81 



tion all but one of these organisms proved to be of the aerogenes section 

 (V.-P. positive, methyl red negative). As these wells were several miles 

 apart the simultaneous appearance of these organisms is difficult to explain. 

 Wood mentions that the time of year rather suggests some connection with 

 the sowing of grain. 



It is felt that the relation of the sanitary survey to the type of colon 

 bacilli present in the water, particularly well supplies, is in need of con- 

 siderable investigation. The lack of correlation in the vicinity of the 

 New Haven, reported by Winslow and Cohen, is difficult to reconcile with 

 the observations of Stokes in Maryland and Wood in England. Possibly 

 local conditions, if taken into proper consideration, may explain the seem- 

 ing discrepancies. 



On the Relative Viability of Bact. coli and Bact. aerogenes in 

 Water. Emulsions of feces were stored in water in bottles or suspended 

 in parchment sacks in running streams by Rogers. He reported that the 

 Bact. coli died off much more rapidly than the Bact. aerogenes. In water 

 kept in a bottle at 20 C., preliminary examination showed only Bact. coli 

 but after 3 days storage the ratio of Bact. aerogenes to Bact. coli was 1 

 to 6. This ratio gradually increased until after 278 days storage the Bact. 

 aerogenes was 39 times as prevalent as Bact. coli. This was of course a 

 prolonged period of storage but it indicates, nevertheless, that the aero- 

 genes group is more resistent and will persist for a much longer period 

 in water than will the coli group. 



In running water the change in the ratio of Bact. aerogenes and Bact. 

 coli was much more rapid. Thus beginning with a fecal emulsion in parch- 

 ment sacks suspended in running water, an initial ratio of 1 Bact. aerogenes 

 to 2.3 Bact. coli was found after 7 days to contain 10 times as many Bact. 

 aerogenes as Bact. coli. The Bact. aerogenes were proportionately more 

 than 20 times as prevalent in a fecal suspension stored in running water for 

 a week. The death rate of Bact. coli (K=0.48) was about twice that of 

 Eact. aerogenes (K=0.93). 



TABLE XLIV. CHANGES IN COLON BACTERIA IN RUNNING WATER. 



(After Rogers 1918) 



Winslow and Cohen report similar, though not such striking results, 

 when storing mixtures of these organisms in bottles. They observed a 



