222 BACTEEIOLOGICAL AND ENZYME CHEMISTRY 



The author has confirmed these observations in experi- 

 ments made for the purpose of tracing the changes taking place 

 when sewage sludge is discharged into sea water ; he found, 

 not only that the ultimate product of oxidation of nitrogen 

 was nitrite rather than nitrate, but also that the actual oxida- 

 tion of ammonia took place more slowly in sea water than 

 in fresh water. 



He has also noticed the same phenomenon of the pro- 

 duction of nitrite, rather than of nitrate, in a case where 

 sewage effluent was being discharged into a stream containing 

 large quantities of calcium chloride from an ammonia soda 

 works. 



So far we have considered, primarily, the oxidation of 

 solutions containing ammonium salts, with no admixture of 

 organic matter, and with more or less pure cultivations of the 

 nitrous and nitric organisms. In nature, however, such 

 conditions of course do not obtain ; we have there to do with 

 organic matter in different stages of decomposition, and with 



