BACTERIOPHAGOUS ANTISERUM 143 



second part of this work, the role which the bacteriophage plays 

 in immunity, and it is evident that the experimental results in 

 immunological investigation will be entirely different if the bac- 

 terial strain employed is, or is not, contaminated by the bacterio- 

 phage; whether it is a resistant strain or a normal strain. 



In a word, the idea of the existence of the bacteriophage im- 

 poses the obligation of always verifying the bacterial cultures 

 with a view to determining that they are, not simply pure, but 

 ultrapure; and this under penalty of obtaining entirely false ex- 

 perimental results as a result of the possible presence of the 

 bacteriophage. 



