FIXATION OF COMPLEMENT 319 



specific amboceptors) ; washed mammalian blood corpuscles 

 and inactivated immune serum hemolytic for such corpuscles 

 (such serum contains only hemolytic amboceptors, no 

 complement). 



The application of the principles involved in this experi- 

 ment to the solution of a number of practical problems is 

 evident. For instance, we are called upon to identify the 

 nature of an obscure infection, latent syphilis, let us say. 

 We know that the blood in such cases contains specific 

 antibodies for the antigen (excitor) of syphilis. We know 

 that the* excitor of syphilis or -important extractives of it 

 are present in the organs of syphilitic fetuses, so that the 

 antigen is easy to obtain. We know that all normal mamma- 

 lian blood contains complement. If, therefore, a mixture be 

 made of syphilitic antigen, of normal guinea-pig blood serum 

 and of the patient's blood serum, we have, providing the 

 patient be syphilitic, all the factors necessary to the union 

 of complement to antigen by the amboceptors of the blood. 

 If, after it has stood for a time, we now add to such a mixture 

 hemolytic amboceptors and red corpuscles to which such 

 amboceptors are specifically related, we get no hemolysis, 

 if the patient be syphilitic, for there is no free complement 

 left for the completion of the hemolytic system on the 

 other hand if the patient be not syphilitic, his blood will 

 contain no amboceptors capable of binding complement and 

 syphilitic antigen together, therefore, there will be free 

 complement available for the hemolytic system and hemolysis 

 results. The application of this principle to the diagnosis 

 of obscure syphilis constitutes what is generally known as 

 "The Wassermann Reaction," but it is plain that the 

 principle is susceptible of application to the identification 

 of other latent infective processes as well. In fact it is being 

 more and more used for that purpose. 



