  Previous extrapolations of lattice QCD results for the nucleon mass to the
physically relevant region of small quark masses, using chiral effective field
theory, are extended and expanded in several directions. A detailed error
analysis is performed. An approach with explicit delta(1232) degrees of freedom
is compared to a calculation with only pion and nucleon degrees of freedom. The
role of the delta(1232) for the low-energy constants of the latter theory is
elucidated. The consistency with the chiral perturbation theory analysis of
pion-nucleon scattering data is examined. It is demonstrated that this
consistency can indeed be achieved if the delta(1232) dominance of the P-wave
pion-nucleon low-energy constant c3 is accounted for. Introduction of the
delta(1232) as an explicit propagating degree of freedom is not crucial in
order to describe the quark-mass dependence of the nucleon mass, in contrast to
the situation with spin observables of the nucleon. The dependence on finite
lattice volume is shown to yield valuable additional constraints. What emerges
is a consistent and stable extrapolation scheme for pion masses below 0.6 GeV.
