NITRIFYING BACTERIA. 433 



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 this 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. 



Our knowledge of these organisms is as yet too in- 

 complete to permit of a satisfactory description of all 

 their morphological and biological peculiarities. What 

 has been said will serve to indicate the direction in 

 which further studies of the subject should be prose- 

 cuted. 



For further details the reader is referred to the orig- 

 inal contributions. 1 



In addition to the bacteria concerned in decomposition 

 and nitrification there are occasionally present in the 

 soil micro-organisms possessing disease-producing prop- 

 erties. Conspicuous among these may be mentioned 

 the bacillus of malignant oedema (vibrion septique of 

 the French), the bacillus of tetanus, and the bacillus of 

 symptomatic anthrax (Rauschbrand, German; charbon 

 symptomatique, French). It is sometimes due to the 

 presence of one or the other of these organisms that 

 wounds to which soil has had access (crushed wounds 

 from the wheels of cars or wagons, wounds received in 

 agricultural work, etc.) are followed by such grave 

 disturbances of the constitution. 



1 Winogradsky : Annales de 1'Institut Pasteur, tomes iv., 1890, and v., 1891. 

 Jordan and Richards : Rep. State Board of Health, Mass., " Purification 

 of Sewage and Water," 1890, vol. ii. p. 864. 

 Frankland, G. C. and P. F. : Proc. Royal Soc. London, 1890, xlvii. 



