42 IMMUNE SERA. 



body is built up of a number of partial-immune 

 bodies, a point to which we have already alluded. 

 In support of this view they offer the following ex- 

 periment. On immunizing a rabbit with ox blood, 

 they obtained a serum hasmolytic not only for ox 

 blood but also for goat blood; on immunizing a 

 rabbit with goat blood they obtained a serum hasmo- 

 lytic for goat blood and ox blood.* 



According to Ehrlich's theory, then, the red cells 

 of the ox possess certain receptors which are identi- 

 cal with receptors possessed by the goat red cells. 

 From this it follows that in a single red cell there 

 are several or many groups each of which is able, 

 when it finds a fitting receptor, to take hold of a 

 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 



* We have already called attention to these exceptions 

 to the rule of specific action. 



