130 



JAMES M. SHERMAN 



From observations on this point no hesitation is felt in con- 

 cluding that the source of the carbon dioxid produced in these 

 experiments was the lactose contained in the medium and not 

 any of the other possible sources. 



It was thought, since the gas produced bj^ this organism is 

 apparently derived from the sugar, that the greater production 

 of carbon dioxid in digested milk over lactose broth might be 

 explained by the greater buffer content of the milk medium. 

 In fact it was noted early in the work that the amount of gas 

 obtained from lactose broth was increased with the addition of 

 phosphate. We therefore compared in other expermients the 

 carbon-dioxid production of these cultures in digested milk 



TABLE 3 

 Carbon-dioxide production in digested milk and in highly buffered lactose broth 



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



and in highly buffered lactose broths. The data obtained from 

 one of these tests are given in table 3. It will be seen that the 

 carbon-dioxid production in lactose broth may be so increased 

 by an increase m the buffer content of the medimn as to give 

 results comparable to those obtained from digested milk. 



The conclusion to be drawn from the experunents reported 

 in this paper is that the carbon dioxid produced by organisms 

 of the Streptococcus kefir type, when grown in ordinary lactose 

 broths, is derived from the carbohydrate portion of the media. 

 With reference to the carbon dioxid produced in the ripening of 

 Cheddar cheese, after the original lactose content of the cheese 

 is exhausted, it would not be safe to draw definite conclusions 

 from these observations. However, from tests with this organ- 



