. Electro-physiology. Electrophysiology. 36 ELECTRO-PHYSIOLOGY CHAP. superposed nets of lilaments, consisting of the cell processes of the muscle-corpuscles, and only connected longitudinally by fine, small fibres. Apart, however, from the fact that the appearance of a muscle-fibre in optical transverse section must then vary with alterations of the objective, according as the cross-section of a fibre-plexus, or the space between two such, is focussed (when in the first case Cohnheim's area?, in the second a mere system of dots, corresponding with the cross-sections of the connecting longitudi
. Electro-physiology. Electrophysiology. 36 ELECTRO-PHYSIOLOGY CHAP. superposed nets of lilaments, consisting of the cell processes of the muscle-corpuscles, and only connected longitudinally by fine, small fibres. Apart, however, from the fact that the appearance of a muscle-fibre in optical transverse section must then vary with alterations of the objective, according as the cross-section of a fibre-plexus, or the space between two such, is focussed (when in the first case Cohnheim's area?, in the second a mere system of dots, corresponding with the cross-sections of the connecting longitudinal fibres, would appear—which never is the case), the comparative study of the development and structure of fully developed muscle- fibres and cells of different animals appears to us to be conclusive evidence against this theory. For the rest, it is sufficient to quote the masterly criticisms of Eollett (20). The muscles of Flies ex- hibit very peculiar structural relations (Fig. 26). In trans- verse section the bundles of fibrils are once more flat and band-like, and usually consist of a single layer of fibrils only. These, however, are so FIG. 26.—Transverse section of striated muscle-fibres disposed ill Series that two. of Musca clomestica. A, Low power; B, highly or tubes into are one magnified; Ms, bands of muscle - columns ui 6V611 three (bundles of fibrils); Sp, sarcoplasm. (Schieft'er- formed fittillc>1 another, and separated by strata of protoplasm, with which they are also filled and sur- rounded. The nuclei lie in the innermost, axial, plasma cylinder, as appears in the longitudinal section of such a fibre. These few examples will give an approximate idea of the multiplicity of figures in cross-section in the " typical''' arthropod muscles. Before we pass on to the structure of the " a-typical" wing- muscles (thoracic fibrils) of insects, the question as to the com- position of " muscle-columns " out of " fibrils " must det
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