MYOLOGY 



Kinds and Structure of Muscles. — Muscles are highly specialized 

 structures which have the property of contractility when stimulated, 

 and thus produce motion. Muscular tissue is sometimes called 

 flesh. Two kinds of muscles are recognized; muscles of locomotion 

 and visceral muscles. 



The muscles of locomotion may be in masses of different shape 

 attached to the skin, the dermal, or to the skin and skeletal structure, 

 the dermo-osseous, or from one bone to another, the skeletal. The 

 visceral muscles form sheets and make up a portion of the wall of 

 many of the hollow organs, such as the intestines, the stomach, 

 the gizzard, the esophagus, and the blood-vessels. A special type 

 of muscle forms the heart. 



When classified with reference to structure, muscular tissue 

 is divided into three types, as follows: voluntary-striated, in- 

 volimtary, and involimtary-striated. The microscopic examination 

 of each of these types of muscle shows it to be made up of fibers, 

 these fibers to be made up of muscle cells, the muscle cell to be in- 

 closed in a delicate tubular sheath, or membrane, called the sarco- 

 lemma. This membrane, tough and elastic, isolates each fiber. 

 The bundles of fibers, called fasciculi, are surrounded by a fibrous 

 sheath, which is called the perimysium internum; and the entire 

 muscle has likewise an investing sheath of connective tissue, called 

 the perimysium externum. The muscular cells show a longitudinal 

 striation marking the fibriUae, and they also show a cross striation. 

 Nuclei are found just beneath the covering, or sarcolemma, in the 

 striated muscle cell (Fig. 77, No. 2). In the involuntary and in the 

 involuntary-striated muscle cell, the nuclei are centrally located. 



The voluntary-striated muscles consist of cylindrical fibers and with 

 a few exceptions, are under the control of the will. A muscle of 

 this type, the regular skeletal form, usually has at each extremity a 

 fibrous structure, called a tendon, by means of which it is attached 

 to the bones. The intermediate fleshy portion of the muscle, in 

 case of considerable bulk, is called the belly of the muscle. 



The involuntary, non-striated, or smooth muscle, cells are spindle- 

 shaped, long, and pale in color (Fig. 77, No. i). The cells lie end to 

 end forming fibers. These fibers do not terminate in tendons, but 



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