Problems of Life and Mind. Second series, George Henry Lewes [e book reading free TXT] 📗
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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
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