SALIX, Medical Properties of. The barks of several species of willow have been long celebrated for their astringent and antifebrile qualities; but from the great difficulty of determining the species, it is not ascertained which kind is entitled to the preference. The Salix Rasselliana (Bedford willow) appears to possess the greatest quantity of tannin ; but the peculiar principle termed salicia seems to exist in the Largest proportion in the S. Helix, or rose willow ; while the S. pcntandra L. (the bay-leaved willow), possesses', both in its hark and leaves, the largest amount of bitterness and resin, and a most balsamic odour. The barks of S. S. fragilis, andS. cuprca (or great round-leaved willow, which yields the broad-leaved willow bark), are also gathered,often indiscriminately. Whichever species is selected, the bark should be stripped in spring from branches not less than three years or more than six years old, and from trees growing in moist rather than swampy places. It should be carefully dried in the shade. The fresh bark has a faint odour somewhat resembling bitter almonds; the dried bark is devoid of odour. The taste is at first mucilaginous, afterwards bitter and astringent. The degree of astringency may be easily tested by adding to a decoction of the bark a solution of gelatine. Tincture of nut-galls does not affect it. According to the analysis of Pelletier and Cavcntou, the bark of S. alba contains a green fatty matter similar to that of cinchona, a yellow slightly bitter colouring matter, tannin, resinous extract, gum, wax, woody fibre, and an organic acid, which with magnesia forms a salt easily soluble in water and alcohol. Since these analyses, salicin has been found. [SALICYLIC GROUP; SALICIN.] Willow bark possesses astringent, tonic, and febrifuge qualities, which render it a valuable substitute for cinchona, and as it often suits the stomach better it is well calculated for the treatment of agues among the poor. In debility of the stomach and relaxation of the
mucous membranes, it is often very serviceable. In the latter cases, an infusion, made with cold water, of the powdered bark of Salix pentandra, is preferable ; but any of the others may be made equal to it by the addition of bruised cinnamon bark. Like all astringeut tonics, it is often useful as an authelnilutic.
Salicin has febrifuge properties, but they are much weaker than those of quinia; it must therefore be given in considerably larger i doses. It may be given in substance or solution, and also in con junction with many other salts, without undergoing decomposition or entering into combination. " In its passage through the system it undergoes oxidation, and is converted into hydruret of salicyle, which is found in the urine. Its presence is detected by a persalt of iron, which strikes an intense violet colour with urine containing it." (Pereira.) Of this property advantage might be Mimi in the treatment of some renal complains.
The barks of many species of willow contain a valuable dyeing prin ciple. It is capable of dyeing drab with the help of a mordant only. For this purpose bitartratc of potato (cream of tartar) is best. If the bark be macerated in ono vat, and the water then containing the colouring principle be drawn off into another vat, the mordant can then be added, and the stuff immersed In it. For the production of drab colour four materials are generally used, the shade resulting being often uncertain and varying in the same piece of cloth, in many spots being fo.ry, as it is technically termed.