32 MICROBES AND TOXINS 



guinea-pigs from their mothers by Caesarean section, by 

 Schottelius and Cohendy on the chick, by Mme. Metchnikoff 

 and by Moro on tadpoles. 



The little guinea-pigs appeared to develop and increase in 

 weight in normal fashion, but Schottelius has questioned the 

 interpretation of these experiments ; he maintains that t he 

 increase in weight was due to food swallowed but not digested. 

 The tadpoles developed badly without microbes. The 

 chickens of Schottelius were * weaklings ' and lived seventeen 

 days at most, becoming increasingly thin and feeble. Their 

 digestive juices were apparently insufficient for digestion, and 

 they only recovered when there was added to the sterile food 

 certain bacteria, among which was the bacillus coli. 



But it is impossible to conclude with certainty from these 

 experiments that life is impossible without microbes ; these 

 new-born animals were placed under conditions too different 

 from the natural ; their intestine was not yet secreting enough 

 ferment, and the food they were getting, sterilised as it was at 

 a high temperature, was not adapted to the hereditary disposi- 

 tion of their alimentary canal. 



It would therefore be necessary to study adult animals 

 free from microbes, but we know that this condition hardly 

 exists. 1 



There are, however, animals which approach it somewhat, 

 namely, the large fruit-eating bats of the tropics (Pteropus 

 medius) recently studied by Metchnikoff. These animals 

 have a large intestine very limited in size ; there is no 

 reservoir in which to accumulate the waste products of their 

 food, and they begin to evacuate faeces one hour after the 

 ingestion of the food from which these are derived. They are 

 obliged to eat a great deal and to evacuate in proportion. 

 They have, properly speaking, no intestinal flora, simply a 

 few bacteria conveyed by the food and changing with the diet. 



1 The intestine of the scorpion is almost always free from microbes ; 

 and the same is the case with the intestine of certain maggots provided 

 with digestive juices sufficiently powerful to digest seeds, wool, and even 

 such resistant microbes as the bacillus of tubercle. 



