PART I.. General Psychology.

GENERAL PSYCHOLOGY.

CHAPTER I.

PHYSICAL PAIN.

Its anatomical and physiological conditions; pain nerves, transmission to the centres—Modifications of the organism accompanying physical pain: circulation, respiration, nutrition, movements—Are they the effects of paint?—Pain is only a sign—The analgesias: unconsciousness of pain and intellectual consciousness—Retardation of pain after sensation—Hyperalgesia—Nature of pain: theory that it is a sensation; theory that it is a quality of sensation—Pain may result from the quality or the intensity of the stimulus—Hypotheses regarding its ultimate cause: it depends on a form of movement, a chemical modification.

Many definitions of pain have, very unnecessarily, been offered. Some are even tautological, others imply a hypothesis as to its nature by relating it to strong stimulations. Let us regard it as an internal state which every one knows by experience, and of which consciousness reveals innumerable modes, but which by its generality and its multiplicity of aspect escapes definition.

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Footnote 11:

“Pain is a powerful and prolonged vibration of the conscious nervous centres, resulting from a strong peripheral excitation, and consequently of a sudden change of condition in the nervous centres” (Richet). “It is the most violent stimulation of certain sensorial regions—a stimulation to which contribute the more extended stimulations of other regions” (Wundt).

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In its primitive form pain is always physical, that is to say, connected with external or internal sensations. Sufficiently precise as regards superficial parts of the body, especially the skin, its localisation is vaguer when it is seated in the deeper parts, the viscera, the instruments of organic life. In the last case, when the pain is of internal and non-peripheral origin, coming from the great sympathetic or the related vagus nerve, it is accompanied by a state of anxiety, of depression, or of anguish, which we shall often encounter, and which frequently causes it to be said that “it seems to the patient that the workings of nature within him are suspended.” For the present, without distinguishing between these two origins, external and internal, we will study the objective characters of physical pain taken in general: first its anatomical and physiological conditions, then the bodily modifications which accompany it and in popular language are called its effects.

The transmission of painful impressions from the periphery to the cortical centres is far from being determined in all the stages of its course.

The nerve terminations, from their outpost position, receive the first shock; but what part do they play? It is known that the nerves of the deep organs and the filaments of the great sympathetic have no specially constructed terminations. The nerves of special sense, on the contrary,—vision, hearing, smell, and taste,—possess special peripheral apparatus (retina, organ of Corti, etc.) of very complex anatomy; it is known that their rôle is specially sensorial; they are above all instruments of knowledge, seldom directly of pain or pleasure. So that the question of nerve terminations in relation to pain may chiefly be confined to the nerves of the tactile apparatus, taking the word in its largest sense. The extreme difficulty of isolating the purely peripheral impression from that which reaches the nerve itself renders almost insoluble the question as to the part played by these peripheral apparatus. Beaunis, relying on the cases of localised anæsthesia in which the patient no longer feels pain but still perceives contact, thinks that analgesia would reach the nerves before acting on their terminations, shut up in more or less resistant capsules.

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Footnote 12:

Sensations internes, Chap. xx., may be read for details on this point.

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Are there special nerves for the transmission of pain? Goldscheider, well known for his researches on cold and heat points on the skin, at first maintained that there are. According to him, the pain-bearing nerve filaments are interlaced with the sensorial nerves, more numerously with the nerves of general sensation (touch, heat, cold), less numerously with those of special sense. If the existence of these special pain nerves were well established, it would have as great an importance for our subject as the discoveries of Sachs and others, on the nervous filaments peculiar to the muscles, have had for the study of the kinæsthetic sense. But this physiologist has since repudiated his first assertion, and maintained that it was misunderstood; he admits pain points (points sensible to pain), but not a specific organ for pain nor special nerves to transmit it. Frey, on the other hand, professes to have proved experimentally both pain nerves and appropriate terminal organs. His observations have been rejected as inaccurate. At the present time there is nothing to establish the existence of pain nerves, and most authors have given strong reasons against the probability of such a discovery. Rejecting this hypothesis, we may admit that an impression of pain, like any other impression, is transmitted by the nerves of general or special sensibility. When it has entered the spinal cord at the posterior roots, the road it follows to reach the higher centres has given rise to much investigation and discussion. According to Schiff, transmission takes place through the grey substance, tactile impressions passing by the posterior fibres; there would thus be two distinct paths, one for the feeling, the other for the sensation properly so-called. Brown-Séquard also admits distinct paths, but through the grey substance alone; the anterior region is devoted to touch, the median to temperature, the posterior to pain. According to Wundt, impressions of touch and temperature have a primary path through the white substance when stimulation is moderate, a secondary path through the grey substance acting as a surplus channel when stimulation is violent. The hypothesis of separate paths, whatever they may be, has the advantage of harmonising with the well-known fact, to which we shall return, that the transmission of pain is slower than sensorial transmission. Lehmann, who takes up a rigidly intellectualist position, cannot admit that the element of feeling has a certain independence in relation to the element of sensation, existing by itself. He believes that the delay is explained by the fact that “pain requires a stronger excitation in the sensorial region than sensation without pain, and that consequently pain is only produced after sensation, as the excitation increases in intensity.” This explanation may be accepted, but it assumes that pain always depends on intensity of stimulus, which is not proved.

