Description. -- These forest-trees vary in size, according to the climate and soil. In diameter they are from three to six feet; in height, from sixty to a hundred feet. They are too well-known to require any botanical description.
    History. -- Quercus is a very extensive and valuable genus, consisting of many species, a large proportion of which grow in the United States. Their usual character is that of astringent, and the three above described are those which have been more partticularly employed in medicine. The bark of the tree is the portion used. White Oak bark is the one chiefly used in medicine. It is of a pale brownish color, faintly odorous, very astringent, with a slight bitterness, tough, breaking with a stringy or fibrous fracture, and not readily powdered. It contains a very large proportion of tannic acid. Black oak bark is also used as an astringent externally, but is rarely employed internally, as it is liable to derange the bowels. It is also used in tanning and for dyeing. Red oak bark also contains considerable tannin, and is chiefly applied externally in the treatment of cancers, indolent ulcers, etc.
    Properties and Uses. -- The bark is slightly tonic, powerfully astringent, and antiseptic. It is useful internally in chronic diarrhoea, chronic mucous discharges, passive hemorrhages, and wherever an internal astringent is required. In colliquative sweats the decoction is usually combined with lime-water. The gargle and injection are extensively used for sore throat, whites, piles, etc. A bath of the decoction is often advantageous in cutaneous diseases, but should only be used when ordered by a physician.
    Dose. -- Of the decoction, one or two fluid ounces; of the extract, from five to twenty grains.