454 ' FAMILY: TRYPANOSOMID^E 



serum killed most of the flagellates in a short time, a percentage of 1 or 2 

 surviving, whereas in dilutions of 1 in 10 only about 90 per cent, were 

 killed. With higher dilutions the number of surviving flagellates increased. 

 The inactivated serum (56° C.) had no trypanocidal action. The agglu- 

 tinin was also destroyed, a result which shows it to be thermolabile, and 

 thus different from the agglutinin which occurs in horse serum. Working 

 with serum of uninfected frogs, similar results were obtained. It thus 

 appears that the agglutinating action of the serum is no indication of 

 the power of the animal to resist infection, for not only were uninfected 

 frogs infected by injection of cultures, but superimposed fatal infections 

 were produced in already infected frogs. These results appear to be 

 analogous to those obtained by Mesnil and Blanchard (1916), who 

 proved that human sera had a marked trypanocidal action on both 

 T. gambiefise and T. hrucei [T. rJiodesiense), both of which may infect 

 human beings. 



Though serological tests may serve to distinguish strains of trypano- 

 somes, it does not follow that the trypanosomes thus differentiated are 

 true species in the zoological sense. As in the case of the immunity test 

 referred to above, different races of one and the same species may show 

 differences in serological reaction. Ponselle (1923a) has produced a certain 

 degree of immunity in mice with a vaccine of T. hrucei. A solution con- 

 sisting of dihydrogen potassium phosphate (H2KPO4) 1'8 grams, hydrogen 

 disodium phosphate (HNa2P04,2H20) 0-2 grams, and distilled water 

 100 c.c. is prepared and sterilized at 115° C. for twenty minutes. To 

 2-5 c.c. of this solution is added with sterile precautions 0*5 c.c. of 

 heart blood of a mouse at the end stage of its infection with T. hrucei. 

 After twenty-four hours at 20° C. the mixture is inoculated intra- 

 peritoneally to mice in a dose of 0"1 c.c. It was found that in four 

 or five days the serum of the mice had acquired definite agglutinating 

 properties against T. hrucei, and that in many cases after eight to 

 ten days the mice were immune to inoculations with doses of trypano- 

 somes which produced the usual rapid and fatal infections in control 

 animals. 



6. CULTURE. — The culture method, though it has been mostly 

 employed to determine infections which are not evident on microscopical 

 examination of the blood, as in the case of T. theileri of cattle and 

 T. melophagium of sheep, has also been used for purposes of identification. 

 Thus, Noller, working with cultures of Crithidia suhulata of Tahafius 

 glaucopis, claims to have proved that this is merely the insect phase of 

 Trypanosoma theileri on account of the exact similarity of the culture 

 forms of each. He also demonstrated the similarity between cultures 

 of the sheep trypanosome and the flagellate of the sheep ked {Melophagus 



