The aim of the experiment described in this paper is to investigate the possibility of describing the motion of a two-dimensional object represented by a sequence of snapshots. The interest of this experiment resides in the fact that the motion patterns we are dealing with are the irregular ones generated when the shape of an object changes the structure of its boundary slightly from frame to frame. The main motivation for considering such kind of motion is given by problems rising in biomedicine. Presently, many diagnostic results are represented by dynamic imagery where a two-dimensional display of an organ must be tracked in a time interval. The experiment is carried out by decomposing the lines representing the contour of the shapes; then a correspondence process is generated to relate segments from frame to frame and a set of low level descriptors are extracted by comparing related segments. Indications concerning a methodology for constructing higher level descriptors are given.