Other Intestinal Bacteria. 169 



brown wrinkled parchment-like growth on agar, and 

 moss-like liquefying colonies on gelatin, is usually repre- 

 sented; but this form is more characteristic of decaying 

 vegetation in the surface layers of the soil than it is of 

 sewage. Vincent (1907) and other French observers 

 consider the determination of the total number of anaerobic 

 bacteria as significant siace the decomposition of organic 

 matter is accompanied by anaerobic growth. It is not 

 claimed, however, that bacteria of this type are character- 

 istic of animal more than of vegetable decompositions, and 

 the total anaerobic count apparently adds nothing of im- 

 portance to the information gained by the ordinary gelatin 

 plate method. The property of liquefaction was formerly 

 believed to be of significance, inasmuch as the liquefying 

 bacteria were regarded as indicative of pollution. 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, streptocci, and B, enteritidis sporogenes, their presence 

 has not been ascertained with sufi&cient constancy, nor has 

 their numerical occurrence been sufficiently investigated 

 to make them of value as indicators of sewage pollution." 

 (Savage, 1906.) 



