  The functional dependence of the high-energy observables of total cross
section and slope parameter on the sizes of the colliding hadrons predicted by
the model of the stochastic vacuum and the corresponding relations used in the
geometric model of Povh and H\"ufner are confronted with the experimental data.
The existence of a universal term in the expression for the slope, due purely
to vacuum effects, independent of the energy and of the particular hadronic
system, is investigated. Accounting for the two independent correlation
functions of the QCD vacuum, we improve the simple and consistent description
given by the model of the stochastic vacuum to the high-energy pp and pbar-p
data, with a new determination of parameters of non-perturbative QCD. The
increase of the hadronic radii with the energy accounts for the energy
dependence of the observables.
