36 
TABLE IV.—Nitrification by Soil Bacteria 
Tim 
in 
Weeks 
Ammonia Medium 
Nitrite Medium 
Soil A 
Soil B 
Control 
Soil A 
Soil B 
Control 
NHs 
NzOs 
N2O5 
NHs 
N2O3 
N2O5 
NHs 
N2O3 
N2O5 
N2O3 
N2O5 
n 2 o 3 
N2O5 
N2O3 
N2O5 
1 
* 
2 
3 
1 
4 
5 
6 
1 
(J) How do these organims differ from those already studied, viz: 
those that grew on the soil, dust and milk plates, in regard 
to the nature of their food supply? 
(k) In what part of a farm sewage disposal system consisting of a 
septic tank and drains, do these organisms function? 
(/) In large municipal sewage disposal plants, how are these or¬ 
ganisms helped in their work by special mechanical devices? 
