Ultrastructural studies on differentiation of nerve cells in the human embryonic and fetal inferior ganglion of the vagus.

Inferior ganglia of the vagus nerve in human embryos and fetuses ranging in C.-R. length from 16 to 220 mm and in age from 7 to 23 weeks were studied by electron microscopy. During the investigated period of development 5 types of cells were distinguished, viz.: 1. primary (apolar) neuroblast, 2. early bipolar neuroblast, 3. intermediate bipolar neuroblast, 4. late bipolar neuroblast, and 5. unipolar neuroblast. The unipolar neuroblasts appear at the end of the embryonic period. In the 9th and 10th week of the fetal period the apolar and early bipolar neuroblasts disappear. In the 23rd week the neuronal cells of the vagus resemble those of adults. The maturation of neurons is associated with 1. structure of nuclear components, 2. cytoplasmic organization with special reference to the rough endoplasmic reticulum, 3. changes of cell shape and development of processes.