"Magic to Medicine," Part 1 of a four-part exploration of what narrator Kathryn Walker calls "the quest to understand human blood and control it," charts the haphazard 2000-year quest for understanding. It begins with Roman physician Galen, whose anatomical studies, though incorrect, were considered gospel for almost 1500 years. The hour also traces the progress of perfecting transfusion, which wouldn't be safe until the 20th century, when blood types were discovered. Indeed, for most of recorded history illnesses were treated the opposite way, with bloodletting. Based on Douglas Starr's book "Blood: An Epic History of Medicine and Commerce."