LARYNX OF. MAMMALIA. 591 



In the Elephant the alae of the thyroid are externally convex 

 and unite anteriorly at an obtuse angle ; the upper cornua are 

 short, the lower ones are notched anteriorly. The cricoid ex- 

 tends posteriorly over the first three tracheal rings. The aryte- 

 noids are long : the lower vocal cord is well-marked ; the upper 

 one indistinct. In the Rhinoceros the wings of the thyroid carti- 

 lage meet at a slightly obtuse angle : there is no notch at the 

 upper margin of the anterior median line; but there is a con- 

 siderable triangular vacancy below, filled up by dense elastic and 

 aponeurotic membrane, to which yielding walls of the larynx 

 some of the fibres of the thyreo-arytenoidei muscles adhere. The 

 cricoid is nearly thrice as deep behind as in front, contributing 

 to the extent of the crico-thyroid interspace. The arytenoid car- 

 tilages are relatively of large size : their base extends half-way 

 across the aperture of the larynx, and from the anterior extremi- 

 ties of these produced bases, the upper and lower ' chordae vocales ' 

 extend forward to the thyroid cartilage and base of the epiglottis. 

 Only the anterior half, therefore, of the ' rima glottidis ' is bounded 

 by vibratile vocalising material, and the ordinary voice of the 

 Rhinoceros is a feeble bleat like that of a calf. Between the 

 upper and lower chordae vocales is the opening of a large sac- 

 culus laryngis, which communicates anteriorly with a crescentic 

 fossa under the base of the epiglottis. A fold of membrane ex- 

 tends on each side from a small semilunar fibro-cartilage at the 

 inner and under side of the base of the epiglottis, downward, in- 

 ward, and forward to the anterior termination of the chordae 

 vocales : these oblique folds form the inner or posterior walls of 

 the anterior fossae of the sacculi laryngis. The anterior or supe- 

 rior labia of the glottis form two broad, thick, slightly everted folds 

 of mucous membrane. In the mass of muscles attached to and 

 passing between the arytenoid cartilages, there are developed 

 about twelve tendons which radiate to be inserted into a central 

 sesamoid cartilage. The epiglottis is of a triangular figure, with 

 the pointed apex curved forward, and having strong glosso- 

 epiglottidei muscles attached to it. 



In the Horse the wings of the thyroid meet at an acute angle, 

 leaving a large inferior notch : the back part of the thyroid forms 

 an almost acute angle with the cricoid : the cricoid has similar 

 proportions to that in Rhinoceros : it has been vertically cleft 

 behind and the moieties divaricated, in fig. 462, i, i. The aryte- 

 noids, ib. f, f, have their bases deflected from each other, keeping 

 patent the ( rima glottidis ' : the ( cartilages of Santorini,' ib. k, A, 

 are hook-shaped. The lower vocal cords, ib. g 9 g, are large and 



