of exit again, the thrill of satisfaction which the consciousness connected with the whole residual brain then receives will reinforce and fix the paths of that moment and make them more likely to be struck into again. The resultant feeling that the old habitual act is at last successfully back again, becomes itself a new stimulus which stamps all the existing currents in. It is matter of experience that such feelings of successful achievement do tend to fix in our memory whatever processes have led to them; and we shall have a good deal more to say upon the subject when we come to the Chapter on the Will.
My conclusion then is this: that some of the restitution of function (especially where the cortical lesion is not too great) is probably due to genuinely vicarious function on the part of the centres that remain; whilst some of it is due to the passing off of inhibitions. In other words, both the vicarious theory and the inhibition theory are true in their measure. But as for determining that measure, or saying which centres are vicarious, and to what extent they can learn new tricks, that is impossible at present.
FINAL CORRECTION OF THE MEYNERT SCHEME.
And now, after learning all these facts, what are we to think of the child and the candle-flame, and of that scheme which provisionally imposed itself on our acceptance after surveying the actions of the frog? (_Cf_. pp. 25-6, _supra_.) It will be remembered that we then considered the lower centres _en masse_ as machines for responding to present sense-impressions exclusively, and the hemispheres as equally exclusive organs of action from inward considerations or ideas; and that, following Meynert, we supposed the hemispheres to have no native tendencies to determinate activity, but to be merely superadded organs for breaking up the various reflexes performed by the lower centres, and combining their motor and sensory elements in novel ways. It will also be remembered that I prophesied that we should be obliged to soften down the sharpness of this distinction after we had completed our survey of the farther facts. The time has now come for that correction to be made.
Wider and completer observations show us both that the lower centres are more spontaneous, and that the hemispheres are more automatic, than the Meynert scheme allows. Schrader's observations in Goltz's Laboratory on hemisphereless frogs[84] and pigeons[85] give an idea quite different from the picture of these creatures which is classically current. Steiner's[86] observations on frogs already went a good way in the same direction, showing, for example, that locomotion is a well-developed function of the medulla oblongata. But Schrader, by great care in the operation, and by keeping the frogs a long time alive, found that at least in some of them the spinal cord would produce movements of locomotion when the frog was smartly roused by a poke, and that swimming and croaking could sometimes be performed when nothing above the medulla oblongata remained.[87] Schrader's hemisphereless frogs moved spontaneously, ate flies, buried themselves in the ground, and in short did many things which before his observations were supposed to be impossible unless the hemispheres remained. Steiner[88] and Vulpian have remarked an even greater vivacity in fishes deprived of their hemispheres. Vulpian says of his brainless carps[89] that three days after the operation one of them darted at food and at a knot tied on the end of a string, holding the latter so tight between his jaws that his head was drawn out of water. Later, "they see morsels of white of egg; the moment these sink through the water in front of them, they follow and seize them, sometimes after they are on the bottom, sometimes before they have reached it. In capturing and swallowing this food they execute just the same movements as the intact carps which are in the same aquarium. The only difference is that they seem to see them at less distance, seek them with less impetuosity and less perseverance in all the points of the bottom of the aquarium, but they struggle (so to speak) sometimes with the sound carps to grasp the morsels. It is certain that they do not confound these bits of white of egg with other white bodies, small pebbles for example, which are at the bottom of the water. The same carp which, three days after operation, seized the knot on a piece of string, no longer snaps at it now, but if one brings it near her, she draws away from it by swimming backwards before it comes into contact with her mouth."[90] Already on pp. 9-10, as the reader may remember, we instanced those adaptations of conduct to new conditions, on the part of the frog's spinal cord and thalami, which led Pflüger and Lewes on the one hand and Goltz on the other to locate in these organs an intelligence akin to that of which the hemispheres are the seat.
When it comes to birds deprived of their hemispheres, the evidence that some of their acts have conscious purpose behind them is quite as persuasive. In pigeons Schrader found that the state of somnolence lasted only three or four days, after which time the birds began indefatigably to walk about the room. They climbed out of boxes in which they were put, jumped over or flew up upon obstacles, and their sight was so perfect that neither in walking nor flying did they ever strike any object in the room. They had also definite ends or purposes, flying straight for more convenient perching places when made uncomfortable by movements imparted to those on which they stood; and of several possible perches they always chose the most convenient.
