Chapter IV: Negative Inductions (1)

84. I fancy some reader exclaiming: “All your reasoning, and all your marshalled facts, are swept away by the irresistible evidence of human patients with injured spinal cords, whose legs have manifested reflex actions, and who nevertheless declared they had _no sensation whatever_ in them. We can never be sure of what passes in an animal; but man can tell us whether he feels an impression, or does not feel it; and since he tells us that he does not feel it, _cannot_, however he may _try_, we conclude that reflex action may take place without sensation.”

As this is the one solitary fact which is held to negative the mass of evidence, anatomical and physiological, in favor of the Sensibility of the spinal cord, it is necessary that we should candidly examine it. No reader will suppose that during the twenty years in which I have advocated the doctrine expounded in this volume, I have not been fully alive to the one fact which prevented the general acceptance of the doctrine. From the first it has seemed to me that the fact has been misinterpreted.

85. Certain injuries to the spinal cord destroy the connection of the parts below the injury with the parts above it; consequently no impression made on the limbs below the injured spot is transmitted to the brain, nor can any cerebral incitation reach those limbs. The patient has lost all consciousness of these limbs, and all control over them. Hunter’s patient on being asked if he felt any pain when the prick caused his leg to kick, answered, “No: but you see my leg does.” This answer has been regarded as a drollery; I think it expressed a physiological truth. For on the assumption that the whole of the cerebro-spinal axis had one uniform _property_, corresponding with its uniform structure, and various _functions_, corresponding with the variety of organs it innervates, a division of this axis would necessarily create two independent seats of Sensibility, and interrupt the consensus of their functions. In such a case it would be absurd to expect that the cerebral segment could be affected by, or co-operate with, what affected the spinal segment.

Now, when a man has a diseased spinal cord, the seat of injury causes, for the time at least, a division of the whole group of centres into two independent groups. For all purposes of sensation and volition it is the same as if he were cut in half; his nervous mechanism _is_ cut in half. How then can any cerebral control be obeyed by his legs; how can any impression on his legs be felt by his cerebrum? As well might we expect the man whose arm has been amputated, to feel the incisions of the scalpel, when that limb is conveyed to the dissecting-table, as to feel by his brain impressions made upon parts wholly divorced from organic connection with the brain.

86. But, it may be objected, this is the very point urged. The man himself does not feel the impressions on his legs when his spine has been injured; he is as insensible to them as to the dissection of his amputated arm. Very true. _He_ does not feel it. But if the amputated arm were to strike the anatomist who began its dissection, if its fingers were to grasp the scalpel, and push it away, or with the thumb to rub off the acid irritating one of the fingers, I do not see how we could refuse to admit that the _arm_ felt although the _man_ did not. And this is the case with the extremities of a man whose spine is injured. _They_ manifest every indication of sensibility. In the frog and pigeon the legs manifest the unmistakable control which we ascribe to volition. It is true that the man himself, when interrogated, declares that he feels nothing; the cerebral segment has attached to it organs of speech and expressive features, by which _its_ sensations can be communicated to others; whereas the spinal segment has _no_ such means of communicating _its_ sensations; but those which it _has_, it _employs_. You can ask the cerebral segment a question, which can be heard, understood, and answered; this is not the case with the spinal segment: yet if you _test_ its sensibility, the result is unequivocal. You cannot ask an animal whether it feels, but you can test its sensibility, and that test suffices.

87. The question we have to decide, therefore, is not whether a patient, with an injured spine, can feel impressions on, or convey voluntary impulses to, limbs below the seat of injury--for as respects the nervous mechanism these limbs are separated from him, no less than if actual amputation had taken place--the question is, whether these separated limbs have any sensibility? And the answer seems to me unequivocally affirmative. I assert, therefore, that if there is ample evidence to show that the spinal centres have sensibility, when separated from the cerebral centres, such evidence can in no respect be weakened by the fact that a man with an injured spine is unconscious of impressions made below the seat of injury; since such a fact necessarily follows from the establishment of two centres: the parts above are then not sensitive to impressions on the parts below; nor are the parts below sensitive to impressions on the parts above; but each segment is sensitive to its own affections.

88. Every one knows that there are animals, low down in the scale, which may be cut in two, each half continuing to live, and each capable of reproducing its lost segments. Would any one, seeing these separated halves move and manifest ordinary signs of sensibility, venture to say that the one half was a living, the other an insentient, mechanism? And since the one half had eyes, mouth, tentacles, etc., while the other half had none of these, would the observer be surprised that the functions of the one differed from those of the other in these respects? Why, then, should he not conclude the same of the two halves of the human mechanism, when disease had divided them?

89. The man, you urge, does not feel the prick on his leg. This is true, because “the man” here designates the seeing, hearing, tasting, smelling, talking, thinking group of organs--to the exclusion of the limb or limbs which are no longer in sensitive connection with this group. When a leg is amputated “the man” remains--a truncated man, indeed, yet still one having all the distinguishing human characters. Yet obviously in strict language we can no longer say that the man is the _same_ as he was. “Man” or “animal” means the complex whole; and each anatomically separable part forms one constituent of that whole. The medulla oblongata and spinal cord innervate certain parts; the mesencephalon innervates others; the cerebrum rises above the whole. If after removing one limb, then another, we continued truncating the organism till we left only the head, should we call _that_ the man? Clearly not. Should we even suppose that the intact brain--the supposed seat of sensation and volition--still felt, and willed? Clearly not. There is absolutely no evidence, however faint, of the isolated head manifesting any sensational and volitional phenomena; whereas there is ample evidence of the truncated spinal cord manifesting some of these phenomena. And this is intelligible when we understand that the nerve-centres stimulate into action the organs they innervate, but do not by themselves play any other part.

90. “The man” then does not feel the prick on his leg, but his leg feels it. The man has no consciousness of what takes place outside the sphere of his sensitive mechanism; and the leg is now outside that sphere. Consciousness--as distinguished from Sentience in general--we have seen to be a resultant of the composition of forces co-operating at the moment; the Sensibility of the spinal cord in the regions below the injury cannot _now_ enter into that composition. It is detached from the upper organs. But inasmuch as the organs it innervates are still living and active, the functions of this detached portion are still displayed. We have seen the dog with divided cord capable of Urination, Defecation, Generation, etc.; its hinder legs, though not moving in a consensus with the forelegs, yet moved independently; and all the normal reflexes of the parts followed on stimulations. To say that “the dog” showed no signs of Sensibility when its hinder limbs were irritated, is identifying “the dog” with the anterior half of the organism which was not in connection with the posterior half. It is equally true that the posterior half showed no signs of Sensibility when the anterior was irritated. The two halves were united by the circulation, nutrition, etc., but disunited as to sensation and volition.

