The objection, that Paulus Ægineta, the physician, in a passage where he refers to Dioscorides for the medical virtues of _Indicum_, applies to it the epithet black, seems to have more weight[636]. It may be added also, that the virtues, in general, which Galen ascribes to the _Indicum nigrum_, appear to be similar to those ascribed by Dioscorides to _Indicum_; and the latter in one place[637], where he speaks of the healing of wounds, uses only the expression _Indicum_, and not _Indicum nigrum_. It is particularly worthy of remark, that Zosimus, the chemist, declares the hyacinth colour of the ancients, that of woad, and the _Indicum nigrum_, to be the same[638] or similar. But to those who know on how slight grounds the ancient physicians ascribed medicinal qualities to many substances, it will not perhaps appear strange, that, in consequence of the same name, they should ascribe the same qualities to two different things. It is not improbable that in cases of external injury, for which the _Indicum nigrum_ was recommended, indigo and Indian ink might produce as much or as little effect. I should consider of far greater importance the opinion of the chemist Zosimus; but unfortunately his writings have not yet been printed. The period in which he lived is still uncertain, and it is not known whether all the chemical manuscripts which bear that name were written by the same author. From what has been said, I think it may, at any rate, be inferred, that in the time of Vitruvius and Pliny, indigo, as well as Indian ink, was procured from India, and that both were named _Indicum_. It is less certain that the Greeks called indigo _Indicum_, and Indian ink _Indian black_. Nay, it appears that indigo, on account of the very dark blue colour which it exhibits both when dry and in the state of a saturated tincture, was often named Indian black. In my opinion, it is proved also that, in the old dye-houses, the workmen collected the scum thrown up by the dye-pans, and dried it into a kind of lake or carmine. I shall now prove what I have already asserted, that indigo was at all times used, and continued without interruption to be imported from India. I shall quote mention made of it in various centuries; but I am convinced that attentive readers may find instances where it occurs in many other writers.