156 



MYOLOGY. 



STRIATED MUSCULAR TISSUE. 



'':m 



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 tei-med jihrillce, which 

 run 2)arallel to each other, maintaining an undivided 

 course throughout. Each fibre is enclosed in a 

 delicate tubular sheath called the sarcolemma or 

 mijulemvia, composed of a transparent and ap- 

 parently homogeneous membrane, tough and elastic, 

 which isolates each fibre, and frequently remains 

 intact after rupture of its contents. The fibres, 

 about -g^ytli of an inch in diameter, are gathered 

 into prismatic or polyhedral fasciculi, and invested 

 with a sheath of connective tissue, which is inflected 

 between the fibres, and called the 'pervniysium 

 internwni ; the entire muscle has likewise an 

 investing sheath of connective tissue, the 'peri- 

 mysium externum, continuous with the above. This connective 



ii 



ill 



of 



Fig. 66, 

 Fasciculus 

 striated muscu- 

 lar fibres. Trans- 

 verse striae seen 

 at a ; b, Union of 

 fibres ^^ith the 

 teudon. 



Fifi. 67. 

 A single striated muscular fibre, showing its com- 

 ponent tibrillas. 



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 



