516 Colonel David Bruce [April 22, 



peculiar distribution. It is found to be restricted to the numerous 

 islands which dot the northern part of the lake, and to a narrow belt 

 of country a few miles wide skirting the shores of the lake. In no 

 part of Uganda can a single case be found more than a few miles 

 from the lake shore. This part of the country — the islands and the 

 shore of the lake — is, however, the most thickly populated, there being 

 here a population of more than 100 to the square mile. In this 

 area since 1901 the disease has raged, and many places have become 

 depopulated. 



In Busoga, where, as we saw, the disease first broke out, cases are 

 found further inland than in Uganda, but here also the same rule 

 holds good. As Mr. Cubbitt, Assistant Collector in Busoga, wrote : 

 " It would seem to be a fairly accurate statement to make, that sleep- 

 ing sickness confines itself to the territories adjoining the lake, 

 roughly speaking, from a ten to twenty mile radius of the coast.'^ 

 The Uganda Prime Minister, Apolo, also gives it as his opinion that 

 a strip along the lake shore, ten miles broad, would cover the in- 

 fected area, and that any cases found further inland are always 

 imported. The islands have been specially affected by the 

 disease. For example, the Island of Buvuma in 1901 had a popula- 

 tion of 22,000 ; in 1903 only 8000 remained alive. 



Now there must be some cause for this peculiar distribution. 

 Sleeping sickness, evidently, cannot be due to a food poison, as has 

 been suggested, since the people living outside the sleeping sickness 

 strip eat the same food, and have the same habits as those living on 

 the lake shore. 



Then again, we have found that the cause of the disease is a 

 trypanosome, a blood parasite, which is not likely to be conveyed in 

 food or clothes, or directly from man to man, but most probably must 

 be carried by some blood-sucking insect. 



This leads to the question : " Does the distribution of sleeping 

 sickness in Uganda coincide with the distribution of any particular 

 biting insect? " 



Knowing that we are dealing with a trypanosome, and knowing 

 that the trypanosome of nagana is carried in South Africa by a tsetse 

 fly (6r. morsitans), naturally we will sus^pect that the trypanosome of 

 this disease is also carried by a tsetse fly. Now on the lake shore 

 near Entebbe a tsetse fly (G.palpalis, Fig. 6) is found in large numbers. 

 This may bo the insect carrier we are in search of. The Prime 

 Minister and Regents, on being consulted, recognised the fly as one 

 known to the Muganda as the kivu, and said it was found along the 

 shores of the lake. They were supplied with several dozen nets, 

 killing bottles and boxes, and on their part promised to have the 

 distribution of this fly and of sleeping sickness worked out. The 

 bishops, missionaries, and Government officials also promised their 

 assistance. 



During June, July and August of last year some 460 collections 

 of biting flies were sent in from all parts of Uganda. As each 



