J. BRONFENBRENNER 533 



suggest that the phenomenon of neutralization of the bacteriophage by the specific 

 antiserum is analogous to neutraUzation of toxin by its homologous antitoxin, since 

 the neutralization occurs according to the law of multiple proportions, and since the 

 ingredients can be recovered in an active state by breaking the union by various 

 procedures.' 



RESISTANCE OF PHAGE TO CHEMICAL AND PHYSICAL INJURY 



In claiming an autonomous, animate nature for the Bacteria phagum intestinale, 

 its relative resistance to the deleterious influence of various chemical and physical 

 agents has been emphasized. It has been stated that in this respect bacteriophage 

 corpuscles occupy an intermediate position between that of vegetative forms and 

 that of spores of B. siibtilis.'^ It has been found, moreover, that, as with bacteria, the 

 suspension of corpuscles of bacteriophage is composed of units having different re- 

 sistance to these agents.^ For example, the resistance to heat of Bacteriophagum in- 

 testinale, according to D'Herelle, becomes greater as the corpuscles of the parasite 

 undergo "condensation" or diminution in size during the first few days following 

 their separation from bacteria. ■• Inversely, the young corpuscles of bacteriophage, 

 according to him, are more resistant to the deleterious effects of repeated freezing 

 and thawing. It seems that slight but consistent differences observed by D'Herelle 

 with respect to heat resistance of phages of diflferent age might be due to some such 

 influences as those observed by Rivers^ in freezing of phage in dilutions differing with 

 respect to the concentration of broth or of salts. This seems the more likely since, dur- 

 ing the aging, the filtrates may have undergone concentration due to evaporation. 

 In general, however, the effect of heat, of cold, and of repeated freezing and thawing 

 cannot be adduced as decisive evidence of the animate nature of phage since, apart 

 from slight quantitative differences, such inanimate substances as complement and 

 trypsin behave essentially in a similar manner.^ 



Several investigators claim that on repeated or prolonged exposure to these agents, 

 Bacteriophagum intestinale apparently develops a certain degree of tolerance, as do 

 other living organisms. However, the experimental evidence thus far presented does 

 not seem convincing. For example, D'Herelle" has found that a certain concentra- 

 tion of glycerol, if added at once, will surely inactivate the phage. If, however, the 

 same total quantity of glycerol is added to the phage in small, repeated doses, at regular 

 intervals, the phage may not be completely inactivated. The failure of complete de- 

 struction by the glycerol was not necessarily due to the increased tolerance developed 

 by the Bacteriophagum intestinale, for an analogous phenomenon takes place, for in- 

 stance, in the case of the coagulation of arsenic sulphide by acid. The amount of acid 

 used up before coagulation of arsenic sulphide takes place is greater when the acid 

 is added gradually than when all the acid is added at once. 



1 Seiffert, W.: loc. cil.; Weiss, E.: /. Immunol., 13, 301. 1927; d'Herelle, F., and Eliava, G.: 

 Compt. rend. Soc. de bioL, 84, 719. 1921. 



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



sPrausnitz, C, and Firle, E.: Ccntralbl.f. Bakleriol., Orig., 93, Beiheft, 148. 1924. 



^d'Herelle, F.: Compt. rend. Soc. de bloL, 83, 247. 1920. 



5 Rivers, T.: /. E.xpcr. Med., 45, 11. 1927. ^Rivers, T.: ibid. 



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



