GENESIS AND EVOLUTION OF AUTOMATIC ACTIVITY, Spinal Phenomena. — The phenomena of automatic nervous life reveal themselves, as we have said, in their simplest elementary form in the mysterious operations of vegetative life, while the sympathetic ganglions, scattered through the web of the tissues, and connected with the central regions by their connective threads, locally govern the phenomena of the local life of the different cell-territories, and act as little eccentric centres which hold in subjection the purely vegetative phenomena.
In the centres, in the purely spinal regions, the mani festations of automatic life again reveal themselves in an independent manner, as though they had a special autonomic character in each of the particular regions of the spinal axis.
This automatic activity is so vivacious in the minute structure of the grey plexuses of the spinal cord, that it persists of itself, exercises itself viotu proprio, apart from all participation of the superior regions of the encephalon; and each segment of the cord, considered as an independent ganglionic centre, may also, even when distinctly isolated, function regularly and give rise to co-ordinated reactions.
In fact, if we cut the spinal cord of living animals into separate segments, as Landry has done,* we shall find that each segment will isolatedly give rise to a series of independent motor phenomena and as long as the blood-currents continue to feed the cells, and these can store up new force after each discharge, and continue to live their morphological life as before, they will continue to produce nerve-force, and inevitably give rise to regularly co-ordinated phenomena, according to previously established habits.
Moreover, the experiments of Ch. Robin, made upon the corpse of a decapitated criminal,- have shown that the automatic activities of the spinal cord in man may in similar circumstances continue to exhibit undiminished energy and power of co-ordination, in the form of regu larly associated movements with a definite object (such as movements of defence made by the hand after a cutaneous excitation), performing these with as much regularity as though the brain had directed them.
We have also true types of automatic reactions in that series of excito-motor processes which succeed each other without a break throughout the medulla oblongata, the region of the vital knot, and in which the cells of this region, like the indefatigable workmen of our great manufactories, work incessantly night and day for the regular maintenance of the foci of inner vation of the heart and the respiratory muscles—and this without break or halt, our whole life long, without the intervention of the conscious personality, and merely through the permanence of the automatic forces.
It is, moreover, a remarkable fact that this automatic power of the spinal organs is so great ; its participa tion in all acts that we primarily accomplish with the concurrence of our conscious will is so effective and regular, that little by little it succeeds in gaining ground in the domain of our conscious dynamic operations, obtaining a greater and greater importance by means of prolonged exercise, and finally ruling over them more or less.
We all know that those partial movements we accom plish in tracing written characters, and in playing musical instruments, are at first executed and followed out .with the participation of the conscious will, and that little by little, as exercise, as it were, oils the auto matic machinery, this comes into play on the smallest excitement, like a well-constructed mechanical contri vance, automatically reproducing the movements learnt, with a neatness, co-ordination, and correctness, all the more perfect because the conscious personality plays a less distinct part in the process.
We all know, more or less, that the action of writing certain phrases, and above all that operation which is the somatic expression of the conscious person ality par excellence—that of affixing our signature to a sheet of paper (which indicates the passage of the conscious will through the hand that expresses it) insensibly becomes an operation which escapes our attention, and which, like certain common phrases that we unconsciously pronounce, takes place of its own accord, simply through the apposition of the pen to the paper, and by reason of the coming into play of mere excito-motor activity.
We therefore see what an enormous part the phe nomena of automatism are called on to play in the manifestations of nervous life, since we already know that these not only regulate the essential phenomena of vegetative life, but in addition play a most important part in calling into activity the great mechanism for the maintenance of the human machine, such as the motor-power of the heart and respiratory apparatus—in a word, the phenomena of visceral life ; and that, more than this, they enter into the processes of purely psycho intellectual life, which have need of their intervention to project outwards their extrinsic manifestations, and escape from the mysterious regions where they have been primitively conceived.