426 Chapter XIII 



The bile, active against certain poisons, does not, however, prevent 

 poisoning by cholera toxin nor by that of botulism, two most typical 

 intestinal intoxications. 



Since diastases and the digestive juices are incapable of affecting 

 micro-organisms and since certain of these latter perish in the intes- 

 tines we must seek some other cause for their destruction. It is 

 probable that the vital competition among the micro-organisms, 

 whose r61e could be foreseen in the buccal cavity, is of still greater 

 importance in relation to the phenomena of pathogenic action or of 

 the innocuousness of infective bacteria in the intestinal canal 1 . This 

 [447] complex and difficult chapter, up to the present, has been studied 

 in a very imperfect fashion. In our observations on cholera we 

 have remarked that under certain conditions the cholera vibrios do 

 not develop on gelatine plates, except in the neighbourhood of 

 certain adjuvant micro-organisms such as the Torulae and the 

 Sarcinae. Guided by this fact we have succeeded in producing 

 intestinal cholera in suckling rabbits, with races of vibrios which, 

 when ingested alone by these animals, remain innocuous or set up 

 the disease only occasionally. We have convinced ourselves of the 

 helpful action of certain representatives of the gastro-intestinal flora 

 upon true cholera 2 . Following on these observations, it was quite 

 natural to suppose that this flora might also contain micro-organisms 

 capable of hindering the development and toxic action of the cholera 

 vibrio. We have even advanced the hypothesis that these "hindering" 

 micro-organisms in the flora of the digestive canal may explain the 

 immunity of animals, of many human individuals, and even of the 

 population of unattacked towns, to intestinal cholera. We should 

 have, then, in the intestinal contents, inhabited by a number of 

 micro-organisms and deprived of bactericidal juices, an important 

 factor which in many cases guarantees a refractory condition. It 

 must be stated, however, that prolonged studies, carried out with 



1 Perhaps the intestinal micro-organisms also play a part in the immunity of the 

 animal against Entozoa. Many of the examples of this immunity are very striking. 

 Certain intestinal worms can live only in the digestive canal of a single or of a very 

 small number of species of animals. When we feed rabbits with a quantity of the 

 cysticerci of the pig these pass living into the small intestine and are there trans- 

 formed into true scolices. But, instead of reproducing themselves, they are expelled 

 and never give rise to the development of taeniae. The immunity against intestinal 

 parasites has never been made the object of special study, and it is only as a pure 

 hypothesis that I offer this suggestion as to the part played by the micro-organisms 

 of the intestinal flora. 



2 Ann. de VInst. Pasteur, Paris, 1894, t. vm, p. 549. 



