Development of the human motor trigeminal nucleus.

The morphometric features of the motor trigeminal nucleus of the developing human brain were examined using complete serial celloidin sections of 13 brains, including 10 fetal brains. Our results suggest that the developmental processes of the motor trigeminal nucleus should be divided into four stages as follows: (1) primary stage, characterized by the early neuronal differentiation; (2) secondary or preparatory stage; (3) tertiary stage, characterized by massive neuronal death, and (4) postnatal stage, characterized by the maturation of neuropils. There were differences between the neuronal death observed in human and animal brains. Possible implications of these observations for the development of the nervous system are discussed.