Instantons and Spin Forces between Massive Quarks

A generalization of Wilson's loop prescription to include spin is proposed. Instantons are shown to generate a spin-spin interaction between quarks. The large splitting between J (3100) and ₂ (2830) may, in fact, be dominated by this mechanism and thus may provide a vivid demonstration of the physical effects of instantons. Heuristic arguments are presented which explain the sign and form of the interaction.