. Electro-physiology. Electrophysiology. cells from >' 'h-nii. (Knoll. into separate laminae (-tig. - 1). The same plan of structure is here to some extent repeated, on a larger scale, that prevails in the far more delicate radial striation of the cortical zone of muscle-cells in many worms and molluscs. But there is one important difference ; the contractile substance is no longer (as in all previous cases) exclusively at the periphery of the formative cell, but appears in more or less con- spicuous bundles (muscle-columns) within the central sarcoplasm also. Hence, as Knoll has pointed ou
. Electro-physiology. Electrophysiology. cells from >' 'h-nii. (Knoll. into separate laminae (-tig. - 1). The same plan of structure is here to some extent repeated, on a larger scale, that prevails in the far more delicate radial striation of the cortical zone of muscle-cells in many worms and molluscs. But there is one important difference ; the contractile substance is no longer (as in all previous cases) exclusively at the periphery of the formative cell, but appears in more or less con- spicuous bundles (muscle-columns) within the central sarcoplasm also. Hence, as Knoll has pointed out, the Salpa muscles in a measure represent the transition to certain arthropod and vertebrate muscles, in which the same structural arrangement is present. A transverse section through the cardiac muscles of Crustacea often exhibits an unmistakable similarity Fl0t ^ _Tra]ls. to Salpa in disposition of sarcoplasm and con- verse section of J A . cardiac muscle- tractile substance, except that the sarcoplasm is, Ceii of Lobster. where possible, even more richly developed, and all the "muscle-columns" lie within the formative cell (Fig. 12). The unusual quantity of protoplasm is explained in both cases by the sustained and strenuous work which is served by these muscles. From these observations we may conclude that there is no fundamental difference in structure between the different muscle- cells of Invertebrates (excepting only the muscular fibres of Arthropoda) ; whereas among Vertebrates we shall find striking. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Biedermann, W. (Wilhelm), 1852-1929; Welby, Frances A. (Frances Alice). London : Macmillan
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