An American text-book of physiology . be; 5, meatus internus, containing the facial (uppermost) and auditory nerves;6 placed on the vestibule of the labyrinth above the fenestra ovalis; a, apex of the petrous bone; 6,internal carotid artery; c, styloid process; d, facial nerve, issuing from the stylo-mastoid foramen; e,mastoid process ; /, squamous part of the bone. tially of yellow elastic cartilage covered with skin, and forming at the entranceof the auditory meatus a cup-shaped depression called the concha. 17?e concha, and to some extent the whole auricle, serves a useful purposein collect
An American text-book of physiology . be; 5, meatus internus, containing the facial (uppermost) and auditory nerves;6 placed on the vestibule of the labyrinth above the fenestra ovalis; a, apex of the petrous bone; 6,internal carotid artery; c, styloid process; d, facial nerve, issuing from the stylo-mastoid foramen; e,mastoid process ; /, squamous part of the bone. tially of yellow elastic cartilage covered with skin, and forming at the entranceof the auditory meatus a cup-shaped depression called the concha. 17?e concha, and to some extent the whole auricle, serves a useful purposein collecting, like the mouth of a speaking-trumpet, the waves of sound fallingupon it; but in many of the lower animals the concha is relatively larger thanin man, and, their ears being freely movable, the auricle becomes of greaterphysiological importance. External Auditory Meatus.—In man the external auditory meatus or audi-tory canal is about one and a quarter inches in length, and it extends from 808 AN AMERICAN TEXT-BOOK OF the bottom and anterior edge of the concha to tlie membrana tympani, or tympanic membrane. Startingfrom the bottom of the conclia,the general direction of the audi-tory canal is first obliquely up-ward and backward for abouthalf an inch, and then inwardand forward. Therefore, to lookinto the ear or to introduce theaural speculum the canal must bestraightened by pulling the pinnaupward and backward. Thecanal-wall is cartilaginous andmovable for about half an inchfrom the exterior, but is osseousfor the rest of its extent; it islined by a reflexion of thin skin,on whose surface, in the cartilag-inous part of the canal, open theducts of numerous sebaceous andceruminous glands. Tympanum.—The middle ear,or tympanum (Figs. 2G6, 267), isshut oif from the auditory canalby the tympanic membrane. It is an air-holding cavity of irregular shape in the petrous bone, and it is broader behind and above than it is below and in front. Posteriorly it is in open c
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Keywords: ., bookautho, bookcentury1800, bookdecade1890, booksubjectphysiology
