Chapter VI

, where we spoke of habitual concatenated movements being

due to a series of secondarily organized reflex arcs (Vol. I. p. 116). The first contraction is the one distinctly willed, and after willing it we let the rest of the chain rattle off of its own accord. How now is such an orderly concatenation of movements originally learned? or in other words, how are paths formed for the first time between one motor centre and another, so that the discharge of the first centre makes the others discharge in due order all along the line?

The phenomenon involves a rapid alternation of motor discharges and resultant afferent impressions, for as long a time as it lasts. They must be associated in one definite order; and the order must once have been _learned_, i.e., it must have been picked out and held to more and more exclusively out of the many other random orders which first presented themselves. The random afferent impressions fell out, those that felt right were selected and grew together in the chain. A chain which we actively teach ourselves by stringing a lot of right-feeling impressions together differs in no essential respect from a chain which we passively learn from someone else who gives us impressions in a certain order. So to make our ideas more precise, let us take a

## particular concatenated movement for an example, and let it be the

recitation of the alphabet, which someone in our childhood taught us to say by heart.

What we have seen so far is how the idea of the sound or articulatory feeling of A may make us say 'A,' that of B, 'B,' and so on. But what we now want to see is _why the sensation that A is uttered should make us say 'B,' why the sensation that B is uttered should make us say 'C,' and so on._

[Illustration: FIG. 89.]

To understand this we must recall what happened when we first learned the letters in their order. Someone repeated A, B, C, D to us over and over again, and we imitated the sounds. Sensory cells corresponding to each letter were awakened in succession in such wise that each one of them (by virtue of our second law) must have 'drained' the cell just previously excited and left a path by which that cell tended ever afterwards to discharge into the cell that drained it. Let S^a, S^b, S^c in figure 89 stand for three of these cells. Each later one of them, as it discharges motorwards, draws a current from the previous one, S^b from S^a, and S^c from S^b. Cell S^b having thus drained S^a, if S^a ever gets excited again, it tends to discharge into S^b; whilst S^c having drained S^b, S^b later discharges into S^c, etc., etc.--all through the dotted lines. Let now the idea of the letter A arise in the mind, or, in other words, let S^a be aroused: what happens? A current runs from S^a not only into the motor cell M^a for pronouncing that letter, but also into the cell S^b. When, a moment later, the effect of M^a's discharge comes back by the afferent nerve and re-excites S^a, this latter cell is inhibited from discharging again into M^a and reproducing the 'primordial motor circle' (which in this case would be the continued utterance of the letter A), by the fact that the process in S^b, already under headway and tending to discharge into its own motor associate M^b, is, _under the existing conditions_, the stronger drainage-channel for S^a's excitement. The result is that M^b discharges and the letter B is pronounced; whilst at the same time S^c receives some of S^b's overflow; and, a moment later when the sound of B enters the ear, discharges into the motor cell for pronouncing C, by a repetition of the same mechanism as before; and so on _ad libitum_. Figure 90 represents the entire set of processes involved.

[Illustration: FIG. 90.]

The only thing that one does not immediately see is the reason why 'under the existing conditions' the path from S^a to S^b should be the stronger drainage-channel for S^a's excitement. If the cells and fibres in the figure constituted the entire brain we might suppose either a mechanical or a psychical reason. The mechanical reason might lie in a general law that cells like S^b and M^b, whose excitement is in a rising phase, are stronger drainers than cells like M^a, which have just discharged; or it might lie in the fact that an irradiation of the current beyond S^b into S^c and M^c has already begun also; and in a still farther law that drainage tends in the direction of the widest irradiations. Either of these suppositions would be a sufficient mechanical reason why, having once said A, we should not say it again. But we must not forget that the process has a psychical side, nor close our eyes to the possibility that the _sort of feeling_ aroused by incipient currents may be the reason why certain of them are instantly inhibited and others helped to flow. There is no doubt that before we have uttered a single letter, the general intention to recite the alphabet is already there; nor is there any doubt that to that intention corresponds a widespread premonitory rising of tensions along the entire system of cells and fibres which are later to be aroused. So long as this rise of tensions _feels good_, so long every current which increases it is furthered, and every current which diminishes it is checked; and this may be the chief one of the 'existing conditions' which make the drainage-channel from S^a to S^b temporarily so strong.[511]

The new paths between the sensory cells of which we have studied the formation are paths of 'association,' and we now see why associations run always in the forward direction; why, for example, we cannot say the alphabet backward, and why, although S^b discharges into S^c, there is no tendency for S^c to discharge into S^b, or at least no more than for it to discharge into S^a.[512] The first-formed paths had, according to the principles which we invoked, to run from cells that had just discharged to those that were discharging; and now, to get currents to run the other way, we must go through a new learning of our letters with their order reversed. There will _then_ be two sets of association-pathways, either of them possible, between the sensible cells. I represent them in Fig. 91, leaving out the motor features for simplicity's sake. The dotted lines are the paths in the backward direction, newly organized from the reception by the ear of the letters in the order C B A.

