present to consciousness as a sensation of given strength, is the correlate of a proportionate molecular disturbance in all the nervous structures concerned, how shall we interpret the sensations distinguished as subjective? In sundry abnormal states, strong feelings of cold or heat are felt throughout the body, though its actual temperature has remained unaltered. As in any case of this kind the total nervous change cannot have been the same as if the skin had fallen or risen in temperature to the degree ordinarily required to produce the feeling, we cannot say that there is a. quantitative equivalence between the amount of nervo?is 'bange and the amount of feeling. The disagreeable smell which, 011 the approacli of a fit, tlie epileptic patient frequently complains of, affords a yet better illustration. Here the outer ends of the afferent nerves being undisturbed, and only certain central structures irritated, the quantity of nervous action is not the same as if the sensation had been generated by an actual smell. More conspicuously still do we see the variability of this relation, when we compare the feelings called efforts with the discharges and muscular strains produced by them under different conditions. If the psychical force known as effort were transformable into a constant quantity of physical force,, then,, in any two cases, equal efforts should produce equal contractions. But they do not. Great exertion in a child fails to evolve from its motor organs the dynamic effect which a small exertion evolves from those of a man. Any one who is fatigued finds that an intenser feeling of strain is requisite to generate a given degree of muscular tension, than when he is fresh. And those prostrated by illness show us that immense expenditures of feeling are needed to perform acts which, during health, need scarcely appreciable expenditures of feeling. Doubtless these differences are partly due to differences in the muscles; which, when undeveloped or when wasted, are excited to smaller amounts of tension by equal amounts of discharge. But we must regard them as partly due to the imperfect development, or the worn state, of the intermediate motor centres and efferent nerves, in which a given feeling excites a smaller molecular disturbance than when they are finished in struct are and in complete repair — a conclusion enforced by the familiar experience that purely nervous acts, as those of thought, require unusual efforts when the brain is tired.
This variability of the quantitative relation between nervous actions and psychical states, is equally seen when we limit our comparisons to those nervous actions and psychical states which occur in the same individual under 11.5 THE DATA OF PSYCHOLOGY.
tlie same bodily conditions. To show that unlike but equally intense sensations may be produced by peripheral disturbances widely unlike in their amounts,, providing they arise in different external sense-organs, is scarcely possible without comparing the amounts of the incident forces; and this we cannot properly do, since we are here confining our attention to correlations within the organism. We are similarly debarred from going at length into the quantitative contrasts between the muscular tensions produced by the same feeling of effort, according as the muscles excited are large or small; for we cannot well establish these contrasts without measuring the muscular tensions by the external actions they are equivalent to. There is, however, one class of appropriate cases — those in which irritations arising within the organism, set up sensations that cause undirected motor discharges. Violent toothache, for example, is due to waves of molecular change sent through one or two minute afferent nerve-fibres; but the bodily contortions show us that the feeling so produced, suffices to send waves of molecular change through various large bundles of efferent nerve- fibres, and to contract numerous muscles with much force, To which of these disturbances, centripetal or centrifugal, is the feeling equivalent? We cannot say to both,, for one is many times the other in amount; and we have no reason to say that it is equivalent to one rather than to the other: the rational inference being that- it is not equivalent to either.
To understand the real relations between objective and subjective changes in the nervous system, we need but to recall certain of the conclusions reached in preceding chapters. The essential principle of nervous organization we have seen to be that the small amounts of motion received, liberate larger amounts, and these again still_ larger amounts. A disturbance in the end of an afferent nerve is multiplied as it traverses the nerve, and the degree of multiplication varies with the length of the nerve; it is much, more multiplied in the first ganglion reached, and increases further in traversing the centripetal nerve; it is again multiplied in the superior centre, to be afterwards augmented in its subsequent centrifugal course; and it is once more multiplied, probably in a far greater degree, in the contractile substance of the excited muscles. Hence the accompanying feeling, which is the subjective aspect of this disturbance at one of its intermediate stages, can be a quantitative equivalent neither of the initial nervous change nor of the terminal nervous change. Moreover, since the multiplication varies in degree, being much greater in the organs of the higher senses than in those of the lower, it follows that the ratio between the amount of feeling and the amount of initial change is far from constant; and the evidence clearly indicates a like inconstancy of the ratio between the amount of feeling and the amount of terminal change, according as one or other muscle or set of muscles is made to act.