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Footnote 13:

Archiv für Anatomie und Physiol., 1885.

Footnote 14:

Goldscheider, Ueber den Schmerz, Berlin, 1894.

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From the spinal cord we reach the medulla, to which some authors assign the chief part. The latest, Sergi, in his book Dolore e Piacere (Milan, 1894), makes it the seat of the affective phenomena in general (pains, pleasures, emotions). What in his opinion testifies to the importance of the medulla in the affective life is the number and nature of the nervous centres situated between the protuberance and the floor of the small ventricle, centres which act on the heart, the vessels, the lungs, the secretions, the intestinal movements. “The vital knot of Flourens is the vital centre and must also be the centre of pleasure and pain, which are merely alterations in the functions of organic life.” In his opinion (which is mine also) the part played by the brain in the genesis of states of feeling has been exaggerated; it only acts in two ways—by rendering the disturbances of organic life, the physical basis of the feelings, apparent to consciousness, and as a cause of stimulation by means of ideas.

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Footnote 15:

Lehmann, Die Hauptgesetze des menschlichen Gefühlslebens, pp. 46 et seq.

Footnote 16:

In his preface Sergi briefly indicates the “antecedents of his theory.” He finds it in the English anatomist Todd, in Hack Tuke, Laycock, Herbert Spencer, Brown-Séquard, etc. I may point out that Vulpian, relying on experiments of doubtful interpretation, localised the emotions exclusively in the medulla, Leçons sur l’Anatomie du système nerveux, xxiv.

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However disposed we may be to restrict the part played by the brain—that is to say the cortical layer—it remains a predominant factor and the final terminus in the process of transmission. Here we plunge into darkness. Researches into cerebral localisation teach us on this subject nothing which is generally admitted. During the first period of such studies, which may be called that of circumscribed localisation à outrance, Ferrier placed the seat of the emotions in the occipital lobes, because, in his opinion, that region of the cortex receives the visceral sensations, because the sexual instinct is dependent upon them, and finally, because these lobes are more developed in women than in men. It is needless to bring forward the numerous criticisms of this thesis. During the second and present period of localisation, which may be called that of disseminated localisation, functional rather than anatomical, authors are little inclined to admit a particular centre for the affective life in general, and still less for pain. All the sensory centres, and even all the motor centres (perhaps there are fundamentally only sensori-motor centres with preponderance of one or the other element), may under certain conditions of activity produce in consciousness a feeling of pleasure or pain.

The hypothesis of a cortical centre is not, therefore, probable; I shall return to this point in discussing the emotions.

II.

The modifications of the organism which accompany physical pain have been so often described that it is enough to trace a slight outline of them. They may be reduced to a single formula: pain is associated with diminution and disorganisation of the vital functions.

1. It acts on the movements of the heart, generally decreasing its frequency; in extreme cases the slackening may go so far as to produce syncope. In animals submitted for experiment in the laboratory, even after removal of the encephalon, painful impressions diminish the cardiac contractions. In man, though the frequency of the pulse is sometimes increased in one form or another, there is always a modification of the rhythm appreciable by the sphygmograph. Bichat was right when he said: “If you wish to know whether pain is real, examine the pulse.”

