GROWTH OF THE FETAL CENTRAL NERVOUS SYSTEM 431 
The absolute fronto-occipital diameter when considered in re- 
lation to age (fig. 32, curve I) is about 1.3 cm. in the middle of 
the third fetal month and increases at first rapidly and then more 
slowly to 9 em. at birth. 
The percentage increment of the fronto-occipital length for 
5-em. intervals of body length (fig. 25, curve I) gradually declines 
O | | 
0 5 10 15 £0 £5 30 3D AO 4d 50 55cm. 
Fig. 8 Field graph and curve of the growth of the cerebral hemispheres in 
fetal life as shown by the fronto-occipital diameter. Abscissa: total body length 
in em. Ordinate: fronto-occipital diameter in em. Individual cases indicated by 
solid dots. Curve drawn to the formula. Y = 0.175X + 0.25. (Data from 
tables 13 and 14.) 
from about 80 per cent in the 5-to-10-cm. interval to about 10 
per cent in the 50-to-55-cm. interval. 
The percentage increment of the fronto-occipital length, when 
calculated for fetal months (fig. 27, curve I), shows an approxi- 
mate rate of growth of 150 per cent in the third fetal month. 
This descends rapidly to 31 per cent in the fifth month and gradu- 
ally to 9.5 per cent in the last fetal month. 
