. Biological lectures delivered at the Marine Biological Laboratory of Wood's Holl [sic]. Biology. 28o BIOLOGICAL LECTURES. have different optical properties from the connecting filamen- tous portion. When contraction sets in, the varicosities on both sides of the intermediate zone (Z, Fig. 7) increase in bulk. Fig. 7. — (I) A schematic representatwn of the muscle cell. N, nucleus; s, sarcoplasm ; fit, myoplasm ; M, microsome of the filament; Z, Zwischenscheibe, or Krause's membrane. (II) The same in a state of contraction. C, the contraction band. (III) Diagram showing the possible mode of fo
. Biological lectures delivered at the Marine Biological Laboratory of Wood's Holl [sic]. Biology. 28o BIOLOGICAL LECTURES. have different optical properties from the connecting filamen- tous portion. When contraction sets in, the varicosities on both sides of the intermediate zone (Z, Fig. 7) increase in bulk. Fig. 7. — (I) A schematic representatwn of the muscle cell. N, nucleus; s, sarcoplasm ; fit, myoplasm ; M, microsome of the filament; Z, Zwischenscheibe, or Krause's membrane. (II) The same in a state of contraction. C, the contraction band. (III) Diagram showing the possible mode of formation of the centrosome by the convergence of the fibrils (/) into one common focus. N, nucleus ; C, centrosome. at the expense of intervening filamentous substance, and at the maximum state of contraction a thick, new zone is formed as the result of such a process, giving rise to what is known as the contraction band {C, Fig. 7, II). This contraction band has the same chemical and physical property as the ordinary thickenings or varicosities of the fibrils, only much more mas- sive and conspicuous, being formed by the fusion of several varicosities on both sides of the intermediate zone (Z). When the relaxation of the muscle sets in, this contraction band resolves itself into a series of smaller varicosities distrib- uted along the fibrils (Fig. 7, I). The contraction of the muscle cell means, therefore, the formation of more stainable substance at the expense of less stainable protoplasmic filaments; and the expansion of the muscle means just the reverse of this process, viz., the conver- sion of the deeply stainable varicosities into the less stainable filamentous substance. Now, coming back to our original subject, the aster, we notice that, so far as we can judge by the use of staining re- agents, the varicosities in the muscle fibrils and those in the. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readab
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectbiology, bookyear1894
