164 PHYSIOLOGY OF ALIMENTATION. 



above downwards it is found that the number of bacteria 

 of this variety also decreases. As another constant inhabi- 

 tant of the alimentary tract beyond the stomach we have the 

 Bacillus coli communis, which according to ESCHERICH first 

 appears in small numbers high up in the small intestine. 

 From here the number of bacteria of this variety increases 

 progressively from above downwards. KOHLBRUGGE ques- 

 tions the presence of the Bacillus coli communis in any por- 

 tion of the small intestine except the region near the ileocaecal 

 valve. The caecum is considered by the last-named author 

 as the distributing depot of the colon bacillus, from which it 

 is supposed to be carried outward toward the rectum. By 

 the term colon bacillus are here understood all the different 

 varieties of this micro-organism which have been described. 



The two above-mentioned bacteria were for a long time 

 held to be the only constant inhabitants of the intestinal canal. 

 Since ESCHERICH'S early work we have become acquainted, 

 however, with a number of others which seem to be constant 

 inhabitants of the large bowel, and the cause here of certain 

 of the putrefactive changes which occur in this region of the 

 intestinal tract and not above it. Under this heading belong 

 the Bacillus putrificus, certain members of the Proteus group, 

 and bacteria very similar to the Bacillus subtilis. The first 

 of these is an anaerobe and the cause of the bacterial decom- 

 position of the proteins of the food. The products of this 

 decomposition give the faeces their odor. The absence, as 

 a rule, of the Bacillus putrificus from the intestine above the 

 ileocaecal valve in the adult explains why the contents of 

 the small intestine are without odor. The faeces of children 

 are also free from odor because their intestinal tracts nowhere 

 harbor this bacillus. Mention must also be made of the Ba- 

 cillus acidophilus, an acid-producing organism which, like the 

 colon bacillus, may at times be pathogenic, at times harmless. 1 



1 ESCHERICH, KOHLBRCGGE, etc.: Centralbl. f. Bakt., etc., 1901, 

 XXX, lteAbth.,p.73. 



