THEORIES OF IMMUNITY. 



So, also, the production of this bacteriolytic 

 property may be represented as follows : 

 Its production requires 



1. The bacterial cell (which is 



injected) . . . molecule^HH-T+X 



2. The tissue cells (from which 



the immune body is pro- 

 duced) . . . molecule=H+.HH-iN'+X 



3. The complement (present in 



fresh blood) . . molecule=i/-t-LH-X 



In this reaction the H groups of the body cell 

 molecule are satisfied by the combination with 

 the similar sets of atom groups in the bacterial 

 cell and in the complement ; they are, however, 

 required for the ordinary metabolism of the body 

 cell molecule ; they must, therefore, be repro- 

 duced or the body cell molecule will die ; being 

 reproduced, they are in excess of the require- 

 ments of the cell — are thrown off and exist in 

 the blood stream as " immune body," ready to 

 combine with fresh bacterial cells as they are in- 

 troduced, i.e., as 



H+i7+X. 



77 



