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.
Source: wiktionary