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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    their bases. In the lower or anterior part of each is seen the group of large cells (t') which form the hypoglossal nucleus; and in the upper or posterior part is seen another and oval group of smaller cells (t), forming part of the nucleus of the spinal-accessory nerve. Behind this group of cells, the part t is finer in texture, consisting of granules, nuclei, small cells, and fine fibres. The posterior pyramid (b) is rather larger than in fig. 19, but it now begins to be bevelled off at its base, just below b; and between it and the spinal-accessory nucleus (t) there is a small triangular and paler mass (b), which is in fact the inner side of the base of the pyramid, where it was joined to its fellow at the bottom of the median fissure, as seen at b, fig. 19, enclosed in the dotted line on the right side. The outer restiform nucleus (c') has increased considerably in dimensions, while the inner nucleus (o) has somewhat diminished (compare figs. 7 & 8, Plate VIII. of human medulla on the right side). The decussating fibres (n, y') proceeding from the side of the spinal-accessory nucleus to the opposite olive and anterior pyramid are less numerous. In fig. 21, Plate IX. the outer restiform nucleus (c') is quite as large as in the preceding figure ; while the inner nucleus (o) is much smaller, and is divided into several separate masses, which are partially blended with the outer nucleus (</). The posterior pyramid (b) has considerably diminished, and the part b at its base has swollen into a larger eminence, which is now directly continuous with the posterior part (t) of the vagal nucleus, and seems to arise out of it (compare fig. 20), while its cells have increased somewhat in size. At the point between t and b there is an oval mass of epithelial cells and fibres (seen at t on the left side) which is continuous with the layer that covers the ventricle; it exists also in Man, but is much smaller than in the Ape. The hypoglossal nucleus (t') has increased considerably in dimensions, pushing, as it were, outward, the oval group of cells (f), which now becomes the nucleus of the vagus, instead of the spinal-accessory nerve. The bundles of fibres (n, y') have ceased to proceed from the side of the spinal-accessory (now the vagal) nucleus to the opposite olive and anterior pyramid, the point whence they issued presenting now only the cut end of a slender column of longitudinal fibres (n) enclosed in a crescent between the horns of the nucleus. In fig. 22, Plate X. the outer restiform nucleus (o') and the scattered masses of the inner nucleus (o) have somewhat diminished and become still more intermixed. At the same time it will be observed that the posterior pyramid (b) is still further reduced, while the part b (which in fig. 20 belongs to the base of the pyramid) has extended in a corre- sponding proportion; so that now the posterior part (t) of the vagal nucleus, and the part b of the posterior pyramid form together a triangular mass (i) uniform in struc- ture, and overlying the slender longitudinal column n and the oval group of cells (t) which gives origin to the upper roots of the vagus nerve. The hypoglossal nucleus (it1) reaches the surface of the ventricle, and completely separates i from its fellow of the opposite side. In fig. 23, Plate X. at^j is seen a large bundle of arciform fibres coming from the outer part of the restiform body, and sweeping forward through the extremity of the caput cornu (e e) to the olivary body (W). The hypoglossal nucleus has con- siderably diminished, and retreated further backward and outward at the inner side of ?,