86 



TABLE XLIX. COLON GROUP PER 100 C. C. IN INDIANAPOLIS WATER SUPPLY 



(Calculated from report of H. E. Jordon 1920) 



Average for 3 years 1917-18-19. 



*Average for five years includes two yews before chlorination. 



f-In two years before chlorination ratio of basin to plant effluent was 13.7. 



In general the proportion of aerogenes (M. R. -V. P. +) strains 

 in the plant effluent was greatest in the warmer months. The relative in- 

 cidence of aerogenes and coli types in the tap samples is not stated but it 

 will be noticed from Table XLIX. that secondary multiplication was most 

 marked in July, August and September. The temperature of the water 

 at these times is quite likely to be very near the optimum for growth of 

 Bact. arogenes and closely allied bacilli. 



The foregoing observations are not sufficiently extensive to warrant 

 final conclusions. They nevertheless do indicate that under some con- 

 ditions there may be a secondary rise in the colon index of a filtered or 

 chlorinated water on storage, and that this is probably due to the growth 

 of the aerogenes section, for the increase is associated with those months 

 when the aerogenes types were relatively more numerous and when the 

 temperature of the water was near the optimum for growth of these forms. 



Are all Varieties and Species of the Aerogenes and Coli Sec- 

 tions of the Same Sanitary Significance? Although the aerogenes 

 group is rare in human feces, it is nevertheless present in small numbers, 

 and similarly Bact. coli, although comparatively infrequent, is occasionally 

 encountered in presumably non-polluted sources. It certainly would be a 

 great aid if some test could be devised which would distinguish the Bact. 

 aerogenes from human feces and those from soils and grains, or which 



