Courtesy of LeonardoDaVinci.net

Anatomical analysis, in Leonardo's view, made it possible to rediscover the mechanics that correspond to emotion: the exact image of muscular movements suggests the movements of the soul. Their presentation presupposes, however, an intuitive sense of perception and a feeling for proper balance, both of which Leonardo seems to value above all else.

Leonardo's anatomical drawings were so precise that many are still used to illustrate medical textbooks. He writes, "The painter who has acquired knowledge of the nature of the sinews, muscles, and tendons will know exactly in the movement of any limb how many and which of the sinews are the cause of it, and which muscle by its swellingis the cause of this sinew's contracting."