384 POISONS,, CONTAGIONS, MIASMS. 



The same numerous causes which are opposed 

 to the formation of complex organic molecules, 

 under ordinary circumstances, occasion their de- 

 composition and transformations when the only 

 antagonist power, the vital principle, no longer 

 counteracts the influence of those causes. Contact 

 with air and the most feeble chemical action now 

 effect changes in the complex molecules ; even the 

 presence of any body the particles of which are 

 undergoing motion or transposition is often sufficient 

 to destroy their state of rest, and to disturb the 

 statical equilibrium in the attractions of their con- 

 stituent elements. An immediate consequence of 

 this is that they arrange themselves according to 

 the different degrees of their mutual attractions, 

 and that new compounds are formed in which che- 

 mical affinity has the ascendancy, and opposes any 

 further change, while the conditions under which 

 these compounds were formed remain unaltered. 



