Nag ana. Tsetse Fly Disease. 597 



constantly present thereafter, and as a rule, encrease steadily np 

 to 2,000,000 or 3,000,000 per cm. In dogs they appear in 4 to 

 6 days, in cats in 5, in Guinea pigs in 5 to 7, and in horses in 7 

 days. In rabbits there were found 60,000 per cm., in dogs 

 100,000 to 300,000, and in Guinea pigs 200,000 to 500,000. In 

 one Guinea pig they did not appear until 6 weeks after inocula- 

 tion and then rapidly encreased to a fatal termination. More 

 commonly a few can be found about a week after inoculation, 

 and then they disappear for a variable period. They have been 

 found in the bone marrow when they could not be recognized in 

 the blood. Again, after subcutaneous flank inoculation in the 

 rat, they were found in the corresponding inguinal glands 1 to 3 

 days before they could be detected in the blood. After death 

 they are found most abundantly in the bone marrow and spleen, 

 but they have not been found in the intestinal contents nor urine 

 except in the case of haemorrhages or local sores. 



No soluble toxin appears to be formed, and no immunization is 

 effected by the serum. Blood serum kept several days until the 

 infusoria had died and then passed through a Berkefeld filter had 

 no apparent effect on the animal economy even in large doses. 

 Blood heated to 122 F. was equally harmless. The same is true 

 of extracts of organs and of bile from infected animals. 



Attempts to secure immunity by injecting the blood serum of 

 affected animals, after it had been sterilized by heat, filtration, 

 or standing one week in vitro proved of absolutely no effect. 

 The blood of the foetus almost at full term proved valueless, and 

 the young born of infected mothers proved fully susceptible 

 when inoculated. The serum of the Guinea-pig, which is 

 naturally somewhat resistant, proved no protection to other ani- 

 mals. Bile mixed with infecting blood in vitro, kills the trypano- 

 soma, but such blood has no protective effect on animals. Sewer 

 rats and white rats inoculated and re-inoculated with the common 

 rat trypanosoma (T. Lewisi) until immune from that organism, 

 show a full susceptibility to the trypanosoma of nagana. 



Flesh feeding and vegetable feeding have made no difference in 

 the susceptibility in the case of rats. Feeding with the hsemato- 

 zoa has produced no immunity. 



It is evident that prevention must follow the same lines as in 

 Surra, due consideration being had of the greater number of 

 genera susceptible. 



