The residuary movements are like these: they are within the soul potentially, but actualize themselves only when the impediment to their doing so has been relaxed; and according as they are thus set free, they begin to move in the blood which remains in the sensory organs, and which is now but scanty, and take on likenesses after the manner of cloud shapes, which in their rapid metamorphoses one compares now to human beings and a moment afterwards to centaurs.