434 RESEARCH IN PROTOZOOLOGY 



mania strains and Herpetomonas strains from plants and insects. 

 In view of Noguchi's former conclusion that L. donovani and 

 L. infantum were identical, it is worthy of note that in the present 

 work, the two showed marked differences. 



An interesting use of serological tests was made by Adler 

 and Theodor (1926) who tried to identify by cross agglutination 

 tests, a protozoon isolated from a vertebrate host, with stages 

 found in invertebrate hosts captured in nature. According to 

 them L. tropica and H. papatasii are identical. 



There has been comparatively little work done on the sero- 

 logical reactions among the trypanosomes, mainly because interest 

 was absorbed in other types of tests (i.e., cross immunity tests). 

 Moreover, at first, they were considered to be only genus-specific, 

 but their efficiency might well be reexamined in light of the recent 

 tendency of authorities, like Wenyon (1926), to combine so many 

 of the formerly recognized species. For example. Mattes (1912), 

 using agglutination tests with T. congolense, T. hriicei, T. equiper- 

 dum and T. gamhiense, found differences in titre between homo- 

 logous, as compared to heterologous, antiserums and test antigens. 

 Levaditi and Mutermilch (1910^), using the phenomenon of 

 "attachment" (initial stage of phagocytosis), differentiated T. 

 brucei, T. togolense (a strain of T. brucei), T. dimorphon (partly 

 T. congolense) and T. gamhiense. Others used in vitro trypanolysis 

 (see previous citations in section on Trypanosomiasis). Robin- 

 son (1926), using complement fixation tests, found that the 

 serums of animals infected with T. congolense reacted with the 

 homologous test antigen, but not with T. equiperdiim, whereas a 

 group reaction existed between T. brucei and T. equiperdiim. 



The serological reactions considered in this chapter are not the 

 only ones that have been used in classification. Cross immunity 

 after recovery from infection with the trypanosomes, leishmanias 

 and piroplasms has been extensively used. Cross immunity after 

 cure with drugs has been used to differentiate strains of try- 

 panosomes, but is too delicate to be of much use in classifica- 

 tion. Thus, by incompletely curing a mouse of trypanosomiasis 

 twenty times, Ritz (1914) obtained seventeen immunologically 

 different relapse strains which could be sharply differentiated by 

 cross immunity tests. It is obvious that so delicate a test could 

 not be used as a criterion for species. This, however, brings up a 

 seeming contradiction which is of tremendous interest immuno- 



