40 Structure and Classification of Micro-organisms 



described under the generic term bacterium. Migula now 

 employs the term to include only bacillary forms without 

 flagella. A pseudomonas is a bacillary form with polar 

 flagella. Some of the flexile bacilli have sinuous move- 

 ments resembling the swimming of a snake or an eel, and 



Fig. 3. Diagram illustrating the morphology of the bacilli: a, 6, 

 c, Various forms of bacilli ; d, e, bacilli with flagella ; /, chain of bacilli, 

 individuals distinct ; g, chain of bacilli, individuals not separated. 



are sometimes described as vibrio; but this name also has 

 passed into disuse, except in France, where spiral organisms 

 are so called. 



Spirilla. If a rod-shaped bacterium is spirally twisted 

 and resembles a corkscrew, it is called spirillum. The rigid 

 forms without flagella are known as spirosoma; rigid forms 

 with flagella, spirilla and microspira. 



A spiral organism of ribbon shape is called spiromonas, 

 while a similar organism of spindle shape is called a spiru- 

 lina. One species of spiral bacteria in whose cytoplasm 



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



Spirilla. 



sulphur granules have been detected has been called ophi- 

 diomonas. 



Spiral organisms with undulating membranes are known as 

 spiroch&ta, but these and the similar genus treponema are 

 now regarded as more correctly placed among the protozoan 

 organisms. 



