\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.
Note: 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.]
   (Zo["o]l.) 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.