89 



the soil, horse, sheep or cow. but it made up 3.2 percent of the pig, 30.8 

 percent of the sewage, and 20 percent of the human strains. 



TABLE LI. FERMENTATION OF SUCROSE BY BACT.-COLI-L1KE BACTERIA 



FROM HUMAN FECES. 



Bact. acidi-lactici was not obtained from the horse nor sheep, and only 

 rarely from the cow (5.0%) or soil (4.0%). The motile variety Bact. 

 acidi-lactici var. Grunthali was particularly abundant among the pig cul- 

 tures (29%) and rare in sewage (5.1%) and man (4%). The non-motile 

 Bact. acidi-lactici var. immobili was restricted to man and sewage entirely, 

 comprising 44 percent of the human and 17.9 percent of the sewage strains. 



If the sucrose negative forms are more indicative of human pollution 

 it would be anticipated that they would be more prevalent in the more in- 

 tensely polluted waters. Observations by the writer on 78 samples col- 

 lected in France were as follows: 



Among 34 samples in which the coli section was present in 1 c. c. 

 or smaller quantities, sucrose negative strains were detected in 23 or (68%), 

 whereas of 44 samples containing the coli section only in 10 c. c. or larger 

 quantities but 13 (29%) showed sucrose negative coli strains. That is, 

 the more polluted supplies apparently did contain a greater proportion 

 of sucrose non-fermenters. More extensive work on the correlation of 

 species of colon bacilli with the source, character of pollution, and history 

 of waters is certainly desirable. 



Resume. From considerations of the requirements for an index of 

 pollution, the colon group appears to be a convenient and desirable one. 

 It is not however, an ideal indicator for the species which it comprises are 

 not all of equal sanitary significance. 



The evidence seems to be clear and definite that the colon group com- 

 prises two subgroups or sections which are characteristically of different 

 habitat; one, typified by Bact. coli, is present in large numbers in feces 

 and sewage, whereas the other, exemplified by Bact. aerogenes, is rare in 



