Fig. 2. Composite trajectories of 50 MAT-LyLu (A,B) and AT-2 cells (C,D) migrating in the absence (A,C) and in the presence (B,D) of an electric field (3 V cm^-1), shown as circular diagrams. In each diagram, the initial point for each trajectory was placed at the centre of the circle. The x axis corresponds to the direction of the electric field. The cathode (`-' pole) was always placed at the right-hand side of the diagram.