The activity of the nervous system is directed, on the one hand, towards unification, integrating the work of all parts of the organism, and, on the other, towards connecting the organism with the surrounding milieu, towards an equilibrium between the system of the organism and the external conditions. The former division of nervous activity may be called lower nervous activity in contradistinction to the latter part, which, because of its complexity and delicacy, may justly take the name of higher nervous activity, usually called animal or human behaviour.