  The scalar-isoscalar field of an effective chiral Lagrangian transforms
differently in either linear or non-linear frameworks: in the former case it is
the counterpart of the pion whereas in the latter it is chiral invariant on its
own. We compare the predictions from these two models for nucleon interactions
and find results which are identical for two-body and rather different for
three-body potentials. Some qualitative features of three-body interactions are
discussed.
