On Naff ana, or Tsetse Fly Disease. 113 



1. Animals which have been repeatedly injected with blood or 

 serum of nagana animals, such blood or serum having been previously 

 freed from living haematozoa, either by nitration, heat or by allowing it 

 to stand for a week or longer, have not shown the slightest degree of 

 an acquired immunity. Eats, rabbits, and dogs have been tested in 

 this manner, but none of these animals have shown any diminution in 

 susceptibility. 



2. Animals repeatedly injected with extracts of the organs of 

 diseased animals have acquired no resistance. 



3. The blood of almost full-term foetuses, prematurely born of 

 highly diseased rabbits, has been tried, but without the slightest 

 success in prevention or cure. 



4. The guinea-pig being a comparatively resistant animal, its serum 

 has been used, but it also has no immunising action. 



5. Repeated inoculations of bile of diseased animals have been with- 

 out preventive or curative effects, although in vitro bile, which is always 

 free from haematozoa, rapidly destroys the haematozoa. Infective blood 

 mixed with sufficient bile becomes non-infective, but confers no immu- 

 nity. 



6. Previous inoculations with the haematozoon of the ordinary rat 

 (T. sanguinis) have also been valueless. 



7. Sewer rats and white rats which have been repeatedly, but unsuc- 

 cessfully, inoculated with the ordinary rat-haematozoon (T. sanguinis), 

 and have been proved to be refractory to further inoculations with this 

 haematozoon, have all contracted nagana when subsequently inocu- 

 lated, and have died in the same time as control animals treated with 

 an equal dose of infective blood. 



8. The young born of infected mothers (dog, guinea-pigs), are no 

 more resistant than those born of normal animals. 



9. As already stated, by constant transmission through different 

 species, the nagana haematozoon has shown no definite loss or gain in 

 the intensity of virulence. 



10. Of immunising sera the diphtheria antitoxin and antistrepto- 

 coccus serum have been used, but, as we expected, without the slightest 

 effect : they neither protect nor cure. 



11. Dieting. Eats have been fed, on the one hand, exclusively 

 with meat, and on the other, with green vegetables ; in neither case has 

 any increased resistance or prolongation of life resulted from this 

 alteration in diet. 



12. Excision of the lymphatic glands immediately after inoculation 

 or after they have begun to show enlargement has been of no avail. 



13. Feeding with haematozoa also conveys no immunity. 



