THEORIES OF IMMUNITY. 



In concluding his review, Ritchie brings for- 

 ward (p. 452, et seq.) the further considerations 

 that follow, and says in regard to them, in 

 substance, that in the first place it is difficult 

 to see how, granted that two substances are 

 necessary for the production of immunity (the 

 immune body and the complement), these sub- 

 stances are to meet the bacterial cell in the first 

 instance except in the body cell. Unless all 

 immune bodies are existent in the serum as w go- 

 betweens" (amboceptors) — substances of an 

 identical nature except that they are utilized for 

 the normal metabolism of the cell until needed 

 for the reactions occurring in immunity — how 

 can the bacterium when it first enters the body 

 come in contact with the immune body for which 

 it has an affinity? The receptor is in the cell 

 (as represented in the formula used to illustrate 

 the reaction) and the bacterial cell receptor must 

 also get into the tissue cell — except it be sup- 

 posed that they exist under normal conditions 

 in the blood stream. It is undoubtedly possible 

 that the immune body may exist in the blood 

 stream as the result of normal metabolism, but 

 this is the only supposition which would explain 



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