Part 20

Insertion.—By a tendon to the basi-branchial of the thyro-hyal.

Shape.—A long transversely flattened fasciculus.

Relations.—Supero-posterior part of the hyoid apparatus along side the genio-hyoideus and the cerato-hyoideus.

Action.—Singly, pulls the tongue to one side; acting with its fellow, pulls the tongue upward.

=Genio-hyoideus= (Fig. 9, No. 7). Location.—Supero-posterior to the hyoid apparatus.

Origin.—From the anterior portion of the inner side of the lower jaw.

Insertion.—To the middle of the outer side of the basi-branchial of the corner of the os hyoides which cornu it completely envelops.

Shape.—A long, rather thick fasciculus.

Relations.—With the stylo-hyoideus and cerato-hyoideus.

Action.—Protrudes the tongue from the mouth.

=Cerato-hyoideus= (Fig. 9, No. 8). (Synonym.—Kerato-hyoideus.)

Location.—Inferior to the hyoid apparatus.

Origin.—By a delicate tendinous slip from the under side of the shaft of the basi-hyal element of the hyoid apparatus.

Insertion.—To a small elevation on the under side of the anterior end of the glosso-hyal.

Shape.—A small round muscular fasciculus becoming tendinous in its anterior half.

Relations.—Superiorly with the hyoid apparatus.

Action.—Singly, pulls the tongue to one side; acting with its fellow, depresses the tongue.

=Sterno-hyoideus.= Location.—Inferior to the hyoid apparatus.

Origin.—From the outer anterior surface of the thyroid bone of the superior larynx.

Insertion.—To the anterior part of the basi-hyal.

Shape.—At first broad and rather fleshy, becomes contracted and somewhat tendinous.

Relations.—Inferior to the hyoid apparatus and superior larynx.

Action.—When the larynx is fixed, acting alone deflects the tongue laterally; acting with its fellow, depresses the tongue. If the base of the tongue is fixed the two pull the larynx forward. Hence muscles of deglutition.

=Depressor-glossus.= Location.—Superior to the basi-hyal.

Origin.—From the under portion of the basi-hyal.

Insertion.—To under part of the glosso-hyal.

Shape.—Small, short.

Relations.—Superiorly with the basi-hyal and glosso-hyal bones.