Prenatal development of the human spinal cord. I. Ventral motor neurons

Differentiation of the ventral motor neurons were followed in the developing human spinal cord from week 8 to week 26 of intrauterine life by thionin staining and the rapid Golgi method. Ventral roots were seen as translucent rootlets by week 8 and the ventral motor neurons were clearly identifiable by week 10, indicating that the ventral grey was earlier to differentiate than the dorsal grey, which showed a small, darkly stained, undifferentiated cell population. Lateral groupings of the motor neurons in the cervical and lumbar enlargements were obvious by week 10. Nissl substance and dendrites had reached an adult pattern by about week 18 of intrauterine life.