Volumetric studies on the red nucleus of the rat at different ages.

The postnatal development of the red nucleus in albino rat was quantitatively studied. Planimetric studies on stained paraffin sections of the midbrain showed that the red nucleus has a rounded contour with tapering ends and a broad centre. The volume of the red nucleus revealed an increase from birth, to reach its maximum at the age of 3 months, then declines until the age of 2 years. However, the size does not regain its newly born value. On the other hand, the number of cells remains constant during the entire life span of the animal.