The sculptor could learn nothing new from paintings where all that is proper to painting is ignored:--plane always preferred to line, the constructive details, perceptible only as projection, not as colour or value (like the insertion of the leg and the thigh), marked by deep lines that look like tattoo marks; and perspective almost entirely ignored, at least till a late period. It is necessary thus to examine Greek painting[16] in order to appreciate, by comparison with this negative art, the very positive influence of mediæval painting or mediæval sculpture. The painting on a flat surface--fresco or panel--which became more and more the chief artistic expression of those times, taught men to consider perspective; and, with perspective and its possibility of figures on many planes, grouping: the pattern that must arise from juxtaposed limbs and heads. It taught them to perceive form no longer as projection or plane; but as line and light and shade, as something whose charm lay mainly in the boundary curves, the silhouette, so much more important in one single, unchangeable position than where, the eye wandering round a statue, the only moderate interest of one point of view is compensated by the additional interest of another. Moreover, painting, itself the product of a much greater interest in colour than Antiquity had known, forced upon men's attention the important influence of colour upon form. For, although the human being, if we abstract the element of colour, if we do it over with white paint, has indeed the broad, somewhat vague form, the indecision of lines which characterises antique sculpture; yet the human being as he really exists, with his coloured hair, eyes, and lips, his cheeks, forehead, and chin patterned with tint, has a much greater sharpness, precision, contrast of form, due to the additional emphasis of the colour. Hence, as pictorial perspective and composition undoubtedly inclined sculptors to seek greater complexities of relief and greater unity of point of view, so the new importance of drawing and colouring suggested to them a new view of form. A human being was no longer a mere arrangement of planes and of masses, homogeneous in texture and colour. He was made of different substances, of hair, skin over fat, muscle, or bone, skin smooth, wrinkled, or stubbly, and, besides this, he was painted different colours. He had, moreover, what the Greeks had calmly whitewashed away, or replaced by an immovable jewel or enamel: that extraordinary and extraordinarily various thing called an Eye. [Footnote 16: At all events, Greek painting preceding or contemporaneous with the great period of sculpture. Later painting was, of course, much more pictorial.]