MICROBIAL DISEASES OF MAN AND ANIMALS. 673 



in Brazil and in other tropical countries. The spirochaete of fowls, Spiro- 

 chceta gallinarum, is transmitted by a tick, Argas miniatus; the means by 

 which the goose spirochaete, Spirochata anserina, is carried is not known. 



TREPONEMA. 

 This single species of this genus is a very important parasite. 



SYPHILIS. 

 Treponema pallidum. 



This disease, in all its diverse forms, is caused by Treponema pallidum. 



The treponema is an exceedingly slender, thread-like organism, with a waved body 



which measures from 6ft to 14^ in length (Fig. 121). It greatly resembles the spirochaetes, 



b ut differs from them in being without an undulating membrane and in having each end 



FIG. 121. Treponema pallidum. (After Schaudinn from Doflein.} 



drawn out to make a very slender flagellum. Very little is known of the life history of 

 the treponema; it multiplies by longitudinal and by transverse division. It is trans-" 

 mitted by the contact of a lesion, containing the parasites, with the broken skin, or with 

 a mucous membrane of an uninfected person. The symptoms of g syphilis are the mani- 

 festations of irritation, and destruction of the tissues of the infected persons by the 

 treponema and by the toxin which it produces. 



Mercury and potassium iodide were formerly almost exclusively em- 

 ployed in treating syphilis. The search for an efficient drug for the treat- 

 ment of trypanosomiasis has led to the discovery of other drugs which 

 are of value in the treatment of syphilis, such as atoxyl (the sodium salt of 

 para-amido-phenyl-arsenic acid) and its acetylated derivative, and of 

 dichlorhydrate-diamido-arseno-benzol. The last named drug seems to 

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