FATE OF HyE:\IATOZOA INGESTED BY TSETSE. 277 



to the Fly Country in the early morning, catch the tlies, return 

 to the top of the Ubombo, and straightway place theux on the 

 animal under experiment. 



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

 perfectly healthy animal, as to have allowed them to puncture 

 one already affected by the disease would naturally vitiate the 

 experiment. 



" The time which elapsed between catching the flies and 

 placing them on the animal under experiment A'aried from four 

 to seven hours " (p. 15). 



Details and charts are given of two experiments, one on a 

 horse, the other on a pointer dog. The animals were allowed to 

 be bitten in the manner indicated by a varying number of flies 

 on different dates, with the result that both contracted the 

 disease. 



With reference to the outcome of the experiments the author 

 remarks: — "As these experiments have had a successful result, 

 I now consider it proved that the Tsetse-fly does commonly, in 

 a state of nature, convey the disease from animal to animal, and 

 that on the other hand there is no proof that the drinking of 

 water or the eating of soiled herbage plays any role in the 

 process" (p. 16). 



Pages 17 to 19 are devoted to " The H/ematozoon or Blood 

 Parasite of the Fly Disease." 



With refei'ence to the possibility of the existence of a resting- 

 stage, the author writes: — "We have seen by the thread 

 experiment that the hivmatozoa retained their vitality only on 

 one occasion for twenty-four hours in a dried condition, and for 

 less than seven days in a moist condition, and that after this they 

 were no longer capable of giving rise to the disease. This proves 

 that under these conditions there had been no spore or resting- 

 stage formation" (p. 18). 



As to " TJie fate of the Hsematozoa ivTien ingested hij the Tsetse- 

 fly" Col. Bruce remarks : — 



" A priori, one would think that the hpematozoa on being taken 

 into the stomach of the Tsetse-fly would soon perish on account 

 of the processes of digestion which one imagines going on. It 

 will therefore be interesting and bear directly on the subject if 

 we trace the history of the haematozoon aftei'it has been removed 

 from the blood-vessels of an affected animal and swallowed by 

 the Tsetse-fly. I therefore caused the flies to feed on an animal 

 suffering from Nagana, whose blood contained numerous ha^ma- 

 tozoa, and at hourly intervals subjected the proboscis, the cojitents 

 of the stomach, and the contents of the lower end of the intestine 

 to mici'oscopical examination. 



***** 



