194 TROPICAL MEDICINE AND HYGIENE 



discovery in 1873 has been accepted as the cause of the 

 disease. These spirilla are now commonly termed 

 spirochaetae. 



The Spirillum obermeieri or Spirochcvta recurrentis is 

 a delicate wavy thread measuring between 15 //, and 

 40 yu, in length by about -25 //, in breadth at its widest 

 part. The number of spirals varies greatly, as also does 



*IG. 54- 



their contour. A common number of spirals is eight, 

 but often two spirilla are joined together, giving the 

 appearance of one long form with sixteen spirals. Some- 

 times the spirals may be short, giving a corkscrew 

 appearance, or they may be only slight undulations. In 

 thick films the spirilla may be in bold curves or figures of 

 eight, with few or no undulations (fig. 54). 



No details of structure can be made out except that 

 it has tapering pointed ends, and that, especially when 

 stained by Romanowsky's method, slight differences in 

 the degree of staining of different parts can be noted, the 