91. Do I then suppose the separated half of an animal to feel pain and pleasure, hope and terror? The reader who has attentively followed the exposition will be at no loss to answer. Pain, pleasure, hope, and terror, are special modes of Sensibility, dependent on particular neural combinations. The organs comprised in the anterior half of the animal furnish the main conditions for these special modes, whereas the organs comprised in the posterior half furnish few or none of those--they contain none of the special Senses, and they are without the chief combining centre, the brain. But since we know that a large amount of normal Sensation is wholly without the special characters of pain, pleasure, hope, or terror, we need not hesitate to assign Sensation to the spinal cord because these characters are absent.

92. All I contend for is that the spinal centres have Sensibility of the same _order_ as the cerebral centres; and that in the normal organism this Sensibility enters as a factor into the general Consciousness--no one portion of the nervous system being really independent of all the others, all co-operating in every result. Over and over again I have had to insist that the property of Sensibility is only the general condition of Sensation; and that each particular sensation receives its _character_ from the organs innervated, _plus_ the reaction of the whole organism. Obviously, therefore, the peculiar character of a sensation, or “state of consciousness,” must vary with the variations in either of these factors. To say that every segment of the spinal cord has Sensibility, is not saying that an excitation of that segment will produce a particular sensation of definite character; because for this definite character there is needed the co-operation of all those parts of the mechanism which enter into the complex product.

* * * * *

93. And here attention must be called to a double fallacy pervading the arguments on the other side. It is always assumed that the reactions of an organ, or part of the organism, when separated from the rest, are typical of their reactions when forming constituents of the normal organism. Nothing of the kind. The movement of a muscle or a limb separated from the body may resemble that movement when normally effected--but only as the movements of a mechanical bird resemble those of a living bird: the modes of production are different. So that were we to grant the postulate of the brain being the exclusive seat of sensation, we should still deny that an action which was effected after removal of the brain was typical of the action effected when the brain was present. The leg of Hunter’s patient jerked when the skin was irritated; but this action could not be altogether the same as the similar action in a leg united with the rest of the sensitive mechanism. Nor is this all. The leg may have been insensible, the spinal segment which innervated it may have been wholly without Sensibility, and still we should have to question the logic which extended such an inference to the very different and far more complex actions of decapitated animals. On this ground:--The leg is, by the hypothesis, insensible because cut off from all connection with the sensitive mechanism. But this is not the case with the decapitated animal: there still remain the essential parts of a sensitive mechanism--all the chief organs are still in activity, still manifesting their functions. Decapitation has produced a great disturbance in the mechanism, and has removed an important centre; but nevertheless every impression excites a connected group of centres, and this group responds.

* * * * *

94. In conclusion, unless we adopt the opinion that Sensation--Consciousness--Sensibility, is something not belonging to the physiological properties of the nervous system in a vital organism (the opinion held by spiritualists), there seems no alternative but to adopt the opinion advocated in this volume, namely, that the physiological properties of the nervous system are inseparable from every segment of that system; and the functions are the manifestation of those properties as determined by the special organs with the co-operation of all.

FOOTNOTES

[1] WORDSWORTH.

[2] Crystals not only grow by assimilation, but even repair injuries, with a certain superficial resemblance to the repair of animal tissues. Thus, according to the experiments of JORDAN cited by Sir JAMES PAGET (_Lectures on Surgical Pathology_, I. 153, and 2d ed. p. 115), an octohedral crystal of alum, if fractured and replaced in a motherlye will in a few days exhibit a complete restoration of the original form. The whole crystal increases, but the increase is greatest on the broken edge, and the octohedral form is completely renewed. (Comp. § 113.)

[3] Cited by DRYSDALE, _Life and the Equivalence of Force_, Part II. p. 149.

[4] RANKE, _Die Lebensbedingungen der Nerven_, 1868, p. 80.

[5] “Il n’y a peut être pas un seul phénomène chimique dans l’organisme qui se fasse par les procédés de la chimie de laboratoire; en particulier il n’y a peut être pas une oxydation qui s’accomplisse par fixation directe d’oxygène.”--CLAUDE BERNARD.

[6] Dr. MADDEN, in his essay _On the Relation of Therapeutics to Medicine_, 1871, p. 5, gives a remarkable illustration of what may be called the frustration of chemical affinity effected by mechanical conditions. “Before calico can be printed, every loose particle of cotton must be removed from the surface in order that the colored inks may not run. This removal is effected by passing the calico over and in contact with a red-hot iron cylinder, and by regulating the rapidity with which the cylinder revolves, the intense heat burns off the loose fibres, yet does no injury to the woven cloth. In other words, the changes in the relation of the high temperature and the cotton are too rapid to admit of the fibre combining with the oxygen. Let the rate of revolution be reduced but very little, and the calico would burst into flames.” Any one who has snuffed a candle with his fingers will understand this. Dr. Madden further instances certain fulminates which can be detonated in contact with gun-cotton without causing it to explode--the extreme rapidity with which the fulminates expand is too great to enable the gun-cotton to adjust its movements to this new motion. Precisely the same kind of thing occurs in organized matter. If the rate of its changes be reduced below a certain point, the ordinary chemical affinities will assert themselves.

[7] I am often reminded of the surprising movements of particles of carbonate of lime in water which my friend Professor PREYER showed me during a visit to Bonn. He had removed one of the concretions, usually found in connection with nerves along the spine of old frogs, and crushed it in water; under the microscope the seeming spontaneity and variety of the movements of the particles was such that had we not known their origin we should certainly have attributed them to vitality: no infusoria could have moved with more seeming spontaneity. It is hardly physiological to conclude that because fragments of tissue manifest ambœbiform movements therefore they are alive (STRICKER, art. _Die Zelle_ in his _Handbuch der Lehre von den Geweben_, 1868, p. 7), or that the heart removed from the body is _alive_ because it still beats. LIEBERKÜHN, _Ueber Bewegungserschsinungen der Zellen_, 1870, pp. 357–359, cites examples of such movements in undeniably dead substances. For Life, we demand not only Movement, but Functional Activity.

