The gray substance of the medulla oblongata and trapezium / by John Dean.

Date:
[1864]
Catalogue details

Licence: Public Domain Mark

Credit: The gray substance of the medulla oblongata and trapezium / by John Dean. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    subsequent chapter. The olivaries are connected with each other and with the raphe by the arciform fibres, and are also united to the hypoglossal nuclei by bundles of fibres, either directly or by the interposition of cell nuclei. The anterolateral nucleus (B) is now very prominent, from the number and size of its cells. These are mostly stellate, sending their processes in all directions, the group being traversed by the arciform fibres and by fibres derived from the central gray substance, as well as by longitudinal fibres. This group is also united to the caput, and in sections higher up to the remains of the cervix, by the cells formerly scattered throughout the antero-lateral columns, but which are afterwards collected into elongated groups (Fig. 3a). The restiform (r, r) and post-pyramidal (p,p) nuclei are now much increased in size, and are quite filled with cells of various dimensions and forms, the cells of both nuclei reaching out into and soon entirely filling the posterior and postero-lateral columns. As we ascend, the nuclei of the hypoglossal and spinal accessory nerves rapidly increase in size and number of cells, the entire substance of the anterior or hypo glossal nucleus (H) being filled with large stellate cells, with the exception only of that portion which forms on each side the lateral boundary of the central canal. The posterior, spinal accessory or vagus nucleus (S), has also equally increased; its group of large, obovate cells is very conspicuous, the remainder of the nucleus being entirely filled with smaller, scattered cells. The caput is mostly filled with granules and smaller nuclei, with a few cells of medium size; numerous cells being scattered throughout the entire lateral and antero-lateral network. (3.) Still higher up (Plate I, Fig. 3; Plate XIII, Fig. 3) the central canal which has been hitherto somewhat elongated, of a narrow oval form, changes to a trian- gular shape with curved sides, the apex pointing forwards, and bridged behind by a thick band of commissural fibres connecting the posterior nuclei, now the nuclei of the vagus roots (Fig. 3a, F). The principal changes to be noticed in this region are the rapid increase in the number of cells forming the post-pyramidal (p, p) and restiform (r, r) nuclei, which fill the entire posterior and postero-lateral columns, encroaching on the caput and thick band of external arciform fibres, with both of which they seem to be connected by numerous bundles of curving or wavy fibres (Fig. 3, a). A remarkable collection of longitudinal fasciculi is here plainly mani- fest, which, beginning a little lower down, comes now distinctly in sight just at the entrance of the vagus roots (?), separating them into anterior and posterior divisions. The cells of the anterolateral nucleus, instead of being collected into compact groups as below, are somewhat scattered, forming various wavy groups which nearly fill the antero-lateral columns of the medulla (B). (4.) As we continue to ascend (Plates I, XIII, Figs. 4, 4) the commissural bridge between the two vagal nuclei is split open, forming the fourth ventricle, on each side of which are situated the nuclei of the hypoglossal and vagal nerves, the anterior portion of the vagus nucleus being especially conspicuous from its crowd of obovate cells. The longitudinal fasciculi in connection with the vagus nucleus are very promi- nent, separating the roots into two divisions, the posterior bundles either entering a small nucleus behind the longitudinal fasciculi, or bending around them towards