As is assumed in the preceding paragraph, the elements of lines may be shapes or masses, as well as points. That is, not only do lines made up of points form shapes, but shapes in their turn, when arranged on a surface, necessarily make lines. Such lines are, as a rule, not continuous; yet since the eye takes the shapes successively and in a given direction, they are nevertheless true lines and possess the qualities of ordinary simple lines. The arrangement of masses in an undulating line, say in a landscape painting, has essentially the same value for feeling as a similar continuous line; compare this with a horizontal arrangement of masses, which has all the quiet and repose of a simple horizontal line. Colors and lines, relying on the direct expressiveness which we have been studying, may stand by themselves, as in an oriental rug; yet in painting they have another function: to represent. And even in the purely ornamental use of color and line, the tendency towards representation is apparent everywhere; either the lines are derivatives of schematized pictures of men and plants and animals, or else such objects are introduced as motives without disguise. In painting, therefore, the color red has value not only as so much red, but as standing for the red of a girl's lips or cheeks; and that curved line is of significance, not as mere line alone, but as the curve of her limbs. In this way the native value of the sense symbols becomes suffused and enriched with the values of the things they represent. The two functions of color and of line should never be indifferent to each other; representation should not become a mere excuse for decoration, the objects represented having no value in themselves; nor should color and line be used as mere signs of interesting objects, without reference to their intrinsic value. On the contrary, the two functions should play into each other's hands. If, for example, the human body is represented, the colors and lines employed should be so disposed that they decorate the surface of the picture and hold us there through their sheer rhythm and quality; yet, at the same time, and through their very ornamental power, they should make us feel the more keenly the values of the object they represent. Between the immediate values of the colors and lines there should exist unity: stimulating colors should go with stimulating lines, quiet colors with quiet lines; and the resulting feeling tone of the medium should be in harmony with the feeling of the objects represented; the one should give the other over again, and so each enforce the other.