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Transmission of S. duttoni 
Summary of Results. 
(1) About 30 “/o of the 0. mouhata from Uganda have been found 
to be immune to infection with S. duttoni. 
(2) When infected ticks are kept at ordinary temperatures (about 
21° C.), the following parts of the body are found to harbour the 
infection :—gut + contents, sexual organs, Malpighian tubules, excrement. 
The following parts were found to be uninfective:—salivary glands, 
coxal fluid. 
(3) When infected ticks are kept at a temperature of about 35° C. 
for two or three days previous to dissection, all the organs of the body, 
including the salivary glands, are found to be infective. Moreover the 
incubation periods that elapse before the appearance of spirochaetes 
in the injected mice are shorter than in the case of the corresponding 
experiments with ticks that had not been kept at a high temperature. 
(4) No spirochaetes have been detected in any of the organs of 
infected ticks that had been kept at a temperature of about 21° C. 
When a tick ingests blood containing spirochaetes, the latter persist 
in the lumen of the gut for periods varying from a few days up to as 
long as four weeks; usually, however, they disappear from the gut 
in the course of nine or ten days. 
(5) When infected ticks are heated to a temperature of 35° C. for 
two or three days, spirochaetes reappear in the lumen of the gut, and 
also appear in all the organs of the tick, and in the coelomic fluid. 
(6) The spirochaetal infection that may follow the bite of an 
infected 0. mouhata results from the entrance of the infective material, 
excreted by the tick whilst feeding, into the open wound caused by the 
tick’s bite. It is not the result of the inoculation of infective material 
from the salivary glands. 
