276 FACULTIES OF BIRDS. 
frame is altered and made light, in a manner con. 
sistent with strength. We see, also, how the mech- 
anism of the anterior extremity is changed, and the 
muscles of the trunk differently directed.”* 
Though it is obvious that birds could not fly with- 
out wings, yet the peculiar mechanism of the pro- 
cess is not, we believe, generally understood. It is 
no uncommon thing to see a goose, while walking 
on the common, spread out its wings to their full 
extent, and begin to flapthem about with great vio- 
lence, and yet the bird is not thereby moved an inch 
from the ground; a circumstance that, without in- 
quiry into the cause, seems contrary to what might 
have been anticipated. By observing the difference 
between this ground-flying (if we may call it so) of 
the goose, and the actual rising of a pheasant, for 
example, into the air, we may arrive at the reason 
why. the goose does not, while the pheasant does, 
ascend. The goose, it may be remarked, keeps her 
wings spread both in the upward and the down- 
ward motion, and, consequently, the resistance of 
the air in the first case will press her body down- 
ward rather than upward ; while,as her evident in- 
tention is not to rise above the ground, she forcibly 
expels the air from her aircells, as may be infer- 
red from the screaming always uttered on those 
occasions, and caused, we have reason to believe, 
by the forcible expulsion of the air. Her body is 
thus rendered specifically heavier, and, consequent- 
ly, resists the upward impulse given by the down- 
ward motion of the wings. The pheasant, on the 
other hand, instead of expelling the air, takes a deep 
inspiration, increasing the size of the body as much 
as possible, inflating at the same time the wing-feath- 
ers, and bulging them outward without separating 
their tips from the sides. While taking deep inspi- 
rations, he may be observed, also, several times 
* Bridgewater Treatise on the Hand, p. 77. 
