446 THE TECHNIC OF COMPLEMENT-FIXATION REACTIONS 



Although these figures suffice for recording purposes, they are not 

 adapted, without some qualifying phrase, for rendering reports to 

 clinicians. According to the inhibition of hemolysis or the degree of 

 hemolysis in the sixth tube containing the maximum quantity of 

 serum the following scheme may be used in reporting the results : 



to 10 = strongly positive = 

 10 to 30 = moderately positive = 

 30 to 50 = slightly positive = (++) 

 50 to 80 = very weakly positive= (+) 

 80 to 90 = doubtful or delayed hemolysis =(=*=) 

 100 = negative = ( ) 



TECHNIC OF THE FOURTH METHOD 



In this method the amount of syphilis antibody in a serum is 

 measured according to the number of hemolytic doses of complement 

 absorbed or fixed with a constant amount of antigen. As previously 

 stated, any organic extract used as antigen may of itself fix a certain 

 amount of complement; a non-syphilitic serum may do the same, 

 and a mixture of the two may fix still more, though the amounts may 

 be relatively small. A peculiarity possessed by a syphilitic serum is 

 that it fixes a large amount of complement when mixed with antigen; 

 as a result, the test becomes a quantitative ancl not a qualitative reac- 

 tion. The only practical means we possess of estimating the amount 

 of complement in a fresh serum is to ascertain the hemolytic dose, 

 i. e., to find the smallest quantity of serum that is just sufficient 

 completely to lyse the test amount of sensitized corpuscles. When 

 this has been done, the quantity of complement used in the reaction 

 may be expressed in terms of hemolytic doses fixed, and not in terms 

 of the amount of fresh serum. 



When properly performed according to this method, which has 

 been modified after the technic of Browning and Mackenzie, the 

 syphilis reaction becomes quite delicate and accurate, but is more 

 complicated than the other methods, and should not be attempted 

 until one is accustomed to the simpler test and thoroughly under- 

 stands the underlying principles of the syphilis reaction and knows 

 the many sources of fallacy. The greater amount of work that it en- 

 tails and the larger quantities of complement-serum and amboceptor 

 that are required may serve as factors against its adoption as a routine 

 method. 



1. Hemolytic Amboceptor and Corpuscles. A stock dilution of 

 antisheep amboceptor is titrated according to the technic given in the 



