278 PHYSIOLOGY 



repeated many (twelve to twenty) times a second, and thus serves to 

 move forward mucus, dust, or an ovum, as the case may be. The 

 movement seems to be entirely automatic, and it is quite unaffected 

 by nerves, at any rate in all the higher animals. 



There is. however, a functional connection between all the cells of 

 a ciliated epithelial surface, so that movement of the cilia, started in one 

 cell, spreads forward as a wave, just as, when the wind blows, waves of 

 bending pass over a field of corn. 



The conditions of ciliary action are the same as those for amoeboid 

 movement of naked cells. 



The minuteness of the object has up to now prevented us from 

 deciding whether the cilium is itself actively contractile, or whether it is 

 simply passively moved by the action of the basal part situated in the 

 hyaline border of the cell. 



