CULTIVATION OF TRYPANOSOMES. 683 



centrosome near the nucleus near the center of the para- ( 



site. The following trypanosomes are found in fish: 

 T. colitis, T. carassii, T. remakii, T. solew, T. borrellii; 

 the following in birds: T. avium, T. eberthii. T. balbianii 

 occurs in oysters, T. rotatorium in frogs. 



Between various animals and the different try- immunity, 

 panosomes a number of examples of natural im- 

 munity are known. The extent to which man is 

 susceptible to sleeping sickness is not known, but 

 since the disease may occur in Europeans as well 

 as in native Africans, it is probable that suscepti- 

 bility is general. Laveran and Mesnil state that 

 sheep, deer and cattle which have recovered from 

 nagana have an active immunity to the disease, 

 and it is thought that the immunity of some ani- 

 mals (e. g., cow) may be increased by injecting 

 infected blood. Koch, and also Schilling, have at- 

 tempted to render trypanosomas suitable for vacci- 

 nation by passing them through asses, and a cer- 

 tain degree of success was reported. The serums 

 of actively immunized animals do not exert a pro- 

 nounced protective or curative action, although 

 they may in some instances prolong the incubation 

 period. Human serum has a certain protective 

 and curative power for rats and mice which have 

 been inoculated with the parasite of nagana. In 

 some instances immune and normal serums kill 

 trypanosomes, as shown by rapid loss of mobility. 



A most interesting bit of experimental therapy 



is that of Ehrlich and Sachs in curing and pro- J 

 tecting mice against mal de caderas by injecting 

 and feeding "trypanroth," a synthetic dye. The 

 dye was less efficient in experimental nagana and 

 in trypanosomatic infections of rats, guinea-pigs 

 and dogs. The immunity and cure established in 



