THE COLON GROUP 153 



media within twenty-four hours, a well-isolated characteristic colony shall be 

 fished and transplanted into a lactose-broth fermentation tube, which shall be 

 incubated at 37C. for forty-eight hours. 



For the purpose of enforcing any regulations which may be based upon these 

 recommendations the following may be considered sufficient evidence of the presence 

 of organisms of the Bacillus coli group. 



F*V^. Formation of gas in fermentation tube containing original sample of water. 



Second. Development of acid-forming colonies on lactose litmus agar plates or 

 bright red colonies on Endo's medium plates, when plates are prepared as directed 

 above under (6). 



Third. The formation of gas, occupying 10% or more of closed arm of the 

 fermentation tube, in lactose peptone broth fermentation tube, inoculated with 

 colony fished from twenty-four-hour lactose litmus agar or Endo's medium plate. 



These steps are selected with reference to demonstrating the presence in the sample 

 examined of aerobic lactose-fermentating organisms. 



3. It is recommended, as a routine procedure, that in addition to 

 five 10 c.c. portions, one i c.c. portion, and one o.i c.c. portion of each 

 sample examined be planted in a lactose peptone broth fermentation 

 tube, in order to demonstrate more fully the extent of pollution in 

 grossly polluted samples. 



The members of the B. coli group are separated by the American 

 Public Health Association according to fermentation activities as 



follows : 



B. Coli Group. 

 Dextrose + 

 Lactose + 



Dulcite + Dulcite 



B. communior B. aerogenes 



B. communis B. acidi-lacti 



i i 



Saccharose + Saccharose - Saccharose + Saccharose - 



B. communior B. communis B. aerogenes B. acidi-lactici. 



Further divisions are made by the use of mannite and raffinose, giving varieties of 

 the above four species. 



Dulcite, like mannite, is a hexatomic alcohol. It is isomeric with mannite and is 

 present in Madagascar manna. 



Raffinose is a trisaccharide; maltose, lactose and saccharose are disaccharides, while 

 dextrose and l<evulose (hexoses) arabinose and xylose (pentoses) are monosaccharides. 



The diagnostic characteristics considered important by the Ameri- 

 can authorities in reporting the colon bacillus (recently designated 

 excretal colon bacillus) are: 



