SIGNIFICANCE OF COLON GROUP IN WATER 157 



in unpolluted waters, and colon bacilli are very rarely 

 present. In 157 samples, typical colon bacilli were 

 found only 5 times out of 157, in i c.c. Lactose ferment- 

 ing organisms appeared in only 8 per cent of the nor- 

 mal samples and in 100 per cent of the polluted ones, 

 in i c.c. Incidentally it may be pointed out that these 

 tables well illustrated the dangers of overgrowths, 

 particularly in large samples. It is clear that the strep- 

 tococci had killed out colon bacilli, originally present, 

 in a large proportion of the loo-c.c. samples of polluted 

 waters and in some of the i-c.c. samples, since, in so 

 many cases, gas formation was followed by the isola- 

 tion of the streptococcus alone. 



Colon Bacilli in Surface Waters. Clark and Gage 

 (1903) have published the results of certain studies of 



DISTRIBUTION OF TOTAL BACTERIA 

 SURFACE-WATERS 



(CLARK AND GAGE. 1903) 



AND B. COLI IN 



* Shores used for pleasure resorts. 



