The twenty-eight tragic masks enumerated by Pollux were used for the ordinary characters of tragedy, and formed a regular part of the stock of the Greek stage-manager. But special masks were required when any unusual character was introduced. Pollux gives a long list of such masks.[736] In the first place there were numbers of mythological beings with strange attributes. Actaeon had to be represented with horns, Argo with a multitude of eyes. Evippe in the play of Euripides had the head of a mare. A special mask of this kind must have been required to depict Io with the ox-horns in the Prometheus Vinctus of Aeschylus. A second class of special masks was needed to represent allegorical figures such as Justice, Persuasion, Deceit, Jealousy. Of this kind are the figures of Death in the Alcestis of Euripides, and Frenzy in the Hercules Furens. Lastly, there were personifications of cities, rivers, and mountains. Five specimens of ancient tragic masks are given in figs. 17, 18. The first is the mask of a youth, the fifth that of a man; the second and third are probably masks of women. The fourth is an example of one of the special masks, and depicts Perseus with the cap of darkness upon his head.[737] [Illustration: FIG. 18.] We come now to the dress of the tragic actors. Nothing is known as to the appearance of this dress in the time of Thespis and his immediate successors. Our information refers solely to the tragic costume as modified and developed by Aeschylus in the course of the fifth century. The object of Aeschylus in these innovations was to add fresh splendour to the costume, and make it worthy of the colossal beings by which his stage was peopled. For this purpose he employed various devices. Among these was the cothurnus, or tragic boot, which was intended to increase the stature of the actors, and to give them an appearance of superhuman grandeur. It was a boot with a wooden sole of enormous thickness attached to it. The wooden sole was painted in various colours.[738] According to some grammarians Aeschylus invented the boot altogether;[739] others say his innovation consisted merely in giving increased thickness to the sole, and so raising the height of the actors.[740] This latter view is probably the correct one. The original of the cothurnus, as already remarked, may very likely have been the hunting boot of the same name worn by Dionysius, which was a boot reaching high up the calf, but with soles of ordinary size. After the time of Aeschylus the tragic cothurnus continued to be a regular feature in theatrical costume down to the latest period of Greek and Roman tragedy.[741] It varied in height according to the dignity and position of the wearers, a king, for instance, being provided with a larger cothurnus than a mere attendant. In this way the physical stature of the persons upon the stage was made to correspond to their social position. In the accompanying illustration (Fig.