The people's common sense medical adviser in plain English, or, Medicine simplified . h we receive knowledge of the myriads of worldsand suns which circle with unfailing precision through iiiHnite space HEARING. 138. Hearing depends upon the sonorous vibrations of theatmosphere. Tlie waves of sound strike the sensitive portions ofthe ear, and their impressions upon the auditory nerves are termed „, ^^ the sensations of hear- Fig. 63. • rp, ... mg. ihe ear is di-vided into three partscalled, respectively,the External, Middleand Internal ear. 139. The externalorgans of hearing aretwo for each an
The people's common sense medical adviser in plain English, or, Medicine simplified . h we receive knowledge of the myriads of worldsand suns which circle with unfailing precision through iiiHnite space HEARING. 138. Hearing depends upon the sonorous vibrations of theatmosphere. Tlie waves of sound strike the sensitive portions ofthe ear, and their impressions upon the auditory nerves are termed „, ^^ the sensations of hear- Fig. 63. • rp, ... mg. ihe ear is di-vided into three partscalled, respectively,the External, Middleand Internal ear. 139. The externalorgans of hearing aretwo for each animal,and placed on oppo-site sides of the the higher orderof vertebrates, theyare so situated as togive expression and Internal external ear. 1. Kxternal car. t. In- prOP^rtion tO theternal auditory meatus. 5. Tynipanuni. 4. Labyrinth, facial organs, and, at 6, EuHtachian tube. .i -• ^^ the same time, to answer the requirements of sensuous life. 140. The External ear is connected with the interior apart-ments, by a prolongation of its orifice termed the external. l(^tl COmtOX SEXSB IISUICAL ADV13BK. auditory meatus. In maa, this ha If-bony portion of the auditoryapparatus is about one inch in length, lined by a continuation ofthe integument of the ear, and has numerous hairs on its surfaceto prevent the intrusion of foreign substances. Between theexternal meatus, and the cavity of the middle ear is the mem-brana tyinpoiU, which is stretched across the opening like thehead of a drum. The tympanum communicates with the phanTixby the eustachian tube, which is a narrow passage lined withdelicate, ciliated epithelium. On the posterior portion it is con-nected with the mastoid cells. Three small bones sure stretchedacross the cavity of the tympanum, and called from their maUeuSj incus and stajHS. Agassiz mentions a fourth, whichhe terms the os obiculare. Each wave of sound falling upon themembrana tympani, throws its molecules into vibrations and iscommun
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Keywords: ., bookcentury180, bookdecade1870, booksubjectmedicine, bookyear1876
