Water extract of dried ginseng, which is known as a histamine liberator and induces degranulation and disruption of mesenteric mast cells, is thought to contain many different chemical factors. The essential component, a saponin extract of dried ginseng, was obtained and administered to albino rats. Even minute amounts (l mg in 0.0l cc of normal saline solution) when locally injected into the mesentery of albino rats caused degranulation of mesenteric mast cells. Degranulation of mesenteric mast cells followed the intraperitoneal injection of a crude water extract, of an alcohol extract of dried ginseng, and a direct injection of both extracts into the connective tissue of mesentery. This degranulation is believed to be a saponin fraction of ginseng in the ginseng extracts.