ON NITRIFICATION 483 



constitutes a source that for convenience shall be here named 

 III. It is then, possible that, like all other organisms, the 

 Nitrosococcus undergoes processes of anabolism and catabolism, 

 in the latter probably giving off carbon dioxide by respiration: 

 this source shall be here named IV. 



1. MgCOs + (NH4)2 SO4 ^ MgS04 + (NH4)2 CO3 .*. NH3 + 

 H2CO3 + H2O + CO2 



II. MgC03 + 2HNO2 -^ Mg (N0o)2 + H2CO3 .-. 

 H2O + CO2 



Duclaux (1896) expressed the opinion, based upon the results 

 of the work of Winogradsky and of Godlewsky, that if the organ- 

 isms were not capable of utilizing the carbon of the carbonate 

 this could be due to the fact that some difference might exist 

 between the carbon dioxide of the atmosphere and that arising 

 from equations I and II above. One point should nevertheless 

 be mentioned as a criticism of this view i. e., that by allowing the 

 carbon dioxide absorbant to be continually present in the system 

 (as was done by Godlewsky and in the above experiments dupli- 

 cating his work) , the action of the bacteria will be dependent not 

 on the quality of the gas but on the velocity of distillation of the 

 latter from solution. With very large surfaces of the culture 

 solutions and relatively large surfaces of the absorbent, the 

 CO2 tension in the gaseous phase of the system will be so slight 

 that the organisms will not be in position to utilize the very 

 slight traces temporarily to be found in the solution, before they 

 are removed from contact with them. 



The question therefore becomes a twofold one: the organism 

 of nitrosofermentation apparently cannot develop in the absence 

 of all traces of gaseous carbon dioxide, yet is able to develop in 

 media free of all traces of fixed organic carbon as was shown by 

 Winogradsky (unless the traces carried in the inoculum may be 

 considered as sufficient to vitiate the results, a conclusion hardly 

 justified in view of the care with which the author. attempted to 

 avoid this a priori objection). 



