THE SP1ROCH&TACE& 631 



ends; varying in length from 8 to 16 /z. and in thickness 

 from 0.3 to 0.5 ju. They possess a delicate undulating 

 membrane, though this is rarely seen in stained preparations. 

 They are motile but not flagellated. They multiply by 

 transverse and occasionally by longitudinal division. 



When stained by the Giemsa method they appear as 

 violet threads (see Fig. 106). When obtained in artificial 

 cultivation they are said (Noguchi) to be soluble in 10 

 per cent, bile salts; to be immobilized and ultimately dis- 

 integrated by 10 per cent, saponin. 



Genus Treponema. To this genus belong the species 

 treponema pallada causing syphilis and treponema pertenue 

 causing frambesia tropica (yaws). 



They are seen in stained preparations and by dark field 

 illumination as tightly wound, short, rigid spirals. They 

 vary in length from 6 to 14 /* and in thickness of the thread 

 from 0.2 to 0.3 p. No undulating membrane is observed 

 (see Fig. 107). 



Multiply by transverse and possibly also by longitudinal 

 division. 



The spirals stain pink by the Giemsa method. 



When obtained in culture (Noguchi) they are dissolved 

 by 10 per cent, bile salts and more slowly by 10 per cent, 

 saponin. 



Genus Leptospira. Type species leptospira icerto hemor- 

 rhagise found by Inado and Ido in infectious jaundice. 

 The genus also includes leptospira icteroides found by 

 Noguchi in yellow fever 1 and described by him as very 

 small, regular, rigid spirals with hook-like prolongations 

 at one or both ends. They vary in length from 7 to 14 /z. 



1 See Jour. Exper. Med., 1919, vol. xxx, p. 13. 



