J. BRONFENBRENNER 527 



is arrested)/ and also in sterile agar.^ And finally, the rate of spread of the phage is 

 conditioned by the density of the medium.^ 



If the autonomous particulate nature of the active principle be assumed, such 

 spreading must be accounted for either by postulating that these particles possess lo- 



FiG. I. — Zone of diffusion of phage through agar at 4° C. Magnification X-S 



comotion,^ or by assuming that they secrete a diffusible enzyme. ^ But independent 

 locomotion, whether ameboid, flagellate, or ciliate, would account for the transport 

 of a given particle in only one direction at a time, whereas the active principle spreads 

 from the focus in all directions simultaneously. The secretion of the active enzyme 

 by the Bacteria phaguni intestinale has been claimed on the basis of evidence^ which 

 was later found to be inadequate.'^ 



' d'Herelle, F.: Lc Bacteriophage, "Monographies de I'lnstitut Pasteur," p. 95. 1921. 



2 von Angerer, K.: loc. cit.; Burgers, T. J., and Bachman, H.: Ztschr. f. Hyg. n. Infektions- 

 krankh., loi, 350. 1924; von Preisz, H.: Die Bakteriophagie. Jena: Gustav Fisher, 1925; Arnold, 

 L.: /. Lah. b° Clin. Med., 8, 720. 1923. 



3 Bronfenbrenner, J., and Korb, C: Proc. Soc. Exper. Biol. 6" Med., 21, 315. 1924. 

 •t Kabelik, J., and Kukula, K.: Compt. rend. Soc. de biol., 92, 1058. 1925. 



sd'Herelle, F. : Le Bacteriophage, "Monographies de I'lnstitut Pasteur," p. 95. 1921; Reichert, 

 F.: Centralbl.f.Bakteriol.,Aht.l,Ong.,gi,2^^. 1924; Marshall, M. S.: J. Infect. Dis., 37, 126. 1925. 



^d'Herelle F.: Le Bacteriophage, "Monographies de I'lnstitut Pasteur," p. 95. 1921. 



7 Bronfenbrenner, J., and Korb, C: /. Exper. Med., 42, 419. 1925; Hauduroy, P., Compt. rend. 

 Soc. de biol., 87, 964. 1922; d'Herelle, F.: The Bacteriophage and Its Behavior, p. 372. 1926. 



