  We present a method for simulating numerically the effect of the adiabatic
growth of black holes on the structure of elliptical galaxies. Using a parallel
self--consistent field code, we add black holes to N--body realizations of
model distribution functions for spherical galaxies, using a continuous
mass--spectrum. The variable particle mass, combined with a simple multiple
timestep integration scheme, makes it possible to evolve the models for many
dynamical times with $N \sim 10^6-10^8$, allowing high spatial and mass
resolution. This paper discusses verification of the code using analytic models
for spherical galaxies, comparing our numerical results of the effect of
central black holes on the structure of the galaxies with previously published
models. The intrinsic and projected properties of the final particle
distribution, including higher order moments of the velocity distribution,
permit comparison with observed characteristics of real galaxies, and constrain
the masses of any central black holes present in those galaxies. Our technique
is promising and is easily extended to axisymmetric and triaxial galaxies.
