Dioscorea villosa. Wild Yam.
Nat. Ord. — Dioscoreaceae. Sex. Syst. — Dioecia Hexandria.
Description. — This plant, sometimes called Colic-root, is a delicate, twining vine, with a perennial root, from which proceeds a smooth, woolly, reddish-brown stem, one or two lines in diameter, and from five to fifteen feet long. The leaves are from two to four inches long, about three-fourths as wide, mostly alternate, occasionally nearly opposite or verticillate in fours, broad-ovate, distinctly cordate and acuminate, nine to eleven-veined, margin entire or wavy, villose with short, soft hairs on the lower surface, and glabrous on the upper. The petioles are elongated, the lowest somewhat verticillate in fours, the next subopposite, the middle and upper alternate, and from two to four. The flowers are dioecious, very small, of a pale-greenish yellow color, and in axillary panicles or racemes. The sterile flowers have six stamens inserted on the base of the divisions of the six-parted perianth ; anthers introrse, with the spikes paniculate ; the fertile flowers have the ovary adherent, with three styles, and simple spikes. Peduncles axillary. Ovaries at first elliptic, but finally almost as broad as long, about three-fourths of an inch in length, three-celled, loculicidally three-valved by splitting through the winged angles. Seeds one or two in each cell, flat, with a membranaceous margin.
History. — This is a slender vine, twining over bushes and fences, in thickets and hedges, and flowering in June and July. It is a native of the United States and Canada, being, however, more common southward, and rare in the New England States. The root is the officinal part ; it is long, woody, contorted, from an eighth to a fourth of an inch in diameter, with many fine, long, scattering fibers, of a light, brownish-yellow color externally, and whitish internally, with a granular fracture, almost smooth, inodorous, except when bruised, then it emits a faint peculiar smell, and a not unpleasant, slightly bitter, sweetish and pungent taste. Water or alcohol are its solvents. No analysis has been made of this root, further than to extract its active constituent, dioscorein.
Properties and Uses. — Antispasmodic. Successfully used by Eclectics in bilious colic in doses of half a pint of the decoction, repeated every half hour or hour; in fact, no other agent seems necessary in this disease, as it gives prompt and permanent relief in the most severe cases. It will likewise allay nausea, also spasms of the bowels, and, combined with equal parts of the bark of Cornus Sericea in decoction, is eminently beneficial in the nausea and vomiting of pregnant women. In ordinary cases the decoction of the .root may be given in doses of from two to four fluidounces, and repeated every half hour until relief is obtained. The tincture is said to be a valuable expectorant and diaphoretic, and in large doses produces emesis. Dose of the tincture from twenty to sixty drops.
Off. Prep. — Decoctum Dioscoreae ; Dioscorein.