Botanical Source.—Balm is a perennial herb, with upright, branching, 4-sided stems, 10 to 20 inches high. The leaves are opposite, broadly ovate, acute, coarsely crenate-serrate, rugose, petioled, and more or less hairy. The flowers are pale-yellow, in axillary dimidiate verticils, and subsessile; the bracts are few, ovate-lanceolate, and petiolate. The calyx is slightly gibbous at base, 13-ribbed, flattish above, upper lip 3-toothed, lower one bifid. Corolla with a recurved-ascending tube; upper lip erect, flattish, lower lip spreading, 3-lobed, middle lobe mostly broadest. Stamens ascending (W.—G.).
History and Description.—Balm is a native of southern France, but is naturalized in various parts of Europe and the United States. It grows in fields, along roadsides, and is well-known as a garden plant, flowering from May to August. The whole plant is medicinal, and should be collected previous to its flowering. In the recent state, it has a lemon-like odor, which is nearly lost by drying. Boiling water extracts its virtues. It is officially described as follows: "Leaves about 5 Cm. (2 inches) long, petiolate, ovate, obtuse, rounded or subcordate at the base, crenate, somewhat hairy, glandular; branches quadrangular; flowers in about 4-flowered cymules, with a tubular, bell-shaped, 5-toothed calyx, a whitish or purplish bilabiate corolla, and 4 stamens; fragrant, aromatic; somewhat astringent and bitterish"—(U. S. P.).
The Nepeta Cataria, Linné, var. B. citriodora, a powerful emmenagogue, is sometimes cultivated and employed by mistake for balm. It has the same odor, but may be distinguished by both surfaces of its leaves being hairy.
Chemical Composition.—Balm contains a bitter substance, some tannin, gum, and a peculiar volatile oil, which is yellowish, or reddish-yellow, very limpid, about 0.89 in density, and possessing the fragrance of the plant in a very high degree. A stearopten is present in it (Bizio); the oil is soluble in 5 parts of alcohol. The yield in oil does not exceed 0.1 per cent. The infusion of balm is incompatible with nitrate of silver, acetate of lead, and sulphate of iron.
Action, Medical Uses, and Dosage.—Balm is moderately stimulant, diaphoretic, and antispasmodic. A warm infusion, drank freely, has been serviceable as a diaphoretic in febrile diseases and painful menstruation, and to assist the operation of other diaphoretic medicines; in combination with ipecacuanha and potassium nitrate, a valuable diaphoretic is formed. It is also occasionally used to assist menstruation. When given in fevers, it may be rendered more agreeable by the addition of lemon juice. The infusion may be taken ad libitum.