New observations upon the structure and formation of certain nervous centres : tending to prove that the cells and fibres of every nervous apparatus form an uninterrupted circuit / by Lionel S. Beale.

  • Beale, Lionel S. (Lionel Smith), 1828-1906.
Date:
1864
Catalogue details

Licence: Public Domain Mark

Credit: New observations upon the structure and formation of certain nervous centres : tending to prove that the cells and fibres of every nervous apparatus form an uninterrupted circuit / by Lionel S. Beale. 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.

    14/52 (page 8)
    hundreds of specimens may be examined without finding one in which such fibres are observed. The drawings represented in figs. 9, 10,13,14,15,16, 17, & 18 show the points I have observed in connexion with this question. A nucleus which cannot at first be distinguished from the ordinary nuclei in connexion with the nerve-fibres, grows somewhat larger than the rest (figs. 9 & 14). I am not pre- pared to say that any nucleus connected with the fibres could or could not undergo the changes about to be described; but the nuclei from which the ganglion-cells are formed exhibit at first nothing peculiar. Sometimes several in different parts of a fibre may enlarge to some extent; but for the most part only one in the course of a long distance will be developed into a ganglion-cell. - Of course the opinion that a ganglion-cell may be developed from any nucleus up to a certain period of its life is quite tenable, and it may be that the actual change is determined by the presence or absence of certain conditions, but this speculation I will not pursue. The enlarged nucleus which is about to become developed into a ganglion-cell soon exhibits a transparent portion at its circumference. From what has been stated, it is clear that every ganglion-cell developed in the course of a nerve-fibre must have a fibre proceeding, as it were, from either pole (bipolar cells); but the difficulty of defining the changes with the utmost certainty arises from the rarity with which single fibres emanating from either end of the cell, like those represented by authors, occur. The only cells exhibiting these characters in the frog that I have seen are, in my opinion, young and imperfectly formed cells. Such an appearance is not uncommon in fully formed cells in ganglia; but in all cases in which I have observed it in the frog, more careful investigation has satisfied me that it was fallacious, and depended upon a fibre really passing close to the cell, without being connected with it, although it appeared at first to emanate from the end opposite to that which certainly terminated in a straight fibre. In the frog I feel almost certain that fully formed cells, with a nerve-fibre coming from the opposite poles, as delineated by Wagner and Kolliker in the pike, do not exist; and I have failed to find examples of the cells represented by Kolliker in three specimens of the pike which I have examined. My want of success, however, probably depends upon imperfect investigation, as such fibres undoubtedly exist in the skate. In the posterior roots of the spinal nerves of the common skate such cells are easily found; but there is a difference in the arrangement of the two fibres, and their relation to the mass of the cell corresponding to that already described in the frog, which deserves more attentive examination. I shall describe the peculiar structure of these cells in another communication. The cells which are not fully developed, delineated in figs. 9, 14,15, & 16, have a fibre coming from either extremity, but, as will presently be shown, there is reason to believe that as the cell grows the arrangement of these fibres soon becomes altered. The appearances represented in fig. 18, when examined by a low power, would be considered to be due to the presence of fibres emanating from either end of the cell, but under a higher power the true arrangement, which is very different, can be clearly demonstrated.