TYPES OF COLON-AEROGENES GROUP IN WATER 317 



lated B. coli cultures. In the B. coli cultures isolated after 

 they had been exposed for a long time to the unfavorable con- 

 ditions of the water there was some evidence of lowered vitality, 

 in the large numbers of cultures which carried the hydrogen ion 

 concentration^ to 5, 5.2 or 5.4. What may possibly be another 

 evidence of attenuation is seen in the number of B. coli cultures 

 which fail to form indol among those isolated after prolonged 

 exposure to the water. 



Many water bacteriologists consider weak gas formation an 

 indication of "attenuation" and therefore evidence of a remote 

 contamination. 



This view is supported by some observations on six cultures of 

 the B. aerogenes type isolated from this bottle of water. Three 

 of these cultures were isolated when the sample was 47 days 

 old and three at 278 days. All of these cultures gave a normal 

 fermentation in glucose. The three cultures isolated at 47 

 days produced from 10 cc. of lactose broth approximately 2.7 cc. 

 of gas consisting of carbon dioxide and hydrogen in the ratio of 

 1.53, 1.54 and 1.48 respectively. This is the normal fermenta- 

 tion for the B. aerogenes type. The three cultures isolated at 

 278 days gave, under similar conditions, 3.77, 3.78 and 3.77 cc. 

 of gas with a ratio of 0.59, 0.56 and 0.51 respectively. These 

 cultures were of course, not identical with those isolated at the 

 earlier date and the evidence of "attenuation" is thus purely 

 circiunstantial. 



However all of these observations considered together point 

 to a slow change, which may be described as a loss of function, 

 in colon cultures held for a long time in water. This change was 

 perceptible only after the culture had been in water for many 

 weeks. 



These results may seem at variance with conclusion reached 

 by Browne who studied changes in bottled water under similar 

 conditions. The conflict is probably only apparent. 



Browne's sample was held only 73 days and in that period 

 there was little evidence of change in our sample. Moreover 



2 It should be remembered that the numbers on Sorensen's scale run inversely 

 as the hydrogen ion concentration. 



