372 



Col. Sir D. Bruce and others. 



[Apr. 18, 



Experiment 721. 



Remarks. — This experiment lasted from April 12 to July 6, a period of 85 days, and 

 remained negative throughout. On the 30th day, 12 flies out of the 50 remained alive ; on 

 the 73rd day only six flies were left. As the flies died they were dissected, but no 

 infected fly was found. 



Experiment 980. 



Remarks. — This experiment lasted 66 daj's, and remained negative. At the end 

 15 flies remained alive. These were killed and dissected. All proved negative. 



These experiments on the development of Trypanosoma gavibicnse in Lake- 

 shore or wild Glossiom palpalis, given somewhat in detail, will suffice to 

 show the method employed, and make it unnecessary to explain the 

 remaining experiments further than is done in Table I. 



It would appear from the fact that none of the healthy monkeys became 

 infected before the 18th day, that not a single fly of the 1840 used was 

 infective when captured. That is to say, that among nearly 2000 Lake-shore 

 flies, not one was naturally infected. On referring to Table IV, in the 

 previous paper in the ' Proceedings ' — a table showing the probable number 

 of naturally -infected flies — this is seen to be by no means exceptional. 



Other points of interest arising out of these experiments are the number 

 of flies which became infective, and the result of injecting their body- 

 contents into healthy animals. 



The following table shows this : — 



Table II. — Number of Flies found Infected with Trypanosomes in the 

 Experiments with Lake-shore Flies and Trypanosoma gamhiense. 



ExjH'riment. 



No. of 



flies used. 



Experiment, 



positive 

 or negative. 



No. of 



iufcct.ed flies 

 found. 



Result 

 of injection of 

 infected Hies. 



Eeinarks. 



624 



60 





1 





T. flraifi type. 



656 



280 





0 







663 



60 



+ 



1 



Positive. 





676 



500 



+ 



1 



Negative. 





721 



50 





0 , 







980 



350 





0 







986 



100 



+ 



1 



Not injected. 





987 



50 



+ 



2 





1 2'. ijamlnense 













and i 2'. ;irij iii 













type. 



089 



50 



+ 



1 ■ 



Negative. 





1020 



100 





0 







102:{ 



50 



•t 



5 



2 positive. 













3 negative. 





1026 



70 



-t 



4 



3 positive. 













1 negative. 





1 1 1 98 



20 





0 





JU72 



100 





0 







