214 ELEMENTS OF WATER BACTERIOLOGY 



animal more than of vegetable decompositions, and the 

 total anaerobic count apparently adds nothing of impor- 

 tance to the information gained by the ordinary gelatin 

 plate method. The property of liquefaction was for- 

 merly believed to be of significance, inasmuch as the 

 liquefying bacteria were regarded as indicative of pollu- 

 tion. This position is, however, no longer tenable, 

 since many bacteria, typical of the purest waters, may 

 cause liquefaction. 



As Savage says in summing up this question: " The 

 number of different species of organisms in sewage 

 is very great, and it is highly probable that many of 

 them occur in all specimens of ordinary sewage; but, 

 except for B. coli, streptococci, and B. enteritidis sporo- 

 genes, their presence has not been ascertained with 

 sufficient constancy, nor has their numerical occurrence 

 been sufficiently investigated to make them of value 

 as indicators of sewage pollution." (Savage, 1906.) 



