Volume 1

A manual of diseases of the nervous system / by W.R. Gowers.

Date:
1886-1888
Catalogue details

Licence: Public Domain Mark

Credit: A manual of diseases of the nervous system / by W.R. Gowers. 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.

    131/488 (page 111)
    In the lo-wer dorsal and upper lumbar cord, from the ninth dorsal to the third lumbar nerves, a group of nerve-cells lies in the inner part of the neck of the posterior horn, the posterior vesicular tract of Lockhart Clarke* (p. v. c. Fig. 62 ; see also Fig. 71). Most of these cells are fusiform in shape, but are placed vertically, so that they appear round or oval in transverse section. Some, however, present processes that run forwards or backwards. Nerve-fibres pass into and by it, which we shall consider subsequently. Although this tract is chiefly developed in the lower dorsal and upper lumbar cord, a few nerve-cells of similar character are met with in the same position in other parts, and are occasionally sufficiently numerous to form a small group. The gelatinous grey matter which forms a cap on the posterior horn, caput cornu posterioris (c. c. p.. Fig. 57) differs considerably in structure from the rest. It resembles closely the granule-layers of the retina in microscopical aspect, and apparently in chemical nature. It has been described as made up of granules, but, according to later researches, consists of a peculiar, translucent material forming an excessively fine network, which behaves to reagents like horny material. Numerous nerve-fibres pass through it, from the posterior roots, and these, coursing forwards, seem to divide it into columns, as it is viewed in transverse section. Although it is developed from the same embryological elements as the true nerve-structures, it has not, according to this view, a nervous function, but is to be regarded rather as a supporting structure, specially developed in connection with the sensory nerve-roots. Its extent and position are, it must be admitted, difficult to reconcile with this view of its nature. A few small ganglion cells lie in this gelatinous substance, chiefly on the inner side. Bundles of vertical fibres are also seen in transverse section, and these are often numerous just above the cap at, especially on the inner side of the horn. Most of these are fibres of the posterior nerve-roots that have a vertical course for a short distance. In Fig. 71 the axis- cylinders of these fibres are seen to be changing from the horizontal to the vertical direction, and their relation to the posterior root-fibres can be distinctly traced. These fibres are sometimes so abundant that some of them probably belong in part to the postero-external columns (posterior ground-fibres). The gelatinous substance contains many vessels, nmning for the most part vertically. White Substance.—We may now examine, in greater detail, the con- stitution of the whibe columns of the cord, and the probable course and function of the fibres they contain. The analysis has been greatly aided by two facts. The first (discovered by Tiirck) is that in certain tracts in the white substance the nerve-fibres undergo secondary degeneration when separated from their cells of origin, a degeneration analogous to that which, as we have already seen, occurs in the nerve-fibres * Continental anatomists have done Lockhart Clarke the questionable honour of throwing aside the name he gave to this group and terming it Clarke's column.