Passage 9.8.2
ἐνταῦθα καὶ Διονύσον ναός ἐστιν Αἰγοβόλου. θύοντες γὰρ τῷ θεῷ προήχθησάν ποτε ὑπὸ μέθης ἐς ὕβριν, ὥστε καὶ τοῦ Διονύσου τὸν ἱερέα ἀποκτείνουσιν· ἀποκτείναντας δὲ αὐτίκα ἐπέλαβε νόσος λοιμώδης, καί σφισιν ἀφίκετο ἴαμα ἐκ Δελφῶν τῷ Διονύσῳ θύειν παῖδα ὡραῖον· ἔτεσι δὲ οὐ πολλοῖς ὕστερον τὸν θεόν φασιν αἶγα ἱερεῖον ὑπαλλάξαι σφίσιν ἀντὶ τοῦ παιδός. δείκνυται δὲ ἐν Ποτνιαῖς καὶ φρέαρ· τὰς δὲ ἵππους τὰς ἐπιχωρίους τοῦ ὕδατος πιούσας τούτου μανῆναι λέγουσιν.
Here too there is a temple of Dionysus "Aigobolos" (Goat-slayer). For once, while sacrificing to the god, the worshippers became so drunken they were driven into reckless violence and even killed the priest of Dionysus. Immediately after having committed this murder, a contagious plague struck them, and an oracle came from Delphi that their cure was to sacrifice to Dionysus a beautiful boy. But not many years later, the god replaced the boy as their sacrificial offering with a goat. At Potniai there is also shown a well, whose water, they say, causes madness to the native horses that drink from it.