ON MATTER AND FOECE. 75 



The brain, the nerves, the muscles, the 

 electric organs, the textures in general, all 

 these are machines set in action chiefly by 

 the potential energy or tension in the food, 

 textures, and air; the supply of oxygen, hy- 

 drogen, and carbon being the first necessary 

 condition. 



The mechanical, chemical, nutritive, muscular, 

 and nervous motions are so related, that it is 

 most difficult to separate the action of any one 

 motion, even the simplest which can occur in 

 the human body. 



When these motions are so increased or 

 diminished as to constitute disease, then the 

 difficulty of isolating any one motion becomes 

 by no means lessened. Still, even in disease, 

 the doctrine of the conservation of energy can 

 enable us to make at least as great an advance 

 as was made in our ideas and language when 

 the doctrine of phlogiston, or the hypothetical 

 inflammable principle which was thought to 

 possess a power of levity, was given up. 



Vital force in disease must cease to be 

 regarded as an imponderable material capable 

 of varying in quantity and quality. We must 

 cease to think that it can be made more active 



