BACTERIOLYSINS AND H&MOLYSINS 129 



corresponding bacterium to this we get the con- 

 dition shown in A II, in which all the bacterial 

 receptors are occupied with immune bodies, or 

 more accurately, with immune bodies which on 

 their part are loaded with bacteriolytic comple- 

 ment c. In the case here presented let us say that 

 it requires the occupation of all of the receptors 

 with complemented interbodies to cause the death 

 of the bacterium. 



If now to an equivalent mixture of comple- 

 ment and inter-body we add an excess of inter-body, 

 it will be possible for only a part of the inter-body to 

 be loaded with complement, leaving a portion of 

 the inter-body uncomplemented. On adding the 

 corresponding bacteria a number of conditions may 

 result; the affinity of the inter-body for the bac- 

 terial receptor may, as a result of the loading with 

 complement, (i) remain unchanged, (2) it may 

 thereby be increased, or (3) be diminished. 



In the figure, B II shows the condition of in- 

 creased affinity. Of the six inter-bodies only those 

 combine with the bacterium which have become 

 laden with complement. In this case, therefore, 

 the excess of inter-bodies will have no influence on 

 the bactericidal effect. The condition is really the 

 same as A II, except that free inter-body is also 

 present. 



C II shows the condition of unchanged affinity. 

 In this case, if we add the bacterium to the mixture 



