Definition of "theriacal"

So it is obſerued by ſome, that there is a vertuous Bezoar, and another without vertue; which appeare to the ſhew alike; But the Vertuous is taken from the Beaſt, that feedeth vpon the Mountaines, where there are Theriacall Herbs; And that without Vertue, from thoſe that feed in the Valleyes, where no ſuch Herbs are.

1631, Francis [Bacon], “V. Century. [Experiments in Consort, Touching the Making Herbs and Fruits Medicinable.]”, in Sylua Syluarum: Or A Naturall Historie. In Ten Centuries. […], 3rd edition, London: […] William Rawley; [p]rinted by J[ohn] H[aviland] for William Lee […], paragraph 499, page 124