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
[2] Lehren, das, institutio. eruditio (Unterweisung, er. in bezug auf Anfänger). – od. durch docere, z.B. im Lehren sehr geschickt, instituendo docendoque peritissimus: durch L. lernen wir, homines dum docent discunt.