22 IMMUNE SERA 



twentieth injection of a series. Park and Atkinson 

 for example, injected a fresh horse with one litre 

 of a toxin neutralized ij times for guinea pigs. 

 At the end of a week the horse had produced a serum 

 containing 60 units per cc. When the toxin was 

 neutralized 6 fold no antitoxin whatever was pro- 

 duced. 



Experimental Evidence for Ehrlich's Theory. 

 According to Ehrlich, then, the formation of specific 

 antibodies must proceed in three stages: 



1. The binding of the haptophore group to the 

 receptor. 



2. The increased production of the receptors 

 following this binding. 



3. The thrusting-off of these increased receptors 

 into the blood. 



So far as the first point is concerned Wassermann l 

 showed that with tetanus, in which, as is well 

 known, all the symptoms are referable to the cen- 

 tral nervous system, tetanus toxin was bound by 

 central nervous system substance in vitro. A 

 I mixture of tetanus poison and normal central 

 nervous system was innocuous to animals, showing 

 that certain , substances present in the central 

 nervous system combine with and thus satisfy the 

 affinity of the haptophore group of the poison. 

 This of course prevents the latter from combining 

 with any cells of the organism. Organs other than 



1 Wassermann and Takaki, Berliner klin. Wochenschr., 1898. 



