The experimental treatment of the isolated elements detected the particular function of each in distributing attention in the field of view. But while all are possibly operative in a given picture, some are given, as we have seen, much more importance than others, and in pictures of different types different elements predominate. In those classes with a general symmetrical framework, such as the altar and Madonna pieces, the elements of interest and direction of attention determine the balance, for they appear as variations in a symmetry which has already, so to speak, disposed of mass and line. They give what action there is, and where they are very strongly operative, they are opposed by salient lines and deep vistas, which act more strongly on the attention than does mass. Interest keeps its predominance throughout the types, except in the portraits, where the head is usually in the central line. But even among the portraits it has a respectable representation, as jewels, embroideries, beautiful hands, etc., count largely too in composition. The direction of attention is most operative among the portraits. Since these pictures represent no action, it must be given by those elements which move and distribute the attention; in accordance with which principle we find line also unusually influential. As remarked above, altar-pieces and Madonna pictures, also largely without action, depend largely for it on the direction of attention. The vista, as said above, rivets and confines the attention. We can, therefore, understand how it is that in the genre pictures it appears very numerous. The active character of these pictures naturally requires to be modified, and the vista introduces a powerful balancing element, which is yet quiet; or, it might be said, inasmuch as energy is certainly expended in plunging down the third dimension, the vista introduces an element of action of counterbalancing character. In the landscape it introduces the principal element of variety. It is always to be found in those parts of the picture which are opposed to other powerful elements, and the "heavier" the other side, the deeper the vista. Also in pictures with two groups it serves as a kind of fulcrum, or unifying element, inasmuch as it rivets the attention between the two detached sides. The direction of suggestion by means of the indication of a line, quite naturally is more frequent in the Madonna picture and portrait classes. Both these types are of large simple outline, so that line would be expected to tell. In a decided majority of cases, combined with vista--the shape being more or less a diagonal slope--it is clear that it acts as a kind of bond between the two sides, carrying the attention without a break from one to the other.