70 COLLECTED STUDIES IN IMMUNITY. 



reactivated by horse serum were unchanged (0.35), but that it required 

 considerably more immune body when goat serum was used for 

 reactivation than it had before, namely, 0.1 cc. This corresponds 

 to a ratio of 3.5 : 1 as compared to the former ratio of 14 : 1. This 

 shows that a constant ratio does not as a matter of fact exist. We 

 must rather assume, as we did for a normal hsemolytic serum, that 

 two entirely independent immune bodies, A and B, are present in 

 the immune serum and that these differ in the ratio of their quan- 

 tities and in the manner in w r hich they are reactivated. The amount 

 of immune body A contained in the immune serum has remained 

 constant, while B after a short time has considerably decreased 

 (to one quarter). This divergence would in fact indicate that the 

 two immune bodies are formed independently of each other. 



We have thus demonstrated that in the phenomenon observed 

 by Bordet not a single immune body, but two different ones, come 

 into play, one of which is related to a complement found only in 

 guinea-pig serum, while the other is related to a complement found 

 in rabbit serum. Through this demonstration Bordet's objection 

 loses all its force and his experiment becomes in fact a new argu- 

 ment for our theory. 



The occurrence of different immune bodies in a hsemolytic serum 

 obtained by immunizing with red blood-cells is not at all surprising 

 in view of our experiments on isolysins described in our third com- 

 munication. We have obtained a whole series of different isolysins 

 by injecting goats with goat blood. At present they number twelve. 

 In the red blood-cells not merely a single group but a large number 

 of different groups must be considered, which, provided there are 

 fitting receptors, can produce a corresponding series of immune 

 bodies. All of these immune bodies again w y ill be anchored by the 

 blood-cells employed in immunization. We may assume that when 

 an animal species A is immunized with blood-cells of species B a 

 hsemolytic serum will be produced which contains a great host of 

 immune bodies. These immune bodies in their entirety are anchored 

 by the blood-cells of species A. 



We are convinced that the duality found by us in the two cases 

 examined is much below the actuality, and that thorough, though 

 to be sure arduous, studies w r ill succeed in discovering a multiplicity 

 heretofore unexpected. For the present, however, this duality of 

 the immune body should suffice to controvert the objections made 

 by Bordet from the Unitarian standpoint. 



