ORNITHOLOGY. 2 09 



The rapidity and variety of motion of which Birds show them- 

 selves capable, may well excite admiration. The Swallow arid the 

 Eagle can dart through the air at the rate of sixty miles an hour; 

 the Falcon at the rate of forty or fifty miles in the same time ; 

 the Passenger Pigeon outstrips the wind, which, when most vio- 

 lent, traverses only sixty miles an hour; the Curlew traverses 

 three elements with ease, running rapidly upon the ground ; 

 perfectly at home on the ocean wave, and borne in the air as it 

 flies swiftly from one continent to another. 



For this fleetness of motion, the skeleton of a bird is strikingly 

 adapted. (Plate XII. fig. 2.) It unites lightness with firmness; 

 the great bones of the limbs, and many of those of the body, are 

 hollow reservoirs of air, communicating with the lungs. Sacs, 

 or bladder-like receptacles, which can be filled with air, are dis- 

 tributed about the body ; some of them internally ; others be- 

 tween the muscles and the skin, down the throat and chest, or along 

 the tendons of the shoulder ; and these communicate with eacii 

 other and with the lungs. The last named organs adhere closely 

 to the ribs, occupying (Plate XII. fig. 2, E.) the hollows between 

 them and on each side of the spine ; the lungs are very large, 

 but can be very little expanded or contracted. To compensate 

 for this incapacity, which might impede their breathing, the ends 

 of the branches of the wind pipe open into them ; but these again 

 communicate with the membranous sacs, or buoyant air cells, 

 that run along the whole length of the body, so that a probe 

 thrust into the lungs of a fowl, easily finds a passage into the in- 

 ternal parts of the frame ; and air blown into the wind-pipe, will 

 be seen to distend the bird's body like air blown into a bladder. 

 By the great development of ^the breathing apparatus, the blood 

 is more rapidly and effectually oxygenized, and muscular energy 

 accumulated for the action of flight; while, by the animal heat 

 which is thus given out, the air contained in -the complex respir- 

 atory apparatus is rarified ; and thus the body is increased in bulk, 

 but rendered specifically lighter. 



The wings of a bird correspond to the arms and hands of man ; 

 but the hand in the bird consists of only two fingers, (Plate XII. 

 fig. 2d, N.,) and a thumb, all of which are rudimentary. From 

 the bones of the bird's hand (M) arise the primaries, or great 

 quill-feathers of the wings, ten in number, and by their form, 

 stiffness, and relative strength, indicating the character and the 

 power of the flight. The secondaries spring from the principal 

 bone of the forearm, (K. L. ;) the number of these varies in dif- 

 ferent species ; they are generally stouter, longer, and more flex- 

 ible than the primaries, and differ less in form from the general 



