96 HEART STIMULANTS 



pulse rate is greatly quickened. With excessive doses the 

 rate gets so quick as to produce the condition of delirium 

 cordis, where, with very frequent incomplete beats the output 

 of blood falls down to zero. This occurs with toxic doses of 

 digitalis and aconitine. There are also many indirect ways 

 by which the heart and circulation may be affected. For 

 example, alcoholic, etherous, and ammoniacal solutions, 

 especially when given in tolerably concentrated form, 

 immediately irritate the mouth, throat, stomach, and other 

 parts with which they come in contact, produce reflex 

 acceleration of the heart, and thus their effects often antici- 

 pate their subsequent actions resulting from their actual 

 conveyance in the blood stream to the heart and other 

 organs. 



Cardiac stimulants are used to counteract failure of the 

 heart's action from shock, physical injury, overwork, or 

 depression dependent on disease. Stimulants, when acting 

 favourably, under the circumstances produce a more vigor- 

 ous heart-beat the pulse, previously slow, is accelerated ; 

 or if quick, unequal, or weak, it becomes slower, stronger, 

 and more regular. The heart pulsating more forcibly, and 

 propelling at each contraction a larger volume of blood, 

 arterial pressure is increased. A combination of two stimu- 

 lants, acting as indicated in more ways than one, is often 

 more effectual than any single drug. Hence alcohol is 

 frequently conjoined with ether, ammonia, or aromatic 

 volatile oils. Strychnine is prescribed with caffeine ; and in 

 serious cases hypodermic injections may be needful. Heat 

 used in the form of warm drinks, and also externally, as 

 warm rugs, fomentations, or poultices, is a heart stimulant, 

 especially when the applications are made to the chest. 



VASO DILATORS dilate the peripheral vessels (arterioles), 

 and thus accelerate the blood-flow through them. This they 

 do either by depressing the vaso-motor centres or by relaxing 

 involuntary muscle. Prominent amongst remedies acting in 

 this way are alcoholic solutions, ether, nitrous ether, amyl- 

 nitrite, nitro-glycerin, and nitrites, which, by dilating 

 peripheral vessels, lower blood pressure. Alcoholic solutions 

 combining the twofold action of stimulating the heart and 

 dilating vessels, usefully combat chill, equalise circulation, 



