C. SUMNER WITHERST1NE, Philadelphia.
PHYSOSTIGMA.—Physostigma (U. S. P.), Calabar bean, or Ordeal bean of old Calabar, is the seed of Physosligma venenosum (nat. ord., Leguminosce): a woody creeper indigenous to western Africa along the River Niger. It con tains the alkaloids physostigmine (also called eserine), eseridine, and calabarine, physosterin (a substance related to cho lesterin), starchy matters, oils, etc.
Physostigmine occurs in colorless, very hygroscopical crystals, readily alter ing to a resin-like mass. It is soluble in alcohol, ether, and chloroform and sparingly soluble in water. It forms salts with the acids, which vary in solu bility; the salicylate and sulphate are official.
Physostigmine salicylate occurs in colorless or slightly-yellowish, lustrous crystals, soluble in 150 parts of water. This salt is least affected by the light, but must be kept dry. Solutions of this salt deteriorate on standing and become brownish-red in color when spoiled for use; when freshly made, they are of a faint-pink color.
Physostigmine sulphate occurs as a white or slightly-yellowish, deliquescent, crystalline powder, of bitter taste. It is freely soluble in water and alcohol. This salt should be kept dry and away from the light.
Eseridine occurs in white, four-sided crystals, soluble in alcohol, ether, and chloroform. Eseridine is a laxative and motor-excitant. It is one-sixth as power ful as physostigmine.
Calabarine is said to act much like strychnine.
Preparations and Doses.—Physos tigma, U. S. P. (Calabar bean), V, to 2 grains.
Extractum physostigmatis, U. S. P. (alcoholic extract), to '/, grain.
Tinctura physostigmatis, U. S. P. (15 per-cent. strength), 5 to 10 minims.
Physostigminm salicylas (U. S. P.), to grain.
Physostigminm sulphas (U. S. P.), to grain.
Physiological Action. — The physio logical action of Calabar bean has been studied by a large number of observers, a summary of whose labors tends to demonstrate that the main effects of the drug are exercised upon the motor centres of the spinal cord. This action involves depression of the respiratory centres of the medulla, and, by reflex ac tion, an increasing paralysis leading to paralytic asphyxia. The cerebral cortex, the sensory nerves, and the sensory nerve-centres suffer no loss of function, while the motor nerve-trunks are scarcely involved under normal circumstances.
Poisonous doses, however, may cause all these structures to be more or less af fected. Wood concludes that "Calabar bean acts directly either upon the mus cle-structure itself or upon the periph eral nerve-endings in the muscles, pro ducing contraction, and not paralysis. The influence of the drug upon the cir culation is entirely subordinate and is not at present completely understood. Early in the poisoning there is a rise of the blood-pressure, which is, in great part, if not altogether, due to a direct stimulation of the cardiac muscle and its contained ganglia. The action of the drug upon the vasomotor centres re mains at present in doubt." Physostigma increases peristaltic ac tion. Traversa (II Policlinico, No. 1, '96) recently studied the action of its main alkaloid, physostigmine, in this direction, and found that it not only ex aggerates the peristaltic movements, but also causes a violent and generalized con traction of the intestine and, finally, tet anus and contractures. If the contrac tion predominates in the longitudinal fibres, the intestine becomes wrinkled; if in the circular, it is beaded, ringed, or, if the contraction is violent and diffuse, ribbon-like. The higher nerve centres (the vagus, spinal cord, and abdominal sympathetic ganglia) have no influence upon the production of these phenomena.
A loop of intestine detached from the body and kept alive by artificial cir culation gave the same reaction to phy sostigmine as intestines in the living body. He concludes, therefore, that the changes in motor activity do not depend upon the modification of the intestinal circulation. Physostigmine produces exaggerated peristalsis and violent and diffuse contractions of the intestine solely by excitation of the peripheral motor apparatus. Traversa further calls attention to the fact that, so far as the intestine is concerned, the action of physostigmine is identical in intensity and duration as well, and of effect with pilocarpine, not only nosographically, but mechanically.