[Comparative development of the mammalian nervous system (author's transl)].

By collecting the results of research from different laboratories it has been possible to picture the probable sequence in which the nervous system develops in certain mammalian species. As the present report is to be referred to current conceptions of the development of the nervous system, special attention will be pain to comparative aspects of the question. Mammalian forms vary greatly in degree of maturity at birth, ranging from the fetus-like newborn rat to the highly mobile, almost self-sufficient, guinea-pig. As identical sequences of development will be demonstrated in both categories of mammals attention will be devoted to discussing the criteria which condition our trusting this sequence of development. Lastly, Man will be considered. It is not easy to decide whether man is a true altricial species or in what sense he can be considered as a special case of precocial species. This point is discussed: Man is altricial from the motor point of view. He is precocial from the sensory point of view and sleep develops during embryonic life in this species.