68 COLLECTED STUDIES IN IMMUNITY. 



different species act directly injuriously on the sensitized blood-cells. 

 Against each of these alexins an antialexin exists which protects 

 the sensitized blood-cells against just this particular alexin. 



It cannot be denied that at first sight this experiment appears 

 to speak strongly in favor of Bordet's theory. If one assumes, as 

 Bordet of course does, that in the immune serum produced by him, 

 one single immune body comes into play, then since this can be reac- 

 tivated as well by rabbit serum as by guinea-pig serum, the com- 

 plement contained in these two species of sera must, according to 

 our theory, possess the same haptophore group. If this were the 

 case, however, the same anticomplement should protect against both 

 complements, and this it does not do. 



We have therefore subjected Bordet's experiment to an exact 

 reexamination and have been able to determine that an exhaustive 

 quantitative analysis presents the experiment in an entirely different 

 light. A hsemolytic serum was produced by treating guinea-pigs 

 with rabbit blood. A preliminary trial of this serum showed that 

 when inactivated it could be reactivated in large amounts as well 

 by guinea-pig serum as by rabbit serum. The anticomplement, 

 derived from other rabbits by treatment with normal guinea-pig 

 serum, 1 was able in the inactive state to completely inhibit the reacti- 

 vation with guinea-pig serum, although the same anticomplement 

 serum in its active state reactivated the inactive immune body. 



We next proceeded to examine these facts quantitatively and 

 found that the simple solvent dose of the serum for 0.5 cc. of a 5% 

 rabbit-blood mixture amounted to 0.075 cc. Then we tried von 

 Dungern's experiment (loc. cit.) to increase this action, by adding 

 to the native immune serum normal guinea-pig serum in amounts so 

 small that they did not themselves exert any solvent action. We 

 found that the full solvent dose had thus been decreased to 0.025 cc. 

 This proved, as in von Dungern's case, that in the immunization a 

 large excess of free immune body was present which could not nearly 

 be satisfied by the amount of complement normally present. Now 

 we could expect that this same increase in power would be effected 

 bv the addition of rabbit serum, but we found instead that rabbit 

 serum even in large amounts did not produce any increase whatever. 



According to Bordet's view such a deviation is absolutely incom- 

 prehensible, and this led us to pursue the case further. We first 



1 In contrast to Bordet we chose normal guinea-pig serum for immunization 

 in order to avoid the disturbing action of an immune body. 



