Nagana (Trypanosoma brucei) 245 



the animal body; the number of parasites injected and the susceptibility 

 of the animal plays an important role as to the variety of disease that 

 ensues. 



The behavior of the parasite in the animal body is noted by exami- 

 nations of the blood. 



The trypanosome is slightly attenuated when it passes through 

 heterogeneous species. 



Cultures of generation one usually infect when incubated from 6 to 

 11 days while longer incubation renders the culture avirulent. 



Cultures of higher generations will infect after 21 days of incu- 

 bation but they are avirulent after 28 days. 



The greater the generation the more marked is the variation in the 

 duration of the disease. 



Rats, mice and dogs succumb from the acute type of Nagana when 

 inoculated with trypanosomal blood. 



The trypanosome multiplies with marked rapidity and regularity in 

 rats and mice while this is not true in dogs, rabbits and guinea-pigs 

 when infected with the blood type of the parasite. 



Rats, mice and dogs suffer from the subacute variety of the disease 

 when inoculated with the in vitro strain of the trypanosome. 



Rabbits and guinea-pigs develop sub-acute and chronic Nagana 

 when infected with the artificially cultivated parasite. 



Rats and mice never develop symptoms of Nagana while dogs, rab- 

 bits and guinea-pigs usually do. 



Nagana is always fatal to rats, mice, dogs and guinea-pigs while 

 in some cases rabbits may recover, apparently spontaneously. 



Rats, mice and dogs are still susceptible to the in vitro culture 

 while only a small percentage of the rabbits and guinea-pigs become 

 infected after receiving enormous doses of this parasite. 



