. Electro-physiology. Electrophysiology. ELECTRO-PHYSIOLOGY M, muscle-column. fibres of the Arthropoda, which, anatomically and functionally, have reached the highest development. In view of certain important differences of structure, that must correspond with no less significant differences in function, two main types of striated fibres may be distinguished, which, although they exist only in certain of the Arthropoda, are always differently localised. These are what Kolliker has termed " tifpical " and " a-tyirical " fibres ; the first presenting essentially the sa
. Electro-physiology. Electrophysiology. ELECTRO-PHYSIOLOGY M, muscle-column. fibres of the Arthropoda, which, anatomically and functionally, have reached the highest development. In view of certain important differences of structure, that must correspond with no less significant differences in function, two main types of striated fibres may be distinguished, which, although they exist only in certain of the Arthropoda, are always differently localised. These are what Kolliker has termed " tifpical " and " a-tyirical " fibres ; the first presenting essentially the same organisation as the fibres of vertebrates, while the second, which exist only in the thoracic muscles of winged insects, are very divergent in structure. With regard Fid. 23.— Transverse sec- . won of muscle-fibre, ji/njrt to the first type, we may distinguish, as in o. .s, sareopiasm. vertebrates, fibres with prismatic columns cle-column. (polygonal in transverse section), and fibres with flat bands of fibril bundles. The muscles of Crustacea (Astacus) are a typical example of the first, exhibiting in cross-section just such a mosaic of polygonal Cohnheirn's arese as we find in most vertebrate muscle-fibres (Fig- 18, ?>). The sareopiasm, however, is always more abundant; it separates not merely single muscle-columns but whole groups of them, forming (as in the muscles of Amphibia) thick and usually nucleated lamella} in the interior of the muscle: the sareopiasm also forms a continuous sheet, greater or less in thickness, immediately be- neath the SarCOlemma (as Fie. 24.—Transverse section of muscle-libre, ll,,hilvs. ill Certain mUSCle-fibreS Of Sarcoplasm clear, muscle-columns dark. (Rollett.) fishes). The muscles of Maja ^ai'iunlo (Fig. 23) afford another elegant illustration of this structure of fibre. In Beetles the polygonal prismatic muscle-columns are very prominent; the sareopiasm lies evenly distributed, or is unequally heaped up in parts of the transv
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