352 



THE BACTERIOPHAGE AND ITS BEHAVIOR 



It is essential to state, tiiat in order to forestall the possible objection 

 that they worked with mixtures of bacteriophages, these authors puri- 

 fied their bacteriophage races by colony (plaque) isolations. Further- 

 more, all of their transfers were effected in the same manner, proceeding 

 each time from a plaque. 



Wolff and Janzen chose two races of Typho-bacteriophage (from my 

 collection) and made serial passages with B. typhosus, with B. colt, 

 and with B. dysenteriae Shiga. The virulences of these two races, as 

 revealed after the passages, were compared with their original virulences. 

 Table 40 presents their findings. 



With bacteriophage No. 1 the "virulence" character did not change. 

 Originally virulent for all three strains, it remained virulent for all three, 



TABLE 40 



VIRULENT FOR 



AFTER 

 PASSAGES 



WITH 

 B. DYSEN- 

 TERIAE 



Bacteriophage No. 1 



B. typhosus . . , 



B. coli 



B. dysenteriae. 



Bacteriophage No. 3 



B. typhosus 



B. coli 



B. 



the strain at whose expense it developed effecting no manifest modifica- 

 tion. With bacteriophage No. 3, on the contrary, the same treatment 

 resulted in a loss of virulence for B. coli and B. dysenteriae when it had 

 developed at the expense of B. typhosus, but it retained its virulence 

 intact, even that for B. typhosus, when it had multiphed at the expense of 

 B. coli or of B. dysenteriae. 



Wolff and Janzen next ascertained the virulences of the two races for 

 different strains of B. typhosus after several passages with B. typhosus 

 or B. coli. The results obtained with bacteriophage No. 3 are given in 

 table 41. 



With the No. 1 race of the Typho-bacteriophage the virulences for 

 these different strains of B. typhosus remained exactly the same, whether 

 the bacteriophage had developed at the expense of B. typhosus, B. coli 

 or the Shiga bacillus. 



