Bone-structure of a bird's wing: three sources of power
Forces of the wing analysed with labels a b c d e f g
In red chalk Leonardo sets out the bone-structure of a bird's wing, keyed with the labels a b - c d - e f - g, and identifies three sources of power in it: the first is b, which draws on the muscle a; the second is d c; the third is f e. He then asks, as a problem in mechanics, what force or weight the joint b a feels when the outer part g exerts its force through f e. A short note above reads only 'Other things'.
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Three sources of power in a bird's wing
Leonardo names three powers in the wing: the first, b, working through muscle a; the second, d c; the third, f e. He treats the wing as a jointed lever and asks what force or weight the segment b a undergoes when part g pushes by way of f e. The labelled bones are drawn as a diagram beneath the text.