Abstract
The author studied histochemically the alteration of succinic dehydrogenase of the brain of rats from late fetal life to adult. The results obtained were as followed.
1. The grey matter, which was generally very slight in activity on the 20th day of gestation, showed a gradually increased activity with advancing development, and revealed varying ages, at which different parts of the brain acquired its adult activities. The white matter was entirely negative throughout its development.
2. The enzyme activity in the neocortex began to increase from 14 days after birth, while that in the basal ganglia from 10 or 14 days. The both regions showed the adult levels of activity at 2 months of age.
3. The ages, at which the enzyme activity began to increase in the diencephalon, were as followed; in the habenular nucleus, ventral thalamic nucleus and nucleus subthalamicus on the 7th day after birth, in the metathalamus on the 10th day, and in almost all nuclei of the thalamus and hypothalamus on the 14th day. The enzyme activity in the hypothalamus, metathalamus and subthalamus reached the adult level at 1 month, but that in the habenular nucleus, thalamus and mamillary body at 2 months.
4. In the midbrain the enzyme activity began to increase from 7 to 14 days of age. The adult activity was gained in the optic tectum at the 2nd month after birth, in the nucleus of the 4th nerve at the 14th day, and in other parts of the midbrain at about the 1st month.
5. The enzyme activity in the pons began to rise from 3 or 5 days of age, and reached the adult level at about 1 month after birth.
6. The cerebellar cortex and nuclei began to show an increase in enzyme activity from 7 days of age, and the latter attained the adult level on the 45th day, while the former on the 2nd month.
7. The enzyme activity in the medulla oblongata began to rise from 5 days of age, and attained the adult level on 21 days.
