ἀνδρὸς σπλάγχνον ἐκμαθεῖν → learn a man's heart, learn a man's inward nature
crasis for ὁ ἐξ.
οὑξ: κατὰ κρᾶσιν ἀντὶ ὁ ἐξ.
crase att. p. ὁ ἐξ.