[Postnatal developmental changes in the posterior cranial fossa area. I. Facies posterior partis petrosae (porus et meatus acusticus internus, fossa subarcuata, apertura externa aqueductus vestibuli, apertura externa canaliculi cochleae)].

1. In the newborn the lateral edge of the internal acoustic pore is located about 13.3 mm, in the 2-year-old about 22.5 mm and in the adults about 28.5 (22 to 34) mm from the paramedian plane of the skull. Also the mean distance from the lateral wall of the skull increases from about 13 to 30 mm in the postnatal period. 2. Without the postnatal development of height and width of the internal acoustic pore the postnatal extension (from a mean value of 5 mm in the newborn to about 10 mm in the 15- to 17-year-old) also the postnatal development of height and width of the internal acoustic meatus were measured. 3. Size, width and position of the subarcuata fossa, the external aperture of the aqueduct of the vestibulum just as the external aperture of the cochlear canaliculus were determined. The results were discussed in detail with the datas of former investigators.