[8] TELESIUS, _De Natura Rerum_, 1586, V. 184. TELESIO might have been saved from the mistake had he attended to what NIPHUS had said on the point in his _Expositio subtilissima_, 1559, p. 245. Comp. also PHILELPHUS, _Epist. Familiarum_, 1502, p. 253, _verso_.

[9] The authorities just cited are ARISTOTLE, _De Anima_, Lib. II. c. I. KANT, _Kritik der Urtheilskraft_. MÜLLER, _Physiology_. BEALE, _Bioplasm_, and _Introduction to Todd and Bowman’s Anatomy_. SCHELLING, _Erster Entwurf_, and _Transcendent. Idealismus_. BICHAT, _Recherches sur la Vie et la Mort_. STAHL, _Theoria Vera Medica_. DUGÈS, _Physiologie Comparée_. BÉCLARD, _Anatomie Générale_. LAMARCK, _Philosophie Zoologique_. COMTE, _Cours de Philosophie Positive_. OWEN’S _Hunterian Lectures_, 1854. HERBERT SPENCER, _Principles of Biology_.

[10] FLETCHER, as quoted by DRYSDALE, _Life and the Equivalence of Force_, Part II. p. 120.

[11] ROBIN et VERDEIL, _Traité de Chimie Anatomique_, 1853.

[12] PAGET, _Lectures on Surgical Pathology_, p. 14.

[13] Comp. HAECKEL, in _Siebold und Kölliker’s Zeitschrift_, 1865, p. 342, and his _Generelle Morphologie_, 1866, I, 135, 336.

[14] In the _Archiv für mikros. Anatomie_, 1865, p. 211.

[15] Here organization is the simplest form of all--molecular organized structure, which in the higher forms becomes tissue structure, and organ structure. The word _structure_ properly means orderly arrangement of different materials; and molecular structure refers to the different proximate principles which constitute the organized substance. Usually, however, the word _structureless_ indicates the absence of _visible_ arrangement of the parts; a cell has structure since it has nucleus and protoplasm.

[16] In the cell-theory established by SCHLEIDEN and SCHWANN, in 1838, and which has formed the basis of modern histology, the cell-wall was endowed with an importance which can no longer be upheld now that the existence of independent organisms, and of cells, without a trace of enveloping membrane has been abundantly observed. Cells without walls were first described by COSTE in the _Comptes Rendus_, 1845, p. 1372. They were also described by CHARLES ROBIN in 1855, _Dict. de la Médicine_, art. _Cellule_. But little notice was taken until MAX SCHULTZE, in his famous essay, _Ueber Muskelkörperchen und was man eine Zelle zu nennen habe_, which appeared in _Reichert und Du Bois Reymond’s Archiv_, 1861,--BRUECKE, in his memoir, _Die Elementarorganismen_, 1861,--and LIONEL BEALE, in his _Structure of the Simple Tissues_, 1861,--all about the same time began the reform in the cell-theory which has effected a decisive change in the classical teaching. LEYDIG claims, and with justice, to have furnished important data in this direction (_Vom Bau des thierischen_ _Körpers_, 1864, I. p. 11). The student interested in this discussion should consult MAX SCHULTZE, _Das Protoplasma der Rhizopoden und der Pflanzenzellen_, 1863; HAECKEL, _Die Radiolarien_, 1862; the controversial papers by REICHERT, in his _Archiv_ (beginning with the Report of 1863), and MAX SCHULTZE, in his _Archiv für mikros. Anat._, with HENLE’S judgment in his _Jahresberichte_, and KÜLLIKER’S summing-up in the last edition of his _Gewebelehre_. For a full yet brief history of the cell-theory see DRYSDALE, _The Protoplasmic Theory of Life_, 1874, pp. 96–106.

[17] At the time this was written, I had some fish ova in the course of development. Out of the same mass, and in the same vessel, all those which were supported by weed at a depth of half an inch from the surface, lived and developed; all those, without exception, that were at a depth of two to four inches, perished. In ordinary parlance, surely, nothing would be objected to in the phrase, “these ova were all in the _same_ Medium”; the water was the same, the weed the same, the vessel the same; yet some difference of temperature and carbonic acid made all the difference between life and death. Another curious fact was observed; I removed eight of these ova with active embryos, and placed them in a large watch-glass containing a solution (one half per cent) of bichromate of ammonia. In this acid the embryos lived and were active fifty-seven hours, although other embryos placed in a similar watch-glass containing pond-water, survived only forty hours. The non-effect of the acid was probably due to the non-absorption which nullifies the effect of certain virulent poisons when they are swallowed; but why the fish should live longer in the acid than in the simple water, I do not at all comprehend.

[18] AGASSIZ, _Essay on Classification_, 1859, p. 15.

[19] HAECKEL, _Generelle Morphologie_, II. 211.

[20] See on this last point RANKE, _Die Lebensbedingungen der Nerven_, 1868, p. 34.

[21] See WALDEYER, art. _Eierstock_, in STRICKER’S _Handbuch der Lehre von den Geweben_, 1870, p. 570. “I found in a fœtus, which, in a case of extra-uterine pregnancy, had lain thirty years in the body of its mother, the structure of the muscles as intact as if it had been born at its full time.”--VIRCHOW, _Cellular Pathologie_, Lect. XIV.

[22] See BEALE, _The Structure of the Simple Tissues_, 1861; the Introd. to his edition of _Todd and Bowman’s Physiological Anatomy_, 1866; and _How to Work with the Microscope_, 4th ed., 1868; also _Bioplasm_, 1872.

[23] “The physical property of the tissue does not depend upon this matter, _nor is its function due to it_.”--Beale, _Introduction to Todd and Bowman_, p. 11. That is to say, he regards even contractility and neurility as physical, not vital facts.

