen,* and lastly fatty matter. 



I took occasion to verify the correctness of the results obtained by 

 Vauquelin, on the milk of the fruit of the carica papaya, during my 

 sojourn at Caraccas, where I examined the sap which flowed from 

 the trunk of the tree itself. This sap is less milky, and much more 

 fluid than that which flows from the fruit ; it had the appearance of 

 milk-and-water. Its odor is rather nauseating, even when coming 

 from the plant ; its taste slightly sour. When exposed to the air it 

 soon coagulates. It contains a considerable portion of matter, which 

 may be compared to animal fibrine, and sugar, wax, and resin, in 

 small quantities. 



Evaporated and burnt, it leaves a saline residue. This juice is 

 employed by the inhabitants for medical purposes. 



SAP OF THE COW-TREE. 



Among the number of astonishing vegetable productions observed 

 in the equinoctial regions, is a tree which yields a milky juice in 

 abundance, similar in its properties to the milk of animals. At the 

 time I left Europe, M. de Humboldt expressly recommended me to di- 

 rect my attention to the milk of the cow-tree. A short time after my 

 arrival in the Cordilleras, on the shore of Caraccas, M. Rivero and 

 myself were able to comply with the wishes of the distinguished 

 traveller.! 



The milk we examined came from the Palo de Lechc, the milk- 

 tree, which is extremely common in the environs of Maracaibo. 



* Vauquelin, Annales de Chimie, t. xlix. p. 219, Ire s6rie. 



t Rivero and Boussingault, Annales de Chim. et de Phys. t. xxxiii. p. 229, 2e s6ne. 



