The smaller frieze of Pergamon, giving incidents in the myth of Telephos, is of a very different type (Fig. 8). Firstly, the subject is not a unity in time and place, but a continuous narration of mythological episodes. It thus resembles the setting in a continuous frieze of a number of metope-subjects. Telephos appears in different situations in a scene which apparently is uniform. This is a decidedly new departure in artistic theory, and it had the profoundest effect on all subsequent art. We need not, of course, see in the Telephos frieze the first appearance of this custom, but it happens to be the earliest surviving monument in which the principle is easily remarked. Moreover, the information as to change of scene is conveyed by means of changes in the background, so that we see in it another new departure: the use of a significant pictorial background instead of the blank wall against which earlier reliefs had been set. Here again the Hellenistic artist revives rather than originates. The pictorial background occurs as early as the ‘Erechtheum’ _poros_ pediment of the Acropolis, but during the fifth and fourth centuries the idea was dropped only to reappear at a later date. We have already seen that relief sculpture at all stages of its history is closely affected by the kindred art of painting. During the fourth century painting underwent changes in the direction of naturalism as marked as, if not more marked than, the corresponding changes in sculpture. The late fourth century and the third century form the great period of Greek painting, in which the names of Parrhasios, Protogenes, and Apelles stand supreme. A true and correct feeling for perspective and a naturalistic scheme of colouring were the main discoveries of the period, discoveries which we are only able to appreciate in very roundabout methods through Pompeian wall-paintings and mummy-cases from the Fayum. All Hellenistic sculpture is profoundly influenced by painting, as we shall see; but naturally the art of relief is nearest akin and shows most clearly the effects of graphic ideas. The Hellenistic reliefs are almost all adaptations of pictures, and the Telephos frieze earns its main interest and reputation because it is one of the first monuments to show this influence very clearly. We find a true use of perspective in part of this frieze, and a deliberate intention to create the impression of depth.