120 THE BACTERIOPHAGE 



Eliava and Pozerski have shown that the neutral salts of qui- 

 nine exert an antiseptic action on the bacteriophage, in three per 

 cent solution killing it in thirty minutes, in one per cent, in a few 

 hours. Emetine hydrochlorate and saponine in the same con- 

 centrations are without action. This susceptibility to the anti- 

 septic action of quinine is singular in a germ which is otherwise 

 relatively resistant to antiseptic activities. It is hardly possible 

 to deduce that the bacteriophage is protozoan in nature, for 

 quinine exerts antiseptic properties toward many bacterial species, 

 although on the contrary, it is without action on the diastases 

 and toxins. 



When a culture is treated with acetone the albuminoid materials 

 of the bouillon are thrown out of solution, and this precipitate 

 encloses the bacteriophagous virus. The greater portion of the 

 virus is, however, destroyed. The bacteriophage reacts like the 

 spore-forming bacteria, which are found, living, in the precipi- 

 tate. In this connection a curious thing has been noted. 

 Ordinarily acetone is considered a sterile fluid, but it is not 

 necessarily so, since it has been found that several containers of 

 acetone have been contaminated by B. subtilis. 



Alcohol gives the same precipitate, but the bacteriophage, con- 

 trary to that which happens with the virus of the tobacco mosaic, 

 is killed in less than forty-eight hours in 90 per cent alcohol. 

 The precipitate, as we will see, contains the secretory products 

 of the bacteriophage. 



UNICITY OF THE BACTERIOPHAGE 



In the preceding chapters detailed experiments have been 

 given which show that whatever the bacteria attacked, the ul- 

 tramicrobes which attack them belong always to the same species. 

 We will return to other proofs shortly. A single statement, 

 grouping these experiments will be given here. 



First. Usually a single strain of bacteriophage will attack 

 several species of bacteria at the same time. 



Second. A strain of the bacteriophage, continued through 

 more than a thousand passages in vitro, always in conjunction 

 with the same bacterial strain, namely, B. dysenteriae Shiga, 

 attacks B. typhosus and B. coli. 



