464 



Mr. E. C. Grey. The Decomposition of 



simply allowing a broth culture of B. coli communis to remain unchanged for 

 three months, or by growth of the gas-producing organism anaerobically in 

 peptone solution containing mannitol in the presence of chalk for about 

 one month. At the end of the period described, if a loopful of the culture 

 be plated out on to agar, many of the colonies which grow at 37° will be 

 found to produce no gas when inoculated into mannitol peptone water 

 tubes. This change may be seen from Table I. 



Table I. — The Disappearance from B. coli communis of the Power to 

 Produce Gas from Mannitol by Continuous Growth of the Normal 

 Organism in Unchanged Cultixres. 





Production of gas. 



History of the culture. 













Mannitol. 



Grlucose. 



Normal ~B. coli recently isolated, average 46 normal 

 strains 



The above-mentioned normal strains after being kept 



in unchanged broth 4 months, average 6 strains 

 Kept in unchanged broth 4 months, average 12 strains 

 4 „ „ 12 „ 

 4 „ 8 „ 

 >> >) 4 ,, ,,9 ,, 



30 mm. gas 



25 „ 



12 „ 

 5 „ 

 2 „ 

 Nil 



21 '0 mm. gas. 



22 -0 

 20 -0 



18 -5 „ 



20 -5 



21 -0 



The strains described in Table I, which did not produce gas from mannitol, 

 were examined after p-rowth on broth during several sub-cultures and were 

 found not to produce gas from mannitol when inoculated from the broth 

 tubes into mannitol peptone water. Thus the acquired character is inherited 

 for a considerable time under these conditions. It will be seen from the 

 foregoing table that no change has been brought about in the power to 

 produce gas from glucose, and this is also true for dulcitol. Nevertheless, 

 if by simple growth in peptone water B. coli communis yields a strain 

 incapable of producing gas from mannitol, it would seem not unlikely that 

 some similar process might, with time, lead to the disappearance of the 

 power to produce gas from glucose, but such has not so far been observed. 



In deciding whether an organism possesses the formic acid decomposing 

 enzyme, which it is suggested here should be used as a criterion of a gas- 

 producing organism, it is not convenient or sufficient to observe whether gas 

 is produced from peptone water containing sodium formate. The test should 

 be made with a mixture of sodium formate and glucose in such proportions 

 that the sodium carbonate which will result from the decomposition of the 

 formate will be approximately sufficient to neutralise the acid which will 



