Structure of the hair rootlets on cochlear sensory cells by tannic acid fixation.

Rootlets of the sensory hairs of the basal turn of the guinea pig cochlea were investigated using the tannic acid fixation method under transmission electron microscopy (TEM). The fine structure of the rootlet was enhanced by adding tannic acid to the prefixative for the specimen. By using the tannic acid fixation method, it is possible to observe the finer filamentous structure of the rootlet in greater detail than is revealed by using the ordinary glutaraldehyde-osmium fixation method. TEM observation by the tannic acid method reveals that the rootlet consists of 50 A diameter protofilaments and an electron-dense background substance. These protofilaments are arranged in an extremely regular pattern. They are considered to be modified microfilaments.