Further researches on the grey substance of the spinal cord / by J. Lockhart Clarke.

  • Jacob Augustus Lockhart Clarke
Date:
1859
Catalogue details

Licence: Public Domain Mark

Credit: Further researches on the grey substance of the spinal cord / 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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    B. Cells of the Gelatinous Sxibstance'^.—The cells of the gelatinous substance, in regard to size, may be described as {a) large, ih) small, and (c) intermediate. (a) The large cells are almost exclusively found amongst the semicircular fibres which run within the external border of the substantia gelatinosa, and never extend beyond the middle of its depth (fig. 1, Plate XIX., and fig. 47, Plate XXII.). They are more or less oval, pyriform, fusiform, crescentic, triangular, or otherwise irregular, and contain distinct nuclei. They all give off processes from two to five or six in number. The fusiform and oval variety are elongated transversely, longitudinally, and in planes intermediate or oblique. Sometimes a fusiform cell tapers at each end into a broad process, whicli attenuates in its course, and either remains single or subdivides into two or more; or it bifurcates at once into two processes at each extremity or only at one. In a transverse section of the cord, some of these processes appear to terminate in one or more of the semicircular or marginal fibres; some run backwards through the posterior columns, or forwards across the gelatinous substance; others pursue a longitudinal course with the fbres of the gelatinous suhstance, or along the verge of the posterior columns. From a cell of another shape three or more processes may be seen to extend in different direc- tions—backwards, forwards, laterally, obliquely, or longitudinally. Frequently a tri- angular cell, resting on the verge of the gelatinous substance, sends a process right and left, and a third through the posterior column along the side of a bundle of the poste- euter the grey substauce iu a more or less lougitucliual direction, or with various degrees of obliquity.” And iu my second couimuuication, Philosophical Transactions, 1853, p. 353, it is stated, “ I believe that they (the longitudinal fibres of the gelatinous substance) are all derived from the fine fibres of the posterior roots,” which must therefore cross the gelatinous substance in an oblique direction. * The cells of the gelatinous substance have been described by Kollikee, Scheodee tan dee Kolk, and by Stilling iu his late work. In my first communication I only incidentally mentioned them in the following passage : “ All (the nerve-cells of the grey substance), except those peculiar to the gelatinous sub- stance, have remarkably delicate processes issuing from their sides.” Upon this passage Stilling takes the opportunity of remarking, that by my peculiar method of preparation the sections are rendered too transparent, so that the finer elementary structures escape observation. This objection is without sufficient foundation. In the first place, I described the gelatinous substance, as I then stated, from examination of t\\Q fresh cord, ti’eated witli acetic acid, and not by means of my “peculiar method” of preparation, which, howevei’, shows the cells and processes in the most perfect manner; secondly, to see these preparations to advantage, the illumination must be adapted to their degrees of transparency. But they may be made of all degrees of transparency and of thickness up to the one-twelfth of an inch. If vStilling has given but a hasty trial to this method and only messed with a little turpentine and Canada balsam, he is not prepared to offer an opinion worth notice. I may add that the few of my preparations that have found their way to the Continent are some of the first that I made, and are very inferior to those I have since made, especially by my modified method. The great thickness, also, of some of these preparations renders them exceed- ingly valuable for tracing the course of fibres, which must often be inevitably cut across in the very thin sections required by other methods. This is evident in Stilling’s large wall-diagram, where the grey sub- stance, particularly of the cervix cornu posterioris, appears chopped up like chaff; so that it is impossible to form any idea of the destination of the fibres. It may not be out of place to state that aU the observa- tions described in this communication have been carefully repeated on sections of the cord hardened simply in chromic acid, and without further preparation.