Philosophy of the Unconscious

by Eduard Von Hartmann

  If such a genius suddenly emerges at the right time as fruit of an unconscious development in unconscious harmony with all Nature, which has been nourished on a material blindly prepared by others, such an unconscious psychical process must be looked upon as in the highest sense a teleological event, for the explanation of which Maudsley probably would only refer to the unsearchable councils of the Creator. Otherwise expressed, the insufficiency of all materialistic explanations in the unconscious-psychical processes is evident the more we rise to an ever more highly organised oentre (whether within one and the same organism or among the many differently constituted individuals of the human race). But since the differences are not of a fundamental kind, but only depend on a difference of the stage of development of the common primitive foundations of the ganglionic cell, this result must also reflect its light upon the conception of the simplest reflex processes in the ganglion cell.

  7. The Morphological Significance of the Parts of the Brain .—The morphological interpretation of the different parts of the brain has only been founded on reliable principles since embryology has come to the aid of comparative anatomy, the importance of which was first clearly recognised by Baer. In the lower orders of worms, e.g., the Turbellaria, the entire central nervous system consists of the bilobed supra-œsophageal ganglion, from which nerve-threads radiate to the different parts of the body. In the Annelida and Articulata this supra-œsophageal ganglion has expanded into an œsophageal ring, and this is continued into the ventral cord; in the larvæ of the Ascidians, in the Amphioxus, and the Vertebrata, on the contrary, the supra-œsophageal ganglion has been prolonged into the spinal cord. In the larva of the Ascidians and the Amphioxus the spinal cord is still a simple uniform strand, which seems to terminate in precisely the same way before and behind, and only with more exact observation can there be perceived in front a slight rounded extremity. In the Cyclostome fishes (Myxine and Petromyzon), at a further stage of embryonic development, this vesicle becomes a pyriform swelling, and thus forms the primitive basis of the vertebrate brain; but then it is differentiated by cross constrictions into several vesicles which lie behind one another in a straight line, and this process of constriction recurs in the embryonic development of all the vertebrata without exception.

  At the outset there are formed three sections—Fore-brain, middle brain, and hind-brain; the first might be designated the olfactory ganglion, the second the optic ganglion, the third the auditory ganglion. But soon there appears a further differentiation, the Intermediate-brain being detached from the Fore-brain, and the After-brain from the Hind-brain; the former, might be termed the finer organ for the perceptions of the sense of touch, the latter the centre for the automatic regulation of complicated organic functions subservient to life. In the Cyclostome fishes these five divisions lying in a straight line behind one another and tolerably equal in value, are preserved without essential change of form; in the cartilaginous fishes Middle-brain and After-brain are prominently developed; in the higher vertebrata, on the other hand, Fore-brain and Hind-brain, so that the former overlaps the Intermediate and Middle brain, the latter the After-brain. A distinction of a similar kind again occurs between the reptilia and birds, on the one hand, and the mammalia on the other. In the former, the Middle-brain and the middle part of the cerebellum undergo a relatively important development; in the latter, the Fore-brain more and more overshadows all the other parts, so that at last in monkeys and man it even overlaps the Hind-brain.1

  In the human brain there belong to the Fore-brain the two cerebral hemispheres, corpora striata, corpus callosum and fornix; to the Intermediate-brain the optic thalami and the other parts which surround the so-called third ventricle, together with the infundibulum and pineal body; to the Middle-brain the corpora quadrigemina and the aqueduct of Sylvius; to the Hind-brain the hemispheres of the cerebellum and the middle lobe; to the after-brain the medulla oblongata, together with the fourth ventricle, the pyramids, olivary bodies, &c. The original functions of the five parts have been preserved unchanged for the intermediate-brain, middle-brain and after-brain; on the other hand, the Hind-brain or cerebellum has its functional sphere already considerably enlarged in the Amphibia and lower mammalia, and the Fore-brain or cerebrum has in the higher mammalia attained such general importance for all the functions of perception, that its original destination as olfactory centre only claims an inconsiderable part of the organ.

