156 



MYOLOGY. 



STRIATED MUSCULAR TISSUE. 



Voluntary or striated muscular tissue forms the mass of the 

 so-called muscles, which terminate at either extremity in fibrous 

 structures termed the tendons, by means of which they are 

 attached to the bones ; the intermediate fleshy portion is often 

 called the belly of the muscle. A muscle is composed of bundles, 

 or fasciculi of fibres, which are the integral parts of 

 the structure. The microscope shows these fibres 

 to consist of fine filaments termed fibrillce, which 

 run parallel to each other, maintaining an undivided 

 course throughout. Each fibre is enclosed in a 

 \ delicate tubular sheath called the sarcolemma or 

 : ; i: | myolemma, composed of a transparent and ap- 

 parently homogeneous membrane, tough and elastic, 

 I II I] which isolates each fibre, and frequently remains 

 intact after rupture of its contents. The fibres, 



fasciculus of about 5tfo tu of au incn in diameter, are gathered 



striated muscu- into prismatic or polyhedral fasciculi, and invested 



verse sTr'iw Teen w ith a sheath of connective tissue, which is inflected 



at , -6, union of between the fibres, and called the nerimiisium 



fibres with the . ' \ / 



tendon. vntcrnv/m, ; the entire muscle has likewise an 



investing sheath of connective tissue, the peri- 



mysium externum, continuous with the above. This connective 



FIG. 67. 



A single striated muscular fibre, showing its com- 

 ponent fibrillse. 



tissue is membranous in structure, its use being to connect the 

 bundles and fibres, and to serve as a matrix for the ramification 

 of blood-vessels, nerves, and absorbents. 



A muscular fibre, examined under a power of 300 diameters 

 or less, will display the transverse waving strice or lines, from 

 which the name " striated " is derived. Longitudinal markings 



