CHAPTER XII. 



THE MECHANICS OF CILIARY MOVEMENT. 

 ACID BACTERIA. THE PHYLOGENY 

 SULPHUR BACTERIA. 



THIONIC 

 OF THE 



The Mechanics of Ciliary Movement. 



Spirilla exhibit both rotatory and translatory movements. 

 These result from the movements of the cihum which in the 

 spiral sulphur bacteria assumes the helicoid form. It is 

 possible by a mathematical treatment of the forces which 

 come into action when this kind of cilium is set in motion, to 

 show that the organism must necessarily exhibit translatory 

 and rotatory movements. 



Axis of 

 rotation 



Fig. 6o. 



In Fig. 60 is shown a helically wound cilium rotating in 

 a clockwise direction. 



The cilium, by its whipping action, leads to a forward 

 force on the spirillum, which may be considered the resultant 

 of a tluid pressure. 



The forces on each point on the cilium system can be 

 analysed. Suppose D' to be any point in the systemu Let 



2T6 



