TYPES OF COLON-AEROGENES GROUP IN WATER 315 



The value from a sanitary standpoint of an ability to distin- 

 guish between different types of colon bacilli rests on the answer 

 which we can give to certain questions. First we are concerned 

 with possibilities of any type of colon bacillus existing normally 

 outside of the digestive tract of animals. If a colon culture of 

 any kind is isolated from water does it necessarily indicate 

 fecal contamination or must we distinguish between those of 

 fecal and those of nonfecal origin? 



Secondly what is the fate of the fecal colon bacillus in water? 

 Does it multiply or decrease rapidly? Does the typical fecal 

 colon bacillus become attenuated so that its characters change 

 and it can no longer be recognized? 



The first question is partially answered by the results of our 

 comparison of the characters of fecal colon with those from 

 other sources, particularly from grains. The marked variation 

 of the grain cultures from the fecal types indicates that water 

 may receive bacteria of the colon-aerogenes group from other 

 than fecal sources. 



Some light has been thrown on the second problem by the 

 observations of Clemesha (1912). He found that the different 

 types of colon did not decrease in water at an equal rate and that 

 in some cases there was an actual increase. 



The characters used by Clemesha differ somewhat from those 

 which we have used and only rough comparisons can be made. 

 We have studied this problem by observations on water held in 

 bottles, and on cultures in parchment sacs in running water^ 

 by watching the progressive changes in streams and by exami- 

 nation of individual samples from various sources. 



While it is realized that the results are not sufficiently com- 

 prehensive to permit any positive conclusions it is hoped that 

 they may present something of value. 



CHANGES IN SAMPLES HELD IN BOTTLES 



In considering bacterial changes in water samples held in 

 bottles, one should remember that the conditions are not neces- 

 sarily comparable with those obtained in streams or reservoirs. 



