Sentence:  ... he saith that some Jasper stones are found having in them the livelie image of a naturall man, with a sheeld at his necke and a speare in his hand, and under his feete a serpent: which stones so marked and signed, he preferreth before all the rest, bicause they are <WSD>antidotaries</WSD> or remedies notablie resisting poison. 
Meaning of the word marked with <WSD> tags:  An antidote.