THE MACHINERY OF FLIGHT 75 
than is the Elevator, but not so much as the De- 
pressor. In most birds that I have examined, I have 
found that the leg muscles show less ridging and 
granulation even than the Elevator. But the 
Moorhen makes great use of his legs. He is both a 
swimmer and a runner. When not swimming he is 
generally walking on the grass beside his pond or 
stream, busied with the search for worms. 
Before I leave the subject of quality of muscle I 
must point out that the inferiority of the pale to the 
red has been noticed also in thoroughbred horses. 
Mr. J. B. Robertson, in his very interesting paper 
on the Principles of Heredity applied to the Racehorse 
(p. 22), writes: “The pale fibres greatly predominate 
in the tissues of a pure sprinter, and the red fibres 
in those of a stayer.” 
The big muscles, the work of which I have 
described, are all massed upon the sternum. Even 
the muscles which bend or straighten the wing at 
the elbow spring not from the humerus or upper- 
arm bone, but from the top of the coracoid and the 
anterior end of the shoulder-blade respectively. I 
once cut off the wing of a domestic Pigeon as close 
as possible to the body and found that it scaled just 
under + oz. The bird weighed 134 oz. Thus the 
two wings together accounted for just under one- 
eighth of the whole. It is wonderful that such 
strength can be combined with such lightness. And 
not only is the wing, as a whole, light; what weight 
it has belongs almost entirely to the bones and muscles 
of the near part. This Pigeon’s wing balanced, 
when rested on a wire 24 inches from its base 
and 10 inches from its tip. The great primary 
