Volumetric growth of the major brain divisions in fetal Macaca nemestrina.

Brains from 22 age-dated fetal Macaca nemestrina were embedded in celloidin and prepared for histological serial sections. A computer-based morphometric system was used to digitize contours of neural structures and to calculate their areas and volumes. Shrinkage of the brain sections was corrected by a multiplication factor relating pre-processed brain volume to the computer-calculated volume of the processed brain. Volume growth of the telencephalon, mesencephalon and pons-medulla was linear over the fetal period of 60 days postconception to near-term at 166 days postconception. Volume growth of the total brain, diencephalon and cerebellum, was curvilinear with respect to age, with slower growth initially and faster growth in the later stages of gestation. Total brain and body grew with an almost 1:1 relation during the fetal period. The proportionate growth of the brain was largely accounted for by telencephalic growth. The other brain divisions all showed different growth rates in relation to growth of the body.