. The cell in development and inheritance. Cells. 56 GENERAL SKETCH OF THE CELL focussed at the centrosome. On this basis he endeavours to explain the position and movements of the nucleus, the succession of division- planes, and many related phenomena.^ Hatschek ('88) and Rabl ('89, '92), on the other hand, have ad- vanced a quite different hypothesis based on physiological con sidera- tions. By " cell-polarity " these authors mean, not a predetermined morphological arrangement of parts in the cell, but a polar differen- tiation of the cell-substance arising secondarily through adap
. The cell in development and inheritance. Cells. 56 GENERAL SKETCH OF THE CELL focussed at the centrosome. On this basis he endeavours to explain the position and movements of the nucleus, the succession of division- planes, and many related phenomena.^ Hatschek ('88) and Rabl ('89, '92), on the other hand, have ad- vanced a quite different hypothesis based on physiological con sidera- tions. By " cell-polarity " these authors mean, not a predetermined morphological arrangement of parts in the cell, but a polar differen- tiation of the cell-substance arising secondarily through adaptation of the cell to its environment in the tissues, and having no necessary relation to the polarity of Van Beneden (Fig. 22, B, C). This is. • « 77^ A Van Beneden. B C Rabl, Hatschek. Fig. 22. — Diagrams of cell-polarity. A. Morphological polarity of Van Beneden. Axis passing through nucleus and centrosome. Chromatin-threads converging toward the centrosome. Physiological polarity of Rabl and Hatschek, /? in a gland-cell, Cin a ciliated cell. typically shown in epithelium, which, as Kolliker and Haeckel long since pointed out, is to be regarded, both ontogenetically and phy- logenetically, as the most primitive form of tissue. The free and basal ends of the cells here differ widely in relation to the food- supply, and show a corresponding structural differentiation. In such cells the nucleus usually lies nearer the basal end, toward the source of food, while the differentiated products of cell-activity are formed either at the free end (cuticular structures, cilia, pigment, zymogen- granules), or at the basal end (muscle-fibres, nerve-fibres). In the non-epithehal tissues the polarity may be lost, though traces of it are often shown as a survival of the epithelial arrangement of the embryonic stages. 1 Cf. p. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance o
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectcells, bookyear1911
