NITRIFYING BACTERIA. 391 



down and building up, resulting ultimately in nitrifica- 

 tion, occurs in all nitrogenous matters that are thrown 

 upon the soil and allowed to decay. It is largely through 

 this means that growing vegetation obtains the nitro- 

 gen necessary for the nutrition of its tissues, and when 

 viewed from this standpoint we appreciate the impor- 

 tance of this process to all life, animal as well as vege- 

 table, upon the earth. 



These very important and interesting nitrifying or- 

 ganisms, of which there appear to be several, have been 

 subjected to considerable study and are found to possess 

 peculiarities of sufficient interest to justify a more or 

 less detailed description. For a long time all efforts to 

 isolate them from the soils in which they were believed 

 to be present, and to cultivate them by the processes 

 commonly employed in bacteriological work, resulted in 

 failure, and it was not until it was found that the ordi- 

 nary methods of bacteriological research were in no way 

 applicable to the study of these bacteria that other, and 

 ultimately successful, methods were devised. By these 

 special devices nitrifying bacteria, capable of oxidizing 

 ammonia to nitric acid, have been isolated and culti- 

 vated, and the more important of their biological pecu- 

 liarities recorded by Winogradsky in Switzerland, by 

 G. C. and P. F. Frankland in England, and by Jordan 

 and Richards in this country. From the similarity of 

 the properties, given by these several observers, of the 

 nitrifying 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 divides as usual for bacteria, but 



