Henry Gray (18251861). Anatomy of the Human Body. 1918.
Two small rounded bodies termed otoconia, each consisting of a mass of minute crystalline grains of carbonate of lime, held together in a mesh of gelatinous tissue, are suspended in the endolymph in contact wish the free ends of the hairs projecting from the maculæ. According to Bowman, a calcareoutmaterial is also sparingly scattered in the cells lining the ampullæ of the semicircular ducts.
FIG. 927 Transverse section of a human semicircular canal and duct (after Rüdinger). (See enlarged image)
The Ductus Cochlearis (membranous cochlea; scala media).The ductus cochlearis consists of a spirally arranged tube enclosed in the bony canal of the cochlea and lying along its outer wall.
As already stated, the osseous spiral lamina extends only part of the distance between the modiolus and the outer wall of the cochlea, while the basilar membrane stretches from its free edge to the outer wall of the cochlea, and completes the roof of the scala tympani. A second and more delicate membrane, the vestibular membrane (Reissneri) extends from the thickened periosteum covering the osseous spiral lamina to the outer wall of the cochlea, where it is attached at some little distance above the outer edge of the basilar membrane. A canal is thus shut off between the scala tympani below and the scala vestibuli above; this is the ductus cochlearis or scala media(Fig. 928). It is triangular on transverse section, its roof being formed by the vestibular membrane, its outer wall by the periosteum lining the bony canal, and its floor by the membrana basilaris and the outer part of the lamina spiralis ossea. Its extremities are closed; the upper is termed the lagena and is attached to the cupula at the upper part of the helicotrema; the lower is lodged in the recessus cochlearis of the vestibule. Near the lower end the ductus cochlearis is brought into continuity with the saccule by a narrow, short canal, the canalis reuniens of Hensen(Fig. 924). On the membrana basilaris is situated the spiral organ of Corti. The vestibular membrane is thin and homogeneous, and is covered on its upper and under surfaces by a layer of epithelium. The periosteum, forming the outer wall of the ductus cochlearis, is greatly thickened and altered in character, and is called the spiral ligament. It projects inward below as a triangular prominence, the basilar crest, which gives attachment to the outer edge of the basilar membrane; immediately above the crest is a concavity, the