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.

    144/488 (page 124)
    Some fibi-es, moreover, pass across tlie intermediate grey substance, aud, reacliiug tlie lateral column, assume a vertical direction. It is probable that some filjres are decussating fibres of the direct pyramidal tract, so tbat part of • tbe anterior commissure is to be regarded as a continuation of tbe decussation of the pyi-amids. Lastly, a few fibres of the anterior commissure have been thought to come from the posterior nerve-roots. The grey commissure contains very fine meduUated nerve-fibres, a large number of which pass backwards in the posterior horn of each side, and appear to be continuous with the fibres of the posterior roots. It is highly probable that, by this means, a considerable number of the posterior root-fibres cross (or fibres from cells in which the root- fibres end), and that thus the partial decussation of the sensory path in the cord is effected, which is known to take place a short distance above the entrance of the nerves. If the grey commissure consisted only of root-fibres, it has been estimated that it could contain only about one half of those of the posterior roots. Some of the fibres that thus cross doubtless find their way to the antero-lateral ascending tract in the opposite lateral column. Others leave the commissure in the middle line, and pass backwards to the posterior median column, but whether these decussate or not we do not know. Within the grey commissure is the central canal of the spinal cord, lined with epithelium, and surrounded by granular material, similar in nature to that which caps the posterior horn. It is often filled up in adult cords. The course of the root-fibres remains to be considered. The anterior roots pass through the anterior columns in bundles which are distribu- ted through an area of the column approximately corresponding to the width of the anterior surface of the cornu. In the grey substance, fibres from most of these bundles pass in three different directions, outwards, inwards, and directly backwards in the middle of the horn, and thus cross each other and the fibres from the anterior commissure. Many of the fibres enter the groups of nerve-cells and certainly end in these cells. Some of those that pass outwards, enter the lateral white column (mixed zone) and probably, after a short course in this, re-enter the grey matter at a higher or lower level. Some of the fibres that pass inwards may pass through the commissure to the opposite anterior horn. The posterior root-fihres, although arranged in a continuous vertical series at their surface attachment, divide into two sets, one of Avhich passes through the captit cornu posterioris (Fig. 71), the other through the adjacent part of the post.-exterual column (Fig. 57). The former course through the gelatinous substance, sometimes in a compact bundle (Fig. 71), sometimes in curves of which the concavity is turned towards the centre of the head. Some of the fibres bend into a longitudinal direction above the caput (Fig. 71) aud are seen in section