Transmission of Sleeping Sickness by the Tsetse Fly. 



499 



preventing the chance of the infection being transmitted by flies in wliich the 

 development of Trypanosoma gaiuhiensc had taken place. 



A. Mechanical Transmission of Trypanosoma gambiense. Interrupted Feeding. 



In interrupted feeding, the cage containing the flies is first placed on the 

 infected animal for some little time, then suddenly transferred to the healthy 

 animal, and so backwards and forwards for 10 to 15 minutes. This is meant 

 to imitate the conditions in Nature, when sick and healthy natives are sitting 

 together on the Lake-shore, and the tsetse flies are continually flitting from 

 one to the other. 



Experiment 1550. Interrupted Feeding. 



Laboratoiy-bred Glossina palpalis and Trypanosoma gamhieiise. From infected to 



healthy monkey. 



Date. 



Day. 



Procedure. 



Remarks. 



1909, 

 Aug. 30—31 



Sept. 1 



„ 2 



„ 3 



4 



„ 5 



6 



Cage changed from infected 

 I to non-infected monkey 

 \ every 15 seconds. This 

 continued for 10 minutes 

 each day. 



65 flies used. 



Sept. 6, healthy monkey 

 sliowed Trypanosoma 

 gambiense. 



Result. — Positive. The infection probably took place on the first day (August 30), as 

 it usually takes seven days before the trypanosomes appear in the blood. 



Experiment 1316. Interrupted Feeding. 



Laboratory-bred Glossina palpalis and Trypanosoma gambiense. Infected ox to 



healthy monkey. 



The two oxen used for this experiment were known to be infective, as their blood, 

 when injected into a clean monkey, gave rise to a gambiense infection. 



Date. 



Day. 



Flies fed on infected oxen 

 and healthy monkey. 



Alternate 

 feeds. 



Eemarks. 



1909. 

 July 15—16 



„ 17—31 

 Aug. 1 



„ 2— Sept. 7... 



1 



2—16 



17 

 18—54 





20 

 20 

 20 

 20 



5 flies used. 

 July 16, 4 flies added. 

 Aug. 1, 20 flies added. 

 Sept. 7, 10 flies left; 



dissected; all negative. 



Monkey remained 



healthy. 



Result. — Negative. The trypanosomes are usually very few and far between in the 

 blood of cattle, which probably accounts for the negative result. 



VOL. LXXXII. — B. 2 Q 



