CH. V] VARIATIONS IN FERMENTING POWER 57 



VI. Fermenting power may he altered by "animal 

 passage." 



Klotz (1906) isolated from water an atypical organism of 

 the B. coli group. This organism, after a residence of 144 

 days' duration in a celluloid sac within the peritoneal cavity 

 of a rabbit, showed a* temporary loss of power to ferment 

 glucose, saccharose and lactose. The loss was most marked 

 in the case of lactose which was, however, again fermented 

 in the 4th subculture into lactose broth, and also by the 8th 

 subculture on ordinary media (agar). 



Peckham (1897) introduced B. coli into the peritoneal 

 cavity in sufficient numbers to set up a fatal inflammatory 

 process. The organism, recovered on the death of the animal 

 4 days later, showed slight changes in fermenting power. 



Horrocks (1911) describes a strain of B. typhosus which, 

 in the course of cultivation, acquired the power to ferment 

 lactose, dulcite and salicin. " Passage " through 4 guineapigs 

 destroyed the power to ferment lactose and dulcite but after 

 4 further passages the power was regained. 



Bahr (1912) describes experiments in which flies were fed 

 on dysentery bacilli (both of the "Shiga" and of the 

 " Flexner " type) and states that the organism recovered from 

 the intestinal tract in several cases, "undoubtedly derived 

 from the bacillus originally fed to the flies," gave different 

 sugar reactions. The sugar reactions had, for 9 months 

 previously, remained constant on repeated trials. One " Shiga " 

 organism had acquired the power to ferment maltose. In the 

 case of a "Flexner" organism, the power of fermenting 

 mannite (upon which the distinction between the acid and 

 non-acid types depends) was diminished, fermentation only 

 occurring after 4 days' incubation. Other organisms of the 

 "Flexner" type had acquired the power to ferment maltose 

 and saccharose. Both types of organism on subculture re- 

 verted to their original characters in the course of several 

 months. 



Adami, Abbott and Nicholson (1899) obtained from human 

 ascitic fluid an atypical B. coli which had completely lost its 

 fermenting power. This power was restored after a series 



