ESTIMATION OF STRENGTH OF MENINGOCOCCUS SERUM 



Titration of a Meningococcus Serum Obtained from the Horse, 

 a. Diminishing Quantities of Antigen. 



The titer of the meningococcus serum is o.ooi c.cm. of antigen. Since i.o c.cm. of 

 antigen binds o.i complement and 0.5 c.cm. does not interfere with hemolysis, the 

 maximum dose of antigen which may be used for the trial is 0.25 c.cm. 



Inasmuch as 0.4 c.cm. of the inactivated serum binds a part of the complement, and 

 0.2 does not at all interfere with hemolysis, the maximum dose of serum to be employed 

 is o.i c.cm. 



The positive reaction must be attributed to the interaction between antigen and 

 antibody, as hardly any complement fixation takes place by using inactivated normal 

 serum with 0.25 c.cm. of antigen. That the reaction is specific is shown by hemolysis 

 occurring when the homologous antigen is substituted by a Staphylococcus extract. 



