any of a group of pharmacologically active substances derived from the parasitic fungus Claviceps purpurea, which grows naturally on rye and other grains. Although highly toxic, ergot alkaloids have been used for centuries by midwives to induce abortion or labor. A number have been isolated, including lysergic acid, and the compounds are sometimes utilized as adrenergic blocking agents (see ergot derivative). Epidemics of ergot poisoning (ergotism) were widespread in Europe until relatively modern times; symptoms included peripheral vasoconstriction (occasionally to the point of gangrene) and changes in mental functioning, including visual hallucinations. Because of the pharmacological relationship between ergot and LSD (lysergic acid diethylamide), the hallucinogenic effects are similar to those of LSD.