We're past the point where scientists argue about where in the body the soul is housed. But our longstanding fascination with the heart continues.
It doesn't think, it doesn't take on multiple roles like other muscles in the body, it just pumps our blood. And we get a fresh take on the heart, its physical job and its continued metaphysical importance to the human condition, in zoologist Bill Schutt's latest book, Pump: A Natural History of the Heart.
Our last visit with the author was a bracing chat about cannibalism across the animal kingdom.
We bring him back to the JX to talk about hearts in humans and whales and antarctic fish and much more.