INFECTIONS OF THE DIGESTIVE TRACT 67 



cultures. If the sediments in fermentation tubes 

 prepared in the manner just mentioned be examined 

 microscopically, it will be found in every case that there 

 has been a fairly abundant growth of microorganisms 

 of the B. coli type. The staphylococci and Gram- 

 positive diplococci will also be found to have multiplied 

 in the anaerobic limb of the tube. As a rule there is 

 little or no evidence of the development of strict 

 anaerobes. 



The gas production and the acid formation which have 

 been noted are probably to be ascribed almost exclusively 

 to the action of organisms of the B. coli group. The 

 presence of streptococcal forms in abundance appears 

 to inhibit the formation of gas, probably by checking the 

 development of the colon bacilli. 



If suspensions of the mixed flora be inoculated into the 

 fermentation tubes containing bouillon without sugar, 

 the results of the bacterial decomposition are different. 

 Here we find either very small gas production or none 

 whatever, and such acids as may be produced are, more- 

 over, bound by alkali, so that the medium, originally 

 neutral, either remains so or becomes faintly alkaline. 

 There is a moderate production of ammonia. This 

 ammonia is united mainly to acetic acid. There is also 

 a production of hydrogen sulphide under these circum- 

 stances. Not rarely there is a small quantity of mercap- 

 tan, but as a rule the amount of mercaptan produced is 

 little more than a trace, and very frequently perhaps 

 usually it is wholly absent. The formation of indol 

 is a constant phenomenon on the bouillon medium, and 



