THE RESINS. 253 



and the "West Indiea. A small quantity is also furnished by 

 other species of the same genus. Deep incisions are made 

 into the wood, out of which the balsam flows. It is said 

 the trees are so full of it that they sometimes burst spon- 

 taneously. The balsam is of a yellow or a yellowish color. 

 That which is thin is generally of a light-yellow, and the 

 thicker of a golden color. In specific gravity it varies 

 from .91 to .99. In it the starch of Canna edulis is invis- 

 ible ; that of the potato visible. It contains from thirty to 

 eighty per cent, of volatile-oil, also amorphous resin, and 

 crystals of a resinous (copaibic) acid. This balsam is used 

 in making varnishes and in the manufacture of tracing- 

 paper. It is also employed in medicine. 



220. .The Elemi Resins come from the Myrrh family 

 (BurseraeecB). The largest quantity is from Idea Idoariba 



. (Rio), Idea viridifiora (Guiana), Amyris Plumiri (Mexico 

 and Yucatan), and Bursera gumrrdfera (Martinique and 

 Guadeloupe). It is not so hard as colophony, and can be 

 kneaded with the hand. It can be cut with a knife, yet 

 this is true of no other resin. The taste is aromatic and 

 bitter, and the smell fennel-like. There are three kinds: 

 (1) balsamic, which is greenish and contains but few crys- 

 tals ; (2) soft, which is yellowish and contains more crystals; 

 (3) hard, which varies from yellow to white, and contains 

 still more crystals than the last. These resins have a 

 specific gravity of 1.02 to 1.08. Among their component 

 elements are found both crystals and amorphous resins, and 

 volatile-oil (3-13 per cent). They are used in the manu- 

 facture of varnish, especially that used by coach painters. 

 In medicine their use is similar to that of turpentine. 



221. A shrub or small tree, about twelve feet high and 

 little less than a foot in diameter, growing in the Mediter^ 



