The study of mental diseases shows us, indeed, in a precise manner, that in a great number of cases the regions of intellectual activity may be spared when the purely emotional regions, the regions of the sensoriunt, are profoundly disturbed. We see a great number of insane patients affected with melancholia, groaning over their fate, over the persecutions to which they are sub jected, mourning incessantly about trifles, and yet capa ble of taking note of what is going on around them, and, in the midst of the disorders of their agitated sensibility, discerning perfectly what happens to them, and sometimes making very just reflections.
This dissociation of the purely emotional and purely intellectual regions, which may be unequally affected, proves, then, distinctly the complete functional independence of the intellectual sphere proper, and that of mental emotivity and sensibility.
Now, where is the seat of this sphere of intellectual activity, which has its own special domain, its peculiar autonomy in the midst of the operations of the brain ; and what are its connections with the different groups of cells in the cortex ? Here again, up to the present time, we have only conjectures and probabilities to offer.
In taking note, however, of the order and progress of those processes of cerebral activity which spread by propagation from the superficial submeningeal regions to the deeper regions of the cortex, we cannot help admitting that the sphere of intellectual activity can only be set in motion secondarily and consecutively to the impression of the plexuses of the sensorium. The plexuses of the sensorium receive the first onset of the external excitations, and sift them to some extent before propagating them to the subjacent zones. They are the natural frontiers by which all the excitations of the external world must necessarily pass. Now, this natural frontier topographically occupies the superficial regions of the cortex ; we may, therefore, provisionally admit that the zones of cells subjacent to the plexuses of the sensorium, with which they are continuous, are those which, without its being possible precisely to limit their thickness, may be considered the field of action of the operations of the intellect proper.
This theory—which squares with the facts of daily observation, which show us every moment how closely connected the activity of the intellect is with that of the senses, and that the intellect, in order to come into play, must first have received its stimulation from the ex ternal world—explains, at the same time, how it is that the phenomena of intellectual activity, from the very fact that they are exercised in an isolated territory of the cortical substance, are apt to show themselves in an automatic manner, under a special aspect, as a com pletely independent sphere of activity.
However it may be, the intellectual sphere, con sidered in itself, participates in the same dynamic mani festations we have observed as regards its fellow, the psychical sphere.
Like this, it becomes active under the influence of the excitations of the external world, which beget in it movement and life ; like it also, it becomes erect in consequence, and develops its natural energies. But here sensibility and emotivity no longer play the first part, as when the plexuses of the sensorium proper are in agitation ; the purely automatic activities of the cells then develop themselves with a specific energy which is very significant. If sensibility be the nant note of the psychical activities, automatism is the characteristic of this special field of the life of the brain.
Everything, in fact, records itself automatically, and outside of the will. Without our knowledge certain ideas present themselves, certain associations are effected among themselves, certain reminiscences are evoked. Everything in this special domain is done in an irre sistible, inevitable, unconscious manner, by means of the automatic activity which reigns as sovereign and governs the series of the operations of the intellect. It is it, indeed, that creates new relations, stores up our memories, and daily tacks them on to more recent events. It is always present, always active, and, by a strange phe nomenon of which we are incessantly the dupes, it comes to light in the form of spontaneity in our ideas, our words, our acts, thus becoming, as we have already indicated, the most living expression of the freshness and vitality of the cerebral which have criven it birth_ Thus, then, the sphere of psychical and that of intellectual activity represent, isolatedly, each from the point of view of its dynamic action, the most complete epitome of the 'fundamental properties of the nervous matter. In the first, the phenomena of sensibility, with all that is most exquisite and most perfect in them, predominate ; in the second, the phenomena of automatic life. These two regions of cerebral activity, united and combined in a co-ordinated effort, inces santly lend each other mutual support. They dovetail into one another in all the daily manifestations of cerebral life, the one borrowing from the other the elements which it needs ; so. that from this intimate consensus, this co-operation of all the vital forces of the nervous elements, laid under requisition in their totality, emerges a new notion, of which we have, so far, but sketched the genesis—a notion of a whole, which is, in a manner, the synthesis of all our mental activities ; that is to say, the notion of our own personality. Upon this subject we are now about to enter.