SYPHILIS 515 



Koch also made extensive observations on the ticks in Ger- 

 man East Africa, and found that of over six hundred examined 

 along the main caravan routes 1 1 per cent, contained spirochetes, 

 and in some localities almost half of the ticks were infected. 

 In places removed from the main lines of commerce he still 

 found them, though in smaller number. It has also been 

 demonstrated that in some places the ticks are found to be 

 infected with the spirochetes although the inhabitants do not 

 suffer from tick fever, a circumstance which is probably due to 

 their having acquired immunity against the disease. 



It is now generally believed that the sp. duttoni is a species 

 distinct from, though closely allied to, the organisms of the 

 relapsing fevers described above. We have mentioned some 

 differences in the clinical characters of the diseases, and there 

 are also differences in the pathogenic effects of the organisms on 

 inoculation. The sp. duttoni, for example, produces a much 

 more severe disease in monkeys, and is pathogenic to more 

 species of the laboratory animals than the sp. obermeieri. The 

 most important differences are, however, brought out by immunity 

 reactions. It was shown by Breinl that the immunity produced 

 by the sp. obermeieri did not protect against the sp. duttoni, 

 and that the converse also held good ; and it has since been 

 established that a similar difference obtains between the 

 sp. duttoni and the organisms of the Asiatic and American 

 varieties of relapsing fever. Corresponding results are 

 obtained on testing the various serum reactions in vitro. 

 As already stated, Noguchi has cultivated the sp. duttoni 

 outside the body, and from a study of its characters agrees 

 that it is a distinct s.pecies. 



Syphilis. 



The cause of syphilis is the organism discovered by Schaudinn 

 and Hoffmann in 1905 and called by them the spirochete pallida, 

 now often known as the treponema pallidum. They described 

 its characters and its occurrence in syphilitic lesions, and their 

 observations have been fully confirmed. Its recognition, at first 

 somewhat difficult, has been rendered comparatively easy by the 

 introduction of new methods. 



Spirochete pallida. — This is a minute spiral-shaped organism, 

 showing usually from eight to twelve curves, though longer forms 

 are met with ; the curves are small (each measuring a little over 

 1 /a), comparatively sharp, and regular (Figs. 156, 157, 158). It 

 may be said to measure 4 to 14 /a in length, while it is extremely 