2. The influence on respiration is more irregular and more unstable; the rhythm becomes abnormal, sometimes rapid, sometimes slow; the inspirations are successively short and deep. But the final result is a notable diminution in the carbonic acid exhaled—that is to say a real slackening of combustion. The temperature is lowered. “I had imagined,” says Mantegazza, “that pain would be accompanied by an increase of heat, muscular action being very intense under the influence of great suffering. Experiment on animals and on myself proved the contrary.” Heidenhain and Mantegazza have in fact noted an average diminution of two degrees centigrade, which, according to the latter, may last an hour and a half or more; it would be due to the contraction of the peripheral blood-vessels.

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Footnote 17:

Mantegazza, Fisiologia del Dolore, chap. iii.

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3. The action of pain on digestion is well known, and shows itself by retardation or disturbance: loss of appetite, arrest of secretions, indigestion, vomiting, diarrhœa, etc. If permanent it acts on the general nutrition, and shows itself in modifications of the urinary secretion, and lasting discoloration of the skin or hair. It is not infrequent to find blanching of the hair, the beard or eyebrows in a few days under the influence of great pain.

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Footnote 18:

For historical and other cases, see Hack Tuke, Influence of the Mind upon the Body, chap. iii.

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4. The motor functions translate pain in two opposite ways: the passive form of depression, arrest, or total suppression of movements, in which the patient seems overcome; the active form, marked by agitation, contortions, convulsions, and cries. The latter case seems to contradict the general formula connecting pain with diminished activity, and seems to me to have been misinterpreted by some authors. This violent excitement, indeed, is an expenditure which quickly makes itself felt and soon leaves the individual enfeebled. It does not flow, as in joy or play, from a surplus of activity; it is weakening, irregular and spasmodic. It seems to me to originate in the instinctive expression of the emotions. The wounded animal shakes the painful part of his body, his paw or his head, as if trying to expel the suffering. All these disorderly and violent motor reactions are a defence of the organism, a useless and often hurtful defence, but resulting from acts which, formerly or under other circumstances, were adapted to their end.

Lehmann experimented on five persons, submitting them in turn to agreeable and disagreeable impressions, in both cases registering the changes in respiration and in the volume of the arm with the help of Mosso’s plethysmograph. His experiments led him to the following conclusions:—

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Footnote 19:

For details of the experiments see Hauptgesetze, etc., pp. 77 et seq., with the accompanying graphic traces.

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Every agreeable impression produces an increase in the volume of the arm and in the height of the pulse, with increased depth of the respiratory cavity.

A disagreeable impression, when weak, immediately produces a diminution in the volume of the arm and the height of the pulse; but almost at once the volume begins to increase, notwithstanding the diminished pulse, and usually passes beyond its normal state, even when the pulse has returned to its first condition. If the impression is strong but not painful these changes are accentuated, and from the first are accompanied by deep inspirations. Finally, if the impression is painful, not only considerable changes of volume, but powerful respiratory movements and disturbance of the voluntary muscles are produced.

Disagreeable stimulation produces at first a spasm of the superficial vessels, relaxation of the deep vessels, and decreased fulness of the heart’s contractions. The first two factors together produce a sudden and strong diminution in the volume of the limbs. The last two factors together produce a diminished height of pulse, and in consequence of the enfeebled cardiac contractions there is a stasis of the venous blood showing itself in the increased volume of the limb.

These bodily modifications, of which I have summarised the chief features, are commonly regarded as the effects of pain, and this opinion seems even to be accepted in many works on psychology. The opinion cannot, however, be accepted. Pain considered as a psychic event, an internal fact, a pure state of consciousness, is not a cause but a symptom. The cause is the stimulation (of whatever nature) which, coming from the exterior environment, acts on the external senses, or coming from the interior environment, acts on the organic life. It is shown in two ways: on the one hand in the state of consciousness which we call pain, on the other by the physical phenomena above enumerated. The consciousness expresses in one way what the organism expresses in another way. This is not a mere opinion, for experiment shows that circulatory, respiratory, and motor modifications are produced when consciousness is probably defective. Mantegazza has shown that if an intact animal is subjected to pricks, cuts, and burns, cardiac troubles follow; but that the same phenomena are produced after the removal of the encephalon. François-Franck, investigating the effects of painful stimulation on the heart, found that the anæsthesia of chloroform suppresses troubles of the heart, while, on the contrary, removal of the cerebral hemispheres fails to abolish them. Formerly, Longet and Vulpian maintained that in animals reduced to the medulla and lower parts of the cerebro-spinal axis the cries and movements that occur when they are pinched are purely reflex; this interpretation has been contested by Brown-Séquard. In human anencephalic (or headless) monsters, cries, movements of suction and the like have been observed during the few days they are able to live. We must then admit either that the state of consciousness we call pain can be produced in the absence of the brain, or else that the physical phenomena can exist alone without their psychic concomitant.

