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

  • Dean, John, M.D.
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 National Library of Medicine (U.S.), through the Medical Heritage Library. The original may be consulted at the National Library of Medicine (U.S.)

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    CHAPTER III. THE HYPOGLOSSAL NUCLEUS AND ROOTS. The Nucleus.—Stilling1 was the first to point out the true origin of the hypoglos- sal roots, from the two groups of nerve cells which make their appearance just above the upper cervical nerves, in front of the central canal, extending laterally to a con- siderable distance on each side. These groups seem to be a continuation of the cell columns from which the anterior spinal roots arise, being situated within what is evidently the posterior portion of the anterior cornua, the anterior portion of which has already been broken up into an open network by the passage of numerous longitudinal fasciculi, to such an extent that the portion in the immediate vicinity of the central canal, together with a branching wing on each side the raphe, alone remains distinct. The form of the hypoglossal nucleus as it appears just above the decussation of the pyramids, is nearly pyramidal, with its apex directed forwards towards the roots, varying but slightly in those mammalia I have examined, from its shape in man, the only difference arising from the greater general concentration of structure in the human medulla. These slight differences will be readily seen by comparing Figs. 17, 18, 19, 20, 21, 22, Plates V and VI, from the human medulla, with the corresponding sections from the sheep, Plates I, II, Figs. 1, 2, 3, 4, 5, 6. Higher up the nucleus increases somewhat in size, and is gradually pushed slightly backwards and outwards, changing its form somewhat, becoming almost square close to the calamus scrlptorius (Plates I, II, Figs. 4, 5; Plate VI, Fig. 21), and having attained its greatest development, gradually diminishes in size, reassum- ing presently its former pyramidal shape, finally becoming covered over by the auditory ganglion. Fig. 7, Plate II, shows the last remains of the hypoglossal which in Fig. 8 is completely merged in the auditory nucleus. The oval cell groups which occupy already a large portion of the nucleus on each side of the middle line, increase rapidly in size and number of cells as they ascend, until their point of greatest development is reached a little above the calamus scriptorius. The cells are mostly quite large, stellate or oblong in shape, and multipolar, resembling in every respect those found in the anterior cornua of the spinal cord, for which they might easily be mistaken.2 1 Medulla Oblongata. Erlangen, 1843. a The great similarity both in the form of the cells and the general relations which these bear to the roots may be seen by comparing one of the figures from my memoir on the spinal cord (Memoirs of the American Academy, 1861, fig. 4), with pi. x, fig. 37 of the present memoir, the principal dif- ference being solely that the cells of the hypoglossal nucleus are much more closely crowded together