EXUDATIONS, JUICES, ETC. 245 
ELASTICA (Caoutchouc, India-Rubber). 
The milk-juice of Hevea Braziliensis, and probably 
other species of Hevea (Fam. Euphorbiacese), trees 
indigenous to Brazil. The milk-juice is obtained by 
making incisions in the bark of the tree ; it is then 
allowed to coagulate and dry. The best grade is known 
as Para Rubber. Rubber is also obtained from a 
number of other plants, as various members of the 
Urticacese and Apocynacese. 
Description. — In elastic flask - shaped masses or 
pieces of varying form and size; light, floating in 
water; externally brownish to brownish black ; inter- 
nally brownish, mottled ; odor slight; nearly tasteless. 
Caoutchouc is insoluble in water, dilute acids, or 
dilute solutions of the alkalies; more or less soluble 
in chloroform, carbon disulphide, oil of turpentine, 
benzin and benzol. 
Constituents. — Caoutchouc consists chiefly of two 
hydrocarbons, one of which is ductile and readily sol- 
uble in chloroform, and the other elastic and less sol- 
uble in chloroform ; it is also contains 1 to 2 per cent, 
of resin, volatile oil, etc. 
GUAIACI RESINA (Guaiac Resin). 
A resin obtained from the stem and branches of 
Guaiacum officinale and Guaiacum sanctum (Fam. Zygo- 
phyllaceie), evergreen trees indigenous to the West 
Indies and the northern part of South America. The 
resin exudes spontaneously or is obtained from inci. 
sions in the bark or by heating the fallen trunks. The 
commercial article comes chiefly from Cuba and Hayti. 
Description. — Usually in irregular masses ; exter- 
nally greenish brown, frequently covered with a green, 
ish powder ; brittle, the fracture having a glassy luster 
and being yellowish green or reddish brown and more 
