SEROLOGICAL METHODS 



viii,7-17 



in this protocol note the first tube in which complete hemolysis occurs. This denotes 

 the end of the anticomplementary action of the antigen. In tlie final test do not use 

 more than one-third of the amount of the antigen which was found to be anticomple- 

 mentary. Example: If 0.5 ml. of the antigen were found to be anticomplementary, do 

 not use more than 0.17 nd. of this bacterial suspension in the final test. It is to be cm- 



TABLE 5 



TITR.A.TION OF ANTIGEN — WITH RESULTS IN A TYPICAL INSTANCE 



phasized again that the amounts set down in Table 5 are arbitrarily chosen. A different 

 series of amounts might be found more suitable for different reagents. There should 

 be no hemolysis in tubes 7 and 8 showing that the antigen alone does not lake the red 

 cells. In the third series, tubes 9 to 14, absence of hemolysis denotes fixation or binding 

 of the complement. The last tube in this series showing complete absence of hemolysis 

 indicates tlie smallest amount of the antigen which will fix complement in the presence 

 of the constant amount of its antiserum used in tliis titration. The fixing power of 

 the antigen should be at least 10 times as great as its anticomplementary action. 

 The titration of the antigen should be made whenever a new bacterial suspension 

 is prepared, or at intervals of 3 to 4 weeks if old saspensions are kept on hand. 



