Ixxiii 



fold of membrane, of the same colour and texture ; from its 

 centre is a short, conical projection, analogous in its position, 

 in front of the glottis, to an epiglottis, and capable of acting 

 as such to a slight extent ; it is devoid of cartilage, but when 

 the tongue is retracted, this process can cover the anterior 

 half of the glottis. The Hyoid bone, or rather cartilage, 

 supports the tongue by a broad basis, from the centre of 

 which a short, strong style passes forwards in the median 

 line ; a similar process descends in front of the thyroid carti- 

 lage, and is attached to it, and to the forepart of the trachea, 

 by elastic ligament ; the cornua are pliant and elastic, and 

 curved backwards in a tortuous form ; they support the pha- 

 rynx and fauces, and admit of considerable expansion. The 

 glottis, or superior larynx is well developed, and bears some 

 resemblance to the rima in mammalia ; its aspect is obliquely 

 upwards and backwards, and is placed, as usual in birds, on 

 the posterior plane of the trachea, though not to the same 

 extent; but it is devoid of all spines, tubercles, and papillae, 

 nor has it the chink-like form so common in that class. The 

 thyroid cartilage bounds the larynx in front, the cricoid be- 

 hind : on the upper edge of the latter are two thin broad plates, 

 passing forwards, from the inner side of the centre of each 

 there is a prominent and firm fibro-mucous body, projecting 

 inwards ; these bodies bear some analogy to arytenoid carti- 

 lages ; they nearly touch, and can easily be made to do so, 

 whereby the opening is divided into two parts ; the anterior, 

 small and triangular, can be covered by the epiglottis when 

 the tongue is retracted ; the posterior is round or oval, and 

 can only be closed by the action of the surrounding muscles 

 pressing its sides into contact during the act of deglutition. 

 These two portions bear a close resemblance in form to the 

 human rima glottidis, when subdivided into two by the approxi- 

 mation of the long, anterior, basilar processes of the arytenoid 

 cartilages (fig. 1) 



The trachea is of considerable length, the rings are all 



