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mind, intelligence, or spirit, and the body retains its powers of organic operation.* It is, thus, as much a machine as is the steam-engine, and the mind its engineer. Remove the mental organ without injuring any of the fine wheels or valves of the machine, and it is still capable of operation, if fed with fuel by some exterior engineer, taking the place of the lost internal directive faculty. This strange fact, then, bears with no force on the question of the immortality of this directive agent. The body is a perfectly arranged instrument by which the mind is enabled to come into contact with the external world, and to feed itself with the spiritual forces inflowing from this world. But the machine has no direct dependence on the mind for its operation. It needs but fuel in the shape of food, and a proper attention to the integrity of its parts, to its perfect action. These the mind, as the directing agent, supplies it; but, as above seen, they may be supplied by an exterior mind, and the machine continue to run-in this case as a simple machine only, and without eliminating thought.
The cerebral hemispheres then, have no necessary or direct connection with the organic operations of the body. They are built up by the action of the whole body, as a special result of its action, and in excess of its organic functions, a product which forms no essential part of the machine. In these hemispheres the forces constantly flowing in from physical nature are changed by some mysterious operation into intelligence. Thus the cerebrum is a separate machine of a higher order, and possessed of the lofty power of eliminating mental food from physical force. The mind, thus formed, is utterly distinct from the body as a whole, depending only on the integrity of the cerebrum, and the question of its faculty of existence, separate from its cerebral organ, is in nowise affected by the retention of the bodily forces after mental death.
Any injury to the lobes affects the intelligence or memory, and they may be removed, piece by piece, with a gradual diminution of the mental faculties. But each lobe appears to contain the full sum of the mental powers. Thus, a person named Vacquerie, in 1821, having lost the left lobe of the brain, retained his intelligence intact through the action of the right hemisphere alone.* Berard gives an instance in which the two anterior lobes were crushed, yet the reasoning powers and sensibilities were retained. Considerable portions of the lobes may be removed, front or back, above or below, in animals, without loss of function, the faculties and perception weakening, and finally, being all lost together.t
* Je reconnais même qu'un certain nombre de phénomènes psychiques persistent chez les pigeons auxquels on a enlevé le cerveau, le cervelet, et une partie du mésocéphale. Brown Sequard's Journal de la Physiologie, 1861. Vol. iv., p. 551.
A frog, seven-eighths of whose cerebral lobes were removed, was found to catch flies with all its natural keenness, and appeared to retain, in a diminished degree, all its faculties, though much less lively than in its natural state.
But on an entire removal of the brain all voluntary motion was lost, and all manifestation of mentality. I
Thus the various portions of the gray substance of the brain appear to perform identical functions, and to form a group of repeating and multiplying organs. This is evidenced in the fact that one hemisphere, or part of a hemisphere, if large enough, is capable of acting alone, and supplying the place of the rest. The brain appears to be a sort of polypus, all its elements having the same functions, each element composed of an undetermined number of cells and fibres, being capable, by its action, of giving rise to all normal images and all their associations, hence to all mental operations.
One element of the hemispheres repeats the action of the sensory centres, and transmits it to the other elements. Hence the development of the cortical layer, increasing the number of these elements, increases the extent of possible intelligence.
Longet, Anatomie et Physiologie du Systeme Nerveux, p. 666. + Flourens, Récherches Experimentales, p. 99. | Taine's Intell., p. 175.
& Professor Humphrey, in a late lecture before the Royal Institution, considers “ that all the parts of the cerebral hemispheres combine in each of the efforts of control, consciousness, memory, and other acts; that all suffer alike from these efforts, and alike need the restoring changes which take place in sleep.”
| Taine, p. 176.
The image, when widely affecting the cerebral elements, strongly affects consciousness, perhaps through the medium of the sensory centres, though more probably it only returns fully to these centres in the case of hallucination or dreaming. It grows the weaker as the number of elements affected decrease, and gradually becomes weakened below the reach of consci
It still subsists, however, in the probably enormous number of elements, and may be suddenly reproduced by competent cause.
All the gray, nervous substance may possess similar powers, the action being elementary and imperceptible in the spinal chord and the other lower ganglia, while in the protuberance perceptible sensations are excited, and in the cerebral lobes this sensation is repeated indefinitely by a series of mutually excitable elements. In these some form of excitement is produced by each sensation, and this action, whatever its nature, is retained in its original form in some portion of or throughout the immense number of elements, being constantly capable of re-excitation, so as to occupy the brain in superior degree, and thus to become a reviving sensation or image.
