THE WINGS. 
85 
wing, weighs more than all the other muscles of its 
body put together, constituting not less than one- 
sixth part of the weight of the whole body ; whereas, 
those of the human body are not one-hundredth part 
as large in proportion. 
Some birds have to seek their food on the wing, 
consisting of such very small insects that many 
hundreds must be swallowed for a meal, and in 
these we accordingly find a spread and power of 
wing truly astonishing. W e cannot take a better 
example than our common Swift, the largest of our 
Swallow tribe, whose well-known scream and rapid 
flight must be familiar to every one. It has to seek 
its livelihood solely in the air, on insects so small 
that we can with difficulty perceive them, even if 
slowly passing before our eyes. It could not there- 
fore live a day, unless gifted with extraordinary 
powers of flight ; it must not only be able to move 
rapidly forward in a straight line, but also be able to 
turn, as quick as thought, to the right or left, up- 
wards or downwards, to catch its minute prey. And 
such is the case; the bird is so light that it weighs 
little more than an ounce, and yet the spread of its 
wings, from tip to tip, is not less than eighteen 
inches. But extraordinary as these proportions are, 
in length of wing, compared with weight, in this 
our British species, they are exceeded in a newly- 
discovered species in the East Indies, called the 
Javanese Crested Swallow'*, whose uncommon 
length of wing indicates a speed far beyond that 
of our Swift. Other birds, again, there are, which 
require additional powers, not in the air, but under 
* Macropteryx longipennis. 