Pain (as a state of consciousness) is only a sign, an index, an internal event revealing to the individual his own disorganisation. The only case in which pain is a cause is when, being firmly fixed in consciousness and completely filling it, it becomes an agent of destruction, but then it is only a secondary cause. That is one of those cases, so frequent in the sciences of life, in which what is primarily an effect becomes in turn a cause. It is therefore an error, though common to most psychologists, to consider pain and pleasure as fundamental elements of the affective life; they are only marks, the foundation is elsewhere. What would be said of a doctor who confused the symptoms of a disease with its essential nature?

We touch here a point so important that it needs emphasis. The thesis that pain is only a symptom, and altogether, in spite of the sovereign part it plays in human life, a superficial phenomenon in relation to the tendencies which lie at the basis of the affective life, finds support in the facts of analgesia, the disappearance of capacity to feel pain. This insensibility presents itself under two forms: spontaneous and artificial.

Spontaneous analgesia is the rule in hysteria; it may vary in degree, position, and extent. The demonologists of the Middle Ages and the Renaissance knew these migrations of insensibility to various parts of the body, and they sought with care for the stigmata diaboli, that is, the regions insensible to pain. Some authors assign to it a purely psychic cause: painful impressions cannot be felt because they are outside the field of consciousness, which in these patients is in an almost permanently disassociated, scattered, and destroyed state. It is, on the contrary, certain that an intense fixed idea, profound concentration of attention, fanatical exaltation, can produce temporary or permanent analgesia. Many soldiers, in the heat of battle, have not felt their wounds. Pascal, plunged in his problems, escaped his neuralgias. The Aïssaouas, the fakirs, certain Lamas of Thibet tear and cut themselves, secured against pain by delirium, and one may well believe that many martyrs, in the midst of their torture, have only experienced a sense of rapture. In certain forms of insanity (maniacal excitement, melancholia, idiocy, etc.) this spontaneous analgesia is frequent, and takes on extraordinary forms. Numerous examples may be found in special treatises. One crushes glass in his mouth for half-an-hour without feeling any pain. Another breaks his leg in a struggle, and a fragment of the tibia projects through the torn skin, yet he continues to pursue the object of his rage, and then sits down to eat without the least sign of pain on his face. There are many who, intentionally or by accident, plunge their arms into boiling water or place them on a red-hot stove, until the skin falls off in shreds, without appearing to be disturbed. An endless series of such facts might be narrated.

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Footnote 20:

Pierre Janet, État Mental des Hystériques.

Footnote 21:

See especially Morel, Traité des Maladies Mentales (pp. 324 et seq.), for a summary of many curious facts.

Footnote 22:

Weir Mitchell (Medical Record, 24th December 1892, quoted by Strong, Psychological Review, 1895, vol. ii. p. 332) reports the following extraordinary case of natural analgesia: Man who died at age of fifty-six, cheerful and corpulent, weighing some 250 pounds; intelligent, and vigorous both in body and mind, with a considerable reputation as a lawyer and politician. Having a finger wounded in a crush during a political campaign, he removed it himself by biting it off and spitting it on to the ground. He had an ulcer on the toe which resisted treatment for three years without ever causing him the slightest pain. He also had an abscess in the hand which spread to the fore-arm and arm, causing enormous swelling and endangering his life; the lancet was used without precaution, and throughout he felt no pain. It was the same with an operation for cataract on both eyes; he remained motionless as a statue. It was only during his last illness that he complained of some pain, but that quickly passed away, and he had returned to his state of natural insensibility before he died.

