The Fermentation Tube 227 



The fundamental differences between B. typhosus and the 

 colon group of bacteria need further elucidation by a thorough 

 study of all the products of fermentation, as has been done by 

 Dubief* and Pere,' but without concordant results as yet. 

 For the typhoid bacillus likewise has a definite action on glu- 

 cose, as has been shown by Brieger and recently by Pere. 

 The latter has shown that when glucose is added to milk, it 

 subsequently coagulates when inoculated by this organism. 

 The action on glucose is moreover readily revealed by the 

 markedly acid reaction of cultures in glucose bouillon. All 

 that the gas test tells us definitely is that the colon bacteria 

 act on glucose with evolution of a certain volume of gas, and 

 that the typhoid bacillus acts upon glucose without the evolu- 

 tion of gas. 



There is one question called up by the fermentation test 

 which will require some attention. The evolution of gas with 

 the simultaneous appearance of acids in the culture fluid might 

 lead us to assume that at least some gas may have been set 

 free from the Na^CO^ used to neutralize the bouillon. Yet by 

 adding increasing quantities of sterile NajCOj solution to a 

 series of fermentation tubes, I was unable to evolve any gas 

 with the typhoid bacillus. It is not unlikely, however, that 

 bacteria capable of setting free much acid may lead to the ac- 

 cumulation of a trifle of gas, not the product of fermentation, in 

 strongly alkaline bouillon. In all cultures in which only 

 small quantities of gas appear this possibility should be borne 

 in mind. 



THE QUANTITATIVE DETERMINATION OF FECAL BACTERIA IN WATER.* 



The bacteriological examination of water in the interest of 

 practical hygiene, has thus far suffered from the difficulty that 

 the kinds of bacteria present are recognizable only when a 

 disproportionate amount of labor is spent in isolating them. 

 Occasionally bacteriological water analysis has taken a certain 



*See the forthcoming Annual Report of the State Board of Health of 

 New York for 1892, for a more detailed statement of this method. 



