FIXATION OF COMPLEMENT 



110 



manner, but these variations are usually so slight 

 that for practical purposes they can be ignored, 

 particularly if a pooled serum from several non- 

 syphilitic cases be used. The technic of titration 

 of complement is carried out as follows: Into each 

 of a series of six tubes is placed 0.2, 0.3, 0.4, 0.5, 0.6, 



Fig. 13. — Titration of complement. With the complement in each tube are placed 

 0.1 c.c. of non-syphilitic serum and 1 dose of antigen. The tubes contain gradually 

 increasing amounts of complement, ranging from 0.2 c.c. (dilution 1-10) to 0.8 c.c. 



0.7 and 0.8 c.c. of 1-10 dilution of guinea-pig serum, 

 together with 0.1 c.c. of pooled non-syphilitic serum 

 previously inactivated by heating at 56° C. for half an 

 hour, and the dose of antigen used in the test (Fig. 

 13) . Sufficient salt solution is then added to bring the 

 volume up to 2 c.c. The tubes are shaken and incu- 



