GROWTH OF THE FETAL CENTRAL NERVOUS SYSTEM 455 
The absolute length of the spinal cord (fig. 23) ascends rather 
sharply from 2.2 em. length at 5 em. (C H) to 9.2 cm. at 25 cm. 
(CH). It then ascends more slowly to 14.2 cm. at birth (50 cm. 
C H). Its empirical formula is: 
Length of spinal cord (em.) = (10.0 C H body 
length (cm.))-467 — 4.0 
The curve of cord length, when plotted against time, is quite 
similar to that plotted against body length, but the rise is a more 
rapid one (fig. 32, curve IV). 
& l | 
cm ‘ 
~ 
O 5 10 i5 £0 
05 30 Dpy 0) 45 50 55cm 
Vig. 20 Field graph and curve of the growth of the brain stem in fetal life as 
shown by the fronto-spinal length. Abscissa: total body length inem. Ordi- 
nate: fronto-spinal length in em. Individual cases indicated by solid dots. 
Curve drawn totheformula: Y = (2.0X)-47—2.2. (Data from tables 31 and 32.) 
The percentage increment of the cord length as calculated for 
5-em. intervals of crown-heel length (fig. 25, curve VIII) is about 
109 per cent for the 5-to-10-cm. interval, falls rapidly to 23 per 
cent for the 15-to-20-cm. interval, and then gradually to 6 per 
cent for the 50-to-55-cm. interval. 
The percentage increment of the spinal-cord length when cal- 
culated for fetal months (fig. 27, curve V) shows a rate of growth 
of approximately 400 per cent in the third month, descending 
rapidly to 26 per cent in the sixth month, and then gradually to 
nearly 6 per cent in the last month of the fetal period. 
