HORSEBACK RIDING, 63 



the quantity of elements furnished to the internal 

 combustion. 



7. Secretion. — Horse-back riding does not exert 

 a special and direct influence upon the secretions ; 

 their activity is often only the consequence of the ac- 

 tivity of other physiological functions, and as they do 

 not concern our therapeutics, we will pass them with 

 a simple mention. Perspiration is the result of in- 

 creased surface circulation, and increases or diminishes 

 with it. Trotting induces it more than any other 

 gait in riding. 



The mouth becomes dry in horse-back exercise, in 

 consequence of the rapid evaporation caused by the 

 frequent passage of the air through the buccal cavity, 

 due to the acceleration of the respiration. The sali- 

 vary glands are not excited as in mastication, and no 

 longer furnish sufficient saliva. As for the secretions 

 of the glands of the stomach and intestines, of the 

 liver and the pancreas, they regulate themselves ac- 

 cording to the needs of the digestion. 



The activity of the cutaneous and pulmonary ex- 

 halation, the increase of perspiration and fluid secre- 

 tions in general, decrease in proportion to the quan- 

 tity of fluid eliminated by the kidneys. As to the 

 urea which they contain, numerous experiments tend 

 to show that muscular exercise, even when carried to 

 excess, does not materially increase or diminish it. 

 The presence of free azote in the expired air explains 

 this fact, as this gas is the result of the complete 



