IMMUNITY. 231 



It should be borne in mind that according to this theory 

 bacteriolysis can take place only where the bacterium becomes 

 united to an amboceptor which is itself united with a comple- 

 ment. A bacterium may become united with a free ambocep- 

 tor i. e., an amboceptor which is not united with a comple- 

 ment but the bacterium in such a case does not undergo 

 bacteriolysis unless a complement subsequently becomes at- 

 tached to the amboceptor. The complement is incapable of 

 uniting directly with a bacterium; it can do this only through 

 the intervention of the amboceptor. But when the comple- 

 ment becomes linked to the bacterium by means of the am- 

 boceptor, the bacterium becomes broken up into minute gran- 

 ules and ultimately disappears. 



The bonds by which the amboceptor attaches itself to the 

 bacterium on the one hand, and to the complement on the 

 other are called haptophor groups or haptophors (h), and 

 similarly this name is given to the bonds of union of the bac- 

 teria and of the complement. The amboceptor thus has two 

 haptophors, one by means of which it attaches itself to the 

 bacterium, the cytophylic haptophor, and one by means of 

 which it attaches itself to the complement, the complemen- 

 tophylic haptophor. The bacteria probably possess each 

 many haptophors, all of the same kind i. e., haptophors 

 capable of uniting with amboceptors of the same kind but 

 for the sake of simplicity the bacterium is represented in the 

 diagram as having only one haptophor. The complement has 

 one haptophor group and one so-called toxophor group (/), and 

 it is by means of the latter group that the complement acts 

 upon the bacterium. The complement may be deprived of 

 this toxophor group, and although it is still capable of uniting 

 with the amboceptor in such a case, it can no longer cause 

 bacteriolysis. This loss of the toxophor group is caused by 

 heating, and is also occurs spontaneously in the serum on 

 standing. Bacteria subjected to the action of heated serum 



