From recent work on the coli-like bacteria it is agreed that they may be divided into two subgroups which are differentiated by the Voges-Proskauer or methyl red reactions. These two groups are quite well correlated with habitat. The B. coli group (Voges-Proskauer negative ? methyl red positive) is characteristically of fecal origin, whereas the B. aerogenes-cloaca group (Voges-Proskauer positive ? methyl red negative) is relatively infrequent in feces, but predominates in the soil and on grains. B. aerogenes, although rarely found in the feces as voided, is a common inhabitant of the upper part of the intestinal tract of man. Under certain conditions it may constitute a considerable portion of the coli-like bacteria of a stool. It thus becomes of some practical significance to differentiate the B. aerogenes of intestinal origin from the B. aerogenes found in soil and on grain. Rogers pointed out that the fermentation of adonitol may be employed for this purpose with a high degree of reliability. It was thought that a study of the fermentation of the polysaccharids from different sources, particularly glycogens from vegetable and animal sources might possibly be of value in differentiating fecal from nonfecal types of B. aerogenes. Historical