SYPHILIS 275 



from a remote period to be a disease which is com- 

 municable from man to man by infective secretions, 

 the earlier efforts to gain a deeper insight into its 

 nature by experimental infection of animals gave 

 either negative or doubtful results. In 1903, 

 Metchnikoff and Roux, in Paris, for the first time 

 reproduced the typical effects of primary and 

 secondary syphilis in apes (chimpanzees and ourang 

 outangs) which they inoculated with infective 

 material obtained from syphilitic persons. They 

 subsequently reproduced the disease in apes by 

 means of the semen of syphilitic subjects and 

 demonstrated that the organs of persons suffering 

 from the final or tertiary form of the disease still 

 harboured the virus. This was of special interest, 

 since tertiary syphilis was usually regarded as non- 

 infective until these observers proved the contrary. 

 In 1905, Schaudinn, a German zoologist, discovered 

 the microorganism which is the cause of this 

 dread disease, a very minute spiral organism which, 

 owing to its small size and the difficulty of seeing 

 it because of its optical properties and resistance 

 to stains, had escaped the observation of many acute 

 observers who in previous decades had searched for 

 the causative agent of syphilis. This microorgan- 

 ism is known as the Spirochaeta pallida, and its 

 discovery has proved of very great practical utility. 

 The search for it is now commonly conducted by 

 means of an instrument known as an ultramicro- 

 scope which reveals the spirochaetes as actively 



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