1910.] The Development of Trypanosomes in Tsetse Flies. 375 



became infected with Trypanosoma gamhiense was 27 days, the longest 

 53 days, and the average 36 days. 



Here follow the experiments, given somewhat more in detail, which gave 

 positive results : — 



Experiment 975. 



To ascertain if any development of Trypanosoma ganibiense tak.es '^\?lcq in the alimentary 

 canal of laboratory-bred Glossina palpalis. 



The following table gives the principal details of the experiment : — 



Date. 



Day 

 of experi- 

 ment. 



Procedure. 



Result. 



Remarks. 



Positive. 



Negative. 



1909. 



June 8—12 



„ 13—15 

 „ 16- 

 July 19 

 July 20—21 

 „ 22— 

 Aug. 3 



1—4 



5-7 

 8—41 



42—43 

 44—55 



Flies' fed on infected 



monkey 

 Flies starved. 

 Flies fed on healthy 



monkey, 1008 

 Flies starved. 

 Flies fed on healthy 



monkey, 1374 



+ 

 + 





16 flies used. 



Aug. 4, 12 remain- 

 ing flies killed 

 and dissected. 



Remarks. — Sixteen laboratory-bred flies were fed on infected monkeys for five days. 

 Thirty-four days after their first feed they became infective, and remained so for at least 

 49 days. On the 56th day the remaining 12 flies were dissected and examined for 

 flagellates. None were found, but the contents of the alimentary canals of the 12 flies, 

 pooled and injected into a healthy monkey, gave rise to Sleeping Sickness. 







Experiment 1549. 







Date. 



Day 

 of experi- 

 ment. 



Procedure. 



Result. 



Remarks. 



Positive. 



Negative. 



1909. 

 Aug. 23—27 



„ 28—29 

 „ 30— 

 Oct. 5 

 Oct. 6—7 



1—4 



5—6 

 7—43 



44—45 



Flies fed on heavily- 

 infected monkey 



Flies starved. 



Flies fed on healthy 

 monkey, 1617 

 Flies starved. 



+ 





50 flies used. 



Oct. 8, 20 remain- 

 ing flies dissected, 

 4 found infected. 



Remarks. — Fifty laboratory -fed flies were fed on an infected monkey daily for five days. 

 Thirty-seven days after their first feed they became infective. Twenty flies remained 

 alive on the 46th day, and on dissection four were found infected with flagellates. A drop 

 of fluid from the alimentary canals of two of these infected flies injected into a monkey 

 gave rise to Sleeping Sickness. 



