156 ELEMENTS OF WATER BACTERIOLOGY 



the city of Boston. For comparison 50 samples of 

 polluted waters from the Charles, Mystic, Neponset, 

 and North Rivers were examined. The colon bacillus 

 was defined by gas production in dextrose broth, 

 coagulation of milk, reduction of nitrates, formation 

 of indol and failure to liquefy gelatin; and organisms 

 which lacked the power to reduce nitrates or to form 

 indol were classed in the " Paracolon group." The 

 results are summarized in the following table: 



PRESENCE OF B. COLI IN POLLUTED AND UNPOLLUTED 

 WATERS 



(WiNSLOW AND HUNNEWELL, IQOa'^) 



Unpolluted Waters 



Samples examined 



Dextrose broth positive 



Lactose plate positive 



Colon group , . . . 



Paracolon group 



B. cloacffi group 



Streptococcus group 



Polluted Waters 



Samples examined 



Dextrose broth positive 



Lactose plate positive 



Colon group 



Paracolon group 



B. cloacae 



Streptococcus group 



153 

 76 



31 

 II 



S 



S 



10 



48 



37 

 26 



4 



As the authors pointed out, these tables indicate that 

 bacteria capable of growth at the body temperature and 

 fermenting dextrose and lactose arc infrequently found 



