Passage 10.23.6
οἱ δὲ ἀρχομένης μὲν τῆς μάχης, καὶ μάλιστα οἱ περὶ τὸν Βρέννον ---οὗτοι δὲ μήκιστοί τε ἦσαν καὶ ἀλκιμώτατοι τῶν Γαλατῶν---τότε μὲν ὑπὸ προθυμίας ἔτι ἀντεῖχον βαλλόμενοί τε πανταχόθεν καὶ οὐχ ἧσσον ὑπὸ τοῦ ῥίγους, μάλιστα οἱ τραυματίαι, ταλαιπωροῦντες· ὡς δὲ καὶ ὁ Βρέννος ἔλαβε τραύματα, ἐκεῖνον μὲν λιποψυχήσαντα ἐκκομίζουσιν ἐκ τῆς μάχης, οἱ δὲ βάρβαροι πανταχόθεν σφίσιν ἐγκειμένων τῶν Ἑλλήνων ὑπέφευγόν τε ἄκοντες καὶ ἑαυτῶν τοὺς ἀδυνάτους διὰ τραύματα ἕπεσθαι καὶ ἀρρωστίαν φονεύουσιν.
At the beginning of the battle, the Gauls—especially those around Brennus, who were the tallest and bravest among them—still resisted with great zeal, although they were being assailed on every side and were suffering severely from the cold, most of all the wounded. But when Brennus himself was wounded and, faint of heart, was carried off the field, then the barbarians, pressed in everywhere by the Greeks, fled unwillingly and killed those among their number who were too weakened by wounds and sickness to keep pace.