抄録
It is the well known fact that the sensory hairs or the stereocilia of the outer hair cells of the cochleae in higher mammals are arranged in a W-formation and that the peripheral or lateral row of the tall hairs of the W-form is shallowly but quite firmly embedded in the tectorial mambrane, making the distinct W-form auditory hair imprints at the undersurface of this membrane.
An attempt to measure the open angle of W-arrangement of the sensory hairs has been made in the guinea pig, cat, human and bat cochleae under the phase contrast microscope from both the surface view of the organ of Corti and the undersurface observation of the tectorial membrane (auditory hair imprints).
The results of the authors' observation showed the open angle of the “W” was wide at the base of the cochlea and gradually diminished toward the upper-half of the basal turn and the lower middle turn where the open angle of the “W” became minimum. Toward the apex of the cochlea, the open angle of the “W” arrangement of the outer sensory hairs again very slowly increased in width, and became maximum at the apical end. Such a transition pattern in the open angle of the “W” of the auditory hairs was most clearly demonstrated in the guinea pig cochlea, less evident in the cat and the human cochleae. On the other hand, in the bat cochlea, the open angle of the “W” was widest at the basal turn of the cochlea and slowly reduced toward the apex. In addition, a conspicuous feature of the outer sensory hairs in the bat cochlea was that the open angles of the “W” were extremely wide throughout the cochlea, as compared with those of the other three mammals.
