CHAPTER XXVIII. 



The Nitrifying Bacteria The Bacillus of Tetanus The Bacillus of Malig- 

 nant Edema The Bacillus of Symptomatic Anthrax Bacterium 

 Welchii Bacillus Sporogenes. 



THE NITRIFYING BACTERIA. 



BY the employment of bacteriological methods in the 

 study of the soil much light has been shed upon the cause 

 and nature of the interesting and momentous biological 

 phenomena there constantly in progress. Of these, the one 

 of the greatest importance comprises those changes that 

 accompany the widespread process of disintegration and 

 decomposition, to which reference has already been made. 

 (See Chapter I.) This resolution of dead complex organic 

 compounds into simpler structures assimilable as food by 

 growing vegetation is dependent upon the activities of 

 bacteria located in the superficial layers of the ground. It 

 is not a simple process, brought about by a single, specific 

 species of bacteria, but represents a sequence of events each 

 of which probably results from the activities of different 

 species or groups of species, working alone or together. Our 

 knowledge upon the subject does not permit of the following in 

 detail of the manifold alterations undergone by dead organic 

 material, but we do know that much of it is ultimately 

 converted into inorganic matters and that carbon dioxide, 

 ammonia and water are always conspicuous end products. 

 When the process of decomposition occurs in the soil it 

 does not cease at this point, but we find still further altera- 



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