CHAPTER FIFTH. 



OF MOTION. 

 SECTION I. 



APPARATUS OF MOTION. 



148. THE power of voluntary motion is the second grand 

 characteristic of animals (57). Though they may not all 

 have the means of transporting themselves from place to 

 place, there is no one which has not the power of executing 

 some motions. The oyster, although fixed to the ground, 

 opens and closes its shell at pleasure ; and the little coral 

 animal protrudes itself from its retreat, and retires again at 

 its will. 



149. The movements of animals are effected by means 

 of muscles, which are organs designed expressly for this 

 purpose, and which make up a large portion of the body, 

 that part which is commonly called flesli. They are com- 

 posed of a series of fleshy bundles, which are readily seen 

 in boiled meat. These bundles are again composed of par- 

 cels of still more delicate fibres, called muscular fibres (45), 

 and in which alone the property of elongation and contrac- 

 tion resides. 



150. The motions of animals and plants depend, there- 

 fore, upon causes essentially different. The expansion and 



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