CALABAR BEAN, the seed of a leguminous plant, Physostigma venenosum, a native of tropical Africa. The plant has a climbing habit like the scarlet runner, and attains a height of about 50 feet, with a stem an inch or two in thickness. The seed pods, which contain two or three seeds or beans, are 6 or 7 inches in length; and the beans are about the size of an ordinary horse bean but much thicker, with a deep chocolate brown colour. They constitute the E-ser-e or ordeal beans of the negroes of Old Calabar, being administered to persons accused of witchcraft or other crimes. In cases where the poisonous material did its deadly work it was held at once to indicate and rightly to punish guilt; but when it was rejected by the stomach of the accused, innocence was held to be satisfactorily established. A form of duelling with the seeds is also known among the natives, in which the two opponents divide a bean, each eating one-half; that quantity has been known to kill both adversaries. Although thus highly poisonous, the bean has nothing in external aspect, taste, or smell to distinguish it from any harmless leguminous seed, and very disastrous effects have resulted from its being incautiously left in the way of children. The beans were first introduced into England in the year 1840; but the plant was not accurately described till 1861, and its physiological effects were investigated in 1863 by Dr Thomas R. Fraser. In that year an alkaloid was isolated from the seeds to which the name physostigmine was applied; and under the name eserine another alkaloid was prepared from them; but it is not yet quite certain that the two substances are essentially different. Dr Fraser’s investigations, which were conducted with an alcoholic extract of the seeds, showed that the active ...