Quark contribution to the nucleon polarizabilities and three-body forces

Lower and upper bounds to the electric polarizability and paramagnetic susc eptibility are explicitly calculated by means of a sum-rule technique and w ithin a large variety of constituent quark models. The role of three-body f orces in the potential model is investigated in detail as well as the effec ts of SU(6) breaking terms. The quark degrees of freedom give a quite sizea ble contribution to the static polarizability and the meson cloud accounts roughly for 30% and 60% of the electric proton and neutron polarizability r espectively. The quark contribution to the paramagnetic susceptibility is e ven higher and the mesonic effects are rather uncertain.