450 ON IRRITANTS AND COUNTER-IRRITANTS. 



first the pain became so severe that I was tempted to withdraw 

 my hand ; but by-and-by the pain became easier, and almost 

 entirely disappeared shortly after I had finally taken my hand 

 away. The explanation of this I fancy to be, that at first the 

 burn caused stasis in the capillaries of the part to which I 



Capillaries 



Point of 

 Stasis 



Artery | H yein 



applied the coal, and that the irritation to the sensory nerves 

 caused the vessels to dilate, as in Loven's experiment. The 

 blood being driven down on the obstructed vessels, produced 

 distension and pain, which was increased when the warmth of 

 the fire caused the larger arteries to dilate still further. But 

 after the warmth began to dilate the capillaries of the hand, the 

 blood passed through the newly enlarged channels, and its 

 impact on the obstiucted vessels being thus removed, the pain 

 ceased. 



In the days when blood-letting was much in vogue, it was 

 found to be a matter of every-day experience that the pain of 

 inflammation was removed for a time by opening a vein ; and 

 although the pain again returned, the abstraction of a further 

 quantity again relieved it. The relief is explained by the 

 general diminution in the blood-pressure after phlebotomy 

 lessening the tension of the vessels of the inflamed part ; while 

 the return of the pain is in all probability due to the fact that 

 after the abstraction of blood the vessels contract, so as to 

 accommodate themselves to their diminished contents, and thus 

 raise the pressure again. Unluckily, however, blood-letting 

 does something more than diminish the tension within the 

 vessels of the inflamed part in common with those of the rest 

 of the body; it drains away the vital fluid, and seriously 

 impairs the power of restoration. It is evident, therefore, that 



