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and active powers are in close correspondence. The definiteness of the nervous dependencies of the organs of sense carries with it a like fixedness in the means of expression. Thus by experiment and observation the conclusions have been readied, that 'the third left frontal convolution' is the initiative surface for intelligent speech; closely connected therewith are the starting points of that action which issues in writing. The parietal region or crown of the head constitutes the motor region of the brain, and may be farther subdivided into specific forms of action, as grasping, clenching the fist, swimming. The temporal lobes are centres of sensory perception, both passively and actively, and are divisible with some certainty between the several senses. The occipital lobes or back portion of the head are conjecturally centres to organic activity, as digestion. The frontal lobes are the surfaces for the initiation of intellectual and moral action; of attention, inhibition and direction. It must be borne in mind, that experiments of excitation in any portion of the cerebrum can go no farther than to indicate the nervous sources of those movements which express certain mental states; the conditions of the state themselves are not disclosed.

It does not follow, therefore, from these conclusions, that pure thought and the communication of thought are equally dependent, or dependent in the same way, on the nervous system. All that the experiments of Ferrier, Friteche, Hitzig, serve to establish is the general completeness of the mechanism of expression. Indeed, the very connections of thought in things belongs to the mind exclusively: even when a verbal sign is put for them, the word of relation is no more than a sign. We may well believe that the same thing is true of that more subtile language of molecular action in the cerebrum.

Guiding or at least steadying, our thought by the image