Chapter IV: Negative Inductions (2)

[128] They state that the cells of the epiblast are the results of direct segmentation, whereas the cells of the other layers are formed at a subsequent period, and are only indirectly results of segmentation. But if the observations of KOWALEWSKY are exact, this is not the case with the hypoblast of the Amphioxus, which is from the first identical with the epiblast.

[129] KÖLLIKER, _Entwicklungsgeschichte des Menschen und der höheren Thiere_, 1861, p. 71.

[130] [According to BALFOUR’S recent observations, a large part of the muscular tissue is derived from the layer of the mesoblast belonging to the hypoblast.]

[131] HIS, _Untersuchungen_, pp. 39, 40.

[132] Quite recently OWSJANNIKOW has pointed out the termination of fibres in the phosphorescent cells of the _Lampyris Noctiluca_. See his paper in the _Mémoires de l’Acad. de St. Petersbourg_, 1868, XI. 17. These phosphorescent cells are said to be ganglion-cells by PANCERI, _Intorno della luce che emana dalle celleule nervose_ (Rendiconto della Accad. delle Scienze, April, 1872); and by EIMER, _Archiv für mikros. Anatomie_, 1872, p. 653. KÖLLIKER also calls the phosphorescent organ a nervous organ. This is not to be interpreted as meaning that neurility is phosphorescence, but simply that in some nerve-cells there is phosphorescent matter, which is called into activity by stimulus of the nerves.

[133] BIDDER und KUPFFER, _Textur des Rückenmarks_, 1857, p. 108. [What is said in the text has been rendered doubtful by the recent researches of Mr. F. BALFOUR, _On the Development of the Spinal Nerves in Elasmobranch Fishes_ (_Philos. Trans._, Vol. CLXVI. Part I.), which show that in these fishes the ganglion has its origin in the spinal cord.]

[134] Comp. PROBLEM I. § 130, with the remarks of CHARLES ROBIN, _Anatomie et Physiologie Cellulaires_, 1873, p. 20.

[135] KLEINENBERG, _Hydra; Eine Anatomisch-Entwickelungs-Untersuchung_, 1872, p. 11. EIMER, _Zoologische Studien auf Capri_, 1873, p. 66.

A similar formation is described by Dr. ALLMAN in the _Myriothela_; he says, however, that he has never been able to trace a direct continuity of the caudal processes of the cells with muscular fibrils. He believes that the processes make their way to the muscular layer through undifferentiated protoplasm.--_Philos. Transactions_, Vol. CLXV. Part II. p. 554.

An intermediate stage between this neuro-muscular tissue and the two differentiated tissues seems presented in the Nematoid worms which have muscles that send off processes into which the nerves pass. GEGENBAUR declares his inability to decide whether these processes are muscles or nerves. BÜTSCHLI thinks the nerve-process blends with the muscle-process.--_Archiv für mikros. Anatomie_, 1873, p. 89.

[136] “The gray matter of the cord seems undoubtedly to be formed by a metamorphosis of the external cells of the epiblast of the neural tube, and is directly continuous with the epithelium; there being no strong line of demarcation between them.”--_Op. cit._, p. 185.

[137] ROBIN, _Anat. et Physiol. Cellulaires_, p. 332.

[138] STILLING, _Bau der Nervenprimitiv-Fasern_, 1856, p. 16.

[139] “There was a time,” says KÖLLIKER, “when I confidently believed that an hypothetical explanation of the arrangement of elements in the spinal cord could be grounded on a basis of fact; but the deeper my insight into the minute anatomy, the less my confidence became; and now I am persuaded that the time is not yet come to frame such an hypothesis.”--_Gewebelehre_, 5te Auf. 1867.

[140] In the Gasteropoda the cells range from 220 μ to 3 μ (μ = 0,001 millimètre).

[141] HAECKEL, _Müller’s Archiv_, 1857. LEYDIG, _Vom Bau des thierischen Körpers_, 1864, I. 84. ROBIN, _Anat. et Physiol. Cellulaires_, p. 89. Should the observations of HEITZMANN be confirmed, there would be ground for believing that neurine is normally fibrillated. He says that the living protoplasm in the Amœba, white blood-corpuscle, etc., is an excessively fine network, which condenses into granules at each contraction. (Cited in the _Jahresberichte über Anat. und Physiol._, 1873, Bd. II.) WALTHER, who examined frozen brains, describes the cells as quite transparent at first, with very rare granules, but gradually while under observation the granules became more numerous. _Centralblatt_, 1868, p. 459. According to MAUTHNER, _Beiträge zur Kenntniss der morphologischen Elemente des Nervensystems_, 1862, p. 41, neurine has three cardinal forms--transparent, finely granular, and coarsely granular.

[142] TRINCHESE, _Struttura del sistema nervoso dei Cefalopodi_, Florence, 1868, p. 7.

[143] An eminent friend of mine was one day insisting to me that the physiological postulate made it _impossible_ for a nerve-cell to be without its ingoing and outgoing fibres; and he was not a little astounded when I replied, “Come into my workroom and I will show you a thousand.”

[144] EICHHORST in _Virchow’s Archiv_, 1875, LXIV. p. 432.

