ACTION OF SMELLIXG SALTS. 40*7 



dilatation of the arterioles, especially of those near the surface, 

 though in cases like that of Alice Bruce it may be due entirely 

 to stoppage of the heart ; while the chief factor in shock is dila- 

 tation of the abdominal veins. The longer duration of shock 

 than of syncope is probably due to the veins recovering their 

 contractility more slowly than the arterioles, 



Having thus formed some sort of idea regarding the pathology 

 of syncope and shock, we come to our third head, viz., the ques- 

 tion of treatment. In syncope, our first idea is to restore the 

 circulation to the brain, and this we do by laying the head 

 level with the body, or perhaps, still better, as recommended 

 by Sir Astley Cooper, on a level somewhat lower than that of 

 the body. 



The next thing is to raise the blood-pressure. Now, this is 

 most easily done by causing the arterioles to contract. We 

 therefore hurry a person who has fainted from the warm room 

 to the cold air, and dash cold water on the face, in order to 

 cause contraction of the vessels on the surface of the body. 

 We also give draughts of cold water to cause contraction of 

 those of the stomach. Besides this we apply ammonia or aro- 

 matic vinegar, which is strong acetic acid, to the nose. Why do 

 we do this ? Many of you know that when ammonia is applied 

 to the nose of a rabbit it causes the heart to stop instantaneously, 

 and one would therefore think that to hold it before a fainting 

 person's nose was to do the very worst possible thing. But we 

 all know that this is not the case. Some time ago a member 

 of this Society asked me this question, and I could at that time 

 give him no satisfactory answer. I have since made some ex- 

 periments on the subject,and I find (what has indeed been already 

 noticed by Kratschmer*) that when ammonia or strong acetic 

 acid is held before the rabbit's nose, it causes contraction of the 

 arterioles. Consequently it prevents the blood-pressure from 

 falling quickly, even should the heart become feeble or stop, 

 and is thus useful in preventing syncope. When the blood- 

 pressure has already become lowered by the occurrence of syncope, 

 contraction of the arterioles causes it to rise, and it is by causing 

 this that acetic acid or ammonia are useful as restoratives. 



* TFiener Sitz. Bericht, 1870, Abt. II, vol. Ixii, p. 24. 



