GENUS: TRYPANOSOMA 453 



technique devised by Watson (1915 and 1920) was used. As antigen, 

 trypanosomes from heavily infected rat's blood were employed. They 

 were separated by repeated centrifugation in saline solutions from the 

 blood-cells and sera. 



The tests were carried out as in the Wassermann test for syphilis. 

 Between the years 1912 and 1919 it was applied to 40,000 horses in Canada, 

 with the result that infection was detected in many animals which clinically 

 were not suspected of suffering from dourine. By adopting the practice 

 of slaughtering all animals giving a positive reaction, the disease has not 

 only been prevented from spreading, but has been almost, if not entirely, 

 stamped out. Writing of these results, Watson (1920) points out that the 

 test is absolutely reliable from a diagnostic point of view. Clinically, 

 the incubation period of the disease may vary from two weeks to three 

 months, but from the results obtained by the serological test it became 

 apparent that the animals show signs of infection in from ten to twenty 

 days. 



Schoening (1924), using the dourine antigen, applied the test to camels 

 to be imported into the United States, and was able to demonstrate that 

 a trypanosome infection was present. The organism in these animals 

 was probably T. evansi, so that the positive result obtained proved that 

 the test is not specific for any particular species of trypanosome. It is 

 evidently what is termed a group reaction. 



Very interesting serological studies with cultures of frog trypanosomes 

 (T. rotatorium) have been made by Noller (1917). He employed the 

 flagellates grown on horse blood-agar plates, so that the cultural forms 

 could be removed with a minimal amount of admixture with the ingre- 

 dients of the culture medium. Horse serum produced sedimentation in 

 emulsions of the flagellates in a dilution of 1 in 20, and a macroscopic 

 agglutination in 1 in 40 to 1 in 80. The flagellates were all killed by the 

 undiluted serum in one hour, while in a dilution of 1 in 10 the majority 

 were killed in this time, and none were alive on the following day. With 

 horse serum inactivated by heating to 56° C, sedimentation alone was 

 obtained, and this only when the undiluted serum was used, whereas the 

 agglutination up to 1 in 80 occurred with the active serum. The inacti- 

 vated serum, moreover, had no trypanocidal action. Guinea-pig serum 

 produced sedimentation in dilutions of 1 in 10 to 1 in 20, but appeared 

 to have little agglutinating power. Its trypanocidal action, however, 

 was marked, but ceased at a dilution of about 1 in 160. As Noller remarks, 

 this result is directly the opposite of that obtained by Mendeleeff- 

 Goldberg (1913) in experiments conducted with cultures in the liquid of 

 N.N.N, medium. The serum of infected frogs (Rmia esculenta) gave sedi- 

 mentation in dilution of 1 in 80 and agglutination in 1 in 40. The undiluted 



