BACTERIA. 39 



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. 



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. 



Certain forms much resembling bacilli in their isolated 

 state, characterized by the formation of long filaments 

 with a peculiar grouping which gives the appearance 

 of a false branching, are described as cladothrix ; others 

 in which true branchings are seen, as streptothrix. One 

 other bacillus-like form, consisting of long, thick, not 

 distinctly segmented, straight threads, is called beggiatoa. 

 The only important difference between it and leptothrix 

 is that its filaments are thick and coarse, while those of 

 leptothrix are very delicate. 



Some of the elongate bacteria have a remarkably 

 twisted form and bear some resemblance to a cork- 

 screw. These are called spirilla (Fig. 4). A subdivision 



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

 d, e, spirochseta. 



of them, whose individuals are not only twisted but are 

 also very flexible, is called spiroch&ta. Though not 

 formerly differentiated from vibrio, these forms are quite 

 distinct. 



A spiral organism of a ribbon shape is called spiro- 



