220 COLLECTED STUDIES IN IMMUNITY. 



been expected, it was found that the complement as such was not 

 bound by the cell. 



The facts, however, are very readily explained if, following Ehrlich 

 and Morgenroth, we regard the amboceptor as a coupler possessing 

 two haptophore groups. Owing to a mutual combination this trans- 

 mits the action of the complement to the cell. In the case just 

 described, it follows at once that the cytophile group of the ambo- 

 ceptor possesses a very slight affinity to the cell receptor. We have 

 therefore only to assume that, in contrast to the usual behavior, the 

 amboceptor in this case, while itself unable to combine with the 

 cell, by combining with the complement takes on increased affinity 

 and so becomes capable of action. 



The significance of the variations in affinity will be discussed 

 connectedly at , a subsequent time. We shall content ourselves 

 here by pointing out that an understanding of the phenomena of 

 immunity is impossible without the assumption that certain hapto- 

 phore groups become increased or decreased in their chemical energy, 

 owing to changes in the total molecule. Chemically, such an assump- 

 tion is a matter of course. We believe that the observations described 

 above constitute additional proof that amboceptor and comple- 

 ment combine with each other. 



In the main this question has already been decided by the beau- 

 tiful investigations of M. Neisser and Wechsberg l on the deflection 

 of complement by an excess of amboceptor. The objections raised 

 against these experiments by Gruber 2 and by Metchnikoff 3 have 

 been completely met by the recent investigations of Lipstein. 4 



The case last described by us is to a certain extent an experi- 

 mentum crucis for the correctness of the views formulated by Ehrlich 

 and Morgenroth for the mechanism of hsemolysin action. We there- 

 fore believe that Bordet's sensitization theory has become unten- 

 able, and that now this question, just as that concerning the plurality 

 of complements, is definitely closed. 



SUBSEQUENT ADDITION. According to recent investigations of Dr. Sachs,, 

 guinea-pig blood-cells, which, because of treatment with inactive dog serum, 

 can no longer be dissolved by guinea-pig serum, owing to blocking by com- 



1 See page 120 et seq. 



2 Gruber, Protocoll der k.k. Gesellschaft der Aerzte in Wien, Wiener klhu 

 Wochenschr. 1901, No. 50. 



3 Metchnikoff, PImmunit6 dans les malad. infect., page 313, Paris, 1901. 



4 See page 132 et seq. 



