Figure 1

Developmental growth curves. Developmental growth curves of different parts and tissues of the human body, each plotted as a percentage of the total gain from birth to 20 years of age (i.e. size at age 20 is 100 on the vertical scale). Height and most body measurements follow the "general" curve. Note that the brain (and the head containing it) develops earlier than any other tissue; at birth it is already 25% of its adult weight, and 90% at age five. Lymphoid tissue reaches its maximum just before adolescence, and then declines to its adult value as the reproductive organs rapidly increase. (Drawn after Scammon, 1930 [25]).