  The enigmatic scaling behaviour of the normal state properties of the high Tc
cuprates has been explained by assuming that a crossover from the two-
dimensional Heisenberg (2D-H) to the one-dimensional spin ladder (1D-SL) regime
takes place at temperature T=T*. For T<T* stripe formation results in the
quantum 1D transport with the characteristic inelastic length L_phi being fully
controlled by the magnetic correlation length xi_m of the even-chain SL,
whereas for T> T* the 2D quantum transport is realized with L_\phi governed by
the 2D-H correlations L_phi=xi_m=exp(J/T)$. Therefore, the pseudogap found in
underdoped (p<p_opt) high Tc's is the spin-gap Delta(p) in even-chain 1D-SL.
