_Action_.--Raises the floor of the mouth and thus brings the hyoid forward.
_Origin_, the two proximal pieces of the cranial horn of the hyoid. The fibres pass caudad parallel to one another and within the middle constrictor of the pharynx.
_Insertion_ into the whole length of the caudal cornu of the hyoid bone.
_Relations_.--Outer surface with the middle constrictor of the pharynx. Inner surface with the pharynx.
_Action_.--Draws craniad the body of the hyoid by bringing its cornua together and bending the joint between the two pieces of the cranial cornua.
The muscles connecting the hyoid and the tongue are described in connection with the description of the tongue.
A. MUSCLES OF THE SHOULDER (connecting the forelimb with the back) (Fig. 68).
=M. trapezius=.--The trapezius muscle is divided in the cat into three portions, the spinotrapezius, the acromiotrapezius, and the clavotrapezius.
=M. spinotrapezius=, or trapezius inferior (Fig. 68, _j_).--The spinotrapezius (caudal part of the human trapezius) is a flat triangular muscle.
_Origin_ from the tips of the spinous processes of all or nearly all the thoracic vertebræ and from the intervening supraspinous ligament. The origin may extend from a point anywhere between the first and fourth spines to any point between the eleventh and thirteenth.
_Insertion_ along an S-shaped line (Fig. 76, _k_-_l_) which crosses the tuberosity of the scapular spine and forms an angle with the spine of about forty-five degrees. The line extends on one side onto the fascia covering the supraspinatus muscle, and on the other side onto the fascia covering the infraspinatus, but does not reach the borders of the scapula. The cranial two-thirds of the insertion is by a flat tendon which is broader craniad.
_Relations._--Outer surface with the cutaneus maximus, and craniad with the acromiotrapezius (_h_). Inner surface with the latissimus dorsi (_m_) caudad and with the rhomboideus, supraspinatus, and infraspinatus craniad. Caudal border free; cranial border in contact with the acromiotrapezius (_h_).
_Action._--Draws the scapula dorsocaudad.
=M. acromiotrapezius=, or trapezius superior (Fig. 68, _h_).--The acromiotrapezius (middle part of the human trapezius) is a flat four-sided muscle just craniad of the spinotrapezius, from the median dorsal line to the scapular spine.
