  We quantitatively examine the extent to which instanton degress of freedom,
contained within standard Monte-carlo generated gauge-field configurations, can
maintain the characteristic features of the mass and renormalisation functions
of the non-perturbative quark propagator. We use over-improved stout-link
smearing to isolate instanton effects on the lattice. Using a variety of
measures, we illustrate how gauge fields consisting almost solely of
instanton-like objects are produced after only 50 sweeps of smearing. We find a
full vacuum, with a packing fraction more than three times larger than
phenomenological models predict. We calculate the overlap quark propagator on
these smeared configurations, and find that even at high levels of smearing the
majority of the characteristic features of the propagator are reproduced. We
thus conclude that instantons contained within standard Monte-carlo generated
gauge-field configurations are the degrees of freedom responsible for the
dynamical generation of mass observed in lattice QCD.
