Today, Halloween, is traditionally marked with bats, pumpkins, ghosts and of course, skeletons. In the 1500′s, one man changed the way the medical world saw the skeletal and muscular systems of the human body. That man, Andreas Vesalius, illustrated anatomical features in his De humani corporis fabrica (On the structure of the human body) in a way never before seen. Although the pages below may seem gruesome (fair warning, gentle readers!), they come from one of the most influential anatomy books of all time.