Spleen. When you lose your temper, you’re said to be “venting your spleen.” Why the spleen? Why not the pancreas? Well, doctors used to think a healthy personality required balancing four fluids, or humours. Too much blood made you sanguine—calm, even apathetic—and you might need leeches. Too much spleen made you melancholy, or bad-tempered, or angry. Modern psychology says venting is good because repressed rage can build up and explode like… well, like a ruptured spleen. Spleen: pent-up anger.