MICROBES, OK BACTERIA. 115 



found on the surface, which also absorb this gas and 

 do not allow it to penetrate into the lower part of 

 the liquid. 



This liquid now becomes the seat of two very 

 distinct actions. In its interior, vibriones succeed to 

 the free globules and zoogloea, of which they appear 

 to be only a higher stage of transformation. These 

 microbes multiply and change the albuminoid matter 

 into more simple substances ; insoluble cellulose, fatty 

 bodies, and gaseous putrid matters. Meanwhile, the 

 microbes on the surface actively consume the products 

 thus developed, transforming them into carbonic acid, 

 nitrogen, and the oxides of nitrogen, etc. This ex- 

 plains why, when there is an insufficiency of oxygen, 

 putrefaction may indeed begin ; but it languishes, and 

 is finally arrested. 



The cause of the fetid odours which escape from 

 putrefying bodies and liquids is not well understood. 

 It may be ascribed to the disengaged gases (carburetted, 

 phosphoretted and sulphuretted hydrogen, and ammo- 

 niacal compounds), and to the circulation of decom- 

 posing organic particles. We also find formic, acetic, 

 lactic, butyric, valerianic, and caproi'c acids, generally 

 combined with ammonia, and the fatty acids which 

 are one result of the successive disintegrations of 

 albuminoid matters. 



When these gases are disengaged, a substance 

 remains which may be compared with humus, or 

 vegetable earth. It is rich in fats, in earthy and 



