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117 Comptes Rendus de la SocĂĂ©tĂ© 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 VĂvants et fossils, p. 113.
122 Seaside Studies, 2d ed., p. 101.
123 Cited by Brown SĂ©quard, 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 fĂĽr 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 ĂĽber die erste Anlage des Wirbelthierleibes, 1868, p. 197.
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 RĂĽckenmarks, 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 ĂĽber Gehirn und RĂĽckenmark, 1865.
148 Archiv fĂĽr mikros. Anat., 1869, p. 217. Compere also Butzke, Archiv fĂĽr 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
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