He arrives with Banquo on the heath, fair and red-bearded, sparing of gesture, full of pride and the sense of animal wellbeing, and satisfied after the battle like a beast who has eaten his fill.

But in the fifth act there is a change.
This is still the big, burly, fleshly, handsome-looking Thane; here is still the same face which in the earlier acts could be superficially good-humoured and sometimes royally courteous.

But now the atmosphere of blood, which pervades the whole tragedy, has entered into the man and subdued him to its own nature; and an indescribable degradation, a slackness and puffiness, has overtaken his features.

He has breathed the air of carnage, and supped full of horrors.

Lady Macbeth complains of the smell of blood on her hand: Macbeth makes no complaint--he has ceased to notice it now; but the same smell is in his nostrils.