72 THE BACTERIOPHAGE AND ITS BEHAVIOR 



it simply remains inert. Their experiments were conducted with B. 

 typhosus, B. coll, B. dysenteriae, and the staphylococcus. 



That bacteriophagy does not occur in bouillon containing a quantity 

 of methyl violet sufficient to affect the vitality of the bacteria has 

 been reported by Tomaselli.''^* 



A somewhat more interesting situation is revealed by those experi- 

 ments in which the antiseptic agent is added to the medium in amounts 

 so small as to allow bacterial development. Certain of my experi- 

 ments were performed for the specific purpose of determining what 

 happens under these conditions, sodium fluoride being selected as the 

 antiseptic. Incidentally, in this series of studies I demonstrated that, 

 contrary to what is stated in a number of physiological text-books, 

 life is perfectly possible in media containing 1 per cent of salt. In such 

 media B. dysenteriae or B. coli live perfectly well. In fact, multipli- 

 cation, in agglutinated floccules, takes place provided the organisms 

 have undergone a preliminary adaptation by a few passages through 

 media of increasing salt concentration. But despite the fact that the 

 bacteria are able to develop in this solution, bacteriophagy will not 

 take place in such a medium. 



A further fact revealed in these studies is that while B. coli develop 

 freely, without a prehminary adaptation, in a bouillon containing 

 0.2 per cent of sodium fluoride bacteriophagy will not take place, even 

 if the bacteriophage introduced is very active. If 10 cc. of this fluoride 

 containing medium is seeded very lightly with B. coli and then 0.1 cc. 

 of an extremely active bacteriophage filtrate is added, the colon bacilli 

 develop as vigorously and as abundantly as in the same medium with- 

 out the bacteriophage. Nevertheless, the bacteriophage is not de- 

 stroyed; it simply remains inert (d'HereUe^''") . 



By this experiment I had designed to show only the fact that the 

 bacteriophage may remain inactive under conditions which permit 

 the development of the bacterium. Brutsaert^"" has extended this 

 study and has sought to determine if the concentration of fluoride, 

 compatible with the development of the bacterium, but inhibitory as 

 regards bacteriophagy, is the same for all bacterial species. He found 

 that the concentration limiting bacteriophagy varies for each species 

 studied (from 0.25 to 0.05 per cent). Indeed, this might have been 

 predicted, for although the bacteriophage remains passive it is cer- 

 tainly not because the fluoride has an effect upon it, but because it 

 modifies the state of the bacterium. This conclusion is supported by 

 the fact that in bouillon containing fluoride the bacteria do not grow 

 normally but in agglutinated clumps. 



