36 Bacteria 



The bacilli divide by transverse fission only, so that the 

 only peculiarity of arrangement is the formation of threads 

 or chains. 



Bacterium. In the older writings, short, stout bacilli 

 were described under the generic term bacterium. Migula 

 now employs the term to include only bacillary forms with- 

 out flagella. 



Pseudomonas. A pseudomonas is a bacillary form with 

 polar flagella. 



Vibrio. Some of the flexile bacilli have sinuous move- 

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

 are sometimes described as -vibrio; but this name also has 

 passed into disuse, except in France, where spiral organisms 

 are so called. 



Long filaments formed by division of bacilli without dis- 

 tinct separations are sometimes called leptothrix, and when 

 such threads form tangled masses surrounded by a jelly- 

 like material, the name myconostoc is sometimes applied to 

 them. 



Spirilla. If a rod-shaped bacterium is spirally twisted 



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

 Spirilla ; d, e, spirochaeta. 



and resembles a corkscrew, it is called spirillum (Fig. 4). 

 The rigid forms without flagella are known as spirosoma; 

 rigid forms with flagella, spirilla and microspira. The 

 flexile forms are called spirochceta and probably have no 

 flagella. 



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 

 sulphur granules have been detected has been called ophi- 

 diomonas. 



