And there are four signs393 by which an internal imposthume is recognised, swelling, pain, injury to the functions, and the things we have mentioned, as are urine, faeces, and their like. And there are five special signs of true pleurisy, that cannot be separated from it, as are difficulty of drawing breath, continuous fever, cough (and) pain in the side; and Avicenna adds the fifth sign to these, a serrated pulse, like the teeth of a saw,394 striking at long intervals with a pause between.