MICROBES IN THE HUMAN BODY 33 



The juices of their small intestine have no power of killing 

 bacteria such as has been alleged in the dog and the cat, so 

 the poverty of their intestinal flora cannot be thus explained. 

 The digestive tube being almost free from bacteria in its 

 whole length, the digestion of the food cannot be attributed to 

 microbes. 



The fruit-bat above-mentioned digests the cellulose of 

 bananas, yet it is precisely for the digestion of cellulose 

 among the herbivora that the necessity of auxiliary microbes 

 has been maintained ; the reason is that cellulose-digesting 

 microbes are known, whereas no ferment has been separated 

 from the digestive tube capable of doing this. But the 

 bacterial ferment has not been isolated either : the question 

 of cellulose digestion is one on which our ignorance is great 

 and which demands fresh investigations. Finally, in the 

 dejecta of the fruit-eating bat the putrefactive poisons phenol, 

 skatol, and indol do not occur, although these are constant 

 among all other mammals including the herbivora. This 

 absence of putrefaction corresponds with the extreme short- 

 ness of the large intestine and the poverty of the intestinal 

 flora. We have then in this animal a good example of an 

 adult animal capable of digesting its food, under normal 

 conditions, by its own digestive juices without the help of 

 bacteria. 



The Intestinal Flora of Man. — Man differs from the 

 bat. He harbours a very abundant intestinal flora in his large 

 intestine which is highly developed and in which the food-stuffs 

 begin to putrefy. 



It is almost impossible to calculate the number of bacteria 

 in our intestine. Gilbert and Dominici have calculated that 

 we discharge daily 11,725 millions, without counting the 

 anaerobes, of which there is a prodigious number. Klein 

 speaks of 9 billions of bacteria discharged every twenty-four 

 hours, of which 100,000 millions are still alive. Strassburger, 

 using a different method of counting, calculates the quantity 

 of bacteria at one-third of the normal dried faeces ; in twenty- 

 four hours a man evacuates 120 billions of bacteria. It would 



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