In general we may say, that in the normal stee the impressions of vegetative life are quite silent and un perceived by the sensorium. The wheels of the inner life of the human machine move without noise. Few persons except medical men, are aware that they possess a heart provided with auricles and ventricles, which contract alternately a great number of times a minute ; a stomach which secretes a juice destined to dissolve the azotised elements of the food ; a pancreas designed to act by means of its secretion upon the fatty elements ; intestinal fibres which contract alternately and force along the alimentary bolus, &c. All these phenomena take place without our knowledge, without our having the slightest notion of them, and, strange to say, those facts in which we are most vitally interested we know least about ! But is this really the case, and are we authorized to think that the different forms of sensibility, which are in activity in the inmost recesses of our tissues, really exist without having a sort of obscure influence upon our seusorium, analogous in this respect to those obscure rays of the spectrum which our eyes do not behold, and which yet have so real arid indubitable an existence ? This does not seem probable to me; for if we think how instantaneously a visceral pain is developed, with what clearness this pain appears when a calculus is fixed in the ductus choledochus, or when a foreign body is introduced into the stomach or intestines, where it instantly produces painful contraction, we cannot help thinking that there are always open roads between the sensorium and the regions of vegetative life ; that there is, it some manner, an incessant relation between these two poles of sensibility ; and we must recognize the fact that there is, in the normal state, a constant though uncon scious afflux of the partial sensibilities of the organism which converge towards the centres, and that they die away there in silence without making any impression. yet bringing an unconscious notion of all that passes in the periphery of the nervous system. We see every day substances with which we are constantly in contact, from habit pass us by unperceived, leaving in the sensorium only an unseized impression, like that pro duced by the atmospheric air on the respiratory tract. Water and bread, which are so frequently in contact with our digestive mucous membranes, furnish us with but obtuse impressions, which yet are consciously per ceived.
It is then probable that if the sympathetic nerves of vegetative life, starting from the peripheral regions, form a continuous network, of which the converging meshes more and more nearly approach the central regions, the histological sensibility which they abstract from the different cell-territories, amidst which they originate, follows the ,same natural channels ; and that this is led up to reverberate within the sensorium, in a disconnected obscure manner it is true, yet, nevertheless, really and permanently.
We cannot fail to recognize in this afflux of all the diffuse sensibilities of the organism, each coming to bring to the sensorium its sensitive note, that series of generating elements which are designed to implant themselves there and develop in us that essential notion of our vital being, which makes us feel ourselves live in all our organic molecules. It is in itself nothing but the unconscious notion of all the partial sensibilities of the organism, concentrated in this grand common reservoir.
2. Unconscious excito-motor impressions arise, with their sister conscious impressions, in the terminal ex pansions of all the sensorial and sensitive nerves.
Mingled with their fellows they enter the converging channels which are open to them, and advance together with them towards the central regions of the spinal axis, having, however, first traversed the chain of the rachi dian ganglions.
Arrived at the grey plexuses of the spinal axis, they become diffused in their meshes, excite the activity of the posterior grey regions (which represent, as it were, a great common sensorium of unconscious life, for this order of radiations), and pass out in centri fugal currents, in the form of co-ordinated motor reactions, which thus represent the last phase of a process originating in the purely sensitive regions.
The unconscious excito-motor sensibiljty„transformed by die action of the cells belonging to the automatic sensorium, by this very circumstance acquires new properties.
It is stored up, seized upon, and condensed on the spot in the tissue of the organs that receive it, thus becoming in this new form, like a projectile rammed home in a fire-arm, capable of being transmitted to a distance along the centrifugal conductors radiating from the spinal cord, veritable reophores designed to favour its dissemination and transport it to a long distance, even into the most distant and eccentric cell-territories.
Thus it directs, in the form of unconscious optic excitations, the different movements of rotation of the ocular globes, the play of the pupil, the accom modation of the sight to different distances ; excites in the sphere of auditory phenomena the unconscious movements of the chain of little bones, to graduate the alternate tension and relaxation of the tympanic mem brane ; co-operates so powerfully in the complex and varied movements of mastication and deglutition ; presides over the succession of the acts of erection and ejaculation ; and, in a word, in different forms, without the intervention of the sensorium, always present, always active, assists in the perfecting of the sense to which it is attached, favours its direction towards an object, governs the play of its mechanism, so as to obtain the maximum of sensorial impression, and thus becomes the indispensable adjunct of conscious impressions.
It is still this unconscious excito-motor sensibility that underlies the different processes of the respiratory phenomena during the whole term of our lives, from our first inspiration to our last sigh.
It maintains the play of the motor ganglions of the medulla oblongata, those central foci of innervation, whence the inspiratory and cardiac muscles draw their unceasing principle of activity. It expends itself at every instant, day and night, in the continual activity of the mysterious laboratories of organic life. It moreover plays an all-important part in the varied series of our movements of progression, in all those of bodily exer cise, in the methodical motor actions that we insensibly bring to perfection by practice and sustained atten tion —such as those of the hand in drawing or writ- I ing—actions which though at first conducted with the conscious participation of the sensorium, insensibly come to be executed under the sole direction of the excita tions of unconscious sensibility.