The tensor group comprises a number both of the extrinsic and intrinsic muscles of the larynx. The crico-arytenoidei postici draw the arytenoids back, external rotation, and consequent abduction, being prevented by other muscles. The anterior fibres of the crico-thyroid and those fibres of the {60} sterno-thyroid inserted anterior to the crico-thyroid articulation approximate the cricoid and thyroid cartilages, and thus tighten the vocal bands. The posterior fibres of the crico-thyroid slide the thyroid upon the cricoid, lengthening the antero-posterior diameter of the larynx. This muscle, acting as a whole, also compresses the alæ of the thyroid with the same effect. The constrictors of the pharynx have a similar function. The hyo-thyroidei, acting in conjunction with the elevators of the hyoid bone, draw the thyroid forward and tilt it downward upon the cricoid. The form and internal tension of the vocal bands are greatly influenced by the thyro-arytenoidei, especially their inner fibres, while the ascending fibres of the muscle draw the inferior portions of the vocal bands upward and prevent the sagging of their edges. This muscle, acting alone, has been thought to cause extreme relaxation of the vocal bands. Modern research renders this statement of relaxation doubtful. The contraction of those fibres of the sterno-thyroidei inserted posteriorly to the crico-thyroid articulation tilts the thyroid upward, and thus relaxes the tension of the bands. The crico-arytenoidei postici rotate the arytenoid cartilages outward, separating the vocal processes, and, acting in conjunction with the posterior fibres of the crico-arytenoidei laterales, draw the cartilages outward and downward. In the cadaveric condition, which is one of relaxation of all the laryngeal muscles, the glottis is neither closed nor widely open; the epiglottis is erect against the dorsum of the tongue; the arytenoid cartilages are slightly separated, so that the glottic opening is a triangle with the base posteriorly, as in the act of inspiration, but the separation is much less than in the act of breathing. This condition is met with in paralysis affecting all the muscles of the organ.