536 THE BACTERIOPHAGE 



sometimes unrelated bacteria.' Occasionally samples of phage isolated from infected 

 animals may not act at all against the bacteria concerned in the infection, showing 

 activity for unrelated bacteria only.^ The fact that bacteriophage may thus act 

 against widely different species of bacteria indicates, according to D'Herelle, that 

 "there is but a single bacteriophage, common to both man and animals, capable by 

 adaptation of acquiring a virulence toward all bacterial species."^ Thus, under "suit- 

 able conditions of the moment," a "Shiga-bacteriophage" may be transformed into 

 a "Staphylo-bacteriophage" or into a "Pestis-bacteriophage" in just the same way as 

 by passages a "horse streptococcus" becomes a "rabbit streptococcus" or a "mouse 

 streptococcus."^ 



However, while several authors claim to have observed such a transformation 

 of phage,5 others have found that this phenomenon is by no means frequent,^ and 

 many investigators have been unable to accomplish such an adaptation of phage, 

 even to closely related species of bacteria. ^^ It has been suggested that, in such in- 

 stances in which the adaptation was apparently successful, the authors have been 

 dealing with polyvalent phages whose potential activity toward new bacterial spe- 

 cies existed from the start and merely became more pronounced with repeated pas- 

 sage in new culture, due to the gradual transformation of the latter under the in- 

 fluence of the phage.* Another explanation of the apparent adaptation lies in the pos- 

 sibility that the lytic filtrates used in these experiments were in fact mixtures of sev- 

 eral independent phages.' This point of view seems particularly suggestive in view of 

 the fact that several of the authors who apparently succeeded in securing the adapta- 

 tion of phages to new species of bacteria have noticed that the activity of these 

 phages for the original species of bacteria was greatly weakened or lost (apparently 

 through elimination of corresponding phage through the repeated dilution) during 

 the process of adaptation.'" 



' d'Herelle, F.: The Bacteriophage and Its Behavior, p. 366. 1926. 



^ Bronfenbrenner, J., Aluckenfuss, R., and Korb, C. : /. Expcr. Med., 44, 608 n. 1926; d'Herelle, 

 F.: The Bacteriophage and Its Behavior, p 508. 1926. 



■5 d'Herelle, F.: The Bacteriophage, Its Role in Immunity, p. 121. Williams & Wilkins, 1922. 

 According to Reichert {loc. cit.), this capacity of the Bacteriophagiim iniestinale to adapt itself to 

 various bacteria is due to the fact that it possesses a number of radicals which exhibit difierent lytic 

 properties. 



4 d'Herelle, F.: The Bacteriophage and Its Behavior, p. 367. 1926. 



sMcKinley, E. B.: /. Lah. b" Clin. Med., 8, 311. 1922-23; lonesco-Mihaiesti, C: J. Ex per. Med., 

 40, 317. 1924; Wollman, E., and Wollman, E.: Compt. rend. Soc. de biol., 96, 332. 1927; Appelmans, 

 R.: Arch, internat. pharm. et therap., 27, 85. 1923. 



fiOtto, R., Munter, H., and Winkler, W. F.: loc. cit. 



'Marshall, M. S.: loc. cit.; Bail, O. : loc. cit.; Matsumoto, T.: Ztschr. f. Immunitdtsforsch. u. 

 expcr. Therap., 41, i. 1924; Epstein, T., and Fejgin, B.: Com pi. rend. Soc. de biol., 95, 908. 1926. 



* Gratia, A.: op. cit., 89, 824. 1923; Seiffert, W.: op. cit., 98, 4S2. 1922. 



'Matsumoto, T.: Wien. klin. Wchnschr., 36, 759. 1923; Bail, O. : loc. cit. 



"lonesco-Mihaiesti, C: loc. cit.; Wollman, E., and Wollman, E.: loc. cit.; Appelmans, R.: loc. 

 cit.; Wolff, L. K., and Janzen, J. W.: Ann. de I'Inst. Pasteur, 37, 1064. 1923. By mixing two inde- 

 pendent phages (coli-phage and staphylococcus-phage) we have been able to imitate this phenomenon 

 of apparent adaptation of one of the phages and gradual elimination of the other, depending on the 

 species of bacteria used for successive passages with this mixed phage. 



