EXPRESSION
The variable expressions of the human face, like the varied tones of the
voice, are sensed and ever changeable. Expression is not always caused by
the contraction of certain muscles, but rather from the combined action of
many muscles as well as the relaxation of their opposing muscles. The same
group act, for example, in both the expression of smiling and laughter, in a
lesser or greater degree.
The eyes and mouth are surrounded by muscles of circular form. These
muscles function primarily to close either mouth or eye. The fibrous ring
that surrounds the eye is attached to the inner angle of the orbit. The fibres
of the outer rim blend or mingle with the bordering muscles of the face.
Another muscle of circular form surrounds the mouth. The inner fibres
operate on the lips, while the outer borders blend with the free ends of the
surrounding facial muscles.
The muscles which encircle the eye and mouth are operated by two distinct
classes, those which control and those which oppose. If the mouth is stretched
laterally and the muscles of the cheek are raised to the lower eyelid a smile
is produced. By muscular action, a paroxysm of laughter affects not only
the face, but the body as well. The breath is drawn in, the chest, a diaphragm,
is convulsed and agitated.
The lips, the depression of the angles of the mouth disclosing the teeth
and the corrugation of the brows denote despair, fear and anger, rage and
other combinations of which the human face is capable.
Features
THE CHIN
Below the cleft of the chin, the chin itself protrudes. Its breadth at the
base is marked by two lines which, prolonged, would meet at the septum of
the nose, making a triangle that wedges upward into the base of the lower lip.
It is bordered on each side by two planes which reach to the angle of the jaw.
Variations in chins present the following comparisons: high or low;
pointed or ball; flat, furrowed or dimpled; elongated, double, etc.
MOVEMENTS OF THE LOWER JAW
THE EYE