VIABILITY OF THE COLON-TYPHOID GROUP 



115 



ured in this way. A\'hen, however, such samples are held for a 

 period of one or two weeks at 19° to 20°C. there is a gradual 

 escajje of CO2 gas as evidenced by a tlecreaso in the hydrogen- 

 ion concentration. It is believed that under the conditions of 

 our experiments the acidity of the dissociated carbonic acid is 



TABLE 1 



Shounng the comparative viabilily of Dad. coli i?t carhoiMlcd lap ivotcr iindvr 

 pressure and in plain (non-carbonated) lap water 



* Figures represent numbers of Baet. coli per centimeter. 



t indicates the absence, and + the presence, of Bact. coli as determined by 

 transferring the specified amount of water (10, 5 or 1 cc.) to broth. This was 

 done when the numbers had become so reduced as to give negative results upon 

 plating 1 cc. quantities. 



the main factor responsible for the death of the bacteria. Other 

 factors, such as differences in osmotic pressure, may also play 

 a part. 



Several of the simpler carbonated beverages were used in the 

 next experiments. It should be realized that certain acids — 