  According to experiments by Gudden, the brain of newborn birds, whose eyes had been extirpated, remained undeveloped, whilst in rabbits the development of the brain was not thereby impeded (Wundt, p. 194); this proves how much more important a part the function of the corpora quadrigemina, excited by the visual sense, plays in the mental life of birds than in that of mammals. If, on the other hand, the olfactory nerve of new-born dogs be divided, they are no longer capable of any intellectual and emotional development, and give the impression of unsympathetic and feeble-minded individuals. This proves how much the mental life of these mammals depends on the sense of smell.

  Now, if we consider that the intelligence displayed by the Middle-brain and Fore-brain, as we saw in the pre ceding section, is only different in degree, it might appear almost a matter of accident that just the Fore-brain or the olfactory ganglion, and not the tactile, visual, or auditory ganglion, has, in the higher vertebrata, attained so enormous a development, that the groups of ganglion-cells adjunct to the original olfactory ganglion have become a kind of universal centre, in which, in addition to the olfactory organ, the other sense-organs also, nay, even all the parts of the body and the lower centres, obtain a central representation. The importance to life of the olfactory organ taken alone would hardly afford sufficient explanation of this; more pertinent seems the consideration that the Fore-brain occupies a position of polar antagonism to the spinal cord and medulla oblongata, that it lies peripherally in respect to the centre or centres of gravity of the central nervous system. This sounds perhaps paradoxical, but has all the deeper significance. As the whole nervous system arises phylogenetically and embryologically from the skin-sense lamina, i.e., from the extreme periphery of the organism, that part of the central nervous system also, which leads to the mental centre of self-consciousness, must have a peripheral importance for the organism as such and its organic life.

  For the organism as such the centre of gravity of the central nervous system lies neither in the too little efficient spinal cord, nor in the cerebral hemispheres, whose conscious - spiritual purposive activity already, appears as something transcending the immediate ends of organic life, but in the parts interposed between Fore-brain and spinal cord, which guide the universal reflex processes of the organism and adapt its vital actions to the external circumstances mirrored in sense-perception. This relation finds also an anatomical expression in the circumstance that the groups of ganglion-cells in the stem of the brain and the spinal cord aggregate into central medullary masses, which send out conducting fibres towards the periphery; in the hemispheres, however, the grey matter forms an external cortical layer to which, tend the diverging conducting paths of the trunk of the brain. This contrast is not yet clearly developed in the more solid or less hollow cerebrum of fishes and amphibia; here the whole mass of the hemispheres is traversed by grey matter in an irregular fashion, so that we have before us a transitional stage from the formation of the nucleus to the cortex. The cerebellar hemispheres, on the other hand, exhibit already in fishes a clearer severance of the cortical layer from the nucleus (comp. W., p. 55–56, note), and this development of the cerebellum in excess of the cerebrum proves that the former has in these animals also to perform functions of a higher order.

  Having already briefly discussed in the foregoing section the functions of the after-brain or medulla oblongata, we now proceed to the consideration in detail of the four other parts of the brain.

  8. The Centres of the Space-Senses .—Of all the parts of the brain, the function of the Middle-brain or of the corpora quadrigem
ina (called bigemina in lower vertebrata) has been longest and most certainly known. The parallel development of the corpora quadrigemina with the acuteness of the sense of sight in the animal kingdom leaves us to infer that this centre has the office of working up the visual impressions, and of reflectorially calling forth those movements which are in relation with visual impressions. Destruction of the corpora quadrigemina produces not only blindness, but also paralysis of the movement of the eye and accommodation. One must therefore assume that the cerebral hemispheres only receive the visual perceptions in the form prepared by the corpora quadrigemina, and that only those movements which are caused by a co-operation of visual and other sense-impressions proceed from the hemispheres, but that such movements or modifications of continuous movements, which are exclusively determined by impressions of sight, are independently cared for mainly by the corpora quadrigemina. The accommodation of the eyes is governed by the posterior, the ocular movements by the anterior tubercles of the corpora quadrigemina; and according to Adamük, stimulation of the anterior tubercles on the right side produces movements of both eyes to the left, on the left side movements to the right. The stimulation of the front of the anterior tubercles causes the visual axes to assume a horizontal direction; that of the middle part raises and renders them convergent; that of the hindermost part leads to a downward movement, with still stronger convergence (Wundt, p. 147).