"If we give the dove the choice of a horizontal bar (_Reck_) or an equally distant table to fly to, she always gives decided preference to the table. Indeed she chooses the table even if it is several meters farther off than the bar or the chair." Placed on the back of a chair, she flies first to the seat and then to the floor, and in general "will forsake a high position, although it give her sufficiently firm support, and in order to reach the ground will make use of the environing objects as intermediate goals of flight, showing a perfectly correct judgment of their distance. Although able to fly directly to the ground, she prefers to make the journey in successive stages...Once on the ground, she hardly ever rises spontaneously into the air."[91] Young rabbits deprived of their hemispheres will stand, run, start at noises, avoid obstacles in their path, and give responsive cries of suffering when hurt. Rats will do the same, and throw themselves moreover into an attitude of defence. Dogs never survive such an operation if performed at once. But Goltz's latest dog, mentioned on p. 70, which is said to have been kept alive for fifty-one days after both hemispheres had been removed by a series of ablations and the corpora striata and thalami had softened away, shows how much the mid-brain centres and the cord can do even in the canine species.
Taken together, the number of reactions shown to exist in the lower centres by these observations make out a pretty good case for the Meynert scheme, as applied to these lower animals. That scheme demands hemispheres which shall be mere supplements or organs of repetition, and in the light of these observations they obviously are so to a great extent. But the Meynert scheme also demands that the reactions of the lower centres shall all be _native_, and we are not absolutely sure that some of those which we have been considering may not have been acquired after the injury; and it furthermore demands that they should be machine-like, whereas the expression of some of them makes us doubt whether they may not be guided by an intelligence of low degree.
Even in the lower animals, then, there is reason to soften down that opposition between the hemispheres and the lower centres which the scheme demands. The hemispheres may, it is true, only supplement the lower centres, but the latter resemble the former in nature and have some small amount at least of 'spontaneity' and choice.
But when we come to monkeys and man the scheme well-nigh breaks down altogether; for we find that the hemispheres do not simply repeat voluntarily actions which the lower centres perform as machines.
There are many functions which the lower centres cannot by themselves perform at all. When the motor cortex is injured in a man or a monkey genuine paralysis ensues, which in man is incurable, and almost or quite equally so in the ape. Dr. Seguin knew a man with hemi-blindness, from cortical injury, which had persisted unaltered for twenty-three years. 'Traumatic inhibition' cannot possibly account for this. The blindness must have been an 'Ausfallserscheinung,' due to the loss of vision's essential organ. It would seem, then, that in these higher creatures the lower centres must be less adequate than they are farther down in the zoological scale; and that even for certain elementary combinations of movement and impression the co-operation of the hemispheres is necessary from the start. Even in birds and dogs the power of _eating properly_ is lost when the frontal lobes are cut off.[92] The plain truth is that neither in man nor beast are the hemispheres the virgin organs which our scheme called them. So far from being unorganized at birth, they must have native tendencies to reaction of a determinate sort.[93] These are the tendencies which we know as _emotions_ and _instincts_, and which we must study with some detail in later chapters of this book. Both instincts and emotions are reactions upon special sorts of objects of _perception_; they depend on the hemispheres; and they are in the first instance reflex, that is, they take place the first time the exciting object is met, are accompanied by no forethought or deliberation, and are irresistible. But they are modifiable to a certain extent by experience, and on later occasions of meeting the exciting object, the instincts especially have less of the blind impulsive character which they had at first. All this will be explained at some length in Chapter XXIV. Meanwhile we can say that the multiplicity of emotional and instinctive reactions in man, together with his extensive associative power, permit of extensive recouplings of the original sensory and motor partners. The _consequences_ of one instinctive reaction often prove to be the inciters of an opposite reaction, and being _suggested_ on later occasions by the original object, may then suppress the first reaction altogether, just as in the case of the child and the flame. For this education the hemispheres do not need to be _tabulæ rasæ_ at first, as the Meynert scheme would have them; and so far from their being educated by the lower centres exclusively, they educate themselves.[94] We have already noticed the absence of reactions from fear and hunger in the ordinary brainless frog. Schrader gives a striking account of the instinctless condition of his brainless pigeons, active as they were in the way of locomotion and voice. "The hemisphereless animal moves in a world of bodies which...are all of equal value for him...He is, to use Goltz's apt expression, _impersonal_...Every object is for him only a space-occupying mass, he turns out of his path for an ordinary pigeon no otherwise than for a stone. He may try to climb over both. All authors agree that they never found any difference, whether it was an inanimate body, a cat, a dog, or a bird of prey which came in their pigeon's way. The creature knows neither friends nor enemies, in the thickest company it lives like a hermit. The languishing cooing of the male awakens no more impression than the rattling of the peas, or the call-whistle which in the days before the injury used to make the birds hasten to be fed. Quite as little as the earlier observers have I seen hemisphereless she-birds answer the courting of the male.
