Revisiting Leonardo on Muscles: Intimations of Mathematical Biology and Biomechanics.

Leonardo da Vinci's extensive drawings and notes devoted to anatomy do not arise in a medical context. He does not engage with surgery or "physic." Rather, his aim is to reveal what he understood to be the divine engineering of God's greatest creation. His earliest anatomical drawings map the conduits for the "spirits" at a deep level not practiced by other artists interested in the human body. The first set of drawings he produced in 1489 describes skulls with brilliant draftsmanship. His notes for these drawings are predominantly concerned with the location of the "common sense" (sensus communis) at the geometrical center of the cranium. The next great set of drawings completed in ca. 1510 expounds the form and functions of the bones and muscles in meticulous mechanical detail, probably in collaboration with the young Paduan doctor, Marcantonio della Torre. Leonardo's greatest realization of mathematics in anatomy comes when he looks at the valves of the heart; in studying the heart he also conceived a casting technique that he adapted to determine the form of the ventricles in the brain, radically revising the traditional arrangement of these structures. In a range of portrayals from diagrammatic to pictorial and from static to dynamic, Leonardo's anatomical research is unrivalled in revealing the mechanics of the human body. His work in this context is an underappreciated precursor of the modern science of biomechanics. (Larger-sized versions of the Leonardo drawings presented here are available as supplementary material in the online version of this article.) [ABSTRACT FROM AUTHOR]