534 THE BACTERIOPHAGE 



The results of Prausnitz/ who claims to have observed the adaptation of phage to 

 phenol, HgCl., and to immune serum, could be confirmed by Munter and Rasch- 

 only so long as they used the strain of bacteria and the phage sent to them by Praus- 

 nitz. In all other instances their attempts to demonstrate the adaptation of phage 

 have been unsuccessful. They explain the positive findings of Prausnitz as due to 

 the lysogenic character of the strain of B. dysenteriae used, and not to adaptation of 

 the phage. 



The adaptation of phage to gradually increasing hydrogen-ion concentration in 

 the experiments of Asheshov^ was successful, according to the author himself, with 

 one sample of phage only, and even in this instance the activity of the phage dimin- 

 ished rapidly during the course of the experiment. It is quite evident that in these ex- 

 periments persistence of traces of phage at a high hydrogen-ion concentration was 

 due not to the "adaptation" of the phage, but to the presence of a small number of 

 bacteria capable of withstanding the acidity of the medium and thus permitting a 

 limited regeneration of phage. 



UNICITY (universality) OF BACTERIOPHAGE 



Quite apart from the indicated possibility of errors in the interpretation of results 

 obtained by these authors, the significance of their findings may also be questioned 

 because the increase in tolerance of the phage, observed by them after adaptation, was 

 usually so small as to be negligible. This is particularly significant in view of their 

 own admissions of the great variability in the behavior of any given sample of phage, 

 when tested at different times.'' 



In the opinion of others, on the contrary, differences in response of various 

 phages to environmental conditions appear to be relatively constant and immu- 

 table. Many authors have used these individual characteristics of different phages 

 as a means of identification and even separation of individual phages out of mixtures.s 

 That these differences are essential and not due to minor effects of variability has 

 been demonstrated not only with respect to resistance to chemical agents,'' to changes 



' d'Herelle, F. : The Bacteriophage and Its Behavior, pp. 354-55. 1926; Prausnitz, C: Centralhl. 

 f. BakterioL, Abt. I, Orig., Suppl., 93, 148. 1924; Prausnitz, C, and Firle, E.: ibid. 



= Munter, H., and Rasch, K.: Ztschr.f. Hyg. 11. Infektionskrankh., 105, 205. 1925. 



^ Asheshov, I. N.: Compt. rend. Sac. de blol., 87, 1343. 1922; /. hifect. Dis., 34, 536. 1924. 



■f Prausnitz, C, and Firle, E.: loc. cit.; Asheshov, I. N.: /. Infect. Dis., 34, 536. 1924; d'Herelle, 

 F.: The Bacteriophage and Its Behavior, p. 368. 1926. For instance, in discussing the attempts of dif- 

 ferent investigators to interpret differences in the behavior of different samples of phage as indicating 

 the existence of many independent and immutable phages, as opposed to D'Herelle's concept of 

 "unicity" of the Bacleriophagum intestinale, this author says: "As for variability in resistance [of 

 phages], clearly if the resistance of each race were a fixed property, this argument would deserve con- 

 sideration. But this is not what is observed. The studies of all authors who have considered this 

 question, even including the collaborators of Bruynoghe, show that from one experiment to another 

 a single bacteriophage presents considerable variations,- — differences as great as are those observed 

 between the different races" (d'Herelle, F.: The Bacteriophage and Its Behavior, p. 368. 1926). 



5 Bruynoghe, R.: Arch, internat. med. exper., i, 17. 1924; Hoder, F.: Centralhl. f. BakterioL, 

 <Jrig-, 93. 424. 1924; Reichert, F.: ibid., 91, 235. 1924. 



^ Wagemans, J.: loc. cit.; Bruynoghe, R.: Arch, internal, vied, exper., i, 17. 1924; Brutsaert, P.: 

 Arch. med. Beiges, 77, 839. 1924; Bronfenbrenner, J., and Korb, C: /. Exper. Med., 42, 821. 1925. 



