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vein :
Transmission-A. By injection of blood of patient removed during life from the median
(a.) During the febrile period when spirilla were present.
(1.) Into Monkeys-after an incubation period of four days pyrexia set in spirilla were found in the peripheral blood, and an attack of relapsing fever was passed through.
(2.) Into Rabbits these shewed no reaction and spirilla were not found in the blood at any time.
(b.) During the apyrexial period when spirilla were absent from the blood stream into a Monkey. The animal continued well. no rise of temperature took place, and spirilla could not be found in the blood on several examinations. It died unexpectedly on the 17th day after injection and all the organs were found to be crowded with spirilla.
B. By Sactorial Insects :-
(a.) Mosquitoes.—I induced mosquitoes of the ordinary variety met with here- the culex-to feed on the patients during the pyrexial periods, and within twenty-four hours after they had gorged themselves I could find no trace of any spirilla-mosquitoes were scarce at that time, and I was able to get only a few, and I think further investigation regarding this means of conveyance should be undertaken whenever practicable, for from the well known fact that malaria is conveyed by mosquitoes it is quite within reason to regard them as carriers of Relapsing Fever.
(b.) Bed Bugs and Ticks.-There are recognised as carriers. I was unsuccessful with the former, and had no opportunity of experimenting with the latter. It has been found that bed bugs are capable of conveying the organisms to monkeys which have thereupon shewn a rise of temperature, accompanied by the presence of spirilla in the peripheral blood. It should be noted, however, that the infected blood was squeezed out of the bugs, and was then injected into the monkeys-the point being that the bug did not introduce the blood and its organisms. Ticks have been recently proved by R. KOCH to convey the disease by experiments which he performed in German East Africa.
C. By Vaccination--that is, by smearing freshly scarified surfaces with the freshly cut surfaces of organs which contained an abundance of the organisms.
(1) Monkeys-results negative.
(2) Rabbits--results negative.
D. By Feeding :-.
(1) A monkey,
(2) A pig,
were fed with organs containing spirilla-Result in both cases negative.
From all these facts we may conclude :—
(1.) That Relapsing Fever is communicated by the bite of suctorial insects. (2.) That an intermediate host probably exists, the tick being one such.
(3.) That the organisin is only present in the peripheral blood at certain definite
times, namely, during the pyrexial periods.
(4.) That when they are absent from the peripheral blood they congregate in the
spleen.
(5.) That the blood during the whole course of the disease remains infectious,
whether the organisms be present or not.
(6.) That treatment is not specific as in malaria but is in the main confined to dealing with symptoms and that the attacks of pyrexia cannot be shortened or terininated.
W. V. M. KOCH, M.D.