  On a bounded, measurable domain of non-negative current-quark mass, realistic
models of QCD's gap equation can simultaneously admit two inequivalent
dynamical chiral symmetry breaking (DCSB) solutions and a solution that is
unambiguously connected with the realisation of chiral symmetry in the Wigner
mode. The Wigner solution and one of the DCSB solutions are destabilised by a
current-quark mass and both disappear when that mass exceeds a critical value.
This critical value also bounds the domain on which the surviving DCSB solution
possesses a chiral expansion. This value can therefore be viewed as an upper
bound on the domain within which a perturbative expansion in the current-quark
mass around the chiral limit is uniformly valid for physical quantities. For a
pseudoscalar meson constituted of equal mass current-quarks, it corresponds to
a mass m_{0^-}~0.45GeV. In our discussion we employ properties of the two DCSB
solutions of the gap equation that enable a valid definition of <bar-q q> in
the presence of a nonzero current-mass. The behaviour of this condensate
indicates that the essentially dynamical component of chiral symmetry breaking
decreases with increasing current-quark mass.
