MUSCLE AND MUSCULAR TISSUE. 152 MUSCLE AND MUSCULAR TISSUE. of till' arteries ami viiiis. oi tlic liacliea and bronchi, of llir laijicr duets of glands, and occurs in the urinary tract, and in the male and female generative orjjans. etc. It consists of long, slen- der, spindle-siiapcd cells from .075 to .2.30 niilli- VOLrNTARY MI'SCLE. Smooth muscle fibres from the sninll intPxtine of a Jrogr. meter in length and from .004 to .010 milli- meter broad. Its substance shows fine longi- tudinal markings. A delicate sheath or tell wall has been described and within this is the semi- tluid granular protoplasm of the cell body. In the centre of the latter 3 -nuc. lies a long rod- shaped nucleus to- ward each end of which a few fine granules are found. These cells are ar- ranged in bundles. the individual cells t3n.S:^^ ^^3, being held together by a cement sub- stance, the bundles being surrounded by more or less con- nective tissue. Blood- voLiNTARY MUSCLE. vcsscls ramifv in one. nuclei; t.m.s., termlna- i, • „nnn„„fi,,p tis- tlon of muscular substance. ""*' connecine lis sue where they break up into capillaries which form a network among the muscle cells. Nerves, mainly of the sympa- thetic system, pass to the individual muscle cells. (2) Striated Voluntary Muscle. This form of muscular tissue constitutes the ordinary volun- ^^'f-^^ww—^ tary muscles of p€V ^iTSfs^^^^ the skeletal system.
^V^J Vj' ^ '^"f' occurs in the
' I / l-^ J^-f^i iliaiihragm. genera- ^. t'Tf KV^yb ♦■^••^ organs.^tc. It Vjf V frL A - x-"' "i- '* composed of long f W^ H )-<'^') ; cylindrical fibres, each one of which represents a highly specialized devel- opment of a single cell. The nniscle filvre consists of the muscle sub- stance proper, the muscle nuclei, and an external sheath or ^arcolcmnia. The muscle substance of a fibre shows a longifuilinal stria- tion which indicates its division into ullimatc fibrillic. while transversely it consists of alter- nate light and dark bands or disks. The light disk is crossed by a delicate dark line, the line or membrane of Krause. A light line across the dark disk (llensen's line) has also been described, but is probably an artefact. TOLCSTARY MrwI.K I.S TllASS- VKftHK HKCTIIIN. w.f., mtiHt'If lUipcf*; cnit. cn- domysjuin; per. pfrlni.vsiuni. INJTXTED TnLfKTARV MCS- CLK. The minute bit of muscular tissue scjiarated ofl' by Krause's line at either end and by the dividing line between the librillie on each side is known as the 'sarcous element of Bowman,' while the appearance presented by the cross-cut ends of the librilUe composing a single fibre is called "(.'ohnheim's field.' Each fibre is inclosed in a transparent, very delicate, but tough and elastic sheath, which can- not always be readily seen, but often shows distinctly, stretching be- tween the separated frag- ments of a fibre which has been broken within it, its toughness and elas- ticity allowing it to re- sist a force sulficient to rupture its more brittle contents. This sheath is known as the sarcolemma or myolcnima. the former term being derived from the Greek words sarx (flesh) and lemma (skin or husk), the latter from the Greek words miui (muscle) and lemma. .Tust beneath the sarcolemma, in the muscle protoplasm, lie the muscle nuclei. They are oval or spindle in shape, their long axes cor- responding to those of the fibre. The individual muscle fibres are held together by a delicate connective tissue called the en<lomysium. The muscle fibres are bound together into bundles or fascicles by a coarser connective tissue, the perimysium, while the entire muscle is sur- rounded by a connective tissue sheath, the epimysiuni. In short muscles single fibres may extend the entire length of the nuisde. In longer muscles the single fibres do not extend the en- tire length of the muscle, averaging 2") to .50 mil- limeters in length, ^"ery long tilircs. 100 to 120 millimeters long, are sometimes found. The fibres taper somewhat at their ends and terminate, if in the middle of the muscle, by a blending of the sarcolemma with the endomysium of the neigh- boring fibres ; if in tendon, periosteum, or peri- <'bonilrium. by union of the sarcolemma with the connective tissue. Striated muscle is extremely vascular. The larger vessels run in the perimy- sium, where they branch, and these smaller branches give ofl" capillaries which form a rec- tangular meshed network among the indiviilual fibres. The larger nerve trunks run in the pcriniy- sium. where they subdivide and send branches to the muscle fibres. Here they terminate in special 'end plates.' See Xervoi's System. m.c
>^-- '^^■'i » -nuc BECTION OF CAROIAC OB HF.ART MTfiCLE (Ptrlrtt^Hl involllll- tory muM'lp). m.c, muscle columns; 7.d.£., lone of let*» differentiated Hnrcoplat*m ; ouc, nucleus. (3) Cardiac or Heart Muficlr (fiirintrd furol- untnnf }fuscJr). This is a typo oi iniiscniar
