84 IMMUNE SERA 



single immune body. Ehrlich and Morgenroth, 

 therefore, claim that the immune body of a haemo- 

 lytic serum is composed of the sum of the partial 

 immune bodies which correspond to the individual 

 receptors used to excite the immunity. It may be 

 assumed, then, that not all of the combining groups 

 of a cell, be this a blood cell or a bacterium, will 

 find fitting receptors in every animal organism, 

 and that therefore not all the possible partial im- 

 mune bodies will be equally developed. In one 

 animal there may be receptors which are not pres- 

 ent in another, and in this way there might be a dif- 

 ferent variety of partial immune bodies in the two 

 animals. This would lead to the possibility of the 

 occurrence of immune bodies, for the same species 

 of blood cell or bacterium, differing from each other 

 in the partial immune bodies composing them, 

 according to the variety of animals used in prepar- 

 ing the serum. 



Metchnikoff's Views Practical Importance of 

 the Point. This view is directly opposed to that of 

 MetchnikofT and Besredka, who believe that a cer- 

 tain immune body, e.g. one specific for ox blood, 

 is always the same no matter from what animal it 

 is derived. The point is not merely theoretical, 

 but under certain circumstances of great practical 

 importance. If we believe, as Ehrlich does, that 

 the immune body differs according to the species of 

 animal from which it is derived, i.e., that it is made 



