Royal Collection (RLW), 19058v; K/P 42v and 19057v; K/P 43v
These superb drawings by the young Leonardo illustrate his effort to analyze the structure of the skull and its component elements within the framework part of his passionate quest for geometrical proportionality.
In the drawing on the left, Leonardo shows the arrangement of the teeth, each of which is depicted individually. Elsewhere, he compares the jaw's motion in chewing to that of the lever: "That tooth has less power in its bite which is more distant from the center of its movement."
The top drawing on the right shows a sagittal cross-section of the base of the skull, depicted as a cross-section of a sphere. In the lower right drawing, the cross-section of the skull is inscribed in a square, and that of the entire head in a rectangle.