218 ye ik vES: a & 
are enabled to deep ; in arty while perched on one foot. 
The ischia, and particularly the ossa pubis are lengthened out 
behind, and the interval between them is widened, files 
to allow the necessary space for the development of the o ; 
The neck and the beak are elongated to reach the ground,: 
but the former has the requisite flexibility for bending back- 
wards when at rest,—consequently, it has many vertebra. 
The trunk, on the contrary, which ser ves as @ point @appui_ 
to the wings, has but little mobility; the sternum, particular! ne 
to which are attached the muscles which lower. the win | 
flight, is of great extent, and has its surface still more énlareed. 
by a salient process in its middle. It is originally composed) 
of five pieces: a middle one, of which this salient lamina 
makes a part; two triangular, anterior, lateral ones, for the. 
articulations of the ribs, and two posterior, which are lateral | 
and bifurcated, to increase its surface. The greater or less 
degree of the ossification of the notches of these last, and the 
extent of the interval they leave between them and the princi-- : 
pal bone, denote a relative strength of wing and power of. 
flight. ‘The diurnal Birds of prey, the Swallows and the 
Humming-birds, lose, as they grow old, all traces of fi oeged 
unossified spaces. | é' 
The fourchette produced by the junction of the two Cclavi- . 
cles, and the two powerful stretchers formed by the coracoid — 
apophyses, keep the shoulders apart, notwithstanding the 
efforts requisite for flight, that act in an opposite direction ; the 
greater the power of flight, the more open and strong is the | 
fourchette. The wing » Supported by the humerus, fore- -arm 
and hand, the latter of ce gp is elongated, and has one finger 
and vestiges of two others, is pieuched throughout its length 
with a range of elastic quills, which greatly extends the sur- 
face that resists the air. Those which belong to the hand are 
termed primaries, and there are always ten; those attached to. 
the fore-arm are called secondaries, but their number varies ; 
_ weaker feathers appended to the humerus are called scapulars ; 
the bone, which is analogous to the thumb, is also furnished 
