Treatise on Painting: the anatomist-painter and the 'wooden' figure
Book II — how muscles clothe bones and change with leanness, fat and age
A text-only leaf of Book II of the Trattato della pittura, headed PARTE. It first finishes the argument that relief is the very soul of painting and that drawing is 'free' because faces vary infinitely. The main chapter (125), a precept of the painter cross-referenced to 'L° B car. 19', warns the anatomist-painter that too much knowledge of bones, cords and muscles can make a stiff, 'wooden' figure. Leonardo urges study of how muscles clothe the bones of the old and lean, which muscles stay legible through any degree of fat and which vanish with the least plumpness, and how muscles merge or divide with fattening, slimming and aging around the joints.
On this page
Relief is the soul of painting; drawing is free
The carried-over passage concludes that a painter ignorant of shading produces work without relief, which relief is the importance and soul of painting. Drawing, by contrast, is free, since one sees infinite faces, all varied, one with a long nose and another short; so the painter too may take this liberty, and where there is liberty there is no rule.
Precept: do not become a 'wooden painter' through anatomy
Chapter 125 warns the anatomist-painter that too much knowledge of bones, cords and muscles, and the wish to show every sinew in the nudes, makes a wooden figure. It directs him to observe how muscles clothe the bones of the old and lean, which muscles remain legible at any degree of fatness and which are lost with the least plumpness, and how several muscles merge into one in fattening while one divides into several in slimming or aging.
Muscles around the joints in the moving figure
The precept continues (again marked 'L° B car. 19') that the painter must note the variety the same muscles make around the joints of any creature's limbs, produced by the differing motions of each member, since on some side of a joint the muscle is entirely lost to view (the sentence carries to the next folio).