Studies on fibrous tissues of the basilar membrane in inner ear

Of a number of electron microscope studies on the basilar membrane of the inner ear cochlear duct so far reported, none seems to have been conducted using PAM of R.R. staining, excellent stainings especially suited for the observation of connective tissue. In this study the basilar membrane of the cochlear duct in young and mature guinea pigs and human fetuses was examined with an electron microscope using these stainings, and obtained the interesting results described below. Fibrils of the basilar membrane, although strongly PAM-positive, all lacked periodic stripes, indicating that they were collagenous fibrils in an immature state. Young guinea pigs clearly differed from mature ones in that numerous fibroblasts were present. In human fetuses, the basilar membrane exhibited no clear fibrillar structure in the 13th week, but had PAM-positive fibrils in the 20th week. By the 23rd week, it had assumed roughly the same structure as in adults, although numerous fibroblasts were still present, and resembled the basilar membrane in young guinea pigs. The basilar membrane is a part of a unique organ, a sensory organ. Though comparison is difficult because of the extremely complicated anatomy of the organ, it is concluded that the fibrils of basilar membrane are collagenous fibrils in a peculiarly immature state, and similar to those in the cartilage and tympanic membrane.