_Origin_ from the ventral border of the malar bone, from opposite the
molar tooth to within three millimeters of the mandibular fossa. The
fibres pass ventrad and have their
_Insertion_ into the mandible at the ventral border of the external
coronoid fossa by means of the aponeurosis which covers the inner
surface of the muscle.
[Illustration: FIG. 65.--MUSCLES ON THE VENTRAL SURFACE OF THE THORAX,
NECK AND HEAD.
The left side shows the first layer of muscles beneath the skin and
skin-muscles; the right side shows the second layer, except in the
head region. _a_, M. masseter; _b_, M. digastricus; _c_, M.
mylohyoideus; _d_, M. stylohyoideus; _e_, M. sternohyoideus; _f_, M.
thyreohyoideus; _g_, M. sternomastoideus; _g′_, M. sternothyreoideus;
_h_, M. cleidomastoideus; _i_, M. levator scapulæ ventralis; _j_, M.
clavotrapezius; _k_, M. clavobrachialis; _l_, M. pectoralis major;
_m_, M. pectoantibrachialis; _n_, part of M. scalenus; _o_, M.
pectoralis minor; _p_, M. xiphihumeralis; _q_, M. latissimus dorsi;
_r_, M. epitrochlearis; _s_, caput longum of M. triceps brachii; _t_,
M. biceps brachii; _t′_, bicipital arch; _u_, M. acromiodeltoideus;
_v_, M. brachialis. 1, parotid gland; 2, submaxillary gland; 3,
lymphatic glands; 4, external ear; 5, external jugular vein; 6,
manubrium; 7, first rib; 8, common carotid artery; 9, molar gland.]