XI. FOURTEEN DAYS INTERVAL OR MORE 
To infect a susceptible animal with Trypanosoma gambiense 
by the bites of tsetse flies fed at least fourteen days previously on an 
infected animal. 
Leopoldville. 
Experiment 79.—Guinea-pig. From January 11 to May 24, 1904, 156 flies fed 
on this animal. Its blood was examined regularly until May 27, and then at 
intervals until October, 1904. Trypanosomes were never seen. The animal died 
in November, 1905. No trypanosomes were seen at the autopsy. 
XII. MISCELLANEOUS 
Experiment 21 i. —Guinea-pig. This animal was used for feeding odd batches 
of tsetse-flies which for various reasons could not be employed in one of the set 
experiments. 
From May 16, 1904, to April 30, 1905, 1,278 flies were fed on it ; 200 of these 
flies were freshly caught, the remaining had been fed at various antecedent periods 
on animals infected with either Trypanosoma gambiense or 'L' ry panosoma dimorphon. 
The blood was examined until August, 1905 ; trypanosomes were never seen. The 
animal died in September, 1905 (cause of death ?). No trypanosomes or signs of 
trypanosomiasis were seen at the autopsy done immediately after death. 
In the Gambia it was thought that the excessively dry atmosphere 
at the season when our experiments were done might have accounted 
for their failure 1 . This objection cannot be made to the Congo 
experiments; when they were done, the average morning humidity 
(6 am.) at Leopoldville was about 45 per cent., at Kasongo about 
94 per cent. 
Experiments 129, 203, 206, in which the animals were not observed 
for a very long period, should probably be disregarded. The 
remaining observations should be considered in conjunction with the 
published reports of similar experiments done in Uganda 8 ' 10, 
Bruce, Nabarro and Greig (8).—These authors publish three experiments in 
''Inch animals were infected with Trypanosoma gambiense , within from two to 
( our and a half weeks from the commencement of the experiment, by the bites of 
from 200 to 1,000 freshly-caught Glossina palpalis. The rapidity with which these 
experiments succeeded is noteworthy. _ 
In five experiments they succeeded in transmitting Trypanosoma gambiense by 
bites of from 250 to 570 flies fed from eight to forty-eight hours previously on 
‘nfected animals. The length of time from the commencement of the experiment 
t0 ihe recognition of the infection varied from seven to ten weeks. 
. r, reig and Gray (10).—In five experiments these authors succeeded in trans¬ 
iting cattle trypanosomes by the bites of Glossina palpalis. The period elapsing 
,. etw 1 e , en the commencement of the experiment and the detection of the parasites in 
^blood of the experimental anima l varied from four and a half to seventeen and 
a weeks; the number of flies fed ranged from 151 to 923. 
N 
