134 
Transmission of S. duttoni 
the egg. He imagined that, after peneti’ating the gut-wall, some of the 
spirochaetes made their way to the salivary glands and from there 
probably were injected into the wound caused by the tick’s bite. 
The following year Breinl, Kinghorn and Todd (1906) attempted to 
transmit 8. duttoni by the bites of Gimex lectularius. The bugs were 
kept at a temperature of about 20° C. and after feeding on infected 
animals were allowed to feed on healthy monkeys; but though, in all, 
several hundreds of this insect were experimented with, the results 
were uniformly negative as regards the transmission of both 8. duttoni 
and recurrentis. 
Nuttall (1907) also attempted to transmit spirochaetes from infected 
to healthy animals by means of bed-bugs. He found that at 12° C. the 
spirochaetes lived in the gut of the bug for as long as 120 hours, but 
when kept at higher temperatures they disappeared much more rapidly. 
At 2-5" C. the parasites were all dead within three hours after being 
ingested into the gut. These experiments, however, were also negative as 
far as the actual transmission of 8. duttoni from one animal to another 
was concerned, although one positive result was obtained with 8. recurren¬ 
tis by interrupted feeding on mice. 
The same year Fiilleborn and Mayer (1907) attempted to transmit 
this disease by the bite of 8tegomyia fasciata, but the results were 
uniformly negative. 
In 1907 Mollers gave an account of his detailed experiments on the 
transmission of 8. duttoni, in which he showed that infected ticks 
(0. mouhata) may feed repeatedly on uninfected animals and yet remain 
infective. Employing ticks imported from German East Africa, he 
succeeded in infecting the first ten out of twelve animals on which they 
were fed. The negative results of the last two experiments were 
probably due to the fact that very few ticks were left alive and 
consequently there were not enough to cause any infection. The tickp 
used in this experiment were fed every two months, so that they 
remained infective at least eighteen months after their first feed 
upon an infected animal. 
Mollers has also shown that infected ticks fed successively on six 
“ clean ” animals, after each feed may lay a batch of infected eggs, the 
ticks hatched out from which are capable of conveying the infection to 
the animals they feed upon. Moreover, not only is the infection carried 
through to the second generation, but also to their offspring; ticks of 
the third generation being found to be infective, even though their 
parents had never fed on an infected animal. 
