BACTERIOPHAGE AS AN ANTIGEN 395 



Insofar as the inactivation of the bacteriophage by an anti-bacterio- 

 phagic serum is concerned there is nothing comparable with what 

 takes place when a toxin is neutralized by an antitoxin. The following 

 points bring out, I beHeve, the complete dissimilarity of the two pheno- 

 mena. 



1. Inactivation does not occur according to definite proportions; 

 the great majority of the corpuscles are inactivated at the start, 

 and then, in order to inactivate the few corpuscles remaining, those 

 endowed with a natural sero-resistance, it is necessary to add greater 

 and greater quantities of the antiserum. 



2. Inactivation of the bacteriophage is an extremely slow process. 



3. The antiserum ''cures" secondary cultures. No one has ever 

 advanced the concept of an antitoxic serum which should cause the 

 bacterium to lose the property of elaborating an antitoxin.* 



4. Different races of the bacteriophage, virulent for a single bacterium, 

 possess markedly different antigenic properties; some apparently have 

 none, for when inoculated into an animal they fail entirely to cause the 

 appearance of an antibacteriophagic property. I do not believe that 

 anyone can recall a comparable fact observed with the toxins. 



5. Certain races of bacteriophage inoculated into an animal do not 

 lead to the formation of an homologous ''anti" property only; the 

 "anti" action is also directed against other races. We know of com- 

 parable facts in connection with the antigenic action of the bacteria, 

 but never with the toxins. 



6. An antibacteriophagic serum neutralizes a virulence of one bac- 

 teriophage and allows others to persist unimpaired. There is nothing 

 comparable to this, quite naturally, with antitoxic sera. 



7. In determining the power of inactivation of several anti-bacterio- 

 phagic sera (derived from animals prepared by inoculations of dif- 

 ferent races of the bacteriophage, but all virulent for a single bacterial 

 species) we find that some sera exert their effect upon many races of the 

 bacteriophage while with other sera the action is specific and limited 

 to the homologous race of bacteriophage. Antitoxic sera show nothing 

 comparable to this.f 



* It is indeed evident, that when the inactivation of the bacteriophage by an 

 antiserum is likened to the neutralization of a toxin by an antitoxin, it necessarily 

 follows that the bacteriophage is likened to a toxin. 



t That is, if we prepare three diphtheria antitoxins, for example, in three differ- 

 ent animals immunized respectively with three different strains of Bad. diph- 

 theriae, each of these three antitoxins may differ from the others quantitatively 

 but not qualitatively. All three manifest an activity on any diphtheria toxin 

 whatever. 



