1910.] Transmission of Sleeving Sickness by the Tsetse Fly. 501 



Table I. — Summary of Eesults of Interrupted Feeding Experiments. 

 Laboratory-bred Glossina palpalis and Trypanosoma garnbictise. 



Experiment. 



Infected 

 animal. 



Healthy 

 animal. 



No. of 



days 

 flies fed. 



Besult. 



Remarks. 



Positive. 



Negative. 



1550 

 1316 

 1543 

 1565 

 1705 



Monkey . . . 

 Oi 



Monkey ... 

 )) ... 



Monkey ... 

 Fowl 



7 

 64 

 12 

 11 



6 



+ 





65 flies used. 

 5 to 29 flies used. 

 50 flies used. 

 30 flies used. 

 60 flies used. 



Monkey ... 

 Ox 



Monkey ... 



B. Mechanical Transmission of Trypanosoma gambiense hi/ Laboratory-Bred 

 Glossina palpalis, with an Interval between the Feeding of the Flies on the 

 Infected and Healthy Animals. 



The following table gives a summary of the results : — 



Table II. 



Experiment. 



No. of 

 days 

 flies fed. 



No. of 

 flies fed. 



Infected 

 animal. 



Healthy 

 animal. 



Interval 

 between 

 feedings. 



Res 



Posi- 

 tive. 



ult. 



Nega- 

 tive. 



1712 



12 



50 



Monkey... 



Monkey... 









1233 



12 



14 







1 „ 







1664 



12 



50 







1 







1665 



12 



40 













1524 



11 



35 







6 „ 







1080 



12 



11 





II 



8 „ 







1801 



13 



70 







24 „ 







1802 



13 



75 







24 „ 







1803 



l.i 



120 





,» 



24 „ 







1274 



15 



7 



„ 



J, 



48 „ 







ConclvMons. 



1. The mechanical transmission of Sleeping Sickness by means of Glossina 

 palpalis can take place if the transference of the flies from the infected to the 

 healthy animal is instantaneous — that is, by interrupted feeding. 



2. This mechanical transmission does not take place if an interval of time 

 comes between the feedings. 



3. Mechanical transmission plays a much smaller part, if any, in the spread 

 of Sleeping Sickness than has been supposed. 



2 Q 2 



