Gr. H. F. Nutt ALL 
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are susceptible to infection with S. duttoni, various species of monkeys, 
rats, mice, rabbits, guinea-pigs, sheep, goats, horses and dogs, etc. having 
been successfully infected. 
Transmission of Relapsing Fever hy Pedicidus and Ciniex. 
It has long been supposed that vermin are responsible for the 
transmission of relapsing fever in Europe. Fltigge (1891) appears to 
have been the first scientific writer to suggest this possibility, and Tictin 
(1897) supposed that bugs (Gimex lectularius) might transmit the disease 
by their bites or by being crushed and their contents entering the skin 
through excoriations due to scratching. He infected monkeys with the 
contents of bugs removed 24 hours after they had fed on relapsing fever 
blood. Karlinski (1902) and likewise Schaudinn observed the survival 
of spirochaetes in bugs for 30 days or more. Christy (1902) and Breinl, 
Kinghorn and Todd (1906) failed to transmit spirochaetosis by bugs. In 
experiments of my own (1907) it was found that S. diittoni survived six 
days in the bug at 12° C., but only for six hours at 20-24° C. Similar 
results were obtained by S. recw'rentis (from Russia). The parasites 
appeared to be merely digested by the bug, the rate of digestion being 
governed by the temperature at which the insects were maintained. In 
but one experiment did I succeed in transmitting relapsing fever to 
a mouse by means of bugs. In this case, I used 35 of the insects, and 
transferred them directly from an infected to an uninfected mouse, 
interrupting their feed upon the first animal and allowing them to 
complete it upon a second clean mouse. We may, therefore, conclude 
that bugs can occasionally transmit relapsing fever. 
We have, on the other hand, conclusive proof that lice are concerned 
in the transmission of the disease. The first important evidence in this 
connection dates from Mackie (1907), in India. This author records an 
outbreak of relapsing fever amongst school children, in which 137 out 
of 170 boys and 35 out of 114 girls, were attacked. The boys were 
found to be more infested with vermin than were the girls. An 
examination of the lice removed from the boys showed 24 ®/o of them 
to contain spirochaetes, whereas only 3“/o of the lice collected from 
the girls contained these microorganisms. As the epidemic increased 
among the girls their verminous condition became more evident, as the 
epidemic decreased among the boys the lice were found less frequently 
upon them. Mackie noted that the spirochaetes multiplied within the 
gut of the lice and that they could be found in the ovary, testis and 