  Not quite so well established is the significance of the (improperly named) optic thalami or of the intermediate-brain. Wundt (p. 198) probably correctly regards them as the tactile centre, according to the analogy of the just-mentioned visual centre, i.e., as the organ which mediates “the functional union of locomotion with the sensations of touch” (perhaps also with the muscular sense or specific feeling of muscular movement). The optic thalami also act independently of the will of the cerebral hemispheres as primary regulators, whereby certainly the will of the hemispheres is not precluded from employing them, in order to enable more complicated movements to be executed by them on a given command. At all events, they must in all bodily movements, even though initiated by the will of the hemispheres, co-operate as regulators, without which the estimation of the movement as a whole and in all its parts would be wanting. We are, namely, always compelled to estimate the degree of our several muscular contractions according to the position which the particular muscles assume at any moment in relation to the other parts of the body; but this position is ascertained by the sense of touch. If the service of the latter is interrupted, the visual sense can in an extreme case act vicariously for the sense of touch, as in the case of a person suffering from Tabes dorsualis of the spinal cord, whose tactile feeling in the lower limbs had been lost; or in the instance of a woman with anæsthesia of one arm, who always let her child fall when she averted her gaze from it. The compensation of the visual sense is here always imperfect, and never attains the direct certainty of reflex action like the regulation by the sense of touch executed by the optic thalami. If the optic thalamus be injured on one side, this reflex regulation is destroyed for one-half of the body. Whilst now the muscles of one-half the body act correctly, those of the other are smitten by a sudden helplessness, which looks astonishingly like paralysis, without indeed being paralysis; and the result is an unsymmetrical locomotion, which is called, on account of the tendency to rotation of the head, “circus movement” (Wundt, p. 196–199). That there is no actual paralysis is evident from this, that the disturbance comes to an end in course of time by the will of the hemispheres learning to correct the faulty movements. The purposive movements to escape made by rabbits or frogs after removal of their hemispheres and corpora striata sequent on cutaneous irritation may be referred to the optic thalami as their centre. A confirmation of this hypothesis is the circumstance that such a frog, after injury of one optic thalamus, carries out its attempts to flee in the form of circus movement.

  The close juxtaposition of the corpora quadrigemina and optic thalami, the demonstrable paths of communication between them, and the circumstance that in lower vertebrata (e.g., frogs) the optic thalami are insignificant, and their functions partially performed by the corpora quadrigemina, seems to point to a closer connection of the two centres, which would correspond to the close affinity of the senses of sight and touch. These two are the only spatial senses which we possess—senses, i.e., which spread out their sensations in space; and the supposition does not seem to me unfounded that the ideal fusion of the tactile and visual space into the indivisible space-perception which we are wont unconsciously to effect must have here a similar physiological foundation, as the blending of the visual space of the right eye with that of the left eye into an indivisible visual space possesses in the chiasma of the optic nerve. In the same way it is not improbable that the union of the corpora quadrigemina with the optic thalami can independently introduce certain movements, which may be termed reflexes to such space-perceptions, as are combined of sensations of sight and touch.

