14 
BIRD-LIFE, 
the cellular keel of the breast-bone, runs along its entire 
length, returns again to the place where it first entered, 
and mounting upwards then first passes oyer to the lungs. 
In the wild Swan ( G . musicus ) it takes only one turn 
through the sternum; while in the mute Swan ((7. olor ) 
nothing of the sort occurs. In the Guineafowl it passes 
into a bony enlargement at the junction of the clavicles. 
In the Capercaillie, several Pheasants and a Duck it 
takes a turn under the outer skin. These modifications 
agree, all, more or less, with the trumpet-like voices of 
these birds. 
The two larynges are not less worthy of notice. The 
upper one of these two, which is moved by three muscles, 
is a simple expansion of the windpipe, with a lateral fissure 
of the glottis; the lower, or second, is quite differently 
formed; it is, without doubt, the true organ of the voice, 
and is generally situate directly above the point where 
the two bronchiae divide; in some few cases, however, 
derived from the bronchiae themselves. According to the 
nature and method of the attachments of its membranes 
to the peculiarly modified firmer portions of the windpipe, 
they are fitted to become thrown into undulation, so as to 
move the column of air in contact with the larnyx in a 
vibrating manner. Frequently the windpipe is peculiarly 
developed in the neighbourhood of the lower larnyx; its 
rings lie in closer apposition, and become expanded to 
form the so-called “ drum,” an ossified, irregular, 
bladder-shaped enlargement of the tube. In the “ drum” 
we distinguish various bands, folds of membrane, and 
cartilaginous rings, all serving to the perfecting of the 
beautiful organs of sound. This has not inaptly been 
compared to a wind-instrument, wherein the lower larynx 
represents the mouthpiece, and the upper one the lower 
