[105] Comptes Rendus, 1862, LIV. p. 965.
[106] “J’espère vous convaincre que tous les éléments anatomiques des nerfs sensitifs, moteurs, vasomoteurs, et autres, ont les mêmes propriétés, et ne sont distincts que par leurs fonctions. Cette question est de la plus haute importance pour la physiologie générale. C’est celle qui domine toute la physiologie des fibres nerveuses.”—Vulpian, Leçons sur la Physiologie du Système Nerveux, p. 11.
[107] Mr. James Andrews.
[108] In the second number of La Revue Philosophique, Paris, 1876, I have treated this question of specific energies more at length than I could find space for in the present volume.
[109] In 1859 I mentioned that if the nerves of a frog’s back be exposed by raising the skin, they may be pricked or even cut without sensible effect, although a slight prick on the skin will excite the nerves, and cause a reflex action. In 1870, Prof. Fick expressed his astonishment at finding that after he had cut out a piece of the skin, leaving it attached to the body by a single nerve, electrical stimulation of this excised skin caused the frog to make the reflex movement of rubbing the irritated surface; whereas electrical stimulation of the nerve-trunk itself produced no reflex effect, only a twitching of a muscle. Pflüger’s Archiv, 1870, p. 327. Brown Séquard tries to establish a distinct species of nerves as conductors of sensitive impressions, from those which are impressionable. The facts on which he founds these two properties simply show that nerves are so disposed that the stimulus which excites them in one place fails in another. He could hardly maintain that a skin nerve contained impressionable fibres at its periphery, and only conducting fibres in its trunk! See his communication to the Royal Society, Proceedings, 1856; and Lectures in the Lancet, 10th July, 1858.
[110] In consequence of this observation some physiologists have maintained that Feeling or Consciousness never arises in cerebral activity, unless the thalami and the connected tracts are at the same time in action. I go further, and maintain that there is no Consciousness (in the restricted meaning of the term) unless the whole organism is involved. Cerebral or spinal activity will be activity of Sensibility; but this is only the basis of Consciousness.
[111] “An unconscious sensation, which Lewes distinguishes from perception, is to me an inconceivable (ist für mich ein Unding).”—Schröder van der Kolk, Die Pathologie des Geistes-Krankheiten, p. 22.
[112] By selective adaptation is meant the varying combination of motor impulses to suit the varying requirements of the effect to be produced. Physical mechanisms are limited to the performance of definite actions; sensitive mechanisms employ fluctuating combinations of elements in response to fluctuations of stimuli. The wheels, levers, springs, and valves of a machine cannot be differently combined according to varying degrees of the motor-force, as the nerves and muscles of an organism are differently combined by varying sensations. An automaton may be constructed to play on the violin, but it will only play the air to which it is set; it cannot vary the performance,—cannot play a false note, or throw in a crescendo here, a largo there, according to a caprice of feeling. We must admit that violinist has his delicate and changing movements guided by sensations, auditory and muscular; any interruption in the sensations would arrest the movements, which in truth incorporate them. And yet it is well known that the violinist may perform while completely “unconscious.” I do not simply refer to the fact that his thoughts and attention may be elsewhere; I refer to such facts as are recorded in Pathology. Trousseau, for example, had an epileptic patient who was occasionally seized with attacks of complete unconsciousness while he was performing in the orchestra; yet, on reawakening to consciousness, he found that he had continued to play, had kept proper time, and played the proper notes.
[113] Claude Bernard, Système Nerveux, 1858, I. 349.
[114] Wordsworth, The Prelude.