MICROBIAL DISEASES OF MAN AND DOMESTIC ANIMALS 903 



is not often fatal and 606" is a specific treatment for it. It can be prevented 

 by avoiding lice and ticks. 



TREPONEMA (Schaudinn, 1905) 

 Two species of this genus are very important parasites. 



SYPHILIS 

 Treponema pallidum Schaudinn, 1905 



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 6/x to 14^ in length (Fig. 194). It greatly resembles the 

 spirochaetes, but differs from them in having each end drawn out to resemble a 





FIG. 194. Treponema pallidum (in centre) and the Spirochata rejringens. 



(Greene's Med. Diagnosis) 



very slender flagellum. Very little is known of the life history of the treponema 

 except that it multiplies by transverse division. It is transmitted by the contact 

 of a lesion, containing the parasites, with the broken skin, or with a mucous mem- 

 brane of an uninfected person. 



Mercury and potassium iodide were formerly almost exclusively 

 employed in treating syphilis. The search for an efficient drug for 

 the treatment of trypanosomiasis has led to the discovery of other 



