44 HORSE-BACK RIDING. 



instrument shows a diminution of arterial tension ; it 

 could not be otherwise, for the blood in the great 

 arterial trunks, finding less resistance from the dilated 

 capillaries at the surface of the body, flows more 

 freely. The result of this is less tension and less 

 resistance to the ventricular contraction ; this is 

 effected more brusquely, and the shock is perceived 

 more distinctly by the finger. It is this instantane- 

 ousness— which does not affect the circulatory ap- 

 paratus — Avhich causes the apparent fulness of the 

 pulse. 



The second proposition of Haller is equally true — 

 neque calefacit — but we must be careful to give it the 

 meaning attached to it by its author. Struck by the 

 increase of temperature which usually accompanies 

 fever, the physicians of former times did not separate 

 the idea of heat from that of fever, and the great 

 physiologists, in adopting their language, have per- 

 petuated their error. Horse-back riding certainly in- 

 creases the temperature of the body, for we have 

 shown that a portion of the heat produced by the 

 combustion which takes place in the muscles is ren- 

 dered sensible to thermoscopic measurement, but 

 this heat is not fever. It is true that on dismount- 

 ing, if the exercise has been somewhat prolonged, a 

 slight trembling is felt in all the limbs ; at the same 

 time the skin is rosy and moist, a gentle perspiration 

 exuding from every pore, but instead of the suffering 

 produced by fever there is a sense of comfort. 