A hemisphereless male will coo all day long and show distinct signs of sexual excitement, but his activity is without any object, it is entirely indifferent to him whether the she-bird be there or not. If one is placed near him, he leaves her unnoticed...As the male pays no attention to the female, so she pays none to her young. The brood may follow the mother ceaselessly calling for food, but they might as well ask it from a stone...The hemisphereless sphereless pigeon is in the highest degree tame, and fears man as little as cat or bird of prey."[95] Putting together now all the facts and reflections which we have been through, it seems to me that _we can no longer hold strictly to the Meynert scheme_. If anywhere, it will apply to the lowest animals; but in them especially the lower centres seem to have a degree of spontaneity and choice. On the whole, I think that we are driven to substitute for it some such general conception as the following, which allows for zoological differences as we know them, and is vague and elastic enough to receive any number of future discoveries of detail.
CONCLUSION.
All the centres, in all animals, whilst they are in one aspect mechanisms, probably are, or at least once were, organs of consciousness in another, although the consciousness is doubtless much more developed in the hemispheres than it is anywhere else. The consciousness must everywhere _prefer_ some of the sensations which it gets to others; and if it can remember these in their absence, however dimly, they must be its _ends_ of desire. If, moreover, it can identify in memory any motor discharges which may have led to such ends, and associate the latter with them, then these motor discharges themselves may in turn become desired as _means_. This is the development of _will_; and its realization must of course be proportional to the possible complication of the consciousness. Even the spinal cord may possibly have some little power of will in this sense, and of effort towards modified behavior in consequence of new experiences of sensibility.[96] All nervous centres have then in the first instance one essential function, that of 'intelligent' action. They feel, prefer one thing to another, and have 'ends.' Like all other organs, however, they _evolve_ from ancestor to descendant, and their evolution takes two directions, the lower centres passing downwards into more unhesitating automatism, and the higher ones upwards into larger intellectuality.[97] Thus it may happen that those functions which can safely grow uniform and fatal become least accompanied by mind, and that their organ, the spinal cord, becomes a more and more soulless machine; whilst on the contrary those functions which it benefits the animal to have adapted to delicate environing variations pass more and more to the hemispheres, whose anatomical structure and attendant consciousness grow more and more elaborate as zoological evolution proceeds. In this way it might come about that in man and the monkeys the basal ganglia should do fewer things by themselves than they can do in dogs, fewer in dogs than in rabbits, fewer in rabbits than in hawks,[98] fewer in hawks than in pigeons, fewer in pigeons than in frogs, fewer in frogs than in fishes, and that the hemispheres should correspondingly do more.
This passage of functions forward to the ever-enlarging hemispheres would be itself one of the evolutive changes, to be explained like the development of the hemispheres themselves, either by fortunate variation or by inherited effects of use. The reflexes, on this view, upon which the education of our human hemispheres depends, would not be due to the basal ganglia alone. They would be tendencies in the hemispheres themselves, modifiable by education, unlike the reflexes of the medulla oblongata, pons, optic lobes and spinal cord. Such cerebral reflexes, if they exist, form a basis quite as good as that which the Meynert scheme offers, for the acquisition of memories and associations which may later result in all sorts of 'changes of partners' in the psychic world. The diagram of the baby and the candle (see page 25) can be re-edited, if need be, as an entirely cortical transaction. The original tendency to touch will be a cortical instinct; the burn will leave an image in another part of the cortex, which, being recalled by association, will inhibit the touching tendency the next time the candle is perceived, and excite the tendency to withdraw--so that the retinal picture will, upon that next time, be coupled with the original motor partner of the pain. We thus get whatever psychological truth the Meynert scheme possesses without entangling ourselves on a dubious anatomy and physiology.
