Lady Macbeth:Macbeth Act 1, scene 5, 38–43
The raven himself is hoarse
That croaks the fatal entrance of Duncan
Under my battlements. Come, you spirits
That tend on mortal thoughts, unsex me here,
And fill me from the crown to the toe topful
Of direst cruelty!
Lady Macbeth, upon receiving word that King Duncan of Scotland will be arriving that night, begins sharpening her talons. She isn't sure there's enough manhood to go around between herself and her husband, so she calls upon scheming spirits to "unsex me here." This is her vivid way of asking to be stripped of feminine weakness and invested with masculine resolve. She imagines herself as a vessel which may be emptied out and refilled "from the crown to the toe." One thing nobody, spirit or otherwise, has ever poured into her is "the milk of human kindness" [see THE MILK OF HUMAN KINDNESS].
The prefix un- is abnormally frequent in Macbeth. The protagonists constantly try to undo what is done, take back what is given, and cancel reality by appending negatives. All the powers of langauge, however, cannot cancel their unconscious conflicts, which manifest themselves in hallucinations and bad dreams.