Exciditur vero os duobus modis: si parvulum est quod laesum est, modiolo, quem χοινικίδα Graeci vocant: si spatiosius, terebris. Utriusque rationem proponam. Modiolus ferramentum concavum teres est, imis oris serratum; per quod medium clavus, ipse quoque interiore orbe cinctus, demittitur. Terebrarum autem duo genera sunt: alterum simile ei quo fabri utuntur: alterum capituli longioris, quod ab acuto mucrone incipit, deinde subito latius fit; atque iterum ab alio principio paulo minus quam aequaliter sursum procedit. Si vitium in angusto est quod comprehendere modiolus possit, ille potius aptatur: et si caries subest, medius clavus in foramen demittitur; si nigrities, angulo scalpri sinus exiguus fit qui clavum recipiat ut, eo insistente, circumactus modiolus delabi non possit: deinde is habena, quasi terebra convertitur. Estque quidam premendi modus, ut et foret et circumagatur; quia si leviter imprimitur parum proficit, si graviter non movetur. Neque alienum est instillare paulum rosae vel lactis, quo magis lubrico circumagatur; quod ipsum tamen, si copiosius est, aciem ferramenti hebetat. Ubi iam iter modiolo impressum est, medius clavus educitur, et ille per se agitur: deinde, quum sanitas inferioris partis scobe cognita est, modiolus removetur. _Perforator for Fistula Lachrymalis._ Greek, λεπτὸν τρύπανον. Galen (xii. 821) says that Archigenes in cases of fistula lachrymalis perforated the nasal bone with a small drill (λεπτὸν τρύπανον), and Paul (VI. xxii) says: Some, after excision of the flesh, use a perforator (τρύπανον) and make a passage for the fluid or matter to the nose. Albucasis figures a drill for this purpose which he says had a triangular iron point and a conical wooden handle. In the find of instruments of the third-century oculist Severus is a drill which Deneffe regards as intended for this purpose. It is 6 cm. in length and 7 mm. on each of its four sides. One end is pointed, the other has a slit for a knife-blade. It is beautifully damascened with silver (Pl. II, fig. 7). _Bone Lever._ Greek, μοχλίσκος, ἀναβολεύς. Instruments for levering fractured bones into position are described in several places. Hippocrates (iii. 117) says: