Active Ingredients. - Willow bark is bitter and astringent. These qualities are referable partly to a certain proportion of tannin, and more particularly to the presence of a crystalline neutral principle called salicine, the composition of. which is C13H18O7. Besides these there are gum, extractive, and other constituents ordinarily occurring in the bark of trees. Salicine, when separated, presents itself in the form of white and silky acicular crystals and laminee; it is bitter and inodorous, and soluble in water and in alcohol.

Physiological Action. - The action of salicine is very slight, if measured by any sensible disturbance which it can cause in the human organism. Various experimenters have taken enormous doses for days and weeks together, without suffering any disturbance of digestion, and with no other noticeable effect than slight disturbance of vision and persistent noises in the ears. One or two cases are related in which the visual disturbances (clouds and sparks of fire) were troublesome even for some days after the medicine was left off. But the most important fact is one that has been fully established by recent experiments, namely, that salicine does not possess the power of arresting putrefaction, and consequently lacks that peculiar property which belongs in pre-eminence to the cinchona alkaloids. Salicine further differs from the cinchona alkaloids in being rapidly decomposed within the organism.

Therapeutic Action. - At the present day salicine is much discredited as a remedy, especially in England. As an antiperiodic, Gar-rod denies its power, or rates it very low; and with this agrees the general feeling. It is nevertheless somewhat puzzling that salicine, if it be really inert, should have acquired so extensive a reputation for curing intermittents; and it is well not to forget the fact that so good an observer as Kuchenmeister declared that salicine somewhat reduces the size of the spleen in the healthy subject. Some of the favorable American reports are especially hard to be explained away, unless we suppose gross carelessness of observation. Yet it cannot be denied that the best authorities have everywhere given up the hopes which were at first excited, of salicine taking the place of quinine. At most it can only be allowed that in very mild cases of intermittents salicine may apparently be used with success. If employed for such a purpose, doses of from ten to sixty grains must be administered between the fits of fever.

Salicine also possesses a doubtful reputation as a repressor of passive haemorrhages and chronic mucous discharges.

Probably it is only as a mild stomachic tonic, in cases of atonic dyspepsia, that salicine will continue to be used. It may be specially convenient when we need a change from other remedies which have begun to lose their power.

Preparations and Dose. - None officinal. Salicine, gr. v. - 3 j. (.30-4.)