What is commonly so called and used in medicine is the sulphate of quinia. The alkaloid quinia is the most valuable of several obtained from Peruvian bark; that is, the bark of different species of cinchona tree.

Quinine is a bitter tonic, but not a stomach tonic only; it acts decidedly, also, on the nervous. system. When this is debilitated, it will do as much good as any medicine, unless in cases where iron or strychnia is suitable, to improve its tone. But the heroic value of quinine is in the treatment of malarial fevers; that is, intermittent, remittent, and pernicious (or congestive) fevers. All of these prevail most in the autumn, although considerably also in the spring of the year. All of them are characterized by periodicity; that is, more or less regular spells, following each other at intervals or periods. Chills occur either once a day, or every other day, or on the first or fourth days; sometimes, only once in seven days. Each chill, also, is followed by a fever, and that by a sweat. Remittent fever does not go off during the interval, but only remits its violence; hence its name.

So marked is the power of Peruvian bark and its alkaloids, especially quinia, to stop chills, and to cure remittent fever, that it may be well called a specific remedy, even an antidote for them.

Dose of quinine, as a simple tonic in cases of weakness, one or two grains every four hours, until from six to eight grains are taken daily. The form of pills is most convenient for this use; one-grain or two-grain pills. For the cure of intermittent (chills, ague), more is needed; from twelve to fifteen grains daily for about three days, and then lessening gradually, to ten, eight, and six grains a day, continuing the latter for two weeks. In pernicious intermittent, in the Southern States, yet larger doses are required. Remittent fever needs the knowledge and judgment of a physician to deal safely with it.

Cinchonia (sulphate) agrees with some persons better than quinine. The latter, in doses amounting to over eight grains daily, makes many people's ears ring, or hum, or roar. Cinchonia hardly ever does this; at least, in moderate doses. Quinidia and cinchonidia also suit certain patients the best.

The popular idea that quinine injures the health, especially when long taken, is entirely mistaken. If prescribed only in ordinary doses (not more than fifteen or twenty grains in twenty-four hours), it does no harm, and, in malarial cases, may often save life, as well as shorten the time of sickness very much. In over-doses, it may cause temporary, or possibly permanent deafness. Extreme doses might even kill, by poisonous action on the brain; but such amounts are never given by physicians. I have known quinine to be taken, as much as from six to eight, or occasionally ten, grains daily, by a delicate person, for years together with good action as a tonic, and no disadvantage.

Quinine may be taken in malarial cases, whether there be fever or not; for example, in periodic attacks of neuralgia. Other diseases, also, in certain localities, take on the periodic form: but for these we must refer to larger medical works.