  These assumptions will hardly meet with opposition when we remember that the left half of the corpora quadrigemina only contains the left half of the binocular visual image, the right half only the corresponding right one, so that both halves of the image can only be brought to blend into a single and whole image by the co-operation of both halves of the organ. Finally, these suppositions also find support in this, that for the regulation of the position of the several bodily parts in space there is yet a second organ, the posterior brain or cerebellum, which, it is true, is influenced also by the other sense-organs (especially the senses of hearing and equilibrium and sense of sight), but likewise is especially determined in its functions by the sense of touch. One may comprehend from this development of the Hind-brain exceeding its original purpose as auditory ganglion that the intermediate-brain, or the optic thalami, may lag behind in their development in most animals, without prejudice to the organism; it would, however, not harmonise with our views on the purposive economy of the organism if two organs existed to fulfil a single purpose. We shall rather have to assume that the perceptions of the sense of touch which take place in the optic thalami and those which occur in the cerebellum are made use of in an altogether different way. Whilst in the cerebellum the impressions of touch are pre-eminently combined with those of the sense of equilibrium, so as to gain as perfect a total perception as possible of the position of the whole body and of its several parts in space, the intuition of the tactile space seems to be prepared in the optic thalami for the perception of the cerebral hemispheres, in like manner as that of visual space in the corpora quadrigemina, and to be fused into the indivisible tactile-visual space even before the entrance into the hemispheres. If this mode of conceiving the matter is correct, it also explains why the consciousness of the hemispheres feels itself unable to dissolve again the fusion of tactile and visual space, although in abstract reflection it perceives the heterogeneity and duality of the two spaces to be beyond a doubt. If this fusion were only a product of the activity of the hemispheres, there would probably be no particular difficulty in producing again the whole element in intuition also. The like holds of the impossibility of decomposing the superficial extension of the visual perception into its non-spatial elements of sensation; whilst, on the other hand, the possibility of this process with the third dimension of space or that of depth is an argument in favour of the supposition that the chief part of the genesis of the perception of depth only appertains to the hemispheres.

  9. The Cerebellum. —The theory of the functions of the cerebellum is still open to considerable doubt. It is certain that the opinion of Gall of a close relation of the same to the sexual functions is incorrect; the centre for the latter is rather still to be sought in the medulla oblongata.1 On the other hand, the parallelism in the development of the muscling of the body and of the cerebellum which runs through the whole vertebrate kingdom shows that this organ must be of importance for an energetic innervation of the muscles, and that the muscles under normal circumstances dra
w a considerable part of their impulse of innervation from the cerebellum. This, however, does not entitle us to designate with Luys the cerebellum the source of energy of all motor innervation, since even after destruction of the cerebellum any energetic movements may be called forth by all the other centres, and these latter can, to a certain extent, compensate for the loss of the cerebellum.

  What we know with the utmost certainty of the cerebellum, because we do not demonstrate it by vivisection, but by the most numerous experiments in the living man, is the fact that it is the organ of dizziness in all its forms. Dizziness may be produced by unilateral injuries of the organ, by one-sided pressure on the same, by cross conduction of a galvanic current, finally by the visual perceptions of moving objects, nay, even by merely imaginary ideas of possible movements, which are connected with certain visual perceptions. As is well known, dizziness is a phenomenon not subject to caprice, i.e., to the will of the cerebral hemispheres, and exhibits itself as disturbance of the involuntary regulation of the bodily movements. As partial disturbance of the function of the cerebellum produces partial disturbance of sensation in both eyes (here too the decussation is a partial one in the same sense as in the corpora quadrigemina), it produces an altered idea of the situation of the eyeball, and thereby an apparent motion of objects, to which there is added with greater degrees of dizziness an obscuration of the field of vision. Since the organ continues to be functional, and endeavours to adapt the deportment to the sensations, if the sensations are pathologically perverted, this adaptation must lead to objectively distorted muscular movements, and these are the rotatory movements, which accompany every dizziness, although in the weakest degrees of giddiness the particular impulses of innervation of the cerebellum are paralysed by opposite ones on the part of the cerebrum (W., p. 207–221).