66 PROPERTIES OF ILEMOLYTIC SERA 



experiments the existence of complementoids in heated sera, 

 these of course being derived from complements. Let us 

 suppose that the haemolytic dose of guinea-pig's complement 

 for the test 1 c.c. of suspension of corpuscles in salt solution 

 is 0-01 c.c. and that each molecule of complement gives rise 

 to a molecule of complementoid. Then when the same 

 amount of corpuscles is suspended in heated serum instead 

 of salt solution and 0-01 c.c. of fresh serum is added, there 

 will be a hundred molecules of complementoid for each com- 

 plement-molecule under this condition complete lysis does 

 not occur. This is probably an exaggerated statement of 

 the case, at least we were unable to show by combination 

 tests that there were as many complementoid molecules 

 as there were originally complement molecules. For the 

 sake of illustration let us put the proportion at fifty comple- 

 mentoid molecules and one complement molecule. We 

 have further shown that when complementoid is brought 

 into contact with red corpuscles treated with immune-body 

 only a small proportion of complementoid combines with 

 them, so that when the corpuscles are afterwards washed 

 and complement is added lysis is not interfered with. But 

 it seems possible that when a large number of molecules 

 with feebler affinity (complementoid) are actually present 

 in the mixture, the combination of those with stronger 

 affinity (complement) may be interfered with. Further- 

 more, when lysis occurs the combining affinity for comple- 

 mentoid molecules is much increased; complete lysis may 

 thus be considerably interfered with by their presence. It 

 therefore appeared reasonable to inquire what the effect 

 would be if the complementoid molecules were removed from 

 the serum. If our supposition is correct, then lysis should occur 

 much more readily, i.e. with a smaller dose of complement. 



Now the complement action may be removed from a serum 

 in two ways, viz. (a) by heating at 65 C., and (b) by bringing 

 the serum into contact with substances for which the com- 



