THE ANATOMY OF THE INDIAN ELEPHANT. 75 



EESPIKATOEY SYSTEM. 



Larynx. 



The thyroid consists of two rhomboidal alse, whose superior 

 and inferior borders respectively converge forwards to the 

 middle line at an obtuse angle. They are continuous in front 

 for the upper half of their depth, and strongly connected by 

 yellow elastic tissue in the lower half. The cornua project very 

 slightly. To the postero-superior angle the cartilaginous tip of 

 the thyro-hyal is articulated by a capsule lined with synovial 

 membrane ; the postero-inferior angle is similarly connected with 

 the prominent lateral facet of the cricoid cartilage. The cricoid 

 and arytaBDoid cartilages differ in no material respect from the 

 same parts in man. Professor Owen observes that " the cricoid 

 extends posteriorly over the first three tracheal rings." ^ This is 

 not the case ; the three upper rings of the trachea are obliquely 

 cut off behind, and their edges are connected with the lower 

 border of the cricoid. The epiglottis is very thin and flexible. 



The crico-ihyroidei are closely united in the middle line (C. and 

 L. — 261, fig. 2, z^). Crico-arytcBnoideus posticus passes vertically 

 to the base of the arytsenoid cartilage, and the muscles of oppo- 

 site sides blend. There is no cerato-cricoideus. Arytcenoideus 

 consists of a single set of fibres, which converge from each side 

 to a transverse median tendon. The upper fibres are continuous 

 with thyro-arytcenoideus, so that the two muscles form a com- 

 plete ring round the larynx. Crico-arytcenoideus springs from 

 the upper half and edge of the side of the cricoid cartilage ; it is 

 almost continuous with thyro-arytcenoideus towards its insertion. 

 Thyro-arytcenoideus arises from the whole depth of the thyroid 

 cartilage in the middle line, including the elastic tissue which 

 closes the inferior vertical notch. The fibres pass downwards 

 and backwards, to be inserted into the outer and posterior sur- 

 faces of the arytsenoid cartilages. The muscle is continuous 

 behind with the upper fibres of arytcenoideus. No depressor of 

 the epiglottis was made out. Hyo-epiglottideus (elevator of the 

 epiglottis) is a strong muscle arising close to its fellow, from 

 which it is separated by a septum of yellow elastic tissue. It 



^ Anat. of Vertehratcs, vol. iii. p. 591. 



