In Macbeth, how does the image pattern of illness and medicine refer to the theme of power? What is the connection between these two?

In Shakespeare's Macbeth, illness and
medicine are tied directly to Lady Macbeth. There is also an illness of character with
Macbeth. For both people, they lose the power they had enjoyed
previously.

In Act V, Lady Macbeth is sleepwalking and
talking in her sleep about the murders she and her husband have committed or been
involved in. Whereas she was so strong at the beginning, now she is losing her
mind.

Macbeth calls for the Doctor, and the physician and
Gentlewoman observe her. They hear things they would rather have no knowledge of.
Macbeth asks for an update:

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How does your patient, doctor?
(42)

The doctor responds that
she seems to have a troubled mind. Macbeth responds by asking him to cure
it:

Cure her
of that. 
Canst thou not minister to a mind diseased, 
Pluck from
the memory a rooted sorrow, 
Raze out the written troubles of the
brain, 
And with some sweet oblivious antidote 
Cleanse the stuff'd
bosom of that perilous stuff 
Which weighs upon the heart?
(46-52)

When the Macbeths
were loyal to King Duncan, they were well, as was the country. As soon a they murder
Duncan, unnatural things begin to occur because the universe's balance had been upset
with the unnatural death of Duncan. When they start on this downward spiral to murder
and deceit, both are robbed of their power. Lady Macbeth, who had been so strongly
committed to their plans and a powerful woman in her own right, has been diminished to a
worried and fragile ghost of the person she once way, haunted by their
actions.

In Macbeth's case, his mind seems unwell as he
envisions the daggers leading him to Duncan's chamber, he turns to quivering jelly when
the deed is done and he returns with the bloody dagger; his men believe him to be mad
when he sees Banquo's ghost; and, ultimately, he becomes a murderous butcher, which is
not the person Macbeth was. The man once known as a fierce warrior and fearless
supporter of the King, is now losing the respect of his followers who smile with their
faces but not with their hearts; they do not trust him, and once Malcolm and the English
army move toward Macbeth, he has no power to command his men who are starting to change
sides to fight with the English. As this comes to Macbeth, he states, "I am sick of
heart..." (V.iii.20) as his sense of power dwindles.

The
illness or disease of Macbeth's soul and wife's soul and psyche
leads to the loss of personal power—poisoning the mind—which in turn, makes them both
powerless.