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tation, which latter would inevitably arise it' the lactic acid ferments 

 were present in a rather considerable number. Only by repeated 

 transferences Lactobacillus is produced, which after some inoculations 

 forms 10 to 13 c.c. of normal acid. 



Hence, there is no doubt as to the presence of Lactobacillus and 

 Lactococcus in normal faeces. They are, however rare, and belong- 

 by no means to the intestinal flora proper, like coli, but to the 

 accidental flora, which consists of all that is introduced and is able 

 to pass the stomach and intestines alive, without multiplying. There 

 seems to be no cause to attribute any important influence to this fact. 



As to the second point, why in the intestinal canal the conditions 

 for the growth of the active lactic acid ferments are wanting, it is 

 that in the contents of the intestines an alcalic reaction exists, and 

 that t lie sugars which are formed or introduced there, in as much 

 as they are not absorbed by the intestinal wall, will surely be 

 attacked by coli, which in these circumstances is the stronger and 

 dispels all competitors. 



Why coli (and aërogenes) so completely defeat the lactic acid 

 ferments, should, to my opinion, be explained by the important 

 fact, not sufficiently considered in literature, that the first men- 

 tioned species can quite well live on peptone only, and multiply at 

 its expense, while the active lactic ferments completely lack this 

 faculty and, beside peptone, require a carbonhydrate for food. 



If, moreover, it is borne in mind that coli in the presence of a 

 carbonhydrate can also feed on other sources of nitrogen than pep- 

 tone, for example on amines and ammonium salts, whereas the active 

 lactic acid ferments cannot, and decidedly want peptones for nitrogen 

 food, it is clear that for the different forms of coli practically every 

 where in the intestinal contents a good feeding material is present, 

 and that in the few localities where it would also be sufficient for 

 the lactic acid ferments, it will be seized upon by coli. Where 

 only peptones occur, coli will moreover increase the already alcalic 

 reaction of the contents and thus, not for itself but for the lactic 

 acid ferments, render the conditions of life more unfavourable. 



Hence it seems evident why in the intestinal canal a coliflora can 

 exist but no lactic acid flora. 



The yellow coloured faeces of babies during the lactation period 

 may be alleged to support this view. They consist microscopically 

 almost solely of bacteria, for far the greater part of common coli- 

 bacteria '), among which there occur real lactic acid ferments, but 



i) For different children not always the same varieties: sometimes, for instance 

 non-fermenting forms reminding of Lactobacillus, for which I before indeed took 

 such bacteria. 



