The discovery of the nervous impulse established that the nervous system was fundamentally mechanistic, and that it was highly dynamic; and all subsequent work has confirmed these earlier views. The stabilities of inanimate dynamic systems are frequently of high importance and rich in applications. It would seem likely that an investigation of the stabilities of the nervous system would yield interesting results, but it is only recently that the importance of stability in the nervous system has been unequivocally recognized. But it has now been established that such properties are of central importance in the processes of integration and co-ordination. Advance has probably been hampered by the difficulties of the subject.