ternus. 27, The gluteus medius. 28, The
gluteus magnus. 29, The biceps flexor cruris. 30, The semi-tendinosus.
31, 32, The gastrocnemius. 33, The tendo Achillis.

_Practical Explanation._ The muscle 1, fig. 46, by its contraction,
raises the eyebrows. The muscle 2, fig. 46, closes the eyelids. The
muscle 3, fig. 46, elevates the upper lip. The muscles 4, 5, fig. 46,
elevate the angles of the mouth. The muscles 6, fig. 46, and 5, fig. 47,
bring the teeth together. The muscle 7, fig. 46, closes the mouth. The
muscle 8, fig. 46, depresses the lower lip. The muscles 9, fig. 46, and
6, fig. 47, bend the neck forward. The muscles 3, 4, fig. 47, elevate the
head and chin. The muscle 22, fig. 46, bends the body forward, and draws
the ribs downward. The muscle 11, fig. 46, brings the shoulder forward.
The muscle 7, fig. 47, draws the shoulder back. The muscles 10, fig. 46,
and 8, fig. 47, elevate the arm. The muscles 11, fig. 46, and 24, fig.
47, bring the arm to the side. The muscle 14, fig. 46, bends the arm at
the elbow. The muscle 10, fig. 47, extends the arm at the elbow. The
muscles 16, 18, fig. 46, bend the wrist and fingers. The muscle 19 bends
the fingers. The muscles 18, 21, 23, fig. 47, extend the wrist. The
muscle 23, fig. 47, extends the fingers. The muscles 26, 27, 28, fig. 46,
bend the lower limbs on the body, at the hip. The muscle 28, fig. 46,
draws one leg over the other, (the position of a tailor when sewing.) The
muscles 27, 28, fig. 47, extend the lower limbs on the body, at the hip.
The muscles 29, 30, 31, fig. 46, extend the leg at the knee. The muscles
29, 30, fig. 47, bend the leg at the knee. The muscles 34, 36, fig. 46,
bend the foot at the ankle, and extend the toes. The muscles 31, 32, 33,
fig. 47, extend the foot at the ankle.]

_Note._ Let the anatomy and physiology of the muscular system be
reviewed, in form of topics, from figs 46, 47, or from the anatomical
outline plates No. 3 and 4.

CHAPTER X.

HYGIENE OF THE MUSCLES

173. _The muscles should be used, in order that the size and strength
of these organs may be adequate to the demand made upon them._ It is a
law of the system that the action and power of an organ are
commensurate, to a certain extent, with the demand made upon it; and
it is a law of the muscular system that, whenever a muscle is called
into frequent use, its fibres increase in thickness within certain
limits, and become capable of acting with greater force; while,