314 L. A. ROGERS 



of glucose, gives a positive Voges-Proskauer reaction, usually 

 fails to form iridol from tryptophane and ferments many car- 

 bohydrates and alcohols. The tendency to produce rapidly a 

 hydrogen ion concentration which will inhibit alkali formation 

 and consequently any subsequent reduction of the acidity has 

 been made use of by Clark (1915) to distinguish the B. coli 

 type from B. aerogenes by the methyl red test. 



The B. coli type is found abundantly in bovine feces while the 

 B. aerogenes type is very rare. In human feces the latter type 

 is more common, but apparently subject to considerable varia- 

 tion. These results agree with the conclusions of some of the 

 earlier workers, particularly Clemesha (1912) who states that 

 sucrose +, dulcite — , adonite — , inuUne — , V. and P. + organ- 

 isms are rare in feces (about 1 to 2 per cent). These characters 

 agree with those of the t3q)ical high ratio or B. aerogenes cul- 

 tures found in feces. 



The work in our laboratories on the colon-aerogenes bacteria 

 of human feces also shows a possible line of demarcation between 

 two varieties of the B. aerogenes type. All of the B. aerogenes 

 cultures isolated from human feces fermented adonite. Many 

 formed indol, GO per cent fermented starch and in other ways 

 showed a higher fermentative abihty than B. aerogenes cultures 

 from other sources. 



On the other hand the collection of cultures from grains, con- 

 sisting very largely of B. aerogenes cultures, contained very few 

 adonite fermenters. Those that did ferment adonite agreed 

 very closely with the adonite fermenters of feces while the non 

 fermenters were less active in the formation of indol and in the 

 fermentation of sucrose, raflBnose, starch, mannite and glycerine. 

 Disregarding, for the present, any question of the value of 

 the differences enumerated for purposes of classification we 

 believe that it is safe to use them as an indication of the original 

 source of the culture. 



It does not necessarily follow that the only source of B. coli 

 or the adonite fermenting B. aerogenes is the intestine of warm 

 blooded animals but the relative frequency with which they 

 occur there makes it highly probable that any culture with these 

 characters, wherever found, came originally from this habitat. 



