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it was found that the resistance was retained for upwards of three 
months in cultures, but lost after a sojourn in the rat louse by which, as 
we have seen, the parasite is transmitted. The drug resistance is lost 
by the flagellate after about TO to 12 days in the louse, and this fact 
may be brought forward in support of the view that the louse is a 
definitive host of the trypanosome and that a sexual development of the 
parasite occurs in the louse—the sexual process, at a stroke, eliminating 
acquii’ed characters previously maintained for thousands of asexual 
generations during the passage by inoculation from rat to rat. 
This observation has a practical bearing in respect to human 
trypanosomiasis where arsenic-resisting strains of T. gambiense would 
be assumed, under certain conditions, as likely to be transmitted by 
Olossina. It will doubtless be found in this case, as with T. lewisi, that 
the passage of the flagellate through its vector renders it again 
susceptible to the action of trypanocidal substances. 
In the time at my disposal I have only been able to dwell upon 
certain aspects of the subject of trypanosomiasis, and to bring out some 
of the many interesting problems which are being gradually solved by 
many workers. 
The preventive measures directed against sleeping sickness have 
been dictated by experience gathered from research into the etiology of 
the disease, and, as our knowledge advances, so will our measures for 
combating the scourge have to be modified. The hope that the disease 
would be exterminated by resorting to the inspection and segregation 
of natives, to depopulation and the destruction of the habitats which 
are suitable breeding grounds of Glossina palpalis, have been but 
partially realised. The prolonged period of incubation and chronicity 
of the disease, coupled with the fact that fatal relapses have been 
known to occur after the lapse of years in appai’ently recovered cases 
render the disease very difficult to combat. A measure of immunity 
appears to be acquired after recovery, judged from animal experiment. 
Although treatment has given results which are encouraging, we are 
still far from the goal we wish to attain. The question of reservoirs 
has grown to be one of the greatest practical importance and the cry 
for the destruction of the game animals which serve as such is growing 
louder. It is for this reason that game destruction is at present being 
carried out over limited areas to see if it exerts any beneficial effect, 
although it appears very doubtful that this measure will prove useful, 
since it will drive the game elsewhere and so scatter the reservoirs into 
