THE NITRIFYING BACTERIA. 533 



rial 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. 



Our knowledge of these organisms is as yet too im- 

 perfect to permit of a complete description. What has 

 been said will serve to indicate the direction in which 

 further studies of the subject should be prosecuted. 

 (For further details, the reader is referred to the original 

 contributions and to current literature on the subject. 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 (Ramchbrand (Ger.) ; charbon 

 xymptomatique (Fr.)). It is sometimes due to the pres- 

 ence 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 consequences. 



1 Winogradsky : Annales de 1'Institut Pasteur, 1890, tome iv. ; 1891, 

 tome v. 



Jordan and Richards : Report of State Board of Health of Massa- 

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



Frankland, G. C. and P. F.: Proceedings of Royal Society, London, 

 1N90, xlvii. 



Wiuogradsky and Omeliansky : " Ueber den Einfluss der organisaten 

 Substangen auf der arbeitder nitrifizierenden Mikroben," Centralblatt 

 fur Bakteriologie, 1899, Abt. ii. Bd. v S. 329. 