[145] AUERBACH (_Ueber einen Plexus Myentericus_, 1862) describes the ganglia as filled with apolar cells, among which only a few are unipolar. STIEDA (_Centralnervensystem der Vögel_, 1868) finds both apolar and unipolar cells in the spinal ganglia of birds. AXMANN (_De Gangliorum Systematis Structura penitiori_, 1847) says the spinal cells are all unipolar. SCHWALBE (_Archiv für mikros. Anat._, 1868) and COURVOISIER (_ibid._, 1869) say the same. So also RANVIER, _Comptes Rendus_, 1875. KÖLLIKER (_Gewebelehre_) speaks decidedly in favor of both apolar and unipolar cells, but thinks the apolar are embryonic. PAGLIANI (_Saggio sullo Stato attuale delle Cognizioni della Fisiologia intorno al Sistema nervoso_, 1873), who represents the views of MOLESCHOTT, admits the existence of apolar and unipolar cells. The authors just cited are those I happen to have before me during the rewriting of this chapter, and the list might easily be extended if needful. AUERBACH, BIDDER, and SCHWEIGGER-SEIDEL describe unipolar cells which in some places present the aspect of bipolar cells simply because two cells lie together, their single poles having opposite directions. I will add that the bipolar cells do not really render the physiological interpretation a whit more easy than the unipolar, for they are simply cells which form enlargements in the course of the nerve-fibres.

[146] When Dr. BEALE says “that it is probable no nerve-cell exists which has only _one single fibre_ connected with it” (_Bioplasm_, p. 186), he has no doubt this in his mind; since he would not, I presume, deny that there are cells each with a single _process_.

[147] DEITERS, _Untersuchungen über Gehirn und Rückenmark_, 1865.

[148] _Archiv für mikros. Anat._, 1869, p. 217. Compere also BUTZKE, _Archiv für Psychiatrie_, 1872, p. 584.

[149] HENLE, _Nervenlehre_, 1871, p. 58, Fig. 21.

[150] When men of such experience and skill as KÖLLIKER, BIDDER, GOLL, and LOCKHART CLARKE declare that they have never seen a cell-process pass directly into a dark-bordered fibre in the anterior root, what are we to say to such figures and descriptions as those given in the works of SCHRÖDER VAN DER KOLK, GRATIOLET, and LUYS? Even did such arrangements exist, no transverse nor longitudinal section could display them, owing to the different planes at which the fibres enter, and the length and irregularity of their course.

[151] Long after the text was written, WILLIGK published in _Virchow’s Archiv_, 1875, LXIV. p. 163, observations of anastomoses which even KÖLLIKER admitted to be undeniable. Yet out of sixty-four preparations, amid hundreds of cells, he could only reckon seven cases of conjunction.

[152] See the history given in STILLING’S learned work, _Ueber den Bau der Nervenprimitiv-Faser_, p. 34; and compare MAX SHULTZE, _De Retinæ Structura_, p. 8, and _Bau der Nasenschleimhaut_, p. 66; WALDEYER, in the _Zeitschrift für rat. Med._, 1863; LISTER and TURNER, _Observations on the Structure of Nerve-Fibres_, in _Quarterly Micros. Journal_, 1859; RANVIER, in the _Archives de Physiologie_, 1872.

[153] _Virchow’s Archiv_, Bd. LXXII. p. 193.

[154] _Monthly Journal of Micros. Science_, 1874, XI. p. 214.

[155] BABUCHIN, _Centralblatt_, 1868, p. 756.

[156] Even so eminent an authority as W. KRAUSE holds this both with regard to the varicose aspect and the double contour: _Handbuch der menschlichen Anatomie_, 1876, I. 367. BUTSCHLI, however, describes the nerves in a living Nematode as varicose: _Archiv für Anat._, 1873, p. 78; and I have somewhere met with an observation of the double contour being visible in the living animal.

[157] BUTZKE, _Archiv für Psychiatrie_, 1872, p. 594, states that the granular substance has the chemical composition of myeline. If this be so, we may suppose the “fibrils of crystallization” to represent the coagulation of the substance which is in solution amid the myeline granules, and corresponds with the axis cylinder of a fibre. I may remark that in almost every good preparation nerve-cells will be found in which, while one process is distinctly granular, another is striated or even fibrillated.

[158] BOLL, _Die Histiologie und Histiogenese der nervösen Centralorgane_, in the _Archiv für Psychiatrie_, 1873, p. 47.

[159] STIEDA, _Studien über das Centralnervensystem der Vögel_, 1868, p. 65. MAUTHNER, _Op. cit._, p. 4.

[160] TURNER and LISTER, _Op. cit._, p. 8.

[161] BLESSIG, _De Retinæ Structura_, 1857.

[162] LUYS, _Recherches sur le Système nerveux_, 1865, p. 267. In a recent and remarkable treatise the student is informed that “plus une cellule est chargée d’un rôle purement mécanique plus elle est volumineuse; plus l’acte qu’elle produit tend à revêtir un caractère psychique plus elle est petite”; to move a limb the _agitation_ of the cerebral cells must _materialize itself_ more and more, “Il a besoin de passer par des cellules, de moins en moins spirituelles et de plus en plus matérielles.... De même pour les cellules sensitives. L’impression extérieure va en se modifiant, en se spiritualisant, de la périphérie au centre.... Un phénomène de l’ordre spirituel ne sanrait devenir sans transition un phénomène d’ordre physique.” And what is this marvellous transition between spiritual and physical? It is the action of medium-sized cells which “travaillent la vibration reçue, la modifient de façon à lui ôter de son spiritualisme et à la rapprocher davantage des ébranlements physiques.” I will not name the estimable author, because he is simply restating what many others implicitly or explicitly teach; but I will only ask the reader to try and realize in thought the process thus described.

