  Correlated velocity patterns and associated large length-scale transmission
of traction forces have been observed in collective live cell migration as a
response to a "wound". We argue that a simple physical model of a force-driven
heterogeneous elastic membrane sliding over a viscous substrate can
qualitatively explain a few experimentally observed facts: (i) the growth of
velocity ordering which spreads from the wound boundary to the interior, (ii)
the exponential tails of the traction force distributions, and (iii) the
swirling pattern of velocities in the interior of the tissue.