Some such shadowy view of the evolution of the centres, of the relation of consciousness to them, and of the hemispheres to the other lobes, is, it seems to me, that in which it is safest to indulge. If it has no other advantage, it at any rate makes us realize how enormous are the gaps in our knowledge, the moment we try to cover the facts by any one formula of a general kind.
FOOTNOTES: [4] It should be said that this particular cut commonly proves fatal.
The text refers to the rare cases which survive.
[5] I confine myself to the frog for simplicity's sake. In higher animals, especially the ape and man, it would seem as if not only determinate combinations of muscles, but limited groups or even single muscles could be innervated from the hemispheres.
[6] I hope that the reader will take no umbrage at my so mixing the physical and mental, and talking of reflex acts and hemispheres and reminiscences in the same breath, as if they were homogeneous quantities and factors of one causal chain. I have done so deliberately; for although I admit that from the radically physical point of view it is easy to conceive of the chain of events amongst the cells and fibres as complete in itself, and that whilst so conceiving it one need make no mention of 'ideas,' I yet suspect that point of view of being an unreal abstraction. Reflexes in centres may take place even where accompanying feelings or ideas guide them. In another chapter I shall try to show reasons for not abandoning this common-sense position; meanwhile language lends itself so much more easily to the mixed way of describing, that I will continue to employ the latter. The more radical-minded reader can always read 'ideational process' for 'idea.'
[7] I shall call it hereafter for shortness 'the Meynert scheme;' for the child-and-flame example, as well as the whole general notion that the hemispheres are a supernumerary surface for the projection and association of sensations and movements natively coupled in the centres below, is due to Th. Meynert, the Austrian anatomist. For a popular account of his views, see his pamphlet 'Zur Mechanik des Gehirnbaues,' Vienna, 1874. His most recent development of them is embodied in his 'Psychiatry,' a clinical treatise on diseases of the forebrain, translated by B. Sachs, New York, 1885.
[8] Geschichte des Materialismus, 2d ed., ii, p. 345.
[9] West Riding Asylum Reports, 1876, p. 267.
[10] For a thorough discussion of the various objections, see Ferrier's 'Functions of the Brain,' 2d ed., pp. 227-234, and François-Franck's 'Leçons sur les Fonctions Motrices du Cerveau' (1887), Leçon 31. The most minutely accurate experiments on irritation of cortical points are those of Paneth, in Pflüger's Archiv, vol 37, p. 528.--Recently the skull has been fearlessly opened by surgeons, and operations upon the human brain performed, sometimes with the happiest results. In some of these operations the cortex has been electrically excited for the purpose of more exactly localizing the spot, and the movements first observed in dogs and monkeys have then been verified in men.
[11] J. Loeb: Beiträge zur Physiologie des Grosshirns; Pflüger's Archiv, xxxix, 293. I simplify the author's statement.
[12] Goltz: Pflüger's Archiv, xlii, 419.
[13] 'Hemiplegia' means one-sided palsy.
later paper (_ibid._ p. 205) Messrs. Beevor and Horsley go into the localization still more minutely, showing spots from which single muscles or single digits can be made to contract.
[15] Nothnagel und Naunyn; Die Localization in den Gehirnkrankheiten [16] An accessible account of the history of our knowledge of motor aphasia is in W. A. Hammond's 'Treatise on the Diseases of the Nervous System,' chapter vii.
[17] The history up to 1885 may be found in A. Christiani: Zur Physiologie des Gehirnes (Berlin, 1885).
[18] Pflüger's Archiv, vol. 44, p. 176. Munk (Berlin Academy Sitzsungberichte, 1889, xxxi) returns to the charge, denying the extirpations of Schrader to be complete: "Microscopic portions of the _Sehsphäre_ must remain."
[19] A. Christiani; Zur Physiol. d. Gehirnes (Berlin, 1885), chaps. ii, iii, iv, H. Munk: Berlin Akad. Stzgsb. 1884, xxiv.
