TRYPANOSOMIASIS EXPEDITION TO SENEGAMBIA 
4' 
one to twelve hours after their capture. Only those flies which were seen to be 
gorged with blood were held to have fed. It may be assumed that all the flies which 
were given an opportunity to feed attempted to do so, and that the proboscis of a 
much larger number of tsetses than 44 pierced the rat's skin. The blood of 
this rat was examined constantly, always without success, for trypanosomes. 
Experiment ia. — Tsetse flies caught near Bakau, where five out of the 
six horses owned in the native village were infected with trypanosomes, were 
allowed to feed at once on an uninfected white rat. 
Oct. 24—25 newly-caught flies fed well. 
2 6 — 2 
28 2 
Nov. 14—30 
This rat was constantly examined, always with negative results, until April 14, 
1903, when it died from sunstroke. 
Experiment XIX. — Flies freshly caught near Bakau were allowed to feed 
upon a young non-infected white rat. 
Oct. 24 — 2 flies fed. 
25— 10 „ „ 
26 — 10 „ „ 
28— 20 „ „ 
29— 8 » » 
30— 12 „ „ 
This rat was constantly examined without result until November 14, when it 
was killed. 
Experiment VIII . — We also attempted to infect a tame rat by allowing it to 
be bitten by tsetse flies which had previously fed on a naturally infected horse 
(Case No I) and on an artificially infected rat (Experiment IX) in the blood of which 
there were a great many parasites. 
A stock of flies, continually replenished by the addition of freshly-caught 
flies, was kept in a cage and fed on successive days alternately on the infected and 
non-infected animals in the following manner : — 
Infected Animals 
Oct. 11 — 12 flies put to feed 
4 filled themselves 
,, 12 — 6 flies ted on Horse I at 4 
p.m. 
Horse died 
Uninfected Rat 
Oct. 12 — 5 flies fed well at 9 a.m. 
,, 15 — 3 out of 6 flies fed, others 
attempted to feed at 9 a.m. 
