The flat chisel is referred to by Celsus in his description of the levelling of an elevation on one side of a depressed fracture of the cranium: Ergo, si ora alteri insedit, satis est id quod eminet plano scalpro excidere; quo sublato, iam rima hiat quantum curationi satis est (VIII. iv). Numerous references occur in other authors. There is a fine example of a flat chisel in the Cologne Museum (Pl. XLI, fig. 2). It is all of steel, and delicately ornamented with spiral indentations. This interesting little instrument was found in the surgeon's outfit already described, and is one of the best authenticated instruments--as regards its having been the property of a surgeon--we possess. The chisel figured by Vulpes, consisting of a cylindrical bronze handle and a flat blade, is, I believe, a variety of scalpel. We have many interesting references to the use of the chisel in bone work. It was used as an osteotome to divide the bone in distorted union: 'If the callus be of stony hardness incise the skin with a scalpel, and divide the union with chisels' (ἐκκοπεῦσι) (Paul, VI. cix). In the removal of supernumerary digits we are to cut away the flesh all round, and either chop the bone through with a chisel (τῷ ἐκκοπεῖ), or remove it by sawing (Paul, VI. xliii). In using the chisel as an osteotome one chisel was often placed behind the bone to steady it while it was being struck by another in front. This method of applying two chisels, which is only described by the Greek authors, is always referred to by the phrase ἐκκοπέων ἀντιθέτων. The following passage from Galen fully describes the manipulation (ii. 687): 'Separate off the membranes adhering to the bone, which being properly done, divide the bone of the rib by means of two chisels placed in opposition to each other _secundum artem_' (ἀντιβαλλομένων δυοῖν ἀλλήλοις ἐκκοπέων ὡς ἔθος). The following passage from Paul shows the chisel used for a similar purpose: 'If part of the clavicle is broken off and unconnected, and if we find it irritating the parts, we must make a straight incision with a scalpel and remove the broken portion and smooth it with chisels (δι' ἐκκοπέων), taking care that the instrument called 'meningophylax' (q. v.), or another chisel, be put under the clavicle (μηνιγγοφύλακος ἢ ἑτέρου ἐκκοπέως) to steady it' (VI. xciii).