MARKER FOR DETERMINING ITS POSITION IN A CAVITY INSIDE THE ORGANISM OF A LIVING BEING

The invention provides a marker whose position in a cavity inside of a living organism can be determined, in particular for detecting local passage speeds of the marker through the gastro-intestinal tract, preferably in the small intestinal tract. The object of the invention is to provide a marker whose magnetization can be reversed with relatively low field intensities. To that end, the marker consists of a first substantially spherical part which contains a magnetizable material and is surrounded on all sides by a second part which is provided with a substantially spherical receptacle adapted to the surface shape of the first part, the receptacle being filled with a low-viscosity fluid.