IN THE ANIMAL ORGANISM. 205 



resistance (by the manifestation of an opposite 

 force), its effect is not annihilated. The falling 

 stone, by means of the amount of motion acquired 

 in its descent, produces an effect when it reaches 

 the table. The impression made on the wood, the 

 velocity communicated by its parts to those of the 

 wood, all this is its effect. 



If we transfer the conceptions of motion, equi- 

 librium, and resistance, to the chemical forces, 

 which, in their modus operandi, approach to the 

 vital force infinitely nearer than gravitation does, 

 we know with the utmost certainty, that they are 

 active only in the case of immediate contact. We 

 know also, that the unequal capacity of chemical 

 compounds to offer resistance to external disturbing 

 influences, to those of heat, or of electricity, which 

 tend to separate their particles, as well as their 

 power of overcoming resistance in other compounds 

 (of causing decomposition) ; that, in a word, the 

 active force in a compound depends on a certain 

 order or arrangement, in which its elementary par- 

 ticles touch each other. 



The same elements, united in a different order, 

 when in contact with other compounds, exert a 

 most unequal power of offering or overcoming re- 

 sistance. In one form the force manifested is 

 available (the body is active, an acid, for example) ; 

 in another not (the body is indifferent, neutral) ; in 

 a third form, the momentum of force is opposed to 

 that of the first (the body is active, but a base). 



