This section is from the book "A Treatise On Therapeutics, And Pharmacology Or Materia Medica Vol1", by George B. Wood. Also available from Amazon: Part 1 and Part 2.
The barks of all the species of willow, possessing a very bitter taste, may be considered as designated by the title above given; for all probably have identical properties; but only that of Salix alba has been recognized by our national standard. This is the common European or white willow, and has been introduced into this country, where it grows extensively.
When dried, willow bark taken from the branches rolls into close quills, which are fibrous, flexible, and difficult to powder. It has a feeble, somewhat aromatic odour, and a peculiar bitter, astringent taste. Water and alcohol extract its virtues. The active ingredients are a peculiar principle called salicin and tannic acid, the latter of which, however, though in considerable proportion, is scarcely sufficient to entitle the medicine to rank among the proper astringents.
The effects of willow bark upon the system, so far as they are obvious, are those of a mild tonic and astringent; but it probably has also an an-tiperiodic action; as it has been used with some success as a substitute for Peruvian bark in intermittents. This, indeed, has been its chief employment; though it is not without efficacy in relaxed and debilitated states of the system, as in the weakness of convalescence, certain conditions of scrofula, passive hemorrhages, etc., in which a slight astrin-gency is indicated along with a tonic influence. Like many other bitters, it has been used as an anthelmintic. The states of preparation in which it may be used are those of powder, infusion or decoction, and of salicin.
The powder is better borne by the stomach than cinchona and many other tonics. The dose of it for other purposes than those of an anti-periodic is half a drachm, repeated three times a day. As a substitute for Peruvian bark, in intermittents, it must be given, during a single intermission, in the quantity of one or two ounces, which may be distributed into doses of a drachm, repeated as often as may be necessary.
The infusion or decoction is made in the proportion of an ounce to the pint of water; and the dose is one or two fluidounces. From one to two pints must be given between the paroxysms of an intermittent. The decoction has been used as a topical application in indolent, flabby, or foul ulcers.
Salicin is by far the most efficient preparation in reference to the anti-periodic effect. Several processes have been suggested for its preparation. Among the best is that of Merck. The boiling concentrated decoction is treated with litharge, in order to precipitate various substances that tend to prevent the crystallization of the salicin. This principle remains in solution, probably holding a portion of the oxide of lead in combination. The lead is thrown down by the addition first of sulphuric acid, and then of sulphuret of barium; and the remaining liquid, being evaporated and pillowed to cool, deposits the salicin, which is purified by repeated solution and crystallization. When pure, it is beautifully white, in minute, soft, shining, slender crystals, inodorous, and very bitter, with the peculiar flavour of the bark. It melts at 230°, and is inflammable at a higher temperature. It is soluble in water, much more so in hot than cold, is soluble also in alcohol, but not in ether, or the volatile oils. It is neuter in relation to acids and alkalies, and is not thrown down by any reagent. Sulphuric acid gives it a bloodred colour; but a more certain test is the odour of meadow-sweet (Spiraea ulmoria), which it yields when heated in solution with chromic acid; salicin being resolved by that acid into the oil of meadow-sweet or sali-cylous acid, among other products. Having been employed to adulterate sulphate of quinia, it is important that there should be some method of detecting it. When taken internally, it gives to the urine the odour of salicylous acid, into which it is probably converted in its passage through the system.
Since the discovery of salicin, this preparation has been almost exclusively used for obtaining the effects of willow bark. At one time, so favourable were the reports of its efficacy in intermittents, that the hope was indulged that it might supersede quinia. But further experience has shown that, though it will often cure intermittents, it cannot be relied on with certainty; and the best that can be said of it is that, when quinia cannot be obtained, it is among the best substitutes of vegetable origin. The dose as an antiperiodic is from two to eight grains, repeated so as to amount to from twenty to forty grains during the intermission. It is less apt to oppress the stomach than quinia.