E. Hindle 
147 
These results prove conclusively that in this case the salivary glands 
were not responsible for the infection that followed this feeding experi¬ 
ment, as they were all uninfected. Moreover, the injection of the coxal 
secretion was not followed by any infection; therefore it was evidently 
not the infective agency. 
The only possible mode of infection in this case was either the 
regurgitation of infective material from the gut, or the excretion of the 
white Malpighian secretion, and the latter was proved by inoculation to 
be infected. This white secretion is voided by the great majority of 
ticks, usually when they are finishing feeding. It is voided by the first 
stage nymphs as often as in the more advanced stages, and is invariably 
infective when it comes from infected ticks. When the coxal fluid is 
secreted it usually runs underneath the body of the tick and mixes with 
the Malpighian secretion, the latter thereby becoming diffused and 
brought into the open wound caused by the tick’s bite. There is no 
doubt that under such conditions a susceptible animal would become 
infected, and the only doubtful point is whether this is the invariable 
method by which animals become infected with spirochaetes, after the 
bite of infected 0. mouhata. From a consideration of the inoculation 
experiments described in the first part of this paper, it seems probable 
that it is the only mode of infection for, at ordinary temperatures, the 
salivary glands do not become infected, whereas the gut and its con¬ 
tents are invariably infective, except in the case of immune ticks. 
In addition we have repeated with success Leishman’s experiment 
(in our case using mice) of allowing ticks to feed on an animal for a 
short period and then transferring them to another in order to complete 
their meal. Under such conditions the ticks have not time to void any 
of the Malpighian secretion on the first animal and it never becomes 
infected; on the contrary, when the same ticks are allowed to feed to 
repletion on a second animal it usually becomes infected, in this case 
the ticks having voided their excrement and also some of the coxal 
fluid. 
In conclusion, therefore, we should like to repeat that our results 
entirely confirm Leishman’s suggestion that, in the case of 0. mouhata 
infected with S. duttoni, the infection they may produce in man and 
other animals is the result of the excretion of infective material from 
the Malpighian tubules and gut, which enters the open wound caused 
by the tick’s bite. 
I am indebted to Prof Nuttall for suggesting to me the line of 
investigation to which this paper relates and for placing his material 
and results at my disposal. 
Parasitology iv 
10 
