584 GASTRO-INTESTINAL BACTERIOLOGY 



and Bacillus bifidus or similar organisms dominate the large intestines 

 from this level to the sigmoid flexure. The remainder of the large 

 intestine to the rectum is somewhat sparsely populated with living 

 bacteria, partly because the fecal mass is relatively desiccated by the 

 absorption of water, partly because of the accumulation of waste 

 products of bacterial activity principally acids resulting from 

 fermentation of lactose, formed higher up in the tract which inhibit 

 the development of bacteria in the lower levels. 1 



It must be remembered that while the greatest number of impor- 

 tant bacteria mentioned above occur at the levels indicated, there is 

 a mechanical transportation of all intestinal bacteria from the higher 

 to the lower levels, so that some organisms of all types are found in 

 the dejecta. It is particularly important to realize that the types 

 of bacteria outlined are those which can be identified by staining 

 methods as numerically prominent at the various intestinal levels; 

 these observations can be corroborated by appropriate cultural 

 methods. Nevertheless, there is a wide disproportion between the 

 numbers of each of the respective bacteria seen in stained preparations 

 and the numbers of each type which develop in artificial media. Thus, 

 Escherich 2 observed that a preponderance of bacteria of normal nurs- 

 lings' feces were Gram-positive bacilli, yet he never succeeded in grow- 

 ing these bacilli in artificial media; the principal types which developed 

 in his cultures were Bacillus coli and Bacillus lactis aerogenes, organ- 

 isms which are numerically in the minority in the intestines, but which 

 grow luxuriantly outside the body. It is now realized that he did 

 not employ suitable conditions of culture to isolate the most prominent 

 types of organisms. Undoubtedly much of the confusion which has 

 attended the study of intestinal bacteriology in the past is attributable 

 to the lack of appreciation of the cultural peculiarities of the intestinal 

 organisms. 



Distribution of the Intestinal Flora of Artificially Fed Infants. 

 Escherich 3 directed attention to the striking dissimilarity between the 

 intestinal flora of the breast-fed and the artificially fed infant; cul- 

 turally, morphologically and chemically the former is more homogen- 

 eous than the latter. The most distinctive features of the dejecta 

 of artificially fed infants are: the relative increase of Gram-negative 

 bacteria of the coli-aerogenes type, and of coccal forms of the Micro- 

 coccus ovalis type, together with a diminution of Bacillus bifidus. 



1 Kendall, Jour. Med. Research, 1911, xxv, 117, et seq. 



2 Loc. cit. 3 Loc. cit. 