[Illustration: FIG. 91.]

The same principles will explain the formation of new paths successively concatenated to no matter how great an extent, but it would obviously be folly to pretend to illustrate by more intricate examples. I will therefore only bring back the case of the child and flame (Vol. I. p. 25), to show how easily it admits of explanation as a 'purely cortical transaction' (_ibid._ p. 80). The sight of the flame stimulates the cortical centre S^1 which discharges by an instinctive reflex path into the centre M^1 for the grasping-movement. This movement produces the feeling of burn, as its effects come back to the centre S^2; and this centre by a second connate path discharges into M^2, the centre for withdrawing the hand. The movement of withdrawal stimulates the centre S^3, and this, as far as we are concerned, is the last thing that happens. Now the next time the child sees the candle, the cortex is in possession of the secondary paths which the first experience left behind. S^2, having been stimulated immediately after S^1, drained the latter, and now S^1 discharges into S^2 before the discharge of M^1 has had time to occur; in other words, the sight of the flame suggests the idea of the burn before it produces its own natural reflex effects. The result is an inhibition of M^1, or an overtaking of it before it is completed, by M^2.--The characteristic physiological feature in all these acquired systems of paths lies in the fact that the new-formed sensory irradiations keep _draining things forward_, and so breaking up the 'motor circles' which would otherwise accrue. But, even apart from catalepsy, we see the 'motor circle' every now and then come back. An infant learning to execute a simple movement at will, without regard to other movements beyond it, keeps repeating it till tired. How reiteratively they babble each new-learned word! And we adults often catch ourselves reiterating some meaningless word over and over again, if by chance we once begin to utter it 'absent-mindedly,' that is, without thinking of any ulterior train of words to which it may belong.

[Illustration: FIG. 92.]

* * * * *

One more observation before closing these already too protracted physiological speculations. Already (Vol. I. p. 71) I have tried to shadow forth a reason why collateral innervation should establish itself after loss of brain-tissue, and why incoming stimuli should find their way out again, after an interval, by their former paths. I can now explain this a little better. Let S^1 be the dog's hearing-centre when he receives the command 'Give your paw.' This _used_ to discharge into the motor centre M^1, of whose discharge S^2 represents the kinæsthetic effect; but now M^1 has been destroyed by an operation, so that S^1 discharges as it can, into other movements of the body, whimpering, raising the wrong paw, etc. The kinæsthetic centre S^2 meanwhile has been awakened by the order S^1, and the poor animal's mind tingles with expectation and desire of certain incoming sensations which are entirely at variance with those which the really executed movements give. None of the latter sensations arouse a 'motor circle,' for they are displeasing and inhibitory. But when, by random accident, S^1 and S^2 _do_ discharge into a path leading through M^2, by which the _paw is again given_, and S^2 is excited at last from without as well as from within, there are no inhibitions and the 'motor circle' is formed: S^1 discharges into M^2 over and over again, and the path from the one spot to the other is so much deepened that at last it becomes organized as the regular channel of efflux when S^1 is aroused. No other path has a chance of being organized in like degree.

[Illustration: FIG. 93.]

* * * * *

[430] Parts of this chapter have appeared in an essay called "The Feeling of Effort," published in the Anniversary Memoirs of the Boston Society of Natural History, 1880; and parts in Scribner's Magazine for Feb. 1888.

[431] I am abstracting at present for simplicity's sake, and so as to keep to the elements of the matter, from the learning of acts by seeing others do them.

[432] Deutsches Archiv f. Klin. Medicin, xxii. 321.

[433] Landry: Mémoire sur la Paralysie du Sens Musculaire, Gazette des Hôpitaux, 1855, p. 270.

[434] Tàkacs: Ueber die Verspätung der Empfindungsleitung, Archiv für Psychiatrie, Bd. x. Heft 3, p. 533. Concerning all such cases see the remarks made above on pp. 205-6.

