XVIIl] HISTORY 305 



ugandense, as Castellani considered that it was distinct from 

 T. gambiense Button. Subsequently Bruce and Nabarro found 

 trypanosomes in the cerebro-spinal fluid of practically all cases, 

 but were puzzled by the fact that some natives shewed these 

 parasites in their blood without presenting any very serious 

 symptoms. Later, when patients suffering from trypanosome 

 fever were kept under observation, it was found that this 

 was merely an early symptom of sleeping sickness and that in 

 the later stages the parasites appear in the cerebro-spinal fluid 

 and the characteristic lethargic symptoms follow. The iden- 

 tity of T. gambiense and T. ugandense was also established by 

 means of inoculating animals with the two strains, when they 

 were found to produce exactly similar effects. 



In 1903, Bruce and Nabarro shewed that sleeping sickness 

 was carried by means of Glossina paipalis, and the manner in 

 which they arrived at this discovery is of some interest. When 

 it was proved that sleeping sickness was caused by the presence 

 of a trypanosome in the blood, Bruce at once considered the 

 possibility of the transmitting agent being a tsetse-fly as he 

 had already proved to be the case in Zululand for another try- 

 panosome disease, Nagana. Large numbers of tsetse-flies were 

 found in the neighbourhood of Entebbe, but these belonged 

 to a different species, Glossina paipalis, from the tsetse-fly of 

 Zululand, G. pallidipes. The Commission, however, decided to 

 find out the distribution of Glossina paipalis, in order to deter- 

 mine whether it bore any relation to that of sleeping sickness, 

 and with this object tsetse-flies were collected from all parts of 

 Uganda together with any records of the disease. When all 

 the information was put together the evidence in favour of the 

 tsetse theory of transmission was almost overwhelming, for in 

 every locality from which sleeping sickness had been recorded 

 the tsetse-fly was found to be present. 



The final proof of this theory was obtained by feeding 

 tsetse-flies on patients suffering from sleeping sickness, and 

 subsequently, after various intervals, on healthy monkeys. 

 The latter were found to become infected with T. gambiense, 

 thus proving that Glossina paipalis can convey trypanosomes 

 from sleeping sickness patients to healthy individuals. It was 



H. B. F. 20 



