The focus of the present review is the study of neutron-rich medium-mass nuclei around major shells or subshells N=20, 28 or 40. Coulomb excitation of secondary beams and in-beam spectroscopy study using the fragmentation of a stable beam have brought a wealth of informations concerning the behaviour of the closed shells when nuclei contain large neutron excesses. Pionneering experiments in this field are presented with special emphasis on the work achieved at the Ganil accelerator
