PHYSOSTIGMINE 305 



.006); H., subcut., gr.i-iss, (.06-.09) ; intratracheaUy, gr.ss, (.03); foals and 

 calves, subcut., gr. 1/12-1/6, (.005-.01) ; D., subcut., gr. 1/100-1/80, (.0006-.002). 



Given usually subcutaneously, intravenously or intratracheally to horses. 

 Eserine decomposes on exposure to the air and solutions do not keep more than 

 a week. The pure salt should be bought in hermetically sealed tubes, as tablets 

 decompose when exposed to air. The salicylate is more stable than the sulphate. 



Physostigmine. 



Action Internal. — Alimentary Tract. — The flow of saliva is at first 

 stimulated, vi^hether by direct excitation of the salivary cells or not, is 

 undetermined. Salivation ceases when the gland is deprived of blood by 

 general vascular contraction. The peristaltic action of the stomach and 

 bowels is increased by the direct local action of the alkaloid on the motor 

 nerve endings (vagus) of the smooth muscles. There are three stages, 

 in reference to this action, observed in poisoning. First, there is stimula- 

 tion of peristaltic action, then tetanic contraction and diminution of the 

 intestinal calibre, and finally relaxation and dilatation of the bowels. 

 The secretions in the digestive tract are augmented by the expulsion of 

 considerable mucus per rectum. When the alkaloid is given to horses, 

 under the skin, within the trachea or intravenously, defecation and expul- 

 sion of gas commonly occur in the space of half an hour, occasionally in 

 a few minutes, and is often considerable in amount (11-20 lbs. of feces). 

 The essential action of the drug is to stimulate the secretory nerve end- 

 ings of glands, and the motor nerve endings of smooth and striated 

 muscle. 



Circulation. — Eserine is readily absorbed, but exerts no influence on 

 the blood. Moderate doses render the cardiac pulsations slower and more 

 forcible, and increase vascular tension. Large toxic doses cause the heart 

 to beat more rapidly and less forcibly. The first effect is due probably to 

 stimulation of the peripheral vagi and heart muscle, and possibly the 

 involuntary muscular fibres in the vessel w-alls. The second phenomenon 

 follows depression of the heart and peripheral vagi, and terminates in 

 cardiac paralysis and diastolic arrest. The action on the circulation is 

 entirely subordinate to the influence of the drug upon the nervous system, 

 and is unimportant from a therapeutical standpoint. 



Nervous System and Muscles. — The essential central action of 

 physostigmine consists in depressing the respiratory centre in the medulla 

 and the cells of the inferior cornua. This has been abundantly and direct- 

 ly proved by application of the alkaloid to the spinal cord. The superior 

 columns are finally depressed; perception of pain is wanting, but that of 

 touch persists. The sensory nerves are not affected, and the motor nerve 

 trunks but slightly. The muscular tremors are due to stimulation of the 

 motor nerve endings or myoneural junctions. These are characteristic of 

 physostigma poisoning in animals, but are not so frequently observed in 

 man. Calabarine may be present in old preparations of physostigma, 

 from decomposition of physostigmine, and acts like strychnine on the 

 spinal cord. In poisoning by such, calabarine may induce convulsions. 

 The involuntary muscles throughout the body are stimulated, including 

 those of the stomach, intestines, gall bladder, bronchial tubes, heart, blood 



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