20 LECTURES ON IMMUNITY 



nocuous serum, the inactivated serum has regained its 

 power of haemolysing bovine erythrocytes. (The guinea- 

 pig serum has in reality a slight haemolytic action on 

 foreign erythrocytes, but in the experiment it need be 

 used in such small dosage as to provoke in itself no visible 

 haemolytic action.) 



Border., 1 who discovered this interesting phenomenon, 

 concluded from his investigations that the agglutinating 

 and haemolytic power, on erythrocytes from a rabbit, of 

 the serum from a guinea-pig which had been treated with 

 five or six injections of erythrocytes (10 c.c. of defibrinated 

 blood) of a rabbit, is due to the presence of two substances, 

 of which the one, the "immune-body," resists an elevation 

 of the temperature for thirty minutes to 55 C., whereas the 

 other, the "alexin" (Ehrlich's "complement"), is destroyed 

 at that temperature, but may be replaced by normal serum 

 from a guinea-pig or even from a rabbit. Bordet expressed 

 the opinion that the " alexin " serves as a sensibilitator, 

 and renders the erythrocytes susceptible to the " immune- 

 body," which they are supposed not to be in their natural 

 state. 



Ehrlich, 2 on the other hand, tried to demonstrate that 

 the haemolysin is a compound of the "immune-body" and 

 the alexin, which compound is partially dissociated. The 

 "immune-body" is stable at higher temperatures, the alexin 

 not. The alexin may be replaced by a similar substance, 

 an alexin contained in many normal sera. As will be seen 

 in the following pages (Chapter VIII), the added alexin is 

 really consumed in the formation of the haemolysin, and 



1 Bordet : Amun. de I'Inst. Pasteur, 12. 692 (1898). 



2 Ehrlich and Morgenroth: Berl. klin. Wochenschrift, No. I (1899). 



