10 SLEEPING SICKNESS.
In a district such as this the problem must inevitably
be settled whether other insects are able to transmit
the Trypanosoma Gambiense from sick to healthy men.
To decide this very careful observations were made, but
not a single case could be discovered in which such
transmission had taken place by means of other insects
than Glossina Palpalis."
There is considerable doubt as to what is the transmitting
agent in the form of human trypanosomiasis now spreading in
Nyassaland and in Rhodesia. The tsetse Glossina Palpalis is said
to be absent from those regions, but Glossina Morsitans is common
and Glossina Fusca is also found.
It is believed that Glossina Morsitans will be incriminated as
it has already been proved to be the natural carrier of Nagana
(T. Brucei) and it is capable of carrying Trypanosoma Gambiense
by laboratory experiment. Some observers however doubt whether
the Rhodesian Trypanosoma is Trypanosoma Gambiense at all or
that the disease is identical with Sleeping Sickness as ordinarily
understood. At present the whole question must remain sub-
judice. The new commission going out under Bruce will doubtless
clear up these points.
There remains one more possible method of transmission, that is
either by contact or by sexual intercourse. Koch believed the
latter to be a probable mode of spread, and he brought some evi-
dence to prove his contention. This theory has not gained ground,
and does not accord with the experience of most observers though
there are experimental grounds for believing it to be possible.
A recent paper by Hindle (Parasitology, March 1911, page 24)
shows that Trypanosoma Gambiense can be absorbed through the
unbroken mucous membrane either of the alimentary tract or of
the female genital passages of the guinea pig.
He did not succeed in transmitting the disease in these animals
from infected male to healthy female or vice vers by natural sexual
intercourse.
Application of infected material to the unbroken skin also gave
rise to infection, so it is possible that in man simple contact with
infected fluid without a skin lesion might suffice to transmit the
disease.