TKYPANOSOMA RHODESIENSE 665 



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 work on the disease is of the highest interest and 

 importance. It is practically certain that the Tr. gambiense is 

 the cause of sleeping sickness, and action taken on this supposi- 

 tion has checked 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 paths and ferries. 



Trypanosoma rhodesiense. — In 1910, Stephens and Fantham 

 observed certain peculiarities in the trypanosomes derived from 

 a case of human trypanosomiasis occurring in an individual 

 who had returned to England from Rhodesia. The organisms 

 frequently presented a very blunt"* posterior extremity and the 

 trophonucleus tended to approach the kinetonucleus and in 

 certain cases to lie behind it. Another feature of the case was 

 that only Gl. morsitans, which up till then had not been sns- 



