TYPES OF COLON-AEROGENES GROUP IN WATER 



321 



cultures isolated were of the B. coli type. From a sample taken 

 immediately above the mouth of the Kensington sewer, 3 B. coli 

 and 13 B. aerogenes cultures, only 2 of which fermented adonite 

 were isolated. A few yards below over half of the cultures 

 isolated were of the B. coli type. Of the 13 B. aerogenes cultures 

 isolated, 7 fermented adonite which we may assume indicated 

 fecal origin. The fermentation tubes made in the usual way 

 and incubated at 37° did not show a greater number of lactose 

 fermenters immediately below the Kensington sewer than just 



TABLE 4 



Relative numbers of B. aerogenes and B. coli in Rock Creek 



above it; that is there was gas in 0.01 cc. dilution but none in 

 the 0.001 cc. dilution in each case. Accurate counts could not 

 be made from the plates but they indicated a great increase at 

 this point. ij 



Samples taken at lower points on Rock Creek showed a slight 

 increase in the proportion of B. aerogenes but below the mouth 

 of Broad Branch and Piney Branch bacteriological conditions 

 as shown by these tests were nearly as bad as just below the 

 Kensington sewer. This is probably due to a badly polluted 

 condition in Piney Branch. 



