Other Intestinal Bacteria. 159 



indicate contamination with old sewage which is not 

 necessarily dangerous. These discordant results are prob- 

 ably to be explained by the different media in which 

 the viability of the bacteria was compared. It seems 

 likely that in sewage where there is a large amount of 

 organic food material present the streptococci may kill 

 out the colon bacilli as they do in the fermentation tube. 

 This would explain Horrocks' results. On the other 

 hand, there is good evidence that the streptococci are less 

 resistant than B. coli to the unfavorable conditions which 

 exist in water of ordinary organic purity. In waters of 

 potable character B. coli is frequently present without the 

 streptococcus; and a negative test for streptococci has 

 little significance. A positive test on the other hand fur- 

 nishes valuable confirmatory evidence of pollution. This 

 evidence is of course of special importance when, through 

 the activity of the streptococci themselves, or from any 

 other cause, the colon isolation has yielded an erroneous 

 negative result. 



The English Committee appointed to consider the 

 standardization of methods for the bacterioscopic exami- 

 nation of water (1904), by a majority vote recommended 

 the enumeration of streptococci as a routine procedure in 

 sanitary water analysis, and the test deserves more careful 

 attention than it has yet received in America. 



There seems even reason to hope that the streptococci 

 may prove of assistance in the important task of differ- 

 entiating human and animal pollution, a task in which 



