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The gaps between the centres first recognized as motor and sensory—gaps which form in man two thirds of the surface of the hemispheres—are thus positively interpreted by Flechsig as intellectual centres strictly so called. [Compare his Gehirn und Seele, 2te Ausgabe, 1896, p. 23.] They have, he considers, a common type of microscopic structure; and the fibres connected with them are a month later in gaining their medullary sheath than are the fibres connected with the other centres. When disordered, they are the starting-point of the insanities, properly so called. Already Wernicke had defined insanity as disease of the organ of association, without so definitely pretending to circumscribe the latter—compare his Grundriss der Psychiatrie, 1894, p. 7. Flechsig goes so far as to say that he finds a difference of symptoms in general paralytics according as their frontal or their more posterior association-centres are diseased. Where it is