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AREOLAR TISSUE, TENDONS, AND 3IUSCLES. 165
appearance of striation, is very delicate and homogeneous. The cells
are united by an intercellular cementing substance. They are closely
packed into fasciculi, which in most cases cross and interlace one with
the other, the spindle-end of the cell fitting in between the bodies of
the other cells. The fasciculi are united at their ends by connective
tissue to the membranous parts, where such })arts occur.
Unstriated muscular tissue is largely distributed in the coats of the
arteries, veins, and viscera. It is also found in the ducts of the sweat-
glands of the skin in the form of minute muscles attached to the hair-
follicles, and in the subcutaneous tissue of the scrotum. This tissue is
supplied by numerous nerves from the sympathetic system and abundant
blood-vessels, though these are fewer in proportion than in voluntary
muscular tissue. In the walls of the stomach and intestines numerous
h^iiphatic vessels are found.
The fibres of the muscular tissue of the heart, however, differ from
those of involuntary muscular organs generally, presenting as they do
transverse striae. These strise are, however, less distinct, and the mus-
cle-fibres are smaller in diameter, than those of voluntary nuiscles. The
fibres are also made uj) of quadrangular cells joined end to end, each cell
having a single oval nucleus situated near its centre ; occasionally two
nuclei are found. The fibres composing this variety of muscle divide
and interlace, though they are not invested by sarcolenuua.
Varieties of Muscees.—General names have been given to mus-
cles significant of the arrangement of their fasciculi. Thus, when the
fasciculi of a muscle are attached to a central tendon obliquely, like the
feathers of a quill pen, the muscle is called pen )u form. If the fasciculi
of a muscle converge from a broad surface and are attached to a narroAV
tendon, the muscle is called radiated. When the fasciculi of a muscle
are turned or twisted upon themselves the muscle is called a torsion
muscle. If the tendon of a muscle passes through a loop or around a
bony process, and its action is thereby diverted from a straight line with
the longitudinal axis of its body, it is called a pidley or trochlear muscle.
Those situated at the opening of tubes ^hich separate one compartment
from another, and the fasciculi of which form circular bands, are called
spkincter muscles ; they generally have no osseous attachment, and their
action is frequently antagonized by others.
Muscles also receive special names according to the regions which they
occupy, their situation in the region, and their origin and insertion.
Thus, the superficial muscles include the subcutaneous muscles, the
in man the rudiments of this muscle are the
panniculus carnosus ;
muscles of expression, those moving the ears, and the platysma myoides.
These muscles contain a greater amount of contractile tissue than those
composing the deeper layers.
Muscles yield to pressure produced by tumors, aneurism or abscess,
and the products of inflammation pass with facility throughout their
tissue, generally taking the course of the areolar partitions.
These organs can be increased in size and firmness, by the enlarge-
ment of the individual fibres, through judicious exercise or training, but
they become smaller by an excess of physical activity or deteriorated by
inaction. The complete rest of the parts following fractures and other