Perinatal growth of spiral ganglion cells in the kitten.

Spiral ganglion cell growth and myelination in the kitten have been studied by means of light and electron microscopy, in one fetus and in kittens of various ages. The growth of spiral ganglion cell bodies and nuclei as studied through their cross-section modifications show two different periods of increase: a period of rapid growth before birth, followed by a slower one after birth up to the first postnatal month. After this stage, the diameter decreases slightly in the adult. Myelination of the cell body begins before birth for the basal part of the cochlea. Myelination is fast during the first postnatal month, then slows down during the following months. Comparison of myelination with the growth of the cell body and its nucleus shows that the postnatal growth of the cell body is due to the increase of the cytoplasmic component of the cell and also to the myelin sheath.