This section is from the book "Botanic Drugs Their Materia Medica, Pharmacology and Therapeutics", by Thomas S. Blair. Also available from Amazon: Botanic Drugs, Their Materia Medica, Pharmacology and Therapeutics.
Wild Yam, Colic-root, Dioscorea villosa. Not official, but listed in the National Formulary. Several species of "yams" are edible. There has been a disagreement over the activity of dioscorea, partly due to the glabrous variety being used instead of the true one. Also proprietary medicine interests have made altogether too sweeping claims regarding it. Conservative medical literature has never claimed more for it than that it contains an acrid resin which is emetic in large doses and in small doses may not be definitely classed. But empirically, and from much credited clinical testimony, it has been used extensively in painful abdominal neuroses manifested as various forms of colic and the so-called cholera morbus. The various forms of enteralgia are more or less amenable to the acrid antispasmodics of minor importance. I have found the fl. dioscorea in 10- to 30-minim doses in hot water to give relief from the cramps and pain in these conditions. Manifestly it is not good therapeutics to omit purgatives, alkalies, and other indicated remedies; but, in many cases, dioscorea is a symptomatic remedy worth while. See also "Colo-cynth" in this connection.