'BACTERtOLYSINS AND HMMOLYSMS 63 



a little normal serum was added. The supernatant 

 clear fluid separated by the centrifuge did not dis- 

 solve sheep red cells. On the addition, however, 

 of substance sensibilatrice it dissolved them com- 

 pletely. 



From this experiment Ehrlich concludes that the 

 substance sensibilatrice possesses one combining 

 group with an intense affinity (active even at o C.), 

 for the red cell, and a second group possessing a 

 weaker affinity (one requiring a higher temperature) 

 for the alexin. 



Nomenclature. In place of the name substance 

 sensibilatrice Ehrlich first introduced the term 

 immune body; later on he called it the amboceptor, 

 to express the idea that it served as a link between 

 alexin and cell. Other names proposed for this sub- 

 stance have been substance fixatrice by Metchnikoff, 

 copula, desmon, preparator by Muller. Instead of 

 the name alexin, Ehrlich now uses the term com- 

 plement in order to express the idea that this body 

 completes the action of the immune body. 



According to Ehrlich the red blood cells possess 

 specific affinity for the immune body, but none 

 whatever for the alexin. The alexin, therefore, 

 possesses no combining group which can attach itself 

 directly to the red blood cell. It acts on these cells 

 only through an intermediary, the immune body, 

 which therefore must possess two binding groups one 

 of which attaches to the red blood cell and the other to 



