COMMON NAMES. Gum Arabic, Egyptian Thorn.
    MEDICINAL PART. The concrete juice or gum.
    Description. -- Vera is a small tree or shrub, but sometimes attains the height of forty feet. The leaves are bipinnate and smooth, leaflets eight or ten pairs. Spines sharp and in pairs. Flowers in globose heads, and the fruit a legume.
    History. -- The tree inhabits the southern portion of Asia and the upper portion of Africa. The gum flows naturally from the bark of the trees, in the form of a thick and rather frothy liquid, and speedily concretes into tears; sometimes the discharge is promoted by wounding the trunk and branches. The more ruptured the tree, the more gum it yields. The best quality of Gum Arabic is colorless, or very pale yellow-white, shining, transparent in small fragments, hard but pulverable, inodorous, and of a sweet and viscous taste. It invariably forms a white powder. Cold or hot water dissolves its own weight, forming a thick mucilaginous solution.
    Properties and Uses. -- The gum is nutritive and demulcent, and exerts a remarkably soothing influence upon irritated or inflamed mucous surfaces, by shielding them from the influence of deleterious agents, atmospheric air, etc. It is useful, in diarrhoea and dysentery, to remove griping and painful stools, in catarrh, cough, hoarseness consumption, gonorrhoea, and all inflammatory conditions of the mucous surfaces. For lung diseases it is especially an indispensable vehicle in which to carry the necessary curative and powerful corrective agents, while at the same time its nutritive qualities also exert a good influence, often supplying the place of food where the stomach is too weak to partake of anything else. It may be given almost ad libitum in powder, lozenge, or solution, alone or combined with syrups, decoctions, etc. It constitutes the menstruum of my well-known Acacian Balsam, see page 469.