76 Roaring in Horses. 



the bezel, is a vertical ridge (Fig. 4, g). The cricoid and 

 thyroid cartilages are united by two lateral ligaments (liga- 

 menta crico-thyroidea lateralia), which are in reality por- 

 tions of the middle crico-thyroid ligament ; they are fixed 

 to the margin of the cricoid cartilage by one border, like the 

 middle ligament ; their upper border, inside the wings of 

 the thyroid cartilage, being thin and free, form the " true 

 vocal cords " (chordce vocales), or, as they are sometimes 

 termed, the inferior thyro-aryt£enoid ligaments (ligamenta 

 thyro - arytcenoidea inferiora), from their fibres arising 

 inside the body of the thyroid cartilage and passing back- 

 wards to the base of the arytsenoid cartilages. Some fibres 

 also passing in the same direction as these, form a superior 

 ligament on each side {ligamenta thyro - arytcenoidea 

 superiora), to form the " vocal bands," which have also been 

 named the "false vocal cords." The lower border of the 

 cricoid cartilage is attached to the upper ring of the trachea 

 by a ligament, the crico-tracheal [ligamentwm crico-tra- 

 cheale). 



The thyroid and cricoid cartilages move upon each other 

 by two true joints, situated on each side behind, the move- 

 ments varying the tension of the vocal cords. 



3. Arytenoid Cartilages (Gartilagines arytwnoideai). 

 Figs. 1, a a; 2, c c; 3,bc; 4, b b. — These two cartilages — 

 very important in relation to the affection with which we 

 are now dealing — surmount the bezel portion of the cricoid 

 cartilage, prolonging the depth of the larynx behind, and 

 curving backwards at their upper margin, where they come 

 in apposition, forming a ewer- like projection ; hence their 

 name. In shape each cartilage is irregularly pyramidal, 

 being somewhat like a prism, or three-sided pyramid, in 

 fact ; there are two angles at the base, the surface of which 

 has a shallow concave surface where it forms a true 

 joint with the cricoid cartilage. The anterior angle is long 

 and narrow, and projects forward into the cavity of the 

 larynx ; from its receiving the insertion of the vocal cord. 



