272 EREMACAUSIS OR DECAY. 



was expressed from the grapes in contact with air, 

 under the conditions therefore necessary to cause 

 its fermentation, still this change did not ensue 

 when the juice was heated in close vessels to the 

 temperature of boiling water. When thus treated, 

 it could be preserved for years without losing its 

 property of fermenting. A fresh exposure to the 

 air at any period caused it to ferment. 



Animal food of every kind, and even the most 

 delicate vegetables, may be preserved unchanged 

 if heated to the temperature of boiling water in 

 vessels from which the air is completely excluded. 

 Food thus prepared has been kept for fifteen years, 

 and upon opening the vessels after this long time, 

 has been found as fresh and well flavoured as when 

 originally placed in them. 



The action of the oxygen in these processes of 

 decomposition is very simple ; it excites changes 

 in the composition of the azotised matters dissolved 

 in the juices ; the mode of combination of the 

 elements of those matters undergoes a disturbance 

 and change in consequence of their contact with 

 oxygen. The oxygen acts here in a similar manner 

 to the friction or motion which effects the mutual 

 decomposition of two salts, the crystallisation of 

 salts from their solution, or the explosion of fulmi- 

 nating mercury. It causes the state of rest to be 

 converted into a state of motion. 



When this condition of intestine motion is once 

 excited, the presence of oxygen is no longer 



