CHARACTERISTICS OF THE COLON-AEROGENES GROUP 101 



evidence supporting or controverting this theory. If the 

 loss of ability to ferment adonitol is effected only after many 

 generations under the new conditions, it is only another way 

 of saying that a variety has been created by a change of en- 

 vironment. If the change takes place in the original cells, 

 it may be considered as an indication of the remoteness of the 

 contamination. 



While none of the liquefying cultures in this collection 

 were isolated from feces there is no doubt that they occur 

 there under certain circumstances. Ford :!0 reports the oc- 

 currence of B. cloacae in feces. Clemesha 31 says that B. clo- 

 acae may be present in human feces in numbers as high as 

 15 or 20 per cent of the total. MacConkey" 2 found occasional 

 gas forming liquefiers in feces. On the other hand, nearly 

 one half of the coli-like organisms isolated from soil by John- 

 son and Levine 33 were liquefiers. Unless we assume that the 

 liquefiers of this group are more resistant to unfavorable con- 

 ditions than the other types and therefore persist longer in 

 water and in the soil it is evident that the principal source 

 of B. cloacae and B. protfus is outside of the intestinal tract. 



CONCLUSIONS 



It may be considered as established by thQ results j] 

 here, supported as they are by the observations of many 

 other investigators, that B. coli (low ratio) and B. aeroyenes 

 (high ratio) are very distinct types. This is based on: (1) 

 a fundamental difference in the course of the fermentation. 

 Carbohydrates arc fermented more readily by B. aeroyencs 

 and B. cloacae with a secondary rapid fermentation of the 

 by-product, resulting in a greater production of CO 2 and a 

 decrease in acidity. The fermentation brought about by 



W. W. Ford, Classification of Intestinal Bacteria in Jour. Med. Res., 

 6, 1, pp. 211-219, 1901. 



;tl W. \V. Clemesha, The Bacteriology of Surface Waters in the Tropics, 

 London, 1912. 



;12 Alfred MacConkey, Further Observations on the Differentiation of Lac- 

 tose-fermenting Bacilli with Special Reference to those of Intestinal Origin 

 in Jour. Hyg., 9, 1, pp. 86-103, 1909. 



38 Loc. cit. 