[163] SCHRÖDER VAN DER KOLK, _Pathologie der Geisteskrankheiten_, 1863, p. 69.

[164] WUNDT, _Physiologische Psychologie_, p. 261. In his _Mechanik der Nerven, 2 Abth._ (published just as this sheet is going to press), he shows that a stimulus is both retarded and weakened in its passage through a ganglion.

[165] TRINCHESE also says that the fibres “provengono dalle cellule e _non son altro che i loro prolungamenti o poli_.”--_Op. cit._, p. 13. An unequivocal example is seen in the _Torpedo_, where the large cells have each their prolongation continuing without interruption into the electrical organ. See the figure given by REICHENHEIM in the _Archiv für Anat._, 1873, Heft VI.

[166] GOLGI, _Sulla struttura della sostanza grizia del Cervello_. ARNDT, _Archiv für mikros. Anat._ 1870, p. 176. RINDFLEISCH also traces these processes into the neuroglia (_ibid._, 1872, p. 453). “Deiters, Boddaert, and other observers have stated that one dark-bordered nerve-fibre enters each cell.... My own observations lead me to conclude that _all_ the fibres are composed of the same material, but that one fibre does not divide until it has passed some distance from the cell, while others give off branches much closer to it.”--BEALE, _Bioplasm_, p. 189.

[167] BEALE, _Bioplasm_, p. 177. MAX SCHULTZE, in _Stricker’s Handbuch_, p. 134. Comp. STILLING, _Nervenprimitiv-Faser_, p. 133. ARNDT, _Archiv_ _für mikros. Anat._, 1868, p. 512; and 1869, p. 237. Weighty as these authorities are, their view is questionable--firstly, because the forms of these cells are too constant and definite in particular places to result from the union of fibrils coming from various origins; but secondly, and mainly, because the teaching of Development is opposed to it.

[168] ROBIN, _Anat. et Physiol. Cellulaires_, p. 335.

[169] _Archives de Physiologie_, 1872, p. 268.

[170] The fact of the existence of cells in the white substance is one which is very difficult of interpretation on the current hypotheses. The cells are found in regular columns and irregularly scattered. BOLL thinks that while in the white substance of both cerebrum and cerebellum there are true nerve-cells as well as connective corpuscles, in the cord there are only the latter. But hitherto there has been no decisive test by which a nerve-cell can be distinguished from a connective corpuscle.

[171] _Monthly Journal of Micros. Science_, XI. 219. This accords with what KUPFFER says respecting the entire absence of cells in the earliest stages observed by him in the sheep. The white substance of the spinal cord he describes as soft, transparent, and gelatinous, in which dark points are visible; these dark points are seen in longitudinal sections to arise from the fibrillation of the substance.--BIDDER und KUPFFER, _Op. cit._, p. 111.

[172] WEISMANN, _Die nachembryonale Entwick. der Musciden_, in the _Zeitschrift für Wissen. Zoologie_, 1864, Bd. XIV. Heft III.

[173] The suggestion in the text has since received a striking confirmation in the observations of SIGMUND MAYER on the regeneration of nerves. The nerve when divided rapidly undergoes fatty degeneration, which is succeeded by a transformation of the myeline and axis cylinder into a homogeneous mass; in this resolved pulp new longitudinal lines of division appear, which subsequently become new fibres, and new nuclei are developed in the remains of the untransformed substance.--_Archiv für Psychiatrie_, Bd. VI. Heft II.

[174] Strong confirmation of various statements in the text, since they were written, has been furnished by the researches of EICHHORST, published in _Virchow’s Archiv_, LXIV. Our knowledge of the development of nerve-tissue in human embryos is so scanty that these researches have a great value. EICHHORST describes the striation of the cells in the cord to begin only at the fourth month; up to this time they are, what I find most invertebrate cells to be, granular, not fibrillar. There is very slight branching of the cell processes until the ninth or tenth month, when the multipolar aspect first appears; the cells are unipolar up to the end of the fourth month. The connection between the white columns and the gray columns is very loose up to the fifth month; and the two are easily separated. Subsequently the union is closer. The substance of the white columns readily separates into bundles and fibres, but that of the gray columns falls into a granular detritus if attempted to be teased out with needles. But after the fifth month this is no longer so. Instead of a granular detritus there appears a network of fine fibres and fibrils. Although the white posterior columns are developed before the fifth month, not a single cell can be seen in the posterior gray columns until the second half of the ninth month. (Yet the fibres are imagined to arise in the cells!) The passage from the granular to the fibrillar state is the same in the cell substance and the neuroglia. The nerve-fibre, as distinguished from a naked axis cylinder, does not appear till the fourth month. It is at first a bipolar prolongation of the nucleus. As it elongates, the nucleus seems to sit _on_ it, and so loosely that it is easily shifted away by pressure on the covering glass. Finally the fibre separates entirely from the nucleus, and _then_ begins to clothe itself with the medullary sheath. Very curious is the observation that so long as the axis cylinder is naked it is never varicose, but with the development of the medulla the primitive axis becomes fluid.

[175] MAYER, _Op. cit._, 393. I cannot, however, agree with MAYER when he says that the continuity of a nerve-fibre with a cell has _never_ been distinctly shown (p. 395); in the Invertebrata and in the Electric fishes such a continuity is undeniable; and it has occasionally been seen in Vertebrata.

