136 ELEMENTS OF ORNITHOLOGY. 
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 
the 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 wines. 
For 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 
will, change the position of the centre of gravity. 
The rapidity of flight may be very great; a Falcon which 
belonged to Henry IV. of France flew from Fontainbleau to 
Malta (1350 miles) inone 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 Kider-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. 
