Salicis Cortex. Willow Bark. Bark of Salix Caprea; Lin. Syst., Dioecia diandria; indigenous. Not officinal.

Description. The bark obtained from the branches is quilled, the epidermis dark-coloured, and the structure fibrous and tough;. it has a slightly aromatic odour, with a bitter and astringent taste.

Prop. & Comp. Its active matters are soluble in water; it contains tannin, gum, extractive matter, and the usual constituents of barks. In addition, it yields a neutral crystalline principle Salicine, which, when pure, occurs in white scaly crystals, with a bitter taste, soluble in water and alcohol; and has the composition (C26 Hl8 O14). Concentrated sulphuric acid turns Salicine of a bright red colour; and when acted on by oxidizing agents, it is converted into Salicylous acid, or hydruret of Salicyle (C14 H5 O4, H); this is identical with the oil of Spiraea Utmaria, and exhales the same peculiar odour.

Therapeutics. Willow bark is tonic and antiperiodic, and has 22 been much recommended in intermittents as a substitute for cinchona; it is generally administered as salicine; this is thought to possess considerable antiperiodic power, but is not likely to supersede quina, though useful as a mild bitter tonic, when given in doses from ten grains to twenty grains. A decoction is sometimes useful in chronic skin affections, as psoriasis. Salicine taken internally appears in the urine as the hydrnret of salicyle, and causes that fluid to strike purple-red with the persalts of iron.

Dose. Of decoction (1 1/2 oz. to 20 fl. oz.) 1 1/2 fl. oz. to 3 fl. oz.; of salicine, 5 gr. to 30 gr.