1909.] Trypanosoma gambiense in Glossina palpalis. 413 



Table IV.— Table to show Probable Number of Naturally infected Flies 



per thousand. 



Expt. 



Place. 



Observer. 



No. of flies 

 fed before 

 infection 

 took place. 



Ees 

 Positive. 



ult. 



Negative. 



Probable No. 



f»f nfl tnTfl 1 1 V 



infected flies 

 per thousand. 







Trypanosoma brucei — Glossina morsitans. 





225 



Zululand 



Bruce 



104 



+ 





9-6 



236 







108 



+ 





9 -2 







Trypanosoma gambiense — Glossina palpalis. 





y4 



TT 



U ganda 



Bruce and Nabarro 



89 



+ 





XX u 



xoO 



>j 



Bruce, Nabarro, and 



850 



+ 





1 *9 

 X u 







Greig 











XoX 



?j 





506 



+ 





1 'Q 



X .7 



Loo 



J? 



Nabarro and Greig 



723 











jj 



Greig and Gray 



866 



+ 





X £4 



om 

 oUl 



T V J -1 



l/eopoldvilie 



33 JJ 



Dutton, Todd, and 



2299 









A K 



457 













Hannington 











a a 

 40 





jj u 



552 









X^OA 



Kwer 



jj jj 



25 









139 



)» 



jj ? j 



262 









141 



>> 



jj >j 



52 









182 



Kasongo 





211 









198 





jj jj 



2659 



+ 





0-4 



203 





J3 JJ 



1789 









213 



>? 



Uganda 



JJ 3J 



717 









52 



Bruce, Hamerton, 



41 











Bateman, and 















Mackie 











214 





j) jj 



3284 



+ 





0-3 



568 



>> 



33 3 3 



178 



+ 





5 6 



571 





33 33 



850 



+ 





1 "2 



53* 





33 3 3 



21 









612 







615 



+ 





1 -6 



674 





33 33 



2315 



+ 



/ 





0-4 



* Animal died. 



were used respectively before an infective one was found. This perhaps 

 explains why Bruce's 85 flies failed to infect. 



In the experiments with Trypanosoma gambiense and Glossina palpalis the 

 average is 2 - 5 per thousand. It is, of course, impossible to tell how many 

 of these positive experiments were infected by mechanical transference or by 

 a late-infective fly ; but, in any case, the proportion is small. If this were 

 not so, all the native population of the Lake shore, and most of the Europeans 

 in Uganda, would long ago have been blotted out. 



) 



