A GENERAL RESUME OF IMMUNITY. 511 



In a similar manner these same English authors have recently found 

 that sensitizers filter equally well whether mixed or not with a 

 strong dose of complement, which latter substance, as already men- 

 tioned, does not succeed in getting through. Ehrlich and Morgen- 

 roth, to be sure, had already made similar observations which 

 corroborate this idea that the alexin and the sensitizer exist side 

 by side in serum without being combined. I established that par- 

 ticipation of the antigen is always necessary in alexin absorption. 

 Partisans of the complementophilic group now admit that such a 

 conception is true in at least the majority of cases; they say, in 

 fact, that the energy of affinity of the complementophilic group 

 is frequently increased as a result of a union of the sensitizer 

 with the antigen. This amounts essentially to accepting the no- 

 tion, to my opinion the only important one, that fixation of alexin 

 is subsequent to the formation of the complex, antibody-antigen. 

 And what is more, the hypothesis of a complementophilic group is 

 in distinct disagreement with certain of Muir's experiments. This 

 author found that blood corpuscles that had fixed the sensitizer and 

 had been saturated with alexin could subsequently, by diffusion, 

 lose a certain amount of their sensitizer, although they retain the 

 complement, and what is. more, in this instance they lose as much 

 sensitizer as if they had not absorbed complement. Consequently 

 it is in no way through the mediation of the sensitizer that the alexin 

 attaches itself to the corpuscles; if this were the case the removal 

 of the sensitizer would necessarily imply that of the alexin, which, 

 as we have just mentioned, does not leave the corpuscles. 



It is clear that if it had been proved that the sensitizer fixes 

 the alexin without the presence of the antigen in even a single 

 instance, the idea of a complementophilic group should be accepted. 

 Ehrlich and Sachs, as we know, thought that they had found this 

 decisive example in dealing with the hemolysis of guinea-pig cor- 

 puscles by a mixture of heated bovine serum and fresh horse serum. 

 But the researches I carried out with Gay are also known, researches 

 which I have subsequently continued and in accordance with which 

 Ehrlich and Sachs' interpretation is completely inaccurate. These 

 researches have been criticised by Sachs and Bauer, which accounts 

 for my reconsideration of the subject in collaboration with Dr. 

 Oswald Streng. Streng and I were able to prove that Sachs and 



