DRUGS ACTING ON THE CIRCULATION 85 



blood-pressure, or causing asphyxia. On the other hand, 

 agencies reducing blood-pressure depress the vagus, or 

 stimulate the accelerator nerve, or both. Thus, the nitrites, 

 as amyl nitrite, nitro-glycerin and spirit of nitrous ether, 

 quicken the heart by lowering vascular tension. External 

 stimuli to sensory nerves reflexly stimulate the heart, as 

 also do many locally irritating agents taken internally ; e.g., 

 strong alcoholic or ammoniacal preparations. 



Since drugs commonly influence more than one part of 

 the mechanism controlling the heart, and since it is difficult 

 to determine the exact physiological details in such complex 

 actions, we shall content ourselves with tabulating the 

 actions of drugs ordinarily employed for their influence on 

 the heart, remembering that while moderate doses produce 

 the effects enumerated below, poisonous doses often give 

 rise to diametrically opposite actions. 



(a) Drugs increasing the force of the heart-beat. 



Digitalis 

 Strophanthus 

 Sparteine 

 Squill 



(b) Drugs increasing the rate of heart-beats. 



Belladonna Stramonium 



Atropine Cocaine 



Hyoscyamus 



(c) Drugs increasing the force and rate of heart-beats. 



Alcohol Strychnine 



Chloroform Cafifeine 



Ether Quinine 



Ammonia Arsenic 

 Ammonium carbonate 



(d) Drugs decreasing the force and rate of the heart-beats. 



Aconite Prussic acid 



Veratrum viride Ergot 



Antimony salts 



The drugs most frequently given to animals for their 

 action on the heart are alcohol, ether, digitalis, strophanthus, 



Barium salts "\ 



Camphor I ^^ ^ot alter rate 



Slow the pulse physostigmine j particularly 



