Aug. 19, 1922] THE BACTERIOPHAGE. [McIrcAf JoukLl 



4. The conception of the bacteriophage being a chemical substance is 

 favoured by the chemical-Hke affinity existing between a given lytic agent and 

 the corresponding susceptible strain. 



I first observed that small amounts of lytic agents lose a certain part of their 

 activity when put together with too thick emulsions of sensitive bacteria. 

 Bordet, with a different technique, could even obtain the complete disappear- 

 ance of traces of lytic agent in the same condition. Still more convincing are 

 the results of Yaumain and of Da Costa, who observed the absorption of rela- 

 tively important amount of lytic agent by dead emulsions of the corresponding 

 sensitive bacteria. This specific affinity which is the necessary condition for 

 a lytic agent for inducing the dissolution of a given bacterium is not favourable 

 to the virus theory, because we question how a virus could be definitely fixed 

 by dead bacilli, which, however, it is unable to attack. 



5. The bacteriophage is not one and the same antigen. Several lytic agents 

 showing antigenic specificity must be considered. 



The coli lytic agent can be completely neutralized by proper amounts of 

 corresponding coli antilytic serum, but is not at all affected by staphylococcus 

 antilytic serum, which, on the other hand, is only able to neutralize staphylo- 

 coccus lytic agent and not coli lytic agent. This neutralization reaction is thus 

 specific, and demonstiates the plurality of the bacteriophage. 



The non-specific results obtained with the alexin fixation reaction and 

 advocated by d'Herelle in favour of the unicity of the bacteriophage, are of no 

 value, because they are vitiated, as can be easily demonstrated, by the 

 presence in the bacteriophage of bacterial dissolution products which have lost 

 their specificity and play therefore the role of common antigen between 

 different lytic agents. 



25 



