  The contribution of the $G_2$ structure function to polarized deep inelastic
scattering is slightly redefined in order to avoid kinematical zeros. Its
strong $Q^2$-dependence implied by the Burkhardt-Cottingham (BC) sum rule
naturally explains the sign change of the generalized Gerasimov-Drell-Hearn
(GDH) sum rule. The status of the BC sum rule and implications for other spin
processes are discussed.
