Thus, then, the phenomena of automatic life, under whatever form they present themselves, occur of them selves and by virtue of the infra- spinal transformation of an incident excitation of reflex sensibility into motor reaction ; and this without the sensorium coming into play, without the intervention of conscious simply as a return effect of the calling into activity of process of unconscious sensibility.
But although the phenomena apparently take place thus, being evolved without the effective participation of the sensorium, it must not be concluded that no frac tion whatever of these excitations is radiated towards it and extinguished in it, somewhat in the manner of obscure rays.
It is very probable that what we have seen to occur as regards the impressions of purely vegetative life may occur as regards this special order of excitations, there being probably an obscure radiation of these latter impressions which extends to the sensorium, and thus transmits to it the vague and unconscious notion of the activity of such or such a portion of our muscular system.
If the sensorium indeed be not directly active in the infinite series of motor acts that we accomplish auto matically, it nevertheless does not remain a complete stranger to the operations which take place within the organism. If it does not interfere directly to regulate the play of such or such an organ, to move, for instance, the crico-arytenoid muscle in a methodic manner for the production of such or such a laryngeal sound, or the accomplishment of such or such an act of digital dex terity ; if the conscious personality cannot discern who are the workmen at work, it has at all events an exact notion of the operation in evolution, knows if the work be accomplished, and the requisite muscular exertion made. We do not feel our muscles in a clear and precise manner when they are in a state of repose ; but when they are in activity, this new condition into which they are thrown develops in the sensoriuni a new mode of existence, so that the unconscious excito-motor sensibility in the dynamic state indirectly strikes upon the sensorium, and thus becomes a new element destined to become absorbed in its plexuses.
Conscious Sensibility (Sensation). —The sensitive exci tations destined to become conscious and enter into rela tion with the phenomena of psycho-intellectual activity, are collected, with their excito-motor fellows in the peripheral plexuses, which serve as a region of emission for both. Starting from this, and taken up by means of the converging fibres, they pass on towards the central regions of the axis, are concentrated in the isolated ganglions of the optic thalamus, and are afterwards radiated, as we have already seen, into the different regions of the cortical periphery. (Fig. 6.-9. 4. 14.) The phenomena of conscious sensibility (or sensa tion) have then as their point of origin, and first halting place, the peripheral regions of the nervous system: It is by the terminal nervous expansions spread out into a network, open, in a manner, to all that comes to impress it, that the external world penetrates and be comes incarnate in us. And for this a special faculty fc,r
receptivity and impressionability in the nervous element thus impressed is in the first place necessary, as a mental and indispensable condition of the phenomenon.
In a word, it is necessary that at the moment the sensorial network receives the vibratory excitation, it shall directly participate in the act which takes place within it. It must become active, acquiesce—become in a manner erect ; and must, by a species of vital assimi lation, convert the purely physical into a physiological excitation, the luminous vibration, for instance, into a nervous one.
This is the fundamental act of which we shall speak again subsequently, and which is the first link of t$iat chain of sensitive phenomena which is evolved through out the nervous It is, in fact, a vulgar truth which reveals itself to simple observation. Every one knows that the simple presence of a physical excitation of a sensorial organ is insufficient to produce a conscious impression, and that an active participation of the sensorial cell in the vibratory movement communicated to it is necessary. Open the eye of a sleeping man—the luminous rays fall in vain upon the retina. It requires a certain time before the nervous cells are wakened up and enter into harmony with the luminous vibrations which ( / excite them. Pinch the skin of a man in profound sleep, cry into his ear under the same conditions. There is the same apathy, the same default of reaction. The purely physical excitation will gradually become deadened if there co in its train a purely vital phenomenon of sensation, which is developed, by a sort_ 1 of active physical food which is _ .
I theimpressed cell.* ‘...., We see, then, judging by what takes place here in this first phase of nervous activity, that the sensitive plexuses of our whole organism are all either isolatedly or simultaneously thrown into vibration, according to their various tonalities. They thus become. like vast vibratory surfaces, of which the oscillations, registered as they arrive, are incessantly transmitted to the other parts of the system, and felt in the sensor um in a correspond ing manner. It is a continuous, regular, imperative work, which is accomplished every moment, from the peripheral to the central regions of the system, and this uninterrupted appeal from the external world is so neces sary, so much the obligatory condition of all cerebral activity, that the latter ceases at once when its means of alimentation from without are cut off (loss of conscious ness, sleep, lethargy), just as we see the phenomena of hmatosis cease, when the atmospheric air suddenly ceases to enter the recesses of the respiratory channels.