But where Michelangelo achieved a triumph of boldness, lesser natures were betrayed into bizarrerie; and this chapel of the Medici, in spite of its grandiose simplicity, proved a stumbling-block to subsequent architects by encouraging them to despise propriety and violate the laws of structure.
"We may assume then that the colossal statues of Giuliano and Lorenzo were studied with a view to their light and shadow as much as to their form; and this is a fact to be remembered by those who visit the chapel where Buonarroti laboured both as architect and sculptor.

Of the two Medici, it is not fanciful to say that the Duke of Urbino is the most immovable of spectral shapes eternalised in marble; while the Duke of Nemours, more graceful and elegant, seems intended to present a contrast to this terrible thought-burdened form.

The allegorical figures, stretched on segments of ellipses beneath the pedestals of the two Dukes, indicate phases of darkness and of light, of death and life.

They are two women and two men; tradition names them Night and Day, Twilight and Dawning.

Thus in the statues themselves and in their attendant genii we have a series of abstractions, symbolising the sleep and waking of existence, action and thought, the gloom of death, the lustre of life, and the intermediate states of sadness and of hope that form the borderland of both.