1910.] I'he Development of Trypanosomes in Tsetse Flies. 371 



Remarks. — Two Imndred and eighty wild tsetse flies, fed for three days on an infected 

 monkey and then on healthy monkeys, failed to transfer the disease. The experiment 

 lasted from April 3 to June 17, and seven healthy monkeys were used. After 66 days 

 eight flies remained alive ; after 75 days only two. None of the flies which died, or were 

 killed and dissected, showed flagellates in the alimentary canal. 



Experiment 663. 



This is the experiment described at length in the ' Proceedings ' (B, vol. 81, 1909). 

 Sixty wild flies were used. One fly became infective after 18 days, and remained infective 

 75 days, when it died. A small quantity of fluid from the gut of this fly injected into a 

 healthy monkey gave rise to Sleeping Sickness. 



Experiment 676. 





Day 





Eesult. 





Date. 



of experi- 

 ment. 







Procedure. 







Remarks. 



Positive. 



Negative. 



1909. 













Apr. 6—8 



1—2 



500 Lake-shore flies 











fed on infected 

 monkey. 









9—10 



3—4 



Flies starved. 









.. 11—16 



5—10 



Flies fed on healthy 

 monkey, 696 









„ 17—18 



11—12 



Flies fed on healthy 

 monkey, 707 









„ 19—20 



13—14 



Flies fed on healthy 

 monkey, 708 









„ 21 



15 



Flies fed on healthy 

 monkey, 709 









>, 22 



16 



Flies fed on healthy 

 monkey, 710 









„ 23— 



17—3(3 



Flies fed on healthy 



+ ■ 





April 23, G7 flies 



May 12 





monkey, 711 







alive 



May 13—14 



37—38 



Flies starved. 









„ 15—16 



39—40 



Flies fetl on healthy 

 monkey, 766 



+ 







„ 17-21 



41—45 



Flies fed on healthy 

 monkey, 770 









„ 22—23 



46—47 









May 23, 22 flies 

 alive. Infected fly 

 found. 



„ 24—28 



48—52 



Flies fed on healthy 

 monkey, 901 







„ 29—30 



53—54 



Flies starTed. 









„ 31— 



55—58 



Flies fed on healthy 







June 3, 1 fly alive. 



June 3 





monkey, 941 









Remarks. — Five hundred Lake-shore tsetse flies were fed for three days on an infected 

 monkey. As none of the Ave healthy monkeys on which these flies were fed during the 

 first 16 days showed any sign of Sleeping Sickness it may be assumed that there was no 

 natu'ially-infected fly among the 500. On or about the 29th day the cage of flies became 

 infective, and remained infective up to the 47th day. On this day a dead fly was found 

 on dissection to contain flagellates, and after the death of this fly no further infection 

 took place. The injection of the infected fly failed, however, to give rise to Sleeping 

 Sickness when injected under the skin of a healthy monkey. 



VOL. LXXXII. — B. 2 G 



