The folds of the limbs' joints, with a spiral line
How relief becomes hollow at the joints, and a note to imitate nature
The right leaf (44r) carries a note on how, in the last folds of a limb's joints, every relief turns into a concavity and every hollow into a bulge when the limb is fully extended, and warns that whoever lacks this knowledge and trusts his own genius rather than imitating nature makes great errors. A margin note and a small drawing are labelled "spiral line" (reverticolo). The left leaf (59v) is nearly blank, bearing only faint pen-trials and a small tower-like sketch at the far edge.
On this page
Relief turns to hollow at a limb's joints
In the final folds of any limb's joints every relief changes into a concavity, and every concavity becomes a bulge when the limb is at its fullest extension. This variety is greater in the middle of the sides than in front, and greater behind than at the sides.
Imitate nature, do not trust your own genius
Leonardo warns that whoever lacks knowledge of how the body's surface behaves at the joints, and relies too much on his own invention, makes very great errors. The remedy is to resort to the imitation of nature.
A spiral line (reverticolo)
A right-margin heading names a "spiral line," and a small drawing beside it is labelled "spiral." It records a coiling line among the sheet's brief sketches.