288 



STATE BOARD OF AGRICULTURE. 



XVII. THE ACTION OF CARBON DIOXIDE UPON BACTERIA WHEN CULTIVATED 



IN MILK. 



To simulate the carbon dioxide content of milk, it became necessary to employ 

 sterilized milk tubes into which were inoculated the various micro-organisms under 

 consideration and to subject one set of these tubes to the action of carbon dioxide 

 conditions. For this purpose we inoculated with identical amounts of the various 

 germs two sets of milk tubes, one set remained exposed to the air, the other set was 

 placed in Novy's anaerobic bottle into which was passed 77.7 per cent of carbon 

 dioxide. This was allowed to stand twenty hours when plates were made from the 

 aerobic set and at the same time from the anaerobic set. Care was taken to use the 

 same measure for each germ under study. In the same way the second series was 

 executed, but instead of using 77.7 per cent of carbon dioxide, 60.02 per cent was used. 

 The result of this work will be found in the table below: — ■ 



TABLE XV. 

 ACTION OP CARBON DIOXIDE UPON BACTERIA WHEN CULTIVATED IN MILK. 



Sterilized milk from which the carbon dioxide has been expelled may be inoculated 

 with micro-organisms, and if exposed to the action of an atmosphere of carbon dioxide 

 shows some retardation in the development of these micro-organisms. Furthermore, 

 the action of the carbon dioxide upon milk cultures corresponds very closely to the 

 action of carbon dioxide upon plate cultures. There appears to be the same retarding 

 and, in some cases, inhibiting influences at work as had been so noticeable in the 

 preceding tables. 



