Bending and Turning; the Counterbalance of Weights
One side shortens as the other lengthens; the central line over the foot and the outthrown arm (equiparanzia)
Alongside a small pen study of a nude leaning on a staff, with a diagram of a bent limb below, this leaf treats the bendings and turnings of the body: a man shortens as much on the side he bends as he lengthens on the opposite side, the bend being at most one-half of the extended part. Rules cross-referenced to Leonardo's Book A (folio 14) state that as one side of a bendable limb lengthens its opposite shortens, while the outer central line of the unbending sides never changes length. The chapter on counterbalance (equiparanzia) requires a figure supporting a weight outside its central line to throw an equal natural or accidental weight to the opposite side, balanced about the line that rises from the center of the planted foot. The example given is a man who, taking a weight in one arm, throws out the opposite arm.
On this page
a. Bendings and turnings: one side shortens as the other extends
In the chapter marked a, a man diminishes as much on the bending side as he grows on the opposite extending side, the bend being at its extreme one-half (subdouble) of the part that stretches. As one side of a bendable limb lengthens, its opposite is shortened, while the outer central line of the unbending sides never grows or shrinks.
Counterbalance (equiparanzia) about the line over the foot
A figure that supports a weight outside itself and outside its central mass-line must throw as much natural or accidental weight to the opposite side as makes an equal balance of weights about the central line rising from the center of the planted foot. This line passes through the whole load carried above that foot set on the ground.
The man who takes a weight in one arm throws out the other
One naturally sees that a man who takes up a weight in one of his arms throws the opposite arm out from himself. If that is not enough to make the counterbalance, he adds still more weight by leaning further.