138 ELEMENTS OF WATER BACTERIOLOGY 



is somewhat ambiguous. In order to clear up the 

 subject, the Laboratory Section of the American PubHc 

 Health Association, at its Washington meeting, in 

 September, 191 2, adopted a resolution recommending 

 determinations of counts at 20 degrees and 37 degrees, 

 and the lactose bile presumptive test as the standard 

 routine procedure in water examinations. 



Recent Criticisms of Lactose Bile Test. During the 

 last two years a nimiber of workers have found that 

 the presence of anaerobic bacilH of the B. sporogenes 

 type, giving a misleading positive result in the lactose 

 bile tube, may be a seriously confusing factor in inter- 

 preting the results of examinations of certain waters. 



Mr. George W. Fuller has recently pointed out that 

 at certain points on the Ohio and Mississippi Rivers 

 the presumptive test yields results apparently far too 

 high to be explained by ordinary pollution, and much 

 higher than the results of a complete isolation test as 

 shown at the same localities. 



Phelps and his associates in the study of the 

 Potomac have observed that in waters showing recent 

 pollution in large amount, the presumptive tests in 

 both lactose bile and lactose broth were efficient and 

 rehable. As the pollution becomes less evident, that 

 is, as purification proceeds, however, these media 

 give increasingly unreliable results. A study of a 

 large number of samples in which confirmatory tests 

 were made showed that as the purification increased, 

 the organisms appearing as fermentation exciters in 

 the presumptive tests were more and more frequently 

 not of the colon type, but instead proved to be organisms 



