85 



teresting and significant to know whether its increased prevalence in stored 

 chlorinated water reported by Hinman, Ellms, H. E. Jordan, and the writer 

 is due to such a secondary multiplication or merely to survival over the 

 less viable Bact. coli. 



That under certain conditions the Bact. aerogenes may multiply and 

 survive for an incredibly long time in water is shown by the following 

 experiment of Wood. He inoculated a hard water, which had been pre- 

 viously boiled and which contained no measurable trace of saline or or- 

 ganic ammonia, with Bact. coli and Bact. aerogenes and determined their 

 incidence and relative viability. The results are indicated in Table XLVII. 



The Bact. coli disappeared quite rapidly; an initial count of 1,250 

 per c. c. decreasing to less than 1 in 100 c. c. after five weeks' storage. With 

 the aerogenes strains, however, there was an increase from 580 to 2,800 

 per c. c. after 33 weeks' storage and the organism was still present in one 

 experiment after 3% years. 



Ellms in his studies on the Milwaukee supply detected colon forms 

 in the chlorinated stored water (basin samples) on only five of the ex- 

 perimental runs but in three of these the colon index (see table XLVIII) was 

 considerably higher than in the chlorinated filter effluents. 



TABLE XLVIII. COLON INDEX IN CHLORINATED FILTERED AND STORED 



WATER. 



(Calculated from report of Ellms 1920) 



* Chlorinated filter effluents. 



Taking into consideration that the filter effluents showed only 26-29 

 percent V. P. positive strains as compared with 70 percent after storage in 

 the basin, the writer feels that the rise of the colon index in the latter was 

 most likely due to multiplication of the aerogenes and cloacae forms. 



That the colon index may increase on storage of a filtered chlorinated 

 water may be shown quite strikingly from the report of the Indianapolis 

 Water Company. 



The incidence of colon bacilli in tap samples was at times 11 to 13 

 times as great as in the water works plant effluent. 



