Elements of histology / by E. Klein.

  • Edward Emanuel Klein
Date:
1884
Catalogue details

Licence: Public Domain Mark

Credit: Elements of histology / by E. Klein. Source: Wellcome Collection.

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    nuclear matter shows no definite boundary. The nuclear membrane when present is a condensed outer stratum of the nuclear matter. In some instances it can be shown that the nuclear fibrils are in continuity with the fibrils of the cell substance. In the moving white blood corpuscles Strieker and linger have seen the nucleus becoming one with the cell substance, and again afterwards differentiated by the appearance of a membrane. 8. During division of the cell the nucleus generally divides before the cell protoplasm. This division of the nucleus was until lately supposed to occur in the same manner as that of the cell pro- toplasm—by simple cleavage. This mode is called the direct division, or Kemak's mode of division. In this division the nucleus is supposed to become constricted, kidney-shaped and hour-glass shaped, and if the division is into more than two, lobed. Nuclei of these shapes are not uncommon; but they need not necessarily indicate direct division, because, being very soft structures, pressure exerted from outside, or the motion of the cell protoplasm, may produce these shapes; and, further, the contractility of the nucleus may and occasionally has been observed to cause these changes of shape. From the observations of recent investigators—Biitschli, Hertwig, Strassburger, Mayzel, van Beneden, Balfour, Eberth, Schleicher, Peremeschko, Flemming, Klein, Arnold, Pfiitzner, Retzius, Bizzozero, and many others—it is now known that in the embryo and adult, in plant and animal, vertebrates and invertebrates, all kinds of cells, before their protoplasm undergoes division, show complicated changes of their nucleus. This manner of division is called the indirect division or karyokinesis. It has been observed by Mayzel, Schleicher, and Flemming, that the nuclear fibrils show movement, hence the name karyokinesis, i.e., kernel-movement. This