[24] In turning over the pages of a work which was celebrated some half-century ago--RUDOLPHI’S _Grundriss der Physiologie_--I was interested to find a clear recognition of this biological principle: “Alle Theile aller Organismen,” he says, I. 233, “sie mögen noch so verschieden in ihrem Bau, in ihrer Mischung, und in ihrer Thätigkeit seyn, sind ohne Ausnahme _als organisch und mithin als lebend zu betrachten_.” In a note he adds that physiologists have considered certain solid parts--epidermis, nail, hair, and bones--to be dead; “but all these are organically developed, and are in direct connection with the other parts.”

[25] VIRCHOW, _Die Cellular Pathologie_, 1860, Lect. I.

[26] BEALE, _Bioplasm_, 104.

[27] KÖLLIKER, _Gewebelehre_, 5th ed., 1867, p. 12.

[28] Nevertheless there are some facts directly contradicting his conclusions. For example, he considers the axis cylinder of the nerve to be formed material, and agrees with MAX SCHULTZE and others as to its fibrillated structure; yet according to LISTER and TURNER, GERLACH and FREY, the axis cylinder is deeply stained by carmine, and in this respect resembles the nucleus of protoplasm.

[29] From the quite recent experiments M. BAILLON has submitted to the _Académie des Sciences_ (15th February, 1875), it appears that although cut flowers absorb colored fluids, the roots when intact only absorb the fluid, and reject the coloring matters, by a veritable dialysis.

[30] GERLACH cited by RANKE, _op. cit._, p. 76.

[31] STEIN, _Der Organismus der Infusionsthierchen_, 1859, p. 76.

[32] STAHL had a profound conviction of the radical difference, though he was not able to point out the conditions involved. See his _Disquisitio de mechanismi et organismi vera diversitate_.

[33] M. FERNAND PAPILLON has shown that animals may be fed with food deprived of phosphates of lime if its place is supplied with magnesia, strontia, or alumina; they make their bones out of these as out of lime. But no such substitution is possible in muscle, nerve, or gland; we cannot replace the phosphate of magnesia in muscles by the phosphate of iron, lime, or potash, as we can replace the iron of a wheel by steel, copper, or brass.

[34] Anatomy resolves the Tissues into Organites (cells, fibres, tubes); here its province ends, and that of Chemistry begins by pointing out the molecular composition of the Organites.

[35] This luminous conception, though vaguely seized by PINEL, was first definitely wrought out by BICHAT. See his _Recherches sur la Vie et la Mort_--and especially his _Anatomie Générale_, 1812, I. p. lxx. It was one of the most germinal conceptions of modern times.

[36] Just as there go other materials besides canvas to make a sail, and others besides iron to make a windlass, so there go other tissues besides the muscular to form a muscle--there is the membranous envelope, the nerve, the blood-vessels, the lymphatics, the tendon, and the fat. Even in Contraction there is another property involved besides the Contractility of the muscular element, namely, the Elasticity of the fibrous wall of the muscular tube; but Contractility is the dominant property, and determines the speciality of the function.

[37] “L’élément musculaire peut être annexé à une foule de mécanismes divers; tantôt à un os, tantôt à un intestin, tantôt à une vessie, tantôt à un vaisseau, tantôt à un conduit excréteur, tantôt enfin à des appareils tout à fait spéciaux à certaines espèces d’animaux.”--CLAUDE BERNARD, _Rapport sur les Progrès de la Physiologie générale_, 1867, p. 38.

[38] VULPIAN, _Leçons sur la Physiologie du Système Nerveux_, 1866, p. 581. In a work just published I find M. LUYS hesitating at the consistent application of this law. After pointing out the identity of the tissue in cerebrum and spinal cord, he is only prepared to say that we cannot deny that there is _no impossibility_ in admitting physiological equivalence where there is morphological equivalence.--LUYS, _Actions Reflexes du Cerveau_, 1874, p. 14.

[39] It is because men converted the result into a principle, and supposed that Life preceded the Organism, that they were led to puzzle themselves over such facts as the continuance of vitality in divided organisms. ARISTOTLE felt the force of the objection: “Plants when divided are seen to live, and so are certain insects, as if still possessing the same Vital Principle (ψυχή) considered specifically (τῷ εἴδει) though not the same numerically (μὴ ἀριθμῷ). Each of these parts has sensation and locomotion for a time; and there is no room for surprise at their not continuing to manifest these properties, seeing that the organs necessary for their preservation are absent.”--_De Anima_, Lib. I. Ch. IV. Compare BASSO, _Philos. Naturalis adversus Aristotelem_, Amsterdam, 1649, p. 260; and TAURELLUS, _Contra Cæsalpinum_, 1650, p. 850; neither of them grappling with the difficulty so firmly as ARISTOTLE.

[40] SPENCER, _Principles of Biology_, 1864, I. 153.

[41] Comp. LAMARCK, _Philos. Zool._, II. 114.

[42] Comp. SPENCER, _op. cit._, II. 362, 363, for good illustrations of this.

[43] AGASSIZ, _Essay on Classification_, p. 91.

[44] “Nulla in corpore animali para ante aliam facta est, et omnes simul creatæ exiatunt.”--HALLER, _Elementa Physiologiæ_, VIII. 148.

[45] QUATREFAGES, _Metamorphoses de l’Homme et des Animaux_, 1862, p. 42.

[46] VON BAER, _Ueber Entwickelungageschichte_, 1828, I. 221.

[47] Curiously enough, while the Nudibranch, which is without a shell, possesses one during its embryonic life, there is another mollusc, _Neritina fluviatilis_, which possessing a shell in its subsequent life is without one during the early periods, and according to CLAPARÈDE begins an independent existence, capable of feeding itself before it acquires one. See his admirable memoir on the _Neritina_, in _Müller’s Archiv_, 1857.

[48] Has any advocate of the hypothesis that animals were created as we see them now, fully formed and wondrously adapted in all their parts to the conditions in which they live, ever considered the hind legs of the seal, which he may have watched in the Zoölogial Gardens? Here is an animal which habitually swims like a fish, and cannot use his hind limbs except as a rudder to propel him through the water; but instead of having a fish-like tail he has two legs flattened together, and nails on the toes--toes and nails being obvious superfluities. Now which is the more rational interpretation, that these limbs, in spite of their non-adaptation, were retained in rigid adherence to a Plan, or that the limbs were inherited from an ancestor who used them as legs, and that these legs have gradually become modified by the fish-like habits of the seal?

