MYOLOGY 
Myology deals with the muscles and their accessory structures. The muscles 
(Musculi) are highly specialized organs, which are characterized by their property 
of contracting in a definite manner when stimulated. They are the active organs 
of motion. The contractile part of the muscle is the muscular tissue. Three kinds 
of muscular tissue are recognized, viz.: (1) Striated or striped; (2) non-striated, 
unstriped or smooth; (3) cardiac, which may be regarded as a specialized variety 
of striated muscle. Only the first of these will be considered in this section. The 
striated muscles are for the most part connected directly or indirectly with the 
skeleton, upon which they act, and are hence often designated as skeletal muscles 
(Musculi skeleti), in distinction from non-striated muscle, which is often spoken 
of as visceral. The striated muscles cover the greater part of the skeleton, and play 
an important part in determining the form of the animal. They are red in color, 
the shade varying in different muscles and under various conditions. Some are in- 
timately associated with and attached to the skin, and are called cutaneous mus- 
cles (Musculi cutanei).. The muscular part of each is composed of bundles of con- 
tractile fibers surrounded by a thin sheath of connective tissue, the perimysium. 
The deseription of the muscles may be arranged under the following heads: (1) 
Name; (2) shape and position; (3) attachments; (4) action; (5) structure; (6) 
relations; (7) blood and nerve supply. 
(1) The name is determined by various considerations, e. g., the action, at- 
tachments, shape, position, direction, etc. In most cases two or more of these are 
combined to produce the name, e. g., flexor carpi radialis, longus colli, obliquus 
externus abdominis. 
A satisfactory comparative nomenclature is exceedingly difficult to work out, and much 
confusion exists in this respect. This is due in great part to the lack of a uniform basis for the 
formation of names and the difficulty in determining homologies in various species. 
(2) The shape is in many cases sufficiently definite and regular to allow the 
use of such terms as triangular, quadrilateral, fan-shaped, fusiform, ete. Some 
muscles are characterized as long, broad, short, ete. Orbicular or ring-like muscles 
circumscribe openings; since the contraction of such a muscle closes the orifice, it 1s 
often termed a sphincter. The position and direction are usually stated with refer- 
ence to the region occupied and to adjacent structures which may be presumed to be 
already known. 
(3) The attachments are in most cases to bone, but many muscles are attached 
to cartilage, ligaments, fascia, or the skin. As a matter of convenience, the term 
origin (Origo) is applied to the attachment which always or more commonly re- 
mains stationary when the muscle contracts; the more movable attachment is 
termed the insertion (Insertio). Such a distinction is often quite arbitrary, and 
cannot always be made, as the action may be reversible or both attachments may be 
freely movable. With respect to the muscles of the limbs, the proximal attachment 
is regarded as the origin and the distal one as the insertion. In all cases the attach- 
ment is made by fibrous tissue, the muscular tissue not coming into direct relation 
with the point of attachment. But when the intermediate fibrous tissue is not evi- 
dent to the naked eye, it is customary to speak of a “‘fleshy attachment.”’ The 
term “tendinous attachment”’ is applied to those cases in which the intermediate 
fibrous tissue—tendon or aponeurosis—is evident. A tendon (Tendo) is a band of 
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