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APPLIED IMMUNOLOGY 



bated for one hour at 37° C, after which 1 c.c. of 

 1-1000 hsemolytic amboceptor and 1 c.c. of 5 per cent, 

 suspension of sheep's corpuscles are added to each 

 tube. After a further incubation of one hour, the de- 

 gree of haemolysis that has taken place in the different 

 tubes is noted. Usually complete hsemolysis has oc- 

 curred in all the tubes containing 0.5 c.c. and more of 

 diluted complement. The 0.5 c.c. tube is therefore 

 said to contain one unit of complement plus the small 

 extra amount allowed for non-specific inhibition due 

 to the presence of patient's serum and antigen. This 

 is the amount of complement to be used in the test 

 proper on that particular day. The table given below 

 will illustrate the titration of complement : 



By making two parallel experiments, it is readily 

 shown that where the complement has been previously 

 subjected to incubation with inactivated normal serum 

 and antigen, in the same doses as are used in the test 

 itself, a larger amount is required for hsemolysis than 



