128 



JAMES M. SHERMAN 



The two cultures employed in this work were obtained from 

 Miss Evans and belonged to the collection used in her studies of 

 cheese. For the determination of carbon-dioxid production the 

 special tube designed by Eldredge and Rogers (1914) has been 

 used. The cultures were grown in 30 cc. of broth and the car- 

 bon dioxid absorbed with barium hydroxid. Titrations were 

 expressed in cubic "centimeters of ^ barium hydroxid neutralized. 



Following the hypothesis that the carbon dioxid formed by 

 this organism might be derived from some source other than the 

 sugar, a number of experiments were run with various sugar-free 

 media but in no instance was a significant amount of this gas 



TABLE 1 



Relation of peptone concentration to carbon-dioxid production 



* Cubic centimeters of fo Ba(0H)2 neutralized. 



obtained. Other experiments were conducted in an effort to 

 show the relation between the amount of carbon dioxid produced 

 and the concentration of nitrogenous constituents of the culture 

 medium. For example the evolution of carbon dioxid was meas- 

 ured from media consisting of 0.2 per cent lactose, 1 per cent 

 dried yeast and varying amounts of peptone. The results of 

 such an experiment are shown in table 1. It may be seen from 

 this table that there was just as much carbon dioxid formed in 

 the broth containing only 1 per cent of peptone as there was in 

 those containing a greater concentration. The results of experi- 

 ments of this type and of numerous tests with various sugar-free 

 media. of various compositions would not indicate that the gas 

 produced by this organism is derived from the nitrogenous 

 portion of the medium. 



