MUSCULAR POWliR. 117 



fectly independent of the will. Tims we find that 

 if any one of the ciliated ten taenia of a polype be cut 

 off, its cilia will continue to vibrate, and will propel 

 it forwards in the fluid for a considerable time, as 

 if it possessed individual volition. Yet in most 

 instances these ciliary motions appear to be of a 

 voluntary character, suddenly ceasing and being 

 renewed, without other obvious cause than the will 

 of the animal. 



It has been conjectured that the cilia are tubular 

 organs, which are distended and protruded by the 

 injection of water from elastic canals placed along 

 their base, through which fluid is impelled by suc- 

 cessive undulations. Ehrenberg states that the 

 cilia of the infusoria are bulbous at the root ; and 

 supposes that they are moved by small muscles 

 attached to the bulb-t Dr. Sharpey, who has 

 given an excellent account of these organs as they 

 occur in the difterent tribes of animals, is of opinion, 

 from a review of the whole of the phenomena, that 

 they are best explained on the supposition of mus- 

 cular act ion 4 



In animals placed a little higher in the scale, we 

 begin to trace the formation of fibres, which at 

 first are irregularly scattered through the soft sub- 

 stance : but as the organization becomes more 

 refined, these fibres are collected into bundles, and 

 compose what are properly called muscles. Mus- 

 cular fibres are attached at their extremities to the 

 parts intended to be moved. In the lower animals, 

 these attachments are principally to the skin, or 

 other external parts, which are subservient to the 



t Ann. Sc. Nat. serie 2, i. 222. 



I Dr. Todd's Cyclop, of Anat. and Physiol, article Cilia, i. 606. 