[176] RANVIER, in the _Comptes Rendus_, 1875, Vol. LXXXI. p. 1276. This observation throws light on the fact that cell processes are sometimes seen entering nerve-roots (§ 124).

The very remarkable observations of Mr. F. BALFOUR, _On the Development of the Spinal Nerves in Elasmobranch Fishes_ (_Philos. Trans._, Vol. CLXVI. p. 1), show that the spinal root, ganglion, and nerve-trunk arise from histological changes in a mass of cells at first all alike; _not_ that ganglion-cells are formed and from their processes elongate into fibres. The nerve, he says, forms a continuation of its root rather than of its ganglion (p. 181); which accords with RANVIER’S view.

[177] In the _Handbuch der menschlichen Anatomie_ of W. KRAUSE, which has just appeared, I am pleased to find a similar view, p. 376.

[178] On this point consult AXEL KEY and RETZIUS, in the _Archiv für mikros. Anat._, 1873, p. 308, where the nutritive disturbance is assigned to the fact that the lymph can no longer take its normal course. WALLER’S observations on the degeneration of the optic nerves, with preservation of the integrity of the retina, after division of the nerves (_Proceedings of Royal Society_, 1856, p. 10), cannot be urged in support of his view, because BERLIN and LEBERT’S observations are directly contradictory of his. SAEMISCH _und_ GRAEFE, _Handbuch der Augenheilkunde_, II. 346. It is said by KRENCHEL that if the nerves be divided, so as to prevent disturbances in the circulation, no peripheral degeneration takes place (cited by ENGELMANN in _Pflüger’s Archiv_, 1875, p. 477).

[179] SCHIFF, _Lehrbuch der Physiologie_, pp. 120, 121.

[180] KÖLLIKER, _Gewebelehre_, 317. SCHWALBE, _Archiv für mikros. Anat._, 1868, p. 51.

[181] I was first shown this in 1858 by the late Prof. HARLESS in Munich, who at the same time showed me that the nerve thus bared of its sheath, if left some hours in gastric juice, split up into regular discs, like the sarcous elements of muscles.

[182] STIEDA, _Bau des centralen Nervensystem der Amphibien und Reptilien_, 1875, p. 41.

[183] BUTZKE, in _Archiv für mikroskopische Anatomie_, Bd. III. Heft 3, p. 596.

[184] Except in the rare cases where there is anastomosis of the muscle-fibres; as, for example, in the heart. [According to ENGELMANN’S remarkable researches, the muscles of the heart form a continuum, so that irritation is propagated from one to the other: _Pflüger’s Archiv_, 1875, p. 465. This is indubitably the case in the embryonic heart, as ECKHARD pointed out.] This I hold to be the main cause of its rhythmic pulsation after removal from the body. Whatever influence the ganglia may have in exciting this pulsation, such influence would be powerless were not the muscles so connected; as may be seen in the other organs which are richly supplied with ganglia, yet do not move spontaneously; and in organs (such as the ureter or the embryonic heart, and the hearts of invertebrata) which move spontaneously, yet have no ganglia.

[185] SCHRÖDER VAN DER KOLK, _Bau und Funktionen der Med. Spinalis_, p. 67.

[186] It is very instructive to learn that for some six months or so the rat is quite incapable of correctly _localizing_ the pain.

[187] VULPIAN, _Leçons sur le Système Nerveux_, p. 288. The experiment has been confirmed by ROSENTHAL, and by BIDDER (_Archiv für Anatomie_, 1865, p. 246), who first (in 1842) attempted this union of different nerves, but arrived at negative results; as did SCHIFF (_Lehrbuch der Physiol_, 1859, p. 134) and GLUGE _et_ THIERNESSE (_Annales des Sciences Naturelles_, 1859, p. 181).

[188] SACHS, in the _Archiv für Anat._, 1874, pp. 195, _sq._

[189] LAPLACE, _Essai Philos. sur les Probabilités_, p. 239.

[190] The mode of termination of nerves in muscles is still a point on which histologists disagree; probably because there is no abrupt termination, but a blending of the one tissue with the other. In the Tardigrades, for example, there is actually no appreciable distinction between nerve and muscle at the point of insertion of the nerve; and if in the higher animals there is an appreciable difference between nerve and muscle, there is an inseparable blending of undifferentiated substance at their point of junction. [According to ENGELMANN’S recent researches, there seems good reason to suppose that muscles are composed of contractile substance and a substance which is a modification of axis-cylinder substance; the first being doubly refracting, the second isotropic: _Pflüger’s Archiv_, 1875, p. 432.]

[191] SCHIFF, _Lehrbuch_, p. 73.

[192] FREUSBERG observed that the reflex movements in the legs of a dog whose spine had been divided were considerably lessened after food or drink. They fell from 95 to 46 pendulum-beats in a minute after a _litre_ of water had been drunk. See his instructive memoir, _Reflex-Lähmungen beim Hunde_, in _Pflüger’s Archiv_, 1874, p. 369.

