CHAPTER X 

 A STUDY OF THE MUSCLES 



Importance of Muscle Tissue. Muscle tissue constitutes 

 or almost half of the weight of the human body. 

 In this kind of tissue is found one fourth of all the 

 blood. But the importance of muscle tissue is appre- 

 ciated, even more fully, when 

 we realize that nearly every 

 kind of movement in the body 

 is due to the action of the 

 muscles. Not only do they 

 bring about the more obvious 

 motions of the arms, the legs, 

 the trunk, and the head, but 

 also to muscular action are 

 due all the contractions of the 

 heart, of the stomach, and of 

 the other internal organs. 

 Every change in the expres- 

 sion of the face, and every 

 variation in the tone of the 

 voice is likewise a result of Fia.ST.-Musdes^of the Head and 

 the action of this all-important 



tissue. Hence we are not surprised that there are over jive 

 hundred separate muscles, which vary in length from the 

 fraction of an inch (within the ear cavity) to over a foot 

 and a half (down the front of the thigh). 



Kinds of Muscle. All of these muscles are in one way or 

 another under the control of the nervous system. Some 

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