The Framework of the Bird 83 
and all but motionless. It is said that, comparatively, 
the muscular energy is greater and the wing-bones more 
powerful in a hummingbird than in any other animal. 
Nature has a puzzling way of achieving similar results 
in a very similar manner in creatures wholly unrelated. 
We have a good example of this in bats and birds, both 
Fic. 59.—Comparison of the size of the keel of the Albatross, Pigeon, and Humming- 
bird, supposing all to have an equal spread of wing. (Courtesy of Dr. F. A. 
Lucas.) 
of which have independently learned to propel them- 
selves through the air by means of their front limbs. 
If we take the breast-bone of a common bat and that 
of a small bird and place them together, few persons 
unacquainted with the bones of the two types could tell 
which was that of the bat,—different as that little crea- 
