396 THE BACTERIOPHAGE AND ITS BEHAVIOR 



It is only necessary to consider the experimental data which have 

 been detailed in this chapter to see the logic of these conclusions. 



And finally, recognizing that an "inactivating principle" is present 

 in an antibacteriophagic serum, the quite logical question is as to its 

 nature. It can not be a sensitizer, for it brings about its effects without 

 the intervention of alexin. Let us note in this connection that this 

 is true for aU antisera to the protobes. The anti-vaccinia sera, and 

 anti-rabies sera, for example, inactivate the corresponding protobes 

 in the same way without the intervention of alexin. This is, then, it 

 appears, a general fact applying definitely to the protobes and to pro- 

 tobes exclusively.* 



The "anti" principle which neutralizes the action of the protobes is, 

 therefore, neither an antitoxin nor a sensitizer, and since it fails to con- 

 form to these recognized immunological principles I have proposed to 

 term the active principle an antiviruHn. 



Study of the antibacteriophagic serum, — and such a study is in reahty 

 only beginning, — assumes a far greater importance in that the facts 

 disclosed will not necessarily be Umited solely to the bacteriophage, 

 but may give us some information regarding the nature of the immunity 

 to the pathogenic protobes. 



In concluding the discussion of this subject I beheve that it may 

 be well to state that for many diseases there may be some question 

 as to whether the causative agent is an ultra virus, that is, a protobe, 

 or a microbe. Scarlet fever, for example, might be included in this 

 class. But it would seem that the question may be settled readily. 

 Does the heated serumf of a convalescent, by itseK, neutrahze the 

 virus present in the blood of a patient? If the answer is in the affirm- 

 ative, the agent is a protobe and not a microbe.J With scarlet 

 fever, for example, if the serum of a convalescent neutrahzes the virus 

 the primary agent is certainly not the streptococcus, at least, not the 

 visible form of the streptococcus. If neutralization does not occur, a 

 microbe is the primary agent,^ — in this case the streptococcus. 



* This question of immunity against the ultraviruses, that is, against protobes, 

 has been treated at length in the last two chapters of the text Immunity in Natural 

 Infectious Disease, to which the reader who may be interested is referred. 



t Prausnitz has shown that the antibacteriophagic substance resists a tempera- 

 ture of 75°C. 



J One can not object that the neutralization may be exercised on a toxin, for a 

 toxin is not a virus; it does not produce a serially transmissible disease. 



