=M. cricothyreoideus= (Fig. 96, _n_).--A broad flat band which with its
fellow covers the ventral surface of the cricoid cartilage and the
cricothyroid ligament.
_Origin._--The lateral half of the ventral surface of the cricoid
cartilage. The muscles diverge so as to leave a part of the cricothyroid
ligament between them.
_Insertion._--The ventral part of the caudal border of the thyroid
cartilage laterad of the median ventral notch.
=M. cricoarytenoideus posterior= (Fig. 105, _b_).--The two muscles cover
the dorsal surface of the larynx.
_Origin._--From the dorsal part of the caudal border of the cricoid
cartilage (3) and from its median dorsal crest. The fibres pass
craniolaterad, converging. The lateral fibres are nearly longitudinal in
direction.
_Insertion._--The dorsal border of the caudal end of the arytenoid
cartilage (4).
_Action._--Moves the arytenoid on its oblique articulation with the
thyroid. The apex of the arytenoid is thus carried laterad, and the
vocal cords are separated so as to widen the glottis.
[Illustration: FIG. 105.--MUSCLES OF THE LARYNX, AS EXPOSED BY REMOVAL
OF MOST OF THE LEFT HALF OF THE THYROID CARTILAGE.
1, epiglottis; 2, portion of the thyroid cartilage (cut); 3, cricoid
cartilage; 4, arytenoid cartilage; 5, trachea. _a_, M. arytenoideus
transversus; _b_, M. cricoarytenoideus posterior; _c_, M.
cricoarytenoideus lateralis; _d_, M. thyreoarytenoideus.]
=M. arytenoideus transversus= (Fig. 105, _a_).--A small unpaired muscle
running transversely between the caudal ends of the arytenoid
cartilages, just beneath the mucous membrane and parallel to the cranial
border of the cricoid cartilage.
=M. glossoepiglotticus.=--A small longitudinal muscle, lying by the side
of its fellow in the frenulum of the epiglottis.
_Origin._--The median fibrous septum of the tongue.
_Insertion._--The dorsal (cranial) surface of the epiglottic cartilage
in the median line near its attached border.
_Action._--Draws the epiglottis craniad.
=M. hyoepiglotticus= is a small bundle of parallel fibres lying in the
frenulum of the epiglottis craniad and dorsad of the body of the hyoid
bone.
_Origin._--The lateral end of the cranial surface of the body of the
hyoid. The two muscles pass craniodorsad, converging, and unite with the
preceding.
_Insertion_ with the preceding. (The lateral portion of the muscle may
continue craniad to the tongue as a second part of the hyoglossus.)
_Action._--Like the preceding.