How then can there be any quantitative relation, it will be jisked. If there is no equivalence between a disturbance set up at the periphery and the produced feeling, and no equivalence between the produced feeling and the motor discharge that follows — if the feeling does not even bear the same ratio to either the initial or the terminal nervous change in different cases; what quantitative relation can there be? The reply is simple. There is a quantitative relation between nervous change and feeling when all other things rernsin the same; and there is a quantitative relation between feeling and resulting contraction when all other things remain the same. Supposing every condition to continue unaltered, then the stimulus conveyed through a given nerve to a given centre, will evoke a feeling that increases and decreases in something like the same proportion as the stimulus increases and decreases; and, supposing a given muscle to be contracted, then the amount of its contraction will bear a tolerably constant ratio to the feeling of effort that accompanies the contraction of it. The nature of these correlations may best be expressed by numbers. If, coming through a given afferent nerve, a disturbance represented by 1 generates a feeling represented by 5, then disturbance 2 will generate feeling 10, and disturbance 5 feeling 25; and if, acting through a given efferent nerve, feeling 5 results in muscular tension 60, feeling 10 will result in muscular tension 120. But to complete this numerical expression of the facts we must suppose these ratios to vary with every set of afferent nerves and every set of efferent nerves. If we say that 1 to 5 represents the ratio of disturbance to feeling in the sense of touch, then to represent it in the sense of hearing will need, say, 1 to 100, and in the sense of sight perhaps I to 1,000; and similarly with the ratios throughout the motor apparatus, according as the muscles are large or small.
; In brief, then, the quantitative correlation of feeling i and nervous change, holds true only within narrow limits. (We have good reason to conclude that at the particular place in a superior nervous centre where, in some mysterious way, an objective change or nervous action causes a subjective change or feeling, there exists a quantitative equivalence between the two: the amount of sensation is proportionate to the amount of molecular transformation that takes place in the vesicular substance affected. But there is no fixed, or even approximate, quantitative relation between this amount of molecular transformation in the sentient centre, and the peripheral disturbance originally causing it, or the disturbance of the motor apparatus which it may eventually cause.
j § 48. The feelings called sensations have alone been con-Isidered thus far; leaving out o?' view the feelings cGs- Itinguished as ^is^ion^Tfluch less definite as they are, land not capable^oFTJeing made at will the objects of obserration and experiment, the emotions are more difficulty to deal with. But having discerned certain general laws to which the simpler feelings conform,, we may now ask •whether, so far as we can see,, they are conformed to by the more complex feelings. We shall find that they are.
The conditions essential to the one are essential to the other. Emotions, like sensations, may be increased or decreased in intensity by altering either the quantity or the quality of the blood. That general abundance of blood is a cause of emotional exaltation, though tolerably certain, is not easily proved; but there is sufficient evidence of the converse fact that, other things equal, depletion is a cause of apathy. The effect of local abundance of blood is undoubted: there is no question that, within limits, the amount of emotion varies as the amount of blood supplied to the great nervous centres. That nervous stimulants intensify the emotions, or, as we say, raise the spirits, is even more manifest than that they make the sensations keener. And it is a familiar truth that sedatives diminish what is distinguished as moral pain, in the same way that they diminish pain arising in the trunk or limbs.
That a feeling lasts an appreciable time, is no less true of an emotion than of a sensation: indeed the per-; sistence is relatively conspicuous. The state of conscious- -ness produced by a flash of lightning, is so brief as to seem instantaneous: only by the help of artificial tests are sensations of this kind found to have measurable durations. But no such tests are needed to prove that emotions continue through appreciable periods. Even a simple emotion, as of angj3£ or fear, does not reach its full strength the moment the cause presents itself; and after the cause is removed it takes some time to die away. When hereafter we deal with the origin of emotions, and recognize the fact that they are of far more involved natures than sensations, and imply the co-operation of extremely intricate nervous structures, we shall understand how this greater duration is necessitated.
Tliat an emotion, like a sensation, leaves behind it a ternporary incapacity, is also true; and as the emotion produced by a momentarv cause lasts longer than a sensation produced by a momentary cause, so does the partial incapacity for a like emotion last longer than the partial incapacity for a like sensation. Passions of all kinds come in gushes or bursts. That they often continue for hours and days, is true; but they are never uniform throughout hours and days. Be it in grief, or joy, or tenderness, there is always a succession of rises and falls of intensity — a paroxysm of violent feeling with an interval of feeling less violent, followed by another paroxysm. And then, after a succession of these comparatively -quick alternations, there comes a calm — a period during which the waves of emotion are feebler: succeeded, it may be, by another series of stronger waves. As in the case of the sensations so in the case of the emotions, this follows from the fact that what is objectively a nervous action and subjectively a feeling, involves waste of the nervous structures concerned.
