TRACHEA 983 



TRACHEA or Windpipe, the flexible tube, composed of a 

 great number of rings, originally cartilaginous but ossifying more 

 or less with age, through which Birds breathe and utter most of 

 their characteristic notes. Its upper end is modified into the 

 LARYNX, and it continues subcutaneously down the neck to the 

 thorax, which it enters between the two branches of the FURCULA, 

 and bifurcates into the two BRONCHI, each of which passes to the 

 LUNG of its own side. The tracheal rings frequently overlap each 

 other in various ways, and, except a few adjoining the larynx, are 

 dorsally complete ; but in Dromxus several in the third quarter of 

 the length of the tube are incomplete ventrally, and permit its 

 inner mucous lining to bulge out so as to form the pouch before 

 mentioned (Emeu, p. 214) which occurs in both sexes and may 

 be 12 inches in length. In the TrocJiili, Platalea, many Tubinares 

 and Sphenisci a great portion of the tube is divided by a median, 

 vertical, cartilaginous septum, extending forward from the bronchial 

 bifui'cation, and consisting of rings which pass laterally into those 

 of the walls, thus perpetuating a condition that in other Birds 

 exists for a short time only in their embryonic development, before 

 the septum has been reduced to the pessulus marking the beginning 

 of the bronchi. Frequently the Trachea is depressed or flattened 

 dorso-ventrally, as in Psittaci, Accipitres, Ckonise and Batitse ; but a 

 very common feature, found in many groups not at all allied to 

 each other, is the dilatation of a portion, generally near the middle, 

 as may be seen in several Cotingidse, Chauna and the males of many 

 Anseres — some of the last-named group presenting even a second 

 dilatation, which may be as in CEdemia fusca close to the larynx,^ 

 but is more usually near the lower end. Still further modifications 

 are exhibited by the males of many or most of the Anseres, some 

 6 or 8 of the lowest rings being fused together and forming what is 

 known as the hulha ossea or labyrinth. Its simplest form seems to 

 be that presented, according to Eyton (Monogr. Anat. p. 125, pi. ii. 

 fig. 2), by Anas or Querquedula formosa, where the enlargement is 

 very slight, but essentially similar to that found generally in the 

 genus Anas- and its many subdivisions, the Garganey (p. 309^) 



^ This structure is, so far as known, quite unique : the enlargement next to 

 the larynx surrounds the tube which communicates with it by an aperture on 

 each side. The lower enlargement, in shape of a flattened bulb, is formed of 

 expanded tracheal rings firmly ossified together. It is the more remarkable 

 since the allied (E. nigra has a very simple trachea. The male of Metopiana 

 peposaca has a bulbous enlargement just above the middle of the trachea very 

 similar to the lower one in CE. fusca. 



^ The statement {Proc. Zool. Soc. 1871, p. 651) as to the female of A. punctata 

 possessing a labyrinth originated in a mistake {op. cit. 1882, p. 454). 



^ Since the footnote on this page was printed Mr. Lucas has most obligingly 

 examined the labyrinth of A. discors, which has nothing exceptional about it. 