[193] M. HERZEN thus describes the effects of stimulating the vagus with varying intensities: “Si l’on se sert de l’appareil de Dubois Raymond, on commence par appliquer une irritation tellement faible qu’elle ne produit aucun effet; on rapproche alors peu à peu lea deux bobines de l’appareil avec le plus grand soin, par fractions de centimètres, par _millimètres_ s’il le faut, et l’on trouve ainsi le degré d’irritation qui accelère les battements du cœur et qui produit le maximum de pulsations dans l’unité de temps admise pour l’expérience. Quand on est là il suffit _d’un millimètre_ de plus pour faire disparaître l’augmentation, un autre millimètre peut produire une diminution, et un _troisième_ peut arrêter le cœur complètement. En reculant alors, en éloignant peu à peu les deux bobines, _on rètourne à la force qui produit l’augmentation des battements_.” HERZEN, _Expériences sur les Centres Modérateurs de l’Action Réflexe_, 1864, p. 68. There have been serious doubts thrown on these experiments; but several experimenters have confirmed their exactness. Quite recently they have been confirmed by BULGHERI, _Il Morgagni_, VIII.; and by ARLOING and TRIPIER, _Archives de Physiologie_, 1872, IV. p. 418. It must be confessed, however, that the whole subject of the heart’s innervation is at present very imperfectly understood.

[194] CAYRADE, _Recherches sur les Mouvements Réflexes_, 1864, p. 58.

[195] A frog’s brain is removed, and the body then suspended by the lower jaw, the legs are allowed to dip into a slightly acidulated liquid, the chemical action of which stimulates the skin.

[196] I saw a patient in the Berlin _Charité_ whose face and left hand were in a constant state of convulsive twitching, but no sooner was a scar on the left hand (where the nerve had been divided) firmly pressed than the twitchings ceased, and _pain_ was felt; on removal of the pressure, pain ceased and the twitchings returned.

[197] _Pflüger’s Archiv_, 1875. No one interested in the Reflex Theory should omit a careful study of the papers by FREUSBERG and GOLTZ. I have drawn freely from them.

[198] Sir JAMES PAGET has an interesting collection of facts which illustrate this Law of Arrest, in his paper on “Stammering with other Organs than those of Speech,” _British Medical Journal_, 1868, Vol. II. p. 437, reprinted in his _Clinical Lectures and Essays_, 1875, p. 77.

[199] _Archives de Physiol._, 1868, p. 157.

[200] _West Riding Lunatic Asylum Reports_, 1874, p. 200.

[201] CLAUDE BERNARD, _Système Nerveux_, I. 383.

[202] See the excellent remarks of Dr. LAUDER BRUNTON on this point in his paper on Inhibition in the _West Riding Lunatic Asylum Reports_, 1874, p. 180.

[203] The interesting question of interference has been experimentally treated by WUNDT in his recently published _Mechanik der Nerven_, 1876, and theoretically as wave-movement by MEDEM, _Grundzüge einer exakten Psychologie_, 1876.

[204] On the distinction between first notions and theoretic conceptions, see _Problems of Life and Mind_, Vol. II. p. 277.

[205] Not transcendental and _a priori_, as Kant teaches; but immanent in Feeling.

[206] The reader will understand that although mechanical relations are modes of Feeling, as all other relations are, yet their aspect is exclusively objective, referring to objects ideally detached from subjects.

[207] ANTOINE CROS, _Les Fonctions supérieures du Système nerveux_, 1875, p. 85.

[208] The solution offered in the present chapter was first offered in _Problems of Life and Mind_, 1875, II. 465, _sq._ I mention this because since the publication of that volume other writers have expressed the same ideas, sometimes using my language and illustrations: e. g. M. TAINE in the _Revue Philosophique_, January, 1877, art., _Les Vibrations cérébrales et la Pensée_.

[209] _Problems of Life and Mind_, Vol. II. pp. 443 and 482.

[210] “The retinal image is the last effect known of the action of objects on us; what happens beyond the retina we know not; our knowledge of the objective process has at present here its limit.”--EWALD HERING, _Beiträge zur Physiologie_, 1862, p. 166. That is to say, we have a definite translation of the process in geometric terms as far as the retina, and thence onwards Geometry fails us, and Neurology and Psychology are invoked.

[211] Compare PROBLEM II. Chap. IV.

[212] “Das Bewusstwerden ist nichts Anderes als ein weiter fortgeschrittenes Erinnern oder Neuwerden des von aussen aufgenommenen Wissens, ein innerliches Wissen dieses Wissens oder ein in sich reflectirtes Wissen.”--JESSEN, _Versuch einer Wissenschaftlichen Begründung der Psychologie_, 1855, p. 477.

[213] In common language a stone or a tree is said to be unconscious; but this is an anthropomorphic extension of the term. In strictness we should no more speak of unconsciousness outside the sphere of Sentience than of darkness outside the sphere of Vision.

[214] The contraction may be effected in the eye out of the organism. See p. 229. It is then no reflex.

[215] _Glasgow Medical Journal_, 1857, p. 451. See also further on, note to p. 426.

[216] MAYER, _Die Elementarorganisation des Seelenorgans_, p. 12, is the authority for the last statement.

[217] _Allgemeine Zeitschrift für Psychiatrie_, Bd. 31, p. 711.

