  Starting from the 4-dimensional gluodynamics, we discuss the statistical
ensemble of torons ( the toron is a self-dual solution with fractional
topological number; it can be understood as a point defect) which interact
strongly. It is shown that the effective Lagrangian describing this statistical
ensemble possesses the fourth derivative kinetic term and leads to the area law
for the Wilson loop. Besides that we derive the effective string action
containing the rigid (extrinsic curvature) term as a consequence of the fourth
derivative action.
