- T 7 
III. DISSECTIONS OF TSETSE FLIES 
The dissections of tsetse flies commenced in the Gambia, 1 with the 
object of finding such a phase of the trypanosomes, were continued 
in the Congo. 
Bruce 14 found scanty trypanosomes in the proboscis of Glossina 
morsitans fed 46 or fewer hours previously on an animal infected 
with nagana; it is quite conceivable that the parasites should be 
mechanically transmitted by the bites of such insects. It was therefore 
important to determine how long after feeding on an infected animal 
Trypanosoma gambiense could be found in the proboscides of 
Glossina pal pal is. A series of 75 dissections* were done at periods 
ranging from one minute to 20 hours after feeding. It was found that 
red cells and trypanosomes were almost always present in the labium 
up to ten minutes after feeding. Later than this the parasites were 
frequently absent, although red cells might still be present. 1 he 
longest period after feeding at which trypanosomes were found was 
if hours; the longest period for red cells was hours. Red cells 
were seen in only six out of 25 dissections done more than two hours 
ifter feeding. 
Koch 9 by pressing the bulb at the base of the tsetse s proboscis 
vas able to obtain a clear fluid in which he frequently found 
rypanosomes. We found that by irritating a fly' held by the wings 
t could frequently be made to spontaneously exude such a fluid ; only 
mce was a trypanosome seen in it, and that in a fly which had fed one 
md a half hours previously on a heavily-infected animal (red cells 
dso present in fluid). It was also found that flies caught after they 
Had fed on an infected animal frequently regurgitated in struggling 
1 drop of blood, as large as a pin’s head, which was full of parasites, 
many of them identical in form with those ingested. This observation 
was made up to 28 hours after the last feed on an infected animal. 
In tins connection it is well to remember that trypanosomes may live apparently 
unaltered in the fly’s stomach for at least 48 hours. Such a regu g ans Q f 
Place during the feeding of the fly can be easily conceived as a possib 
transmission of the parasite. __ _- 
,, * The fl ies previously fed and kept in test tubes v Y ere , c ^r g t ^ e 'fly wa s cut off 
t h !», Wlngs wi,h “ little"struggling as possible. The head t JL lir Jtation. and the 
a quick cut of a fine pair ,of scissors, in order to prevent regurgUation, of 
proboscis was then detached and dissected for examination in a tin) 
normal salt solution. 
