436 IMMUNOLOGY 



The mechanism of complement fixation may be discussed with 

 reference to plain alcoholic and cholesterolized antigens, respec- 

 tively. When one adds a plain alcoholic extract of heart muscle 

 to saline the lipoids are dispersed in the saline and to some extent 

 peptized by it. Those finely dispersed lipoid particles can adsorb 

 reagin globulin and the resulting complex will bind complement. 



When a cholesterolized alcoholic extract is added to saline, the 

 cholesterol is dispersed as fine particles more rapidly than the 

 lipoids present. The latter are, however, dispersed and adsorbed 

 by the cholesterol particles. The lipoids form more or less of a sur- 

 face film over the latter. Because of the presence of cliolesterol, 

 tliere is little or no peptization of lipoids by the saline. For this 

 reason the sensitivity of the antigen is increased. The lipoid-coated 

 particles of cholesterol adsorb syphilitic reagin from positive serum 

 and the resulting antigen-reagin complex adsorbs complement in 

 the same way that antigen-antibody complexes are known to adsorb 

 or fix complement. 



Summary. — In this chapter a large amount of material has 

 been presented in relatively few pages. It is obviously impossible 

 to summarize condensed material of this type adequately. To 

 facilitate a rapid review of the chapter the following conclusions 

 and observations may be suggestive : 



1. Syphilis was probably introduced into Europe from the 

 West Indies about 1493. It acquired its name from a Latin poem 

 written by Fracastoro in 1530. 



2. The etiological factor is Treponema pallidum discovered by 

 Schaudinn and Hoffmann in 1905. 



3. In the primary stage of syphilis, only laboratory methods 

 designed to detect the parasite are of value in diagnosis. 



4. In the secondary and later stages of the disease, the labora- 

 tory methods used as an aid in the diagnosis of syphilis are those 

 designed to detect syphilitic reagin in the blood or spinal fluid of 

 the patient. The frequency of occurrence of syphilitic reagin in 

 the various stages of syphilis is discussed. The data given are 

 based upon complement fixation and fiocculation tests. 



5. In 1905, Wassermann and Bruck became interested in the 

 bacterial complement fixation test previously discussed. They 

 modified the Bordet-GengoVi technique and undoubtedly improved 

 its efficiency. As soon as it was established that Treponema pal- 



