. Chordate anatomy. Chordata; Anatomy, Comparative. THE SENSE ORGANS 421 Proof of the static function of utriculus, sacculus, and semicircular canals has been obtained by extirpation experiments upon lower animals. An animal without these parts of the ear is unable to orient its body in space. The action of the endolymph upon the hairs of the cristae and maculae is intensified by the presence of small calcareous crystals or otoconia in the endolymph. The Organ of Hearing. The organ of hearing is the cochlear duct, otherwise known as the scala media, which is attached to the outer side of the s
. Chordate anatomy. Chordata; Anatomy, Comparative. THE SENSE ORGANS 421 Proof of the static function of utriculus, sacculus, and semicircular canals has been obtained by extirpation experiments upon lower animals. An animal without these parts of the ear is unable to orient its body in space. The action of the endolymph upon the hairs of the cristae and maculae is intensified by the presence of small calcareous crystals or otoconia in the endolymph. The Organ of Hearing. The organ of hearing is the cochlear duct, otherwise known as the scala media, which is attached to the outer side of the spiral bony cochlea. The cochlear duct is connected with the sacculus by means of a narrow tubular ductus reuniens. The sacculus is COCHLEAR DUCT OUTER /\HAIR CELLS. l/DE ITERS CELLS -GANGLION CELL SCALA TYMPANI Fig. 370.—A stereqgram of a portion of the organ of Corti (spiral organ) of man. The precise function of the tectorial membrane is uncertain. It may serve as a damp- ener or it may intensify the action of the "sound waves" upon the sensory hair cells. (Redrawn after Fritz Kahn, " Der Mensch," Albert Miiller, Zurich.) also connected with a slender endolymphatic duct, which terminates in a swollen saccus endolymphaticus near the dura. The utriculus connects with the sacculus through the utriculo-saccular duct by means of the endolymphatic duct. (Fig. 367, G) Throughout the two and a half turns of its extent, the membranous duct of the cochlea is triangular in cross section, and is attached at its apex and base to the surrounding bone. The side lying towards the greater curvature of the cochlea consists of a much thickened periosteum, the spiral ligament. The upper side, the vestibular membrane, consists of a thin sheet of connective tissue, covered on both sides by flattened epithelium. As in reptiles, the apex of the triangle is fastened to the thin bony lamina which projects into the perilymphatic cavity and partly divides this into a dorsal cavity,
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