SEROLOGICAL METHODS IN THE STUDY OF PROTOZOA 429 



of this work, however, it is difficult to evaluate the correspondence 

 between the serological tests and the presence of infection be- 

 cause criteria for the latter are so uncertain. 



Just as in the complement fixation studies in trypanosomiasis, 

 the most extensive work on precipitins has been concerned with 

 attempts to devise a diagnostic test for dourine. Precipitins were 

 probably first demonstrated in trypanosomiasis by Mayer (1905) 

 with saline extracts of T. briicei after digestion for a week with 

 trypsin. Uhlenhuth and Woithe (1908) obtained positive results 

 in dogs and horses infected with T. cqtiipcrdurn but negative ones 

 in infected rabbits. The first successful work with dourine in- 

 fections, which compared favorably with complement fixation 

 tests, was reported by Winkler and Wyschelessky (1911) and 

 was confirmed by Ruppert (191 2) with test antigens prepared 

 by extracting isolated trypanosomes in from ten to twenty parts 

 saline in a shaking machine for from one to three days, cen- 

 trifuging and filtering. They used the ring test. Lanfranchi (1912) 

 reversed the usual procedure (tested for antigen instead of anti- 

 body) by mixing serums of animals infected with T. brucei or 

 T. eqidpcrdum with serums of dogs highly immunized with T. 

 brucei; although he reported favorable results, the experimental 

 details are too few to evaluate the method. 



Dahmen (1922) concluded that alcoholic extracts were superior 

 to aqueous in the precipitin test and with them he devised his so- 

 called lipoid precipitation method which he considered superior to 

 complement fixation. Fuest (1922) also concluded that Dahmen's 

 lipoid precipitation method with alcoholic extracts was more 

 sensitive than complement fixation, as manifested by these facts 

 of 1016 horses studied, 83 reacted positively in the precipitin 

 test, 73 in complement fixation ; of 56 known-infected horses, 

 53 reacted positively in the precipitin test, 40 in complement fixa- 

 tion. 



Agglutination of T. lewisi by immune rat serum was noted in 

 1900 by Laveran and Mesnil and has been repeatedly observed in 

 this and other species by many observers. Among the pathogenic 

 trypanosomes, prior to 191 1, only low titres were obtained with 

 little indication of more promising results, but thereafter it 

 was clearly demonstrated that with proper technique, agglutinins 

 of high titre could be demonstrated in animals either infected 

 or immunized. Lange {1911) found that normal serums never 



