Abstract: A cage of experimental animals comprises a body, a position detection part to be assembled with the body and a cover for covering the body. The body has a cylindrical cover projected from a bottom thereof, a keeping space defined between a side wall of the body and the cylindrical cover for keeping experimental animals. The position detection part has a position detector at the circumferential surface thereof for detecting the behavioral movement of the animal.

Abstract: An observation apparatus comprises a transparent keeping cage having cylindrical outer and inner walls defining an annular keeping space therebetween, a group of circumferential position detectors, a group of standing action detectors, a group of inner peripheral position detectors, a group of outer peripheral position detectors, and a data processing unit for processing detection signals produced by the detectors to determine the actions of an experimental animal through the analysis of the detection signals produced by the detectors. The detectors of each group are arranged on a circle at equal angular arrangement. Four detectors each belonging to one of the four groups of detectors are arranged in a set on the same radius and driven simultanelously or sequentially, and the sets of the detectors are driven sequentially one at a time to avoid interference between the detectors. The data processing unit is simple and compact in construction and has amplifiers for each set of the detectors.