BACTERIA SUSCEPTIBLE TO BACTERIOPHAGY 253 



regard to the mutant form, 1 . A reduction in the agglutinability by an 

 anti-A serum. 2. An increase in the agglutinability by an anti-typhoid 

 serum. 3. The production of antisera which agglutinate B. typhosus 

 more strongly than they do the original paratyphoid A organism, this 

 property becoming more manifest during the course of successive 

 transfers. 



These authors have confirmed these findings by agglutinin absorption 

 experiments. Weil has shown that the bacillus of Gaertner, which is 

 agglutinated to the titre by an anti-typhoid serum, may have itscoagglu- 

 tinating action increased and at the same time retain intact its specific 

 agglutinating power. |.But the anti-typhoid serum used by Bachmann 

 and de la Barrera, deprived of its partial agglutinins by saturation 

 with the bacillus of Gaertner, also lost its activity for the original 

 para A strain, although it still agglutinated B. typhosus at 1 : 3200, and 

 the mutant form of para A at 1 : 1600. 



By exhausting the anti-typhoid serum with the original paratyphoid 

 A heated to 100°C. they obtained a serum which no longer had any 

 action upon the original para A, but it agglutinated B. typhosus at 

 1 : 3200 and the mutant form at 1 : 1600. 



As for the anti-serum produced to the Fe mutant, absorption with 

 heated bacilli removed all action for the original para A but did not 

 impair its activity for B. typhosus and for the F4 and Fe mutants. 



These facts can only mean that there has been a transformation 

 of the antigenic properties brought about through the action of the 

 bacteriophage. 



"We have witnessed, then," say Bachmann and de la Barrera, "a 

 progressive evolution, in which the properties of these organisms become 

 increasingly unlike the original para A bacillus and approximate more 

 closely those of B. typhosus." 



One might go still further and question whether the bacterial species 

 belonging to the colon-typhoid-dysentery group do not result from 

 mutations brought about through the intervention of the bacteriophage. 

 Baerthleins obtained in one case the transformation of a B. paratyphosus 

 B into a B. typhosus, and one immediately wonders if, in this successful 

 case, he was not working with a mixed strain of B. paratyphosus B. 

 Some experiments to be described later seem to substantiate this inter- 

 pretation. At the very beginning of my experiments I emphasized 

 the fact that the question of the bacteriophage is certainly a dominating 

 one in the study of bacteria and the communications published during 

 the last three years seem to show, indeed, that this statement was 



