An Si3N4 sintered body produced by reactive sintering of silicon, wherein a compound of at least one element selected from the group consisting of Y, Yb and Sm is contained by 0. The display screen graphics data is uncompressed pixel-level data representing graphics content displayable on a display screen attached to the computer in a normal display mode. Furthermore, as for an introducing path and a discharging path that connect the external fluid devices and the fluid device unit, the introducing path, which is short, is connected to the discharging path, which is long. An animal access region is formed between the hopper and the tray. A stop support is formed to underlie the flexible support to prevent damage to the flexible support in a rest position. An extension portion extending towards an LED substrate is formed on a side surface of the reflecting plate, the side surface where the LEDs are arranged.