16 IMMUNE SERA. 



the alexin remained uncombined. At the higher 

 temperature the alexin also exerted its affinity, for 

 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 which 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 affin- 

 ity for the red cell. Immune body and comple- 

 ment have no very great affinity for each other. 

 At o C. they may exist in serum side by side, and 

 they combine only at higher temperatures. 



The amount of immune body which combines 

 with the red cells may vary greatly, as the experi- 

 ments of Bordet and of Ehrlich clearly show. Some 

 red cells combine with only just enough immune 

 body to effect their solution. Others are able to so 

 saturate themselves with immune body that they 



