15. The breath in the heart is supplied by means of the neighbouring organ, which is called the lungs, and is a receptacle for air, drawing the breath from without through the windpipe inserted in it, which extends to the mouth. The heart being placed in the midst of this organ (and itself also moving incessantly in imitation of the action of the ever-moving fire), draws to itself, somewhat as the bellows do in the forges, a supply from the adjacent air, filling its recesses by dilatation, and while it fans its own fiery element, breathes upon the adjoining tubes; and this it does not cease to do, drawing the external air into its own recesses by dilatation, and by compression infusing the air from itself into the tubes.