. Animal and vegetable physiology, considered with reference to natural theology. Biology; Physiology; Plant physiology; Natural theology. HEARING. 299 rious elevations and depressions, which form a series of pa- rabolic curves, apparently for the purpose of collecting the sonorous undulations of the air, and of directing them into a funnel-shaped canal (m,) termed the meatus auditoriiis,. which leads to the internal ear. This canal is composed partly of cartilage, and partly of bone; and the integument lining it is furnished with numerous small glands, which supply a thick oily fluid, of an a
. Animal and vegetable physiology, considered with reference to natural theology. Biology; Physiology; Plant physiology; Natural theology. HEARING. 299 rious elevations and depressions, which form a series of pa- rabolic curves, apparently for the purpose of collecting the sonorous undulations of the air, and of directing them into a funnel-shaped canal (m,) termed the meatus auditoriiis,. which leads to the internal ear. This canal is composed partly of cartilage, and partly of bone; and the integument lining it is furnished with numerous small glands, which supply a thick oily fluid, of an acrid quality, apparently de- signed to prevent the intrusion of insects: the passage is also guarded by hairs, which appear intended for a similar pur- pose. The meatus is closed at the bottom by a membrane (d,) which is stretched across it like the skin of a drum, and has been termed, from this resemblance, the membrane of the tympanum, or the ear-drum.'^ It performs, indeed, an of- fice corresponding to its name; for the sonorous undulations of the air, which have been collected, and directed inwards by the grooves of the concha, strike upon the ear-drum, and throw it into a similar state of vibration. The ear-drum is * The Inner surface of the ear-drum is shown in this figure, the cavity of the tympanum, which is behind it, being- laid Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Roget, Peter Mark, 1779-1869. Philadelphia, Carey, Lea & Blanchard
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