UPAS, a Javanese word meaning poison, and specially applied to the poison derived from the gum of the anchar tree (Antiaris toxicaria), a member of the fig-family (Moraceae), and a native of the Sunda Islands, which was commonly used to envenom the darts of the natives. The name of the upas tree has become famous from the mendacious account (professedly by one Foersch, who was a surgeon at Samarang in 1773) published in the London Magazine, December 1783, and popularized by Erasmus Darwin in “Loves of the Plants” (Botanic Garden, pt. ii). The tree was said to destroy all animal life within a radius of 15 m. or more. The poison was fetched by condemned malefactors, of whom scarcely two out of twenty returned. All this is pure fable, and in good part not even traditional fable, but mere invention. The milky juice of the tree contains an active principle named antiarin, which has been recommended as a cardiac stimulant. It is without any properties, however, that entitle it to clinical employment.The tree is described as one of the largest in the forests of Java, the straight cylindrical stem rising without a branch to the height of 60 to 80 ft. It has a whitish bark and on being wounded yields plentifully the milky juice from which which the poison is prepared.
For a full account of the tree, see Bennett and Brown, Plantae Javanicae rariores, p. 52 (1838).