THE NITRIFYING BACTERIA 605 



The sulphates and chloride (a) are mixed in 50 c.c. of the 

 distilled water, and the phosphate and carbonate (6) in 

 the remaining 50 c.c., in separate flasks. 



Each flask is then sterilized with its contents, which after 

 cooling are mixed; the mixture representing the solution 

 of mineral salts is to be added to the silicic acid, little by 

 little, until the proper degree of consistency is obtained (that 

 of ordinary nutrient gelatin). This part of the process is 

 best conducted in a culture-dish. If it is desired to separate 

 the colonies, as in an ordinary plate, the inoculation and 

 mixing of the material introduced must be done before 

 gelatinization is complete; if the material is to be distributed 

 over only the surface of the medium, then the mixture 

 must first be allowed to solidify. 



By the use of the silicate-gelatin Winogradsky has isolated 

 from the gelatinous film in the bottom of fluids undergoing 

 nitrification a bacillus which he believes to be associated 

 with the nitro-monas in the nitrifying process. 



The developments in this field of study are of such breadth 

 and importance that they can scarcely be comprehended 

 in a book of this character. For particulars the reader is 

 referred to the special books and journals dealing with the 

 subject. 



In addition to the bacteria concerned in the various trans- 

 formation of nitrogen, there are occasionally present in the 

 soil microorganisms possessing disease-producing properties. 

 Conspicuous among these may be mentioned the bacillus 

 of malignant edema (vibrion septique of the French), the 

 bacillus of tetanus, and the bacillus of symptomatic anthrax 

 (Rauschbrand (Ger.); charbon symptomatique (Fr.)). It is 

 sometimes due to the presence of one or the other of these 