[49] MILNE EDWARDS, _Intro. à la Zoologie Générale_, 1851, p. 9.

[50] VON BAER, _op. cit._, I. 203.

[51] WOLFF, _Theorie der Generation_, 1764, § 67. The reader will find abundant and valuable corroboration of this biological principle in SIR JAMES PAGET’S _Lectures on Surgical Pathology_.

[52] VON BAER, _Selbstbiographie_, 1866, p. 319.

[53] MILNE EDWARDS, _Intro. à la Zoologie Générale_, 176.

[54] VON BAER, _Ueber Entwickelungsgeschichte_, I. 147.

[55] LOTZE, art. _Lebenskraft_, in _Wagner’s Handwörterbuch der Physiologie_, p. XXVI.

[56] I had kept these tritons four years in the hope that they would breed; but in spite of their being subjected to great varieties of treatment--for months well supplied with food, and for months reduced almost to starvation--they never showed the slightest tendency to breed; another among the many illustrations of the readiness with which the generative system is affected even in very hardy and not very impressionable animals. CLAPARÈDE observed the still more surprising fact that the _Neritina fluviatilis_ (a river snail) not only will not lay eggs, but will not even feed in captivity. He attributes it to the stillness of the water in the aquarium, so unlike that of the running streams in which the mollusc lives. See _Müller’s Archiv_, 1857.

[57] BRONN, _Morphologische Studien über die Gestaltungs-Gesetze_, 1858. Compare the note on § 11.

[58] DARWIN, _On Domestication_, II. 340. In the _Annales des Sciences_, 1862, p. 358, M. MALM describes a fish in his collection, the tail of which had been broken, and the bone which grew out at the injured spot had formed a second tail with terminal fin.

[59] In the memoir on the _Anatomy and Physiology of the Nematoids_, by Dr. CHARLTON BASTIAN, which appeared in the _Philosophical Transactions_ for 1866, we read that even these lowly organized worms have little power of repair. Speaking of the “paste eels” (_Anguilulidæ_), he says, “I may state as the result of many experiments with these that the power they possess of repairing injuries seems very low. I have cut off portions of the posterior extremity, and though I watched the animal for days after, could never recognize any attempt at repair.” Perhaps, however, the season may have some influence; and Dr. WILLIAMS’S denial respecting the Naïs may be thus explained. [What is said above was written in 1868, and published in the June number of the _Fortnightly Review_. In the August of that year the question of reproduction of lost limbs was treated by Prof. ROLLESTON in his _Address to the British Medical Association_, in which he showed cogent evidence for the conclusion that the reproduction of limbs only exists is animals that have feeble respiration, and consequently slow vital processes.]

[60] This beautiful and transparent larva reminds one in many respects of the Pike as it poises itself in the water awaiting its prey. It is enabled to do so without the slightest exertion by the air-bladders which it possesses in the two kidney-shaped rudiments of tracheæ, and which in the gnat become developed into the respiratory apparatus. The resemblance to the air-bladder of fishes is not simply that it serves a similar purpose of sustaining the body in the water, it is in both cases a rudiment of the respiratory apparatus, which in the fish never becomes developed. WEISMANN calls attention to an organ in the larvæ of certain insects (the _Culicidæ_), which have what he calls a tracheal _gill_, which gill has this striking analogy with the fish-gill that it separates the air from the water, and not, as a trachea, direct from the atmosphere. See his remarkable memoir _Die nachembryonale Entwickelung des Muscidens_, in _Siebold und Kölliker’s Zeitschrift_, 1864, p. 223.

[61] _The Variation of Animals and Plants_, 1868, II. p. 272.

[62] _Origin of Species_, 5th ed. p. 96.

[63] Mr. Darwin has himself, in the following passage, stated a somewhat similar view, and rejected it: “In one sense the conditions of life may be said not only to cause variability, but likewise to include Natural Selection, for _the conditions determine whether this or that variety shall survive_. But when man is the selecting agent, we clearly see that the two elements of change are distinct; the conditions cause the variability, the will of man acting either consciously or unconsciously accumulates the variations in certain directions, and this answers to the survival of the fittest under nature.” (p. 168.)

[64] Even in the nerve-sheaths of some Annelids there are muscles.

[65] SPENCER, _Principles of Biology_, II. 72

[66] FAIVRE, _Variabilité de l’Espèce_, p. 15.

[67] These luminous organs would furnish an interesting digression if space permitted it. The student is referred to the chapter in MILNE EDWARDS’S _Leçons sur la Physiologie et l’Anatomie Comparée_, 1863, VIII. 94, sq. LEYDIG, _Histologie_, 1857, p. 343. KÖLLIKER, _Microscopical Journal_, 1858, VIII. 166, and MAX SCHULTZE, _Archiv für mikros. Anat._, 1865, p. 124. My friend SCHULTZE was kind enough to show me some of his preparations of the organs of _Lempyris splendidula_, from which the drawings in his memoir were made. They reminded me of the electric organs in fishes by a certain faint analogy, the trachea in the one holding the position of nerves in the other. I may remark, in passing, that it is not every phosphorescent animal that has distinct luminous organs. There is a lizard (_Pterodactylus Gecko_) which occasionally becomes luminous. “A singular circumstance occurred to the colonial surgeon, who related it to me. He was lying awake in bed when a lizard fell from the ceiling upon the top of his mosquito-curtain; at the moment of touching it the lizard became brilliantly luminous, illuminating the objects in the neighborhood, much to the astonishment of the doctor.” COLLINGWOOD, _Rambles of a Naturalist_, 1868, p. 169.

[68] MAX SCHULTZE, _Zur Kenntniss der electrischen Organe der Fische_, 1858–9.

[69] LEYDIG, _Histologie_, 1857, p. 45.

[70] OWEN, _Anatomy of The Vertebrates_, 1866, I. 358.

[71] DAVY, _Researches, Physiological and Anatomical_, 139, I. 33.

