450 THE TECHNIC OF COMPLEMENT-FIXATION REACTIONS 



reactions may be secured with about 5 per cent, of normal serums. For 

 this reason, when conducting tests for diagnostic purposes, I control the 

 cholesterinized extracts with less sensitive antigens, such as alcoholic 

 extract of syphilitic liver and acetone-insoluble lipoids. 



4. It is highly important that these extracts be carefully standardized 

 and that any serum, even if but slightly anticomplementary, be dis- 

 carded. 



5. In our experience, repeated negative reactions with satisfactory 

 cholesterinized antigens constitute the best evidences of the absence of 

 lues or testify to the recovery from a luetic infection. The treatment of 

 syphilis should be continued until the patient's serum reacts negatively 

 with alcoholic extract of syphilitic liver, and finally with cholesterinized 

 extracts. The disease cannot be regarded as cured until the reaction 

 has remained negative for a year or two at least, and treatment must not 

 be discontinued until this result is secured, or it is shown that the se- 

 rum is " Wassermann fast" and that it is impossible to secure a nega- 

 tive reaction. 



6. For the less experienced worker, or when but one antigen is being 

 used in conducting the reaction, a properly prepared alcoholic extract of 

 syphilitic liver is to be recommended. One drawback to the use of this 

 extract is the difficulty of obtaining suitable tissues for the preparation 

 of the antigen. It has been my practice for many years to preserve the 

 livers of as many still-born fetuses as I could obtain in 70 per cent, 

 alcohol, and to discard them later unless on section they showed the 

 presence of numerous spirochetes. These antigens are usually more 

 sensitive than similar extracts of normal liver, but it is important to 

 remember that not every extract is satisfactory simply because it is 

 prepared of syphilitic tissues. 



7. A suitable preparation of acetone-insoluble lipoids, prepared after 

 the method of Noguchi, constitutes a sensitive, reliable, and satisfactory 

 antigen. When properly titrated and standardized and used with inac- 

 tivated serums, this antigen may prove quite sensitive and safe. Nogu- 

 chi, in his efforts to simplify the technic of the syphilis reaction, impreg- 

 nated filter-paper with this antigen and allowed it to dry. This prepara- 

 tion is unstable and generally unsatisfactory. The antigen is best pre- 

 served in a stock bottle or in ampules, and is diluted with salt solution 

 just before being used in the test. Under these conditions we have found 

 these extracts to be quite stable. 



4. Plain alcoholic extract of human, guinea-pig, and beef heart are 

 easily prepared, are quite inexpensive, and when properly standardized 



