OTHER INTESTINAL BACTERIA 213 



only 3-5 hours old as only young vegetative cells will 

 grow on plates. Transplants from the closed arm of 

 such tubes will grow on dextrose liver agar plates incu- 

 bated under anaerobic conditions. 



The organisms of the B. sporogenes group are large 

 stout bacilli often occurring in chains. They liquefy 

 gelatin vigorously and on agar produce fine discrete 

 gray colonies. They vigorously ferment dextrose, lac- 

 tose and saccharose, producing acid and gas, and in sugar 

 agar each colony will be marked by one or more gas 

 bubbles surrounded by a delicate whitish fringe. The 

 organism is strongly pathogenic for guinea pigs, by 

 which character it is distinguished from the B. butyricus 

 of Botkin. B. welchii differs from B. sporogenes chiefly 

 in lacking motility and in forming spores with less read- 

 iness (Klotz and Holman, 1911). 



The researches of Klein and Houston (Klein and 

 Houston, 1898, 1899) have shown that the B. sporogenes 

 occurs in English sewage in numbers varying from 30 to 

 2 200 per c.c. and that it is often absent in considerable 

 volumes of pure water. In Boston sewage it may 

 usually be isolated from .01 or .001 of a c.c. (Winslow 

 and Belcher, 1904). Since the spores of an anaerobic 

 bacillus may persist for an indefinite period in polluted 

 waters, their presence need not necessarily indicate 

 recent or dangerous pollution. 



Vincent (1907) and other French observers consider the 

 determination of the total number of anaerobic bacteria 

 as significant, since the decomposition of organic matter 

 is accompanied by anaerobic growth. It is not claimed, 

 however, that bacteria of this type are characteristic of 



