202 GENERAL ORNITHOLOGY. 
partly over each other on alternate sides is Merhing like that upon which a cooper fastens 
the ends of any one barrel-hoop without any nailing or tying. The rings are in some birds 
perfectly cartilaginous: in most they become 
osseous. The trachea is moved by lateral 
muscles, which not only shorten the tube by 
approximating the rings, but also drag the 
whole structure backward, by their atcach- 
ment to the clavicle and sternum. The strip, 
Fig. 97.—1, 2, left hand, two tracheal rings, sepa- OF two strips, of muscle lying upon each side 
rate, as in fig. 96, ; 1, 2, right hand, the same put of the trachea, is the contractor trachee (fig. 
together, as in fig. 96, a. (After Macgillivray.) : 
_ 101, 1, ss, ss); the most anterior, when there 
are two, as soon as it leaves the tube to go to the clavicle, becomes the cleido-trachealis, or 
cleido-hyoid, fig. 101, 1, f, f; the other is similarly the sterno-trachealis. The latter may be a 
direct continuation of the contractor, as in fig. 101, 1, the loose strips under q, or apparently 
arise separately from the side of the lower end of the tube, as in fig. 101,16, e. (Other muscles 
are to be described with the larynx superior and inferior.) The trachea is long in birds, pro- 
portionate to the extension of the neck ; it is very flexuous, following with ease the bends of 
the neck in which it lies so loosely. Its cross section is oval or circular; but all that relates 
to the configuration and course of the pipe requires special description, —so variable is the 
organ in different birds. It is subject to dilatations and contractions in any part of its extent, 
and to deviations from its usual direct course to the lungs. Minor modifications must be 
passed over. The most remarkable expansions of the lower part of the tube occur in many 
sea-ducks and mergansers (F'uliguline and Mergine), and some other birds; several lower rings 
of the trachea being enormously enlarged and welded together into a great bony and mem- 
branous box, of wholly irregular, unsymmetrical contour. Such a structure, represented in 
figs. 3 and 98, is termed a tracheal tympanum, or laby- 
rinth. It is not a part of the voice-organ proper, but 
may act as a reverberatory chamber to increase the vol- 
ume of the sound, without however modulating it. Being 
chiefly developed in the male, it is a kind of secondary 
sexual organ. The vagaries of the wind-pipe are still 
more remarkable. Very generally, in cranes and swans, 
the trachea enters the keel of the sternum, which is exca- 
vated to receive it, and where it forms one or more coils 
before emerging to pass to the lungs. This curious wind- 
ing is carried to an extreme in our Grus americana, the 
whooping crane, in which the wind-pipe is about as long 
as the whole bird, and about half of it — over two feet of 
it!— is coiled away in the breast-bone (fig. 99). The 
3 same thing occurs in G. canadensis to a less extent (fig. 
Re ee ee ere eee 100). In a Guinea-fowl, Guttera cristata, a loop of the 
islandica, seen from behind, nat. size. Dr. trachea is received in a cup formed by the apex of the 
cee clavicles. In various birds, as some of the curassows (Cra- 
cide), the capercaillie (Tetrao urogallus), a goose, Anseranas semipalmata, and the female of the 
curious snipe, Rhynchea australis, the trachea folds between the pectoral muscles and the skin. 
The Larynx (the Gr. name, Adpvyé, larugx) is the peculiarly modified upper end of the 
trachea (fig. 101, 1, and 3 to 12). In mammals it is a complicated voice-organ, containing the 
vocal chords and other consonantal apparatus; in birds the construction is simpler, as the 
larynx merely modulates the sound already produced in the lower end of the tube. It lies in 
