134 MANUAL OF BACTERIOLOGY. 



Green plants convert the stable compounds of nitrogen, the 

 carbon dioxide of the atmosphere and water into the complej 

 and unstable albumens and carbohydrates which serve as 

 food for animals. Animals, on the other hand, convert these 

 unstable and complex compounds back into simpler forms, 

 The work of changing them back into the simple and stable 

 condition, in which they serve as the food for plants, is per- 

 formed by animal life in part only, and its completion is left tc 

 the activities of bacteria. It is the work of bacteria in this 

 direction which we call decomposition. Without that work the 

 existence of life upon the earth, as we understand it, would soon 

 come to an end, and the dead and undecomposed bodies oi 

 living things and their products of all kinds would lie about 

 unchanged, as they had fallen. 



Bacterium termo is the name formerly given to a supposed 

 species of bacteria which was credited with being the producei 

 of putrefaction. The individuals were represented as bein 

 short rods, mostly growing in pairs, and actively motile. The 

 term has been abandoned since it appears to have included i 

 number of different species. 





