Related entries: Salix Nigra.—Black Willow - Methyl Salicylas (U. S. P.)—Methyl Salicylate - Betula Lenta.—Black Birch - Oleum Betulae Volatile (U. S. P.)—Volatile Oil of Betula - Gaultheria.—Wintergreen - Oleum Gaultheriae (U. S. P.)—Oil of Gaultheria
The bark of Salix alba, Linné.
COMMON NAMES: Willow, White willow, European willow.
ILLUSTRATION: Bentley and Trimen, Med. Plants, 234.
Botanical Source.—The white willow is a tree 30 to 80 feet in height, with many round, widely spreading branches, silky when young, and a thick, brown bark, full of cracks; that of the smaller branches smooth and greenish. The leaves are alternate, on short petioles, lanceolate, or elliptic-lanceolate, broadest a little above the middle, pointed, tapering toward each end, acutely serrate, with the lower serratures glandular; both sides of a grayish, somewhat glaucous, green, beautifully silky, with close-pressed, silvery hairs, especially on the under surface, and which is very dense and brilliant on the uppermost, or youngest leaves; the lowermost on each branch, like the bracteas, are smaller, more obtuse, and greener. Stipules variable, either roundish or oblong, small, and often wanting. The flowers and leaves appear coincidently. The aments are borne on short stalks, with 3 or 4 spreading, leafy bracteas, and are terminal, cylindrical, and elongated. Scales brown, elliptical, lanceolate, pubescent at the margin; those of the barren aments narrower toward the base; of the fertile, dilated and convolute in that part. Stamens 2, yellow, rather longer than the scales, with 1 obtuse gland before and 1 behind; filaments hairy in their lower part. Anthers roundish and yellow. The ovary is very nearly sessile, green, smooth, ovate-lanceolate, bluntish, and longer than the scale. Style short; stigmas short, thick, 2-parted, recurved, and nearly sessile. Capsule ovate, brown, smooth, and rather small (L.—W.—G.).
History and Description.—The white or European willow is a large tree of rapid growth, native of Europe, and introduced into this country. Its flowers appear from March to June. The bark, which is the medicinal part, is readily removed from the stem during the months of July, August, and September. The dried bark is met with more or less quilled, pliable and tough, with a faint odor, and a bitter taste, combined with some astringency. Water takes up its medicinal properties, the decoction having a dark-reddish color, and which is precipitated abundantly by gelatin, carbonates of potassium, and ammonium. Lime-water gives at first a blue, and then a buff-colored precipitate. Ferric chloride throws down a dark-green tannate of iron. If the decoction contains much salicin, concentrated sulphuric acid reddens it. This species belongs to the group of willows known as the crack willows. A species much resembling it is the Salix fragilis, Linné. There are numerous species of Salix, many of which, undoubtedly, possess analogous medicinal virtues. The best rule to follow is to select those whose barks possess great bitterness, combined with astringency. Among those which have been used are the S. alba, S. caprea, S. russelliana, S. purpurea, S. nigra, and S. pentandra. The Weeping willow, or Babylonian willow (Salix babylonica) is cultivated as an ornamental tree.
Chemical Composition.—White-willow bark, according to Pelletier and Caventou, consists of bitter, yellow coloring matter, green fatty matter, tannic acid, resin, etc. The chief constituent, however, as with all the willows, is the glucosid salicin (see Salicinum). Tannin is also prominent, and is more abundant in the crack willows, while salicin seems to predominate in the purple willows. Johanson (1875) showed the presence of benzohelicin (C20H20O8), a glucosid previously obtained (Piria, 1851) by acting upon populin with nitric acid (compare Salicinum).
Robert W. Beek (Amer. Jour. Pharm., 1891, p. 581) obtained from the bark of Salix lucida, 1.09 per cent of salicin; from the leaves, 0.3 per. cent. The bark of S. alba yielded 0.56 per cent, that of S. nigra, 0.73 per cent of salicin. The leaves of S. alba contained 6.48 per cent of tannin, while the quantity of tannin in the barks of S. alba and S. nigra varied from 3.3 to 4.3 per cent.
Action, Medical Uses, and Dosage.—Willow bark is tonic, antiperiodic, and an astringent bitter. It has been given in intermittents, dyspepsia, connected with debility of the digestive organs, passive hemorrhages, chronic mucous discharges, in convalescence from acute diseases, and in worms. Although occasionally substituted for the cinchona bark, it is inferior in activity. In chronic diarrhoea and dysentery, the tonic and astringent combination of the willow renders it very eligible. It may be given in substance, in doses of 1 drachm of the powder, repeated as indicated; or of the decoction, 1 or 2 fluid ounces, 4 or 5 times a day. The decoction has also proved efficient as a local application to foul and indolent ulcers.