[435] Proceedings of American Soc. for Psychical Research, p. 95.

[436] In reality the movement cannot even be _started_ correctly in some cases without the kinæsthetic impression. Thus Dr. Strümpell relates how turning over the boy's hand made him bend the little finger instead of the forefinger, when his eye was closed. "Ordered to point, e.g., towards the left with his left arm, the arm was usually raised straight forward, and then wandered about in groping uncertainty, sometimes getting the right position and then leaving it again. Similarly with the lower limbs. If the patient, lying in bed, had, immediately after the tying of his eyes, to lay the left leg over the right, it often happened that he moved it farther over towards the left, and that it lay over the side of the bed in apparently the most intolerably-uncomfortable position. The turning of the head, too, from right to left, or towards certain objects known to the patient, only ensued correctly when the patient, immediately before his eye was bandaged, specially refreshed his perception as to what the required movement was to be." In another anæsthetic of Dr. Strümpell's (described in the same essay) the arm could not be moved _at all_ unless the eyes were opened, however energetic the volition. The variations in these hysteric cases are great. Some patients cannot move the anæsthetic part _at all_ when the eyes are closed. Others move it perfectly well, and can even write continuous sentences with the anæsthetic hand. The causes of such differences are as yet incompletely unexplored. M. Binet suggests (Revue Philosophique, xxv. 478) that in those who cannot move the hand at all the sensation of light is required as a 'dynamogenic' agent (see above, p. 377); and that in those who can move it skilfully the anæsthesia is only a pseudo-insensibility and that the limb is in reality governed by a dissociated or secondary consciousness. This latter explanation is certainly correct. Professor G. E. Müller (Pflüger's Archiv, xlv. 90) invokes the fact of individual differences of imagination to account for the cases who cannot write at all. Their kinæsthetic images properly so called may be weak, he says, and their optical images insufficiently powerful to supplement them without a 'fillip' from sensation. Janet's observation that hysteric anæsthesias may carry amnesias with them would perfectly legitimate Müller's supposition. What we now want is a minute examination of the individual cases. Meanwhile Binet's article above referred to, and Bastian's paper in Brain for April 1887, contain important discussions of the question. In a later note I shall return to the subject again (see p. 520).

[437] Professor Beaunis found that the accuracy with which a certain tenor sang was not lost when his vocal cords were made anæsthetic by cocain. He concludes that the guiding sensations here are resident in the laryngeal muscles themselves. They are much more probably in the ear. (Beaunis, Les Sensations Internes (1889), p. 253).

[438] As the feeling of heat, for example, is the last psychic antecedent of sweating, as the feeling of bright light is that of the pupil's contraction, as the sight or smell of carrion is that of the movements of disgust, as the remembrance of a blunder may be that of a blush, so the idea of a movement's sensible effects might be that of the movement itself. It is true that the idea of sweating will not commonly make us sweat, nor that of blushing make us blush. But in certain nauseated states the idea of vomiting will make us vomit; and a kind of sequence which is in this case realized only exceptionally might be the rule with the so-called voluntary muscles. It all depends on the nervous connections between the centres of ideation and the discharging paths. These may differ from one sort of centre to another. They do differ somewhat from one individual to another. Many persons never blush at the idea of their blunders, but only when the actual blunder is committed; others blush at the idea; and some do not blush at all. According to Lotze, with some persons "It is possible to weep at will by trying to recall that peculiar feeling in the trigeminal nerve which habitually precedes tears. Some can even succeed in sweating voluntarily, by the lively recollection of the characteristic skin-sensations, and the voluntary reproduction of an indescribable sort of feeling of relaxation, which ordinarily precedes the flow of perspiration." (Med. Psych., p. 303.) The commoner type of exceptional case is that in which the idea of the _stimulus_, not that of the effects, provokes the effects. Thus we read of persons who contract their pupils at will by strongly imagining a brilliant light. A gentleman once informed me (strangely enough I cannot recall who he was, but I have an impression of his being a medical man) that he could sweat at will by imagining himself on the brink of a precipice. The sweating palms of fear are sometimes producible by imagining a terrible object (cf. Manouvrier in Rev. Phil., xxii. 203). One of my students, whose eyes were made to water by sitting in the dentist's chair before a bright window, can now shed tears by imagining that situation again. One might doubtless collect a large number of idiosyncratic cases of this sort. They teach us how greatly the centres vary in their power to discharge through certain channels. All that we need, now, to account for the differences observed between the psychic antecedents of the voluntary and involuntary movements is that centres producing ideas of the movement's sensible effects should be able to instigate the former, but be out of gear with the latter, unless in exceptional individuals. The famous case of Col. Townsend, who could stop his heart at will, is well known. See, on this whole matter, D. H. Tuke: Illustrations of the Influence of the Mind on the Body, chap. xiv. § 3; also J. Braid: Observations on Trance or Human Hybernation (1850). The latest reported case of voluntary control of the heart is by Dr. S. A. Pease, in Boston Medical and Surgical Journal, May 30, 1889.

