Anatomy and physiology : designed for academies and families . ibrations are calledsounds. The meatus auditorius is a canal partly cartilaginousand partly osseous, about an inch in length, which extends Why are artisans and scholars generally near-sighted ? Why are sailorsand hunters long-sighted ? How should children be taught to view ob-jects? Of hovj many parts is the ear composed? Of what does the ex-ternal ear consist ? Describe the pinna. The meatus auditorius. ANATOMT OP THE ORGANS OP HEARING. 283 inwards from the pinna to the tympanum. It is narrowerin the middle, than at each extremit
Anatomy and physiology : designed for academies and families . ibrations are calledsounds. The meatus auditorius is a canal partly cartilaginousand partly osseous, about an inch in length, which extends Why are artisans and scholars generally near-sighted ? Why are sailorsand hunters long-sighted ? How should children be taught to view ob-jects? Of hovj many parts is the ear composed? Of what does the ex-ternal ear consist ? Describe the pinna. The meatus auditorius. ANATOMT OP THE ORGANS OP HEARING. 283 inwards from the pinna to the tympanum. It is narrowerin the middle, than at each extremity. It is lined by anextremely thin pouch of cuticle, which, when withdrawn,after maceration, preserves the form of the canal. Somestiff, short hairs are also found in the interior of the channel,which stretch across the tube, and prevent the ingress ofinsects. Beneath the cuticle are a number of small cerumi-nous follicles, which secrete the wax of the ear. The ex-ternal ear is plentifully supplied with blood vessels, andnerves from the fifth pair. Fig. Flpc- 194, Represents the temporal bone in which the organs of hearing are , The squamous or thin portion of the temporal bone. 2, 2, The petrous , The mastoid process behind the ear. 4, The styloid process. 5, The externalopening of the meatus auditorius. The membrana tympani, or drum of the ear, is a thinsemi-transparent membrane, of an oval shape. It is aboutthree-eighths of an inch in diameter. It is inserted into agroove around the circumference of the meatus, near its ter-mination. It is placed obliquely across the area of that is concave towards the meatus, and convex towards thetympanum. It is composed of three layers, — an externalcuticular; a middlebrows and muscular; and an internalmucous. The middle ear consists of an irregular bony cavity, situ-ated within the temporal bone. It is called the tympanum. What are found in the interior surface of this canal, and what is theiruse ? Where
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Keywords: ., bookcentury1800, bookdecade1840, booksubjectanatomy, bookyear1847
