428 THE TECHNIC OF COMPLEMENT-FIXATION REACTIONS 



practically every other disease liable to afflict humanity. The careful 

 work of Citron was largely instrumental in preserving the importance 

 of the reaction until a better understanding of the technic resulted in 

 improved and more careful work, with a greater respect for the real value 

 of the Wassermann reaction. 



Although the true explanation of the mechanism of complement 

 fixation in syphilis is still lacking, sufficient work has been done to show 

 that the specific nature of the reaction is dependent upon a peculiar 

 luetic antibody, and that the older belief in the specificity of antigen, in 

 so far as it insisted upon the presence of the Treponema pallidum in the 

 tissues extracted for "antigen," is largely disproved. While the method 

 cannot be said to be absolutely diagnostic of syphilis, since positive 

 reactions were had in frambesia (yaws) and leprosy, yet it is practically 

 so, especially in those countries where these two infections are unknown 

 or are relatively infrequent. 



Principles and Theories of the Syphilitic Reaction. The discovery 

 that the antigen in the Wassermann reaction is not necessarily biologically 

 specific, but may be furnished by a variety of different lipoids 1 from 

 normal or syphilitic tissues, opened up an entirely new phase of the 

 well-known theory of complement fixation, and separated the syphilitic 

 reaction from the classic Bordet-Gengou phenomenon, as based upon the 

 absorption of fixation of complement by a specific antigen and its anti- 

 body. 



As is now well known, the lipoids have always been chiefly concerned 

 in the reaction, although Wassermann and Detre and their coworkers 

 naturally ascribed the complement-fixing powers of their extracts to the 

 presence of the Treponema pallidum. It is, indeed, fortunate that pure 

 cultures of the treponema were not available at the time the original 

 studies were made, for these would naturally have been employed as 

 antigen, and as subsequent work with pallidum antigens has shown 

 complement fixation to be quite irregular and less reliable than when 

 lipoidal extracts are used, this result, coupled with the imperfect under- 

 standing and faulty technic of the earlier investigations, would probably 

 have yielded results so discouraging as to constitute weighty drawbacks 

 to the full development of the reaction. 



Notwithstanding the large amount of work that has been done in an 

 effort to ascertain the true nature of the syphilitic reaction, a correct 



term "lipoid" ("fat-like") is applied to compounds that are soluble in 

 ether, alcohol, chloroform, and benzol, but every lipoid is not soluble in all these 

 reagents. 



