282 A MANUAL OF BACTERIOLOGY 



first shown by Mlintz and Schloesing 1 to be due 

 to the action of microbes in the soil. Although 

 these savants had previously described a microbe 

 causing nitrification, it was not until 1890 that Dr. 

 P. F. Frankland, F.RS., 2 M. Winogradsky, 3 and Mr. 

 R. Warington, F.RS., 4 simultaneously described the 

 true cause of nitrification. The nitrifying microbes 

 were isolated by the fractional dilution method. 



(1) Frankland' s researches. Dr. and Mrs. Frank- 

 land have isolated a nitrifying microbe from soil. 

 ' Nitrification having been in the first instance in- 

 duced in a particular ammoniacal solution by means 

 of a small quantity of garden soil, was carried on 

 through twenty-four generations, a minute quantity 

 on the point of a sterilised needle being introduced 

 from one nitrifying solution to the other. From 

 several of these generations gelatine-plates were 

 poured, and the resulting colonies inoculated into 

 identical ammoniacal solutions, to see if nitrification 

 would ensue ; but although these experiments were 

 repeated many times, on no occasion were they 

 successful.' In other words, the microbe in ques- 

 tion refused to grow on gelatine. The ammoniacal 

 solution, already referred to, contained : 1000 cc. 

 of distilled water, 100 cc. of salt solution, 5 0'5 



1 Comptes Rendus, vol. xlviii. p. 301 ; vol. Ixxxv. p. 1018 ; 

 vol. Ixxxix. pp. 891 and 1074. 



2 Philosophical Transactions, vol. clxxxi. pp. 107-128. 



3 Annales de FInstitut Pasteur, 1890, p. 213 seq. 



4 Journal of Chemical Society, 1891, pp. 484-529 ; Chemical 

 News, vol. Ixi. (1890), p. 135. 



5 This solution contained 1 gramme of potassium phosphate, 

 0*2 gramme of crystallised magnesium sulphate, and O'l gramme 

 of calcium chloride (fused) in 1000 cc. of water. 



