Remarks on Quekett's Histology, On Kölliker's Human histology, and on the physiological importance of the nucleus of the cell / by Martin Barry, M.D.

  • Barry, M. (Martin), 1802-1855.
Date:
[1854]
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Licence: Public Domain Mark

Credit: Remarks on Quekett's Histology, On Kölliker's Human histology, and on the physiological importance of the nucleus of the cell / by Martin Barry, M.D. Source: Wellcome Collection.

Provider: This material has been provided by The University of Glasgow Library. The original may be consulted at The University of Glasgow Library.

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    not only in other reproducing cells, but in newly formed cells arising for whatever purpose. On this subject, see my papers in the Phil. Trans, for 1841. And in these, see especially the drawings from na- ture illustrative of the mode of origin of the epithelium tables and cylinders, and the pigmentum nigrum.^ On comparing these with niy drawings of the ovum cells just referred to,^ the reader will find abundant evidence that the process is the same in both. ASSIMILATION. Why, in the development of the ovum, the formation of many cells which for every generation come into existence and speedily disappear by entering into the formation of the more aristocratic two ? Why all this cell-life ? I apprehend, with Carpenter, that the jirocess is one of assimilation. Where cells are merely I'eproducing cells, their membrane is the wall of a living laboratory raised for the perfoimance of its own functions by the more essential part. THE NUCLEOLUS. The ovum cells absorb, assimilate, and reproduce. So do other cells. In these functions the prime mover is the nucleolus. 1. The nucleolus absorbs. The most remarkable example of this, is the suctorial power manifested by the protrusion of the parietal uncovered nucleolus of the germ spot into the aperture of the vitellary membrane, to take up the equivalent, corresponding, or counterpart, from the spermatozoon.* But where is there to be found a cell in which the nucleus is not at first parietal in its cell? And where does there exist a nucleolated nucleus in which the nucleolus is not at first parietal in its nucleus ? Another proof of absorption by the nucleolus is furnished by the originally flat form of the nucleus. The mammiferous blood-discs or nuclei are even biconcave; a provision perhaps for absorption by the nucleolus on both sides. And I have only to refer to embryonic blood, for instance to that of the foetal ox about an inch in length, for cells whose membranes at the part where the nucleolus lies present, like the germ vesicle, an orifice.* In mere nuclei, too, it is often seen that at the veiy part where the nucleolus lies the nucleal investment ceases—the nucleolus lying un- covered and open to the exterior.^ 2. The nucleolus assimilates. This is shown in the ovum cells by the germ-spot process. There it is the nucleolus that initiates and completes every change. As I have already said, it becomes nodular, gives off its nodules, thus segments the more or less dis- ^ I'liil. Trans., 1841, Plate XXL, figs, 86 to 100. » Pliil. Trans., 1840. 3 It is the mysterious centre [nucleolus] of a nucleus which is the point of fecundation, and the place of origin of two cells constituting the foundation of the new being,—Piiil. Trans., 1840. P. 567. * Phil. Trans., 1R41. Plate XVII., fig. 28, „, «. » Piiil. Tr,.n8., ]« J1. Plate XVII., fig. 29 ». Plate XX.. fig. 63 «, ^, >.