[439] Prof. Harless, in an article which in many respects forestalls what I have to say (Der Apparat des Willens, in Fichte's Zeitschrift f. Philos., Bd. 38, 1861), uses the convenient word _Effectsbild_ to designate these images.

[440] The best modern statement I know is by Jaccoud: Des Paraplégies et de l'Ataxie du Mouvement (Paris, 1864), p. 591.

[441] Leidesdorf u. Meynert's Vierteljsch. f. Psychiatrie, Bd. i. Heft i. S. 36-7 (1867). Physiologische Psychologie, 1st ed. S. 316.

[442] Professor Fouillée, who defends them in the Revue Philosophique, xxviii, 561 ff., also admits (p. 574) that they are the same whatever be the movement, and that all our discrimination of _which_ movement we are innervating is afferent, consisting of sensations after, and of sensory images before, the act.

[443] Cf. Souriau in Rev. Philosophique, xxii. 454.--Professor G. E. Müller thus describes some of his experiments with weights: If, after lifting a weight of 8000 grams a number of times we suddenly get a weight of only 500 grams to lift, "this latter weight is then lifted with a velocity which strikes every onlooker, so that the receptacle for the weight with all its contents often flies high up as if it carried the arm along with it, and the energy with which it is raised is sometimes so entirely out of proportion to the weight itself, that the contents of the receptacle are slung out upon the table in spite of the mechanical obstacles which such a result has to overcome. A more palpable proof that the trouble here is a wrong adaptation of the motor impulse could not be given." Pflüger's Archiv, xlv. 47. Compare also p. 57, and the quotation from Hering on the same page.

[444] Archiv für Psychiatrie, iii. 618-635. Bernhardt strangely enough seems to think that what his experiments disprove is the existence of afferent muscular feelings, not those of efferent innervation--apparently because he deems that the peculiar thrill of the electricity ought to overpower all other afferent feelings from the part. But it is far more natural to interpret his results the other way, even aside from the certainty yielded by other evidence that passive muscular feelings exist. This other evidence, after being compendiously summed up by Sachs in Reichert und Du Bois' Archiv (1874), pp. 174-188, is, as far as the anatomical and physiological grounds go, again thrown into doubt by Mays, Zeitschrift f. Biologie, Bd. xx.

[445] Functions of the Brain, p. 228.

[446] Vorlesungen über Menschen und Thierseele, i. 222.

[447] In some instances we get an opposite result. Dr. H. Charlton Bastian (British Medical Journal (1869), p. 461, note), says:

"Ask a man whose lower extremities are completely paralyzed, whether, when he ineffectually wills to move either of these limbs, he is conscious of an expenditure of energy in any degree proportionate to that which he would have experienced if his muscles had naturally responded to his volition. He will tell us rather that he has a sense only of his utter powerlessness, and that his volition is a mere mental act, carrying with it no feelings of expended energy such as he is accustomed to experience when his muscles are in powerful action, and from which action and its consequences alone, as I think, he can derive any adequate notion of resistance."

[448] Münsterberg's words may be added: "In lifting an object in the hand I can discover no sensation of volitional energy. I perceive in the first place a slight tension about the head, but that this results from a contraction in the head muscles, and not from a feeling of the brain-discharge, is shown by the simple fact that I get the tension on the right side of the head when I move the right arm, whereas the motor discharge takes place in the opposite side of the brain.... In maximal contractions of body- and limb-muscles there occur, as if it were to reinforce them, those special contractions of the muscles of the face [especially frowning and clinching teeth] and those tensions of the skin of the head. These sympathetic movements, felt particularly on the side which makes the effort, are perhaps the immediate ground why we ascribe our awareness of maximal contraction to the region of the head, and call it a consciousness of force, instead of a peripheral sensation." (Die Willenshandlung (1888), pp. 73, 82.) Herr Münsterberg's work is a little masterpiece, which appeared after my text was written. I shall have repeatedly to refer to it again, and cordially recommend to the reader its most thorough refutation of the Innervationsgefühl-theory.

