  We investigate a lattice Nambu--Jona-Lasinio model both by the Monte Carlo
method and Schwinger-Dyson equations. A comparison allows the discussion of
finite size effects and the extrapolation to infinite volume. We pay special
attention to the identification of particles and resonances. This enables us to
discuss renormalisation group flows in the neighbourhood of the critical
coupling where the chiral symmetry breaking phase transition takes place. In no
region of the bare parameter space do we find renormalisability for the model.