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The artificial analgesias, produced by chloroform and the various anæsthetics employed in surgical operations, are more instructive. It has been asked if the movements, objurgations, and cries of some patients do not prove that the analgesia is not complete, even when it seems so. Richet has expressed the opinion that it is not consciousness but recollection which is defective; he regards the pain as so rapid that it is only a mathematical movement and leaves no echo behind it, there being a series of evanescent states of consciousness. It is quite possible to maintain this hypothesis; but the most important fact recorded by this author seems to me to be that, when pain has disappeared, a certain degree of knowledge of it remains. In other words, there is a process of scission: the feeling man has disappeared, the intellectual man remains. In many simple operations the contact of the instrument is often felt, but not the pain. But there are more complex cases. "In an operation for fissure of the anus with fistula, the patient felt the contact of the scissors and easily distinguished four incisions; she could not speak, but felt no suffering. In the course of a similar operation I asked the patient, ‘How old are you?’ She replied that she was forty-one, but when restored to consciousness she could recall no sensation of wound or burn and complained that the operation had not taken place. I asked another during the operation, ‘How are you getting on?’ the reply was, ‘Not badly.’ At the same moment I pricked her vigorously; she felt nothing. Again, in another case when I introduced a forceps into the mouth to hold the tongue the patient said, ‘Take away that cigarette.’ On awaking he could remember nothing. Another when a quill was passed beneath his nose said, ‘Do not tickle me’ at the moment when the large arteries were being tied, the most painful part of the operation. Finally, a man under chloroform, while his spermatic cord was being tied, heard the clock strike and tranquilly remarked, ‘Half-past eleven,’ recalling nothing when he awoke."

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Footnote 23:

Richet, Recherches expérimentales et cliniques sur la Sensibilité, pp. 258, 259.

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I have quoted these facts to show the extent to which pain, as a state of consciousness, is separable, how it can be added or cast off, and to what extent it presents the character of an epiphenomenon.

This relative independence of the pain-phenomenon, against which the intellectualists have always rebelled, seems to me corroborated by the retardation which I have already noted in passing. If we strike a corn while walking, we feel the shock before the pain; the cold of the knife is felt before the pain of the incision. Beau estimates that pain is delayed seven-tenths of a second behind the tactile impression. Burckhardt, by precise investigation, fixes the rapidity of transmission in the cord at 12 m. 9 per second for painful impressions, and 43 m. 3 for the others. In certain diseases like tabes dorsalis the pain may be separated from the needle-prick which causes it by from one to two seconds. Many other facts may be quoted. If a fold of the skin is seized in a pressure forceps, stopping at the moment when the pressure is sufficient, pain, not felt at first, gradually appears, coming in waves, and being at last unbearable. A man whose thumb was seized in a machine only knew of his injury by feeling his arm drawn, and only began to suffer a quarter of an hour afterwards. It has also been remarked that the syncope produced by violent shocks and traumatism does not appear at once; between the accident and the fainting several minutes may elapse.

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Footnote 24:

See on this point Lehmann’s embarrassed explanation, Hauptgesetze, etc., pp. 51 et seq.

Footnote 25:

Richet (op. cit., pp. 289, 290 and 315, 316) gives many illustrations.

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Pain is the result of a sum of impulses. Naunyn has shown that, in tabes, a mechanical stimulus (like a hair on the cutaneous surface of the foot), which is below the threshold of consciousness both as contact and as pain, if repeated from 60 to 600 times a second, is perceived at the end of from six to twenty seconds, and soon becomes an intolerable pain to the patient.

Although excessive sensibility to pain (hyperalgesia) belongs to the pathology of our subject, which will be dealt with in a later chapter, it is necessary to say a few words about it in contrasting it with analgesia, especially in view of the conclusions here reached. This condition is more difficult to observe than insensibility, because here there is only a difference of degree, not the difference between being and not being. But in some cases there is so great a disproportion between the stimulus and the subject’s reaction that we may say without hesitation that sensibility is no longer normal.

It has been observed, in a general manner, that the lower races are not very sensitive to pain. Thus Negroes in Egypt endure, almost without suffering, the most extensive surgical operations (Pruner Bey), and Mantegazza (op. cit., chap. xxvi.) reports a large number of examples. In the peasant sensibility is usually less keen than in the town-dweller, and it may be admitted without hesitation that susceptibility to pain increases with civilisation; what is called stoicism should often be called a feeble degree of sensibility. Hyperalgesia is best seen in cases of extreme nervous over-excitement. In some it is generalised, constituting the “supplicium neuricum,” and the patient says that he is the prey of unspeakable torments. It is less frequent in the case of the special nerves, but is sometimes met. One suffers from the slightest noise, and cannot tolerate the least smell. Pitres quotes the case of a person who shut herself up in a dark room, only coming out at night with a thick shade against the rays of the stars. Those who entered her dark room during the day had to wear sombre clothes, completely concealing the shirt-collar, of which the white reflection was horribly disagreeable to her. Cutaneous hyperalgesia is very common, sometimes extending over the whole body, sometimes disseminated in patches. Weir Mitchell, in his book on injuries of the nerves, reports numerous examples; among others, a wounded soldier to whom the mere crumpling of paper caused atrocious pain. Opium-smokers, when they interrupt their habits, feel the least breath of air as icy cold, and complain of intolerable pains in all parts of the body. Hyperalgesia of the deep tissues is also frequent among the hysterical and hypochondriacal.

