266 THE BACTERIOPHAGE AND ITS BEHAVIOR 



This is not, however, a fixed mutation, for transplants into bouillon 

 result in the growth of the ordinary forms characteristic of mixed 

 cultures,- — isolated cocci, diplococci, chains of 4 to 5 elements, and small 

 masses. These mixed cultures strongly suggest a mixture of staphy- 

 lococci and streptococci. 



This observation suggests the following possibility: Is not the 

 "streptococcus" the result of an irreversible mutation of the staphylo- 

 coccus, a mutation brought about through the action of a bacteriophage? 



17. The enter ococcus 



A bacteriophage virulent for this organism has been isolated by Beck- 

 erich and Hauduroy^^ from the excreta of a horse. The race isolated 

 was also virulent for some strains of B. coli and for B. dysenteriae Hiss. 



18. The streptococcus {Streptococcus pyogenes) 



Piorkowski^-6 has isolated a bacteriophage virulent for this organism. 

 I have also found one in the excreta of a horse. When isolated it 

 possessed a virulence, although weak, for a strain of the streptococcus 

 of strangles. It was impossible for me to enhance the virulence of this 

 race and it was finally lost in the course of passages. McKinley,^''" 

 as well as Eichhorn, have also isolated races active for the streptococcus. 



Such are the bacteria which, up to the present time, have been recog- 

 nized as susceptible to bacteriophagy. Is the list completed? It is 

 hardly probable. 



3. Phenomena simulating bacteriophagy (pseudo-bacteriophagy) 



In finishing this chapter I may mention two phenomena reported as 

 being due to bacteriophagy, but which, as a matter of fact are entirely 

 different. 



Lemos Monteiro,'*" then Kraus and Gomez,''^^ and later Pico^^^ have 

 described as bacteriophagy the partial clearing observed in bouillon 

 cultures of B. anthracis. Upon several occasions I have observed this 

 phenomenon (while attempting to obtain a virulent bacteriophage for 

 the anthrax bacillus) and have obtained it by adding to a young bouillon 

 culture of B. anthracis a large amount of filtrate from a culture of this 

 same organism. The clearing is strictly proportional to the quantity 

 of filtrate added. If, to 10 cc. of a culture, less than a cubic centimeter 

 of filtrate is added no appreciable clearing can be detected. Further- 



