As the virtues of the bark reside mainly in its alkaloids, and these are closely analogous in their effects, it will be most convenient to treat first of quinia, as the one best known and most used; and afterwards to point out any difference that may exist between its operation and that of the bark itself, or the other alkaloids. The effects of quinia are usually obtained from the sulphate; and this may be considered, in the following observations, as representing the alkaloid.

When sulphate of quinia is administered to a healthy person, in quantities not exceeding six grains daily, in doses of half a grain or a grain, it produces effects very analogous, if not identical with those of the simple bitters. At first no sensible effects whatever may be experienced; but, after a short time, the appetite is increased, the food appears to be more rapidly digested, the pulse becomes somewhat fuller and stronger, if not accelerated, the temperature of the surface is correspondingly elevated, the processes of sanguification and nutrition arc promoted, and other vital functions are moderately stimulated either directly or indirectly. In other words, the medicine operates as a pure tonic, according to the definition of the term given in this work. In irritable states of the digestive organs, or of the system at large, these effects are sometimes exalted, by the free use of the medicine, into a moderately febrile state, with anorexia, gastric oppression, thirst, a furred tongue, accelerated pulse, heat and dryness of the surface, and headache or other cephalic uneasiness. This condition, however, is probably not the direct result of the action of the medicine upon the system at large, but indirect, and symptomatic of some local irritation produced by it, especially in the stomach or other parts of the digestive apparatus. This state of excessive excitement is rarely experienced in health; because, with an increase in the quantity of quiuia administered, other effects are developed, of a contrary tendency, which overcome its general excitant influence.

Given to the amount of from six to twelve grains daily, in divided doses, or to a less amount in a single dose, sulphate of quinia evinces a tendency to act specially upon the brain, and often produces very decided effects upon that organ. The quantity, however, necessary to the production of obvious cerebral symptoms, varies greatly in different individuals; some evincing an extraordinary susceptibility to the influence of even small doses, while others scarcely feel the largest quantity above mentioned. The first cerebral phenomenon usually presented is abnormal sound, such as buzzing, roaring like that of a strong wind or of a cataract, singing, hissing, ringing, etc. Along with this there is generally more or less hardness of hearing, which, indeed, is one of the most characteristic effects of quinia. Uneasy sensations in the head are also frequent, as of weight, fulness, tension, and sometimes positive pain, though very seldom severe. The circulation is not much affected; the pulse being sometimes increased sometimes diminished in frequency, but for the most part little altered.

When, instead of the quantities above mentioned, from twelve to sixty grains or more are given daily, in divided doses, the effect upon the cerebral functions is increased, and a decided sedative influence upon the circulation produced, as evinced by a diminution of the frequency and force of the pulse, proportionate to the amount of the salt used. Along with the abnormal sounds before referred to, there is now giddiness or dizziness; the individual, if erect, often staggers; occasionally there is irregular muscular movement; the hardness of hearing is not unfre-quently increased to positive deafness, and in a few instances vision is disturbed and blindness induced. At first, if the individual dose is large, there may be flushing of the face, headache, and sometimes epistaxis, indicating decided sanguineous determination to the head; and occasionally, though very rarely, active delirium occurs. In experiments upon dogs, even meningitis has in some relatively few instances been brought on by very large doses. (Briquet, Traite Therap. du Quinquina, p. 161.) But these evidences of over-excitement of the brain give way to others indicating a reduction of nervous power, such as diminished hearing and sight, uncontrollable tremblings, depressed spirits, sighing or yawning, and very rarely a kind of mental disorder, compared by Dr. James McCaw of Virginia to delirium tremens. (Stethoscope, ii. 666.) In some instances, a tendency to drowsiness or stupor is evinced; in others, morbid wakefulness; but in the greater number, neither the one nor the other. Though the pulse is at first sometimes temporarily excited by these large doses, probably in sympathy with the excited brain, it in general soon becomes slower, and always feebler. The pulsations of the heart are often reduced ten or twelve in the minute, sometimes as much as twenty or twenty-five; and the whole number in the minute to forty, but seldom if ever lower. In strength, the pulse is diminished very nearly in proportion to the dose, as shown by the experiments of Briquet upon dogs, by means of Poiseuille's haemadynameter; and, in extreme cases, it may be so much reduced as no longer to be felt at the wrist The skin at the same time becomes cool, pale, and moist, and the face pale or livid, and shrunk.

This prostration under the use of quinia may be carried so far as to constitute real poisoning. Death has often been produced in dogs by-excessive doses; and in one case, cited by M. Guersent. the same result is said to have taken place in the human subject* Giacomniini. who first called attention to the powerful sedative influence of quinia, records the case of an individual, who took by accident about three drachms of the sulphate. Extreme prostration came on, with an almost absent pulse, cold skin, slow respiration, feeble voice, and apparently imminent danger of death, which was, however, averted. In these prostrate cases, the pupil is often dilated, and there is sometimes coma.