Treatment.—Emetics, stomach pump, castor-oil, followed by ammonia and other diffusible stimulants. Artificial respiration should be resorted to and kept up for a long time.
CALABAR BEAN
A strong emulsion of Calabar bean, Physostigma venenosum (N.O. Leguminosæ), is used on the West Coast of Africa as a test of innocence in cases of suspected witchcraft. In 1864 some children in Liverpool were poisoned by eating some of these beans, which had been swept out of a ship from Africa on to a heap of rubbish. The poisonous alkaloid is physostigmine or eserine.
Symptoms.—Vomiting, giddiness, irregular action of the heart. The mental faculties are unaffected. The eyes are bright and the pupils contracted; in which latter it differs most strikingly from atropine, hyoscyamine, and daturine, where dilatation of the pupil is the rule. The late Sir R. Christison considered that its primary action is on the heart, causing paralysis of that organ, and that the insensibility and coma are only secondary. Dr. Harley considers that it is not a cardiac, but a respiratory poison. Later experiments have shown that the paralysis produced is due to the action of the drug on the spinal cord and not on the nerve trunks. It appears also that death is due to a failure of the respiration, for the heart in animals has been found still beating for one and a half hours after death. The contraction of the pupil, when locally applied, is probably brought about by its paralytic action on the peripheral sympathetic nerve fibres of the iris; and it is stated that when very large doses of physostigmine are given, the pupils dilate, pointing to oculo-motor palsy. A few drops of the extract placed in the eye cause powerful contraction of the pupil.
Fatal Dose.—Six beans produced death in a boy six years of age.
Chemical Analysis.—The alkaloid eserine should be extracted in the usual way, benzene being used as a solvent in the place of chloroform and ether.
Eserine gives the following chemical reactions:
1. If an aqueous solution of the salt be boiled and then strong nitric acid added, the solution turns a yellowish-orange colour, changed to violet on addition of caustic soda in excess; the violet is discharged on acidulation, but returns on re-alkalising the solution.
2. A solution of eserine in ammonia solution gives a blue residue on evaporation to dryness. Dilute acids produce a red-coloured solution with it, which is fluorescent by reflected light.
3. Bromine water produces a red turbid solution with eserine, which clears on heating.