Sentence:  The parte of Euacuation by lettyng of blud, is <WSD>incision</WSD> or cuttyng of the vayne, wherby the bloud, whiche is cause of syckenes or grefe to the hole body, or any particular part therof, doth most aptly passe. 
Meaning of the word marked with <WSD> tags:  The act of cutting into a substance.