[449] Physiologische Optik, p. 600.

[450] [The left and sound eye is here supposed covered. If both eyes look at the same field there are double images which still more perplex the judgment. The patient, however, learns to see correctly before many days or weeks are over.--W. J.]

[451] Alfred Graefe, in Handbuch der gesammten Augenheilkunde, Bd. vi. pp. 18-21.

[452] Professor G. E. Müller (Zur Grundlegung der Psychophysik (1878), p. 318,) was the first to explain the phenomenon after the manner advocated in the text. Still unacquainted with his book, I published my own similar explanation two years later.

Professor Mach in his wonderfully original little work 'Beiträge zur Analyse der Empfindungen,' p. 57, describes an artificial way of getting translocation, and explains the effect likewise by the feeling of innervation. "Turn your eyes," he says, "as far as possible towards the left and press against the right sides of the orbits two large lumps of putty. If you then try to look as quickly as possible towards the right, this succeeds, on account of the incompletely spherical form of the eyes, only imperfectly, and the objects consequently appear translocated very considerably towards the right. The _bare will_ to look rightwards gives to all images on the retina a greater _rightwards value_, to express it shortly. The experiment is at first surprising."--I regret to say that I cannot myself make it succeed--I know not for what reason. But even where it does succeed it seems to me that the conditions are much too complicated for Professor Mach's theoretic conclusions to be safely drawn. The putty squeezed into the orbit, and the pressure of the eyeball against it must give rise to peripheral sensations _strong_ enough, at any rate (if only of the right kind), to justify any amount of false perception of our eyeball's position, quite apart from the innervation feelings which Professor Mach supposes to coexist.

[453] An illusion in principle exactly analogous to that of the patient under discussion can be produced experimentally in anyone in a way which Hering has described in his Lehre von Binocularen Sehen, pp. 13-14. I will quote Helmholtz's account of it, which is especially valuable as coming from a believer in the _Innervationsgefühl_: "Let the two eyes first look parallel, then let the right eye be closed whilst the left still looks at the infinitely distant object _a_. The directions of both eyes will thus remain unaltered, and _a_ will be seen in its right place. Now accommodate the left eye for a point _f_ [a needle in Hering's experiment] lying on the optical axis between it and _a_, only very near. The position of the left eye and its optical axis, as well as the place of the retinal image upon it... are wholly unaltered by this movement. But the consequence is that an apparent movement of the object occurs--a movement towards the left. As soon as we accommodate again for distance the object returns to its old place. Now what alters itself in this experiment is only the position of the closed right eye: its optical axis, when the effort is made to accommodate for the point _f_, also converges towards this point.... Conversely it is possible for me to make my optical axes diverge, even with closed eyes, so that in the above experiment the right eye should turn far to the right of _a_. This divergence is but slowly reached, and gives me therefore no illusory movement. But when I suddenly relax my effort to make it, and the right optical axis springs back to the parallel position, I immediately see the object which the left eye fixates shift its position towards the left. Thus not only the position of the seeing eye _a_, but also that of the closed eye _b_, influences our judgment of the direction in which the seen object lies. The open eye remaining fixed, and the closed eye moving towards the right or left, the object seen by the open eye appears also to move towards the right or left" (Physiol. Optik, pp. 607-8.)

[454] Beiträge zur Analyse der Empfindungen, p. 65.

[455] P. 68.

[456] I owe the interpretation in the text to my friend and former student, Mr. E. S. Drown, whom I set to observe the phenomenon before I had observed it myself. Concerning the vacillations in our interpretation of relative motion over retina and skin, see above, p. 173.

Herr Münsterberg gives additional reasons against the feeling of innervation, of which I will quote a couple. First, our ideas of movement are all _faint_ ideas, resembling in this the copies of sensations in memory. Were they feelings of the outgoing discharge, they would be original states of consciousness, not copies; and ought by analogy to be _vivid_ like other original states.--Second, our unstriped muscles yield no feelings in contracting, nor can they be contracted at will, differing thus in _two_ peculiarities from the voluntary muscles. What more natural than to suppose that the two peculiarities hang together, and that the reason why we cannot contract our intestines, for example, at will, is, that we have no memory-images of how their contraction feels? Were the supposed innervation-feeling always the 'mental cue,' one doesn't see why we might not have it even where, as here, the contractions themselves are unfelt, and why it might not bring the contractions about. (Die Willenshandlung, pp 87-8.)