The centres which are the seats uf emotions undergo disintegration in the genesis of emotions; and, other things remaining equal, thereupon become less capable of generating emotions until they are re-integrated. I say, other things remaining equal, because the^jrise of jm._emption brings blood to the parts implicated, and so long as the afflux is increasing the intensity of the emotion may increase, notwithstanding the waste that has taken place; but the several conditions on which activity depends having become constant, a diminished capacity for emotion inevitably follows each gu^F*oi*^motion.
That daily rises and falls of strength, consequent on daily periodicities of waste and repair, occur in the emotions as in the sensations, is also tolerably manifest. Cultivated people, mostly leading lives that exercise their bra'ns too much and their muscles too little, and placed in social conditions that commonly bring- the strongest excitements towards the close of the day, are subject to an abnormal periodicity. But those whose lives conform best to the laws of health, exhibit early in the day a general joyousness and emotional vivacity greater than they do towards its close, when approaching sleepiness is shown by a flagging interest in the things and actions around.
These complex feelings that are cent-'ally initiated are also like the simple feelings that are peripherally initiated, in having general discharges as well as special discharges: indeed their general discharges are the more conspicuous of the two. A sensation is often visibly followed only by local movement: unless very strong its effect on the organism as a whole is unobtrusive. But an emotion, besides the more obvious changes it works in the muscles of the face, habitually works changes, external and internal, throughout the body at large. The respiration, the circulation, the digestion, as well as the attitudes and movements, are influenced by it even when moderate; and everyone knows how strong passions, pleasurable or painful, pro-. foundly disturb the whole system.
§ 49. Nothing has yet been said about the most conspicuous and most important distinction existing among the feelings. Every feeling, besides its minor variations of intensity, exists under two strongly-contrasted degrees of intensity. There is a vivid form of it which we call an actual feeling, and there is a faint form of it which we call an ideal feeling, What is the nature of this difference as interpreted from our present stand-point?
When studying nerve-structure, we saw that, in addition to connections formed by grey matter between the central ends of afferent and efferent nerves, these have connections with centripetal and commissural nerves, \rfiicli 12-i THE DATA OF PSYCHOLOGY.
are again connected with more distant nerves. Anil when studying nerve - function,, we saw that a disturbance set up by an afferent nerve in its ganglion, does not affect exclusively the efferent nerve., but that part of it, conveyed through centripetal and commissural nerves, affects other centres, and these again others, until it has reverberated throughout the entire nervous system. "What follows? These reverberations are feeble disturb ances. And every centre, liable as it is to be strongly disturbed through its afferent or centripetal nerve, is liable also to be feebly disturbed by these reverberations arriving through other nerves. What then must happen with each of the libero-rtwtor elements composing those higher centres in which nervous changes become changes of consciousness?
"When it is affected through the direct and fully-opened route, by that peripheral impression to which it stands organically related, it evolves much molecular motion, becomes an active propagator of disturbances throughout the nervous system, and is the seat of what we call a real feeling; but when it is affected by these secondary waves diffused from other strongly excited parts, it becomes, as compared with them (or with itself under the previous condition) a generator of but little molecular motion, and is the seat of that faint feeling which we distinguish as ideal. In brief, those vivid states of consciousness which we know as sensations, accompany direct and therefore strong excitations of nervecentres; while the faint states of consciousness which we know as remembered sensations, or ideas of sensations, accompany indirect, and therefore weak, excitations of the same nerve-centres.
That the contrast of intensity between the effects of direct and indirect excitations, though it holds generally, does not hold without exception, is a fact quite reconcilable with this interpretation. For, on the one hand, a direct excitation may be very feeble; while, on the other hand, through a concurrence of diffused disturbances, an indirect excitation may rise to considerable strength. Hence, occasionally, an ideal feeling will become almost or quite equal in vividness to a real feeling. Especially may this happen when the nerve-centre concerned is surcharged with blood; since a small disturbance may then set up in it an amount of change equal to that which a great disturbance produces when only the ordinary quantity of blood is present. And it is a matter of observation that congested nerve-centres are those in which indirectly-excited feelings reach an intensity scarcely less than that of directly-excited feelings.
When we pass from the feelings called sensations, of which the strong forms are peripherally initiated, to the feelings called emotions, of which the strong forms are centrally initiated, we find the difference between the strong and the weak forms by no means so great; so that, in fact, ideal emotion passes into actual emotion without any line of demarcation. Obviously this is what might be anticipated. For whether ideal or actual, emotion is an accompaniment of an indirect excitation: it is not an immediate result of peripheral impressions, either simple or combined; but a mediate or remote result of them. Hence, all emotions, vivid and faint, being the subjective aspects of objective nervous changes that are produced indirectly, are distinguishable only according to the degree of indirectness of the excitation, and this admits of insensible gradations.
