ABSTRACT
Without dwelling on the origins of the nervous apparatus 1 we may note that at an early stage of its differentiation, when it first constitutes a nervous ‘system’ capable of ensuring individuality of behaviour in multicellular organisms, three kinds of cell elements appear: receptive, 2 motor, and connective. By the morphological grouping of elements of the same category motor and connecting centres, also called centres of reflex activity, may be formed.
