The most valuable substance extracted from coca is cocaine, which from its power of producing local and superficial anaesthesia has been much used of recent years in operations on the eyes, teeth, etc. Cocaine rapidly became a fashionable nerve stimulant and sedative; but its use has been accompanied with many fatal accidents, and with the introduction of a new disease, namely, a morbid longing for cocaine, or cocainism. Thus the fairy's wand, that stayed the hunger of the poor and enduring Indian in the Andes, has become a viper in the bosom of a self-indulgent society. The sale of cocaine to the public, other than as a drug, has been forbidden in France, and will probably also be rendered illegal in America.

The scientific study of cocaine has led to a better comprehension of the mysterious qualities of the coca leaf. The first effect is sedative, rapidly followed by stimulation, in which the heart beats are quickened, the nervous system becomes more active, the intelligence more acute, and the muscles pass more easily into a state of contraction. Dr. Mantegazza says that when he was under the influence of coca he had an irresistible inclination to gymnastic exercise. The absence of the sense of hunger seems to be due not only to the anaesthetic effect of the cocaine on the nerve ends of the stomach, but also to the fact that coca is an actual economiser of food, and so modifies the vital processes in muscle as to affect its chemical activity, and to render it capable of performing an equal and greater amount of work with a lesser consumption of carbo-hydrates (Stockman). The absence of emaciation, subsequent debility or other bad results after the most exalted powers of the organism have been called forth, point to coca being more than a nerve stimulant, and also an actual economiser of the bodily expenditure. If it diminishes the consumption of carbohydrates during muscular activity, that is to say, if it enables the machine to work with less fuel, less oxygen will be required, and hence is explained the effect of coca in preventing breathlessness during the ascent of high mountains. Excessive quantities of coca cause headache, giddiness, mental aberration, and ultimately nervous breakdown.