GROWTH OF THE FETAL CENTRAL NERVOUS SYSTEM 427 
The percentage increment of the hemispheres, when calculated 
by fetal months (fig. 28, curve V), shows an approximate rate 
of growth of 600 per cent in the fourth fetal month. This rate 
descends rapidly at first, and then more slowly to about 22 per 
cent in the tenth fetal month. 
TABLE i1 
Volume of both cerebral hemispheres 
Formula: Volume of both cerebral hemispheres (cc.) = (0.12 crown-heel length 
(em:))*2" 
(115 cases) 
OBSERVED VOLUME OF 
BOTH HEMISPHERES 
DIFFERENCE 
CROWN-HEEL LENGTH 
BETWEEN 
CALCULATED 
VOLUME) OF 1) soe an AD NUMBER 
Range Mean ee Mint Mean HEMISPHERES ee ae Ween 
cm. cm. cc cc. cc cc. cc 
Oto 5 
5 to 10 
10 to 15 12.5 8.6 2.2 5.2 3.65 —1.55 12 
15 to 20 16.9 | 20.5 AS5|l2ez 9.5 —2.7 14 
20 to 25 22.4) 46.2 18.0 29.4 22.9 —6.5 16 
25 to 30 Piel 62.5 25.4 | 46.6 43.0 —3.6 12 
30 to 35 SZEON| Lode eoOs om Oe. 79.1 +3.0 18 
35 to 40 37.2 | 210.8 95.5 | 131.4 118.2 —13.2 17 
40 to 45 42.3 | 239.3 | 184.2 | 184.8 178.1 —6.7 il 
45 to 50 48.0 | 380.4 | 201.2 | 277.0 266.5 —10.5 a 
50 to 55 52.2 | 377.3 | 302.0 | 334.4 348.3 —13.9 8 
TABLE 12 
Calculated volume of both cerebral hemispheres at 5-cm. intervals of crown-heel length 
VOLUME OF BOTH 
CEREBRAL 
HEMISPHERES 
INCREMENT IN EACH 
5-CM. INTERVAL RATIO OF NEW-BORN 
CROWN-HEEL LENGTH 
ce. 
1.79 
6.52 
16.33 
33.27 
59.51 
97.31 
149.0 
216.9 
303.6 
411.2 
cc. 
4.73 
9.81 
16.94 
26.24 
37.80 
51.69 
69.7 
86.7 
107.6 
per cent 
264.0 
150.0 
103.0 
78.8 
63.5 
53.2 
45.5 
40.0 
34.5 
per cent 
onoonne 
me & OO Re SD 
Hy Oo et et 
