Mus"cle (?), n. [F., fr. L.
musculus a muscle, a little mouse, dim. of mus a mouse.
See Mouse, and cf. sense 3 (below).] 1.
(Anat.) (a) An organ which, by its
contraction, produces motion. See Illust. of Muscles of
the Human Body, in Appendix. (b) The contractile
tissue of which muscles are largely made up.
&fist; Muscles are of two kinds, striated and
nonstriated. The striated muscles, which, in most of the
higher animals, constitute the principal part of the flesh, exclusive
of the fat, are mostly under the control of the will, or
voluntary, and are made up of great numbers of elongated
fibres bound together into bundles and inclosed in a sheath of
connective tissue, the perimysium. Each fiber is inclosed in a
delicate membrane (the sarcolemma), is made up of alternate
segments of lighter and darker material which give it a transversely
striated appearance, and contains, scattered through its substance,
protoplasmic nuclei, the so-called muscle corpuscles.
The nonstriated muscles are involuntary. They constitute
a large part of the walls of the alimentary canal, blood vessels,
uterus, and bladder, and are found also in the iris, skin, etc. They
are made up of greatly elongated cells, usually grouped in bundles or
sheets.
2. Muscular strength or development; as, to
show one's muscle by lifting a heavy weight.
[Colloq.]
3. [AS. muscle, L. musculus a
muscle, mussel. See above.] (Zoöl.) See
Mussel.
Muscle curve (Physiol.), contraction
curve of a muscle; a myogram; the curve inscribed, upon a prepared
surface, by means of a myograph when acted upon by a contracting
muscle. The character of the curve represents the extent of the
contraction.
