This section is from the book "Materia Medica Pharmacy, Pharmacology And Therapeutics", by W. Hale White. Also available from Amazon: Materia Medica Pharmacy, Pharmacology And Therapeutics..
Hedeoma. - Synonym. - Pennyroyal. The leaves and tops of He-deoma pulegioides (Linne) Persoon (nat. ord. Labiate).
North America, south to Georgia, and west to Dakota; in sandy fields.
Leaves opposite, short-petioled, about 12 mm. long, oblong-ovate, obscurely serrate, glandular beneath; branches roundish-quadrangular, hairy; flowers in small axillary cymules, with a tubular ovoid, bilabiate and five-toothed calyx, and a pale blue, spotted, bilabiate corolla, containing two sterile and two fertile, exserted stamens; odor strong, mintlike; taste warm and pungent.
The chief constituent is the official volatile oil.
Synonym. - Oil of Pennyroyal. A volatile oil distilled from Hedeoma.
A pale yellowish, limpid liquid, having a characteristic, pungent, mint-like odor and taste. Sp. gr., 0.930 to 0.940.
Freely in Alcohol.
Dose, 1 to 5 m.; .06 to .30 c.c.
Pennyroyal is a gentle aromatic stimulant, and may be given in flatulent colic and sick stomach. The oil is in common use locally applied as a remedy for mosquito bites.