[20] Luciani und Seppili: Die Functions-Localization auf der Grosshirnrinde (Deutsch von Fraenkel), Leipzig, 1886, Dogs M, N, and S. Goltz in Pflüger's Archiv, vol. 34, pp. 490-6; vol. 42, p. 454. Cf.
also Munk: Berlin Akad. Stzgsb. 1886, vii, viii, pp. 113-121, and Loeb: [21] Berlin Akad. Sitzungsberichte, 1886, vii, viii, p. 124.
[22] H. Munk: Functionen der Grosshirnrinde (Berlin, 1881), pp. 36-40.
Ferrier: Functions, etc., 2d ed., chap, ix, pt. i. Brown and Schaefer, Philos. Transactions, vol. 179, p. 321. Luciani u. Seppili, op. cit.
pp. 131-138. Lannegrace found traces of sight with both occipital lobes destroyed, and in one monkey even when angular gyri and occipital lobes were destroyed altogether. His paper is in the Archives de Médecine Expérimentale for January and March, 1889. I only know it from the abstract in the Neurologisches Centralblatt, 1889, pp. 108-420. The reporter doubts the evidence of vision in the monkey. It appears to have consisted in avoiding obstacles and in emotional disturbance in the presence of men.
[23] Localization of Cerebral Disease (1878), pp. 117-8.
[24] For cases see Flechsig: Die Leitungsbahnen in Gehirn u. Rückenmark Ferrier's Localization, etc., p. 11; François-Franck's Cerveau Moteur, p. 63, note.
[25] E. C. Seguin: Hemianopsia of Cerebral Origin, in Journal of Nervous and Mental Disease, vol. xiii, p. 30. Nothnagel und Naunyn: Ueber die Localization der Gehirnkrankheiten (Wiesbaden, 1887), p. 16.
[26] Die Seelenblindheit, etc., p. 51 ff. The mental blindness was in this woman's case moderate in degree.
He gives, however, no case in support of his opinion that double-sided cortical lesion may make one stone-blind and yet not destroy one's visual images; so that I do not know whether it is an observation of fact or an _a priori_ assumption.
[29] In a case published by C. S. Freund: Archiv f. Psychiatrie, vol. xx, the occipital lobes were injured, but their cortex was not destroyed, on both sides. There was still vision. Cf. pp. 291-5.
[30] I say 'need,' for I do not of course deny the _possible_ coexistence of the two symptoms. Many a brain-lesion might block optical associations and at the same time impair optical imagination, without entirely stopping vision. Such a case seems to have been the remarkable one from Charcot which I shall give rather fully in the chapter on Imagination.
[31] Freund (in the article cited above 'Ueber optische Aphasie und Seelenblindheit') and Bruns ('Ein Fall von Alexie,' etc., in the Neurologisches Centralblatt for 1888, pp. 581, 509) explain their cases by broken-down conduction. Wilbrand, whose painstaking monograph on mental blindness was referred to a moment ago, gives none but _a priori_ reasons for his belief that the optical 'Erinnerungsfeld' must be locally distinct from the Wahrnehmungsfeld (cf. pp. 84, 93). The _a priori_ reasons are really the other way. Mauthner ('Gehirn u. Auge' (1881), p. 487 ff.) tries to show that the 'mental blindness' of Munk's dogs and apes after occipital mutilation was not such, but real dimness of sight. The best case of mental blindness yet reported is that by Lissauer, as above. The reader will also do well to read Bernard: De l'Aphasie (1885) chap. v; Ballet: Le Langage Intérieur (1886), chap.
viii; and Jas. Boss's little book on Aphasia (1887), p. 74.
[32] For a case see Wernicke's Lehrb. d. Gehirnkrankheiten, vol. ii, p.
554 (1881).
[33] The latest account of them is the paper 'Über die optischen Centren u. Bahnen' by von Monakow in the Archiv für Psychiatrie, vol.
xx, p. 714.
[34] Die Functions-Localization, etc., Dog X; see also p. 161.
[36] Brain, vol. xi, p. 10.
[38] Der aphasische Symptomencomplex (1874). See in Fig. 11 the convolution marked WERNICKE.
[39] 'The Pathology of Sensory Aphasia,' 'Brain,' July, 1889.
[40] Nothnagel und Naunyn; _op. cit._ plates.
