vi FLIGHT 257 
shifting the centre of gravity, none are, I believe, except 
in quite exceptional birds, efficacious, and I doubt 
whether any bird makes much use of them. The 
problem, then, remains: when the body is suspended 
from the wings and the centre of gravity lies at a point 
farther back, how is a nearly horizontal position 
maintained? Hold up a bird, that has just been shot, 
by the wings, and the hinder part of the body will drop 
till the incline from the tail to the head (with the partial 
exception explained on p. 227) is a very steep one. 
This it is, no doubt, that has caused ornithologists to 
look for some means by which the bird could at 
pleasure move the centre of gravity forwards. The 
true explanation is that during horizontal flight the 
body is maintained in its position, with only a slight 
upward incline, not by balance, but by muscular effort. 
If you watch a Pigeon’s movements and see how 
instantaneously, without a motion of head or legs, he 
changes the inclination of his body, you can hardly 
doubt that it is the work of musclest The muscle 
called the Latissimus Dorsi, which I have described 
in connection with respiration, arises from the verte- 
bra and attaches to the humerus (L. D. fig. 56). 
During the downstroke it contracts, hauls upon the 
wings, and thus raises the hinder quarters. The 
enormous strength of the Great Pectorals prevents all 
possibility of the wings yielding when thus pulled by 
the Latissimus. The body must rise, since the wings 
will not give. And, thus, indirectly, in addition to their 
other work, the Great Pectorals help to bring the body 
to the horizontal. When the wing rotates beyond a 
1 See Bronn’s 7hzer-Retch, vol. “ Aves,” p. 229. 
s 
