  Exploratory simulations of four-nucleon interactions are performed taking
into account the dynamical effects of internal nucleon loops. The four-nucleon
interactions in the isoscalar and isovector channels are described by Yukawa
interactions with auxiliary scalar fields. The nucleon mass and the average
field lengths of the scalar fields are determined as a function of nucleon
hopping parameter and Yukawa coupling strengths. There are no problems with
"exceptional configurations" at strong couplings which make quenched
simulations unreliable.