[41] Ballet's and Bernard's works cited on p. 51 are the most accessible documents of Charcot's school. Bastian's book on the Brain as an Organ of Mind (last three chapters) is also good.
[42] For details, see Ferrier's 'Functions,' chap. ix, pt. iii, and Chas. K. Mills: Transactions of Congress of American Physicians and [43] Functions of the Brain, chap. x, § 14.
[45] Lezioni di Fisiologia sperimentale sul sistema nervoso encefalico anæsthesia in a cat with motor symptoms from ablation of sigmoid gyrus.
Luciani got hyperæsthesia coexistent with cortical motor defect in a dog, by simultaneously hemisecting the spinal cord (Luciani u. Seppili, _op. cit._ p. 234). Goltz frequently found hyperæsthesia of the whole body to accompany motor defect after ablation of both frontal lobes, and he once found it after ablating the motor zone (Pflüger's Archiv, vol. 34, p. 471).
[47] Philos. Transactions, vol. 179, p. 20 ff.
[49] Pp. 15-17.
[52] Trans. of Congress, etc., p. 272.
[53] See Exner's Unters. üb. Localization, plate xxv.
[54] Cf. Ferrier's Functions, etc., chap. iv, and chap. x, §§ 6 to 9.
Localization im Gehirn (1888), p. 72.
[59] Trans. of Congress of Am. Phys. and Surg. 1888, vol. i, p. 343.
Beevor and Horsley's paper on electric stimulation of the monkey's brain is the most beautiful work yet done for precision. See Phil.
Trans., vol. 179, p. 205, especially the plates.
[61] By Luys in his generally preposterous book 'The Brain'; also by Horsley.
[62] C. Mercier: The Nervous System and the Mind, p. 124.
[63] The frontal lobes as yet remain a puzzle. Wundt tries to explain them as an organ of 'apperception' (Grundzüge d. Physiologischen Psychologie, 3d ed., vol. i, p. 233 ff.), but I confess myself unable to apprehend clearly the Wundtian philosophy so far as this word enters into it, so must be contented with this bare reference.--Until quite recently it was common to talk of an 'ideational centre' as of something distinct from the aggregate of other centres. Fortunately this custom is already on the wane.
[64] Rech. Exp. sur le Fonctionnement des Centres Psycho-moteurs (Brussels, 1885).
[66] I ought to add, however, that François-Franck (Fonctions Motrices, p. 370) got, in two dogs and a cat, a different result from this sort of 'circumvallation.'
[67] For this word, see T. K. Clifford's Lectures and Essays (1879), vol. ii, p. 72.
[68] See below, Chapter VIII.
[69] Cf. Ferrier's Functions, pp. 120, 147, 414. See also Vulpian: Leçons sur la Physiol. du Syst. Nerveux, p. 548; Luciani u. Seppili, _op. cit._ pp. 404-5; H. Maudsley: Physiology of Mind (1876), pp. 138 ff., 197 ff., and 241 ff. In G. H. Lewes's Physical Basis of Mind, Problem IV: 'The Reflex Theory,' a very full history of the question is given.
10, p. 174.
[71] Goltz: Verrichtungen des Grosshirns, p. 78.
[75] The Nervous System and the Mind (1888), chaps. iii, vi; also in Brain, vol. xi, p. 361.
[76] Brown-Séquard has given a resume of his opinions in the Archives de Physiologie for Oct. 1889, 5me. Série, vol. i, p 751.
[77] Goltz first applied the inhibition theory to the brain in his 'Verrichtungen des Grosshirns,' p. 39 ff. On the general philosophy of Inhibition the reader may consult Brunton's 'Pharmakology and Therapeutics,' p. 154 ff., and also 'Nature,' vol. 27, p. 419 ff.
Physiol. Abth. p. 38. (Experiments on new-born puppies.)
contradictory.
whole question. Compare also Wundt's Physiol. Psych., 3d ed., i, 225 ff., and Luciani u. Seppili, pp. 243, 293.
[83] The Chapters on Habit, Association, Memory, and Perception will change our present preliminary conjecture that that is one of its essential uses, into an unshakable conviction.
[86] Untersuchungen über die Physiologie des Froschhirns. 1885.
developed when the medulla oblongata is cut through just behind the cerebellum.
