From Richard Selzer’s Diary, on pain:
One purpose of these cries of pain, then, might be to summon help, to notify fellow members of the tribe of one’s predicament so that they will come running. But I think there is more to it than that. For the sufferer, these outcries have a kind of magical property of their own, offering not only an outlet for the emotion but a means of letting out the pain. Hollering, all by itself, gives a measure of relief. To cry out ow! or aiee! requires that the noise be carried away from the body on a cloud of warm, humid air that had been within the lungs of the sufferer. The expulsion of this air, and with it the sound, is an attempt to exteriorize the pain, to dispossess oneself of it, as though the vowels of pain were in some magical way the pain itself. It is not hard to see why the medieval church came to believe that a body writhing, racked, and uttering unearthly, primitive cries was possessed by devils. Faced with such a sufferer, authorities of the church deemed exorcism both necessary and compassionate. “Go ahead and holler,” says the nurse to patient. “You feel better. Don’t hold it in.” It is wise advice that has been passed down for millennia of human suffering.