Insertion into the caudal side of the cartilaginous part of the stylohyoid opposite the origin of the styloglossus.

Relations.—Ventral surface with the digastric. Dorsal surface with the tympanic bulla (3).

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.

[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).