MOTOR DEPRESSANTS. 149 



brought about by its powerful stimulation of the in- 

 testinal walls, as well as by increasing the amount of 

 intestinal secretion, thus rapidly causing the expul- 

 sion of gas and faeces (in the horse within fifteen to 

 thirty minutes after intratracheal injection). The 

 frequency of tlie heart beats are increased, but de- 

 creased in force, while arterial tension, though at first 

 lowered, is raised. Over-doses cause dyspnoea by a 

 tetanic action on the respiratory muscles, death taking 

 place from CO^ poisoning induced by the paralysis of 

 respiration. Physostigmine contracts the pupil and 

 the ciliary muscle, producing a marked myosis and 

 reducing intraocular pressure. Its myotic effects are 

 noticeable in the horse thirty minutes after adminis- 

 tration ; in carnivora, in from fifteen to twenty min- 

 utes. The elimination of physostigmine, while exe- 

 cuted to some extent by bile, saliva, and gastric 

 fluids, is accomplished chiefly by the kidneys, the 

 urine of an animal under its action being capable of 

 poisoning another. 



Antagonists, for its effect on the heart, respiration, 

 and pupil, are atropine and chloral hydrate. 



Therapeutics. — In colic due to intestinal obstruc- 

 tion, etc., constipation, intestinal torpor — physostig- 

 mine combined with equal quantity of pilocarpine. 

 In tetanus— to diminish reflex excitability; in cho- 

 rea, epilepsy, and as antagonists in strychnine and 

 atropine poisoning; in eye diseases, as a myotic, to 

 relieve congestion and inflammation of the eyeball, 

 to reduce intraocular tension, and, alternated with 

 atropine, to reduce adhesions of the iris; also to re- 



