144 



THE METHOD OF COMPLEMENT FIXATION. 



0.15 old tuberculin is thus sufficient of its own accord to bind complement, 

 their experiment, Wassermann and Bruck found that, 



In 



This, however, in no way proves the existence of "antituberculin" in the extract of 

 tuberculous organs, as it is perfectly possible and even probable that o.i of the organ 

 extract contains 0.05 c.c. at least of tubercle bacillus substance (tuberculin) which when 

 added to o.i of tuberculin used for antigen, is sufficient to give an amount of tuberculin 

 perfectly capable, as has been seen, of binding complement by its own activity. 



In order to overcome this possibility one must work with such small 

 but at the same time maximum amounts of antigen and antibodies, that at 

 least double the quantity of each of these reagents does not, of its own 

 accord, bind complement. For tuberculin this is estimated as follows: 



Twelve-hundredths is the maximum non-binding or hemolytic dose. 

 For the complement fixation test where the object is to demonstrate anti- 

 tuberculin amboceptors, the maximum amount of antigen to be used is 

 therefore 0.06 T. or one-half of the maximum non-binding dose. 



In the same way the hemolytic dose, and the antibody containing reagent, 

 should be estimated. 



