MICROBES IN THE HUMAN BODY 39 



faecal matter. As to the poisons found in the small intestine, 

 these are nothing but the digestive juices themselves, from the 

 pancreas and intestinal mucous membrane ; the fact of their 

 toxicity when injected into the veins of a rabbit does not prove 

 in the least that they are noxious to the animal producing 

 them. It is, in fact, a very rough way of studying the toxicity 

 of faecal matter to inoculate extracts of it into animals. The 

 biological and chemical study of the intestinal bacteria in their 

 capacity as ferments is the necessary and proper introduction to 

 the problem of intestinal putrefaction. 



The diminution of toxicity which Falloise discovered on 

 incubating faeces represents only the primary phase of the 

 phenomena which occur under such conditions, namely, a 

 preliminary fermentation which produces acid and suspends the 

 putrefaction ; it is only after the third day that true putrefaction 

 can begin, the reaction having then become alkaline. 



Finkelstein's argument was the speedy effects of change of 

 diet on an intestinal disorder ; but this action may equally well 

 be explained by the intervention of microbes ; the flora also 

 varies with the diet. In the intestine, as in a culture flask, 

 different cultures can be got with the same microbes when the 

 media originate on the one hand from meat and on the other 

 from vegetables. 



In studies so difficult as these, no good result can be got by 

 treating faecal material and injecting it in quantity. It is 

 necessary to proceed analytically, isolating patiently the 

 bacterial species of the intestines, studying them in a condition 

 of purity, as every ferment ought to be studied, studying 

 secondly their actions in association, and studying finally the 

 poisons they produce, phenols, indol, skatol, etc. It is by 

 this method that the action of B. putrificus, B. perfringens, 

 and B. sporogenes in intestinal decomposition has been 

 rendered certain as has been the role of B. proteus in infantile 

 diarrhoea. 



Mutual Assistance and Mutual Antagonism. These 

 legions of microbes do not escape the law of competition which 

 prevails throughout life. They have not all the same demands 



