A SEM STUDY OF STRUCTURE IN THE RABBIT COCHLEAE / 解剖学报

ABSTRACT

Five inner ears were removed from five rabbits under aneasthesia. The hard, thick bones of outer and middle ears were trimmed off, and the auditory ossicles were taken away. The cochleae were fixed with 2％ glutaraldehyde in phosphate buffer for eight hours, then they were decalcified in 10％ EDTA-2Na solution for ten days, and the softened shells of the cochleae were stripped off, and post-fixed in 1％ OsO_4 for an hour, dried at critical point, coated with gold, and observed under SEM.The rabbit cochlea shows two and a half turns, the modiolus is about 3.5mm high, and the organ of Corti lies on the basilar membrane of the spiral lamina. The outer hair cells usually form three parallel rows on the middle and basal turns but occasionally four rows on the top half turn. The inner hair cells form only a single row. Every bunch of the outer hairs consists of about 93-114 stereocilia which together show a "W" shape. Every bunch of inner hairs has about 50 cilia which together show an arch shape. The cilia on the top turn are longer than those on the base. The length and width of the inner and outer hair cells and four other kinds of cells were measured according to photos, and the numbers of these kinds of cells were estimated.Other three cochleae fixed at the time of 1, 2 or 4 hours after death were also observed. In the cochlea fixed four hours after death, the majority of the auditory hairs were found fallen down, which means the fixation of cochlea should be carried out within less than four hours after death.Some of the structural similarities and differences of cochleae among rabbit,human being and guinea pig were also compared in this paper.