BA CTERIOL YSINS A ND HJEMOL YSINS 83 



by treating an animal with rabbit blood will fit only 

 to a certain group in the blood cells of rabbits; an 

 amboceptor produced by treating an animal with 

 chicken blood will fit only to parts of the red cells 

 of chickens; antibodies produced by treating an 

 animal with cholera bacilli will fit only to this 

 species of bacteria and combine only with the mem- 

 bers of it. Keeping to the well-known simile of Emil 

 Fischer, the relation is like that between lock and 

 key, each lock being fitted only by a particular key. 



To repeat for the point is of the greatest 

 importance the role of the immune body consists 

 in tying the complements of normal serum, which 

 have no affinity for the red cells or for the bacteria, 

 indirectly to these cells so that their solution and 

 digestion may be effected by the complements. 

 In other words, the immune body serves to con- 

 centrate on the corpuscular element to be dis- 

 solved all the widely distributed complement found 

 in normal serum. 



Difference between a Specific Serum and a Normal 

 One. The difference, then, between a specific 

 hsemolytic or a specific bactericidal serum and a 

 normal one consists in this that the specific serum 

 contains an immune body which is specific for a 

 certain cellular element and by means of which the 

 complement present in all normal serum can be con- 

 centrated on this element to cause its solution. We 

 shall return to this subject later. 



