OF BODIES DESTITUTE OF NITROGEN. 273 



necessary. The smallest particle of an azotised 

 body in this act of decomposition exercises an 

 influence upon the particles in contact with it, and 

 the state of motion is thus propagated through the 

 substance. The air may now be completely excluded, 

 but the fermentation or putrefaction proceeds unin- 

 terruptedly to its completion. It has been remarked 

 that the mere contact of carbonic acid is sufficient 

 to produce fermentation in the juices of several 

 fruits. 



The contact of ammonia and alkalies in general 

 may be mentioned amongst the chemical condi- 

 tions which determine the commencement of 

 eremacausis ; for their presence causes many 

 substances to absorb oxygen and to decay, in 

 which neither oxygen nor alkalies alone produce 

 that change. 



Thus alcohol does not combine with the oxygen 

 of the air at common temperatures. But a solution 

 of potash in alcohol absorbs oxygen with much 

 rapidity, and acquires a brown colour. The alcohol 

 is found after a short time to contain acetic acid, 

 formic acid, and the products of the decomposition 

 of aldehyde by alkalies, including aldehyde resin, 

 which gives the liquid a brown colour. 



The most general condition for the production of 

 eremacausis in organic matter is contact with a 

 body already in the state of eremacausis or putre- 

 faction. We have here an instance of true conta- 