[218] AUBERT, _Grundrüge der physiol. Optik_, 1876, p. 633. “The accommodative movement of the eye is to be considered voluntary. It is true we contract the pupil without being conscious of the contraction of muscular fibres, _but this holds good for every voluntary movement_. When a person raises the tone of his voice he is not conscious that by muscular contraction he makes his chordæ vocales more tense; he attains his object without being aware of the means by which he does so. The same is applicable to accommodation for near objects and to the contraction of the pupil accompanying it. The fact that _this last is only an associated movement does not deprive it of its voluntary character_, for there is perhaps no single muscle which can contract entirely by itself.” DONDERS, _On the Anomalies of Accommodation_, 1864, p. 574. Professor BEER of Bonn has the rare power of contracting or dilating the pupils of his eye at will; here ideas act as motors. When he thinks of a very dark space the pupil dilates, when of a very bright spot the pupil contracts. (NOBLE, _The Human Mind_, 1858, p. 124.) I believe this to be only an exaggerated form of the normal tendency. In all of us the mechanism is so disposed that the feelings of dilatation are associated with feelings (and consequently ideas) of darkness; and by this association a reversal of the process obtains, so that the idea of darkness calls up the feeling it symbolizes.

[219] SPENCER, _Principles of Psychology_, I. 499.

[220] DESCARTES expressly calls them sensitive machines. He refuses them Thought, but neither “la vie ou le sentiment.” He adds, “Mon opinion n’est pas que les bêtes voient comme nous lorsque nous sentons que nous voyons.”--_Œuvres_, IV. p. 339. This example is cited by him in proof of human automatism: “Que ce n’est point par l’entremise de notre âme que les yeux se ferment, puisque c’est contre notre volonté, laquelle est sa seule ou du moins sa principale action; mais c’est à cause que la machine de notre corps est tellement composée que le mouvement de cette main vers nos yeux excite un autre mouvement en notre cerveau qui conduit les esprits animaux dans les muscles qui font abaisser les paupières.” All indeed that we assign to Sensibility, he assigns to these hypothetical animal spirits, and thence he concludes, “Qu’il ne reste rien en nous que nous devions attribuer à notre âme sinon nos pensées.”--_Les Passions de l’Âme_, art. 13 and 17. Comp. _Discours de la Méthode_, partie iv.

[221] DESCARTES compares the animal mechanism to that of the grottos and fountains at Versailles, the nerves to the water-tubes:--“Les objets extérieurs qui par leur seul présence, agissent contre les organes des sens, et qui par ce moyen, la déterminent à se mouvoir en plusieurs diverses façons, selon comme les parties du cerveau sont disposées, sont comme les étrangers, qui entrant dans quelques unes des grottes de ces fontaines causent euxmêmes sans y penser les mouvements qui s’y font en leur présence: car ils n’y peuvent entrer qu’en marchant sur certains carreaux tellement disposés, que s’ils approchent d’une Diane qui se baigne, ils la font cacher dans les roseaux; et s’ils passent outre pour la poursuivre, ils feront venir vers eux un Neptune qui les menacera de son trident; ou s’ils vont de quelque autre costé, ils en feront sortir un monstre marin qui leur vomira de l’eau contre la face.”--_Traité de l’Homme_, 1664, p. 12. Ingenious as the comparison is, it only illustrates how machines may be constructed to imitate animal actions. Diana always hides herself when a certain spot is trodden upon; and Neptune always appears when another spot is trodden upon. There is no fluctuation, no sensibility discerning differences and determining variations. Compare the following experiment: A monkey was placed on the table and a shrill whistle made close to its ear: “Immediately the ear was pricked and the animal turned with an air of intense surprise, with eyes widely opened and pupils dilated, to the direction whence the sound proceeded. On repetition of the experiment several times, though the pricking of the ear and the turning of the head and eyes constantly occurred, the look of surprise and dilatation of the pupils ceased to be manifested.”--FERRIER, _The Functions of the Brain_, 1876, p. 171. A mechanical monkey would always have reacted in precisely the same way on each stimulus.

[222] Printed in the _Fortnightly Review_, November, 1874, from which all my citations are made.

[223] SCHIFF, _Lehrbuch der Physiol._, 1858, p. 212. HERMANN, _Physiology_, translated by GAMGEE, 1875, p. 511.

[224] Meanwhile the reader is referred to SCHRÖDER VAN DER KOLK, _Pathologie der Geisteskrankheiten_, 1863, p. 51; or JESSEN, _Physiologie des menschlichen Denkens_, 1872, p. 66.

[225] GRIESINGER, _Les Maladies Mentales_, p. 96.

[226] M. LUYS cites the case of a patient who conversed quite rationally with a visitor “sans en avoir conscience, et ne se souvenait de rien”; and he draws the extraordinary conclusion that the conversation “s’opérait en vertu des forces réflexes.”--_Études de Physiologie et de Pathologie Cérébrales_, 1874, p. 117. Is it not obvious that the patient must have been conscious at the time, though the consciousness vanished like that in a dream? The persistent consciousness is the continuous linking on of one state with previous states--the apperception of the past.

[227] ABERCROMBIE, _Inquiries concerning the Intellectual Powers_, 1840, p. 151. WIGAN, _The Duality of the Mind_, 1844, p. 270. DESPINE, _La Psychologie Naturelle_, 1868, I. 54.

[228] Dr. HUGHLINGS JACKSON has quite recently cited some curious examples in his own practice. See _West Riding Lunatic Asylum Reports for 1875_.

[229] PROBLEMS, Vol. II. p. 478, _sq._

[230] “Le sentiment fait naître le mouvement, et le mouvement donne naissance au sentiment.”--VAN DEEN, _Traités et Découvertes sur la Moëlle Épinière_, 1841, p. 102.

[231] Dr. CARPENTER tells a similar story of Admiral CODRINGTON, who, when a midshipman, could always be awakened from the profoundest slumber if the word “signal” were uttered; whereas no other word disturbed him.

