Though not recognized by the Pharmacopoeias, and scarcely known in this country except as an imported curiosity, the substance thus named exercises over the system an influence so extraordinary, that it would be scarcely justifiable to pass it wholly unnoticed. It consists of the dried leaves of Erythroxylon Coca, a South American shrub, extensively cultivated in Peru, Bolivia, and other neighbouring countries, where its produce was in common use before the Spanish conquest. The leaves bear a considerable resemblance in size and form to those of the Chinese tea plants, and when dried have a somewhat similar odour. Their taste is peculiar, with some bitterness and astringency in decoction. Water and alcohol extract their virtues. Besides the ordinary constituents of vegetables, they have been found to contain a concrete odorous principle, tannic acid, and a peculiar crystallizable alkaloid, called cocaina, on which their virtues probably depend.

The effects of coca on the system appear to be of the same character as those of tea and coffee, though more powerful. It has an excitant influence on the nervous system, induces wakefulness, and supports the strength under an amount of physical exertion which would be impossible without it. The natives of Peru employ it habitually to invigorate them on the occasion of any unusual exertion, as in long foot-journeys in the mountains, where they act as porters, in the labour of the mines, etc.; and, while under its influence, they can support fatigue whole days, even without food, except at night. They carry with them, on such occasions, a bag of the dried leaves, which they chew continually. They who are accustomed to its use, like tobacco-chewers, suffer greatly from the want of it, and find it difficult, if not impossible, to break the habit when once formed; yet experience has not shown that it causes any great injury to the health, or in any appreciable degree shortens life. The amount consumed by an Indian daily, under the circumstances mentioned, is said by Dr. Reis (Bulletin Gen. de Therap., Fev. 28, 1866) to be from fifteen to twenty-five grammes (about four to six drachms). From the accounts of intelligent persons who have used the coca, it appears to exhilarate the spirits, invigorate the faculties both mental and physical, inspire courage, and, in fact, to be a powerful nervous stimulant, as this term is defined in the present work. In excessive doses, as thirty or forty grammes, for example, it excites the circulation, and induces a febrile condition, often attended with hallucination and delirium.

As a medicine, it would probably be found useful in most of the affections to which the nervous stimulants are applicable, and especially such as are benefited by the use of tea and coffee. In South America it has been employed successfully in the treatment of intermittent fever. An apothecary of La Paz has prepared a sulphate of cocaina, which is said to be analogous in antiperiodic powers to sulphate of quinia. (Fuentes, Journ. de Pharm. et de Chim., Oct. 1866, p. 268.) Coca is most conveniently used in the form of infusion, made in the proportion of an ounce to the pint of boiling water, of which one-third or one-half, representing the virtues of three or four drachms of the leaves, may be taken daily.