MOTILITY— CAPSULES 3 



Motility of bacteria, — A large number of bacteria pos- 

 sess the power of movement, accomplished by means of 

 cilia or flagella, forming spiral processes, of which some- 

 times one is present, sometimes several, and which keep 

 up an incessant vibration. 



This motility must not be confounded with oscillatory 

 movements (also, however, to be understood as originated by 





1 



Fig. 1. — Forms of Bacteria, Magnified about 700 times, (After Baumgarten.) 



the bacteria themselves) , nor with such motion as occurs in 

 inert particles suspended in a fluid medium, and which is 

 known as the ' molecular movement of Brown ' {Brownian 

 movement) . 



Capsules of bacteria, — Capsules are formed by swelling 

 of the membrane, and are best seen in those micro- 

 organisms which are found in groups — viz. the diplococci, 

 streptococci, tetracocci, and sarcinas ; but various bacilli 

 also, such as Pfeififer's capsule-bacillus and the Bacillus 



n 2 



