Sentence:  Ay, sir; there are a crew of wretched souls / That stay his cure: their malady convinces / The great assay of art; but at his touch— / Such sanctity hath heaven given his hand— / They presently <WSD>amend</WSD>. 
Meaning of the word marked with <WSD> tags:  To be healed, to be cured, to recover (from an illness).