Leonardo da Vinci (1452-1519), was also one of the most original and perceptive anatomists of his or any other era. He spent over 25 years investigating the workings of the human body and never published any of his findings. The musculo-skeletal drawings that Leonardo made in the winter of 1510-11, known as "Anatomical Manuscript A, " which are the subject of this book, are the only group of such drawings in which he approached complete coverage of the human form. They represent some of the best anatomical renderings ever created. This book presents a complete discussion of all the drawings in Manuscript A and does something that has never been done before. It presents each drawing and Leonardo's accompanying notes twice: in Leonardo's original "mirror-writing" (backward writing legible only when held up to a mirror) and in translation in each note's original position. These annotations make clear that Leonardo's conclusions about how the muscles and bones work together is the result of his own physical investigations, and the excitement of discovery captured in these notes is palpable.