§ 50. One more general truth must be set down to complete the outline. The foregoing inferences joined with some contained in the last chapter, introduce us to it.
IT §§ 36, 37, it was pointed out that nerve-centres disintegrated by action, are perpetually re-integrating themselves, and again becoming fit for action. We saw that repair partially makes up for waste from instant to instant, and that the arrears of repair are made up daily during that period of quiescence when waste almost ceases.
126 THE 'DATA OF PSYCHOLOGY.
further saw that the restoration of a nerve-centre to its st??to of integrity, is not only the filling up of its quantum of decomposable matter, but is also the replacing of molecules most exposed to disturbance, and consequently the production of a comparatively-unstable state. And we saw how, after a period of profound repose, there thus arises a con-- dition of the nerve-centres such that very slight stimuli cause nervous discharges.
This law applies not generally only, but specially to each nerve-centre and each of its component parts. In proportion as any part of a nerve-centre has been for a long time unused — in proportion, that is, as repair of it has gone on day after day and night after night unhindered by appreciable waste, it must be brought to a state of more than ordinary instability — a state of excessive readiness to decompose and discharge. What must happen? In common with all other parts, it is exposed to these reverberations which from instant to instant fill the nervous system. Its extreme instability must render it unusually sensitive to these reverberations — unusually ready to undergo change, - to yield up molecular motion, and to become the seat of ^ the concomitant ideal feeling. Besides a great liability to the ideal feeling this same condition must entail a great strength of it; and so while the instability continues, a strong ideal feeling will be perpetually aroused. As, however, the nerve-centre in which such secondary molecular changes and accompanying ideal feelings are thus set up, is somewhat wasted by them, it follows that after they have gone on for a considerable period the instability of the centre will be diminished: it will no longer be so easily decomposed by indirect disturbances, and the jfeeling will not be produced. - ' " Here we have the interpretation of what are called lesires. Desires are^ ideal feelings that arise when^tho *eal feelin^To^liicli they correspond have not been jx- ^rienced for some time. They are then liable to be excited by various of tlie indirect disturbances reflected from part1 to part of the nervous system. They are usually vivid and persistent in proportion to the previous period of rest — -more vivid and more persistent than ideal feelings of the same kind under ordinary conditions. But after a prolonged period during which they continue to arise and almost monopolize consciousness, they become feebler and finally die away.
§ 51. Such are the leading truths of -ZEstho-Physiology, set forth with as much fulness as is here requisite. Sensation and emotion in their relations to nervous action,, have been dealt with generally; and whatever has been said of special sensations and special emotions has been said merely to illustrate a law which holds among all the rest. The concomitants,, subjective and objective,, of each particular kind of sensation and each particular kind of emotion, I here pass over. They may be studied to great advantage in the works of Professor Bain on The Senses and the Intellect, and _ The. Emotions and the Will; in which he has given an elaborate account of the connection between each particular feeling, simple or complex, and its various physical accompaniments. To these works I must commend the reader who wishes to trace out these minor correlations. As data for the present treatise, the only facts needful to be carried with us are those set forth in the preceding sections. They may be summed up thus.
Feeling of whatever kind is directly known by each person in no other place than his own consciousness. That feelings exist in the world beyond consciousness, is a belief reached only through an involved combination of inferences. That., alike in human and inferior beings, feelings are accompaniments of changes in the peculiar strujoture known as the nervous system, is also an jncliTec.tLyestablished belief. And that the feelings alone cognizable by any individual are products of the action of his own i*ervous system,, which lie has never seen and on whicli he can try no experiments, is a belief only to be arrived at through a farther chain of reasoning. Nevertheless, the evidence, though so indirect, is so extensive, so varied, and so congruous, that we may accept the conclusion without hesitation.
The conclusion having been accepted — provisionally if not permanently — its validity is shown by leading us to anticipate truly, in one set of cases after another, the particular subjective phenomena that accompany particular objective phenomena. We have seen that the several circumstances which facilitate or hinder nervous action, are also circumstances which facilitate or hinder feeling. We have seen that as nervous action occupies appreciable time, so feeling occupies appreciable time. We have seen that each feeling leaves a partial incapacity for a like feeling, as each nervous action leaves a partial incapacity for a like nervous action. We have seen that, other things equal, the intensities of feelings vary as the intensities of the correlative nervous actions. We have seen that the difference between direct and indirect nervous disturbances, corresponds to the difference between the vivid feelings we call real and the faint feelings we call idea^ And we have seen that certain more special objective phenomena which nervous actions present, have answering subjective phenomena in the forms of feeling we distinguish as desires.
