ON IRRITANTS AND COUNTER-IRRITANTS, 

 WITH REMARKS ON THE USE OF BLIS- 

 TERS IN RHEUMATISM. 



(Eeprinted from St. Bartholomew^ s Hospital Reports, rol. xi, 1875.) 



UxDER the terms irritants and counter-irritants we include 

 those substances which first cause redness and then inflamma- 

 tion when applied to the surface of the body. When they are 

 used for their effect upon the part to which they are applied, as 

 e.g., a blister to a callous ulcer, they may be termed irritants ; 

 when used for their effect on a distant part, e.g., a blister to the 

 chest in pneumonia, they may be termed counter-irritants. 



But, before beginning to say a word about their action, it may 

 be advisable to try to clear the way by correcting a common 

 error regarding congestion and its relation to inflammation. 

 Congestion generally means that there is more blood than usual 

 in some part or other of the body ; but the blood may be either 

 .•streaming rapidly through the vessels, or stagnant in them, so 

 that the condition in the two cases is utterly different. When 

 the sympathetic nerve is cut in the neck of a rabbit, the vessels 

 of its ear become dilated, the ear itself becomes rosy-red, and 

 the warm blood coursing rapidly through it raises its temperature. 

 We then say that the ear is congested.* If we tie a ligature 

 round a finger, and leave it there for some time, the finger gets 

 swollen, cold, and blue, and we again say the finger is congested. 

 But the different colour of the parts is enough to show us that 

 there is a great and important difference between the congestion 

 in the ear and that in the finger ; and as the colour is due to 

 the blood shining through the vessels and tissues, we at once 

 ascribe the rosy colour of the rabbit's ear to bright arterial 



* In his lectures on Stirgical Pathology, Sir James Paget wise y designates 

 what I have here ealleJ congestion, as determination of blood to a part, and 

 limits the term congestion to the condititon which is present after stasis has 

 begun. 



