212 THE MUSCULAR SYSTEM 



tinuous along a fold termed the mesotendon. The arrangement is shown in 

 Fig. 171/ The articular synovial membranes in some places form extra-articular 

 pouches, which facilitate the play of tendons. 



The fasciae are sheets of connective tissue, mainly of the white fibrous variety, 

 with a greater or less admixture of elastic fibers in certain cases. Two layers may 

 usually be recognized. Of these, the superficial fascia (Fascia subcutanea) is com- 

 posed of loose connective tissue which may contain more or less fat and is sub- 

 cutaneous. The deep fascia is composed of one or more layers of dense fibrous 

 tissue spread over the surface of the muscles chiefly. Its deep face may be very 

 loosely attached to the underlying structures or may fuse with the epimysium, 

 tendons, bones, or ligaments. In some parts, especially the limbs, septal plates 

 pass between the muscles and are attached to the bones or ligaments; these are 

 termed intermuscular septa. In this way many muscles are inclosed in fibrous 

 sheaths which hold them in position. Not uncommonly special bands stretch 

 across the grooves in which tendons play, converting these into canals. Such 

 bands are termed vaginal or annular ligaments. The deep fascia is often so dis- 

 tinctly tendinous in structure, furnishing attachment to special tensor muscles, 

 as to render the distinction between fascia and aponeurosis quite arbitrary. Bursse 

 occur in certain situations between the fascia and underlying structures (subfascial 

 bursse), or between the fascia and the skin (subcutaneous bursse). 



It is convenient to divide the description of a muscle into seven heads, viz.: 

 (1) Name, followed by important synonyms; (2) position and form; (3) attach- 

 ments; (4) action; (5) structure; (6) relations; (7) blood and nerve supply. 



1. The name is determined by various factors, viz.: (a) The action, e. g., 

 extensor, adductor, etc.; {b) the shape, e. g., quadratus, triangularis; (c) the direc- 

 tion, e. g., rectus, obliquus; (d) the position, e. g., the subscapularis, iliacus; (e) 

 the division (into heads, etc.), e. g., biceps, triceps, etc.; (J) the size, e. g., major, 

 minor, etc.; (^f) the attachments, e. g., sterno-cephalicus, mastoido-humeralis ; 

 (h) the structure, e. g., semitendinosus. In most cases two or more of these factors 

 have combined to produce the name, e. g., adductor magnus, longus colli, obliquus 

 externus abdominis. 



2. The shape is, in many cases, sufficiently definite to allow the use of such 

 terms as triangular, (luadrilateral, fan-shaped, long, flat, fusiform, ring-like, etc. 



3. The attachments are in most cases to bone, but many muscles are attached 

 to cartilage, ligaments, fascia, the skin, etc. It is usual to apply the term origin 

 to the attachment which always or more commonly remains fixed when the muscle 

 contracts. The term insertion designates the movable attachment. Such a 

 distinction cannot always be made, as the action may be reversible, or both at- 

 tachments may be freely movable. 



4. The action belongs rather to physiological study, but is briefly indicated 

 in anatomical descriptions. 



5. The structure includes the direction of the muscle-fibers, the arrangement 

 of the tendons, the synovial membranes, and any other accessory structures, e. g., 

 annular ligaments and reinforcing sheaths and Imnds. The relation of the muscle- 

 fibers to the tendon varies, and this fact has given rise to special terms. Thus a 

 muscle in which the fibers converge to either side of the tendon is termed bipennate ; 

 wiiile one in which this arrangement exists only on one side of the tendon is called 

 unipennate. The terms fleshy and tendinous are used to indicate the relative 

 amounts of muscular and tendinous tissue. The nuiscular tissue is often spoken of 

 as the belly (Venter) of the muscle. In the case of the long muscles, the origin is 



'The student will note in dissection that transition forms occur; also that the same sheath 

 may belong to two or more tendons in common, e. g., the sheath of the two flexors on the back of 

 the carpus. In such cases the synovial membrane is reflected from one tendon to the other, and 

 may form a secondary mesotenon. 



