This section is from the book "An Experimental History Of The Materia Medica", by William Lewis.
Millefolium Pharm. Edinb. Millefolium vulgare album, & millefolium purpureum C. B. Achillea, Myriophyllon, Chiliophyllon, Militaris herba, Stratiotes, Carpentaria, Lumbus veneris, & Supercilium veneris. Achillaea Millefolium Linn. Milfoil or Yarrow: a plant with rough stiff leaves, divided into small seg-ments, set in pairs along a middle rib like feathers: the little flowers stand thick together in form of an umbel on the top of the stiff stalk, and consist: each of several whitish or pale pur-plish petala set round a kind of loose disk of the same colour, followed by small crooked seeds. It is perennial, grows plentifully by the sides of fields and on sandy commons, and is found in flower greatest part of the sumrner.
The leaves and flowers of milsoil are greatly recommended by some of the German physi-cians (a) as mild corroborants, vulneraries, and antispasmodics, in diarrhoeas, hemorrhagies, hypochondriacal and other disorders. They promise, by their sensible qualities, to be of no inconsiderable activity. They have an agreeable though weak aromatic smell, and a bitter-ish, roughish, somewhat pungent taste. The leaves are chiefly directed for medicinal use, as having the greatest bitterishness and austerity: the flowers have the strongest and most subtile smell, arc remarkably acrid, and promise to be of most efficacy, if the plant has really any such efficacy as an anodyne or antispasmodic. Dr. Grew observes, that the young roots have a glowing warm taste, approaching to that of contrayerva, and thinks they might in some measure supply its place; but adds, that they lose much of their virtue in being dried (b), from whence it may be presumed that their active matter is of another kind.
The virtue of the leaves and flowers is extracted both by watery and spirituous menstrua: the astringency most perfectly by the former, their aromatic warmth and pungency by the latter, and both of them equally by a mixture of the two. The flowers, distilled with water, yield a penetrating essential oil, possessing the flavour of the milsoil in perfection, though rather less agreeable than the flowers themselves, in consistence somewhat; thick and tenacious, in colour remarkably variable, sometimes of a greenish yellow, sometimes of a deep green, sometimes of a bluish green, and sometimes of a fine blue: these differences seem to depend in great measure, on the foil in which the plant is produced; the flowers gathered from moist rich grounds yielding generally a blue oil; whereas those, which are collected from dry commons, afford only, so far as I have observed, a green one with a greater or less admixture of yellow: the decoction remaining after the separation of this volatile principle, leaves, on being infpif-fated, a dark brownish mass, ungratefully austere, bitterish, and somewhat saline. On in-fpiffating the yellowish tincture made in rectified spirit, scarcely any thing of the flavour of milfoil exhales or distils with the menstruum: the remaining deep yellow extract is more agreeable in smell than the flowers themselves, of a moderately warm penetrating taste, somewhat like that of camphor, but much milder, accompanied with a slight bitterishness and fubaftrin-gency.
(a) Stahl, Dissert. de therapeia paffionis hypochondriacae. Hoffman, De praesiania remed. domett. § 18.
(b) Idea of philos. hist. of plants, § 29. Of diversities of tastes, chap. v. § 2.