Fig. 5. Time evolution of protrusion of a macrophage after incubation with 10 µM Latrunculin A for 4 minutes. Phase contrast images at the beginning of the pulse (A), at the end of the viscoelastic response (B), at the end of the force pulse (C) and after relaxation (D) are shown. Note that the flow velocity in the viscoelastic regime (v1.6 µm second^-1) is much higher then in the case of control cells.