THE NITRIFYING BACTERIA. 509 



breaking down and building up, resulting ultimately 

 in nitrification, occurs in all nitrogenous matters that 

 are deposited upon the soil and allowed to decay. It is 

 largely through this means that growing vegetation 

 obtains the nitrogen necessary for the nutrition of its 

 tissues, and when viewed from this standpoint we ap- 

 preciate the importance of this process to all life, ani- 

 mal as well as vegetable, upon the earth. 



These very important and interesting nitrifying 

 organisms, of which there appear to be several, have 

 been the subject of much study, and are found to 

 possess peculiarities of sufficient interest to justify a 

 brief description. All efforts to isolate them from the 

 soils and to cultivate them by the processes commonly 

 employed in bacteriological work, result in failure. 

 They can be successfully studied only through the 

 employment of special methods. 



Nitrifying bacteria, capable of oxidizing ammonia to 

 nitric acid, have been isolated and cultivated, and the 

 more important of their biological peculiarities recorded 

 by Winogradsky in Switzerland, by G. C. and P. F. 

 Frankland in England, and by Chester, Jordan, and 

 Richards in this country. From the similarity of the 

 properties, given by these several observers, of the nitri- 

 fying organisms isolated by them, it seems likely that 

 they have all been working with either the same organism 

 or very closely allied species. 



The organism generally known as the nitro-monas of 

 Winogradsky is a short, oval, and frequently almost 

 spherical cell. It reproduces by segmentation as usual 

 for bacteria, but there is little tendency for the daughter- 

 cells to adhere together or to form chains. In cultures 



