This is a slice of the midline vermis in the cerebellum of a 60-day-old rat that was injected with 3H-thymidine on 2 consecutive days: P16 and P17.
The labeled cells in the MOLECULAR LAYER are judged to be endothelial cells and glia; neurogenesis is finished there. Unlabeled cells in the GRANULAR LAYER predominate throughout most lobules. Heavily labeled granule cells are still prominent but definitely in the minority in superficial lobules of the centralis, culmen, declive, and uvula. Labeled granule cells are more numerous in the superficial parts of the tuber and pyramis. By the morning of P16, the majority of granule cells have already been generated.
Most probable composition of the external germinal layer (egl) on P16:
1. Basket cell precursors are absent.
2. Stellate cell precursors are absent.
3. There are many fewer granule cell precursors.