296 BACTERIOLOGY 



of hemoglobin occurs. But, if after a reasonable interval 

 of time we now add to the mixture in which no hemolysis 

 has occurred, a small amount of unheated normal (not 

 immune) serum — hemolysis sets in almost at once and may 

 proceed to completion. Obviously in washing the corpuscles 

 and in heating the serum we have eliminated a factor 

 necessary to hemolysis, which factor is readily supplied by 

 a small quantity of fresh, unheated serum from a non-immune 

 animal.^ 



Equally obviously, three factors are concerned in this 

 reaction: blood corpuscles, a something in the serum of the 

 immune animal that is not ailected by heating; and a 

 something that is destroyed by the heating. 



The heat-proof body is the amboceptor of the third order 

 of Ehrlich or the "immune body" — or the "intermediary 

 body" or the "antibody" as it is severally called. The 

 heat-sensitive body is the "complement" of Ehrlich or the 

 "alexin" of Buchner and Bordet. The blood corpuscles of 

 the alien species represent the "antigen" — i. e., the body 

 which when injected into the animal being immunized 

 stimulates or generates the production of the antibodies, 

 immune bodies or amboceptors as we may choose to call them. 



We have already learned that amboceptors, or antibodies 

 of this order are conceived by Ehrlich to possess two hapto- 

 phore groups; the one having the power to unite with a 

 corresponding haptophore of the "complement," the other 

 with a corresponding side chain haptophore, or combining 

 group, of the body to be destroyed — in this case, the alien 

 blood corpuscles. When this combination is complete the 

 complement by its ferment-like action, destroys the blood 



'Has this any resemblance to the reaction known as "Pfeiffer's phe- 



