52 IIORSE-BACK RIDING. 



Vulplan has shown that the nervous fibre has a 

 pecuHar action which he calls nnirility. According 

 to this author, the action of the nervous cell takes 

 place only under the influence of the neurility of the 

 fibre, and the nervous centres lose all their activity as 

 soon as they cease to receive arterial blood. Ner- 

 vous power is the result of the action of the blood on 

 the brain and spinal marrow. 



The same writer says again, we are led to the inev- 

 itable conclusion that neurility is the distinct fun- 

 damental independent physiological attribute of the 

 nervous fibre, and that the existence of this property 

 is inseparable from the integrity of the structure and 

 nutrition of the anatomical elements. 



Gavarret thus explains the nervous action : ''Like 

 the muscular fibre during contraction, the nervous 

 fibre under a direct excitant, or when propagating 

 some communicated excitement, is perceptibly in- 

 creased in heat. In the nervous as in the muscular 

 system, this momentary elevation of temperature is in 

 reality perhaps nothing more than the result of the 

 momentary increase of internal combustion. In view 

 of these facts, we cannot but recognize that neurility 

 and muscular contractility have the same relation to 

 heat. The activity of the nervous system and the 

 intensity of the internal combustion correspond to 

 each other and increase and diminish together. In 

 the nervous centres the result of combustion is trans- 

 formed into neurility, the different nervous filaments 