[232] Compare an interesting personal example given by JOUFFROY, quoted in Sir W. HAMILTON’S _Lectures_, I. 331.

[233] _Lancet_, 10th July, 1858.

[234] MARSHALL HALL in _Philos. Trans._, 1833. _Lectures on the Nervous System and its Diseases_, 1836. _New Memoir on the Nervous System_, 1843.

[235] MÜLLER, _Physiology_, I. 721.

[236] It is better simply to remove the brain, than to remove the whole head, which causes a serious loss of blood. An etherized animal may be operated on with ease and accuracy. For many experiments, mere division of the spinal cord is better than decapitation. Great variations in the results must be expected, because the condition of the animal, its age and sex--whether fasting or digesting--whether the season be spring or summer--and a hundred other causes, complicate the experiment.

[237] VOLKMANN, quoted by PFLÜGER.

[238] UNZER, _The Principles of Physiology_ (translated for the Sydenham Society), p. 235.

[239] Even so eminent an investigator as GOLTZ has fallen into this confusion. He introduces an experiment to prove that the brainless frog is insensible to pain by the words “when an animal, placed under circumstances which would be very painful, makes no movement, although quite capable of moving, the least we can say is that it is improbable that the animal has sensation” (_Nervencentren des Frosches_, p. 127). I need not discuss the proof itself, having already done so in _Nature_, Vol. IX. p. 84. The point to which I wish to call attention is the confusion of insensibility in general with insensibility to pain.

[240] See DUCHENNE, _De Électrisation localisée_, p. 398. GRIESINGER cites various examples of insane patients who have burned the flesh off their bones while manifesting a total indifference to these injuries. _Maladies Mentales_, p. 94. FALRET says, “Nous avons vu plusieurs fois des aliénés s’inciser, s’amputer eux-mêmes diverses parties du corps sans paraître ressentir aucune souffrance.” _Leçons cliniques de Médicine Mentale_, 1854, I. 189. Patients incapable of feeling the contact of a hot iron with their skin have felt subjective burnings in the skin thus objectively insensible.

[241] CROS, _Les Fonctions supérieures du Syst. nerveux_, 1875, p. 27.

[242] _Virchow’s Archiv_, Bd. XXVIII. p. 30.

[243] The idea of a _fixed anatomical mechanism_ for reflexion, such as that of an excito-motory system, is completely refuted by the fact that the gray substance may anywhere be cut sway, and yet so long as a small bridge of gray substance remains the stimulation will be propagated through it. The idea of a _fixed pathway_ is also refuted by the fact of the variations in the reflex responses, and the necessary irradiation even for very simple reflexes. Take, for example, that of breathing. An irritation of the bronchial filaments is transmitted by the pneumogastric to its centre in the medulla oblongata; from this, however, it is immediately irradiated _downwards_ to the cervical and dorsal regions, which innervate the muscles of chest and diaphragm, and _upwards_ to the brain, whether the stimulation awaken consciousness or not. One may say, indeed, that inasmuch as under normal conditions the bronchial irritation always causes a movement of a particular group of muscles, there is to this extent a fixed pathway of discharge; but, as I have formerly explained, this is only an expression of the particular tension of particular centres, and is variable with that tension; the other centres are also affected, even when they are not excited to discharge.

[244] LALLEMAND, _Recherches sur L’Encéphale_, III. 310.

[245] _West Riding Lunatic Asylum Reports_, 1875, Vol. V. pp. 252, _sq._

[246] GALL _et_ SPURZHEIM, _Anat. et Physiol. du Système Nerveux_, I. 83.

[247] Printed in the _British and Foreign Medical Review_, Jan. 1845.

[248] GRIESINGER, _Abhandlungen_, 1872. The first volume contains a reprint of this memoir.

[249] LANDRY, _Traité des Paralysies_, I. 55. Conf. ZIEMSSEN, _Chorea_ in the _Handbuch der speciellen Pathologie_, Bd. XII. 2, p. 408. And LUYS, _Études de physiol. et pathol. cérébrales_, 1874, pp. 89–94.

[250] SUE, _Recherches Philosophiques sur la Vitalité et le Galvanisme_, p. 9. He was not consistent, however, but adopted Bichat’s opinion respecting the sensibility of the viscera, p. 68.

[251] LEGALLOIS, _Expériences sur le principe de la vie_. Published, I conclude, in 1811; the edition I use is the one printed in the _Encyclopédie des Sciences Medicales_, IV.

[252] WILSON PHILIP, _Experimental Inquiry into the Laws of the Vital Functions_, pp. 209, 210.

[253] LONGET, _Traité de Physiologie_, II. 105.

[254] He cites Cuvier, Majendie, Deamoulins, and Mayo as maintaining this error.

[255] GRAINGER, _Structure and Functions of the Spinal Cord_, p. 66.

[256] NASSE, _Unters. zur Physiologie und Pathologie_, Vol. II. Part 2.

[257] CARUS, _System der Physiologie_, III. 101.

[258] J. W. ARNOLD, _Die Lehre von der Reflex-Function_, 86.

[259] PFLÜGER, _Die sensorischen Functionen des Rückenmarks der Wirbelthiere_.

[260] Except AUERBACH, who repeated and varied the experiments; and FUNKE, who partially adopted the conclusions in his systematic treatise on Physiology.

[261] SCHIFF, _Lehrbuch der Physiologie_, 208.

