434 THE TECHNIC OF COMPLEMENT-FIXATION REACTIONS 



may be negative at first with the aqueous and the alcoholic extracts, 

 and as treatment is continued it may finally be negative with the 

 cholesterinized extracts. In a certain percentage of cases, especially 

 those of old infections of the central nervous system, the reaction is 

 positive with the cholesterinized extract and negative with the other 

 extracts; strong reactions of this character usually indicate syphilitic 

 infection. Occasionally a weak (10 per cent, or less, inhibition of 

 hemolysis) reaction may be had with the serum of a person who denies 

 syphilis. 



Third Method. One disadvantage of the regular Wassermann 

 technic is that it may not readily show improvement of the patient 

 while the treatment is going on. For instance, if complete fixation 

 of complement occurs with 0.2 c.c. of serum, one does not know 

 whether this is the smallest fixing dose, or whether there might be a 

 fixation even with much smaller quantities of serum. This is very 

 important in examining cases during the course of the treatment, as 

 otherwise improvement in the condition may be overlooked. Just 

 as soon, however, as the reaction with 0.2 c.c. of serum is a degree 

 less than absolutely positive, then the various steps, down to com- 

 plete negative reactions, are readily observed and recorded by the 

 usual Wassermann technic. This disadvantage may be overcome 

 by using at least six different doses of serum: 0.01, 0.02, 0.04, 0.06, 

 0.08, 0.1 c.c. In this way a means is afforded for judging of the 

 strength of the reaction, and the effect of anti-syphilitic treatment is 

 readily observed. 



Fourth Method. It has previously been pointed out that the 

 syphilis reaction is dependent upon the fact that while hemolytic 

 complement may be rendered inactive or fixed by serum alone and 

 organic extract alone, it is characteristic of syphilis that a mixture of 

 serum and extract will absorb or fix more complement than the sum of 

 the amounts absorbed by these two substances alone. In the foregoing 

 methods no attempt has been made to measure the amount of com- 

 plement absorbed by serum and antigen alone, but sufficient comple- 

 ment has been furnished to allow for this non-specific fixation, and 

 we are content to show that the serum and antigen alone do not 

 absorb enough complement to interfere with hemolysis, so that any 

 inhibition of hemolysis may be interpreted as specific complement 

 fixation. 



Browning and Mackenzie have devised a technic whereby it is 

 possible to estimate the actual amounts of complement absorbed, 



