148 



Elements of Water Bacteriology. 



showed gas in 24 hours, 73 per cent after 48 hours, 

 and the remaining 27 per cent only after 72 hours, so 

 that the 72-hour period is frequently necessary. Sawin 

 (1907) reports comparative results with dextrose broth 

 and bile on different classes of waters, the most striking 



COMPARATIVE PRESUMPTIVE TESTS WITH DEXTROSE 

 BROTH AND LACTOSE BILE. 

 (SAWIN, 1907.) 



