And since to move anything, or do anything, is impossible without strength, and holding the breath produces strength in creatures which inhale, the holding of that breath which comes from without, but in creatures which do not respire, of that which is connatural (which explains why winged insects, when they move, are perceived to make a humming noise, due to the friction of the connatural spirit colliding with the diaphragm of the holoptera); and since every animal moves if some sense perception, either internal or external, occurs in the primary organ of sense, accordingly if sleeping and waking are affections of this organ, the place in which and the organ in which sleep and waking originate, is evident.