244 



MOTION AND COORDINATION 



striated muscular tissue far exceeds the others in amount 

 and forms all those muscles that can be felt from the sur- 

 face of the body. The non-striated muscle is found in the 

 walls of the food canal, blood vessels, air passages, and 

 other tubes of the body ; while the muscular tissue of the 

 heart is confined entirely to that organ. 



Striated Muscle Cells. The cells of the striated mus- 

 cles are slender, thread-like structures, having an average 

 length of i| inches (35 millimeters) and 

 a diameter of about -%^-Q of an inch (60 /*). 

 Because of their great length they are 

 called fibers, or fiber cells. They are 

 marked by a number of dark, transverse 

 bands, or stripes, called striations, 1 which 

 seem to divide them into a number of sec- 

 tions, or disks (Fig. 108). A thin sac-like 

 covering, called the sarcolemma^ surrounds 

 the entire cell and just beneath this are a 

 number of nuclei. 2 



Within the sarcolemma are minute fibrils 

 and a semiliquid substance, called the sar- 



' ~~, coplasm. At each end the cell tapers to a 

 striated muscle r - t 



cell highly magni- point from which the sarcolemma appears 

 fied, showing stria- to continue as a fine thread, and this, by 

 tions and nuclei, attaching itself to the inclosing sheath, 



Attached to the cell ,1-1^1 ,, . , , , r , 



is the termination holds the cell in place. Most of the muscle 

 of a nerve fiber. ce ^ s receive, at some portion of their length, 

 the termination of a nerve fiber. This 

 penetrates the sarcolemma and spreads out upon a kind of 

 disk, having several nuclei, known as the end plate. 



1 On account of the striations of these cells the muscles which they form are 

 called striated muscles. 



2 The striated muscle cells, having many nuclei, are said to be multi-nucleated. 



