450 Trypcmosoina leivisi 
could not. Those who succeeded were MacNeal (1904), Nuttall (1908), 
Manteufel (1908), and Breinl and Hindle (1909) who at that time could 
not find the developmental changes. Those who failed were ourselves 
who at that period could not find the developmental stages, although 
we have since succeeded in doing so. 
(iii) Experiments tvith other arthropods. 
We carried out two experiments with Gamasiis sp., a mite which is 
occasionally found on rats; two with bugs (Acanthia lectidaria) and 
one each with Ornithodoros mouhata nymphs and adults ; but in all cases 
with negative results. It is of course conceivable that if more of these 
experiments had been performed a positive result might have been 
attained. 
In all of these experiments the arthropod was taken from a well- 
infected rat and then placed on a ‘ clean ’ rat. The bugs which we 
u.sed, on being dissected, shewed the developmental forms which we 
have described on p. 386, while the tick-nymphs were used seven days 
alter they had come from an infected rat and their guts were full of 
active trypanosomes. 
Expenment 22. Four Gamasus which were taken from a wild rat infected 
with T. lewisi were immediately placed on a ‘ clean ’ white rat, but no infection 
resulted. 
Experiment 23. Two Gamasus were taken from a rat heavily infected with 
T. lexvisi and put on a ‘ clean ’ white rat, but no infection followed. 
Experiment 24. About four days after some bugs {Acanthia lectularia) had fed 
on a rat infected with T. lewisi, they were allowed to feed on a ‘ clean ’ white rat. 
The result was negative. 
Experiment 2.5. About six days after some bugs had fed on an infected rat, 
they were fed on a ‘clean’ white rat, with negative results. 
Experiment 26. Several nymphs of Ornithodoros mouhata were fed on an in¬ 
fected rat and seven days after were fed on a ‘ clean ’ animal, but no infection 
resulted. 
Experiment 27. Two adult 0. mouhata which had recently fed on a rat infected 
with T. levnsi were fed on a ‘clean’ white rat which however did not develop 
infection. 
We thus see that, although we have previously (1910) shewn that 
T. leivisi persists for a definite period in the gut of the bug and the 
adult tick 0 . mouhata, yet we could not obtain infection with these 
arthropods. It is certainly possible that these arthropods may oc¬ 
casionally transmit the infection, and that this depends on the behaviour 
