The painter who is familiar with the nature of the sinews, muscles, and tendons, will know very well, in giving movement to a limb, how many and which sinews cause it; and which muscle, by swelling, causes the contraction of that sinew; and which sinews, expanded into the thinnest cartilage, surround and support the said muscle.

Summary

This quote by Leonardo da Vinci highlights the importance of understanding the anatomy of the human body for a painter. Da Vinci emphasizes that a painter who is well-versed in the sinews, muscles, and tendons will have a comprehensive understanding of how different limbs move. They will know which sinews contribute to the movement of a limb, which muscles cause the contraction of specific sinews through swelling, and how other sinews, even in their thinnest cartilage form, support and encompass the muscles. Overall, this understanding of anatomy enables a painter to accurately capture movement and portrayal of the human form in their artwork.