188 
Transmission of S. duttoni 
Technique. 
The ticks used in the following experiments came from Uganda and 
most of them were found to be infected with S. duttoni. In all cases, 
however, the ticks were fed once or twice in the laboratory on mice 
heavily infected with 8. duttoni, in order to make certain that they had 
been exposed to infection. Except in the case of certain experiments 
described below, the ticks were kept in glass jars at a uniform temperature 
of about 21° C., and under these conditions remained healthy for several 
months. 
In those experiments undertaken to decide, by inoculation, which 
organs of 0. moubata become infected, the tick was carefully dissected 
in 0‘8 “/o salt solution, and after its organs had been isolated, each was 
washed in several changes of saline in order to remove any spirochaetes 
which might have adhered to the outside of the organ. It is very 
difficult to perform this dissection without rupturing the gut, and 
therefore this washing had to be very thorough in order to make 
certain that none of its contents remained on the outside of other 
organs. After the isolation of the various parts, each organ was 
emulsified in normal saline solution and injected intraperitoneally into 
a mouse. Usually films were made from a part of each organ that was 
injected and, after staining, examined for spirochaetes. The mice used 
in these experiments were examined daily for about four weeks after 
the inoculation, and if spirochaetes had not appeared in the blood in 
this time, it was assumed that no infection had taken place. 
The experiments may be divided into two groups according to 
whether the ticks had remained at a moderate temperature (about 
21° C.), or had been maintained at a temperature of 35°-37°C. for 
some time previous to the dissection. 
In the following protocols the results have been arranged as 
follows:—In column 1, ‘Tick material injected,’ is given the part of the 
tick which was inoculated into the mouse. Under ‘ Result of Inocula¬ 
tion ’ is expressed by means of a positive (-t-) or negative (—) sign, 
whether the mouse became infected or not. Under ‘Incubation period’ 
is given the number of days wlfich elapsed, prior to the appearance of 
spirochaetes in the blood of the mouse. In the last column—‘ Micro¬ 
scopical examination ’—is given the result of the examination of the 
tick material for spirochaetes, their presence or absence being denoted 
by a +, or — sign, respectively. 
