This section is from the book "The London Medical Dictionary", by Bartholomew Parr. Also available from Amazon: London Medical Dictionary.
(French). Indian rubber, or elastic gu m. Called also Cayenne resin, and cautchuc. It is prepared from the juice of a tree in Cayenne or other parts of South America. The Mexicans call it olin, or olli; the Spaniards of that kingdom, ule; Aublet, hevea Guianansis; Jacquin, echites co-rymbosa; and Linnaeus, in his Supplementum Plan-tarum, iatropha elastica. The hevea is the proper genus; though it is procured also from the urceola, described in the Asiatic Researches, v. 5. the artocarpus, the Indian, and probably our own, fig tree. The hevea is a monoicous plant of the family of the tithyma-loides, nearly allied to the croton. The Indians obtain the juice of this tree by incisions made, through the bark in its lower part, from whence it oozes out, under the form of vegetable milk, and is received in a vessel placed under the incisions. The milk, on exposure, gradually inspissates into a soft, reddish, elastic resin, and is commonly brought to Europe in the form of pear shaped bottles. It is soluble in rectified oil of turpentine, oil of wax. and of lavender, but more perfectly in ether. M. Bernard, in the Journal de Physique for 1781, has given many experiments on this substance, and has shown it to consist of a fat oil, insoluble in water or ardent spirit, but soluble in any oily fluid. The volatile alkali which it contains, is apparently furnished by the smoke in which the bottles are dried. The distinguishing properties of the substance are, its solidity, flexibility, and elasticity, and its quality of resisting the action of aqueous, spirituous, saline, oily, and other common solvents: from these properties it becomes extremely fit for bougies, catheters, and pessaries; to which purposes it is only medically applied.