causing Disease in Man in Nyasaland,. 



217 



Eesult of the Dissection of the Infected Flies. 



Table IV. — Laboratory-bred Flies. Positive Experiments. Time, in days, 

 means the number of days which elapsed between the first infective feed 

 and the death and dissection of the fly. 



Expt. 



Time, 



days. 



Proboscis. 



Proventri- 

 cuius. 



Crop. 



Fore- 

 gut. 



Mid- 

 gut. 



Hind- 

 gut. 



Salivary 

 glands. 



2067 



42 









+ 



+ 



+ 





2067 



50 





+ + 





+ 



+ 





+ + 



2067 



51 









+ 



+ 







In Experiment 2067, 30 flies were used ; all were dissected and three 

 found infected — 10 per cent. This experiment was carefully carried out 

 from beginning to end, and yet only one fly was found with invasion of the 

 salivary glands. This one fly seems to have done all the mischief, infecting 

 one after the other a dog, monkey, antelope, and finally another monkey. 

 There is some doubt about this last monkey, as the fly died 50 days after its 

 first infective feed, and the monkey had only come into use the day before. 

 This particular fly, however, is reported not to have fed on that day, no fresh 

 blood having been found in its intestine. It may be that it attempted to 

 feed and so infected the monkey, but was unable to draw blood. If this fly 

 did not infect the last monkey, it is difficult to explain its infection, as all 

 the remaining flies were dissected on the 54th day and all found to be 

 negative. 



In Experiment 2394 none of the flies were dissected. 



Table V. — Laboratory-bred Flies. Negative Experiments. 



Expt. 



Time, 

 days. 



Proboscis. 



Proventri- 

 culus. 



Crop. 



Fore- 

 gut. 



Mid- 

 gut. 



Hind- 

 gut. 



Salivary 

 glands. 



1499 



11 





+ + 



! 



+ + 



+ 







2018 



24 





+ + 





+ + 



+ + 



+ + 





2018 



30 









+ 



+ 







2018a 



13 









+ + 



+ + 



+ 





2018a 



14 









+ + 



+ + 



+ 





2018a 



15 









+ 



+ 







2018a 



17 









+ + 



+ + 



+ 





2018a 



18 









+ + 



+ + 



+ + 





2018a 



35 









+ 



+ 







2018a 



35 









+ 



+ 







2226 



32 









+ + 



+ + 



+ 





One hundred and eighty-five flies were dissected and 11 found infected 

 — 5'9 per cent. In none was there found any development in the proboscis 

 nor invasion of the salivary glands. 



