§195. The Ostium.--The entrance to the house was called the _ōstium_. This includes the doorway and the door itself, and the word is applied to either, though _forēs_ and _iānua_ are the more precise words for the door. In the poorer houses (§194) the _ōstium_ was directly on the street, and there can be no doubt that it originally opened directly into the _ātrium_; in other words, the ancient _ātrium_ was separated from the street only by its own wall. The refinement of later times led to the introduction of a hall or passageway between the _vestibulum_ and the _ātrium_, and the _ōstium_ opened into this hall and gradually gave its name to it. The threshold (_līmen_) was broad, the door being placed well back, and often had the word _salvē_ worked on it in mosaic. Over the door were words of good omen, _Nihil intret malī_, for example, or a charm against fire. In the great houses where an _ōstiārius_ or _iānitor_ (§150) was kept on duty, his place was behind the door, and sometimes he had here a small room. A dog was often kept chained in the _ōstium_, or in default of one a picture was painted on the wall or worked in mosaic on the floor (Fig. 41) with the warning beneath it: _Cavē canem!_ The hallway was closed on the side of the _ātrium_ with a curtain (_vēlum_). This hallway was not so long that through it persons in the _ātrium_ could not see passers-by in the street. [Illustration: FIGURE 42. IMPLUVIUM IN TUSCAN ATRIUM] [Illustration: FIGURE 43. SECTION OF TUSCAN ATRIUM]