Περὶ δὲ πρίσιος, ὅταν καταλάβῃ ἀνάγκη πρίσαι ἄνθρωπον, ὧδε γινώσκειν· ἢν ἐξ ἀρχῆς λαβὼν τὸ ἴημα πρίῃς, οὐ χρὴ ἐκπρίειν τὸ ὀστέον πρὸς τὴν μήνιγγα αὐτίκα· οὐ γὰρ συμφέρει τὴν μήνιγγα ψιλὴν εἶναι τοῦ ὀστέου ἐπὶ πουλὺν χρόνον κακοπαθοῦσαν, ἀλλὰ τελευτῶσά πη καὶ διεμύδησεν. ἔστι δὲ καὶ ἕτερος κίνδυνος, ἢν αὐτίκα ἀφαιρέῃς πρὸς τὴν μήνιγγα ἐκπρίσας τὸ ὀστέον, τρῶσαι ἐν τῷ ἔργῳ τῷ πρίονι τὴν μήνιγγα. ἀλλὰ χρὴ πρίοντα, ἐπειδὰν ὀλίγον πάνυ δέῃ διαπεπρίσθαι, καὶ ἤδη κινέηται τὸ ὀστέον, παύσασθαι πρίοντα, καὶ ἐᾷν ἐπὶ τὸ αὐτόματον ἀποστῆναι τὸ ὀστέον. ἐν γὰρ τῷ διαπριωτῷ ὀστέῳ καὶ ἐπιλελειμμένῳ τῆς πρίσιος οὐκ ἂν ἐπιγένοιτο κακὸν οὐδέν· λεπτὸν γὰρ τὸ λειπόμενον ἤδη γίνεται. Τὰ δὲ λοιπὰ ἰῆσθαι χρὴ, ὡς ἂν δοκέῃ ξυμφέρειν τῷ ἕλκεϊ. πρίοντα δὲ χρὴ πυκινὰ ἐξαιρέειν τὸν πρίονα τῆς θερμασίης εἵνεκα τοῦ ὀστέου, καὶ ὕδατι ψυχρῷ ἐναποβάπτειν. θερμαινόμενος γὰρ ὑπὸ τῆς περιόδου ὁ πρίων, καὶ τὸ ὀστέον ἐκθερμαίνων καὶ ἀναξηραίνων, κατακαίει, καὶ μεῖζον ποιέει ἀφίστασθαι τὸ ὀστέον τὸ περιέχον τὴν πρίσιν, ἢ ὅσον μέλλει ἀφίστασθαι. καὶ ἢν αὐτίκα βούλῃ ἐκπρῖσαι τὸ πρὸς τὴν μήνιγγα, ἔπειτα ἀφελέειν τὸ ὀστέον, ὡσαύτως χρὴ πυκινά τε ἐξαιρέειν τὸν πρίονα, καὶ ἐναποβάπτειν τῷ ὕδατι τῷ ψυχρῷ.
(Hippocrates, Peri tōn en kephalēi trōmatōn 21)
Concerning trephination, when necessity compels you to trephine a patient, here is what you must know: if you trephine, having undertaken (the patient’s) care from the beginning, you should not excise the bone down to the membrane straightaway. For it is not good for the membrane to be bare of bone and subject to damaging exposure for a long time; otherwise it may finally become macerated. And there is also another danger, that, if you trephine down to the membrane and at once remove the bone, you may, in the procedure, damage the membrane with the trephine.Rather, during trephination, when the bone lacks a very little of being sawn through and can already be moved, you should stop trephining and let the bone separate on its own. For in the case of bone which is sawn through but lacks some trephining no harm will occur, since the bone left (undivided) is now thin. The rest of the treatment should be that which seems appropriate to the wound. When trephining it is necessary to remove the trephine frequently on account of the heat transmitted to the bone and to dip it in cold water. For the trephine, heated by rotation, in turn, by heating and drying the bone, scorches it and causes more of the bone surrounding the trephination site to separate than would normally do so. If you want to trephine down to the membrane immediately, and then remove the bone, you must, in the same way, take the trephine out frequently and dip it in cold water. (tr. Maury Hanson)