“Well, neither do we, ‘very precisely,’ to be frank⁠—at least, as far as blushing is concerned. The situation is not quite clear; for the dilatory muscles which are presumably set in action by the vasomotor nerves haven’t yet been demonstrated in relation to the blood-vessels. How the cock really swells his comb, or any of the other well-known instances come about, is still a mystery, particularly where it is a question of emotional influences in play. We assume that a connection subsists between the outer rind of the cerebrum and the vascular centre in the medulla. Certain stimuli⁠—for instance, let us say, like your being powerfully embarrassed, set up the connection, and the nerves that control the blood-vessels function toward the face, and they expand and fill, and you get a face like a turkey-cock, all swelled up with blood so you can’t see out of your eyes. On the other hand, suppose you are in suspense, something is going to happen⁠—it may be something tremendously beautiful, for aught I care⁠—the blood-vessels that feed the skin contract, it gets pale and cold and sunken, you look like a dead man, with big, lead-coloured eye-sockets and a peaked nose. But the Sympathicus makes your heart thump away like a good fellow.”