Revelation, Rationality, Knowledge & Truth — Page 520
ORGANIC SYSTEMS AND EVOLUTION and the third ossicle. The third (stapes or stirrup) connects with the membrane of the oval window which in turn vibrates and transmits the vibration to the fluid in the internal ear. . The internal ear is a series of sacs and ducts which together perform the function of hearing and balance. This is the most complicated part of the whole ear comprising three separate spaces hollowed out inside the temporal bone. These spaces make up the bony labyrinth, comprising the vestibule, the cochlea and the semicircular canals, all filled with a fluid called perilymph. The membranes are lined with nerve endings extremely sensitive to the movement of fluid. In the fluid of the bony semicircular canals are the membranous canals which contain another fluid called endolymph. In a similar fashion, a membranous cochlea is situated in the perilymph of the bony cochlea and it is also filled with endolymph. The sound waves cause the tympanic membrane to vibrate as they strike it. These vibrations are enormously amplified by the ossicles and transmitted by them to the perilymph. The perilymph conducts them through the membrane to the endolymph. . The waves of the endolymph are transmitted to tiny hairlike receptors which are stimulated and conduct nerve impulses through the nerve fibres to the brain centre (cerebrum). . The function of balance is performed by the three loop shaped tubes of the semicircular canals which lie at right angles to one another in three different planes. The fluid within them rocks when the head is turned, even slightly, in any of the three planes. The signals are constantly transmitted to the cerebrum through nerves and are interpreted there. By this interpretation we learn which way we are positioned and in which direction our position is changing. Right, left, front, back, above and below are all 495