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Footnote 26:

Pitres, Leçons Cliniques sur l’Hystérie, i. p. 182.

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It must be remarked in passing that just as insensibility to pain (analgesia) is independent of incapacity to receive sensorial impressions (anæsthesia), so hyperalgesia is distinct from hyperæsthesia. The latter is a power of perception much surpassing the average; it is known that certain races and individuals possess extraordinary visual, auditory, or olfactive acuteness; the tactile hyperæsthesia of the blind is also known, and in hypnotised subjects the delicacy of the senses has sometimes seemed miraculous. Hyperalgesia then, like analgesia, shows that pain is relatively independent of the sensations which arouse it.

III.

We may conclude, from what goes before, that though physical pain (of which alone I am speaking at present) is always bound to an internal or external sensation, and forms part of a psychic complexus, it may be separated and disjoined. It has then its own conditions of existence, and we may, in advance, say as much for pleasure.

What are these conditions of existence? or, more simply, what is pain in its nature? At the present time there are two distinct doctrines on this point: one, which counts few adherents, regards physical pain as properly a sensation; the other, more generally admitted, regards it as a quality of sensation, or more correctly, as an accompaniment, a concomitant.

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Footnote 27:

The debates on this subject have chiefly been carried on by American psychologists. See Rutgers Marshall, Pain, Pleasure, and Æsthetics (1895); Nichols, “Origin of Pleasure and of Pain” (Philosophical Review, i. pp. 403 and 518); Strong, “Psychology of Pain” (Psychological Review, July 1895, and for criticisms and replies, Sept. and Nov. 1895, Jan. 1896); Luckey, “Some Recent Studies of Pain” (Am. Journal of Psychology, Oct. 1895).

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The first, though recent in its complete form, is not without antecedents. It found a momentary support in the supposed discovery of pain-bearing nerves. Nichols, one of the promoters of this hypothesis, has developed it in this direction; but the attempt has proved futile. Strong, one of its warmest partisans, supported himself on other grounds. In his opinion the difficulty arises from the ambiguity of the word pain, which may mean two things—displeasure (Unlust), or physical pain in the positive sense. He reduces the latter to cuts, pricks, burns—in short, to those pains that affect the skin. It is, in his opinion, strictly a sensation like blue or red—not an attribute, but a substantive. The pain of a burn, for instance, is a mixture of two sensations, heat and pain. General sensibility is composed of four kinds of sensibility: touch, heat, cold, and pain. Each can be abolished separately. Cocaine and chloroform suppress pain, not touch; saponine suppresses touch, not pain; syringomyelia destroys sensibility to pain and heat, not touch; in some forms of neuritis there is suppression of touch without analgesia. These various facts are invoked as the chief arguments in favour of the hypothesis of pain-sensation, though they may all be explained also by the other doctrine.

This hypothesis is full of difficulties. First, there is the absence of anatomical basis, of special organs and nerves. It will be necessary to return to this important point when dealing with pleasure (Chap. iii.). Nichols tells us that there is nothing to prove that nerves of pain do not exist, though they have not been experimentally established—which is indeed something; that histological research could not determine in the peripheral apparatus what belongs to touch and what belongs to pain; and that proof must be deduced from cases of tactile sensation without pain and vice versâ—which fails to constitute any degree of proof. Moreover, the distinction set up between displeasure (moral pain?) and physical pain is arbitrary, factitious, wholly unjustified. There is, however, a still less admissible distinction. Strong expressly declares that he limits himself to pains localised on the cutaneous surface. Now by what right can we cut off the group of physical—strictly physical—pains, the states of torture originating in the internal organs, the multiple neuralgias as intolerable as any external pain, without speaking of discomfort, prostration, exhaustion? Are these also sensations, or something else? We are not told. Finally—and Strong himself has stated the objection—it must be acknowledged that we should here have a strange kind of sensations which do not externalise themselves. While other impressions, visual, auditory, tactile, gustatory, olfactive, are referred to causes which provoke them, the pains of a prick, a cut, a burn remain strictly subjective and are not located in the needle, the knife, the burning coal, as we locate a sound in the bell, a bitter taste in absinth. The only possible reply (which the partisans of pain-sensation have not made) would be that this phenomenon has a character of its own; it always remains a sensation, and never becomes a perception, whence the absence of externalisation. But then why assimilate it to blue or red? Moreover, pain-sensation, as it exists in the adult, approaches so closely to the affective state, that what is essential in the doctrine of pain-sensation vanishes. Whatever may be thought of the probability of some future discovery of terminal organs for physical pain, as Rutgers Marshall remarks, it must be agreed that there is no proof of the existence in the environment of a special stimulus to which physical pain specially corresponds, and for that reason also it would be a great mistake to place in the well-determined class “sensation,” a mental state which lacks one of the most marked characteristics of sensation in general. That conclusion is mine also.

