抄録
The normal development of the external ear, especially the external auditory meatus, in the ddN mice was studied histologically with the light microscope. The development of the external ear begins on the 12th day after gestation with the formation of the primitive external auditory meatus from the 1st branchial cleft. On the 13th day, the meatus extends inwards to near the tubotympanic resess, and reaches the primitive middle ear adjacently on the 14th day. On the 17th day, the canal stretches along the tympanic cavity and participates in the early formation of the tympanic membrane. Complex twists, turns and expands of the primitive external auditory meatus become obvious on the 18th day. The same tendencies continue after birth, with fusion, ramification and formation of an irregular epithelial cord as the development of the external auditory meatus nears completion.
