5) To what extent do events occurring during regeneration re semble those seen in development? Questions like these remain open, particularly in relation to the mammalian central nervous system and to the effects of lesions or disease. The first chapters of this volume are concerned primarily with normal and abnormal development of the nervous system. New concepts have emerged over the past few years as a result of experiments made on the development of the higher nervous system in mammals. Thus, the principles of cell death, competition, selective retraction of specific processes, and the...