_Action._--Draws the hyoid backward and thus gives a firmer surface of origin for the styloglossus. =M. mylohyoideus= (Fig. 65, _c_).--The mylohyoid is a large thin muscle seen after the reflection of the digastric, filling with its fellow of the opposite side the whole angle between the rami of the lower jaw. Its fibres are transverse. _Origin_ from the middle of the medial surface of the body of the mandible between the caudal opening of the mandibular canal and the symphysis of the jaw. [Illustration: FIG. 67.--MUSCLES OF TONGUE, HYOID BONE, AND PHARYNX. _a_, M. tragicus lateralis; _b_, M. jugulohyoideus; _c_, M. pterygoideus externus; _d_, partially cut surface of M. pterygoideus internus; _e_, M. styloglossus; _f_, M. genioglossus; _g_, M. geniohyoideus; _h_, M. hyoglossus; _i_, M. glossopharyngeus; _j_, M. constrictor pharyngis medius; _k_, M. constrictor pharyngis inferior; _l_, M. stylopharyngeus; _m_, M. sternohyoideus (cut); _n_, M. cricothyreoideus; _o_, M. sternothyreoideus (cut); _p_, M. thyreohyoideus. 1, mandible; 1′, angular process of mandible; 2, stylomandibular ligament; 3, bulla tympani; 4, trachea; 5, œsophagus; 6, thyroid gland; 7, isthmus of the thyroid gland.] _Insertion_ with the opposite muscle into a median raphe which extends from the symphysis of the jaw to the hyoid bone and is closely united to the external surface of the geniohyoid. Some of the fibres gain insertion into the body of the hyoid bone through their insertion into the tendon of the stylohyoid (_d_). _Relations_.--Outer surface with the submentalis (Fig. 64, _c_) and the digastric (Fig. 65, _b_). Lateral edge with the masseter (_a_), the digastric (_b_), and the mandibula. Caudal border with the stylohyoid (_d_). Inner (dorsal) surface with the geniohyoid (Fig. 67, _g_), the hyoglossus (Fig. 67, _h_), and the genioglossus (Fig. 67, _f_). _Action_.--Raises the floor of the mouth and thus brings the hyoid forward. =M. ceratohyoideus.= _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. III. MUSCLES OF THE BODY. =1. Muscles of the Back.= 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.