The Muscles and Fasciae. 



THE Muscles are the active organs of locomotion. They are formed of bundles 

 of reddish fibres, consisting chemically of fibrine, and endowed with the pro- 

 perty of contractility. Two kinds of muscular tissue are found in the animal 

 body, viz., that of voluntary or animal life, and that of involuntary or organic 

 life. 



The muscles of animal life (striped muscles) are capable of being either exerted 

 or controlled by the efforts of the will. They are composed of bundles of fibres 

 inclosed in a delicate web of areolar tissue. Each bundle consists of numerous 

 smaller ones, inclosed in a similar fibro-areolar covering, and these again of primi- 

 tive fasciculi. 



The primitive fasciculi consist of a number of filaments, inclosed in a tubular 

 sheath of transparent, elastic, and apparently homogeneous membrane, named by 

 Bowman the " Sarcolemma." The primitive fasciculi are cylindriform or prismatic. 

 Their breadth varies in man from 5 ^ to $%$ of an inch, the average of the ma- 

 jority being about 3 ^ n ; their length is not always in proportion to the length of 

 the muscle, but depends on the arrangement of the tendons. This form of muscular 

 fibre is especially characterized by being apparently marked with very fine, dark, 

 parallel lines or strise, which pass transversely round them, in curved or wavy 

 parallel lines, from T^^TT to y^Ju^ of an inch apart. Other stria? pass longitu- 

 dinally over the tubes, indicating the direction of the primitive fibrils of which 

 the primitive fasciculus is composed. They are less distinct than the former. 



The primitive fibrik constitute the proper contractile tissue of the muscle. 

 Each fibril is cylindriform, somewhat flattened, about Tg lTyTT f an i ncn i n thick- 

 ness, and marked by transverse striae placed at the same distance from each other 

 as the striae on the surface of the fasciculus. Each fibril apparently consists of a 

 single row of minute particles, named " sarcous elements" by Bowman, connected 

 together like a string of beads. Closer examination, however, shows that the 

 elementary particles are little masses of pellucid substance, having a rectangular 

 outline, and appearing dark in the centre. These appearances would favor the 

 suggestion that the elementary particles of which the fibrils are composed are 

 possibly nucleated cells, cohering in a linear series, the transverse marks between 

 them corresponding to their line of junction. Kolliker, however, considers "the 

 sarcous elements as artificial products, occasioned by the breaking up of the fibrils 

 at the parts where they are thinner." 



This form of muscular fibre composes the whole of the voluntary muscles, all 

 the muscles of the ear, those of the larynx, pharynx, tongue, and upper half of 

 the oesophagus, the heart, and the walls of the large veins at the point where they 

 open into it. 



The muscks of organic life (unstriped muscles} consist of flattened bands, or of 

 elongated, spindle-shaped fibres, flattened, of a pale color, from 77 '<5TJ to 3iVtf f 

 an inch broad, homogeneous in texture, having a finely mottled aspect, which 

 sometimes appears granular, the granules being occasionally arranged in a linear 

 series, so as to present a striated appearance. Each fibre contains a cylindrical 



1 The Muscles and Fasciae are described conjointly, in order that the student may consider the 

 arrangement of the latter in his dissection of the former. It is rare for the student of anatomy 

 in this country to have the opportunity of dissecting the fasciae separately ; and it is for this 

 reason, as well as from the close connection that exists between the muscles and their investing 

 aponeuroses, that they are considered together. Some general observations are first made on 

 the anatomy of the muscles and fasciae, the special description being given in connection with 

 the different regions. 



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