Adrenal cortex of mice: circadian cycle of mitotic activity and volume of cell nuclei.

Male mice (19--20 g) were observed to have mitotic peaks in the zona fasciculata of the adrenal cortex during morning hours and in the first half of the day, while high values of nuclear volumes were characteristic of the said mice in the second half of the day and at night. In the zona glomerulosa, the mitotic index was increased in the second half of the day and in the evening hours, and the nuclear volume was greater at night-time.