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174 ANATOMY.

strictor muscles, being advaneed forward into the face. It also differs
from the facial muscles hy being- enclosed in a sheath of thin fascia, and
is suj)plied by a different motor nerve. It arises from the lower margin
of the outer surface of the alveolar })rocesses of the superior and inferior
maxillary bones oj)posite the molar teeth, from the anterior surface of
the ptervgo-maxillaiy ligament, which is a narrow band of tendinous
fibres extending from the upper extremity of the hanudar process
of the internal ])terygoitl plate of the s})henoid bone to the mylo-hyoid
ridge of the inferior maxillary bone, close to the position of the wisdom
tooth. From this extensive origin its fibres ])ass forward, converge,
and become thickened as they ivacii the lateral margin of the orbicularis
oris. At this point its central fibres decussate, those from the U})[)er
]>ortion becoming blended with the nuiscles of the lower lip, and those
from the lower portion blending with the muscles of the upper lip. The
superior and inferior fibres of the nuiscle continue forward without
decussation, inosculating with the superficial fibres of tiie orbicidaiis
oris, becoming lost on the opj)osite side of the mouth.
Rel((tions.— J^y its superficial surface with a considerable quantity
of soft adipose tissue, which separates it from behind forward from the
ramus of the jaw, a small part of the temporal niuscle, the masseter
nuiscle, the muscles of ex])ression connected with the angle of the
mouth, the parotid duct, which ])icrces the muscle opposite the second
molar tooth of the up])er jaw, and the fiicial artery and vein ; branches
of the fiicial and buccal nerves pass over it. By its deep surfiice it is in
relation with the buccal glands and mucous membrane of the vestibule
of the mouth.
Actions of thk Okal Miscles.—When the whole of the orbicu-
laris oris muscle is brought into independent action, it closes the lips
l)oth vertically and transversely, and when a forced action is brought
about, it projects the lips and wrinkles the integuments; when acting
jointly with the buccinator, the lips are closecl and elongated trans-
versely. A\'hen the associatt'd muscles wiiich converge from nearlv all
points act singly, they draw the orbicularis oris in the longitudinal direc-
tion of their fibres. WJien two or more nmscles act together, the line of
traction will be between these muscles, the direction depending upon the
relative power of each muscle.
The common elevators of the lip and nose and the depressors of the
wing of the nose act ujion these ])arts in oi>p()sition to each other, the
former elevating, the latter depressing. Tiic muscles which are inserted
at the angles of tiie mouth not only elevate and draw the angle back-
ward, but in (h)ing so they push the cheeks u|)ward and thus elevate the
margin of the lower eyelid, as is shown by the ex])ression of the mouth
and cheeks in merriment ; while those which depress the angles also
depress the cheeks, as illustrated by the face in grief.

The Muscles of the Ear.
The auricular nuiscles are those that belong to the pinna of the ear.
There are several minute bundles of muscular fibres which extend from
one point to another in the pinna ; also three larger muscles, two aris-