. Elements of the comparative anatomy of vertebrates. Anatomy, Comparative. AUDITORY ORGAN 229 raa. Fig. 183.âRight Membkanods Labykinth OF musicus, from the inner side. (After G. Retzius.) Letters as before. In many Reptiles the free end of the ductus endolymphaticiis is situated close under the roof of the skull beneath the parieto- occipital suture, and in the Ascalabota the duct even leaves the â¢cranial capsule, passes back between the muscles of the neck, and in the region of the pectoral arch becomes swollen to form a large folded sac, from which finger-shaped processes extend t
. Elements of the comparative anatomy of vertebrates. Anatomy, Comparative. AUDITORY ORGAN 229 raa. Fig. 183.âRight Membkanods Labykinth OF musicus, from the inner side. (After G. Retzius.) Letters as before. In many Reptiles the free end of the ductus endolymphaticiis is situated close under the roof of the skull beneath the parieto- occipital suture, and in the Ascalabota the duct even leaves the â¢cranial capsule, passes back between the muscles of the neck, and in the region of the pectoral arch becomes swollen to form a large folded sac, from which finger-shaped processes extend to the ventral surface of the vertebral colunm and to the sub-mucous tissue of the pharynx. These processes may also branch out in a labyrinthic manner into the â¢orbit, and they are always filled with a white semi- solid mass of calcareous substance, as in Anura: calcareous matter is present in the ductus endolym- phaticus of all Vertebrates, at any rate in the embryo. In Birds, the duct does not pass out of the cranial â cavity. A tympanic membrane is present in Birds and all Reptiles except Hatteria, Snakes, and Amphisbte- mians; and in the two last- mentioned groups the tympanic cavity and Eustachian tube are also wanting. In Crocodiles the tympanic cavity is very complicated, and in them as well as in Birds, the two Eustachian canals open by a single median aperture into the pharynx. The osseo-cartilaginous â columella is well developed in the Sauropsida, and is not distinct from the stapedial plate ; in Hatteria it is continuous distally with the hyoid (p. 92). In certain Lizards (, Ascalabota, Monitor), an indication of the development of an external auditory passage is seen, the tympanic membrane being partially covered posteriorly by a small fold of skin, usually enclosing the anterior border of the digastric muscle; and in Crocodiles there is a definite integumentary valve moved by muscles. In certain Birds also {, Owls), there is a moveable valve. Mamma
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectanatomycomparative
