BROWNIAN MOVEMENT 



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power of locomotion. These motile bacteria, when observed in fluid, 

 shoot and dart about like a school of minnows in clear water. Bac- 

 teria which are truly motile possess organs of locomotion in the 

 shape of exceedingly fine slender threads or filaments called flagella 

 (singular flagellum). These filaments are found at one or both ends, 

 or all around the body. Generally, only bacilli and spirilla possess 

 flagella, but a very few cocci also have them. We classify flagellate 

 bacteria as follows: 



Monotricha one flagellum at one end. 



Amphitricha one flagellum at each end. 



Lophotricha several flagella at one end. 



Peritricha flagella all around the bacterium. 



Atricha no flagella. 



FIG. 14 



FIG. 15 



Fraenkel's pneumococcus, pure culture in 

 litmus milk, showing capsule. X 1000. 

 (Author's preparation.) 



Anthrax bacillus in the blood of an infected 

 cow, showing capsule. X 1000. (From a 

 preparation of Dr. L. E. Day.) 



Characteristics. Flagella are, as a rule, exceedingly slender fila- 

 ments, several times longer than the bacterium itself. They are wavy 

 in outline and terminate in a blunt or slightly club-shaped extremity. 

 They cannot be stained by the ordinary bacterial staining methods, 

 but require a special complicated technic. They break off easily 

 from the bacterium, but as far as known they are easily regenerated. 

 They arise out of the ectoplasm, but are probably also connected 

 with the entoplasm. 



Brownian Movement. Even those bacteria which have no flagella, 

 and which in consequence have no true locomotion when examined 

 in a drop of water, present a peculiar oscillating, trembling motion, 

 but this movement is not confined to living bacteria. Dead bacteria 

 or very minute particles of solid matter, when suspended in fluid, 

 show a similar motion, which is called the Brownian movement, 

 because it was first described by the botanist Brown. It is now 



