BACTERIA. 39 



described under the generic term bacterium. This genus, 

 like some of the species it comprehended, has now passed 

 out of use. Some of the flexile bacilli, whose movements 

 are sinuous, much resembling the swimming of a snake 

 or an eel, were described as vibrio ; but this name also has 

 passed into disuse except in France, where the spirilla 

 are all called vibrio. 



The long filaments formed by the division of bacilli 

 without their distinct separation are sometimes called 

 leptothrix, and when these long threads form distinct 

 masses surrounded by a jelly-like material the name 

 myconostoc is sometimes applied to them. 



Some of the elongate bacteria have a remarkably 

 twisted form and bear some resemblance to a cork- 

 screw. These are called spirilla (Fig. 4) (sometimes 



FlG. 4. — Diagram illustrating the morphology of the spirilla: a, b, c, spirilla; 



d, e, spirocheta. 



vibrio). A subdivision of them, whose individuals are 

 not only twisted, but are also very flexible, is called 

 spirocheta. The spirocheta of relapsing fever is the only 

 described species of this genus. 



A spiral organism of a ribbon shape is called spiro- 

 monas, while a similar organism of spindle shape is 

 called a spiruliiia. One species of spiral bacteria in 

 whose protoplasm sulphur-grounds have been detected 

 has been called ophidiomonas. 



Some of the spirilla are exceedingly long and deli- 

 cate, as the spirochseta of relapsing fever ; others which 

 are stouter, like the spirillum of cholera, habitually occur 



