Tympanic epithelial migration.

The literature on tympanic epidermal migration is reviewed. From isotope experiments and whole-mount autoradiographs the tympanic mitotic activity appeared to be confined to an area close to the annulus typmpanicus. A very slow migratory activity was observed of labelled cells, situated in the basal cell layer. Perforation of the tympanic membrane showed no effect on the position of the labels. This slow migration is considered to differ from the rapid epithelial migration described by several authors. The latter migration is suggested to occur in the upper layers of the stratum corneum, and to represent a physiological mechanism taking care of the removal of keratin from the tympanic membrane. The extrusion and displacement of ear grommets might be at least partly attributable to this phenomenon.