34 MORPHOLOGY 



The flagella on a bacterial cell are very hard to demonstrate. 

 It is only by the most careful technique and the use of special 

 mordants that they can be revealed. They cannot be seen 

 definitely in unstained preparations or preparations stained 

 in the ordinary manner. The protoplasm of the flagella does 

 not readily enter into chemical combination with the ordinary 

 bacteriological stains. This points to the fact that its pro- 

 toplasm is different from that contained within the cell. The 

 flagella may be often revealed by the deposition of stains 

 (AgNO 3 , etc.) on the outside of the limiting membrane. 

 Many bacteria discard their flagella when they are removed 

 from the medium in which they are growing. Consequently 

 they are very hard to place intact on a slide. They are very 

 sensitive and the flagella are very easily disintegrated during 

 the process of staining. It has been noted that the staining 

 power of a flagellum often varies with the species of bacteria. 

 Mordants are used with the stains in order that the flagella 

 may be demonstrated at all. 



As a flagellate bacterium moves it progresses in a definite 

 manner. The mono- and lophotrichous bacteria move with 

 the flagellum or flagella in front like certain infusoria, and 

 rotate these organs in a circular fashion in a direction longi- 

 tudinal to the long axis of the cell. The cell itself, in certain 

 species, rotates freely when in motion. The peritrichous 

 bacteria move in a longitudinal direction as the other bacteria 

 and in addition may possess an end-over-end motion, tumb- 

 ling similar to a somersault. 