[88] Berlin Akad. Sitzungsberichte for 1886.
44, p. 219 ff. It is possible that this symptom may be an effect of traumatic inhibition, however.
[93] A few years ago one of the strongest arguments for the theory that the hemispheres are purely supernumerary was Soltmann's often-quoted observation that in new-born puppies the motor zone of the cortex is not excitable by electricity and only becomes so in the course of a fortnight, presumably after the experiences of the lower centres have educated it to motor duties. Paneth's later observations, however, seem to show that Soltmann may have been misled through overnarcotizing his victims (Pflüger's Archiv, vol. 37, p. 202). In the Neurologisches Centralblatt for 1889, p. 513, Bechterew returns to the subject on Soltmann's side without, however, noticing Paneth's work.
[94] Münsterberg (Die Willenshandlung, 1888, p. 134) challenges Meynert's scheme _in toto_, saying that whilst we have in our personal experience plenty of examples of acts which were at first voluntary becoming secondarily automatic and reflex, we have no conscious record of a single originally reflex act growing voluntary.--As far as conscious record is concerned, we could not possibly have it even if the Meynert scheme were wholly true, for the education of the hemispheres which that scheme postulates must in the nature of things antedate recollection. But it seems to me that Münsterberg's rejection of the scheme may possibly be correct as regards reflexes from the _lower centres_. Everywhere in this department of psychogenesis we are made to feel how ignorant we really are.
[96] Naturally, as Schiff long ago pointed out (Lehrb. d. Muskel-u.
Nervenphysiologie, 1859, p. 213 ff.), the 'Rückenmarksseele,' if it now exist, can have no higher sense-consciousness, for its incoming currents are solely from the skin. But it may, in its dim way, both feel, prefer, and desire. See, for the view favorable to the text: G. H. Lewes, The Physiology of Common Life (1860), chap. ix. Goltz (Nervencentren des Frosches 1869, pp. 102-130) thinks that the frog's cord has no adaptative power. This may be the case in such experiments as his, because the beheaded frog's short span of life does not give it time to learn the new tricks asked for. But Rosenthal (Biologisches Centralblatt, vol. iv, p. 247) and Mendelssohn (Berlin Akad.
Sitzungsberichte, 1885, p. 107) in their investigations on the simple reflexes of the frog's cord, show that there is some adaptation to new conditions, inasmuch as when usual paths of conduction are interrupted by a cut, new paths are taken. According to Rosenthal, these grow more pervious (i.e. require a smaller stimulus) in proportion as they are more often traversed.
[97] Whether this evolution takes place through the inheritance of habits acquired, or through the preservation of lucky variations, is an alternative which we need not discuss here. We shall consider it in the last chapter in the book. For our present purpose the _modus operandi_ of the evolution makes no difference, provided it be admitted to occur.
CHAPTER III.
ON SOME GENERAL CONDITIONS OF BRAIN-ACTIVITY.
The elementary properties of nerve-tissue on which the brain-functions depend are far from being satisfactorily made out. The scheme that suggests itself in the first instance to the mind, because it is so obvious, is certainly false: I mean the notion that each cell stands for an idea or part of an idea, and that the ideas are associated or 'bound into bundles' (to use a phrase of Locke's) by the fibres. If we make a symbolic diagram on a blackboard, of the laws of association between ideas, we are inevitably led to draw circles, or closed figures of some kind, and to connect them by lines. When we hear that the nerve-centres contain cells which send off fibres, we say that Nature has realized our diagram for us, and that the mechanical substratum of thought is plain. In _some_ way, it is true, our diagram must be realized in the brain; but surely in no such visible and palpable way as we at first suppose.[99] An enormous number of the cellular bodies in the hemispheres are fibreless. Where fibres are sent off they soon divide into untraceable ramifications; and nowhere do we see a simple coarse anatomical connection, like a line on the blackboard, between two cells. Too much anatomy has been found to order for theoretic purposes, even by the anatomists; and the popular-science notions of cells and fibres are almost wholly wide of the truth. Let us therefore relegate the subject of the _intimate_ workings of the brain to the physiology of the future, save in respect to a few points of which a word must now be said. And first of THE SUMMATION OF STIMULI