CHAPTER XXVIII 



Researches on intestinal flora — Sour milk. 



The problem of our intestinal flora is so vast and so 

 difiicult that it demands years of research. Numerous 

 facts had already been accumulated by Science on 

 this subject, but it was stiU far from being elucidated. 



Certain scientists affirmed that microbes favour 

 digestion by decomposing food residues in the intes- 

 tine and are therefore not merely useful, but necessary 

 to the organism. Others entertained a diametrically 

 opposed opinion. The first thing, therefore, was to 

 know which of the two opinions was founded on fact. 

 Metchnikofi studied the case of the bat, in which the 

 digestive tube is short and the large bowel not even 

 diSerentiated. As he had supposed, a priori, in this 

 animal, whose life duration is relatively long, the 

 intestine contains few or no micro-organisms, which 

 proves that digestion can be accomplished without 

 their intermediary. Moreover, this was before long 

 amply confirmed by the researches of MM. Cohendy, 

 Wollman, and other scientists who succeeded in 

 briQging up chickens and tadpoles in conditions of 

 absolute sterility. 



Having acquired the conviction that microbes are 

 not indispensable to digestion, Metchnikoff studied the 

 part they play in the organism. It is universaUy 

 admitted that the products of putrefaction are toxic, 



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