83 



Similarly, Bowles, working with waters in the Panama Canal Zone, 

 where the conditions simulate those of the tropics, notes that the aerogenes 

 types are extremely prevalent long after the Bact. coli forms have died off. 

 The supplies in the canal zone consist of impounded reservoirs and are 

 treated with sulphate, filtered, and in some instances chlorinated after fil- 

 tration. The reservoirs are policed and adequately protected against pol- 

 luion. In the Chagres River during the rainy weather Bact. coli was pres- 

 ent in 1 c. c. but during the dry season Bact. coli was found only in 50 c. c. 

 samples while Bact. aerogenes, he says, was present in large numbers. Dur- 

 ing the dry season, the reservoirs, acting as sedimentation basins, effect con- 

 siderable (wonderful) purification. He states that many examinations may 

 be made this time of year without getting any test for Bact. coli, but that 

 Bact. aerogenes is present. 



There is no question, therefore, as to the relative viability of Bact. 

 coli and Bact. aerogenes (and Bact. cloacae) in water. The latter is much 

 more resistant, will persist for considerably greater periods, so that when 

 present alone (that is, not accompanied by Bact. coli) in natural waters, 

 it may merely indicate pollution or contamination so remote that the Bact. 

 coli, and consequently the dangerous intestinal disease producing forms, 

 have died off. In fact, Clemesha maintains that the presence of Bact. aero- 

 genes is a favorable indication that self-purification is rapidly taking place. 



Relative Resistance of Coli and Aerogenes Types to Chlorina- 

 tion and Filtration. Greenfield and Skorup state that there is no differ- 

 ence in the resistance of these two forms to treatment. 



Ellms in experimental studies with the Milwaukee water supply found 

 the aerogenes type less resistant particularly to chlorination, but that on sub- 

 sequent storage these forms became the predominating colon type. 



TABLE XLVI. RELATIVE INCIDENCE OF COLI AND AEROGENES SECTIONS 



IN RAW AND TREATED WATER SUPPLY OF MILWAUKEE. 



(After Ellms 1920) 



Levine recorded the following experiences with the water supply of 

 Dijon, France. The raw water examined daily for six months yielded 96 

 positive results for members of the colon group with Bact. aerogenes pres- 

 ent in 16.6 percent of these. The tap samples during the same period (the 

 water was treated with .07 to 0.1 part per million of chlorine, then stored 

 in distribution reservoirs) showed only three positively confirmed tests, 

 but Bact. aerogenes was present in each instance or 100 percent of the posi- 

 tively confirmed gas tubes. 



