The ancients were fully aware of the value of the information to be gained by searching the recesses of a lesion with a rod of metal. Celsus (v. 28) says regarding fistulae: Ante omnia autem demitti specillum in fistulam convenit, ut quo tendat et quam alte perveniat scire possimus; simul etiam protinus humida an siccior sit: quod extracto specillo patet. Si vero os in vicino est id quoque disci potest si iam necne eo fistula penetraverit et quatenus nocuerit; nam si molle est quod ultimo specillo contingitur, intra carnem adhuc vitium est, si magis id renititur, ad os ventum est. Ibi deinde si labitur specillum, nondum caries est: si non labitur sed aequali innititur, caries quidem, verum adhuc levis est: si inaequale quoque et asperum subest, vehementius os exesum est. At cartilago ubi subsit, ipsa sedes docet; perventumque esse ad eam ex renisu patet. 'But first it is well to put a probe into the fistula to learn where it goes and how deeply it reaches, also whether it is moist or rather dry as is evident when the probe is withdrawn. Further, if there be bone adjacent, it is possible to learn whether the fistula has entered it or not and how deeply it has caused disease. For if the part is soft which is reached by the end of the probe the disease is still intermuscular; if the resistance be greater it has reached the bone: if there the probe slip there is as yet no caries. If it does not slip but meets with a uniform resistance there is indeed caries, but it is as yet slight. If what is below is uneven and rough the bone is seriously eroded, and whether there is cartilage below will be known by the situation, and if the disease has reached it will be evident from the resistance.' These remarks show that with the probe the ancients had cultivated the tactus eruditus to a high degree, and the remarks of Aetius and Paul are equally to the point. The tips of the probes which have survived vary considerably in size and shape. Some have a point which is almost sharp like a stylet; in others the natural thickness of the shaft is kept right to the tip, which is simply rounded off or there is an oval enlargement like that on our olivary probes and sounds. In rare cases the enlargement is globular. The oval enlargement was named by the Greeks πυρήν, which means 'olive-kernel'. The sixteenth-century translators uniformly render this by 'nucleus', which is a convenient term to use, but it has no classical Latin authority. Indeed, there is no classical Latin equivalent used by medical authors. Theodorus Priscianus uses _baca_ (_sic_), a berry, and _bacula_, little berry, and in the _Additamenta_ (I. viii. 21, ed. Rose) he uses the transliteration _pyrena meles_. But this is African Latin.