[457] Revue Philosophique, xxiii. 442.

[458] _Ibid._ xx. 604.

[459] Herr Sternberg (Pflüger's Archiv, xxxvii. p. 1) thinks that he proves the feeling of innervation by the fact that when we have willed to make a movement we generally think that it is made. We have already seen some of the facts on pp. 105-6, above. S. cites from Exner the fact that if we put a piece of hard rubber between our back teeth and bite, our front teeth seem actually to approach each other, although it is physically impossible for them to do so. He proposes the following experiment: Lay the palm of the hand on a table with the forefinger overlapping its edge and flexed back as far as possible, whilst the table keeps the other fingers extended; then try to flex the terminal joint of the forefinger without looking. You do not do it, and yet you think that you do. Here again the innervation, according to the author, is felt as an executed movement. It seems to me, as I said in the previous place, that the illusion is in all these cases due to the inveterate association of ideas. Normally our will to move has always been followed by the sensation that we _have_ moved, except when the simultaneous sensation of an external resistance was there. The result is that where we feel no external resistance, and the muscles and tendons tighten, the invariably associated idea is intense enough to be hallucinatory. In the experiment with the teeth, the resistance customarily met with when our masseters contract is a soft one. We do not close our teeth on a thing like hard rubber once in a million times; so when we do so, we imagine the habitual result.--Persons with _amputated limbs_ more often than not continue to feel them as if they were still there, and can, moreover, give themselves the feeling of moving them at will. The life-long sensorial associate of the idea of 'working one's toes,' e.g. (uncorrected by any opposite sensation, since no real sensation of non-movement can come from non-existing toes), follows the idea and swallows it up. The man thinks that his toes are 'working' (cf. Proceedings of American Soc. for Psych. Research, p. 249).

Herr Loeb also comes to the rescue of the feeling of innervation with observations of his own made after my text was written, but they convince me no more than the arguments of others. Loeb's facts are these (Pflüger's Archiv, xliv. p. 1): If we stand before a vertical surface, and if, with our hands _at different heights_, we _simultaneously_ make with them what seem to us equally extensive movements, that movement always turns out really shorter which is made with the arm whose muscles (in virtue of the arm's position) are already the more contracted. The same result ensues when the arms are laterally unsymmetrical. Loeb assumes that both arms contract by virtue of a common innervation, but that although this innervation is relatively less effective upon the more contracted arm, our _feeling_ of its equal strength overpowers the disparity of the incoming sensations of movement which the two limbs send back, and makes us think that the spaces they traverse are the same. "The sensation of the extent and direction of our voluntary movements depends accordingly upon the impulse of our will to move, and not upon the feelings set up by the motion in the active organ." Now if this is the elementary law which Loeb calls it, why does it only manifest its effect when both hands are moving simultaneously? Why not when the _same_ hand makes _successive_ movements? and especially why not when both hands move symmetrically or at the same level, but _one of them_ is _weighted_? A weighted hand surely requires a stronger innervation than an unweighted one to move an equal distance upwards; and yet, as Loeb confesses, we do not tend to overestimate the path which it traverses under these circumstances. The fact is that the illusion which Loeb has studied is a complex resultant of many factors. One of them, it seems to me, is an instinctive tendency to _revert to the type of the bilateral movements of childhood_. In adult life we move our arms for the most

## part in alternation; but in infancy the free movements of the arms are

almost always similar on both sides, symmetrical when the direction of motion is horizontal, and with the hands on the same level when it is vertical. The most natural innervation, when the movements are rapidly performed, is one which takes the movement hack to this form. Our _estimation_ meanwhile of the lengths severally traversed by the two hands is mainly based, as such estimations with closed eyes usually are (see Loeb's own earlier paper, _Untersuchungen über den Fühlraum der Hand_, in Pflüger's Archiv, xli. 107), upon the apparent velocity and duration of the movement. The duration is the same for both hands, since the movements begin and end simultaneously. The velocities of the two hands are under the experimental conditions almost impossible of comparison. It is well known how imperfect a discrimination of _weights_ we have when we 'heft' them simultaneously, one in either hand; and G. E. Müller has well shown (Pflüger's Archiv, xlv. 57) that the velocity of the lift is the main factor in determining our judgment of weight. It is hardly possible to conceive of more unfavorable conditions for making an accurate comparison of the length of two movements than those which govern the experiments which are under discussion. The only prominent sign is the duration, which would lead us to infer the equality of the two movements. We consequently deem them equal, though a native tendency in our motor centres keeps them from being so.

