[en] It has been shown, using both (e,e') (γ,γ') and (p,p') reactions that appreciable amounts of M1 strength are observed in heavy rare-earth nuclei. Using the combined results of various reactions, it is shown that near E_x ≅ 3.0 MeV, M1 strength is mainly of orbital character whereas at higher energies 6.0 MeV < E_x < 9 MeV mainly spin M1 strength results. Starting from the Nilsson model, detailed calculations for the whole rare-earth region have been carried out. The authors present new results that indicate a strong correlation between the variation in orbital M1 strength and ground-state quadrupole deformation. Thereby, a unique relation pointing towards a partly collective origin of M1 strength near E_x ≅ 3 MeV is pointed out, even though the actual, collective scissor mode appears at higher energies. Relations to the interacting boson model are discussed. Finally, the spin-flip strength at higher energies is also calculated and discussed at some length