Most of us think about our circulatory system only when something goes wrong, but the amazing story of how it goes right--"magnificently right," as author Steven Vogel puts it--is equally worthy of our attention. It is physically remarkable, bringing food to (and removing waste from) a hundred trillion cells, coursing through 60,000 miles of arteries and veins (equivalent to over twice around the earth at the equator). And it is also intriguing. For...