THEORIES OF IMMUNITY. 



nity in this group of diseases, Ehrlich supposed 

 that in this immune body there exist two hapto- 

 phorous atom-groups of affinities — not one as 

 before — and that one of them was concerned 

 in satisfying a similar haptophorous atom-group 

 (receptor) in the blood corpuscle (of the same 

 nature as the receptor in the tissue cells in anti- 

 toxine immunity) ; and the second haptophorous 

 atom-group of affinities (receptor) is satisfied by 

 a similar group in the complement, which, as has 

 been seen, exists in the serum (blood stream?) 

 of fresh animals. 



In the complement there is supposed to exist 

 a group of affinities analogous to the toxophor- 

 ous group of the toxines — except that now it is 

 supposed to exist normally in the blood stream 

 (or cells of the body, according to Metchnikoff ), 

 and this atom-group acts as the hemolytic or 

 bacteriolytic, or, in general, the cytolytic sub- 

 stance. 



The experimental evidence upon which this 

 theory rests is as follows: If a goat be treated 

 with repeated doses of sheep's blood, there devel- 

 ops in its serum the capacity of dissolving 



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