. Electro-physiology . Pio. 19.—Transverse section of two float-muscles of Hippo- riiini>iig. (Ifa), Bundles of fibrils (muscle - columns); (>», sarcoplasm. (Rollett.) muscles of the same animal; and the same is true of the position of the nucleus. Two groups of striated fibres can again be distinguished in vertebrates, those which have much, and those which have little, sarcoplasm. The fibres of the first group, generally, look rather dark when examined with the microscope, owing to the large num- ber of interstitial " gran- ules " with which the sarcoplasm is studded; th
. Electro-physiology . Pio. 19.—Transverse section of two float-muscles of Hippo- riiini>iig. (Ifa), Bundles of fibrils (muscle - columns); (>», sarcoplasm. (Rollett.) muscles of the same animal; and the same is true of the position of the nucleus. Two groups of striated fibres can again be distinguished in vertebrates, those which have much, and those which have little, sarcoplasm. The fibres of the first group, generally, look rather dark when examined with the microscope, owing to the large num- ber of interstitial " gran- ules " with which the sarcoplasm is studded; the cross-strise are in- 5 ' distinct, the longitudinal well marked. The a- plasmic fibres, on the other hand, are clearer and transparent, with sharp transverse striae. In the same sense, we have already, in describing the structure of the uni- nuclear muscle-cells of invertebrates and vertebrates, had occasion to distinguish between clear and dark, plasmic and a-plasmic elements; cardiac muscle-cells in particular being universally dark and plasmic. The float muscles of the Sea- horse (Hippocampus) exhibit a peculiarly typical example of plasmic, multinuclear muscle-fibres in the Verte- brates. In transverse sec- tion the flat bands of muscle- fibrils (muscle-columns) are seen, as in the muscles of Salpa, or the cardiac muscle of Crustacea (supra), form- ing irregular groups and columns in the sarcoplasm, which is here excessively abundant, and presents a thick cortical layer in which the nuclei are embedded (Fig. 19). Similar bands of muscle-columns are found in the lateral muscles of the carp, which are also characterised by an abundance of nucleated sarcoplasm lying close under the sarcolemma (Fig. 20). Other muscle-fibres (lateral trunk-muscles) in the same fish—
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