336 ANNUAL, REPORT OF THE Off. Doc. 



the experimental fields of Rotliamsted contained more nitrates as the 

 amount of ammonium salts applied to the soil increased. 



In 1878 Messrs. Schlosing and Miintz^'' laid before the French 

 Academy the results of an experiment tending to prove that nitrilica- 

 tion was due to the action of an organized ferment. A glass tube 

 one meter long was filled with ignited quartz sand and powdered 

 limestone. Through this sewage was passed at intervals. During 

 the first twenty days the sewage which passed the filter remained 

 unaltered, after which nitric acid began to appear until the filtrate 

 no longer contained any ammonium salt, but only nitrates. Thus it 

 was shown that active nitrification was going on within the body 

 of the filter, and it was suspected that micro-organisms so abund- 

 antly present in the same were the active agents of the change. 



To demonstrate this point, chloroform vapor, a well-known germi- 

 cide, was passed through the filter; as a result it was found that ten 

 days after the introduction of the vapor all nitrates had disappeared, 

 and the sewage passed through unchanged. In other words, the 

 chloroform vapor had so paralyzed the micro-organisms present as 

 to completely check the process of nitrification. 



Messrs, Schlosing and' Miintz were, however, unable to isolate any 

 specific ferment capable of inducing nitrification, and nothing was 

 accomplished toward this end until the year 1886. Celli-Zucco^^ and 

 Heraeus^^ at this time succeeded in isolating from water rich in 

 nitrates a number of forms of bacteria, which, however, only pos- 

 sessed very feeble nitrifying properties. 



Frank-^ simultaneously with the latter attempted a similar isola- 

 tion of the nitrifying organism, but without result, and concluded 

 that nitrification was not due to the direct action of bacteria, but 

 that it was a purely chemical process. This view was opposed by a 

 number of writers, notably, Landolt, Piatt and Baumann.^^ 



In 1888-89 Warrington^*^ and also Frankland^^ studied a large num- 

 ber of soil bacteria, but neither was able to find one which produced 

 any thing approaching active nitrification. Frankland maintained, 

 however, that the nitrifying organism was present, but had not been 

 isolated. 



In 1890 Frankland^^ succeeded in cultivating a spherical (coccoid) 

 organism about 0.8 micromillimeters in diameter, which possessed 

 the power of converting ammonium salts into nitrous, but not into 

 nitric acid. The separation was by means of the dilution method 

 in media containing only inorganic salts. In this the form in ques- 

 tion grew most successfully. 



This fact, and other points in the investigation of Frankland, at 

 once revealed the important principle that the organism of nitrifica- 

 tion does not grow normally in media rich in organic matter, and 

 that, therefore, the ordinary method of separation by means of 