[460] This is by no means an unplausible opinion. See Vol. I. p. 65.

[461] Maine de Biran, Royer Collard, Sir John Herschel, Dr. Carpenter, Dr. Martineau, all seem to posit a force-sense by which, in becoming aware of an outer resistance to our will, we are taught the existence of an outer world. I hold that every peripheral sensation gives us an outer world. An insect crawling on our skin gives us as 'outward' an impression as a hundred pounds weighing on our back.--I have read M. A. Bertrand's criticism of my views (La Psychologie de l'Effort, 1889); but as he seems to think that I deny the _feeling_ of effort altogether, I can get no profit from it, despite his charming way of saying things.

[462] Bowditch and Southard in Journal of Physiology, vol. iii. No. 3. It was found in these experiments that the maximum of accuracy was reached when two seconds of time elapsed between locating the object by eye or hand and starting to touch it. When the mark was located with one hand, and the other hand had to touch it, the error was considerably greater than when the same hand both located and touched it.

[463] The same caution must be shown in discussing pathological cases. There are remarkable discrepancies in the effects of peripheral anæsthesia upon the voluntary power. Such cases as I quoted in the text (p. 490) are by no means the only type. In those cases the patients could move their limbs accurately when the eyes were open, and inaccurately when they were shut. In other cases, however, the anæsthetic patients _cannot move their limbs at all_ when the eyes are shut. (For reports of two such cases see Bastian in 'Brain,' Binet in Rev. Philos., xxv. 478.) M. Binet explains these (hysterical) cases as requiring the 'dynamogenic' stimulus of light (see above, p. 377). They _might_, however, be cases of such congenitally defective optical imagination that the 'mental cue' was normally 'tactile;' and that when this tactile cue failed through functional inertness of the kinæsthetic centres, the only optical cue strong enough to determine the discharge had to be an actual _sensation_ of the eye.--There is still a third class of cases in which the limbs have lost all sensibility, even for movements passively imprinted, but in which voluntary movements can be accurately executed even when the eyes are closed. MM. Binet and Féré have reported some of these interesting cases, which are found amongst the hysterical hemianæsthetics. They can, for example, write accurately at will, although their eyes are closed and they have no feeling of the writing taking place, and many of them do not know when it begins or stops. Asked to write repeatedly the letter _a_, and then say how many times they have written it, some are able to assign the number and some are not. Some of them admit that they are guided by visual imagination of what is being done. Cf. Archives de Physiologie, Oct. 1887, pp. 363-5. Now it would seem at first sight that feelings of outgoing innervation must exist in these cases and be kept account of. There are no other guiding impressions, either immediate or remote, of which the patient is conscious; and unless feelings of innervation be there, the writing would seem miraculous. But if such feelings are present in these cases, and suffice to direct accurately the succession of movements, why do they not suffice in those other anæsthetic cases in which movement becomes disorderly when the eyes are closed? _Innervation_ is there, or there would be no movement; why is the _feeling_ of the innervation gone? The truth seems to be, as M. Binet supposes (Rev. Philos., xxiii. p. 479), that these cases are not arguments for the feeling of innervation. They are pathological curiosities; and the patients are not really anæsthetic, but are victims of that curious dissociation or splitting-off of one part of their consciousness from the rest which we are just beginning to understand, thanks to Messrs. Janet, Binet, and Gurney, and in which the split-off part (in this case the kinæsthetic sensations) may nevertheless remain to produce its usual effects. Compare what was said above, p. 491.

[464] Medicinische Psychologie, p. 293. In his admirably acute chapter on the Will this author has most explicitly maintained the position that what we call muscular exertion is an afferent and not an efferent feeling; "We must affirm universally that in the muscular feeling we are not sensible of _the force_ on its way to produce an effect, but only of the _sufferance_ already produced in our movable organs, the muscles, after the force has, in a manner unobservable by us, exerted upon them its causality" (p. 311). How often the battles of psychology have to be fought over again, each time with heavier armies and bigger trains, though not always with such able generals!

[465] Ch. Féré: Sensation et Mouvement (1887),