156 



MYOLOGY. 



STRIA.TED MUSCULAll TISSUE. 



Voluntary or striated muscular tissue forms tlie 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 fihrilloe, which run 

 parallel to each other, maintaining an undivided 

 course throughout. Each fibre is enclosed in a 

 delicate tubular sheath called the sarcolemma or 

 myolemma, 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 5^-J-oth 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 perimysium 

 internum ; the entire muscle has likewise an 

 investing sheath of connective tissue, the jperi- 

 mysium externum, continuous with the above. This connective 



Fiu. 68. 

 Fasciculus of 

 l^striated muscu- 

 lar fibres. Trans- 

 verse sti'isB seen 

 at a ; 6, U nion of 

 fibres with the 

 tendon. 



Fig. 67. 

 A single striated muscular fibre, showing its com- 

 ponent fibrillae. 



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 strioi or lines, from 

 which the name " striated " is derived. Longitudinal markings 



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