146 
Transmission of S. diittoni 
The method in which an infected tick produces spirochaetal 
INFECTION IN THE ANIMAL IT FEEDS UPON. 
The results of the inoculation experiments with ticks that had been 
kept at 21° C., show that the salivary gland probably never becomes 
infected at this temperature, and yet these ticks produced spirochaetal 
infections, when they were fed upon healthy mice, as readily as those 
ticks that had been kept for some time at 36° C., and whose salivary 
glands were infected. 
It is evident, therefore, that the salivary glands are not usually 
responsible for any spirochaetal infection that may follow the bite of a 
tick infected with S. duttoni. 
In order to decide definitely the exact mode of infection, the follow¬ 
ing experiment was performed and the results are given in detail. 
Three adult specimens of 0. moubata, which had been kept at a 
uniform temperature of 21° C., were allowed to feed on a healthy mouse. 
After feeding, each of the ticks passed one or two drops of the clear 
coxal secretion and also voided some o’f their white excrement (Malpighian 
secretion) from the anus. The mouse became infected after an incuba¬ 
tion period of 10 days. 
Some of the coxal secretion from these ticks was injected into a 
mouse but no infection was produced. On the other hand, a mouse 
which was injected with some of the white excrement voided by the 
ticks, became infected after an incubation period of 11 days, which is 
only one day longer than that of the mouse used for the feeding 
experiment (10 days). 
Each of the three ticks used in this experiment was dissected and 
its organs injected into mice, in the manner described above (p. 138). 
Tick 1. Adult ? . Was immune to Spirochaeta duttoni, as none of the mice injected 
from it became infected. 
Tick 2. Adult d . 
Tick material injected 
Result of 
inoculation 
Incubation 
period (days) 
Microscopical 
examination 
Gut + contents 
+ 
9 
- 
Malpighian tubules 
- 
- 
- 
Salivary glands 
- 
- 
- 
Testis 
+ 
7 
- 
Tick 3. Adult ? . 
Gut + contents 
+ 
8 
Malpighian tubules 
+ 
8 
- 
Salivary glands 
- 
- 
- 
Ovary 
+ 
7 
- 
