458 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; the Wassermann Reaction with Varying Amounts 

 of Patient's Serum. 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 seven different doses of serum: 0.01, 0.02, 0.04, 0.06, 

 0.08, 0.1, 0.2 c.c. In this way a means is afforded for judging of the 

 strength of the reaction, and the effect of antisyphilitic treatment is 

 readily observed. 



Fourth Method ; the Wassermann Reaction with Varying Amounts 

 of Complement. 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 mixutre of serum and extract 

 will absorb or fix more complement than the sum of the amounts absorb- 

 ed by these two substances alone. In the foregoing methods no attempt 

 has been made to measure the amount of complement absorbed by serum 

 and antigen alone, but sufficient complement 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 andThomsen have devised a technic where- 

 by it is possible to estimate the actual amounts of complement absorbed, 



