136 ELEMENTS or OENITHOLOGY. 



neck, to enable that delicate grasping organ, the beak, to per- 

 form all needed manipulations. 



So complete is the packing of parts towards the centre of 

 I be body, that even the hard structures which serve to grind 

 the food are not in the form of teeth in the mouth, but of stones 

 swallowed down and held in the modified stomach * or " giz- 

 zard." The voice-organ, also, instead of being at the top of the 

 throat (as in man and beasts) is at the bottom of it, and many of 

 the muscles are largely reduced to strings or " tendons" for a 

 great part of their extent. 



But very powerful muscles are needed to work the wings, 

 and this again demands a vigorous circulation with very pure 

 blood and a body lightened as much as possible. These con- 

 ditions are admirably fulfilled in most birds by a provision for 

 the entrance of air into their very bones. This diminishes the 

 specific gravity of the body, while it helps to purify the blood 

 and so facilitate the action of the muscles, and therefore flight. 

 A Bird may be said to breathe not only with its lungs, but with 

 its whole frame. Hence the lightness of Aquatic Birds on the 

 water, swimming most easily with a boat-shaped body and oar- 

 like feet ; some also, such as the Swans, being provided with 

 sails, in the shape of their raised and slightly expanded wings. 



Tor flight nothing could be better than the shape of the body 

 of most birds, which is in the form of two cones united by their 

 bases, with a small rounded head and pointed beak in front, 

 poised on a neck which, by its protrusion or retraction, can, at 

 wUl, change the position of the centre of gravity. 



The rapidity of flight may be very great ; a Falcon which 

 belonged to Henry IV. of Trance flew from Fontainbleau to 

 Malta (1350 miles) in one day. The race-horse " Eclipse " went 

 a mile a minute for a short time ; but a Hawk at full speed has 

 been calculated to fly at the rate of 150 miles in one hour, and 

 an Eider-duck at 90. The distances also which birds traverse 

 are prodigious. Our Swifts and Swallows fly to the Gold 

 Coast of Africa, and our Cuckoos to the Cape of Good Hope. 



All this wonderful work, facilitated by the arrangement above 

 noted, is directly effected exclusively by means of certain 

 feathers of larger size than those which clothe the body, never 

 by expanded skin as in the Bat. 



All Birds, as before said, have this characteristic external 



* See below, p. 208. 



