213 
Although the chronicity of the disease is well known, it seems 
impossible that large percentages of populations, whose vocation does 
not keep them constantly on the water, should-become infected in 
such a way in places where tsetse flies are far from plentiful, like 
Kalombe (17 per cent, infected), Dibwe (18 per cent.), Miambwe 
(/percent.), Lokula (6 per cent.) in the Congo Free State. 
It seems certain that such a mechanical transmission cannot be 
the only way in which Trypanosoma gambiense is transmitted from 
man to man. We believe either that something is wrong in the way 
in which Glossina palpalis has been used in these experiments, or 
that Trypanosoma gambiense can be conveyed by some other means 
than by it.* 
The status of cattle trypanosomiasis (see page 233) in the Congo Free State 
furnishes an additional objection to explaining the propagation of trypanosomiasis 
by mechanical transmission alone. A considerable percentage of the cattle are 
infected. Trypanosomes are very rarely seen in their blood. Enormous quantities 
(to to 5oc.cm. or more) of infected blood must be injected into susceptible animals 
before they become infected, and failures to infect are common. It does not seem 
possible that the mere mechanical transmission of an infinitesimal quantity of 
blood from animal to animal by an insect’s proboscis can adequately explain the 
distribution of a strain of trypanosomes possessing so little virulence in direct 
inoculations. 
II. ATTEMPTS TO TRANSMIT TRYPANOSOMES BY 
VARIOUS BLOOD-SUCKING ARTHROPODS 
If the tsetse fly is merely a mechanical transmitter of trypanosomes, 
there seems no reason why other blood-sucking arthropods should not 
also transmit them. To test this possibility the experiments described 
below were made with the “ Congo floor maggot ” (larva of 
Auchmeromyia luteola ), Anophelines (Pyretophorus coslalis ), Simu- 
hum and Ornilhodorus moubaia. None of them were successful. As 
before, animals showing large numbers of trypanosomes in their blood 
were preferred for the infecting feeds. 
1 EXPERIMENTS with larvae of auchmeromyia luteola 
I. FRESHLY-CAUGHT LARVAE 
to) To ascertain whether larvae caught in native huts in an area 
where sleeping sickness is endemic contain trypanosomes in a state capable 
°f infecting susceptible animals. __ 
differ/i e 9 ui t erdu ’», usually only transmitted by coitus, may be spread in a totally 
nt manner by the bites of fleas (25). 
