An American text-book of physiology . thought to have the duty of vibrating in response to any agitationimparted to the perilymph, without regard to its periodic character; they THE SENSE OF HEARING. 833 might thus be termed sense organs for the perception of noises. Evidencewill be adduced later (p. 848) lor the belief that they are peripheral organsfor the preservation of static equilibrium. The hair-cells on the cristae of the ampullse of the semicircular canals seemto have a special function in giving rise to sensations caused by changing theposition of the head ; they thus are organs conc
An American text-book of physiology . thought to have the duty of vibrating in response to any agitationimparted to the perilymph, without regard to its periodic character; they THE SENSE OF HEARING. 833 might thus be termed sense organs for the perception of noises. Evidencewill be adduced later (p. 848) lor the belief that they are peripheral organsfor the preservation of static equilibrium. The hair-cells on the cristae of the ampullse of the semicircular canals seemto have a special function in giving rise to sensations caused by changing theposition of the head ; they thus are organs concerned with the preservation ofthe equilibrium of the body. Judgment of Direction and Distance.—The distance and direction fromwhich sounds come to the ear are not perceived directly, but our estimate ofthem is a judgment based on the loudness and quality of the sound sensation,combined with a power of reasoning from past experience. Thus, in seeking todiscover the direction whence a sound comes, it is usual for an observer to turn. Fig. 284.—End-bulbs from human conjunctiva (from Quain, after Lofagworth): A, ramification of nerve-fibres in the mucous membrane, and their termination in end-bulbs, as seen with a lens; b, end-bulb,highly magnified; a, nucleated capsule; b, core, the outlines of its component cells not seen; c, enteringnerve-fibre branching, its two divisions to end in the bulb at d. the head to the position in which the sound is heard loudest, and thus to forman opinion to the direction whence it comes. Errors of judgment as to thedirection are frequent, owing to the sound reflected from some object appearinglouder than that coming in a direct line from its source. It is said that whenthere is total deafness in. one ear every sound seems to have its origin on theside of the healthy ear. The quality as well as the loudness of a sound variesaccording to the distance of its source. Thus, the lower tones die away earliestas a sound recedes, bringing the overto
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