CHAPTER XI. 



THE MUSCLES. 



COVERING up the bones and attached to their surfaces at certain 

 definite places is the soft, red., fleshy portion of the body: the mus- 

 cular substance. This consists of not one homogeneous environing 

 mass, but of a great number of distinct fleshy masses, called muscles. 

 These are of various forms and sizes; number about four hundred; 

 and are, for the most part, arranged in pairs. It is mainly to the 

 shape and disposition of these muscles that the body owes the regu- 

 larity of its contour. 



It is by the power of these skeletal muscles that the animal is 

 able to move about, procure means of sustenance, care for its young, 

 etc. ; but it must be borne in mind that muscles not so powerful as 

 are the skeletal muscles, but muscles, nevertheless are contained 

 within the viscera and blood-vessel walls. These muscles have very 

 important functions to perform in aiding the processes of metab- 

 olism : that balance which when disturbed produces, not health, but 

 disease. 



Any animal motion means muscle. Muscular tissue is empowered 

 with contractility; that is, an ability to shorten itself when acted upon 

 by any stimulus. By its shortening it produces movement to parts to 

 which one or both of its ends are attached. The resultant motions 

 may be the very common ones of walking, running, various manual 

 employment, etc., or the peristaltic movements of stomach and in- 

 testines, or the variations in the sizes of the lumen of the blood- 

 vessels. Any animal movement should at once recall to the mind of 

 the student that it is the' resultant of some muscular contractility 

 produced by the influence of a stimulus to it, whether that be nerv- 

 ous, electrical, mechanical, or thermal. 



Muscular tissue consists of fibers bound together into those dis- 

 tinct organs already mentioned as muscles, and in this condition is 

 known as the meat of animals. 



In the fine anatomy of the muscles I have followed the writings 

 of Professor Shaefer, as they appear in Quain's "Anatomy," of which 

 this is an abstract. 



Varieties. When seen under the microscope, these fibers are 

 found to be cross-striped, or striated; as many of them are under the 

 control of the will, they are usually spoken of as being voluntary. 

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