28 
PRINCIPLES OF BACTERIOLOGY 
Flagella (from Latin flagellum, meaning whip).—All 
minute objects suspended in fluids are found to be in con¬ 
stant motion; this, however, is not true locomotion, but is 
irregular and jerky, and is called Brownian movement 
(after the Scotch investigator, Brown). Some bacteria, 
however, possess the property of true, independent mobil¬ 
ity which is due to the presence of one or more long, 
delicate, thread-like filaments called flagella (Fig. 3). 
They have to be stained by special methods. 
Spores.—Most of the bacteria when placed in unfavor¬ 
able environment, that is, when deprived of things es¬ 
sential to their nutrition or in the presence of harmful 
substances, die and undergo slow disintegration. But a 
few bacteria are able to pass into a latent stage of exist¬ 
ence similar to hibernation of animals, during which the 
chemical interchange is at the lowest ebb. 
This is accomplished by the bacteria developing within 
their endoplasm highly refractile, oval bodies called spores 
(from Greek sporos, meaning seed). The spores are 
highly resistant to heat and disinfectants and thus endow 
the bacterium with a special resistance against destruc¬ 
tion. 
Spore formation is not a reproductive process. When 
