Mode of Infection 623 



This leaves the transmission of the micro-organism un- 

 accounted for. When we come to consider Spirochaete 

 duttoni, however, we find our knowledge much further 

 advanced. On Nov. 26, 1904, Dutton and Todd announced 

 that they had discovered a spirillum to be the specific 

 object in the causation of tick fever in the Congo, and on 

 the same date Ross and Milne * published the same fact. 

 Dutton and Todd subsequently withdrew their claim to 

 priority of the discovery. On Feb. 4, 1905, Ross published 

 in the " British Medical Journal " the following cablegram 

 from Dutton and Todd, then working on the Congo : "Spirilla 



Fig. 185. Ornithodorus moubata. Tick that transmits African 

 relapsing fever: a, Viewed from above; b, viewed from below (Robert 

 Koch). 



cause human tick fever; naturally infected Orinthodorus 

 infect monkey." It was not until Nov. n, 1905, that the 

 paper upon the subject was read and published in the same 

 journal by Dutton and Todd, and the etiology of the disease 

 made clear. These observers found that the horse-tick, 

 Ornithodorus moubata (Murray) is the intermediate host of 

 the spirilla or spirochaete causing the disease, and that when 

 these ticks were permitted to bite infected human beings, 

 and then subsequently transferred to monkeys, the latter 

 sickened with the typical infection. 



The matter received confirmation and addition through 

 the studies of Koch,f who studied the ticks, observed the 



* "British Medical Journal," Nov. 26, 1904. 



f "Berliner klin. Wochenschrift," Feb. 12, 1906. 