[72] “If it could be demonstrated that any complex organ existed which could not possibly have been formed by numerous successive slight modifications, my theory would absolutely break down.”--DARWIN, _Origin of Species_, 5th ed. p. 227. In several passages insistence is made on this. “Natura non facit saltum” may be perfectly true; but without impugning the Law of Continuity we may urge that the Law of Discontinuity is equally true. The one is an abstract ideal conception; the other is a concrete ideal conception. According to the one, every change from rest to motion, or from one state to another, must pass through infinites; according to the other every change is abrupt. In my First Series, Vol. I. p. 327, I have shown how, on mechanical principles, every change in an organism must be abrupt. A glance at the metamorphoses of the embryo, or the stages of insect-development, will show very sudden and abrupt changes. Let me also cite Mr. Darwin against himself: “When we remember such cases as the formation of the more complex galls, and certain monstrosities, which cannot be accounted for by reversion, cohesion, etc., and _sudden, strongly marked deviations of structure_, such as the appearance of a moss-rose on a common rose, we must admit that the organization of the individual is capable through _its own laws of growth, under certain conditions_, of undergoing great modifications, independent of the gradual accumulation of slight inherited modifications.”--_Origin_, p. 151. See also note to § 130, further on, p. 142.

[73] On the Nutrition of Monads, see the remarkable memoir by CIENKOWSKI, in the _Archiv für mikros. Anatomie_, I. 221, sq.

[74] PAGET, _Lectures on Surgical Pathology_, edited by TURNER, 1865, p. 19.

[75] It has recently been shown that certain Crustacea vary not only from species to species, but from genus to genus, when living in water of different degrees of saltness. By continued dilution of the salt water an _Artemia_ was developed into another species, and this again into a _Branchipus_--a genus of large dimensions, with an extra abdominal segment, and a different tail; a genus, moreover, which is propagated sexually, whereas the _Artemia_ is parthenogenetic, as a rule. See _Nature_, 1876, June 8, p. 133.

The exceeding importance of this fact is, that it proves specific and even generic differences to originate simply through the gradual changes of the medium and the adaptation of the organism to these new conditions. It also disproves the very common notion--adopted even by Mr. DARWIN himself--that “organic beings must be exposed _during several generations_ to new conditions to cause any appreciable amount of variation.” Again, “Natural Selection, if it be a true principle, will banish the belief of any great and sudden modification of structure.”--Comp. note to § 121, p. 132.

[76] Compare LEYDIG, _Vom Bau des thierischeu Körpers_, 1864, p. 27.

[77] FERDINAND COHN, _Die contractile Gewebe im Pflanzenreich_, 1862. By a series of numerous well-devised experiments, Cohn found that in the stamen of the _centauria_ a tissue exists which is excitable by the same stimula as muscle is, and which reacts like muscle, describing a similar curve when excited, and, after reaching its maximum, relaxing. Like the muscle it becomes fatigued by repeated contraction, and recovers its powers by repose. Like the muscle it may be rendered tetanic. (The researches of Dr. BURDON SANDERSON and Mr. DARWIN have since placed beyond a doubt the Contractility and Sensibility of certain plants.)

[78] MIVART, _The Genesis of Species_, 1871, p. 23.

[79] DOHRN, _Der Ursprung der Wirbelthiere und das Princip des Functionswechsels_, 1875, p 74.

[80] SIGMUND MAYER, _Die peripherische Nervenzelle und die sympathische Nervensystem_, 1876.

[81] On these cells see note to § 140.

[82] These terms designate the surface aspect of a transverse section, of what more correctly should be called the gray columna. See Figs. 3 to 6.

[83] But this only in the higher animals. In reptiles and amphibia the medulla descends into the cervical region, as far as the second and third cervical vertebræ. This should be remembered in experimenting.

[84] FOSTER and BALFOUR, _Elements of Embryology_, Part I., 1874. Comp. SCHWALBE, art. _Die Retina_, in the _Handbuch der Augenheilkunde_ of GRAEFE _and_ SÄMISCH, 1874, I. 363.

[85] The development of the olfactory lobe and bulb is similar; it need not be followed here.

[86] German anatomists divide this axis into trunk and crown (_Hirnstamm_ and _Hirnmantel_). There is convenience in this division. If we remove all the gray matter of the cerebrum, with all the white matter radiating from it, until we again come upon gray matter--and if we then cut the cerebellum from its descending strands of white matter--we shall have removed the _crown_, and leave the _trunk_ remaining. This trunk is constituted by the corpora striata, nucleus lentiformis, optic thalami, corpora quadrigemina, crura cerebri, pons, medulla oblongata, and medulla spinalis. From this trunk all the organs of the body are directly innervated (except those innervated from the sympathetic?).

[87] “On s’est préoccupé du rôle spécial que pouvaient jouer les ganglions périphériques situés dans le voisinage de certaines organes; et on a prétendu que les nerfs ne jouissaient de leur propriété d’agir sur ces organes qu’après avoir traversé ces ganglions. On avait admis que l’excitation portée sur le filet nerveux avant son entré dans le ganglion restait sans effet; que pour obtenir l’action excitatrice des fonctions de l’organe il fallait exciter le nerf entre lui et le ganglion voisin.”--CLAUDE BERNARD, _Systéme Nerveux_, II. 169. But on proceeding to verify these statements by experiment, BERNARD is led to the conclusion, “que le ganglion n’a pas d’influence propre sur le mode de l’excitation transmise à l’organe.”

I was delighted to find my opposition to the current teaching respecting the central functions of ganglionic cells thoroughly borne out by the elaborate researches of SIGMUND MAYER (_Archiv für Psychiatrie_, Bd. VI. Heft 2). Having artificially produced such cells, he pertinently asks, How can we attribute central functions to cells which appear in the process of regeneration of a divided nerve! The error has its origin in the confusion of functions with properties.

[88] It is often, though incorrectly, stated that every segment of an annulose animal has its separate ganglion. The fact is, that while the ganglia are usually fewer than the segments, they are sometimes more numerous.

[89] It has been proved that the cells of the cornea and the pigment cells of the skin contract under nervous excitation. We cannot suppose that although these are the only cells which have hitherto been brought under experimental observation, they are the only cells subject to nerve-influence. We may safely assume that wherever a nerve-fibre terminates, its action will be transformed into an excitation of the part. Habitually, however, motor-nerves are spoken of as muscle-nerves.

[90] On Deduction, see _Problems: First Series_, Vol. II. p. 159

[91] I do not here touch upon the question as to whether these actions of the senses are _sensations_, because that question demands that we should first settle what is _Sensation_. I may at once, however, say that what is ordinarily understood as a sensation of _color_, or a sensation of _sound_, is, in my opinion, not possible without the cerebrum. But the sensibility of the eye and ear is manifestly preserved.

