(Calabar Bean.)

Origin. - The seed of Physostigrna venenosum Balfour, a lofty, half-shrubby, climbing plant (somewhat resembling the scarlet runner or Spanish bean of our gardens), growing near the mouths of the Niger and Old Calabar Rivers in Western Africa, and attaining a height of 40 or 50 feet (12-15 M.).

Description and Properties. - The seeds are about 1 to 1 1/4 inches (25-30 Mm.) long, 3/5 to 3/4 inch (15-20 Mm.) broad, and 3/5 to 3/5 inch (10-15 Mm.) thick; oblong and somewhat reniform; testa granular, chocolate-brown, with a broad, black groove extending the entire length of the convex edge; embryo with a short, curved radicle and two large, white concavo-convexed cotyledons; inodorous; taste beanlike.

The drug contains an alkaloid, physostigmine (also known as eserine), which is the principal constituent; calabarine, to which the drug owes its tetanizing properties; and eseridine (a laxative and motor excitant); besides a neutral principle, physosterin, related to cholesterin.

Dose. - 1-4 grains (0.065-0.25 Gm.) [1 1/2 grains (0.1 Gm.), U. S. P.].

Official Preparations

Extractum Physostigmatis - Extracti Physostigmatis - Extract of Physostigrna.Dose, 1/16-1/6 grain (0.004-0.01 Gm.) [1/8 grain (0.005 Gm.), U. S. P.].

Tinctura Physostigmatis - Tincturae Physostigmatis - Tincture of Physostigrna. - Dose, 5-10 minims (0.3-0.6 Cc.) [15 minims (1 Cc.), U. S. P.].

The alkaloid, physostigmine, is not official. It occurs in colorless or slightly pinkish crystals; sparingly soluble in water; readily soluble in alcohol.

Dose. - 1/100-1/20 grain (0.0006-0.003 Gm.). The salicylate and sulphate of physostigmine are official.

Physostigminae Salicylas - Physostigminae Salicylatis - Physostigmine Salicylate (Eserine Salicylate), U. S. P.

Description and Properties. - Colorless or faintly yellowish, shining, acicular, or short, columnar crystals, odorless, and of a bitter taste; acquiring a reddish tint when exposed to light and air; soluble in 150 parts of water and 12 parts of alcohol. The salicylate should be kept in small, dark amber-colored, and well-stoppered vials.

Dose. - 1/120-1/30 grain (0.0005-0.002 Gm.) [1/64 grain (0.001 Gm.), U. S. P.].

Physostigminae Sulphas - Physostigminae Sulphatis - Physostigmine Sulphate (Eserine Sulphate), U. S. P.

Description and Properties. - A white, or yellowish-white, micro-crystalline powder, odorless, and of a bitter taste. It is very deliquescent when exposed to moist air, gradually turning reddish in air and light. Very soluble in water and alcohol; still more so at the boiling-point of these liquids. It should be kept in small, dark amber-colored, and well- stoppered vials.

Dose. - 1/120-1/30 grain (0.0005-0.002 Gm.) [1/64 grain (0.001 Gm.), U. S. P.].

Antagonists and Incompatibles. - The action of physostigma upon the heart, respiration, and pupils is antagonized by atropine; that on the spinal cord, by chloral; while, in a general way, the motor excitants, particularly the tetanizing agents, are therapeutically antagonistic.

The caustic alkalies and tannic acid are chemically incompatible.

Synergists. - The motor depressants.

Physiological Action. - Externally and Locally. - No external action of physostigma and its preparations is noted, unless it be its effect upon the pupil, which outward application contracts, and the slight abolition of functional activity in the motor and sensory nerves, occasioned, it is said, by a strong solution of physostigmine.

Internally. - Digestive System. - The administration of the drug tends to stimulate the salivary, gastric, and intestinal secretions, and, by acting upon the muscular coats of the stomach and intestines, to increase peristalsis. Nausea, retching, vomiting, and purging may result. The intestinal contractions set up are very powerful, so much so that physostigmine has been used as a remedy for intestinal paresis following abdominal operations.

Circulatory System. - No influence on the blood has been detected. Small doses increase arterial tension, the heart's action becoming slower and stronger.

Nervous System. - The higher cerebral centers are not primarily affected by this drug in man. The medulla and cord are the main structures involved. After a transient stimulation depression sets in, the spinal reflexes being abolished, and final poisoning of the medullary centers occurs.

Respiratory System. - Small doses stimulate respiration. Larger amounts primarily depress the respiratory centers, stimulate the peripheries of the pulmonary vagi, and contract the caliber of the bronchial tubes, even to the extent of serious constriction, death usually resulting from asphyxia.

The breathing is first quickened and then retarded, the effect of the drug upon the respiration being more powerful than its circulatory influence, the heart continuing to beat for some time after pulmonary action has ceased.

Although the effect upon the heart is somewhat obscure, it appears that under poisonous doses the cardiac pulsations are greatly reduced, being slow and feeble, and finally ceasing altogether. It is reasonably supposed that this action is due to primary stimulation of the peripheral vagi, influencing the cardiac ganglia, and also to the effect upon the vasomotor centers. The subsequent exhaustion and relaxation of the arteries are doubtless the result of a similar influence.

There is marked elevation of blood-pressure under moderate doses, although there may occur a brief period of depression. Toxic doses are accompanied by a notable decrease of arterial tension, the cardiac ganglia being seized with paralysis, and the heart finally arrested in diastole.

Secretions. - All of the secretions, notably the tears, sweat, saliva, mucous secretions, pancreas, and bile, are markedly augmented.

Temperature - A slight depression has been noted.

Eye. - Applied locally to the conjunctiva or introduced into the circulation, whether by ingestion or injection, physostigmine causes myosis or contraction of the pupil by stimulating the peripheral endings of the oculomotor nerves, possibly by a depression of the sympathetic fibers.