54 VARIATIONS IN FERMENTING POWER [ch. v 



access to the bladder. This organism was isolated and on 

 cultivation was found to ferment glucose, lactose and sac- 

 charose with the production of much gas. After two years 

 the patient recovered spontaneously from the pneumaturia, 

 though the organism was discovered still to be present in the 

 bladder. Cultures, however, failed to yield gas on sugar 

 media. About a year later the strain, which had been sub- 

 cultured throughout this interval, suddenly re-acquired the 

 property of producing gas, and "shortly after" the patient 

 commenced to suffer again from pneumaturia. 



The clock-like precision with which these two strains, one 

 on artificial media and the other in the human body, are 

 stated to have exhibited this spontaneous variation, after the 

 same interval of time and in spite of the difference in their 

 respective environment, may perhaps excuse some incredulity. 

 One suspects that further investigation would have shown 

 the modification to exist in the sugar media employed rather 

 than in the bacteria. 



III. Fermenting properties may he modified by the 

 conditions of growth. 



1. The influence of temperature. Wilson (1910) isolated 

 B. typhosus from the urine of a " carrier." At a temperature 

 of 22° C. this organism fermented lactose litmus-agar in 2 days 

 but at a temperature of 37° C. no acidity was produced after 

 a month's incubation. The absence of acidity at the higher 

 temperature might be accounted for on the supposition that 

 the products of the proteid decomposition, at this temperature, 

 neutralised the acid formed during the process of fermen- 

 tation. Wilson proved that this was not the true explanation 

 by estimating the amount of lactose present and showing 

 that it had not been attacked. 



Coplans (1909) mentions some strains of B. coli which 

 showed the reverse phenomenon, fermenting dulcite more 

 readily at 37° than at 20° C. 



Adami has described an alteration in the fermenting pro- 

 perties of B. coli comimunis after subjection to a high tem- 

 perature in the presence of peritoneal fluid. 



