664 TRYPANOSOMIASIS 



was suggested that these cases were on the way to develop sleep- 

 ing sickness. A very important observation was that while in 

 sleeping sickness areas a large proportion of the native popula- 

 tion harboured trypanosomes, this was not the case where sleep- 

 ing 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 trypanosomes, 

 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 trypanosome fever and sleeping sick- 

 ness 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 trypanosome 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. 

 Continued observation of prolonged cases of trypanosome 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. There is now practi- 

 cally no doubt that the two conditions are etiologically identical. 

 The best authorities are agreed that morphologically no difference 

 between the Tr. gambiense and the Tr. ugandense can be 

 recognised, and from considerations of priority the former term is 

 now alone employed. 



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 

 possible that both phenomena occur, that not every infection 

 results in multiplication of the parasite in the body of the 

 victim, and that in certain cases where multiplication does occur 

 a resistance is developed which enables the body to kill the 

 parasites. The occurrence of the mononuclear reaction is here 

 significant; it has been suggested that, when this resistance is 

 weak, the organism gains entrance to the spinal canal, and that 

 then sleeping sickness results. 



The whole of the recent work on the disease is of the highest 

 interest and importance. The strongest evidence may be said 

 to exist that the Tr. gambiense is the cause of sleeping 

 sickness, and action taken on this supposition has had a very 

 important effect in checking the ravages of the disease in Uganda, 

 where the natives have been deported from the fly areas, and the 

 brushwood in which the insects lodge has been cut down in the 

 neighbourhood of ferries. 



