THE BACTERIA IN DIFFERENT MEDIA. 151 



truly an organized ferment. Indeed, chloroform, 

 this anaesthetic, suspends nitrification, and seems 

 even to kill the ferment. 



Leaving, then, this phenomenon, but little 

 known, we may distinguish in the agents of pu- 

 trefaction, or more generally of fermentation, two 

 groups of micro-organisms, one oxidizing, the 

 other reducing. 



The first are observed upon the surface of 

 liquids undergoing putrefaction. We may distin- 

 guish a great number of forms, Bacterium termo, 

 Monas crepusculum, Spirillum, etc. We ought 

 also to include Mycoderma aceti, which, like the 

 others, vegetates on the surface of liquids, and 

 a great number of organisms of which we cannot 

 speak here. 



The second are met, on the contrary, in the 

 interior of liquids or of fermentable bodies; they 

 are analogous to the butyric and lactic ferments, 

 and perhaps to the other agents of diseases of 

 wine and beer previously enumerated. 



En resume, the little beings which we have been 

 considering have an important role : they cause 

 the return of dead organic matter to the atmos- 

 phere and to water. 



" Without them, organic matter, even exposed 

 to the air, would not be destroyed or would be 

 transformed with extreme slowness, in consequence 

 of a slow combustion produced by oxygen. With 

 them, on the contrary, its destruction takes a 

 rapid march and becomes complete. If, then, the 

 equilibrium is maintained between living nature 



