66 MARGARET C. PERRY AND W. F. MONFORT 



United States Treasury Department (1914) standard if more 

 than two organisms were fomid in 100 cc; of these 29, 3 are 

 sporebearers, 1 is typical Bad. aerogenes not necessarily of fecal 

 origin (Rogers 1918), 9 are anomalous with respect to those 

 reactions accepted as indicative of high and low gas ratio; 16 are 

 within the class of low ratio organisms on the basis of the methyl 

 red and Voges-Proskauer reactions, and of these but 3 uric acid 

 negative strains conform to recognized types. 



An organism which requires prolonged invigoration to be 

 restored to, or to acquire, conventional reactions with sugar 

 broths and other media is far removed from the organism typical 

 of fecal pollution. Considering the opportunity thus afforded 

 for change in the original characters, a conclusion as to what 

 must be regarded as essential indicators of pollution must take 

 into account the undoubtedly wide variation of bacilli of the 

 general colon-aerogenes group occurring in waters. Invigora- 

 tion might lead an organism, long away from, or originating 

 quite outside, the alimentary tract, to acquire the characters of 

 typical fecal inhabitants. While it is important to ascertain the 

 ultimate genetic relation between members of the group, it is one 

 thing to say that these forms are of common, remote origin, and 

 a very different one to say that the existent, feebly reacting, yet 

 convertible forms are identical - with, and of equal diagnostic 

 importance with, organisms freshly isolated from feces under 

 laboratory conditions: that is, to attribute to them as originally 

 present in a water supply all the newly acquired characters. 

 The uric acid reaction, however, admits of repetition without 

 change so far as we have found with the limited number of strains 

 isolated. 



It is important that the laboratory procedure be as quickly 

 completed as is reasonably possible, and that characters be 

 neither lost nor acquired. Water seriously polluted shows gas 

 production within much less than 24 hours. The readiness of 

 strains to react is perhaps of greater diagnostic significance than 

 the appearance of gas at twenty-four hours and at forty-eight 

 hours as now observed. Levine (1920) considers the rate of 

 gas production more significant than the total volume of gas 

 formed. Burton suggested shortening preliminary enrichment 



