On the basis of the average criterion of the qualitative behaviour of
the Hamiltonian dynamical systems, the significance of the anisotropy
and inhomogenity assumptions is discussed. For two different approxima
tions of the galaxy as a rigid body and as an N-body system we use the
Ricci scalar in order to detect the degree of stochasticity. This dem
onstrates that inhomogeneities in the model give a more effective mech
anism of stochasticity of the system than its anisotropies.