TRACHEA OF THE PARROTS. 33 



111 these latter birds, therefore, the organs of voice are of the 

 most simple construction. Other tribes of birds correspond 

 with these several gradations, as we shall subsequently have 

 occasion to observe ; and intermediate stations are occupied by 

 others. For example, the trachea of the Parrots differs from 

 all those which we have examined in having two pairs of 

 muscles to the lower larynx. 



Plate XII, Fig. 9, represents the windpipe of a Parrot. 

 The glosso-hyal bone is marked a ; the basi-hyal, h ; the uro- 

 hyal, c; the apo-hyals, d d\ the cerato-hyals, e e. The bones 

 of the larynx are the thyroid, /"; the lateral appendages of the 

 thyroid, g ; the cricoid, h ; and the arytenoid, i. The tra- 

 chea, j k, is much enlarged at the commencement, and then 

 gradually tapers. It is composed of sixty-five strong rings, of 

 which the upper four are incomplete. The rest are contracted 

 in the middle, before, and behind, so as to overlap each other 

 in a manner to be afterwards described. The inferior larynx, 

 k, is extremely compressed in a lateral direction. None of 

 the rings are much enlarged ; the last complete ring is curved, 

 but has no dissepiment ; and the last ring, which is dimidiate, 

 is strong, and much curved. 



Fig. 10 represents this part, viewed laterally. The last 

 entire ring is marked b ; the dimidiate terminal ring, c ; the 

 first bronchial ring, d ; the bronchus, d e, of which the num- 

 ber of half rings is twelve. 



The muscles of the larynx are only three, namely, the thyro- 

 hyoideus, the thyro-arytenoideus, Fig. 11, and the thyro-cri- 

 coideus. Fig. 12. Those of the lower larynx are two. Viewed 

 from before they are represented by Fig. 9, in which / / are 

 the sterno-trachealis, which I do not consider as a muscle of 

 the inferior larynx, it being generally a continuation of the con- 

 tractor muscle ; m m, the tracheali-bronchiales, which arise 

 from several of the lower rings of the trachea, and are inserted 

 into the first and second bronchial rings ; n n, a pair of short 

 strong muscles arising from some of the last tracheal rings to 

 be inserted into the last ring of the trachea, which being dimi- 

 diate, is moveable, like those of the bronchi. Fig. 13 shews 

 this muscle in the lateral aspect of the trachea ; and in Fig. 1 4 

 is seen the trachpali-bronchialis, which lies over it. 



VOL. II. D 



