The above paragraph really gives us all the information we possess about the instrument. It is evidently a slender chisel. A passage in Aretaeus (_Morb. Chron._ ii. 9) is held by some to refer to lithotripsy (digital). The reading, however, is dubious. _Rectal Speculum._ Greek, ἑδροδιαστολεύς, μικρὸν διόπτριον, κατοπτήρ. The earliest mention of the rectal speculum is to be found in the treatise on fistula by Hippocrates: Ὕπτιον κατακλίνας τὸν ἄνθρωπον κατοπτῆρι κατιδὼν τὸ διαβεβρωμένον τοῦ ἀρχοῦ. 'Laying the patient on his back and examining the ulcerated part of the bowel by means of the rectal speculum' (iii. 331). Again, a little further on, he mentions its use in the treatment of piles; and Paul (VI. lxxviii) says: 'With regard to blind fistulae Leonidas says: "We dilate the anus, as we do the female vagina, with the anal or small speculum"' (τῷ ἑδροδιαστολεῖ (τῷ μικρῷ διοπτρίῳ λέγω) διαστεῖλαι τὴν ἕδραν ὡς γυναικεῖον κόλπον). There is a rectal speculum in the Naples Museum (No. 78,031). It is a two-bladed instrument, working with a hinge in the middle. It is O·15 m. in length, and the greatest stretch of the blades is O·07 m. It represents an instrument used to dilate the vagina as well as the rectum, and got its name 'small dilator' in contradistinction to the other vaginal speculum, which we shall see was worked by a screw, and was called the speculum magnum. The rectal speculum was also called κατοπτήρ, in contradistinction to the vaginal speculum which was called διόπτρα. In Galen's Lexicon they are explained as follows: Κατοπτῆρι, τῷ καλουμένῳ ἑδροδιαστολεῖ, ὥσπερ γε καὶ διόπτρα ὁ γυναικῶν διαστολεύς. 'The catopter, which is called the anal dilator, in the same way as the diopter is called the female dilator.' Pl. XLVI, fig. 1 shows one of two similar rectal specula from Pompeii (Naples Museum). _Vaginal Speculum._ Greek, διόπτρα; Latin, _speculum magnum matricis_ (late). Soranus is the first author who makes mention of the speculum specially made for the vagina. The original Greek of this chapter of Soranus is lost, but we have a Latin translation of it preserved to us by Moschion. The heading of this chapter in Soranus, which was No. xxxiv, was Περὶ διοπτρισμοῦ. I shall give part of this chapter from Moschion: QUA DISCIPLINA ORGANO APERIENDAE SINT MULIERES.