874 IMMUNOLOGY 



solution, the suspected antibody was not present (test negative); if the 

 cells remain entire and unlysed and the supernatant clear, the suspected 

 antibody was present in the serum (test positive). From the foregoing 

 brief resume, it is obvious that this test demands careful preparation 

 and standardization of the component parts for its successful execution. 

 It differs from the nonspecific complement fixation or Wassermann test 

 widely used in syphilis only in that the test antigen is derived from the 

 immunizing organism or antigen. The test antigen for the Wassermann 

 test, on the other hand, involves the use of a lipoid extracted from 

 normal tissue, such as beef heart. 



The specific complement fixation test has been most satisfactorily 

 standardized in amoebiasis and in dourine of horses. The successful 

 cultivation of Endamoeha histolytica, the causative agent of amoebic 

 dysentery, made amoebae available in sufficient quantities to provide a 

 suitable antigen, and since the work of Craig in 1927 the complement 

 fixation test for amoebiasis has been intensively studied (see Craig, 

 1937; Meleney and Frye, 1937; Paulson and Andrews, 1938). The con- 

 sensus of opinion seems to be that the test has to be carefully carried 

 out to be dependable and that at best it can be used only as an adjunct 

 to fecal diagnosis. 



The sum total of published work through 1910 indicated that com- 

 plement-fixing antibodies could be demonstrated in various trypano- 

 somiases under controlled conditions, but there was little to indicate 

 that they could be used for diagnosis. From 1911 onward, however, 

 the test was perfected and used extensively for the diagnosis of dourine 

 caused by Trypanosoma equiperdum in horses and mules. It was stand- 

 ardized mainly through the efforts of Mohler, Eichhorn, and Buck 

 (1913), E. A. Watson (1920), who used an aqueous antigen; and 

 Dahmen (1922), who used both aqueous and alcoholic extracts. Ac- 

 cording to Watson, the test is often positive before symptoms are ap- 

 parent and during latent stages, and in practice no animal should be 

 considered free of the disease unless negative two months after a last 

 exposure. C. M. Johnson and Kelser (1937) concluded that the test 

 is distinctly valuable in revealing active cases of Chagas's disease. 



Little success has attended workers using specific complement fixation 

 in malaria and the leishmaniases, especially kala azar, owing perhaps 

 to the low titer of serums from infected persons and the difficulty of 



