XVIII. CONCERNING THE PLURALITY OF COMPLE- 

 MENTS OF THE SERUM. 1 



By Professor Dr. P. EHRLICH and Dr. H. SACHS. 



THE continued study of the hsemolysins of blood serum has not 

 only considerably extended our knowledge of the origin and mechan- 

 ism of the immunity reaction directed against cells, but has revealed 

 to us an unsuspected complexity of cellular metabolism to which 

 the numerous protective bodies circulating in the blood owe their 

 existence. It is probably everywhere conceded at the present day 

 that the specific cytotoxins produced through immunization consist 

 of two substances, amboceptor and complement; and we must regard 

 it as proven that the cytotoxic substances in normal serum are also 

 of complex constitution. 2 A simple alexin action, in Buchner's sense, 

 does not exist. But even within the limits of this complicated field, 

 Ehrlich and Morgenroth through their experimental work, have 

 come to a further pluralistic conception, so that the closer analysis 

 of the factors making up the cytotoxic function of a serum is enor- 

 mously complicated. Thus it has been found in immunization with 

 cells, that not merely a single kind of amboceptor is developed in 

 the blood serum, but that a large number of different types of ambo- 

 ceptors appear, which vary both in their cytophile and complemento- 

 phile groups. Furthermore, a number of facts and theoretical con- 

 siderations (discussed in detail in the Sixth Haemolysin commu- 

 nication) could be satisfactorily explained only by the assumption 

 of a plurality of complements, and were absolutely irreconcilable 

 with the Unitarian assumption of only one complement in each serum. 



After all this one might well regard the pluralistic conception 

 as well founded, and abandon all further theoretic argument along 

 this line. But Bordet, 3 the strongest supporter of the Unitarian 



1 Reprint from the Berl. klin. Wochenschr. 1902, Nos. 14 and 15. 



2 See the previous study. 



3 Bordet, Sur le mode d'action des serums cytolitiques, etc. Annales de 

 I'lnstit. Pasteur, May, 1901. 



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