ELIMINATION OF SPUEIOUS TESTS FOR B. COLI 



351 



Because of our skepticism as to the importance of the quantity 

 of gas in the presumptive test, complete records were not kept. 

 Since the appearance of the new standard methods, however, we 

 have made numerous observations which need not be tabulated 

 to show that the amount of gas appearing in the presumptive 



TABLE 6 

 First appearance of gas in presumptive tests from which B. coli was isolated. 



TABLE 7 

 First appearance of gas in presiwiptive tests from lohich B. coli was not isolated 



test is of little importance. B. coli may frequently be isolated 

 from tubes showing only a trace of gas or tubes full of gas may 

 be due to sporulating aerobes or anaerobes only. 



SUMMARY 



This report deals with the question of the true interpretation 

 to be placed upon the presumptive test for B. coli as a criterion 

 of polluted water. It is pointed out that spurious tests are 



