BEARING, ORGAN OF. The ear (in the wide acceptation of the term). Organon audit6s s. auris.—Fr. L'organe de l'ouie au l'oreillc. Germ. Des Gehiirargan oder des Ohr.—As the apparatus of vision naturally admits of being divided into two parts, viz, the eye-ball and its appendages, so we can distinguish in the apparatus of hearing a fundamental organ, and parts accessory to the perfect performance of its function. The fundamental organ of hearing is what is commonly called the internal ear, or from the complexity of its structure, the labyrinth. The accessory organs consist of the middle ear or tympanum and external ear.* If we extend our observations to the animal series, and trace the apparatus of hearing along the descending scale, we shall find that the accessory parts gradually disappear, and that the sense of hearing comes at last to have for its organ merely a representative of the laby rinth in the higher animals. This part even,
having laid aside much of its complicated structure, presents itself under the form simply of a membraneous pouch containing a fluid, with a calcareous concretion suspended in it, on which the auditory nervous filaments are expanded.
The labyrinth being in the apparatus of hear ing exactly what the eye-ball is in that of vision, may be distinguished by the name of ear-bulb. The ear-bulb, like the eye-ball, consists of a hard external case, in the interior of which are con tained membraneous and nervous parts and humours. The accessory parts of the apparatus of hearing have also their prototypes in the accessory organs of the apparatus of vision.
The different parts of the apparatus of hear ing are situated in the interior and on the sur face of the temporal bone. See the description of the temporal bone in the article CRANIUM.