TRYPANOSOMA OF SLEEPING SICKNESS 561 



macronucleus ; there also occurred rosettes, consisting of from 

 four to twenty individuals attached by their posterior extremities. 

 Oval forms were also observed. It was found that monkeys 

 could not be inoculated with the trypanosomes from the stomach 

 of the fly, and this observation corresponds with what Bruce 

 found to be true of the trypanosome of nagana in glossina 

 morsitans. 



Early in the Uganda investigations the question arose as to 

 whether the trypanosoma of sleeping sickness was different from 

 Tr. gambiense. This was forced on the inquirers by the fact 

 that a very large proportion of the natives in the sleeping 

 sickness area were found to harbour trypanosomes in their 

 blood, although not apparently suffering from the disease. 

 Several cases were carefully examined in which trypanosomes 

 were constantly present in the blood, but in which the patients 

 from time to time suffered from fever, and during these pyrexial 

 periods trypanosomes were found in the cerebro- spinal fluid. 

 It was suggested that these cases were on the way to develop 

 sleeping sickness. A very important observation was that 

 while in sleeping sickness areas a large proportion of the native 

 population harboured trypanosomes, this was not the case 

 where sleeping sickness did not occur. Further, it was found 

 that trypanosomes from the cerebro -spinal fluid of sleeping 

 sickness cases and from the blood of persons harbouring try- 

 panosomes, but not suffering from disease symptoms, gave rise 

 in monkeys to the same group of chronic effects which resembled 

 the last stages of the disease in man. These facts led the 

 Commissioners to incline to the idea that trypanosoma fever 

 and sleeping sickness are due to the same cause, and represent 

 different stages of the same disease. It has already been 

 pointed out that a fatal termination can occur in trypanosoma 

 fever by an acute febrile attack or from intercurrent disease, 

 and thus the terminal lethargic stage may only develop in a 

 certain proportion of cases. The view of the identity of the 

 two conditions has continued to gain ground. The best 

 authorities are agreed that morphologically no difference 

 between the two organisms can be recognised, and the con- 

 tinued observation of prolonged cases of trypanosoma fever, 

 both in Uganda by Greig and Gray and in this country 

 by Manson, has shown that sometimes the termination of a 

 case is by the onset of typical sleeping sickness. 



The prevalence of trypanosomes in the blood of apparently 

 healthy natives has raised the question of the possibility of 

 tolerance existing and of immunity being established. It is 

 36 



