Fig. (16) Histogram showing the number of labeled mitochondria per each adrenal medullary cell either adrenalin cell or noradrenalin cell of respective animals in 10 groups during the development and aging from fetal day 19 to postnatal month 24. The number of labeled mitochondria per cell increased from perinatal stage to juvenile stage at postnatal day 14, then decreased from adult stage at month 1 to month 24.