42 THOMPSON YATES AND JOHNSTON LABORATORIES REPORT 
Infected Animals — contd. Uninfected Rat — contd. 
Oct. 21 — 5 flies fed on rat, Experiment Oct. 16 — 5 flies fed well. 
IX, 3 at 1 p.m., 2 at 6 p.m., 
many trypanosomes in 
blood. 
,, 22 5 flies fed on Experiment 
IX 
„ 24 — 25 flies fed on Experiment IX ,, 25 — Many of 25 flies pierced the 
this p.m. skin, but none succeeded in 
getting full meal. 
,, 26 — 2 flies fed on Experiment IX 
,, 29 — 6 flies fed on Experiment IX ,, 3c — All flies fed on rat. 
The conditions of this experiment were purposely made as broad as possible. 
The sole object of the experiment was to see whether Glossina palpalis would transmit 
the Gambian horse trypanosome in the same way as Glossina morsitans does Trypano- 
soma brucei. 
With this end in view, flies which had fed at any previous period on either of 
the infected animals were allowed to teed indiscriminately on the test animal. 
This was examined constantly until April 14, when it was killed by sunstroke. 
Its blood was, as in all the transmission experiments, examined, at first, daily, both 
with and without the centrifuge, and always in vain. The autopsy revealed nothing 
abnormal. 
Although tsetse flies could be found near McCarthy Island, where we made 
our headquarters from January to April, it was never possible to catch them in sufficient 
numbers to make the success of a repetition of these experiments probable. 
It is maintained that the tsetse fly carries Nagana from animal to animal in a 
mechanical way, and that probably no biological change in the parasite intervenes. We, 
therefore, determined to repeat these experiments, using intead of Glossina, two varieties 
of Stomoxys (not yet identified), which were very plentiful in the Upper Rivei^ and 
easily caught. 
Experiment CI. — During a period of eight days, a number of Stomoxys, about 
one hundred altogether, were caught from two horses and placed in the same cage. 
One of these horses (Horse No. VI) was a naturally infected animal, and at this 
time its blood contained on an average five parasites to a preparation. The other 
(Experiment LXXXVII) was a young native stallion which had been artificallv infected 
with the human parasite from rat EXIX (O. strain). The flies had an opportunity 
of feeding within twenty-four hours of the time at which they were caught, on a young, 
non-infected white rat, aand they were allowed to feed daily on the same animal for a 
period of eight days. The rat has been under observation up to the present date and 
has never become infected. 
