148 UNIVERSITY OF WISCONSIN STUDIES 



nitrites. The nitrates were unaffected. This, except for the 

 decrease in the nitrites, follows very closely what was found 

 under similar conditions for B. mesentericus var. ruber in 

 pure cultures. The cultures, however, showed a considerable 

 overgrowth of B. subtilis. 



B. subtilis and B. pyccyaneus. In both sets of flasks the 

 bacteria grew practically equally well. 



In the aerobic flasks the free ammonia and the organic 

 nitrogen were decreased, while the nitrites and nitrates w r ere 

 both increased. 



In the anaerobic flasks the free ammonia was increased 

 with a decrease in the organic nitrogen and nitrites. The ni- 

 trates were unaffected. 



B. cloacae and B. mesentericus var. ruber. B. mesenteri- 

 cus var. rubrr overgrew B. cloacae in both sets of flasks. 



In the aerobic flasks the chemical action was more irreg- 

 ular than was found for B. mesentericus var. ruber in pure 

 culture, but in general coincided very closely to it, The most 

 marked effect was on the nitrites and nitrates. The nitrates 

 were decreased with an increase in the nitrites. 



In the anaerobic flasks the action was much more typical 

 of B. mesentericus var. ruber, the free ammonia being in- 

 creased with a decrease in the organic nitrogen. The nitrates 

 were decreased and the nitrites were increased. 



B. cloacae and B. proteus. The action of these bacteria 

 was very irregular and typical of neither. This was true for 

 both the anaerobic and aerobic flasks. 



The nitrites were generally increased. In one experiment 

 all of the nitrogen was reduced in amount. 



B. proteus and B. mesentericus var. ruber. In the 

 anaerobic flasks the tendency was to decrease both the free 

 ammonia and the organic nitrogen, while the nitrites and 

 nitrates were increased. These results follow those obtained 

 from B. proteus more closely than B. mesentericus var. ruber. 



The cultures showed a slight overgrowth of B. proteus in 

 the anaerobic flasks. 



B. pyocyaneus, B. proteus, B. pyocyaneus and B. mesen- 

 tericus var. ruber. Neither of these gave results in either 

 set of flasks. 



