The =arytenoid cartilages= (=cartilago arytenoidea=) (Fig. 104, 4) are triangular pyramids with base and sides nearly equilateral triangles. One side articulates with an oblique facet on the cranial border of the cricoid near the mid-dorsal line. Near the opposite apex is attached the vocal cord. At the lateral angle of the base is attached on its dorsal side the posterior cricoarytenoid muscle (Fig. 105, _b_), and on its ventral side the thyroarytenoid (Fig. 105, _d_) and lateral cricoarytenoid (Fig. 105, _c_) muscles. The movements produced by these muscles carry the arytenoid ends of the vocal cords toward or from the median plane and thus open or close the glottis. The =epiglottic cartilage= (Fig. 104, 2) is flexible (fibro-cartilage) and of a cordate form. It is so curved that its caudal surface is convex dorsoventrally and concave from side to side. It supports the epiglottis. Its cranial surface presents a slight median ridge for attachment of muscles. By its base it is attached to the midventral part of the cranial border of the thyroid cartilage (1). Its position varies so that it either stands erect with its apex directed craniad to allow the passage of air to the lungs, or, as in the act of swallowing, it is turned caudad over the aditus laryngis so as to allow food to pass over it and into the œsophagus. The =vocal cords= are two fibrous elastic bands. Each is attached at one end to the apex of the arytenoid cartilage, and at the other end to the median ridge on the dorsal surface of the thyroid. Each supports a projecting fold of mucous membrane, the vibration of which causes the voice. MUSCLES OF THE LARYNX.--1. Muscles moving the entire larynx. A. =Elevators. M. thyreohyoideus= (Fig. 96, _p_, page 229).--A flat band on the lateral side of the larynx. _Origin_ on the lateral part of the caudal border of the thyroid cartilage. _Insertion_ on the medial two-thirds of the caudal border of the caudal cornu of the hyoid. _Action._--Raises the larynx. The stylohyoid (Fig. 65, _d_, page 109) and the median and inferior constrictors (Fig. 96, _j_ and _k_) of the pharynx, already described, have the same action. B. =Depressors.=--The sternothyroid (Fig. 65, _g′_), already described (p. 141). 2. Muscles which move the parts of the larynx one upon another. A. =Muscles on the Outer Surface of the Larynx.= =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.