322 EREMACAUSIS OR DECAY. 



CHAPTER VI. 



EREMACAUSIS, OR DECAY. 



In organic nature, besides the processes of decom- 

 position named fermentation and putrefaction, an- 

 other and not less striking class of changes occurs, 

 which bodies suffer from the influence of the air. 

 This is the act of gradual combination of the com- 

 bustible elements of a body with the oxygen of the 

 air; a slow combustion or oxidation, to which we 

 shall apply the term of eremacausis. 



The conversion of wood into humus, the formation 

 of acetic acid out of alcohol, nitrification, and numer- 

 ous other processes, are of this nature. Vegetable 

 juices of every kind, parts of animal and vegetable 

 substances, moist sawdust, blood, &c., cannot be 

 exposed to the air, without suffering immediately a 

 progressive change of color and properties, during 

 which oxygen is absorbed. These changes do not 

 take place when water is excluded, or when the 

 substances are exposed to the temperature of 32^, 

 and it has been observed that different bodies require 

 different degrees of heat, in order to effect the 

 absorption of oxygen, and, consequently, their ere- 

 macausis. The property of suffering this change is 

 possessed in the highest degree by substances con- 

 taining nitrogen. 



When vegetable juices are evaporated by a gentle 

 heat in the air, a brown or brownish-black substance 

 is precipitated as a product of the action of oxygen 

 upon them. This substance, which appears to pos- 

 sess similar properties from whatever juice it is 

 obtained, has received the name of extractive matter ; 

 it is insoluble or very sparingly soluble in water, but 

 is dissolved with facility by alkalies. By the action 

 of air on solid animal or vegetable matters, a similar 



