156 ELEMENTS OF WATEE 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 



(WlNSLOW AND HUNNEWELL, IQO2 b ) 



Unpolluted Waters 



Samples examined 157 



Dextrose broth positive 40 



Lactose plate positive 13 



Colon group 5 



Paracolon group 5 



B. cloacae group 



Streptococcus group 3 



Polluted Waters 



I C.C. 



Samples examined 50 



Dextrose broth positive 50 



Lactose plate positive 50 



Colon group 18 



Paracolon group 6 



B. cloacae i 



Streptococcus group 25 



76 



3i 

 ii 



5 



5 



10 



48 



37 

 26 



As the authors pointed out, these tables indicate that 

 bacteria capable of growth at the body temperature and 

 fermenting dextrose and lactose are infrequently found 



