[Scanning electron microscopic observation on the cochlea treated with frozen resin cracking method].

By the use of frozen resin cracking method , scanning electron microscopy (SEM) makes it possible to investigate the deeper and finer structures of the inner ear. Another merit of this method is to obtain any sections of the organs without any significant artifactual damages to the tissues. The inner ears of the guinea pig were fixed and stained with osmic acid. After the cracking procedure frozen specimens were subjected to CO2 critical point drying, the conductive coating of carbon and gold successively, and finally submitted to SEM observation. Some of the remarkable findings are as follows: 1) The cellular pattern of stria vascularis, spiral prominence and outer sulcus was different each other in the lateral wall of the cochlear duct . 2) A considerably big space was found around nerve fibers within the osseous spiral lamina. Small holes of about 3ls in diameter were also noted on the lower surface of the osseous spiral lamina. These holes and the space might be intercommunicated between cortilymph and perilymph in the scala tympani. 3) The tectorial membrane seemed to be composed of two layers, namely, the upper fibrous and the lower basal or granular layer. Regarding the relation of the tectorial membrane to hairs of the hair cells, situations were fairly different between outer and inner hair cells. Tips of hairs in the outermost row of outer hair cells penetrated into the granular layer of the membrane making a firm contact. On the other hand, at the lateral side of the outermost row, hairs of the inner hair cells were attached to the tectorial membrane with granular substances protruding from the undersurface of the granular layer. 4) At the hook region, hair cells became less in number mainly at the outermost row closer to the cecum vestibuli.