BACTERIOPHAGE AS AN ANTIGEN 407 



is related to the extent of the virulences. With a poly virulent race I 

 have found that it is sufficient to give repeated injections of the bac- 

 teriophage, to see, after a variable length of time, the animals begin to 

 emaciate and finally die spontaneously. With some animals death oc- 

 curred after only 5 injections; with others a far greater number was 

 necessary — in one case 17. On the contrary, in another experiment using 

 a bacteriophage whose virulence was strictly limited to one strain of 

 StapJujlococcus albus six rabbits withstood a series of 30 injections with- 

 out showing emaciation or any other obvious disturbance. After the 

 completion of this long ''immunizing" course, four of the rabbits were 

 inoculated with variable quantities of a culture of Staphylococcus 

 aureus. Two succumbed like the controls which had received a like 

 dose. There was, then, no antiphylaxis toward this strain of the 

 staphylococcus which was refractory to the action of the univirulent 

 bacteriophage used in the preparatory injections. The remaining two 

 of the original 6 ''immunized" rabbits received weekly injections of 

 a suspension of the multivirulent Staphylo-bacteriophage. After the 

 fifth and sixth injections a developing emaciation became obvious, 

 and without any further treatment the rabbits died, one on the twelfth, 

 the other on the sixteenth day after the last injection. 



One might conclude that as regards the staphylococcus, antiphylaxis 

 is a function of the virulence range of the race of bacteriophage in- 

 jected. 



This phenomenon of antiphylaxis is of very great interest from the 

 immunological point of view, for it is entirely possible that under cer- 

 tain circumstances it may occur naturally. It represents the first 

 example of a contra-immunity, in the true sense of the word, either 

 active or passive. 



As a matter of fact it is very difficult to formulate an explanatory 

 hypothesis as to the nature of this singular phenomenon, for almost 

 any idea advanced leads to rather strange deductions. If it were 

 only a bacterial antiphylaxis, that is, a sensitization to the bacterium, 

 the many facts which will appear in the following pages would permit 

 us to understand it. But it is a toxin antiphylaxis. How is this to be 

 explained? 



If we should find that the serum of an animal showed an anti-anti- 

 toxic property it would unquestionably be because we had injected 

 an antitoxin. Following out this line of reasoning it must be that 

 a suspension of the Shiga-bacteriophage contains an antitoxin for the 

 Shiga bacillus. Whence is this antitoxin derived? If it exists in the 



