i6o 



THE TECHNIQUE OF COMPLEMENT FIXATION. 



With 0.25 c.c. of antigen the titre of this meningococcus serum is 0.0005 c.c. of 

 serum. One could with this constant quantity of serum, and varying quantities of 

 antigen, titrate the minimum amount of antigen necessary for complement fixation. It 

 would even be preferable for such a test to employ 0.005 c - c - f the serum, as this amount 

 surely binds no complement. If such a titration is undertaken it will be found that 

 0.005 c - c - f serum with 0.05 c.c. of extract can bind o.i c.c. of complement. 



Similarly the antibodies contained in the blood serum or spinal fluid of a 

 patient can be determined by means of complement fixation. 



If it is desired to demonstrate the antigen instead of antibody, one pro- 

 ceeds as follows: 



c. Demonstration of meningococcus antigen in the spinal fluid of a patient 

 with a possible meningitis. 



