INFECTIONS OF THE DIGESTIVE TRACT 191 



life a fact not widely known. I have met with excep- 

 tionally robust adults in whom bifidus was very promi- 

 nently represented, if one may trust the microscopical 

 fields and the primary * fermentation-tube sediments. 

 Whether bifidus ever assumes a pathological character in 

 man is uncertain. I may refer here to the observation 

 that a Gram-positive bacterium indistinguishable from 

 typical bifidus in its microscopical characters is sometimes 

 almost the exclusive inhabitant of the lower digestive 

 tract in children with chronic intestinal indigestion char- 

 acterized by abdominal distention and retarded growth. 

 In sugar bouillon these fsecal bacteria show the typical 

 varied morphological characters of B. bifidus of nurslings, 

 but whether the organisms from these pathological cases 

 are really identical with those obtained from the in- 

 testine of normal infants is uncertain because no ade- 

 quate biochemical observations have been made. I 

 think the possibility should be borne in mind that a bac- 

 terial form which is entirely physiological when dominant 

 during infancy may not be equally physiological when 

 it constitutes the dominant type in later years. The 

 mere persistence of B. bifidus as the leading large-intes- 

 tinal microorganism may carry with it certain physio- 

 logical disadvantages, such as relatively feeble powers of 

 defense against some harmful bacteria. 



INFECTIONS THROUGH ANAEROBIC BACTERIA 



The anaerobes of the human intestine have received far 

 less attention than the aerobic and optionally anaerobic 



1 Made from direct inoculation of the faeces. 



