This section is from the book "An Experimental History Of The Materia Medica", by William Lewis.
Pennyroyal: a plant of the mint kind; differing from the mints strictly so called, in the flowers being disposed, not in spikes on the tops, but in thick clutters, at distances, round the joints of the stalks; and the upper segment of the flower not being nipped at the extremity.
1. Pulegium Pharm. Lond. & Edinb. Pulegium latifolium C. B. Mentha paluftris five pulegium Pharm. Paris. Pulegium regium Ger. emac. Mentha pulegium Linn. Common pennyroyal: with somewhat oval obtuse leaves, and trailing stalks, striking root at the joints. It grows wild on moist commons and in watery places, and flowers in June.
2. Pulegium erectum: Pulegium erectum officinarum Dale: Pulegium mas Ger. emac. Upright pennyroyal; with the stamina standing out from the flowers; said to be a native of Spain, common in our gardens, and usually substituted in our markets to the foregoing species.
3. Pulegium cervinum: Pulegium angusti-folium C. B. Mentha aquatica satureiae folio
T'ourn. Mentha cervina Linn. Harts pennyroyal, with small oblong narrow leaves; said to grow wild about Montpellier.
All the pennyroyals are warm pungent herbs, somewhat similar to mint, but more acrid and less agreeable both in smell and taste, less proper in common nauseae and weakness of the stomach, more efficacious as warm carminatives and deobstruents in hysteric cases and disorders of the bread: the last species is the strongest, though least ungrateful, of the three. Their active principle is an essential oil; of a more volatile nature than that of mint, coming over hastily with water at the beginning of the distil-lation, and rising also in great part with highly-rectified spirit; in taste very pungent, and of a strong smell; when newly drawn, of a yellowish colour with a cast of green; by age turning brownish. The oil, and a simple† and spiritu-ous‡ water strongly impregnated with it, by drawing off a gallon of water or proof spirit from a pound and a half of the dry leaves, are kept in the shops,