The opposite doctrine, which has of late been called the quale-theory, is often maintained in an unsatisfactory form, because in fact it reduces itself to an affirmation of quantity. The pain which accompanies sensation may depend either on its intensity or on its quality alone.

It is needless to insist on the first case, since many old authors never cease repeating that the painful impression is the result of a stimulation which is strong, intense, violent, prolonged.

On the contrary, it is necessary to remark that this exclusive affirmation cannot be applied everywhere and always. This evidently appears in the cases of hyperalgesia, which is the reason why I brought them forward. The very disagreeable sensation which is caused by a knife against the skin certainly comes from the nature rather than the intensity of the stimulus. Beaunis remarks that certain odours, tastes, and contacts are painful at once, and do not need to be intense. Did the contact of the quill which threw Weir Mitchell’s patient into a state of anguish act by its intensity? No doubt we must recognise that hyperalgesias constitute a group apart, not strictly comparable with ordinary cases; they are pathological forms, variable in degree; but the pathological is merely an exaggeration of the normal. The error of those who refer pain solely to intensity of stimulation is in considering objective conditions only; they forget the part played by the sentient subjects. Pains which depend on the quality of the stimulus are especially of subjective origin, because the degree of excitability in the patient’s nervous elements is the essential ruling factor.

If we admit that these two conditions—intensity and quality—act one upon the other, what afterwards happens? What is the intimate nature of the pain-producing process? The hypothesis which is most natural and simple, and in agreement with the mechanical conceptions predominant in the biological sciences, would be founded on the admission that pain corresponds to a particular form of movement. On this supposition, the affective nervous road, from the periphery to the centres, would be traversed by three different kinds of movement or of molecular disturbance: the first giving birth to pure sensation, that is to say a state of knowledge, an intellectual state; the second, which may or may not be present, giving birth to pain; the third, also either present or absent, giving birth to pleasure.

There is another possible hypothesis, quite different from the others, which I should be willing to accept, but which cannot be presented as more than a theory. It would consist in attributing the genesis of pain to chemical modifications in the tissues and nerves, especially the production of local or general toxins in the organism. Pain would thus be one of the forms of auto-intoxication. Oppenheimer alone seems to me to have worked in this direction. In his opinion, as regards the origin of pain, “the real cause, in any sensorial or other organ, resides in a change in the tissues, especially a chemical change, by which either the products of destruction rise above the normal average, or else modifications result from the presence of a foreign body in the organism.” The connection between the peripheral tissues and the centres would be by the vaso-motor nerves (constrictor or dilator). The tissues would be the terminal organs of pain, the vaso-motors the paths of conduction. In organs which only undergo slight changes when active (tendons, ligaments, bones, etc.) conscious sensibility is almost absent. “Pain is not, as many believe, the highest degree of sensation produced in the organs of special sense; it is the most intense sensation produced in the vaso-motor nerves under the influence of violent stimulation.”

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Footnote 28:

Schmerz. und Temperaturempfindung, Berlin, 1893.

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This hypothesis will perhaps be justified by the future. I shall return to it when studying the emotions. We shall then see that these are accompanied by deep and well-established chemical modifications in the organism.

Physical pain is a large subject, which, as may be seen, has not been neglected of late, and concerning which there is still much to say. It is not possible, however, to deal further with it here, since it only occupies a limited area in the psychology of the emotions.