Muscular system. Computer-enhanced historical engraving of a standing male figure in posterior view, showing the skeletal muscle system. This drawing appeared in a book by Bernhard Siegfried Albinus, published in 1747. Albinus (1697-1770) was Professor of Medicine at Leiden University. The superficial skeletal muscles are seen in accurate detail. Skeletal muscles are attached by tendons to bones of the skeleton. Also known as voluntary muscles, these muscles are under direct conscious control. Skeletal muscle accounts for up to 45 per cent of body weight.