Chap, hi The absorption of Nitrogen 337 



to a peculiar condition of attenuation of the organism. At 

 the same time a suspicion began to make itself felt that 

 possibly it might be a question of two organisms rather than 

 one. Further cultures followed, in which he was successful 

 in isolating the organism by which nitrites are formed, and 

 he found it to agree with the description already given by 

 Schloesing and Muntz. 



In the same year (1890) in which this work was done, 

 a paper was published by Professor and Mrs. Frankland, 

 in which they claimed to have isolated the microbe. 



The complete failure of this organism to produce nitrates 

 when vigorous, or indeed under any conditions, led to a 

 search for a microbe that should be capable of doing 

 this only. But though pursued with great care, the search 

 led to no further result than that of 1880. A culture could 

 be obtained which would not act on ammonia but would 

 oxidize nitrites, but no organism possessing the power 

 could be isolated from it. As we shall see later, the dis- 

 covery of the microbe was reserved for Winogradsky. 



It was thus made possible to speak definitely of a nitrous 

 organism. Warington said it could not be cultivated on 

 gelatine or agar-agar, but it would grow slowly in weak 

 broth. It produced nitrites in solutions of asparagin, in 

 milk, in urine, and in solutions of urea, as well as in culture 

 fluids containing inorganic compounds of ammonia. It was 

 incapable of reducing nitrates to nitrites. 



We must now turn to the work of Winogradsky ; part of 

 this was synchronous with the researches of Warington, 

 but his more important results were obtained after 1890. 

 His investigations followed upon his researches into the 

 peculiarities of the sulphur and iron bacteria, to which 

 reference will be made later. He had found in connexion with 

 this research that they are distinguished from the majority 

 of bacteria by their behaviour to organic food materials. 

 His studies of the nitrifying organisms led to one of the 



GREEN Y 



