The preparations of cinchona are known as "astringent bitters": they contain, in addition to bitter principles, two tannic acids. As bitters they act as stomachic tonics; that is, promote appetite, the flow of gastric juice, and the digestive power. Long continued, as is the case with all the other bitters, they set up a gastric catarrh, and digestion becomes painful and labored. They differ from the simple bitters in exercising an astringent action on the intestinal mucous membrane, and cause constipation. The red bark is more decidedly astringent than the yellow or pale bark.

Since the time of Sir John Pringle, who made the first experiments on this point, cinchona has been known to possess antiseptic properties. The powdered bark, applied to unhealthy wounds, arrests putrefactive decomposition, and promotes healing. The alkaloids are destructive of the minute organisms, on the presence of which fermentative changes depend, and hence, when added to milk, urine, and other animal fluids, will prevent decomposition (Binz, Herbst, Baxter, etc.). Quinine, the most active of the alkaloids, is not equally destructive of all minute organisms: some, it merely inhibits; others, it kills. The bacteria of septic fluids resist its toxic action to a great extent, and are only inhibited by the largest quantity.

When the crude bark is introduced into the stomach, the alkaloids are dissolved out by the acid gastric juice, in which they are freely soluble. Any portion of the bark, or of the alkaloids, escaping solution in the gastric juice, probably, passes out with the other unabsorbed contents of the intestine. The alkaline reaction of the intestinal juices will cause precipitation of the alkaloids, which, forming insoluble combinations with the bile-acids, will not be absorbed. From the stomach the alkaloids diffuse into the blood with facility. In the alkaline blood, it is probable that the alkaloids are held in solution by the carbonic acid (Kerner). No changes visible by the unassisted eye are discernible in the blood, for, notwithstanding the observations of the older writers, who affirm that the blood was dark and unco-agulable, the moderns deny the existence of such alterations (Briquet, Schwalbe). Quinine acts in a definite manner on certain constituents of the blood—on the haemoglobin, impairing its power to transport active oxygen or ozone, into which the ordinary oxygen of the air is converted. This is demonstrated in the following manner: Mix with old turpentine, that is, turpentine long exposed to the air, and therefore holding ozone, some tincture of guaiacum; if, now, some haemoglobin or a drop of blood be added to the mixture, the tincture of guaiacum assumes a blue color, the change of color being due to the oxidation of the guaiacum by the active oxygen or ozone contained in the haemoglobin (Hermann). The addition of certain substances, notably of quinine, prevents the reaction; in other words, destroys the ozonizing action of the blood. Binz has shown that so small a quantity of quinine as one part to twenty thousand exerts this action to a considerable extent. As soon as the blood is withdrawn from the peculiar influence exerted by the walls of the blood-vessels, as was some time ago shown by Pfluger and Zuntz, its alkalinity begins to decline, and presently it exhibits an acid reaction. Correspondingly with the progress of this acidification, A. Schmidt has shown that the quantity of contained oxygen diminishes and the carbonic acid increases. These changes, leading finally to the death of the blood, are greatly retarded by the addition of quinine (Schulte, Binz, Ransone, Kerner). From these observations we draw the conclusion that quinine lessens the oxidizing or ozonizing function of the blood.

Binz and his pupils have shown that quinine inhibits or lessens the activity of the white blood-corpuscles, and indeed destroys them, or arrests their production; for, in cats poisoned by this agent, the number of white corpuscles was found to be considerably less than in un-poisoned animals (Scharrenbroich, Martin, Jerusalimsky, Geltowsky). By all the observers just named, by Baxter, who made a series of very carefully conducted experiments, and by Cutter, it has been established that quinine inhibits the amoeboid movements of the white corpuscles. These bodies, as other masses of protoplasm, are in constant motion, changing their form and appropriating the materials of their nutrition. Such movements are called amoeboid, and they are arrested by quinine, even in so small a quantity as one part to four thousand; hence it is called a protoplasmic poison. Quinine has also the power to prevent or arrest the migration of the white corpuscles from the vessels. This Binz was the first to demonstrate, using the method employed by Cohnheim for exhibiting the phenomena. This is now generally conceded, although denied by Schwalbe; but, as the observations of Geltowsky show, the quantity of quinine necessary to produce the result varies with the animal experimented on, and ranges from one part in four thousand to one part in eight hundred, outside of the body (Appert). No amount, short of a fatal dose, can affect the movements of the white corpuscles in the living warm-blooded animal, according to Geltowsky, who, therefore, holds to the same view as Schwalbe on this point. In opposition to the views of Binz must also be placed Schtschepotjaw, who has studied the effects of small quantities. 15 Quinine also affects the rate of movement of the heart. An important distinction exists between the action of small and large doses. It is a matter of daily observation that ordinary medicinal doses of quinine (from two to five grains) increase the action of the heart, while experiments with large doses have demonstrated that this agent depresses the circulation. Observations on the intra-cranial circulation, as seen through the retina and drum membrane, have demonstrated that an artificial hyperaemia results from the administration of medicinal doses. On the other hand, as Favier was the first to observe, quinine in large doses depresses the heart, arrests it in the diastole without impairing its contractility, and lowers the arterial tension (Chirone, Briquet). Quinine acts on the cardiac motor ganglia, and hence occur the feebleness of the heart's movements and in part the general lowering of the vascular tension (Lewizky). Besides these effects, it unquestionably depresses the vaso-motor system, after a short preliminary stimulation, probably (Jerusalimsky, Lewizky, Briquet). This depression of the heart from large doses occurs after the vagi are divided (Briquet, Schlockow, Kohler, Lewizky), and is more conspicuous when the agent is introduced into the jugular vein, indicating that the impression made on the heart is not through an increase of inhibition, but on the cardiac ganglia. Immersion of the heart in a quinine solution quickly arrests its movements.

In the normal condition of the human subject, quinine does not appreciably affect the temperature. In the course of some carefully conducted experiments a few years ago, I found that the maximum doses caused not more than a half-degree decline in a healthy adult. In fever, however, the influence of antipyretic doses is prompt and decided. This result may be attributed to several factors: to the depression of the heart and arterial tension, to the suspension of the oxidizing power of the blood, and to the inhibition of the white corpuscles. Jurgensen was the first to observe that quinine prevented the rise of temperature produced by certain physiological acts, as, for example, active exercise, but Kerner has more particularly developed the experimental evidence proving this fact. By active gymnastics, the temperature was found to be elevated two to three degrees Centigrade; but the previous exhibition of a full dose of quinine prevented this rise of the body-heat. Kerner also ascertained that the increased cutaneous secretion, the result of active exercise, was prevented by the administration of sufficient quinine. From all of these facts, it seems evident that the lowering of the temperature by this agent depends on diminished production of heat rather than increased radiation and loss by cooling of the skin. This statement seems confirmed by the experiment of Lewizky, made in Hering's laboratory, by wrapping a rabbit in protective envelopes to prevent loss of heat by cooling, and then practicing the intra-venous injection of quinine; the resuit was a depression of temperature as in animals not so enveloped. To such experiments, the author opposes the insuperable objection that the temperature in rabbits kept at rest declines, and to a remarkable extent, without the administration of any medicament. Nevertheless, the fact of the reduction of temperature by quinine is undoubted. By Popow, who admits the diminution of temperature, the influence of quinine over the body-heat is referred to some unknown biological process.