τὸ δ' ἐξαίφνης τὸ ἐν ἀναισθήτῳ χρόνῳ διὰ μικρότητα ἐκστάν → suddenly refers to what has departed from its former condition in a time imperceptible because of its smallness
παλήσειε: 3 л. sing. aor. 1 opt. к παλέω.