Sentence:  'T is written in the Hebrew Chronicle, / How the physicians, leaving pill and potion, / Prescribed, by way of <WSD>blister</WSD>, a young belle, / When old King David's blood grew dull in motion, / And that the medicine answered very well ... 
Meaning of the word marked with <WSD> tags:  Something applied to the skin to raise a blister; a vesicatory or other applied medicine.