. Outlines of zoology. Zoology. LIFE-HISTORIES. 179 as long. After impregnation the female brings forth numerous embryos viviparously, sixty to eighty at a time, and altogether about 1500. Most of these find their way through the wall of the intestine into blood vessels, and are swept along in the blood stream to the muscles ; occasionally some seem to migrate actively, boring their way, especially through connective tissue, to the muscle fibres. There they grow, coil themselves spirally, and become encysted within a sheath, at first membranous and afterwards calcareous (Figs. 79 and 80). The
. Outlines of zoology. Zoology. LIFE-HISTORIES. 179 as long. After impregnation the female brings forth numerous embryos viviparously, sixty to eighty at a time, and altogether about 1500. Most of these find their way through the wall of the intestine into blood vessels, and are swept along in the blood stream to the muscles ; occasionally some seem to migrate actively, boring their way, especially through connective tissue, to the muscle fibres. There they grow, coil themselves spirally, and become encysted within a sheath, at first membranous and afterwards calcareous (Figs. 79 and 80). The cyst is partly due to the muscle, and partly to the parasite. In these cysts, which may be sometimes counted in millions, the young Trichina? remain passive, unless the flesh of their host be eaten by another,— pig eating rat, man eating pig. In the alimentary canal of the new host the capsule is dissolved, the embryos are set free, and become rapidly reproductive. Among the numerous other parasitic Nematodes the following may be noted:—The giant palisade worm (Eustrongylusgigas) occurs in the renal region of domestic animals, etc. ; the female may be 3 ft. long. The. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Thomson, J. Arthur (John Arthur), 1861-1933. Edinburgh, Glasgow and London, H. Frowde and Hodder & Stoughton
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Keywords: ., bookauthorth, bookcentury1800, bookdecade1890, booksubjectzoology
