502 EREMACAUSIS OR DECAY. 



CHAPTER VII. 



Eremacausis or decay of bodies destitute of Nitrogen : formation of 

 Acetic Acid. 



All those substances which appear to possess the property of 

 entering spontaneously into fermentation and putrefaction, do not 

 in reality suffer those changes without some previous disturbance 

 in the attraction of their elements. Eremacausis always pre- 

 cedes fermentation and putrefaction, and it is not until after the 

 absorption of a certain quantity of oxygen that the signs of a trans- 

 formation in the interior of the substances show themselves. 



It is a very general error to suppose that organic substances 

 have the power of undergoing change spontaneously, without the 

 aid of an external cause. When they are not already in a state 

 of change, it is necessary, before they can assume that state, that 

 the existing equilibrium of their elements should be disturbed ; 

 and the most common cause of this disturbance is undoubtedly 

 the atmosphere which surrounds all bodies. 



The juices of the fruit or other parts of a plant prone to de- 

 composition, retain their properties unchanged as long as they 

 are protected from immediate contact with the air, that is, as 

 long as the cells or organs in which they are contained resist the 

 iufluence of the air. It is not until after the juices have been 

 exposed to the air, and have absorbed a certain quantity of 

 oxygen, that the substances dissolved in them begin to be decom- 

 posed. 



The beautiful experiments of Gay-Lussac upon the fermenta- 

 tion of the juice of grapes, as well as the important practical 

 improvements to which they have led, are the best proofs that the 

 atmosphere possesses an influence upon the changes of organic 

 substances. The juice of grapes expressed under a receiver 



