$6 HORSE-BACK RIDING. 



ing the natural movement of its contents greatly favor 

 defecation. 



But the mechanical excitement of the muscular 

 fibres would soon exhaust its contractility if the 

 natural physiological agent, the blood, did not come 

 to its assistance. Every thing, in fact, combines to 

 cause it to flow into the alimentary canal — the pres- 

 ence of food, the increased activity of the circulation 

 caused by riding, the contraction due to the mechan- 

 ical excitement in the fibre cellule, and fed by com- 

 bustion. At the same time the glands, and the entire 

 secretory apparatus depending on digestion, gorged 

 with blood, furnish abundant material for their por- 

 tion of the work, and lead powerfully with the mus- 

 cular contractions in the elaboration of the materials 

 for new tissues. 



The blood which enters the stomach penetrates also 

 the nerves which control it, and checks the fantasies 

 of this capricious organ. 



The increased circulation has another effect, that 

 of promoting the venous absorption ; and the greater 

 pressure on the chyme in the alimentary canal, in con- 

 sequence of the contraction of the muscular fibre, 

 greatly favors its passage into the chyliferous vessels. 



When the mechanical excitement of riding, like 

 that of the will, causes the fibre-cell to act, it acquires 

 more tonicity, the contractions cease to be languid 

 and furnish more effective aid to the work of diges- 

 tion. The effect of riding upon this last differs ac- 



