£910. | Reservoir of the Virus of Sleeping Sickness. 321 
3. If Glossina palpalis can be infected with the Virus of Sleeping Sickness by 
Feeding on the Blood of Trypanosoma gambiense-rnfected Antelope, what. 
Percentage are found to be so Infected ? 
It has been shown now that antelope can be infected with the virus of 
Sleeping Sickness, that when so infected they can infect the fly, and the fly 
in its turn can convey the disease to susceptible animals. 
These facts form a serious sequence of events, which constitute a danger 
not formerly appreciated in the administrative measures adopted to check 
the spread of the disease. What is the extent of the danger? A part of 
this large and important query can be answered if one can give an idea of 
the percentage of Glossina palpalis that become infected with the virus of 
Sleeping Sickness after they have fed on the infected antelope. 
Throughout all these experiments only clean laboratory-bred flies were: 
employed. The fact that there is no hereditary transmission of trypano- 
somes in Glossina palpalis is considered to have been so conclusively proved 
that two of the members of the Commission have allowed several hundreds 
of clean laboratory-bred flies to bite them. Further, no evidence has ever 
been obtained by the Commission that these flies became infected with any 
flagellate by contact with other flies or fouled cages. Thus, any flagellates 
found in the laboratory-bred Glossina palpalis in these experiments must be 
considered to be derived from the infected antelope. 
- In some of the experiments the flies were fed, for varying periods, upon 
fowls. As will be shown in a further paper, the Commission found an avian 
trypanosome in some of the fowls obtained for experimental purposes. It. 
would, therefore, be a fair criticism to state that a percentage of the 
flagellates found on dissection of the Glossina were avian in origin, were it. 
not for the fact that negative experiments went to prove that this fowl 
trypanosome did not develop in the Glossina. It is also true that on one 
occasion the Commission thought they had succeeded in infecting a fowl 
with Trypanosoma gambiense ; it may, therefore, be argued that the fowls 
fed upon in some of these experiments were naturally infected with 
Trypanosoma gambtense, and that the Glossina obtained their infection frony 
such naturally-infected fowls and not from the antelope. Though many 
experiments were devised and carried out to try and confirm this one 
positive result, all efforts to infect fowls with Sleeping Sickness were so 
uniformly negative that the Commission must consider the one “ positive” 
result to be an error. 
A reference to Table III will show that Glossina palpalis were infected by 
antelope blood where no fowls were ever fed on; in fact, it will be noticed 
