FIXATION OF COMPLEMENT 99 



In the comparative tests with the cholesterinized 

 extract of human heart, of thirty-three cases there 

 were six in the first group, that is, equally positive 

 with the two extracts; four in the second group, in 

 which the cholesterinized human heart-extract gave a 

 distinctly stronger reaction than the syphilitic liver 

 antigen; sixteen in the third group, in which both 

 antigens gave negative results; seven in the fourth 

 group, which were negative with the syphilitic anti- 

 gen but positive with the cholesterinized heart-extract. 



In the first series, therefore, the results with the 

 two antigens disagreed in 42 out of 100 cases, and in 

 the second series in 11 out of 33 cases. We see from 

 these results that the cholesterinized extracts appar- 

 ently give a more " delicate " reaction than the ex- 

 tract of syphilitic liver, but we also find that many 

 weakly positive results are obtained by them in non- 

 syphilitic cases. This fact alone is quite sufficient, in 

 our opinion, to offset any advantage in delicacy of the 

 reaction obtained with the use of cholesterinized ex- 

 tracts. We feel that just as high a percentage of 

 positive results is obtained in known or clinically ap- 

 parent syphilitics with the syphilitic liver-extract as is 

 obtained with the cholesterinized antigens, and the 

 former do not give positive results in non-syphilitic 

 cases. The success in detecting mild degrees of syphi- 

 litic infection is doubtless due in part to the use of one 



