585 
upon the Action of the Arteries. 
a rabbit, and in that animal the par vagum was separated from 
the intercostal nerve, which cannot be readily done in the dog; 
and it was found when the par vagum alone was irritated, no 
change took place in the action of the artery. The carotid 
artery was chosen as the only one in the body of sufficient 
size that can be readily exposed, to which the nervous branches 
supplying it can readily be traced from their trunk. 
This experiment was repeated three different times, so as 
to leave no doubt respecting the result. 
Having ascertained by these experiments that the increase 
and diminution of the action of an artery does not depend upon 
irritability, but nervous influence, I made the following expe- 
riments, to determine whether heat or cold had the greatest 
effect in stimulating the nerves to action. 
The wrist of one arm was surrounded by bladders filled 
with ice, and after having remained in that state five minutes, 
the pulse was felt at the same time in that and in the opposite 
wrist, and the beats were found evidently strongest in the 
cooled wrist. This experiment was then made with water 
heated to 120° or 130*, beyond which the heat could not be 
submitted to, and the pulse was found to be softer and weaker 
than that in the other arm. 
When one wrist was cooled and the other heated, the stroke 
of the pulse in the cooled arm had great force beyond that 
in the heated one. 
f 
These experiments were repeated upon several young men x 
at different ages, and on several women, with an uniform re- 
sult, and explain the glow produced by the cold bath, and the 
other beneficial effects of cold bathing, in a more satisfactory 
manner than has been hitherto done. 
