Elements of animal physiology, chiefly human . THE SENSATION OP HEAHING. 159 356. The Nose is the triangular-shaped organ situatedin the middle of the face. Its roof is formed by thecribriform plate of the ethmoid bone of the skull, throughthe sieve-like apertures of which the olfactory filaments(false nerves) pass. It is bounded in front and laterallyby the oiasal bones and cartilages; its floor is formed bythe hard and soft palate. It is divided into two cavitiesby the nasal septum (which consists partly of bone, thevomer, and partly of cartilage). These cavities open outinto the air in fron
Elements of animal physiology, chiefly human . THE SENSATION OP HEAHING. 159 356. The Nose is the triangular-shaped organ situatedin the middle of the face. Its roof is formed by thecribriform plate of the ethmoid bone of the skull, throughthe sieve-like apertures of which the olfactory filaments(false nerves) pass. It is bounded in front and laterallyby the oiasal bones and cartilages; its floor is formed bythe hard and soft palate. It is divided into two cavitiesby the nasal septum (which consists partly of bone, thevomer, and partly of cartilage). These cavities open outinto the air in front of the nose by means of the twonostrilsj and into the pharynx behind, by the two pos- Cribriform Plate ofEthmoid Bone. Superior TurbinatedBone. Middle Turbinated Inferior TurbinatedBone. Autrum Cavity in iiaxillary Bone. Molar • Bono Pig. 74. terior naves (nostrils) situated immediately over the sidesof the velum or soft palate. 357. Sound.—The external cause of sound is meremechanical movement. Sound is almost invariably pro-duced by air in a state of sonorous vibration, that is, airoscillating backwards and foriuards with great the wave movement be either too quick or too slow, itwill not produce sound. 358. The Sensation of Hearing is excited in the brainby means of a molecular movement, set up in the nervefibrils of the internal ear or labrynth, by the rapid vibra-tion of some external elastic body, and transmitted tothe brain by the auditory nerve. The essential parts of 160 ANIMAL PHYSIOLOGY. the organs of hearing are the membranous lahyrinth, andthe scala media of the cochlea. 359. The Organs of Hearing (the ears)—each consist ofthree parts, viz.:— (1.) The external ear, comprising the pinna or auricle,the gristly appendage attached to the side of the head, Vestibule
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