[92] It has been observed that removal of the cerebellum affects the pigment cells of the skin. No doubt other parts are also affected, but the changes have hitherto escaped observation.

[93] OWSJANNIKOW describes the results of removing carefully the cranial ganglia of the crayfish; and these effects MEYER observes to be identical with those which follow removal of the large claw of the crayfish! A. B. MEYER, _Das Hemmungsnerven-system des Herzens_, 1869, p. 23. Let me add that the phenomena described by M. FAIVRE as following the destruction of one subœsophageal ganglion in the _Dytiscus_, are so little to be referred to the mere absence of the ganglion, that I find them not to occur when the whole head is removed.

[94] PFLÜGER, _Die Sensorischen Funktionen des Rückenmarks_,1858. AUERBACH, _Günzburg’s Zeitschrift_. Jahrgang IV. p. 486. LEWES, _Leeds Meeting of British Association_, 1858, and _Physiology of Common Life_, 1860.

This recognition of sensation, and even of volition, in spinal actions may be found in the writings of WHYTT, UNZER, PROCHASKA, LEGALLOIS, and MAYO; but the establishment of the Reflex Theory had displaced it, and its revival dates from PFLÜGER.

[95] FRIEDLÄNDER (_Versuch über die innern Sinne_, 1826, I. 77) declares it to be a rational necessity: “Die Annahme eines Nervenfluidums ist Nothwendigkeit der Vernunft.”

[96] These terms and the conception they embody were proposed by me in 1859 in a paper “On the necessity of a reform in Nerve-physiology,” read at the Aberdeen meeting of the British Association, and were reproduced in the _Physiology of Common Life_. (Prof. OWEN, probably in forgetfulness of my suggestion, proposed “neuricity.” _Lectures on the Comp. Anat. of Vertebrates_, 1866, I. p. 318.) The terms were fortunate enough to meet with acceptance from some physiologists both in England and France; and the conception has been more widely accepted than the terms. The most distinguished approver was Prof. VULPIAN. “Faute d’une meilleure détermination on peut, avec M. Lewes, donner à la propriété physiologique des fibres nerveuses le nom de _neurilité_; c’est là ce qui correspondra à la oontractilitè des fibres musculaires.” _Leçons sur la physiologie du système nerveux_, 1866, p. 220. He also adopted my suggestion (since modified) of Sensibility as the property of ganglionic cells. Compare also GAVARRET, _Phénomènes physiques de la Vie_, 1869, pp. 213 and 222. TAULE, _Notions sur la nature de la matière organisée_, 1866, p. 131. CHARLES ROBIN, _Anatomie et physiologie cellulaires_, 1873, p. 166.

By these channels, and by the German, Italian, Russian, Polish, and Hungarian translations of my work, the suggestions were carried over Europe, crept into scientific journals, and became known to writers who never heard of me. I only mention these facts lest the reader should suppose that my views had been anticipated by certain continental writers.

[97] “La force nerveuse n’existe pas comme puissance independant des propriétés de tissu. Elle consiste en l’action des parties excités, sur les parties excitables, l’état de l’excitation des premières agissant comme impression ou stimulation sur les secondes.”--LANDRY, _Traité des Paralysies_, 1859, I. 142.

[98] “Le système nerveux est tout à la fois l’origine des sensations et l’origine des mouvements. Mais est-ce par une propriété unique, ou par deux propriétés diverses qu’il détermine deux phénomènes aussi distincts!” FLOURENS, _Recherches sur les propriétés et les fonctions du Système Nerveux_, 1824, p. 1. He concludes that “la puissance nerveuse n’est pas unique; il n’y a pas une seule propriété, il y en a deux,” p. 24. In this he has been generally followed.

[99] “I have raised and stretched the thick orbital nerve of horses on the handle of a scalpel, like a string on the bridge of a violin, without exciting the least sensation; but as soon as mechanical or chemical irritation had given rise to inflammation of the nerve a gentle touch caused violent pain.”--ROMBERG, _Nervous Diseases_ (translated for the Sydenham Society), I. 10.

[100] The experiments of HALLER, _Sur la nature sensible et irritable des parties_, I. 245; and the remarks of PROCHASKA, DE FUNCTIONIBUS SYSTEMATIS NERVOSI (translated by LAYCOCK in the volume published by the _Sydenham Society_, p. 396), ought to have sufficed. See further on, Chap. V.

[101] In mammals about three days, in birds four days, in frogs fourteen to twenty days.

[102] RUTHERFORD, in _Journal of Anatomy_, 1873, No. VIII. p. 331. (FLEISCHL denies that the nerve _in situ_ has different degrees of reaction. _Sitzungsberichte der Wiener Akad._, December, 1876.)

[103] MUNK, in the _Archiv für Anat._, 1860, p. 798.

[104] HALLER, _Mémoires sur la nature sensible et irritable des parties_.

[105] _Comptes Rendus_, 1862, LIV. p. 965.

[106] “J’espère vous convaincre que tous les éléments anatomiques des nerfs sensitifs, moteurs, vasomoteurs, et autres, ont les mêmes propriétés, et ne sont distincts que par leurs fonctions. Cette question est de la plus haute importance pour la physiologie générale. C’est celle qui domine toute la physiologie des fibres nerveuses.”--VULPIAN, _Leçons sur la Physiologie du Système Nerveux_, p. 11.

[107] Mr. JAMES ANDREWS.

[108] In the second number of _La Revue Philosophique_, Paris, 1876, I have treated this question of specific energies more at length than I could find space for in the present volume.

[109] In 1859 I mentioned that if the nerves of a frog’s back be exposed by raising the skin, they may be pricked or even cut without sensible effect, although a slight prick on the skin will excite the nerves, and cause a reflex action. In 1870, Prof. FICK expressed his astonishment at finding that after he had cut out a piece of the skin, leaving it attached to the body by a single nerve, electrical stimulation of this excised skin caused the frog to make the reflex movement of rubbing the irritated surface; whereas electrical stimulation of the nerve-trunk itself produced no reflex effect, only a twitching of a muscle. _Pflüger’s Archiv_, 1870, p. 327. BROWN SÉQUARD tries to establish a distinct species of nerves as _conductors_ of sensitive impressions, from those which are _impressionable_. The facts on which he founds these two properties simply show that nerves are so disposed that the stimulus which excites them in one place fails in another. He could hardly maintain that a skin nerve contained impressionable fibres at its periphery, and only conducting fibres in its trunk! See his communication to the Royal Society, _Proceedings_, 1856; and _Lectures_ in the _Lancet_, 10th July, 1858.

