SIGNIFICANCE OF COLON GEOUP 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 BACTERL\ AND B. COLI IN 

 SURFACE-WATERS 



* Shores used for pleasure resorts. 



