SURFACE REGIONS AND VASCULAR AREAS. 451 



if we can lessen the tension in the vessels of an inilamed part, 

 either by causing the arteries to contract or the capillaries to 

 dilate, we shall do more service to the body than if we weaken 

 the whole of it to relieve a part. This, I believe, we can do by 

 means of counter-irritants. I have already mentioned that the 

 application of an irritant causes contraction of the vessels of 

 other parts of the body, at the same time that it induces 

 dilatation in those of the injured part, but this action will not 

 afford us much help, if all the vessels are contracted alike, for 

 then the blood would pour with increased pressure into the 

 dilated vessels of the inflamed part, and the pain would be 

 worse than before. But clinical experience shows that irritation 

 to the surface of the body will relieve ioternal pain, and a 

 mustard poultice or blister to the side in pleurisy frequen^tly, 

 indeed generally, gives more or less relief. And there are 

 several facts which tend to show that just as irritation applied 

 to different portions of the skin will induce definite reflex 

 movements distinct from each other,* so irritation applied to 

 different parts of the surface will induce contraction in different 

 sets of vessels, a definite correspondence existing between the 

 part irritated and the set of vessels which contract. Ludwig 

 and Lovent observed that when the sensory nerve of one ear 

 was irritated, dilatation of the vessels was sometimes observed 

 in the other ear also, although it was much less, and generally 

 was replaced by contraction sooner than on the side operated 

 upon; and Callenfelst noticed that pinching one ear caused 

 contraction in the vessels of the other. Plunging one hand into 

 cold water has been observed to cause cooling of the opposite 

 hand, an effect which must be due to contraction of the vessels. 

 But the most important experiments on this point are those of 

 Zulzer,§ who painted cantharides collodion repeatedly over a 

 part of the back of a rabbit for 14 days. At the end of this 

 time he found tliat the vessels underneath the skin were much 

 dilated and filled with blood, and the superficial muscles were 



* Sanders-Ezn, Ludwig' s Arheiten, 1867, p. 11. 



t Ludwig's Arheiten, 1866, p, 11. 



X Callenfels, Zeitsch.f. rat. Med., 1855 ; Bd. yii, p. 191. 



§ Ziilzer, Deutsche Klinik, 1865. 



2 G 2 



