[Postnatal development of the sound-transporting apparatus in the middle ear of rabbits]

The middle ear apparatus realized a multiplicatory function during the transfer of the vibrational energy, depending on the area ratio of pars tensa of tympanic membrane and of stapes footplate as well as the lever ratio of long arms of manubrium and of incus. These structures exhibit a size increase during the postnatal development, but the sequel on the multiplicatory function in rabbits is unknown. The middle ear structures of 46 rabbits, 1 to 30 d old, were prepared and measured. The area of pars tensa and the levers of malleus and incus increase with age. After the 10th d of life, no statistical significant growth were measurable. But the calculated multiplicatory factor of single animals indicate the end of the development at the 15th postnatal d. In contrast, the cochlear function attains the adult values not till the 26th d of life. It is 10 d longer than the middle ear growth.