140 THE STRUCTURE AND LIFE OF BIRDS cHap. 
This great air-chamber is entirely wanting in the Duck. 
Yet the quack of the Duck is loud and sonorous, that 
of the Drake is thin and without any body in it. In 
some species of Crane, the trachea winds round 
about within the keel of the breastbone, which is 
Fic. 35, showing convolutions of Trachea of Mantchurian Crane. 
4, Network of bones ; 47, Trachea dividing into two bronchi; c/, Clavicle; co, Cora- 
coid ; sc, Scapula; 27, Trachea at entrance into keel. 
formed of two thin sheets with, in places, a light bony 
network in between: after all these windings it at 
length divides and enters the lungs. Cranes have a 
loud and striking crow, but it is not nearly so striking 
as the crow of the barndoor Cock, whose windpipe 
takes the shortest course to the lungs. The whistling 
