466 



Mr. E. C. Grey. The Decomposition of 



(1) The non-production of gas from formate peptone water alone was due, 

 in part, to the natural alkalinity of the medium. To demonstrate this 

 varying quantities of N/10 H2SO4 were added to a series of sodium formate 

 peptone water tubes, which were then inoculated with a loopful of a broth 

 culture of B. coli communis, It was found that in those tubes in which the 

 reaction to litmus was nearest to neutral, there was a slight production of 

 gas, whereas those which were distinctly alkaline or acid showed no gas 

 at all. 



(2) The manner in which the inoculation is made is also of importance. 

 Several tubes of sodium formate peptone water were inoculated each with a 

 loopful of a broth culture of B. coli, and another set of tubes were inoculated 

 each with a loopful of an agar growth of the same organism. The former 

 set of tubes produced no gas, the latter produced one-tenth of a Durham 

 tube. This difference in the production of gas cannot be due simply to the 

 size of the inoculation, for even when kept for 10 days the formate tubes 

 inoculated from the original broth culture showed no production of gas. 

 Probably, therefore, the bacillus when grown on agar contains more of the 

 formic acid decomposing ferment than when grown in broth. 



(3) The decomposition of sodium formate is not assisted in the same 

 degree by mannitol as it is by glucose and the other sugars or by sorbitol, 

 and it may be possible that this phenomenon is related to the fact already 

 mentioned, that the power to produce gas from mannitol disappears from 

 old broth cultures of B. coli communis, when these have remained unchanged 

 for some months, and still more readily when the fluid contains mannitol 

 and the products therefrom. 



It should be noted also that, since less acid is produced from a hexahydric 

 alcohol than from the same weight of a hexose when fermented by B. coli 

 communis, the fact that the alcohol does not assist so well in the acceleration 

 of the decomposition of the formate by the organism is in harmony with the 

 view that it is the neutralisation of the medium by the acid produced by 

 the carbohydrate or allied substance which is of assistance for the further 

 decomposition of the formate. 



The fact that in any particular experiment no gas may be produced from 

 glucose peptone water is not a complete proof that an organism cannot 

 produce gas at all from glucose, for the acid produced under circumstances 

 in which 110 precaution is taken to neutralise the medium inhibits the 

 decomposition of formic acid. 