Thus, impossible as it is to get immediate proof that 'feeling andjiervous action are the inner and outer faces of *^3^^S^9]i^9.£eJ £e* the, hypothesis that they are so harmonizes with all the observed facts; and, as elsewhere shown (Mrst Principles,. § 4QJ. no other verification is possible for us than that wEict results from the establishment of complete congruity among our experiences.
CHAPTEE YIL § 52. We may now enter on our special topic. Tims far we Have been occupied with the data of Psychology, and not with Psychology properly so-called. Here leaving the foundations we pass to the superstructure.
Not a few readers will be surprised by the assertion that none of the truths we have been contemplating are psychological truths. Since the anatomy and physiology of the nervous system have occupied so much attention, and since it has been growing manifest that there is a fundamental connection between nervous changes and psychical, states, there has arisen a confusion between the phenomena which underlie Psychology and the phenomena of Psychology itself. In reality, all the facts ascertained by those who have made nerve- structure and nerve-function.their studies, are facts of a simpler order than those rightly termed psychological; though they are facts entering into the composition of psychological facts.
Most will admit without hesitation that the first five chapters.of this part consist o£ propositions which are exclusively. mQx.pholqgical and physiological. In them TTJfe "structure of the nervous system, its functions, the conditions to its action, &c., have been dealt with purely as physical phenomena — phenomena as purely physical as the absorption K j 130 THE DATA OF PSYCHOLOGY.
of nutriment or the circulation of the "blood. Whatever ' ' implications may have arisen from the use of words that carry with them indirect meanings,, the direct meanings of all the propositions set down have nowhere implied consciousness or feeling; and, ignoring consciousness or feeling, they have left out that which is tacitly or avowedly contained in every proposition of Psychology.
It will probably be thought, however, that at any rate truths belonging to Psychology proper are to be found in the last chapter. Dealing as the last chapter does with the connections between nervous changes and feelings, it necessarily becomes, by including a psychical element, a part of psychical science. To this the rejoinder is that, though it can scarcely be excluded absolutely from the body of this science, yet it does not strictly fall within that body. ^Esthophysiology has a position that is entirely unique. It belongs neither to the objective world nor the subjective world; but i taking a term from each, occupies itself with the correlation , j1 of the two. It may with as much propriety be included in the domain of physical science as in the domain of psychical science j and must be left where it stands, as the 1, link between them.
j * Perhaps this explanation will increase rather than decrease the surprise produced by the assertion that was to be justified. To clear up the confusion, we must examine more carefully the distinction between the truths which are strictly psychological and those which merely enter into the composition of psychological truths.
§ 53. Throughout the preceding chapters, including even the last, every proposition set down has expressed some relation of phenomena occurring within the limits of the organism. The subject-matter has been the character of a structure; or the effect which a disturbance set up in one *" place has in causing motion in another; or the connection between the physical state of the whole or a part of the organism,, and some general or local nervous process; or the variable intensity of an action in a nerve -centre as determined by a preceding like action; or the interdependence of internal physical changes and internal psychical changes. That is to say,, the attention has everywhere been directed exclusively to co-existences and sequences of which the body alone is the sphere. Distinct or tacit reference has, indeed,, frequently been made to some external force. Either a disturbing agent lying beyond the limits of the organism has been referred to in general terms, 01% for illustration's sake,, this or the other kind of disturbing agent has been named. But such references, vague or distinct, have been made merely because it was needful to suppose something by which an organic change was set up; not because this something had to be included in the proposi--tion set down, which in eveiy case formulated an internal relation only. The entanglement of phenomena is such, that we can never cut off absolutely from all others the particular phenomena we are dealing with; but,, because we presuppose these other phenomena, it does not follow that the science to which they pertain forms part of the science with which we are specially occupied. For instance, it is impossible to describe, or think of, a chemical' experiment that discloses some chemical relation, without making distinct or tacit references to physical relations — the pouring and mixture of liquids, the ascent of bubbles of disengaged gas, the falling of a precipitate; but it is not therefore held that we are including physics in our chemistry. Similarly, it must be admitted that though the foregoing chapters have tacitly assumed environing forces, yet this assumption has been simply incidental to the study of internal coexistences and sequences.