Strong and lively sensations are those chat startle and forcefully rouse the mind because they are either quite pleasant or else very unpleasant; such are pain, tickling sensations, extremes of beat or cold, and generally all those accompanied not only by traces in the brain but also by movement of spirits toward the body's interior parts,.e., by a movement of spirits conducive to changing lhe body's position and to exciting the passions, as we shall explain elsewhere.