A curious regulation concerning the usage of these three doors is mentioned by Pollux.[594] He says that the central door was reserved for the principal character, the door to the right for the secondary characters, the door to the left for those of least significance. It is plain that this statement must be taken with very considerable deductions. In the first place, it only applies to tragedy, and only to those plays in which the background represented a palace or similar building. Even then it cannot have been by any means universal. In fact it only applies to dramas of the type of the Oedipus Tyrannus, in which the principal character is at the same time a person of the highest rank. In such cases it is very likely that his rule about the doors was observed. It would be in harmony with the statuesque and conventional character of Greek tragedy. But there are many plays in which it would be absurd to suppose that any such regulation was adopted. For instance, in the Antigone it can hardly be imagined that the tyrant Creon entered only by a side-door, while the central door, with its regal splendour, was reserved for the oppressed heroine Antigone. Similarly, in the Electra, it is ridiculous to suppose that Clytaemnestra entered from the inferior part of the palace, Electra from the more magnificent. There can be no doubt that Pollux, in his statement about the doors, has been following his favourite practice, and has made a general rule out of a few special instances. The openings at the back of the stage always led out of some building, tent, cavern, or other dwelling-place. They could only therefore be used by persons who were supposed to be inside the dwelling-place. People coming from the neighbourhood, or from a distance, had to enter the stage in a different way. For this purpose doors in the side-wings were provided.[595] The subject of these side-entrances on to the stage has been much discussed in recent years.[596] Many scholars have endeavoured to prove that they were a late invention, confined to the Hellenistic theatre, and that they never existed in the fifth century. They suppose that in the old Athenian theatre the only side-entrances were those in the orchestra, and that the actors who entered or departed otherwise than through the back-scene always used the orchestra for this purpose. Now it is no doubt true, as we have already shown, that they used it sometimes. There are about twenty cases in which actors and chorus leave together in a sort of procession, chiefly at the end of a play[597]; and there are two cases in which they enter together.[598] There are also those scenes—about five in number—when the actors enter in chariots.[599] On all these occasions it can hardly be doubted that the actors entered and departed through the orchestra. But the other examples which have been brought forward are entirely conjectural. It is said that, when the actors and the chorus were supposed to come from the same place,