SPIROCHAETES 



27 



interpreted as the cause of relapsing fever in Europe and an- 

 other named Treponema duttoni, was identified as the cause of 

 "tick fever" in Africa. Relapsing fevers of other localities have 



Fig. 15— TREPONEMA 

 PALLIDUM 



The cause of much human suffering. 

 These pernicious spirochaetes have 

 the power of invading human tissues 

 of all kinds. The organisms are very 

 delicate, but after silver nitrate im- 

 pregnation they are easily seen 



From a photomicrograph by the author 

 Magnification, 1000 



since been attributed to different species of spirochaetes, variously 

 called Spirosoma, Spiroschaudinnia, again Treponema, or even 

 Spirochaeta. 



The Spread of Spirochaete Diseases 



In many diseases caused by these minute spirochaetes the 

 infection is passed from individual to individual by contact. Such 

 is the case, for example, in syphilis which is universally dis- 

 tributed, or in the African skin disease known as yaws or pian 

 or framboesia (caused by Treponema schaudinni) and discov- 

 ered by the Italian-British pathologist, Aldo Castellani (1875- 

 ), a well-known student of tropical diseases. In other types 

 of spirochaete diseases, however, the human victim does not 

 transmit the organisms directly to others, but infects some blood- 

 sucking insect, e.g., a mite or a tick, in which the spirochaetes live 

 and multiply. These animals in turn pass the spirochaetes to 

 other humans. The discovery of arthropod-borne diseases was 

 one of the greatest discoveries in the history of preventive medi- 

 cine. It was first made by American pathologists, Theobold 

 Smith (1859- ) and several collaborators, in connection 



with a blood disease of Texas cattle, variously called Texas 



