COUNTER-IEKITANTS 697 



happens. The terms referring to the degree of action in- 

 herent in agents are as follows : 



1. A rubefacient, causing hypersemia. 



2. A vesicant, or epispastic, inducing blistering. 



3. A pustulant, creating pustules. 



4 An escharotic, or caustic, occasioning death of the 

 tissues. 



The same agent, as has already been pointed out, may 

 produce one or more of these actions according to circum- 

 stances. The inner aspect of limbs and the flexures of joints 

 are peculiarly sensitive, owing to the thinness of the skin 

 over these areas. If a counter-irritant is rubbed properly 

 into the skin it may penetrate into the mucous layer. 



Reference has been made to the local influence of irri- 

 tants. We will now direct attention to their remote effect. 

 It is certainly known that irritation of the surface decidedly 

 affects distant organs. Brown-Sequard noted contraction of 

 vessels in one arm when the other was immersed in cold 

 water. Severe burns of the surface are followed by duo- 

 denal ulcers. The preceding and succeeding remarks enable 

 us to partially account for the remote influence of counter- 

 irritants, but although we know their practical value, it is 

 not within our present knowledge to offer theories wholly 

 explaining their effect. 



The influence of counter-irritants may be summed up 

 in reflex action; i. e., the production and conduction of an 

 impulse from the periphery to nerve centres, thereby modi- 

 fying the nerve functions and blood supply in distant 

 parts. 



The skin is commonly the point of application. It nor- 

 mally is an, organ of protection, respiration, secretion and 

 special sense, and, through its medium, a regulator of tem- 

 perature, responding to such natural stimuli as heat, cold, 

 moisture and dryness. Such an unnatural and considerable 

 stimulation as is produced by counter-irritants consequently 

 creates very sensible alterations in the bodily functions. 



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