580 



MOTION. 



muscular contraction, for it is involuntary ; there is no 

 nervous or muscular tissue in the immediate neighbour- 

 hood of the cilia, and it continues for several hours after 

 death or removal from the body, provided the portion of 

 tissue under examination be kept moist. Its independence 

 of the nervous system is shown also in its occurrence in 

 Fig. 146.* fig. 147^ 



the lowest invertebrate animals apparently unprovided 

 with anything analagous to a nervous system, in its per- 

 sistence in animals killed by prussic acid, by narcotic or 

 other poisons, and after the direct application of nar- 

 cotics to the ciliary surface, or the discharge of a Leyden 

 jar, or of a galvanic shock through it. The vapour of 

 chloroform arrests the motion; but it is renewed on the 

 discontinuance of the application (Lister). According to 

 Kiihne, the movement ceases in an atmosphere deprived 

 of oxygen, but is revived on the admission of this gas. 

 Carbonic acid stops the movement. The contact of various 

 substances will stop the motion altogether ; but this seems 

 to depend chiefly on destruction of the delicate substance 

 of which the cilia are composed. 



Little or nothing is known with certainty regarding 

 the nature of ciliary action. As Dr. Sharpey observes, 

 however, it is a special manifestation of a similar pro- 

 perty to that by which the other motions of animals are 



* Fig. 146. Spheroidal ciliated cells from the mouth of the frog ; 

 magnified 300 diameters (Sharpey). 



t Fig. 147. Columnar ciliated epithelium cells from the human nasal 

 membrane; magnified 300 diameters (Sharpey). 



