THE MICROBES OF THE SOIL 283 



gramme of ammonium chloride, and 5 grammes of 

 carbonate of lime (pure) ; and in this solution the 

 microbe grew and multiplied. As this solution con- 

 tains no organic matter, it will be seen that nitrifica- 

 tion can take place in purely mineral solutions. This 

 power of growing in mineral solutions prevented the 

 development of other microbes (present in the soil 

 used for inoculation) which require organic matter 

 for their growth. After proving that the microbe 

 refused to grow on gelatine, 'experiments were 

 commenced to endeavour to isolate the microbe by 

 the dilution method. For this purpose a number 

 of series of dilutions were made by the addition, to 

 sterilised distilled water, of a very small quantity 

 of an ammoniacal solution which had nitrified. It 

 was hoped that the attenuation would be so perfect 

 that ultimately the nitrifying microbe alone would 

 be introduced. After a very large number of 

 experiments had been made in this direction, the 

 authors at length succeeded in obtaining an at- 

 tenuation consisting of about one-millionth of the 

 original nitrifying solution employed, which not 

 only nitrified, 1 but, on inoculation into gelatine- 

 peptone, refused to grow, and was seen, tinder the 

 microscope, to consist of numerous characteristic 

 bacilli hardly longer than broad, which may be 

 described as bacillococci.' 



The chief characters of the Frankland Bacillus of 

 nitrification (Fig. 56 A) are the following : 



(a) The solutions in which the isolated microbe 



1 The presence of nitrous acid was ascertained by both 

 diphenylainine and sulphanilic acid. 



