IIORSE-BACK RIDING. 53 



collect this neurility, and, dispersed in all directions, it 

 goes to increase the activity of the different organs of 

 the system ; . . . . thus in the animal there are 

 three dynamic manifestations, the production of heat, 

 muscular contraction, and nervous activity, which are 

 derived directly from the action of the oxygen of the 

 air upon the organic materials of the blood." 



The nervous action simply gives the impulse to the 

 phenomena of combustion ; once commenced, the 

 action of the oxygen upon the materials of the blood 

 continues and produces an effect out of proportion 

 with the primitive expenditure of the impulsive 

 force. 



How can we refuse to recognize the immense influ- 

 ence that the circulation exercises over the production 

 of nervous phenomena ? 



Then comes the question, if there does exist so in- 

 timate a relation between these two functions, circu- 

 lation and innervation, within what limits are they 

 exercised, and in what proportion does the disturb- 

 ance of one react upon the other } However, what 

 seems incontestable is that the nervous tissue is sub- 

 ject to the same laws as the other tissues of the 

 organism ; like them, it is nourished, expands, and is 

 regenerated. The blood is the agent of these trans- 

 formations, and the circulation is effected in them in 

 the same manner as everywhere else, is subject to the 

 same modifying causes. The integrity of this func- 

 tion depends upon the integrity of the nervous ac- 



