J*r 
452 Trypanosoma leivisi 
2. Fleas (G. fasciatus and 0. agyrtes) were constantly found associated 
with wild rats infected with T. lewisi. We think that these two species 
of fleas are the chief carriers of the parasite from rat to rat in this 
region. 
3. We tried transmission experiments with fleas {C. fasciatus and 
C. agyrtes), lice {H. spinulosus), bugs (A. lectularia), ticks (0. moubata, 
nymphs and adults), and Gamasus sp., but only obtained a positive 
result by the agency of fleas. 
4. In the transmission experiments the arthropod was transferred 
from an infected to an uninfected animal. 16 “/o of 138 experiments 
with fleas were successful, 80—98“/o of the fleas used were non-infective, 
while 2—20 “/o were infective. 
5. Distant transmission occurs with fleas. This was observed by 
one of us in January, 1909. 
6. ‘Mechanical’ transmission occurs sometimes with fleas. 
7. Infective fleas do not transmit the power of infection to their 
young. 
8. The mechanism of infection in the case of mechanical transmission 
is by the bite of the flea; in the case of the distant infection it is 
not so. 
9. The infective forms of T. leivisi for distant transmission are 
probably the ‘small trypanosomes’ which we have described elsewhere 
(1910). The forms of T. lewisi found prior to the small trypanosomes 
in the developmental cycle are not infective. 
10. The development of the trypanosomes in the flea is not 
interfered with by the flea feeding on a rat immune to the disease. 
11. Seventeen experiments with lice were performed, but no 
transmission was obtained by their agency. 1139 lice were used. No 
confirmation of Baldrey’s infective cycle in lice could be obtained. 
12. We could trace no connection between transmission of infection 
by lice and the presence in them of ‘ developmental forms.’ 
13. No transmission of T. lewisi by other arthropods was obtained. 
These negative results had no connection with the presence in the 
arthropods of ‘ developmental forms.’ 
In conclusion we would like to thank Professor Nuttall for his 
kindness in inoculating our animals and pi'oviding us with the 
material for our experiments, and for his interest and advice in our 
work. 
