Under contrary conditions, when the plexuses of the sensorium no longer receive a sufficient quantity of blood, as regards their assimilative properties, inverse phenomena are produced.
The elements of the sensor/um are affected with a species of general torpor which causes their vital energies to sink below their normal pitch, and they accordingly exhibit that general condition of diffused languishing of the' mental forces, in which the processes of personality are only manifested in a dull, vague, and diffuse manner. The patients, then a prey to certain forms of melancholy with stupor, present a more or less complete passivity, an apathy and profound in difference for all that comes in contact with them ; and usually this torpid condition is only the return effect of a sort of amesthesia of the central regions which goes hand in hand with that of the peripheral regions.* There is still another series of morbid phenomena in which the notion of personality, and consciousness of the external world may be suddenly suspended by the effect of a momentary arrest of the circulation in the plexuses of the sensorium.
We now know, thanks to the labours of modern physiology, that intra-cephalic circulatory disturbances are frequent in epileptics, and that at the moment of the attack the loss of consciousness is produced by a spasm of the vessels, which interferes with the course of the blood through the cerebral substance. It some times happens that these circulatory disturbances, far from taking place throughout all the extent of the regions of the sensoriiem, as at the moment of the great epileptic attacks with complete loss of consciousness, exercise their influence only within limited regions of the cerebral substance. There are then local arrests
of circulation in certain cell-territories, which are for the moment in a state of collapse—true partial ischmias — while in others the cerebral activity continues its function in an independent manner. We see individuals, as if in a state of somnambulism, act unconsciously, commit extravagant actions, even crimes, without having any conscious idea of the things of the external world ; and at the end of several hours, or even of several days, emerge from this condition of partial stupor of their sensorium, quite astonished and stupified by the words they have pronounced and the deeds they have done during this period of interregnum of their conscious personality (unconscious alienations).* Finally, we may remember that the notion of our p_n-sonality, which in its constitution and its very exist ence is under the jurisdiction of the organic machinery i 1 the midst of which it lives, is regularly eclipsed every twelve hours, when the cerebral cells relapse into the condition of sleep.
The cerebral cell, in fact, like the peripheral cell (sensorial cells of the retina), becomes fatigued at the end of a certain period of activity ; its sensibility be comes more or less rapidly dulled. It is fatigued, and perforce falls into a state of collapse, which is nothing but physiological sleep. At this period it ceases to attract blood to it, the circulation slackens, and in pro portion as the period of sleep becomes better and better marked, and loss of consciousness of surrounding circumstances occurs, the notion of our personality at the same time grows dull, and finally becomes extinct, and this in a more or less complete manner, according to the temperament and habits of each person.