. Evolution and disease . 232 evolutiojsj and disease. One of the most remarkable diverticula known to meexists in the neck of the Emu {Dromcsiis novce-Jiollandice),which demands consideration, as it serves as an admir-able physiological type of diverticula in Fig. 118.—Tiacheal poudi of the Lmu. (After Wune.) In the emu there is a natural defect in the trachea ata spot varying in position between the fiftieth and sixty-fifth rings. This spot has the form of an oblong slit,which in the adult bird is about seven centimetres in TUMOURS AND CANCERS. 233 length ; the width varies from ei
. Evolution and disease . 232 evolutiojsj and disease. One of the most remarkable diverticula known to meexists in the neck of the Emu {Dromcsiis novce-Jiollandice),which demands consideration, as it serves as an admir-able physiological type of diverticula in Fig. 118.—Tiacheal poudi of the Lmu. (After Wune.) In the emu there is a natural defect in the trachea ata spot varying in position between the fiftieth and sixty-fifth rings. This spot has the form of an oblong slit,which in the adult bird is about seven centimetres in TUMOURS AND CANCERS. 233 length ; the width varies from eight to twelve millimetres,according to the retracted or distended condition of thewindpipe. The mucous membrane lining the tracheapasses through this slit, and forms a large bag or sac,which lies between the trachea and the skin (fig. 118).During the breeding season, the birds inflate the sac withair and produce a peculiar drumming sound whichresembles the booming noise made by blowing forciblyacross the opening of a large but narrow-necked bottleThis cyst is not present in the emu chick, only the slitin the trachea ; as the bird grows, so the mucous mem-brane becomes slowly protruded through it. On oneoccasion I have found this cyst filled with fluid mucus,du
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectabnormalitieshuman
