Botanical name: 

The rhizome of Dioscorea villosa, Linné (Nat. Ord. Dioscoreaceae). A vine found throughout the United States. Dose, 5 to 60 grains.
Common Names: Wild Yam, Colic Root.

Principal Constituents.—An acrid, alcohol-soluble resin, and a substance closely allied to saponin.
Preparations.—1. Decoctum Dioscoreae, Decoction of Dioscorea (Dioscorea, 1 ounce; Water, 16 fluidounces). Dose, 2 to 6 fluidounces.
2. Specific Medicine Dioscorea. Dose, 5 to 60 drops.
Specific Indications.—Bilious colic; other spasmodic colicky contractions; skin and conjunctivae yellow, with nausea and colicky pain; tongue coated, stomach deranged, and paroxysmal pain in the abdomen; twisting or boring pain, radiating from the umbilical region, with spasmodic contraction of the belly-muscles; colic with tenderness on pressure, which gives relief to the spasmodic action.

Action and Therapy.—The decoction of dioscorea has been wonderfully effective in some cases of bilious colic and has signally failed in others. If it does not give relief in a half hour it is not likely to succeed. The specific medicine administered in hot water has the same effect. Dioscorea is probably less anodyne than antispasmodic, and it is due to the latter action that colic is relieved. Not alone does it succeed in cases of bilious colic, but it acts similarly in paroxysmal pain, with contraction of the muscular tissues, in cholera morbus, indigestion, and dysenteric tenesmus. Ovarian neuralgia and spasmodic dysmenorrhea sometimes yield quickly to it. In all disorders it seems best adapted to irritable and excitable conditions and is less efficient when due to atony. Though dioscorea has been used largely for nearly a century, its true place in therapeutics is still undetermined, probably because so many impossible claims have been made for it. Hepatic colic depends upon so many different conditions that it may help some cases quickly while others are unaffected by it. When large gall-stones are attempting to pass it is probably without power to relieve. Morphine is a better relaxant and is anodyne. Dioscorea seems best adapted to paroxysmal pain due to contraction of the nonstriated musculature of tubular organs, when brought on by any irritant or form of irritation. It does not dissolve calculi. Usually, while there is much tenderness in cases requiring dioscorea, the distress is gradually relieved by pressure.

The Eclectic Materia Medica, Pharmacology and Therapeutics, 1922, was written by Harvey Wickes Felter, M.D.