Co UNTER-lRRITA NTS. 5 3 I 



Phenomena of counter-irritation. When a counter-irritant is 

 applied to the skin, the^ra^ effect is rubef orient and stimulant. 

 The cutaneous vessels are dilated by a direct action on their 

 nerves, and the local circulation becomes more free ; whilst the 

 irritation of the sensory nerves causes pain of a hot burning 

 character. The cardiac action is accelerated, the cutaneous 

 vessels generally reflexly contracted, the blood pressure rises, 

 the temperature is elevated, and the breathing slowed. The 

 highest centres are also roused by the painful impression : per- 

 ception, consciousness, and the emotions are variously disturbed. 

 Cutaneous anaesthesia follows : the nerves are depressed, pain 

 is relieved, excepting that caused by the application itself. 



Prolonged application is generally required to induce the 

 second degree of counter-irritation vesication. The reddened 

 area now becomes inflamed ; plasma escapes from the vessels, 

 followed by corpuscles ; the epidermis is raised, and a vesicle is 

 formed containing a quantity of fluid. The previous anaesthesia 

 is now replaced by considerable local pain, which, if extensive, 

 may depress the viscera weakening and slowing the heart, 

 lowering the pulse, further slowing the respiration, lowering 

 the temperature and diminishing nervous energy. 



The third degree of counter-irritation, pustulation, is different 

 in kind from vesication as well as more severe, the result 

 being not uniform inflammation, but a crop of painful, 

 " angry " pimples or pustules, which are very slow to heal. 

 The remote effects are the same as before, but greater. 



Theory of the action of counter-irritation. Such are the 

 phenomena of this method, obvious to all. But it is held by 

 some that not only the functional activity, but the nutrition of 

 internal parts may be affected by means of it. The doctrine of 

 counter-irritation may be said to be, that when a part at some 

 distance beneath the surface of the body, such as a joint, or 

 even remote from it, such as the lungs, is in a condition of 

 inflammation, pain, unnatural activity, or overgrowth, an 

 alterative effect may be produced upon its nutrition, by altering 

 the condition of an area of skin superficial to it, or even 

 at a distance from it. A second or " counter " seat of " irrita- 

 tion " is set up to relieve the deeper and more vital part. Now 

 we may conclude with respect to this theory : 



1. That rubefacients and vesicants will afford relief to the 

 circulation of parts in immediate vascular .connection with the 

 selected area, by attracting blood and draining off plasma; to 

 the same extent the general circulation will be depressed, and 

 visceral congestion or inflammation will be diminished. At th 

 same time the heart will be relieved. 