[262] LANDRY, _Traité des Paralysies_, 1859, maintains that the cord is a centre of sensation, and that there is in it a faculty _analogous_ to the perception and judgment of the brain. Compare pp. 163 _et sq._ and 305. He also cites an essay by Dr. PATON of Edinburgh (_Edinburgh Medical Journal_, 1846), in which the sensational and volitional claims of the spinal cord are advanced.

[263] GOLTZ, _Beiträge zur Lehre von den Functionen der Nervencentren des Froeches_, 1869.

[264] _Pflüger’s Archiv_, Bd. XIV. p. 158.

[265] See Prob. II. § 183.

[266] “Il y a donc une mémoire par le cerveau et une mémoire par l’automate. Tous les organes ont une mémoire propre, c’est à dire _une tendance à_ reproduire les séries d’actes qu’ils ont plusieurs fois executés.”--GRATIOLET, _Anat. du Système Nerveux_, 1857, p. 464.

[267] To obviate misunderstanding let me say that, unless the contrary is specified, I use the term Brain throughout this argument as equivalent to the cerebral hemispheres, because it is in these that sensation, volition, and consciousness are localized by the generality of writers, many of whom, indeed, regard the cells of the gray matter of the convolutions as the exclusive seat of these phenomena, dividing these cells into sensational, emotional, and intellectual. There are physiologists who extend sensation to the cerebral ganglia and gray masses of the medulla oblongata; but the medulla spinalis is so clearly continuous with the medulla oblongata that there is a glaring inconsistency in excluding sensation from the one if it is accorded to the other; and the grounds on which sensitive phenomena are admitted in the absence of the hemispheres, force us to admit analogous phenomena in the absence of the ganglia and medulla oblongata: in each case the phenomena are less complex and varied as the mechanisms become less complex.

[268] Compare LUSSANA e LEMOIGNE, _Fisiologia dei centri encefalici_, 1871, II. 239, 240, 330.

[269] See a very interesting case of this special loss of memory in a priest who still occupied himself reading classic authors and performing his official duties many months after an injury to the brain. LUSSANA e LEMOIGNE, _Fisiologia dei centri encefalici_, I. 201.

[270] BOUILLAUD, _Recherches Expérimentales sur les Fonctions du Cerveau en général_, 1830, p. 5, _sq._

[271] LONGET, _Traité de Physiologie_, II. 240.

[272] DALTON, _Human Physiology_, Philadelphia, 1859, p. 362.

[273] DALTON, p. 362.

[274] DALTON, p. 363.

[275] FLOURENS, p. 89.

[276] LEYDEN in the _Berliner klinische Wochenschrift_, 1867, No. 7. MEISSNER, _Jahresbericht über Physiol._, 1867, p. 410.

[277] VOIT in the _Sitzungsberichte der Münchener Academie_, 1868, p. 105. Comp. also GOLTZ in _Pflüger’s Archiv_, Bd. XIV. 435.

[278] VULPIAN, _Système Nerveux_, 542–48.

[279] For other examples see GINTRAC, _Pathologie Interne_, 1868, VI. 51–57.

[280] If the water is perfectly still the fish sinks to the bottom and remains motionless until the water be stirred. Mere _contact_ does not suffice; there must be intermittent pulses from the moving water.

[281] LUSSANA e LEMOIGNE, _Op. cit._, I. 15.

[282] _Archives de Physiologie_, 1869, p. 539.

[283] BRÜCKE, _Physiologie_, II. p. 53. While these sheets are passing through the press, GOLTZ has published his second series of experiments on the brain. The following detail is a good illustration of what is said in the text: A dog deprived of a portion of both hemispheres displayed a marked imperfection in the execution of ordinary instincts. Although sight was impaired he could see, and recognize men and certain objects: the sight of a whip made him cower, but the sight of meat did not suffice to set the feeding mechanism in action. When meat was suspended above his head, the scent caused him to sniff about in search, but he failed to find it, and even when he was so placed that he could see the suspended meat, the _unusual_ impression failed to guide him. If the meat were held towards him, or placed before him in a dish, he took it at once--this being the customary stimulation. So also, if the hand were held up, in the usual way when dogs are made to leap for food, this dog sprang vigorously up and caught the food; but he would spring up in the same way when the hand was held empty, and continue fruitlessly springing, whereas an uninjured dog ceases to spring when he sees the hand is empty.--_Pflüger’s Archiv_, Bd. XIV. p. 419.

[284] GRATIOLET, _Anat. Comparée du Système Nerveux_, 1857, p. 459.

[285] LUSSANA e LEMOIGNE, _Op. cit._, I. 363.

[286] _Virchow’s Archiv_, Bd. LX. pp. 130–33. Yet there are many physiologists who persist in placing the _motorium commune_ in the _corpora strata_! And they place the _sensorium commune_ in the optic thalami, although, not to mention the ambiguous evidence of Pathology, the experiments of NOTHENGEL and VEYSSIÈRE show that destruction of the thalami does not destroy sensation. See VEYSSIÈRE, _Recherches sur l’hémianesthésie de cause cérébrale_, 1874, pp. 83, 84. I may observe, in passing, that the notion of the _corpora striata_ being the necessary channel for volitional impulses, and the _optic thalami_ for reflex actions, is utterly disproved by the experimental evidence recorded in the text, as well as in § 66.

[287] _Pflüger’s Archiv_, Bde. VIII. and IX.

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