You’d think that, by now, scientists would have gotten every body part identified and classified. But as the eternal mystery of the appendix proves, there are still parts of our body we have failed to grasp. Take for example the news that we have a new organ. No, we didn’t grow one over the decades as part of evolution (though some would wish we indeed grew more hands or arms). No, we’ve had the mesentery for as long as we had intestines, but it’s only now that it’s being raised to the status of “organ” from “anonymous tissue structure”.