Researches on the intimate structure of the brain. 2nd ser. / by J. Lockhart Clarke.

  • Clarke, J. Lockhart (Jacob Lockhart), 1817-1880.
Date:
1868
Catalogue details

Licence: Public Domain Mark

Credit: Researches on the intimate structure of the brain. 2nd ser. / by J. Lockhart Clarke. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    projects into the restiform body (c) and constitutes its grey nucleus, or the restiform ganglion. In figs. 4 & 5, we find the same changes carried to a still greater extent. In the latter the decussating bundles of the anterior pyramids come only from the central grey substance and roots of the anterior cornua at the sides of the canal, and scarcely at all, as they did in fig. 4, from the lateral columns (d'), in which now the original net- work is again distinguishable; but it is larger, closer, more beautiful than we found it in fig. 1, and contains in its meshes bundles that have no share in the formation of the anterior pyramids*. The central grey substance, on each side of the median line, with the corresponding cornu, are now represented by t' tV oe (compare figs. 1, 2, 3, 4 & 5). In fig. 6, which represents a transverse section a little higher up, just below the bulb of the posterior pyramids, we see that the anterior part (t') of the central grey substance immediately surrounding the canal, is distinct from the posterior part (t), which covers it as by a kind of slanting roof. This latter is the vesicular tract or nucleus which gives origin to the upper roots of the spinal-accessory nerves. The anterior part (t1) is the vesicular tract or nucleus of the hypoglossal nerve, and is the analogue of a portion of the anterior or motor cornu of the spinal cord. These cornua are now scarcely distinguishable, but their places are traversed by roots of the hypoglossal nerves in their passage outward from their nuclei. Traversed also by these roots, and lying on the outer and back part of each anterior pyramid (y), is a layer of small cells which, higher up, form the anterior or inner part of the lamina of the olivary body (h, figs. 7 & 8). On the outer side of this layer is another distinct group of cells (s) connected by a network in the lateral column, and by nerve-fibres from the grey tubercle (e). This is the antero- lateral nucleus. Meanwhile the post-pyramidal and restiform nuclei {b\ o) have increased in size, and from these, especially the post pyramidal, proceed the chief portion of the decussating fibres which sweep round the front of the canal to enter the anterior pyramids. (4) In ascending the medulla, the changes just described continue to increase in extent, and an important modification may be observed to take place. Fig. 7 repre- sents a transverse section on a level with the lower part of .the olivary bodies. Here the posterior pyramid (b) is nearly filled with its grey substance (V); and that of the resti- form body (o) has also greatly increased, although it is still covered by a considerable layer of white substance (c), by which it is separated, on the one side, from the postpy- ramidal nucleus (b'), and on the other side from the grey tubercle of Rolando (e). The spinal-accessory nucleus (t) and the hypoglossal nucleus (f) have become enlarged and somewhat modified in shape. The latter (t'), on each side and in front of the elongated canal, now contains the large multipolar cells which give origin to the upper roots of the hypoglossal nerve (cc). As in fig. 6, a number of fibres proceeding from the poste- rior pyramids (V) sweep round in a direction forward and inward, and decussate in front of the hypoglossal nucleus; but instead of plunging into the opposite anterior pyramid, as they didin fig. 5, they terminate in the opposite lateral and olivary column. Further outward and forward, other arciform fibres, proceeding from the grey tubercle (e), and * See my memoir on the Medulla Oblongata, fig. 19, Plate XY. Philosophical Transactions, Part I. 1858. 2 p 2
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