258 THE BACTERIOPHAGE AND ITS BEHAVIOR 



For the first two strains, both bright yellow, she found in smears, 

 along with the fine bacilli, some long, tortuous filaments, but all were 

 motile and were Gram-positive. With the canary yellow strain growth 

 was luxuriant and spreading, extending rapidly over the agar. This 

 culture was formed of minute bacilli only slightly motile. All of the 

 organisms were alike: they were Gram-positive. With all three strains, 

 the pigment was soluble in alcohol. 



The three chromogenic strains were agglutinated by the sera of rabbits 

 prepared by injections of cultures of proteus Xig. With one of the 

 two bright yellow strains agglutination occurred in a dilution of 1 : 1600, 

 with the other strain of this type and with the canary yellow strain the 

 titre was only 1:200. Fejgin prepared rabbits by injections of these 

 three strains. Each of the three sera agglutinated the original proteus 

 Xi9 strain to a titre of 1:3200. The antigenic power, therefore, re- 

 mained intact although agglutinability was strongly diminished, at least 

 for two of the three strains. In any case these interesting experiments 

 indicate that there are actually mutant forms of B. proteus. 



Fejgin had previously isolated different mutant forms from guinea- 

 pigs infected by injections of proteus Xig. With these strains positive 

 serological reactions were obtained with the sera of rabbits prepared by 

 injections of the mutant strains obtained in vitro through the action of 

 the bacteriophage. The Castellani reaction demonstrated an almost 

 complete identity for the mutants produced in vivo and those obtained 

 in vitro. 



In agreement with this author we must conclude that through the 

 action of the bacteriophage abrupt mutations take place and that for 

 B. proteus JYig these mutations are stable and heritable. 



11. The bacillus of swine fever 



A bacteriophage virulent for this organism has been isolated by 

 Burgers and Bachmann^^' from an old, naturally mixed culture. They 

 have observed plaques on agar but the bacteriophage was lost in the 

 course of a series of passages. 



12. B. diphtheriae (Conjnehacterium diphtheriae) 



I have isolated two races of the bacteriophage, virulent solely for 

 atoxic strains of this bacillus, from the excreta of two horses immunized 

 by the injection of cidtures of diphtheria bacilli.^'^ 



Blair^" has isolated races of the bacteriophage virulent for Coryne- 

 haderium diphtheriae by different methods. He gave a guinea-pig an 



