CHAPTER XIV 



MUSCLES AND EXERCISE 



132. Use of Muscles. About one half of the weight 

 of the body is due to the muscles, or lean meat, of which 

 it is composed. Muscles are useful organs, for without 

 them we could not live for a moment. Let us see what 

 they do. Most of the muscles are fastened to bones, 

 which they completely cover, so as to make the human 

 form less angular and more beautiful in outline. Many 

 of the vital organs of the body, as the heart, arteries, 

 and stomach, are made almost entirely of muscle tissue. 

 All motion of the body as a whole, and of its various 

 parts, is accomplished by the contraction of the muscles 

 that are attached to bones. Speaking and singing are 

 accomplished by very delicately adjusted muscles of the 

 chest, throat, and mouth. In fact, you cannot name a 

 single function of the body or of any of its parts that 

 does not depend directly or indirectly upon the action 

 of muscles. 



133. Description of Muscles. The human body has 

 Qvzrfive hundred muscles which can be controlled by the 

 will, and a large number over which we appear to have 

 no control whatever. The first we call voluntary and 

 the second involuntary muscles. 



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