146 ATLAS OF BACTERIOLOGY. 



tion is particularly the function of a small, special 

 group of bacteria which are cultivated with difficulty 

 and do not thrive upon our ordinary nutrient media. 



According to Winogradsky, who has done the most 

 work in this department, the facts of tho case are as 

 follows : The soil of Europe contains, widely distrib- 

 uted, two micro-organisms, one of which (nitroso- 

 monas) converts ammonia into nitrite, the other (called 

 nitromonas, later nitrobacter) converts nitrite into 

 nitrate. Both varieties are obtained mixed when bits 

 of earth in flasks are dissolved in boiling water 

 (Wiuogradsky took the water of a fresh-water lake) 

 containing 1 gm. ammonium sulphate and 1 gm. potas- 

 sium phosphate to 1 litre. About 1.0 gm. basic mag- 

 nesium carbonate is added to each flask containing 

 100 c.c. Considerable development of nitrites takes 

 place, and gradually nitrates are also formed. By 

 inoculation of new flasks the nitrifying organisms 

 are obtained gradually in a purer state, and silicic- 

 acid plates finally permit, with difficulty, a pure cul- 

 ture. Burri and Stutzer have recently cultivated upon 

 the ordinary nutrient media a vigorous nitrate pro- 

 ducer (from nitrite), but it forms nitrates only upon 

 inorganic nutrient solutions (C. B., Vol. I., Part II., 

 731). 



P. F. Eichter (C. B., XVIII. , Part I., p. 129) ob- 

 served on several occasions a pronounced nitrite 

 reaction in fresh urine evacuated with the catheter. 

 From one specimen he isolated a coccus of medium 

 size, which in twenty minutes produced a very in- 

 tense nitrite reaction in fresh urine. In addition it 

 reduced nitrate to nitrite. 



