THEIR MODE OF ACTION. 357 



friction, is sufficient to cause a disturbance in the 

 equilibrium of the attraction of their constituents; 

 they arrange themselves either into new, more sim- 

 ple, and permanent combinations, or if a foreign 

 attraction exercise its influence upon it, they arrange 

 themselves in accordance with that attraction. 



The special characters of food, that is of sub- 

 stances fitted for assimilation, are absence of active 

 chemical properties, and the capability of yielding 

 to transformations. 



The equilibrium in the chemical attractions of 

 the constituents of the food is disturbed by the 

 vital principle, as we know it may be by many 

 other causes. But the union of its elements, so as 

 to produce new combinations and forms, indicates 

 the presence of a peculiar mode of attraction, and 

 the existence of a power distinct from all other 

 powers of nature, namely, the vital principle. 



All bodies of simple composition possess a greater 

 or less disposition to form combinations. Thus 

 oxalic acid is one of the simplest of the organic 

 acids, while stearic acid is one of the most complex ; 

 and the former is the strongest, the latter one of 

 the weakest in respect to active chemical character. 

 By virtue of this disposition, simple compounds 

 produce changes in very body which offers no 

 resistance to their action ; they enter into combi- 

 nation and cause decomposition. 



The vital principle opposes to the continual 

 action of the atmosphere, moisture and tempera- 



