Entomology : with special reference to its biological and economic aspects . sects differ greatly in form and areinserted frequently by means of chitinoustendons. A muscle is a bundle of long t»^ L^i-* fibers, each of which has an outer elastic striated nmsde fiber of .,.,., an insect. membrane, or savcolcnuna, withni wlucn are several nuclei; thus the fiber represents several cells. which have become confluent. With rare exceptions ( alary muscles and possibly a few thoracic muscles) the muscle fibers of an insect presentFig. 110. , a striated appearance, ownig to alternate light and darkband
Entomology : with special reference to its biological and economic aspects . sects differ greatly in form and areinserted frequently by means of chitinoustendons. A muscle is a bundle of long t»^ L^i-* fibers, each of which has an outer elastic striated nmsde fiber of .,.,., an insect. membrane, or savcolcnuna, withni wlucn are several nuclei; thus the fiber represents several cells. which have become confluent. With rare exceptions ( alary muscles and possibly a few thoracic muscles) the muscle fibers of an insect presentFig. 110. , a striated appearance, ownig to alternate light and darkbands (Fig. 109), the for-mer being singly refracting,or isotropic, and the latterdoubly refracting, or aniso-tropic. The minute structure ofthese fibers, being extremelyditficult of interpretation,has given rise to much dif-ference of opinion. Themost plausible view is thatof van Gehuchten, Janetand others, who hold that lK)th kintls of dark bands (iMgno) consist of highly elastic threads of spongioplasni (aniso-tropic) embedded in a matrix of clear, semi-tluid, nutritive. Minute structure of a striated musclefiber. A, longitudinal section; B, trans-verse section in the region of /; C, trans-verse section in the region of . /,longitudinal fibrillse; n, Krauses mem-brane; nl, nucleus; r, radial fibrillae; 3,sarcolemma.—After Janet. 05 ENTOMOLOGY hyaloplasm (isotropic). The spongioplasmic threads of thelong bands extend longitudinally and those of the short bands{ Krauses menibrane ) radially, in respect to the form ofthe fiber. Moreover, the attenuated extremities of the longi-tudinal fibrillje connect with the radial fibrillae, the points ofconnection being marked by slight thickenings, or nodes,which go to make up Krauses membrane. Under nervous stimulus a muscle shortens and thickensbecause its component fibers do, and this in turn is attributedto the shortening and thickening of the longitudinal the stimulus ceases, the radial fibrill?e, by their elas-ticity,
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectentomology, bookyear1
