30 MICROBES AND TOXINS 



centuries there have been microbes within living beings, and 

 there must have become established a sort of understanding, or 

 adaptation between the intestinal flora and the intestine. Just 

 as plant roots absorb from the soil the fluids elaborated by 

 the bacteria, so the intestinal villi absorb the juices prepared 

 by the microbes of the intestine. These microbes accumulate 

 and their presence in masses stimulates the intestinal muscles. 

 Further, the normal intestinal flora opposes an invasion by 

 foreign bacteria which might be or might become pathogenic. 

 Consequently the intestinal bacteria both nourish and protect ; 

 they are useful, salutary, and providential. 



The opposite opinion is maintained by Metchnikoff. The 

 digestive ferments prepare the nutritive materials without any of 

 this problematical assistance from the microbes. The intestinal 

 flora is injurious (taking of course the point of view which 

 interests us most, that of mankind), because long before the 

 food stuffs leave the body, the bacteria induce in them fermenta- 

 tions the products of which, absorbed by the mucous membrane, 

 are for the most part poisonous. 



From the point of view of nature, it is quite normal for the 

 albuminous excreta of our food to putrefy and thus return into 

 the general circulation of matter ; but it is regrettable when this 

 takes place in our bodies, for phenols, skatol, and indol, among 

 other products, penetrate into our circulation and affect the cells 

 of our arteries and brain. It would be to our advantage if the 

 food-stuffs were expelled immediately after useful digestion, and 

 before the terminal phase, the putrefaction, begins in the waste 

 products. And since in the part of the intestine which pro- 

 perly speaking is the digesting part, the small 'intestine, there 

 are practically no bacteria, and since on the other hand they 

 swarm in the large intestine where there are scarcely any diges. 

 tive ferments, it is evident that, on the whole, the intestinal 

 flora is injurious. The ideal condition would be to live free 

 from bacteria while the world remained populated by them. 

 Is a life of such purity possible ? 



Aseptic breeding. — There are, it has been said, certain 

 Arctic animals, both birds and mammals, without intestinal 



