Obtained from the dried tuberous root of Exogo-nium Purga. The active principle is a double resin, or one separable into two, called jalapin and convolvulin, the latter being the more important. Jalap is a hydragogue cathartic, and creates a feeling of nausea. In overdoses it causes severe vomiting and purging. The stools produced by its action are large and watery. It is seldom used alone, but is often combined with calomel. Average dose, gr. xv.-I Gm. The compound powder, Pulvis Jalapae Compositus, contains jalap and cream of tartar.