THEORIES OF IMMUNITY. 



complement present was still free in the super- 

 natant fluid. Therefore the affinity of the im- 

 mune body for the corpuscles was greater than 

 its affinity for the complement. This last ex- 

 periment also shows that at 0° C. the immune 

 body and the complement must have existed 

 free, side by side. (Ritchie, I. c, p. 245.) 



The reactions that are supposed to take place 

 may be expressed by the following formulae: 

 Hemolysis requires for its appearance 



1. The blood cell. 



2. The immune body (in the serum of 

 the immune animal). 



3. The complement (in the serum of the 

 fresh animal). 



These may be represented as follows : 



1. The blood cell molecule=H+]N"+X 



2. The immune body " =H+i7+X 



3. Complement " =i7+L+X 



The H group of the complement binds the 

 molecule to the immune body by one of its H 

 groups, and the second H group in the immune 



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