Betula C. B. Betula alba Linn, Birch: a tree or shrub, common in moid woods; with numerous very flexible branches; and some-what oval, sharp pointed, Terraced, deep green leaves, hanging on long and weak pedicles; producing small scaly cones, which contain little winged seeds. The bark, which appears externally white and chapt, consists of a thick brittle substance, of a dark brownish red colour, covered with three or four whitish, very thin, smooth, flexible, tough, semitransparent, membranous coats.

On deeply wounding or boring the trunk of the birch tree early in the spring, there issues by degrees a very large quantity of a limpid, watery, sweetish juice. It is said, that one tree will bleed a gallon or two in a day; that the juice extracted near the root is much more watery, and of less taste, than that obtained from the upper part of the trunk or from the branches; and that after the leaves have begun to appear, the juice loses its sweetness and becomes disagreeable. This juice has been drank as an antiscorbutic and deobstruent. It sen-sibly promotes urine, and if taken freely, loosens the belly. In keeping, it soon turns four, unless defended from the air, by covering its surface with a little oil: by fermentation, it is converted into a weak vinous liquor. In-fpiffated to the consistence of a thin syrup, and set in a cool place for some weeks, it yields brownish saline concretions, approaching, as Marggraf observes, to the nature of manna.

The leaves and the bark of the tree have been employed, chiefly externally, as resolvents, detergents, and antiseptics. Simon Paulii relates, that an universal pruriginous scabies, which had been received by infection, was cured by bathing with a decoction of the bark and young branches, in which some nitre and tartar had been dissolved. With regard to the leaves, they discover to the touch a resinous unctuosity, and to the taste an unpleasant bitterness; rubbed a little, they yield a pretty strong, and not disagreeable, smell. The bark has no smell: the thin membranes have no taste; the thicker brittle part has a slight roughish. one. This last gives a pale yellowish tincture to rectified spirit, and a deep yellowish red to water: the watery infusion strikes a brownish black colour with solution of chalybeate vitriol, but immediately throws off the colouring matter and becomes limpid, whereas the generality of these kinds of black mixtures retain their blackness for a length of time: on infpiffating the infusion, the remaining extract proves moderately austere. The bark of this tree has been recommended also in fumigations, for correcting contagious air. The membranes are highly inflammable, in burning yield no particular smell, and give out a resinous exudation of no smell or taste. The brittle part is less inflammable, emits a strong acid vapour, and no resin.