J. BRONFENBRENNER 535 



of temperature/ or to size and character of plaques,- but particularly in connection 

 with the strict serological specificity existing even among closely related phages.-^ 

 This specificity, as stated earlier, is quite characteristic for each phage and, in the 

 case of polyvalent phages, is independent of the nature of the bacterial substratum 

 used for obtaining such phages.'' The contrary conclusions of D'Herelle as to the 

 similarity of the antigenic nature of different "races" of Bacteria phagum intestinale 

 were drawn by him on the basis of the complement-fixation tests, and have been 

 shown to be due to a non-specific fixation of complement by the rabbit serum used 

 by him as a source of antibody. Sachs and Klopstock,' Sanderson,^ and Flu^ have 

 independently called attention to the fact that rabbit serum fixes complement in the 

 presence of various phages, as it does also when peptone, broth, or bacterial extracts 

 are employed as antigen. 



Moreover, it has been shown repeatedly that the secondary growth of bacteria 

 appearing after the completion of lysis of susceptible bacteria by a given bacterio- 

 phage is specifically resistant to this bacteriophage, but is often susceptible to lysis 

 by some of the closely related varieties.^ According to D'Herelle, this phenomenon 

 does not prove the plurality of phages, for he has observed a similar phenomenon 

 by using a single polyvalent phage acting on B. typhosus, B. coli, and B. dysenteriae. 

 When grown in the presence of this phage, B. typhosus gave resistants which were 

 susceptible to the lytic action of the filtrate obtained by growing B. coll or B. dysen- 

 teriae in the presence of the same phage. 



The writer has repeated these experiments, using a similar polyvalent phage, but 

 has failed to confirm the findings of D'Herelle.' 



Another characteristic differentiating various phages from one another is their 

 respective specificity or extent of activity ("virulence," in the terminology of D'- 

 Herelle). Usually, when recovered from convalescent human beings or animals, the 

 samples of phage are active exclusively or mainly against the species of bacteria con- 

 cerned in the infection. Often, however, not only recently isolated and thus poten- 

 tially mixed samples of phage, but also purified (ultra-pure) phages, act on several and 



' Osumi, S.: loc. cit.; Wagemans, J.: loc. cit.; Bruynoghe, R.: Arch, internal, med. exper., i, 17. 

 1924; Gratia, A.: Compt. rend. Soc. de biol., 89, 821. 1923. 



^Wagemans. J.: Ice. cit.; Bruynoghe, R.: Arch, internat. med. exper., i, 17. 1924; Hoder, F.: 

 loc. cit.; Okuda, S.: Arch. f. Hyg., 92, 109. 1923-24; Matsumoto, T.: Centralbl. f. Baktcriol., Orig., 

 91, 413. 1924. 



i Seiffert, W.: loc. cit.; Wagemans, J.: loc. cit.; Bruynoghe, R.: Arch, internat. med. exper., i, 

 17. 1924; Gratia, A.: loc. cit.; Bail, O., and Watanabe, T.: Wicn. klin. Wchnschr., 35, 169. 1922; 

 Bruynoghe, R., and Appelmans, R.: Compt. rend. Soc. de biol., 87, 96. 1922. 



"• Seiffert, W.: loc. cit.; Wagemans, J.: loc. cit.; Bruynoghe, R.: Arch, internal, med. exper., i, 

 17. 1924. 



5 Sachs, H., Klopstock, A., and Takenomata, N.: Klin. Wchnschr., 3, 21. 1924. 



^Sanderson, E. S.: J. Immunol., 10, 625. 1925. 



7 Flu, P. C.: Centralbl. f. Bakteriol., 97, 224. 1926. 



*Bru3Tioghe, R.: Arch, internat. med. exper., i, 17. 1924; Hoder, F.: loc. cit.; Gratia, A.: loc. 

 cit.; Matsumoto, T.: loc. cit.; Wien klin. Wchnschr., 36, 759. 1923; Bail, O.: Ztschr. f. Immunitats- 

 forsch. u. exper. Therap., Orig., 38, 57. 1923. 



» Unpublished experiments in collaboration with Muckenfuss in 1926. 



