The death of Enrico Ferri brings to a close a period of struggle in the science that seeks to combat the formidable problem of crime. With his talent for assimilation and propaganda, Ferri applied in the sociological and judicial field the discoveries which complemented and were proof of the advances that had been made in the study of crime and punishment, through the work of Cesare Beccaria. In his work, Ferri frequently made use of the promising examples set by the United States, with special reference to the preventive measures adopted against juvenile delinquency. In the field of prevention, Ferri advanced decisively and made definite gains for the science with his affirmation, Sostituitivi Penali