Beneath conscious sensations descend an immense number of analogous mental conditions, more and more removed from consciousness, this successive lowering corresponding to the successive attenuation of the nervous system, and leading to the foot of the zoological series. Thus as the human body represents in its gradual development the whole extent of the animal kingdom, so the human intelligence runs through the whole gamut of animal intelligence, and culminates in its superior powers of abstract thought, with all their concomitant relations. It must be borne strictly in mind that the brain is but the organ through which the mind affects the body, and that the loss of this action upon the body, through injury to the brain, does not argue nor necessitate any positive or final loss of mentality.
In vain we attempt to bridge the abyss already noticed as existing between the physical and mental, between the crude nerve excitation and its related mental action. Taine argues, however, that though we cannot reduce the two ideas together,
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the facts may be reducible. Two notions of one cause seem often essentially different when we gain knowledge of them in two different ways. Ideas of the same object received by two different senses are often difficult to reconcile, and could not be made to agree had we not other means of learning their connection.
Now our mode of gaining an idea of nervous motion is absolutely different from that of gaining an idea of sensation. The points of view are widely separate, and we have no means of learning their relations. In consciousness we perceive the action from a direct point of view. In external perception we see it indirectly. The molecular movement is only a sign of the mental event. The only real events in nature, so far as our comprehension goes, are sensation and its elements. These overlap each other like the text of a book its interlinear translation, the physical element of sensation being the text, its mental result the translation into a widely different language. But the text commences plainly readable at its commencement, growing indistinct and finally illegible as we trace it inward from the surface. The translation commences unreadable, and grows distinct only at its termination. At no point are we able to perceive the relation between the two languages, though convinced that it exists.
Modern metaphysics rudely overturn many of our cherished ideas of human mentality. The notion of the Ego, for instance, as a continuous existence in which events succeed each other with the distinct and unchangeable relation of cause and effect, is boldly pronounced a delusion. It is claimed that force only denotes the succession of events without any traceable relation or any necessary succession.* The Ego, in this view, is a simple succession of sensations, not a vital whole, but a constantly broken and reproduced state from sensation to sensation. This, however, is but a hypothesis, based on the fact that we cannot trace the absolute connection between sensations, and does not disprove their possible relation as cause and effect. In fact this relation cannot be clearly proved nor disproved as long as the connection between perception and sensation remains an absolute mystery. *
* The Law of Causation is but the familiar truth that invariability of succession is found by observation to obtain between every fact in nature and some other fact which has preceded it. The only notion of a cause is such a notion as can be gained by experience.—Mill's Logic, vol. i., p. 117.
A cause acting from without, and consciousness acting from within, must appear different and irreconcilable. The points of view are so widely removed, and events seen so absolutely on two distinct sides, that it is impossible to get round the corners and discover that these are but the two sides of a single fact. They appear instead two separate facts.
This intricate work, this vaguely translated organic mystery, is read by physiologists only from the beginning, by psychologists only from the end. Each sees but one language, and each argues solely from the indications of his imperfect text. They are yet far asunder, and may never meet, the two languages being apparently irreducible. Meanwhile each argues stoutly from his own point of view, unwilling to acknowledge that all their facts may meet and combine into one great series somewhere in the unseen.
The forces of exterior nature, the physiological facts of nervous excitation, pass over this mysterious interval and be. come mental facts and forces, forming the basis of our knowledge. All we know is included in the word sensation. Our idea of a body simply consists of the connection between a number of sensations. Thus, its form and size are to us but sensations of sight; its tangible forin and size but complex sensations of touch; its weight and hardness, muscular sensations; its color, a visual sensation ; the thought of any of these sensations makes us think of the others, and the whole combine into a mixed state of consciousness, which may be termed a complex idea.t
* Tout les exemples qui confirment une vérité générale, de quelque nombre qu'ils soient, ne suffisent pas pour établir la nécessité de cette même vérité; car il ne suit pas que ce qui est arrivé arrivera toujours de même. — Leibnitz, Nouveaux Essais, preface.
| Mill's System of Logic, vol. i., p. 62.