QUALITATIVE BACTERIOLOGICAL ANALYSIS. 83 



P. F. and G. C. Frankland tested Heraeus' statements that 

 M. prodigiosns and B. ramosus possessed nitrifying powers, but 

 tailed to obtain any evidence of nitrifying action ; on the 

 contrary both organisms were found to be capable of reducing 

 nitric to nitrous acid. The Franklands believed that the indica- 

 tions of nitrous acid which Heraeus obtained on growing these 

 organisms in diluted urine were due to reduction of the small 

 quantity of nitrates almost invariably found in normal urine, 

 and not to any oxidation of the ammonia at all. They also 

 experimented with no less than thirty-three different cultures 

 obtained from air and water, but in every case the results were 

 negative. They found, however, that nitrification was readily 

 induced when a small quantity of ordinary garden soil was 

 introduced into a solution containing potassium phosphate, 

 crystallised magnesium sulphate, fused calcium chloride, 

 ammonium chloride, and carbonate of lime. By passing a few 

 drops of the nitrified fluid through a series of dilutions in 

 distilled water, a fluid was obtained which contained numerous 

 micro-organisms of a very short bacillary form which could not 

 be cultivated on gelatine-peptone. A portion of this fluid 

 induced strong nitrification in a sterile ammoniacal solution. It 

 was noticed that the solutions which had undergone nitrification 

 by the organisms contained in the fluid remained perfectly clear, 

 whilst solutions which underwent nitrification from a mixture of 

 the nitrifying and non-nitrifying bacteria generally exhibited a 

 thin surface film. The pure culture of the nitrifying organism, 

 obtained by the method of fractional dilution, showed only a 

 very short bacillus, about 0'8 /*. long, hardly longer than broad, 

 and exhibiting only vibratory motion. This micro-organism 

 transformed ammoniacal into nitrous nitrogen in amounts which 

 could be quantitatively estimated by the usual chemical means. 

 The formation of nitric nitrogen was not observed in solutions 

 inoculated with a pure culture of the organism in question. 



Winogradsky, in 1890, made some very important contribu- 

 tions to our knowledge of nitrifying organisms. In his earliest 

 experiments he employed a medium containing 1 gramme of 

 ammonium sulphate, 1 gramme of potassium phosphate, to the 

 litre of water from Lake Zurich ; to 100 c.c. of this fluid, placed 

 in a flask, 0*5 to 1 gramme of basic carbonate of magnesia, 