[110] In consequence of this observation some physiologists have maintained that Feeling or Consciousness never arises in cerebral activity, unless the thalami and the connected tracts are at the same time in action. I go further, and maintain that there is no Consciousness (in the restricted meaning of the term) _unless the whole organism is involved_. Cerebral or spinal activity will be activity of Sensibility; but this is only the basis of Consciousness.

[111] “An unconscious sensation, which Lewes distinguishes from perception, is to me an inconceivable (ist für mich ein Unding).”--SCHRÖDER VAN DER KOLK, _Die Pathologie des Geistes-Krankheiten_, p. 22.

[112] By selective adaptation is meant the varying combination of motor impulses to suit the varying requirements of the effect to be produced. Physical mechanisms are limited to the performance of definite actions; sensitive mechanisms employ fluctuating combinations of elements in response to fluctuations of stimuli. The wheels, levers, springs, and valves of a machine cannot be differently combined according to varying degrees of the motor-force, as the nerves and muscles of an organism are differently combined by varying sensations. An automaton may be constructed to play on the violin, but it will only play the air to which it is _set_; it cannot vary the performance,--cannot play a false note, or throw in a _crescendo_ here, a _largo_ there, according to a caprice of feeling. We must admit that violinist has his delicate and changing movements guided by sensations, auditory and muscular; any interruption in the sensations would arrest the movements, which in truth _incorporate_ them. And yet it is well known that the violinist may perform while completely “unconscious.” I do not simply refer to the fact that his thoughts and attention may be elsewhere; I refer to such facts as are recorded in Pathology. TROUSSEAU, for example, had an epileptic patient who was occasionally seized with attacks of complete unconsciousness while he was performing in the orchestra; yet, on reawakening to consciousness, he found that he had continued to play, had kept proper time, and played the proper notes.

[113] CLAUDE BERNARD, _Système Nerveux_, 1858, I. 349.

[114] WORDSWORTH, _The Prelude_.

[115] “On peut dire que toujours un phénomène de mouvement reconnait pour point de départ une impression sensitive.”--CLAUDE BERNARD, I. 267.

[116] Since this was written Prof. MICHAEL FOSTER and Mr. DEW SMITH have published their very important researches on the motions of the heart, which establish beyond a doubt that, in the molluscs at least, there is no co-operation of either centre or nerve.--_Proceedings of the Royal Society_, 18th March, 1875. (_See also Studies from the Physiological Laboratory of Cambridge_, Part II., 1876.) Mr. Foster knows that I had independently, and from a totally different line of research, arrived at the same conclusion respecting the heart’s movement.

[117] _Comptes Rendus de la Socíété de Biologie_, 1847, I. 40. In 1856 he showed that not only were the muscles of the iris directly stimulated by light (and this not by its calorific or chemical rays), but that sixteen days after removal of the eye from the orbit, this effect was observable in the eel. Yet a very few days after extirpation of the eye the nerves are disintegrated.--_Proceedings of the Royal Society_, 1856, p. 234.

DONDERS has the following observations: “The movements of the iris are of two kinds--reflex and voluntary. Reflex action is exhibited as constriction of the pupil in consequence of the stimulus of incident light upon the retina. Fontana has shown that the light falling upon the iris produces no remarkable contraction. We have confirmed this result by causing the image of a small distant light to fall, by means of a convex lens, upon the iris, whereby, during slight perception of light, a doubtful contraction occurred, which gave way to a strong contraction so soon as the light entering the pupil excited a vivid perception. Nevertheless, the experiments of Harless and Budge have shown that even after death, so long as irritability remains, the pupil still contracts upon the continued action of light. Of the correctness of this we have satisfied ourselves. In a dog killed by loss of blood the one eye was closed, the other opened and turned to the light: after the lapse of an hour, the pupil of the opened eye was perceptibly smaller than that of the closed eye. The latter now remained also exposed to the light, and on the following day the diameter of both eyes was equal. The upper jaw, alone with the eyes, was taken out of some frogs; one eye was exposed to the light, while the other was covered with a closely folded piece of black paper: after the lapse of half an hour the pupil turned to the light was narrow, the other wide. But the latter also contracted almost immediately after the removal of the paper.”--DONDERS, _On the Anomalies of Accommodation and Refraction of the Eye_. Trans. of the New Sydenham Society, p. 572.

[118] The experiment often fails, but I have seen it several times succeed.

[119] _Pflüger’s Archiv_, 1872, p. 618.

[120] See his Researches in _Pflüger’s Archiv, Bde._ II. and IV.

[121] D’ORBIGNY, _Des Mollusques Vívants et fossils_, p. 113.

[122] _Seaside Studies_, 2d ed., p. 101.

[123] Cited by BROWN SÉQUARD, _Journal de la Physiologie_, 1858, p. 359.

[124] Dr. NORRIS has recorded some striking observations in his paper on “Muscular Irritability” in the _Journal of Anatomy_, 1867, No. II. p. 217. Here is the only one I can find room for: “On taking up the _dead_ frog and touching the limb (which during life had been paralysed by section of its nerve) with my finger, _it was suddenly shot out as if alive_. I placed the body down, and one or two _apparently spontaneous movements_ of small extent afterwards occurred. On touching the skin gently with the point of a needle, by the slight pressure upon the muscle beneath, movements of the limb were also induced, but this high degree of exaltation very rapidly disappeared.”

[125] See their papers in the _Archiv für Psychiatrie_, 1875, Bd. V. Heft 3.

[126] This latter statement will be justified when I come to expound the Triple Process, which I have named the _Psychological Spectrum_.

[127] FOSTER and BALFOUR, _Elements of Embryology_, 1874, Part I. p. 52. HIS, _Untersuchungen über die erste Anlage des Wirbelthierleibes_, 1868, p. 197.