GENERAL FUNCTIONS OF MICROBES 15 



which is so prejudicial to nitrification. Probably the two 

 functions balance and regulate each other. The nitrogen 

 liberated by the denitrifying bacteria is, however, not lost ; it 

 may be taken up by the bacteria which fix nitrogen. It is 

 nevertheless true that farmers ought to be on their guard 

 against the denitrifying organisms and avoid putting on the 

 soil farmyard manure, especially if fresh, along with nitrates. 

 Formerly in the manufacture of saltpetre cultivated soil was 



$ 

 



FIG. 6. Nitrifying bacteria (after Winogradsky). 



A. Nitrous ferment from Zurich. 



B. The same in the motile form with flagella. 



C. Nitrous ferment from Kazan. 



D. Nitrous ferment from Java, motile cells and groups of cells. 



freely sprinkled with urine. If the deposits of nitrate in Chili 

 and Peru should some day be exhausted, it would not be 

 impossible to make it with the help of bacteria (not to speak of 

 the electrical methods which have already been employed). 

 Saltpetre is produced everywhere when suitable conditions of 

 moisture and organic matter are given. The saltpetre of 



