TSETSE FLY DISEASE. 415 



" On account, then, of the lack of absolute proof furnislied hy 

 the last experiments, I set myself on 22d November to try to infect 

 susceptible animals with the disease by being bitten by tsetse 

 flies brought frequently to the top of the Ubombo from the low 

 country and straightway placed on the animal. 



" The greatest care was taken that the flies were caught on a 

 perfectly healthy animal, as to have allowed them to puncture 

 one already affected by the disease would naturally vitiate an 

 experiment. 



" The time which elapsed between catching the flies and placing 

 them on the animal under experiment varied from four to seven 

 hours. 



" The following experiment gives the dates, the number of flies 

 used, and the result : — 



" Exp. 225. Horse in good condition. 

 " Nov. 22. Brought up ten tsetse flies from the low country and 

 placed them on this horse. 

 „ 28. Ten fresh flies. 

 „ 30. Nine 

 "Dec. 1. Five 



2. Thirteen „ 

 4. Twenty „ 

 „ 6. Seven „ 

 „ 8. Thirty „ 

 „ 11. Eleven „ 

 „ 14. Fourteen „ 



„ 15, To-day this horse is seen to be out of sorts, his 

 temperature has risen, and his blood contains the 

 hsematozoa of fly disease." 



The temperature of this horse was 99° on 19th November, and 

 after fluctuating a good deal between 99° and 102°, rose to over 

 102° on 15th December, when the haijmatozoa were discovered in 

 his blood, and was over 104° on 17th December. 



Dr. Bruce adds — " From this case, then, and from the evidence 

 I have already brouglit forward, I consider myself justified in 

 believing that the tsetse fly in a state of nature does convey the 

 disease to susceptible animals, and the question now arises, from 

 what source does the fly obtain the living virus." 



