46 COLONEL Brtl^CE'S FURTHER REPORT. 



site rather than continuing investi^-ations upon purely clinical 

 lines. Other publications of the year 1896 worthy of notice from 

 our present point of view are a further Report by Sir Harry 

 Johnston [138] dealing with the British Central Africa Protec- 

 torate, and "The Great Rift Valley," by Dr. J. W. Gregory [139]. 

 According to Sir Harry Johnston the Tsetse-fly is already fast 

 disappearing from British Central Africa, and "the unchecked 

 increase of the negro population" should be encouraged as a 

 means of hastening its "entire extinction." Dr. Gregory described 

 how, in the Tsetse-haunted belt of forest between Witu and the 

 coast, he endeavoured to protect his camels by the Galla method 

 of raising clouds of smoke. 



With the publication in 1897 of Col. David Bruce's "Further 

 Report on the Tsetse-Fly Disease or Nagana, in Zululand " [142], 

 not only was the disease conclusively pi'oved to be due to a 

 ha^matozoon, bvit also, by means of a brilliant series of pre- 

 liminary experiments, the part played by the Tsetse in trans- 

 mitting the malady was finally established. Since the Report 

 will be found fully analysed elsewhere (.see Chapter VII., 

 Appendix A), there is no need to say more about it here. 



From this time onward the litei^ature of the Tsetse-flies con- 

 sists mainly of statements in books of travel and Government 

 Reports. These statements contain much additional information 

 as to the geographical range of the genus Glossina, but do not 

 add greatly to our knowledge in other respects. Of the further 

 contributions furnished by the year 1897, the most important is 

 that contained in Sir Harry Johnston's work entitled " British 

 Central Africa " [145], wherein several pages are devoted to the 

 Tsetse-fly. The problem raised in West Africa by the occurrence 

 of several species of Glossina was alluded to in the same 

 year by the late Miss Mary Kingsley [148], who pointed out 

 that it would be usele.ss to make a practicable road for draught 

 animals from the Gold Coast to its hinterland, " because of the 

 horse-sickness and Tsetse-fly which occur as .soon as you get into 

 the forest behind the littoral region." . In the course of remarks 

 on the Tsetse-fly in " The New Africa," by Mes.srs. Schulz and 

 Hammar [149], also published in 1897, the interesting statement 

 is made that in 1874 donkeys safely performed the journey from 

 Delagoa Bay to Lydenburg, in the Transvaal, " when that 

 country was thickly infested with flies that killed cattle, horses, 

 and even the few camels that were impoi'ted as an experiment." 

 It is admitted, howeA'er, that donkeys succumb like other animals 



