BIOLOGICAL VARIATIONS OF BACTERIA 



395 



results too indefinite to be reported at the present time. The 

 writer intends to continue work along this line, and also with 

 respect to pathogenicity, which seems to suggest itself as a 

 fruitful subject for investigation. 



In summing up, it can be said that glucose and phenol, par- 

 ticularly the former, cause partial inhibition or total disappear- 

 ance of acid and enzyme formation in some strains of B. coli. 

 These changes together with the suspension of the production 

 of indol and the characteristic colon growth on potato, makes 

 the B. coli approach the B. typhi type. These changes have 

 been noted time and again but in varying degrees, in those strains 



TABLE IX 



Changes produced by glucose and phenol in various strains of B. coli and the complete or 

 incomplete reversion towards their previous biological characteristics. The coinplete- 

 ness of the change and the incompleteness of the reversion in strain No. 95 is note- 

 worthy, as such a change might be regarded in the light of a mutation instead of a 

 variation 



* SI. = slight. 



