gth of 1-1/2 inches (35
millimeters) and a diameter of about 1/400 of an inch (60 {~GREEK SMALL LETTER MU~}). Because of
their great length they are called fibers, or fiber cells. They are marked
by a number of dark, transverse bands, or stripes, called striations,(83)
which seem to divide them into a number of sections, or disks (Fig. 108).
A thin sac-like covering, called the _sarcolemma_, surrounds the entire
cell and just beneath this are a number of nuclei.(84)

[Fig. 108]

Fig. 108--*A striated muscle cell* highly magnified, showing striations and
nuclei. Attached to the cell is the termination of a nerve fiber.

Within the sarcolemma are minute fibrils and a semiliquid substance,
called the _sarcoplasm_. At each end the cell tapers to a point from which
the sarcolemma appears to continue as a fine thread, and this, by
attaching itself to the inclosing sheath, holds the cell in place. Most of
the muscle cells receive, at some portion of their length, the termination
of a nerve fiber. This penetrates the sarcolemma and spreads out upon a
kind of disk, having several nuclei, known as the _end plate_.

*The "Muscle-organ."*--We must distinguish between the term "muscle" as
applied to the muscular tissue and the term as applied to a working group
of muscular tissue, which is an organ. In the muscle, or muscle-organ, is
found a definite grouping of muscle fibers such as will enable a large
number of them to act together in the production of the same movement. An
examination of one of the striated muscles shows the individual fibers to
lie parallel in small bundles, each bundle being surrounded by a thin
layer of connective tissue. (See Practical Work.) These small bundles are
bound into larger ones by thicker sheaths and these in turn may be bound
into bundles of still larger size (Fig. 109). The sheaths surrounding the
fiber bundles are connected with one another and also with the outer
covering of the muscle, known as

[Fig. 109]

Fig. 109--*Diagram* of a section of a muscle, showing the perimysium and
the bundles of fiber cells.

[Fig. 110]

Fig. 110--*A muscle-organ in position.* The tendons connect at one end with
the bones and at the other end with the fiber cells and perimysium. (See
text.)

*The Perimysium.*--The plan of the muscle-org