64 IMMUNE SERA 



the alexin of normal serum. As already stated, the 

 group which attaches to the red blood cell possesses 

 a much stronger affinity than that which combines 

 with the alexin. This follows from the last two 

 experiments of Ehrlich before cited, in which he 

 showed that at the lower temperature, and with 

 both substances present with the blood cells, only 

 the immune body combined with the cells, while 

 the alexin remained uncombined. At the higher 

 temperature the alexin also exerted its affinity, foi 

 then the red cells combined with all the immune 

 body and with part of the alexin. We saw that 

 after a time the red cells partially dissolved, but 

 that complete solution occurred only after some 

 fresh alexin had been added. This showed that 

 although the red cells had combined with all the 

 immune body necessary for their solution, they had 

 been unable to bind all the alexin necessary. We 

 may say, therefore, that that group of the immune 

 body w r hich combines with the red cell has a 

 stronger affinity than that which combines with the 

 alexin. 



Role of the Immune Body. According to Ehrlich, 

 then, the role of the immune body consists in this, 

 that it attaches itself to the red cell on the one hand, 

 and to the complement on the other, and in this way 

 brings the digestive powers of the latter to bear 

 upon the cell, the complement possessing no affinity 

 for the red cell. Immune body and complement 



